# don't push out -i
-i
+tests/-i
+builtins/-i
+CWRU/-i
+CWRU/old-changelogs/-i
+lib/readline/-i
+doc/-i
*.save
.DS_Store
Otherwise, it's a prefix and likely doesn't exist, so we'll stick
with the default backslash completion quoting style.
Fixes completion quoting issue from Aaron Laws <dartme18@gmail.com>
+
+ 8/29
+ ----
+builtins/declare.def
+ - declare_invalid_opts: reject attempts to use -n with -i, since you
+ can't have nameref variables referring to positional parameters
+
+lib/readline/isearch.c
+ - rl_display_search: if the search string contains a control char,
+ display it using the same translation (^C) as in other places
+ Report and patch from Grisha Levit <grishalevit@gmail.com>
+
+ 9/4
+ ---
+lib/readline/input.c
+ - rl_getc: add RL_STATE_MOREINPUT to the list of states that cause
+ a received SIGINT to call _rl_abort_internal
+
+lib/readline/display.c
+ - rl_redisplay: put setting RL_STATE_REDISPLAYING outside the calls
+ to _rl_block_sigint and _rl_release_sigint
+
+lib/readline/text.c
+ - _rl_readstr_init: set RL_STATE_READSTR before calling rl_message
+ to prompt for the command name so we know we're in readstr if we
+ get a SIGINT
+
+lib/readline/signals.c
+ - _rl_release_sigint: after calling RL_CHECK_SIGNALS, call _rl_abort_internal
+ if the state indicates that we are in one of the places that can
+ call rl_message. That takes care of the case where redisplay gets a
+ SIGINT while `blocking' it.
+ Report from Grisha Levit <grishalevit@gmail.com>
--- /dev/null
+_\bB_\bA_\bS_\bH(1) General Commands Manual _\bB_\bA_\bS_\bH(1)
+
+N\bNA\bAM\bME\bE
+ bash - GNU Bourne-Again SHell
+
+S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
+ b\bba\bas\bsh\bh [options] [command_string | file]
+
+C\bCO\bOP\bPY\bYR\bRI\bIG\bGH\bHT\bT
+ Bash is Copyright (C) 1989-2025 by the Free Software Foundation, Inc.
+
+D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
+ B\bBa\bas\bsh\bh is a command language interpreter that executes commands read from
+ the standard input, from a string, or from a file. It is a reimplemen-
+ tation and extension of the Bourne shell, the historical Unix command
+ language interpreter. B\bBa\bas\bsh\bh also incorporates useful features from the
+ _\bK_\bo_\br_\bn and _\bC shells (k\bks\bsh\bh and c\bcs\bsh\bh).
+
+ POSIX is the name for a family of computing standards based on Unix.
+ B\bBa\bas\bsh\bh is intended to be a conformant implementation of the Shell and
+ Utilities portion of the IEEE POSIX specification (IEEE Standard
+ 1003.1). B\bBa\bas\bsh\bh POSIX mode (hereafter referred to as _\bp_\bo_\bs_\bi_\bx _\bm_\bo_\bd_\be) changes
+ the shell's behavior where its default operation differs from the stan-
+ dard to strictly conform to the standard. See S\bSE\bEE\bE A\bAL\bLS\bSO\bO below for a
+ reference to a document that details how posix mode affects b\bba\bas\bsh\bh's be-
+ havior. B\bBa\bas\bsh\bh can be configured to be POSIX-conformant by default.
+
+O\bOP\bPT\bTI\bIO\bON\bNS\bS
+ All of the single-character shell options documented in the description
+ of the s\bse\bet\bt builtin command, including -\b-o\bo, can be used as options when
+ the shell is invoked. In addition, b\bba\bas\bsh\bh interprets the following op-
+ tions when it is invoked:
+
+ -\b-c\bc If the -\b-c\bc option is present, then commands are read from the
+ first non-option argument _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b__\bs_\bt_\br_\bi_\bn_\bg. If there are argu-
+ ments after the _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b__\bs_\bt_\br_\bi_\bn_\bg, the first argument is as-
+ signed to $\b$0\b0 and any remaining arguments are assigned to the
+ positional parameters. The assignment to $\b$0\b0 sets the name of
+ the shell, which is used in warning and error messages.
+
+ -\b-i\bi If the -\b-i\bi option is present, the shell is _\bi_\bn_\bt_\be_\br_\ba_\bc_\bt_\bi_\bv_\be.
+
+ -\b-l\bl Make b\bba\bas\bsh\bh act as if it had been invoked as a login shell (see
+ I\bIN\bNV\bVO\bOC\bCA\bAT\bTI\bIO\bON\bN below).
+
+ -\b-r\br If the -\b-r\br option is present, the shell becomes _\br_\be_\bs_\bt_\br_\bi_\bc_\bt_\be_\bd
+ (see R\bRE\bES\bST\bTR\bRI\bIC\bCT\bTE\bED\bD S\bSH\bHE\bEL\bLL\bL below).
+
+ -\b-s\bs If the -\b-s\bs option is present, or if no arguments remain after
+ option processing, the shell reads commands from the standard
+ input. This option allows the positional parameters to be
+ set when invoking an interactive shell or when reading input
+ through a pipe.
+
+ -\b-D\bD Print a list of all double-quoted strings preceded by $\b$ on
+ the standard output. These are the strings that are subject
+ to language translation when the current locale is not C\bC or
+ P\bPO\bOS\bSI\bIX\bX. This implies the -\b-n\bn option; no commands will be exe-
+ cuted.
+
+ [\b[-\b-+\b+]\b]O\bO [\b[_\bs_\bh_\bo_\bp_\bt_\b__\bo_\bp_\bt_\bi_\bo_\bn]\b]
+ _\bs_\bh_\bo_\bp_\bt_\b__\bo_\bp_\bt_\bi_\bo_\bn is one of the shell options accepted by the
+ s\bsh\bho\bop\bpt\bt builtin (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below). If
+ _\bs_\bh_\bo_\bp_\bt_\b__\bo_\bp_\bt_\bi_\bo_\bn is present, -\b-O\bO sets the value of that option; +\b+O\bO
+ unsets it. If _\bs_\bh_\bo_\bp_\bt_\b__\bo_\bp_\bt_\bi_\bo_\bn is not supplied, b\bba\bas\bsh\bh prints the
+ names and values of the shell options accepted by s\bsh\bho\bop\bpt\bt on
+ the standard output. If the invocation option is +\b+O\bO, the
+ output is displayed in a format that may be reused as input.
+
+ -\b--\b- A -\b--\b- signals the end of options and disables further option
+ processing. Any arguments after the -\b--\b- are treated as a
+ shell script filename (see below) and arguments passed to
+ that script. An argument of -\b- is equivalent to -\b--\b-.
+
+ B\bBa\bas\bsh\bh also interprets a number of multi-character options. These op-
+ tions must appear on the command line before the single-character op-
+ tions to be recognized.
+
+ -\b--\b-d\bde\beb\bbu\bug\bgg\bge\ber\br
+ Arrange for the debugger profile to be executed before the shell
+ starts. Turns on extended debugging mode (see the description
+ of the e\bex\bxt\btd\bde\beb\bbu\bug\bg option to the s\bsh\bho\bop\bpt\bt builtin below).
+
+ -\b--\b-d\bdu\bum\bmp\bp-\b-p\bpo\bo-\b-s\bst\btr\bri\bin\bng\bgs\bs
+ Equivalent to -\b-D\bD, but the output is in the GNU _\bg_\be_\bt_\bt_\be_\bx_\bt "po"
+ (portable object) file format.
+
+ -\b--\b-d\bdu\bum\bmp\bp-\b-s\bst\btr\bri\bin\bng\bgs\bs
+ Equivalent to -\b-D\bD.
+
+ -\b--\b-h\bhe\bel\blp\bp Display a usage message on standard output and exit success-
+ fully.
+
+ -\b--\b-i\bin\bni\bit\bt-\b-f\bfi\bil\ble\be _\bf_\bi_\bl_\be
+ -\b--\b-r\brc\bcf\bfi\bil\ble\be _\bf_\bi_\bl_\be
+ Execute commands from _\bf_\bi_\bl_\be instead of the standard personal ini-
+ tialization file _\b~_\b/_\b._\bb_\ba_\bs_\bh_\br_\bc if the shell is interactive (see I\bIN\bN-\b-
+ V\bVO\bOC\bCA\bAT\bTI\bIO\bON\bN below).
+
+ -\b--\b-l\blo\bog\bgi\bin\bn
+ Equivalent to -\b-l\bl.
+
+ -\b--\b-n\bno\boe\bed\bdi\bit\bti\bin\bng\bg
+ Do not use the GNU r\bre\bea\bad\bdl\bli\bin\bne\be library to read command lines when
+ the shell is interactive.
+
+ -\b--\b-n\bno\bop\bpr\bro\bof\bfi\bil\ble\be
+ Do not read either the system-wide startup file _\b/_\be_\bt_\bc_\b/_\bp_\br_\bo_\bf_\bi_\bl_\be or
+ any of the personal initialization files _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bp_\br_\bo_\bf_\bi_\bl_\be,
+ _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bl_\bo_\bg_\bi_\bn, or _\b~_\b/_\b._\bp_\br_\bo_\bf_\bi_\bl_\be. By default, b\bba\bas\bsh\bh reads these
+ files when it is invoked as a login shell (see I\bIN\bNV\bVO\bOC\bCA\bAT\bTI\bIO\bON\bN be-
+ low).
+
+ -\b--\b-n\bno\bor\brc\bc Do not read and execute the personal initialization file
+ _\b~_\b/_\b._\bb_\ba_\bs_\bh_\br_\bc if the shell is interactive. This option is on by de-
+ fault if the shell is invoked as s\bsh\bh.
+
+ -\b--\b-p\bpo\bos\bsi\bix\bx
+ Enable posix mode; change the behavior of b\bba\bas\bsh\bh where the default
+ operation differs from the POSIX standard to match the standard.
+
+ -\b--\b-r\bre\bes\bst\btr\bri\bic\bct\bte\bed\bd
+ The shell becomes restricted (see R\bRE\bES\bST\bTR\bRI\bIC\bCT\bTE\bED\bD S\bSH\bHE\bEL\bLL\bL below).
+
+ -\b--\b-v\bve\ber\brb\bbo\bos\bse\be
+ Equivalent to -\b-v\bv.
+
+ -\b--\b-v\bve\ber\brs\bsi\bio\bon\bn
+ Show version information for this instance of b\bba\bas\bsh\bh on the stan-
+ dard output and exit successfully.
+
+A\bAR\bRG\bGU\bUM\bME\bEN\bNT\bTS\bS
+ If arguments remain after option processing, and neither the -\b-c\bc nor the
+ -\b-s\bs option has been supplied, the first argument is treated as the name
+ of a file containing shell commands (a _\bs_\bh_\be_\bl_\bl _\bs_\bc_\br_\bi_\bp_\bt). When b\bba\bas\bsh\bh is in-
+ voked in this fashion, $\b$0\b0 is set to the name of the file, and the posi-
+ tional parameters are set to the remaining arguments. B\bBa\bas\bsh\bh reads and
+ executes commands from this file, then exits. B\bBa\bas\bsh\bh's exit status is
+ the exit status of the last command executed in the script. If no com-
+ mands are executed, the exit status is 0. B\bBa\bas\bsh\bh first attempts to open
+ the file in the current directory, and, if no file is found, searches
+ the directories in P\bPA\bAT\bTH\bH for the script.
+
+I\bIN\bNV\bVO\bOC\bCA\bAT\bTI\bIO\bON\bN
+ A _\bl_\bo_\bg_\bi_\bn _\bs_\bh_\be_\bl_\bl is one whose first character of argument zero is a -\b-, or
+ one started with the -\b--\b-l\blo\bog\bgi\bin\bn option.
+
+ An _\bi_\bn_\bt_\be_\br_\ba_\bc_\bt_\bi_\bv_\be _\bs_\bh_\be_\bl_\bl is one started without non-option arguments (un-
+ less -\b-s\bs is specified) and without the -\b-c\bc option, and whose standard in-
+ put and standard error are both connected to terminals (as determined
+ by _\bi_\bs_\ba_\bt_\bt_\by(3)), or one started with the -\b-i\bi option. B\bBa\bas\bsh\bh sets P\bPS\bS1\b1 and $\b$-\b-
+ includes i\bi if the shell is interactive, so a shell script or a startup
+ file can test this state.
+
+ The following paragraphs describe how b\bba\bas\bsh\bh executes its startup files.
+ If any of the files exist but cannot be read, b\bba\bas\bsh\bh reports an error.
+ Tildes are expanded in filenames as described below under T\bTi\bil\bld\bde\be E\bEx\bxp\bpa\ban\bn-\b-
+ s\bsi\bio\bon\bn in the E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN section.
+
+ When b\bba\bas\bsh\bh is invoked as an interactive login shell, or as a non-inter-
+ active shell with the -\b--\b-l\blo\bog\bgi\bin\bn option, it first reads and executes com-
+ mands from the file _\b/_\be_\bt_\bc_\b/_\bp_\br_\bo_\bf_\bi_\bl_\be, if that file exists. After reading
+ that file, it looks for _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bp_\br_\bo_\bf_\bi_\bl_\be, _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bl_\bo_\bg_\bi_\bn, and _\b~_\b/_\b._\bp_\br_\bo_\bf_\bi_\bl_\be,
+ in that order, and reads and executes commands from the first one that
+ exists and is readable. The -\b--\b-n\bno\bop\bpr\bro\bof\bfi\bil\ble\be option may be used when the
+ shell is started to inhibit this behavior.
+
+ When an interactive login shell exits, or a non-interactive login shell
+ executes the e\bex\bxi\bit\bt builtin command, b\bba\bas\bsh\bh reads and executes commands
+ from the file _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bl_\bo_\bg_\bo_\bu_\bt, if it exists.
+
+ When an interactive shell that is not a login shell is started, b\bba\bas\bsh\bh
+ reads and executes commands from _\b~_\b/_\b._\bb_\ba_\bs_\bh_\br_\bc, if that file exists. The
+ -\b--\b-n\bno\bor\brc\bc option inhibits this behavior. The -\b--\b-r\brc\bcf\bfi\bil\ble\be _\bf_\bi_\bl_\be option causes
+ b\bba\bas\bsh\bh to use _\bf_\bi_\bl_\be instead of _\b~_\b/_\b._\bb_\ba_\bs_\bh_\br_\bc.
+
+ When b\bba\bas\bsh\bh is started non-interactively, to run a shell script, for ex-
+ ample, it looks for the variable B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV in the environment, expands
+ its value if it appears there, and uses the expanded value as the name
+ of a file to read and execute. B\bBa\bas\bsh\bh behaves as if the following com-
+ mand were executed:
+
+ if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
+
+ but does not use the value of the P\bPA\bAT\bTH\bH variable to search for the file-
+ name.
+
+ If b\bba\bas\bsh\bh is invoked with the name s\bsh\bh, it tries to mimic the startup be-
+ havior of historical versions of s\bsh\bh as closely as possible, while con-
+ forming to the POSIX standard as well. When invoked as an interactive
+ login shell, or a non-interactive shell with the -\b--\b-l\blo\bog\bgi\bin\bn option, it
+ first attempts to read and execute commands from _\b/_\be_\bt_\bc_\b/_\bp_\br_\bo_\bf_\bi_\bl_\be and
+ _\b~_\b/_\b._\bp_\br_\bo_\bf_\bi_\bl_\be, in that order. The -\b--\b-n\bno\bop\bpr\bro\bof\bfi\bil\ble\be option inhibits this behav-
+ ior. When invoked as an interactive shell with the name s\bsh\bh, b\bba\bas\bsh\bh looks
+ for the variable E\bEN\bNV\bV, expands its value if it is defined, and uses the
+ expanded value as the name of a file to read and execute. Since a
+ shell invoked as s\bsh\bh does not attempt to read and execute commands from
+ any other startup files, the -\b--\b-r\brc\bcf\bfi\bil\ble\be option has no effect. A non-in-
+ teractive shell invoked with the name s\bsh\bh does not attempt to read any
+ other startup files.
+
+ When invoked as s\bsh\bh, b\bba\bas\bsh\bh enters posix mode after reading the startup
+ files.
+
+ When b\bba\bas\bsh\bh is started in posix mode, as with the -\b--\b-p\bpo\bos\bsi\bix\bx command line
+ option, it follows the POSIX standard for startup files. In this mode,
+ interactive shells expand the E\bEN\bNV\bV variable and read and execute com-
+ mands from the file whose name is the expanded value. No other startup
+ files are read.
+
+ B\bBa\bas\bsh\bh attempts to determine when it is being run with its standard input
+ connected to a network connection, as when executed by the historical
+ and rarely-seen remote shell daemon, usually _\br_\bs_\bh_\bd, or the secure shell
+ daemon _\bs_\bs_\bh_\bd. If b\bba\bas\bsh\bh determines it is being run non-interactively in
+ this fashion, it reads and executes commands from _\b~_\b/_\b._\bb_\ba_\bs_\bh_\br_\bc, if that
+ file exists and is readable. B\bBa\bas\bsh\bh does not read this file if invoked
+ as s\bsh\bh. The -\b--\b-n\bno\bor\brc\bc option inhibits this behavior, and the -\b--\b-r\brc\bcf\bfi\bil\ble\be op-
+ tion makes b\bba\bas\bsh\bh use a different file instead of _\b~_\b/_\b._\bb_\ba_\bs_\bh_\br_\bc, but neither
+ _\br_\bs_\bh_\bd nor _\bs_\bs_\bh_\bd generally invoke the shell with those options or allow
+ them to be specified.
+
+ If the shell is started with the effective user (group) id not equal to
+ the real user (group) id, and the -\b-p\bp option is not supplied, no startup
+ files are read, shell functions are not inherited from the environment,
+ the S\bSH\bHE\bEL\bLL\bLO\bOP\bPT\bTS\bS, B\bBA\bAS\bSH\bHO\bOP\bPT\bTS\bS, C\bCD\bDP\bPA\bAT\bTH\bH, and G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE variables, if they ap-
+ pear in the environment, are ignored, and the effective user id is set
+ to the real user id. If the -\b-p\bp option is supplied at invocation, the
+ startup behavior is the same, but the effective user id is not reset.
+
+D\bDE\bEF\bFI\bIN\bNI\bIT\bTI\bIO\bON\bNS\bS
+ The following definitions are used throughout the rest of this docu-
+ ment.
+ b\bbl\bla\ban\bnk\bk A space or tab.
+ w\bwh\bhi\bit\bte\bes\bsp\bpa\bac\bce\be
+ A character belonging to the s\bsp\bpa\bac\bce\be character class in the cur-
+ rent locale, or for which _\bi_\bs_\bs_\bp_\ba_\bc_\be(3) returns true.
+ w\bwo\bor\brd\bd A sequence of characters considered as a single unit by the
+ shell. Also known as a t\bto\bok\bke\ben\bn.
+ n\bna\bam\bme\be A _\bw_\bo_\br_\bd consisting only of alphanumeric characters and under-
+ scores, and beginning with an alphabetic character or an under-
+ score. Also referred to as an i\bid\bde\ben\bnt\bti\bif\bfi\bie\ber\br.
+ m\bme\bet\bta\bac\bch\bha\bar\bra\bac\bct\bte\ber\br
+ A character that, when unquoted, separates words. One of the
+ following:
+ |\b| &\b& ;\b; (\b( )\b) <\b< >\b> s\bsp\bpa\bac\bce\be t\bta\bab\bb n\bne\bew\bwl\bli\bin\bne\be
+ c\bco\bon\bnt\btr\bro\bol\bl o\bop\bpe\ber\bra\bat\bto\bor\br
+ A _\bt_\bo_\bk_\be_\bn that performs a control function. It is one of the fol-
+ lowing symbols:
+ |\b||\b| &\b& &\b&&\b& ;\b; ;\b;;\b; ;\b;&\b& ;\b;;\b;&\b& (\b( )\b) |\b| |\b|&\b& <\b<n\bne\bew\bwl\bli\bin\bne\be>\b>
+
+R\bRE\bES\bSE\bER\bRV\bVE\bED\bD W\bWO\bOR\bRD\bDS\bS
+ _\bR_\be_\bs_\be_\br_\bv_\be_\bd _\bw_\bo_\br_\bd_\bs are words that have a special meaning to the shell. The
+ following words are recognized as reserved when unquoted and either the
+ first word of a command (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR below), the third word of a
+ c\bca\bas\bse\be or s\bse\bel\ble\bec\bct\bt command (only i\bin\bn is valid), or the third word of a f\bfo\bor\br
+ command (only i\bin\bn and d\bdo\bo are valid):
+
+ !\b! c\bca\bas\bse\be c\bco\bop\bpr\bro\boc\bc d\bdo\bo d\bdo\bon\bne\be e\bel\bli\bif\bf e\bel\bls\bse\be e\bes\bsa\bac\bc f\bfi\bi f\bfo\bor\br f\bfu\bun\bnc\bct\bti\bio\bon\bn i\bif\bf i\bin\bn s\bse\bel\ble\bec\bct\bt
+ t\bth\bhe\ben\bn u\bun\bnt\bti\bil\bl w\bwh\bhi\bil\ble\be {\b{ }\b} t\bti\bim\bme\be [\b[[\b[ ]\b]]\b]
+
+S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR
+ This section describes the syntax of the various forms of shell com-
+ mands.
+
+ S\bSi\bim\bmp\bpl\ble\be C\bCo\bom\bmm\bma\ban\bnd\bds\bs
+ A _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd is a sequence of optional variable assignments fol-
+ lowed by b\bbl\bla\ban\bnk\bk-separated words and redirections, and terminated by a
+ _\bc_\bo_\bn_\bt_\br_\bo_\bl _\bo_\bp_\be_\br_\ba_\bt_\bo_\br. The first word specifies the command to be executed,
+ and is passed as argument zero. The remaining words are passed as ar-
+ guments to the invoked command.
+
+ The return value of a _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd is its exit status, or 128+_\bn if
+ the command is terminated by signal _\bn.
+
+ P\bPi\bip\bpe\bel\bli\bin\bne\bes\bs
+ A _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be is a sequence of one or more commands separated by one of
+ the control operators |\b| or |\b|&\b&. The format for a pipeline is:
+
+ [t\bti\bim\bme\be [-\b-p\bp]] [ ! ] _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b1 [ [|\b|||\b|&\b&] _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b2 ... ]
+
+ The standard output of _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b1 is connected via a pipe to the standard
+ input of _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b2. This connection is performed before any redirec-
+ tions specified by the _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b1(see R\bRE\bED\bDI\bIR\bRE\bEC\bCT\bTI\bIO\bON\bN below). If |\b|&\b& is the
+ pipeline operator, _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b1's standard error, in addition to its stan-
+ dard output, is connected to _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b2's standard input through the
+ pipe; it is shorthand for 2\b2>\b>&\b&1\b1 |\b|. This implicit redirection of the
+ standard error to the standard output is performed after any redirec-
+ tions specified by _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b1.
+
+ The return status of a pipeline is the exit status of the last command,
+ unless the p\bpi\bip\bpe\bef\bfa\bai\bil\bl option is enabled. If p\bpi\bip\bpe\bef\bfa\bai\bil\bl is enabled, the
+ pipeline's return status is the value of the last (rightmost) command
+ to exit with a non-zero status, or zero if all commands exit success-
+ fully. If the reserved word !\b! precedes a pipeline, the exit status of
+ that pipeline is the logical negation of the exit status as described
+ above. If a pipeline is executed synchronously, the shell waits for
+ all commands in the pipeline to terminate before returning a value.
+
+ If the t\bti\bim\bme\be reserved word precedes a pipeline, the shell reports the
+ elapsed as well as user and system time consumed by its execution when
+ the pipeline terminates. The -\b-p\bp option changes the output format to
+ that specified by POSIX. When the shell is in posix mode, it does not
+ recognize t\bti\bim\bme\be as a reserved word if the next token begins with a "-".
+ The value of the T\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable is a format string that specifies
+ how the timing information should be displayed; see the description of
+ T\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT below under S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs.
+
+ When the shell is in posix mode, t\bti\bim\bme\be may appear by itself as the only
+ word in a simple command. In this case, the shell displays the total
+ user and system time consumed by the shell and its children. The T\bTI\bIM\bME\bE-\b-
+ F\bFO\bOR\bRM\bMA\bAT\bT variable specifies the format of the time information.
+
+ Each command in a multi-command pipeline, where pipes are created, is
+ executed in a _\bs_\bu_\bb_\bs_\bh_\be_\bl_\bl, which is a separate process. See C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXE\bE-\b-
+ C\bCU\bUT\bTI\bIO\bON\bN E\bEN\bNV\bVI\bIR\bRO\bON\bNM\bME\bEN\bNT\bT for a description of subshells and a subshell envi-
+ ronment. If the l\bla\bas\bst\btp\bpi\bip\bpe\be option is enabled using the s\bsh\bho\bop\bpt\bt builtin
+ (see the description of s\bsh\bho\bop\bpt\bt below), and job control is not active,
+ the last element of a pipeline may be run by the shell process.
+
+ L\bLi\bis\bst\bts\bs
+ A _\bl_\bi_\bs_\bt is a sequence of one or more pipelines separated by one of the
+ operators ;\b;, &\b&, &\b&&\b&, or |\b||\b|, and optionally terminated by one of ;\b;, &\b&, or
+ <\b<n\bne\bew\bwl\bli\bin\bne\be>\b>.
+
+ Of these list operators, &\b&&\b& and |\b||\b| have equal precedence, followed by ;\b;
+ and &\b&, which have equal precedence.
+
+ A sequence of one or more newlines may appear in a _\bl_\bi_\bs_\bt instead of a
+ semicolon to delimit commands.
+
+ If a command is terminated by the control operator &\b&, the shell exe-
+ cutes the command in the _\bb_\ba_\bc_\bk_\bg_\br_\bo_\bu_\bn_\bd in a subshell. The shell does not
+ wait for the command to finish, and the return status is 0. These are
+ referred to as _\ba_\bs_\by_\bn_\bc_\bh_\br_\bo_\bn_\bo_\bu_\bs commands. Commands separated by a ;\b; are
+ executed sequentially; the shell waits for each command to terminate in
+ turn. The return status is the exit status of the last command exe-
+ cuted.
+
+ AND and OR lists are sequences of one or more pipelines separated by
+ the &\b&&\b& and |\b||\b| control operators, respectively. AND and OR lists are
+ executed with left associativity. An AND list has the form
+
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b1 &\b&&\b& _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b2
+
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b2 is executed if, and only if, _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b1 returns an exit status
+ of zero (success).
+
+ An OR list has the form
+
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b1 |\b||\b| _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b2
+
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b2 is executed if, and only if, _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b1 returns a non-zero exit
+ status. The return status of AND and OR lists is the exit status of
+ the last command executed in the list.
+
+ C\bCo\bom\bmp\bpo\bou\bun\bnd\bd C\bCo\bom\bmm\bma\ban\bnd\bds\bs
+ A _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd _\bc_\bo_\bm_\bm_\ba_\bn_\bd is one of the following. In most cases a _\bl_\bi_\bs_\bt in a
+ command's description may be separated from the rest of the command by
+ one or more newlines, and may be followed by a newline in place of a
+ semicolon.
+
+ (_\bl_\bi_\bs_\bt) _\bl_\bi_\bs_\bt is executed in a subshell (see C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN E\bEN\bNV\bVI\bIR\bRO\bON\bN-\b-
+ M\bME\bEN\bNT\bT below for a description of a subshell environment). Vari-
+ able assignments and builtin commands that affect the shell's
+ environment do not remain in effect after the command completes.
+ The return status is the exit status of _\bl_\bi_\bs_\bt.
+
+ { _\bl_\bi_\bs_\bt; }
+ _\bl_\bi_\bs_\bt is executed in the current shell environment. _\bl_\bi_\bs_\bt must be
+ terminated with a newline or semicolon. This is known as a
+ _\bg_\br_\bo_\bu_\bp _\bc_\bo_\bm_\bm_\ba_\bn_\bd. The return status is the exit status of _\bl_\bi_\bs_\bt.
+
+ Note that unlike the metacharacters (\b( and )\b), {\b{ and }\b} are _\br_\be_\b-
+ _\bs_\be_\br_\bv_\be_\bd _\bw_\bo_\br_\bd_\bs and must occur where a reserved word is permitted
+ to be recognized. Since they do not cause a word break, they
+ must be separated from _\bl_\bi_\bs_\bt by whitespace or another shell
+ metacharacter.
+
+ ((_\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn))
+ The arithmetic _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn is evaluated according to the rules
+ described below under A\bAR\bRI\bIT\bTH\bHM\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN. If the value of
+ the expression is non-zero, the return status is 0; otherwise
+ the return status is 1. The _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn undergoes the same ex-
+ pansions as if it were within double quotes, but unescaped dou-
+ ble quote characters in _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn are not treated specially and
+ are removed. Since this can potentially result in empty
+ strings, this command treats those as expressions that evaluate
+ to 0.
+
+ [\b[[\b[ _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn ]\b]]\b]
+ Evaluate the conditional expression _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn and return a sta-
+ tus of zero (true) or non-zero (false). Expressions are com-
+ posed of the primaries described below under C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bS-\b-
+ S\bSI\bIO\bON\bNS\bS. The words between the [\b[[\b[ and ]\b]]\b] do not undergo word
+ splitting and pathname expansion. The shell performs tilde ex-
+ pansion, parameter and variable expansion, arithmetic expansion,
+ command substitution, process substitution, and quote removal on
+ those words. Conditional operators such as -\b-f\bf must be unquoted
+ to be recognized as primaries.
+
+ When used with [\b[[\b[, the <\b< and >\b> operators sort lexicographically
+ using the current locale.
+
+ When the =\b==\b= and !\b!=\b= operators are used, the string to the right
+ of the operator is considered a pattern and matched according to
+ the rules described below under P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg, as if the e\bex\bxt\bt-\b-
+ g\bgl\blo\bob\bb shell option were enabled. The =\b= operator is equivalent to
+ =\b==\b=. If the n\bno\boc\bca\bas\bse\bem\bma\bat\btc\bch\bh shell option is enabled, the match is
+ performed without regard to the case of alphabetic characters.
+ The return value is 0 if the string matches (=\b==\b=) or does not
+ match (!\b!=\b=) the pattern, and 1 otherwise. If any part of the
+ pattern is quoted, the quoted portion is matched as a string:
+ every character in the quoted portion matches itself, instead of
+ having any special pattern matching meaning.
+
+ An additional binary operator, =\b=~\b~, is available, with the same
+ precedence as =\b==\b= and !\b!=\b=. When it is used, the string to the
+ right of the operator is considered a POSIX extended regular ex-
+ pression and matched accordingly (using the POSIX _\br_\be_\bg_\bc_\bo_\bm_\bp and
+ _\br_\be_\bg_\be_\bx_\be_\bc interfaces usually described in _\br_\be_\bg_\be_\bx(3)). The return
+ value is 0 if the string matches the pattern, and 1 otherwise.
+ If the regular expression is syntactically incorrect, the condi-
+ tional expression's return value is 2. If the n\bno\boc\bca\bas\bse\bem\bma\bat\btc\bch\bh shell
+ option is enabled, the match is performed without regard to the
+ case of alphabetic characters.
+
+ If any part of the pattern is quoted, the quoted portion is
+ matched literally, as above. If the pattern is stored in a
+ shell variable, quoting the variable expansion forces the entire
+ pattern to be matched literally. Treat bracket expressions in
+ regular expressions carefully, since normal quoting and pattern
+ characters lose their meanings between brackets.
+
+ The match succeeds if the pattern matches any part of the
+ string. Anchor the pattern using the ^\b^ and $\b$ regular expression
+ operators to force it to match the entire string.
+
+ The array variable B\bBA\bAS\bSH\bH_\b_R\bRE\bEM\bMA\bAT\bTC\bCH\bH records which parts of the
+ string matched the pattern. The element of B\bBA\bAS\bSH\bH_\b_R\bRE\bEM\bMA\bAT\bTC\bCH\bH with
+ index 0 contains the portion of the string matching the entire
+ regular expression. Substrings matched by parenthesized subex-
+ pressions within the regular expression are saved in the remain-
+ ing B\bBA\bAS\bSH\bH_\b_R\bRE\bEM\bMA\bAT\bTC\bCH\bH indices. The element of B\bBA\bAS\bSH\bH_\b_R\bRE\bEM\bMA\bAT\bTC\bCH\bH with in-
+ dex _\bn is the portion of the string matching the _\bnth parenthe-
+ sized subexpression. B\bBa\bas\bsh\bh sets B\bBA\bAS\bSH\bH_\b_R\bRE\bEM\bMA\bAT\bTC\bCH\bH in the global
+ scope; declaring it as a local variable will lead to unexpected
+ results.
+
+ Expressions may be combined using the following operators,
+ listed in decreasing order of precedence:
+
+ (\b( _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn )\b)
+ Returns the value of _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn. This may be used to
+ override the normal precedence of operators.
+ !\b! _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn
+ True if _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn is false.
+ _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b1 &\b&&\b& _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b2
+ True if both _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b1 and _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b2 are true.
+ _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b1 |\b||\b| _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b2
+ True if either _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b1 or _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b2 is true.
+
+ The &\b&&\b& and |\b||\b| operators do not evaluate _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b2 if the value
+ of _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn_\b1 is sufficient to determine the return value of
+ the entire conditional expression.
+
+ f\bfo\bor\br _\bn_\ba_\bm_\be [ [ i\bin\bn _\bw_\bo_\br_\bd _\b._\b._\b. ] ; ] d\bdo\bo _\bl_\bi_\bs_\bt ; d\bdo\bon\bne\be
+ First, expand The list of words following i\bin\bn, generating a list
+ of items. Then, the variable _\bn_\ba_\bm_\be is set to each element of
+ this list in turn, and _\bl_\bi_\bs_\bt is executed each time. If the i\bin\bn
+ _\bw_\bo_\br_\bd is omitted, the f\bfo\bor\br command executes _\bl_\bi_\bs_\bt once for each po-
+ sitional parameter that is set (see P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS below). The re-
+ turn status is the exit status of the last command that exe-
+ cutes. If the expansion of the items following i\bin\bn results in an
+ empty list, no commands are executed, and the return status is
+ 0.
+
+ f\bfo\bor\br (( _\be_\bx_\bp_\br_\b1 ; _\be_\bx_\bp_\br_\b2 ; _\be_\bx_\bp_\br_\b3 )) [;] d\bdo\bo _\bl_\bi_\bs_\bt ; d\bdo\bon\bne\be
+ First, evaluate the arithmetic expression _\be_\bx_\bp_\br_\b1 according to the
+ rules described below under A\bAR\bRI\bIT\bTH\bHM\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN. Then, re-
+ peatedly evaluate the arithmetic expression _\be_\bx_\bp_\br_\b2 until it eval-
+ uates to zero. Each time _\be_\bx_\bp_\br_\b2 evaluates to a non-zero value,
+ execute _\bl_\bi_\bs_\bt and evaluate the arithmetic expression _\be_\bx_\bp_\br_\b3. If
+ any expression is omitted, it behaves as if it evaluates to 1.
+ The return value is the exit status of the last command in _\bl_\bi_\bs_\bt
+ that is executed, or non-zero if any of the expressions is in-
+ valid.
+
+ Use the b\bbr\bre\bea\bak\bk and c\bco\bon\bnt\bti\bin\bnu\bue\be builtins (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS
+ below) to control loop execution.
+
+ s\bse\bel\ble\bec\bct\bt _\bn_\ba_\bm_\be [ i\bin\bn _\bw_\bo_\br_\bd ] ; d\bdo\bo _\bl_\bi_\bs_\bt ; d\bdo\bon\bne\be
+ First, expand the list of words following i\bin\bn, generating a list
+ of items, and print the set of expanded words the standard er-
+ ror, each preceded by a number. If the i\bin\bn _\bw_\bo_\br_\bd is omitted,
+ print the positional parameters (see P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS below). s\bse\bel\ble\bec\bct\bt
+ then displays the P\bPS\bS3\b3 prompt and reads a line from the standard
+ input. If the line consists of a number corresponding to one of
+ the displayed words, then s\bse\bel\ble\bec\bct\bt sets the value of _\bn_\ba_\bm_\be to that
+ word. If the line is empty, s\bse\bel\ble\bec\bct\bt displays the words and
+ prompt again. If EOF is read, s\bse\bel\ble\bec\bct\bt completes and returns 1.
+ Any other value sets _\bn_\ba_\bm_\be to null. The line read is saved in
+ the variable R\bRE\bEP\bPL\bLY\bY. The _\bl_\bi_\bs_\bt is executed after each selection
+ until a b\bbr\bre\bea\bak\bk command is executed. The exit status of s\bse\bel\ble\bec\bct\bt is
+ the exit status of the last command executed in _\bl_\bi_\bs_\bt, or zero if
+ no commands were executed.
+
+ c\bca\bas\bse\be _\bw_\bo_\br_\bd i\bin\bn [ [(] _\bp_\ba_\bt_\bt_\be_\br_\bn [ |\b| _\bp_\ba_\bt_\bt_\be_\br_\bn ] ... ) _\bl_\bi_\bs_\bt ;; ] ... e\bes\bsa\bac\bc
+ A c\bca\bas\bse\be command first expands _\bw_\bo_\br_\bd, and tries to match it against
+ each _\bp_\ba_\bt_\bt_\be_\br_\bn in turn, proceeding from first to last, using the
+ matching rules described under P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg below. A pat-
+ tern list is a set of one or more patterns separated by , and
+ the ) operator terminates the pattern list. The _\bw_\bo_\br_\bd is ex-
+ panded using tilde expansion, parameter and variable expansion,
+ arithmetic expansion, command substitution, process substitution
+ and quote removal. Each _\bp_\ba_\bt_\bt_\be_\br_\bn examined is expanded using
+ tilde expansion, parameter and variable expansion, arithmetic
+ expansion, command substitution, process substitution, and quote
+ removal. If the n\bno\boc\bca\bas\bse\bem\bma\bat\btc\bch\bh shell option is enabled, the match
+ is performed without regard to the case of alphabetic charac-
+ ters. A _\bc_\bl_\ba_\bu_\bs_\be is a pattern list and an associated _\bl_\bi_\bs_\bt.
+
+ When a match is found, c\bca\bas\bse\be executes the corresponding _\bl_\bi_\bs_\bt. If
+ the ;\b;;\b; operator terminates the case clause, the c\bca\bas\bse\be command
+ completes after the first match. Using ;\b;&\b& in place of ;\b;;\b; causes
+ execution to continue with the _\bl_\bi_\bs_\bt associated with the next
+ pattern list. Using ;\b;;\b;&\b& in place of ;\b;;\b; causes the shell to test
+ the next pattern list in the statement, if any, and execute any
+ associated _\bl_\bi_\bs_\bt if the match succeeds, continuing the case
+ statement execution as if the pattern list had not matched. The
+ exit status is zero if no pattern matches.
+
+ Otherwise, it is the exit status of the last command executed in
+ the last _\bl_\bi_\bs_\bt executed.
+
+ i\bif\bf _\bl_\bi_\bs_\bt; t\bth\bhe\ben\bn _\bl_\bi_\bs_\bt; [ e\bel\bli\bif\bf _\bl_\bi_\bs_\bt; t\bth\bhe\ben\bn _\bl_\bi_\bs_\bt; ] ... [ e\bel\bls\bse\be _\bl_\bi_\bs_\bt; ] f\bfi\bi
+ The i\bif\bf _\bl_\bi_\bs_\bt is executed. If its exit status is zero, the t\bth\bhe\ben\bn
+ _\bl_\bi_\bs_\bt is executed. Otherwise, each e\bel\bli\bif\bf _\bl_\bi_\bs_\bt is executed in
+ turn, and if its exit status is zero, the corresponding t\bth\bhe\ben\bn
+ _\bl_\bi_\bs_\bt is executed and the command completes. Otherwise, the e\bel\bls\bse\be
+ _\bl_\bi_\bs_\bt is executed, if present. The exit status is the exit sta-
+ tus of the last command executed, or zero if no condition tested
+ true.
+
+ w\bwh\bhi\bil\ble\be _\bl_\bi_\bs_\bt_\b-_\b1; d\bdo\bo _\bl_\bi_\bs_\bt_\b-_\b2; d\bdo\bon\bne\be
+ u\bun\bnt\bti\bil\bl _\bl_\bi_\bs_\bt_\b-_\b1; d\bdo\bo _\bl_\bi_\bs_\bt_\b-_\b2; d\bdo\bon\bne\be
+ The w\bwh\bhi\bil\ble\be command continuously executes the list _\bl_\bi_\bs_\bt_\b-_\b2 as long
+ as the last command in the list _\bl_\bi_\bs_\bt_\b-_\b1 returns an exit status of
+ zero. The u\bun\bnt\bti\bil\bl command is identical to the w\bwh\bhi\bil\ble\be command, ex-
+ cept that the test is negated: _\bl_\bi_\bs_\bt_\b-_\b2 is executed as long as the
+ last command in _\bl_\bi_\bs_\bt_\b-_\b1 returns a non-zero exit status. The exit
+ status of the w\bwh\bhi\bil\ble\be and u\bun\bnt\bti\bil\bl commands is the exit status of the
+ last command executed in _\bl_\bi_\bs_\bt_\b-_\b2, or zero if none was executed.
+
+ C\bCo\bop\bpr\bro\boc\bce\bes\bss\bse\bes\bs
+ A _\bc_\bo_\bp_\br_\bo_\bc_\be_\bs_\bs is a shell command preceded by the c\bco\bop\bpr\bro\boc\bc reserved word. A
+ coprocess is executed asynchronously in a subshell, as if the command
+ had been terminated with the &\b& control operator, with a two-way pipe
+ established between the executing shell and the coprocess.
+
+ The syntax for a coprocess is:
+
+ c\bco\bop\bpr\bro\boc\bc [_\bN_\bA_\bM_\bE] _\bc_\bo_\bm_\bm_\ba_\bn_\bd [_\br_\be_\bd_\bi_\br_\be_\bc_\bt_\bi_\bo_\bn_\bs]
+
+ This creates a coprocess named _\bN_\bA_\bM_\bE. _\bc_\bo_\bm_\bm_\ba_\bn_\bd may be either a simple
+ command or a compound command (see above). _\bN_\bA_\bM_\bE is a shell variable
+ name. If _\bN_\bA_\bM_\bE is not supplied, the default name is C\bCO\bOP\bPR\bRO\bOC\bC.
+
+ The recommended form to use for a coprocess is
+
+ c\bco\bop\bpr\bro\boc\bc _\bN_\bA_\bM_\bE { _\bc_\bo_\bm_\bm_\ba_\bn_\bd [_\br_\be_\bd_\bi_\br_\be_\bc_\bt_\bi_\bo_\bn_\bs]; }
+
+ This form is preferred because simple commands result in the coprocess
+ always being named C\bCO\bOP\bPR\bRO\bOC\bC, and it is simpler to use and more complete
+ than the other compound commands.
+
+ If _\bc_\bo_\bm_\bm_\ba_\bn_\bd is a compound command, _\bN_\bA_\bM_\bE is optional. The word following
+ c\bco\bop\bpr\bro\boc\bc determines whether that word is interpreted as a variable name:
+ it is interpreted as _\bN_\bA_\bM_\bE if it is not a reserved word that introduces
+ a compound command. If _\bc_\bo_\bm_\bm_\ba_\bn_\bd is a simple command, _\bN_\bA_\bM_\bE is not al-
+ lowed; this is to avoid confusion between _\bN_\bA_\bM_\bE and the first word of
+ the simple command.
+
+ When the coprocess is executed, the shell creates an array variable
+ (see A\bAr\brr\bra\bay\bys\bs below) named _\bN_\bA_\bM_\bE in the context of the executing shell.
+ The standard output of _\bc_\bo_\bm_\bm_\ba_\bn_\bd is connected via a pipe to a file de-
+ scriptor in the executing shell, and that file descriptor is assigned
+ to _\bN_\bA_\bM_\bE[0]. The standard input of _\bc_\bo_\bm_\bm_\ba_\bn_\bd is connected via a pipe to a
+ file descriptor in the executing shell, and that file descriptor is as-
+ signed to _\bN_\bA_\bM_\bE[1]. This pipe is established before any redirections
+ specified by the command (see R\bRE\bED\bDI\bIR\bRE\bEC\bCT\bTI\bIO\bON\bN below). The file descriptors
+ can be utilized as arguments to shell commands and redirections using
+ standard word expansions. Other than those created to execute command
+ and process substitutions, the file descriptors are not available in
+ subshells.
+
+ The process ID of the shell spawned to execute the coprocess is avail-
+ able as the value of the variable _\bN_\bA_\bM_\bE_PID. The w\bwa\bai\bit\bt builtin may be
+ used to wait for the coprocess to terminate.
+
+ Since the coprocess is created as an asynchronous command, the c\bco\bop\bpr\bro\boc\bc
+ command always returns success. The return status of a coprocess is
+ the exit status of _\bc_\bo_\bm_\bm_\ba_\bn_\bd.
+
+ S\bSh\bhe\bel\bll\bl F\bFu\bun\bnc\bct\bti\bio\bon\bn D\bDe\bef\bfi\bin\bni\bit\bti\bio\bon\bns\bs
+ A shell function is an object that is called like a simple command and
+ executes a compound command with a new set of positional parameters.
+ Shell functions are declared as follows:
+
+ _\bf_\bn_\ba_\bm_\be () _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd [_\br_\be_\bd_\bi_\br_\be_\bc_\bt_\bi_\bo_\bn]
+ f\bfu\bun\bnc\bct\bti\bio\bon\bn _\bf_\bn_\ba_\bm_\be [()] _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd [_\br_\be_\bd_\bi_\br_\be_\bc_\bt_\bi_\bo_\bn]
+ This defines a function named _\bf_\bn_\ba_\bm_\be. The reserved word f\bfu\bun\bnc\bct\bti\bio\bon\bn
+ is optional. If the f\bfu\bun\bnc\bct\bti\bio\bon\bn reserved word is supplied, the
+ parentheses are optional. The _\bb_\bo_\bd_\by of the function is the com-
+ pound command _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd (see C\bCo\bom\bmp\bpo\bou\bun\bnd\bd C\bCo\bom\bmm\bma\ban\bnd\bds\bs above).
+ That command is usually a _\bl_\bi_\bs_\bt of commands between { and }, but
+ may be any command listed under C\bCo\bom\bmp\bpo\bou\bun\bnd\bd C\bCo\bom\bmm\bma\ban\bnd\bds\bs above. If the
+ f\bfu\bun\bnc\bct\bti\bio\bon\bn reserved word is used, but the parentheses are not sup-
+ plied, the braces are recommended. _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd is executed
+ whenever _\bf_\bn_\ba_\bm_\be is specified as the name of a simple command.
+ When in posix mode, _\bf_\bn_\ba_\bm_\be must be a valid shell _\bn_\ba_\bm_\be and may not
+ be the name of one of the POSIX _\bs_\bp_\be_\bc_\bi_\ba_\bl _\bb_\bu_\bi_\bl_\bt_\bi_\bn_\bs. In default
+ mode, a function name can be any unquoted shell word that does
+ not contain $\b$.
+
+ Any redirections (see R\bRE\bED\bDI\bIR\bRE\bEC\bCT\bTI\bIO\bON\bN below) specified when a function is
+ defined are performed when the function is executed.
+
+ The exit status of a function definition is zero unless a syntax error
+ occurs or a readonly function with the same name already exists. When
+ executed, the exit status of a function is the exit status of the last
+ command executed in the body. (See F\bFU\bUN\bNC\bCT\bTI\bIO\bON\bNS\bS below.)
+
+C\bCO\bOM\bMM\bME\bEN\bNT\bTS\bS
+ In a non-interactive shell, or an interactive shell in which the i\bin\bnt\bte\ber\br-\b-
+ a\bac\bct\bti\biv\bve\be_\b_c\bco\bom\bmm\bme\ben\bnt\bts\bs option to the s\bsh\bho\bop\bpt\bt builtin is enabled (see S\bSH\bHE\bEL\bLL\bL
+ B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below), a word beginning with #\b# introduces a comment.
+ A word begins at the beginning of a line, after unquoted whitespace, or
+ after an operator. The comment causes that word and all remaining
+ characters on that line to be ignored. An interactive shell without
+ the i\bin\bnt\bte\ber\bra\bac\bct\bti\biv\bve\be_\b_c\bco\bom\bmm\bme\ben\bnt\bts\bs option enabled does not allow comments. The
+ i\bin\bnt\bte\ber\bra\bac\bct\bti\biv\bve\be_\b_c\bco\bom\bmm\bme\ben\bnt\bts\bs option is enabled by default in interactive
+ shells.
+
+Q\bQU\bUO\bOT\bTI\bIN\bNG\bG
+ _\bQ_\bu_\bo_\bt_\bi_\bn_\bg is used to remove the special meaning of certain characters or
+ words to the shell. Quoting can be used to disable special treatment
+ for special characters, to prevent reserved words from being recognized
+ as such, and to prevent parameter expansion.
+
+ Each of the _\bm_\be_\bt_\ba_\bc_\bh_\ba_\br_\ba_\bc_\bt_\be_\br_\bs listed above under D\bDE\bEF\bFI\bIN\bNI\bIT\bTI\bIO\bON\bNS\bS has special
+ meaning to the shell and must be quoted if it is to represent itself.
+
+ When the command history expansion facilities are being used (see H\bHI\bIS\bS-\b-
+ T\bTO\bOR\bRY\bY E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN below), the _\bh_\bi_\bs_\bt_\bo_\br_\by _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn character, usually !\b!, must
+ be quoted to prevent history expansion.
+
+ There are four quoting mechanisms: the _\be_\bs_\bc_\ba_\bp_\be _\bc_\bh_\ba_\br_\ba_\bc_\bt_\be_\br, single quotes,
+ double quotes, and dollar-single quotes.
+
+ A non-quoted backslash (\\b\) is the _\be_\bs_\bc_\ba_\bp_\be _\bc_\bh_\ba_\br_\ba_\bc_\bt_\be_\br. It preserves the
+ literal value of the next character that follows, removing any special
+ meaning it has, with the exception of <newline>. If a \\b\<newline> pair
+ appears, and the backslash is not itself quoted, the \\b\<newline> is
+ treated as a line continuation (that is, it is removed from the input
+ stream and effectively ignored).
+
+ Enclosing characters in single quotes preserves the literal value of
+ each character within the quotes. A single quote may not occur between
+ single quotes, even when preceded by a backslash.
+
+ Enclosing characters in double quotes preserves the literal value of
+ all characters within the quotes, with the exception of $\b$, `\b`, \\b\, and,
+ when history expansion is enabled, !\b!. When the shell is in posix mode,
+ the !\b! has no special meaning within double quotes, even when history
+ expansion is enabled. The characters $\b$ and `\b` retain their special
+ meaning within double quotes. The backslash retains its special mean-
+ ing only when followed by one of the following characters: $\b$, `\b`, "\b", \\b\,
+ or <\b<n\bne\bew\bwl\bli\bin\bne\be>\b>. Backslashes preceding characters without a special mean-
+ ing are left unmodified.
+
+ A double quote may be quoted within double quotes by preceding it with
+ a backslash. If enabled, history expansion will be performed unless an
+ !\b! appearing in double quotes is escaped using a backslash. The back-
+ slash preceding the !\b! is not removed.
+
+ The special parameters *\b* and @\b@ have special meaning when in double
+ quotes (see P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS below).
+
+ Character sequences of the form $\b$'_\bs_\bt_\br_\bi_\bn_\bg' are treated as a special
+ variant of single quotes. The sequence expands to _\bs_\bt_\br_\bi_\bn_\bg, with back-
+ slash-escaped characters in _\bs_\bt_\br_\bi_\bn_\bg replaced as specified by the ANSI C
+ standard. Backslash escape sequences, if present, are decoded as fol-
+ lows:
+ \\b\a\ba alert (bell)
+ \\b\b\bb backspace
+ \\b\e\be
+ \\b\E\bE an escape character
+ \\b\f\bf form feed
+ \\b\n\bn new line
+ \\b\r\br carriage return
+ \\b\t\bt horizontal tab
+ \\b\v\bv vertical tab
+ \\b\\\b\ backslash
+ \\b\'\b' single quote
+ \\b\"\b" double quote
+ \\b\?\b? question mark
+ \\b\_\bn_\bn_\bn The eight-bit character whose value is the octal value
+ _\bn_\bn_\bn (one to three octal digits).
+ \\b\x\bx_\bH_\bH The eight-bit character whose value is the hexadecimal
+ value _\bH_\bH (one or two hex digits).
+ \\b\u\bu_\bH_\bH_\bH_\bH The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value _\bH_\bH_\bH_\bH (one to four hex digits).
+ \\b\U\bU_\bH_\bH_\bH_\bH_\bH_\bH_\bH_\bH
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value _\bH_\bH_\bH_\bH_\bH_\bH_\bH_\bH (one to eight hex digits).
+ \\b\c\bc_\bx A control-_\bx character.
+
+ The expanded result is single-quoted, as if the dollar sign had not
+ been present.
+
+ T\bTr\bra\ban\bns\bsl\bla\bat\bti\bin\bng\bg S\bSt\btr\bri\bin\bng\bgs\bs
+ A double-quoted string preceded by a dollar sign ($\b$"_\bs_\bt_\br_\bi_\bn_\bg") causes the
+ string to be translated according to the current locale. The _\bg_\be_\bt_\bt_\be_\bx_\bt
+ infrastructure performs the lookup and translation, using the L\bLC\bC_\b_M\bME\bES\bS-\b-
+ S\bSA\bAG\bGE\bES\bS, T\bTE\bEX\bXT\bTD\bDO\bOM\bMA\bAI\bIN\bND\bDI\bIR\bR, and T\bTE\bEX\bXT\bTD\bDO\bOM\bMA\bAI\bIN\bN shell variables. If the current
+ locale is C\bC or P\bPO\bOS\bSI\bIX\bX, if there are no translations available, or if the
+ string is not translated, the dollar sign is ignored, and the string is
+ treated as double-quoted as described above. This is a form of double
+ quoting, so the string remains double-quoted by default, whether or not
+ it is translated and replaced. If the n\bno\boe\bex\bxp\bpa\ban\bnd\bd_\b_t\btr\bra\ban\bns\bsl\bla\bat\bti\bio\bon\bn option is
+ enabled using the s\bsh\bho\bop\bpt\bt builtin, translated strings are single-quoted
+ instead of double-quoted. See the description of s\bsh\bho\bop\bpt\bt below under
+ S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS.
+
+P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS
+ A _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is an entity that stores values. It can be a _\bn_\ba_\bm_\be, a num-
+ ber, or one of the special characters listed below under S\bSp\bpe\bec\bci\bia\bal\bl P\bPa\bar\bra\ba-\b-
+ m\bme\bet\bte\ber\brs\bs. A _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be is a parameter denoted by a _\bn_\ba_\bm_\be. A variable has a
+ _\bv_\ba_\bl_\bu_\be and zero or more _\ba_\bt_\bt_\br_\bi_\bb_\bu_\bt_\be_\bs. Attributes are assigned using the
+ d\bde\bec\bcl\bla\bar\bre\be builtin command (see d\bde\bec\bcl\bla\bar\bre\be below in S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS).
+ The e\bex\bxp\bpo\bor\brt\bt and r\bre\bea\bad\bdo\bon\bnl\bly\by builtins assign specific attributes.
+
+ A parameter is set if it has been assigned a value. The null string is
+ a valid value. Once a variable is set, it may be unset only by using
+ the u\bun\bns\bse\bet\bt builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+
+ A _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be is assigned to using a statement of the form
+
+ _\bn_\ba_\bm_\be=[_\bv_\ba_\bl_\bu_\be]
+
+ If _\bv_\ba_\bl_\bu_\be is not given, the variable is assigned the null string. All
+ _\bv_\ba_\bl_\bu_\be_\bs undergo tilde expansion, parameter and variable expansion, com-
+ mand substitution, arithmetic expansion, and quote removal (see E\bEX\bXP\bPA\bAN\bN-\b-
+ S\bSI\bIO\bON\bN below). If the variable has its i\bin\bnt\bte\beg\bge\ber\br attribute set, then _\bv_\ba_\bl_\bu_\be
+ is evaluated as an arithmetic expression even if the $\b$(\b((\b(...)\b))\b) expansion
+ is not used (see A\bAr\bri\bit\bth\bhm\bme\bet\bti\bic\bc E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn below). Word splitting and path-
+ name expansion are not performed. Assignment statements may also ap-
+ pear as arguments to the a\bal\bli\bia\bas\bs, d\bde\bec\bcl\bla\bar\bre\be, t\bty\byp\bpe\bes\bse\bet\bt, e\bex\bxp\bpo\bor\brt\bt, r\bre\bea\bad\bdo\bon\bnl\bly\by, and
+ l\blo\boc\bca\bal\bl builtin commands (_\bd_\be_\bc_\bl_\ba_\br_\ba_\bt_\bi_\bo_\bn commands). When in posix mode,
+ these builtins may appear in a command after one or more instances of
+ the c\bco\bom\bmm\bma\ban\bnd\bd builtin and retain these assignment statement properties.
+
+ In the context where an assignment statement is assigning a value to a
+ shell variable or array index, the "+=" operator appends to or adds to
+ the variable's previous value. This includes arguments to _\bd_\be_\bc_\bl_\ba_\br_\ba_\bt_\bi_\bo_\bn
+ commands such as d\bde\bec\bcl\bla\bar\bre\be that accept assignment statements. When "+="
+ is applied to a variable for which the i\bin\bnt\bte\beg\bge\ber\br attribute has been set,
+ the variable's current value and _\bv_\ba_\bl_\bu_\be are each evaluated as arithmetic
+ expressions, and the sum of the results is assigned as the variable's
+ value. The current value is usually an integer constant, but may be an
+ expression. When "+=" is applied to an array variable using compound
+ assignment (see A\bAr\brr\bra\bay\bys\bs below), the variable's value is not unset (as it
+ is when using "="), and new values are appended to the array beginning
+ at one greater than the array's maximum index (for indexed arrays) or
+ added as additional key-value pairs in an associative array. When ap-
+ plied to a string-valued variable, _\bv_\ba_\bl_\bu_\be is expanded and appended to
+ the variable's value.
+
+ A variable can be assigned the _\bn_\ba_\bm_\be_\br_\be_\bf attribute using the -\b-n\bn option to
+ the d\bde\bec\bcl\bla\bar\bre\be or l\blo\boc\bca\bal\bl builtin commands (see the descriptions of d\bde\bec\bcl\bla\bar\bre\be
+ and l\blo\boc\bca\bal\bl below) to create a _\bn_\ba_\bm_\be_\br_\be_\bf, or a reference to another vari-
+ able. This allows variables to be manipulated indirectly. Whenever
+ the nameref variable is referenced, assigned to, unset, or has its at-
+ tributes modified (other than using or changing the _\bn_\ba_\bm_\be_\br_\be_\bf attribute
+ itself), the operation is actually performed on the variable specified
+ by the nameref variable's value. A nameref is commonly used within
+ shell functions to refer to a variable whose name is passed as an argu-
+ ment to the function. For instance, if a variable name is passed to a
+ shell function as its first argument, running
+
+ declare -n ref=$1
+
+ inside the function creates a local nameref variable r\bre\bef\bf whose value is
+ the variable name passed as the first argument. References and assign-
+ ments to r\bre\bef\bf, and changes to its attributes, are treated as references,
+ assignments, and attribute modifications to the variable whose name was
+ passed as $\b$1\b1. If the control variable in a f\bfo\bor\br loop has the nameref
+ attribute, the list of words can be a list of shell variables, and a
+ name reference is established for each word in the list, in turn, when
+ the loop is executed. Array variables cannot be given the n\bna\bam\bme\ber\bre\bef\bf at-
+ tribute. However, nameref variables can reference array variables and
+ subscripted array variables. Namerefs can be unset using the -\b-n\bn option
+ to the u\bun\bns\bse\bet\bt builtin. Otherwise, if u\bun\bns\bse\bet\bt is executed with the name of
+ a nameref variable as an argument, the variable referenced by the
+ nameref variable is unset.
+
+ When the shell starts, it reads its environment and creates a shell
+ variable from each environment variable that has a valid name, as de-
+ scribed below (see E\bEN\bNV\bVI\bIR\bRO\bON\bNM\bME\bEN\bNT\bT).
+
+ P\bPo\bos\bsi\bit\bti\bio\bon\bna\bal\bl P\bPa\bar\bra\bam\bme\bet\bte\ber\brs\bs
+ A _\bp_\bo_\bs_\bi_\bt_\bi_\bo_\bn_\ba_\bl _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is a parameter denoted by one or more digits,
+ other than the single digit 0. Positional parameters are assigned from
+ the shell's arguments when it is invoked, and may be reassigned using
+ the s\bse\bet\bt builtin command. Positional parameters may not be assigned to
+ with assignment statements. The positional parameters are temporarily
+ replaced when a shell function is executed (see F\bFU\bUN\bNC\bCT\bTI\bIO\bON\bNS\bS below).
+
+ When a positional parameter consisting of more than a single digit is
+ expanded, it must be enclosed in braces (see E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN below). Without
+ braces, a digit following $ can only refer to one of the first nine po-
+ sitional parameters ($\b$1\b1-\b-$\b$9\b9) or the special parameter $\b$0\b0 (see the next
+ section).
+
+ S\bSp\bpe\bec\bci\bia\bal\bl P\bPa\bar\bra\bam\bme\bet\bte\ber\brs\bs
+ The shell treats several parameters specially. These parameters may
+ only be referenced; assignment to them is not allowed. Special parame-
+ ters are denoted by one of the following characters.
+
+ *\b* ($\b$*\b*) Expands to the positional parameters, starting from one.
+ When the expansion is not within double quotes, each positional
+ parameter expands to a separate word. In contexts where word
+ expansions are performed, those words are subject to further
+ word splitting and pathname expansion. When the expansion oc-
+ curs within double quotes, it expands to a single word with the
+ value of each parameter separated by the first character of the
+ I\bIF\bFS\bS variable. That is, "\b"$\b$*\b*"\b" is equivalent to "\b"$\b$1\b1_\bc$\b$2\b2_\bc.\b..\b..\b."\b", where
+ _\bc is the first character of the value of the I\bIF\bFS\bS variable. If
+ I\bIF\bFS\bS is unset, the parameters are separated by spaces. If I\bIF\bFS\bS is
+ null, the parameters are joined without intervening separators.
+ @\b@ ($\b$@\b@) Expands to the positional parameters, starting from one.
+ In contexts where word splitting is performed, this expands each
+ positional parameter to a separate word; if not within double
+ quotes, these words are subject to word splitting. In contexts
+ where word splitting is not performed, such as the value portion
+ of an assignment statement, this expands to a single word with
+ each positional parameter separated by a space. When the expan-
+ sion occurs within double quotes, and word splitting is per-
+ formed, each parameter expands to a separate word. That is,
+ "\b"$\b$@\b@"\b" is equivalent to "\b"$\b$1\b1"\b" "\b"$\b$2\b2"\b" .\b..\b..\b. If the double-quoted expan-
+ sion occurs within a word, the expansion of the first parameter
+ is joined with the expansion of the beginning part of the origi-
+ nal word, and the expansion of the last parameter is joined with
+ the expansion of the last part of the original word. When there
+ are no positional parameters, "\b"$\b$@\b@"\b" and $\b$@\b@ expand to nothing
+ (i.e., they are removed).
+ #\b# ($\b$#\b#) Expands to the number of positional parameters in decimal.
+ ?\b? ($\b$?\b?) Expands to the exit status of the most recently executed
+ command.
+ -\b- ($\b$-\b-) Expands to the current option flags as specified upon invo-
+ cation, by the s\bse\bet\bt builtin command, or those set by the shell
+ itself (such as the -\b-i\bi option).
+ $\b$ ($\b$$\b$) Expands to the process ID of the shell. In a subshell, it
+ expands to the process ID of the parent shell, not the subshell.
+ !\b! ($\b$!\b!)Expands to the process ID of the job most recently placed
+ into the background, whether executed as an asynchronous command
+ or using the b\bbg\bg builtin (see J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL below).
+ 0\b0 ($\b$0\b0) Expands to the name of the shell or shell script. This is
+ set at shell initialization. If b\bba\bas\bsh\bh is invoked with a file of
+ commands, $\b$0\b0 is set to the name of that file. If b\bba\bas\bsh\bh is
+ started with the -\b-c\bc option, then $\b$0\b0 is set to the first argument
+ after the string to be executed, if one is present. Otherwise,
+ it is set to the filename used to invoke b\bba\bas\bsh\bh, as given by argu-
+ ment zero.
+
+ S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs
+ The shell sets following variables:
+
+ _\b_ ($\b$_\b_, an underscore) This has a number of meanings depending on
+ context. At shell startup, _\b_ is set to the pathname used to in-
+ voke the shell or shell script being executed as passed in the
+ environment or argument list. Subsequently, it expands to the
+ last argument to the previous simple command executed in the
+ foreground, after expansion. It is also set to the full path-
+ name used to invoke each command executed and placed in the en-
+ vironment exported to that command. When checking mail, $\b$_\b_ ex-
+ pands to the name of the mail file currently being checked.
+ B\bBA\bAS\bSH\bH Expands to the full filename used to invoke this instance of
+ b\bba\bas\bsh\bh.
+ B\bBA\bAS\bSH\bHO\bOP\bPT\bTS\bS
+ A colon-separated list of enabled shell options. Each word in
+ the list is a valid argument for the -\b-s\bs option to the s\bsh\bho\bop\bpt\bt
+ builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below). The options
+ appearing in B\bBA\bAS\bSH\bHO\bOP\bPT\bTS\bS are those reported as _\bo_\bn by s\bsh\bho\bop\bpt\bt. If
+ this variable is in the environment when b\bba\bas\bsh\bh starts up, the
+ shell enables each option in the list before reading any startup
+ files. If this variable is exported, child shells will enable
+ each option in the list. This variable is read-only.
+ B\bBA\bAS\bSH\bHP\bPI\bID\bD
+ Expands to the process ID of the current b\bba\bas\bsh\bh process. This
+ differs from $\b$$\b$ under certain circumstances, such as subshells
+ that do not require b\bba\bas\bsh\bh to be re-initialized. Assignments to
+ B\bBA\bAS\bSH\bHP\bPI\bID\bD have no effect. If B\bBA\bAS\bSH\bHP\bPI\bID\bD is unset, it loses its spe-
+ cial properties, even if it is subsequently reset.
+ B\bBA\bAS\bSH\bH_\b_A\bAL\bLI\bIA\bAS\bSE\bES\bS
+ An associative array variable whose members correspond to the
+ internal list of aliases as maintained by the a\bal\bli\bia\bas\bs builtin.
+ Elements added to this array appear in the alias list; however,
+ unsetting array elements currently does not remove aliases from
+ the alias list. If B\bBA\bAS\bSH\bH_\b_A\bAL\bLI\bIA\bAS\bSE\bES\bS is unset, it loses its special
+ properties, even if it is subsequently reset.
+ B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC
+ An array variable whose values are the number of parameters in
+ each frame of the current b\bba\bas\bsh\bh execution call stack. The number
+ of parameters to the current subroutine (shell function or
+ script executed with .\b. or s\bso\bou\bur\brc\bce\be) is at the top of the stack.
+ When a subroutine is executed, the number of parameters passed
+ is pushed onto B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC. The shell sets B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC only when in
+ extended debugging mode (see the description of the e\bex\bxt\btd\bde\beb\bbu\bug\bg op-
+ tion to the s\bsh\bho\bop\bpt\bt builtin below). Setting e\bex\bxt\btd\bde\beb\bbu\bug\bg after the
+ shell has started to execute a script, or referencing this vari-
+ able when e\bex\bxt\btd\bde\beb\bbu\bug\bg is not set, may result in inconsistent val-
+ ues. Assignments to B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC have no effect, and it may not be
+ unset.
+ B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV
+ An array variable containing all of the parameters in the cur-
+ rent b\bba\bas\bsh\bh execution call stack. The final parameter of the last
+ subroutine call is at the top of the stack; the first parameter
+ of the initial call is at the bottom. When a subroutine is exe-
+ cuted, the shell pushes the supplied parameters onto B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV.
+ The shell sets B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV only when in extended debugging mode
+ (see the description of the e\bex\bxt\btd\bde\beb\bbu\bug\bg option to the s\bsh\bho\bop\bpt\bt builtin
+ below). Setting e\bex\bxt\btd\bde\beb\bbu\bug\bg after the shell has started to execute
+ a script, or referencing this variable when e\bex\bxt\btd\bde\beb\bbu\bug\bg is not set,
+ may result in inconsistent values. Assignments to B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV
+ have no effect, and it may not be unset.
+ B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV0\b0
+ When referenced, this variable expands to the name of the shell
+ or shell script (identical to $\b$0\b0; see the description of special
+ parameter 0 above). Assigning a value to B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV0\b0 sets $\b$0\b0 to
+ the same value. If B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV0\b0 is unset, it loses its special
+ properties, even if it is subsequently reset.
+ B\bBA\bAS\bSH\bH_\b_C\bCM\bMD\bDS\bS
+ An associative array variable whose members correspond to the
+ internal hash table of commands as maintained by the h\bha\bas\bsh\bh
+ builtin. Adding elements to this array makes them appear in the
+ hash table; however, unsetting array elements currently does not
+ remove command names from the hash table. If B\bBA\bAS\bSH\bH_\b_C\bCM\bMD\bDS\bS is un-
+ set, it loses its special properties, even if it is subsequently
+ reset.
+ B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMM\bMA\bAN\bND\bD
+ Expands to the command currently being executed or about to be
+ executed, unless the shell is executing a command as the result
+ of a trap, in which case it is the command executing at the time
+ of the trap. If B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMM\bMA\bAN\bND\bD is unset, it loses its special
+ properties, even if it is subsequently reset.
+ B\bBA\bAS\bSH\bH_\b_E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN_\b_S\bST\bTR\bRI\bIN\bNG\bG
+ The command argument to the -\b-c\bc invocation option.
+ B\bBA\bAS\bSH\bH_\b_L\bLI\bIN\bNE\bEN\bNO\bO
+ An array variable whose members are the line numbers in source
+ files where each corresponding member of F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE was invoked.
+ $\b${\b{B\bBA\bAS\bSH\bH_\b_L\bLI\bIN\bNE\bEN\bNO\bO[\b[_\b$_\bi]\b]}\b} is the line number in the source file
+ ($\b${\b{B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE[\b[_\b$_\bi_\b+_\b1]\b]}\b}) where $\b${\b{F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE[\b[_\b$_\bi]\b]}\b} was called (or
+ $\b${\b{B\bBA\bAS\bSH\bH_\b_L\bLI\bIN\bNE\bEN\bNO\bO[\b[_\b$_\bi_\b-_\b1]\b]}\b} if referenced within another shell func-
+ tion). Use L\bLI\bIN\bNE\bEN\bNO\bO to obtain the current line number. Assign-
+ ments to B\bBA\bAS\bSH\bH_\b_L\bLI\bIN\bNE\bEN\bNO\bO have no effect, and it may not be unset.
+ B\bBA\bAS\bSH\bH_\b_L\bLO\bOA\bAD\bDA\bAB\bBL\bLE\bES\bS_\b_P\bPA\bAT\bTH\bH
+ A colon-separated list of directories in which the e\ben\bna\bab\bbl\ble\be com-
+ mand looks for dynamically loadable builtins.
+ B\bBA\bAS\bSH\bH_\b_M\bMO\bON\bNO\bOS\bSE\bEC\bCO\bON\bND\bDS\bS
+ Each time this variable is referenced, it expands to the value
+ returned by the system's monotonic clock, if one is available.
+ If there is no monotonic clock, this is equivalent to E\bEP\bPO\bOC\bCH\bHS\bSE\bEC\bC-\b-
+ O\bON\bND\bDS\bS. If B\bBA\bAS\bSH\bH_\b_M\bMO\bON\bNO\bOS\bSE\bEC\bCO\bON\bND\bDS\bS is unset, it loses its special prop-
+ erties, even if it is subsequently reset.
+ B\bBA\bAS\bSH\bH_\b_R\bRE\bEM\bMA\bAT\bTC\bCH\bH
+ An array variable whose members are assigned by the =\b=~\b~ binary
+ operator to the [\b[[\b[ conditional command. The element with index
+ 0 is the portion of the string matching the entire regular ex-
+ pression. The element with index _\bn is the portion of the string
+ matching the _\bnth parenthesized subexpression.
+ B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE
+ An array variable whose members are the source filenames where
+ the corresponding shell function names in the F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE array
+ variable are defined. The shell function $\b${\b{F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE[\b[_\b$_\bi]\b]}\b} is de-
+ fined in the file $\b${\b{B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE[\b[_\b$_\bi]\b]}\b} and called from
+ $\b${\b{B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE[\b[_\b$_\bi_\b+_\b1]\b]}\b}. Assignments to B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE have no ef-
+ fect, and it may not be unset.
+ B\bBA\bAS\bSH\bH_\b_S\bSU\bUB\bBS\bSH\bHE\bEL\bLL\bL
+ Incremented by one within each subshell or subshell environment
+ when the shell begins executing in that environment. The ini-
+ tial value is 0. If B\bBA\bAS\bSH\bH_\b_S\bSU\bUB\bBS\bSH\bHE\bEL\bLL\bL is unset, it loses its spe-
+ cial properties, even if it is subsequently reset.
+ B\bBA\bAS\bSH\bH_\b_T\bTR\bRA\bAP\bPS\bSI\bIG\bG
+ Set to the signal number corresponding to the trap action being
+ executed during its execution. See the description of t\btr\bra\bap\bp un-
+ der S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below for information about signal
+ numbers and trap execution.
+ B\bBA\bAS\bSH\bH_\b_V\bVE\bER\bRS\bSI\bIN\bNF\bFO\bO
+ A readonly array variable whose members hold version information
+ for this instance of b\bba\bas\bsh\bh. The values assigned to the array
+ members are as follows:
+ B\bBA\bAS\bSH\bH_\b_V\bVE\bER\bRS\bSI\bIN\bNF\bFO\bO[\b[0]\b] The major version number (the _\br_\be_\bl_\be_\ba_\bs_\be).
+ B\bBA\bAS\bSH\bH_\b_V\bVE\bER\bRS\bSI\bIN\bNF\bFO\bO[\b[1]\b] The minor version number (the _\bv_\be_\br_\bs_\bi_\bo_\bn).
+ B\bBA\bAS\bSH\bH_\b_V\bVE\bER\bRS\bSI\bIN\bNF\bFO\bO[\b[2]\b] The patch level.
+ B\bBA\bAS\bSH\bH_\b_V\bVE\bER\bRS\bSI\bIN\bNF\bFO\bO[\b[3]\b] The build version.
+ B\bBA\bAS\bSH\bH_\b_V\bVE\bER\bRS\bSI\bIN\bNF\bFO\bO[\b[4]\b] The release status (e.g., _\bb_\be_\bt_\ba).
+ B\bBA\bAS\bSH\bH_\b_V\bVE\bER\bRS\bSI\bIN\bNF\bFO\bO[\b[5]\b] The value of M\bMA\bAC\bCH\bHT\bTY\bYP\bPE\bE.
+ B\bBA\bAS\bSH\bH_\b_V\bVE\bER\bRS\bSI\bIO\bON\bN
+ Expands to a string describing the version of this instance of
+ b\bba\bas\bsh\bh (e.g., 5.2.37(3)-release).
+ C\bCO\bOM\bMP\bP_\b_C\bCW\bWO\bOR\bRD\bD
+ An index into $\b${\b{C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDS\bS}\b} of the word containing the current
+ cursor position. This variable is available only in shell func-
+ tions invoked by the programmable completion facilities (see
+ P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn below).
+ C\bCO\bOM\bMP\bP_\b_K\bKE\bEY\bY
+ The key (or final key of a key sequence) used to invoke the cur-
+ rent completion function. This variable is available only in
+ shell functions and external commands invoked by the programma-
+ ble completion facilities (see P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn below).
+ C\bCO\bOM\bMP\bP_\b_L\bLI\bIN\bNE\bE
+ The current command line. This variable is available only in
+ shell functions and external commands invoked by the programma-
+ ble completion facilities (see P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn below).
+ C\bCO\bOM\bMP\bP_\b_P\bPO\bOI\bIN\bNT\bT
+ The index of the current cursor position relative to the begin-
+ ning of the current command. If the current cursor position is
+ at the end of the current command, the value of this variable is
+ equal to $\b${\b{#\b#C\bCO\bOM\bMP\bP_\b_L\bLI\bIN\bNE\bE}\b}. This variable is available only in
+ shell functions and external commands invoked by the programma-
+ ble completion facilities (see P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn below).
+ C\bCO\bOM\bMP\bP_\b_T\bTY\bYP\bPE\bE
+ Set to an integer value corresponding to the type of attempted
+ completion that caused a completion function to be called: _\bT_\bA_\bB,
+ for normal completion, _\b?, for listing completions after succes-
+ sive tabs, _\b!, for listing alternatives on partial word comple-
+ tion, _\b@, to list completions if the word is not unmodified, or
+ _\b%, for menu completion. This variable is available only in
+ shell functions and external commands invoked by the programma-
+ ble completion facilities (see P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn below).
+ C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS
+ The set of characters that the r\bre\bea\bad\bdl\bli\bin\bne\be library treats as word
+ separators when performing word completion. If C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS
+ is unset, it loses its special properties, even if it is subse-
+ quently reset.
+ C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDS\bS
+ An array variable (see A\bAr\brr\bra\bay\bys\bs below) consisting of the individ-
+ ual words in the current command line. The line is split into
+ words as r\bre\bea\bad\bdl\bli\bin\bne\be would split it, using C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS as de-
+ scribed above. This variable is available only in shell func-
+ tions invoked by the programmable completion facilities (see
+ P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn below).
+ C\bCO\bOP\bPR\bRO\bOC\bC An array variable (see A\bAr\brr\bra\bay\bys\bs below) created to hold the file
+ descriptors for output from and input to an unnamed coprocess
+ (see C\bCo\bop\bpr\bro\boc\bce\bes\bss\bse\bes\bs above).
+ D\bDI\bIR\bRS\bST\bTA\bAC\bCK\bK
+ An array variable (see A\bAr\brr\bra\bay\bys\bs below) containing the current con-
+ tents of the directory stack. Directories appear in the stack
+ in the order they are displayed by the d\bdi\bir\brs\bs builtin. Assigning
+ to members of this array variable may be used to modify directo-
+ ries already in the stack, but the p\bpu\bus\bsh\bhd\bd and p\bpo\bop\bpd\bd builtins must
+ be used to add and remove directories. Assigning to this vari-
+ able does not change the current directory. If D\bDI\bIR\bRS\bST\bTA\bAC\bCK\bK is un-
+ set, it loses its special properties, even if it is subsequently
+ reset.
+ E\bEP\bPO\bOC\bCH\bHR\bRE\bEA\bAL\bLT\bTI\bIM\bME\bE
+ Each time this parameter is referenced, it expands to the number
+ of seconds since the Unix Epoch (see _\bt_\bi_\bm_\be(3)) as a floating-
+ point value with micro-second granularity. Assignments to
+ E\bEP\bPO\bOC\bCH\bHR\bRE\bEA\bAL\bLT\bTI\bIM\bME\bE are ignored. If E\bEP\bPO\bOC\bCH\bHR\bRE\bEA\bAL\bLT\bTI\bIM\bME\bE is unset, it loses
+ its special properties, even if it is subsequently reset.
+ E\bEP\bPO\bOC\bCH\bHS\bSE\bEC\bCO\bON\bND\bDS\bS
+ Each time this parameter is referenced, it expands to the number
+ of seconds since the Unix Epoch (see _\bt_\bi_\bm_\be(3)). Assignments to
+ E\bEP\bPO\bOC\bCH\bHS\bSE\bEC\bCO\bON\bND\bDS\bS are ignored. If E\bEP\bPO\bOC\bCH\bHS\bSE\bEC\bCO\bON\bND\bDS\bS is unset, it loses
+ its special properties, even if it is subsequently reset.
+ E\bEU\bUI\bID\bD Expands to the effective user ID of the current user, initial-
+ ized at shell startup. This variable is readonly.
+ F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE
+ An array variable containing the names of all shell functions
+ currently in the execution call stack. The element with index 0
+ is the name of any currently-executing shell function. The bot-
+ tom-most element (the one with the highest index) is "main".
+ This variable exists only when a shell function is executing.
+ Assignments to F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE have no effect. If F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE is unset,
+ it loses its special properties, even if it is subsequently re-
+ set.
+
+ This variable can be used with B\bBA\bAS\bSH\bH_\b_L\bLI\bIN\bNE\bEN\bNO\bO and B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE.
+ Each element of F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE has corresponding elements in
+ B\bBA\bAS\bSH\bH_\b_L\bLI\bIN\bNE\bEN\bNO\bO and B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE to describe the call stack. For in-
+ stance, $\b${\b{F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE[\b[_\b$_\bi]\b]}\b} was called from the file
+ $\b${\b{B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE[\b[_\b$_\bi_\b+_\b1]\b]}\b} at line number $\b${\b{B\bBA\bAS\bSH\bH_\b_L\bLI\bIN\bNE\bEN\bNO\bO[\b[_\b$_\bi]\b]}\b}. The
+ c\bca\bal\bll\ble\ber\br builtin displays the current call stack using this infor-
+ mation.
+ G\bGR\bRO\bOU\bUP\bPS\bS An array variable containing the list of groups of which the
+ current user is a member. Assignments to G\bGR\bRO\bOU\bUP\bPS\bS have no effect.
+ If G\bGR\bRO\bOU\bUP\bPS\bS is unset, it loses its special properties, even if it
+ is subsequently reset.
+ H\bHI\bIS\bST\bTC\bCM\bMD\bD
+ The history number, or index in the history list, of the current
+ command. Assignments to H\bHI\bIS\bST\bTC\bCM\bMD\bD have no effect. If H\bHI\bIS\bST\bTC\bCM\bMD\bD is
+ unset, it loses its special properties, even if it is subse-
+ quently reset.
+ H\bHO\bOS\bST\bTN\bNA\bAM\bME\bE
+ Automatically set to the name of the current host.
+ H\bHO\bOS\bST\bTT\bTY\bYP\bPE\bE
+ Automatically set to a string that uniquely describes the type
+ of machine on which b\bba\bas\bsh\bh is executing. The default is system-
+ dependent.
+ L\bLI\bIN\bNE\bEN\bNO\bO Each time this parameter is referenced, the shell substitutes a
+ decimal number representing the current sequential line number
+ (starting with 1) within a script or function. When not in a
+ script or function, the value substituted is not guaranteed to
+ be meaningful. If L\bLI\bIN\bNE\bEN\bNO\bO is unset, it loses its special proper-
+ ties, even if it is subsequently reset.
+ M\bMA\bAC\bCH\bHT\bTY\bYP\bPE\bE
+ Automatically set to a string that fully describes the system
+ type on which b\bba\bas\bsh\bh is executing, in the standard GNU _\bc_\bp_\bu_\b-_\bc_\bo_\bm_\b-
+ _\bp_\ba_\bn_\by_\b-_\bs_\by_\bs_\bt_\be_\bm format. The default is system-dependent.
+ M\bMA\bAP\bPF\bFI\bIL\bLE\bE
+ An array variable (see A\bAr\brr\bra\bay\bys\bs below) created to hold the text
+ read by the m\bma\bap\bpf\bfi\bil\ble\be builtin when no variable name is supplied.
+ O\bOL\bLD\bDP\bPW\bWD\bD The previous working directory as set by the c\bcd\bd command.
+ O\bOP\bPT\bTA\bAR\bRG\bG The value of the last option argument processed by the g\bge\bet\bto\bop\bpt\bts\bs
+ builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+ O\bOP\bPT\bTI\bIN\bND\bD The index of the next argument to be processed by the g\bge\bet\bto\bop\bpt\bts\bs
+ builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+ O\bOS\bST\bTY\bYP\bPE\bE Automatically set to a string that describes the operating sys-
+ tem on which b\bba\bas\bsh\bh is executing. The default is system-depen-
+ dent.
+ P\bPI\bIP\bPE\bES\bST\bTA\bAT\bTU\bUS\bS
+ An array variable (see A\bAr\brr\bra\bay\bys\bs below) containing a list of exit
+ status values from the commands in the most-recently-executed
+ foreground pipeline, which may consist of only a simple command
+ (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR above). B\bBa\bas\bsh\bh sets P\bPI\bIP\bPE\bES\bST\bTA\bAT\bTU\bUS\bS after executing
+ multi-element pipelines, timed and negated pipelines, simple
+ commands, subshells created with the ( operator, the [\b[[\b[ and (\b((\b(
+ compound commands, and after error conditions that result in the
+ shell aborting command execution.
+ P\bPP\bPI\bID\bD The process ID of the shell's parent. This variable is read-
+ only.
+ P\bPW\bWD\bD The current working directory as set by the c\bcd\bd command.
+ R\bRA\bAN\bND\bDO\bOM\bM Each time this parameter is referenced, it expands to a random
+ integer between 0 and 32767. Assigning a value to R\bRA\bAN\bND\bDO\bOM\bM ini-
+ tializes (seeds) the sequence of random numbers. Seeding the
+ random number generator with the same constant value produces
+ the same sequence of values. If R\bRA\bAN\bND\bDO\bOM\bM is unset, it loses its
+ special properties, even if it is subsequently reset.
+ R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_A\bAR\bRG\bGU\bUM\bME\bEN\bNT\bT
+ Any numeric argument given to a r\bre\bea\bad\bdl\bli\bin\bne\be command that was de-
+ fined using "bind -x" (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below) when it
+ was invoked.
+ R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_L\bLI\bIN\bNE\bE
+ The contents of the r\bre\bea\bad\bdl\bli\bin\bne\be line buffer, for use with "bind -x"
+ (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+ R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_M\bMA\bAR\bRK\bK
+ The position of the mark (saved insertion point) in the r\bre\bea\bad\bdl\bli\bin\bne\be
+ line buffer, for use with "bind -x" (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS
+ below). The characters between the insertion point and the mark
+ are often called the _\br_\be_\bg_\bi_\bo_\bn.
+ R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_P\bPO\bOI\bIN\bNT\bT
+ The position of the insertion point in the r\bre\bea\bad\bdl\bli\bin\bne\be line buffer,
+ for use with "bind -x" (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+ R\bRE\bEP\bPL\bLY\bY Set to the line of input read by the r\bre\bea\bad\bd builtin command when
+ no arguments are supplied.
+ S\bSE\bEC\bCO\bON\bND\bDS\bS
+ Each time this parameter is referenced, it expands to the number
+ of seconds since shell invocation. If a value is assigned to
+ S\bSE\bEC\bCO\bON\bND\bDS\bS, the value returned upon subsequent references is the
+ number of seconds since the assignment plus the value assigned.
+ The number of seconds at shell invocation and the current time
+ are always determined by querying the system clock at one-second
+ resolution. If S\bSE\bEC\bCO\bON\bND\bDS\bS is unset, it loses its special proper-
+ ties, even if it is subsequently reset.
+ S\bSH\bHE\bEL\bLL\bLO\bOP\bPT\bTS\bS
+ A colon-separated list of enabled shell options. Each word in
+ the list is a valid argument for the -\b-o\bo option to the s\bse\bet\bt
+ builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below). The options
+ appearing in S\bSH\bHE\bEL\bLL\bLO\bOP\bPT\bTS\bS are those reported as _\bo_\bn by s\bse\bet\bt -\b-o\bo. If
+ this variable is in the environment when b\bba\bas\bsh\bh starts up, the
+ shell enables each option in the list before reading any startup
+ files. If this variable is exported, child shells will enable
+ each option in the list. This variable is read-only.
+ S\bSH\bHL\bLV\bVL\bL Incremented by one each time an instance of b\bba\bas\bsh\bh is started.
+ S\bSR\bRA\bAN\bND\bDO\bOM\bM
+ Each time it is referenced, this variable expands to a 32-bit
+ pseudo-random number. The random number generator is not linear
+ on systems that support _\b/_\bd_\be_\bv_\b/_\bu_\br_\ba_\bn_\bd_\bo_\bm or _\ba_\br_\bc_\b4_\br_\ba_\bn_\bd_\bo_\bm(3), so each
+ returned number has no relationship to the numbers preceding it.
+ The random number generator cannot be seeded, so assignments to
+ this variable have no effect. If S\bSR\bRA\bAN\bND\bDO\bOM\bM is unset, it loses its
+ special properties, even if it is subsequently reset.
+ U\bUI\bID\bD Expands to the user ID of the current user, initialized at shell
+ startup. This variable is readonly.
+
+ The shell uses the following variables. In some cases, b\bba\bas\bsh\bh assigns a
+ default value to a variable; these cases are noted below.
+
+ B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT
+ The value is used to set the shell's compatibility level. See
+ S\bSH\bHE\bEL\bLL\bL C\bCO\bOM\bMP\bPA\bAT\bTI\bIB\bBI\bIL\bLI\bIT\bTY\bY M\bMO\bOD\bDE\bE below for a description of the various
+ compatibility levels and their effects. The value may be a dec-
+ imal number (e.g., 4.2) or an integer (e.g., 42) corresponding
+ to the desired compatibility level. If B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT is unset or
+ set to the empty string, the compatibility level is set to the
+ default for the current version. If B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT is set to a
+ value that is not one of the valid compatibility levels, the
+ shell prints an error message and sets the compatibility level
+ to the default for the current version. A subset of the valid
+ values correspond to the compatibility levels described below
+ under S\bSH\bHE\bEL\bLL\bL C\bCO\bOM\bMP\bPA\bAT\bTI\bIB\bBI\bIL\bLI\bIT\bTY\bY M\bMO\bOD\bDE\bE. For example, 4.2 and 42 are
+ valid values that correspond to the c\bco\bom\bmp\bpa\bat\bt4\b42\b2 s\bsh\bho\bop\bpt\bt option and
+ set the compatibility level to 42. The current version is also
+ a valid value.
+ B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV
+ If this parameter is set when b\bba\bas\bsh\bh is executing a shell script,
+ its expanded value is interpreted as a filename containing com-
+ mands to initialize the shell before it reads and executes com-
+ mands from the script. The value of B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV is subjected to
+ parameter expansion, command substitution, and arithmetic expan-
+ sion before being interpreted as a filename. P\bPA\bAT\bTH\bH is not used
+ to search for the resultant filename.
+ B\bBA\bAS\bSH\bH_\b_X\bXT\bTR\bRA\bAC\bCE\bEF\bFD\bD
+ If set to an integer corresponding to a valid file descriptor,
+ b\bba\bas\bsh\bh writes the trace output generated when "set -x" is enabled
+ to that file descriptor, instead of the standard error. The
+ file descriptor is closed when B\bBA\bAS\bSH\bH_\b_X\bXT\bTR\bRA\bAC\bCE\bEF\bFD\bD is unset or as-
+ signed a new value. Unsetting B\bBA\bAS\bSH\bH_\b_X\bXT\bTR\bRA\bAC\bCE\bEF\bFD\bD or assigning it the
+ empty string causes the trace output to be sent to the standard
+ error. Note that setting B\bBA\bAS\bSH\bH_\b_X\bXT\bTR\bRA\bAC\bCE\bEF\bFD\bD to 2 (the standard error
+ file descriptor) and then unsetting it will result in the stan-
+ dard error being closed.
+ C\bCD\bDP\bPA\bAT\bTH\bH The search path for the c\bcd\bd command. This is a colon-separated
+ list of directories where the shell looks for directories speci-
+ fied as arguments to the c\bcd\bd command. A sample value is
+ ".:~:/usr".
+ C\bCH\bHI\bIL\bLD\bD_\b_M\bMA\bAX\bX
+ Set the number of exited child status values for the shell to
+ remember. B\bBa\bas\bsh\bh will not allow this value to be decreased below
+ a POSIX-mandated minimum, and there is a maximum value (cur-
+ rently 8192) that this may not exceed. The minimum value is
+ system-dependent.
+ C\bCO\bOL\bLU\bUM\bMN\bNS\bS
+ Used by the s\bse\bel\ble\bec\bct\bt compound command to determine the terminal
+ width when printing selection lists. Automatically set if the
+ c\bch\bhe\bec\bck\bkw\bwi\bin\bns\bsi\biz\bze\be option is enabled or in an interactive shell upon
+ receipt of a S\bSI\bIG\bGW\bWI\bIN\bNC\bCH\bH.
+ C\bCO\bOM\bMP\bPR\bRE\bEP\bPL\bLY\bY
+ An array variable from which b\bba\bas\bsh\bh reads the possible completions
+ generated by a shell function invoked by the programmable com-
+ pletion facility (see P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn below). Each ar-
+ ray element contains one possible completion.
+ E\bEM\bMA\bAC\bCS\bS If b\bba\bas\bsh\bh finds this variable in the environment when the shell
+ starts with value "t", it assumes that the shell is running in
+ an Emacs shell buffer and disables line editing.
+ E\bEN\bNV\bV Expanded and executed similarly to B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV (see I\bIN\bNV\bVO\bOC\bCA\bAT\bTI\bIO\bON\bN
+ above) when an interactive shell is invoked in posix mode.
+ E\bEX\bXE\bEC\bCI\bIG\bGN\bNO\bOR\bRE\bE
+ A colon-separated list of shell patterns (see P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg)
+ defining the set of filenames to be ignored by command search
+ using P\bPA\bAT\bTH\bH. Files whose full pathnames match one of these pat-
+ terns are not considered executable files for the purposes of
+ completion and command execution via P\bPA\bAT\bTH\bH lookup. This does not
+ affect the behavior of the [\b[, t\bte\bes\bst\bt, and [\b[[\b[ commands. Full path-
+ names in the command hash table are not subject to E\bEX\bXE\bEC\bCI\bIG\bGN\bNO\bOR\bRE\bE.
+ Use this variable to ignore shared library files that have the
+ executable bit set, but are not executable files. The pattern
+ matching honors the setting of the e\bex\bxt\btg\bgl\blo\bob\bb shell option.
+ F\bFC\bCE\bED\bDI\bIT\bT The default editor for the f\bfc\bc builtin command.
+ F\bFI\bIG\bGN\bNO\bOR\bRE\bE
+ A colon-separated list of suffixes to ignore when performing
+ filename completion (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE below). A filename whose suf-
+ fix matches one of the entries in F\bFI\bIG\bGN\bNO\bOR\bRE\bE is excluded from the
+ list of matched filenames. A sample value is ".o:~".
+ F\bFU\bUN\bNC\bCN\bNE\bES\bST\bT
+ If set to a numeric value greater than 0, defines a maximum
+ function nesting level. Function invocations that exceed this
+ nesting level cause the current command to abort.
+ G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE
+ A colon-separated list of patterns defining the set of file
+ names to be ignored by pathname expansion. If a file name
+ matched by a pathname expansion pattern also matches one of the
+ patterns in G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE, it is removed from the list of matches.
+ The pattern matching honors the setting of the e\bex\bxt\btg\bgl\blo\bob\bb shell op-
+ tion.
+ G\bGL\bLO\bOB\bBS\bSO\bOR\bRT\bT
+ Controls how the results of pathname expansion are sorted. The
+ value of this variable specifies the sort criteria and sort or-
+ der for the results of pathname expansion. If this variable is
+ unset or set to the null string, pathname expansion uses the
+ historical behavior of sorting by name, in ascending lexico-
+ graphic order as determined by the L\bLC\bC_\b_C\bCO\bOL\bLL\bLA\bAT\bTE\bE shell variable.
+
+ If set, a valid value begins with an optional _\b+, which is ig-
+ nored, or _\b-, which reverses the sort order from ascending to de-
+ scending, followed by a sort specifier. The valid sort speci-
+ fiers are _\bn_\ba_\bm_\be, _\bn_\bu_\bm_\be_\br_\bi_\bc, _\bs_\bi_\bz_\be, _\bm_\bt_\bi_\bm_\be, _\ba_\bt_\bi_\bm_\be, _\bc_\bt_\bi_\bm_\be, and _\bb_\bl_\bo_\bc_\bk_\bs,
+ which sort the files on name, names in numeric rather than lexi-
+ cographic order, file size, modification time, access time, in-
+ ode change time, and number of blocks, respectively. If any of
+ the non-name keys compare as equal (e.g., if two files are the
+ same size), sorting uses the name as a secondary sort key.
+
+ For example, a value of _\b-_\bm_\bt_\bi_\bm_\be sorts the results in descending
+ order by modification time (newest first).
+
+ The _\bn_\bu_\bm_\be_\br_\bi_\bc specifier treats names consisting solely of digits
+ as numbers and sorts them using their numeric value (so "2"
+ sorts before "10", for example). When using _\bn_\bu_\bm_\be_\br_\bi_\bc, names con-
+ taining non-digits sort after all the all-digit names and are
+ sorted by name using the traditional behavior.
+
+ A sort specifier of _\bn_\bo_\bs_\bo_\br_\bt disables sorting completely; b\bba\bas\bsh\bh re-
+ turns the results in the order they are read from the file sys-
+ tem, ignoring any leading _\b-.
+
+ If the sort specifier is missing, it defaults to _\bn_\ba_\bm_\be, so a
+ value of _\b+ is equivalent to the null string, and a value of _\b-
+ sorts by name in descending order. Any invalid value restores
+ the historical sorting behavior.
+ H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL
+ A colon-separated list of values controlling how commands are
+ saved on the history list. If the list of values includes
+ _\bi_\bg_\bn_\bo_\br_\be_\bs_\bp_\ba_\bc_\be, lines which begin with a s\bsp\bpa\bac\bce\be character are not
+ saved in the history list. A value of _\bi_\bg_\bn_\bo_\br_\be_\bd_\bu_\bp_\bs causes lines
+ matching the previous history entry not to be saved. A value of
+ _\bi_\bg_\bn_\bo_\br_\be_\bb_\bo_\bt_\bh is shorthand for _\bi_\bg_\bn_\bo_\br_\be_\bs_\bp_\ba_\bc_\be and _\bi_\bg_\bn_\bo_\br_\be_\bd_\bu_\bp_\bs. A value
+ of _\be_\br_\ba_\bs_\be_\bd_\bu_\bp_\bs causes all previous lines matching the current line
+ to be removed from the history list before that line is saved.
+ Any value not in the above list is ignored. If H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL is
+ unset, or does not include a valid value, b\bba\bas\bsh\bh saves all lines
+ read by the shell parser on the history list, subject to the
+ value of H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE. If the first line of a multi-line compound
+ command was saved, the second and subsequent lines are not
+ tested, and are added to the history regardless of the value of
+ H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL. If the first line was not saved, the second and
+ subsequent lines of the command are not saved either.
+ H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE
+ The name of the file in which command history is saved (see H\bHI\bIS\bS-\b-
+ T\bTO\bOR\bRY\bY below). B\bBa\bas\bsh\bh assigns a default value of _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bh_\bi_\bs_\bt_\bo_\br_\by.
+ If H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE is unset or null, the shell does not save the com-
+ mand history when it exits.
+ H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bES\bSI\bIZ\bZE\bE
+ The maximum number of lines contained in the history file. When
+ this variable is assigned a value, the history file is trun-
+ cated, if necessary, to contain no more than the number of his-
+ tory entries that total no more than that number of lines by re-
+ moving the oldest entries. If the history list contains multi-
+ line entries, the history file may contain more lines than this
+ maximum to avoid leaving partial history entries. The history
+ file is also truncated to this size after writing it when a
+ shell exits or by the h\bhi\bis\bst\bto\bor\bry\by builtin. If the value is 0, the
+ history file is truncated to zero size. Non-numeric values and
+ numeric values less than zero inhibit truncation. The shell
+ sets the default value to the value of H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE after reading
+ any startup files.
+ H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE
+ A colon-separated list of patterns used to decide which command
+ lines should be saved on the history list. If a command line
+ matches one of the patterns in the value of H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE, it is
+ not saved on the history list. Each pattern is anchored at the
+ beginning of the line and must match the complete line (b\bba\bas\bsh\bh
+ does not implicitly append a "*\b*"). Each pattern is tested
+ against the line after the checks specified by H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL are
+ applied. In addition to the normal shell pattern matching char-
+ acters, "&\b&" matches the previous history line. A backslash es-
+ capes the "&\b&"; the backslash is removed before attempting a
+ match. If the first line of a multi-line compound command was
+ saved, the second and subsequent lines are not tested, and are
+ added to the history regardless of the value of H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE. If
+ the first line was not saved, the second and subsequent lines of
+ the command are not saved either. The pattern matching honors
+ the setting of the e\bex\bxt\btg\bgl\blo\bob\bb shell option.
+ H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE subsumes some of the function of H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL. A pat-
+ tern of "&" is identical to "ignoredups", and a pattern of "[
+ ]*" is identical to "ignorespace". Combining these two pat-
+ terns, separating them with a colon, provides the functionality
+ of "ignoreboth".
+ H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE
+ The number of commands to remember in the command history (see
+ H\bHI\bIS\bST\bTO\bOR\bRY\bY below). If the value is 0, commands are not saved in
+ the history list. Numeric values less than zero result in every
+ command being saved on the history list (there is no limit).
+ The shell sets the default value to 500 after reading any
+ startup files.
+ H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT
+ If this variable is set and not null, its value is used as a
+ format string for _\bs_\bt_\br_\bf_\bt_\bi_\bm_\be(3) to print the time stamp associated
+ with each history entry displayed by the h\bhi\bis\bst\bto\bor\bry\by builtin. If
+ this variable is set, the shell writes time stamps to the his-
+ tory file so they may be preserved across shell sessions. This
+ uses the history comment character to distinguish timestamps
+ from other history lines.
+ H\bHO\bOM\bME\bE The home directory of the current user; the default argument for
+ the c\bcd\bd builtin command. The value of this variable is also used
+ when performing tilde expansion.
+ H\bHO\bOS\bST\bTF\bFI\bIL\bLE\bE
+ Contains the name of a file in the same format as _\b/_\be_\bt_\bc_\b/_\bh_\bo_\bs_\bt_\bs
+ that should be read when the shell needs to complete a hostname.
+ The list of possible hostname completions may be changed while
+ the shell is running; the next time hostname completion is at-
+ tempted after the value is changed, b\bba\bas\bsh\bh adds the contents of
+ the new file to the existing list. If H\bHO\bOS\bST\bTF\bFI\bIL\bLE\bE is set, but has
+ no value, or does not name a readable file, b\bba\bas\bsh\bh attempts to
+ read _\b/_\be_\bt_\bc_\b/_\bh_\bo_\bs_\bt_\bs to obtain the list of possible hostname comple-
+ tions. When H\bHO\bOS\bST\bTF\bFI\bIL\bLE\bE is unset, b\bba\bas\bsh\bh clears the hostname list.
+ I\bIF\bFS\bS The _\bI_\bn_\bt_\be_\br_\bn_\ba_\bl _\bF_\bi_\be_\bl_\bd _\bS_\be_\bp_\ba_\br_\ba_\bt_\bo_\br that is used for word splitting af-
+ ter expansion and to split lines into words with the r\bre\bea\bad\bd
+ builtin command. Word splitting is described below under E\bEX\bXP\bPA\bAN\bN-\b-
+ S\bSI\bIO\bON\bN. The default value is "<space><tab><newline>".
+ I\bIG\bGN\bNO\bOR\bRE\bEE\bEO\bOF\bF
+ Controls the action of an interactive shell on receipt of an E\bEO\bOF\bF
+ character as the sole input. If set, the value is the number of
+ consecutive E\bEO\bOF\bF characters which must be typed as the first
+ characters on an input line before b\bba\bas\bsh\bh exits. If the variable
+ is set but does not have a numeric value, or the value is null,
+ the default value is 10. If it is unset, E\bEO\bOF\bF signifies the end
+ of input to the shell.
+ I\bIN\bNP\bPU\bUT\bTR\bRC\bC
+ The filename for the r\bre\bea\bad\bdl\bli\bin\bne\be startup file, overriding the de-
+ fault of _\b~_\b/_\b._\bi_\bn_\bp_\bu_\bt_\br_\bc (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE below).
+ I\bIN\bNS\bSI\bID\bDE\bE_\b_E\bEM\bMA\bAC\bCS\bS
+ If this variable appears in the environment when the shell
+ starts, b\bba\bas\bsh\bh assumes that it is running inside an Emacs shell
+ buffer and may disable line editing, depending on the value of
+ T\bTE\bER\bRM\bM.
+ L\bLA\bAN\bNG\bG Used to determine the locale category for any category not
+ specifically selected with a variable starting with L\bLC\bC_\b_.
+ L\bLC\bC_\b_A\bAL\bLL\bL This variable overrides the value of L\bLA\bAN\bNG\bG and any other L\bLC\bC_\b_
+ variable specifying a locale category.
+ L\bLC\bC_\b_C\bCO\bOL\bLL\bLA\bAT\bTE\bE
+ This variable determines the collation order used when sorting
+ the results of pathname expansion, and determines the behavior
+ of range expressions, equivalence classes, and collating se-
+ quences within pathname expansion and pattern matching.
+ L\bLC\bC_\b_C\bCT\bTY\bYP\bPE\bE
+ This variable determines the interpretation of characters and
+ the behavior of character classes within pathname expansion and
+ pattern matching.
+ L\bLC\bC_\b_M\bME\bES\bSS\bSA\bAG\bGE\bES\bS
+ This variable determines the locale used to translate double-
+ quoted strings preceded by a $\b$.
+ L\bLC\bC_\b_N\bNU\bUM\bME\bER\bRI\bIC\bC
+ This variable determines the locale category used for number
+ formatting.
+ L\bLC\bC_\b_T\bTI\bIM\bME\bE
+ This variable determines the locale category used for data and
+ time formatting.
+ L\bLI\bIN\bNE\bES\bS Used by the s\bse\bel\ble\bec\bct\bt compound command to determine the column
+ length for printing selection lists. Automatically set if the
+ c\bch\bhe\bec\bck\bkw\bwi\bin\bns\bsi\biz\bze\be option is enabled or in an interactive shell upon
+ receipt of a S\bSI\bIG\bGW\bWI\bIN\bNC\bCH\bH.
+ M\bMA\bAI\bIL\bL If the value is set to a file or directory name and the M\bMA\bAI\bIL\bLP\bPA\bAT\bTH\bH
+ variable is not set, b\bba\bas\bsh\bh informs the user of the arrival of
+ mail in the specified file or Maildir-format directory.
+ M\bMA\bAI\bIL\bLC\bCH\bHE\bEC\bCK\bK
+ Specifies how often (in seconds) b\bba\bas\bsh\bh checks for mail. The de-
+ fault is 60 seconds. When it is time to check for mail, the
+ shell does so before displaying the primary prompt. If this
+ variable is unset, or set to a value that is not a number
+ greater than or equal to zero, the shell disables mail checking.
+ M\bMA\bAI\bIL\bLP\bPA\bAT\bTH\bH
+ A colon-separated list of filenames to be checked for mail. The
+ message to be printed when mail arrives in a particular file may
+ be specified by separating the filename from the message with a
+ "?". When used in the text of the message, $\b$_\b_ expands to the
+ name of the current mailfile. For example:
+ M\bMA\bAI\bIL\bLP\bPA\bAT\bTH\bH='/var/mail/bfox?"You have mail":~/shell-mail?"$_ has mail!"'
+ B\bBa\bas\bsh\bh can be configured to supply a default value for this vari-
+ able (there is no value by default), but the location of the
+ user mail files that it uses is system dependent (e.g.,
+ /var/mail/$\b$U\bUS\bSE\bER\bR).
+ O\bOP\bPT\bTE\bER\bRR\bR If set to the value 1, b\bba\bas\bsh\bh displays error messages generated by
+ the g\bge\bet\bto\bop\bpt\bts\bs builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+ O\bOP\bPT\bTE\bER\bRR\bR is initialized to 1 each time the shell is invoked or a
+ shell script is executed.
+ P\bPA\bAT\bTH\bH The search path for commands. It is a colon-separated list of
+ directories in which the shell looks for commands (see C\bCO\bOM\bMM\bMA\bAN\bND\bD
+ E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN below). A zero-length (null) directory name in the
+ value of P\bPA\bAT\bTH\bH indicates the current directory. A null directory
+ name may appear as two adjacent colons, or as an initial or
+ trailing colon. The default path is system-dependent, and is
+ set by the administrator who installs b\bba\bas\bsh\bh. A common value is
+ /usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin
+ P\bPO\bOS\bSI\bIX\bXL\bLY\bY_\b_C\bCO\bOR\bRR\bRE\bEC\bCT\bT
+ If this variable is in the environment when b\bba\bas\bsh\bh starts, the
+ shell enters posix mode before reading the startup files, as if
+ the -\b--\b-p\bpo\bos\bsi\bix\bx invocation option had been supplied. If it is set
+ while the shell is running, b\bba\bas\bsh\bh enables posix mode, as if the
+ command "set -o posix" had been executed. When the shell enters
+ posix mode, it sets this variable if it was not already set.
+ P\bPR\bRO\bOM\bMP\bPT\bT_\b_C\bCO\bOM\bMM\bMA\bAN\bND\bD
+ If this variable is set, and is an array, the value of each set
+ element is executed as a command prior to issuing each primary
+ prompt. If this is set but not an array variable, its value is
+ used as a command to execute instead.
+ P\bPR\bRO\bOM\bMP\bPT\bT_\b_D\bDI\bIR\bRT\bTR\bRI\bIM\bM
+ If set to a number greater than zero, the value is used as the
+ number of trailing directory components to retain when expanding
+ the \\b\w\bw and \\b\W\bW prompt string escapes (see P\bPR\bRO\bOM\bMP\bPT\bTI\bIN\bNG\bG below).
+ Characters removed are replaced with an ellipsis.
+ P\bPS\bS0\b0 The value of this parameter is expanded (see P\bPR\bRO\bOM\bMP\bPT\bTI\bIN\bNG\bG below)
+ and displayed by interactive shells after reading a command and
+ before the command is executed.
+ P\bPS\bS1\b1 The value of this parameter is expanded (see P\bPR\bRO\bOM\bMP\bPT\bTI\bIN\bNG\bG below)
+ and used as the primary prompt string. The default value is
+ "\s-\v\$ ".
+ P\bPS\bS2\b2 The value of this parameter is expanded as with P\bPS\bS1\b1 and used as
+ the secondary prompt string. The default is "> ".
+ P\bPS\bS3\b3 The value of this parameter is used as the prompt for the s\bse\bel\ble\bec\bct\bt
+ command (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR above).
+ P\bPS\bS4\b4 The value of this parameter is expanded as with P\bPS\bS1\b1 and the
+ value is printed before each command b\bba\bas\bsh\bh displays during an ex-
+ ecution trace. The first character of the expanded value of P\bPS\bS4\b4
+ is replicated multiple times, as necessary, to indicate multiple
+ levels of indirection. The default is "+ ".
+ S\bSH\bHE\bEL\bLL\bL This variable expands to the full pathname to the shell. If it
+ is not set when the shell starts, b\bba\bas\bsh\bh assigns to it the full
+ pathname of the current user's login shell.
+ T\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT
+ The value of this parameter is used as a format string specify-
+ ing how the timing information for pipelines prefixed with the
+ t\bti\bim\bme\be reserved word should be displayed. The %\b% character intro-
+ duces an escape sequence that is expanded to a time value or
+ other information. The escape sequences and their meanings are
+ as follows; the brackets denote optional portions.
+ %\b%%\b% A literal %\b%.
+ %\b%[\b[_\bp]\b][\b[l\bl]\b]R\bR The elapsed time in seconds.
+ %\b%[\b[_\bp]\b][\b[l\bl]\b]U\bU The number of CPU seconds spent in user mode.
+ %\b%[\b[_\bp]\b][\b[l\bl]\b]S\bS The number of CPU seconds spent in system mode.
+ %\b%P\bP The CPU percentage, computed as (%U + %S) / %R.
+
+ The optional _\bp is a digit specifying the _\bp_\br_\be_\bc_\bi_\bs_\bi_\bo_\bn, the number
+ of fractional digits after a decimal point. A value of 0 causes
+ no decimal point or fraction to be output. t\bti\bim\bme\be prints at most
+ six digits after the decimal point; values of _\bp greater than 6
+ are changed to 6. If _\bp is not specified, t\bti\bim\bme\be prints three dig-
+ its after the decimal point.
+
+ The optional l\bl specifies a longer format, including minutes, of
+ the form _\bM_\bMm_\bS_\bS._\bF_\bFs. The value of _\bp determines whether or not
+ the fraction is included.
+
+ If this variable is not set, b\bba\bas\bsh\bh acts as if it had the value
+ $\b$'\b'\\b\n\bnr\bre\bea\bal\bl\\b\t\bt%\b%3\b3l\blR\bR\\b\n\bnu\bus\bse\ber\br\\b\t\bt%\b%3\b3l\blU\bU\\b\n\bns\bsy\bys\bs\\b\t\bt%\b%3\b3l\blS\bS'\b'. If the value is null,
+ b\bba\bas\bsh\bh does not display any timing information. A trailing new-
+ line is added when the format string is displayed.
+ T\bTM\bMO\bOU\bUT\bT If set to a value greater than zero, the r\bre\bea\bad\bd builtin uses the
+ value as its default timeout. The s\bse\bel\ble\bec\bct\bt command terminates if
+ input does not arrive after T\bTM\bMO\bOU\bUT\bT seconds when input is coming
+ from a terminal. In an interactive shell, the value is inter-
+ preted as the number of seconds to wait for a line of input af-
+ ter issuing the primary prompt. B\bBa\bas\bsh\bh terminates after waiting
+ for that number of seconds if a complete line of input does not
+ arrive.
+ T\bTM\bMP\bPD\bDI\bIR\bR If set, b\bba\bas\bsh\bh uses its value as the name of a directory in which
+ b\bba\bas\bsh\bh creates temporary files for the shell's use.
+ a\bau\but\bto\bo_\b_r\bre\bes\bsu\bum\bme\be
+ This variable controls how the shell interacts with the user and
+ job control. If this variable is set, simple commands consist-
+ ing of only a single word, without redirections, are treated as
+ candidates for resumption of an existing stopped job. There is
+ no ambiguity allowed; if there is more than one job beginning
+ with or containing the word, this selects the most recently ac-
+ cessed job. The _\bn_\ba_\bm_\be of a stopped job, in this context, is the
+ command line used to start it, as displayed by j\bjo\bob\bbs\bs. If set to
+ the value _\be_\bx_\ba_\bc_\bt, the word must match the name of a stopped job
+ exactly; if set to _\bs_\bu_\bb_\bs_\bt_\br_\bi_\bn_\bg, the word needs to match a sub-
+ string of the name of a stopped job. The _\bs_\bu_\bb_\bs_\bt_\br_\bi_\bn_\bg value pro-
+ vides functionality analogous to the %\b%?\b? job identifier (see J\bJO\bOB\bB
+ C\bCO\bON\bNT\bTR\bRO\bOL\bL below). If set to any other value (e.g., _\bp_\br_\be_\bf_\bi_\bx), the
+ word must be a prefix of a stopped job's name; this provides
+ functionality analogous to the %\b%_\bs_\bt_\br_\bi_\bn_\bg job identifier.
+ h\bhi\bis\bst\btc\bch\bha\bar\brs\bs
+ The two or three characters which control history expansion,
+ quick substitution, and tokenization (see H\bHI\bIS\bST\bTO\bOR\bRY\bY E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN be-
+ low). The first character is the _\bh_\bi_\bs_\bt_\bo_\br_\by _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn character,
+ the character which begins a history expansion, normally "!\b!".
+ The second character is the _\bq_\bu_\bi_\bc_\bk _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\bt_\bi_\bo_\bn character, nor-
+ mally "^\b^". When it appears as the first character on the line,
+ history substitution repeats the previous command, replacing one
+ string with another. The optional third character is the _\bh_\bi_\bs_\b-
+ _\bt_\bo_\br_\by _\bc_\bo_\bm_\bm_\be_\bn_\bt character, normally "#\b#", which indicates that the
+ remainder of the line is a comment when it appears as the first
+ character of a word. The history comment character disables
+ history substitution for the remaining words on the line. It
+ does not necessarily cause the shell parser to treat the rest of
+ the line as a comment.
+
+ A\bAr\brr\bra\bay\bys\bs
+ B\bBa\bas\bsh\bh provides one-dimensional indexed and associative array variables.
+ Any variable may be used as an indexed array; the d\bde\bec\bcl\bla\bar\bre\be builtin ex-
+ plicitly declares an array. There is no maximum limit on the size of
+ an array, nor any requirement that members be indexed or assigned con-
+ tiguously. Indexed arrays are referenced using arithmetic expressions
+ that must expand to an integer (see A\bAR\bRI\bIT\bTH\bHM\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN below) and
+ are zero-based; associative arrays are referenced using arbitrary
+ strings. Unless otherwise noted, indexed array indices must be non-
+ negative integers.
+
+ The shell performs parameter and variable expansion, arithmetic expan-
+ sion, command substitution, and quote removal on indexed array sub-
+ scripts. Since this can potentially result in empty strings, subscript
+ indexing treats those as expressions that evaluate to 0.
+
+ The shell performs tilde expansion, parameter and variable expansion,
+ arithmetic expansion, command substitution, and quote removal on asso-
+ ciative array subscripts. Empty strings cannot be used as associative
+ array keys.
+
+ B\bBa\bas\bsh\bh automatically creates an indexed array if any variable is assigned
+ to using the syntax
+ _\bn_\ba_\bm_\be[_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt]=_\bv_\ba_\bl_\bu_\be .
+ The _\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt is treated as an arithmetic expression that must evaluate
+ to a number greater than or equal to zero. To explicitly declare an
+ indexed array, use
+ d\bde\bec\bcl\bla\bar\bre\be -\b-a\ba _\bn_\ba_\bm_\be
+ (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+ d\bde\bec\bcl\bla\bar\bre\be -\b-a\ba _\bn_\ba_\bm_\be[_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt]
+ is also accepted; the _\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt is ignored.
+
+ Associative arrays are created using
+ d\bde\bec\bcl\bla\bar\bre\be -\b-A\bA _\bn_\ba_\bm_\be
+ .
+
+ Attributes may be specified for an array variable using the d\bde\bec\bcl\bla\bar\bre\be and
+ r\bre\bea\bad\bdo\bon\bnl\bly\by builtins. Each attribute applies to all members of an array.
+
+ Arrays are assigned using compound assignments of the form _\bn_\ba_\bm_\be=(\b(value_\b1
+ ... value_\bn)\b), where each _\bv_\ba_\bl_\bu_\be may be of the form [_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt]=_\bs_\bt_\br_\bi_\bn_\bg.
+ Indexed array assignments do not require anything but _\bs_\bt_\br_\bi_\bn_\bg. Each
+ _\bv_\ba_\bl_\bu_\be in the list is expanded using the shell expansions described be-
+ low under E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN, but _\bv_\ba_\bl_\bu_\bes that are valid variable assignments in-
+ cluding the brackets and subscript do not undergo brace expansion and
+ word splitting, as with individual variable assignments.
+
+ When assigning to indexed arrays, if the optional brackets and sub-
+ script are supplied, that index is assigned to; otherwise the index of
+ the element assigned is the last index assigned to by the statement
+ plus one. Indexing starts at zero.
+
+ When assigning to an associative array, the words in a compound assign-
+ ment may be either assignment statements, for which the subscript is
+ required, or a list of words that is interpreted as a sequence of al-
+ ternating keys and values: _\bn_\ba_\bm_\be=(\b( _\bk_\be_\by_\b1 _\bv_\ba_\bl_\bu_\be_\b1 _\bk_\be_\by_\b2 _\bv_\ba_\bl_\bu_\be_\b2 ...)\b). These
+ are treated identically to _\bn_\ba_\bm_\be=(\b( [_\bk_\be_\by_\b1]=_\bv_\ba_\bl_\bu_\be_\b1 [_\bk_\be_\by_\b2]=_\bv_\ba_\bl_\bu_\be_\b2 ...)\b).
+ The first word in the list determines how the remaining words are in-
+ terpreted; all assignments in a list must be of the same type. When
+ using key/value pairs, the keys may not be missing or empty; a final
+ missing value is treated like the empty string.
+
+ This syntax is also accepted by the d\bde\bec\bcl\bla\bar\bre\be builtin. Individual array
+ elements may be assigned to using the _\bn_\ba_\bm_\be[_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt]=_\bv_\ba_\bl_\bu_\be syntax in-
+ troduced above.
+
+ When assigning to an indexed array, if _\bn_\ba_\bm_\be is subscripted by a nega-
+ tive number, that number is interpreted as relative to one greater than
+ the maximum index of _\bn_\ba_\bm_\be, so negative indices count back from the end
+ of the array, and an index of -1 references the last element.
+
+ The "+=" operator appends to an array variable when assigning using the
+ compound assignment syntax; see P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS above.
+
+ An array element is referenced using ${_\bn_\ba_\bm_\be[_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt]}. The braces
+ are required to avoid conflicts with pathname expansion. If _\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt
+ is @\b@ or *\b*, the word expands to all members of _\bn_\ba_\bm_\be, unless noted in the
+ description of a builtin or word expansion. These subscripts differ
+ only when the word appears within double quotes. If the word is dou-
+ ble-quoted, ${_\bn_\ba_\bm_\be[*]} expands to a single word with the value of each
+ array member separated by the first character of the I\bIF\bFS\bS special vari-
+ able, and ${_\bn_\ba_\bm_\be[@]} expands each element of _\bn_\ba_\bm_\be to a separate word.
+ When there are no array members, ${_\bn_\ba_\bm_\be[@]} expands to nothing. If the
+ double-quoted expansion occurs within a word, the expansion of the
+ first parameter is joined with the beginning part of the expansion of
+ the original word, and the expansion of the last parameter is joined
+ with the last part of the expansion of the original word. This is
+ analogous to the expansion of the special parameters *\b* and @\b@ (see S\bSp\bpe\be-\b-
+ c\bci\bia\bal\bl P\bPa\bar\bra\bam\bme\bet\bte\ber\brs\bs above).
+
+ ${#_\bn_\ba_\bm_\be[_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt]} expands to the length of ${_\bn_\ba_\bm_\be[_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt]}. If
+ _\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt is *\b* or @\b@, the expansion is the number of elements in the ar-
+ ray.
+
+ If the _\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt used to reference an element of an indexed array eval-
+ uates to a number less than zero, it is interpreted as relative to one
+ greater than the maximum index of the array, so negative indices count
+ back from the end of the array, and an index of -1 references the last
+ element.
+
+ Referencing an array variable without a subscript is equivalent to ref-
+ erencing the array with a subscript of 0. Any reference to a variable
+ using a valid subscript is valid; b\bba\bas\bsh\bh creates an array if necessary.
+
+ An array variable is considered set if a subscript has been assigned a
+ value. The null string is a valid value.
+
+ It is possible to obtain the keys (indices) of an array as well as the
+ values. ${!\b!_\bn_\ba_\bm_\be[_\b@]} and ${!\b!_\bn_\ba_\bm_\be[_\b*]} expand to the indices assigned in
+ array variable _\bn_\ba_\bm_\be. The treatment when in double quotes is similar to
+ the expansion of the special parameters _\b@ and _\b* within double quotes.
+
+ The u\bun\bns\bse\bet\bt builtin is used to destroy arrays. u\bun\bns\bse\bet\bt _\bn_\ba_\bm_\be[_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt] un-
+ sets the array element at index _\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt, for both indexed and asso-
+ ciative arrays. Negative subscripts to indexed arrays are interpreted
+ as described above. Unsetting the last element of an array variable
+ does not unset the variable. u\bun\bns\bse\bet\bt _\bn_\ba_\bm_\be, where _\bn_\ba_\bm_\be is an array, re-
+ moves the entire array. u\bun\bns\bse\bet\bt _\bn_\ba_\bm_\be[_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt] behaves differently de-
+ pending on whether _\bn_\ba_\bm_\be is an indexed or associative array when _\bs_\bu_\bb_\b-
+ _\bs_\bc_\br_\bi_\bp_\bt is *\b* or @\b@. If _\bn_\ba_\bm_\be is an associative array, this unsets the el-
+ ement with subscript *\b* or @\b@. If _\bn_\ba_\bm_\be is an indexed array, unset re-
+ moves all of the elements but does not remove the array itself.
+
+ When using a variable name with a subscript as an argument to a com-
+ mand, such as with u\bun\bns\bse\bet\bt, without using the word expansion syntax de-
+ scribed above, (e.g., unset a[4]), the argument is subject to pathname
+ expansion. Quote the argument if pathname expansion is not desired
+ (e.g., unset 'a[4]').
+
+ The d\bde\bec\bcl\bla\bar\bre\be, l\blo\boc\bca\bal\bl, and r\bre\bea\bad\bdo\bon\bnl\bly\by builtins each accept a -\b-a\ba option to
+ specify an indexed array and a -\b-A\bA option to specify an associative ar-
+ ray. If both options are supplied, -\b-A\bA takes precedence. The r\bre\bea\bad\bd
+ builtin accepts a -\b-a\ba option to assign a list of words read from the
+ standard input to an array. The s\bse\bet\bt and d\bde\bec\bcl\bla\bar\bre\be builtins display array
+ values in a way that allows them to be reused as assignments. Other
+ builtins accept array name arguments as well (e.g., m\bma\bap\bpf\bfi\bil\ble\be); see the
+ descriptions of individual builtins below for details. The shell pro-
+ vides a number of builtin array variables.
+
+E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN
+ Expansion is performed on the command line after it has been split into
+ words. The shell performs these expansions: _\bb_\br_\ba_\bc_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, _\bt_\bi_\bl_\bd_\be _\be_\bx_\b-
+ _\bp_\ba_\bn_\bs_\bi_\bo_\bn, _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br _\ba_\bn_\bd _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, _\bc_\bo_\bm_\bm_\ba_\bn_\bd _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\bt_\bi_\bo_\bn, _\ba_\br_\bi_\bt_\bh_\b-
+ _\bm_\be_\bt_\bi_\bc _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, _\bw_\bo_\br_\bd _\bs_\bp_\bl_\bi_\bt_\bt_\bi_\bn_\bg, _\bp_\ba_\bt_\bh_\bn_\ba_\bm_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, and _\bq_\bu_\bo_\bt_\be _\br_\be_\bm_\bo_\bv_\ba_\bl.
+
+ The order of expansions is: brace expansion; tilde expansion, parameter
+ and variable expansion, arithmetic expansion, and command substitution
+ (done in a left-to-right fashion); word splitting; pathname expansion;
+ and quote removal.
+
+ On systems that can support it, there is an additional expansion avail-
+ able: _\bp_\br_\bo_\bc_\be_\bs_\bs _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\bt_\bi_\bo_\bn. This is performed at the same time as
+ tilde, parameter, variable, and arithmetic expansion and command sub-
+ stitution.
+
+ _\bQ_\bu_\bo_\bt_\be _\br_\be_\bm_\bo_\bv_\ba_\bl is always performed last. It removes quote characters
+ present in the original word, not ones resulting from one of the other
+ expansions, unless they have been quoted themselves.
+
+ Only brace expansion, word splitting, and pathname expansion can in-
+ crease the number of words of the expansion; other expansions expand a
+ single word to a single word. The only exceptions to this are the ex-
+ pansions of "\b"$\b$@\b@"\b" and "\b"$\b${\b{_\bn_\ba_\bm_\be[\b[@\b@]\b]}\b}"\b", and, in most cases, $\b$*\b* and
+ $\b${\b{_\bn_\ba_\bm_\be[\b[*\b*]\b]}\b} as explained above (see P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS).
+
+ B\bBr\bra\bac\bce\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
+ _\bB_\br_\ba_\bc_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn is a mechanism to generate arbitrary strings sharing a
+ common prefix and suffix, either of which can be empty. This mechanism
+ is similar to _\bp_\ba_\bt_\bh_\bn_\ba_\bm_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, but the filenames generated need not
+ exist. Patterns to be brace expanded are formed from an optional _\bp_\br_\be_\b-
+ _\ba_\bm_\bb_\bl_\be, followed by either a series of comma-separated strings or a se-
+ quence expression between a pair of braces, followed by an optional
+ _\bp_\bo_\bs_\bt_\bs_\bc_\br_\bi_\bp_\bt. The preamble is prefixed to each string contained within
+ the braces, and the postscript is then appended to each resulting
+ string, expanding left to right.
+
+ Brace expansions may be nested. The results of each expanded string
+ are not sorted; brace expansion preserves left to right order. For ex-
+ ample, a{\b{d,c,b}\b}e expands into "ade ace abe".
+
+ A sequence expression takes the form _\bx.\b..\b._\by[\b[.\b..\b._\bi_\bn_\bc_\br]\b], where _\bx and _\by are
+ either integers or single letters, and _\bi_\bn_\bc_\br, an optional increment, is
+ an integer. When integers are supplied, the expression expands to each
+ number between _\bx and _\by, inclusive. If either _\bx or _\by begins with a
+ zero, each generated term will contain the same number of digits, zero-
+ padding where necessary. When letters are supplied, the expression ex-
+ pands to each character lexicographically between _\bx and _\by, inclusive,
+ using the C locale. Note that both _\bx and _\by must be of the same type
+ (integer or letter). When the increment is supplied, it is used as the
+ difference between each term. The default increment is 1 or -1 as ap-
+ propriate.
+
+ Brace expansion is performed before any other expansions, and any char-
+ acters special to other expansions are preserved in the result. It is
+ strictly textual. B\bBa\bas\bsh\bh does not apply any syntactic interpretation to
+ the context of the expansion or the text between the braces.
+
+ A correctly-formed brace expansion must contain unquoted opening and
+ closing braces, and at least one unquoted comma or a valid sequence ex-
+ pression. Any incorrectly formed brace expansion is left unchanged.
+
+ A "{" or Q , may be quoted with a backslash to prevent its being con-
+ sidered part of a brace expression. To avoid conflicts with parameter
+ expansion, the string "${" is not considered eligible for brace expan-
+ sion, and inhibits brace expansion until the closing "}".
+
+ This construct is typically used as shorthand when the common prefix of
+ the strings to be generated is longer than in the above example:
+
+ mkdir /usr/local/src/bash/{old,new,dist,bugs}
+ or
+ chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
+
+ Brace expansion introduces a slight incompatibility with historical
+ versions of s\bsh\bh. s\bsh\bh does not treat opening or closing braces specially
+ when they appear as part of a word, and preserves them in the output.
+ B\bBa\bas\bsh\bh removes braces from words as a consequence of brace expansion.
+ For example, a word entered to s\bsh\bh as "file{1,2}" appears identically in
+ the output. B\bBa\bas\bsh\bh outputs that word as "file1 file2" after brace expan-
+ sion. Start b\bba\bas\bsh\bh with the +\b+B\bB option or disable brace expansion with
+ the +\b+B\bB option to the s\bse\bet\bt command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below) for
+ strict s\bsh\bh compatibility.
+
+ T\bTi\bil\bld\bde\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
+ If a word begins with an unquoted tilde character ("~\b~"), all of the
+ characters preceding the first unquoted slash (or all characters, if
+ there is no unquoted slash) are considered a _\bt_\bi_\bl_\bd_\be_\b-_\bp_\br_\be_\bf_\bi_\bx. If none of
+ the characters in the tilde-prefix are quoted, the characters in the
+ tilde-prefix following the tilde are treated as a possible _\bl_\bo_\bg_\bi_\bn _\bn_\ba_\bm_\be.
+ If this login name is the null string, the tilde is replaced with the
+ value of the shell parameter H\bHO\bOM\bME\bE. If H\bHO\bOM\bME\bE is unset, the tilde expands
+ to the home directory of the user executing the shell instead. Other-
+ wise, the tilde-prefix is replaced with the home directory associated
+ with the specified login name.
+
+ If the tilde-prefix is a "~+", the value of the shell variable P\bPW\bWD\bD re-
+ places the tilde-prefix. If the tilde-prefix is a "~-", the shell sub-
+ stitutes the value of the shell variable O\bOL\bLD\bDP\bPW\bWD\bD, if it is set. If the
+ characters following the tilde in the tilde-prefix consist of a number
+ _\bN, optionally prefixed by a "+" or a "-", the tilde-prefix is replaced
+ with the corresponding element from the directory stack, as it would be
+ displayed by the d\bdi\bir\brs\bs builtin invoked with the characters following the
+ tilde in the tilde-prefix as an argument. If the characters following
+ the tilde in the tilde-prefix consist of a number without a leading "+"
+ or "-", tilde expansion assumes "+".
+
+ The results of tilde expansion are treated as if they were quoted, so
+ the replacement is not subject to word splitting and pathname expan-
+ sion.
+
+ If the login name is invalid, or the tilde expansion fails, the tilde-
+ prefix is unchanged.
+
+ B\bBa\bas\bsh\bh checks each variable assignment for unquoted tilde-prefixes imme-
+ diately following a :\b: or the first =\b=, and performs tilde expansion in
+ these cases. Consequently, one may use filenames with tildes in as-
+ signments to P\bPA\bAT\bTH\bH, M\bMA\bAI\bIL\bLP\bPA\bAT\bTH\bH, and C\bCD\bDP\bPA\bAT\bTH\bH, and the shell assigns the ex-
+ panded value.
+
+ B\bBa\bas\bsh\bh also performs tilde expansion on words satisfying the conditions
+ of variable assignments (as described above under P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS) when they
+ appear as arguments to simple commands. B\bBa\bas\bsh\bh does not do this, except
+ for the _\bd_\be_\bc_\bl_\ba_\br_\ba_\bt_\bi_\bo_\bn commands listed above, when in posix mode.
+
+ P\bPa\bar\bra\bam\bme\bet\bte\ber\br E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
+ The "$\b$" character introduces parameter expansion, command substitution,
+ or arithmetic expansion. The parameter name or symbol to be expanded
+ may be enclosed in braces, which are optional but serve to protect the
+ variable to be expanded from characters immediately following it which
+ could be interpreted as part of the name.
+
+ When braces are used, the matching ending brace is the first "}\b}" not
+ escaped by a backslash or within a quoted string, and not within an em-
+ bedded arithmetic expansion, command substitution, or parameter expan-
+ sion.
+
+ The basic form of parameter expansion is
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br}
+
+ which substitutes the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br. The braces are required when
+ _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is a positional parameter with more than one digit, or when
+ _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is followed by a character which is not to be interpreted as
+ part of its name. The _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is a shell parameter as described
+ above P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS) or an array reference (A\bAr\brr\bra\bay\bys\bs).
+
+ If the first character of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is an exclamation point (!\b!), and
+ _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is not a _\bn_\ba_\bm_\be_\br_\be_\bf, it introduces a level of indirection. B\bBa\bas\bsh\bh
+ uses the value formed by expanding the rest of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br as the new _\bp_\ba_\b-
+ _\br_\ba_\bm_\be_\bt_\be_\br; this new parameter is then expanded and that value is used in
+ the rest of the expansion, rather than the expansion of the original
+ _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br. This is known as _\bi_\bn_\bd_\bi_\br_\be_\bc_\bt _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn. The value is subject
+ to tilde expansion, parameter expansion, command substitution, and
+ arithmetic expansion. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is a nameref, this expands to the
+ name of the parameter referenced by _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br instead of performing the
+ complete indirect expansion, for compatibility. The exceptions to this
+ are the expansions of ${!\b!_\bp_\br_\be_\bf_\bi_\bx*\b*} and ${!\b!_\bn_\ba_\bm_\be[_\b@]} described below. The
+ exclamation point must immediately follow the left brace in order to
+ introduce indirection.
+
+ In each of the cases below, _\bw_\bo_\br_\bd is subject to tilde expansion, parame-
+ ter expansion, command substitution, and arithmetic expansion.
+
+ When not performing substring expansion, using the forms documented be-
+ low (e.g., :\b:-\b-), b\bba\bas\bsh\bh tests for a parameter that is unset or null.
+ Omitting the colon tests only for a parameter that is unset.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br:\b:-\b-_\bw_\bo_\br_\bd}
+ U\bUs\bse\be D\bDe\bef\bfa\bau\bul\blt\bt V\bVa\bal\blu\bue\bes\bs. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is unset or null, the expan-
+ sion of _\bw_\bo_\br_\bd is substituted. Otherwise, the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
+ is substituted.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br:\b:=\b=_\bw_\bo_\br_\bd}
+ A\bAs\bss\bsi\big\bgn\bn D\bDe\bef\bfa\bau\bul\blt\bt V\bVa\bal\blu\bue\bes\bs. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is unset or null, the ex-
+ pansion of _\bw_\bo_\br_\bd is assigned to _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br, and the expansion is
+ the final value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br. Positional parameters and special
+ parameters may not be assigned in this way.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br:\b:?\b?_\bw_\bo_\br_\bd}
+ D\bDi\bis\bsp\bpl\bla\bay\by E\bEr\brr\bro\bor\br i\bif\bf N\bNu\bul\bll\bl o\bor\br U\bUn\bns\bse\bet\bt. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is null or unset,
+ the shell writes the expansion of _\bw_\bo_\br_\bd (or a message to that ef-
+ fect if _\bw_\bo_\br_\bd is not present) to the standard error and, if it is
+ not interactive, exits with a non-zero status. An interactive
+ shell does not exit, but does not execute the command associated
+ with the expansion. Otherwise, the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is sub-
+ stituted.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br:\b:+\b+_\bw_\bo_\br_\bd}
+ U\bUs\bse\be A\bAl\blt\bte\ber\brn\bna\bat\bte\be V\bVa\bal\blu\bue\be. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is null or unset, nothing is
+ substituted, otherwise the expansion of _\bw_\bo_\br_\bd is substituted.
+ The value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is not used.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br:\b:_\bo_\bf_\bf_\bs_\be_\bt}
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br:\b:_\bo_\bf_\bf_\bs_\be_\bt:\b:_\bl_\be_\bn_\bg_\bt_\bh}
+ S\bSu\bub\bbs\bst\btr\bri\bin\bng\bg E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn. Expands to up to _\bl_\be_\bn_\bg_\bt_\bh characters of the
+ value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br starting at the character specified by _\bo_\bf_\bf_\b-
+ _\bs_\be_\bt. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@ or *\b*, an indexed array subscripted by @\b@
+ or *\b*, or an associative array name, the results differ as de-
+ scribed below. If :\b:_\bl_\be_\bn_\bg_\bt_\bh is omitted (the first form above),
+ this expands to the substring of the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br starting
+ at the character specified by _\bo_\bf_\bf_\bs_\be_\bt and extending to the end of
+ the value. If _\bo_\bf_\bf_\bs_\be_\bt is omitted, it is treated as 0. If _\bl_\be_\bn_\bg_\bt_\bh
+ is omitted, but the colon after _\bo_\bf_\bf_\bs_\be_\bt is present, it is treated
+ as 0. _\bl_\be_\bn_\bg_\bt_\bh and _\bo_\bf_\bf_\bs_\be_\bt are arithmetic expressions (see A\bAR\bRI\bIT\bTH\bH-\b-
+ M\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN below).
+
+ If _\bo_\bf_\bf_\bs_\be_\bt evaluates to a number less than zero, the value is
+ used as an offset in characters from the end of the value of _\bp_\ba_\b-
+ _\br_\ba_\bm_\be_\bt_\be_\br. If _\bl_\be_\bn_\bg_\bt_\bh evaluates to a number less than zero, it is
+ interpreted as an offset in characters from the end of the value
+ of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br rather than a number of characters, and the expan-
+ sion is the characters between _\bo_\bf_\bf_\bs_\be_\bt and that result. Note
+ that a negative offset must be separated from the colon by at
+ least one space to avoid being confused with the :\b:-\b- expansion.
+
+ If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@ or *\b*, the result is _\bl_\be_\bn_\bg_\bt_\bh positional parame-
+ ters beginning at _\bo_\bf_\bf_\bs_\be_\bt. A negative _\bo_\bf_\bf_\bs_\be_\bt is taken relative
+ to one greater than the greatest positional parameter, so an
+ offset of -1 evaluates to the last positional parameter (or 0 if
+ there are no positional parameters). It is an expansion error
+ if _\bl_\be_\bn_\bg_\bt_\bh evaluates to a number less than zero.
+
+ If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is an indexed array name subscripted by @ or *, the
+ result is the _\bl_\be_\bn_\bg_\bt_\bh members of the array beginning with ${_\bp_\ba_\br_\ba_\b-
+ _\bm_\be_\bt_\be_\br[_\bo_\bf_\bf_\bs_\be_\bt]}. A negative _\bo_\bf_\bf_\bs_\be_\bt is taken relative to one
+ greater than the maximum index of the specified array. It is an
+ expansion error if _\bl_\be_\bn_\bg_\bt_\bh evaluates to a number less than zero.
+
+ Substring expansion applied to an associative array produces un-
+ defined results.
+
+ Substring indexing is zero-based unless the positional parame-
+ ters are used, in which case the indexing starts at 1 by de-
+ fault. If _\bo_\bf_\bf_\bs_\be_\bt is 0, and the positional parameters are used,
+ $\b$0\b0 is prefixed to the list.
+
+ ${!\b!_\bp_\br_\be_\bf_\bi_\bx*\b*}
+ ${!\b!_\bp_\br_\be_\bf_\bi_\bx@\b@}
+ N\bNa\bam\bme\bes\bs m\bma\bat\btc\bch\bhi\bin\bng\bg p\bpr\bre\bef\bfi\bix\bx. Expands to the names of variables whose
+ names begin with _\bp_\br_\be_\bf_\bi_\bx, separated by the first character of the
+ I\bIF\bFS\bS special variable. When _\b@ is used and the expansion appears
+ within double quotes, each variable name expands to a separate
+ word.
+
+ ${!\b!_\bn_\ba_\bm_\be[_\b@]}
+ ${!\b!_\bn_\ba_\bm_\be[_\b*]}
+ L\bLi\bis\bst\bt o\bof\bf a\bar\brr\bra\bay\by k\bke\bey\bys\bs. If _\bn_\ba_\bm_\be is an array variable, expands to
+ the list of array indices (keys) assigned in _\bn_\ba_\bm_\be. If _\bn_\ba_\bm_\be is
+ not an array, expands to 0 if _\bn_\ba_\bm_\be is set and null otherwise.
+ When _\b@ is used and the expansion appears within double quotes,
+ each key expands to a separate word.
+
+ ${#\b#_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br}
+ P\bPa\bar\bra\bam\bme\bet\bte\ber\br l\ble\ben\bng\bgt\bth\bh. Substitutes the length in characters of the
+ expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is *\b* or @\b@, the value
+ substituted is the number of positional parameters. If _\bp_\ba_\br_\ba_\bm_\be_\b-
+ _\bt_\be_\br is an array name subscripted by *\b* or @\b@, the value substi-
+ tuted is the number of elements in the array. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is
+ an indexed array name subscripted by a negative number, that
+ number is interpreted as relative to one greater than the maxi-
+ mum index of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br, so negative indices count back from the
+ end of the array, and an index of -1 references the last ele-
+ ment.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br#\b#_\bw_\bo_\br_\bd}
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br#\b##\b#_\bw_\bo_\br_\bd}
+ R\bRe\bem\bmo\bov\bve\be m\bma\bat\btc\bch\bhi\bin\bng\bg p\bpr\bre\bef\bfi\bix\bx p\bpa\bat\btt\bte\ber\brn\bn. The _\bw_\bo_\br_\bd is expanded to produce
+ a pattern just as in pathname expansion, and matched against the
+ expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br using the rules described under P\bPa\bat\bt-\b-
+ t\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg below. If the pattern matches the beginning of
+ the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br, then the result of the expansion is the
+ expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br with the shortest matching pattern
+ (the "#" case) or the longest matching pattern (the "##" case)
+ deleted. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@ or *\b*, the pattern removal operation
+ is applied to each positional parameter in turn, and the expan-
+ sion is the resultant list. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is an array variable
+ subscripted with @\b@ or *\b*, the pattern removal operation is ap-
+ plied to each member of the array in turn, and the expansion is
+ the resultant list.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br%\b%_\bw_\bo_\br_\bd}
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br%\b%%\b%_\bw_\bo_\br_\bd}
+ R\bRe\bem\bmo\bov\bve\be m\bma\bat\btc\bch\bhi\bin\bng\bg s\bsu\buf\bff\bfi\bix\bx p\bpa\bat\btt\bte\ber\brn\bn. The _\bw_\bo_\br_\bd is expanded to produce
+ a pattern just as in pathname expansion, and matched against the
+ expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br using the rules described under P\bPa\bat\bt-\b-
+ t\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg below. If the pattern matches a trailing portion
+ of the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br, then the result of the ex-
+ pansion is the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br with the shortest
+ matching pattern (the "%" case) or the longest matching pattern
+ (the "%%" case) deleted. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@ or *\b*, the pattern
+ removal operation is applied to each positional parameter in
+ turn, and the expansion is the resultant list. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is
+ an array variable subscripted with @\b@ or *\b*, the pattern removal
+ operation is applied to each member of the array in turn, and
+ the expansion is the resultant list.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br/\b/_\bp_\ba_\bt_\bt_\be_\br_\bn/\b/_\bs_\bt_\br_\bi_\bn_\bg}
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br/\b//\b/_\bp_\ba_\bt_\bt_\be_\br_\bn/\b/_\bs_\bt_\br_\bi_\bn_\bg}
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br/\b/#\b#_\bp_\ba_\bt_\bt_\be_\br_\bn/\b/_\bs_\bt_\br_\bi_\bn_\bg}
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br/\b/%\b%_\bp_\ba_\bt_\bt_\be_\br_\bn/\b/_\bs_\bt_\br_\bi_\bn_\bg}
+ P\bPa\bat\btt\bte\ber\brn\bn s\bsu\bub\bbs\bst\bti\bit\btu\but\bti\bio\bon\bn. The _\bp_\ba_\bt_\bt_\be_\br_\bn is expanded to produce a pat-
+ tern and matched against the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br as de-
+ scribed under P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg below. The longest match of _\bp_\ba_\bt_\b-
+ _\bt_\be_\br_\bn in the expanded value is replaced with _\bs_\bt_\br_\bi_\bn_\bg. _\bs_\bt_\br_\bi_\bn_\bg un-
+ dergoes tilde expansion, parameter and variable expansion,
+ arithmetic expansion, command and process substitution, and
+ quote removal.
+
+ In the first form above, only the first match is replaced. If
+ there are two slashes separating _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br and _\bp_\ba_\bt_\bt_\be_\br_\bn (the sec-
+ ond form above), all matches of _\bp_\ba_\bt_\bt_\be_\br_\bn are replaced with
+ _\bs_\bt_\br_\bi_\bn_\bg. If _\bp_\ba_\bt_\bt_\be_\br_\bn is preceded by #\b# (the third form above), it
+ must match at the beginning of the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br.
+ If _\bp_\ba_\bt_\bt_\be_\br_\bn is preceded by %\b% (the fourth form above), it must
+ match at the end of the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br.
+
+ If the expansion of _\bs_\bt_\br_\bi_\bn_\bg is null, matches of _\bp_\ba_\bt_\bt_\be_\br_\bn are
+ deleted and the /\b/ following _\bp_\ba_\bt_\bt_\be_\br_\bn may be omitted.
+
+ If the p\bpa\bat\bts\bsu\bub\bb_\b_r\bre\bep\bpl\bla\bac\bce\bem\bme\ben\bnt\bt shell option is enabled using s\bsh\bho\bop\bpt\bt,
+ any unquoted instances of &\b& in _\bs_\bt_\br_\bi_\bn_\bg are replaced with the
+ matching portion of _\bp_\ba_\bt_\bt_\be_\br_\bn.
+
+ Quoting any part of _\bs_\bt_\br_\bi_\bn_\bg inhibits replacement in the expansion
+ of the quoted portion, including replacement strings stored in
+ shell variables. Backslash escapes &\b& in _\bs_\bt_\br_\bi_\bn_\bg; the backslash
+ is removed in order to permit a literal &\b& in the replacement
+ string. Backslash can also be used to escape a backslash; \\b\\\b\
+ results in a literal backslash in the replacement. Users should
+ take care if _\bs_\bt_\br_\bi_\bn_\bg is double-quoted to avoid unwanted interac-
+ tions between the backslash and double-quoting, since backslash
+ has special meaning within double quotes. Pattern substitution
+ performs the check for unquoted &\b& after expanding _\bs_\bt_\br_\bi_\bn_\bg; shell
+ programmers should quote any occurrences of &\b& they want to be
+ taken literally in the replacement and ensure any instances of &\b&
+ they want to be replaced are unquoted.
+
+ Like the pattern removal operators, double quotes surrounding
+ the replacement string quote the expanded characters, while dou-
+ ble quotes enclosing the entire parameter substitution do not,
+ since the expansion is performed in a context that doesn't take
+ any enclosing double quotes into account.
+
+ If the n\bno\boc\bca\bas\bse\bem\bma\bat\btc\bch\bh shell option is enabled, the match is per-
+ formed without regard to the case of alphabetic characters.
+
+ If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@ or *\b*, the substitution operation is applied to
+ each positional parameter in turn, and the expansion is the re-
+ sultant list. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is an array variable subscripted
+ with @\b@ or *\b*, the substitution operation is applied to each mem-
+ ber of the array in turn, and the expansion is the resultant
+ list.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br^\b^_\bp_\ba_\bt_\bt_\be_\br_\bn}
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br^\b^^\b^_\bp_\ba_\bt_\bt_\be_\br_\bn}
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br,\b,_\bp_\ba_\bt_\bt_\be_\br_\bn}
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br,\b,,\b,_\bp_\ba_\bt_\bt_\be_\br_\bn}
+ C\bCa\bas\bse\be m\bmo\bod\bdi\bif\bfi\bic\bca\bat\bti\bio\bon\bn. This expansion modifies the case of alpha-
+ betic characters in _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br. First, the _\bp_\ba_\bt_\bt_\be_\br_\bn is expanded
+ to produce a pattern as described below under P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg.
+ B\bBa\bas\bsh\bh then examines characters in the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
+ against _\bp_\ba_\bt_\bt_\be_\br_\bn as described below. If a character matches the
+ pattern, its case is converted. The pattern should not attempt
+ to match more than one character.
+
+ Using "^" converts lowercase letters matching _\bp_\ba_\bt_\bt_\be_\br_\bn to upper-
+ case; "," converts matching uppercase letters to lowercase. The
+ ^\b^ and ,\b, variants examine the first character in the expanded
+ value and convert its case if it matches _\bp_\ba_\bt_\bt_\be_\br_\bn; the ^\b^^\b^ and ,\b,,\b,
+ variants examine all characters in the expanded value and con-
+ vert each one that matches _\bp_\ba_\bt_\bt_\be_\br_\bn. If _\bp_\ba_\bt_\bt_\be_\br_\bn is omitted, it
+ is treated like a ?\b?, which matches every character.
+
+ If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@ or *\b*, the case modification operation is ap-
+ plied to each positional parameter in turn, and the expansion is
+ the resultant list. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is an array variable sub-
+ scripted with @\b@ or *\b*, the case modification operation is applied
+ to each member of the array in turn, and the expansion is the
+ resultant list.
+
+ ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br@\b@_\bo_\bp_\be_\br_\ba_\bt_\bo_\br}
+ P\bPa\bar\bra\bam\bme\bet\bte\ber\br t\btr\bra\ban\bns\bsf\bfo\bor\brm\bma\bat\bti\bio\bon\bn. The expansion is either a transforma-
+ tion of the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br or information about _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
+ itself, depending on the value of _\bo_\bp_\be_\br_\ba_\bt_\bo_\br. Each _\bo_\bp_\be_\br_\ba_\bt_\bo_\br is a
+ single letter:
+ U\bU The expansion is a string that is the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
+ with lowercase alphabetic characters converted to upper-
+ case.
+ u\bu The expansion is a string that is the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
+ with the first character converted to uppercase, if it is
+ alphabetic.
+ L\bL The expansion is a string that is the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
+ with uppercase alphabetic characters converted to lower-
+ case.
+ Q\bQ The expansion is a string that is the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
+ quoted in a format that can be reused as input.
+ E\bE The expansion is a string that is the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
+ with backslash escape sequences expanded as with the
+ $\b$'\b'...'\b' quoting mechanism.
+ P\bP The expansion is a string that is the result of expanding
+ the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br as if it were a prompt string (see
+ P\bPR\bRO\bOM\bMP\bPT\bTI\bIN\bNG\bG below).
+ A\bA The expansion is a string in the form of an assignment
+ statement or d\bde\bec\bcl\bla\bar\bre\be command that, if evaluated, recre-
+ ates _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br with its attributes and value.
+ K\bK Produces a possibly-quoted version of the value of _\bp_\ba_\br_\ba_\b-
+ _\bm_\be_\bt_\be_\br, except that it prints the values of indexed and
+ associative arrays as a sequence of quoted key-value
+ pairs (see A\bAr\brr\bra\bay\bys\bs above). The keys and values are quoted
+ in a format that can be reused as input.
+ a\ba The expansion is a string consisting of flag values rep-
+ resenting _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br's attributes.
+ k\bk Like the K transformation, but expands the keys and val-
+ ues of indexed and associative arrays to separate words
+ after word splitting.
+
+ If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@ or *\b*, the operation is applied to each posi-
+ tional parameter in turn, and the expansion is the resultant
+ list. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is an array variable subscripted with @\b@ or
+ *\b*, the operation is applied to each member of the array in turn,
+ and the expansion is the resultant list.
+
+ The result of the expansion is subject to word splitting and
+ pathname expansion as described below.
+
+ C\bCo\bom\bmm\bma\ban\bnd\bd S\bSu\bub\bbs\bst\bti\bit\btu\but\bti\bio\bon\bn
+ _\bC_\bo_\bm_\bm_\ba_\bn_\bd _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\bt_\bi_\bo_\bn allows the output of a command to replace the com-
+ mand itself. There are two standard forms:
+
+ $\b$(\b(_\bc_\bo_\bm_\bm_\ba_\bn_\bd)\b)
+ or (deprecated)
+ `\b`_\bc_\bo_\bm_\bm_\ba_\bn_\bd`\b`.
+
+ B\bBa\bas\bsh\bh performs the expansion by executing _\bc_\bo_\bm_\bm_\ba_\bn_\bd in a subshell environ-
+ ment and replacing the command substitution with the standard output of
+ the command, with any trailing newlines deleted. Embedded newlines are
+ not deleted, but they may be removed during word splitting. The com-
+ mand substitution $\b$(\b(c\bca\bat\bt _\bf_\bi_\bl_\be)\b) can be replaced by the equivalent but
+ faster $\b$(\b(<\b< _\bf_\bi_\bl_\be)\b).
+
+ With the old-style backquote form of substitution, backslash retains
+ its literal meaning except when followed by $\b$, `\b`, or \\b\. The first
+ backquote not preceded by a backslash terminates the command substitu-
+ tion. When using the $(_\bc_\bo_\bm_\bm_\ba_\bn_\bd) form, all characters between the
+ parentheses make up the command; none are treated specially.
+
+ There is an alternate form of command substitution:
+
+ $\b${\b{_\bc _\bc_\bo_\bm_\bm_\ba_\bn_\bd;\b;}\b}
+
+ which executes _\bc_\bo_\bm_\bm_\ba_\bn_\bd in the current execution environment and cap-
+ tures its output, again with trailing newlines removed.
+
+ The character _\bc following the open brace must be a space, tab, newline,
+ or |\b|, and the close brace must be in a position where a reserved word
+ may appear (i.e., preceded by a command terminator such as semicolon).
+ B\bBa\bas\bsh\bh allows the close brace to be joined to the remaining characters in
+ the word without being followed by a shell metacharacter as a reserved
+ word would usually require.
+
+ Any side effects of _\bc_\bo_\bm_\bm_\ba_\bn_\bd take effect immediately in the current exe-
+ cution environment and persist in the current environment after the
+ command completes (e.g., the e\bex\bxi\bit\bt builtin exits the shell).
+
+ This type of command substitution superficially resembles executing an
+ unnamed shell function: local variables are created as when a shell
+ function is executing, and the r\bre\bet\btu\bur\brn\bn builtin forces _\bc_\bo_\bm_\bm_\ba_\bn_\bd to com-
+ plete; however, the rest of the execution environment, including the
+ positional parameters, is shared with the caller.
+
+ If the first character following the open brace is a |\b|, the construct
+ expands to the value of the R\bRE\bEP\bPL\bLY\bY shell variable after _\bc_\bo_\bm_\bm_\ba_\bn_\bd exe-
+ cutes, without removing any trailing newlines, and the standard output
+ of _\bc_\bo_\bm_\bm_\ba_\bn_\bd remains the same as in the calling shell. B\bBa\bas\bsh\bh creates R\bRE\bE-\b-
+ P\bPL\bLY\bY as an initially-unset local variable when _\bc_\bo_\bm_\bm_\ba_\bn_\bd executes, and re-
+ stores R\bRE\bEP\bPL\bLY\bY to the value it had before the command substitution after
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd completes, as with any local variable.
+
+ Command substitutions may be nested. To nest when using the backquoted
+ form, escape the inner backquotes with backslashes.
+
+ If the substitution appears within double quotes, b\bba\bas\bsh\bh does not perform
+ word splitting and pathname expansion on the results.
+
+ A\bAr\bri\bit\bth\bhm\bme\bet\bti\bic\bc E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
+ Arithmetic expansion evaluates an arithmetic expression and substitutes
+ the result. The format for arithmetic expansion is:
+
+ $\b$(\b((\b(_\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn)\b))\b)
+
+ The _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn undergoes the same expansions as if it were within dou-
+ ble quotes, but unescaped double quote characters in _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn are not
+ treated specially and are removed. All tokens in the expression un-
+ dergo parameter and variable expansion, command substitution, and quote
+ removal. The result is treated as the arithmetic expression to be
+ evaluated. Since the way Bash handles double quotes can potentially
+ result in empty strings, arithmetic expansion treats those as expres-
+ sions that evaluate to 0. Arithmetic expansions may be nested.
+
+ The evaluation is performed according to the rules listed below under
+ A\bAR\bRI\bIT\bTH\bHM\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN. If _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn is invalid, b\bba\bas\bsh\bh prints a message
+ to standard error indicating failure, does not perform the substitu-
+ tion, and does not execute the command associated with the expansion.
+
+ P\bPr\bro\boc\bce\bes\bss\bs S\bSu\bub\bbs\bst\bti\bit\btu\but\bti\bio\bon\bn
+ _\bP_\br_\bo_\bc_\be_\bs_\bs _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\bt_\bi_\bo_\bn allows a process's input or output to be referred
+ to using a filename. It takes the form of <\b<(\b(_\bl_\bi_\bs_\bt)\b) or >\b>(\b(_\bl_\bi_\bs_\bt)\b). The
+ process _\bl_\bi_\bs_\bt is run asynchronously, and its input or output appears as
+ a filename. This filename is passed as an argument to the current com-
+ mand as the result of the expansion.
+
+ If the >\b>(\b(_\bl_\bi_\bs_\bt)\b) form is used, writing to the file provides input for
+ _\bl_\bi_\bs_\bt. If the <\b<(\b(_\bl_\bi_\bs_\bt)\b) form is used, reading the file obtains the output
+ of _\bl_\bi_\bs_\bt. No space may appear between the <\b< or >\b> and the left parenthe-
+ sis, otherwise the construct would be interpreted as a redirection.
+
+ Process substitution is supported on systems that support named pipes
+ (_\bF_\bI_\bF_\bO_\bs) or the _\b/_\bd_\be_\bv_\b/_\bf_\bd method of naming open files.
+
+ When available, process substitution is performed simultaneously with
+ parameter and variable expansion, command substitution, and arithmetic
+ expansion.
+
+ W\bWo\bor\brd\bd S\bSp\bpl\bli\bit\btt\bti\bin\bng\bg
+ The shell scans the results of parameter expansion, command substitu-
+ tion, and arithmetic expansion that did not occur within double quotes
+ for _\bw_\bo_\br_\bd _\bs_\bp_\bl_\bi_\bt_\bt_\bi_\bn_\bg. Words that were not expanded are not split.
+
+ The shell treats each character of I\bIF\bFS\bS as a delimiter, and splits the
+ results of the other expansions into words using these characters as
+ field terminators.
+
+ An _\bI_\bF_\bS _\bw_\bh_\bi_\bt_\be_\bs_\bp_\ba_\bc_\be character is whitespace as defined above (see D\bDe\bef\bfi\bin\bni\bi-\b-
+ t\bti\bio\bon\bns\bs) that appears in the value of I\bIF\bFS\bS. Space, tab, and newline are
+ always considered IFS whitespace, even if they don't appear in the lo-
+ cale's s\bsp\bpa\bac\bce\be category.
+
+ If I\bIF\bFS\bS is unset, field splitting acts as if its value were
+ <\b<s\bsp\bpa\bac\bce\be>\b><\b<t\bta\bab\bb>\b><\b<n\bne\bew\bwl\bli\bin\bne\be>\b>, and treats these characters as IFS whitespace.
+ If the value of I\bIF\bFS\bS is null, no word splitting occurs, but implicit
+ null arguments (see below) are still removed.
+
+ Word splitting begins by removing sequences of IFS whitespace charac-
+ ters from the beginning and end of the results of the previous expan-
+ sions, then splits the remaining words.
+
+ If the value of I\bIF\bFS\bS consists solely of IFS whitespace, any sequence of
+ IFS whitespace characters delimits a field, so a field consists of
+ characters that are not unquoted IFS whitespace, and null fields result
+ only from quoting.
+
+ If I\bIF\bFS\bS contains a non-whitespace character, then any character in the
+ value of I\bIF\bFS\bS that is not IFS whitespace, along with any adjacent IFS
+ whitespace characters, delimits a field. This means that adjacent non-
+ IFS-whitespace delimiters produce a null field. A sequence of IFS
+ whitespace characters also delimits a field.
+
+ Explicit null arguments ("\b""\b" or '\b''\b') are retained and passed to commands
+ as empty strings. Unquoted implicit null arguments, resulting from the
+ expansion of parameters that have no values, are removed. Expanding a
+ parameter with no value within double quotes produces a null field,
+ which is retained and passed to a command as an empty string.
+
+ When a quoted null argument appears as part of a word whose expansion
+ is non-null, word splitting removes the null argument portion, leaving
+ the non-null expansion. That is, the word "-d''" becomes "-d" after
+ word splitting and null argument removal.
+
+ P\bPa\bat\bth\bhn\bna\bam\bme\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
+ After word splitting, unless the -\b-f\bf option has been set, b\bba\bas\bsh\bh scans
+ each word for the characters *\b*, ?\b?, and [\b[. If one of these characters
+ appears, and is not quoted, then the word is regarded as a _\bp_\ba_\bt_\bt_\be_\br_\bn, and
+ replaced with a sorted list of filenames matching the pattern (see P\bPa\bat\bt-\b-
+ t\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg below) subject to the value of the G\bGL\bLO\bOB\bBS\bSO\bOR\bRT\bT shell vari-
+ able.
+
+ If no matching filenames are found, and the shell option n\bnu\bul\bll\blg\bgl\blo\bob\bb is
+ not enabled, the word is left unchanged. If the n\bnu\bul\bll\blg\bgl\blo\bob\bb option is
+ set, and no matches are found, the word is removed. If the f\bfa\bai\bil\blg\bgl\blo\bob\bb
+ shell option is set, and no matches are found, b\bba\bas\bsh\bh prints an error
+ message and does not execute the command. If the shell option n\bno\boc\bca\bas\bse\be-\b-
+ g\bgl\blo\bob\bb is enabled, the match is performed without regard to the case of
+ alphabetic characters.
+
+ When a pattern is used for pathname expansion, the character "." at the
+ start of a name or immediately following a slash must be matched ex-
+ plicitly, unless the shell option d\bdo\bot\btg\bgl\blo\bob\bb is set. In order to match
+ the filenames _\b. and _\b._\b., the pattern must begin with "." (for example,
+ ".?"), even if d\bdo\bot\btg\bgl\blo\bob\bb is set. If the g\bgl\blo\bob\bbs\bsk\bki\bip\bpd\bdo\bot\bts\bs shell option is en-
+ abled, the filenames _\b. and _\b._\b. never match, even if the pattern begins
+ with a ".". When not matching pathnames, the "." character is not
+ treated specially.
+
+ When matching a pathname, the slash character must always be matched
+ explicitly by a slash in the pattern, but in other matching contexts it
+ can be matched by a special pattern character as described below under
+ P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg.
+
+ See the description of s\bsh\bho\bop\bpt\bt below under S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS for a
+ description of the n\bno\boc\bca\bas\bse\beg\bgl\blo\bob\bb, n\bnu\bul\bll\blg\bgl\blo\bob\bb, g\bgl\blo\bob\bbs\bsk\bki\bip\bpd\bdo\bot\bts\bs, f\bfa\bai\bil\blg\bgl\blo\bob\bb, and
+ d\bdo\bot\btg\bgl\blo\bob\bb shell options.
+
+ The G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE shell variable may be used to restrict the set of file
+ names matching a _\bp_\ba_\bt_\bt_\be_\br_\bn. If G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE is set, each matching file
+ name that also matches one of the patterns in G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE is removed
+ from the list of matches. If the n\bno\boc\bca\bas\bse\beg\bgl\blo\bob\bb option is set, the match-
+ ing against the patterns in G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE is performed without regard to
+ case. The filenames _\b. and _\b._\b. are always ignored when G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE is set
+ and not null. However, setting G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE to a non-null value has the
+ effect of enabling the d\bdo\bot\btg\bgl\blo\bob\bb shell option, so all other filenames be-
+ ginning with a "." match. To get the old behavior of ignoring file-
+ names beginning with a ".", make ".*" one of the patterns in G\bGL\bLO\bOB\bBI\bIG\bG-\b-
+ N\bNO\bOR\bRE\bE. The d\bdo\bot\btg\bgl\blo\bob\bb option is disabled when G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE is unset. The
+ G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE pattern matching honors the setting of the e\bex\bxt\btg\bgl\blo\bob\bb shell op-
+ tion.
+
+ The value of the G\bGL\bLO\bOB\bBS\bSO\bOR\bRT\bT shell variable controls how the results of
+ pathname expansion are sorted, as described above under S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bi-\b-
+ a\bab\bbl\ble\bes\bs.
+
+ P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg
+
+ Any character that appears in a pattern, other than the special pattern
+ characters described below, matches itself. The NUL character may not
+ occur in a pattern. A backslash escapes the following character; the
+ escaping backslash is discarded when matching. The special pattern
+ characters must be quoted if they are to be matched literally.
+
+ The special pattern characters have the following meanings:
+
+ *\b* Matches any string, including the null string. When the
+ g\bgl\blo\bob\bbs\bst\bta\bar\br shell option is enabled, and *\b* is used in a
+ pathname expansion context, two adjacent *\b*s used as a
+ single pattern match all files and zero or more directo-
+ ries and subdirectories. If followed by a /\b/, two adja-
+ cent *\b*s match only directories and subdirectories.
+ ?\b? Matches any single character.
+ [\b[...]\b] Matches any one of the characters enclosed between the
+ brackets. This is known as a _\bb_\br_\ba_\bc_\bk_\be_\bt _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn and
+ matches a single character. A pair of characters sepa-
+ rated by a hyphen denotes a _\br_\ba_\bn_\bg_\be _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn; any charac-
+ ter that falls between those two characters, inclusive,
+ using the current locale's collating sequence and charac-
+ ter set, matches. If the first character following the [\b[
+ is a !\b! or a ^\b^ then any character not within the range
+ matches. To match a -\b-, include it as the first or last
+ character in the set. To match a ]\b], include it as the
+ first character in the set.
+
+ The sorting order of characters in range expressions, and
+ the characters included in the range, are determined by
+ the current locale and the values of the L\bLC\bC_\b_C\bCO\bOL\bLL\bLA\bAT\bTE\bE or
+ L\bLC\bC_\b_A\bAL\bLL\bL shell variables, if set. To obtain the tradi-
+ tional interpretation of range expressions, where [\b[a\ba-\b-d\bd]\b]
+ is equivalent to [\b[a\bab\bbc\bcd\bd]\b], set the value of the L\bLC\bC_\b_C\bCO\bOL\bLL\bLA\bAT\bTE\bE
+ or L\bLC\bC_\b_A\bAL\bLL\bL shell variables to C\bC, or enable the g\bgl\blo\bob\bba\bas\bsc\bci\bi-\b-
+ i\bir\bra\ban\bng\bge\bes\bs shell option.
+
+ Within a bracket expression, _\bc_\bh_\ba_\br_\ba_\bc_\bt_\be_\br _\bc_\bl_\ba_\bs_\bs_\be_\bs can be
+ specified using the syntax [\b[:\b:_\bc_\bl_\ba_\bs_\bs:\b:]\b], where _\bc_\bl_\ba_\bs_\bs is one
+ of the following classes defined in the POSIX standard:
+
+ a\bal\bln\bnu\bum\bm a\bal\blp\bph\bha\ba a\bas\bsc\bci\bii\bi b\bbl\bla\ban\bnk\bk c\bcn\bnt\btr\brl\bl d\bdi\big\bgi\bit\bt g\bgr\bra\bap\bph\bh l\blo\bow\bwe\ber\br p\bpr\bri\bin\bnt\bt
+ p\bpu\bun\bnc\bct\bt s\bsp\bpa\bac\bce\be u\bup\bpp\bpe\ber\br w\bwo\bor\brd\bd x\bxd\bdi\big\bgi\bit\bt
+
+ A character class matches any character belonging to that
+ class. The w\bwo\bor\brd\bd character class matches letters, digits,
+ and the character _.
+
+ Within a bracket expression, an _\be_\bq_\bu_\bi_\bv_\ba_\bl_\be_\bn_\bc_\be _\bc_\bl_\ba_\bs_\bs can be
+ specified using the syntax [\b[=\b=_\bc=\b=]\b], which matches all char-
+ acters with the same collation weight (as defined by the
+ current locale) as the character _\bc.
+
+ Within a bracket expression, the syntax [\b[.\b._\bs_\by_\bm_\bb_\bo_\bl.\b.]\b]
+ matches the collating symbol _\bs_\by_\bm_\bb_\bo_\bl.
+
+ If the e\bex\bxt\btg\bgl\blo\bob\bb shell option is enabled using the s\bsh\bho\bop\bpt\bt builtin, the
+ shell recognizes several extended pattern matching operators. In the
+ following description, a _\bp_\ba_\bt_\bt_\be_\br_\bn_\b-_\bl_\bi_\bs_\bt is a list of one or more patterns
+ separated by a |\b|. Composite patterns may be formed using one or more
+ of the following sub-patterns:
+
+ ?\b?(\b(_\bp_\ba_\bt_\bt_\be_\br_\bn_\b-_\bl_\bi_\bs_\bt)\b)
+ Matches zero or one occurrence of the given patterns.
+ *\b*(\b(_\bp_\ba_\bt_\bt_\be_\br_\bn_\b-_\bl_\bi_\bs_\bt)\b)
+ Matches zero or more occurrences of the given patterns.
+ +\b+(\b(_\bp_\ba_\bt_\bt_\be_\br_\bn_\b-_\bl_\bi_\bs_\bt)\b)
+ Matches one or more occurrences of the given patterns.
+ @\b@(\b(_\bp_\ba_\bt_\bt_\be_\br_\bn_\b-_\bl_\bi_\bs_\bt)\b)
+ Matches one of the given patterns.
+ !\b!(\b(_\bp_\ba_\bt_\bt_\be_\br_\bn_\b-_\bl_\bi_\bs_\bt)\b)
+ Matches anything except one of the given patterns.
+
+ The e\bex\bxt\btg\bgl\blo\bob\bb option changes the behavior of the parser, since the paren-
+ theses are normally treated as operators with syntactic meaning. To
+ ensure that extended matching patterns are parsed correctly, make sure
+ that e\bex\bxt\btg\bgl\blo\bob\bb is enabled before parsing constructs containing the pat-
+ terns, including shell functions and command substitutions.
+
+ When matching filenames, the d\bdo\bot\btg\bgl\blo\bob\bb shell option determines the set of
+ filenames that are tested: when d\bdo\bot\btg\bgl\blo\bob\bb is enabled, the set of file-
+ names includes all files beginning with ".", but _\b. and _\b._\b. must be
+ matched by a pattern or sub-pattern that begins with a dot; when it is
+ disabled, the set does not include any filenames beginning with "." un-
+ less the pattern or sub-pattern begins with a ".". If the g\bgl\blo\bob\bbs\bsk\bki\bip\bpd\bdo\bot\bts\bs
+ shell option is enabled, the filenames _\b. and _\b._\b. never appear in the
+ set. As above, "." only has a special meaning when matching filenames.
+
+ Complicated extended pattern matching against long strings is slow, es-
+ pecially when the patterns contain alternations and the strings contain
+ multiple matches. Using separate matches against shorter strings, or
+ using arrays of strings instead of a single long string, may be faster.
+
+ Q\bQu\buo\bot\bte\be R\bRe\bem\bmo\bov\bva\bal\bl
+ After the preceding expansions, all unquoted occurrences of the charac-
+ ters \\b\, '\b', and "\b" that did not result from one of the above expansions
+ are removed.
+
+R\bRE\bED\bDI\bIR\bRE\bEC\bCT\bTI\bIO\bON\bN
+ Before a command is executed, its input and output may be _\br_\be_\bd_\bi_\br_\be_\bc_\bt_\be_\bd
+ using a special notation interpreted by the shell. _\bR_\be_\bd_\bi_\br_\be_\bc_\bt_\bi_\bo_\bn allows
+ commands' file handles to be duplicated, opened, closed, made to refer
+ to different files, and can change the files the command reads from and
+ writes to. When used with the e\bex\bxe\bec\bc builtin, redirections modify file
+ handles in the current shell execution environment. The following
+ redirection operators may precede or appear anywhere within a _\bs_\bi_\bm_\bp_\bl_\be
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd or may follow a _\bc_\bo_\bm_\bm_\ba_\bn_\bd. Redirections are processed in the or-
+ der they appear, from left to right.
+
+ Each redirection that may be preceded by a file descriptor number may
+ instead be preceded by a word of the form {_\bv_\ba_\br_\bn_\ba_\bm_\be}. In this case, for
+ each redirection operator except >\b>&\b&-\b- and <\b<&\b&-\b-, the shell allocates a
+ file descriptor greater than or equal to 10 and assigns it to _\bv_\ba_\br_\bn_\ba_\bm_\be.
+ If {_\bv_\ba_\br_\bn_\ba_\bm_\be} precedes >\b>&\b&-\b- or <\b<&\b&-\b-, the value of _\bv_\ba_\br_\bn_\ba_\bm_\be defines the file
+ descriptor to close. If {_\bv_\ba_\br_\bn_\ba_\bm_\be} is supplied, the redirection per-
+ sists beyond the scope of the command, which allows the shell program-
+ mer to manage the file descriptor's lifetime manually without using the
+ e\bex\bxe\bec\bc builtin. The v\bva\bar\brr\bre\bed\bdi\bir\br_\b_c\bcl\blo\bos\bse\be shell option manages this behavior.
+
+ In the following descriptions, if the file descriptor number is omit-
+ ted, and the first character of the redirection operator is "<", the
+ redirection refers to the standard input (file descriptor 0). If the
+ first character of the redirection operator is ">", the redirection
+ refers to the standard output (file descriptor 1).
+
+ The _\bw_\bo_\br_\bd following the redirection operator in the following descrip-
+ tions, unless otherwise noted, is subjected to brace expansion, tilde
+ expansion, parameter and variable expansion, command substitution,
+ arithmetic expansion, quote removal, pathname expansion, and word
+ splitting. If it expands to more than one word, b\bba\bas\bsh\bh reports an error.
+
+ The order of redirections is significant. For example, the command
+
+ ls >\b> dirlist 2>\b>&\b&1
+
+ directs both standard output and standard error to the file _\bd_\bi_\br_\bl_\bi_\bs_\bt,
+ while the command
+
+ ls 2>\b>&\b&1 >\b> dirlist
+
+ directs only the standard output to file _\bd_\bi_\br_\bl_\bi_\bs_\bt, because the standard
+ error was directed to the standard output before the standard output
+ was redirected to _\bd_\bi_\br_\bl_\bi_\bs_\bt.
+
+ B\bBa\bas\bsh\bh handles several filenames specially when they are used in redirec-
+ tions, as described in the following table. If the operating system on
+ which b\bba\bas\bsh\bh is running provides these special files, b\bba\bas\bsh\bh uses them;
+ otherwise it emulates them internally with the behavior described be-
+ low.
+
+ /\b/d\bde\bev\bv/\b/f\bfd\bd/\b/_\bf_\bd
+ If _\bf_\bd is a valid integer, duplicate file descriptor _\bf_\bd.
+ /\b/d\bde\bev\bv/\b/s\bst\btd\bdi\bin\bn
+ File descriptor 0 is duplicated.
+ /\b/d\bde\bev\bv/\b/s\bst\btd\bdo\bou\but\bt
+ File descriptor 1 is duplicated.
+ /\b/d\bde\bev\bv/\b/s\bst\btd\bde\ber\brr\br
+ File descriptor 2 is duplicated.
+ /\b/d\bde\bev\bv/\b/t\btc\bcp\bp/\b/_\bh_\bo_\bs_\bt/\b/_\bp_\bo_\br_\bt
+ If _\bh_\bo_\bs_\bt is a valid hostname or Internet address, and _\bp_\bo_\br_\bt
+ is an integer port number or service name, b\bba\bas\bsh\bh attempts
+ to open the corresponding TCP socket.
+ /\b/d\bde\bev\bv/\b/u\bud\bdp\bp/\b/_\bh_\bo_\bs_\bt/\b/_\bp_\bo_\br_\bt
+ If _\bh_\bo_\bs_\bt is a valid hostname or Internet address, and _\bp_\bo_\br_\bt
+ is an integer port number or service name, b\bba\bas\bsh\bh attempts
+ to open the corresponding UDP socket.
+
+ A failure to open or create a file causes the redirection to fail.
+
+ Redirections using file descriptors greater than 9 should be used with
+ care, as they may conflict with file descriptors the shell uses inter-
+ nally.
+
+ R\bRe\bed\bdi\bir\bre\bec\bct\bti\bin\bng\bg I\bIn\bnp\bpu\but\bt
+ Redirecting input opens the file whose name results from the expansion
+ of _\bw_\bo_\br_\bd for reading on file descriptor _\bn, or the standard input (file
+ descriptor 0) if _\bn is not specified.
+
+ The general format for redirecting input is:
+
+ [_\bn]<\b<_\bw_\bo_\br_\bd
+
+ R\bRe\bed\bdi\bir\bre\bec\bct\bti\bin\bng\bg O\bOu\but\btp\bpu\but\bt
+ Redirecting output opens the file whose name results from the expansion
+ of _\bw_\bo_\br_\bd for writing on file descriptor _\bn, or the standard output (file
+ descriptor 1) if _\bn is not specified. If the file does not exist it is
+ created; if it does exist it is truncated to zero size.
+
+ The general format for redirecting output is:
+
+ [_\bn]>\b>_\bw_\bo_\br_\bd
+
+ If the redirection operator is >\b>, and the n\bno\boc\bcl\blo\bob\bbb\bbe\ber\br option to the s\bse\bet\bt
+ builtin command has been enabled, the redirection fails if the file
+ whose name results from the expansion of _\bw_\bo_\br_\bd exists and is a regular
+ file. If the redirection operator is >\b>|\b|, or the redirection operator
+ is >\b> and the n\bno\boc\bcl\blo\bob\bbb\bbe\ber\br option to the s\bse\bet\bt builtin is not enabled, b\bba\bas\bsh\bh
+ attempts the redirection even if the file named by _\bw_\bo_\br_\bd exists.
+
+ A\bAp\bpp\bpe\ben\bnd\bdi\bin\bng\bg R\bRe\bed\bdi\bir\bre\bec\bct\bte\bed\bd O\bOu\but\btp\bpu\but\bt
+ Redirecting output in this fashion opens the file whose name results
+ from the expansion of _\bw_\bo_\br_\bd for appending on file descriptor _\bn, or the
+ standard output (file descriptor 1) if _\bn is not specified. If the file
+ does not exist it is created.
+
+ The general format for appending output is:
+
+ [_\bn]>\b>>\b>_\bw_\bo_\br_\bd
+
+ R\bRe\bed\bdi\bir\bre\bec\bct\bti\bin\bng\bg S\bSt\bta\ban\bnd\bda\bar\brd\bd O\bOu\but\btp\bpu\but\bt a\ban\bnd\bd S\bSt\bta\ban\bnd\bda\bar\brd\bd E\bEr\brr\bro\bor\br
+ This construct redirects both the standard output (file descriptor 1)
+ and the standard error output (file descriptor 2) to the file whose
+ name is the expansion of _\bw_\bo_\br_\bd.
+
+ There are two formats for redirecting standard output and standard er-
+ ror:
+
+ &\b&>\b>_\bw_\bo_\br_\bd
+ and
+ >\b>&\b&_\bw_\bo_\br_\bd
+
+ Of the two forms, the first is preferred. This is semantically equiva-
+ lent to
+
+ >\b>_\bw_\bo_\br_\bd 2>\b>&\b&1
+
+ When using the second form, _\bw_\bo_\br_\bd may not expand to a number or -\b-. If
+ it does, other redirection operators apply (see D\bDu\bup\bpl\bli\bic\bca\bat\bti\bin\bng\bg F\bFi\bil\ble\be D\bDe\be-\b-
+ s\bsc\bcr\bri\bip\bpt\bto\bor\brs\bs below) for compatibility reasons.
+
+ A\bAp\bpp\bpe\ben\bnd\bdi\bin\bng\bg S\bSt\bta\ban\bnd\bda\bar\brd\bd O\bOu\but\btp\bpu\but\bt a\ban\bnd\bd S\bSt\bta\ban\bnd\bda\bar\brd\bd E\bEr\brr\bro\bor\br
+ This construct appends both the standard output (file descriptor 1) and
+ the standard error output (file descriptor 2) to the file whose name is
+ the expansion of _\bw_\bo_\br_\bd.
+
+ The format for appending standard output and standard error is:
+
+ &\b&>\b>>\b>_\bw_\bo_\br_\bd
+
+ This is semantically equivalent to
+
+ >\b>>\b>_\bw_\bo_\br_\bd 2>\b>&\b&1
+
+ (see D\bDu\bup\bpl\bli\bic\bca\bat\bti\bin\bng\bg F\bFi\bil\ble\be D\bDe\bes\bsc\bcr\bri\bip\bpt\bto\bor\brs\bs below).
+
+ H\bHe\ber\bre\be D\bDo\boc\bcu\bum\bme\ben\bnt\bts\bs
+ This type of redirection instructs the shell to read input from the
+ current source until it reads a line containing only _\bd_\be_\bl_\bi_\bm_\bi_\bt_\be_\br (with no
+ trailing blanks). All of the lines read up to that point then become
+ the standard input (or file descriptor _\bn if _\bn is specified) for a com-
+ mand.
+
+ The format of here-documents is:
+
+ [_\bn]<\b<<\b<[-\b-]_\bw_\bo_\br_\bd
+ _\bh_\be_\br_\be_\b-_\bd_\bo_\bc_\bu_\bm_\be_\bn_\bt
+ _\bd_\be_\bl_\bi_\bm_\bi_\bt_\be_\br
+
+ The shell does not perform parameter and variable expansion, command
+ substitution, arithmetic expansion, or pathname expansion on _\bw_\bo_\br_\bd.
+
+ If any part of _\bw_\bo_\br_\bd is quoted, the _\bd_\be_\bl_\bi_\bm_\bi_\bt_\be_\br is the result of quote re-
+ moval on _\bw_\bo_\br_\bd, and the lines in the here-document are not expanded. If
+ _\bw_\bo_\br_\bd is unquoted, the _\bd_\be_\bl_\bi_\bm_\bi_\bt_\be_\br is _\bw_\bo_\br_\bd itself, and the here-document
+ text is treated similarly to a double-quoted string: all lines of the
+ here-document are subjected to parameter expansion, command substitu-
+ tion, and arithmetic expansion, the character sequence \\b\<\b<n\bne\bew\bwl\bli\bin\bne\be>\b> is
+ treated literally, and \\b\ must be used to quote the characters \\b\, $\b$, and
+ `\b`; however, double quote characters have no special meaning.
+
+ If the redirection operator is <\b<<\b<-\b-, then the shell strips all leading
+ tab characters from input lines and the line containing _\bd_\be_\bl_\bi_\bm_\bi_\bt_\be_\br.
+ This allows here-documents within shell scripts to be indented in a
+ natural fashion.
+
+ If the delimiter is not quoted, the shell treats the \\b\<\b<n\bne\bew\bwl\bli\bin\bne\be>\b> se-
+ quence as a line continuation: the two lines are joined and the back-
+ slash-newline is removed. This happens while reading the here-docu-
+ ment, before the check for the ending delimiter, so joined lines can
+ form the end delimiter.
+
+ H\bHe\ber\bre\be S\bSt\btr\bri\bin\bng\bgs\bs
+ A variant of here documents, the format is:
+
+ [_\bn]<\b<<\b<<\b<_\bw_\bo_\br_\bd
+
+ The _\bw_\bo_\br_\bd undergoes tilde expansion, parameter and variable expansion,
+ command substitution, arithmetic expansion, and quote removal. Path-
+ name expansion and word splitting are not performed. The result is
+ supplied as a single string, with a newline appended, to the command on
+ its standard input (or file descriptor _\bn if _\bn is specified).
+
+ D\bDu\bup\bpl\bli\bic\bca\bat\bti\bin\bng\bg F\bFi\bil\ble\be D\bDe\bes\bsc\bcr\bri\bip\bpt\bto\bor\brs\bs
+ The redirection operator
+
+ [_\bn]<\b<&\b&_\bw_\bo_\br_\bd
+
+ is used to duplicate input file descriptors. If _\bw_\bo_\br_\bd expands to one or
+ more digits, file descriptor _\bn is made to be a copy of that file de-
+ scriptor. It is a redirection error if the digits in _\bw_\bo_\br_\bd do not spec-
+ ify a file descriptor open for input. If _\bw_\bo_\br_\bd evaluates to -\b-, file de-
+ scriptor _\bn is closed. If _\bn is not specified, this uses the standard
+ input (file descriptor 0).
+
+ The operator
+
+ [_\bn]>\b>&\b&_\bw_\bo_\br_\bd
+
+ is used similarly to duplicate output file descriptors. If _\bn is not
+ specified, this uses the standard output (file descriptor 1). It is a
+ redirection error if the digits in _\bw_\bo_\br_\bd do not specify a file descrip-
+ tor open for output. If _\bw_\bo_\br_\bd evaluates to -\b-, file descriptor _\bn is
+ closed. As a special case, if _\bn is omitted, and _\bw_\bo_\br_\bd does not expand
+ to one or more digits or -\b-, this redirects the standard output and
+ standard error as described previously.
+
+ M\bMo\bov\bvi\bin\bng\bg F\bFi\bil\ble\be D\bDe\bes\bsc\bcr\bri\bip\bpt\bto\bor\brs\bs
+ The redirection operator
+
+ [_\bn]<\b<&\b&_\bd_\bi_\bg_\bi_\bt-\b-
+
+ moves the file descriptor _\bd_\bi_\bg_\bi_\bt to file descriptor _\bn, or the standard
+ input (file descriptor 0) if _\bn is not specified. _\bd_\bi_\bg_\bi_\bt is closed after
+ being duplicated to _\bn.
+
+ Similarly, the redirection operator
+
+ [_\bn]>\b>&\b&_\bd_\bi_\bg_\bi_\bt-\b-
+
+ moves the file descriptor _\bd_\bi_\bg_\bi_\bt to file descriptor _\bn, or the standard
+ output (file descriptor 1) if _\bn is not specified.
+
+ O\bOp\bpe\ben\bni\bin\bng\bg F\bFi\bil\ble\be D\bDe\bes\bsc\bcr\bri\bip\bpt\bto\bor\brs\bs f\bfo\bor\br R\bRe\bea\bad\bdi\bin\bng\bg a\ban\bnd\bd W\bWr\bri\bit\bti\bin\bng\bg
+ The redirection operator
+
+ [_\bn]<\b<>\b>_\bw_\bo_\br_\bd
+
+ opens the file whose name is the expansion of _\bw_\bo_\br_\bd for both reading and
+ writing on file descriptor _\bn, or on file descriptor 0 if _\bn is not spec-
+ ified. If the file does not exist, it is created.
+
+A\bAL\bLI\bIA\bAS\bSE\bES\bS
+ _\bA_\bl_\bi_\ba_\bs_\be_\bs allow a string to be substituted for a word that is in a posi-
+ tion in the input where it can be the first word of a simple command.
+ Aliases have names and corresponding values that are set and unset us-
+ ing the a\bal\bli\bia\bas\bs and u\bun\bna\bal\bli\bia\bas\bs builtin commands (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS
+ below).
+
+ If the shell reads an unquoted word in the right position, it checks
+ the word to see if it matches an alias name. If it matches, the shell
+ replaces the word with the alias value, and reads that value as if it
+ had been read instead of the word. The shell doesn't look at any char-
+ acters following the word before attempting alias substitution.
+
+ The characters /\b/, $\b$, `\b`, and =\b= and any of the shell _\bm_\be_\bt_\ba_\bc_\bh_\ba_\br_\ba_\bc_\bt_\be_\br_\bs or
+ quoting characters listed above may not appear in an alias name. The
+ replacement text may contain any valid shell input, including shell
+ metacharacters. The first word of the replacement text is tested for
+ aliases, but a word that is identical to an alias being expanded is not
+ expanded a second time. This means that one may alias l\bls\bs to l\bls\bs -\b-F\bF, for
+ instance, and b\bba\bas\bsh\bh does not try to recursively expand the replacement
+ text.
+
+ If the last character of the alias value is a _\bb_\bl_\ba_\bn_\bk, the shell checks
+ the next command word following the alias for alias expansion.
+
+ Aliases are created and listed with the a\bal\bli\bia\bas\bs command, and removed with
+ the u\bun\bna\bal\bli\bia\bas\bs command.
+
+ There is no mechanism for using arguments in the replacement text. If
+ arguments are needed, use a shell function (see F\bFU\bUN\bNC\bCT\bTI\bIO\bON\bNS\bS below) in-
+ stead.
+
+ Aliases are not expanded when the shell is not interactive, unless the
+ e\bex\bxp\bpa\ban\bnd\bd_\b_a\bal\bli\bia\bas\bse\bes\bs shell option is set using s\bsh\bho\bop\bpt\bt (see the description of
+ s\bsh\bho\bop\bpt\bt under S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+
+ The rules concerning the definition and use of aliases are somewhat
+ confusing. B\bBa\bas\bsh\bh always reads at least one complete line of input, and
+ all lines that make up a compound command, before executing any of the
+ commands on that line or the compound command. Aliases are expanded
+ when a command is read, not when it is executed. Therefore, an alias
+ definition appearing on the same line as another command does not take
+ effect until the shell reads the next line of input, and an alias defi-
+ nition in a compound command does not take effect until the shell
+ parses and executes the entire compound command. The commands follow-
+ ing the alias definition on that line, or in the rest of a compound
+ command, are not affected by the new alias. This behavior is also an
+ issue when functions are executed. Aliases are expanded when a func-
+ tion definition is read, not when the function is executed, because a
+ function definition is itself a command. As a consequence, aliases de-
+ fined in a function are not available until after that function is exe-
+ cuted. To be safe, always put alias definitions on a separate line,
+ and do not use a\bal\bli\bia\bas\bs in compound commands.
+
+ For almost every purpose, shell functions are preferable to aliases.
+
+F\bFU\bUN\bNC\bCT\bTI\bIO\bON\bNS\bS
+ A shell function, defined as described above under S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR,
+ stores a series of commands for later execution. When the name of a
+ shell function is used as a simple command name, the shell executes the
+ list of commands associated with that function name. Functions are ex-
+ ecuted in the context of the calling shell; there is no new process
+ created to interpret them (contrast this with the execution of a shell
+ script).
+
+ When a function is executed, the arguments to the function become the
+ positional parameters during its execution. The special parameter #\b# is
+ updated to reflect the new positional parameters. Special parameter 0\b0
+ is unchanged. The first element of the F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE variable is set to the
+ name of the function while the function is executing.
+
+ All other aspects of the shell execution environment are identical be-
+ tween a function and its caller with these exceptions: the D\bDE\bEB\bBU\bUG\bG and
+ R\bRE\bET\bTU\bUR\bRN\bN traps (see the description of the t\btr\bra\bap\bp builtin under S\bSH\bHE\bEL\bLL\bL
+ B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below) are not inherited unless the function has been
+ given the t\btr\bra\bac\bce\be attribute (see the description of the d\bde\bec\bcl\bla\bar\bre\be builtin
+ below) or the -\b-o\bo f\bfu\bun\bnc\bct\btr\bra\bac\bce\be shell option has been enabled with the s\bse\bet\bt
+ builtin (in which case all functions inherit the D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN
+ traps), and the E\bER\bRR\bR trap is not inherited unless the -\b-o\bo e\ber\brr\brt\btr\bra\bac\bce\be shell
+ option has been enabled.
+
+ Variables local to the function are declared with the l\blo\boc\bca\bal\bl builtin
+ command (_\bl_\bo_\bc_\ba_\bl _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be_\bs). Ordinarily, variables and their values are
+ shared between the function and its caller. If a variable is declared
+ l\blo\boc\bca\bal\bl, the variable's visible scope is restricted to that function and
+ its children (including the functions it calls).
+
+ In the following description, the _\bc_\bu_\br_\br_\be_\bn_\bt _\bs_\bc_\bo_\bp_\be is a currently- execut-
+ ing function. Previous scopes consist of that function's caller and so
+ on, back to the "global" scope, where the shell is not executing any
+ shell function. A local variable at the current scope is a variable
+ declared using the l\blo\boc\bca\bal\bl or d\bde\bec\bcl\bla\bar\bre\be builtins in the function that is
+ currently executing.
+
+ Local variables "shadow" variables with the same name declared at pre-
+ vious scopes. For instance, a local variable declared in a function
+ hides variables with the same name declared at previous scopes, includ-
+ ing global variables: references and assignments refer to the local
+ variable, leaving the variables at previous scopes unmodified. When
+ the function returns, the global variable is once again visible.
+
+ The shell uses _\bd_\by_\bn_\ba_\bm_\bi_\bc _\bs_\bc_\bo_\bp_\bi_\bn_\bg to control a variable's visibility
+ within functions. With dynamic scoping, visible variables and their
+ values are a result of the sequence of function calls that caused exe-
+ cution to reach the current function. The value of a variable that a
+ function sees depends on its value within its caller, if any, whether
+ that caller is the global scope or another shell function. This is
+ also the value that a local variable declaration shadows, and the value
+ that is restored when the function returns.
+
+ For example, if a variable _\bv_\ba_\br is declared as local in function _\bf_\bu_\bn_\bc_\b1,
+ and _\bf_\bu_\bn_\bc_\b1 calls another function _\bf_\bu_\bn_\bc_\b2, references to _\bv_\ba_\br made from
+ within _\bf_\bu_\bn_\bc_\b2 resolve to the local variable _\bv_\ba_\br from _\bf_\bu_\bn_\bc_\b1, shadowing
+ any global variable named _\bv_\ba_\br.
+
+ The u\bun\bns\bse\bet\bt builtin also acts using the same dynamic scope: if a variable
+ is local to the current scope, u\bun\bns\bse\bet\bt unsets it; otherwise the unset
+ will refer to the variable found in any calling scope as described
+ above. If a variable at the current local scope is unset, it remains
+ so (appearing as unset) until it is reset in that scope or until the
+ function returns. Once the function returns, any instance of the vari-
+ able at a previous scope becomes visible. If the unset acts on a vari-
+ able at a previous scope, any instance of a variable with that name
+ that had been shadowed becomes visible (see below how the l\blo\boc\bca\bal\blv\bva\bar\br_\b_u\bun\bn-\b-
+ s\bse\bet\bt shell option changes this behavior).
+
+ The F\bFU\bUN\bNC\bCN\bNE\bES\bST\bT variable, if set to a numeric value greater than 0, de-
+ fines a maximum function nesting level. Function invocations that ex-
+ ceed the limit cause the entire command to abort.
+
+ If the builtin command r\bre\bet\btu\bur\brn\bn is executed in a function, the function
+ completes and execution resumes with the next command after the func-
+ tion call. If r\bre\bet\btu\bur\brn\bn is supplied a numeric argument, that is the func-
+ tion's return status; otherwise the function's return status is the
+ exit status of the last command executed before the r\bre\bet\btu\bur\brn\bn. Any com-
+ mand associated with the R\bRE\bET\bTU\bUR\bRN\bN trap is executed before execution re-
+ sumes. When a function completes, the values of the positional parame-
+ ters and the special parameter #\b# are restored to the values they had
+ prior to the function's execution.
+
+ The -\b-f\bf option to the d\bde\bec\bcl\bla\bar\bre\be or t\bty\byp\bpe\bes\bse\bet\bt builtin commands lists function
+ names and definitions. The -\b-F\bF option to d\bde\bec\bcl\bla\bar\bre\be or t\bty\byp\bpe\bes\bse\bet\bt lists the
+ function names only (and optionally the source file and line number, if
+ the e\bex\bxt\btd\bde\beb\bbu\bug\bg shell option is enabled). Functions may be exported so
+ that child shell processes (those created when executing a separate
+ shell invocation) automatically have them defined with the -\b-f\bf option to
+ the e\bex\bxp\bpo\bor\brt\bt builtin. The -\b-f\bf option to the u\bun\bns\bse\bet\bt builtin deletes a func-
+ tion definition.
+
+ Functions may be recursive. The F\bFU\bUN\bNC\bCN\bNE\bES\bST\bT variable may be used to limit
+ the depth of the function call stack and restrict the number of func-
+ tion invocations. By default, b\bba\bas\bsh\bh imposes no limit on the number of
+ recursive calls.
+
+A\bAR\bRI\bIT\bTH\bHM\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN
+ The shell allows arithmetic expressions to be evaluated, under certain
+ circumstances (see the l\ble\bet\bt and d\bde\bec\bcl\bla\bar\bre\be builtin commands, the (\b((\b( com-
+ pound command, the arithmetic f\bfo\bor\br command, the [\b[[\b[ conditional command,
+ and A\bAr\bri\bit\bth\bhm\bme\bet\bti\bic\bc E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn).
+
+ Evaluation is done in the largest fixed-width integers available, with
+ no check for overflow, though division by 0 is trapped and flagged as
+ an error. The operators and their precedence, associativity, and val-
+ ues are the same as in the C language. The following list of operators
+ is grouped into levels of equal-precedence operators. The levels are
+ listed in order of decreasing precedence.
+
+ _\bi_\bd+\b++\b+ _\bi_\bd-\b--\b-
+ variable post-increment and post-decrement
+ +\b++\b+_\bi_\bd -\b--\b-_\bi_\bd
+ variable pre-increment and pre-decrement
+ -\b- +\b+ unary minus and plus
+ !\b! ~\b~ logical and bitwise negation
+ *\b**\b* exponentiation
+ *\b* /\b/ %\b% multiplication, division, remainder
+ +\b+ -\b- addition, subtraction
+ <\b<<\b< >\b>>\b> left and right bitwise shifts
+ <\b<=\b= >\b>=\b= <\b< >\b>
+ comparison
+ =\b==\b= !\b!=\b= equality and inequality
+ &\b& bitwise AND
+ ^\b^ bitwise exclusive OR
+ |\b| bitwise OR
+ &\b&&\b& logical AND
+ |\b||\b| logical OR
+ _\be_\bx_\bp_\br?\b?_\be_\bx_\bp_\br:\b:_\be_\bx_\bp_\br
+ conditional operator
+ =\b= *\b*=\b= /\b/=\b= %\b%=\b= +\b+=\b= -\b-=\b= <\b<<\b<=\b= >\b>>\b>=\b= &\b&=\b= ^\b^=\b= |\b|=\b=
+ assignment
+ _\be_\bx_\bp_\br_\b1 ,\b, _\be_\bx_\bp_\br_\b2
+ comma
+
+ Shell variables are allowed as operands; parameter expansion is per-
+ formed before the expression is evaluated. Within an expression, shell
+ variables may also be referenced by name without using the parameter
+ expansion syntax. This means you can use "x", where _\bx is a shell vari-
+ able name, in an arithmetic expression, and the shell will evaluate its
+ value as an expression and use the result. A shell variable that is
+ null or unset evaluates to 0 when referenced by name in an expression.
+
+ The value of a variable is evaluated as an arithmetic expression when
+ it is referenced, or when a variable which has been given the _\bi_\bn_\bt_\be_\bg_\be_\br
+ attribute using d\bde\bec\bcl\bla\bar\bre\be -\b-i\bi is assigned a value. A null value evaluates
+ to 0. A shell variable need not have its _\bi_\bn_\bt_\be_\bg_\be_\br attribute enabled to
+ be used in an expression.
+
+ Integer constants follow the C language definition, without suffixes or
+ character constants. Constants with a leading 0 are interpreted as oc-
+ tal numbers. A leading 0x or 0X denotes hexadecimal. Otherwise, num-
+ bers take the form [_\bb_\ba_\bs_\be_\b#]n, where the optional _\bb_\ba_\bs_\be is a decimal num-
+ ber between 2 and 64 representing the arithmetic base, and _\bn is a num-
+ ber in that base. If _\bb_\ba_\bs_\be_\b# is omitted, then base 10 is used. When
+ specifying _\bn, if a non-digit is required, the digits greater than 9 are
+ represented by the lowercase letters, the uppercase letters, @, and _,
+ in that order. If _\bb_\ba_\bs_\be is less than or equal to 36, lowercase and up-
+ percase letters may be used interchangeably to represent numbers be-
+ tween 10 and 35.
+
+ Operators are evaluated in precedence order. Sub-expressions in paren-
+ theses are evaluated first and may override the precedence rules above.
+
+C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bSS\bSI\bIO\bON\bNS\bS
+ Conditional expressions are used by the [\b[[\b[ compound command and the
+ t\bte\bes\bst\bt and [\b[ builtin commands to test file attributes and perform string
+ and arithmetic comparisons. The t\bte\bes\bst\bt and [\b[ commands determine their
+ behavior based on the number of arguments; see the descriptions of
+ those commands for any other command-specific actions.
+
+ Expressions are formed from the unary or binary primaries listed below.
+ Unary expressions are often used to examine the status of a file or
+ shell variable. Binary operators are used for string, numeric, and
+ file attribute comparisons.
+
+ B\bBa\bas\bsh\bh handles several filenames specially when they are used in expres-
+ sions. If the operating system on which b\bba\bas\bsh\bh is running provides these
+ special files, bash will use them; otherwise it will emulate them in-
+ ternally with this behavior: If any _\bf_\bi_\bl_\be argument to one of the pri-
+ maries is of the form _\b/_\bd_\be_\bv_\b/_\bf_\bd_\b/_\bn, then b\bba\bas\bsh\bh checks file descriptor _\bn.
+ If the _\bf_\bi_\bl_\be argument to one of the primaries is one of _\b/_\bd_\be_\bv_\b/_\bs_\bt_\bd_\bi_\bn,
+ _\b/_\bd_\be_\bv_\b/_\bs_\bt_\bd_\bo_\bu_\bt, or _\b/_\bd_\be_\bv_\b/_\bs_\bt_\bd_\be_\br_\br, b\bba\bas\bsh\bh checks file descriptor 0, 1, or 2,
+ respectively.
+
+ Unless otherwise specified, primaries that operate on files follow sym-
+ bolic links and operate on the target of the link, rather than the link
+ itself.
+
+ When used with [\b[[\b[, or when the shell is in posix mode, the <\b< and >\b> op-
+ erators sort lexicographically using the current locale. When the
+ shell is not in posix mode, the t\bte\bes\bst\bt command sorts using ASCII order-
+ ing.
+
+ -\b-a\ba _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists.
+ -\b-b\bb _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is a block special file.
+ -\b-c\bc _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is a character special file.
+ -\b-d\bd _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is a directory.
+ -\b-e\be _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists.
+ -\b-f\bf _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is a regular file.
+ -\b-g\bg _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is set-group-id.
+ -\b-h\bh _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is a symbolic link.
+ -\b-k\bk _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and its "sticky" bit is set.
+ -\b-p\bp _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is a named pipe (FIFO).
+ -\b-r\br _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is readable.
+ -\b-s\bs _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and has a size greater than zero.
+ -\b-t\bt _\bf_\bd True if file descriptor _\bf_\bd is open and refers to a terminal.
+ -\b-u\bu _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and its set-user-id bit is set.
+ -\b-w\bw _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is writable.
+ -\b-x\bx _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is executable.
+ -\b-G\bG _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is owned by the effective group id.
+ -\b-L\bL _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is a symbolic link.
+ -\b-N\bN _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and has been modified since it was last ac-
+ cessed.
+ -\b-O\bO _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is owned by the effective user id.
+ -\b-S\bS _\bf_\bi_\bl_\be
+ True if _\bf_\bi_\bl_\be exists and is a socket.
+ -\b-o\bo _\bo_\bp_\bt_\bn_\ba_\bm_\be
+ True if the shell option _\bo_\bp_\bt_\bn_\ba_\bm_\be is enabled. See the list of
+ options under the description of the -\b-o\bo option to the s\bse\bet\bt
+ builtin below.
+ -\b-v\bv _\bv_\ba_\br_\bn_\ba_\bm_\be
+ True if the shell variable _\bv_\ba_\br_\bn_\ba_\bm_\be is set (has been assigned a
+ value). If _\bv_\ba_\br_\bn_\ba_\bm_\be is an indexed array variable name sub-
+ scripted by _\b@ or _\b*, this returns true if the array has any set
+ elements. If _\bv_\ba_\br_\bn_\ba_\bm_\be is an associative array variable name sub-
+ scripted by _\b@ or _\b*, this returns true if an element with that
+ key is set.
+ -\b-R\bR _\bv_\ba_\br_\bn_\ba_\bm_\be
+ True if the shell variable _\bv_\ba_\br_\bn_\ba_\bm_\be is set and is a name refer-
+ ence.
+ -\b-z\bz _\bs_\bt_\br_\bi_\bn_\bg
+ True if the length of _\bs_\bt_\br_\bi_\bn_\bg is zero.
+ _\bs_\bt_\br_\bi_\bn_\bg
+ -\b-n\bn _\bs_\bt_\br_\bi_\bn_\bg
+ True if the length of _\bs_\bt_\br_\bi_\bn_\bg is non-zero.
+
+ _\bs_\bt_\br_\bi_\bn_\bg_\b1 =\b==\b= _\bs_\bt_\br_\bi_\bn_\bg_\b2
+ _\bs_\bt_\br_\bi_\bn_\bg_\b1 =\b= _\bs_\bt_\br_\bi_\bn_\bg_\b2
+ True if the strings are equal. =\b= should be used with the t\bte\bes\bst\bt
+ command for POSIX conformance. When used with the [\b[[\b[ command,
+ this performs pattern matching as described above (C\bCo\bom\bmp\bpo\bou\bun\bnd\bd C\bCo\bom\bm-\b-
+ m\bma\ban\bnd\bds\bs).
+ _\bs_\bt_\br_\bi_\bn_\bg_\b1 !\b!=\b= _\bs_\bt_\br_\bi_\bn_\bg_\b2
+ True if the strings are not equal.
+ _\bs_\bt_\br_\bi_\bn_\bg_\b1 <\b< _\bs_\bt_\br_\bi_\bn_\bg_\b2
+ True if _\bs_\bt_\br_\bi_\bn_\bg_\b1 sorts before _\bs_\bt_\br_\bi_\bn_\bg_\b2 lexicographically.
+ _\bs_\bt_\br_\bi_\bn_\bg_\b1 >\b> _\bs_\bt_\br_\bi_\bn_\bg_\b2
+ True if _\bs_\bt_\br_\bi_\bn_\bg_\b1 sorts after _\bs_\bt_\br_\bi_\bn_\bg_\b2 lexicographically.
+
+ _\bf_\bi_\bl_\be_\b1 -\b-e\bef\bf _\bf_\bi_\bl_\be_\b2
+ True if _\bf_\bi_\bl_\be_\b1 and _\bf_\bi_\bl_\be_\b2 refer to the same device and inode num-
+ bers.
+ _\bf_\bi_\bl_\be_\b1 -n\bnt\bt _\bf_\bi_\bl_\be_\b2
+ True if _\bf_\bi_\bl_\be_\b1 is newer (according to modification date) than
+ _\bf_\bi_\bl_\be_\b2, or if _\bf_\bi_\bl_\be_\b1 exists and _\bf_\bi_\bl_\be_\b2 does not.
+ _\bf_\bi_\bl_\be_\b1 -o\bot\bt _\bf_\bi_\bl_\be_\b2
+ True if _\bf_\bi_\bl_\be_\b1 is older than _\bf_\bi_\bl_\be_\b2, or if _\bf_\bi_\bl_\be_\b2 exists and _\bf_\bi_\bl_\be_\b1
+ does not.
+
+ _\ba_\br_\bg_\b1 O\bOP\bP _\ba_\br_\bg_\b2
+ O\bOP\bP is one of -\b-e\beq\bq, -\b-n\bne\be, -\b-l\blt\bt, -\b-l\ble\be, -\b-g\bgt\bt, or -\b-g\bge\be. These arithmetic
+ binary operators return true if _\ba_\br_\bg_\b1 is equal to, not equal to,
+ less than, less than or equal to, greater than, or greater than
+ or equal to _\ba_\br_\bg_\b2, respectively. _\ba_\br_\bg_\b1 and _\ba_\br_\bg_\b2 may be positive
+ or negative integers. When used with the [\b[[\b[ command, _\ba_\br_\bg_\b1 and
+ _\ba_\br_\bg_\b2 are evaluated as arithmetic expressions (see A\bAR\bRI\bIT\bTH\bHM\bME\bET\bTI\bIC\bC
+ E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN above). Since the expansions the [\b[[\b[ command performs
+ on _\ba_\br_\bg_\b1 and _\ba_\br_\bg_\b2 can potentially result in empty strings, arith-
+ metic expression evaluation treats those as expressions that
+ evaluate to 0.
+
+S\bSI\bIM\bMP\bPL\bLE\bE C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN
+ When the shell executes a simple command, it performs the following ex-
+ pansions, assignments, and redirections, from left to right, in the
+ following order.
+
+ 1. The words that the parser has marked as variable assignments
+ (those preceding the command name) and redirections are saved
+ for later processing.
+
+ 2. The words that are not variable assignments or redirections are
+ expanded. If any words remain after expansion, the first word
+ is taken to be the name of the command and the remaining words
+ are the arguments.
+
+ 3. Redirections are performed as described above under R\bRE\bED\bDI\bIR\bRE\bEC\bCT\bTI\bIO\bON\bN.
+
+ 4. The text after the =\b= in each variable assignment undergoes tilde
+ expansion, parameter expansion, command substitution, arithmetic
+ expansion, and quote removal before being assigned to the vari-
+ able.
+
+ If no command name results, the variable assignments affect the current
+ shell environment. In the case of such a command (one that consists
+ only of assignment statements and redirections), assignment statements
+ are performed before redirections. Otherwise, the variables are added
+ to the environment of the executed command and do not affect the cur-
+ rent shell environment. If any of the assignments attempts to assign a
+ value to a readonly variable, an error occurs, and the command exits
+ with a non-zero status.
+
+ If no command name results, redirections are performed, but do not af-
+ fect the current shell environment. A redirection error causes the
+ command to exit with a non-zero status.
+
+ If there is a command name left after expansion, execution proceeds as
+ described below. Otherwise, the command exits. If one of the expan-
+ sions contained a command substitution, the exit status of the command
+ is the exit status of the last command substitution performed. If
+ there were no command substitutions, the command exits with a zero sta-
+ tus.
+
+C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN
+ After a command has been split into words, if it results in a simple
+ command and an optional list of arguments, the shell performs the fol-
+ lowing actions.
+
+ If the command name contains no slashes, the shell attempts to locate
+ it. If there exists a shell function by that name, that function is
+ invoked as described above in F\bFU\bUN\bNC\bCT\bTI\bIO\bON\bNS\bS. If the name does not match a
+ function, the shell searches for it in the list of shell builtins. If
+ a match is found, that builtin is invoked.
+
+ If the name is neither a shell function nor a builtin, and contains no
+ slashes, b\bba\bas\bsh\bh searches each element of the P\bPA\bAT\bTH\bH for a directory con-
+ taining an executable file by that name. B\bBa\bas\bsh\bh uses a hash table to re-
+ member the full pathnames of executable files (see h\bha\bas\bsh\bh under S\bSH\bHE\bEL\bLL\bL
+ B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below). Bash performs a full search of the directo-
+ ries in P\bPA\bAT\bTH\bH only if the command is not found in the hash table. If
+ the search is unsuccessful, the shell searches for a defined shell
+ function named c\bco\bom\bmm\bma\ban\bnd\bd_\b_n\bno\bot\bt_\b_f\bfo\bou\bun\bnd\bd_\b_h\bha\ban\bnd\bdl\ble\be. If that function exists, it
+ is invoked in a separate execution environment with the original com-
+ mand and the original command's arguments as its arguments, and the
+ function's exit status becomes the exit status of that subshell. If
+ that function is not defined, the shell prints an error message and re-
+ turns an exit status of 127.
+
+ If the search is successful, or if the command name contains one or
+ more slashes, the shell executes the named program in a separate execu-
+ tion environment. Argument 0 is set to the name given, and the remain-
+ ing arguments to the command are set to the arguments given, if any.
+
+ If this execution fails because the file is not in executable format,
+ and the file is not a directory, it is assumed to be a _\bs_\bh_\be_\bl_\bl _\bs_\bc_\br_\bi_\bp_\bt, a
+ file containing shell commands, and the shell creates a new instance of
+ itself to execute it. Bash tries to determine whether the file is a
+ text file or a binary, and will not execute files it determines to be
+ binaries. This subshell reinitializes itself, so that the effect is as
+ if a new shell had been invoked to handle the script, with the excep-
+ tion that the locations of commands remembered by the parent (see h\bha\bas\bsh\bh
+ below under S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS are retained by the child.
+
+ If the program is a file beginning with #\b#!\b!, the remainder of the first
+ line specifies an interpreter for the program. The shell executes the
+ specified interpreter on operating systems that do not handle this exe-
+ cutable format themselves. The arguments to the interpreter consist of
+ a single optional argument following the interpreter name on the first
+ line of the program, followed by the name of the program, followed by
+ the command arguments, if any.
+
+C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN E\bEN\bNV\bVI\bIR\bRO\bON\bNM\bME\bEN\bNT\bT
+ The shell has an _\be_\bx_\be_\bc_\bu_\bt_\bi_\bo_\bn _\be_\bn_\bv_\bi_\br_\bo_\bn_\bm_\be_\bn_\bt, which consists of the follow-
+ ing:
+
+ +\bo Open files inherited by the shell at invocation, as modified by
+ redirections supplied to the e\bex\bxe\bec\bc builtin.
+
+ +\bo The current working directory as set by c\bcd\bd, p\bpu\bus\bsh\bhd\bd, or p\bpo\bop\bpd\bd, or
+ inherited by the shell at invocation.
+
+ +\bo The file creation mode mask as set by u\bum\bma\bas\bsk\bk or inherited from
+ the shell's parent.
+
+ +\bo Current traps set by t\btr\bra\bap\bp.
+
+ +\bo Shell parameters that are set by variable assignment or with s\bse\bet\bt
+ or inherited from the shell's parent in the environment.
+
+ +\bo Shell functions defined during execution or inherited from the
+ shell's parent in the environment.
+
+ +\bo Options enabled at invocation (either by default or with com-
+ mand-line arguments) or by s\bse\bet\bt.
+
+ +\bo Options enabled by s\bsh\bho\bop\bpt\bt.
+
+ +\bo Shell aliases defined with a\bal\bli\bia\bas\bs.
+
+ +\bo Various process IDs, including those of background jobs, the
+ value of $\b$$\b$, and the value of P\bPP\bPI\bID\bD.
+
+ When a simple command other than a builtin or shell function is to be
+ executed, it is invoked in a separate execution environment that con-
+ sists of the following. Unless otherwise noted, the values are inher-
+ ited from the shell.
+
+ +\bo The shell's open files, plus any modifications and additions
+ specified by redirections to the command.
+
+ +\bo The current working directory.
+
+ +\bo The file creation mode mask.
+
+ +\bo Shell variables and functions marked for export, along with
+ variables exported for the command, passed in the environment.
+
+ +\bo Traps caught by the shell are reset to the values inherited from
+ the shell's parent, and traps ignored by the shell are ignored.
+
+ A command invoked in this separate environment cannot affect the
+ shell's execution environment.
+
+ A _\bs_\bu_\bb_\bs_\bh_\be_\bl_\bl is a copy of the shell process.
+
+ Command substitution, commands grouped with parentheses, and asynchro-
+ nous commands are invoked in a subshell environment that is a duplicate
+ of the shell environment, except that traps caught by the shell are re-
+ set to the values that the shell inherited from its parent at invoca-
+ tion. Builtin commands that are invoked as part of a pipeline, except
+ possibly in the last element depending on the value of the l\bla\bas\bst\btp\bpi\bip\bpe\be
+ shell option, are also executed in a subshell environment. Changes
+ made to the subshell environment cannot affect the shell's execution
+ environment.
+
+ When the shell is in posix mode, subshells spawned to execute command
+ substitutions inherit the value of the -\b-e\be option from their parent
+ shell. When not in posix mode, b\bba\bas\bsh\bh clears the -\b-e\be option in such sub-
+ shells. See the description of the i\bin\bnh\bhe\ber\bri\bit\bt_\b_e\ber\brr\bre\bex\bxi\bit\bt shell option below
+ for how to control this behavior when not in posix mode.
+
+ If a command is followed by a &\b& and job control is not active, the de-
+ fault standard input for the command is the empty file _\b/_\bd_\be_\bv_\b/_\bn_\bu_\bl_\bl. Oth-
+ erwise, the invoked command inherits the file descriptors of the call-
+ ing shell as modified by redirections.
+
+E\bEN\bNV\bVI\bIR\bRO\bON\bNM\bME\bEN\bNT\bT
+ When a program is invoked it is given an array of strings called the
+ _\be_\bn_\bv_\bi_\br_\bo_\bn_\bm_\be_\bn_\bt. This is a list of _\bn_\ba_\bm_\be-_\bv_\ba_\bl_\bu_\be pairs, of the form
+ _\bn_\ba_\bm_\be=_\bv_\ba_\bl_\bu_\be.
+
+ The shell provides several ways to manipulate the environment. On in-
+ vocation, the shell scans its own environment and creates a parameter
+ for each name found, automatically marking it for _\be_\bx_\bp_\bo_\br_\bt to child
+ processes. Executed commands inherit the environment. The e\bex\bxp\bpo\bor\brt\bt, d\bde\be-\b-
+ c\bcl\bla\bar\bre\be -\b-x\bx, and u\bun\bns\bse\bet\bt commands modify the environment by adding and
+ deleting parameters and functions. If the value of a parameter in the
+ environment is modified, the new value automatically becomes part of
+ the environment, replacing the old. The environment inherited by any
+ executed command consists of the shell's initial environment, whose
+ values may be modified in the shell, less any pairs removed by the u\bun\bn-\b-
+ s\bse\bet\bt or e\bex\bxp\bpo\bor\brt\bt -\b-n\bn commands, plus any additions via the e\bex\bxp\bpo\bor\brt\bt and d\bde\be-\b-
+ c\bcl\bla\bar\bre\be -\b-x\bx commands.
+
+ If any parameter assignments, as described above in P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS, appear
+ before a _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd, the variable assignments are part of that com-
+ mand's environment for as long as it executes. These assignment state-
+ ments affect only the environment seen by that command. If these as-
+ signments precede a call to a shell function, the variables are local
+ to the function and exported to that function's children.
+
+ If the -\b-k\bk option is set (see the s\bse\bet\bt builtin command below), then _\ba_\bl_\bl
+ parameter assignments are placed in the environment for a command, not
+ just those that precede the command name.
+
+ When b\bba\bas\bsh\bh invokes an external command, the variable _\b_ is set to the
+ full pathname of the command and passed to that command in its environ-
+ ment.
+
+E\bEX\bXI\bIT\bT S\bST\bTA\bAT\bTU\bUS\bS
+ The exit status of an executed command is the value returned by the
+ _\bw_\ba_\bi_\bt_\bp_\bi_\bd system call or equivalent function. Exit statuses fall between
+ 0 and 255, though, as explained below, the shell may use values above
+ 125 specially. Exit statuses from shell builtins and compound commands
+ are also limited to this range. Under certain circumstances, the shell
+ will use special values to indicate specific failure modes.
+
+ For the shell's purposes, a command which exits with a zero exit status
+ has succeeded. So while an exit status of zero indicates success, a
+ non-zero exit status indicates failure.
+
+ When a command terminates on a fatal signal _\bN, b\bba\bas\bsh\bh uses the value of
+ 128+_\bN as the exit status.
+
+ If a command is not found, the child process created to execute it re-
+ turns a status of 127. If a command is found but is not executable,
+ the return status is 126.
+
+ If a command fails because of an error during expansion or redirection,
+ the exit status is greater than zero.
+
+ Shell builtin commands return a status of 0 (_\bt_\br_\bu_\be) if successful, and
+ non-zero (_\bf_\ba_\bl_\bs_\be) if an error occurs while they execute. All builtins
+ return an exit status of 2 to indicate incorrect usage, generally in-
+ valid options or missing arguments.
+
+ The exit status of the last command is available in the special parame-
+ ter $?.
+
+ B\bBa\bas\bsh\bh itself returns the exit status of the last command executed, un-
+ less a syntax error occurs, in which case it exits with a non-zero
+ value. See also the e\bex\bxi\bit\bt builtin command below.
+
+S\bSI\bIG\bGN\bNA\bAL\bLS\bS
+ When b\bba\bas\bsh\bh is interactive, in the absence of any traps, it ignores
+ S\bSI\bIG\bGT\bTE\bER\bRM\bM (so that k\bki\bil\bll\bl 0\b0 does not kill an interactive shell), and
+ catches and handles S\bSI\bIG\bGI\bIN\bNT\bT (so that the w\bwa\bai\bit\bt builtin is interruptible).
+ When b\bba\bas\bsh\bh receives S\bSI\bIG\bGI\bIN\bNT\bT, it breaks out of any executing loops. In
+ all cases, b\bba\bas\bsh\bh ignores S\bSI\bIG\bGQ\bQU\bUI\bIT\bT. If job control is in effect, b\bba\bas\bsh\bh ig-
+ nores S\bSI\bIG\bGT\bTT\bTI\bIN\bN, S\bSI\bIG\bGT\bTT\bTO\bOU\bU, and S\bSI\bIG\bGT\bTS\bST\bTP\bP.
+
+ The t\btr\bra\bap\bp builtin modifies the shell's signal handling, as described be-
+ low.
+
+ Non-builtin commands b\bba\bas\bsh\bh executes have signal handlers set to the val-
+ ues inherited by the shell from its parent, unless t\btr\bra\bap\bp sets them to be
+ ignored, in which case the child process will ignore them as well.
+ When job control is not in effect, asynchronous commands ignore S\bSI\bIG\bGI\bIN\bNT\bT
+ and S\bSI\bIG\bGQ\bQU\bUI\bIT\bT in addition to these inherited handlers. Commands run as a
+ result of command substitution ignore the keyboard-generated job con-
+ trol signals S\bSI\bIG\bGT\bTT\bTI\bIN\bN, S\bSI\bIG\bGT\bTT\bTO\bOU\bU, and S\bSI\bIG\bGT\bTS\bST\bTP\bP.
+
+ The shell exits by default upon receipt of a S\bSI\bIG\bGH\bHU\bUP\bP. Before exiting,
+ an interactive shell resends the S\bSI\bIG\bGH\bHU\bUP\bP to all jobs, running or
+ stopped. The shell sends S\bSI\bIG\bGC\bCO\bON\bNT\bT to stopped jobs to ensure that they
+ receive the S\bSI\bIG\bGH\bHU\bUP\bP (see J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL below for more information about
+ running and stopped jobs). To prevent the shell from sending the sig-
+ nal to a particular job, remove it from the jobs table with the d\bdi\bis\bso\bow\bwn\bn
+ builtin (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below) or mark it not to receive
+ S\bSI\bIG\bGH\bHU\bUP\bP using d\bdi\bis\bso\bow\bwn\bn -\b-h\bh.
+
+ If the h\bhu\bup\bpo\bon\bne\bex\bxi\bit\bt shell option has been set using s\bsh\bho\bop\bpt\bt, b\bba\bas\bsh\bh sends a
+ S\bSI\bIG\bGH\bHU\bUP\bP to all jobs when an interactive login shell exits.
+
+ If b\bba\bas\bsh\bh is waiting for a command to complete and receives a signal for
+ which a trap has been set, it will not execute the trap until the com-
+ mand completes. If b\bba\bas\bsh\bh is waiting for an asynchronous command via the
+ w\bwa\bai\bit\bt builtin, and it receives a signal for which a trap has been set,
+ the w\bwa\bai\bit\bt builtin will return immediately with an exit status greater
+ than 128, immediately after which the shell executes the trap.
+
+ When job control is not enabled, and b\bba\bas\bsh\bh is waiting for a foreground
+ command to complete, the shell receives keyboard-generated signals such
+ as S\bSI\bIG\bGI\bIN\bNT\bT (usually generated by ^\b^C\bC) that users commonly intend to send
+ to that command. This happens because the shell and the command are in
+ the same process group as the terminal, and ^\b^C\bC sends S\bSI\bIG\bGI\bIN\bNT\bT to all
+ processes in that process group. Since b\bba\bas\bsh\bh does not enable job con-
+ trol by default when the shell is not interactive, this scenario is
+ most common in non-interactive shells.
+
+ When job control is enabled, and b\bba\bas\bsh\bh is waiting for a foreground com-
+ mand to complete, the shell does not receive keyboard-generated sig-
+ nals, because it is not in the same process group as the terminal.
+ This scenario is most common in interactive shells, where b\bba\bas\bsh\bh attempts
+ to enable job control by default. See J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL below for more in-
+ formation about process groups.
+
+ When job control is not enabled, and b\bba\bas\bsh\bh receives S\bSI\bIG\bGI\bIN\bNT\bT while waiting
+ for a foreground command, it waits until that foreground command termi-
+ nates and then decides what to do about the S\bSI\bIG\bGI\bIN\bNT\bT:
+
+ 1. If the command terminates due to the S\bSI\bIG\bGI\bIN\bNT\bT, b\bba\bas\bsh\bh concludes that
+ the user meant to send the S\bSI\bIG\bGI\bIN\bNT\bT to the shell as well, and acts
+ on the S\bSI\bIG\bGI\bIN\bNT\bT (e.g., by running a S\bSI\bIG\bGI\bIN\bNT\bT trap, exiting a non-in-
+ teractive shell, or returning to the top level to read a new
+ command).
+
+ 2. If the command does not terminate due to S\bSI\bIG\bGI\bIN\bNT\bT, the program
+ handled the S\bSI\bIG\bGI\bIN\bNT\bT itself and did not treat it as a fatal sig-
+ nal. In that case, b\bba\bas\bsh\bh does not treat S\bSI\bIG\bGI\bIN\bNT\bT as a fatal sig-
+ nal, either, instead assuming that the S\bSI\bIG\bGI\bIN\bNT\bT was used as part
+ of the program's normal operation (e.g., emacs uses it to abort
+ editing commands) or deliberately discarded. However, b\bba\bas\bsh\bh will
+ run any trap set on S\bSI\bIG\bGI\bIN\bNT\bT, as it does with any other trapped
+ signal it receives while it is waiting for the foreground com-
+ mand to complete, for compatibility.
+
+ When job control is enabled, b\bba\bas\bsh\bh does not receive keyboard-generated
+ signals such as S\bSI\bIG\bGI\bIN\bNT\bT while it is waiting for a foreground command.
+ An interactive shell does not pay attention to the S\bSI\bIG\bGI\bIN\bNT\bT, even if the
+ foreground command terminates as a result, other than noting its exit
+ status. If the shell is not interactive, and the foreground command
+ terminates due to the S\bSI\bIG\bGI\bIN\bNT\bT, b\bba\bas\bsh\bh pretends it received the S\bSI\bIG\bGI\bIN\bNT\bT it-
+ self (scenario 1 above), for compatibility.
+
+J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL
+ _\bJ_\bo_\bb _\bc_\bo_\bn_\bt_\br_\bo_\bl refers to the ability to selectively stop (_\bs_\bu_\bs_\bp_\be_\bn_\bd) the ex-
+ ecution of processes and continue (_\br_\be_\bs_\bu_\bm_\be) their execution at a later
+ point. A user typically employs this facility via an interactive in-
+ terface supplied jointly by the operating system kernel's terminal dri-
+ ver and b\bba\bas\bsh\bh.
+
+ The shell associates a _\bj_\bo_\bb with each pipeline. It keeps a table of
+ currently executing jobs, which the j\bjo\bob\bbs\bs command will display. Each
+ job has a _\bj_\bo_\bb _\bn_\bu_\bm_\bb_\be_\br, which j\bjo\bob\bbs\bs displays between brackets. Job num-
+ bers start at 1. When b\bba\bas\bsh\bh starts a job asynchronously (in the _\bb_\ba_\bc_\bk_\b-
+ _\bg_\br_\bo_\bu_\bn_\bd), it prints a line that looks like:
+
+ [1] 25647
+
+ indicating that this job is job number 1 and that the process ID of the
+ last process in the pipeline associated with this job is 25647. All of
+ the processes in a single pipeline are members of the same job. B\bBa\bas\bsh\bh
+ uses the _\bj_\bo_\bb abstraction as the basis for job control.
+
+ To facilitate the implementation of the user interface to job control,
+ each process has a _\bp_\br_\bo_\bc_\be_\bs_\bs _\bg_\br_\bo_\bu_\bp _\bI_\bD, and the operating system maintains
+ the notion of a _\bc_\bu_\br_\br_\be_\bn_\bt _\bt_\be_\br_\bm_\bi_\bn_\ba_\bl _\bp_\br_\bo_\bc_\be_\bs_\bs _\bg_\br_\bo_\bu_\bp _\bI_\bD. This terminal
+ process group ID is associated with the _\bc_\bo_\bn_\bt_\br_\bo_\bl_\bl_\bi_\bn_\bg _\bt_\be_\br_\bm_\bi_\bn_\ba_\bl.
+
+ Processes that have the same process group ID are said to be part of
+ the same _\bp_\br_\bo_\bc_\be_\bs_\bs _\bg_\br_\bo_\bu_\bp. Members of the _\bf_\bo_\br_\be_\bg_\br_\bo_\bu_\bn_\bd process group
+ (processes whose process group ID is equal to the current terminal
+ process group ID) receive keyboard-generated signals such as S\bSI\bIG\bGI\bIN\bNT\bT.
+ Processes in the foreground process group are said to be _\bf_\bo_\br_\be_\bg_\br_\bo_\bu_\bn_\bd
+ processes. _\bB_\ba_\bc_\bk_\bg_\br_\bo_\bu_\bn_\bd processes are those whose process group ID dif-
+ fers from the controlling terminal's; such processes are immune to key-
+ board-generated signals. Only foreground processes are allowed to read
+ from or, if the user so specifies with "stty tostop", write to the con-
+ trolling terminal. The system sends a S\bSI\bIG\bGT\bTT\bTI\bIN\bN (\b(S\bSI\bIG\bGT\bTT\bTO\bOU\bU)\b) signal to
+ background processes which attempt to read from (write to when "tostop"
+ is in effect) the terminal, which, unless caught, suspends the process.
+
+ If the operating system on which b\bba\bas\bsh\bh is running supports job control,
+ b\bba\bas\bsh\bh contains facilities to use it. Typing the _\bs_\bu_\bs_\bp_\be_\bn_\bd character (typ-
+ ically ^\b^Z\bZ, Control-Z) while a process is running stops that process and
+ returns control to b\bba\bas\bsh\bh. Typing the _\bd_\be_\bl_\ba_\by_\be_\bd _\bs_\bu_\bs_\bp_\be_\bn_\bd character (typi-
+ cally ^\b^Y\bY, Control-Y) causes the process stop when it attempts to read
+ input from the terminal, and returns control to b\bba\bas\bsh\bh. The user then
+ manipulates the state of this job, using the b\bbg\bg command to continue it
+ in the background, the f\bfg\bg command to continue it in the foreground, or
+ the k\bki\bil\bll\bl command to kill it. The suspend character takes effect imme-
+ diately, and has the additional side effect of discarding any pending
+ output and typeahead. To force a background process to stop, or stop a
+ process that's not associated with the current terminal session, send
+ it the S\bSI\bIG\bGS\bST\bTO\bOP\bP signal using k\bki\bil\bll\bl.
+
+ There are a number of ways to refer to a job in the shell. The %\b% char-
+ acter introduces a job specification (jobspec).
+
+ Job number _\bn may be referred to as %\b%n\bn. A job may also be referred to
+ using a prefix of the name used to start it, or using a substring that
+ appears in its command line. For example, %\b%c\bce\be refers to a job whose
+ command name begins with c\bce\be. Using %\b%?\b?c\bce\be, on the other hand, refers to
+ any job containing the string c\bce\be in its command line. If the prefix or
+ substring matches more than one job, b\bba\bas\bsh\bh reports an error.
+
+ The symbols %\b%%\b% and %\b%+\b+ refer to the shell's notion of the _\bc_\bu_\br_\br_\be_\bn_\bt _\bj_\bo_\bb.
+ A single % (with no accompanying job specification) also refers to the
+ current job. %\b%-\b- refers to the _\bp_\br_\be_\bv_\bi_\bo_\bu_\bs _\bj_\bo_\bb. When a job starts in the
+ background, a job stops while in the foreground, or a job is resumed in
+ the background, it becomes the current job. The job that was the cur-
+ rent job becomes the previous job. When the current job terminates,
+ the previous job becomes the current job. If there is only a single
+ job, %\b%+\b+ and %\b%-\b- can both be used to refer to that job. In output per-
+ taining to jobs (e.g., the output of the j\bjo\bob\bbs\bs command), the current job
+ is always marked with a +\b+, and the previous job with a -\b-.
+
+ Simply naming a job can be used to bring it into the foreground: %\b%1\b1 is
+ a synonym for "fg %1", bringing job 1 from the background into the
+ foreground. Similarly, "%1 &" resumes job 1 in the background, equiva-
+ lent to "bg %1".
+
+ The shell learns immediately whenever a job changes state. Normally,
+ b\bba\bas\bsh\bh waits until it is about to print a prompt before notifying the
+ user about changes in a job's status so as to not interrupt any other
+ output, though it will notify of changes in a job's status after a
+ foreground command in a list completes, before executing the next com-
+ mand in the list. If the -\b-b\bb option to the s\bse\bet\bt builtin command is en-
+ abled, b\bba\bas\bsh\bh reports status changes immediately. B\bBa\bas\bsh\bh executes any trap
+ on S\bSI\bIG\bGC\bCH\bHL\bLD\bD for each child that terminates.
+
+ When a job terminates and b\bba\bas\bsh\bh notifies the user about it, b\bba\bas\bsh\bh removes
+ the job from the table. It will not appear in j\bjo\bob\bbs\bs output, but w\bwa\bai\bit\bt
+ will report its exit status, as long as it's supplied the process ID
+ associated with the job as an argument. When the table is empty, job
+ numbers start over at 1.
+
+ If a user attempts to exit b\bba\bas\bsh\bh while jobs are stopped (or, if the
+ c\bch\bhe\bec\bck\bkj\bjo\bob\bbs\bs shell option has been enabled using the s\bsh\bho\bop\bpt\bt builtin, run-
+ ning), the shell prints a warning message, and, if the c\bch\bhe\bec\bck\bkj\bjo\bob\bbs\bs option
+ is enabled, lists the jobs and their statuses. The j\bjo\bob\bbs\bs command may
+ then be used to inspect their status. If the user immediately attempts
+ to exit again, without an intervening command, b\bba\bas\bsh\bh does not print an-
+ other warning, and terminates any stopped jobs.
+
+ When the shell is waiting for a job or process using the w\bwa\bai\bit\bt builtin,
+ and job control is enabled, w\bwa\bai\bit\bt will return when the job changes
+ state. The -\b-f\bf option causes w\bwa\bai\bit\bt to wait until the job or process ter-
+ minates before returning.
+
+P\bPR\bRO\bOM\bMP\bPT\bTI\bIN\bNG\bG
+ When executing interactively, b\bba\bas\bsh\bh displays the primary prompt P\bPS\bS1\b1 when
+ it is ready to read a command, and the secondary prompt P\bPS\bS2\b2 when it
+ needs more input to complete a command.
+
+ B\bBa\bas\bsh\bh examines the value of the array variable P\bPR\bRO\bOM\bMP\bPT\bT_\b_C\bCO\bOM\bMM\bMA\bAN\bND\bD just be-
+ fore printing each primary prompt. If any elements in P\bPR\bRO\bOM\bMP\bPT\bT_\b_C\bCO\bOM\bMM\bMA\bAN\bND\bD
+ are set and non-null, Bash executes each value, in numeric order, just
+ as if it had been typed on the command line. B\bBa\bas\bsh\bh displays P\bPS\bS0\b0 after
+ it reads a command but before executing it.
+
+ B\bBa\bas\bsh\bh displays P\bPS\bS4\b4 as described above before tracing each command when
+ the -\b-x\bx option is enabled.
+
+ B\bBa\bas\bsh\bh allows the prompt strings P\bPS\bS0\b0, P\bPS\bS1\b1, P\bPS\bS2\b2, and P\bPS\bS4\b4, to be customized
+ by inserting a number of backslash-escaped special characters that are
+ decoded as follows:
+
+ \\b\a\ba An ASCII bell character (07).
+ \\b\d\bd The date in "Weekday Month Date" format (e.g., "Tue May
+ 26").
+ \\b\D\bD{\b{_\bf_\bo_\br_\bm_\ba_\bt}\b}
+ The _\bf_\bo_\br_\bm_\ba_\bt is passed to _\bs_\bt_\br_\bf_\bt_\bi_\bm_\be(3) and the result is in-
+ serted into the prompt string; an empty _\bf_\bo_\br_\bm_\ba_\bt results in
+ a locale-specific time representation. The braces are
+ required.
+ \\b\e\be An ASCII escape character (033).
+ \\b\h\bh The hostname up to the first ".".
+ \\b\H\bH The hostname.
+ \\b\j\bj The number of jobs currently managed by the shell.
+ \\b\l\bl The basename of the shell's terminal device name (e.g.,
+ "ttys0").
+ \\b\n\bn A newline.
+ \\b\r\br A carriage return.
+ \\b\s\bs The name of the shell: the basename of $\b$0\b0 (the portion
+ following the final slash).
+ \\b\t\bt The current time in 24-hour HH:MM:SS format.
+ \\b\T\bT The current time in 12-hour HH:MM:SS format.
+ \\b\@\b@ The current time in 12-hour am/pm format.
+ \\b\A\bA The current time in 24-hour HH:MM format.
+ \\b\u\bu The username of the current user.
+ \\b\v\bv The b\bba\bas\bsh\bh version (e.g., 2.00).
+ \\b\V\bV The b\bba\bas\bsh\bh release, version + patch level (e.g., 2.00.0)
+ \\b\w\bw The value of the P\bPW\bWD\bD shell variable ($\b$P\bPW\bWD\bD), with $\b$H\bHO\bOM\bME\bE
+ abbreviated with a tilde (uses the value of the
+ P\bPR\bRO\bOM\bMP\bPT\bT_\b_D\bDI\bIR\bRT\bTR\bRI\bIM\bM variable).
+ \\b\W\bW The basename of $\b$P\bPW\bWD\bD, with $\b$H\bHO\bOM\bME\bE abbreviated with a
+ tilde.
+ \\b\!\b! The history number of this command.
+ \\b\#\b# The command number of this command.
+ \\b\$\b$ If the effective UID is 0, a #\b#, otherwise a $\b$.
+ \\b\_\bn_\bn_\bn The character corresponding to the octal number _\bn_\bn_\bn.
+ \\b\\\b\ A backslash.
+ \\b\[\b[ Begin a sequence of non-printing characters, which could
+ be used to embed a terminal control sequence into the
+ prompt.
+ \\b\]\b] End a sequence of non-printing characters.
+
+ The command number and the history number are usually different: the
+ history number of a command is its position in the history list, which
+ may include commands restored from the history file (see H\bHI\bIS\bST\bTO\bOR\bRY\bY be-
+ low), while the command number is the position in the sequence of com-
+ mands executed during the current shell session. After the string is
+ decoded, it is expanded via parameter expansion, command substitution,
+ arithmetic expansion, and quote removal, subject to the value of the
+ p\bpr\bro\bom\bmp\bpt\btv\bva\bar\brs\bs shell option (see the description of the s\bsh\bho\bop\bpt\bt command under
+ S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below). This can have unwanted side effects if
+ escaped portions of the string appear within command substitution or
+ contain characters special to word expansion.
+
+R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE
+ This is the library that handles reading input when using an interac-
+ tive shell, unless the -\b--\b-n\bno\boe\bed\bdi\bit\bti\bin\bng\bg option is supplied at shell invoca-
+ tion. Line editing is also used when using the -\b-e\be option to the r\bre\bea\bad\bd
+ builtin. By default, the line editing commands are similar to those of
+ emacs; a vi-style line editing interface is also available. Line edit-
+ ing can be enabled at any time using the -\b-o\bo e\bem\bma\bac\bcs\bs or -\b-o\bo v\bvi\bi options to
+ the s\bse\bet\bt builtin (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below). To turn off line
+ editing after the shell is running, use the +\b+o\bo e\bem\bma\bac\bcs\bs or +\b+o\bo v\bvi\bi options
+ to the s\bse\bet\bt builtin.
+
+ R\bRe\bea\bad\bdl\bli\bin\bne\be N\bNo\bot\bta\bat\bti\bio\bon\bn
+ This section uses Emacs-style editing concepts and uses its notation
+ for keystrokes. Control keys are denoted by C-_\bk_\be_\by, e.g., C-n means
+ Control-N. Similarly, _\bm_\be_\bt_\ba keys are denoted by M-_\bk_\be_\by, so M-x means
+ Meta-X. The Meta key is often labeled "Alt" or "Option".
+
+ On keyboards without a _\bM_\be_\bt_\ba key, M-_\bx means ESC _\bx, i.e., press and re-
+ lease the Escape key, then press and release the _\bx key, in sequence.
+ This makes ESC the _\bm_\be_\bt_\ba _\bp_\br_\be_\bf_\bi_\bx. The combination M-C-_\bx means ESC Con-
+ trol-_\bx: press and release the Escape key, then press and hold the Con-
+ trol key while pressing the _\bx key, then release both.
+
+ On some keyboards, the Meta key modifier produces characters with the
+ eighth bit (0200) set. You can use the e\ben\bna\bab\bbl\ble\be-\b-m\bme\bet\bta\ba-\b-k\bke\bey\by variable to
+ control whether or not it does this, if the keyboard allows it. On
+ many others, the terminal or terminal emulator converts the metafied
+ key to a key sequence beginning with ESC as described in the preceding
+ paragraph.
+
+ If your _\bM_\be_\bt_\ba key produces a key sequence with the ESC meta prefix, you
+ can make M-_\bk_\be_\by key bindings you specify (see R\bRe\bea\bad\bdl\bli\bin\bne\be K\bKe\bey\by B\bBi\bin\bnd\bdi\bin\bng\bgs\bs be-
+ low) do the same thing by setting the f\bfo\bor\brc\bce\be-\b-m\bme\bet\bta\ba-\b-p\bpr\bre\bef\bfi\bix\bx variable.
+
+ R\bRe\bea\bad\bdl\bli\bin\bne\be commands may be given numeric _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs, which normally act as
+ a repeat count. Sometimes, however, it is the sign of the argument
+ that is significant. Passing a negative argument to a command that
+ acts in the forward direction (e.g., k\bki\bil\bll\bl-\b-l\bli\bin\bne\be) makes that command act
+ in a backward direction. Commands whose behavior with arguments devi-
+ ates from this are noted below.
+
+ The _\bp_\bo_\bi_\bn_\bt is the current cursor position, and _\bm_\ba_\br_\bk refers to a saved
+ cursor position. The text between the point and mark is referred to as
+ the _\br_\be_\bg_\bi_\bo_\bn. R\bRe\bea\bad\bdl\bli\bin\bne\be has the concept of an _\ba_\bc_\bt_\bi_\bv_\be _\br_\be_\bg_\bi_\bo_\bn: when the re-
+ gion is active, r\bre\bea\bad\bdl\bli\bin\bne\be redisplay highlights the region using the
+ value of the a\bac\bct\bti\biv\bve\be-\b-r\bre\beg\bgi\bio\bon\bn-\b-s\bst\bta\bar\brt\bt-\b-c\bco\bol\blo\bor\br variable. The e\ben\bna\bab\bbl\ble\be-\b-a\bac\bct\bti\biv\bve\be-\b-r\bre\be-\b-
+ g\bgi\bio\bon\bn variable turns this on and off. Several commands set the region
+ to active; those are noted below.
+
+ When a command is described as _\bk_\bi_\bl_\bl_\bi_\bn_\bg text, the text deleted is saved
+ for possible future retrieval (_\by_\ba_\bn_\bk_\bi_\bn_\bg). The killed text is saved in a
+ _\bk_\bi_\bl_\bl _\br_\bi_\bn_\bg. Consecutive kills accumulate the deleted text into one
+ unit, which can be yanked all at once. Commands which do not kill text
+ separate the chunks of text on the kill ring.
+
+ R\bRe\bea\bad\bdl\bli\bin\bne\be I\bIn\bni\bit\bti\bia\bal\bli\biz\bza\bat\bti\bio\bon\bn
+ R\bRe\bea\bad\bdl\bli\bin\bne\be is customized by putting commands in an initialization file
+ (the _\bi_\bn_\bp_\bu_\bt_\br_\bc file). The name of this file is taken from the value of
+ the I\bIN\bNP\bPU\bUT\bTR\bRC\bC shell variable. If that variable is unset, the default is
+ _\b~_\b/_\b._\bi_\bn_\bp_\bu_\bt_\br_\bc. If that file does not exist or cannot be read, r\bre\bea\bad\bdl\bli\bin\bne\be
+ looks for _\b/_\be_\bt_\bc_\b/_\bi_\bn_\bp_\bu_\bt_\br_\bc. When a program that uses the r\bre\bea\bad\bdl\bli\bin\bne\be library
+ starts up, r\bre\bea\bad\bdl\bli\bin\bne\be reads the initialization file and sets the key
+ bindings and variables found there, before reading any user input.
+
+ There are only a few basic constructs allowed in the inputrc file.
+ Blank lines are ignored. Lines beginning with a #\b# are comments. Lines
+ beginning with a $\b$ indicate conditional constructs. Other lines denote
+ key bindings and variable settings.
+
+ The default key-bindings in this section may be changed using key bind-
+ ing commands in the _\bi_\bn_\bp_\bu_\bt_\br_\bc file. Programs that use the r\bre\bea\bad\bdl\bli\bin\bne\be li-
+ brary, including b\bba\bas\bsh\bh, may add their own commands and bindings.
+
+ For example, placing
+
+ M-Control-u: universal-argument
+ or
+ C-Meta-u: universal-argument
+
+ into the _\bi_\bn_\bp_\bu_\bt_\br_\bc would make M-C-u execute the r\bre\bea\bad\bdl\bli\bin\bne\be command _\bu_\bn_\bi_\bv_\be_\br_\b-
+ _\bs_\ba_\bl_\b-_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt.
+
+ Key bindings may contain the following symbolic character names: _\bD_\bE_\bL,
+ _\bE_\bS_\bC, _\bE_\bS_\bC_\bA_\bP_\bE, _\bL_\bF_\bD, _\bN_\bE_\bW_\bL_\bI_\bN_\bE, _\bR_\bE_\bT, _\bR_\bE_\bT_\bU_\bR_\bN, _\bR_\bU_\bB_\bO_\bU_\bT (a destructive back-
+ space), _\bS_\bP_\bA_\bC_\bE, _\bS_\bP_\bC, and _\bT_\bA_\bB.
+
+ In addition to command names, r\bre\bea\bad\bdl\bli\bin\bne\be allows keys to be bound to a
+ string that is inserted when the key is pressed (a _\bm_\ba_\bc_\br_\bo). The differ-
+ ence between a macro and a command is that a macro is enclosed in sin-
+ gle or double quotes.
+
+ R\bRe\bea\bad\bdl\bli\bin\bne\be K\bKe\bey\by B\bBi\bin\bnd\bdi\bin\bng\bgs\bs
+ The syntax for controlling key bindings in the _\bi_\bn_\bp_\bu_\bt_\br_\bc file is simple.
+ All that is required is the name of the command or the text of a macro
+ and a key sequence to which it should be bound. The key sequence may
+ be specified in one of two ways: as a symbolic key name, possibly with
+ _\bM_\be_\bt_\ba_\b- or _\bC_\bo_\bn_\bt_\br_\bo_\bl_\b- prefixes, or as a key sequence composed of one or
+ more characters enclosed in double quotes. The key sequence and name
+ are separated by a colon. There can be no whitespace between the name
+ and the colon.
+
+ When using the form k\bke\bey\byn\bna\bam\bme\be:_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be or _\bm_\ba_\bc_\br_\bo, _\bk_\be_\by_\bn_\ba_\bm_\be is the name
+ of a key spelled out in English. For example:
+
+ Control-u: universal-argument
+ Meta-Rubout: backward-kill-word
+ Control-o: "> output"
+
+ In the above example, _\bC_\b-_\bu is bound to the function u\bun\bni\biv\bve\ber\brs\bsa\bal\bl-\b-a\bar\brg\bgu\bum\bme\ben\bnt\bt,
+ _\bM_\b-_\bD_\bE_\bL is bound to the function b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-k\bki\bil\bll\bl-\b-w\bwo\bor\brd\bd, and _\bC_\b-_\bo is bound to
+ run the macro expressed on the right hand side (that is, to insert the
+ text "> output" into the line).
+
+ In the second form, "\b"k\bke\bey\bys\bse\beq\bq"\b":_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be or _\bm_\ba_\bc_\br_\bo, k\bke\bey\bys\bse\beq\bq differs
+ from k\bke\bey\byn\bna\bam\bme\be above in that strings denoting an entire key sequence may
+ be specified by placing the sequence within double quotes. Some GNU
+ Emacs style key escapes can be used, as in the following example, but
+ none of the symbolic character names are recognized.
+
+ "\C-u": universal-argument
+ "\C-x\C-r": re-read-init-file
+ "\e[11~": "Function Key 1"
+
+ In this example, _\bC_\b-_\bu is again bound to the function u\bun\bni\biv\bve\ber\brs\bsa\bal\bl-\b-a\bar\brg\bgu\bum\bme\ben\bnt\bt.
+ _\bC_\b-_\bx _\bC_\b-_\br is bound to the function r\bre\be-\b-r\bre\bea\bad\bd-\b-i\bin\bni\bit\bt-\b-f\bfi\bil\ble\be, and _\bE_\bS_\bC _\b[ _\b1 _\b1 _\b~ is
+ bound to insert the text "Function Key 1".
+
+ The full set of GNU Emacs style escape sequences available when speci-
+ fying key sequences is
+ \\b\C\bC-\b- A control prefix.
+ \\b\M\bM-\b- Adding the meta prefix or converting the following char-
+ acter to a meta character, as described below under
+ f\bfo\bor\brc\bce\be-\b-m\bme\bet\bta\ba-\b-p\bpr\bre\bef\bfi\bix\bx.
+ \\b\e\be An escape character.
+ \\b\\\b\ Backslash.
+ \\b\"\b" Literal ", a double quote.
+ \\b\'\b' Literal ', a single quote.
+
+ In addition to the GNU Emacs style escape sequences, a second set of
+ backslash escapes is available:
+ \\b\a\ba alert (bell)
+ \\b\b\bb backspace
+ \\b\d\bd delete
+ \\b\f\bf form feed
+ \\b\n\bn newline
+ \\b\r\br carriage return
+ \\b\t\bt horizontal tab
+ \\b\v\bv vertical tab
+ \\b\_\bn_\bn_\bn The eight-bit character whose value is the octal value
+ _\bn_\bn_\bn (one to three digits).
+ \\b\x\bx_\bH_\bH The eight-bit character whose value is the hexadecimal
+ value _\bH_\bH (one or two hex digits).
+
+ When entering the text of a macro, single or double quotes must be used
+ to indicate a macro definition. Unquoted text is assumed to be a func-
+ tion name. The backslash escapes described above are expanded in the
+ macro body. Backslash quotes any other character in the macro text,
+ including " and '.
+
+ B\bBa\bas\bsh\bh will display or modify the current r\bre\bea\bad\bdl\bli\bin\bne\be key bindings with the
+ b\bbi\bin\bnd\bd builtin command. The -\b-o\bo e\bem\bma\bac\bcs\bs or -\b-o\bo v\bvi\bi options to the s\bse\bet\bt builtin
+ (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below) change the editing mode during in-
+ teractive use.
+
+ R\bRe\bea\bad\bdl\bli\bin\bne\be V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs
+ R\bRe\bea\bad\bdl\bli\bin\bne\be has variables that can be used to further customize its behav-
+ ior. A variable may be set in the _\bi_\bn_\bp_\bu_\bt_\br_\bc file with a statement of the
+ form
+
+ s\bse\bet\bt _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be_\b-_\bn_\ba_\bm_\be _\bv_\ba_\bl_\bu_\be
+ or using the b\bbi\bin\bnd\bd builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+
+ Except where noted, r\bre\bea\bad\bdl\bli\bin\bne\be variables can take the values O\bOn\bn or O\bOf\bff\bf
+ (without regard to case). Unrecognized variable names are ignored.
+ When r\bre\bea\bad\bdl\bli\bin\bne\be reads a variable value, empty or null values, "on" (case-
+ insensitive), and "1" are equivalent to O\bOn\bn. All other values are
+ equivalent to O\bOf\bff\bf.
+
+ The b\bbi\bin\bnd\bd -\b-V\bV command lists the current r\bre\bea\bad\bdl\bli\bin\bne\be variable names and val-
+ ues (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below).
+
+ The variables and their default values are:
+
+ a\bac\bct\bti\biv\bve\be-\b-r\bre\beg\bgi\bio\bon\bn-\b-s\bst\bta\bar\brt\bt-\b-c\bco\bol\blo\bor\br
+ A string variable that controls the text color and background
+ when displaying the text in the active region (see the descrip-
+ tion of e\ben\bna\bab\bbl\ble\be-\b-a\bac\bct\bti\biv\bve\be-\b-r\bre\beg\bgi\bio\bon\bn below). This string must not take
+ up any physical character positions on the display, so it should
+ consist only of terminal escape sequences. It is output to the
+ terminal before displaying the text in the active region. This
+ variable is reset to the default value whenever the terminal
+ type changes. The default value is the string that puts the
+ terminal in standout mode, as obtained from the terminal's ter-
+ minfo description. A sample value might be "\e[01;33m".
+ a\bac\bct\bti\biv\bve\be-\b-r\bre\beg\bgi\bio\bon\bn-\b-e\ben\bnd\bd-\b-c\bco\bol\blo\bor\br
+ A string variable that "undoes" the effects of a\bac\bct\bti\biv\bve\be-\b-r\bre\be-\b-
+ g\bgi\bio\bon\bn-\b-s\bst\bta\bar\brt\bt-\b-c\bco\bol\blo\bor\br and restores "normal" terminal display appear-
+ ance after displaying text in the active region. This string
+ must not take up any physical character positions on the dis-
+ play, so it should consist only of terminal escape sequences.
+ It is output to the terminal after displaying the text in the
+ active region. This variable is reset to the default value
+ whenever the terminal type changes. The default value is the
+ string that restores the terminal from standout mode, as ob-
+ tained from the terminal's terminfo description. A sample value
+ might be "\e[0m".
+ b\bbe\bel\bll\bl-\b-s\bst\bty\byl\ble\be (\b(a\bau\bud\bdi\bib\bbl\ble\be)\b)
+ Controls what happens when r\bre\bea\bad\bdl\bli\bin\bne\be wants to ring the terminal
+ bell. If set to n\bno\bon\bne\be, r\bre\bea\bad\bdl\bli\bin\bne\be never rings the bell. If set to
+ v\bvi\bis\bsi\bib\bbl\ble\be, r\bre\bea\bad\bdl\bli\bin\bne\be uses a visible bell if one is available. If
+ set to a\bau\bud\bdi\bib\bbl\ble\be, r\bre\bea\bad\bdl\bli\bin\bne\be attempts to ring the terminal's bell.
+ b\bbi\bin\bnd\bd-\b-t\btt\bty\by-\b-s\bsp\bpe\bec\bci\bia\bal\bl-\b-c\bch\bha\bar\brs\bs (\b(O\bOn\bn)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be attempts to bind the control characters
+ that are treated specially by the kernel's terminal driver to
+ their r\bre\bea\bad\bdl\bli\bin\bne\be equivalents. These override the default r\bre\bea\bad\bdl\bli\bin\bne\be
+ bindings described here. Type "stty -a" at a b\bba\bas\bsh\bh prompt to see
+ your current terminal settings, including the special control
+ characters (usually c\bcc\bch\bha\bar\brs\bs). This binding takes place on each
+ call to r\bre\bea\bad\bdl\bli\bin\bne\be, so changes made by "stty" can take effect.
+ b\bbl\bli\bin\bnk\bk-\b-m\bma\bat\btc\bch\bhi\bin\bng\bg-\b-p\bpa\bar\bre\ben\bn (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be attempts to briefly move the cursor to an
+ opening parenthesis when a closing parenthesis is inserted.
+ c\bco\bol\blo\bor\bre\bed\bd-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn-\b-p\bpr\bre\bef\bfi\bix\bx (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, when listing completions, r\bre\bea\bad\bdl\bli\bin\bne\be displays the
+ common prefix of the set of possible completions using a differ-
+ ent color. The color definitions are taken from the value of
+ the L\bLS\bS_\b_C\bCO\bOL\bLO\bOR\bRS\bS environment variable. If there is a color defini-
+ tion in $\b$L\bLS\bS_\b_C\bCO\bOL\bLO\bOR\bRS\bS for the custom suffix ".readline-colored-com-
+ pletion-prefix", r\bre\bea\bad\bdl\bli\bin\bne\be uses this color for the common prefix
+ instead of its default.
+ c\bco\bol\blo\bor\bre\bed\bd-\b-s\bst\bta\bat\bts\bs (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be displays possible completions using dif-
+ ferent colors to indicate their file type. The color defini-
+ tions are taken from the value of the L\bLS\bS_\b_C\bCO\bOL\bLO\bOR\bRS\bS environment
+ variable.
+ c\bco\bom\bmm\bme\ben\bnt\bt-\b-b\bbe\beg\bgi\bin\bn (\b("#\b#")\b)
+ The string that the r\bre\bea\bad\bdl\bli\bin\bne\be i\bin\bns\bse\ber\brt\bt-\b-c\bco\bom\bmm\bme\ben\bnt\bt command inserts.
+ This command is bound to M\bM-\b-#\b# in emacs mode and to #\b# in vi com-
+ mand mode.
+ c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn-\b-d\bdi\bis\bsp\bpl\bla\bay\by-\b-w\bwi\bid\bdt\bth\bh (\b(-\b-1\b1)\b)
+ The number of screen columns used to display possible matches
+ when performing completion. The value is ignored if it is less
+ than 0 or greater than the terminal screen width. A value of 0
+ causes matches to be displayed one per line. The default value
+ is -1.
+ c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn-\b-i\big\bgn\bno\bor\bre\be-\b-c\bca\bas\bse\be (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be performs filename matching and completion
+ in a case-insensitive fashion.
+ c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn-\b-m\bma\bap\bp-\b-c\bca\bas\bse\be (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, and c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn-\b-i\big\bgn\bno\bor\bre\be-\b-c\bca\bas\bse\be is enabled, r\bre\bea\bad\bdl\bli\bin\bne\be
+ treats hyphens (_\b-) and underscores (_\b_) as equivalent when per-
+ forming case-insensitive filename matching and completion.
+ c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn-\b-p\bpr\bre\bef\bfi\bix\bx-\b-d\bdi\bis\bsp\bpl\bla\bay\by-\b-l\ble\ben\bng\bgt\bth\bh (\b(0\b0)\b)
+ The maximum length in characters of the common prefix of a list
+ of possible completions that is displayed without modification.
+ When set to a value greater than zero, r\bre\bea\bad\bdl\bli\bin\bne\be replaces common
+ prefixes longer than this value with an ellipsis when displaying
+ possible completions. If a completion begins with a period, and
+ e\bea\bad\bdl\bli\bin\bne\be is completing filenames, it uses three underscores in-
+ stead of an ellipsis.
+ c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn-\b-q\bqu\bue\ber\bry\by-\b-i\bit\bte\bem\bms\bs (\b(1\b10\b00\b0)\b)
+ This determines when the user is queried about viewing the num-
+ ber of possible completions generated by the p\bpo\bos\bss\bsi\bib\bbl\ble\be-\b-c\bco\bom\bmp\bpl\ble\be-\b-
+ t\bti\bio\bon\bns\bs command. It may be set to any integer value greater than
+ or equal to zero. If the number of possible completions is
+ greater than or equal to the value of this variable, r\bre\bea\bad\bdl\bli\bin\bne\be
+ asks whether or not the user wishes to view them; otherwise
+ r\bre\bea\bad\bdl\bli\bin\bne\be simply lists them on the terminal. A zero value means
+ r\bre\bea\bad\bdl\bli\bin\bne\be should never ask; negative values are treated as zero.
+ c\bco\bon\bnv\bve\ber\brt\bt-\b-m\bme\bet\bta\ba (\b(O\bOn\bn)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be converts characters it reads that have
+ the eighth bit set to an ASCII key sequence by clearing the
+ eighth bit and prefixing it with an escape character (converting
+ the character to have the meta prefix). The default is _\bO_\bn, but
+ r\bre\bea\bad\bdl\bli\bin\bne\be sets it to _\bO_\bf_\bf if the locale contains characters whose
+ encodings may include bytes with the eighth bit set. This vari-
+ able is dependent on the L\bLC\bC_\b_C\bCT\bTY\bYP\bPE\bE locale category, and may
+ change if the locale changes. This variable also affects key
+ bindings; see the description of f\bfo\bor\brc\bce\be-\b-m\bme\bet\bta\ba-\b-p\bpr\bre\bef\bfi\bix\bx below.
+ d\bdi\bis\bsa\bab\bbl\ble\be-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be inhibits word completion. Completion
+ characters are inserted into the line as if they had been mapped
+ to s\bse\bel\blf\bf-\b-i\bin\bns\bse\ber\brt\bt.
+ e\bec\bch\bho\bo-\b-c\bco\bon\bnt\btr\bro\bol\bl-\b-c\bch\bha\bar\bra\bac\bct\bte\ber\brs\bs (\b(O\bOn\bn)\b)
+ When set to O\bOn\bn, on operating systems that indicate they support
+ it, r\bre\bea\bad\bdl\bli\bin\bne\be echoes a character corresponding to a signal gener-
+ ated from the keyboard.
+ e\bed\bdi\bit\bti\bin\bng\bg-\b-m\bmo\bod\bde\be (\b(e\bem\bma\bac\bcs\bs)\b)
+ Controls whether r\bre\bea\bad\bdl\bli\bin\bne\be uses a set of key bindings similar to
+ _\bE_\bm_\ba_\bc_\bs or _\bv_\bi. e\bed\bdi\bit\bti\bin\bng\bg-\b-m\bmo\bod\bde\be can be set to either e\bem\bma\bac\bcs\bs or v\bvi\bi.
+ e\bem\bma\bac\bcs\bs-\b-m\bmo\bod\bde\be-\b-s\bst\btr\bri\bin\bng\bg (\b(@\b@)\b)
+ If the _\bs_\bh_\bo_\bw_\b-_\bm_\bo_\bd_\be_\b-_\bi_\bn_\b-_\bp_\br_\bo_\bm_\bp_\bt variable is enabled, this string is
+ displayed immediately before the last line of the primary prompt
+ when emacs editing mode is active. The value is expanded like a
+ key binding, so the standard set of meta- and control- prefixes
+ and backslash escape sequences is available. The \1 and \2 es-
+ capes begin and end sequences of non-printing characters, which
+ can be used to embed a terminal control sequence into the mode
+ string.
+ e\ben\bna\bab\bbl\ble\be-\b-a\bac\bct\bti\biv\bve\be-\b-r\bre\beg\bgi\bio\bon\bn (\b(O\bOn\bn)\b)
+ When this variable is set to _\bO_\bn, r\bre\bea\bad\bdl\bli\bin\bne\be allows certain com-
+ mands to designate the region as _\ba_\bc_\bt_\bi_\bv_\be. When the region is ac-
+ tive, r\bre\bea\bad\bdl\bli\bin\bne\be highlights the text in the region using the value
+ of the a\bac\bct\bti\biv\bve\be-\b-r\bre\beg\bgi\bio\bon\bn-\b-s\bst\bta\bar\brt\bt-\b-c\bco\bol\blo\bor\br variable, which defaults to the
+ string that enables the terminal's standout mode. The active
+ region shows the text inserted by bracketed-paste and any match-
+ ing text found by incremental and non-incremental history
+ searches.
+ e\ben\bna\bab\bbl\ble\be-\b-b\bbr\bra\bac\bck\bke\bet\bte\bed\bd-\b-p\bpa\bas\bst\bte\be (\b(O\bOn\bn)\b)
+ When set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be configures the terminal to insert each
+ paste into the editing buffer as a single string of characters,
+ instead of treating each character as if it had been read from
+ the keyboard. This is called _\bb_\br_\ba_\bc_\bk_\be_\bt_\be_\bd_\b-_\bp_\ba_\bs_\bt_\be _\bm_\bo_\bd_\be; it prevents
+ r\bre\bea\bad\bdl\bli\bin\bne\be from executing any editing commands bound to key se-
+ quences appearing in the pasted text.
+ e\ben\bna\bab\bbl\ble\be-\b-k\bke\bey\byp\bpa\bad\bd (\b(O\bOf\bff\bf)\b)
+ When set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be tries to enable the application keypad
+ when it is called. Some systems need this to enable the arrow
+ keys.
+ e\ben\bna\bab\bbl\ble\be-\b-m\bme\bet\bta\ba-\b-k\bke\bey\by (\b(O\bOn\bn)\b)
+ When set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be tries to enable any meta modifier key
+ the terminal claims to support. On many terminals, the Meta key
+ is used to send eight-bit characters; this variable checks for
+ the terminal capability that indicates the terminal can enable
+ and disable a mode that sets the eighth bit of a character
+ (0200) if the Meta key is held down when the character is typed
+ (a meta character).
+ e\bex\bxp\bpa\ban\bnd\bd-\b-t\bti\bil\bld\bde\be (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be performs tilde expansion when it attempts
+ word completion.
+ f\bfo\bor\brc\bce\be-\b-m\bme\bet\bta\ba-\b-p\bpr\bre\bef\bfi\bix\bx (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be modifies its behavior when binding key
+ sequences containing \M- or Meta- (see K\bKe\bey\by B\bBi\bin\bnd\bdi\bin\bng\bgs\bs above) by
+ converting a key sequence of the form \M-_\bC or Meta-_\bC to the two-
+ character sequence E\bES\bSC\bC _\bC (adding the meta prefix). If
+ f\bfo\bor\brc\bce\be-\b-m\bme\bet\bta\ba-\b-p\bpr\bre\bef\bfi\bix\bx is set to O\bOf\bff\bf (the default), r\bre\bea\bad\bdl\bli\bin\bne\be uses the
+ value of the c\bco\bon\bnv\bve\ber\brt\bt-\b-m\bme\bet\bta\ba variable to determine whether to per-
+ form this conversion: if c\bco\bon\bnv\bve\ber\brt\bt-\b-m\bme\bet\bta\ba is O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be performs
+ the conversion described above; if it is O\bOf\bff\bf, r\bre\bea\bad\bdl\bli\bin\bne\be converts
+ _\bC to a meta character by setting the eighth bit (0200).
+ h\bhi\bis\bst\bto\bor\bry\by-\b-p\bpr\bre\bes\bse\ber\brv\bve\be-\b-p\bpo\boi\bin\bnt\bt (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, the history code attempts to place point at the
+ same location on each history line retrieved with p\bpr\bre\bev\bvi\bio\bou\bus\bs-\b-h\bhi\bis\bs-\b-
+ t\bto\bor\bry\by or n\bne\bex\bxt\bt-\b-h\bhi\bis\bst\bto\bor\bry\by.
+ h\bhi\bis\bst\bto\bor\bry\by-\b-s\bsi\biz\bze\be (\b(u\bun\bns\bse\bet\bt)\b)
+ Set the maximum number of history entries saved in the history
+ list. If set to zero, any existing history entries are deleted
+ and no new entries are saved. If set to a value less than zero,
+ the number of history entries is not limited. By default, b\bba\bas\bsh\bh
+ sets the maximum number of history entries to the value of the
+ H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE shell variable. Setting _\bh_\bi_\bs_\bt_\bo_\br_\by_\b-_\bs_\bi_\bz_\be to a non-numeric
+ value will set the maximum number of history entries to 500.
+ h\bho\bor\bri\biz\bzo\bon\bnt\bta\bal\bl-\b-s\bsc\bcr\bro\bol\bll\bl-\b-m\bmo\bod\bde\be (\b(O\bOf\bff\bf)\b)
+ Setting this variable to O\bOn\bn makes r\bre\bea\bad\bdl\bli\bin\bne\be use a single line for
+ display, scrolling the input horizontally on a single screen
+ line when it becomes longer than the screen width rather than
+ wrapping to a new line. This setting is automatically enabled
+ for terminals of height 1.
+ i\bin\bnp\bpu\but\bt-\b-m\bme\bet\bta\ba (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be enables eight-bit input (that is, it does
+ not clear the eighth bit in the characters it reads), regardless
+ of what the terminal claims it can support. The default is _\bO_\bf_\bf,
+ but r\bre\bea\bad\bdl\bli\bin\bne\be sets it to _\bO_\bn if the locale contains characters
+ whose encodings may include bytes with the eighth bit set. This
+ variable is dependent on the L\bLC\bC_\b_C\bCT\bTY\bYP\bPE\bE locale category, and its
+ value may change if the locale changes. The name m\bme\bet\bta\ba-\b-f\bfl\bla\bag\bg is a
+ synonym for i\bin\bnp\bpu\but\bt-\b-m\bme\bet\bta\ba.
+ i\bis\bse\bea\bar\brc\bch\bh-\b-t\bte\ber\brm\bmi\bin\bna\bat\bto\bor\brs\bs (\b("C\bC-\b-[\b[C\bC-\b-j\bj")\b)
+ The string of characters that should terminate an incremental
+ search without subsequently executing the character as a com-
+ mand. If this variable has not been given a value, the charac-
+ ters _\bE_\bS_\bC and C\bC-\b-j\bj terminate an incremental search.
+ k\bke\bey\bym\bma\bap\bp (\b(e\bem\bma\bac\bcs\bs)\b)
+ Set the current r\bre\bea\bad\bdl\bli\bin\bne\be keymap. The set of valid keymap names
+ is _\be_\bm_\ba_\bc_\bs_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bs_\bt_\ba_\bn_\bd_\ba_\br_\bd_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bm_\be_\bt_\ba_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bc_\bt_\bl_\bx_\b, _\bv_\bi_\b, _\bv_\bi_\b-_\bc_\bo_\bm_\b-
+ _\bm_\ba_\bn_\bd, and _\bv_\bi_\b-_\bi_\bn_\bs_\be_\br_\bt. _\bv_\bi is equivalent to _\bv_\bi_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd; _\be_\bm_\ba_\bc_\bs is
+ equivalent to _\be_\bm_\ba_\bc_\bs_\b-_\bs_\bt_\ba_\bn_\bd_\ba_\br_\bd. The default value is _\be_\bm_\ba_\bc_\bs; the
+ value of e\bed\bdi\bit\bti\bin\bng\bg-\b-m\bmo\bod\bde\be also affects the default keymap.
+ k\bke\bey\bys\bse\beq\bq-\b-t\bti\bim\bme\beo\bou\but\bt (\b(5\b50\b00\b0)\b)
+ Specifies the duration r\bre\bea\bad\bdl\bli\bin\bne\be will wait for a character when
+ reading an ambiguous key sequence (one that can form a complete
+ key sequence using the input read so far, or can take additional
+ input to complete a longer key sequence). If r\bre\bea\bad\bdl\bli\bin\bne\be does not
+ receive any input within the timeout, it uses the shorter but
+ complete key sequence. The value is specified in milliseconds,
+ so a value of 1000 means that r\bre\bea\bad\bdl\bli\bin\bne\be will wait one second for
+ additional input. If this variable is set to a value less than
+ or equal to zero, or to a non-numeric value, r\bre\bea\bad\bdl\bli\bin\bne\be waits un-
+ til another key is pressed to decide which key sequence to com-
+ plete.
+ m\bma\bar\brk\bk-\b-d\bdi\bir\bre\bec\bct\bto\bor\bri\bie\bes\bs (\b(O\bOn\bn)\b)
+ If set to O\bOn\bn, completed directory names have a slash appended.
+ m\bma\bar\brk\bk-\b-m\bmo\bod\bdi\bif\bfi\bie\bed\bd-\b-l\bli\bin\bne\bes\bs (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be displays history lines that have been
+ modified with a preceding asterisk (*\b*).
+ m\bma\bar\brk\bk-\b-s\bsy\bym\bml\bli\bin\bnk\bke\bed\bd-\b-d\bdi\bir\bre\bec\bct\bto\bor\bri\bie\bes\bs (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, completed names which are symbolic links to direc-
+ tories have a slash appended, subject to the value of m\bma\bar\brk\bk-\b-d\bdi\bi-\b-
+ r\bre\bec\bct\bto\bor\bri\bie\bes\bs.
+ m\bma\bat\btc\bch\bh-\b-h\bhi\bid\bdd\bde\ben\bn-\b-f\bfi\bil\ble\bes\bs (\b(O\bOn\bn)\b)
+ This variable, when set to O\bOn\bn, forces r\bre\bea\bad\bdl\bli\bin\bne\be to match files
+ whose names begin with a "." (hidden files) when performing
+ filename completion. If set to O\bOf\bff\bf, the user must include the
+ leading "." in the filename to be completed.
+ m\bme\ben\bnu\bu-\b-c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-d\bdi\bis\bsp\bpl\bla\bay\by-\b-p\bpr\bre\bef\bfi\bix\bx (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, menu completion displays the common prefix of the
+ list of possible completions (which may be empty) before cycling
+ through the list.
+ o\bou\but\btp\bpu\but\bt-\b-m\bme\bet\bta\ba (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be displays characters with the eighth bit
+ set directly rather than as a meta-prefixed escape sequence.
+ The default is _\bO_\bf_\bf, but r\bre\bea\bad\bdl\bli\bin\bne\be sets it to _\bO_\bn if the locale
+ contains characters whose encodings may include bytes with the
+ eighth bit set. This variable is dependent on the L\bLC\bC_\b_C\bCT\bTY\bYP\bPE\bE lo-
+ cale category, and its value may change if the locale changes.
+ p\bpa\bag\bge\be-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs (\b(O\bOn\bn)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be uses an internal pager resembling _\bm_\bo_\br_\be(1)
+ to display a screenful of possible completions at a time.
+ p\bpr\bre\bef\bfe\ber\br-\b-v\bvi\bis\bsi\bib\bbl\ble\be-\b-b\bbe\bel\bll\bl
+ See b\bbe\bel\bll\bl-\b-s\bst\bty\byl\ble\be.
+ p\bpr\bri\bin\bnt\bt-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs-\b-h\bho\bor\bri\biz\bzo\bon\bnt\bta\bal\bll\bly\by (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be displays completions with matches sorted
+ horizontally in alphabetical order, rather than down the screen.
+ r\bre\bev\bve\ber\brt\bt-\b-a\bal\bll\bl-\b-a\bat\bt-\b-n\bne\bew\bwl\bli\bin\bne\be (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be will undo all changes to history lines
+ before returning when executing a\bac\bcc\bce\bep\bpt\bt-\b-l\bli\bin\bne\be. By default, his-
+ tory lines may be modified and retain individual undo lists
+ across calls to r\bre\bea\bad\bdl\bli\bin\bne\be.
+ s\bse\bea\bar\brc\bch\bh-\b-i\big\bgn\bno\bor\bre\be-\b-c\bca\bas\bse\be (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, r\bre\bea\bad\bdl\bli\bin\bne\be performs incremental and non-incremental
+ history list searches in a case-insensitive fashion.
+ s\bsh\bho\bow\bw-\b-a\bal\bll\bl-\b-i\bif\bf-\b-a\bam\bmb\bbi\big\bgu\buo\bou\bus\bs (\b(O\bOf\bff\bf)\b)
+ This alters the default behavior of the completion functions.
+ If set to O\bOn\bn, words which have more than one possible completion
+ cause the matches to be listed immediately instead of ringing
+ the bell.
+ s\bsh\bho\bow\bw-\b-a\bal\bll\bl-\b-i\bif\bf-\b-u\bun\bnm\bmo\bod\bdi\bif\bfi\bie\bed\bd (\b(O\bOf\bff\bf)\b)
+ This alters the default behavior of the completion functions in
+ a fashion similar to s\bsh\bho\bow\bw-\b-a\bal\bll\bl-\b-i\bif\bf-\b-a\bam\bmb\bbi\big\bgu\buo\bou\bus\bs. If set to O\bOn\bn, words
+ which have more than one possible completion without any possi-
+ ble partial completion (the possible completions don't share a
+ common prefix) cause the matches to be listed immediately in-
+ stead of ringing the bell.
+ s\bsh\bho\bow\bw-\b-m\bmo\bod\bde\be-\b-i\bin\bn-\b-p\bpr\bro\bom\bmp\bpt\bt (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, add a string to the beginning of the prompt indi-
+ cating the editing mode: emacs, vi command, or vi insertion.
+ The mode strings are user-settable (e.g., _\be_\bm_\ba_\bc_\bs_\b-_\bm_\bo_\bd_\be_\b-_\bs_\bt_\br_\bi_\bn_\bg).
+ s\bsk\bki\bip\bp-\b-c\bco\bom\bmp\bpl\ble\bet\bte\bed\bd-\b-t\bte\bex\bxt\bt (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, this alters the default completion behavior when
+ inserting a single match into the line. It's only active when
+ performing completion in the middle of a word. If enabled,
+ r\bre\bea\bad\bdl\bli\bin\bne\be does not insert characters from the completion that
+ match characters after point in the word being completed, so
+ portions of the word following the cursor are not duplicated.
+ v\bvi\bi-\b-c\bcm\bmd\bd-\b-m\bmo\bod\bde\be-\b-s\bst\btr\bri\bin\bng\bg (\b((\b(c\bcm\bmd\bd)\b))\b)
+ If the _\bs_\bh_\bo_\bw_\b-_\bm_\bo_\bd_\be_\b-_\bi_\bn_\b-_\bp_\br_\bo_\bm_\bp_\bt variable is enabled, this string is
+ displayed immediately before the last line of the primary prompt
+ when vi editing mode is active and in command mode. The value
+ is expanded like a key binding, so the standard set of meta- and
+ control- prefixes and backslash escape sequences is available.
+ The \1 and \2 escapes begin and end sequences of non-printing
+ characters, which can be used to embed a terminal control se-
+ quence into the mode string.
+ v\bvi\bi-\b-i\bin\bns\bs-\b-m\bmo\bod\bde\be-\b-s\bst\btr\bri\bin\bng\bg (\b((\b(i\bin\bns\bs)\b))\b)
+ If the _\bs_\bh_\bo_\bw_\b-_\bm_\bo_\bd_\be_\b-_\bi_\bn_\b-_\bp_\br_\bo_\bm_\bp_\bt variable is enabled, this string is
+ displayed immediately before the last line of the primary prompt
+ when vi editing mode is active and in insertion mode. The value
+ is expanded like a key binding, so the standard set of meta- and
+ control- prefixes and backslash escape sequences is available.
+ The \1 and \2 escapes begin and end sequences of non-printing
+ characters, which can be used to embed a terminal control se-
+ quence into the mode string.
+ v\bvi\bis\bsi\bib\bbl\ble\be-\b-s\bst\bta\bat\bts\bs (\b(O\bOf\bff\bf)\b)
+ If set to O\bOn\bn, a character denoting a file's type as reported by
+ _\bs_\bt_\ba_\bt(2) is appended to the filename when listing possible com-
+ pletions.
+
+ R\bRe\bea\bad\bdl\bli\bin\bne\be C\bCo\bon\bnd\bdi\bit\bti\bio\bon\bna\bal\bl C\bCo\bon\bns\bst\btr\bru\buc\bct\bts\bs
+ R\bRe\bea\bad\bdl\bli\bin\bne\be implements a facility similar in spirit to the conditional
+ compilation features of the C preprocessor which allows key bindings
+ and variable settings to be performed as the result of tests. There
+ are four parser directives available.
+
+ $\b$i\bif\bf The $\b$i\bif\bf construct allows bindings to be made based on the edit-
+ ing mode, the terminal being used, or the application using
+ r\bre\bea\bad\bdl\bli\bin\bne\be. The text of the test, after any comparison operator,
+ extends to the end of the line; unless otherwise noted, no char-
+ acters are required to isolate it.
+
+ m\bmo\bod\bde\be The m\bmo\bod\bde\be=\b= form of the $\b$i\bif\bf directive is used to test
+ whether r\bre\bea\bad\bdl\bli\bin\bne\be is in emacs or vi mode. This may be
+ used in conjunction with the s\bse\bet\bt k\bke\bey\bym\bma\bap\bp command, for in-
+ stance, to set bindings in the _\be_\bm_\ba_\bc_\bs_\b-_\bs_\bt_\ba_\bn_\bd_\ba_\br_\bd and
+ _\be_\bm_\ba_\bc_\bs_\b-_\bc_\bt_\bl_\bx keymaps only if r\bre\bea\bad\bdl\bli\bin\bne\be is starting out in
+ emacs mode.
+
+ t\bte\ber\brm\bm The t\bte\ber\brm\bm=\b= form may be used to include terminal-specific
+ key bindings, perhaps to bind the key sequences output by
+ the terminal's function keys. The word on the right side
+ of the =\b= is tested against both the full name of the ter-
+ minal and the portion of the terminal name before the
+ first -\b-. This allows _\bx_\bt_\be_\br_\bm to match both _\bx_\bt_\be_\br_\bm and
+ _\bx_\bt_\be_\br_\bm_\b-_\b2_\b5_\b6_\bc_\bo_\bl_\bo_\br, for instance.
+
+ v\bve\ber\brs\bsi\bio\bon\bn
+ The v\bve\ber\brs\bsi\bio\bon\bn test may be used to perform comparisons
+ against specific r\bre\bea\bad\bdl\bli\bin\bne\be versions. The v\bve\ber\brs\bsi\bio\bon\bn expands
+ to the current r\bre\bea\bad\bdl\bli\bin\bne\be version. The set of comparison
+ operators includes =\b=, (and =\b==\b=), !\b!=\b=, <\b<=\b=, >\b>=\b=, <\b<, and >\b>.
+ The version number supplied on the right side of the op-
+ erator consists of a major version number, an optional
+ decimal point, and an optional minor version (e.g., 7\b7.\b.1\b1).
+ If the minor version is omitted, it defaults to 0\b0. The
+ operator may be separated from the string v\bve\ber\brs\bsi\bio\bon\bn and
+ from the version number argument by whitespace.
+
+ _\ba_\bp_\bp_\bl_\bi_\bc_\ba_\bt_\bi_\bo_\bn
+ The _\ba_\bp_\bp_\bl_\bi_\bc_\ba_\bt_\bi_\bo_\bn construct is used to include application-
+ specific settings. Each program using the r\bre\bea\bad\bdl\bli\bin\bne\be li-
+ brary sets the _\ba_\bp_\bp_\bl_\bi_\bc_\ba_\bt_\bi_\bo_\bn _\bn_\ba_\bm_\be, and an initialization
+ file can test for a particular value. This could be used
+ to bind key sequences to functions useful for a specific
+ program. For instance, the following command adds a key
+ sequence that quotes the current or previous word in
+ b\bba\bas\bsh\bh:
+
+ $\b$i\bif\bf Bash
+ # Quote the current or previous word
+ "\C-xq": "\eb\"\ef\""
+ $\b$e\ben\bnd\bdi\bif\bf
+
+ _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be
+ The _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be construct provides simple equality tests for
+ r\bre\bea\bad\bdl\bli\bin\bne\be variables and values. The permitted comparison
+ operators are _\b=, _\b=_\b=, and _\b!_\b=. The variable name must be
+ separated from the comparison operator by whitespace; the
+ operator may be separated from the value on the right
+ hand side by whitespace. String and boolean variables
+ may be tested. Boolean variables must be tested against
+ the values _\bo_\bn and _\bo_\bf_\bf.
+
+ $\b$e\bel\bls\bse\be Commands in this branch of the $\b$i\bif\bf directive are executed if the
+ test fails.
+
+ $\b$e\ben\bnd\bdi\bif\bf This command, as seen in the previous example, terminates an $\b$i\bif\bf
+ command.
+
+ $\b$i\bin\bnc\bcl\blu\bud\bde\be
+ This directive takes a single filename as an argument and reads
+ commands and key bindings from that file. For example, the fol-
+ lowing directive would read _\b/_\be_\bt_\bc_\b/_\bi_\bn_\bp_\bu_\bt_\br_\bc:
+
+ $\b$i\bin\bnc\bcl\blu\bud\bde\be _\b/_\be_\bt_\bc_\b/_\bi_\bn_\bp_\bu_\bt_\br_\bc
+
+ S\bSe\bea\bar\brc\bch\bhi\bin\bng\bg
+ R\bRe\bea\bad\bdl\bli\bin\bne\be provides commands for searching through the command history
+ (see H\bHI\bIS\bST\bTO\bOR\bRY\bY below) for lines containing a specified string. There are
+ two search modes: _\bi_\bn_\bc_\br_\be_\bm_\be_\bn_\bt_\ba_\bl and _\bn_\bo_\bn_\b-_\bi_\bn_\bc_\br_\be_\bm_\be_\bn_\bt_\ba_\bl.
+
+ Incremental searches begin before the user has finished typing the
+ search string. As each character of the search string is typed, r\bre\bea\bad\bd-\b-
+ l\bli\bin\bne\be displays the next entry from the history matching the string typed
+ so far. An incremental search requires only as many characters as
+ needed to find the desired history entry. When using emacs editing
+ mode, type C\bC-\b-r\br to search backward in the history for a particular
+ string. Typing C\bC-\b-s\bs searches forward through the history. The charac-
+ ters present in the value of the i\bis\bse\bea\bar\brc\bch\bh-\b-t\bte\ber\brm\bmi\bin\bna\bat\bto\bor\brs\bs variable are used
+ to terminate an incremental search. If that variable has not been as-
+ signed a value, _\bE_\bS_\bC and C\bC-\b-j\bj terminate an incremental search. C\bC-\b-g\bg
+ aborts an incremental search and restores the original line. When the
+ search is terminated, the history entry containing the search string
+ becomes the current line.
+
+ To find other matching entries in the history list, type C\bC-\b-r\br or C\bC-\b-s\bs as
+ appropriate. This searches backward or forward in the history for the
+ next entry matching the search string typed so far. Any other key se-
+ quence bound to a r\bre\bea\bad\bdl\bli\bin\bne\be command terminates the search and executes
+ that command. For instance, a newline terminates the search and ac-
+ cepts the line, thereby executing the command from the history list. A
+ movement command will terminate the search, make the last line found
+ the current line, and begin editing.
+
+ R\bRe\bea\bad\bdl\bli\bin\bne\be remembers the last incremental search string. If two C\bC-\b-r\brs are
+ typed without any intervening characters defining a new search string,
+ r\bre\bea\bad\bdl\bli\bin\bne\be uses any remembered search string.
+
+ Non-incremental searches read the entire search string before starting
+ to search for matching history entries. The search string may be typed
+ by the user or be part of the contents of the current line.
+
+ R\bRe\bea\bad\bdl\bli\bin\bne\be C\bCo\bom\bmm\bma\ban\bnd\bd N\bNa\bam\bme\bes\bs
+ The following is a list of the names of the commands and the default
+ key sequences to which they are bound. Command names without an accom-
+ panying key sequence are unbound by default.
+
+ In the following descriptions, _\bp_\bo_\bi_\bn_\bt refers to the current cursor posi-
+ tion, and _\bm_\ba_\br_\bk refers to a cursor position saved by the s\bse\bet\bt-\b-m\bma\bar\brk\bk com-
+ mand. The text between the point and mark is referred to as the _\br_\be_\b-
+ _\bg_\bi_\bo_\bn. R\bRe\bea\bad\bdl\bli\bin\bne\be has the concept of an _\ba_\bc_\bt_\bi_\bv_\be _\br_\be_\bg_\bi_\bo_\bn: when the region is
+ active, r\bre\bea\bad\bdl\bli\bin\bne\be redisplay highlights the region using the value of the
+ a\bac\bct\bti\biv\bve\be-\b-r\bre\beg\bgi\bio\bon\bn-\b-s\bst\bta\bar\brt\bt-\b-c\bco\bol\blo\bor\br variable. The e\ben\bna\bab\bbl\ble\be-\b-a\bac\bct\bti\biv\bve\be-\b-r\bre\beg\bgi\bio\bon\bn r\bre\bea\bad\bdl\bli\bin\bne\be
+ variable turns this on and off. Several commands set the region to ac-
+ tive; those are noted below.
+
+ C\bCo\bom\bmm\bma\ban\bnd\bds\bs f\bfo\bor\br M\bMo\bov\bvi\bin\bng\bg
+ b\bbe\beg\bgi\bin\bnn\bni\bin\bng\bg-\b-o\bof\bf-\b-l\bli\bin\bne\be (\b(C\bC-\b-a\ba)\b)
+ Move to the start of the current line. This may also be bound
+ to the Home key on some keyboards.
+ e\ben\bnd\bd-\b-o\bof\bf-\b-l\bli\bin\bne\be (\b(C\bC-\b-e\be)\b)
+ Move to the end of the line. This may also be bound to the End
+ key on some keyboards.
+ f\bfo\bor\brw\bwa\bar\brd\bd-\b-c\bch\bha\bar\br (\b(C\bC-\b-f\bf)\b)
+ Move forward a character. This may also be bound to the right
+ arrow key on some keyboards.
+ b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-c\bch\bha\bar\br (\b(C\bC-\b-b\bb)\b)
+ Move back a character. This may also be bound to the left arrow
+ key on some keyboards.
+ f\bfo\bor\brw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-f\bf)\b)
+ Move forward to the end of the next word. Words are composed of
+ alphanumeric characters (letters and digits).
+ b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-b\bb)\b)
+ Move back to the start of the current or previous word. Words
+ are composed of alphanumeric characters (letters and digits).
+ s\bsh\bhe\bel\bll\bl-\b-f\bfo\bor\brw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-C\bC-\b-f\bf)\b)
+ Move forward to the end of the next word. Words are delimited
+ by non-quoted shell metacharacters.
+ s\bsh\bhe\bel\bll\bl-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-C\bC-\b-b\bb)\b)
+ Move back to the start of the current or previous word. Words
+ are delimited by non-quoted shell metacharacters.
+ p\bpr\bre\bev\bvi\bio\bou\bus\bs-\b-s\bsc\bcr\bre\bee\ben\bn-\b-l\bli\bin\bne\be
+ Attempt to move point to the same physical screen column on the
+ previous physical screen line. This will not have the desired
+ effect if the current r\bre\bea\bad\bdl\bli\bin\bne\be line does not take up more than
+ one physical line or if point is not greater than the length of
+ the prompt plus the screen width.
+ n\bne\bex\bxt\bt-\b-s\bsc\bcr\bre\bee\ben\bn-\b-l\bli\bin\bne\be
+ Attempt to move point to the same physical screen column on the
+ next physical screen line. This will not have the desired ef-
+ fect if the current r\bre\bea\bad\bdl\bli\bin\bne\be line does not take up more than one
+ physical line or if the length of the current r\bre\bea\bad\bdl\bli\bin\bne\be line is
+ not greater than the length of the prompt plus the screen width.
+ c\bcl\ble\bea\bar\br-\b-d\bdi\bis\bsp\bpl\bla\bay\by (\b(M\bM-\b-C\bC-\b-l\bl)\b)
+ Clear the screen and, if possible, the terminal's scrollback
+ buffer, then redraw the current line, leaving the current line
+ at the top of the screen.
+ c\bcl\ble\bea\bar\br-\b-s\bsc\bcr\bre\bee\ben\bn (\b(C\bC-\b-l\bl)\b)
+ Clear the screen, then redraw the current line, leaving the cur-
+ rent line at the top of the screen. With a numeric argument,
+ refresh the current line without clearing the screen.
+ r\bre\bed\bdr\bra\baw\bw-\b-c\bcu\bur\brr\bre\ben\bnt\bt-\b-l\bli\bin\bne\be
+ Refresh the current line.
+
+ C\bCo\bom\bmm\bma\ban\bnd\bds\bs f\bfo\bor\br M\bMa\ban\bni\bip\bpu\bul\bla\bat\bti\bin\bng\bg t\bth\bhe\be H\bHi\bis\bst\bto\bor\bry\by
+ a\bac\bcc\bce\bep\bpt\bt-\b-l\bli\bin\bne\be (\b(N\bNe\bew\bwl\bli\bin\bne\be,\b, R\bRe\bet\btu\bur\brn\bn)\b)
+ Accept the line regardless of where the cursor is. If this line
+ is non-empty, add it to the history list according to the state
+ of the H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL and H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE variables. If the line is a
+ modified history line, restore the history line to its original
+ state.
+ p\bpr\bre\bev\bvi\bio\bou\bus\bs-\b-h\bhi\bis\bst\bto\bor\bry\by (\b(C\bC-\b-p\bp)\b)
+ Fetch the previous command from the history list, moving back in
+ the list. This may also be bound to the up arrow key on some
+ keyboards.
+ n\bne\bex\bxt\bt-\b-h\bhi\bis\bst\bto\bor\bry\by (\b(C\bC-\b-n\bn)\b)
+ Fetch the next command from the history list, moving forward in
+ the list. This may also be bound to the down arrow key on some
+ keyboards.
+ b\bbe\beg\bgi\bin\bnn\bni\bin\bng\bg-\b-o\bof\bf-\b-h\bhi\bis\bst\bto\bor\bry\by (\b(M\bM-\b-<\b<)\b)
+ Move to the first line in the history.
+ e\ben\bnd\bd-\b-o\bof\bf-\b-h\bhi\bis\bst\bto\bor\bry\by (\b(M\bM-\b->\b>)\b)
+ Move to the end of the input history, i.e., the line currently
+ being entered.
+ o\bop\bpe\ber\bra\bat\bte\be-\b-a\ban\bnd\bd-\b-g\bge\bet\bt-\b-n\bne\bex\bxt\bt (\b(C\bC-\b-o\bo)\b)
+ Accept the current line for execution as if a newline had been
+ entered, and fetch the next line relative to the current line
+ from the history for editing. A numeric argument, if supplied,
+ specifies the history entry to use instead of the current line.
+ f\bfe\bet\btc\bch\bh-\b-h\bhi\bis\bst\bto\bor\bry\by
+ With a numeric argument, fetch that entry from the history list
+ and make it the current line. Without an argument, move back to
+ the first entry in the history list.
+ r\bre\bev\bve\ber\brs\bse\be-\b-s\bse\bea\bar\brc\bch\bh-\b-h\bhi\bis\bst\bto\bor\bry\by (\b(C\bC-\b-r\br)\b)
+ Search backward starting at the current line and moving "up"
+ through the history as necessary. This is an incremental
+ search. This command sets the region to the matched text and
+ activates the region.
+ f\bfo\bor\brw\bwa\bar\brd\bd-\b-s\bse\bea\bar\brc\bch\bh-\b-h\bhi\bis\bst\bto\bor\bry\by (\b(C\bC-\b-s\bs)\b)
+ Search forward starting at the current line and moving "down"
+ through the history as necessary. This is an incremental
+ search. This command sets the region to the matched text and
+ activates the region.
+ n\bno\bon\bn-\b-i\bin\bnc\bcr\bre\bem\bme\ben\bnt\bta\bal\bl-\b-r\bre\bev\bve\ber\brs\bse\be-\b-s\bse\bea\bar\brc\bch\bh-\b-h\bhi\bis\bst\bto\bor\bry\by (\b(M\bM-\b-p\bp)\b)
+ Search backward through the history starting at the current line
+ using a non-incremental search for a string supplied by the
+ user. The search string may match anywhere in a history line.
+ n\bno\bon\bn-\b-i\bin\bnc\bcr\bre\bem\bme\ben\bnt\bta\bal\bl-\b-f\bfo\bor\brw\bwa\bar\brd\bd-\b-s\bse\bea\bar\brc\bch\bh-\b-h\bhi\bis\bst\bto\bor\bry\by (\b(M\bM-\b-n\bn)\b)
+ Search forward through the history using a non-incremental
+ search for a string supplied by the user. The search string may
+ match anywhere in a history line.
+ h\bhi\bis\bst\bto\bor\bry\by-\b-s\bse\bea\bar\brc\bch\bh-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd
+ Search backward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string must match at the beginning of a history line. This is a
+ non-incremental search. This may be bound to the Page Up key on
+ some keyboards.
+ h\bhi\bis\bst\bto\bor\bry\by-\b-s\bse\bea\bar\brc\bch\bh-\b-f\bfo\bor\brw\bwa\bar\brd\bd
+ Search forward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string must match at the beginning of a history line. This is a
+ non-incremental search. This may be bound to the Page Down key
+ on some keyboards.
+ h\bhi\bis\bst\bto\bor\bry\by-\b-s\bsu\bub\bbs\bst\btr\bri\bin\bng\bg-\b-s\bse\bea\bar\brc\bch\bh-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd
+ Search backward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string may match anywhere in a history line. This is a non-in-
+ cremental search.
+ h\bhi\bis\bst\bto\bor\bry\by-\b-s\bsu\bub\bbs\bst\btr\bri\bin\bng\bg-\b-s\bse\bea\bar\brc\bch\bh-\b-f\bfo\bor\brw\bwa\bar\brd\bd
+ Search forward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string may match anywhere in a history line. This is a non-in-
+ cremental search.
+ y\bya\ban\bnk\bk-\b-n\bnt\bth\bh-\b-a\bar\brg\bg (\b(M\bM-\b-C\bC-\b-y\by)\b)
+ Insert the first argument to the previous command (usually the
+ second word on the previous line) at point. With an argument _\bn,
+ insert the _\bnth word from the previous command (the words in the
+ previous command begin with word 0). A negative argument in-
+ serts the _\bnth word from the end of the previous command. Once
+ the argument _\bn is computed, this uses the history expansion fa-
+ cilities to extract the _\bnth word, as if the "!_\bn" history expan-
+ sion had been specified.
+ y\bya\ban\bnk\bk-\b-l\bla\bas\bst\bt-\b-a\bar\brg\bg (\b(M\bM-\b-.\b.,\b, M\bM-\b-_\b_)\b)
+ Insert the last argument to the previous command (the last word
+ of the previous history entry). With a numeric argument, behave
+ exactly like y\bya\ban\bnk\bk-\b-n\bnt\bth\bh-\b-a\bar\brg\bg. Successive calls to y\bya\ban\bnk\bk-\b-l\bla\bas\bst\bt-\b-a\bar\brg\bg
+ move back through the history list, inserting the last word (or
+ the word specified by the argument to the first call) of each
+ line in turn. Any numeric argument supplied to these successive
+ calls determines the direction to move through the history. A
+ negative argument switches the direction through the history
+ (back or forward). This uses the history expansion facilities
+ to extract the last word, as if the "!$" history expansion had
+ been specified.
+ s\bsh\bhe\bel\bll\bl-\b-e\bex\bxp\bpa\ban\bnd\bd-\b-l\bli\bin\bne\be (\b(M\bM-\b-C\bC-\b-e\be)\b)
+ Expand the line by performing shell word expansions. This per-
+ forms alias and history expansion, $\b$'_\bs_\bt_\br_\bi_\bn_\bg' and $\b$"_\bs_\bt_\br_\bi_\bn_\bg" quot-
+ ing, tilde expansion, parameter and variable expansion, arith-
+ metic expansion, command and process substitution, word split-
+ ting, and quote removal. An explicit argument suppresses com-
+ mand and process substitution. See H\bHI\bIS\bST\bTO\bOR\bRY\bY E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN below for
+ a description of history expansion.
+ h\bhi\bis\bst\bto\bor\bry\by-\b-e\bex\bxp\bpa\ban\bnd\bd-\b-l\bli\bin\bne\be (\b(M\bM-\b-^\b^)\b)
+ Perform history expansion on the current line. See H\bHI\bIS\bST\bTO\bOR\bRY\bY E\bEX\bX-\b-
+ P\bPA\bAN\bNS\bSI\bIO\bON\bN below for a description of history expansion.
+ m\bma\bag\bgi\bic\bc-\b-s\bsp\bpa\bac\bce\be
+ Perform history expansion on the current line and insert a
+ space. See H\bHI\bIS\bST\bTO\bOR\bRY\bY E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN below for a description of history
+ expansion.
+ a\bal\bli\bia\bas\bs-\b-e\bex\bxp\bpa\ban\bnd\bd-\b-l\bli\bin\bne\be
+ Perform alias expansion on the current line. See A\bAL\bLI\bIA\bAS\bSE\bES\bS above
+ for a description of alias expansion.
+ h\bhi\bis\bst\bto\bor\bry\by-\b-a\ban\bnd\bd-\b-a\bal\bli\bia\bas\bs-\b-e\bex\bxp\bpa\ban\bnd\bd-\b-l\bli\bin\bne\be
+ Perform history and alias expansion on the current line.
+ i\bin\bns\bse\ber\brt\bt-\b-l\bla\bas\bst\bt-\b-a\bar\brg\bgu\bum\bme\ben\bnt\bt (\b(M\bM-\b-.\b.,\b, M\bM-\b-_\b_)\b)
+ A synonym for y\bya\ban\bnk\bk-\b-l\bla\bas\bst\bt-\b-a\bar\brg\bg.
+ e\bed\bdi\bit\bt-\b-a\ban\bnd\bd-\b-e\bex\bxe\bec\bcu\but\bte\be-\b-c\bco\bom\bmm\bma\ban\bnd\bd (\b(C\bC-\b-x\bx C\bC-\b-e\be)\b)
+ Invoke an editor on the current command line, and execute the
+ result as shell commands. B\bBa\bas\bsh\bh attempts to invoke $\b$V\bVI\bIS\bSU\bUA\bAL\bL, $\b$E\bED\bD-\b-
+ I\bIT\bTO\bOR\bR, and _\be_\bm_\ba_\bc_\bs as the editor, in that order.
+
+ C\bCo\bom\bmm\bma\ban\bnd\bds\bs f\bfo\bor\br C\bCh\bha\ban\bng\bgi\bin\bng\bg T\bTe\bex\bxt\bt
+ _\be_\bn_\bd_\b-_\bo_\bf_\b-_\bf_\bi_\bl_\be (\b(u\bus\bsu\bua\bal\bll\bly\by C\bC-\b-d\bd)\b)
+ The character indicating end-of-file as set, for example, by
+ _\bs_\bt_\bt_\by(1). If this character is read when there are no characters
+ on the line, and point is at the beginning of the line, r\bre\bea\bad\bdl\bli\bin\bne\be
+ interprets it as the end of input and returns E\bEO\bOF\bF.
+ d\bde\bel\ble\bet\bte\be-\b-c\bch\bha\bar\br (\b(C\bC-\b-d\bd)\b)
+ Delete the character at point. If this function is bound to the
+ same character as the tty E\bEO\bOF\bF character, as C\bC-\b-d\bd commonly is, see
+ above for the effects. This may also be bound to the Delete key
+ on some keyboards.
+ b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-d\bde\bel\ble\bet\bte\be-\b-c\bch\bha\bar\br (\b(R\bRu\bub\bbo\bou\but\bt)\b)
+ Delete the character behind the cursor. When given a numeric
+ argument, save the deleted text on the kill ring.
+ f\bfo\bor\brw\bwa\bar\brd\bd-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-d\bde\bel\ble\bet\bte\be-\b-c\bch\bha\bar\br
+ Delete the character under the cursor, unless the cursor is at
+ the end of the line, in which case the character behind the cur-
+ sor is deleted.
+ q\bqu\buo\bot\bte\bed\bd-\b-i\bin\bns\bse\ber\brt\bt (\b(C\bC-\b-q\bq,\b, C\bC-\b-v\bv)\b)
+ Add the next character typed to the line verbatim. This is how
+ to insert characters like C\bC-\b-q\bq, for example.
+ t\bta\bab\bb-\b-i\bin\bns\bse\ber\brt\bt (\b(C\bC-\b-v\bv T\bTA\bAB\bB)\b)
+ Insert a tab character.
+ s\bse\bel\blf\bf-\b-i\bin\bns\bse\ber\brt\bt (\b(a\ba,\b, b\bb,\b, A\bA,\b, 1\b1,\b, !\b!,\b, ...)\b)
+ Insert the character typed.
+ b\bbr\bra\bac\bck\bke\bet\bte\bed\bd-\b-p\bpa\bas\bst\bte\be-\b-b\bbe\beg\bgi\bin\bn
+ This function is intended to be bound to the "bracketed paste"
+ escape sequence sent by some terminals, and such a binding is
+ assigned by default. It allows r\bre\bea\bad\bdl\bli\bin\bne\be to insert the pasted
+ text as a single unit without treating each character as if it
+ had been read from the keyboard. The pasted characters are in-
+ serted as if each one was bound to s\bse\bel\blf\bf-\b-i\bin\bns\bse\ber\brt\bt instead of exe-
+ cuting any editing commands.
+ Bracketed paste sets the region to the inserted text and acti-
+ vates the region.
+ t\btr\bra\ban\bns\bsp\bpo\bos\bse\be-\b-c\bch\bha\bar\brs\bs (\b(C\bC-\b-t\bt)\b)
+ Drag the character before point forward over the character at
+ point, moving point forward as well. If point is at the end of
+ the line, then this transposes the two characters before point.
+ Negative arguments have no effect.
+ t\btr\bra\ban\bns\bsp\bpo\bos\bse\be-\b-w\bwo\bor\brd\bds\bs (\b(M\bM-\b-t\bt)\b)
+ Drag the word before point past the word after point, moving
+ point past that word as well. If point is at the end of the
+ line, this transposes the last two words on the line.
+ s\bsh\bhe\bel\bll\bl-\b-t\btr\bra\ban\bns\bsp\bpo\bos\bse\be-\b-w\bwo\bor\brd\bds\bs (\b(M\bM-\b-C\bC-\b-t\bt)\b)
+ Drag the word before point past the word after point, moving
+ point past that word as well. If the insertion point is at the
+ end of the line, this transposes the last two words on the line.
+ Word boundaries are the same as s\bsh\bhe\bel\bll\bl-\b-f\bfo\bor\brw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd and
+ s\bsh\bhe\bel\bll\bl-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd.
+ u\bup\bpc\bca\bas\bse\be-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-u\bu)\b)
+ Uppercase the current (or following) word. With a negative ar-
+ gument, uppercase the previous word, but do not move point.
+ d\bdo\bow\bwn\bnc\bca\bas\bse\be-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-l\bl)\b)
+ Lowercase the current (or following) word. With a negative ar-
+ gument, lowercase the previous word, but do not move point.
+ c\bca\bap\bpi\bit\bta\bal\bli\biz\bze\be-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-c\bc)\b)
+ Capitalize the current (or following) word. With a negative ar-
+ gument, capitalize the previous word, but do not move point.
+ o\bov\bve\ber\brw\bwr\bri\bit\bte\be-\b-m\bmo\bod\bde\be
+ Toggle overwrite mode. With an explicit positive numeric argu-
+ ment, switches to overwrite mode. With an explicit non-positive
+ numeric argument, switches to insert mode. This command affects
+ only e\bem\bma\bac\bcs\bs mode; v\bvi\bi mode does overwrite differently. Each call
+ to _\br_\be_\ba_\bd_\bl_\bi_\bn_\be_\b(_\b) starts in insert mode.
+ In overwrite mode, characters bound to s\bse\bel\blf\bf-\b-i\bin\bns\bse\ber\brt\bt replace the
+ text at point rather than pushing the text to the right. Char-
+ acters bound to b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-d\bde\bel\ble\bet\bte\be-\b-c\bch\bha\bar\br replace the character be-
+ fore point with a space. By default, this command is unbound,
+ but may be bound to the Insert key on some keyboards.
+
+ K\bKi\bil\bll\bli\bin\bng\bg a\ban\bnd\bd Y\bYa\ban\bnk\bki\bin\bng\bg
+ k\bki\bil\bll\bl-\b-l\bli\bin\bne\be (\b(C\bC-\b-k\bk)\b)
+ Kill the text from point to the end of the current line. With a
+ negative numeric argument, kill backward from the cursor to the
+ beginning of the line.
+ b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-k\bki\bil\bll\bl-\b-l\bli\bin\bne\be (\b(C\bC-\b-x\bx R\bRu\bub\bbo\bou\but\bt)\b)
+ Kill backward to the beginning of the current line. With a neg-
+ ative numeric argument, kill forward from the cursor to the end
+ of the line.
+ u\bun\bni\bix\bx-\b-l\bli\bin\bne\be-\b-d\bdi\bis\bsc\bca\bar\brd\bd (\b(C\bC-\b-u\bu)\b)
+ Kill backward from point to the beginning of the line, saving
+ the killed text on the kill-ring.
+ k\bki\bil\bll\bl-\b-w\bwh\bho\bol\ble\be-\b-l\bli\bin\bne\be
+ Kill all characters on the current line, no matter where point
+ is.
+ k\bki\bil\bll\bl-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-d\bd)\b)
+ Kill from point to the end of the current word, or if between
+ words, to the end of the next word. Word boundaries are the
+ same as those used by f\bfo\bor\brw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd.
+ b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-k\bki\bil\bll\bl-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-R\bRu\bub\bbo\bou\but\bt)\b)
+ Kill the word behind point. Word boundaries are the same as
+ those used by b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd.
+ s\bsh\bhe\bel\bll\bl-\b-k\bki\bil\bll\bl-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-C\bC-\b-d\bd)\b)
+ Kill from point to the end of the current word, or if between
+ words, to the end of the next word. Word boundaries are the
+ same as those used by s\bsh\bhe\bel\bll\bl-\b-f\bfo\bor\brw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd.
+ s\bsh\bhe\bel\bll\bl-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-k\bki\bil\bll\bl-\b-w\bwo\bor\brd\bd
+ Kill the word behind point. Word boundaries are the same as
+ those used by s\bsh\bhe\bel\bll\bl-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd.
+ u\bun\bni\bix\bx-\b-w\bwo\bor\brd\bd-\b-r\bru\bub\bbo\bou\but\bt (\b(C\bC-\b-w\bw)\b)
+ Kill the word behind point, using white space as a word bound-
+ ary, saving the killed text on the kill-ring.
+ u\bun\bni\bix\bx-\b-f\bfi\bil\ble\ben\bna\bam\bme\be-\b-r\bru\bub\bbo\bou\but\bt
+ Kill the word behind point, using white space and the slash
+ character as the word boundaries, saving the killed text on the
+ kill-ring.
+ d\bde\bel\ble\bet\bte\be-\b-h\bho\bor\bri\biz\bzo\bon\bnt\bta\bal\bl-\b-s\bsp\bpa\bac\bce\be (\b(M\bM-\b-\\b\)\b)
+ Delete all spaces and tabs around point.
+ k\bki\bil\bll\bl-\b-r\bre\beg\bgi\bio\bon\bn
+ Kill the text in the current region.
+ c\bco\bop\bpy\by-\b-r\bre\beg\bgi\bio\bon\bn-\b-a\bas\bs-\b-k\bki\bil\bll\bl
+ Copy the text in the region to the kill buffer, so it can be
+ yanked immediately.
+ c\bco\bop\bpy\by-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd
+ Copy the word before point to the kill buffer. The word bound-
+ aries are the same as b\bba\bac\bck\bkw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd.
+ c\bco\bop\bpy\by-\b-f\bfo\bor\brw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd
+ Copy the word following point to the kill buffer. The word
+ boundaries are the same as f\bfo\bor\brw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd.
+ y\bya\ban\bnk\bk (\b(C\bC-\b-y\by)\b)
+ Yank the top of the kill ring into the buffer at point.
+ y\bya\ban\bnk\bk-\b-p\bpo\bop\bp (\b(M\bM-\b-y\by)\b)
+ Rotate the kill ring, and yank the new top. Only works follow-
+ ing y\bya\ban\bnk\bk or y\bya\ban\bnk\bk-\b-p\bpo\bop\bp.
+
+ N\bNu\bum\bme\ber\bri\bic\bc A\bAr\brg\bgu\bum\bme\ben\bnt\bts\bs
+ d\bdi\big\bgi\bit\bt-\b-a\bar\brg\bgu\bum\bme\ben\bnt\bt (\b(M\bM-\b-0\b0,\b, M\bM-\b-1\b1,\b, ...,\b, M\bM-\b--\b-)\b)
+ Add this digit to the argument already accumulating, or start a
+ new argument. M-- starts a negative argument.
+ u\bun\bni\biv\bve\ber\brs\bsa\bal\bl-\b-a\bar\brg\bgu\bum\bme\ben\bnt\bt
+ This is another way to specify an argument. If this command is
+ followed by one or more digits, optionally with a leading minus
+ sign, those digits define the argument. If the command is fol-
+ lowed by digits, executing u\bun\bni\biv\bve\ber\brs\bsa\bal\bl-\b-a\bar\brg\bgu\bum\bme\ben\bnt\bt again ends the nu-
+ meric argument, but is otherwise ignored. As a special case, if
+ this command is immediately followed by a character that is nei-
+ ther a digit nor minus sign, the argument count for the next
+ command is multiplied by four. The argument count is initially
+ one, so executing this function the first time makes the argu-
+ ment count four, a second time makes the argument count sixteen,
+ and so on.
+
+ C\bCo\bom\bmp\bpl\ble\bet\bti\bin\bng\bg
+ c\bco\bom\bmp\bpl\ble\bet\bte\be (\b(T\bTA\bAB\bB)\b)
+ Attempt to perform completion on the text before point. B\bBa\bas\bsh\bh
+ attempts completion by first checking for any programmable com-
+ pletions for the command word (see P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn be-
+ low), otherwise treating the text as a variable (if the text be-
+ gins with $\b$), username (if the text begins with ~\b~), hostname (if
+ the text begins with @\b@), or command (including aliases, func-
+ tions, and builtins) in turn. If none of these produces a
+ match, it falls back to filename completion.
+ p\bpo\bos\bss\bsi\bib\bbl\ble\be-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs (\b(M\bM-\b-?\b?)\b)
+ List the possible completions of the text before point. When
+ displaying completions, r\bre\bea\bad\bdl\bli\bin\bne\be sets the number of columns used
+ for display to the value of c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn-\b-d\bdi\bis\bsp\bpl\bla\bay\by-\b-w\bwi\bid\bdt\bth\bh, the value
+ of the shell variable C\bCO\bOL\bLU\bUM\bMN\bNS\bS, or the screen width, in that or-
+ der.
+ i\bin\bns\bse\ber\brt\bt-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs (\b(M\bM-\b-*\b*)\b)
+ Insert all completions of the text before point that would have
+ been generated by p\bpo\bos\bss\bsi\bib\bbl\ble\be-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs, separated by a space.
+ m\bme\ben\bnu\bu-\b-c\bco\bom\bmp\bpl\ble\bet\bte\be
+ Similar to c\bco\bom\bmp\bpl\ble\bet\bte\be, but replaces the word to be completed with
+ a single match from the list of possible completions. Repeat-
+ edly executing m\bme\ben\bnu\bu-\b-c\bco\bom\bmp\bpl\ble\bet\bte\be steps through the list of possible
+ completions, inserting each match in turn. At the end of the
+ list of completions, m\bme\ben\bnu\bu-\b-c\bco\bom\bmp\bpl\ble\bet\bte\be rings the bell (subject to
+ the setting of b\bbe\bel\bll\bl-\b-s\bst\bty\byl\ble\be) and restores the original text. An
+ argument of _\bn moves _\bn positions forward in the list of matches;
+ a negative argument moves backward through the list. This com-
+ mand is intended to be bound to T\bTA\bAB\bB, but is unbound by default.
+ m\bme\ben\bnu\bu-\b-c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd
+ Identical to m\bme\ben\bnu\bu-\b-c\bco\bom\bmp\bpl\ble\bet\bte\be, but moves backward through the list
+ of possible completions, as if m\bme\ben\bnu\bu-\b-c\bco\bom\bmp\bpl\ble\bet\bte\be had been given a
+ negative argument. This command is unbound by default.
+ e\bex\bxp\bpo\bor\brt\bt-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs
+ Perform completion on the word before point as described above
+ and write the list of possible completions to r\bre\bea\bad\bdl\bli\bin\bne\be's output
+ stream using the following format, writing information on sepa-
+ rate lines:
+
+ +\bo the number of matches _\bN;
+ +\bo the word being completed;
+ +\bo _\bS:_\bE, where _\bS and _\bE are the start and end offsets of the
+ word in the r\bre\bea\bad\bdl\bli\bin\bne\be line buffer; then
+ +\bo each match, one per line
+
+ If there are no matches, the first line will be "0", and this
+ command does not print any output after the _\bS:_\bE. If there is
+ only a single match, this prints a single line containing it.
+ If there is more than one match, this prints the common prefix
+ of the matches, which may be empty, on the first line after the
+ _\bS:_\bE, then the matches on subsequent lines. In this case, _\bN will
+ include the first line with the common prefix.
+
+ The user or application should be able to accommodate the possi-
+ bility of a blank line. The intent is that the user or applica-
+ tion reads _\bN lines after the line containing _\bS:_\bE to obtain the
+ match list. This command is unbound by default.
+
+ d\bde\bel\ble\bet\bte\be-\b-c\bch\bha\bar\br-\b-o\bor\br-\b-l\bli\bis\bst\bt
+ Deletes the character under the cursor if not at the beginning
+ or end of the line (like d\bde\bel\ble\bet\bte\be-\b-c\bch\bha\bar\br). At the end of the line,
+ it behaves identically to p\bpo\bos\bss\bsi\bib\bbl\ble\be-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs. This command is
+ unbound by default.
+
+ c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-f\bfi\bil\ble\ben\bna\bam\bme\be (\b(M\bM-\b-/\b/)\b)
+ Attempt filename completion on the text before point.
+
+ p\bpo\bos\bss\bsi\bib\bbl\ble\be-\b-f\bfi\bil\ble\ben\bna\bam\bme\be-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs (\b(C\bC-\b-x\bx /\b/)\b)
+ List the possible completions of the text before point, treating
+ it as a filename.
+
+ c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-u\bus\bse\ber\brn\bna\bam\bme\be (\b(M\bM-\b-~\b~)\b)
+ Attempt completion on the text before point, treating it as a
+ username.
+
+ p\bpo\bos\bss\bsi\bib\bbl\ble\be-\b-u\bus\bse\ber\brn\bna\bam\bme\be-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs (\b(C\bC-\b-x\bx ~\b~)\b)
+ List the possible completions of the text before point, treating
+ it as a username.
+
+ c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-v\bva\bar\bri\bia\bab\bbl\ble\be (\b(M\bM-\b-$\b$)\b)
+ Attempt completion on the text before point, treating it as a
+ shell variable.
+
+ p\bpo\bos\bss\bsi\bib\bbl\ble\be-\b-v\bva\bar\bri\bia\bab\bbl\ble\be-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs (\b(C\bC-\b-x\bx $\b$)\b)
+ List the possible completions of the text before point, treating
+ it as a shell variable.
+
+ c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-h\bho\bos\bst\btn\bna\bam\bme\be (\b(M\bM-\b-@\b@)\b)
+ Attempt completion on the text before point, treating it as a
+ hostname.
+
+ p\bpo\bos\bss\bsi\bib\bbl\ble\be-\b-h\bho\bos\bst\btn\bna\bam\bme\be-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs (\b(C\bC-\b-x\bx @\b@)\b)
+ List the possible completions of the text before point, treating
+ it as a hostname.
+
+ c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-c\bco\bom\bmm\bma\ban\bnd\bd (\b(M\bM-\b-!\b!)\b)
+ Attempt completion on the text before point, treating it as a
+ command name. Command completion attempts to match the text
+ against aliases, reserved words, shell functions, shell
+ builtins, and finally executable filenames, in that order.
+
+ p\bpo\bos\bss\bsi\bib\bbl\ble\be-\b-c\bco\bom\bmm\bma\ban\bnd\bd-\b-c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bns\bs (\b(C\bC-\b-x\bx !\b!)\b)
+ List the possible completions of the text before point, treating
+ it as a command name.
+
+ d\bdy\byn\bna\bam\bmi\bic\bc-\b-c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-h\bhi\bis\bst\bto\bor\bry\by (\b(M\bM-\b-T\bTA\bAB\bB)\b)
+ Attempt completion on the text before point, comparing the text
+ against history list entries for possible completion matches.
+
+ d\bda\bab\bbb\bbr\bre\bev\bv-\b-e\bex\bxp\bpa\ban\bnd\bd
+ Attempt menu completion on the text before point, comparing the
+ text against lines from the history list for possible completion
+ matches.
+
+ c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-i\bin\bnt\bto\bo-\b-b\bbr\bra\bac\bce\bes\bs (\b(M\bM-\b-{\b{)\b)
+ Perform filename completion and insert the list of possible com-
+ pletions enclosed within braces so the list is available to the
+ shell (see B\bBr\bra\bac\bce\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn above).
+
+ K\bKe\bey\byb\bbo\boa\bar\brd\bd M\bMa\bac\bcr\bro\bos\bs
+ s\bst\bta\bar\brt\bt-\b-k\bkb\bbd\bd-\b-m\bma\bac\bcr\bro\bo (\b(C\bC-\b-x\bx (\b()\b)
+ Begin saving the characters typed into the current keyboard
+ macro.
+ e\ben\bnd\bd-\b-k\bkb\bbd\bd-\b-m\bma\bac\bcr\bro\bo (\b(C\bC-\b-x\bx )\b))\b)
+ Stop saving the characters typed into the current keyboard macro
+ and store the definition.
+ c\bca\bal\bll\bl-\b-l\bla\bas\bst\bt-\b-k\bkb\bbd\bd-\b-m\bma\bac\bcr\bro\bo (\b(C\bC-\b-x\bx e\be)\b)
+ Re-execute the last keyboard macro defined, by making the char-
+ acters in the macro appear as if typed at the keyboard.
+ p\bpr\bri\bin\bnt\bt-\b-l\bla\bas\bst\bt-\b-k\bkb\bbd\bd-\b-m\bma\bac\bcr\bro\bo (\b()\b)
+ Print the last keyboard macro defined in a format suitable for
+ the _\bi_\bn_\bp_\bu_\bt_\br_\bc file.
+
+ M\bMi\bis\bsc\bce\bel\bll\bla\ban\bne\beo\bou\bus\bs
+ r\bre\be-\b-r\bre\bea\bad\bd-\b-i\bin\bni\bit\bt-\b-f\bfi\bil\ble\be (\b(C\bC-\b-x\bx C\bC-\b-r\br)\b)
+ Read in the contents of the _\bi_\bn_\bp_\bu_\bt_\br_\bc file, and incorporate any
+ bindings or variable assignments found there.
+ a\bab\bbo\bor\brt\bt (\b(C\bC-\b-g\bg)\b)
+ Abort the current editing command and ring the terminal's bell
+ (subject to the setting of b\bbe\bel\bll\bl-\b-s\bst\bty\byl\ble\be).
+ d\bdo\bo-\b-l\blo\bow\bwe\ber\brc\bca\bas\bse\be-\b-v\bve\ber\brs\bsi\bio\bon\bn (\b(M\bM-\b-A\bA,\b, M\bM-\b-B\bB,\b, M\bM-\b-_\bx,\b, ...)\b)
+ If the metafied character _\bx is uppercase, run the command that
+ is bound to the corresponding metafied lowercase character. The
+ behavior is undefined if _\bx is already lowercase.
+ p\bpr\bre\bef\bfi\bix\bx-\b-m\bme\bet\bta\ba (\b(E\bES\bSC\bC)\b)
+ Metafy the next character typed. E\bES\bSC\bC f\bf is equivalent to M\bMe\bet\bta\ba-\b-f\bf.
+ u\bun\bnd\bdo\bo (\b(C\bC-\b-_\b_,\b, C\bC-\b-x\bx C\bC-\b-u\bu)\b)
+ Incremental undo, separately remembered for each line.
+ r\bre\bev\bve\ber\brt\bt-\b-l\bli\bin\bne\be (\b(M\bM-\b-r\br)\b)
+ Undo all changes made to this line. This is like executing the
+ u\bun\bnd\bdo\bo command enough times to return the line to its initial
+ state.
+ t\bti\bil\bld\bde\be-\b-e\bex\bxp\bpa\ban\bnd\bd (\b(M\bM-\b-&\b&)\b)
+ Perform tilde expansion on the current word.
+ s\bse\bet\bt-\b-m\bma\bar\brk\bk (\b(C\bC-\b-@\b@,\b, M\bM-\b-<\b<s\bsp\bpa\bac\bce\be>\b>)\b)
+ Set the mark to the point. If a numeric argument is supplied,
+ set the mark to that position.
+ e\bex\bxc\bch\bha\ban\bng\bge\be-\b-p\bpo\boi\bin\bnt\bt-\b-a\ban\bnd\bd-\b-m\bma\bar\brk\bk (\b(C\bC-\b-x\bx C\bC-\b-x\bx)\b)
+ Swap the point with the mark. Set the current cursor position
+ to the saved position, then set the mark to the old cursor posi-
+ tion.
+ c\bch\bha\bar\bra\bac\bct\bte\ber\br-\b-s\bse\bea\bar\brc\bch\bh (\b(C\bC-\b-]\b])\b)
+ Read a character and move point to the next occurrence of that
+ character. A negative argument searches for previous occur-
+ rences.
+ c\bch\bha\bar\bra\bac\bct\bte\ber\br-\b-s\bse\bea\bar\brc\bch\bh-\b-b\bba\bac\bck\bkw\bwa\bar\brd\bd (\b(M\bM-\b-C\bC-\b-]\b])\b)
+ Read a character and move point to the previous occurrence of
+ that character. A negative argument searches for subsequent oc-
+ currences.
+ s\bsk\bki\bip\bp-\b-c\bcs\bsi\bi-\b-s\bse\beq\bqu\bue\ben\bnc\bce\be
+ Read enough characters to consume a multi-key sequence such as
+ those defined for keys like Home and End. CSI sequences begin
+ with a Control Sequence Indicator (CSI), usually _\bE_\bS_\bC _\b[. If this
+ sequence is bound to "\e[", keys producing CSI sequences have no
+ effect unless explicitly bound to a r\bre\bea\bad\bdl\bli\bin\bne\be command, instead of
+ inserting stray characters into the editing buffer. This is un-
+ bound by default, but usually bound to _\bE_\bS_\bC _\b[.
+ i\bin\bns\bse\ber\brt\bt-\b-c\bco\bom\bmm\bme\ben\bnt\bt (\b(M\bM-\b-#\b#)\b)
+ Without a numeric argument, insert the value of the r\bre\bea\bad\bdl\bli\bin\bne\be
+ c\bco\bom\bmm\bme\ben\bnt\bt-\b-b\bbe\beg\bgi\bin\bn variable at the beginning of the current line. If
+ a numeric argument is supplied, this command acts as a toggle:
+ if the characters at the beginning of the line do not match the
+ value of c\bco\bom\bmm\bme\ben\bnt\bt-\b-b\bbe\beg\bgi\bin\bn, insert the value; otherwise delete the
+ characters in c\bco\bom\bmm\bme\ben\bnt\bt-\b-b\bbe\beg\bgi\bin\bn from the beginning of the line. In
+ either case, the line is accepted as if a newline had been
+ typed. The default value of c\bco\bom\bmm\bme\ben\bnt\bt-\b-b\bbe\beg\bgi\bin\bn causes this command
+ to make the current line a shell comment. If a numeric argument
+ causes the comment character to be removed, the line will be ex-
+ ecuted by the shell.
+ s\bsp\bpe\bel\bll\bl-\b-c\bco\bor\brr\bre\bec\bct\bt-\b-w\bwo\bor\brd\bd (\b(C\bC-\b-x\bx s\bs)\b)
+ Perform spelling correction on the current word, treating it as
+ a directory or filename, in the same way as the c\bcd\bds\bsp\bpe\bel\bll\bl shell
+ option. Word boundaries are the same as those used by
+ s\bsh\bhe\bel\bll\bl-\b-f\bfo\bor\brw\bwa\bar\brd\bd-\b-w\bwo\bor\brd\bd.
+ g\bgl\blo\bob\bb-\b-c\bco\bom\bmp\bpl\ble\bet\bte\be-\b-w\bwo\bor\brd\bd (\b(M\bM-\b-g\bg)\b)
+ Treat the word before point as a pattern for pathname expansion,
+ with an asterisk implicitly appended, then use the pattern to
+ generate a list of matching file names for possible completions.
+ g\bgl\blo\bob\bb-\b-e\bex\bxp\bpa\ban\bnd\bd-\b-w\bwo\bor\brd\bd (\b(C\bC-\b-x\bx *\b*)\b)
+ Treat the word before point as a pattern for pathname expansion,
+ and insert the list of matching file names, replacing the word.
+ If a numeric argument is supplied, append a *\b* before pathname
+ expansion.
+ g\bgl\blo\bob\bb-\b-l\bli\bis\bst\bt-\b-e\bex\bxp\bpa\ban\bns\bsi\bio\bon\bns\bs (\b(C\bC-\b-x\bx g\bg)\b)
+ Display the list of expansions that would have been generated by
+ g\bgl\blo\bob\bb-\b-e\bex\bxp\bpa\ban\bnd\bd-\b-w\bwo\bor\brd\bd and redisplay the line. If a numeric argument
+ is supplied, append a *\b* before pathname expansion.
+ d\bdu\bum\bmp\bp-\b-f\bfu\bun\bnc\bct\bti\bio\bon\bns\bs
+ Print all of the functions and their key bindings to the r\bre\bea\bad\bd-\b-
+ l\bli\bin\bne\be output stream. If a numeric argument is supplied, the out-
+ put is formatted in such a way that it can be made part of an
+ _\bi_\bn_\bp_\bu_\bt_\br_\bc file.
+ d\bdu\bum\bmp\bp-\b-v\bva\bar\bri\bia\bab\bbl\ble\bes\bs
+ Print all of the settable r\bre\bea\bad\bdl\bli\bin\bne\be variables and their values to
+ the r\bre\bea\bad\bdl\bli\bin\bne\be output stream. If a numeric argument is supplied,
+ the output is formatted in such a way that it can be made part
+ of an _\bi_\bn_\bp_\bu_\bt_\br_\bc file.
+ d\bdu\bum\bmp\bp-\b-m\bma\bac\bcr\bro\bos\bs
+ Print all of the r\bre\bea\bad\bdl\bli\bin\bne\be key sequences bound to macros and the
+ strings they output to the r\bre\bea\bad\bdl\bli\bin\bne\be output stream. If a numeric
+ argument is supplied, the output is formatted in such a way that
+ it can be made part of an _\bi_\bn_\bp_\bu_\bt_\br_\bc file.
+ e\bex\bxe\bec\bcu\but\bte\be-\b-n\bna\bam\bme\bed\bd-\b-c\bco\bom\bmm\bma\ban\bnd\bd (\b(M\bM-\b-x\bx)\b)
+ Read a bindable r\bre\bea\bad\bdl\bli\bin\bne\be command name from the input and execute
+ the function to which it's bound, as if the key sequence to
+ which it was bound appeared in the input. If this function is
+ supplied with a numeric argument, it passes that argument to the
+ function it executes.
+ d\bdi\bis\bsp\bpl\bla\bay\by-\b-s\bsh\bhe\bel\bll\bl-\b-v\bve\ber\brs\bsi\bio\bon\bn (\b(C\bC-\b-x\bx C\bC-\b-v\bv)\b)
+ Display version information about the current instance of b\bba\bas\bsh\bh.
+
+ P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn
+ When a user attempts word completion for a command or an argument to a
+ command for which a completion specification (a _\bc_\bo_\bm_\bp_\bs_\bp_\be_\bc) has been de-
+ fined using the c\bco\bom\bmp\bpl\ble\bet\bte\be builtin (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below),
+ r\bre\bea\bad\bdl\bli\bin\bne\be invokes the programmable completion facilities.
+
+ First, b\bba\bas\bsh\bh identifies the command name. If a compspec has been de-
+ fined for that command, the compspec is used to generate the list of
+ possible completions for the word. If the command word is the empty
+ string (completion attempted at the beginning of an empty line), b\bba\bas\bsh\bh
+ uses any compspec defined with the -\b-E\bE option to c\bco\bom\bmp\bpl\ble\bet\bte\be. The -\b-I\bI op-
+ tion to c\bco\bom\bmp\bpl\ble\bet\bte\be indicates that the command word is the first non-as-
+ signment word on the line, or after a command delimiter such as ;\b; or |\b|.
+ This usually indicates command name completion.
+
+ If the command word is a full pathname, b\bba\bas\bsh\bh searches for a compspec
+ for the full pathname first. If there is no compspec for the full
+ pathname, b\bba\bas\bsh\bh attempts to find a compspec for the portion following
+ the final slash. If those searches do not result in a compspec, or if
+ there is no compspec for the command word, b\bba\bas\bsh\bh uses any compspec de-
+ fined with the -\b-D\bD option to c\bco\bom\bmp\bpl\ble\bet\bte\be as the default. If there is no
+ default compspec, b\bba\bas\bsh\bh performs alias expansion on the command word as
+ a final resort, and attempts to find a compspec for the command word
+ resulting from any successful expansion.
+
+ If a compspec is not found, b\bba\bas\bsh\bh performs its default completion as de-
+ scribed above under C\bCo\bom\bmp\bpl\ble\bet\bti\bin\bng\bg. Otherwise, once a compspec has been
+ found, b\bba\bas\bsh\bh uses it to generate the list of matching words.
+
+ First, b\bba\bas\bsh\bh performs the _\ba_\bc_\bt_\bi_\bo_\bn_\bs specified by the compspec. This only
+ returns matches which are prefixes of the word being completed. When
+ the -\b-f\bf or -\b-d\bd option is used for filename or directory name completion,
+ b\bba\bas\bsh\bh uses the shell variable F\bFI\bIG\bGN\bNO\bOR\bRE\bE to filter the matches.
+
+ Next, programmable completion generates matches specified by a pathname
+ expansion pattern supplied as an argument to the -\b-G\bG option. The words
+ generated by the pattern need not match the word being completed. B\bBa\bas\bsh\bh
+ uses the F\bFI\bIG\bGN\bNO\bOR\bRE\bE variable to filter the matches, but does not use the
+ G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE shell variable.
+
+ Next, completion considers the string specified as the argument to the
+ -\b-W\bW option. The string is first split using the characters in the I\bIF\bFS\bS
+ special variable as delimiters. This honors shell quoting within the
+ string, in order to provide a mechanism for the words to contain shell
+ metacharacters or characters in the value of I\bIF\bFS\bS. Each word is then
+ expanded using brace expansion, tilde expansion, parameter and variable
+ expansion, command substitution, and arithmetic expansion, as described
+ above under E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN. The results are split using the rules described
+ above under W\bWo\bor\brd\bd S\bSp\bpl\bli\bit\btt\bti\bin\bng\bg. The results of the expansion are prefix-
+ matched against the word being completed, and the matching words become
+ possible completions.
+
+ After these matches have been generated, b\bba\bas\bsh\bh executes any shell func-
+ tion or command specified with the -\b-F\bF and -\b-C\bC options. When the command
+ or function is invoked, b\bba\bas\bsh\bh assigns values to the C\bCO\bOM\bMP\bP_\b_L\bLI\bIN\bNE\bE,
+ C\bCO\bOM\bMP\bP_\b_P\bPO\bOI\bIN\bNT\bT, C\bCO\bOM\bMP\bP_\b_K\bKE\bEY\bY, and C\bCO\bOM\bMP\bP_\b_T\bTY\bYP\bPE\bE variables as described above under
+ S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs. If a shell function is being invoked, b\bba\bas\bsh\bh also sets
+ the C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDS\bS and C\bCO\bOM\bMP\bP_\b_C\bCW\bWO\bOR\bRD\bD variables. When the function or command
+ is invoked, the first argument ($\b$1\b1) is the name of the command whose
+ arguments are being completed, the second argument ($\b$2\b2) is the word be-
+ ing completed, and the third argument ($\b$3\b3) is the word preceding the
+ word being completed on the current command line. There is no filter-
+ ing of the generated completions against the word being completed; the
+ function or command has complete freedom in generating the matches and
+ they do not need to match a prefix of the word.
+
+ Any function specified with -\b-F\bF is invoked first. The function may use
+ any of the shell facilities, including the c\bco\bom\bmp\bpg\bge\ben\bn and c\bco\bom\bmp\bpo\bop\bpt\bt builtins
+ described below, to generate the matches. It must put the possible
+ completions in the C\bCO\bOM\bMP\bPR\bRE\bEP\bPL\bLY\bY array variable, one per array element.
+
+ Next, any command specified with the -\b-C\bC option is invoked in an envi-
+ ronment equivalent to command substitution. It should print a list of
+ completions, one per line, to the standard output. Backslash will es-
+ cape a newline, if necessary. These are added to the set of possible
+ completions.
+
+ External commands that are invoked to generate completions ( "external
+ completers") receive the word preceding the completion word as an argu-
+ ment, as described above. This provides context that is sometimes use-
+ ful, but may include information that is considered sensitive or part
+ of a word expansion that will not appear in the command line after ex-
+ pansion. That word may be visible in process listings or in audit
+ logs. This may be a concern to users and completion specification au-
+ thors if there is sensitive information on the command line before ex-
+ pansion, since completion takes place before words are expanded. If
+ this is an issue, completion authors should use functions as wrappers
+ around external commands and pass context information to the external
+ command in a different way. External completers can infer context from
+ the C\bCO\bOM\bMP\bP_\b_L\bLI\bIN\bNE\bE and C\bCO\bOM\bMP\bP_\b_P\bPO\bOI\bIN\bNT\bT environment variables, but they need to
+ ensure they break words in the same way r\bre\bea\bad\bdl\bli\bin\bne\be does, using the
+ C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS variable.
+
+ After generating all of the possible completions, b\bba\bas\bsh\bh applies any fil-
+ ter specified with the -\b-X\bX option to the completions in the list. The
+ filter is a pattern as used for pathname expansion; a &\b& in the pattern
+ is replaced with the text of the word being completed. A literal &\b& may
+ be escaped with a backslash; the backslash is removed before attempting
+ a match. Any completion that matches the pattern is removed from the
+ list. A leading !\b! negates the pattern; in this case b\bba\bas\bsh\bh removes any
+ completion that does not match the pattern. If the n\bno\boc\bca\bas\bse\bem\bma\bat\btc\bch\bh shell
+ option is enabled, b\bba\bas\bsh\bh performs the match without regard to the case
+ of alphabetic characters.
+
+ Finally, programmable completion adds any prefix and suffix specified
+ with the -\b-P\bP and -\b-S\bS options, respectively, to each completion, and re-
+ turns the result to r\bre\bea\bad\bdl\bli\bin\bne\be as the list of possible completions.
+
+ If the previously-applied actions do not generate any matches, and the
+ -\b-o\bo d\bdi\bir\brn\bna\bam\bme\bes\bs option was supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be when the compspec was de-
+ fined, b\bba\bas\bsh\bh attempts directory name completion.
+
+ If the -\b-o\bo p\bpl\blu\bus\bsd\bdi\bir\brs\bs option was supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be when the compspec
+ was defined, b\bba\bas\bsh\bh attempts directory name completion and adds any
+ matches to the set of possible completions.
+
+ By default, if a compspec is found, whatever it generates is returned
+ to the completion code as the full set of possible completions. The
+ default b\bba\bas\bsh\bh completions and the r\bre\bea\bad\bdl\bli\bin\bne\be default of filename comple-
+ tion are disabled. If the -\b-o\bo b\bba\bas\bsh\bhd\bde\bef\bfa\bau\bul\blt\bt option was supplied to c\bco\bom\bm-\b-
+ p\bpl\ble\bet\bte\be when the compspec was defined, and the compspec generates no
+ matches, b\bba\bas\bsh\bh attempts its default completions. If the compspec and,
+ if attempted, the default b\bba\bas\bsh\bh completions generate no matches, and the
+ -\b-o\bo d\bde\bef\bfa\bau\bul\blt\bt option was supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be when the compspec was de-
+ fined, programmable completion performs r\bre\bea\bad\bdl\bli\bin\bne\be's default completion.
+
+ The options supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be and c\bco\bom\bmp\bpo\bop\bpt\bt can control how r\bre\bea\bad\bdl\bli\bin\bne\be
+ treats the completions. For instance, the _\b-_\bo _\bf_\bu_\bl_\bl_\bq_\bu_\bo_\bt_\be option tells
+ r\bre\bea\bad\bdl\bli\bin\bne\be to quote the matches as if they were filenames. See the de-
+ scription of c\bco\bom\bmp\bpl\ble\bet\bte\be below for details.
+
+ When a compspec indicates that it wants directory name completion, the
+ programmable completion functions force r\bre\bea\bad\bdl\bli\bin\bne\be to append a slash to
+ completed names which are symbolic links to directories, subject to the
+ value of the m\bma\bar\brk\bk-\b-d\bdi\bir\bre\bec\bct\bto\bor\bri\bie\bes\bs r\bre\bea\bad\bdl\bli\bin\bne\be variable, regardless of the set-
+ ting of the m\bma\bar\brk\bk-\b-s\bsy\bym\bml\bli\bin\bnk\bke\bed\bd-\b-d\bdi\bir\bre\bec\bct\bto\bor\bri\bie\bes\bs r\bre\bea\bad\bdl\bli\bin\bne\be variable.
+
+ There is some support for dynamically modifying completions. This is
+ most useful when used in combination with a default completion speci-
+ fied with c\bco\bom\bmp\bpl\ble\bet\bte\be -\b-D\bD. It's possible for shell functions executed as
+ completion functions to indicate that completion should be retried by
+ returning an exit status of 124. If a shell function returns 124, and
+ changes the compspec associated with the command on which completion is
+ being attempted (supplied as the first argument when the function is
+ executed), programmable completion restarts from the beginning, with an
+ attempt to find a new compspec for that command. This can be used to
+ build a set of completions dynamically as completion is attempted,
+ rather than loading them all at once.
+
+ For instance, assuming that there is a library of compspecs, each kept
+ in a file corresponding to the name of the command, the following de-
+ fault completion function would load completions dynamically:
+ _completion_loader()
+ {
+ . "/etc/bash_completion.d/$1.sh" \
+ >/dev/null 2>&1 && return 124
+ }
+ complete -D -F _completion_loader \
+ -o bashdefault -o default
+
+H\bHI\bIS\bST\bTO\bOR\bRY\bY
+ When the -\b-o\bo h\bhi\bis\bst\bto\bor\bry\by option to the s\bse\bet\bt builtin is enabled, the shell
+ provides access to the _\bc_\bo_\bm_\bm_\ba_\bn_\bd _\bh_\bi_\bs_\bt_\bo_\br_\by, the list of commands previously
+ typed. The value of the H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE variable is used as the number of
+ commands to save in a history list: the shell saves the text of the
+ last H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE commands (default 500). The shell stores each command in
+ the history list prior to parameter and variable expansion (see E\bEX\bXP\bPA\bAN\bN-\b-
+ S\bSI\bIO\bON\bN above) but after history expansion is performed, subject to the
+ values of the shell variables H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE and H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL.
+
+ On startup, b\bba\bas\bsh\bh initializes the history list by reading history en-
+ tries from the file named by the H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE variable (default
+ _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bh_\bi_\bs_\bt_\bo_\br_\by). That file is referred to as the _\bh_\bi_\bs_\bt_\bo_\br_\by _\bf_\bi_\bl_\be. The
+ history file is truncated, if necessary, to contain no more than the
+ number of history entries specified by the value of the H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bES\bSI\bIZ\bZE\bE
+ variable. If H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bES\bSI\bIZ\bZE\bE is unset, or set to null, a non-numeric
+ value, or a numeric value less than zero, the history file is not trun-
+ cated.
+
+ When the history file is read, lines beginning with the history comment
+ character followed immediately by a digit are interpreted as timestamps
+ for the following history line. These timestamps are optionally dis-
+ played depending on the value of the H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable. When
+ present, history timestamps delimit history entries, making multi-line
+ entries possible.
+
+ When a shell with history enabled exits, b\bba\bas\bsh\bh copies the last $\b$H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE
+ entries from the history list to $\b$H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE. If the h\bhi\bis\bst\bta\bap\bpp\bpe\ben\bnd\bd shell
+ option is enabled (see the description of s\bsh\bho\bop\bpt\bt under S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN
+ C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below), b\bba\bas\bsh\bh appends the entries to the history file, other-
+ wise it overwrites the history file. If H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE is unset or null, or
+ if the history file is unwritable, the history is not saved. After
+ saving the history, b\bba\bas\bsh\bh truncates the history file to contain no more
+ than H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bES\bSI\bIZ\bZE\bE lines as described above.
+
+ If the H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable is set, the shell writes the timestamp
+ information associated with each history entry to the history file,
+ marked with the history comment character, so timestamps are preserved
+ across shell sessions. This uses the history comment character to dis-
+ tinguish timestamps from other history lines. As above, when using
+ H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT, the timestamps delimit multi-line history entries.
+
+ The f\bfc\bc builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below) will list or
+ edit and re-execute a portion of the history list. The h\bhi\bis\bst\bto\bor\bry\by builtin
+ can display or modify the history list and manipulate the history file.
+ When using command-line editing, search commands are available in each
+ editing mode that provide access to the history list.
+
+ The shell allows control over which commands are saved on the history
+ list. The H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL and H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE variables are used to save only a
+ subset of the commands entered. If the c\bcm\bmd\bdh\bhi\bis\bst\bt shell option is en-
+ abled, the shell attempts to save each line of a multi-line command in
+ the same history entry, adding semicolons where necessary to preserve
+ syntactic correctness. The l\bli\bit\bth\bhi\bis\bst\bt shell option modifies c\bcm\bmd\bdh\bhi\bis\bst\bt by
+ saving the command with embedded newlines instead of semicolons. See
+ the description of the s\bsh\bho\bop\bpt\bt builtin below under S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS
+ for information on setting and unsetting shell options.
+
+H\bHI\bIS\bST\bTO\bOR\bRY\bY E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN
+ The shell supports a history expansion feature that is similar to the
+ history expansion in c\bcs\bsh\bh. This section describes what syntax features
+ are available.
+
+ History expansion is enabled by default for interactive shells, and can
+ be disabled using the +\b+H\bH option to the s\bse\bet\bt builtin command (see S\bSH\bHE\bEL\bLL\bL
+ B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below). Non-interactive shells do not perform history
+ expansion by default, but it can be enabled with "set -H".
+
+ History expansions introduce words from the history list into the input
+ stream, making it easy to repeat commands, insert the arguments to a
+ previous command into the current input line, or fix errors in previous
+ commands quickly.
+
+ History expansion is performed immediately after a complete line is
+ read, before the shell breaks it into words, and is performed on each
+ line individually. The shell attempts to inform the history expansion
+ functions about quoting still in effect from previous lines.
+
+ It takes place in two parts. The first is to determine which history
+ list entry to use during substitution. The second is to select por-
+ tions of that entry to include into the current one.
+
+ The entry selected from the history is the _\be_\bv_\be_\bn_\bt, and the portions of
+ that entry that are acted upon are _\bw_\bo_\br_\bd_\bs. Various _\bm_\bo_\bd_\bi_\bf_\bi_\be_\br_\bs are avail-
+ able to manipulate the selected words. The entry is split into words
+ in the same fashion as when reading input, so that several _\bm_\be_\bt_\ba_\bc_\bh_\ba_\br_\ba_\bc_\b-
+ _\bt_\be_\br-separated words surrounded by quotes are considered one word. The
+ _\be_\bv_\be_\bn_\bt _\bd_\be_\bs_\bi_\bg_\bn_\ba_\bt_\bo_\br selects the event, the optional _\bw_\bo_\br_\bd _\bd_\be_\bs_\bi_\bg_\bn_\ba_\bt_\bo_\br se-
+ lects words from the event, and various optional _\bm_\bo_\bd_\bi_\bf_\bi_\be_\br_\bs are avail-
+ able to manipulate the selected words.
+
+ History expansions are introduced by the appearance of the history ex-
+ pansion character, which is !\b! by default. History expansions may ap-
+ pear anywhere in the input, but do not nest.
+
+ Only backslash (\\b\) and single quotes can quote the history expansion
+ character, but the history expansion character is also treated as
+ quoted if it immediately precedes the closing double quote in a double-
+ quoted string.
+
+ Several characters inhibit history expansion if found immediately fol-
+ lowing the history expansion character, even if it is unquoted: space,
+ tab, newline, carriage return, =\b=, and the other shell metacharacters
+ defined above.
+
+ There is a special abbreviation for substitution, active when the _\bq_\bu_\bi_\bc_\bk
+ _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\bt_\bi_\bo_\bn character (described above under h\bhi\bis\bst\btc\bch\bha\bar\brs\bs) is the first
+ character on the line. It selects the previous history list entry, us-
+ ing an event designator equivalent to !\b!!\b!, and substitutes one string
+ for another in that entry. It is described below under E\bEv\bve\ben\bnt\bt D\bDe\bes\bsi\big\bgn\bna\ba-\b-
+ t\bto\bor\brs\bs. This is the only history expansion that does not begin with the
+ history expansion character.
+
+ Several shell options settable with the s\bsh\bho\bop\bpt\bt builtin will modify his-
+ tory expansion behavior (see the description of the s\bsh\bho\bop\bpt\bt builtin be-
+ low).and If the h\bhi\bis\bst\btv\bve\ber\bri\bif\bfy\by shell option is enabled, and r\bre\bea\bad\bdl\bli\bin\bne\be is be-
+ ing used, history substitutions are not immediately passed to the shell
+ parser. Instead, the expanded line is reloaded into the r\bre\bea\bad\bdl\bli\bin\bne\be edit-
+ ing buffer for further modification. If r\bre\bea\bad\bdl\bli\bin\bne\be is being used, and
+ the h\bhi\bis\bst\btr\bre\bee\bed\bdi\bit\bt shell option is enabled, a failed history substitution
+ is reloaded into the r\bre\bea\bad\bdl\bli\bin\bne\be editing buffer for correction.
+
+ The -\b-p\bp option to the h\bhi\bis\bst\bto\bor\bry\by builtin command shows what a history ex-
+ pansion will do before using it. The -\b-s\bs option to the h\bhi\bis\bst\bto\bor\bry\by builtin
+ will add commands to the end of the history list without actually exe-
+ cuting them, so that they are available for subsequent recall.
+
+ The shell allows control of the various characters used by the history
+ expansion mechanism (see the description of h\bhi\bis\bst\btc\bch\bha\bar\brs\bs above under S\bSh\bhe\bel\bll\bl
+ V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs). The shell uses the history comment character to mark his-
+ tory timestamps when writing the history file.
+
+ E\bEv\bve\ben\bnt\bt D\bDe\bes\bsi\big\bgn\bna\bat\bto\bor\brs\bs
+ An event designator is a reference to an entry in the history list.
+ The event designator consists of the portion of the word beginning with
+ the history expansion character and ending with the word designator if
+ present, or the end of the word. Unless the reference is absolute,
+ events are relative to the current position in the history list.
+
+ !\b! Start a history substitution, except when followed by a b\bbl\bla\ban\bnk\bk,
+ newline, carriage return, =, or, when the e\bex\bxt\btg\bgl\blo\bob\bb shell option
+ is enabled using the s\bsh\bho\bop\bpt\bt builtin, (.
+ !\b!_\bn Refer to history list entry _\bn.
+ !\b!-\b-_\bn Refer to the current entry minus _\bn.
+ !\b!!\b! Refer to the previous entry. This is a synonym for "!-1".
+ !\b!_\bs_\bt_\br_\bi_\bn_\bg
+ Refer to the most recent command preceding the current position
+ in the history list starting with _\bs_\bt_\br_\bi_\bn_\bg.
+ !\b!?\b?_\bs_\bt_\br_\bi_\bn_\bg[\b[?\b?]\b]
+ Refer to the most recent command preceding the current position
+ in the history list containing _\bs_\bt_\br_\bi_\bn_\bg. The trailing ?\b? may be
+ omitted if _\bs_\bt_\br_\bi_\bn_\bg is followed immediately by a newline. If
+ _\bs_\bt_\br_\bi_\bn_\bg is missing, this uses the string from the most recent
+ search; it is an error if there is no previous search string.
+ ^\b^_\bs_\bt_\br_\bi_\bn_\bg_\b1^\b^_\bs_\bt_\br_\bi_\bn_\bg_\b2^\b^
+ Quick substitution. Repeat the previous command, replacing
+ _\bs_\bt_\br_\bi_\bn_\bg_\b1 with _\bs_\bt_\br_\bi_\bn_\bg_\b2. Equivalent to "!!:s^_\bs_\bt_\br_\bi_\bn_\bg_\b1^_\bs_\bt_\br_\bi_\bn_\bg_\b2^"
+ (see M\bMo\bod\bdi\bif\bfi\bie\ber\brs\bs below).
+ !\b!#\b# The entire command line typed so far.
+
+ W\bWo\bor\brd\bd D\bDe\bes\bsi\big\bgn\bna\bat\bto\bor\brs\bs
+ Word designators are used to select desired words from the event. They
+ are optional; if the word designator isn't supplied, the history expan-
+ sion uses the entire event. A :\b: separates the event specification from
+ the word designator. It may be omitted if the word designator begins
+ with a ^\b^, $\b$, *\b*, -\b-, or %\b%. Words are numbered from the beginning of the
+ line, with the first word being denoted by 0 (zero). Words are in-
+ serted into the current line separated by single spaces.
+
+ 0\b0 (\b(z\bze\ber\bro\bo)\b)
+ The zeroth word. For the shell, this is the command word.
+ _\bn The _\bnth word.
+ ^\b^ The first argument: word 1.
+ $\b$ The last word. This is usually the last argument, but will ex-
+ pand to the zeroth word if there is only one word in the line.
+ %\b% The first word matched by the most recent "?_\bs_\bt_\br_\bi_\bn_\bg?" search, if
+ the search string begins with a character that is part of a
+ word. By default, searches begin at the end of each line and
+ proceed to the beginning, so the first word matched is the one
+ closest to the end of the line.
+ _\bx-\b-_\by A range of words; "-_\by" abbreviates "0-_\by".
+ *\b* All of the words but the zeroth. This is a synonym for "_\b1_\b-_\b$".
+ It is not an error to use *\b* if there is just one word in the
+ event; it expands to the empty string in that case.
+ x\bx*\b* Abbreviates _\bx_\b-_\b$.
+ x\bx-\b- Abbreviates _\bx_\b-_\b$ like x\bx*\b*, but omits the last word. If x\bx is miss-
+ ing, it defaults to 0.
+
+ If a word designator is supplied without an event specification, the
+ previous command is used as the event, equivalent to !\b!!\b!.
+
+ M\bMo\bod\bdi\bif\bfi\bie\ber\brs\bs
+ After the optional word designator, the expansion may include a se-
+ quence of one or more of the following modifiers, each preceded by a
+ ":". These modify, or edit, the word or words selected from the his-
+ tory event.
+
+ h\bh Remove a trailing pathname component, leaving only the head.
+ t\bt Remove all leading pathname components, leaving the tail.
+ r\br Remove a trailing suffix of the form _\b._\bx_\bx_\bx, leaving the basename.
+ e\be Remove all but the trailing suffix.
+ p\bp Print the new command but do not execute it.
+ q\bq Quote the substituted words, escaping further substitutions.
+ x\bx Quote the substituted words as with q\bq, but break into words at
+ b\bbl\bla\ban\bnk\bks\bs and newlines. The q\bq and x\bx modifiers are mutually exclu-
+ sive; expansion uses the last one supplied.
+ s\bs/\b/_\bo_\bl_\bd/\b/_\bn_\be_\bw/\b/
+ Substitute _\bn_\be_\bw for the first occurrence of _\bo_\bl_\bd in the event
+ line. Any character may be used as the delimiter in place of /.
+ The final delimiter is optional if it is the last character of
+ the event line. A single backslash quotes the delimiter in _\bo_\bl_\bd
+ and _\bn_\be_\bw. If & appears in _\bn_\be_\bw, it is replaced with _\bo_\bl_\bd. A sin-
+ gle backslash quotes the &. If _\bo_\bl_\bd is null, it is set to the
+ last _\bo_\bl_\bd substituted, or, if no previous history substitutions
+ took place, the last _\bs_\bt_\br_\bi_\bn_\bg in a !\b!?\b?_\bs_\bt_\br_\bi_\bn_\bg[\b[?\b?]\b] search. If _\bn_\be_\bw is
+ null, each matching _\bo_\bl_\bd is deleted.
+ &\b& Repeat the previous substitution.
+ g\bg Cause changes to be applied over the entire event line. This is
+ used in conjunction with ":\b:s\bs" (e.g., ":\b:g\bgs\bs/\b/_\bo_\bl_\bd/\b/_\bn_\be_\bw/\b/") or ":\b:&\b&".
+ If used with ":\b:s\bs", any delimiter can be used in place of /, and
+ the final delimiter is optional if it is the last character of
+ the event line. An a\ba may be used as a synonym for g\bg.
+ G\bG Apply the following "s\bs" or "&\b&" modifier once to each word in the
+ event line.
+
+S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS
+ Unless otherwise noted, each builtin command documented in this section
+ as accepting options preceded by -\b- accepts -\b--\b- to signify the end of the
+ options. The :\b:, t\btr\bru\bue\be, f\bfa\bal\bls\bse\be, and t\bte\bes\bst\bt/[\b[ builtins do not accept options
+ and do not treat -\b--\b- specially. The e\bex\bxi\bit\bt, l\blo\bog\bgo\bou\but\bt, r\bre\bet\btu\bur\brn\bn, b\bbr\bre\bea\bak\bk, c\bco\bon\bn-\b-
+ t\bti\bin\bnu\bue\be, l\ble\bet\bt, and s\bsh\bhi\bif\bft\bt builtins accept and process arguments beginning
+ with -\b- without requiring -\b--\b-. Other builtins that accept arguments but
+ are not specified as accepting options interpret arguments beginning
+ with -\b- as invalid options and require -\b--\b- to prevent this interpreta-
+ tion.
+
+ :\b: [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
+ No effect; the command does nothing beyond expanding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs
+ and performing any specified redirections. The return status is
+ zero.
+
+ .\b. [-\b-p\bp _\bp_\ba_\bt_\bh] _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
+ s\bso\bou\bur\brc\bce\be [-\b-p\bp _\bp_\ba_\bt_\bh] _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
+ The .\b. command (s\bso\bou\bur\brc\bce\be) reads and execute commands from _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
+ in the current shell environment and returns the exit status of
+ the last command executed from _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be.
+
+ If _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be does not contain a slash, .\b. searches for it. If the
+ -\b-p\bp option is supplied, .\b. treats _\bp_\ba_\bt_\bh as a colon-separated list
+ of directories in which to find _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be; otherwise, .\b. uses the
+ entries in P\bPA\bAT\bTH\bH to find the directory containing _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be.
+ _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be does not need to be executable. When b\bba\bas\bsh\bh is not in
+ posix mode, it searches the current directory if _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is not
+ found in P\bPA\bAT\bTH\bH, but does not search the current directory if -\b-p\bp
+ is supplied. If the s\bso\bou\bur\brc\bce\bep\bpa\bat\bth\bh option to the s\bsh\bho\bop\bpt\bt builtin com-
+ mand is turned off, .\b. does not search P\bPA\bAT\bTH\bH.
+
+ If any _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs are supplied, they become the positional para-
+ meters when _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is executed. Otherwise the positional pa-
+ rameters are unchanged.
+
+ If the -\b-T\bT option is enabled, .\b. inherits any trap on D\bDE\bEB\bBU\bUG\bG; if it
+ is not, any D\bDE\bEB\bBU\bUG\bG trap string is saved and restored around the
+ call to .\b., and .\b. unsets the D\bDE\bEB\bBU\bUG\bG trap while it executes. If -\b-T\bT
+ is not set, and the sourced file changes the D\bDE\bEB\bBU\bUG\bG trap, the new
+ value persists after .\b. completes. The return status is the sta-
+ tus of the last command executed from _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be (0 if no commands
+ are executed), and non-zero if _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is not found or cannot
+ be read.
+
+ a\bal\bli\bia\bas\bs [-\b-p\bp] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be] ...]
+ With no arguments or with the -\b-p\bp option, a\bal\bli\bia\bas\bs prints the list
+ of aliases in the form a\bal\bli\bia\bas\bs _\bn_\ba_\bm_\be=_\bv_\ba_\bl_\bu_\be on standard output.
+ When arguments are supplied, define an alias for each _\bn_\ba_\bm_\be whose
+ _\bv_\ba_\bl_\bu_\be is given. A trailing space in _\bv_\ba_\bl_\bu_\be causes the next word
+ to be checked for alias substitution when the alias is expanded
+ during command parsing. For each _\bn_\ba_\bm_\be in the argument list for
+ which no _\bv_\ba_\bl_\bu_\be is supplied, print the name and value of the
+ alias _\bn_\ba_\bm_\be. a\bal\bli\bia\bas\bs returns true unless a _\bn_\ba_\bm_\be is given (without
+ a corresponding =_\bv_\ba_\bl_\bu_\be) for which no alias has been defined.
+
+ b\bbg\bg [_\bj_\bo_\bb_\bs_\bp_\be_\bc ...]
+ Resume each suspended job _\bj_\bo_\bb_\bs_\bp_\be_\bc in the background, as if it
+ had been started with &\b&. If _\bj_\bo_\bb_\bs_\bp_\be_\bc is not present, the shell
+ uses its notion of the _\bc_\bu_\br_\br_\be_\bn_\bt _\bj_\bo_\bb. b\bbg\bg _\bj_\bo_\bb_\bs_\bp_\be_\bc returns 0 unless
+ run when job control is disabled or, when run with job control
+ enabled, any specified _\bj_\bo_\bb_\bs_\bp_\be_\bc was not found or was started
+ without job control.
+
+ b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] [-\b-l\bls\bsv\bvS\bSV\bVX\bX]
+ b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] [-\b-q\bq _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn] [-\b-u\bu _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn] [-\b-r\br _\bk_\be_\by_\bs_\be_\bq]
+ b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] -\b-f\bf _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
+ b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] -\b-x\bx _\bk_\be_\by_\bs_\be_\bq[:] _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd
+ b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] _\bk_\be_\by_\bs_\be_\bq:_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be
+ b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] -\b-p\bp|-\b-P\bP [_\br_\be_\ba_\bd_\bl_\bi_\bn_\be_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd]
+ b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] _\bk_\be_\by_\bs_\be_\bq:_\br_\be_\ba_\bd_\bl_\bi_\bn_\be_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd
+ b\bbi\bin\bnd\bd _\br_\be_\ba_\bd_\bl_\bi_\bn_\be_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b-_\bl_\bi_\bn_\be
+ Display current r\bre\bea\bad\bdl\bli\bin\bne\be key and function bindings, bind a key
+ sequence to a r\bre\bea\bad\bdl\bli\bin\bne\be function or macro or to a shell command,
+ or set a r\bre\bea\bad\bdl\bli\bin\bne\be variable. Each non-option argument is a key
+ binding or command as it would appear in a r\bre\bea\bad\bdl\bli\bin\bne\be initializa-
+ tion file such as _\b._\bi_\bn_\bp_\bu_\bt_\br_\bc, but each binding or command must be
+ passed as a separate argument; e.g., '"\C-x\C-r":
+ re-read-init-file'. In the following descriptions, output
+ available to be re-read is formatted as commands that would ap-
+ pear in a r\bre\bea\bad\bdl\bli\bin\bne\be initialization file or that would be supplied
+ as individual arguments to a b\bbi\bin\bnd\bd command. Options, if sup-
+ plied, have the following meanings:
+ -\b-m\bm _\bk_\be_\by_\bm_\ba_\bp
+ Use _\bk_\be_\by_\bm_\ba_\bp as the keymap to be affected by the subsequent
+ bindings. Acceptable _\bk_\be_\by_\bm_\ba_\bp names are _\be_\bm_\ba_\bc_\bs_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bs_\bt_\ba_\bn_\b-
+ _\bd_\ba_\br_\bd_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bm_\be_\bt_\ba_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bc_\bt_\bl_\bx_\b, _\bv_\bi_\b, _\bv_\bi_\b-_\bm_\bo_\bv_\be_\b, _\bv_\bi_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd,
+ and _\bv_\bi_\b-_\bi_\bn_\bs_\be_\br_\bt. _\bv_\bi is equivalent to _\bv_\bi_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd (_\bv_\bi_\b-_\bm_\bo_\bv_\be
+ is also a synonym); _\be_\bm_\ba_\bc_\bs is equivalent to _\be_\bm_\ba_\bc_\bs_\b-_\bs_\bt_\ba_\bn_\b-
+ _\bd_\ba_\br_\bd.
+ -\b-l\bl List the names of all r\bre\bea\bad\bdl\bli\bin\bne\be functions.
+ -\b-p\bp Display r\bre\bea\bad\bdl\bli\bin\bne\be function names and bindings in such a
+ way that they can be used as an argument to a subsequent
+ b\bbi\bin\bnd\bd command or in a r\bre\bea\bad\bdl\bli\bin\bne\be initialization file. If
+ arguments remain after option processing, b\bbi\bin\bnd\bd treats
+ them as r\bre\bea\bad\bdl\bli\bin\bne\be command names and restricts output to
+ those names.
+ -\b-P\bP List current r\bre\bea\bad\bdl\bli\bin\bne\be function names and bindings. If
+ arguments remain after option processing, b\bbi\bin\bnd\bd treats
+ them as r\bre\bea\bad\bdl\bli\bin\bne\be command names and restricts output to
+ those names.
+ -\b-s\bs Display r\bre\bea\bad\bdl\bli\bin\bne\be key sequences bound to macros and the
+ strings they output in such a way that they can be used
+ as an argument to a subsequent b\bbi\bin\bnd\bd command or in a r\bre\bea\bad\bd-\b-
+ l\bli\bin\bne\be initialization file.
+ -\b-S\bS Display r\bre\bea\bad\bdl\bli\bin\bne\be key sequences bound to macros and the
+ strings they output.
+ -\b-v\bv Display r\bre\bea\bad\bdl\bli\bin\bne\be variable names and values in such a way
+ that they can be used as an argument to a subsequent b\bbi\bin\bnd\bd
+ command or in a r\bre\bea\bad\bdl\bli\bin\bne\be initialization file.
+ -\b-V\bV List current r\bre\bea\bad\bdl\bli\bin\bne\be variable names and values.
+ -\b-f\bf _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
+ Read key bindings from _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be.
+ -\b-q\bq _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn
+ Display key sequences that invoke the named r\bre\bea\bad\bdl\bli\bin\bne\be
+ _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn.
+ -\b-u\bu _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn
+ Unbind all key sequences bound to the named r\bre\bea\bad\bdl\bli\bin\bne\be
+ _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn.
+ -\b-r\br _\bk_\be_\by_\bs_\be_\bq
+ Remove any current binding for _\bk_\be_\by_\bs_\be_\bq.
+ -\b-x\bx _\bk_\be_\by_\bs_\be_\bq[\b[:\b: ]\b]_\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd
+ Cause _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd to be executed whenever _\bk_\be_\by_\bs_\be_\bq is en-
+ tered. The separator between _\bk_\be_\by_\bs_\be_\bq and _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd is
+ either whitespace or a colon optionally followed by
+ whitespace. If the separator is whitespace, _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\b-
+ _\bm_\ba_\bn_\bd must be enclosed in double quotes and r\bre\bea\bad\bdl\bli\bin\bne\be ex-
+ pands any of its special backslash-escapes in _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\b-
+ _\bm_\ba_\bn_\bd before saving it. If the separator is a colon, any
+ enclosing double quotes are optional, and r\bre\bea\bad\bdl\bli\bin\bne\be does
+ not expand the command string before saving it. Since
+ the entire key binding expression must be a single argu-
+ ment, it should be enclosed in single quotes. When
+ _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd is executed, the shell sets the R\bRE\bEA\bAD\bD-\b-
+ L\bLI\bIN\bNE\bE_\b_L\bLI\bIN\bNE\bE variable to the contents of the r\bre\bea\bad\bdl\bli\bin\bne\be line
+ buffer and the R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_P\bPO\bOI\bIN\bNT\bT and R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_M\bMA\bAR\bRK\bK variables
+ to the current location of the insertion point and the
+ saved insertion point (the mark), respectively. The
+ shell assigns any numeric argument the user supplied to
+ the R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_A\bAR\bRG\bGU\bUM\bME\bEN\bNT\bT variable. If there was no argu-
+ ment, that variable is not set. If the executed command
+ changes the value of any of R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_L\bLI\bIN\bNE\bE, R\bRE\bEA\bAD\bD-\b-
+ L\bLI\bIN\bNE\bE_\b_P\bPO\bOI\bIN\bNT\bT, or R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_M\bMA\bAR\bRK\bK, those new values will be
+ reflected in the editing state.
+ -\b-X\bX List all key sequences bound to shell commands and the
+ associated commands in a format that can be reused as an
+ argument to a subsequent b\bbi\bin\bnd\bd command.
+
+ The return value is 0 unless an unrecognized option is supplied
+ or an error occurred.
+
+ b\bbr\bre\bea\bak\bk [_\bn]
+ Exit from within a f\bfo\bor\br, w\bwh\bhi\bil\ble\be, u\bun\bnt\bti\bil\bl, or s\bse\bel\ble\bec\bct\bt loop. If _\bn is
+ specified, b\bbr\bre\bea\bak\bk exits _\bn enclosing loops. _\bn must be >= 1. If _\bn
+ is greater than the number of enclosing loops, all enclosing
+ loops are exited. The return value is 0 unless _\bn is not greater
+ than or equal to 1.
+
+ b\bbu\bui\bil\blt\bti\bin\bn _\bs_\bh_\be_\bl_\bl_\b-_\bb_\bu_\bi_\bl_\bt_\bi_\bn [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
+ Execute the specified shell builtin _\bs_\bh_\be_\bl_\bl_\b-_\bb_\bu_\bi_\bl_\bt_\bi_\bn, passing it
+ _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs, and return its exit status. This is useful when
+ defining a function whose name is the same as a shell builtin,
+ retaining the functionality of the builtin within the function.
+ The c\bcd\bd builtin is commonly redefined this way. The return sta-
+ tus is false if _\bs_\bh_\be_\bl_\bl_\b-_\bb_\bu_\bi_\bl_\bt_\bi_\bn is not a shell builtin command.
+
+ c\bca\bal\bll\ble\ber\br [_\be_\bx_\bp_\br]
+ Returns the context of any active subroutine call (a shell func-
+ tion or a script executed with the .\b. or s\bso\bou\bur\brc\bce\be builtins).
+
+ Without _\be_\bx_\bp_\br, c\bca\bal\bll\ble\ber\br displays the line number and source file-
+ name of the current subroutine call. If a non-negative integer
+ is supplied as _\be_\bx_\bp_\br, c\bca\bal\bll\ble\ber\br displays the line number, subroutine
+ name, and source file corresponding to that position in the cur-
+ rent execution call stack. This extra information may be used,
+ for example, to print a stack trace. The current frame is frame
+ 0.
+
+ The return value is 0 unless the shell is not executing a sub-
+ routine call or _\be_\bx_\bp_\br does not correspond to a valid position in
+ the call stack.
+
+ c\bcd\bd [-\b-L\bL] [-\b-@\b@] [_\bd_\bi_\br]
+ c\bcd\bd -\b-P\bP [-\b-e\be] [-\b-@\b@] [_\bd_\bi_\br]
+ Change the current directory to _\bd_\bi_\br. if _\bd_\bi_\br is not supplied,
+ the value of the H\bHO\bOM\bME\bE shell variable is used as _\bd_\bi_\br. If _\bd_\bi_\br is
+ the empty string, c\bcd\bd treats it as an error. The variable C\bCD\bDP\bPA\bAT\bTH\bH
+ exists, and _\bd_\bi_\br does not begin with a slash (/), c\bcd\bd uses it as a
+ search path: the shell searches each directory name in C\bCD\bDP\bPA\bAT\bTH\bH
+ for _\bd_\bi_\br. Alternative directory names in C\bCD\bDP\bPA\bAT\bTH\bH are separated by
+ a colon (:). A null directory name in C\bCD\bDP\bPA\bAT\bTH\bH is the same as the
+ current directory, i.e., ".".
+
+ The -\b-P\bP option causes c\bcd\bd to use the physical directory structure
+ by resolving symbolic links while traversing _\bd_\bi_\br and before pro-
+ cessing instances of _\b._\b. in _\bd_\bi_\br (see also the -\b-P\bP option to the
+ s\bse\bet\bt builtin command).
+
+ The -\b-L\bL option forces c\bcd\bd to follow symbolic links by resolving
+ the link after processing instances of _\b._\b. in _\bd_\bi_\br. If _\b._\b. appears
+ in _\bd_\bi_\br, c\bcd\bd processes it by removing the immediately previous
+ pathname component from _\bd_\bi_\br, back to a slash or the beginning of
+ _\bd_\bi_\br, and verifying that the portion of _\bd_\bi_\br it has processed to
+ that point is still a valid directory name after removing the
+ pathname component. If it is not a valid directory name, c\bcd\bd re-
+ turns a non-zero status. If neither -\b-L\bL nor -\b-P\bP is supplied, c\bcd\bd
+ behaves as if -\b-L\bL had been supplied.
+
+ If the -\b-e\be option is supplied with -\b-P\bP, and c\bcd\bd cannot successfully
+ determine the current working directory after a successful di-
+ rectory change, it returns a non-zero status.
+
+ On systems that support it, the -\b-@\b@ option presents the extended
+ attributes associated with a file as a directory.
+
+ An argument of -\b- is converted to $\b$O\bOL\bLD\bDP\bPW\bWD\bD before attempting the
+ directory change.
+
+ If c\bcd\bd uses a non-empty directory name from C\bCD\bDP\bPA\bAT\bTH\bH, or if -\b- is
+ the first argument, and the directory change is successful, c\bcd\bd
+ writes the absolute pathname of the new working directory to the
+ standard output.
+
+ If the directory change is successful, c\bcd\bd sets the value of the
+ P\bPW\bWD\bD environment variable to the new directory name, and sets the
+ O\bOL\bLD\bDP\bPW\bWD\bD environment variable to the value of the current working
+ directory before the change.
+
+ The return value is true if the directory was successfully
+ changed; false otherwise.
+
+ c\bco\bom\bmm\bma\ban\bnd\bd [-\b-p\bpV\bVv\bv] _\bc_\bo_\bm_\bm_\ba_\bn_\bd [_\ba_\br_\bg ...]
+ The c\bco\bom\bmm\bma\ban\bnd\bd builtin runs _\bc_\bo_\bm_\bm_\ba_\bn_\bd with _\ba_\br_\bg_\bs suppressing the nor-
+ mal shell function lookup for _\bc_\bo_\bm_\bm_\ba_\bn_\bd. Only builtin commands or
+ commands found in the P\bPA\bAT\bTH\bH named _\bc_\bo_\bm_\bm_\ba_\bn_\bd are executed. If the
+ -\b-p\bp option is supplied, the search for _\bc_\bo_\bm_\bm_\ba_\bn_\bd is performed using
+ a default value for P\bPA\bAT\bTH\bH that is guaranteed to find all of the
+ standard utilities.
+
+ If either the -\b-V\bV or -\b-v\bv option is supplied, c\bco\bom\bmm\bma\ban\bnd\bd prints a de-
+ scription of _\bc_\bo_\bm_\bm_\ba_\bn_\bd. The -\b-v\bv option displays a single word in-
+ dicating the command or filename used to invoke _\bc_\bo_\bm_\bm_\ba_\bn_\bd; the -\b-V\bV
+ option produces a more verbose description.
+
+ If the -\b-V\bV or -\b-v\bv option is supplied, the exit status is zero if
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd was found, and non-zero if not. If neither option is
+ supplied and an error occurred or _\bc_\bo_\bm_\bm_\ba_\bn_\bd cannot be found, the
+ exit status is 127. Otherwise, the exit status of the c\bco\bom\bmm\bma\ban\bnd\bd
+ builtin is the exit status of _\bc_\bo_\bm_\bm_\ba_\bn_\bd.
+
+ c\bco\bom\bmp\bpg\bge\ben\bn [-\b-V\bV _\bv_\ba_\br_\bn_\ba_\bm_\be] [_\bo_\bp_\bt_\bi_\bo_\bn] [_\bw_\bo_\br_\bd]
+ Generate possible completion matches for _\bw_\bo_\br_\bd according to the
+ _\bo_\bp_\bt_\bi_\bo_\bns, which may be any option accepted by the c\bco\bom\bmp\bpl\ble\bet\bte\be
+ builtin with the exceptions of -\b-p\bp, -\b-r\br, -\b-D\bD, -\b-E\bE, and -\b-I\bI, and write
+ the matches to the standard output.
+
+ If the -\b-V\bV option is supplied, c\bco\bom\bmp\bpg\bge\ben\bn stores the generated com-
+ pletions into the indexed array variable _\bv_\ba_\br_\bn_\ba_\bm_\be instead of
+ writing them to the standard output.
+
+ When using the -\b-F\bF or -\b-C\bC options, the various shell variables set
+ by the programmable completion facilities, while available, will
+ not have useful values.
+
+ The matches will be generated in the same way as if the program-
+ mable completion code had generated them directly from a comple-
+ tion specification with the same flags. If _\bw_\bo_\br_\bd is specified,
+ only those completions matching _\bw_\bo_\br_\bd will be displayed or
+ stored.
+
+ The return value is true unless an invalid option is supplied,
+ or no matches were generated.
+
+ c\bco\bom\bmp\bpl\ble\bet\bte\be [-\b-a\bab\bbc\bcd\bde\bef\bfg\bgj\bjk\bks\bsu\buv\bv] [-\b-o\bo _\bc_\bo_\bm_\bp_\b-_\bo_\bp_\bt_\bi_\bo_\bn] [-\b-D\bDE\bEI\bI] [-\b-A\bA _\ba_\bc_\bt_\bi_\bo_\bn]
+ [-\b-G\bG _\bg_\bl_\bo_\bb_\bp_\ba_\bt] [-\b-W\bW _\bw_\bo_\br_\bd_\bl_\bi_\bs_\bt] [-\b-F\bF _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn] [-\b-C\bC _\bc_\bo_\bm_\bm_\ba_\bn_\bd]
+ [-\b-X\bX _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt] [-\b-P\bP _\bp_\br_\be_\bf_\bi_\bx] [-\b-S\bS _\bs_\bu_\bf_\bf_\bi_\bx] _\bn_\ba_\bm_\be [_\bn_\ba_\bm_\be ...]
+ c\bco\bom\bmp\bpl\ble\bet\bte\be -\b-p\bpr\br [-\b-D\bDE\bEI\bI] [_\bn_\ba_\bm_\be ...]
+ Specify how arguments to each _\bn_\ba_\bm_\be should be completed.
+
+ If the -\b-p\bp option is supplied, or if no options or _\bn_\ba_\bm_\bes are sup-
+ plied, print existing completion specifications in a way that
+ allows them to be reused as input. The -\b-r\br option removes a com-
+ pletion specification for each _\bn_\ba_\bm_\be, or, if no _\bn_\ba_\bm_\bes are sup-
+ plied, all completion specifications.
+
+ The -\b-D\bD option indicates that other supplied options and actions
+ should apply to the "default" command completion; that is, com-
+ pletion attempted on a command for which no completion has pre-
+ viously been defined. The -\b-E\bE option indicates that other sup-
+ plied options and actions should apply to "empty" command com-
+ pletion; that is, completion attempted on a blank line. The -\b-I\bI
+ option indicates that other supplied options and actions should
+ apply to completion on the initial non-assignment word on the
+ line, or after a command delimiter such as ;\b; or |\b|, which is usu-
+ ally command name completion. If multiple options are supplied,
+ the -\b-D\bD option takes precedence over -\b-E\bE, and both take precedence
+ over -\b-I\bI. If any of -\b-D\bD, -\b-E\bE, or -\b-I\bI are supplied, any other _\bn_\ba_\bm_\be
+ arguments are ignored; these completions only apply to the case
+ specified by the option.
+
+ The process of applying these completion specifications when at-
+ tempting word completion is described above under P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be
+ C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn.
+
+ Other options, if specified, have the following meanings. The
+ arguments to the -\b-G\bG, -\b-W\bW, and -\b-X\bX options (and, if necessary, the
+ -\b-P\bP and -\b-S\bS options) should be quoted to protect them from expan-
+ sion before the c\bco\bom\bmp\bpl\ble\bet\bte\be builtin is invoked.
+
+ -\b-o\bo _\bc_\bo_\bm_\bp_\b-_\bo_\bp_\bt_\bi_\bo_\bn
+ The _\bc_\bo_\bm_\bp_\b-_\bo_\bp_\bt_\bi_\bo_\bn controls several aspects of the comp-
+ spec's behavior beyond the simple generation of comple-
+ tions. _\bc_\bo_\bm_\bp_\b-_\bo_\bp_\bt_\bi_\bo_\bn may be one of:
+ b\bba\bas\bsh\bhd\bde\bef\bfa\bau\bul\blt\bt
+ Perform the rest of the default b\bba\bas\bsh\bh completions
+ if the compspec generates no matches.
+ d\bde\bef\bfa\bau\bul\blt\bt Use r\bre\bea\bad\bdl\bli\bin\bne\be's default filename completion if
+ the compspec generates no matches.
+ d\bdi\bir\brn\bna\bam\bme\bes\bs
+ Perform directory name completion if the comp-
+ spec generates no matches.
+ f\bfi\bil\ble\ben\bna\bam\bme\bes\bs
+ Tell r\bre\bea\bad\bdl\bli\bin\bne\be that the compspec generates file-
+ names, so it can perform any filename-specific
+ processing (such as adding a slash to directory
+ names, quoting special characters, or suppress-
+ ing trailing spaces). This is intended to be
+ used with shell functions.
+ f\bfu\bul\bll\blq\bqu\buo\bot\bte\be
+ Tell r\bre\bea\bad\bdl\bli\bin\bne\be to quote all the completed words
+ even if they are not filenames.
+ n\bno\boq\bqu\buo\bot\bte\be Tell r\bre\bea\bad\bdl\bli\bin\bne\be not to quote the completed words
+ if they are filenames (quoting filenames is the
+ default).
+ n\bno\bos\bso\bor\brt\bt Tell r\bre\bea\bad\bdl\bli\bin\bne\be not to sort the list of possible
+ completions alphabetically.
+ n\bno\bos\bsp\bpa\bac\bce\be Tell r\bre\bea\bad\bdl\bli\bin\bne\be not to append a space (the de-
+ fault) to words completed at the end of the
+ line.
+ p\bpl\blu\bus\bsd\bdi\bir\brs\bs
+ After generating any matches defined by the
+ compspec, attempt directory name completion and
+ add any matches to the results of the other ac-
+ tions.
+ -\b-A\bA _\ba_\bc_\bt_\bi_\bo_\bn
+ The _\ba_\bc_\bt_\bi_\bo_\bn may be one of the following to generate a
+ list of possible completions:
+ a\bal\bli\bia\bas\bs Alias names. May also be specified as -\b-a\ba.
+ a\bar\brr\bra\bay\byv\bva\bar\br
+ Array variable names.
+ b\bbi\bin\bnd\bdi\bin\bng\bg R\bRe\bea\bad\bdl\bli\bin\bne\be key binding names.
+ b\bbu\bui\bil\blt\bti\bin\bn Names of shell builtin commands. May also be
+ specified as -\b-b\bb.
+ c\bco\bom\bmm\bma\ban\bnd\bd Command names. May also be specified as -\b-c\bc.
+ d\bdi\bir\bre\bec\bct\bto\bor\bry\by
+ Directory names. May also be specified as -\b-d\bd.
+ d\bdi\bis\bsa\bab\bbl\ble\bed\bd
+ Names of disabled shell builtins.
+ e\ben\bna\bab\bbl\ble\bed\bd Names of enabled shell builtins.
+ e\bex\bxp\bpo\bor\brt\bt Names of exported shell variables. May also be
+ specified as -\b-e\be.
+ f\bfi\bil\ble\be File and directory names, similar to r\bre\bea\bad\bdl\bli\bin\bne\be's
+ filename completion. May also be specified as
+ -\b-f\bf.
+ f\bfu\bun\bnc\bct\bti\bio\bon\bn
+ Names of shell functions.
+ g\bgr\bro\bou\bup\bp Group names. May also be specified as -\b-g\bg.
+ h\bhe\bel\blp\bpt\bto\bop\bpi\bic\bc
+ Help topics as accepted by the h\bhe\bel\blp\bp builtin.
+ h\bho\bos\bst\btn\bna\bam\bme\be
+ Hostnames, as taken from the file specified by
+ the H\bHO\bOS\bST\bTF\bFI\bIL\bLE\bE shell variable.
+ j\bjo\bob\bb Job names, if job control is active. May also
+ be specified as -\b-j\bj.
+ k\bke\bey\byw\bwo\bor\brd\bd Shell reserved words. May also be specified as
+ -\b-k\bk.
+ r\bru\bun\bnn\bni\bin\bng\bg Names of running jobs, if job control is active.
+ s\bse\ber\brv\bvi\bic\bce\be Service names. May also be specified as -\b-s\bs.
+ s\bse\bet\bto\bop\bpt\bt Valid arguments for the -\b-o\bo option to the s\bse\bet\bt
+ builtin.
+ s\bsh\bho\bop\bpt\bt Shell option names as accepted by the s\bsh\bho\bop\bpt\bt
+ builtin.
+ s\bsi\big\bgn\bna\bal\bl Signal names.
+ s\bst\bto\bop\bpp\bpe\bed\bd Names of stopped jobs, if job control is active.
+ u\bus\bse\ber\br User names. May also be specified as -\b-u\bu.
+ v\bva\bar\bri\bia\bab\bbl\ble\be
+ Names of all shell variables. May also be spec-
+ ified as -\b-v\bv.
+ -\b-C\bC _\bc_\bo_\bm_\bm_\ba_\bn_\bd
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd is executed in a subshell environment, and its
+ output is used as the possible completions. Arguments
+ are passed as with the -\b-F\bF option.
+ -\b-F\bF _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn
+ The shell function _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn is executed in the current
+ shell environment. When the function is executed, the
+ first argument ($\b$1\b1) is the name of the command whose ar-
+ guments are being completed, the second argument ($\b$2\b2) is
+ the word being completed, and the third argument ($\b$3\b3) is
+ the word preceding the word being completed on the cur-
+ rent command line. When _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn finishes, programmable
+ completion retrieves the possible completions from the
+ value of the C\bCO\bOM\bMP\bPR\bRE\bEP\bPL\bLY\bY array variable.
+ -\b-G\bG _\bg_\bl_\bo_\bb_\bp_\ba_\bt
+ Expand the pathname expansion pattern _\bg_\bl_\bo_\bb_\bp_\ba_\bt to gener-
+ ate the possible completions.
+ -\b-P\bP _\bp_\br_\be_\bf_\bi_\bx
+ Add _\bp_\br_\be_\bf_\bi_\bx to the beginning of each possible completion
+ after all other options have been applied.
+ -\b-S\bS _\bs_\bu_\bf_\bf_\bi_\bx
+ Append _\bs_\bu_\bf_\bf_\bi_\bx to each possible completion after all
+ other options have been applied.
+ -\b-W\bW _\bw_\bo_\br_\bd_\bl_\bi_\bs_\bt
+ Split the _\bw_\bo_\br_\bd_\bl_\bi_\bs_\bt using the characters in the I\bIF\bFS\bS spe-
+ cial variable as delimiters, and expand each resulting
+ word. Shell quoting is honored within _\bw_\bo_\br_\bd_\bl_\bi_\bs_\bt, in or-
+ der to provide a mechanism for the words to contain
+ shell metacharacters or characters in the value of I\bIF\bFS\bS.
+ The possible completions are the members of the resul-
+ tant list which match a prefix of the word being com-
+ pleted.
+ -\b-X\bX _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt
+ _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt is a pattern as used for pathname expansion.
+ It is applied to the list of possible completions gener-
+ ated by the preceding options and arguments, and each
+ completion matching _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt is removed from the list.
+ A leading !\b! in _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt negates the pattern; in this
+ case, any completion not matching _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt is removed.
+
+ The return value is true unless an invalid option is supplied,
+ an option other than -\b-p\bp, -\b-r\br, -\b-D\bD, -\b-E\bE, or -\b-I\bI is supplied without a
+ _\bn_\ba_\bm_\be argument, an attempt is made to remove a completion speci-
+ fication for a _\bn_\ba_\bm_\be for which no specification exists, or an er-
+ ror occurs adding a completion specification.
+
+ c\bco\bom\bmp\bpo\bop\bpt\bt [-\b-o\bo _\bo_\bp_\bt_\bi_\bo_\bn] [-\b-D\bDE\bEI\bI] [+\b+o\bo _\bo_\bp_\bt_\bi_\bo_\bn] [_\bn_\ba_\bm_\be]
+ Modify completion options for each _\bn_\ba_\bm_\be according to the _\bo_\bp_\b-
+ _\bt_\bi_\bo_\bns, or for the currently-executing completion if no _\bn_\ba_\bm_\bes are
+ supplied. If no _\bo_\bp_\bt_\bi_\bo_\bns are supplied, display the completion
+ options for each _\bn_\ba_\bm_\be or the current completion. The possible
+ values of _\bo_\bp_\bt_\bi_\bo_\bn are those valid for the c\bco\bom\bmp\bpl\ble\bet\bte\be builtin de-
+ scribed above.
+
+ The -\b-D\bD option indicates that other supplied options should apply
+ to the "default" command completion; the -\b-E\bE option indicates
+ that other supplied options should apply to "empty" command com-
+ pletion; and the -\b-I\bI option indicates that other supplied options
+ should apply to completion on the initial word on the line.
+ These are determined in the same way as the c\bco\bom\bmp\bpl\ble\bet\bte\be builtin.
+
+ If multiple options are supplied, the -\b-D\bD option takes precedence
+ over -\b-E\bE, and both take precedence over -\b-I\bI.
+
+ The return value is true unless an invalid option is supplied,
+ an attempt is made to modify the options for a _\bn_\ba_\bm_\be for which no
+ completion specification exists, or an output error occurs.
+
+ c\bco\bon\bnt\bti\bin\bnu\bue\be [_\bn]
+ c\bco\bon\bnt\bti\bin\bnu\bue\be resumes the next iteration of the enclosing f\bfo\bor\br, w\bwh\bhi\bil\ble\be,
+ u\bun\bnt\bti\bil\bl, or s\bse\bel\ble\bec\bct\bt loop. If _\bn is specified, b\bba\bas\bsh\bh resumes the _\bnth
+ enclosing loop. _\bn must be >= 1. If _\bn is greater than the num-
+ ber of enclosing loops, the shell resumes the last enclosing
+ loop (the "top-level" loop). The return value is 0 unless _\bn is
+ not greater than or equal to 1.
+
+ d\bde\bec\bcl\bla\bar\bre\be [-\b-a\baA\bAf\bfF\bFg\bgi\biI\bIl\bln\bnr\brt\btu\bux\bx] [-\b-p\bp] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be] ...]
+ t\bty\byp\bpe\bes\bse\bet\bt [-\b-a\baA\bAf\bfF\bFg\bgi\biI\bIl\bln\bnr\brt\btu\bux\bx] [-\b-p\bp] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be] ...]
+ Declare variables and/or give them attributes. If no _\bn_\ba_\bm_\bes are
+ given then display the values of variables or functions. The -\b-p\bp
+ option will display the attributes and values of each _\bn_\ba_\bm_\be.
+ When -\b-p\bp is used with _\bn_\ba_\bm_\be arguments, additional options, other
+ than -\b-f\bf and -\b-F\bF, are ignored.
+
+ When -\b-p\bp is supplied without _\bn_\ba_\bm_\be arguments, d\bde\bec\bcl\bla\bar\bre\be will display
+ the attributes and values of all variables having the attributes
+ specified by the additional options. If no other options are
+ supplied with -\b-p\bp, d\bde\bec\bcl\bla\bar\bre\be will display the attributes and values
+ of all shell variables. The -\b-f\bf option restricts the display to
+ shell functions.
+
+ The -\b-F\bF option inhibits the display of function definitions; only
+ the function name and attributes are printed. If the e\bex\bxt\btd\bde\beb\bbu\bug\bg
+ shell option is enabled using s\bsh\bho\bop\bpt\bt, the source file name and
+ line number where each _\bn_\ba_\bm_\be is defined are displayed as well.
+ The -\b-F\bF option implies -\b-f\bf.
+
+ The -\b-g\bg option forces variables to be created or modified at the
+ global scope, even when d\bde\bec\bcl\bla\bar\bre\be is executed in a shell function.
+ It is ignored when d\bde\bec\bcl\bla\bar\bre\be is not executed in a shell function.
+
+ The -\b-I\bI option causes local variables to inherit the attributes
+ (except the _\bn_\ba_\bm_\be_\br_\be_\bf attribute) and value of any existing vari-
+ able with the same _\bn_\ba_\bm_\be at a surrounding scope. If there is no
+ existing variable, the local variable is initially unset.
+
+ The following options can be used to restrict output to vari-
+ ables with the specified attribute or to give variables attrib-
+ utes:
+ -\b-a\ba Each _\bn_\ba_\bm_\be is an indexed array variable (see A\bAr\brr\bra\bay\bys\bs
+ above).
+ -\b-A\bA Each _\bn_\ba_\bm_\be is an associative array variable (see A\bAr\brr\bra\bay\bys\bs
+ above).
+ -\b-f\bf Each _\bn_\ba_\bm_\be refers to a shell function.
+ -\b-i\bi The variable is treated as an integer; arithmetic evalua-
+ tion (see A\bAR\bRI\bIT\bTH\bHM\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN above) is performed when
+ the variable is assigned a value.
+ -\b-l\bl When the variable is assigned a value, all upper-case
+ characters are converted to lower-case. The upper-case
+ attribute is disabled.
+ -\b-n\bn Give each _\bn_\ba_\bm_\be the _\bn_\ba_\bm_\be_\br_\be_\bf attribute, making it a name
+ reference to another variable. That other variable is
+ defined by the value of _\bn_\ba_\bm_\be. All references, assign-
+ ments, and attribute modifications to _\bn_\ba_\bm_\be, except those
+ using or changing the -\b-n\bn attribute itself, are performed
+ on the variable referenced by _\bn_\ba_\bm_\be's value. The nameref
+ attribute cannot be applied to array variables.
+ -\b-r\br Make _\bn_\ba_\bm_\bes readonly. These names cannot then be assigned
+ values by subsequent assignment statements or unset.
+ -\b-t\bt Give each _\bn_\ba_\bm_\be the _\bt_\br_\ba_\bc_\be attribute. Traced functions in-
+ herit the D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN traps from the calling shell.
+ The trace attribute has no special meaning for variables.
+ -\b-u\bu When the variable is assigned a value, all lower-case
+ characters are converted to upper-case. The lower-case
+ attribute is disabled.
+ -\b-x\bx Mark each _\bn_\ba_\bm_\be for export to subsequent commands via the
+ environment.
+
+ Using "+" instead of "-" turns off the specified attribute in-
+ stead, with the exceptions that +\b+a\ba and +\b+A\bA may not be used to de-
+ stroy array variables and +\b+r\br will not remove the readonly at-
+ tribute.
+
+ When used in a function, d\bde\bec\bcl\bla\bar\bre\be and t\bty\byp\bpe\bes\bse\bet\bt make each _\bn_\ba_\bm_\be lo-
+ cal, as with the l\blo\boc\bca\bal\bl command, unless the -\b-g\bg option is sup-
+ plied. If a variable name is followed by =_\bv_\ba_\bl_\bu_\be, the value of
+ the variable is set to _\bv_\ba_\bl_\bu_\be. When using -\b-a\ba or -\b-A\bA and the com-
+ pound assignment syntax to create array variables, additional
+ attributes do not take effect until subsequent assignments.
+
+ The return value is 0 unless an invalid option is encountered,
+ an attempt is made to define a function using "-f foo=bar", an
+ attempt is made to assign a value to a readonly variable, an at-
+ tempt is made to assign a value to an array variable without us-
+ ing the compound assignment syntax (see A\bAr\brr\bra\bay\bys\bs above), one of
+ the _\bn_\ba_\bm_\be_\bs is not a valid shell variable name, an attempt is made
+ to turn off readonly status for a readonly variable, an attempt
+ is made to turn off array status for an array variable, or an
+ attempt is made to display a non-existent function with -\b-f\bf.
+
+ d\bdi\bir\brs\bs [\b[-\b-c\bcl\blp\bpv\bv]\b] [\b[+\b+_\bn]\b] [\b[-\b-_\bn]\b]
+ Without options, display the list of currently remembered direc-
+ tories. The default display is on a single line with directory
+ names separated by spaces. Directories are added to the list
+ with the p\bpu\bus\bsh\bhd\bd command; the p\bpo\bop\bpd\bd command removes entries from
+ the list. The current directory is always the first directory
+ in the stack.
+
+ Options, if supplied, have the following meanings:
+ -\b-c\bc Clears the directory stack by deleting all of the en-
+ tries.
+ -\b-l\bl Produces a listing using full pathnames; the default
+ listing format uses a tilde to denote the home directory.
+ -\b-p\bp Print the directory stack with one entry per line.
+ -\b-v\bv Print the directory stack with one entry per line, pre-
+ fixing each entry with its index in the stack.
+ +\b+_\bn Displays the _\bnth entry counting from the left of the list
+ shown by d\bdi\bir\brs\bs when invoked without options, starting with
+ zero.
+ -\b-_\bn Displays the _\bnth entry counting from the right of the
+ list shown by d\bdi\bir\brs\bs when invoked without options, starting
+ with zero.
+
+ The return value is 0 unless an invalid option is supplied or _\bn
+ indexes beyond the end of the directory stack.
+
+ d\bdi\bis\bso\bow\bwn\bn [-\b-a\bar\br] [-\b-h\bh] [_\bi_\bd ...]
+ Without options, remove each _\bi_\bd from the table of active jobs.
+ Each _\bi_\bd may be a job specification _\bj_\bo_\bb_\bs_\bp_\be_\bc or a process ID _\bp_\bi_\bd;
+ if _\bi_\bd is a _\bp_\bi_\bd, d\bdi\bis\bso\bow\bwn\bn uses the job containing _\bp_\bi_\bd as _\bj_\bo_\bb_\bs_\bp_\be_\bc.
+
+ If the -\b-h\bh option is supplied, d\bdi\bis\bso\bow\bwn\bn does not remove the jobs
+ corresponding to each _\bi_\bd from the jobs table, but rather marks
+ them so the shell does not send S\bSI\bIG\bGH\bHU\bUP\bP to the job if the shell
+ receives a S\bSI\bIG\bGH\bHU\bUP\bP.
+
+ If no _\bi_\bd is supplied, the -\b-a\ba option means to remove or mark all
+ jobs; the -\b-r\br option without an _\bi_\bd argument removes or marks run-
+ ning jobs. If no _\bi_\bd is supplied, and neither the -\b-a\ba nor the -\b-r\br
+ option is supplied, d\bdi\bis\bso\bow\bwn\bn removes or marks the current job.
+
+ The return value is 0 unless an _\bi_\bd does not specify a valid job.
+
+ e\bec\bch\bho\bo [-\b-n\bne\beE\bE] [_\ba_\br_\bg ...]
+ Output the _\ba_\br_\bgs, separated by spaces, followed by a newline.
+ The return status is 0 unless a write error occurs. If -\b-n\bn is
+ specified, the trailing newline is not printed.
+
+ If the -\b-e\be option is given, e\bec\bch\bho\bo interprets the following back-
+ slash-escaped characters. The -\b-E\bE option disables interpretation
+ of these escape characters, even on systems where they are in-
+ terpreted by default. The x\bxp\bpg\bg_\b_e\bec\bch\bho\bo shell option determines
+ whether or not e\bec\bch\bho\bo interprets any options and expands these es-
+ cape characters. e\bec\bch\bho\bo does not interpret -\b--\b- to mean the end of
+ options.
+
+ e\bec\bch\bho\bo interprets the following escape sequences:
+ \\b\a\ba alert (bell)
+ \\b\b\bb backspace
+ \\b\c\bc suppress further output
+ \\b\e\be
+ \\b\E\bE an escape character
+ \\b\f\bf form feed
+ \\b\n\bn new line
+ \\b\r\br carriage return
+ \\b\t\bt horizontal tab
+ \\b\v\bv vertical tab
+ \\b\\\b\ backslash
+ \\b\0\b0_\bn_\bn_\bn The eight-bit character whose value is the octal value
+ _\bn_\bn_\bn (zero to three octal digits).
+ \\b\x\bx_\bH_\bH The eight-bit character whose value is the hexadecimal
+ value _\bH_\bH (one or two hex digits).
+ \\b\u\bu_\bH_\bH_\bH_\bH The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value _\bH_\bH_\bH_\bH (one to four hex digits).
+ \\b\U\bU_\bH_\bH_\bH_\bH_\bH_\bH_\bH_\bH
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value _\bH_\bH_\bH_\bH_\bH_\bH_\bH_\bH (one to eight hex digits).
+
+ e\bec\bch\bho\bo writes any unrecognized backslash-escaped characters un-
+ changed.
+
+ e\ben\bna\bab\bbl\ble\be [-\b-a\ba] [-\b-d\bdn\bnp\bps\bs] [-\b-f\bf _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be] [_\bn_\ba_\bm_\be ...]
+ Enable and disable builtin shell commands. Disabling a builtin
+ allows an executable file which has the same name as a shell
+ builtin to be executed without specifying a full pathname, even
+ though the shell normally searches for builtins before files.
+
+ If -\b-n\bn is supplied, each _\bn_\ba_\bm_\be is disabled; otherwise, _\bn_\ba_\bm_\bes are
+ enabled. For example, to use the t\bte\bes\bst\bt binary found using P\bPA\bAT\bTH\bH
+ instead of the shell builtin version, run "enable -n test".
+
+ If no _\bn_\ba_\bm_\be arguments are supplied, or if the -\b-p\bp option is sup-
+ plied, print a list of shell builtins. With no other option ar-
+ guments, the list consists of all enabled shell builtins. If -\b-n\bn
+ is supplied, print only disabled builtins. If -\b-a\ba is supplied,
+ the list printed includes all builtins, with an indication of
+ whether or not each is enabled. The -\b-s\bs option means to restrict
+ the output to the POSIX _\bs_\bp_\be_\bc_\bi_\ba_\bl builtins.
+
+ The -\b-f\bf option means to load the new builtin command _\bn_\ba_\bm_\be from
+ shared object _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be, on systems that support dynamic loading.
+ If _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be does not contain a slash, B\bBa\bas\bsh\bh will use the value of
+ the B\bBA\bAS\bSH\bH_\b_L\bLO\bOA\bAD\bDA\bAB\bBL\bLE\bES\bS_\b_P\bPA\bAT\bTH\bH variable as a colon-separated list of
+ directories in which to search for _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be. The default for
+ B\bBA\bAS\bSH\bH_\b_L\bLO\bOA\bAD\bDA\bAB\bBL\bLE\bES\bS_\b_P\bPA\bAT\bTH\bH is system-dependent, and may include "." to
+ force a search of the current directory. The -\b-d\bd option will
+ delete a builtin previously loaded with -\b-f\bf. If _\b-_\bs is used with
+ _\b-_\bf, the new builtin becomes a POSIX special builtin.
+
+ If no options are supplied and a _\bn_\ba_\bm_\be is not a shell builtin,
+ e\ben\bna\bab\bbl\ble\be will attempt to load _\bn_\ba_\bm_\be from a shared object named
+ _\bn_\ba_\bm_\be, as if the command were "enable -f _\bn_\ba_\bm_\be _\bn_\ba_\bm_\be".
+
+ The return value is 0 unless a _\bn_\ba_\bm_\be is not a shell builtin or
+ there is an error loading a new builtin from a shared object.
+
+ e\bev\bva\bal\bl [_\ba_\br_\bg ...]
+ Concatenate the _\ba_\br_\bgs together into a single command, separating
+ them with spaces. B\bBa\bas\bsh\bh then reads and execute this command, and
+ returns its exit status as the return status of e\bev\bva\bal\bl. If there
+ are no _\ba_\br_\bg_\bs, or only null arguments, e\bev\bva\bal\bl returns 0.
+
+ e\bex\bxe\bec\bc [-\b-c\bcl\bl] [-\b-a\ba _\bn_\ba_\bm_\be] [_\bc_\bo_\bm_\bm_\ba_\bn_\bd [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]]
+ If _\bc_\bo_\bm_\bm_\ba_\bn_\bd is specified, it replaces the shell without creating
+ a new process. _\bc_\bo_\bm_\bm_\ba_\bn_\bd cannot be a shell builtin or function.
+ The _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs become the arguments to _\bc_\bo_\bm_\bm_\ba_\bn_\bd. If the -\b-l\bl option
+ is supplied, the shell places a dash at the beginning of the ze-
+ roth argument passed to _\bc_\bo_\bm_\bm_\ba_\bn_\bd. This is what _\bl_\bo_\bg_\bi_\bn(1) does.
+ The -\b-c\bc option causes _\bc_\bo_\bm_\bm_\ba_\bn_\bd to be executed with an empty envi-
+ ronment. If -\b-a\ba is supplied, the shell passes _\bn_\ba_\bm_\be as the zeroth
+ argument to the executed command.
+
+ If _\bc_\bo_\bm_\bm_\ba_\bn_\bd cannot be executed for some reason, a non-interactive
+ shell exits, unless the e\bex\bxe\bec\bcf\bfa\bai\bil\bl shell option is enabled. In
+ that case, it returns a non-zero status. An interactive shell
+ returns a non-zero status if the file cannot be executed. A
+ subshell exits unconditionally if e\bex\bxe\bec\bc fails.
+
+ If _\bc_\bo_\bm_\bm_\ba_\bn_\bd is not specified, any redirections take effect in the
+ current shell, and the return status is 0. If there is a redi-
+ rection error, the return status is 1.
+
+ e\bex\bxi\bit\bt [_\bn]
+ Cause the shell to exit with a status of _\bn. If _\bn is omitted,
+ the exit status is that of the last command executed. Any trap
+ on E\bEX\bXI\bIT\bT is executed before the shell terminates.
+
+ e\bex\bxp\bpo\bor\brt\bt [-\b-f\bfn\bn] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be]] ...
+ e\bex\bxp\bpo\bor\brt\bt -\b-p\bp [\b[-\b-f\bf]\b]
+ The supplied _\bn_\ba_\bm_\be_\bs are marked for automatic export to the envi-
+ ronment of subsequently executed commands. If the -\b-f\bf option is
+ given, the _\bn_\ba_\bm_\be_\bs refer to functions.
+
+ The -\b-n\bn option unexports, or removes the export attribute, from
+ each _\bn_\ba_\bm_\be. If no _\bn_\ba_\bm_\be_\bs are given, or if only the -\b-p\bp option is
+ supplied, e\bex\bxp\bpo\bor\brt\bt displays a list of names of all exported vari-
+ ables on the standard output. Using -\b-p\bp and -\b-f\bf together displays
+ exported functions. The -\b-p\bp option displays output in a form
+ that may be reused as input.
+
+ e\bex\bxp\bpo\bor\brt\bt allows the value of a variable to be set when it is ex-
+ ported or unexported by following the variable name with =_\bv_\ba_\bl_\bu_\be.
+ This sets the value of the variable to _\bv_\ba_\bl_\bu_\be while modifying the
+ export attribute. e\bex\bxp\bpo\bor\brt\bt returns an exit status of 0 unless an
+ invalid option is encountered, one of the _\bn_\ba_\bm_\be_\bs is not a valid
+ shell variable name, or -\b-f\bf is supplied with a _\bn_\ba_\bm_\be that is not a
+ function.
+
+ f\bfa\bal\bls\bse\be Does nothing; returns a non-zero status.
+
+ f\bfc\bc [-\b-e\be _\be_\bn_\ba_\bm_\be] [-\b-l\bln\bnr\br] [_\bf_\bi_\br_\bs_\bt] [_\bl_\ba_\bs_\bt]
+ f\bfc\bc -\b-s\bs [_\bp_\ba_\bt=_\br_\be_\bp] [_\bc_\bm_\bd]
+ The first form selects a range of commands from _\bf_\bi_\br_\bs_\bt to _\bl_\ba_\bs_\bt
+ from the history list and displays or edits and re-executes
+ them. _\bF_\bi_\br_\bs_\bt and _\bl_\ba_\bs_\bt may be specified as a string (to locate
+ the last command beginning with that string) or as a number (an
+ index into the history list, where a negative number is used as
+ an offset from the current command number).
+
+ When listing, a _\bf_\bi_\br_\bs_\bt or _\bl_\ba_\bs_\bt of 0 is equivalent to -1 and -0 is
+ equivalent to the current command (usually the f\bfc\bc command); oth-
+ erwise 0 is equivalent to -1 and -0 is invalid. If _\bl_\ba_\bs_\bt is not
+ specified, it is set to the current command for listing (so that
+ "fc -l -10" prints the last 10 commands) and to _\bf_\bi_\br_\bs_\bt otherwise.
+ If _\bf_\bi_\br_\bs_\bt is not specified, it is set to the previous command for
+ editing and -16 for listing.
+
+ If the -\b-l\bl option is supplied, the commands are listed on the
+ standard output. The -\b-n\bn option suppresses the command numbers
+ when listing. The -\b-r\br option reverses the order of the commands.
+
+ Otherwise, f\bfc\bc invokes the editor named by _\be_\bn_\ba_\bm_\be on a file con-
+ taining those commands. If _\be_\bn_\ba_\bm_\be is not supplied, f\bfc\bc uses the
+ value of the F\bFC\bCE\bED\bDI\bIT\bT variable, and the value of E\bED\bDI\bIT\bTO\bOR\bR if F\bFC\bCE\bED\bDI\bIT\bT
+ is not set. If neither variable is set, f\bfc\bc uses _\bv_\bi_\b. When edit-
+ ing is complete, f\bfc\bc reads the file containing the edited com-
+ mands and echoes and executes them.
+
+ In the second form, f\bfc\bc re-executes _\bc_\bo_\bm_\bm_\ba_\bn_\bd after replacing each
+ instance of _\bp_\ba_\bt with _\br_\be_\bp. _\bC_\bo_\bm_\bm_\ba_\bn_\bd is interpreted the same as
+ _\bf_\bi_\br_\bs_\bt above.
+
+ A useful alias to use with f\bfc\bc is "r="fc -s"", so that typing "r
+ cc" runs the last command beginning with "cc" and typing "r" re-
+ executes the last command.
+
+ If the first form is used, the return value is zero unless an
+ invalid option is encountered or _\bf_\bi_\br_\bs_\bt or _\bl_\ba_\bs_\bt specify history
+ lines out of range. When editing and re-executing a file of
+ commands, the return value is the value of the last command exe-
+ cuted or failure if an error occurs with the temporary file. If
+ the second form is used, the return status is that of the re-ex-
+ ecuted command, unless _\bc_\bm_\bd does not specify a valid history en-
+ try, in which case f\bfc\bc returns a non-zero status.
+
+ f\bfg\bg [_\bj_\bo_\bb_\bs_\bp_\be_\bc]
+ Resume _\bj_\bo_\bb_\bs_\bp_\be_\bc in the foreground, and make it the current job.
+ If _\bj_\bo_\bb_\bs_\bp_\be_\bc is not present, f\bfg\bg uses the shell's notion of the
+ _\bc_\bu_\br_\br_\be_\bn_\bt _\bj_\bo_\bb. The return value is that of the command placed
+ into the foreground, or failure if run when job control is dis-
+ abled or, when run with job control enabled, if _\bj_\bo_\bb_\bs_\bp_\be_\bc does not
+ specify a valid job or _\bj_\bo_\bb_\bs_\bp_\be_\bc specifies a job that was started
+ without job control.
+
+ g\bge\bet\bto\bop\bpt\bts\bs _\bo_\bp_\bt_\bs_\bt_\br_\bi_\bn_\bg _\bn_\ba_\bm_\be [_\ba_\br_\bg ...]
+ g\bge\bet\bto\bop\bpt\bts\bs is used by shell scripts and functions to parse posi-
+ tional parameters and obtain options and their arguments. _\bo_\bp_\bt_\b-
+ _\bs_\bt_\br_\bi_\bn_\bg contains the option characters to be recognized; if a
+ character is followed by a colon, the option is expected to have
+ an argument, which should be separated from it by white space.
+ The colon and question mark characters may not be used as option
+ characters.
+
+ Each time it is invoked, g\bge\bet\bto\bop\bpt\bts\bs places the next option in the
+ shell variable _\bn_\ba_\bm_\be, initializing _\bn_\ba_\bm_\be if it does not exist, and
+ the index of the next argument to be processed into the variable
+ O\bOP\bPT\bTI\bIN\bND\bD. O\bOP\bPT\bTI\bIN\bND\bD is initialized to 1 each time the shell or a
+ shell script is invoked. When an option requires an argument,
+ g\bge\bet\bto\bop\bpt\bts\bs places that argument into the variable O\bOP\bPT\bTA\bAR\bRG\bG.
+
+ The shell does not reset O\bOP\bPT\bTI\bIN\bND\bD automatically; it must be manu-
+ ally reset between multiple calls to g\bge\bet\bto\bop\bpt\bts\bs within the same
+ shell invocation to use a new set of parameters.
+
+ When it reaches the end of options, g\bge\bet\bto\bop\bpt\bts\bs exits with a return
+ value greater than zero. O\bOP\bPT\bTI\bIN\bND\bD is set to the index of the
+ first non-option argument, and _\bn_\ba_\bm_\be is set to ?.
+
+ g\bge\bet\bto\bop\bpt\bts\bs normally parses the positional parameters, but if more
+ arguments are supplied as _\ba_\br_\bg values, g\bge\bet\bto\bop\bpt\bts\bs parses those in-
+ stead.
+
+ g\bge\bet\bto\bop\bpt\bts\bs can report errors in two ways. If the first character
+ of _\bo_\bp_\bt_\bs_\bt_\br_\bi_\bn_\bg is a colon, g\bge\bet\bto\bop\bpt\bts\bs uses _\bs_\bi_\bl_\be_\bn_\bt error reporting.
+ In normal operation, g\bge\bet\bto\bop\bpt\bts\bs prints diagnostic messages when it
+ encounters invalid options or missing option arguments. If the
+ variable O\bOP\bPT\bTE\bER\bRR\bR is set to 0, g\bge\bet\bto\bop\bpt\bts\bs does not display any error
+ messages, even if the first character of _\bo_\bp_\bt_\bs_\bt_\br_\bi_\bn_\bg is not a
+ colon.
+
+ If g\bge\bet\bto\bop\bpt\bts\bs detects an invalid option, it places ? into _\bn_\ba_\bm_\be and,
+ if not silent, prints an error message and unsets O\bOP\bPT\bTA\bAR\bRG\bG. If
+ g\bge\bet\bto\bop\bpt\bts\bs is silent, it assigns the option character found to O\bOP\bP-\b-
+ T\bTA\bAR\bRG\bG and does not print a diagnostic message.
+
+ If a required argument is not found, and g\bge\bet\bto\bop\bpt\bts\bs is not silent,
+ it sets the value of _\bn_\ba_\bm_\be to a question mark (?\b?), unsets O\bOP\bPT\bTA\bAR\bRG\bG,
+ and prints a diagnostic message. If g\bge\bet\bto\bop\bpt\bts\bs is silent, it sets
+ the value of _\bn_\ba_\bm_\be to a colon (:\b:) and sets O\bOP\bPT\bTA\bAR\bRG\bG to the option
+ character found.
+
+ g\bge\bet\bto\bop\bpt\bts\bs returns true if an option, specified or unspecified, is
+ found. It returns false if the end of options is encountered or
+ an error occurs.
+
+ h\bha\bas\bsh\bh [-\b-l\blr\br] [-\b-p\bp _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be] [-\b-d\bdt\bt] [_\bn_\ba_\bm_\be]
+ Each time h\bha\bas\bsh\bh is invoked, it remembers the full pathname of the
+ command _\bn_\ba_\bm_\be as determined by searching the directories in
+ $\b$P\bPA\bAT\bTH\bH. Any previously-remembered pathname associated with _\bn_\ba_\bm_\be
+ is discarded. If the -\b-p\bp option is supplied, h\bha\bas\bsh\bh uses _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
+ as the full pathname of the command.
+
+ The -\b-r\br option causes the shell to forget all remembered loca-
+ tions. Assigning to the P\bPA\bAT\bTH\bH variable also clears all hashed
+ filenames. The -\b-d\bd option causes the shell to forget the remem-
+ bered location of each _\bn_\ba_\bm_\be.
+
+ If the -\b-t\bt option is supplied, h\bha\bas\bsh\bh prints the full pathname cor-
+ responding to each _\bn_\ba_\bm_\be. If multiple _\bn_\ba_\bm_\be arguments are sup-
+ plied with -\b-t\bt, h\bha\bas\bsh\bh prints the _\bn_\ba_\bm_\be before the corresponding
+ hashed full pathname. The -\b-l\bl option displays output in a format
+ that may be reused as input.
+
+ If no arguments are given, or if only -\b-l\bl is supplied, h\bha\bas\bsh\bh
+ prints information about remembered commands. The -\b-t\bt, -\b-d\bd, and
+ -\b-p\bp options (the options that act on the _\bn_\ba_\bm_\be arguments) are mu-
+ tually exclusive. Only one will be active. If more than one is
+ supplied, -\b-t\bt has higher priority than -\b-p\bp, and both have higher
+ priority than -\b-d\bd.
+
+ The return status is zero unless a _\bn_\ba_\bm_\be is not found or an in-
+ valid option is supplied.
+
+ h\bhe\bel\blp\bp [-\b-d\bdm\bms\bs] [_\bp_\ba_\bt_\bt_\be_\br_\bn]
+ Display helpful information about builtin commands. If _\bp_\ba_\bt_\bt_\be_\br_\bn
+ is specified, h\bhe\bel\blp\bp gives detailed help on all commands matching
+ _\bp_\ba_\bt_\bt_\be_\br_\bn as described below; otherwise it displays a list of all
+ the builtins and shell compound commands.
+
+ Options, if supplied, have the follow meanings:
+
+ -\b-d\bd Display a short description of each _\bp_\ba_\bt_\bt_\be_\br_\bn
+ -\b-m\bm Display the description of each _\bp_\ba_\bt_\bt_\be_\br_\bn in a manpage-like
+ format
+ -\b-s\bs Display only a short usage synopsis for each _\bp_\ba_\bt_\bt_\be_\br_\bn
+
+ If _\bp_\ba_\bt_\bt_\be_\br_\bn contains pattern matching characters (see P\bPa\bat\btt\bte\ber\brn\bn
+ M\bMa\bat\btc\bch\bhi\bin\bng\bg above) it's treated as a shell pattern and h\bhe\bel\blp\bp prints
+ the description of each help topic matching _\bp_\ba_\bt_\bt_\be_\br_\bn.
+
+ If not, and _\bp_\ba_\bt_\bt_\be_\br_\bn exactly matches the name of a help topic,
+ h\bhe\bel\blp\bp prints the description associated with that topic. Other-
+ wise, h\bhe\bel\blp\bp performs prefix matching and prints the descriptions
+ of all matching help topics.
+
+ The return status is 0 unless no command matches _\bp_\ba_\bt_\bt_\be_\br_\bn.
+
+ h\bhi\bis\bst\bto\bor\bry\by [\b[_\bn]\b]
+ h\bhi\bis\bst\bto\bor\bry\by -\b-c\bc
+ h\bhi\bis\bst\bto\bor\bry\by -\b-d\bd _\bo_\bf_\bf_\bs_\be_\bt
+ h\bhi\bis\bst\bto\bor\bry\by -\b-d\bd _\bs_\bt_\ba_\br_\bt-_\be_\bn_\bd
+ h\bhi\bis\bst\bto\bor\bry\by -\b-a\ban\bnr\brw\bw [_\bf_\bi_\bl_\be_\bn_\ba_\bm_\be]
+ h\bhi\bis\bst\bto\bor\bry\by -\b-p\bp _\ba_\br_\bg [_\ba_\br_\bg ...]
+ h\bhi\bis\bst\bto\bor\bry\by -\b-s\bs _\ba_\br_\bg [_\ba_\br_\bg ...]
+ With no options, display the command history list with numbers.
+ Entries prefixed with a *\b* have been modified. An argument of _\bn
+ lists only the last _\bn entries. If the shell variable H\bHI\bIS\bST\bTT\bTI\bIM\bME\bE-\b-
+ F\bFO\bOR\bRM\bMA\bAT\bT is set and not null, it is used as a format string for
+ _\bs_\bt_\br_\bf_\bt_\bi_\bm_\be(3) to display the time stamp associated with each dis-
+ played history entry. If h\bhi\bis\bst\bto\bor\bry\by uses H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT, it does
+ not print an intervening space between the formatted time stamp
+ and the history entry.
+
+ If _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is supplied, h\bhi\bis\bst\bto\bor\bry\by uses it as the name of the his-
+ tory file; if not, it uses the value of H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE. If _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
+ is not supplied and H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE is unset or null, the -\b-a\ba,\b, -\b-n\bn,\b, -\b-r\br,\b,
+ and -\b-w\bw options have no effect.
+
+ Options, if supplied, have the following meanings:
+ -\b-c\bc Clear the history list by deleting all the entries. This
+ can be used with the other options to replace the history
+ list.
+ -\b-d\bd _\bo_\bf_\bf_\bs_\be_\bt
+ Delete the history entry at position _\bo_\bf_\bf_\bs_\be_\bt. If _\bo_\bf_\bf_\bs_\be_\bt
+ is negative, it is interpreted as relative to one greater
+ than the last history position, so negative indices count
+ back from the end of the history, and an index of -1
+ refers to the current h\bhi\bis\bst\bto\bor\bry\by -\b-d\bd command.
+ -\b-d\bd _\bs_\bt_\ba_\br_\bt-_\be_\bn_\bd
+ Delete the range of history entries between positions
+ _\bs_\bt_\ba_\br_\bt and _\be_\bn_\bd, inclusive. Positive and negative values
+ for _\bs_\bt_\ba_\br_\bt and _\be_\bn_\bd are interpreted as described above.
+ -\b-a\ba Append the "new" history lines to the history file.
+ These are history lines entered since the beginning of
+ the current b\bba\bas\bsh\bh session, but not already appended to the
+ history file.
+ -\b-n\bn Read the history lines not already read from the history
+ file and add them to the current history list. These are
+ lines appended to the history file since the beginning of
+ the current b\bba\bas\bsh\bh session.
+ -\b-r\br Read the history file and append its contents to the cur-
+ rent history list.
+ -\b-w\bw Write the current history list to the history file, over-
+ writing the history file.
+ -\b-p\bp Perform history substitution on the following _\ba_\br_\bg_\bs and
+ display the result on the standard output, without stor-
+ ing the results in the history list. Each _\ba_\br_\bg must be
+ quoted to disable normal history expansion.
+ -\b-s\bs Store the _\ba_\br_\bg_\bs in the history list as a single entry.
+ The last command in the history list is removed before
+ adding the _\ba_\br_\bg_\bs.
+
+ If the H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable is set, h\bhi\bis\bst\bto\bor\bry\by writes the time
+ stamp information associated with each history entry to the his-
+ tory file, marked with the history comment character as de-
+ scribed above. When the history file is read, lines beginning
+ with the history comment character followed immediately by a
+ digit are interpreted as timestamps for the following history
+ entry.
+
+ The return value is 0 unless an invalid option is encountered,
+ an error occurs while reading or writing the history file, an
+ invalid _\bo_\bf_\bf_\bs_\be_\bt or range is supplied as an argument to -\b-d\bd, or the
+ history expansion supplied as an argument to -\b-p\bp fails.
+
+ j\bjo\bob\bbs\bs [-\b-l\bln\bnp\bpr\brs\bs] [ _\bj_\bo_\bb_\bs_\bp_\be_\bc ... ]
+ j\bjo\bob\bbs\bs -\b-x\bx _\bc_\bo_\bm_\bm_\ba_\bn_\bd [ _\ba_\br_\bg_\bs ... ]
+ The first form lists the active jobs. The options have the fol-
+ lowing meanings:
+ -\b-l\bl List process IDs in addition to the normal information.
+ -\b-n\bn Display information only about jobs that have changed
+ status since the user was last notified of their status.
+ -\b-p\bp List only the process ID of the job's process group
+ leader.
+ -\b-r\br Display only running jobs.
+ -\b-s\bs Display only stopped jobs.
+
+ If _\bj_\bo_\bb_\bs_\bp_\be_\bc is supplied, j\bjo\bob\bbs\bs restricts output to information
+ about that job. The return status is 0 unless an invalid option
+ is encountered or an invalid _\bj_\bo_\bb_\bs_\bp_\be_\bc is supplied.
+
+ If the -\b-x\bx option is supplied, j\bjo\bob\bbs\bs replaces any _\bj_\bo_\bb_\bs_\bp_\be_\bc found in
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd or _\ba_\br_\bg_\bs with the corresponding process group ID, and ex-
+ ecutes _\bc_\bo_\bm_\bm_\ba_\bn_\bd, passing it _\ba_\br_\bg_\bs, returning its exit status.
+
+ k\bki\bil\bll\bl [-\b-s\bs _\bs_\bi_\bg_\bs_\bp_\be_\bc | -\b-n\bn _\bs_\bi_\bg_\bn_\bu_\bm | -\b-_\bs_\bi_\bg_\bs_\bp_\be_\bc] _\bi_\bd [ ... ]
+ k\bki\bil\bll\bl -\b-l\bl|-\b-L\bL [_\bs_\bi_\bg_\bs_\bp_\be_\bc | _\be_\bx_\bi_\bt_\b__\bs_\bt_\ba_\bt_\bu_\bs]
+ Send the signal specified by _\bs_\bi_\bg_\bs_\bp_\be_\bc or _\bs_\bi_\bg_\bn_\bu_\bm to the processes
+ named by each _\bi_\bd. Each _\bi_\bd may be a job specification _\bj_\bo_\bb_\bs_\bp_\be_\bc or
+ a process ID _\bp_\bi_\bd. _\bs_\bi_\bg_\bs_\bp_\be_\bc is either a case-insensitive signal
+ name such as S\bSI\bIG\bGK\bKI\bIL\bLL\bL (with or without the S\bSI\bIG\bG prefix) or a sig-
+ nal number; _\bs_\bi_\bg_\bn_\bu_\bm is a signal number. If _\bs_\bi_\bg_\bs_\bp_\be_\bc is not sup-
+ plied, then k\bki\bil\bll\bl sends S\bSI\bIG\bGT\bTE\bER\bRM\bM.
+
+ The -\b-l\bl option lists the signal names. If any arguments are sup-
+ plied when -\b-l\bl is given, k\bki\bil\bll\bl lists the names of the signals cor-
+ responding to the arguments, and the return status is 0. The
+ _\be_\bx_\bi_\bt_\b__\bs_\bt_\ba_\bt_\bu_\bs argument to -\b-l\bl is a number specifying either a sig-
+ nal number or the exit status of a process terminated by a sig-
+ nal; if it is supplied, k\bki\bil\bll\bl prints the name of the signal that
+ caused the process to terminate. k\bki\bil\bll\bl assumes that process exit
+ statuses are greater than 128; anything less than that is a sig-
+ nal number. The -\b-L\bL option is equivalent to -\b-l\bl.
+
+ k\bki\bil\bll\bl returns true if at least one signal was successfully sent,
+ or false if an error occurs or an invalid option is encountered.
+
+ l\ble\bet\bt _\ba_\br_\bg [_\ba_\br_\bg ...]
+ Each _\ba_\br_\bg is evaluated as an arithmetic expression (see A\bAR\bRI\bIT\bTH\bH-\b-
+ M\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN above). If the last _\ba_\br_\bg evaluates to 0, l\ble\bet\bt
+ returns 1; otherwise l\ble\bet\bt returns 0.
+
+ l\blo\boc\bca\bal\bl [_\bo_\bp_\bt_\bi_\bo_\bn] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be] ... | - ]
+ For each argument, create a local variable named _\bn_\ba_\bm_\be and assign
+ it _\bv_\ba_\bl_\bu_\be. The _\bo_\bp_\bt_\bi_\bo_\bn can be any of the options accepted by d\bde\be-\b-
+ c\bcl\bla\bar\bre\be. When l\blo\boc\bca\bal\bl is used within a function, it causes the
+ variable _\bn_\ba_\bm_\be to have a visible scope restricted to that func-
+ tion and its children. It is an error to use l\blo\boc\bca\bal\bl when not
+ within a function.
+
+ If _\bn_\ba_\bm_\be is -, it makes the set of shell options local to the
+ function in which l\blo\boc\bca\bal\bl is invoked: any shell options changed
+ using the s\bse\bet\bt builtin inside the function after the call to l\blo\bo-\b-
+ c\bca\bal\bl are restored to their original values when the function re-
+ turns. The restore is performed as if a series of s\bse\bet\bt commands
+ were executed to restore the values that were in place before
+ the function.
+
+ With no operands, l\blo\boc\bca\bal\bl writes a list of local variables to the
+ standard output.
+
+ The return status is 0 unless l\blo\boc\bca\bal\bl is used outside a function,
+ an invalid _\bn_\ba_\bm_\be is supplied, or _\bn_\ba_\bm_\be is a readonly variable.
+
+ l\blo\bog\bgo\bou\but\bt [\b[_\bn]\b]
+ Exit a login shell, returning a status of _\bn to the shell's par-
+ ent.
+
+ m\bma\bap\bpf\bfi\bil\ble\be [-\b-d\bd _\bd_\be_\bl_\bi_\bm] [-\b-n\bn _\bc_\bo_\bu_\bn_\bt] [-\b-O\bO _\bo_\br_\bi_\bg_\bi_\bn] [-\b-s\bs _\bc_\bo_\bu_\bn_\bt] [-\b-t\bt] [-\b-u\bu _\bf_\bd] [-\b-C\bC
+ _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk] [-\b-c\bc _\bq_\bu_\ba_\bn_\bt_\bu_\bm] [_\ba_\br_\br_\ba_\by]
+ r\bre\bea\bad\bda\bar\brr\bra\bay\by [-\b-d\bd _\bd_\be_\bl_\bi_\bm] [-\b-n\bn _\bc_\bo_\bu_\bn_\bt] [-\b-O\bO _\bo_\br_\bi_\bg_\bi_\bn] [-\b-s\bs _\bc_\bo_\bu_\bn_\bt] [-\b-t\bt] [-\b-u\bu _\bf_\bd] [-\b-C\bC
+ _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk] [-\b-c\bc _\bq_\bu_\ba_\bn_\bt_\bu_\bm] [_\ba_\br_\br_\ba_\by]
+ Read lines from the standard input, or from file descriptor _\bf_\bd
+ if the -\b-u\bu option is supplied, into the indexed array variable
+ _\ba_\br_\br_\ba_\by. The variable M\bMA\bAP\bPF\bFI\bIL\bLE\bE is the default _\ba_\br_\br_\ba_\by. Options, if
+ supplied, have the following meanings:
+ -\b-d\bd Use the first character of _\bd_\be_\bl_\bi_\bm to terminate each input
+ line, rather than newline. If _\bd_\be_\bl_\bi_\bm is the empty string,
+ m\bma\bap\bpf\bfi\bil\ble\be will terminate a line when it reads a NUL charac-
+ ter.
+ -\b-n\bn Copy at most _\bc_\bo_\bu_\bn_\bt lines. If _\bc_\bo_\bu_\bn_\bt is 0, copy all lines.
+ -\b-O\bO Begin assigning to _\ba_\br_\br_\ba_\by at index _\bo_\br_\bi_\bg_\bi_\bn. The default
+ index is 0.
+ -\b-s\bs Discard the first _\bc_\bo_\bu_\bn_\bt lines read.
+ -\b-t\bt Remove a trailing _\bd_\be_\bl_\bi_\bm (default newline) from each line
+ read.
+ -\b-u\bu Read lines from file descriptor _\bf_\bd instead of the stan-
+ dard input.
+ -\b-C\bC Evaluate _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk each time _\bq_\bu_\ba_\bn_\bt_\bu_\bm lines are read. The
+ -\b-c\bc option specifies _\bq_\bu_\ba_\bn_\bt_\bu_\bm.
+ -\b-c\bc Specify the number of lines read between each call to
+ _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk.
+
+ If -\b-C\bC is specified without -\b-c\bc, the default quantum is 5000.
+ When _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk is evaluated, it is supplied the index of the next
+ array element to be assigned and the line to be assigned to that
+ element as additional arguments. _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk is evaluated after
+ the line is read but before the array element is assigned.
+
+ If not supplied with an explicit origin, m\bma\bap\bpf\bfi\bil\ble\be will clear _\ba_\br_\b-
+ _\br_\ba_\by before assigning to it.
+
+ m\bma\bap\bpf\bfi\bil\ble\be returns zero unless an invalid option or option argument
+ is supplied, _\ba_\br_\br_\ba_\by is invalid or unassignable, or if _\ba_\br_\br_\ba_\by is
+ not an indexed array.
+
+ p\bpo\bop\bpd\bd [-n\bn] [+_\bn] [-_\bn]
+ Remove entries from the directory stack. The elements are num-
+ bered from 0 starting at the first directory listed by d\bdi\bir\brs\bs, so
+ p\bpo\bop\bpd\bd is equivalent to "popd +0." With no arguments, p\bpo\bop\bpd\bd re-
+ moves the top directory from the stack, and changes to the new
+ top directory. Arguments, if supplied, have the following mean-
+ ings:
+ -\b-n\bn Suppress the normal change of directory when removing di-
+ rectories from the stack, only manipulate the stack.
+ +\b+_\bn Remove the _\bnth entry counting from the left of the list
+ shown by d\bdi\bir\brs\bs, starting with zero, from the stack. For
+ example: "popd +0" removes the first directory, "popd +1"
+ the second.
+ -\b-_\bn Remove the _\bnth entry counting from the right of the list
+ shown by d\bdi\bir\brs\bs, starting with zero. For example: "popd
+ -0" removes the last directory, "popd -1" the next to
+ last.
+
+ If the top element of the directory stack is modified, and the
+ _\b-_\bn option was not supplied, p\bpo\bop\bpd\bd uses the c\bcd\bd builtin to change
+ to the directory at the top of the stack. If the c\bcd\bd fails, p\bpo\bop\bpd\bd
+ returns a non-zero value.
+
+ Otherwise, p\bpo\bop\bpd\bd returns false if an invalid option is supplied,
+ the directory stack is empty, or _\bn specifies a non-existent di-
+ rectory stack entry.
+
+ If the p\bpo\bop\bpd\bd command is successful, b\bba\bas\bsh\bh runs d\bdi\bir\brs\bs to show the
+ final contents of the directory stack, and the return status is
+ 0.
+
+ p\bpr\bri\bin\bnt\btf\bf [-\b-v\bv _\bv_\ba_\br] _\bf_\bo_\br_\bm_\ba_\bt [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
+ Write the formatted _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs to the standard output under the
+ control of the _\bf_\bo_\br_\bm_\ba_\bt. The -\b-v\bv option assigns the output to the
+ variable _\bv_\ba_\br rather than printing it to the standard output.
+
+ The _\bf_\bo_\br_\bm_\ba_\bt is a character string which contains three types of
+ objects: plain characters, which are simply copied to standard
+ output, character escape sequences, which are converted and
+ copied to the standard output, and format specifications, each
+ of which causes printing of the next successive _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt. In
+ addition to the standard _\bp_\br_\bi_\bn_\bt_\bf(3) format characters c\bcC\bCs\bsS\bS-\b-
+ n\bnd\bdi\bio\bou\bux\bxX\bXe\beE\bEf\bfF\bFg\bgG\bGa\baA\bA, p\bpr\bri\bin\bnt\btf\bf interprets the following additional for-
+ mat specifiers:
+ %\b%b\bb causes p\bpr\bri\bin\bnt\btf\bf to expand backslash escape sequences in the
+ corresponding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt in the same way as e\bec\bch\bho\bo -\b-e\be.
+ %\b%q\bq causes p\bpr\bri\bin\bnt\btf\bf to output the corresponding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt in a
+ format that can be reused as shell input. %\b%q\bq and %\b%Q\bQ use
+ the $\b$'\b''\b' quoting style if any characters in the argument
+ string require it, and backslash quoting otherwise. If
+ the format string uses the _\bp_\br_\bi_\bn_\bt_\bf alternate form, these
+ two formats quote the argument string using single
+ quotes.
+ %\b%Q\bQ like %\b%q\bq, but applies any supplied precision to the _\ba_\br_\bg_\bu_\b-
+ _\bm_\be_\bn_\bt before quoting it.
+ %\b%(\b(_\bd_\ba_\bt_\be_\bf_\bm_\bt)\b)T\bT
+ causes p\bpr\bri\bin\bnt\btf\bf to output the date-time string resulting
+ from using _\bd_\ba_\bt_\be_\bf_\bm_\bt as a format string for _\bs_\bt_\br_\bf_\bt_\bi_\bm_\be(3).
+ The corresponding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt is an integer representing the
+ number of seconds since the epoch. This format specifier
+ recognizes two special argument values: -1 represents the
+ current time, and -2 represents the time the shell was
+ invoked. If no argument is specified, conversion behaves
+ as if -1 had been supplied. This is an exception to the
+ usual p\bpr\bri\bin\bnt\btf\bf behavior.
+
+ The %b, %q, and %T format specifiers all use the field width and
+ precision arguments from the format specification and write that
+ many bytes from (or use that wide a field for) the expanded ar-
+ gument, which usually contains more characters than the origi-
+ nal.
+
+ The %n format specifier accepts a corresponding argument that is
+ treated as a shell variable name.
+
+ The %s and %c format specifiers accept an l (long) modifier,
+ which forces them to convert the argument string to a wide-char-
+ acter string and apply any supplied field width and precision in
+ terms of characters, not bytes. The %S and %C format specifiers
+ are equivalent to %ls and %lc, respectively.
+
+ Arguments to non-string format specifiers are treated as C con-
+ stants, except that a leading plus or minus sign is allowed, and
+ if the leading character is a single or double quote, the value
+ is the numeric value of the following character, using the cur-
+ rent locale.
+
+ The _\bf_\bo_\br_\bm_\ba_\bt is reused as necessary to consume all of the _\ba_\br_\bg_\bu_\b-
+ _\bm_\be_\bn_\bt_\bs. If the _\bf_\bo_\br_\bm_\ba_\bt requires more _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs than are supplied,
+ the extra format specifications behave as if a zero value or
+ null string, as appropriate, had been supplied. The return
+ value is zero on success, non-zero if an invalid option is sup-
+ plied or a write or assignment error occurs.
+
+ p\bpu\bus\bsh\bhd\bd [-\b-n\bn] [+_\bn] [-_\bn]
+ p\bpu\bus\bsh\bhd\bd [-\b-n\bn] [_\bd_\bi_\br]
+ Add a directory to the top of the directory stack, or rotate the
+ stack, making the new top of the stack the current working di-
+ rectory. With no arguments, p\bpu\bus\bsh\bhd\bd exchanges the top two ele-
+ ments of the directory stack. Arguments, if supplied, have the
+ following meanings:
+ -\b-n\bn Suppress the normal change of directory when rotating or
+ adding directories to the stack, only manipulate the
+ stack.
+ +\b+_\bn Rotate the stack so that the _\bnth directory (counting from
+ the left of the list shown by d\bdi\bir\brs\bs, starting with zero)
+ is at the top.
+ -\b-_\bn Rotates the stack so that the _\bnth directory (counting
+ from the right of the list shown by d\bdi\bir\brs\bs, starting with
+ zero) is at the top.
+ _\bd_\bi_\br Adds _\bd_\bi_\br to the directory stack at the top.
+
+ After the stack has been modified, if the -\b-n\bn option was not sup-
+ plied, p\bpu\bus\bsh\bhd\bd uses the c\bcd\bd builtin to change to the directory at
+ the top of the stack. If the c\bcd\bd fails, p\bpu\bus\bsh\bhd\bd returns a non-zero
+ value.
+
+ Otherwise, if no arguments are supplied, p\bpu\bus\bsh\bhd\bd returns zero un-
+ less the directory stack is empty. When rotating the directory
+ stack, p\bpu\bus\bsh\bhd\bd returns zero unless the directory stack is empty or
+ _\bn specifies a non-existent directory stack element.
+
+ If the p\bpu\bus\bsh\bhd\bd command is successful, b\bba\bas\bsh\bh runs d\bdi\bir\brs\bs to show the
+ final contents of the directory stack.
+
+ p\bpw\bwd\bd [-\b-L\bLP\bP]
+ Print the absolute pathname of the current working directory.
+ The pathname printed contains no symbolic links if the -\b-P\bP option
+ is supplied or the -\b-o\bo p\bph\bhy\bys\bsi\bic\bca\bal\bl option to the s\bse\bet\bt builtin command
+ is enabled. If the -\b-L\bL option is used, the pathname printed may
+ contain symbolic links. The return status is 0 unless an error
+ occurs while reading the name of the current directory or an in-
+ valid option is supplied.
+
+ r\bre\bea\bad\bd [-\b-E\bEe\ber\brs\bs] [-\b-a\ba _\ba_\bn_\ba_\bm_\be] [-\b-d\bd _\bd_\be_\bl_\bi_\bm] [-\b-i\bi _\bt_\be_\bx_\bt] [-\b-n\bn _\bn_\bc_\bh_\ba_\br_\bs] [-\b-N\bN _\bn_\bc_\bh_\ba_\br_\bs]
+ [-\b-p\bp _\bp_\br_\bo_\bm_\bp_\bt] [-\b-t\bt _\bt_\bi_\bm_\be_\bo_\bu_\bt] [-\b-u\bu _\bf_\bd] [_\bn_\ba_\bm_\be ...]
+ Read one line from the standard input, or from the file descrip-
+ tor _\bf_\bd supplied as an argument to the -\b-u\bu option, split it into
+ words as described above under W\bWo\bor\brd\bd S\bSp\bpl\bli\bit\btt\bti\bin\bng\bg, and assign the
+ first word to the first _\bn_\ba_\bm_\be, the second word to the second
+ _\bn_\ba_\bm_\be, and so on. If there are more words than names, the re-
+ maining words and their intervening delimiters are assigned to
+ the last _\bn_\ba_\bm_\be. If there are fewer words read from the input
+ stream than names, the remaining names are assigned empty val-
+ ues. The characters in the value of the I\bIF\bFS\bS variable are used
+ to split the line into words using the same rules the shell uses
+ for expansion (described above under W\bWo\bor\brd\bd S\bSp\bpl\bli\bit\btt\bti\bin\bng\bg). The back-
+ slash character (\\b\) removes any special meaning for the next
+ character read and is used for line continuation.
+
+ Options, if supplied, have the following meanings:
+ -\b-a\ba _\ba_\bn_\ba_\bm_\be
+ The words are assigned to sequential indices of the array
+ variable _\ba_\bn_\ba_\bm_\be, starting at 0. _\ba_\bn_\ba_\bm_\be is unset before any
+ new values are assigned. Other _\bn_\ba_\bm_\be arguments are ig-
+ nored.
+ -\b-d\bd _\bd_\be_\bl_\bi_\bm
+ The first character of _\bd_\be_\bl_\bi_\bm terminates the input line,
+ rather than newline. If _\bd_\be_\bl_\bi_\bm is the empty string, r\bre\bea\bad\bd
+ will terminate a line when it reads a NUL character.
+ -\b-e\be If the standard input is coming from a terminal, r\bre\bea\bad\bd
+ uses r\bre\bea\bad\bdl\bli\bin\bne\be (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE above) to obtain the line.
+ R\bRe\bea\bad\bdl\bli\bin\bne\be uses the current (or default, if line editing
+ was not previously active) editing settings, but uses
+ r\bre\bea\bad\bdl\bli\bin\bne\be's default filename completion.
+ -\b-E\bE If the standard input is coming from a terminal, r\bre\bea\bad\bd
+ uses r\bre\bea\bad\bdl\bli\bin\bne\be (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE above) to obtain the line.
+ R\bRe\bea\bad\bdl\bli\bin\bne\be uses the current (or default, if line editing
+ was not previously active) editing settings, but uses
+ bash's default completion, including programmable comple-
+ tion.
+ -\b-i\bi _\bt_\be_\bx_\bt
+ If r\bre\bea\bad\bdl\bli\bin\bne\be is being used to read the line, r\bre\bea\bad\bd places
+ _\bt_\be_\bx_\bt into the editing buffer before editing begins.
+ -\b-n\bn _\bn_\bc_\bh_\ba_\br_\bs
+ r\bre\bea\bad\bd returns after reading _\bn_\bc_\bh_\ba_\br_\bs characters rather than
+ waiting for a complete line of input, unless it encoun-
+ ters EOF or r\bre\bea\bad\bd times out, but honors a delimiter if it
+ reads fewer than _\bn_\bc_\bh_\ba_\br_\bs characters before the delimiter.
+ -\b-N\bN _\bn_\bc_\bh_\ba_\br_\bs
+ r\bre\bea\bad\bd returns after reading exactly _\bn_\bc_\bh_\ba_\br_\bs characters
+ rather than waiting for a complete line of input, unless
+ it encounters EOF or r\bre\bea\bad\bd times out. Any delimiter char-
+ acters in the input are not treated specially and do not
+ cause r\bre\bea\bad\bd to return until it has read _\bn_\bc_\bh_\ba_\br_\bs characters.
+ The result is not split on the characters in I\bIF\bFS\bS; the in-
+ tent is that the variable is assigned exactly the charac-
+ ters read (with the exception of backslash; see the -\b-r\br
+ option below).
+ -\b-p\bp _\bp_\br_\bo_\bm_\bp_\bt
+ Display _\bp_\br_\bo_\bm_\bp_\bt on standard error, without a trailing new-
+ line, before attempting to read any input, but only if
+ input is coming from a terminal.
+ -\b-r\br Backslash does not act as an escape character. The back-
+ slash is considered to be part of the line. In particu-
+ lar, a backslash-newline pair may not then be used as a
+ line continuation.
+ -\b-s\bs Silent mode. If input is coming from a terminal, charac-
+ ters are not echoed.
+ -\b-t\bt _\bt_\bi_\bm_\be_\bo_\bu_\bt
+ Cause r\bre\bea\bad\bd to time out and return failure if it does not
+ read a complete line of input (or a specified number of
+ characters) within _\bt_\bi_\bm_\be_\bo_\bu_\bt seconds. _\bt_\bi_\bm_\be_\bo_\bu_\bt may be a
+ decimal number with a fractional portion following the
+ decimal point. This option is only effective if r\bre\bea\bad\bd is
+ reading input from a terminal, pipe, or other special
+ file; it has no effect when reading from regular files.
+ If r\bre\bea\bad\bd times out, it saves any partial input read into
+ the specified variable _\bn_\ba_\bm_\be, and the exit status is
+ greater than 128. If _\bt_\bi_\bm_\be_\bo_\bu_\bt is 0, r\bre\bea\bad\bd returns immedi-
+ ately, without trying to read any data. In this case,
+ the exit status is 0 if input is available on the speci-
+ fied file descriptor, or the read will return EOF, non-
+ zero otherwise.
+ -\b-u\bu _\bf_\bd Read input from file descriptor _\bf_\bd instead of the stan-
+ dard input.
+
+ Other than the case where _\bd_\be_\bl_\bi_\bm is the empty string, r\bre\bea\bad\bd ig-
+ nores any NUL characters in the input.
+
+ If no _\bn_\ba_\bm_\be_\bs are supplied, r\bre\bea\bad\bd assigns the line read, without
+ the ending delimiter but otherwise unmodified, to the variable
+ R\bRE\bEP\bPL\bLY\bY.
+
+ The exit status is zero, unless end-of-file is encountered, r\bre\bea\bad\bd
+ times out (in which case the status is greater than 128), a
+ variable assignment error (such as assigning to a readonly vari-
+ able) occurs, or an invalid file descriptor is supplied as the
+ argument to -\b-u\bu.
+
+ r\bre\bea\bad\bdo\bon\bnl\bly\by [-\b-a\baA\bAf\bf] [-\b-p\bp] [_\bn_\ba_\bm_\be[=_\bw_\bo_\br_\bd] ...]
+ The given _\bn_\ba_\bm_\be_\bs are marked readonly; the values of these _\bn_\ba_\bm_\be_\bs
+ may not be changed by subsequent assignment or unset. If the -\b-f\bf
+ option is supplied, each _\bn_\ba_\bm_\be refers to a shell function. The
+ -\b-a\ba option restricts the variables to indexed arrays; the -\b-A\bA op-
+ tion restricts the variables to associative arrays. If both op-
+ tions are supplied, -\b-A\bA takes precedence. If no _\bn_\ba_\bm_\be arguments
+ are supplied, or if the -\b-p\bp option is supplied, print a list of
+ all readonly names. The other options may be used to restrict
+ the output to a subset of the set of readonly names. The -\b-p\bp op-
+ tion displays output in a format that may be reused as input.
+
+ r\bre\bea\bad\bdo\bon\bnl\bly\by allows the value of a variable to be set at the same
+ time the readonly attribute is changed by following the variable
+ name with =_\bv_\ba_\bl_\bu_\be. This sets the value of the variable is to
+ _\bv_\ba_\bl_\bu_\be while modifying the readonly attribute.
+
+ The return status is 0 unless an invalid option is encountered,
+ one of the _\bn_\ba_\bm_\be_\bs is not a valid shell variable name, or -\b-f\bf is
+ supplied with a _\bn_\ba_\bm_\be that is not a function.
+
+ r\bre\bet\btu\bur\brn\bn [_\bn]
+ Stop executing a shell function or sourced file and return the
+ value specified by _\bn to its caller. If _\bn is omitted, the return
+ status is that of the last command executed. If r\bre\bet\btu\bur\brn\bn is exe-
+ cuted by a trap handler, the last command used to determine the
+ status is the last command executed before the trap handler. If
+ r\bre\bet\btu\bur\brn\bn is executed during a D\bDE\bEB\bBU\bUG\bG trap, the last command used to
+ determine the status is the last command executed by the trap
+ handler before r\bre\bet\btu\bur\brn\bn was invoked.
+
+ When r\bre\bet\btu\bur\brn\bn is used to terminate execution of a script being ex-
+ ecuted by the .\b. (s\bso\bou\bur\brc\bce\be) command, it causes the shell to stop
+ executing that script and return either _\bn or the exit status of
+ the last command executed within the script as the exit status
+ of the script. If _\bn is supplied, the return value is its least
+ significant 8 bits.
+
+ Any command associated with the R\bRE\bET\bTU\bUR\bRN\bN trap is executed before
+ execution resumes after the function or script.
+
+ The return status is non-zero if r\bre\bet\btu\bur\brn\bn is supplied a non-nu-
+ meric argument, or is used outside a function and not during ex-
+ ecution of a script by .\b. or s\bso\bou\bur\brc\bce\be.
+
+ s\bse\bet\bt [-\b-a\bab\bbe\bef\bfh\bhk\bkm\bmn\bnp\bpt\btu\buv\bvx\bxB\bBC\bCE\bEH\bHP\bPT\bT] [-\b-o\bo _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be] [-\b--\b-] [-\b-] [_\ba_\br_\bg ...]
+ s\bse\bet\bt [+\b+a\bab\bbe\bef\bfh\bhk\bkm\bmn\bnp\bpt\btu\buv\bvx\bxB\bBC\bCE\bEH\bHP\bPT\bT] [+\b+o\bo _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be] [-\b--\b-] [-\b-] [_\ba_\br_\bg ...]
+ s\bse\bet\bt -\b-o\bo
+ s\bse\bet\bt +\b+o\bo Without options, display the name and value of each shell vari-
+ able in a format that can be reused as input for setting or re-
+ setting the currently-set variables. Read-only variables cannot
+ be reset. In posix mode, only shell variables are listed. The
+ output is sorted according to the current locale. When options
+ are specified, they set or unset shell attributes. Any argu-
+ ments remaining after option processing are treated as values
+ for the positional parameters and are assigned, in order, to $\b$1\b1,
+ $\b$2\b2, ..., $\b$_\bn. Options, if specified, have the following mean-
+ ings:
+ -\b-a\ba Each variable or function that is created or modified is
+ given the export attribute and marked for export to the
+ environment of subsequent commands.
+ -\b-b\bb Report the status of terminated background jobs immedi-
+ ately, rather than before the next primary prompt or af-
+ ter a foreground command terminates. This is effective
+ only when job control is enabled.
+ -\b-e\be Exit immediately if a _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be (which may consist of a
+ single _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd), a _\bl_\bi_\bs_\bt, or a _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd _\bc_\bo_\bm_\bm_\ba_\bn_\bd
+ (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR above), exits with a non-zero status.
+ The shell does not exit if the command that fails is
+ part of the command list immediately following a w\bwh\bhi\bil\ble\be
+ or u\bun\bnt\bti\bil\bl reserved word, part of the test following the
+ i\bif\bf or e\bel\bli\bif\bf reserved words, part of any command executed
+ in a &\b&&\b& or |\b||\b| list except the command following the fi-
+ nal &\b&&\b& or |\b||\b|, any command in a pipeline but the last
+ (subject to the state of the p\bpi\bip\bpe\bef\bfa\bai\bil\bl shell option), or
+ if the command's return value is being inverted with !\b!.
+ If a compound command other than a subshell returns a
+ non-zero status because a command failed while -\b-e\be was
+ being ignored, the shell does not exit. A trap on E\bER\bRR\bR,
+ if set, is executed before the shell exits. This option
+ applies to the shell environment and each subshell envi-
+ ronment separately (see C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN E\bEN\bNV\bVI\bIR\bRO\bON\bNM\bME\bEN\bNT\bT
+ above), and may cause subshells to exit before executing
+ all the commands in the subshell.
+
+ If a compound command or shell function executes in a
+ context where -\b-e\be is being ignored, none of the commands
+ executed within the compound command or function body
+ will be affected by the -\b-e\be setting, even if -\b-e\be is set
+ and a command returns a failure status. If a compound
+ command or shell function sets -\b-e\be while executing in a
+ context where -\b-e\be is ignored, that setting will not have
+ any effect until the compound command or the command
+ containing the function call completes.
+ -\b-f\bf Disable pathname expansion.
+ -\b-h\bh Remember the location of commands as they are looked up
+ for execution. This is enabled by default.
+ -\b-k\bk All arguments in the form of assignment statements are
+ placed in the environment for a command, not just those
+ that precede the command name.
+ -\b-m\bm Monitor mode. Job control is enabled. This option is
+ on by default for interactive shells on systems that
+ support it (see J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL above). All processes run
+ in a separate process group. When a background job com-
+ pletes, the shell prints a line containing its exit sta-
+ tus.
+ -\b-n\bn Read commands but do not execute them. This may be used
+ to check a shell script for syntax errors. This is ig-
+ nored by interactive shells.
+ -\b-o\bo _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be
+ The _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be can be one of the following:
+ a\bal\bll\ble\bex\bxp\bpo\bor\brt\bt
+ Same as -\b-a\ba.
+ b\bbr\bra\bac\bce\bee\bex\bxp\bpa\ban\bnd\bd
+ Same as -\b-B\bB.
+ e\bem\bma\bac\bcs\bs Use an emacs-style command line editing inter-
+ face. This is enabled by default when the shell
+ is interactive, unless the shell is started with
+ the -\b--\b-n\bno\boe\bed\bdi\bit\bti\bin\bng\bg option. This also affects the
+ editing interface used for r\bre\bea\bad\bd -\b-e\be.
+ e\ber\brr\bre\bex\bxi\bit\bt Same as -\b-e\be.
+ e\ber\brr\brt\btr\bra\bac\bce\be
+ Same as -\b-E\bE.
+ f\bfu\bun\bnc\bct\btr\bra\bac\bce\be
+ Same as -\b-T\bT.
+ h\bha\bas\bsh\bha\bal\bll\bl Same as -\b-h\bh.
+ h\bhi\bis\bst\bte\bex\bxp\bpa\ban\bnd\bd
+ Same as -\b-H\bH.
+ h\bhi\bis\bst\bto\bor\bry\by Enable command history, as described above under
+ H\bHI\bIS\bST\bTO\bOR\bRY\bY. This option is on by default in inter-
+ active shells.
+ i\big\bgn\bno\bor\bre\bee\beo\bof\bf
+ The effect is as if the shell command
+ "IGNOREEOF=10" had been executed (see S\bSh\bhe\bel\bll\bl
+ V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs above).
+ k\bke\bey\byw\bwo\bor\brd\bd Same as -\b-k\bk.
+ m\bmo\bon\bni\bit\bto\bor\br Same as -\b-m\bm.
+ n\bno\boc\bcl\blo\bob\bbb\bbe\ber\br
+ Same as -\b-C\bC.
+ n\bno\boe\bex\bxe\bec\bc Same as -\b-n\bn.
+ n\bno\bog\bgl\blo\bob\bb Same as -\b-f\bf.
+ n\bno\bol\blo\bog\bg Currently ignored.
+ n\bno\bot\bti\bif\bfy\by Same as -\b-b\bb.
+ n\bno\bou\bun\bns\bse\bet\bt Same as -\b-u\bu.
+ o\bon\bne\bec\bcm\bmd\bd Same as -\b-t\bt.
+ p\bph\bhy\bys\bsi\bic\bca\bal\bl
+ Same as -\b-P\bP.
+ p\bpi\bip\bpe\bef\bfa\bai\bil\bl
+ If set, the return value of a pipeline is the
+ value of the last (rightmost) command to exit
+ with a non-zero status, or zero if all commands
+ in the pipeline exit successfully. This option
+ is disabled by default.
+ p\bpo\bos\bsi\bix\bx Enable posix mode; change the behavior of b\bba\bas\bsh\bh
+ where the default operation differs from the
+ POSIX standard to match the standard. See S\bSE\bEE\bE
+ A\bAL\bLS\bSO\bO below for a reference to a document that
+ details how posix mode affects bash's behavior.
+ p\bpr\bri\biv\bvi\bil\ble\beg\bge\bed\bd
+ Same as -\b-p\bp.
+ v\bve\ber\brb\bbo\bos\bse\be Same as -\b-v\bv.
+ v\bvi\bi Use a vi-style command line editing interface.
+ This also affects the editing interface used for
+ r\bre\bea\bad\bd -\b-e\be.
+ x\bxt\btr\bra\bac\bce\be Same as -\b-x\bx.
+ If -\b-o\bo is supplied with no _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be, s\bse\bet\bt prints the
+ current shell option settings. If +\b+o\bo is supplied with
+ no _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be, s\bse\bet\bt prints a series of s\bse\bet\bt commands to
+ recreate the current option settings on the standard
+ output.
+ -\b-p\bp Turn on _\bp_\br_\bi_\bv_\bi_\bl_\be_\bg_\be_\bd mode. In this mode, the shell does
+ not read the $\b$E\bEN\bNV\bV and $\b$B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV files, shell functions
+ are not inherited from the environment, and the S\bSH\bHE\bEL\bL-\b-
+ L\bLO\bOP\bPT\bTS\bS, B\bBA\bAS\bSH\bHO\bOP\bPT\bTS\bS, C\bCD\bDP\bPA\bAT\bTH\bH, and G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE variables, if
+ they appear in the environment, are ignored. If the
+ shell is started with the effective user (group) id not
+ equal to the real user (group) id, and the -\b-p\bp option is
+ not supplied, these actions are taken and the effective
+ user id is set to the real user id. If the -\b-p\bp option is
+ supplied at startup, the effective user id is not reset.
+ Turning this option off causes the effective user and
+ group ids to be set to the real user and group ids.
+ -\b-r\br Enable restricted shell mode. This option cannot be un-
+ set once it has been set.
+ -\b-t\bt Exit after reading and executing one command.
+ -\b-u\bu Treat unset variables and parameters other than the spe-
+ cial parameters "@" and "*", or array variables sub-
+ scripted with "@" or "*", as an error when performing
+ parameter expansion. If expansion is attempted on an
+ unset variable or parameter, the shell prints an error
+ message, and, if not interactive, exits with a non-zero
+ status.
+ -\b-v\bv Print shell input lines as they are read.
+ -\b-x\bx After expanding each _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd, f\bfo\bor\br command, c\bca\bas\bse\be
+ command, s\bse\bel\ble\bec\bct\bt command, or arithmetic f\bfo\bor\br command, dis-
+ play the expanded value of P\bPS\bS4\b4, followed by the command
+ and its expanded arguments or associated word list, to
+ the standard error.
+ -\b-B\bB The shell performs brace expansion (see B\bBr\bra\bac\bce\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
+ above). This is on by default.
+ -\b-C\bC If set, b\bba\bas\bsh\bh does not overwrite an existing file with
+ the >\b>, >\b>&\b&, and <\b<>\b> redirection operators. Using the
+ redirection operator >\b>|\b| instead of >\b> will override this
+ and force the creation of an output file.
+ -\b-E\bE If set, any trap on E\bER\bRR\bR is inherited by shell functions,
+ command substitutions, and commands executed in a sub-
+ shell environment. The E\bER\bRR\bR trap is normally not inher-
+ ited in such cases.
+ -\b-H\bH Enable !\b! style history substitution. This option is on
+ by default when the shell is interactive.
+ -\b-P\bP If set, the shell does not resolve symbolic links when
+ executing commands such as c\bcd\bd that change the current
+ working directory. It uses the physical directory
+ structure instead. By default, b\bba\bas\bsh\bh follows the logical
+ chain of directories when performing commands which
+ change the current directory.
+ -\b-T\bT If set, any traps on D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN are inherited by
+ shell functions, command substitutions, and commands ex-
+ ecuted in a subshell environment. The D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN
+ traps are normally not inherited in such cases.
+ -\b--\b- If no arguments follow this option, unset the positional
+ parameters. Otherwise, set the positional parameters to
+ the _\ba_\br_\bgs, even if some of them begin with a -\b-.
+ -\b- Signal the end of options, and assign all remaining _\ba_\br_\bgs
+ to the positional parameters. The -\b-x\bx and -\b-v\bv options are
+ turned off. If there are no _\ba_\br_\bgs, the positional para-
+ meters remain unchanged.
+
+ The options are off by default unless otherwise noted. Using +
+ rather than - causes these options to be turned off. The op-
+ tions can also be specified as arguments to an invocation of the
+ shell. The current set of options may be found in $\b$-\b-. The re-
+ turn status is always zero unless an invalid option is encoun-
+ tered.
+
+ s\bsh\bhi\bif\bft\bt [_\bn]
+ Rename positional parameters from _\bn+1 ... to $\b$1\b1 .\b..\b..\b..\b. Parameters
+ represented by the numbers $\b$#\b# down to $\b$#\b#-_\bn+1 are unset. _\bn must
+ be a non-negative number less than or equal to $\b$#\b#. If _\bn is 0,
+ no parameters are changed. If _\bn is not given, it is assumed to
+ be 1. If _\bn is greater than $\b$#\b#, the positional parameters are
+ not changed. The return status is greater than zero if _\bn is
+ greater than $\b$#\b# or less than zero; otherwise 0.
+
+ s\bsh\bho\bop\bpt\bt [-\b-p\bpq\bqs\bsu\bu] [-\b-o\bo] [_\bo_\bp_\bt_\bn_\ba_\bm_\be ...]
+ Toggle the values of settings controlling optional shell behav-
+ ior. The settings can be either those listed below, or, if the
+ -\b-o\bo option is used, those available with the -\b-o\bo option to the s\bse\bet\bt
+ builtin command.
+
+ With no options, or with the -\b-p\bp option, display a list of all
+ settable options, with an indication of whether or not each is
+ set; if any _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs are supplied, the output is restricted to
+ those options. The -\b-p\bp option displays output in a form that may
+ be reused as input.
+
+ Other options have the following meanings:
+ -\b-s\bs Enable (set) each _\bo_\bp_\bt_\bn_\ba_\bm_\be.
+ -\b-u\bu Disable (unset) each _\bo_\bp_\bt_\bn_\ba_\bm_\be.
+ -\b-q\bq Suppresses normal output (quiet mode); the return status
+ indicates whether the _\bo_\bp_\bt_\bn_\ba_\bm_\be is set or unset. If multi-
+ ple _\bo_\bp_\bt_\bn_\ba_\bm_\be arguments are supplied with -\b-q\bq, the return
+ status is zero if all _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs are enabled; non-zero oth-
+ erwise.
+ -\b-o\bo Restricts the values of _\bo_\bp_\bt_\bn_\ba_\bm_\be to be those defined for
+ the -\b-o\bo option to the s\bse\bet\bt builtin.
+
+ If either -\b-s\bs or -\b-u\bu is used with no _\bo_\bp_\bt_\bn_\ba_\bm_\be arguments, s\bsh\bho\bop\bpt\bt
+ shows only those options which are set or unset, respectively.
+ Unless otherwise noted, the s\bsh\bho\bop\bpt\bt options are disabled (unset)
+ by default.
+
+ The return status when listing options is zero if all _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs
+ are enabled, non-zero otherwise. When setting or unsetting op-
+ tions, the return status is zero unless an _\bo_\bp_\bt_\bn_\ba_\bm_\be is not a
+ valid shell option.
+
+ The list of s\bsh\bho\bop\bpt\bt options is:
+
+ a\bar\brr\bra\bay\by_\b_e\bex\bxp\bpa\ban\bnd\bd_\b_o\bon\bnc\bce\be
+ If set, the shell suppresses multiple evaluation of as-
+ sociative and indexed array subscripts during arithmetic
+ expression evaluation, while executing builtins that can
+ perform variable assignments, and while executing
+ builtins that perform array dereferencing.
+ a\bas\bss\bso\boc\bc_\b_e\bex\bxp\bpa\ban\bnd\bd_\b_o\bon\bnc\bce\be
+ Deprecated; a synonym for a\bar\brr\bra\bay\by_\b_e\bex\bxp\bpa\ban\bnd\bd_\b_o\bon\bnc\bce\be.
+ a\bau\but\bto\boc\bcd\bd If set, a command name that is the name of a directory
+ is executed as if it were the argument to the c\bcd\bd com-
+ mand. This option is only used by interactive shells.
+ b\bba\bas\bsh\bh_\b_s\bso\bou\bur\brc\bce\be_\b_f\bfu\bul\bll\blp\bpa\bat\bth\bh
+ If set, filenames added to the B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE array vari-
+ able are converted to full pathnames (see S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bi-\b-
+ a\bab\bbl\ble\bes\bs above).
+ c\bcd\bda\bab\bbl\ble\be_\b_v\bva\bar\brs\bs
+ If set, an argument to the c\bcd\bd builtin command that is
+ not a directory is assumed to be the name of a variable
+ whose value is the directory to change to.
+ c\bcd\bds\bsp\bpe\bel\bll\bl If set, the c\bcd\bd command attempts to correct minor errors
+ in the spelling of a directory component. Minor errors
+ include transposed characters, a missing character, and
+ one extra character. If c\bcd\bd corrects the directory name,
+ it prints the corrected filename, and the command pro-
+ ceeds. This option is only used by interactive shells.
+ c\bch\bhe\bec\bck\bkh\bha\bas\bsh\bh
+ If set, b\bba\bas\bsh\bh checks that a command found in the hash ta-
+ ble exists before trying to execute it. If a hashed
+ command no longer exists, b\bba\bas\bsh\bh performs a normal path
+ search.
+ c\bch\bhe\bec\bck\bkj\bjo\bob\bbs\bs
+ If set, b\bba\bas\bsh\bh lists the status of any stopped and running
+ jobs before exiting an interactive shell. If any jobs
+ are running, b\bba\bas\bsh\bh defers the exit until a second exit is
+ attempted without an intervening command (see J\bJO\bOB\bB C\bCO\bON\bN-\b-
+ T\bTR\bRO\bOL\bL above). The shell always postpones exiting if any
+ jobs are stopped.
+ c\bch\bhe\bec\bck\bkw\bwi\bin\bns\bsi\biz\bze\be
+ If set, b\bba\bas\bsh\bh checks the window size after each external
+ (non-builtin) command and, if necessary, updates the
+ values of L\bLI\bIN\bNE\bES\bS and C\bCO\bOL\bLU\bUM\bMN\bNS\bS, using the file descriptor
+ associated with the standard error if it is a terminal.
+ This option is enabled by default.
+ c\bcm\bmd\bdh\bhi\bis\bst\bt If set, b\bba\bas\bsh\bh attempts to save all lines of a multiple-
+ line command in the same history entry. This allows
+ easy re-editing of multi-line commands. This option is
+ enabled by default, but only has an effect if command
+ history is enabled, as described above under H\bHI\bIS\bST\bTO\bOR\bRY\bY.
+ c\bco\bom\bmp\bpa\bat\bt3\b31\b1
+ c\bco\bom\bmp\bpa\bat\bt3\b32\b2
+ c\bco\bom\bmp\bpa\bat\bt4\b40\b0
+ c\bco\bom\bmp\bpa\bat\bt4\b41\b1
+ c\bco\bom\bmp\bpa\bat\bt4\b42\b2
+ c\bco\bom\bmp\bpa\bat\bt4\b43\b3
+ c\bco\bom\bmp\bpa\bat\bt4\b44\b4
+ These control aspects of the shell's compatibility mode
+ (see S\bSH\bHE\bEL\bLL\bL C\bCO\bOM\bMP\bPA\bAT\bTI\bIB\bBI\bIL\bLI\bIT\bTY\bY M\bMO\bOD\bDE\bE below).
+ c\bco\bom\bmp\bpl\ble\bet\bte\be_\b_f\bfu\bul\bll\blq\bqu\buo\bot\bte\be
+ If set, b\bba\bas\bsh\bh quotes all shell metacharacters in file-
+ names and directory names when performing completion.
+ If not set, b\bba\bas\bsh\bh removes metacharacters such as the dol-
+ lar sign from the set of characters that will be quoted
+ in completed filenames when these metacharacters appear
+ in shell variable references in words to be completed.
+ This means that dollar signs in variable names that ex-
+ pand to directories will not be quoted; however, any
+ dollar signs appearing in filenames will not be quoted,
+ either. This is active only when bash is using back-
+ slashes to quote completed filenames. This variable is
+ set by default, which is the default bash behavior in
+ versions through 4.2.
+ d\bdi\bir\bre\bex\bxp\bpa\ban\bnd\bd
+ If set, b\bba\bas\bsh\bh replaces directory names with the results
+ of word expansion when performing filename completion.
+ This changes the contents of the r\bre\bea\bad\bdl\bli\bin\bne\be editing
+ buffer. If not set, b\bba\bas\bsh\bh attempts to preserve what the
+ user typed.
+ d\bdi\bir\brs\bsp\bpe\bel\bll\bl
+ If set, b\bba\bas\bsh\bh attempts spelling correction on directory
+ names during word completion if the directory name ini-
+ tially supplied does not exist.
+ d\bdo\bot\btg\bgl\blo\bob\bb If set, b\bba\bas\bsh\bh includes filenames beginning with a "." in
+ the results of pathname expansion. The filenames _\b. and
+ _\b._\b. must always be matched explicitly, even if d\bdo\bot\btg\bgl\blo\bob\bb is
+ set.
+ e\bex\bxe\bec\bcf\bfa\bai\bil\bl
+ If set, a non-interactive shell will not exit if it can-
+ not execute the file specified as an argument to the
+ e\bex\bxe\bec\bc builtin. An interactive shell does not exit if
+ e\bex\bxe\bec\bc fails.
+ e\bex\bxp\bpa\ban\bnd\bd_\b_a\bal\bli\bia\bas\bse\bes\bs
+ If set, aliases are expanded as described above under
+ A\bAL\bLI\bIA\bAS\bSE\bES\bS. This option is enabled by default for interac-
+ tive shells.
+ e\bex\bxt\btd\bde\beb\bbu\bug\bg
+ If set at shell invocation, or in a shell startup file,
+ arrange to execute the debugger profile before the shell
+ starts, identical to the -\b--\b-d\bde\beb\bbu\bug\bgg\bge\ber\br option. If set af-
+ ter invocation, behavior intended for use by debuggers
+ is enabled:
+ 1\b1.\b. The -\b-F\bF option to the d\bde\bec\bcl\bla\bar\bre\be builtin displays the
+ source file name and line number corresponding to
+ each function name supplied as an argument.
+ 2\b2.\b. If the command run by the D\bDE\bEB\bBU\bUG\bG trap returns a
+ non-zero value, the next command is skipped and
+ not executed.
+ 3\b3.\b. If the command run by the D\bDE\bEB\bBU\bUG\bG trap returns a
+ value of 2, and the shell is executing in a sub-
+ routine (a shell function or a shell script exe-
+ cuted by the .\b. or s\bso\bou\bur\brc\bce\be builtins), the shell
+ simulates a call to r\bre\bet\btu\bur\brn\bn.
+ 4\b4.\b. B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC and B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV are updated as described
+ in their descriptions above).
+ 5\b5.\b. Function tracing is enabled: command substitu-
+ tion, shell functions, and subshells invoked with
+ (\b( _\bc_\bo_\bm_\bm_\ba_\bn_\bd )\b) inherit the D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN traps.
+ 6\b6.\b. Error tracing is enabled: command substitution,
+ shell functions, and subshells invoked with (\b(
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd )\b) inherit the E\bER\bRR\bR trap.
+ e\bex\bxt\btg\bgl\blo\bob\bb If set, enable the extended pattern matching features
+ described above under P\bPa\bat\bth\bhn\bna\bam\bme\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn.
+ e\bex\bxt\btq\bqu\buo\bot\bte\be
+ If set, $\b$'_\bs_\bt_\br_\bi_\bn_\bg' and $\b$"_\bs_\bt_\br_\bi_\bn_\bg" quoting is performed
+ within $\b${\b{_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br}\b} expansions enclosed in double
+ quotes. This option is enabled by default.
+ f\bfa\bai\bil\blg\bgl\blo\bob\bb
+ If set, patterns which fail to match filenames during
+ pathname expansion result in an expansion error.
+ f\bfo\bor\brc\bce\be_\b_f\bfi\big\bgn\bno\bor\bre\be
+ If set, the suffixes specified by the F\bFI\bIG\bGN\bNO\bOR\bRE\bE shell
+ variable cause words to be ignored when performing word
+ completion even if the ignored words are the only possi-
+ ble completions. See S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs above for a de-
+ scription of F\bFI\bIG\bGN\bNO\bOR\bRE\bE. This option is enabled by de-
+ fault.
+ g\bgl\blo\bob\bba\bas\bsc\bci\bii\bir\bra\ban\bng\bge\bes\bs
+ If set, range expressions used in pattern matching
+ bracket expressions (see P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg above) behave
+ as if in the traditional C locale when performing com-
+ parisons. That is, pattern matching does not take the
+ current locale's collating sequence into account, so b\bb
+ will not collate between A\bA and B\bB, and upper-case and
+ lower-case ASCII characters will collate together.
+ g\bgl\blo\bob\bbs\bsk\bki\bip\bpd\bdo\bot\bts\bs
+ If set, pathname expansion will never match the file-
+ names _\b. and _\b._\b., even if the pattern begins with a ".".
+ This option is enabled by default.
+ g\bgl\blo\bob\bbs\bst\bta\bar\br
+ If set, the pattern *\b**\b* used in a pathname expansion con-
+ text will match all files and zero or more directories
+ and subdirectories. If the pattern is followed by a /\b/,
+ only directories and subdirectories match.
+ g\bgn\bnu\bu_\b_e\ber\brr\brf\bfm\bmt\bt
+ If set, shell error messages are written in the standard
+ GNU error message format.
+ h\bhi\bis\bst\bta\bap\bpp\bpe\ben\bnd\bd
+ If set, the history list is appended to the file named
+ by the value of the H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE variable when the shell ex-
+ its, rather than overwriting the file.
+ h\bhi\bis\bst\btr\bre\bee\bed\bdi\bit\bt
+ If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, the user is given
+ the opportunity to re-edit a failed history substitu-
+ tion.
+ h\bhi\bis\bst\btv\bve\ber\bri\bif\bfy\by
+ If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, the results of his-
+ tory substitution are not immediately passed to the
+ shell parser. Instead, the resulting line is loaded
+ into the r\bre\bea\bad\bdl\bli\bin\bne\be editing buffer, allowing further modi-
+ fication.
+ h\bho\bos\bst\btc\bco\bom\bmp\bpl\ble\bet\bte\be
+ If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, b\bba\bas\bsh\bh will attempt to
+ perform hostname completion when a word containing a @\b@
+ is being completed (see C\bCo\bom\bmp\bpl\ble\bet\bti\bin\bng\bg under R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE
+ above). This is enabled by default.
+ h\bhu\bup\bpo\bon\bne\bex\bxi\bit\bt
+ If set, b\bba\bas\bsh\bh will send S\bSI\bIG\bGH\bHU\bUP\bP to all jobs when an inter-
+ active login shell exits.
+ i\bin\bnh\bhe\ber\bri\bit\bt_\b_e\ber\brr\bre\bex\bxi\bit\bt
+ If set, command substitution inherits the value of the
+ e\ber\brr\bre\bex\bxi\bit\bt option, instead of unsetting it in the subshell
+ environment. This option is enabled when posix mode is
+ enabled.
+ i\bin\bnt\bte\ber\bra\bac\bct\bti\biv\bve\be_\b_c\bco\bom\bmm\bme\ben\bnt\bts\bs
+ In an interactive shell, a word beginning with #\b# causes
+ that word and all remaining characters on that line to
+ be ignored, as in a non-interactive shell (see C\bCO\bOM\bMM\bME\bEN\bNT\bTS\bS
+ above). This option is enabled by default.
+ l\bla\bas\bst\btp\bpi\bip\bpe\be
+ If set, and job control is not active, the shell runs
+ the last command of a pipeline not executed in the back-
+ ground in the current shell environment.
+ l\bli\bit\bth\bhi\bis\bst\bt If set, and the c\bcm\bmd\bdh\bhi\bis\bst\bt option is enabled, multi-line
+ commands are saved to the history with embedded newlines
+ rather than using semicolon separators where possible.
+ l\blo\boc\bca\bal\blv\bva\bar\br_\b_i\bin\bnh\bhe\ber\bri\bit\bt
+ If set, local variables inherit the value and attributes
+ of a variable of the same name that exists at a previous
+ scope before any new value is assigned. The nameref at-
+ tribute is not inherited.
+ l\blo\boc\bca\bal\blv\bva\bar\br_\b_u\bun\bns\bse\bet\bt
+ If set, calling u\bun\bns\bse\bet\bt on local variables in previous
+ function scopes marks them so subsequent lookups find
+ them unset until that function returns. This is identi-
+ cal to the behavior of unsetting local variables at the
+ current function scope.
+ l\blo\bog\bgi\bin\bn_\b_s\bsh\bhe\bel\bll\bl
+ The shell sets this option if it is started as a login
+ shell (see I\bIN\bNV\bVO\bOC\bCA\bAT\bTI\bIO\bON\bN above). The value may not be
+ changed.
+ m\bma\bai\bil\blw\bwa\bar\brn\bn
+ If set, and a file that b\bba\bas\bsh\bh is checking for mail has
+ been accessed since the last time it was checked, b\bba\bas\bsh\bh
+ displays the message "The mail in _\bm_\ba_\bi_\bl_\bf_\bi_\bl_\be has been
+ read".
+ n\bno\bo_\b_e\bem\bmp\bpt\bty\by_\b_c\bcm\bmd\bd_\b_c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn
+ If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, b\bba\bas\bsh\bh does not search
+ P\bPA\bAT\bTH\bH for possible completions when completion is at-
+ tempted on an empty line.
+ n\bno\boc\bca\bas\bse\beg\bgl\blo\bob\bb
+ If set, b\bba\bas\bsh\bh matches filenames in a case-insensitive
+ fashion when performing pathname expansion (see P\bPa\bat\bth\bhn\bna\bam\bme\be
+ E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn above).
+ n\bno\boc\bca\bas\bse\bem\bma\bat\btc\bch\bh
+ If set, b\bba\bas\bsh\bh matches patterns in a case-insensitive
+ fashion when performing matching while executing c\bca\bas\bse\be or
+ [\b[[\b[ conditional commands, when performing pattern substi-
+ tution word expansions, or when filtering possible com-
+ pletions as part of programmable completion.
+ n\bno\boe\bex\bxp\bpa\ban\bnd\bd_\b_t\btr\bra\ban\bns\bsl\bla\bat\bti\bio\bon\bn
+ If set, b\bba\bas\bsh\bh encloses the translated results of $\b$"\b"..."\b"
+ quoting in single quotes instead of double quotes. If
+ the string is not translated, this has no effect.
+ n\bnu\bul\bll\blg\bgl\blo\bob\bb
+ If set, pathname expansion patterns which match no files
+ (see P\bPa\bat\bth\bhn\bna\bam\bme\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn above) expand to nothing and are
+ removed, rather than expanding to themselves.
+ p\bpa\bat\bts\bsu\bub\bb_\b_r\bre\bep\bpl\bla\bac\bce\bem\bme\ben\bnt\bt
+ If set, b\bba\bas\bsh\bh expands occurrences of &\b& in the replacement
+ string of pattern substitution to the text matched by
+ the pattern, as described under P\bPa\bar\bra\bam\bme\bet\bte\ber\br E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
+ above. This option is enabled by default.
+ p\bpr\bro\bog\bgc\bco\bom\bmp\bp
+ If set, enable the programmable completion facilities
+ (see P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn above). This option is en-
+ abled by default.
+ p\bpr\bro\bog\bgc\bco\bom\bmp\bp_\b_a\bal\bli\bia\bas\bs
+ If set, and programmable completion is enabled, b\bba\bas\bsh\bh
+ treats a command name that doesn't have any completions
+ as a possible alias and attempts alias expansion. If it
+ has an alias, b\bba\bas\bsh\bh attempts programmable completion us-
+ ing the command word resulting from the expanded alias.
+ p\bpr\bro\bom\bmp\bpt\btv\bva\bar\brs\bs
+ If set, prompt strings undergo parameter expansion, com-
+ mand substitution, arithmetic expansion, and quote re-
+ moval after being expanded as described in P\bPR\bRO\bOM\bMP\bPT\bTI\bIN\bNG\bG
+ above. This option is enabled by default.
+ r\bre\bes\bst\btr\bri\bic\bct\bte\bed\bd_\b_s\bsh\bhe\bel\bll\bl
+ The shell sets this option if it is started in re-
+ stricted mode (see R\bRE\bES\bST\bTR\bRI\bIC\bCT\bTE\bED\bD S\bSH\bHE\bEL\bLL\bL below). The value
+ may not be changed. This is not reset when the startup
+ files are executed, allowing the startup files to dis-
+ cover whether or not a shell is restricted.
+ s\bsh\bhi\bif\bft\bt_\b_v\bve\ber\brb\bbo\bos\bse\be
+ If set, the s\bsh\bhi\bif\bft\bt builtin prints an error message when
+ the shift count exceeds the number of positional parame-
+ ters.
+ s\bso\bou\bur\brc\bce\bep\bpa\bat\bth\bh
+ If set, the .\b. (s\bso\bou\bur\brc\bce\be) builtin uses the value of P\bPA\bAT\bTH\bH to
+ find the directory containing the file supplied as an
+ argument when the -\b-p\bp option is not supplied. This op-
+ tion is enabled by default.
+ v\bva\bar\brr\bre\bed\bdi\bir\br_\b_c\bcl\blo\bos\bse\be
+ If set, the shell automatically closes file descriptors
+ assigned using the _\b{_\bv_\ba_\br_\bn_\ba_\bm_\be_\b} redirection syntax (see
+ R\bRE\bED\bDI\bIR\bRE\bEC\bCT\bTI\bIO\bON\bN above) instead of leaving them open when the
+ command completes.
+ x\bxp\bpg\bg_\b_e\bec\bch\bho\bo
+ If set, the e\bec\bch\bho\bo builtin expands backslash-escape se-
+ quences by default. If the p\bpo\bos\bsi\bix\bx shell option is also
+ enabled, e\bec\bch\bho\bo does not interpret any options.
+
+ s\bsu\bus\bsp\bpe\ben\bnd\bd [-\b-f\bf]
+ Suspend the execution of this shell until it receives a S\bSI\bIG\bGC\bCO\bON\bNT\bT
+ signal. A login shell, or a shell without job control enabled,
+ cannot be suspended; the -\b-f\bf option will override this and force
+ the suspension. The return status is 0 unless the shell is a
+ login shell or job control is not enabled and -\b-f\bf is not sup-
+ plied.
+
+ t\bte\bes\bst\bt _\be_\bx_\bp_\br
+ [\b[ _\be_\bx_\bp_\br ]\b]
+ Return a status of 0 (true) or 1 (false) depending on the evalu-
+ ation of the conditional expression _\be_\bx_\bp_\br. Each operator and
+ operand must be a separate argument. Expressions are composed
+ of the primaries described above under C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bSS\bSI\bIO\bON\bNS\bS.
+ t\bte\bes\bst\bt does not accept any options, nor does it accept and ignore
+ an argument of -\b--\b- as signifying the end of options.
+
+ Expressions may be combined using the following operators,
+ listed in decreasing order of precedence. The evaluation de-
+ pends on the number of arguments; see below. t\bte\bes\bst\bt uses operator
+ precedence when there are five or more arguments.
+ !\b! _\be_\bx_\bp_\br True if _\be_\bx_\bp_\br is false.
+ (\b( _\be_\bx_\bp_\br )\b)
+ Returns the value of _\be_\bx_\bp_\br. This may be used to override
+ normal operator precedence.
+ _\be_\bx_\bp_\br_\b1 -a\ba _\be_\bx_\bp_\br_\b2
+ True if both _\be_\bx_\bp_\br_\b1 and _\be_\bx_\bp_\br_\b2 are true.
+ _\be_\bx_\bp_\br_\b1 -o\bo _\be_\bx_\bp_\br_\b2
+ True if either _\be_\bx_\bp_\br_\b1 or _\be_\bx_\bp_\br_\b2 is true.
+
+ t\bte\bes\bst\bt and [\b[ evaluate conditional expressions using a set of rules
+ based on the number of arguments.
+
+ 0 arguments
+ The expression is false.
+ 1 argument
+ The expression is true if and only if the argument is not
+ null.
+ 2 arguments
+ If the first argument is !\b!, the expression is true if and
+ only if the second argument is null. If the first argu-
+ ment is one of the unary conditional operators listed
+ above under C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bSS\bSI\bIO\bON\bNS\bS, the expression is
+ true if the unary test is true. If the first argument is
+ not a valid unary conditional operator, the expression is
+ false.
+ 3 arguments
+ The following conditions are applied in the order listed.
+ If the second argument is one of the binary conditional
+ operators listed above under C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bSS\bSI\bIO\bON\bNS\bS, the
+ result of the expression is the result of the binary test
+ using the first and third arguments as operands. The -\b-a\ba
+ and -\b-o\bo operators are considered binary operators when
+ there are three arguments. If the first argument is !\b!,
+ the value is the negation of the two-argument test using
+ the second and third arguments. If the first argument is
+ exactly (\b( and the third argument is exactly )\b), the result
+ is the one-argument test of the second argument. Other-
+ wise, the expression is false.
+ 4 arguments
+ The following conditions are applied in the order listed.
+ If the first argument is !\b!, the result is the negation of
+ the three-argument expression composed of the remaining
+ arguments. If the first argument is exactly (\b( and the
+ fourth argument is exactly )\b), the result is the two-argu-
+ ment test of the second and third arguments. Otherwise,
+ the expression is parsed and evaluated according to
+ precedence using the rules listed above.
+ 5 or more arguments
+ The expression is parsed and evaluated according to
+ precedence using the rules listed above.
+
+ When the shell is in posix mode, or if the expression is part of
+ the [\b[[\b[ command, the <\b< and >\b> operators sort using the current lo-
+ cale. If the shell is not in posix mode, the t\bte\bes\bst\bt and [\b[ com-
+ mands sort lexicographically using ASCII ordering.
+
+ The historical operator-precedence parsing with 4 or more argu-
+ ments can lead to ambiguities when it encounters strings that
+ look like primaries. The POSIX standard has deprecated the -\b-a\ba
+ and -\b-o\bo primaries and enclosing expressions within parentheses.
+ Scripts should no longer use them. It's much more reliable to
+ restrict test invocations to a single primary, and to replace
+ uses of -\b-a\ba and -\b-o\bo with the shell's &\b&&\b& and |\b||\b| list operators.
+
+ t\bti\bim\bme\bes\bs Print the accumulated user and system times for the shell and
+ for processes run from the shell. The return status is 0.
+
+ t\btr\bra\bap\bp [-\b-l\blp\bpP\bP] [[_\ba_\bc_\bt_\bi_\bo_\bn] _\bs_\bi_\bg_\bs_\bp_\be_\bc ...]
+ The _\ba_\bc_\bt_\bi_\bo_\bn is a command that is read and executed when the shell
+ receives any of the signals _\bs_\bi_\bg_\bs_\bp_\be_\bc. If _\ba_\bc_\bt_\bi_\bo_\bn is absent (and
+ there is a single _\bs_\bi_\bg_\bs_\bp_\be_\bc) or -\b-, each specified _\bs_\bi_\bg_\bs_\bp_\be_\bc is reset
+ to the value it had when the shell was started. If _\ba_\bc_\bt_\bi_\bo_\bn is
+ the null string the signal specified by each _\bs_\bi_\bg_\bs_\bp_\be_\bc is ignored
+ by the shell and by the commands it invokes.
+
+ If no arguments are supplied, t\btr\bra\bap\bp displays the actions associ-
+ ated with each trapped signal as a set of t\btr\bra\bap\bp commands that can
+ be reused as shell input to restore the current signal disposi-
+ tions. If -\b-p\bp is given, and _\ba_\bc_\bt_\bi_\bo_\bn is not present, then t\btr\bra\bap\bp
+ displays the actions associated with each _\bs_\bi_\bg_\bs_\bp_\be_\bc or, if none
+ are supplied, for all trapped signals, as a set of t\btr\bra\bap\bp commands
+ that can be reused as shell input to restore the current signal
+ dispositions. The -\b-P\bP option behaves similarly, but displays
+ only the actions associated with each _\bs_\bi_\bg_\bs_\bp_\be_\bc argument. -\b-P\bP re-
+ quires at least one _\bs_\bi_\bg_\bs_\bp_\be_\bc argument. The -\b-P\bP or -\b-p\bp options may
+ be used in a subshell environment (e.g., command substitution)
+ and, as long as they are used before t\btr\bra\bap\bp is used to change a
+ signal's handling, will display the state of its parent's traps.
+
+ The -\b-l\bl option prints a list of signal names and their corre-
+ sponding numbers. Each _\bs_\bi_\bg_\bs_\bp_\be_\bc is either a signal name defined
+ in <_\bs_\bi_\bg_\bn_\ba_\bl_\b._\bh>, or a signal number. Signal names are case insen-
+ sitive and the S\bSI\bIG\bG prefix is optional. If -\b-l\bl is supplied with
+ no _\bs_\bi_\bg_\bs_\bp_\be_\bc arguments, it prints a list of valid signal names.
+
+ If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bEX\bXI\bIT\bT (0), _\ba_\bc_\bt_\bi_\bo_\bn is executed on exit from the
+ shell. If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is D\bDE\bEB\bBU\bUG\bG, _\ba_\bc_\bt_\bi_\bo_\bn is executed before every
+ _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd, _\bf_\bo_\br command, _\bc_\ba_\bs_\be command, _\bs_\be_\bl_\be_\bc_\bt command, ((
+ arithmetic command, [[ conditional command, arithmetic _\bf_\bo_\br com-
+ mand, and before the first command executes in a shell function
+ (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR above). Refer to the description of the
+ e\bex\bxt\btd\bde\beb\bbu\bug\bg shell option (see s\bsh\bho\bop\bpt\bt above) for details of its ef-
+ fect on the D\bDE\bEB\bBU\bUG\bG trap. If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is R\bRE\bET\bTU\bUR\bRN\bN, _\ba_\bc_\bt_\bi_\bo_\bn is exe-
+ cuted each time a shell function or a script executed with the .\b.
+ or s\bso\bou\bur\brc\bce\be builtins finishes executing.
+
+ If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bER\bRR\bR, _\ba_\bc_\bt_\bi_\bo_\bn is executed whenever a pipeline
+ (which may consist of a single simple command), a list, or a
+ compound command returns a non-zero exit status, subject to the
+ following conditions. The E\bER\bRR\bR trap is not executed if the
+ failed command is part of the command list immediately following
+ a w\bwh\bhi\bil\ble\be or u\bun\bnt\bti\bil\bl reserved word, part of the test in an _\bi_\bf state-
+ ment, part of a command executed in a &\b&&\b& or |\b||\b| list except the
+ command following the final &\b&&\b& or |\b||\b|, any command in a pipeline
+ but the last (subject to the state of the p\bpi\bip\bpe\bef\bfa\bai\bil\bl shell op-
+ tion), or if the command's return value is being inverted using
+ !\b!. These are the same conditions obeyed by the e\ber\brr\bre\bex\bxi\bit\bt (-\b-e\be) op-
+ tion.
+
+ When the shell is not interactive, signals ignored upon entry to
+ the shell cannot be trapped or reset. Interactive shells permit
+ trapping signals ignored on entry. Trapped signals that are not
+ being ignored are reset to their original values in a subshell
+ or subshell environment when one is created. The return status
+ is false if any _\bs_\bi_\bg_\bs_\bp_\be_\bc is invalid; otherwise t\btr\bra\bap\bp returns true.
+
+ t\btr\bru\bue\be Does nothing, returns a 0 status.
+
+ t\bty\byp\bpe\be [-\b-a\baf\bft\btp\bpP\bP] _\bn_\ba_\bm_\be [_\bn_\ba_\bm_\be ...]
+ Indicate how each _\bn_\ba_\bm_\be would be interpreted if used as a command
+ name.
+
+ If the -\b-t\bt option is used, t\bty\byp\bpe\be prints a string which is one of
+ _\ba_\bl_\bi_\ba_\bs, _\bk_\be_\by_\bw_\bo_\br_\bd, _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn, _\bb_\bu_\bi_\bl_\bt_\bi_\bn, or _\bf_\bi_\bl_\be if _\bn_\ba_\bm_\be is an alias,
+ shell reserved word, function, builtin, or executable file, re-
+ spectively. If the _\bn_\ba_\bm_\be is not found, t\bty\byp\bpe\be prints nothing and
+ returns a non-zero exit status.
+
+ If the -\b-p\bp option is used, t\bty\byp\bpe\be either returns the pathname of
+ the executable file that would be found by searching $\b$P\bPA\bAT\bTH\bH for
+ _\bn_\ba_\bm_\be or nothing if "type -t name" would not return _\bf_\bi_\bl_\be. The -\b-P\bP
+ option forces a P\bPA\bAT\bTH\bH search for each _\bn_\ba_\bm_\be, even if "type -t
+ name" would not return _\bf_\bi_\bl_\be. If _\bn_\ba_\bm_\be is present in the table of
+ hashed commands, -\b-p\bp and -\b-P\bP print the hashed value, which is not
+ necessarily the file that appears first in P\bPA\bAT\bTH\bH.
+
+ If the -\b-a\ba option is used, t\bty\byp\bpe\be prints all of the places that
+ contain a command named _\bn_\ba_\bm_\be. This includes aliases, reserved
+ words, functions, and builtins, but the path search options (-\b-p\bp
+ and -\b-P\bP) can be supplied to restrict the output to executable
+ files. t\bty\byp\bpe\be does not consult the table of hashed commands when
+ using -\b-a\ba with -\b-p\bp, and only performs a P\bPA\bAT\bTH\bH search for _\bn_\ba_\bm_\be.
+
+ The -\b-f\bf option suppresses shell function lookup, as with the c\bco\bom\bm-\b-
+ m\bma\ban\bnd\bd builtin. t\bty\byp\bpe\be returns true if all of the arguments are
+ found, false if any are not found.
+
+ u\bul\bli\bim\bmi\bit\bt [-\b-H\bHS\bS] -\b-a\ba
+ u\bul\bli\bim\bmi\bit\bt [-\b-H\bHS\bS] [-\b-b\bbc\bcd\bde\bef\bfi\bik\bkl\blm\bmn\bnp\bpq\bqr\brs\bst\btu\buv\bvx\bxP\bPR\bRT\bT [_\bl_\bi_\bm_\bi_\bt]]
+ Provides control over the resources available to the shell and
+ to processes it starts, on systems that allow such control.
+
+ The -\b-H\bH and -\b-S\bS options specify whether the hard or soft limit is
+ set for the given resource. A hard limit cannot be increased by
+ a non-root user once it is set; a soft limit may be increased up
+ to the value of the hard limit. If neither -\b-H\bH nor -\b-S\bS is speci-
+ fied, u\bul\bli\bim\bmi\bit\bt sets both the soft and hard limits.
+
+ The value of _\bl_\bi_\bm_\bi_\bt can be a number in the unit specified for the
+ resource or one of the special values h\bha\bar\brd\bd, s\bso\bof\bft\bt, or u\bun\bnl\bli\bim\bmi\bit\bte\bed\bd,
+ which stand for the current hard limit, the current soft limit,
+ and no limit, respectively. If _\bl_\bi_\bm_\bi_\bt is omitted, u\bul\bli\bim\bmi\bit\bt prints
+ the current value of the soft limit of the resource, unless the
+ -\b-H\bH option is given. When more than one resource is specified,
+ the limit name and unit, if appropriate, are printed before the
+ value. Other options are interpreted as follows:
+ -\b-a\ba Report all current limits; no limits are set.
+ -\b-b\bb The maximum socket buffer size.
+ -\b-c\bc The maximum size of core files created.
+ -\b-d\bd The maximum size of a process's data segment.
+ -\b-e\be The maximum scheduling priority ("nice").
+ -\b-f\bf The maximum size of files written by the shell and its
+ children.
+ -\b-i\bi The maximum number of pending signals.
+ -\b-k\bk The maximum number of kqueues that may be allocated.
+ -\b-l\bl The maximum size that may be locked into memory.
+ -\b-m\bm The maximum resident set size (many systems do not honor
+ this limit).
+ -\b-n\bn The maximum number of open file descriptors (most systems
+ do not allow this value to be set).
+ -\b-p\bp The pipe size in 512-byte blocks (this may not be set).
+ -\b-q\bq The maximum number of bytes in POSIX message queues.
+ -\b-r\br The maximum real-time scheduling priority.
+ -\b-s\bs The maximum stack size.
+ -\b-t\bt The maximum amount of cpu time in seconds.
+ -\b-u\bu The maximum number of processes available to a single
+ user.
+ -\b-v\bv The maximum amount of virtual memory available to the
+ shell and, on some systems, to its children.
+ -\b-x\bx The maximum number of file locks.
+ -\b-P\bP The maximum number of pseudoterminals.
+ -\b-R\bR The maximum time a real-time process can run before
+ blocking, in microseconds.
+ -\b-T\bT The maximum number of threads.
+
+ If _\bl_\bi_\bm_\bi_\bt is supplied, and the -\b-a\ba option is not used, _\bl_\bi_\bm_\bi_\bt is
+ the new value of the specified resource. If no option is sup-
+ plied, then -\b-f\bf is assumed.
+
+ Values are in 1024-byte increments, except for -\b-t\bt, which is in
+ seconds; -\b-R\bR, which is in microseconds; -\b-p\bp, which is in units of
+ 512-byte blocks; -\b-P\bP, -\b-T\bT, -\b-b\bb, -\b-k\bk, -\b-n\bn, and -\b-u\bu, which are unscaled
+ values; and, when in posix mode, -\b-c\bc and -\b-f\bf, which are in
+ 512-byte increments. The return status is 0 unless an invalid
+ option or argument is supplied, or an error occurs while setting
+ a new limit.
+
+ u\bum\bma\bas\bsk\bk [-\b-p\bp] [-\b-S\bS] [_\bm_\bo_\bd_\be]
+ Set the user file-creation mask to _\bm_\bo_\bd_\be. If _\bm_\bo_\bd_\be begins with a
+ digit, it is interpreted as an octal number; otherwise it is in-
+ terpreted as a symbolic mode mask similar to that accepted by
+ _\bc_\bh_\bm_\bo_\bd(1). If _\bm_\bo_\bd_\be is omitted, u\bum\bma\bas\bsk\bk prints the current value of
+ the mask. The -\b-S\bS option without a _\bm_\bo_\bd_\be argument prints the mask
+ in a symbolic format; the default output is an octal number. If
+ the -\b-p\bp option is supplied, and _\bm_\bo_\bd_\be is omitted, the output is in
+ a form that may be reused as input. The return status is zero
+ if the mode was successfully changed or if no _\bm_\bo_\bd_\be argument was
+ supplied, and non-zero otherwise.
+
+ u\bun\bna\bal\bli\bia\bas\bs [-a\ba] [_\bn_\ba_\bm_\be ...]
+ Remove each _\bn_\ba_\bm_\be from the list of defined aliases. If -\b-a\ba is
+ supplied, remove all alias definitions. The return value is
+ true unless a supplied _\bn_\ba_\bm_\be is not a defined alias.
+
+ u\bun\bns\bse\bet\bt [-f\bfv\bv] [-n\bn] [_\bn_\ba_\bm_\be ...]
+ For each _\bn_\ba_\bm_\be, remove the corresponding variable or function.
+ If the -\b-v\bv option is given, each _\bn_\ba_\bm_\be refers to a shell variable,
+ and that variable is removed. If -\b-f\bf is specified, each _\bn_\ba_\bm_\be
+ refers to a shell function, and the function definition is re-
+ moved. If the -\b-n\bn option is supplied, and _\bn_\ba_\bm_\be is a variable
+ with the _\bn_\ba_\bm_\be_\br_\be_\bf attribute, _\bn_\ba_\bm_\be will be unset rather than the
+ variable it references. -\b-n\bn has no effect if the -\b-f\bf option is
+ supplied. Read-only variables and functions may not be unset.
+ When variables or functions are removed, they are also removed
+ from the environment passed to subsequent commands. If no op-
+ tions are supplied, each _\bn_\ba_\bm_\be refers to a variable; if there is
+ no variable by that name, a function with that name, if any, is
+ unset. Some shell variables may not be unset. If any of
+ B\bBA\bAS\bSH\bH_\b_A\bAL\bLI\bIA\bAS\bSE\bES\bS, B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV0\b0, B\bBA\bAS\bSH\bH_\b_C\bCM\bMD\bDS\bS, B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMM\bMA\bAN\bND\bD, B\bBA\bAS\bSH\bH_\b_S\bSU\bUB\bB-\b-
+ S\bSH\bHE\bEL\bLL\bL, B\bBA\bAS\bSH\bHP\bPI\bID\bD, C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS, D\bDI\bIR\bRS\bST\bTA\bAC\bCK\bK, E\bEP\bPO\bOC\bCH\bHR\bRE\bEA\bAL\bLT\bTI\bIM\bME\bE,
+ E\bEP\bPO\bOC\bCH\bHS\bSE\bEC\bCO\bON\bND\bDS\bS, F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE, G\bGR\bRO\bOU\bUP\bPS\bS, H\bHI\bIS\bST\bTC\bCM\bMD\bD, L\bLI\bIN\bNE\bEN\bNO\bO, R\bRA\bAN\bND\bDO\bOM\bM, S\bSE\bEC\bC-\b-
+ O\bON\bND\bDS\bS, or S\bSR\bRA\bAN\bND\bDO\bOM\bM are unset, they lose their special properties,
+ even if they are subsequently reset. The exit status is true
+ unless a _\bn_\ba_\bm_\be is readonly or may not be unset.
+
+ w\bwa\bai\bit\bt [-\b-f\bfn\bn] [-\b-p\bp _\bv_\ba_\br_\bn_\ba_\bm_\be] [_\bi_\bd ...]
+ Wait for each specified child process _\bi_\bd and return the termina-
+ tion status of the last _\bi_\bd. Each _\bi_\bd may be a process ID _\bp_\bi_\bd or
+ a job specification _\bj_\bo_\bb_\bs_\bp_\be_\bc; if a jobspec is supplied, w\bwa\bai\bit\bt
+ waits for all processes in the job.
+
+ If no options or _\bi_\bds are supplied, w\bwa\bai\bit\bt waits for all running
+ background jobs and the last-executed process substitution, if
+ its process id is the same as $\b$!\b!, and the return status is zero.
+
+ If the -\b-n\bn option is supplied, w\bwa\bai\bit\bt waits for any one of the
+ given _\bi_\bds or, if no _\bi_\bds are supplied, any job or process substi-
+ tution, to complete and returns its exit status. If none of the
+ supplied _\bi_\bds is a child of the shell, or if no _\bi_\bds are supplied
+ and the shell has no unwaited-for children, the exit status is
+ 127.
+
+ If the -\b-p\bp option is supplied, w\bwa\bai\bit\bt assigns the process or job
+ identifier of the job for which the exit status is returned to
+ the variable _\bv_\ba_\br_\bn_\ba_\bm_\be named by the option argument. The vari-
+ able, which cannot be readonly, will be unset initially, before
+ any assignment. This is useful only when used with the -\b-n\bn op-
+ tion.
+
+ Supplying the -\b-f\bf option, when job control is enabled, forces
+ w\bwa\bai\bit\bt to wait for each _\bi_\bd to terminate before returning its sta-
+ tus, instead of returning when it changes status.
+
+ If none of the _\bi_\bds specify one of the shell's active child
+ processes, the return status is 127. If w\bwa\bai\bit\bt is interrupted by
+ a signal, any _\bv_\ba_\br_\bn_\ba_\bm_\be will remain unset, and the return status
+ will be greater than 128, as described under S\bSI\bIG\bGN\bNA\bAL\bLS\bS above.
+ Otherwise, the return status is the exit status of the last _\bi_\bd.
+
+S\bSH\bHE\bEL\bLL\bL C\bCO\bOM\bMP\bPA\bAT\bTI\bIB\bBI\bIL\bLI\bIT\bTY\bY M\bMO\bOD\bDE\bE
+ Bash-4.0 introduced the concept of a _\bs_\bh_\be_\bl_\bl _\bc_\bo_\bm_\bp_\ba_\bt_\bi_\bb_\bi_\bl_\bi_\bt_\by _\bl_\be_\bv_\be_\bl, speci-
+ fied as a set of options to the shopt builtin (c\bco\bom\bmp\bpa\bat\bt3\b31\b1, c\bco\bom\bmp\bpa\bat\bt3\b32\b2, c\bco\bom\bm-\b-
+ p\bpa\bat\bt4\b40\b0, c\bco\bom\bmp\bpa\bat\bt4\b41\b1, and so on). There is only one current compatibility
+ level -- each option is mutually exclusive. The compatibility level is
+ intended to allow users to select behavior from previous versions that
+ is incompatible with newer versions while they migrate scripts to use
+ current features and behavior. It's intended to be a temporary solu-
+ tion.
+
+ This section does not mention behavior that is standard for a particu-
+ lar version (e.g., setting c\bco\bom\bmp\bpa\bat\bt3\b32\b2 means that quoting the right hand
+ side of the regexp matching operator quotes special regexp characters
+ in the word, which is default behavior in bash-3.2 and subsequent ver-
+ sions).
+
+ If a user enables, say, c\bco\bom\bmp\bpa\bat\bt3\b32\b2, it may affect the behavior of other
+ compatibility levels up to and including the current compatibility
+ level. The idea is that each compatibility level controls behavior
+ that changed in that version of b\bba\bas\bsh\bh, but that behavior may have been
+ present in earlier versions. For instance, the change to use locale-
+ based comparisons with the [\b[[\b[ command came in bash-4.1, and earlier
+ versions used ASCII-based comparisons, so enabling c\bco\bom\bmp\bpa\bat\bt3\b32\b2 will enable
+ ASCII-based comparisons as well. That granularity may not be suffi-
+ cient for all uses, and as a result users should employ compatibility
+ levels carefully. Read the documentation for a particular feature to
+ find out the current behavior.
+
+ Bash-4.3 introduced a new shell variable: B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT. The value as-
+ signed to this variable (a decimal version number like 4.2, or an inte-
+ ger corresponding to the c\bco\bom\bmp\bpa\bat\bt_\bN_\bN option, like 42) determines the com-
+ patibility level.
+
+ Starting with bash-4.4, b\bba\bas\bsh\bh began deprecating older compatibility lev-
+ els. Eventually, the options will be removed in favor of B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT.
+
+ Bash-5.0 was the final version for which there was an individual shopt
+ option for the previous version. B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT is the only mechanism to
+ control the compatibility level in versions newer than bash-5.0.
+
+ The following table describes the behavior changes controlled by each
+ compatibility level setting. The c\bco\bom\bmp\bpa\bat\bt_\bN_\bN tag is used as shorthand for
+ setting the compatibility level to _\bN_\bN using one of the following mecha-
+ nisms. For versions prior to bash-5.0, the compatibility level may be
+ set using the corresponding c\bco\bom\bmp\bpa\bat\bt_\bN_\bN shopt option. For bash-4.3 and
+ later versions, the B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT variable is preferred, and it is re-
+ quired for bash-5.1 and later versions.
+
+ c\bco\bom\bmp\bpa\bat\bt3\b31\b1
+ +\bo Quoting the rhs of the [\b[[\b[ command's regexp matching oper-
+ ator (=~) has no special effect.
+
+ c\bco\bom\bmp\bpa\bat\bt3\b32\b2
+ +\bo The <\b< and >\b> operators to the [\b[[\b[ command do not consider
+ the current locale when comparing strings; they use ASCII
+ ordering.
+
+ c\bco\bom\bmp\bpa\bat\bt4\b40\b0
+ +\bo The <\b< and >\b> operators to the [\b[[\b[ command do not consider
+ the current locale when comparing strings; they use ASCII
+ ordering. B\bBa\bas\bsh\bh versions prior to bash-4.1 use ASCII col-
+ lation and _\bs_\bt_\br_\bc_\bm_\bp(3); bash-4.1 and later use the current
+ locale's collation sequence and _\bs_\bt_\br_\bc_\bo_\bl_\bl(3).
+
+ c\bco\bom\bmp\bpa\bat\bt4\b41\b1
+ +\bo In posix mode, t\bti\bim\bme\be may be followed by options and still
+ be recognized as a reserved word (this is POSIX interpre-
+ tation 267).
+ +\bo In _\bp_\bo_\bs_\bi_\bx mode, the parser requires that an even number of
+ single quotes occur in the _\bw_\bo_\br_\bd portion of a double-
+ quoted parameter expansion and treats them specially, so
+ that characters within the single quotes are considered
+ quoted (this is POSIX interpretation 221).
+
+ c\bco\bom\bmp\bpa\bat\bt4\b42\b2
+ +\bo The replacement string in double-quoted pattern substitu-
+ tion does not undergo quote removal, as it does in ver-
+ sions after bash-4.2.
+ +\bo In posix mode, single quotes are considered special when
+ expanding the _\bw_\bo_\br_\bd portion of a double-quoted parameter
+ expansion and can be used to quote a closing brace or
+ other special character (this is part of POSIX interpre-
+ tation 221); in later versions, single quotes are not
+ special within double-quoted word expansions.
+
+ c\bco\bom\bmp\bpa\bat\bt4\b43\b3
+ +\bo Word expansion errors are considered non-fatal errors
+ that cause the current command to fail, even in posix
+ mode (the default behavior is to make them fatal errors
+ that cause the shell to exit).
+ +\bo When executing a shell function, the loop state
+ (while/until/etc.) is not reset, so b\bbr\bre\bea\bak\bk or c\bco\bon\bnt\bti\bin\bnu\bue\be in
+ that function will break or continue loops in the calling
+ context. Bash-4.4 and later reset the loop state to pre-
+ vent this.
+
+ c\bco\bom\bmp\bpa\bat\bt4\b44\b4
+ +\bo The shell sets up the values used by B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV and
+ B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC so they can expand to the shell's positional
+ parameters even if extended debugging mode is not en-
+ abled.
+ +\bo A subshell inherits loops from its parent context, so
+ b\bbr\bre\bea\bak\bk or c\bco\bon\bnt\bti\bin\bnu\bue\be will cause the subshell to exit.
+ Bash-5.0 and later reset the loop state to prevent the
+ exit
+ +\bo Variable assignments preceding builtins like e\bex\bxp\bpo\bor\brt\bt and
+ r\bre\bea\bad\bdo\bon\bnl\bly\by that set attributes continue to affect variables
+ with the same name in the calling environment even if the
+ shell is not in posix mode.
+
+ c\bco\bom\bmp\bpa\bat\bt5\b50\b0
+ +\bo Bash-5.1 changed the way $\b$R\bRA\bAN\bND\bDO\bOM\bM is generated to intro-
+ duce slightly more randomness. If the shell compatibil-
+ ity level is set to 50 or lower, it reverts to the method
+ from bash-5.0 and previous versions, so seeding the ran-
+ dom number generator by assigning a value to R\bRA\bAN\bND\bDO\bOM\bM will
+ produce the same sequence as in bash-5.0.
+ +\bo If the command hash table is empty, bash versions prior
+ to bash-5.1 printed an informational message to that ef-
+ fect, even when producing output that can be reused as
+ input. Bash-5.1 suppresses that message when the -\b-l\bl op-
+ tion is supplied.
+
+ c\bco\bom\bmp\bpa\bat\bt5\b51\b1
+ +\bo The u\bun\bns\bse\bet\bt builtin treats attempts to unset array sub-
+ scripts @\b@ and *\b* differently depending on whether the ar-
+ ray is indexed or associative, and differently than in
+ previous versions.
+ +\bo Arithmetic commands ( (\b((\b(...)\b))\b) ) and the expressions in an
+ arithmetic for statement can be expanded more than once.
+ +\bo Expressions used as arguments to arithmetic operators in
+ the [\b[[\b[ conditional command can be expanded more than
+ once.
+ +\bo The expressions in substring parameter brace expansion
+ can be expanded more than once.
+ +\bo The expressions in the $\b$(\b((\b(...)\b))\b) word expansion can be ex-
+ panded more than once.
+ +\bo Arithmetic expressions used as indexed array subscripts
+ can be expanded more than once.
+ +\bo t\bte\bes\bst\bt -\b-v\bv, when given an argument of A\bA[\b[@\b@]\b], where A\bA is an
+ existing associative array, will return true if the array
+ has any set elements. Bash-5.2 will look for and report
+ on a key named @\b@.
+ +\bo The ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br[\b[:\b:]\b]=\b=_\bv_\ba_\bl_\bu_\be} word expansion will return
+ _\bv_\ba_\bl_\bu_\be, before any variable-specific transformations have
+ been performed (e.g., converting to lowercase). Bash-5.2
+ will return the final value assigned to the variable.
+ +\bo Parsing command substitutions will behave as if extended
+ globbing (see the description of the s\bsh\bho\bop\bpt\bt builtin above)
+ is enabled, so that parsing a command substitution con-
+ taining an extglob pattern (say, as part of a shell func-
+ tion) will not fail. This assumes the intent is to en-
+ able extglob before the command is executed and word ex-
+ pansions are performed. It will fail at word expansion
+ time if extglob hasn't been enabled by the time the com-
+ mand is executed.
+
+ c\bco\bom\bmp\bpa\bat\bt5\b52\b2
+ +\bo The t\bte\bes\bst\bt builtin uses its historical algorithm to parse
+ parenthesized subexpressions when given five or more ar-
+ guments.
+ +\bo If the -\b-p\bp or -\b-P\bP option is supplied to the b\bbi\bin\bnd\bd builtin,
+ b\bbi\bin\bnd\bd treats any arguments remaining after option process-
+ ing as bindable command names, and displays any key se-
+ quences bound to those commands, instead of treating the
+ arguments as key sequences to bind.
+
+R\bRE\bES\bST\bTR\bRI\bIC\bCT\bTE\bED\bD S\bSH\bHE\bEL\bLL\bL
+ If b\bba\bas\bsh\bh is started with the name r\brb\bba\bas\bsh\bh, or the -\b-r\br option is supplied at
+ invocation, the shell becomes _\br_\be_\bs_\bt_\br_\bi_\bc_\bt_\be_\bd. A restricted shell is used
+ to set up an environment more controlled than the standard shell. It
+ behaves identically to b\bba\bas\bsh\bh with the exception that the following are
+ disallowed or not performed:
+
+ +\bo Changing directories with c\bcd\bd.
+
+ +\bo Setting or unsetting the values of S\bSH\bHE\bEL\bLL\bL, P\bPA\bAT\bTH\bH, H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE, E\bEN\bNV\bV,
+ or B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV.
+
+ +\bo Specifying command names containing /\b/.
+
+ +\bo Specifying a filename containing a /\b/ as an argument to the .\b.
+ builtin command.
+
+ +\bo Using the -\b-p\bp option to the .\b. builtin command to specify a
+ search path.
+
+ +\bo Specifying a filename containing a slash as an argument to the
+ h\bhi\bis\bst\bto\bor\bry\by builtin command.
+
+ +\bo Specifying a filename containing a slash as an argument to the
+ -\b-p\bp option to the h\bha\bas\bsh\bh builtin command.
+
+ +\bo Importing function definitions from the shell environment at
+ startup.
+
+ +\bo Parsing the values of B\bBA\bAS\bSH\bHO\bOP\bPT\bTS\bS and S\bSH\bHE\bEL\bLL\bLO\bOP\bPT\bTS\bS from the shell en-
+ vironment at startup.
+
+ +\bo Redirecting output using the >, >|, <>, >&, &>, and >> redirec-
+ tion operators.
+
+ +\bo Using the e\bex\bxe\bec\bc builtin command to replace the shell with another
+ command.
+
+ +\bo Adding or deleting builtin commands with the -\b-f\bf and -\b-d\bd options
+ to the e\ben\bna\bab\bbl\ble\be builtin command.
+
+ +\bo Using the e\ben\bna\bab\bbl\ble\be builtin command to enable disabled shell
+ builtins.
+
+ +\bo Specifying the -\b-p\bp option to the c\bco\bom\bmm\bma\ban\bnd\bd builtin command.
+
+ +\bo Turning off restricted mode with s\bse\bet\bt +\b+r\br or s\bsh\bho\bop\bpt\bt -\b-u\bu r\bre\be-\b-
+ s\bst\btr\bri\bic\bct\bte\bed\bd_\b_s\bsh\bhe\bel\bll\bl.
+
+ These restrictions are enforced after any startup files are read.
+
+ When a command that is found to be a shell script is executed (see C\bCO\bOM\bM-\b-
+ M\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN above), r\brb\bba\bas\bsh\bh turns off any restrictions in the shell
+ spawned to execute the script.
+
+S\bSE\bEE\bE A\bAL\bLS\bSO\bO
+ _\bB_\ba_\bs_\bh _\bR_\be_\bf_\be_\br_\be_\bn_\bc_\be _\bM_\ba_\bn_\bu_\ba_\bl, Brian Fox and Chet Ramey
+ _\bT_\bh_\be _\bG_\bn_\bu _\bR_\be_\ba_\bd_\bl_\bi_\bn_\be _\bL_\bi_\bb_\br_\ba_\br_\by, Brian Fox and Chet Ramey
+ _\bT_\bh_\be _\bG_\bn_\bu _\bH_\bi_\bs_\bt_\bo_\br_\by _\bL_\bi_\bb_\br_\ba_\br_\by, Brian Fox and Chet Ramey
+ _\bP_\bo_\br_\bt_\ba_\bb_\bl_\be _\bO_\bp_\be_\br_\ba_\bt_\bi_\bn_\bg _\bS_\by_\bs_\bt_\be_\bm _\bI_\bn_\bt_\be_\br_\bf_\ba_\bc_\be _\b(_\bP_\bO_\bS_\bI_\bX_\b) _\bP_\ba_\br_\bt _\b2_\b: _\bS_\bh_\be_\bl_\bl _\ba_\bn_\bd _\bU_\bt_\bi_\bl_\bi_\b-
+ _\bt_\bi_\be_\bs, IEEE --
+ http://pubs.opengroup.org/onlinepubs/9799919799/
+ http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
+ _\bs_\bh(1), _\bk_\bs_\bh(1), _\bc_\bs_\bh(1)
+ _\be_\bm_\ba_\bc_\bs(1), _\bv_\bi(1)
+ _\br_\be_\ba_\bd_\bl_\bi_\bn_\be(3)
+
+F\bFI\bIL\bLE\bES\bS
+ _\b/_\bb_\bi_\bn_\b/_\bb_\ba_\bs_\bh
+ The b\bba\bas\bsh\bh executable
+ _\b/_\be_\bt_\bc_\b/_\bp_\br_\bo_\bf_\bi_\bl_\be
+ The systemwide initialization file, executed for login shells
+ _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bp_\br_\bo_\bf_\bi_\bl_\be
+ The personal initialization file, executed for login shells
+ _\b~_\b/_\b._\bb_\ba_\bs_\bh_\br_\bc
+ The individual per-interactive-shell startup file
+ _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bl_\bo_\bg_\bo_\bu_\bt
+ The individual login shell cleanup file, executed when a login
+ shell exits
+ _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bh_\bi_\bs_\bt_\bo_\br_\by
+ The default value of H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE, the file in which bash saves the
+ command history
+ _\b~_\b/_\b._\bi_\bn_\bp_\bu_\bt_\br_\bc
+ Individual _\br_\be_\ba_\bd_\bl_\bi_\bn_\be initialization file
+
+A\bAU\bUT\bTH\bHO\bOR\bRS\bS
+ Brian Fox, Free Software Foundation
+ bfox@gnu.org
+
+ Chet Ramey, Case Western Reserve University
+ chet.ramey@case.edu
+
+B\bBU\bUG\bG R\bRE\bEP\bPO\bOR\bRT\bTS\bS
+ If you find a bug in b\bba\bas\bsh\bh, you should report it. But first, you should
+ make sure that it really is a bug, and that it appears in the latest
+ version of b\bba\bas\bsh\bh. The latest version is always available from
+ _\bf_\bt_\bp_\b:_\b/_\b/_\bf_\bt_\bp_\b._\bg_\bn_\bu_\b._\bo_\br_\bg_\b/_\bp_\bu_\bb_\b/_\bg_\bn_\bu_\b/_\bb_\ba_\bs_\bh_\b/ and _\bh_\bt_\bt_\bp_\b:_\b/_\b/_\bg_\bi_\bt_\b._\bs_\ba_\bv_\ba_\bn_\b-
+ _\bn_\ba_\bh_\b._\bg_\bn_\bu_\b._\bo_\br_\bg_\b/_\bc_\bg_\bi_\bt_\b/_\bb_\ba_\bs_\bh_\b._\bg_\bi_\bt_\b/_\bs_\bn_\ba_\bp_\bs_\bh_\bo_\bt_\b/_\bb_\ba_\bs_\bh_\b-_\bm_\ba_\bs_\bt_\be_\br_\b._\bt_\ba_\br_\b._\bg_\bz.
+
+ Once you have determined that a bug actually exists, use the _\bb_\ba_\bs_\bh_\bb_\bu_\bg
+ command to submit a bug report. If you have a fix, you are encouraged
+ to mail that as well! You may send suggestions and "philosophical" bug
+ reports to _\bb_\bu_\bg_\b-_\bb_\ba_\bs_\bh_\b@_\bg_\bn_\bu_\b._\bo_\br_\bg or post them to the Usenet newsgroup
+ g\bgn\bnu\bu.\b.b\bba\bas\bsh\bh.\b.b\bbu\bug\bg.
+
+ ALL bug reports should include:
+
+ The version number of b\bba\bas\bsh\bh
+ The hardware and operating system
+ The compiler used to compile
+ A description of the bug behavior
+ A short script or "recipe" which exercises the bug
+
+ _\bb_\ba_\bs_\bh_\bb_\bu_\bg inserts the first three items automatically into the template
+ it provides for filing a bug report.
+
+ Comments and bug reports concerning this manual page should be directed
+ to _\bc_\bh_\be_\bt_\b._\br_\ba_\bm_\be_\by_\b@_\bc_\ba_\bs_\be_\b._\be_\bd_\bu.
+
+B\bBU\bUG\bGS\bS
+ It's too big and too slow.
+
+ There are some subtle differences between b\bba\bas\bsh\bh and traditional versions
+ of s\bsh\bh, mostly because of the POSIX specification.
+
+ Aliases are confusing in some uses.
+
+ Shell builtin commands and functions are not stoppable/restartable.
+
+ Compound commands and command lists of the form "a ; b ; c" are not
+ handled gracefully when combined with process suspension. When a
+ process is stopped, the shell immediately executes the next command in
+ the list or breaks out of any existing loops. It suffices to enclose
+ the command in parentheses to force it into a subshell, which may be
+ stopped as a unit, or to start the command in the background and imme-
+ diately bring it into the foreground.
+
+ Array variables may not (yet) be exported.
+
+GNU Bash 5.3 2025 August 25 _\bB_\bA_\bS_\bH(1)
--- /dev/null
+This is bash.info, produced by makeinfo version 7.2 from bashref.texi.
+
+This text is a brief description of the features that are present in the
+Bash shell (version 5.3, 7 August 2025).
+
+ This is Edition 5.3, last updated 7 August 2025, of ‘The GNU Bash
+Reference Manual’, for ‘Bash’, Version 5.3.
+
+ Copyright © 1988-2025 Free Software Foundation, Inc.
+
+ Permission is granted to copy, distribute and/or modify this
+ document under the terms of the GNU Free Documentation License,
+ Version 1.3 or any later version published by the Free Software
+ Foundation; with no Invariant Sections, no Front-Cover Texts, and
+ no Back-Cover Texts. A copy of the license is included in the
+ section entitled "GNU Free Documentation License".
+INFO-DIR-SECTION Basics
+START-INFO-DIR-ENTRY
+* Bash: (bash). The GNU Bourne-Again SHell.
+END-INFO-DIR-ENTRY
+
+\1f
+File: bash.info, Node: Top, Next: Introduction, Prev: (dir), Up: (dir)
+
+Bash Features
+*************
+
+This text is a brief description of the features that are present in the
+Bash shell (version 5.3, 7 August 2025). The Bash home page is
+<http://www.gnu.org/software/bash/>.
+
+ This is Edition 5.3, last updated 7 August 2025, of ‘The GNU Bash
+Reference Manual’, for ‘Bash’, Version 5.3.
+
+ Bash contains features that appear in other popular shells, and some
+features that only appear in Bash. Some of the shells that Bash has
+borrowed concepts from are the Bourne Shell (‘sh’), the Korn Shell
+(‘ksh’), and the C-shell (‘csh’ and its successor, ‘tcsh’). The
+following menu breaks the features up into categories, noting which
+features were inspired by other shells and which are specific to Bash.
+
+ This manual is meant as a brief introduction to features found in
+Bash. The Bash manual page should be used as the definitive reference
+on shell behavior.
+
+* Menu:
+
+* Introduction:: An introduction to the shell.
+* Definitions:: Some definitions used in the rest of this
+ manual.
+* Basic Shell Features:: The shell "building blocks".
+* Shell Builtin Commands:: Commands that are a part of the shell.
+* Shell Variables:: Variables used or set by Bash.
+* Bash Features:: Features found only in Bash.
+* Job Control:: What job control is and how Bash allows you
+ to use it.
+* Command Line Editing:: Chapter describing the command line
+ editing features.
+* Using History Interactively:: Command History Expansion
+* Installing Bash:: How to build and install Bash on your system.
+* Reporting Bugs:: How to report bugs in Bash.
+* Major Differences From The Bourne Shell:: A terse list of the differences
+ between Bash and historical
+ versions of /bin/sh.
+* GNU Free Documentation License:: Copying and sharing this documentation.
+* Indexes:: Various indexes for this manual.
+
+\1f
+File: bash.info, Node: Introduction, Next: Definitions, Up: Top
+
+1 Introduction
+**************
+
+* Menu:
+
+* What is Bash?:: A short description of Bash.
+* What is a shell?:: A brief introduction to shells.
+
+\1f
+File: bash.info, Node: What is Bash?, Next: What is a shell?, Up: Introduction
+
+1.1 What is Bash?
+=================
+
+Bash is the shell, or command language interpreter, for the GNU
+operating system. The name is an acronym for the ‘Bourne-Again SHell’,
+a pun on Stephen Bourne, the author of the direct ancestor of the
+current Unix shell ‘sh’, which appeared in the Seventh Edition Bell Labs
+Research version of Unix.
+
+ Bash is largely compatible with ‘sh’ and incorporates useful features
+from the Korn shell ‘ksh’ and the C shell ‘csh’. It is intended to be a
+conformant implementation of the IEEE POSIX Shell and Tools portion of
+the IEEE POSIX specification (IEEE Standard 1003.1). It offers
+functional improvements over ‘sh’ for both interactive and programming
+use.
+
+ While the GNU operating system provides other shells, including a
+version of ‘csh’, Bash is the default shell. Like other GNU software,
+Bash is quite portable. It currently runs on nearly every version of
+Unix and a few other operating systems − independently-supported ports
+exist for Windows and other platforms.
+
+\1f
+File: bash.info, Node: What is a shell?, Prev: What is Bash?, Up: Introduction
+
+1.2 What is a shell?
+====================
+
+At its base, a shell is simply a macro processor that executes commands.
+The term macro processor means functionality where text and symbols are
+expanded to create larger expressions.
+
+ A Unix shell is both a command interpreter and a programming
+language. As a command interpreter, the shell provides the user
+interface to the rich set of GNU utilities. The programming language
+features allow these utilities to be combined. Users can create files
+containing commands, and these become commands themselves. These new
+commands have the same status as system commands in directories such as
+‘/bin’, allowing users or groups to establish custom environments to
+automate their common tasks.
+
+ Shells may be used interactively or non-interactively. In
+interactive mode, they accept input typed from the keyboard. When
+executing non-interactively, shells execute commands read from a file or
+a string.
+
+ A shell allows execution of GNU commands, both synchronously and
+asynchronously. The shell waits for synchronous commands to complete
+before accepting more input; asynchronous commands continue to execute
+in parallel with the shell while it reads and executes additional
+commands. The “redirection” constructs permit fine-grained control of
+the input and output of those commands. Moreover, the shell allows
+control over the contents of commands' environments.
+
+ Shells also provide a small set of built-in commands (“builtins”)
+implementing functionality impossible or inconvenient to obtain via
+separate utilities. For example, ‘cd’, ‘break’, ‘continue’, and ‘exec’
+cannot be implemented outside of the shell because they directly
+manipulate the shell itself. The ‘history’, ‘getopts’, ‘kill’, or ‘pwd’
+builtins, among others, could be implemented in separate utilities, but
+they are more convenient to use as builtin commands. All of the shell
+builtins are described in subsequent sections.
+
+ While executing commands is essential, most of the power (and
+complexity) of shells is due to their embedded programming languages.
+Like any high-level language, the shell provides variables, flow control
+constructs, quoting, and functions.
+
+ Shells offer features geared specifically for interactive use rather
+than to augment the programming language. These interactive features
+include job control, command line editing, command history and aliases.
+This manual describes how Bash provides all of these features.
+
+\1f
+File: bash.info, Node: Definitions, Next: Basic Shell Features, Prev: Introduction, Up: Top
+
+2 Definitions
+*************
+
+These definitions are used throughout the remainder of this manual.
+
+‘POSIX’
+ A family of open system standards based on Unix. Bash is primarily
+ concerned with the Shell and Utilities portion of the POSIX 1003.1
+ standard.
+
+‘blank’
+ A space or tab character.
+
+‘whitespace’
+ A character belonging to the ‘space’ character class in the current
+ locale, or for which ‘isspace()’ returns true.
+
+‘builtin’
+ A command that is implemented internally by the shell itself,
+ rather than by an executable program somewhere in the file system.
+
+‘control operator’
+ A ‘token’ that performs a control function. It is a ‘newline’ or
+ one of the following: ‘||’, ‘&&’, ‘&’, ‘;’, ‘;;’, ‘;&’, ‘;;&’, ‘|’,
+ ‘|&’, ‘(’, or ‘)’.
+
+‘exit status’
+ The value returned by a command to its caller. The value is
+ restricted to eight bits, so the maximum value is 255.
+
+‘field’
+ A unit of text that is the result of one of the shell expansions.
+ After expansion, when executing a command, the resulting fields are
+ used as the command name and arguments.
+
+‘filename’
+ A string of characters used to identify a file.
+
+‘job’
+ A set of processes comprising a pipeline, and any processes
+ descended from it, that are all in the same process group.
+
+‘job control’
+ A mechanism by which users can selectively stop (suspend) and
+ restart (resume) execution of processes.
+
+‘metacharacter’
+ A character that, when unquoted, separates words. A metacharacter
+ is a ‘space’, ‘tab’, ‘newline’, or one of the following characters:
+ ‘|’, ‘&’, ‘;’, ‘(’, ‘)’, ‘<’, or ‘>’.
+
+‘name’
+ A ‘word’ consisting solely of letters, numbers, and underscores,
+ and beginning with a letter or underscore. ‘Name’s are used as
+ shell variable and function names. Also referred to as an
+ ‘identifier’.
+
+‘operator’
+ A ‘control operator’ or a ‘redirection operator’. *Note
+ Redirections::, for a list of redirection operators. Operators
+ contain at least one unquoted ‘metacharacter’.
+
+‘process group’
+ A collection of related processes each having the same process
+ group ID.
+
+‘process group ID’
+ A unique identifier that represents a ‘process group’ during its
+ lifetime.
+
+‘reserved word’
+ A ‘word’ that has a special meaning to the shell. Most reserved
+ words introduce shell flow control constructs, such as ‘for’ and
+ ‘while’.
+
+‘return status’
+ A synonym for ‘exit status’.
+
+‘signal’
+ A mechanism by which a process may be notified by the kernel of an
+ event occurring in the system.
+
+‘special builtin’
+ A shell builtin command that has been classified as special by the
+ POSIX standard.
+
+‘token’
+ A sequence of characters considered a single unit by the shell. It
+ is either a ‘word’ or an ‘operator’.
+
+‘word’
+ A sequence of characters treated as a unit by the shell. Words may
+ not include unquoted ‘metacharacters’.
+
+\1f
+File: bash.info, Node: Basic Shell Features, Next: Shell Builtin Commands, Prev: Definitions, Up: Top
+
+3 Basic Shell Features
+**********************
+
+Bash is an acronym for ‘Bourne-Again SHell’. The Bourne shell is the
+traditional Unix shell originally written by Stephen Bourne. All of the
+Bourne shell builtin commands are available in Bash, and the rules for
+evaluation and quoting are taken from the POSIX specification for the
+"standard" Unix shell.
+
+ This chapter briefly summarizes the shell's "building blocks":
+commands, control structures, shell functions, shell parameters, shell
+expansions, redirections, which are a way to direct input and output
+from and to named files, and how the shell executes commands.
+
+* Menu:
+
+* Shell Syntax:: What your input means to the shell.
+* Shell Commands:: The types of commands you can use.
+* Shell Functions:: Grouping commands by name.
+* Shell Parameters:: How the shell stores values.
+* Shell Expansions:: How Bash expands parameters and the various
+ expansions available.
+* Redirections:: A way to control where input and output go.
+* Executing Commands:: What happens when you run a command.
+* Shell Scripts:: Executing files of shell commands.
+
+\1f
+File: bash.info, Node: Shell Syntax, Next: Shell Commands, Up: Basic Shell Features
+
+3.1 Shell Syntax
+================
+
+* Menu:
+
+* Shell Operation:: The basic operation of the shell.
+* Quoting:: How to remove the special meaning from characters.
+* Comments:: How to specify comments.
+
+When the shell reads input, it proceeds through a sequence of
+operations. If the input indicates the beginning of a comment, the
+shell ignores the comment symbol (‘#’), and the rest of that line.
+
+ Otherwise, roughly speaking, the shell reads its input and divides
+the input into words and operators, employing the quoting rules to
+select which meanings to assign various words and characters.
+
+ The shell then parses these tokens into commands and other
+constructs, removes the special meaning of certain words or characters,
+expands others, redirects input and output as needed, executes the
+specified command, waits for the command's exit status, and makes that
+exit status available for further inspection or processing.
+
+\1f
+File: bash.info, Node: Shell Operation, Next: Quoting, Up: Shell Syntax
+
+3.1.1 Shell Operation
+---------------------
+
+The following is a brief description of the shell's operation when it
+reads and executes a command. Basically, the shell does the following:
+
+ 1. Reads its input from a file (*note Shell Scripts::), from a string
+ supplied as an argument to the ‘-c’ invocation option (*note
+ Invoking Bash::), or from the user's terminal.
+
+ 2. Breaks the input into words and operators, obeying the quoting
+ rules described in *note Quoting::. These tokens are separated by
+ ‘metacharacters’. This step performs alias expansion (*note
+ Aliases::).
+
+ 3. Parses the tokens into simple and compound commands (*note Shell
+ Commands::).
+
+ 4. Performs the various shell expansions (*note Shell Expansions::),
+ breaking the expanded tokens into lists of filenames (*note
+ Filename Expansion::) and commands and arguments.
+
+ 5. Performs any necessary redirections (*note Redirections::) and
+ removes the redirection operators and their operands from the
+ argument list.
+
+ 6. Executes the command (*note Executing Commands::).
+
+ 7. Optionally waits for the command to complete and collects its exit
+ status (*note Exit Status::).
+
+\1f
+File: bash.info, Node: Quoting, Next: Comments, Prev: Shell Operation, Up: Shell Syntax
+
+3.1.2 Quoting
+-------------
+
+* Menu:
+
+* Escape Character:: How to remove the special meaning from a single
+ character.
+* Single Quotes:: How to inhibit all interpretation of a sequence
+ of characters.
+* Double Quotes:: How to suppress most of the interpretation of a
+ sequence of characters.
+* ANSI-C Quoting:: How to expand ANSI-C sequences in quoted strings.
+* Locale Translation:: How to translate strings into different languages.
+
+Quoting is used to remove the special meaning of certain characters or
+words to the shell. Quoting can be used to disable special treatment
+for special characters, to prevent reserved words from being recognized
+as such, and to prevent parameter expansion.
+
+ Each of the shell metacharacters (*note Definitions::) has special
+meaning to the shell and must be quoted if it is to represent itself.
+
+ When the command history expansion facilities are being used (*note
+History Interaction::), the “history expansion” character, usually ‘!’,
+must be quoted to prevent history expansion. *Note Bash History
+Facilities::, for more details concerning history expansion.
+
+ There are four quoting mechanisms: the “escape character”, single
+quotes, double quotes, and dollar-single quotes.
+
+\1f
+File: bash.info, Node: Escape Character, Next: Single Quotes, Up: Quoting
+
+3.1.2.1 Escape Character
+........................
+
+A non-quoted backslash ‘\’ is the Bash escape character. It preserves
+the literal value of the next character that follows, removing any
+special meaning it has, with the exception of ‘newline’. If a
+‘\newline’ pair appears, and the backslash itself is not quoted, the
+‘\newline’ is treated as a line continuation (that is, it is removed
+from the input stream and effectively ignored).
+
+\1f
+File: bash.info, Node: Single Quotes, Next: Double Quotes, Prev: Escape Character, Up: Quoting
+
+3.1.2.2 Single Quotes
+.....................
+
+Enclosing characters in single quotes (‘'’) preserves the literal value
+of each character within the quotes. A single quote may not occur
+between single quotes, even when preceded by a backslash.
+
+\1f
+File: bash.info, Node: Double Quotes, Next: ANSI-C Quoting, Prev: Single Quotes, Up: Quoting
+
+3.1.2.3 Double Quotes
+.....................
+
+Enclosing characters in double quotes (‘"’) preserves the literal value
+of all characters within the quotes, with the exception of ‘$’, ‘`’,
+‘\’, and, when history expansion is enabled, ‘!’. When the shell is in
+POSIX mode (*note Bash POSIX Mode::), the ‘!’ has no special meaning
+within double quotes, even when history expansion is enabled. The
+characters ‘$’ and ‘`’ retain their special meaning within double quotes
+(*note Shell Expansions::). The backslash retains its special meaning
+only when followed by one of the following characters: ‘$’, ‘`’, ‘"’,
+‘\’, or ‘newline’. Within double quotes, backslashes that are followed
+by one of these characters are removed. Backslashes preceding
+characters without a special meaning are left unmodified.
+
+ A double quote may be quoted within double quotes by preceding it
+with a backslash. If enabled, history expansion will be performed
+unless an ‘!’ appearing in double quotes is escaped using a backslash.
+The backslash preceding the ‘!’ is not removed.
+
+ The special parameters ‘*’ and ‘@’ have special meaning when in
+double quotes (*note Shell Parameter Expansion::).
+
+\1f
+File: bash.info, Node: ANSI-C Quoting, Next: Locale Translation, Prev: Double Quotes, Up: Quoting
+
+3.1.2.4 ANSI-C Quoting
+......................
+
+Character sequences of the form ‘$'STRING'’ are treated as a special
+kind of single quotes. The sequence expands to STRING, with
+backslash-escaped characters in STRING replaced as specified by the ANSI
+C standard. Backslash escape sequences, if present, are decoded as
+follows:
+
+‘\a’
+ alert (bell)
+‘\b’
+ backspace
+‘\e’
+‘\E’
+ An escape character (not in ANSI C).
+‘\f’
+ form feed
+‘\n’
+ newline
+‘\r’
+ carriage return
+‘\t’
+ horizontal tab
+‘\v’
+ vertical tab
+‘\\’
+ backslash
+‘\'’
+ single quote
+‘\"’
+ double quote
+‘\?’
+ question mark
+‘\NNN’
+ The eight-bit character whose value is the octal value NNN (one to
+ three octal digits).
+‘\xHH’
+ The eight-bit character whose value is the hexadecimal value HH
+ (one or two hex digits).
+‘\uHHHH’
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHH (one to four hex digits).
+‘\UHHHHHHHH’
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHHHHHH (one to eight hex digits).
+‘\cX’
+ A control-X character.
+
+The expanded result is single-quoted, as if the dollar sign had not been
+present.
+
+\1f
+File: bash.info, Node: Locale Translation, Prev: ANSI-C Quoting, Up: Quoting
+
+3.1.2.5 Locale-Specific Translation
+...................................
+
+* Menu:
+
+* Creating Internationalized Scripts:: How to use translations and different
+ languages in your scripts.
+
+Prefixing a double-quoted string with a dollar sign (‘$’), such as
+$"hello, world", causes the string to be translated according to the
+current locale. The ‘gettext’ infrastructure performs the lookup and
+translation, using the ‘LC_MESSAGES’, ‘TEXTDOMAINDIR’, and ‘TEXTDOMAIN’
+shell variables, as explained below. See the gettext documentation for
+additional details not covered here. If the current locale is ‘C’ or
+‘POSIX’, if there are no translations available, or if the string is not
+translated, the dollar sign is ignored, and the string is treated as
+double-quoted as described above. Since this is a form of double
+quoting, the string remains double-quoted by default, whether or not it
+is translated and replaced. If the ‘noexpand_translation’ option is
+enabled using the ‘shopt’ builtin (*note The Shopt Builtin::),
+translated strings are single-quoted instead of double-quoted.
+
+ The rest of this section is a brief overview of how you use gettext
+to create translations for strings in a shell script named SCRIPTNAME.
+There are more details in the gettext documentation.
+
+\1f
+File: bash.info, Node: Creating Internationalized Scripts, Up: Locale Translation
+
+Once you've marked the strings in your script that you want to translate
+using $"...", you create a gettext "template" file using the command
+
+ bash --dump-po-strings SCRIPTNAME > DOMAIN.pot
+
+The DOMAIN is your “message domain”. It's just an arbitrary string
+that's used to identify the files gettext needs, like a package or
+script name. It needs to be unique among all the message domains on
+systems where you install the translations, so gettext knows which
+translations correspond to your script. You'll use the template file to
+create translations for each target language. The template file
+conventionally has the suffix ‘.pot’.
+
+ You copy this template file to a separate file for each target
+language you want to support (called "PO" files, which use the suffix
+‘.po’). PO files use various naming conventions, but when you are
+working to translate a template file into a particular language, you
+first copy the template file to a file whose name is the language you
+want to target, with the ‘.po’ suffix. For instance, the Spanish
+translations of your strings would be in a file named ‘es.po’, and to
+get started using a message domain named "example," you would run
+
+ cp example.pot es.po
+
+Ultimately, PO files are often named DOMAIN.po and installed in
+directories that contain multiple translation files for a particular
+language.
+
+ Whichever naming convention you choose, you will need to translate
+the strings in the PO files into the appropriate languages. This has to
+be done manually.
+
+ When you have the translations and PO files complete, you'll use the
+gettext tools to produce what are called "MO" files, which are compiled
+versions of the PO files the gettext tools use to look up translations
+efficiently. MO files are also called "message catalog" files. You use
+the ‘msgfmt’ program to do this. For instance, if you had a file with
+Spanish translations, you could run
+
+ msgfmt -o es.mo es.po
+
+to produce the corresponding MO file.
+
+ Once you have the MO files, you decide where to install them and use
+the ‘TEXTDOMAINDIR’ shell variable to tell the gettext tools where they
+are. Make sure to use the same message domain to name the MO files as
+you did for the PO files when you install them.
+
+ Your users will use the ‘LANG’ or ‘LC_MESSAGES’ shell variables to
+select the desired language.
+
+ You set the ‘TEXTDOMAIN’ variable to the script's message domain. As
+above, you use the message domain to name your translation files.
+
+ You, or possibly your users, set the ‘TEXTDOMAINDIR’ variable to the
+name of a directory where the message catalog files are stored. If you
+install the message files into the system's standard message catalog
+directory, you don't need to worry about this variable.
+
+ The directory where the message catalog files are stored varies
+between systems. Some use the message catalog selected by the
+‘LC_MESSAGES’ shell variable. Others create the name of the message
+catalog from the value of the ‘TEXTDOMAIN’ shell variable, possibly
+adding the ‘.mo’ suffix. If you use the ‘TEXTDOMAIN’ variable, you may
+need to set the ‘TEXTDOMAINDIR’ variable to the location of the message
+catalog files, as above. It's common to use both variables in this
+fashion: ‘$TEXTDOMAINDIR’/‘$LC_MESSAGES’/LC_MESSAGES/‘$TEXTDOMAIN’.mo.
+
+ If you used that last convention, and you wanted to store the message
+catalog files with Spanish (es) and Esperanto (eo) translations into a
+local directory you use for custom translation files, you could run
+
+ TEXTDOMAIN=example
+ TEXTDOMAINDIR=/usr/local/share/locale
+
+ cp es.mo ${TEXTDOMAINDIR}/es/LC_MESSAGES/${TEXTDOMAIN}.mo
+ cp eo.mo ${TEXTDOMAINDIR}/eo/LC_MESSAGES/${TEXTDOMAIN}.mo
+
+ When all of this is done, and the message catalog files containing
+the compiled translations are installed in the correct location, your
+users will be able to see translated strings in any of the supported
+languages by setting the ‘LANG’ or ‘LC_MESSAGES’ environment variables
+before running your script.
+
+\1f
+File: bash.info, Node: Comments, Prev: Quoting, Up: Shell Syntax
+
+3.1.3 Comments
+--------------
+
+In a non-interactive shell, or an interactive shell in which the
+‘interactive_comments’ option to the ‘shopt’ builtin is enabled (*note
+The Shopt Builtin::), a word beginning with ‘#’ introduces a comment. A
+word begins at the beginning of a line, after unquoted whitespace, or
+after an operator. The comment causes that word and all remaining
+characters on that line to be ignored. An interactive shell without the
+‘interactive_comments’ option enabled does not allow comments. The
+‘interactive_comments’ option is enabled by default in interactive
+shells. *Note Interactive Shells::, for a description of what makes a
+shell interactive.
+
+\1f
+File: bash.info, Node: Shell Commands, Next: Shell Functions, Prev: Shell Syntax, Up: Basic Shell Features
+
+3.2 Shell Commands
+==================
+
+A simple shell command such as ‘echo a b c’ consists of the command
+itself followed by arguments, separated by spaces.
+
+ More complex shell commands are composed of simple commands arranged
+together in a variety of ways: in a pipeline in which the output of one
+command becomes the input of a second, in a loop or conditional
+construct, or in some other grouping.
+
+* Menu:
+
+* Reserved Words:: Words that have special meaning to the shell.
+* Simple Commands:: The most common type of command.
+* Pipelines:: Connecting the input and output of several
+ commands.
+* Lists:: How to execute commands sequentially.
+* Compound Commands:: Shell commands for control flow.
+* Coprocesses:: Two-way communication between commands.
+* GNU Parallel:: Running commands in parallel.
+
+\1f
+File: bash.info, Node: Reserved Words, Next: Simple Commands, Up: Shell Commands
+
+3.2.1 Reserved Words
+--------------------
+
+Reserved words are words that have special meaning to the shell. They
+are used to begin and end the shell's compound commands.
+
+ The following words are recognized as reserved when unquoted and the
+first word of a command (see below for exceptions):
+
+‘if’ ‘then’ ‘elif’ ‘else’ ‘fi’ ‘time’
+‘for’ ‘in’ ‘until’ ‘while’ ‘do’ ‘done’
+‘case’ ‘esac’ ‘coproc’‘select’‘function’
+‘{’ ‘}’ ‘[[’ ‘]]’ ‘!’
+
+‘in’ is recognized as a reserved word if it is the third word of a
+‘case’ or ‘select’ command. ‘in’ and ‘do’ are recognized as reserved
+words if they are the third word in a ‘for’ command.
+
+\1f
+File: bash.info, Node: Simple Commands, Next: Pipelines, Prev: Reserved Words, Up: Shell Commands
+
+3.2.2 Simple Commands
+---------------------
+
+A simple command is the kind of command that's executed most often.
+It's just a sequence of words separated by ‘blank’s, terminated by one
+of the shell's control operators (*note Definitions::). The first word
+generally specifies a command to be executed, with the rest of the words
+being that command's arguments.
+
+ The return status (*note Exit Status::) of a simple command is its
+exit status as provided by the POSIX 1003.1 ‘waitpid’ function, or 128+N
+if the command was terminated by signal N.
+
+\1f
+File: bash.info, Node: Pipelines, Next: Lists, Prev: Simple Commands, Up: Shell Commands
+
+3.2.3 Pipelines
+---------------
+
+A ‘pipeline’ is a sequence of one or more commands separated by one of
+the control operators ‘|’ or ‘|&’.
+
+ The format for a pipeline is
+ [time [-p]] [!] COMMAND1 [ | or |& COMMAND2 ] ...
+
+The output of each command in the pipeline is connected via a pipe to
+the input of the next command. That is, each command reads the previous
+command's output. This connection is performed before any redirections
+specified by COMMAND1.
+
+ If ‘|&’ is the pipeline operator, COMMAND1's standard error, in
+addition to its standard output, is connected to COMMAND2's standard
+input through the pipe; it is shorthand for ‘2>&1 |’. This implicit
+redirection of the standard error to the standard output is performed
+after any redirections specified by COMMAND1, consistent with that
+shorthand.
+
+ If the reserved word ‘time’ precedes the pipeline, Bash prints timing
+statistics for the pipeline once it finishes. The statistics currently
+consist of elapsed (wall-clock) time and user and system time consumed
+by the command's execution. The ‘-p’ option changes the output format
+to that specified by POSIX. When the shell is in POSIX mode (*note Bash
+POSIX Mode::), it does not recognize ‘time’ as a reserved word if the
+next token begins with a ‘-’. The value of the ‘TIMEFORMAT’ variable is
+a format string that specifies how the timing information should be
+displayed. *Note Bash Variables::, for a description of the available
+formats. Providing ‘time’ as a reserved word permits the timing of
+shell builtins, shell functions, and pipelines. An external ‘time’
+command cannot time these easily.
+
+ When the shell is in POSIX mode (*note Bash POSIX Mode::), you can
+use ‘time’ by itself as a simple command. In this case, the shell
+displays the total user and system time consumed by the shell and its
+children. The ‘TIMEFORMAT’ variable specifies the format of the time
+information.
+
+ If a pipeline is not executed asynchronously (*note Lists::), the
+shell waits for all commands in the pipeline to complete.
+
+ Each command in a multi-command pipeline, where pipes are created, is
+executed in its own “subshell”, which is a separate process (*note
+Command Execution Environment::). If the ‘lastpipe’ option is enabled
+using the ‘shopt’ builtin (*note The Shopt Builtin::), and job control
+is not active, the last element of a pipeline may be run by the shell
+process.
+
+ The exit status of a pipeline is the exit status of the last command
+in the pipeline, unless the ‘pipefail’ option is enabled (*note The Set
+Builtin::). If ‘pipefail’ is enabled, the pipeline's return status is
+the value of the last (rightmost) command to exit with a non-zero
+status, or zero if all commands exit successfully. If the reserved word
+‘!’ precedes the pipeline, the exit status is the logical negation of
+the exit status as described above. If a pipeline is not executed
+asynchronously (*note Lists::), the shell waits for all commands in the
+pipeline to terminate before returning a value. The return status of an
+asynchronous pipeline is 0.
+
+\1f
+File: bash.info, Node: Lists, Next: Compound Commands, Prev: Pipelines, Up: Shell Commands
+
+3.2.4 Lists of Commands
+-----------------------
+
+A ‘list’ is a sequence of one or more pipelines separated by one of the
+operators ‘;’, ‘&’, ‘&&’, or ‘||’, and optionally terminated by one of
+‘;’, ‘&’, or a ‘newline’.
+
+ Of these list operators, ‘&&’ and ‘||’ have equal precedence,
+followed by ‘;’ and ‘&’, which have equal precedence.
+
+ A sequence of one or more newlines may appear in a ‘list’ to delimit
+commands, equivalent to a semicolon.
+
+ If a command is terminated by the control operator ‘&’, the shell
+executes the command asynchronously in a subshell. This is known as
+executing the command in the “background”, and these are referred to as
+“asynchronous” commands. The shell does not wait for the command to
+finish, and the return status is 0 (true). When job control is not
+active (*note Job Control::), the standard input for asynchronous
+commands, in the absence of any explicit redirections, is redirected
+from ‘/dev/null’.
+
+ Commands separated by a ‘;’ are executed sequentially; the shell
+waits for each command to terminate in turn. The return status is the
+exit status of the last command executed.
+
+ AND and OR lists are sequences of one or more pipelines separated by
+the control operators ‘&&’ and ‘||’, respectively. AND and OR lists are
+executed with left associativity.
+
+ An AND list has the form
+ COMMAND1 && COMMAND2
+
+COMMAND2 is executed if, and only if, COMMAND1 returns an exit status of
+zero (success).
+
+ An OR list has the form
+ COMMAND1 || COMMAND2
+
+COMMAND2 is executed if, and only if, COMMAND1 returns a non-zero exit
+status.
+
+ The return status of AND and OR lists is the exit status of the last
+command executed in the list.
+
+\1f
+File: bash.info, Node: Compound Commands, Next: Coprocesses, Prev: Lists, Up: Shell Commands
+
+3.2.5 Compound Commands
+-----------------------
+
+* Menu:
+
+* Looping Constructs:: Shell commands for iterative action.
+* Conditional Constructs:: Shell commands for conditional execution.
+* Command Grouping:: Ways to group commands.
+
+Compound commands are the shell programming language constructs. Each
+construct begins with a reserved word or control operator and is
+terminated by a corresponding reserved word or operator. Any
+redirections (*note Redirections::) associated with a compound command
+apply to all commands within that compound command unless explicitly
+overridden.
+
+ In most cases a list of commands in a compound command's description
+may be separated from the rest of the command by one or more newlines,
+and may be followed by a newline in place of a semicolon.
+
+ Bash provides looping constructs, conditional commands, and
+mechanisms to group commands and execute them as a unit.
+
+\1f
+File: bash.info, Node: Looping Constructs, Next: Conditional Constructs, Up: Compound Commands
+
+3.2.5.1 Looping Constructs
+..........................
+
+Bash supports the following looping constructs.
+
+ Note that wherever a ‘;’ appears in the description of a command's
+syntax, it may be replaced with one or more newlines.
+
+‘until’
+ The syntax of the ‘until’ command is:
+
+ until TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
+
+ Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
+ status which is not zero. The return status is the exit status of
+ the last command executed in CONSEQUENT-COMMANDS, or zero if none
+ was executed.
+
+‘while’
+ The syntax of the ‘while’ command is:
+
+ while TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
+
+ Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
+ status of zero. The return status is the exit status of the last
+ command executed in CONSEQUENT-COMMANDS, or zero if none was
+ executed.
+
+‘for’
+ The syntax of the ‘for’ command is:
+
+ for NAME [ [in WORDS ...] ; ] do COMMANDS; done
+
+ Expand WORDS (*note Shell Expansions::), and then execute COMMANDS
+ once for each word in the resultant list, with NAME bound to the
+ current word. If ‘in WORDS’ is not present, the ‘for’ command
+ executes the COMMANDS once for each positional parameter that is
+ set, as if ‘in "$@"’ had been specified (*note Special
+ Parameters::).
+
+ The return status is the exit status of the last command that
+ executes. If there are no items in the expansion of WORDS, no
+ commands are executed, and the return status is zero.
+
+ There is an alternate form of the ‘for’ command which is similar to
+ the C language:
+
+ for (( EXPR1 ; EXPR2 ; EXPR3 )) [;] do COMMANDS ; done
+
+ First, evaluate the arithmetic expression EXPR1 according to the
+ rules described below (*note Shell Arithmetic::). Then, repeatedly
+ evaluate the arithmetic expression EXPR2 until it evaluates to
+ zero. Each time EXPR2 evaluates to a non-zero value, execute
+ COMMANDS and evaluate the arithmetic expression EXPR3. If any
+ expression is omitted, it behaves as if it evaluates to 1. The
+ return value is the exit status of the last command in COMMANDS
+ that is executed, or non-zero if any of the expressions is invalid.
+
+ Use the ‘break’ and ‘continue’ builtins (*note Bourne Shell
+Builtins::) to control loop execution.
+
+\1f
+File: bash.info, Node: Conditional Constructs, Next: Command Grouping, Prev: Looping Constructs, Up: Compound Commands
+
+3.2.5.2 Conditional Constructs
+..............................
+
+‘if’
+ The syntax of the ‘if’ command is:
+
+ if TEST-COMMANDS; then
+ CONSEQUENT-COMMANDS;
+ [elif MORE-TEST-COMMANDS; then
+ MORE-CONSEQUENTS;]
+ [else ALTERNATE-CONSEQUENTS;]
+ fi
+
+ The TEST-COMMANDS list is executed, and if its return status is
+ zero, the CONSEQUENT-COMMANDS list is executed. If TEST-COMMANDS
+ returns a non-zero status, each ‘elif’ list is executed in turn,
+ and if its exit status is zero, the corresponding MORE-CONSEQUENTS
+ is executed and the command completes. If ‘else
+ ALTERNATE-CONSEQUENTS’ is present, and the final command in the
+ final ‘if’ or ‘elif’ clause has a non-zero exit status, then
+ ALTERNATE-CONSEQUENTS is executed. The return status is the exit
+ status of the last command executed, or zero if no condition tested
+ true.
+
+‘case’
+ The syntax of the ‘case’ command is:
+
+ case WORD in
+ [ [(] PATTERN [| PATTERN]...) COMMAND-LIST ;;]...
+ esac
+
+ ‘case’ will selectively execute the COMMAND-LIST corresponding to
+ the first PATTERN that matches WORD, proceeding from the first
+ pattern to the last. The match is performed according to the rules
+ described below in *note Pattern Matching::. If the ‘nocasematch’
+ shell option (see the description of ‘shopt’ in *note The Shopt
+ Builtin::) is enabled, the match is performed without regard to the
+ case of alphabetic characters. The ‘|’ is used to separate
+ multiple patterns in a pattern list, and the ‘)’ operator
+ terminates the pattern list. A pattern list and an associated
+ COMMAND-LIST is known as a CLAUSE.
+
+ Each clause must be terminated with ‘;;’, ‘;&’, or ‘;;&’. The WORD
+ undergoes tilde expansion, parameter expansion, command
+ substitution, process substitution, arithmetic expansion, and quote
+ removal (*note Shell Parameter Expansion::) before the shell
+ attempts to match the pattern. Each PATTERN undergoes tilde
+ expansion, parameter expansion, command substitution, arithmetic
+ expansion, process substitution, and quote removal.
+
+ There may be an arbitrary number of ‘case’ clauses, each terminated
+ by a ‘;;’, ‘;&’, or ‘;;&’. The first pattern that matches
+ determines the command-list that is executed. It's a common idiom
+ to use ‘*’ as the final pattern to define the default case, since
+ that pattern will always match.
+
+ Here is an example using ‘case’ in a script that could be used to
+ describe one interesting feature of an animal:
+
+ echo -n "Enter the name of an animal: "
+ read ANIMAL
+ echo -n "The $ANIMAL has "
+ case $ANIMAL in
+ horse | dog | cat) echo -n "four";;
+ man | kangaroo ) echo -n "two";;
+ *) echo -n "an unknown number of";;
+ esac
+ echo " legs."
+
+ If the ‘;;’ operator is used, the ‘case’ command completes after
+ the first pattern match. Using ‘;&’ in place of ‘;;’ causes
+ execution to continue with the COMMAND-LIST associated with the
+ next clause, if any. Using ‘;;&’ in place of ‘;;’ causes the shell
+ to test the patterns in the next clause, if any, and execute any
+ associated COMMAND-LIST if the match succeeds, continuing the case
+ statement execution as if the pattern list had not matched.
+
+ The return status is zero if no PATTERN matches. Otherwise, the
+ return status is the exit status of the last COMMAND-LIST executed.
+
+‘select’
+
+ The ‘select’ construct allows the easy generation of menus. It has
+ almost the same syntax as the ‘for’ command:
+
+ select NAME [in WORDS ...]; do COMMANDS; done
+
+ First, expand the list of words following ‘in’, generating a list
+ of items, and print the set of expanded words on the standard error
+ stream, each preceded by a number. If the ‘in WORDS’ is omitted,
+ print the positional parameters, as if ‘in "$@"’ had been
+ specified. ‘select’ then displays the ‘PS3’ prompt and reads a
+ line from the standard input. If the line consists of a number
+ corresponding to one of the displayed words, then ‘select’ sets the
+ value of NAME to that word. If the line is empty, ‘select’
+ displays the words and prompt again. If ‘EOF’ is read, ‘select’
+ completes and returns 1. Any other value read causes NAME to be
+ set to null. The line read is saved in the variable ‘REPLY’.
+
+ The COMMANDS are executed after each selection until a ‘break’
+ command is executed, at which point the ‘select’ command completes.
+
+ Here is an example that allows the user to pick a filename from the
+ current directory, and displays the name and index of the file
+ selected.
+
+ select fname in *;
+ do
+ echo you picked $fname \($REPLY\)
+ break;
+ done
+
+‘((...))’
+ (( EXPRESSION ))
+
+ The arithmetic EXPRESSION is evaluated according to the rules
+ described below (*note Shell Arithmetic::). The EXPRESSION
+ undergoes the same expansions as if it were within double quotes,
+ but unescaped double quote characters in EXPRESSION are not treated
+ specially and are removed. Since this can potentially result in
+ empty strings, this command treats those as expressions that
+ evaluate to 0. If the value of the expression is non-zero, the
+ return status is 0; otherwise the return status is 1.
+
+‘[[...]]’
+ [[ EXPRESSION ]]
+
+ Evaluate the conditional expression EXPRESSION and return a status
+ of zero (true) or non-zero (false). Expressions are composed of
+ the primaries described below in *note Bash Conditional
+ Expressions::. The words between the ‘[[’ and ‘]]’ do not undergo
+ word splitting and filename expansion. The shell performs tilde
+ expansion, parameter and variable expansion, arithmetic expansion,
+ command substitution, process substitution, and quote removal on
+ those words. Conditional operators such as ‘-f’ must be unquoted
+ to be recognized as primaries.
+
+ When used with ‘[[’, the ‘<’ and ‘>’ operators sort
+ lexicographically using the current locale.
+
+ When the ‘==’ and ‘!=’ operators are used, the string to the right
+ of the operator is considered a pattern and matched according to
+ the rules described below in *note Pattern Matching::, as if the
+ ‘extglob’ shell option were enabled. The ‘=’ operator is identical
+ to ‘==’. If the ‘nocasematch’ shell option (see the description of
+ ‘shopt’ in *note The Shopt Builtin::) is enabled, the match is
+ performed without regard to the case of alphabetic characters. The
+ return value is 0 if the string matches (‘==’) or does not match
+ (‘!=’) the pattern, and 1 otherwise.
+
+ If you quote any part of the pattern, using any of the shell's
+ quoting mechanisms, the quoted portion is matched literally. This
+ means every character in the quoted portion matches itself, instead
+ of having any special pattern matching meaning.
+
+ An additional binary operator, ‘=~’, is available, with the same
+ precedence as ‘==’ and ‘!=’. When you use ‘=~’, the string to the
+ right of the operator is considered a POSIX extended regular
+ expression pattern and matched accordingly (using the POSIX
+ ‘regcomp’ and ‘regexec’ interfaces usually described in regex(3)).
+ The return value is 0 if the string matches the pattern, and 1 if
+ it does not. If the regular expression is syntactically incorrect,
+ the conditional expression returns 2. If the ‘nocasematch’ shell
+ option (see the description of ‘shopt’ in *note The Shopt
+ Builtin::) is enabled, the match is performed without regard to the
+ case of alphabetic characters.
+
+ You can quote any part of the pattern to force the quoted portion
+ to be matched literally instead of as a regular expression (see
+ above). If the pattern is stored in a shell variable, quoting the
+ variable expansion forces the entire pattern to be matched
+ literally.
+
+ The match succeeds if the pattern matches any part of the string.
+ If you want to force the pattern to match the entire string, anchor
+ the pattern using the ‘^’ and ‘$’ regular expression operators.
+
+ For example, the following will match a line (stored in the shell
+ variable ‘line’) if there is a sequence of characters anywhere in
+ the value consisting of any number, including zero, of characters
+ in the ‘space’ character class, immediately followed by zero or one
+ instances of ‘a’, then a ‘b’:
+
+ [[ $line =~ [[:space:]]*(a)?b ]]
+
+ That means values for ‘line’ like ‘aab’, ‘ aaaaaab’, ‘xaby’, and ‘
+ ab’ will all match, as will a line containing a ‘b’ anywhere in its
+ value.
+
+ If you want to match a character that's special to the regular
+ expression grammar (‘^$|[]()\.*+?’), it has to be quoted to remove
+ its special meaning. This means that in the pattern ‘xxx.txt’, the
+ ‘.’ matches any character in the string (its usual regular
+ expression meaning), but in the pattern ‘"xxx.txt"’, it can only
+ match a literal ‘.’.
+
+ Likewise, if you want to include a character in your pattern that
+ has a special meaning to the regular expression grammar, you must
+ make sure it's not quoted. If you want to anchor a pattern at the
+ beginning or end of the string, for instance, you cannot quote the
+ ‘^’ or ‘$’ characters using any form of shell quoting.
+
+ If you want to match ‘initial string’ at the start of a line, the
+ following will work:
+ [[ $line =~ ^"initial string" ]]
+ but this will not:
+ [[ $line =~ "^initial string" ]]
+ because in the second example the ‘^’ is quoted and doesn't have
+ its usual special meaning.
+
+ It is sometimes difficult to specify a regular expression properly
+ without using quotes, or to keep track of the quoting used by
+ regular expressions while paying attention to shell quoting and the
+ shell's quote removal. Storing the regular expression in a shell
+ variable is often a useful way to avoid problems with quoting
+ characters that are special to the shell. For example, the
+ following is equivalent to the pattern used above:
+
+ pattern='[[:space:]]*(a)?b'
+ [[ $line =~ $pattern ]]
+
+ Shell programmers should take special care with backslashes, since
+ backslashes are used by both the shell and regular expressions to
+ remove the special meaning from the following character. This
+ means that after the shell's word expansions complete (*note Shell
+ Expansions::), any backslashes remaining in parts of the pattern
+ that were originally not quoted can remove the special meaning of
+ pattern characters. If any part of the pattern is quoted, the
+ shell does its best to ensure that the regular expression treats
+ those remaining backslashes as literal, if they appeared in a
+ quoted portion.
+
+ The following two sets of commands are _not_ equivalent:
+
+ pattern='\.'
+
+ [[ . =~ $pattern ]]
+ [[ . =~ \. ]]
+
+ [[ . =~ "$pattern" ]]
+ [[ . =~ '\.' ]]
+
+ The first two matches will succeed, but the second two will not,
+ because in the second two the backslash will be part of the pattern
+ to be matched. In the first two examples, the pattern passed to
+ the regular expression parser is ‘\.’. The backslash removes the
+ special meaning from ‘.’, so the literal ‘.’ matches. In the
+ second two examples, the pattern passed to the regular expression
+ parser has the backslash quoted (e.g., ‘\\\.’), which will not
+ match the string, since it does not contain a backslash. If the
+ string in the first examples were anything other than ‘.’, say ‘a’,
+ the pattern would not match, because the quoted ‘.’ in the pattern
+ loses its special meaning of matching any single character.
+
+ Bracket expressions in regular expressions can be sources of errors
+ as well, since characters that are normally special in regular
+ expressions lose their special meanings between brackets. However,
+ you can use bracket expressions to match special pattern characters
+ without quoting them, so they are sometimes useful for this
+ purpose.
+
+ Though it might seem like a strange way to write it, the following
+ pattern will match a ‘.’ in the string:
+
+ [[ . =~ [.] ]]
+
+ The shell performs any word expansions before passing the pattern
+ to the regular expression functions, so you can assume that the
+ shell's quoting takes precedence. As noted above, the regular
+ expression parser will interpret any unquoted backslashes remaining
+ in the pattern after shell expansion according to its own rules.
+ The intention is to avoid making shell programmers quote things
+ twice as much as possible, so shell quoting should be sufficient to
+ quote special pattern characters where that's necessary.
+
+ The array variable ‘BASH_REMATCH’ records which parts of the string
+ matched the pattern. The element of ‘BASH_REMATCH’ with index 0
+ contains the portion of the string matching the entire regular
+ expression. Substrings matched by parenthesized subexpressions
+ within the regular expression are saved in the remaining
+ ‘BASH_REMATCH’ indices. The element of ‘BASH_REMATCH’ with index N
+ is the portion of the string matching the Nth parenthesized
+ subexpression.
+
+ Bash sets ‘BASH_REMATCH’ in the global scope; declaring it as a
+ local variable will lead to unexpected results.
+
+ Expressions may be combined using the following operators, listed
+ in decreasing order of precedence:
+
+ ‘( EXPRESSION )’
+ Returns the value of EXPRESSION. This may be used to override
+ the normal precedence of operators.
+
+ ‘! EXPRESSION’
+ True if EXPRESSION is false.
+
+ ‘EXPRESSION1 && EXPRESSION2’
+ True if both EXPRESSION1 and EXPRESSION2 are true.
+
+ ‘EXPRESSION1 || EXPRESSION2’
+ True if either EXPRESSION1 or EXPRESSION2 is true.
+
+ The ‘&&’ and ‘||’ operators do not evaluate EXPRESSION2 if the
+ value of EXPRESSION1 is sufficient to determine the return value of
+ the entire conditional expression.
+
+\1f
+File: bash.info, Node: Command Grouping, Prev: Conditional Constructs, Up: Compound Commands
+
+3.2.5.3 Grouping Commands
+.........................
+
+Bash provides two ways to group a list of commands to be executed as a
+unit. When commands are grouped, redirections may be applied to the
+entire command list. For example, the output of all the commands in the
+list may be redirected to a single stream.
+
+‘()’
+ ( LIST )
+
+ Placing a list of commands between parentheses forces the shell to
+ create a subshell (*note Command Execution Environment::), and each
+ of the commands in LIST is executed in that subshell environment.
+ Since the LIST is executed in a subshell, variable assignments do
+ not remain in effect after the subshell completes.
+
+‘{}’
+ { LIST; }
+
+ Placing a list of commands between curly braces causes the list to
+ be executed in the current shell environment. No subshell is
+ created. The semicolon (or newline) following LIST is required.
+
+ In addition to the creation of a subshell, there is a subtle
+difference between these two constructs due to historical reasons. The
+braces are reserved words, so they must be separated from the LIST by
+‘blank’s or other shell metacharacters. The parentheses are operators,
+and are recognized as separate tokens by the shell even if they are not
+separated from the LIST by whitespace.
+
+ The exit status of both of these constructs is the exit status of
+LIST.
+
+\1f
+File: bash.info, Node: Coprocesses, Next: GNU Parallel, Prev: Compound Commands, Up: Shell Commands
+
+3.2.6 Coprocesses
+-----------------
+
+A ‘coprocess’ is a shell command preceded by the ‘coproc’ reserved word.
+A coprocess is executed asynchronously in a subshell, as if the command
+had been terminated with the ‘&’ control operator, with a two-way pipe
+established between the executing shell and the coprocess.
+
+ The syntax for a coprocess is:
+
+ coproc [NAME] COMMAND [REDIRECTIONS]
+
+This creates a coprocess named NAME. COMMAND may be either a simple
+command (*note Simple Commands::) or a compound command (*note Compound
+Commands::). NAME is a shell variable name. If NAME is not supplied,
+the default name is ‘COPROC’.
+
+ The recommended form to use for a coprocess is
+
+ coproc NAME { COMMAND; }
+
+This form is preferred because simple commands result in the coprocess
+always being named ‘COPROC’, and it is simpler to use and more complete
+than the other compound commands.
+
+ There are other forms of coprocesses:
+
+ coproc NAME COMPOUND-COMMAND
+ coproc COMPOUND-COMMAND
+ coproc SIMPLE-COMMAND
+
+If COMMAND is a compound command, NAME is optional. The word following
+‘coproc’ determines whether that word is interpreted as a variable name:
+it is interpreted as NAME if it is not a reserved word that introduces a
+compound command. If COMMAND is a simple command, NAME is not allowed;
+this is to avoid confusion between NAME and the first word of the simple
+command.
+
+ When the coprocess is executed, the shell creates an array variable
+(*note Arrays::) named NAME in the context of the executing shell. The
+standard output of COMMAND is connected via a pipe to a file descriptor
+in the executing shell, and that file descriptor is assigned to NAME[0].
+The standard input of COMMAND is connected via a pipe to a file
+descriptor in the executing shell, and that file descriptor is assigned
+to NAME[1]. This pipe is established before any redirections specified
+by the command (*note Redirections::). The file descriptors can be
+utilized as arguments to shell commands and redirections using standard
+word expansions. Other than those created to execute command and
+process substitutions, the file descriptors are not available in
+subshells.
+
+ The process ID of the shell spawned to execute the coprocess is
+available as the value of the variable ‘NAME_PID’. The ‘wait’ builtin
+may be used to wait for the coprocess to terminate.
+
+ Since the coprocess is created as an asynchronous command, the
+‘coproc’ command always returns success. The return status of a
+coprocess is the exit status of COMMAND.
+
+\1f
+File: bash.info, Node: GNU Parallel, Prev: Coprocesses, Up: Shell Commands
+
+3.2.7 GNU Parallel
+------------------
+
+There are ways to run commands in parallel that are not built into Bash.
+GNU Parallel is a tool to do just that.
+
+ GNU Parallel, as its name suggests, can be used to build and run
+commands in parallel. You may run the same command with different
+arguments, whether they are filenames, usernames, hostnames, or lines
+read from files. GNU Parallel provides shorthand references to many of
+the most common operations (input lines, various portions of the input
+line, different ways to specify the input source, and so on). Parallel
+can replace ‘xargs’ or feed commands from its input sources to several
+different instances of Bash.
+
+ For a complete description, refer to the GNU Parallel documentation,
+which is available at
+<https://www.gnu.org/software/parallel/parallel_tutorial.html>.
+
+\1f
+File: bash.info, Node: Shell Functions, Next: Shell Parameters, Prev: Shell Commands, Up: Basic Shell Features
+
+3.3 Shell Functions
+===================
+
+Shell functions are a way to group commands for later execution using a
+single name for the group. They are executed just like a "regular"
+simple command. When the name of a shell function is used as a simple
+command name, the shell executes the list of commands associated with
+that function name. Shell functions are executed in the current shell
+context; there is no new process created to interpret them.
+
+ Functions are declared using this syntax:
+ FNAME () COMPOUND-COMMAND [ REDIRECTIONS ]
+
+ or
+
+ function FNAME [()] COMPOUND-COMMAND [ REDIRECTIONS ]
+
+ This defines a shell function named FNAME. The reserved word
+‘function’ is optional. If the ‘function’ reserved word is supplied,
+the parentheses are optional. The “body” of the function is the
+compound command COMPOUND-COMMAND (*note Compound Commands::). That
+command is usually a LIST enclosed between { and }, but may be any
+compound command listed above. If the ‘function’ reserved word is used,
+but the parentheses are not supplied, the braces are recommended. When
+the shell is in POSIX mode (*note Bash POSIX Mode::), FNAME must be a
+valid shell name and may not be the same as one of the special builtins
+(*note Special Builtins::). When not in POSIX mode, a function name can
+be any unquoted shell word that does not contain ‘$’.
+
+ Any redirections (*note Redirections::) associated with the shell
+function are performed when the function is executed. Function
+definitions are deleted using the ‘-f’ option to the ‘unset’ builtin
+(*note Bourne Shell Builtins::).
+
+ The exit status of a function definition is zero unless a syntax
+error occurs or a readonly function with the same name already exists.
+When executed, the exit status of a function is the exit status of the
+last command executed in the body.
+
+ Note that for historical reasons, in the most common usage the curly
+braces that surround the body of the function must be separated from the
+body by ‘blank’s or newlines. This is because the braces are reserved
+words and are only recognized as such when they are separated from the
+command list by whitespace or another shell metacharacter. When using
+the braces, the LIST must be terminated by a semicolon, a ‘&’, or a
+newline.
+
+ COMPOUND-COMMAND is executed whenever FNAME is specified as the name
+of a simple command. Functions are executed in the context of the
+calling shell; there is no new process created to interpret them
+(contrast this with the execution of a shell script).
+
+ When a function is executed, the arguments to the function become the
+positional parameters during its execution (*note Positional
+Parameters::). The special parameter ‘#’ that expands to the number of
+positional parameters is updated to reflect the new set of positional
+parameters. Special parameter ‘0’ is unchanged. The first element of
+the ‘FUNCNAME’ variable is set to the name of the function while the
+function is executing.
+
+ All other aspects of the shell execution environment are identical
+between a function and its caller with these exceptions: the ‘DEBUG’ and
+‘RETURN’ traps are not inherited unless the function has been given the
+‘trace’ attribute using the ‘declare’ builtin or the ‘-o functrace’
+option has been enabled with the ‘set’ builtin, (in which case all
+functions inherit the ‘DEBUG’ and ‘RETURN’ traps), and the ‘ERR’ trap is
+not inherited unless the ‘-o errtrace’ shell option has been enabled.
+*Note Bourne Shell Builtins::, for the description of the ‘trap’
+builtin.
+
+ The ‘FUNCNEST’ variable, if set to a numeric value greater than 0,
+defines a maximum function nesting level. Function invocations that
+exceed the limit cause the entire command to abort.
+
+ If the builtin command ‘return’ is executed in a function, the
+function completes and execution resumes with the next command after the
+function call. Any command associated with the ‘RETURN’ trap is
+executed before execution resumes. When a function completes, the
+values of the positional parameters and the special parameter ‘#’ are
+restored to the values they had prior to the function's execution. If
+‘return’ is supplied a numeric argument, that is the function's return
+status; otherwise the function's return status is the exit status of the
+last command executed before the ‘return’.
+
+ Variables local to the function are declared with the ‘local’ builtin
+(“local variables”). Ordinarily, variables and their values are shared
+between a function and its caller. These variables are visible only to
+the function and the commands it invokes. This is particularly
+important when a shell function calls other functions.
+
+ In the following description, the “current scope” is a currently-
+executing function. Previous scopes consist of that function's caller
+and so on, back to the "global" scope, where the shell is not executing
+any shell function. A local variable at the current local scope is a
+variable declared using the ‘local’ or ‘declare’ builtins in the
+function that is currently executing.
+
+ Local variables "shadow" variables with the same name declared at
+previous scopes. For instance, a local variable declared in a function
+hides variables with the same name declared at previous scopes,
+including global variables: references and assignments refer to the
+local variable, leaving the variables at previous scopes unmodified.
+When the function returns, the global variable is once again visible.
+
+ The shell uses “dynamic scoping” to control a variable's visibility
+within functions. With dynamic scoping, visible variables and their
+values are a result of the sequence of function calls that caused
+execution to reach the current function. The value of a variable that a
+function sees depends on its value within its caller, if any, whether
+that caller is the global scope or another shell function. This is also
+the value that a local variable declaration shadows, and the value that
+is restored when the function returns.
+
+ For example, if a variable ‘var’ is declared as local in function
+‘func1’, and ‘func1’ calls another function ‘func2’, references to ‘var’
+made from within ‘func2’ resolve to the local variable ‘var’ from
+‘func1’, shadowing any global variable named ‘var’.
+
+ The following script demonstrates this behavior. When executed, the
+script displays
+
+ In func2, var = func1 local
+
+ func1()
+ {
+ local var='func1 local'
+ func2
+ }
+
+ func2()
+ {
+ echo "In func2, var = $var"
+ }
+
+ var=global
+ func1
+
+ The ‘unset’ builtin also acts using the same dynamic scope: if a
+variable is local to the current scope, ‘unset’ unsets it; otherwise the
+unset will refer to the variable found in any calling scope as described
+above. If a variable at the current local scope is unset, it remains so
+(appearing as unset) until it is reset in that scope or until the
+function returns. Once the function returns, any instance of the
+variable at a previous scope becomes visible. If the unset acts on a
+variable at a previous scope, any instance of a variable with that name
+that had been shadowed becomes visible (see below how the
+‘localvar_unset’ shell option changes this behavior).
+
+ The ‘-f’ option to the ‘declare’ (‘typeset’) builtin command (*note
+Bash Builtins::) lists function names and definitions. The ‘-F’ option
+to ‘declare’ or ‘typeset’ lists the function names only (and optionally
+the source file and line number, if the ‘extdebug’ shell option is
+enabled). Functions may be exported so that child shell processes
+(those created when executing a separate shell invocation) automatically
+have them defined with the ‘-f’ option to the ‘export’ builtin (*note
+Bourne Shell Builtins::). The ‘-f’ option to the ‘unset’ builtin (*note
+Bourne Shell Builtins::) deletes a function definition.
+
+ Functions may be recursive. The ‘FUNCNEST’ variable may be used to
+limit the depth of the function call stack and restrict the number of
+function invocations. By default, Bash places no limit on the number of
+recursive calls.
+
+\1f
+File: bash.info, Node: Shell Parameters, Next: Shell Expansions, Prev: Shell Functions, Up: Basic Shell Features
+
+3.4 Shell Parameters
+====================
+
+* Menu:
+
+* Positional Parameters:: The shell's command-line arguments.
+* Special Parameters:: Parameters denoted by special characters.
+
+A “parameter” is an entity that stores values. It can be a ‘name’, a
+number, or one of the special characters listed below. A “variable” is
+a parameter denoted by a ‘name’. A variable has a ‘value’ and zero or
+more ‘attributes’. Attributes are assigned using the ‘declare’ builtin
+command (see the description of the ‘declare’ builtin in *note Bash
+Builtins::). The ‘export’ and ‘readonly’ builtins assign specific
+attributes.
+
+ A parameter is set if it has been assigned a value. The null string
+is a valid value. Once a variable is set, it may be unset only by using
+the ‘unset’ builtin command.
+
+ A variable is assigned to using a statement of the form
+ NAME=[VALUE]
+If VALUE is not given, the variable is assigned the null string. All
+VALUEs undergo tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote removal (*note
+Shell Parameter Expansion::). If the variable has its ‘integer’
+attribute set, then VALUE is evaluated as an arithmetic expression even
+if the ‘$((...))’ expansion is not used (*note Arithmetic Expansion::).
+Word splitting and filename expansion are not performed. Assignment
+statements may also appear as arguments to the ‘alias’, ‘declare’,
+‘typeset’, ‘export’, ‘readonly’, and ‘local’ builtin commands
+(“declaration commands”). When in POSIX mode (*note Bash POSIX Mode::),
+these builtins may appear in a command after one or more instances of
+the ‘command’ builtin and retain these assignment statement properties.
+For example,
+ command export var=value
+
+ In the context where an assignment statement is assigning a value to
+a shell variable or array index (*note Arrays::), the ‘+=’ operator
+appends to or adds to the variable's previous value. This includes
+arguments to declaration commands such as ‘declare’ that accept
+assignment statements. When ‘+=’ is applied to a variable for which the
+‘integer’ attribute has been set, the variable's current value and VALUE
+are each evaluated as arithmetic expressions, and the sum of the results
+is assigned as the variable's value. The current value is usually an
+integer constant, but may be an expression. When ‘+=’ is applied to an
+array variable using compound assignment (*note Arrays::), the
+variable's value is not unset (as it is when using ‘=’), and new values
+are appended to the array beginning at one greater than the array's
+maximum index (for indexed arrays), or added as additional key-value
+pairs in an associative array. When applied to a string-valued
+variable, VALUE is expanded and appended to the variable's value.
+
+ A variable can be assigned the ‘nameref’ attribute using the ‘-n’
+option to the ‘declare’ or ‘local’ builtin commands (*note Bash
+Builtins::) to create a “nameref”, or a reference to another variable.
+This allows variables to be manipulated indirectly. Whenever the
+nameref variable is referenced, assigned to, unset, or has its
+attributes modified (other than using or changing the nameref attribute
+itself), the operation is actually performed on the variable specified
+by the nameref variable's value. A nameref is commonly used within
+shell functions to refer to a variable whose name is passed as an
+argument to the function. For instance, if a variable name is passed to
+a shell function as its first argument, running
+ declare -n ref=$1
+inside the function creates a local nameref variable ‘ref’ whose value
+is the variable name passed as the first argument. References and
+assignments to ‘ref’, and changes to its attributes, are treated as
+references, assignments, and attribute modifications to the variable
+whose name was passed as ‘$1’.
+
+ If the control variable in a ‘for’ loop has the nameref attribute,
+the list of words can be a list of shell variables, and a name reference
+is established for each word in the list, in turn, when the loop is
+executed. Array variables cannot be given the nameref attribute.
+However, nameref variables can reference array variables and subscripted
+array variables. Namerefs can be unset using the ‘-n’ option to the
+‘unset’ builtin (*note Bourne Shell Builtins::). Otherwise, if ‘unset’
+is executed with the name of a nameref variable as an argument, the
+variable referenced by the nameref variable is unset.
+
+ When the shell starts, it reads its environment and creates a shell
+variable from each environment variable that has a valid name, as
+described below (*note Environment::).
+
+\1f
+File: bash.info, Node: Positional Parameters, Next: Special Parameters, Up: Shell Parameters
+
+3.4.1 Positional Parameters
+---------------------------
+
+A “positional parameter” is a parameter denoted by one or more digits,
+other than the single digit ‘0’. Positional parameters are assigned
+from the shell's arguments when it is invoked, and may be reassigned
+using the ‘set’ builtin command. Positional parameter ‘N’ may be
+referenced as ‘${N}’, or as ‘$N’ when ‘N’ consists of a single digit.
+Positional parameters may not be assigned to with assignment statements.
+The ‘set’ and ‘shift’ builtins are used to set and unset them (*note
+Shell Builtin Commands::). The positional parameters are temporarily
+replaced when a shell function is executed (*note Shell Functions::).
+
+ When a positional parameter consisting of more than a single digit is
+expanded, it must be enclosed in braces. Without braces, a digit
+following ‘$’ can only refer to one of the first nine positional
+parameters ($1\-$9) or the special parameter $0 (see below).
+
+\1f
+File: bash.info, Node: Special Parameters, Prev: Positional Parameters, Up: Shell Parameters
+
+3.4.2 Special Parameters
+------------------------
+
+The shell treats several parameters specially. These parameters may
+only be referenced; assignment to them is not allowed. Special
+parameters are denoted by one of the following characters.
+
+‘*’
+ ($*) Expands to the positional parameters, starting from one. When
+ the expansion is not within double quotes, each positional
+ parameter expands to a separate word. In contexts where word
+ expansions are performed, those words are subject to further word
+ splitting and filename expansion. When the expansion occurs within
+ double quotes, it expands to a single word with the value of each
+ parameter separated by the first character of the ‘IFS’ variable.
+ That is, ‘"$*"’ is equivalent to ‘"$1C$2C..."’, where C is the
+ first character of the value of the ‘IFS’ variable. If ‘IFS’ is
+ unset, the parameters are separated by spaces. If ‘IFS’ is null,
+ the parameters are joined without intervening separators.
+
+‘@’
+ ($@) Expands to the positional parameters, starting from one. In
+ contexts where word splitting is performed, this expands each
+ positional parameter to a separate word; if not within double
+ quotes, these words are subject to word splitting. In contexts
+ where word splitting is not performed, such as the value portion of
+ an assignment statement, this expands to a single word with each
+ positional parameter separated by a space. When the expansion
+ occurs within double quotes, and word splitting is performed, each
+ parameter expands to a separate word. That is, ‘"$@"’ is
+ equivalent to ‘"$1" "$2" ...’. If the double-quoted expansion
+ occurs within a word, the expansion of the first parameter is
+ joined with the expansion of the beginning part of the original
+ word, and the expansion of the last parameter is joined with the
+ expansion of the last part of the original word. When there are no
+ positional parameters, ‘"$@"’ and ‘$@’ expand to nothing (i.e.,
+ they are removed).
+
+‘#’
+ ($#) Expands to the number of positional parameters in decimal.
+
+‘?’
+ ($?) Expands to the exit status of the most recently executed
+ command.
+
+‘-’
+ ($-, a hyphen.) Expands to the current option flags as specified
+ upon invocation, by the ‘set’ builtin command, or those set by the
+ shell itself (such as the ‘-i’ option).
+
+‘$’
+ ($$) Expands to the process ID of the shell. In a subshell, it
+ expands to the process ID of the invoking shell, not the subshell.
+
+‘!’
+ ($!) Expands to the process ID of the job most recently placed
+ into the background, whether executed as an asynchronous command or
+ using the ‘bg’ builtin (*note Job Control Builtins::).
+
+‘0’
+ ($0) Expands to the name of the shell or shell script. This is set
+ at shell initialization. If Bash is invoked with a file of
+ commands (*note Shell Scripts::), ‘$0’ is set to the name of that
+ file. If Bash is started with the ‘-c’ option (*note Invoking
+ Bash::), then ‘$0’ is set to the first argument after the string to
+ be executed, if one is present. Otherwise, it is set to the
+ filename used to invoke Bash, as given by argument zero.
+
+\1f
+File: bash.info, Node: Shell Expansions, Next: Redirections, Prev: Shell Parameters, Up: Basic Shell Features
+
+3.5 Shell Expansions
+====================
+
+Expansion is performed on the command line after it has been split into
+‘token’s. Bash performs these expansions:
+
+ • brace expansion
+ • tilde expansion
+ • parameter and variable expansion
+ • command substitution
+ • arithmetic expansion
+ • word splitting
+ • filename expansion
+ • quote removal
+
+* Menu:
+
+* Brace Expansion:: Expansion of expressions within braces.
+* Tilde Expansion:: Expansion of the ~ character.
+* Shell Parameter Expansion:: How Bash expands variables to their values.
+* Command Substitution:: Using the output of a command as an argument.
+* Arithmetic Expansion:: How to use arithmetic in shell expansions.
+* Process Substitution:: A way to write and read to and from a
+ command.
+* Word Splitting:: How the results of expansion are split into separate
+ arguments.
+* Filename Expansion:: A shorthand for specifying filenames matching patterns.
+* Quote Removal:: How and when quote characters are removed from
+ words.
+
+ The order of expansions is: brace expansion; tilde expansion,
+parameter and variable expansion, arithmetic expansion, and command
+substitution (done in a left-to-right fashion); word splitting; filename
+expansion; and quote removal.
+
+ On systems that can support it, there is an additional expansion
+available: “process substitution”. This is performed at the same time
+as tilde, parameter, variable, and arithmetic expansion and command
+substitution.
+
+ “Quote removal” is always performed last. It removes quote
+characters present in the original word, not ones resulting from one of
+the other expansions, unless they have been quoted themselves. *Note
+Quote Removal:: for more details.
+
+ Only brace expansion, word splitting, and filename expansion can
+increase the number of words of the expansion; other expansions expand a
+single word to a single word. The only exceptions to this are the
+expansions of ‘"$@"’ and ‘$*’ (*note Special Parameters::), and
+‘"${NAME[@]}"’ and ‘${NAME[*]}’ (*note Arrays::).
+
+\1f
+File: bash.info, Node: Brace Expansion, Next: Tilde Expansion, Up: Shell Expansions
+
+3.5.1 Brace Expansion
+---------------------
+
+Brace expansion is a mechanism to generate arbitrary strings sharing a
+common prefix and suffix, either of which can be empty. This mechanism
+is similar to “filename expansion” (*note Filename Expansion::), but the
+filenames generated need not exist. Patterns to be brace expanded are
+formed from an optional PREAMBLE, followed by either a series of
+comma-separated strings or a sequence expression between a pair of
+braces, followed by an optional POSTSCRIPT. The preamble is prefixed to
+each string contained within the braces, and the postscript is then
+appended to each resulting string, expanding left to right.
+
+ Brace expansions may be nested. The results of each expanded string
+are not sorted; brace expansion preserves left to right order. For
+example,
+ bash$ echo a{d,c,b}e
+ ade ace abe
+
+ A sequence expression takes the form ‘X..Y[..INCR]’, where X and Y
+are either integers or letters, and INCR, an optional increment, is an
+integer. When integers are supplied, the expression expands to each
+number between X and Y, inclusive. If either X or Y begins with a zero,
+each generated term will contain the same number of digits, zero-padding
+where necessary. When letters are supplied, the expression expands to
+each character lexicographically between X and Y, inclusive, using the C
+locale. Note that both X and Y must be of the same type (integer or
+letter). When the increment is supplied, it is used as the difference
+between each term. The default increment is 1 or -1 as appropriate.
+
+ Brace expansion is performed before any other expansions, and any
+characters special to other expansions are preserved in the result. It
+is strictly textual. Bash does not apply any syntactic interpretation
+to the context of the expansion or the text between the braces.
+
+ A correctly-formed brace expansion must contain unquoted opening and
+closing braces, and at least one unquoted comma or a valid sequence
+expression. Any incorrectly formed brace expansion is left unchanged.
+
+ A ‘{’ or ‘,’ may be quoted with a backslash to prevent its being
+considered part of a brace expression. To avoid conflicts with
+parameter expansion, the string ‘${’ is not considered eligible for
+brace expansion, and inhibits brace expansion until the closing ‘}’.
+
+ This construct is typically used as shorthand when the common prefix
+of the strings to be generated is longer than in the above example:
+ mkdir /usr/local/src/bash/{old,new,dist,bugs}
+ or
+ chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
+
+ Brace expansion introduces a slight incompatibility with historical
+versions of ‘sh’. ‘sh’ does not treat opening or closing braces
+specially when they appear as part of a word, and preserves them in the
+output. Bash removes braces from words as a consequence of brace
+expansion. For example, a word entered to ‘sh’ as ‘file{1,2}’ appears
+identically in the output. Bash outputs that word as ‘file1 file2’
+after brace expansion. Start Bash with the ‘+B’ option or disable brace
+expansion with the ‘+B’ option to the ‘set’ command (*note Shell Builtin
+Commands::) for strict ‘sh’ compatibility.
+
+\1f
+File: bash.info, Node: Tilde Expansion, Next: Shell Parameter Expansion, Prev: Brace Expansion, Up: Shell Expansions
+
+3.5.2 Tilde Expansion
+---------------------
+
+If a word begins with an unquoted tilde character (‘~’), all of the
+characters up to the first unquoted slash (or all characters, if there
+is no unquoted slash) are considered a “tilde-prefix”. If none of the
+characters in the tilde-prefix are quoted, the characters in the
+tilde-prefix following the tilde are treated as a possible “login name”.
+If this login name is the null string, the tilde is replaced with the
+value of the ‘HOME’ shell variable. If ‘HOME’ is unset, the tilde
+expands to the home directory of the user executing the shell instead.
+Otherwise, the tilde-prefix is replaced with the home directory
+associated with the specified login name.
+
+ If the tilde-prefix is ‘~+’, the value of the shell variable ‘PWD’
+replaces the tilde-prefix. If the tilde-prefix is ‘~-’, the shell
+substitutes the value of the shell variable ‘OLDPWD’, if it is set.
+
+ If the characters following the tilde in the tilde-prefix consist of
+a number N, optionally prefixed by a ‘+’ or a ‘-’, the tilde-prefix is
+replaced with the corresponding element from the directory stack, as it
+would be displayed by the ‘dirs’ builtin invoked with the characters
+following tilde in the tilde-prefix as an argument (*note The Directory
+Stack::). If the tilde-prefix, sans the tilde, consists of a number
+without a leading ‘+’ or ‘-’, tilde expansion assumes ‘+’.
+
+ The results of tilde expansion are treated as if they were quoted, so
+the replacement is not subject to word splitting and filename expansion.
+
+ If the login name is invalid, or the tilde expansion fails, the
+tilde-prefix is left unchanged.
+
+ Bash checks each variable assignment for unquoted tilde-prefixes
+immediately following a ‘:’ or the first ‘=’, and performs tilde
+expansion in these cases. Consequently, one may use filenames with
+tildes in assignments to ‘PATH’, ‘MAILPATH’, and ‘CDPATH’, and the shell
+assigns the expanded value.
+
+ The following table shows how Bash treats unquoted tilde-prefixes:
+
+‘~’
+ The value of ‘$HOME’.
+‘~/foo’
+ ‘$HOME/foo’
+
+‘~fred/foo’
+ The directory or file ‘foo’ in the home directory of the user
+ ‘fred’.
+
+‘~+/foo’
+ ‘$PWD/foo’
+
+‘~-/foo’
+ ‘${OLDPWD-'~-'}/foo’
+
+‘~N’
+ The string that would be displayed by ‘dirs +N’.
+
+‘~+N’
+ The string that would be displayed by ‘dirs +N’.
+
+‘~-N’
+ The string that would be displayed by ‘dirs -N’.
+
+ Bash also performs tilde expansion on words satisfying the conditions
+of variable assignments (*note Shell Parameters::) when they appear as
+arguments to simple commands. Bash does not do this, except for the
+declaration commands listed above, when in POSIX mode.
+
+\1f
+File: bash.info, Node: Shell Parameter Expansion, Next: Command Substitution, Prev: Tilde Expansion, Up: Shell Expansions
+
+3.5.3 Shell Parameter Expansion
+-------------------------------
+
+The ‘$’ character introduces parameter expansion, command substitution,
+or arithmetic expansion. The parameter name or symbol to be expanded
+may be enclosed in braces, which are optional but serve to protect the
+variable to be expanded from characters immediately following it which
+could be interpreted as part of the name. For example, if the first
+positional parameter has the value ‘a’, then ‘${11}’ expands to the
+value of the eleventh positional parameter, while ‘$11’ expands to ‘a1’.
+
+ When braces are used, the matching ending brace is the first ‘}’ not
+escaped by a backslash or within a quoted string, and not within an
+embedded arithmetic expansion, command substitution, or parameter
+expansion.
+
+ The basic form of parameter expansion is ${PARAMETER}, which
+substitutes the value of PARAMETER. The PARAMETER is a shell parameter
+as described above (*note Shell Parameters::) or an array reference
+(*note Arrays::). The braces are required when PARAMETER is a
+positional parameter with more than one digit, or when PARAMETER is
+followed by a character that is not to be interpreted as part of its
+name.
+
+ If the first character of PARAMETER is an exclamation point (!), and
+PARAMETER is not a nameref, it introduces a level of indirection. Bash
+uses the value formed by expanding the rest of PARAMETER as the new
+PARAMETER; this new parameter is then expanded and that value is used in
+the rest of the expansion, rather than the expansion of the original
+PARAMETER. This is known as ‘indirect expansion’. The value is subject
+to tilde expansion, parameter expansion, command substitution, and
+arithmetic expansion. If PARAMETER is a nameref, this expands to the
+name of the variable referenced by PARAMETER instead of performing the
+complete indirect expansion, for compatibility. The exceptions to this
+are the expansions of ${!PREFIX*} and ${!NAME[@]} described below. The
+exclamation point must immediately follow the left brace in order to
+introduce indirection.
+
+ In each of the cases below, WORD is subject to tilde expansion,
+parameter expansion, command substitution, and arithmetic expansion.
+
+ When not performing substring expansion, using the forms described
+below (e.g., ‘:-’), Bash tests for a parameter that is unset or null.
+Omitting the colon results in a test only for a parameter that is unset.
+Put another way, if the colon is included, the operator tests for both
+PARAMETER's existence and that its value is not null; if the colon is
+omitted, the operator tests only for existence.
+
+‘${PARAMETER:−WORD}’
+ If PARAMETER is unset or null, the expansion of WORD is
+ substituted. Otherwise, the value of PARAMETER is substituted.
+
+ $ v=123
+ $ echo ${v-unset}
+ 123
+ $ echo ${v:-unset-or-null}
+ 123
+ $ unset v
+ $ echo ${v-unset}
+ unset
+ $ v=
+ $ echo ${v-unset}
+
+ $ echo ${v:-unset-or-null}
+ unset-or-null
+
+‘${PARAMETER:=WORD}’
+ If PARAMETER is unset or null, the expansion of WORD is assigned to
+ PARAMETER, and the result of the expansion is the final value of
+ PARAMETER. Positional parameters and special parameters may not be
+ assigned in this way.
+
+ $ unset var
+ $ : ${var=DEFAULT}
+ $ echo $var
+ DEFAULT
+ $ var=
+ $ : ${var=DEFAULT}
+ $ echo $var
+
+ $ var=
+ $ : ${var:=DEFAULT}
+ $ echo $var
+ DEFAULT
+ $ unset var
+ $ : ${var:=DEFAULT}
+ $ echo $var
+ DEFAULT
+
+‘${PARAMETER:?WORD}’
+ If PARAMETER is null or unset, the shell writes the expansion of
+ WORD (or a message to that effect if WORD is not present) to the
+ standard error and, if it is not interactive, exits with a non-zero
+ status. An interactive shell does not exit, but does not execute
+ the command associated with the expansion. Otherwise, the value of
+ PARAMETER is substituted.
+
+ $ var=
+ $ : ${var:?var is unset or null}
+ bash: var: var is unset or null
+ $ echo ${var?var is unset}
+
+ $ unset var
+ $ : ${var?var is unset}
+ bash: var: var is unset
+ $ : ${var:?var is unset or null}
+ bash: var: var is unset or null
+ $ var=123
+ $ echo ${var:?var is unset or null}
+ 123
+
+‘${PARAMETER:+WORD}’
+ If PARAMETER is null or unset, nothing is substituted, otherwise
+ the expansion of WORD is substituted. The value of PARAMETER is
+ not used.
+
+ $ var=123
+ $ echo ${var:+var is set and not null}
+ var is set and not null
+ $ echo ${var+var is set}
+ var is set
+ $ var=
+ $ echo ${var:+var is set and not null}
+
+ $ echo ${var+var is set}
+ var is set
+ $ unset var
+ $ echo ${var+var is set}
+
+ $ echo ${var:+var is set and not null}
+
+ $
+
+‘${PARAMETER:OFFSET}’
+‘${PARAMETER:OFFSET:LENGTH}’
+ This is referred to as Substring Expansion. It expands to up to
+ LENGTH characters of the value of PARAMETER starting at the
+ character specified by OFFSET. If PARAMETER is ‘@’ or ‘*’, an
+ indexed array subscripted by ‘@’ or ‘*’, or an associative array
+ name, the results differ as described below. If :LENGTH is omitted
+ (the first form above), this expands to the substring of the value
+ of PARAMETER starting at the character specified by OFFSET and
+ extending to the end of the value. If OFFSET is omitted, it is
+ treated as 0. If LENGTH is omitted, but the colon after OFFSET is
+ present, it is treated as 0. LENGTH and OFFSET are arithmetic
+ expressions (*note Shell Arithmetic::).
+
+ If OFFSET evaluates to a number less than zero, the value is used
+ as an offset in characters from the end of the value of PARAMETER.
+ If LENGTH evaluates to a number less than zero, it is interpreted
+ as an offset in characters from the end of the value of PARAMETER
+ rather than a number of characters, and the expansion is the
+ characters between OFFSET and that result.
+
+ Note that a negative offset must be separated from the colon by at
+ least one space to avoid being confused with the ‘:-’ expansion.
+
+ Here are some examples illustrating substring expansion on
+ parameters and subscripted arrays:
+
+ $ string=01234567890abcdefgh
+ $ echo ${string:7}
+ 7890abcdefgh
+ $ echo ${string:7:0}
+
+ $ echo ${string:7:2}
+ 78
+ $ echo ${string:7:-2}
+ 7890abcdef
+ $ echo ${string: -7}
+ bcdefgh
+ $ echo ${string: -7:0}
+
+ $ echo ${string: -7:2}
+ bc
+ $ echo ${string: -7:-2}
+ bcdef
+ $ set -- 01234567890abcdefgh
+ $ echo ${1:7}
+ 7890abcdefgh
+ $ echo ${1:7:0}
+
+ $ echo ${1:7:2}
+ 78
+ $ echo ${1:7:-2}
+ 7890abcdef
+ $ echo ${1: -7}
+ bcdefgh
+ $ echo ${1: -7:0}
+
+ $ echo ${1: -7:2}
+ bc
+ $ echo ${1: -7:-2}
+ bcdef
+ $ array[0]=01234567890abcdefgh
+ $ echo ${array[0]:7}
+ 7890abcdefgh
+ $ echo ${array[0]:7:0}
+
+ $ echo ${array[0]:7:2}
+ 78
+ $ echo ${array[0]:7:-2}
+ 7890abcdef
+ $ echo ${array[0]: -7}
+ bcdefgh
+ $ echo ${array[0]: -7:0}
+
+ $ echo ${array[0]: -7:2}
+ bc
+ $ echo ${array[0]: -7:-2}
+ bcdef
+
+ If PARAMETER is ‘@’ or ‘*’, the result is LENGTH positional
+ parameters beginning at OFFSET. A negative OFFSET is taken
+ relative to one greater than the greatest positional parameter, so
+ an offset of -1 evaluates to the last positional parameter (or 0 if
+ there are no positional parameters). It is an expansion error if
+ LENGTH evaluates to a number less than zero.
+
+ The following examples illustrate substring expansion using
+ positional parameters:
+
+ $ set -- 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+ $ echo ${@:7}
+ 7 8 9 0 a b c d e f g h
+ $ echo ${@:7:0}
+
+ $ echo ${@:7:2}
+ 7 8
+ $ echo ${@:7:-2}
+ bash: -2: substring expression < 0
+ $ echo ${@: -7:2}
+ b c
+ $ echo ${@:0}
+ ./bash 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+ $ echo ${@:0:2}
+ ./bash 1
+ $ echo ${@: -7:0}
+
+
+ If PARAMETER is an indexed array name subscripted by ‘@’ or ‘*’,
+ the result is the LENGTH members of the array beginning with
+ ‘${PARAMETER[OFFSET]}’. A negative OFFSET is taken relative to one
+ greater than the maximum index of the specified array. It is an
+ expansion error if LENGTH evaluates to a number less than zero.
+
+ These examples show how you can use substring expansion with
+ indexed arrays:
+
+ $ array=(0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h)
+ $ echo ${array[@]:7}
+ 7 8 9 0 a b c d e f g h
+ $ echo ${array[@]:7:2}
+ 7 8
+ $ echo ${array[@]: -7:2}
+ b c
+ $ echo ${array[@]: -7:-2}
+ bash: -2: substring expression < 0
+ $ echo ${array[@]:0}
+ 0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+ $ echo ${array[@]:0:2}
+ 0 1
+ $ echo ${array[@]: -7:0}
+
+
+ Substring expansion applied to an associative array produces
+ undefined results.
+
+ Substring indexing is zero-based unless the positional parameters
+ are used, in which case the indexing starts at 1 by default. If
+ OFFSET is 0, and the positional parameters are used, ‘$0’ is
+ prefixed to the list.
+
+‘${!PREFIX*}’
+‘${!PREFIX@}’
+ Expands to the names of variables whose names begin with PREFIX,
+ separated by the first character of the ‘IFS’ special variable.
+ When ‘@’ is used and the expansion appears within double quotes,
+ each variable name expands to a separate word.
+
+‘${!NAME[@]}’
+‘${!NAME[*]}’
+ If NAME is an array variable, expands to the list of array indices
+ (keys) assigned in NAME. If NAME is not an array, expands to 0 if
+ NAME is set and null otherwise. When ‘@’ is used and the expansion
+ appears within double quotes, each key expands to a separate word.
+
+‘${#PARAMETER}’
+ Substitutes the length in characters of the value of PARAMETER. If
+ PARAMETER is ‘*’ or ‘@’, the value substituted is the number of
+ positional parameters. If PARAMETER is an array name subscripted
+ by ‘*’ or ‘@’, the value substituted is the number of elements in
+ the array. If PARAMETER is an indexed array name subscripted by a
+ negative number, that number is interpreted as relative to one
+ greater than the maximum index of PARAMETER, so negative indices
+ count back from the end of the array, and an index of -1 references
+ the last element.
+
+‘${PARAMETER#WORD}’
+‘${PARAMETER##WORD}’
+ The WORD is expanded to produce a pattern and matched against the
+ expanded value of PARAMETER according to the rules described below
+ (*note Pattern Matching::). If the pattern matches the beginning
+ of the expanded value of PARAMETER, then the result of the
+ expansion is the expanded value of PARAMETER with the shortest
+ matching pattern (the ‘#’ case) or the longest matching pattern
+ (the ‘##’ case) deleted. If PARAMETER is ‘@’ or ‘*’, the pattern
+ removal operation is applied to each positional parameter in turn,
+ and the expansion is the resultant list. If PARAMETER is an array
+ variable subscripted with ‘@’ or ‘*’, the pattern removal operation
+ is applied to each member of the array in turn, and the expansion
+ is the resultant list.
+
+‘${PARAMETER%WORD}’
+‘${PARAMETER%%WORD}’
+ The WORD is expanded to produce a pattern and matched against the
+ expanded value of PARAMETER according to the rules described below
+ (*note Pattern Matching::). If the pattern matches a trailing
+ portion of the expanded value of PARAMETER, then the result of the
+ expansion is the value of PARAMETER with the shortest matching
+ pattern (the ‘%’ case) or the longest matching pattern (the ‘%%’
+ case) deleted. If PARAMETER is ‘@’ or ‘*’, the pattern removal
+ operation is applied to each positional parameter in turn, and the
+ expansion is the resultant list. If PARAMETER is an array variable
+ subscripted with ‘@’ or ‘*’, the pattern removal operation is
+ applied to each member of the array in turn, and the expansion is
+ the resultant list.
+
+‘${PARAMETER/PATTERN/STRING}’
+‘${PARAMETER//PATTERN/STRING}’
+‘${PARAMETER/#PATTERN/STRING}’
+‘${PARAMETER/%PATTERN/STRING}’
+ The PATTERN is expanded to produce a pattern and matched against
+ the expanded value of PARAMETER as described below (*note Pattern
+ Matching::). The longest match of PATTERN in the expanded value is
+ replaced with STRING. STRING undergoes tilde expansion, parameter
+ and variable expansion, arithmetic expansion, command and process
+ substitution, and quote removal.
+
+ In the first form above, only the first match is replaced. If
+ there are two slashes separating PARAMETER and PATTERN (the second
+ form above), all matches of PATTERN are replaced with STRING. If
+ PATTERN is preceded by ‘#’ (the third form above), it must match at
+ the beginning of the expanded value of PARAMETER. If PATTERN is
+ preceded by ‘%’ (the fourth form above), it must match at the end
+ of the expanded value of PARAMETER.
+
+ If the expansion of STRING is null, matches of PATTERN are deleted
+ and the ‘/’ following PATTERN may be omitted.
+
+ If the ‘patsub_replacement’ shell option is enabled using ‘shopt’
+ (*note The Shopt Builtin::), any unquoted instances of ‘&’ in
+ STRING are replaced with the matching portion of PATTERN. This is
+ intended to duplicate a common ‘sed’ idiom.
+
+ Quoting any part of STRING inhibits replacement in the expansion of
+ the quoted portion, including replacement strings stored in shell
+ variables. Backslash escapes ‘&’ in STRING; the backslash is
+ removed in order to permit a literal ‘&’ in the replacement string.
+ Users should take care if STRING is double-quoted to avoid unwanted
+ interactions between the backslash and double-quoting, since
+ backslash has special meaning within double quotes. Pattern
+ substitution performs the check for unquoted ‘&’ after expanding
+ STRING, so users should ensure to properly quote any occurrences of
+ ‘&’ they want to be taken literally in the replacement and ensure
+ any instances of ‘&’ they want to be replaced are unquoted.
+
+ For instance,
+
+ var=abcdef
+ rep='& '
+ echo ${var/abc/& }
+ echo "${var/abc/& }"
+ echo ${var/abc/$rep}
+ echo "${var/abc/$rep}"
+
+ will display four lines of "abc def", while
+
+ var=abcdef
+ rep='& '
+ echo ${var/abc/\& }
+ echo "${var/abc/\& }"
+ echo ${var/abc/"& "}
+ echo ${var/abc/"$rep"}
+
+ will display four lines of "& def". Like the pattern removal
+ operators, double quotes surrounding the replacement string quote
+ the expanded characters, while double quotes enclosing the entire
+ parameter substitution do not, since the expansion is performed in
+ a context that doesn't take any enclosing double quotes into
+ account.
+
+ Since backslash can escape ‘&’, it can also escape a backslash in
+ the replacement string. This means that ‘\\’ will insert a literal
+ backslash into the replacement, so these two ‘echo’ commands
+
+ var=abcdef
+ rep='\\&xyz'
+ echo ${var/abc/\\&xyz}
+ echo ${var/abc/$rep}
+
+ will both output ‘\abcxyzdef’.
+
+ It should rarely be necessary to enclose only STRING in double
+ quotes.
+
+ If the ‘nocasematch’ shell option (see the description of ‘shopt’
+ in *note The Shopt Builtin::) is enabled, the match is performed
+ without regard to the case of alphabetic characters.
+
+ If PARAMETER is ‘@’ or ‘*’, the substitution operation is applied
+ to each positional parameter in turn, and the expansion is the
+ resultant list. If PARAMETER is an array variable subscripted with
+ ‘@’ or ‘*’, the substitution operation is applied to each member of
+ the array in turn, and the expansion is the resultant list.
+
+‘${PARAMETER^PATTERN}’
+‘${PARAMETER^^PATTERN}’
+‘${PARAMETER,PATTERN}’
+‘${PARAMETER,,PATTERN}’
+ This expansion modifies the case of alphabetic characters in
+ PARAMETER. First, the PATTERN is expanded to produce a pattern as
+ described below in *note Pattern Matching::.
+
+ ‘Bash’ then examines characters in the expanded value of PARAMETER
+ against PATTERN as described below. If a character matches the
+ pattern, its case is converted. The pattern should not attempt to
+ match more than one character.
+
+ Using ‘^’ converts lowercase letters matching PATTERN to uppercase;
+ ‘,’ converts matching uppercase letters to lowercase. The ‘^’ and
+ ‘,’ variants examine the first character in the expanded value and
+ convert its case if it matches PATTERN; the ‘^^’ and ‘,,’ variants
+ examine all characters in the expanded value and convert each one
+ that matches PATTERN. If PATTERN is omitted, it is treated like a
+ ‘?’, which matches every character.
+
+ If PARAMETER is ‘@’ or ‘*’, the case modification operation is
+ applied to each positional parameter in turn, and the expansion is
+ the resultant list. If PARAMETER is an array variable subscripted
+ with ‘@’ or ‘*’, the case modification operation is applied to each
+ member of the array in turn, and the expansion is the resultant
+ list.
+
+‘${PARAMETER@OPERATOR}’
+ The expansion is either a transformation of the value of PARAMETER
+ or information about PARAMETER itself, depending on the value of
+ OPERATOR. Each OPERATOR is a single letter:
+
+ ‘U’
+ The expansion is a string that is the value of PARAMETER with
+ lowercase alphabetic characters converted to uppercase.
+ ‘u’
+ The expansion is a string that is the value of PARAMETER with
+ the first character converted to uppercase, if it is
+ alphabetic.
+ ‘L’
+ The expansion is a string that is the value of PARAMETER with
+ uppercase alphabetic characters converted to lowercase.
+ ‘Q’
+ The expansion is a string that is the value of PARAMETER
+ quoted in a format that can be reused as input.
+ ‘E’
+ The expansion is a string that is the value of PARAMETER with
+ backslash escape sequences expanded as with the ‘$'...'’
+ quoting mechanism.
+ ‘P’
+ The expansion is a string that is the result of expanding the
+ value of PARAMETER as if it were a prompt string (*note
+ Controlling the Prompt::).
+ ‘A’
+ The expansion is a string in the form of an assignment
+ statement or ‘declare’ command that, if evaluated, recreates
+ PARAMETER with its attributes and value.
+ ‘K’
+ Produces a possibly-quoted version of the value of PARAMETER,
+ except that it prints the values of indexed and associative
+ arrays as a sequence of quoted key-value pairs (*note
+ Arrays::). The keys and values are quoted in a format that
+ can be reused as input.
+ ‘a’
+ The expansion is a string consisting of flag values
+ representing PARAMETER's attributes.
+ ‘k’
+ Like the ‘K’ transformation, but expands the keys and values
+ of indexed and associative arrays to separate words after word
+ splitting.
+
+ If PARAMETER is ‘@’ or ‘*’, the operation is applied to each
+ positional parameter in turn, and the expansion is the resultant
+ list. If PARAMETER is an array variable subscripted with ‘@’ or
+ ‘*’, the operation is applied to each member of the array in turn,
+ and the expansion is the resultant list.
+
+ The result of the expansion is subject to word splitting and
+ filename expansion as described below.
+
+\1f
+File: bash.info, Node: Command Substitution, Next: Arithmetic Expansion, Prev: Shell Parameter Expansion, Up: Shell Expansions
+
+3.5.4 Command Substitution
+--------------------------
+
+Command substitution allows the output of a command to replace the
+command itself. The standard form of command substitution occurs when a
+command is enclosed as follows:
+ $(COMMAND)
+or (deprecated)
+ `COMMAND`.
+
+Bash performs command substitution by executing COMMAND in a subshell
+environment and replacing the command substitution with the standard
+output of the command, with any trailing newlines deleted. Embedded
+newlines are not deleted, but they may be removed during word splitting.
+The command substitution ‘$(cat FILE)’ can be replaced by the equivalent
+but faster ‘$(< FILE)’.
+
+ With the old-style backquote form of substitution, backslash retains
+its literal meaning except when followed by ‘$’, ‘`’, or ‘\’. The first
+backquote not preceded by a backslash terminates the command
+substitution. When using the ‘$(COMMAND)’ form, all characters between
+the parentheses make up the command; none are treated specially.
+
+ There is an alternate form of command substitution:
+
+ ${C COMMAND; }
+
+which executes COMMAND in the current execution environment and captures
+its output, again with trailing newlines removed.
+
+ The character C following the open brace must be a space, tab,
+newline, or ‘|’, and the close brace must be in a position where a
+reserved word may appear (i.e., preceded by a command terminator such as
+semicolon). Bash allows the close brace to be joined to the remaining
+characters in the word without being followed by a shell metacharacter
+as a reserved word would usually require.
+
+ Any side effects of COMMAND take effect immediately in the current
+execution environment and persist in the current environment after the
+command completes (e.g., the ‘exit’ builtin exits the shell).
+
+ This type of command substitution superficially resembles executing
+an unnamed shell function: local variables are created as when a shell
+function is executing, and the ‘return’ builtin forces COMMAND to
+complete; however, the rest of the execution environment, including the
+positional parameters, is shared with the caller.
+
+ If the first character following the open brace is a ‘|’, the
+construct expands to the value of the ‘REPLY’ shell variable after
+COMMAND executes, without removing any trailing newlines, and the
+standard output of COMMAND remains the same as in the calling shell.
+Bash creates ‘REPLY’ as an initially-unset local variable when COMMAND
+executes, and restores ‘REPLY’ to the value it had before the command
+substitution after COMMAND completes, as with any local variable.
+
+ For example, this construct expands to ‘12345’, and leaves the shell
+variable ‘X’ unchanged in the current execution environment:
+
+
+ ${ local X=12345 ; echo $X; }
+
+(not declaring ‘X’ as local would modify its value in the current
+environment, as with normal shell function execution), while this
+construct does not require any output to expand to ‘12345’:
+
+ ${| REPLY=12345; }
+
+and restores ‘REPLY’ to the value it had before the command
+substitution.
+
+ Command substitutions may be nested. To nest when using the
+backquoted form, escape the inner backquotes with backslashes.
+
+ If the substitution appears within double quotes, Bash does not
+perform word splitting and filename expansion on the results.
+
+\1f
+File: bash.info, Node: Arithmetic Expansion, Next: Process Substitution, Prev: Command Substitution, Up: Shell Expansions
+
+3.5.5 Arithmetic Expansion
+--------------------------
+
+Arithmetic expansion evaluates an arithmetic expression and substitutes
+the result. The format for arithmetic expansion is:
+
+ $(( EXPRESSION ))
+
+ The EXPRESSION undergoes the same expansions as if it were within
+double quotes, but unescaped double quote characters in EXPRESSION are
+not treated specially and are removed. All tokens in the expression
+undergo parameter and variable expansion, command substitution, and
+quote removal. The result is treated as the arithmetic expression to be
+evaluated. Since the way Bash handles double quotes can potentially
+result in empty strings, arithmetic expansion treats those as
+expressions that evaluate to 0. Arithmetic expansions may be nested.
+
+ The evaluation is performed according to the rules listed below
+(*note Shell Arithmetic::). If the expression is invalid, Bash prints a
+message indicating failure to the standard error, does not perform the
+substitution, and does not execute the command associated with the
+expansion.
+
+\1f
+File: bash.info, Node: Process Substitution, Next: Word Splitting, Prev: Arithmetic Expansion, Up: Shell Expansions
+
+3.5.6 Process Substitution
+--------------------------
+
+Process substitution allows a process's input or output to be referred
+to using a filename. It takes the form of
+ <(LIST)
+or
+ >(LIST)
+The process LIST is run asynchronously, and its input or output appears
+as a filename. This filename is passed as an argument to the current
+command as the result of the expansion.
+
+ If the ‘>(LIST)’ form is used, writing to the file provides input for
+LIST. If the ‘<(LIST)’ form is used, reading the file obtains the
+output of LIST. Note that no space may appear between the ‘<’ or ‘>’
+and the left parenthesis, otherwise the construct would be interpreted
+as a redirection.
+
+ Process substitution is supported on systems that support named pipes
+(FIFOs) or the ‘/dev/fd’ method of naming open files.
+
+ When available, process substitution is performed simultaneously with
+parameter and variable expansion, command substitution, and arithmetic
+expansion.
+
+\1f
+File: bash.info, Node: Word Splitting, Next: Filename Expansion, Prev: Process Substitution, Up: Shell Expansions
+
+3.5.7 Word Splitting
+--------------------
+
+The shell scans the results of parameter expansion, command
+substitution, and arithmetic expansion that did not occur within double
+quotes for word splitting. Words that were not expanded are not split.
+
+ The shell treats each character of ‘$IFS’ as a delimiter, and splits
+the results of the other expansions into fields using these characters
+as field terminators.
+
+ An “IFS whitespace” character is whitespace as defined above (*note
+Definitions::) that appears in the value of ‘IFS’. Space, tab, and
+newline are always considered IFS whitespace, even if they don't appear
+in the locale's ‘space’ category.
+
+ If ‘IFS’ is unset, word splitting behaves as if its value were
+‘<space><tab><newline>’, and treats these characters as IFS whitespace.
+If the value of ‘IFS’ is null, no word splitting occurs, but implicit
+null arguments (see below) are still removed.
+
+ Word splitting begins by removing sequences of IFS whitespace
+characters from the beginning and end of the results of the previous
+expansions, then splits the remaining words.
+
+ If the value of ‘IFS’ consists solely of IFS whitespace, any sequence
+of IFS whitespace characters delimits a field, so a field consists of
+characters that are not unquoted IFS whitespace, and null fields result
+only from quoting.
+
+ If ‘IFS’ contains a non-whitespace character, then any character in
+the value of ‘IFS’ that is not IFS whitespace, along with any adjacent
+IFS whitespace characters, delimits a field. This means that adjacent
+non-IFS-whitespace delimiters produce a null field. A sequence of IFS
+whitespace characters also delimits a field.
+
+ Explicit null arguments (‘""’ or ‘''’) are retained and passed to
+commands as empty strings. Unquoted implicit null arguments, resulting
+from the expansion of parameters that have no values, are removed.
+Expanding a parameter with no value within double quotes produces a null
+field, which is retained and passed to a command as an empty string.
+
+ When a quoted null argument appears as part of a word whose expansion
+is non-null, word splitting removes the null argument portion, leaving
+the non-null expansion. That is, the word ‘-d''’ becomes ‘-d’ after
+word splitting and null argument removal.
+
+\1f
+File: bash.info, Node: Filename Expansion, Next: Quote Removal, Prev: Word Splitting, Up: Shell Expansions
+
+3.5.8 Filename Expansion
+------------------------
+
+* Menu:
+
+* Pattern Matching:: How the shell matches patterns.
+
+After word splitting, unless the ‘-f’ option has been set (*note The Set
+Builtin::), Bash scans each word for the characters ‘*’, ‘?’, and ‘[’.
+If one of these characters appears, and is not quoted, then the word is
+regarded as a PATTERN, and replaced with a sorted list of filenames
+matching the pattern (*note Pattern Matching::), subject to the value of
+the ‘GLOBSORT’ shell variable (*note Bash Variables::).
+
+ If no matching filenames are found, and the shell option ‘nullglob’
+is disabled, the word is left unchanged. If the ‘nullglob’ option is
+set, and no matches are found, the word is removed. If the ‘failglob’
+shell option is set, and no matches are found, Bash prints an error
+message and does not execute the command. If the shell option
+‘nocaseglob’ is enabled, the match is performed without regard to the
+case of alphabetic characters.
+
+ When a pattern is used for filename expansion, the character ‘.’ at
+the start of a filename or immediately following a slash must be matched
+explicitly, unless the shell option ‘dotglob’ is set. In order to match
+the filenames ‘.’ and ‘..’, the pattern must begin with ‘.’ (for
+example, ‘.?’), even if ‘dotglob’ is set. If the ‘globskipdots’ shell
+option is enabled, the filenames ‘.’ and ‘..’ never match, even if the
+pattern begins with a ‘.’. When not matching filenames, the ‘.’
+character is not treated specially.
+
+ When matching a filename, the slash character must always be matched
+explicitly by a slash in the pattern, but in other matching contexts it
+can be matched by a special pattern character as described below (*note
+Pattern Matching::).
+
+ See the description of ‘shopt’ in *note The Shopt Builtin::, for a
+description of the ‘nocaseglob’, ‘nullglob’, ‘globskipdots’, ‘failglob’,
+and ‘dotglob’ options.
+
+ The ‘GLOBIGNORE’ shell variable may be used to restrict the set of
+file names matching a pattern. If ‘GLOBIGNORE’ is set, each matching
+file name that also matches one of the patterns in ‘GLOBIGNORE’ is
+removed from the list of matches. If the ‘nocaseglob’ option is set,
+the matching against the patterns in ‘GLOBIGNORE’ is performed without
+regard to case. The filenames ‘.’ and ‘..’ are always ignored when
+‘GLOBIGNORE’ is set and not null. However, setting ‘GLOBIGNORE’ to a
+non-null value has the effect of enabling the ‘dotglob’ shell option, so
+all other filenames beginning with a ‘.’ match. To get the old behavior
+of ignoring filenames beginning with a ‘.’, make ‘.*’ one of the
+patterns in ‘GLOBIGNORE’. The ‘dotglob’ option is disabled when
+‘GLOBIGNORE’ is unset. The ‘GLOBIGNORE’ pattern matching honors the
+setting of the ‘extglob’ shell option.
+
+ The value of the ‘GLOBSORT’ shell variable controls how the results
+of pathname expansion are sorted, as described below (*note Bash
+Variables::).
+
+\1f
+File: bash.info, Node: Pattern Matching, Up: Filename Expansion
+
+3.5.8.1 Pattern Matching
+........................
+
+Any character that appears in a pattern, other than the special pattern
+characters described below, matches itself. The NUL character may not
+occur in a pattern. A backslash escapes the following character; the
+escaping backslash is discarded when matching. The special pattern
+characters must be quoted if they are to be matched literally.
+
+ The special pattern characters have the following meanings:
+‘*’
+ Matches any string, including the null string. When the ‘globstar’
+ shell option is enabled, and ‘*’ is used in a filename expansion
+ context, two adjacent ‘*’s used as a single pattern match all files
+ and zero or more directories and subdirectories. If followed by a
+ ‘/’, two adjacent ‘*’s match only directories and subdirectories.
+‘?’
+ Matches any single character.
+‘[...]’
+ Matches any one of the characters enclosed between the brackets.
+ This is known as a “bracket expression” and matches a single
+ character. A pair of characters separated by a hyphen denotes a
+ “range expression”; any character that falls between those two
+ characters, inclusive, using the current locale's collating
+ sequence and character set, matches. If the first character
+ following the ‘[’ is a ‘!’ or a ‘^’ then any character not within
+ the range matches. To match a ‘−’, include it as the first or last
+ character in the set. To match a ‘]’, include it as the first
+ character in the set.
+
+ The sorting order of characters in range expressions, and the
+ characters included in the range, are determined by the current
+ locale and the values of the ‘LC_COLLATE’ and ‘LC_ALL’ shell
+ variables, if set.
+
+ For example, in the default C locale, ‘[a-dx-z]’ is equivalent to
+ ‘[abcdxyz]’. Many locales sort characters in dictionary order, and
+ in these locales ‘[a-dx-z]’ is typically not equivalent to
+ ‘[abcdxyz]’; it might be equivalent to ‘[aBbCcDdxYyZz]’, for
+ example. To obtain the traditional interpretation of ranges in
+ bracket expressions, you can force the use of the C locale by
+ setting the ‘LC_COLLATE’ or ‘LC_ALL’ environment variable to the
+ value ‘C’, or enable the ‘globasciiranges’ shell option.
+
+ Within a bracket expression, “character classes” can be specified
+ using the syntax ‘[:’CLASS‘:]’, where CLASS is one of the following
+ classes defined in the POSIX standard:
+ alnum alpha ascii blank cntrl digit graph lower
+ print punct space upper word xdigit
+ A character class matches any character belonging to that class.
+ The ‘word’ character class matches letters, digits, and the
+ character ‘_’.
+
+ For instance, the following pattern will match any character
+ belonging to the ‘space’ character class in the current locale,
+ then any upper case letter or ‘!’, a dot, and finally any lower
+ case letter or a hyphen.
+
+ [[:space:]][[:upper:]!].[-[:lower:]]
+
+ Within a bracket expression, an “equivalence class” can be
+ specified using the syntax ‘[=’C‘=]’, which matches all characters
+ with the same collation weight (as defined by the current locale)
+ as the character C.
+
+ Within a bracket expression, the syntax ‘[.’SYMBOL‘.]’ matches the
+ collating symbol SYMBOL.
+
+ If the ‘extglob’ shell option is enabled using the ‘shopt’ builtin,
+the shell recognizes several extended pattern matching operators. In
+the following description, a PATTERN-LIST is a list of one or more
+patterns separated by a ‘|’. When matching filenames, the ‘dotglob’
+shell option determines the set of filenames that are tested, as
+described above. Composite patterns may be formed using one or more of
+the following sub-patterns:
+
+‘?(PATTERN-LIST)’
+ Matches zero or one occurrence of the given patterns.
+
+‘*(PATTERN-LIST)’
+ Matches zero or more occurrences of the given patterns.
+
+‘+(PATTERN-LIST)’
+ Matches one or more occurrences of the given patterns.
+
+‘@(PATTERN-LIST)’
+ Matches one of the given patterns.
+
+‘!(PATTERN-LIST)’
+ Matches anything except one of the given patterns.
+
+ The ‘extglob’ option changes the behavior of the parser, since the
+parentheses are normally treated as operators with syntactic meaning.
+To ensure that extended matching patterns are parsed correctly, make
+sure that ‘extglob’ is enabled before parsing constructs containing the
+patterns, including shell functions and command substitutions.
+
+ When matching filenames, the ‘dotglob’ shell option determines the
+set of filenames that are tested: when ‘dotglob’ is enabled, the set of
+filenames includes all files beginning with ‘.’, but the filenames ‘.’
+and ‘..’ must be matched by a pattern or sub-pattern that begins with a
+dot; when it is disabled, the set does not include any filenames
+beginning with ‘.’ unless the pattern or sub-pattern begins with a ‘.’.
+If the ‘globskipdots’ shell option is enabled, the filenames ‘.’ and
+‘..’ never appear in the set. As above, ‘.’ only has a special meaning
+when matching filenames.
+
+ Complicated extended pattern matching against long strings is slow,
+especially when the patterns contain alternations and the strings
+contain multiple matches. Using separate matches against shorter
+strings, or using arrays of strings instead of a single long string, may
+be faster.
+
+\1f
+File: bash.info, Node: Quote Removal, Prev: Filename Expansion, Up: Shell Expansions
+
+3.5.9 Quote Removal
+-------------------
+
+After the preceding expansions, all unquoted occurrences of the
+characters ‘\’, ‘'’, and ‘"’ that did not result from one of the above
+expansions are removed.
+
+\1f
+File: bash.info, Node: Redirections, Next: Executing Commands, Prev: Shell Expansions, Up: Basic Shell Features
+
+3.6 Redirections
+================
+
+Before a command is executed, its input and output may be “redirected”
+using a special notation interpreted by the shell. “Redirection” allows
+commands' file handles to be duplicated, opened, closed, made to refer
+to different files, and can change the files the command reads from and
+writes to. When used with the ‘exec’ builtin, redirections modify file
+handles in the current shell execution environment. The following
+redirection operators may precede or appear anywhere within a simple
+command or may follow a command. Redirections are processed in the
+order they appear, from left to right.
+
+ Each redirection that may be preceded by a file descriptor number may
+instead be preceded by a word of the form {VARNAME}. In this case, for
+each redirection operator except ‘>&-’ and ‘<&-’, the shell allocates a
+file descriptor greater than or equal to 10 and assigns it to {VARNAME}.
+If {VARNAME} precedes ‘>&-’ or ‘<&-’, the value of VARNAME defines the
+file descriptor to close. If {VARNAME} is supplied, the redirection
+persists beyond the scope of the command, which allows the shell
+programmer to manage the file descriptor's lifetime manually without
+using the ‘exec’ builtin. The ‘varredir_close’ shell option manages
+this behavior (*note The Shopt Builtin::).
+
+ In the following descriptions, if the file descriptor number is
+omitted, and the first character of the redirection operator is ‘<’, the
+redirection refers to the standard input (file descriptor 0). If the
+first character of the redirection operator is ‘>’, the redirection
+refers to the standard output (file descriptor 1).
+
+ The WORD following the redirection operator in the following
+descriptions, unless otherwise noted, is subjected to brace expansion,
+tilde expansion, parameter and variable expansion, command substitution,
+arithmetic expansion, quote removal, filename expansion, and word
+splitting. If it expands to more than one word, Bash reports an error.
+
+ The order of redirections is significant. For example, the command
+ ls > DIRLIST 2>&1
+directs both standard output (file descriptor 1) and standard error
+(file descriptor 2) to the file DIRLIST, while the command
+ ls 2>&1 > DIRLIST
+directs only the standard output to file DIRLIST, because the standard
+error was made a copy of the standard output before the standard output
+was redirected to DIRLIST.
+
+ Bash handles several filenames specially when they are used in
+redirections, as described in the following table. If the operating
+system on which Bash is running provides these special files, Bash uses
+them; otherwise it emulates them internally with the behavior described
+below.
+
+‘/dev/fd/FD’
+ If FD is a valid integer, duplicate file descriptor FD.
+
+‘/dev/stdin’
+ File descriptor 0 is duplicated.
+
+‘/dev/stdout’
+ File descriptor 1 is duplicated.
+
+‘/dev/stderr’
+ File descriptor 2 is duplicated.
+
+‘/dev/tcp/HOST/PORT’
+ If HOST is a valid hostname or Internet address, and PORT is an
+ integer port number or service name, Bash attempts to open the
+ corresponding TCP socket.
+
+‘/dev/udp/HOST/PORT’
+ If HOST is a valid hostname or Internet address, and PORT is an
+ integer port number or service name, Bash attempts to open the
+ corresponding UDP socket.
+
+ A failure to open or create a file causes the redirection to fail.
+
+ Redirections using file descriptors greater than 9 should be used
+with care, as they may conflict with file descriptors the shell uses
+internally.
+
+3.6.1 Redirecting Input
+-----------------------
+
+Redirecting input opens the file whose name results from the expansion
+of WORD for reading on file descriptor ‘n’, or the standard input (file
+descriptor 0) if ‘n’ is not specified.
+
+ The general format for redirecting input is:
+ [N]<WORD
+
+3.6.2 Redirecting Output
+------------------------
+
+Redirecting output opens the file whose name results from the expansion
+of WORD for writing on file descriptor N, or the standard output (file
+descriptor 1) if N is not specified. If the file does not exist it is
+created; if it does exist it is truncated to zero size.
+
+ The general format for redirecting output is:
+ [N]>[|]WORD
+
+ If the redirection operator is ‘>’, and the ‘noclobber’ option to the
+‘set’ builtin command has been enabled, the redirection fails if the
+file whose name results from the expansion of WORD exists and is a
+regular file. If the redirection operator is ‘>|’, or the redirection
+operator is ‘>’ and the ‘noclobber’ option to the ‘set’ builtin is not
+enabled, Bash attempts the redirection even if the file named by WORD
+exists.
+
+3.6.3 Appending Redirected Output
+---------------------------------
+
+Redirecting output in this fashion opens the file whose name results
+from the expansion of WORD for appending on file descriptor N, or the
+standard output (file descriptor 1) if N is not specified. If the file
+does not exist it is created.
+
+ The general format for appending output is:
+ [N]>>WORD
+
+3.6.4 Redirecting Standard Output and Standard Error
+----------------------------------------------------
+
+This construct redirects both the standard output (file descriptor 1)
+and the standard error output (file descriptor 2) to the file whose name
+is the expansion of WORD.
+
+ There are two formats for redirecting standard output and standard
+error:
+ &>WORD
+and
+ >&WORD
+Of the two forms, the first is preferred. This is semantically
+equivalent to
+ >WORD 2>&1
+ When using the second form, WORD may not expand to a number or ‘-’.
+If it does, other redirection operators apply (see Duplicating File
+Descriptors below) for compatibility reasons.
+
+3.6.5 Appending Standard Output and Standard Error
+--------------------------------------------------
+
+This construct appends both the standard output (file descriptor 1) and
+the standard error output (file descriptor 2) to the file whose name is
+the expansion of WORD.
+
+ The format for appending standard output and standard error is:
+ &>>WORD
+This is semantically equivalent to
+ >>WORD 2>&1
+ (see Duplicating File Descriptors below).
+
+3.6.6 Here Documents
+--------------------
+
+This type of redirection instructs the shell to read input from the
+current source until it reads a line containing only DELIMITER (with no
+trailing blanks). All of the lines read up to that point then become
+the standard input (or file descriptor N if N is specified) for a
+command.
+
+ The format of here-documents is:
+ [N]<<[−]WORD
+ HERE-DOCUMENT
+ DELIMITER
+
+ The shell does not perform parameter and variable expansion, command
+substitution, arithmetic expansion, or filename expansion on WORD.
+
+ If any part of WORD is quoted, the DELIMITER is the result of quote
+removal on WORD, and the lines in the here-document are not expanded.
+If WORD is unquoted, DELIMITER is WORD itself, and the here-document
+text is treated similarly to a double-quoted string: all lines of the
+here-document are subjected to parameter expansion, command
+substitution, and arithmetic expansion, the character sequence
+‘\newline’ is treated literally, and ‘\’ must be used to quote the
+characters ‘\’, ‘$’, and ‘`’; however, double quote characters have no
+special meaning.
+
+ If the redirection operator is ‘<<-’, the shell strips leading tab
+characters from input lines and the line containing DELIMITER. This
+allows here-documents within shell scripts to be indented in a natural
+fashion.
+
+ If the delimiter is not quoted, the shell treats the ‘\<newline>’
+sequence as a line continuation: the two lines are joined and the
+backslash-newline is removed. This happens while reading the
+here-document, before the check for the ending delimiter, so joined
+lines can form the end delimiter.
+
+3.6.7 Here Strings
+------------------
+
+A variant of here documents, the format is:
+ [N]<<< WORD
+
+ The WORD undergoes tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote removal. Filename
+expansion and word splitting are not performed. The result is supplied
+as a single string, with a newline appended, to the command on its
+standard input (or file descriptor N if N is specified).
+
+3.6.8 Duplicating File Descriptors
+----------------------------------
+
+The redirection operator
+ [N]<&WORD
+is used to duplicate input file descriptors. If WORD expands to one or
+more digits, file descriptor N is made to be a copy of that file
+descriptor. It is a redirection error if the digits in WORD do not
+specify a file descriptor open for input. If WORD evaluates to ‘-’,
+file descriptor N is closed. If N is not specified, this uses the
+standard input (file descriptor 0).
+
+ The operator
+ [N]>&WORD
+is used similarly to duplicate output file descriptors. If N is not
+specified, this uses the standard output (file descriptor 1). It is a
+redirection error if the digits in WORD do not specify a file descriptor
+open for output. If WORD evaluates to ‘-’, file descriptor N is closed.
+As a special case, if N is omitted, and WORD does not expand to one or
+more digits or ‘-’, this redirects the standard output and standard
+error as described previously.
+
+3.6.9 Moving File Descriptors
+-----------------------------
+
+The redirection operator
+ [N]<&DIGIT-
+moves the file descriptor DIGIT to file descriptor N, or the standard
+input (file descriptor 0) if N is not specified. DIGIT is closed after
+being duplicated to N.
+
+ Similarly, the redirection operator
+ [N]>&DIGIT-
+moves the file descriptor DIGIT to file descriptor N, or the standard
+output (file descriptor 1) if N is not specified.
+
+3.6.10 Opening File Descriptors for Reading and Writing
+-------------------------------------------------------
+
+The redirection operator
+ [N]<>WORD
+opens the file whose name is the expansion of WORD for both reading and
+writing on file descriptor N, or on file descriptor 0 if N is not
+specified. If the file does not exist, it is created.
+
+\1f
+File: bash.info, Node: Executing Commands, Next: Shell Scripts, Prev: Redirections, Up: Basic Shell Features
+
+3.7 Executing Commands
+======================
+
+* Menu:
+
+* Simple Command Expansion:: How Bash expands simple commands before
+ executing them.
+* Command Search and Execution:: How Bash finds commands and runs them.
+* Command Execution Environment:: The environment in which Bash
+ executes commands that are not
+ shell builtins.
+* Environment:: The environment given to a command.
+* Exit Status:: The status returned by commands and how Bash
+ interprets it.
+* Signals:: What happens when Bash or a command it runs
+ receives a signal.
+
+\1f
+File: bash.info, Node: Simple Command Expansion, Next: Command Search and Execution, Up: Executing Commands
+
+3.7.1 Simple Command Expansion
+------------------------------
+
+When the shell executes a simple command, it performs the following
+expansions, assignments, and redirections, from left to right, in the
+following order.
+
+ 1. The words that the parser has marked as variable assignments (those
+ preceding the command name) and redirections are saved for later
+ processing.
+
+ 2. The words that are not variable assignments or redirections are
+ expanded (*note Shell Expansions::). If any words remain after
+ expansion, the first word is taken to be the name of the command
+ and the remaining words are the arguments.
+
+ 3. Redirections are performed as described above (*note
+ Redirections::).
+
+ 4. The text after the ‘=’ in each variable assignment undergoes tilde
+ expansion, parameter expansion, command substitution, arithmetic
+ expansion, and quote removal before being assigned to the variable.
+
+ If no command name results, the variable assignments affect the
+current shell environment. In the case of such a command (one that
+consists only of assignment statements and redirections), assignment
+statements are performed before redirections. Otherwise, the variables
+are added to the environment of the executed command and do not affect
+the current shell environment. If any of the assignments attempts to
+assign a value to a readonly variable, an error occurs, and the command
+exits with a non-zero status.
+
+ If no command name results, redirections are performed, but do not
+affect the current shell environment. A redirection error causes the
+command to exit with a non-zero status.
+
+ If there is a command name left after expansion, execution proceeds
+as described below. Otherwise, the command exits. If one of the
+expansions contained a command substitution, the exit status of the
+command is the exit status of the last command substitution performed.
+If there were no command substitutions, the command exits with a zero
+status.
+
+\1f
+File: bash.info, Node: Command Search and Execution, Next: Command Execution Environment, Prev: Simple Command Expansion, Up: Executing Commands
+
+3.7.2 Command Search and Execution
+----------------------------------
+
+After a command has been split into words, if it results in a simple
+command and an optional list of arguments, the shell performs the
+following actions.
+
+ 1. If the command name contains no slashes, the shell attempts to
+ locate it. If there exists a shell function by that name, that
+ function is invoked as described in *note Shell Functions::.
+
+ 2. If the name does not match a function, the shell searches for it in
+ the list of shell builtins. If a match is found, that builtin is
+ invoked.
+
+ 3. If the name is neither a shell function nor a builtin, and contains
+ no slashes, Bash searches each element of ‘$PATH’ for a directory
+ containing an executable file by that name. Bash uses a hash table
+ to remember the full pathnames of executable files to avoid
+ multiple ‘PATH’ searches (see the description of ‘hash’ in *note
+ Bourne Shell Builtins::). Bash performs a full search of the
+ directories in ‘$PATH’ only if the command is not found in the hash
+ table. If the search is unsuccessful, the shell searches for a
+ defined shell function named ‘command_not_found_handle’. If that
+ function exists, it is invoked in a separate execution environment
+ with the original command and the original command's arguments as
+ its arguments, and the function's exit status becomes the exit
+ status of that subshell. If that function is not defined, the
+ shell prints an error message and returns an exit status of 127.
+
+ 4. If the search is successful, or if the command name contains one or
+ more slashes, the shell executes the named program in a separate
+ execution environment. Argument 0 is set to the name given, and
+ the remaining arguments to the command are set to the arguments
+ supplied, if any.
+
+ 5. If this execution fails because the file is not in executable
+ format, and the file is not a directory, it is assumed to be a
+ “shell script”, a file containing shell commands, and the shell
+ executes it as described in *note Shell Scripts::.
+
+ 6. If the command was not begun asynchronously, the shell waits for
+ the command to complete and collects its exit status.
+
+\1f
+File: bash.info, Node: Command Execution Environment, Next: Environment, Prev: Command Search and Execution, Up: Executing Commands
+
+3.7.3 Command Execution Environment
+-----------------------------------
+
+The shell has an “execution environment”, which consists of the
+following:
+
+ • Open files inherited by the shell at invocation, as modified by
+ redirections supplied to the ‘exec’ builtin.
+
+ • The current working directory as set by ‘cd’, ‘pushd’, or ‘popd’,
+ or inherited by the shell at invocation.
+
+ • The file creation mode mask as set by ‘umask’ or inherited from the
+ shell's parent.
+
+ • Current traps set by ‘trap’.
+
+ • Shell parameters that are set by variable assignment or with ‘set’
+ or inherited from the shell's parent in the environment.
+
+ • Shell functions defined during execution or inherited from the
+ shell's parent in the environment.
+
+ • Options enabled at invocation (either by default or with
+ command-line arguments) or by ‘set’.
+
+ • Options enabled by ‘shopt’ (*note The Shopt Builtin::).
+
+ • Shell aliases defined with ‘alias’ (*note Aliases::).
+
+ • Various process IDs, including those of background jobs (*note
+ Lists::), the value of ‘$$’, and the value of ‘$PPID’.
+
+ When a simple command other than a builtin or shell function is to be
+executed, it is invoked in a separate execution environment that
+consists of the following. Unless otherwise noted, the values are
+inherited from the shell.
+
+ • The shell's open files, plus any modifications and additions
+ specified by redirections to the command.
+
+ • The current working directory.
+
+ • The file creation mode mask.
+
+ • Shell variables and functions marked for export, along with
+ variables exported for the command, passed in the environment
+ (*note Environment::).
+
+ • Traps caught by the shell are reset to the values inherited from
+ the shell's parent, and traps ignored by the shell are ignored.
+
+ A command invoked in this separate environment cannot affect the
+shell's execution environment.
+
+ A “subshell” is a copy of the shell process.
+
+ Command substitution, commands grouped with parentheses, and
+asynchronous commands are invoked in a subshell environment that is a
+duplicate of the shell environment, except that traps caught by the
+shell are reset to the values that the shell inherited from its parent
+at invocation. Builtin commands that are invoked as part of a pipeline,
+except possibly in the last element depending on the value of the
+‘lastpipe’ shell option (*note The Shopt Builtin::), are also executed
+in a subshell environment. Changes made to the subshell environment
+cannot affect the shell's execution environment.
+
+ When the shell is in POSIX mode, subshells spawned to execute command
+substitutions inherit the value of the ‘-e’ option from the parent
+shell. When not in POSIX mode, Bash clears the ‘-e’ option in such
+subshells See the description of the ‘inherit_errexit’ shell option
+(*note Bash Builtins::) for how to control this behavior when not in
+POSIX mode.
+
+ If a command is followed by a ‘&’ and job control is not active, the
+default standard input for the command is the empty file ‘/dev/null’.
+Otherwise, the invoked command inherits the file descriptors of the
+calling shell as modified by redirections.
+
+\1f
+File: bash.info, Node: Environment, Next: Exit Status, Prev: Command Execution Environment, Up: Executing Commands
+
+3.7.4 Environment
+-----------------
+
+When a program is invoked it is given an array of strings called the
+“environment”. This is a list of name-value pairs, of the form
+‘name=value’.
+
+ Bash provides several ways to manipulate the environment. On
+invocation, the shell scans its own environment and creates a parameter
+for each name found, automatically marking it for ‘export’ to child
+processes. Executed commands inherit the environment. The ‘export’,
+‘declare -x’, and ‘unset’ commands modify the environment by adding and
+deleting parameters and functions. If the value of a parameter in the
+environment is modified, the new value automatically becomes part of the
+environment, replacing the old. The environment inherited by any
+executed command consists of the shell's initial environment, whose
+values may be modified in the shell, less any pairs removed by the
+‘unset’ and ‘export -n’ commands, plus any additions via the ‘export’
+and ‘declare -x’ commands.
+
+ If any parameter assignment statements, as described in *note Shell
+Parameters::, appear before a simple command, the variable assignments
+are part of that command's environment for as long as it executes.
+These assignment statements affect only the environment seen by that
+command. If these assignments precede a call to a shell function, the
+variables are local to the function and exported to that function's
+children.
+
+ If the ‘-k’ option is set (*note The Set Builtin::), then all
+parameter assignments are placed in the environment for a command, not
+just those that precede the command name.
+
+ When Bash invokes an external command, the variable ‘$_’ is set to
+the full pathname of the command and passed to that command in its
+environment.
+
+\1f
+File: bash.info, Node: Exit Status, Next: Signals, Prev: Environment, Up: Executing Commands
+
+3.7.5 Exit Status
+-----------------
+
+The exit status of an executed command is the value returned by the
+‘waitpid’ system call or equivalent function. Exit statuses fall
+between 0 and 255, though, as explained below, the shell may use values
+above 125 specially. Exit statuses from shell builtins and compound
+commands are also limited to this range. Under certain circumstances,
+the shell will use special values to indicate specific failure modes.
+
+ For the shell's purposes, a command which exits with a zero exit
+status has succeeded. So while an exit status of zero indicates
+success, a non-zero exit status indicates failure. This seemingly
+counter-intuitive scheme is used so there is one well-defined way to
+indicate success and a variety of ways to indicate various failure
+modes.
+
+ When a command terminates on a fatal signal whose number is N, Bash
+uses the value 128+N as the exit status.
+
+ If a command is not found, the child process created to execute it
+returns a status of 127. If a command is found but is not executable,
+the return status is 126.
+
+ If a command fails because of an error during expansion or
+redirection, the exit status is greater than zero.
+
+ The exit status is used by the Bash conditional commands (*note
+Conditional Constructs::) and some of the list constructs (*note
+Lists::).
+
+ All of the Bash builtins return an exit status of zero if they
+succeed and a non-zero status on failure, so they may be used by the
+conditional and list constructs. All builtins return an exit status of
+2 to indicate incorrect usage, generally invalid options or missing
+arguments.
+
+ The exit status of the last command is available in the special
+parameter $? (*note Special Parameters::).
+
+ Bash itself returns the exit status of the last command executed,
+unless a syntax error occurs, in which case it exits with a non-zero
+value. See also the ‘exit’ builtin command (*note Bourne Shell
+Builtins::).
+
+\1f
+File: bash.info, Node: Signals, Prev: Exit Status, Up: Executing Commands
+
+3.7.6 Signals
+-------------
+
+When Bash is interactive, in the absence of any traps, it ignores
+‘SIGTERM’ (so that ‘kill 0’ does not kill an interactive shell), and
+catches and handles ‘SIGINT’ (so that the ‘wait’ builtin is
+interruptible). When Bash receives a ‘SIGINT’, it breaks out of any
+executing loops. In all cases, Bash ignores ‘SIGQUIT’. If job control
+is in effect (*note Job Control::), Bash ignores ‘SIGTTIN’, ‘SIGTTOU’,
+and ‘SIGTSTP’.
+
+ The ‘trap’ builtin modifies the shell's signal handling, as described
+below (*note Bourne Shell Builtins::).
+
+ Non-builtin commands Bash executes have signal handlers set to the
+values inherited by the shell from its parent, unless ‘trap’ sets them
+to be ignored, in which case the child process will ignore them as well.
+When job control is not in effect, asynchronous commands ignore ‘SIGINT’
+and ‘SIGQUIT’ in addition to these inherited handlers. Commands run as
+a result of command substitution ignore the keyboard-generated job
+control signals ‘SIGTTIN’, ‘SIGTTOU’, and ‘SIGTSTP’.
+
+ The shell exits by default upon receipt of a ‘SIGHUP’. Before
+exiting, an interactive shell resends the ‘SIGHUP’ to all jobs, running
+or stopped. The shell sends ‘SIGCONT’ to stopped jobs to ensure that
+they receive the ‘SIGHUP’ (*Note Job Control::, for more information
+about running and stopped jobs). To prevent the shell from sending the
+‘SIGHUP’ signal to a particular job, remove it from the jobs table with
+the ‘disown’ builtin (*note Job Control Builtins::) or mark it not to
+receive ‘SIGHUP’ using ‘disown -h’.
+
+ If the ‘huponexit’ shell option has been set using ‘shopt’ (*note The
+Shopt Builtin::), Bash sends a ‘SIGHUP’ to all jobs when an interactive
+login shell exits.
+
+ If Bash is waiting for a command to complete and receives a signal
+for which a trap has been set, it will not execute the trap until the
+command completes. If Bash is waiting for an asynchronous command via
+the ‘wait’ builtin, and it receives a signal for which a trap has been
+set, the ‘wait’ builtin will return immediately with an exit status
+greater than 128, immediately after which the shell executes the trap.
+
+ When job control is not enabled, and Bash is waiting for a foreground
+command to complete, the shell receives keyboard-generated signals such
+as ‘SIGINT’ (usually generated by ‘^C’) that users commonly intend to
+send to that command. This happens because the shell and the command
+are in the same process group as the terminal, and ‘^C’ sends ‘SIGINT’
+to all processes in that process group. Since Bash does not enable job
+control by default when the shell is not interactive, this scenario is
+most common in non-interactive shells.
+
+ When job control is enabled, and Bash is waiting for a foreground
+command to complete, the shell does not receive keyboard-generated
+signals, because it is not in the same process group as the terminal.
+This scenario is most common in interactive shells, where Bash attempts
+to enable job control by default. See *note Job Control::, for a more
+in-depth discussion of process groups.
+
+ When job control is not enabled, and Bash receives ‘SIGINT’ while
+waiting for a foreground command, it waits until that foreground command
+terminates and then decides what to do about the ‘SIGINT’:
+
+ 1. If the command terminates due to the ‘SIGINT’, Bash concludes that
+ the user meant to send the ‘SIGINT’ to the shell as well, and acts
+ on the ‘SIGINT’ (e.g., by running a ‘SIGINT’ trap, exiting a
+ non-interactive shell, or returning to the top level to read a new
+ command).
+
+ 2. If the command does not terminate due to ‘SIGINT’, the program
+ handled the ‘SIGINT’ itself and did not treat it as a fatal signal.
+ In that case, Bash does not treat ‘SIGINT’ as a fatal signal,
+ either, instead assuming that the ‘SIGINT’ was used as part of the
+ program's normal operation (e.g., ‘emacs’ uses it to abort editing
+ commands) or deliberately discarded. However, Bash will run any
+ trap set on ‘SIGINT’, as it does with any other trapped signal it
+ receives while it is waiting for the foreground command to
+ complete, for compatibility.
+
+ When job control is enabled, Bash does not receive keyboard-generated
+signals such as ‘SIGINT’ while it is waiting for a foreground command.
+An interactive shell does not pay attention to the ‘SIGINT’, even if the
+foreground command terminates as a result, other than noting its exit
+status. If the shell is not interactive, and the foreground command
+terminates due to the ‘SIGINT’, Bash pretends it received the ‘SIGINT’
+itself (scenario 1 above), for compatibility.
+
+\1f
+File: bash.info, Node: Shell Scripts, Prev: Executing Commands, Up: Basic Shell Features
+
+3.8 Shell Scripts
+=================
+
+A shell script is a text file containing shell commands. When such a
+file is used as the first non-option argument when invoking Bash, and
+neither the ‘-c’ nor ‘-s’ option is supplied (*note Invoking Bash::),
+Bash reads and executes commands from the file, then exits. This mode
+of operation creates a non-interactive shell. If the filename does not
+contain any slashes, the shell first searches for the file in the
+current directory, and looks in the directories in ‘$PATH’ if not found
+there.
+
+ Bash tries to determine whether the file is a text file or a binary,
+and will not execute files it determines to be binaries.
+
+ When Bash runs a shell script, it sets the special parameter ‘0’ to
+the name of the file, rather than the name of the shell, and the
+positional parameters are set to the remaining arguments, if any are
+given. If no additional arguments are supplied, the positional
+parameters are unset.
+
+ A shell script may be made executable by using the ‘chmod’ command to
+turn on the execute bit. When Bash finds such a file while searching
+the ‘$PATH’ for a command, it creates a new instance of itself to
+execute it. In other words, executing
+ filename ARGUMENTS
+is equivalent to executing
+ bash filename ARGUMENTS
+
+if ‘filename’ is an executable shell script. This subshell
+reinitializes itself, so that the effect is as if a new shell had been
+invoked to interpret the script, with the exception that the locations
+of commands remembered by the parent (see the description of ‘hash’ in
+*note Bourne Shell Builtins::) are retained by the child.
+
+ The GNU operating system, and most versions of Unix, make this a part
+of the operating system's command execution mechanism. If the first
+line of a script begins with the two characters ‘#!’, the remainder of
+the line specifies an interpreter for the program and, depending on the
+operating system, one or more optional arguments for that interpreter.
+Thus, you can specify Bash, ‘awk’, Perl, or some other interpreter and
+write the rest of the script file in that language.
+
+ The arguments to the interpreter consist of one or more optional
+arguments following the interpreter name on the first line of the script
+file, followed by the name of the script file, followed by the rest of
+the arguments supplied to the script. The details of how the
+interpreter line is split into an interpreter name and a set of
+arguments vary across systems. Bash will perform this action on
+operating systems that do not handle it themselves. Note that some
+older versions of Unix limit the interpreter name and a single argument
+to a maximum of 32 characters, so it's not portable to assume that using
+more than one argument will work.
+
+ Bash scripts often begin with ‘#! /bin/bash’ (assuming that Bash has
+been installed in ‘/bin’), since this ensures that Bash will be used to
+interpret the script, even if it is executed under another shell. It's
+a common idiom to use ‘env’ to find ‘bash’ even if it's been installed
+in another directory: ‘#!/usr/bin/env bash’ will find the first
+occurrence of ‘bash’ in ‘$PATH’.
+
+\1f
+File: bash.info, Node: Shell Builtin Commands, Next: Shell Variables, Prev: Basic Shell Features, Up: Top
+
+4 Shell Builtin Commands
+************************
+
+* Menu:
+
+* Bourne Shell Builtins:: Builtin commands inherited from the Bourne
+ Shell.
+* Bash Builtins:: Table of builtins specific to Bash.
+* Modifying Shell Behavior:: Builtins to modify shell attributes and
+ optional behavior.
+* Special Builtins:: Builtin commands classified specially by
+ POSIX.
+
+Builtin commands are contained within the shell itself. When the name
+of a builtin command is used as the first word of a simple command
+(*note Simple Commands::), the shell executes the command directly,
+without invoking another program. Builtin commands are necessary to
+implement functionality impossible or inconvenient to obtain with
+separate utilities.
+
+ This section briefly describes the builtins which Bash inherits from
+the Bourne Shell, as well as the builtin commands which are unique to or
+have been extended in Bash.
+
+ Several builtin commands are described in other chapters: builtin
+commands which provide the Bash interface to the job control facilities
+(*note Job Control Builtins::), the directory stack (*note Directory
+Stack Builtins::), the command history (*note Bash History Builtins::),
+and the programmable completion facilities (*note Programmable
+Completion Builtins::).
+
+ Many of the builtins have been extended by POSIX or Bash.
+
+ Unless otherwise noted, each builtin command documented as accepting
+options preceded by ‘-’ accepts ‘--’ to signify the end of the options.
+The ‘:’, ‘true’, ‘false’, and ‘test’/‘[’ builtins do not accept options
+and do not treat ‘--’ specially. The ‘exit’, ‘logout’, ‘return’,
+‘break’, ‘continue’, ‘let’, and ‘shift’ builtins accept and process
+arguments beginning with ‘-’ without requiring ‘--’. Other builtins
+that accept arguments but are not specified as accepting options
+interpret arguments beginning with ‘-’ as invalid options and require
+‘--’ to prevent this interpretation.
+
+\1f
+File: bash.info, Node: Bourne Shell Builtins, Next: Bash Builtins, Up: Shell Builtin Commands
+
+4.1 Bourne Shell Builtins
+=========================
+
+The following shell builtin commands are inherited from the Bourne
+Shell. These commands are implemented as specified by the POSIX
+standard.
+
+‘: (a colon)’
+ : [ARGUMENTS]
+
+ Do nothing beyond expanding ARGUMENTS and performing redirections.
+ The return status is zero.
+
+‘. (a period)’
+ . [-p PATH] FILENAME [ARGUMENTS]
+
+ The ‘.’ command reads and execute commands from the FILENAME
+ argument in the current shell context.
+
+ If FILENAME does not contain a slash, ‘.’ searches for it. If ‘-p’
+ is supplied, ‘.’ treats PATH as a colon-separated list of
+ directories in which to find FILENAME; otherwise, ‘.’ uses the
+ directories in ‘PATH’ to find FILENAME. FILENAME does not need to
+ be executable. When Bash is not in POSIX mode, it searches the
+ current directory if FILENAME is not found in ‘$PATH’, but does not
+ search the current directory if ‘-p’ is supplied. If the
+ ‘sourcepath’ option (*note The Shopt Builtin::) is turned off, ‘.’
+ does not search ‘PATH’.
+
+ If any ARGUMENTS are supplied, they become the positional
+ parameters when FILENAME is executed. Otherwise the positional
+ parameters are unchanged.
+
+ If the ‘-T’ option is enabled, ‘.’ inherits any trap on ‘DEBUG’; if
+ it is not, any ‘DEBUG’ trap string is saved and restored around the
+ call to ‘.’, and ‘.’ unsets the ‘DEBUG’ trap while it executes. If
+ ‘-T’ is not set, and the sourced file changes the ‘DEBUG’ trap, the
+ new value persists after ‘.’ completes. The return status is the
+ exit status of the last command executed from FILENAME, or zero if
+ no commands are executed. If FILENAME is not found, or cannot be
+ read, the return status is non-zero. This builtin is equivalent to
+ ‘source’.
+
+‘break’
+ break [N]
+
+ Exit from a ‘for’, ‘while’, ‘until’, or ‘select’ loop. If N is
+ supplied, ‘break’ exits the Nth enclosing loop. N must be greater
+ than or equal to 1. The return status is zero unless N is not
+ greater than or equal to 1.
+
+‘cd’
+ cd [-L] [-@] [DIRECTORY]
+ cd -P [-e] [-@] [DIRECTORY]
+
+ Change the current working directory to DIRECTORY. If DIRECTORY is
+ not supplied, the value of the ‘HOME’ shell variable is used as
+ DIRECTORY. If DIRECTORY is the empty string, ‘cd’ treats it as an
+ error. If the shell variable ‘CDPATH’ exists, and DIRECTORY does
+ not begin with a slash, ‘cd’ uses it as a search path: ‘cd’
+ searches each directory name in ‘CDPATH’ for DIRECTORY, with
+ alternative directory names in ‘CDPATH’ separated by a colon (‘:’).
+ A null directory name in ‘CDPATH’ means the same thing as the
+ current directory.
+
+ The ‘-P’ option means not to follow symbolic links: symbolic links
+ are resolved while ‘cd’ is traversing DIRECTORY and before
+ processing an instance of ‘..’ in DIRECTORY.
+
+ By default, or when the ‘-L’ option is supplied, symbolic links in
+ DIRECTORY are resolved after ‘cd’ processes an instance of ‘..’ in
+ DIRECTORY.
+
+ If ‘..’ appears in DIRECTORY, ‘cd’ processes it by removing the
+ immediately preceding pathname component, back to a slash or the
+ beginning of DIRECTORY, and verifying that the portion of DIRECTORY
+ it has processed to that point is still a valid directory name
+ after removing the pathname component. If it is not a valid
+ directory name, ‘cd’ returns a non-zero status.
+
+ If the ‘-e’ option is supplied with ‘-P’ and ‘cd’ cannot
+ successfully determine the current working directory after a
+ successful directory change, it returns a non-zero status.
+
+ On systems that support it, the ‘-@’ option presents the extended
+ attributes associated with a file as a directory.
+
+ If DIRECTORY is ‘-’, it is converted to ‘$OLDPWD’ before attempting
+ the directory change.
+
+ If ‘cd’ uses a non-empty directory name from ‘CDPATH’, or if ‘-’ is
+ the first argument, and the directory change is successful, ‘cd’
+ writes the absolute pathname of the new working directory to the
+ standard output.
+
+ If the directory change is successful, ‘cd’ sets the value of the
+ ‘PWD’ environment variable to the new directory name, and sets the
+ ‘OLDPWD’ environment variable to the value of the current working
+ directory before the change.
+
+ The return status is zero if the directory is successfully changed,
+ non-zero otherwise.
+
+‘continue’
+ continue [N]
+
+ ‘continue’ resumes the next iteration of an enclosing ‘for’,
+ ‘while’, ‘until’, or ‘select’ loop. If N is supplied, Bash resumes
+ the execution of the Nth enclosing loop. N must be greater than or
+ equal to 1. The return status is zero unless N is not greater than
+ or equal to 1.
+
+‘eval’
+ eval [ARGUMENTS]
+
+ The ARGUMENTS are concatenated together into a single command,
+ separated by spaces. Bash then reads and executes this command and
+ returns its exit status as the exit status of ‘eval’. If there are
+ no arguments or only empty arguments, the return status is zero.
+
+‘exec’
+ exec [-cl] [-a NAME] [COMMAND [ARGUMENTS]]
+
+ If COMMAND is supplied, it replaces the shell without creating a
+ new process. COMMAND cannot be a shell builtin or function. The
+ ARGUMENTS become the arguments to COMMAND If the ‘-l’ option is
+ supplied, the shell places a dash at the beginning of the zeroth
+ argument passed to COMMAND. This is what the ‘login’ program does.
+ The ‘-c’ option causes COMMAND to be executed with an empty
+ environment. If ‘-a’ is supplied, the shell passes NAME as the
+ zeroth argument to COMMAND.
+
+ If COMMAND cannot be executed for some reason, a non-interactive
+ shell exits, unless the ‘execfail’ shell option is enabled. In
+ that case, it returns a non-zero status. An interactive shell
+ returns a non-zero status if the file cannot be executed. A
+ subshell exits unconditionally if ‘exec’ fails.
+
+ If COMMAND is not specified, redirections may be used to affect the
+ current shell environment. If there are no redirection errors, the
+ return status is zero; otherwise the return status is non-zero.
+
+‘exit’
+ exit [N]
+
+ Exit the shell, returning a status of N to the shell's parent. If
+ N is omitted, the exit status is that of the last command executed.
+ Any trap on ‘EXIT’ is executed before the shell terminates.
+
+‘export’
+ export [-fn] [-p] [NAME[=VALUE]]
+
+ Mark each NAME to be passed to subsequently executed commands in
+ the environment. If the ‘-f’ option is supplied, the NAMEs refer
+ to shell functions; otherwise the names refer to shell variables.
+
+ The ‘-n’ option means to unexport each name: no longer mark it for
+ export. If no NAMEs are supplied, or if only the ‘-p’ option is
+ given, ‘export’ displays a list of names of all exported variables
+ on the standard output. Using ‘-p’ and ‘-f’ together displays
+ exported functions. The ‘-p’ option displays output in a form that
+ may be reused as input.
+
+ ‘export’ allows the value of a variable to be set at the same time
+ it is exported or unexported by following the variable name with
+ =VALUE. This sets the value of the variable is to VALUE while
+ modifying the export attribute.
+
+ The return status is zero unless an invalid option is supplied, one
+ of the names is not a valid shell variable name, or ‘-f’ is
+ supplied with a name that is not a shell function.
+
+‘false’
+ false
+
+ Does nothing; returns a non-zero status.
+
+‘getopts’
+ getopts OPTSTRING NAME [ARG ...]
+
+ ‘getopts’ is used by shell scripts or functions to parse positional
+ parameters and obtain options and their arguments. OPTSTRING
+ contains the option characters to be recognized; if a character is
+ followed by a colon, the option is expected to have an argument,
+ which should be separated from it by whitespace. The colon (‘:’)
+ and question mark (‘?’) may not be used as option characters.
+
+ Each time it is invoked, ‘getopts’ places the next option in the
+ shell variable NAME, initializing NAME if it does not exist, and
+ the index of the next argument to be processed into the variable
+ ‘OPTIND’. ‘OPTIND’ is initialized to 1 each time the shell or a
+ shell script is invoked. When an option requires an argument,
+ ‘getopts’ places that argument into the variable ‘OPTARG’.
+
+ The shell does not reset ‘OPTIND’ automatically; it must be
+ manually reset between multiple calls to ‘getopts’ within the same
+ shell invocation to use a new set of parameters.
+
+ When it reaches the end of options, ‘getopts’ exits with a return
+ value greater than zero. ‘OPTIND’ is set to the index of the first
+ non-option argument, and NAME is set to ‘?’.
+
+ ‘getopts’ normally parses the positional parameters, but if more
+ arguments are supplied as ARG values, ‘getopts’ parses those
+ instead.
+
+ ‘getopts’ can report errors in two ways. If the first character of
+ OPTSTRING is a colon, ‘getopts’ uses _silent_ error reporting. In
+ normal operation, ‘getopts’ prints diagnostic messages when it
+ encounters invalid options or missing option arguments. If the
+ variable ‘OPTERR’ is set to 0, ‘getopts’ does not display any error
+ messages, even if the first character of ‘optstring’ is not a
+ colon.
+
+ If ‘getopts’ detects an invalid option, it places ‘?’ into NAME
+ and, if not silent, prints an error message and unsets ‘OPTARG’.
+ If ‘getopts’ is silent, it assigns the option character found to
+ ‘OPTARG’ and does not print a diagnostic message.
+
+ If a required argument is not found, and ‘getopts’ is not silent,
+ it sets the value of NAME to a question mark (‘?’), unsets
+ ‘OPTARG’, and prints a diagnostic message. If ‘getopts’ is silent,
+ it sets the value of NAME to a colon (‘:’), and sets ‘OPTARG’ to
+ the option character found.
+
+ ‘getopts’ returns true if an option, specified or unspecified, is
+ found. It returns false when it encounters the end of options or
+ if an error occurs.
+
+‘hash’
+ hash [-r] [-p FILENAME] [-dt] [NAME]
+
+ Each time ‘hash’ is invoked, it remembers the full filenames of the
+ commands specified as NAME arguments, so they need not be searched
+ for on subsequent invocations. The commands are found by searching
+ through the directories listed in ‘$PATH’. Any
+ previously-remembered filename associated with NAME is discarded.
+ The ‘-p’ option inhibits the path search, and ‘hash’ uses FILENAME
+ as the location of NAME.
+
+ The ‘-r’ option causes the shell to forget all remembered
+ locations. Assigning to the ‘PATH’ variable also clears all hashed
+ filenames. The ‘-d’ option causes the shell to forget the
+ remembered location of each NAME.
+
+ If the ‘-t’ option is supplied, ‘hash’ prints the full pathname
+ corresponding to each NAME. If multiple NAME arguments are
+ supplied with ‘-t’, ‘hash’ prints each NAME before the
+ corresponding hashed full path. The ‘-l’ option displays output in
+ a format that may be reused as input.
+
+ If no arguments are given, or if only ‘-l’ is supplied, ‘hash’
+ prints information about remembered commands. The ‘-t’, ‘-d’, and
+ ‘-p’ options (the options that act on the NAME arguments) are
+ mutually exclusive. Only one will be active. If more than one is
+ supplied, ‘-t’ has higher priority than ‘-p’, and both have higher
+ priority than ‘-d’.
+
+ The return status is zero unless a NAME is not found or an invalid
+ option is supplied.
+
+‘pwd’
+ pwd [-LP]
+
+ Print the absolute pathname of the current working directory. If
+ the ‘-P’ option is supplied, or the ‘-o physical’ option to the
+ ‘set’ builtin (*note The Set Builtin::) is enabled, the pathname
+ printed will not contain symbolic links. If the ‘-L’ option is
+ supplied, the pathname printed may contain symbolic links. The
+ return status is zero unless an error is encountered while
+ determining the name of the current directory or an invalid option
+ is supplied.
+
+‘readonly’
+ readonly [-aAf] [-p] [NAME[=VALUE]] ...
+
+ Mark each NAME as readonly. The values of these names may not be
+ changed by subsequent assignment or unset. If the ‘-f’ option is
+ supplied, each NAME refers to a shell function. The ‘-a’ option
+ means each NAME refers to an indexed array variable; the ‘-A’
+ option means each NAME refers to an associative array variable. If
+ both options are supplied, ‘-A’ takes precedence. If no NAME
+ arguments are supplied, or if the ‘-p’ option is supplied, print a
+ list of all readonly names. The other options may be used to
+ restrict the output to a subset of the set of readonly names. The
+ ‘-p’ option displays output in a format that may be reused as
+ input.
+
+ ‘readonly’ allows the value of a variable to be set at the same
+ time the readonly attribute is changed by following the variable
+ name with =VALUE. This sets the value of the variable is to VALUE
+ while modifying the readonly attribute.
+
+ The return status is zero unless an invalid option is supplied, one
+ of the NAME arguments is not a valid shell variable or function
+ name, or the ‘-f’ option is supplied with a name that is not a
+ shell function.
+
+‘return’
+ return [N]
+
+ Stop executing a shell function or sourced file and return the
+ value N to its caller. If N is not supplied, the return value is
+ the exit status of the last command executed. If ‘return’ is
+ executed by a trap handler, the last command used to determine the
+ status is the last command executed before the trap handler. If
+ ‘return’ is executed during a ‘DEBUG’ trap, the last command used
+ to determine the status is the last command executed by the trap
+ handler before ‘return’ was invoked.
+
+ When ‘return’ is used to terminate execution of a script being
+ executed with the ‘.’ (‘source’) builtin, it returns either N or
+ the exit status of the last command executed within the script as
+ the exit status of the script. If N is supplied, the return value
+ is its least significant 8 bits.
+
+ Any command associated with the ‘RETURN’ trap is executed before
+ execution resumes after the function or script.
+
+ The return status is non-zero if ‘return’ is supplied a non-numeric
+ argument or is used outside a function and not during the execution
+ of a script by ‘.’ or ‘source’.
+
+‘shift’
+ shift [N]
+
+ Shift the positional parameters to the left by N: the positional
+ parameters from N+1 ... ‘$#’ are renamed to ‘$1’ ... ‘$#’-N.
+ Parameters represented by the numbers ‘$#’ down to ‘$#’-N+1 are
+ unset. N must be a non-negative number less than or equal to ‘$#’.
+ If N is not supplied, it is assumed to be 1. If N is zero or
+ greater than ‘$#’, the positional parameters are not changed. The
+ return status is zero unless N is greater than ‘$#’ or less than
+ zero, non-zero otherwise.
+
+‘test’
+‘[’
+ test EXPR
+
+ Evaluate a conditional expression EXPR and return a status of 0
+ (true) or 1 (false). Each operator and operand must be a separate
+ argument. Expressions are composed of the primaries described
+ below in *note Bash Conditional Expressions::. ‘test’ does not
+ accept any options, nor does it accept and ignore an argument of
+ ‘--’ as signifying the end of options. When using the ‘[’ form,
+ the last argument to the command must be a ‘]’.
+
+ Expressions may be combined using the following operators, listed
+ in decreasing order of precedence. The evaluation depends on the
+ number of arguments; see below. ‘test’ uses operator precedence
+ when there are five or more arguments.
+
+ ‘! EXPR’
+ True if EXPR is false.
+
+ ‘( EXPR )’
+ Returns the value of EXPR. This may be used to override
+ normal operator precedence.
+
+ ‘EXPR1 -a EXPR2’
+ True if both EXPR1 and EXPR2 are true.
+
+ ‘EXPR1 -o EXPR2’
+ True if either EXPR1 or EXPR2 is true.
+
+ The ‘test’ and ‘[’ builtins evaluate conditional expressions using
+ a set of rules based on the number of arguments.
+
+ 0 arguments
+ The expression is false.
+
+ 1 argument
+ The expression is true if, and only if, the argument is not
+ null.
+
+ 2 arguments
+ If the first argument is ‘!’, the expression is true if and
+ only if the second argument is null. If the first argument is
+ one of the unary conditional operators (*note Bash Conditional
+ Expressions::), the expression is true if the unary test is
+ true. If the first argument is not a valid unary operator,
+ the expression is false.
+
+ 3 arguments
+ The following conditions are applied in the order listed.
+
+ 1. If the second argument is one of the binary conditional
+ operators (*note Bash Conditional Expressions::), the
+ result of the expression is the result of the binary test
+ using the first and third arguments as operands. The
+ ‘-a’ and ‘-o’ operators are considered binary operators
+ when there are three arguments.
+ 2. If the first argument is ‘!’, the value is the negation
+ of the two-argument test using the second and third
+ arguments.
+ 3. If the first argument is exactly ‘(’ and the third
+ argument is exactly ‘)’, the result is the one-argument
+ test of the second argument.
+ 4. Otherwise, the expression is false.
+
+ 4 arguments
+ The following conditions are applied in the order listed.
+
+ 1. If the first argument is ‘!’, the result is the negation
+ of the three-argument expression composed of the
+ remaining arguments.
+ 2. If the first argument is exactly ‘(’ and the fourth
+ argument is exactly ‘)’, the result is the two-argument
+ test of the second and third arguments.
+ 3. Otherwise, the expression is parsed and evaluated
+ according to precedence using the rules listed above.
+
+ 5 or more arguments
+ The expression is parsed and evaluated according to precedence
+ using the rules listed above.
+
+ If the shell is in POSIX mode, or if the expression is part of the
+ ‘[[’ command, the ‘<’ and ‘>’ operators sort using the current
+ locale. If the shell is not in POSIX mode, the ‘test’ and ‘[’
+ commands sort lexicographically using ASCII ordering.
+
+ The historical operator-precedence parsing with 4 or more arguments
+ can lead to ambiguities when it encounters strings that look like
+ primaries. The POSIX standard has deprecated the ‘-a’ and ‘-o’
+ primaries and enclosing expressions within parentheses. Scripts
+ should no longer use them. It's much more reliable to restrict
+ test invocations to a single primary, and to replace uses of ‘-a’
+ and ‘-o’ with the shell's ‘&&’ and ‘||’ list operators. For
+ example, use
+
+ test -n string1 && test -n string2
+
+ instead of
+
+ test -n string1 -a -n string2
+
+‘times’
+ times
+
+ Print out the user and system times used by the shell and its
+ children. The return status is zero.
+
+‘trap’
+ trap [-lpP] [ACTION] [SIGSPEC ...]
+
+ The ACTION is a command that is read and executed when the shell
+ receives any of the signals SIGSPEC. If ACTION is absent (and
+ there is a single SIGSPEC) or equal to ‘-’, each specified
+ SIGSPEC's disposition is reset to the value it had when the shell
+ was started. If ACTION is the null string, then the signal
+ specified by each SIGSPEC is ignored by the shell and commands it
+ invokes.
+
+ If no arguments are supplied, ‘trap’ prints the actions associated
+ with each trapped signal as a set of ‘trap’ commands that can be
+ reused as shell input to restore the current signal dispositions.
+
+ If ACTION is not present and ‘-p’ has been supplied, ‘trap’
+ displays the trap commands associated with each SIGSPEC, or, if no
+ SIGSPECs are supplied, for all trapped signals, as a set of ‘trap’
+ commands that can be reused as shell input to restore the current
+ signal dispositions. The ‘-P’ option behaves similarly, but
+ displays only the actions associated with each SIGSPEC argument.
+ ‘-P’ requires at least one SIGSPEC argument. The ‘-P’ or ‘-p’
+ options may be used in a subshell environment (e.g., command
+ substitution) and, as long as they are used before ‘trap’ is used
+ to change a signal's handling, will display the state of its
+ parent's traps.
+
+ The ‘-l’ option prints a list of signal names and their
+ corresponding numbers. Each SIGSPEC is either a signal name or a
+ signal number. Signal names are case insensitive and the ‘SIG’
+ prefix is optional. If ‘-l’ is supplied with no SIGSPEC arguments,
+ it prints a list of valid signal names.
+
+ If a SIGSPEC is ‘0’ or ‘EXIT’, ACTION is executed when the shell
+ exits. If a SIGSPEC is ‘DEBUG’, ACTION is executed before every
+ simple command, ‘for’ command, ‘case’ command, ‘select’ command, ((
+ arithmetic command, [[ conditional command, arithmetic ‘for’
+ command, and before the first command executes in a shell function.
+ Refer to the description of the ‘extdebug’ shell option (*note The
+ Shopt Builtin::) for details of its effect on the ‘DEBUG’ trap. If
+ a SIGSPEC is ‘RETURN’, ACTION is executed each time a shell
+ function or a script executed with the ‘.’ or ‘source’ builtins
+ finishes executing.
+
+ If a SIGSPEC is ‘ERR’, ACTION is executed whenever a pipeline
+ (which may consist of a single simple command), a list, or a
+ compound command returns a non-zero exit status, subject to the
+ following conditions. The ‘ERR’ trap is not executed if the failed
+ command is part of the command list immediately following an
+ ‘until’ or ‘while’ reserved word, part of the test following the
+ ‘if’ or ‘elif’ reserved words, part of a command executed in a ‘&&’
+ or ‘||’ list except the command following the final ‘&&’ or ‘||’,
+ any command in a pipeline but the last, (subject to the state of
+ the ‘pipefail’ shell option), or if the command's return status is
+ being inverted using ‘!’. These are the same conditions obeyed by
+ the ‘errexit’ (‘-e’) option.
+
+ When the shell is not interactive, signals ignored upon entry to a
+ non-interactive shell cannot be trapped or reset. Interactive
+ shells permit trapping signals ignored on entry. Trapped signals
+ that are not being ignored are reset to their original values in a
+ subshell or subshell environment when one is created.
+
+ The return status is zero unless a SIGSPEC does not specify a valid
+ signal; non-zero otherwise.
+
+‘true’
+ true
+
+ Does nothing, returns a 0 status.
+
+‘umask’
+ umask [-p] [-S] [MODE]
+
+ Set the shell process's file creation mask to MODE. If MODE begins
+ with a digit, it is interpreted as an octal number; if not, it is
+ interpreted as a symbolic mode mask similar to that accepted by the
+ ‘chmod’ command. If MODE is omitted, ‘umask’ prints the current
+ value of the mask. If the ‘-S’ option is supplied without a MODE
+ argument, ‘umask’ prints the mask in a symbolic format; the default
+ output is an octal number. If the ‘-p’ option is supplied, and
+ MODE is omitted, the output is in a form that may be reused as
+ input. The return status is zero if the mode is successfully
+ changed or if no MODE argument is supplied, and non-zero otherwise.
+
+ Note that when the mode is interpreted as an octal number, each
+ number of the umask is subtracted from ‘7’. Thus, a umask of ‘022’
+ results in permissions of ‘755’.
+
+‘unset’
+ unset [-fnv] [NAME]
+
+ Remove each variable or function NAME. If the ‘-v’ option is
+ given, each NAME refers to a shell variable and that variable is
+ removed. If the ‘-f’ option is given, the NAMEs refer to shell
+ functions, and the function definition is removed. If the ‘-n’
+ option is supplied, and NAME is a variable with the ‘nameref’
+ attribute, NAME will be unset rather than the variable it
+ references. ‘-n’ has no effect if the ‘-f’ option is supplied. If
+ no options are supplied, each NAME refers to a variable; if there
+ is no variable by that name, a function with that name, if any, is
+ unset. Readonly variables and functions may not be unset. When
+ variables or functions are removed, they are also removed from the
+ environment passed to subsequent commands. Some shell variables
+ may not be unset. Some shell variables lose their special behavior
+ if they are unset; such behavior is noted in the description of the
+ individual variables. The return status is zero unless a NAME is
+ readonly or may not be unset.
+
+\1f
+File: bash.info, Node: Bash Builtins, Next: Modifying Shell Behavior, Prev: Bourne Shell Builtins, Up: Shell Builtin Commands
+
+4.2 Bash Builtin Commands
+=========================
+
+This section describes builtin commands which are unique to or have been
+extended in Bash. Some of these commands are specified in the POSIX
+standard.
+
+‘alias’
+ alias [-p] [NAME[=VALUE] ...]
+
+ Without arguments or with the ‘-p’ option, ‘alias’ prints the list
+ of aliases on the standard output in a form that allows them to be
+ reused as input. If arguments are supplied, define an alias for
+ each NAME whose VALUE is given. If no VALUE is given, print the
+ name and value of the alias NAME. A trailing space in VALUE causes
+ the next word to be checked for alias substitution when the alias
+ is expanded during command parsing. ‘alias’ returns true unless a
+ NAME is given (without a corresponding =VALUE) for which no alias
+ has been defined. Aliases are described in *note Aliases::.
+
+‘bind’
+ bind [-m KEYMAP] [-lsvSVX]
+ bind [-m KEYMAP] [-q FUNCTION] [-u FUNCTION] [-r KEYSEQ]
+ bind [-m KEYMAP] -f FILENAME
+ bind [-m KEYMAP] -x KEYSEQ[: ]SHELL-COMMAND
+ bind [-m KEYMAP] KEYSEQ:FUNCTION-NAME
+ bind [-m KEYMAP] KEYSEQ:READLINE-COMMAND
+ bind [-m KEYMAP] -p|-P [READLINE-COMMAND]
+ bind READLINE-COMMAND-LINE
+
+ Display current Readline (*note Command Line Editing::) key and
+ function bindings, bind a key sequence to a Readline function or
+ macro or to a shell command, or set a Readline variable. Each
+ non-option argument is a key binding or command as it would appear
+ in a Readline initialization file (*note Readline Init File::), but
+ each binding or command must be passed as a separate argument;
+ e.g., ‘"\C-x\C-r":re-read-init-file’.
+
+ In the following descriptions, options that display output in a
+ form available to be re-read format their output as commands that
+ would appear in a Readline initialization file or that would be
+ supplied as individual arguments to a ‘bind’ command.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-m KEYMAP’
+ Use KEYMAP as the keymap to be affected by the subsequent
+ bindings. Acceptable KEYMAP names are ‘emacs’,
+ ‘emacs-standard’, ‘emacs-meta’, ‘emacs-ctlx’, ‘vi’, ‘vi-move’,
+ ‘vi-command’, and ‘vi-insert’. ‘vi’ is equivalent to
+ ‘vi-command’ (‘vi-move’ is also a synonym); ‘emacs’ is
+ equivalent to ‘emacs-standard’.
+
+ ‘-l’
+ List the names of all Readline functions.
+
+ ‘-p’
+ Display Readline function names and bindings in such a way
+ that they can be used as an argument to a subsequent ‘bind’
+ command or in a Readline initialization file. If arguments
+ remain after option processing, ‘bind’ treats them as readline
+ command names and restricts output to those names.
+
+ ‘-P’
+ List current Readline function names and bindings. If
+ arguments remain after option processing, ‘bind’ treats them
+ as readline command names and restricts output to those names.
+
+ ‘-s’
+ Display Readline key sequences bound to macros and the strings
+ they output in such a way that they can be used as an argument
+ to a subsequent ‘bind’ command or in a Readline initialization
+ file.
+
+ ‘-S’
+ Display Readline key sequences bound to macros and the strings
+ they output.
+
+ ‘-v’
+ Display Readline variable names and values in such a way that
+ they can be used as an argument to a subsequent ‘bind’ command
+ or in a Readline initialization file.
+
+ ‘-V’
+ List current Readline variable names and values.
+
+ ‘-f FILENAME’
+ Read key bindings from FILENAME.
+
+ ‘-q FUNCTION’
+ Display key sequences that invoke the named Readline FUNCTION.
+
+ ‘-u FUNCTION’
+ Unbind all key sequences bound to the named Readline FUNCTION.
+
+ ‘-r KEYSEQ’
+ Remove any current binding for KEYSEQ.
+
+ ‘-x KEYSEQ:SHELL-COMMAND’
+ Cause SHELL-COMMAND to be executed whenever KEYSEQ is entered.
+ The separator between KEYSEQ and SHELL-COMMAND is either
+ whitespace or a colon optionally followed by whitespace. If
+ the separator is whitespace, SHELL-COMMAND must be enclosed in
+ double quotes and Readline expands any of its special
+ backslash-escapes in SHELL-COMMAND before saving it. If the
+ separator is a colon, any enclosing double quotes are
+ optional, and Readline does not expand the command string
+ before saving it. Since the entire key binding expression
+ must be a single argument, it should be enclosed in single
+ quotes. When SHELL-COMMAND is executed, the shell sets the
+ ‘READLINE_LINE’ variable to the contents of the Readline line
+ buffer and the ‘READLINE_POINT’ and ‘READLINE_MARK’ variables
+ to the current location of the insertion point and the saved
+ insertion point (the MARK), respectively. The shell assigns
+ any numeric argument the user supplied to the
+ ‘READLINE_ARGUMENT’ variable. If there was no argument, that
+ variable is not set. If the executed command changes the
+ value of any of ‘READLINE_LINE’, ‘READLINE_POINT’, or
+ ‘READLINE_MARK’, those new values will be reflected in the
+ editing state.
+
+ ‘-X’
+ List all key sequences bound to shell commands and the
+ associated commands in a format that can be reused as an
+ argument to a subsequent ‘bind’ command.
+
+ The return status is zero unless an invalid option is supplied or
+ an error occurs.
+
+‘builtin’
+ builtin [SHELL-BUILTIN [ARGS]]
+
+ Execute the specified shell builtin SHELL-BUILTIN, passing it ARGS,
+ and return its exit status. This is useful when defining a shell
+ function with the same name as a shell builtin, retaining the
+ functionality of the builtin within the function. The return
+ status is non-zero if SHELL-BUILTIN is not a shell builtin command.
+
+‘caller’
+ caller [EXPR]
+
+ Returns the context of any active subroutine call (a shell function
+ or a script executed with the ‘.’ or ‘source’ builtins).
+
+ Without EXPR, ‘caller’ displays the line number and source filename
+ of the current subroutine call. If a non-negative integer is
+ supplied as EXPR, ‘caller’ displays the line number, subroutine
+ name, and source file corresponding to that position in the current
+ execution call stack. This extra information may be used, for
+ example, to print a stack trace. The current frame is frame 0.
+
+ The return value is 0 unless the shell is not executing a
+ subroutine call or EXPR does not correspond to a valid position in
+ the call stack.
+
+‘command’
+ command [-pVv] COMMAND [ARGUMENTS ...]
+
+ The ‘command’ builtin runs COMMAND with ARGUMENTS ignoring any
+ shell function named COMMAND. Only shell builtin commands or
+ commands found by searching the ‘PATH’ are executed. If there is a
+ shell function named ‘ls’, running ‘command ls’ within the function
+ will execute the external command ‘ls’ instead of calling the
+ function recursively. The ‘-p’ option means to use a default value
+ for ‘PATH’ that is guaranteed to find all of the standard
+ utilities. The return status in this case is 127 if COMMAND cannot
+ be found or an error occurred, and the exit status of COMMAND
+ otherwise.
+
+ If either the ‘-V’ or ‘-v’ option is supplied, ‘command’ prints a
+ description of COMMAND. The ‘-v’ option displays a single word
+ indicating the command or file name used to invoke COMMAND; the
+ ‘-V’ option produces a more verbose description. In this case, the
+ return status is zero if COMMAND is found, and non-zero if not.
+
+‘declare’
+ declare [-aAfFgiIlnrtux] [-p] [NAME[=VALUE] ...]
+
+ Declare variables and give them attributes. If no NAMEs are given,
+ then display the values of variables or shell functions instead.
+
+ The ‘-p’ option will display the attributes and values of each
+ NAME. When ‘-p’ is used with NAME arguments, additional options,
+ other than ‘-f’ and ‘-F’, are ignored.
+
+ When ‘-p’ is supplied without NAME arguments, ‘declare’ will
+ display the attributes and values of all variables having the
+ attributes specified by the additional options. If no other
+ options are supplied with ‘-p’, ‘declare’ will display the
+ attributes and values of all shell variables. The ‘-f’ option
+ restricts the display to shell functions.
+
+ The ‘-F’ option inhibits the display of function definitions; only
+ the function name and attributes are printed. If the ‘extdebug’
+ shell option is enabled using ‘shopt’ (*note The Shopt Builtin::),
+ the source file name and line number where each NAME is defined are
+ displayed as well. ‘-F’ implies ‘-f’.
+
+ The ‘-g’ option forces variables to be created or modified at the
+ global scope, even when ‘declare’ is executed in a shell function.
+ It is ignored in when ‘declare’ is not executed in a shell
+ function.
+
+ The ‘-I’ option causes local variables to inherit the attributes
+ (except the ‘nameref’ attribute) and value of any existing variable
+ with the same NAME at a surrounding scope. If there is no existing
+ variable, the local variable is initially unset.
+
+ The following options can be used to restrict output to variables
+ with the specified attributes or to give variables attributes:
+
+ ‘-a’
+ Each NAME is an indexed array variable (*note Arrays::).
+
+ ‘-A’
+ Each NAME is an associative array variable (*note Arrays::).
+
+ ‘-f’
+ Each NAME refers to a shell function.
+
+ ‘-i’
+ The variable is to be treated as an integer; arithmetic
+ evaluation (*note Shell Arithmetic::) is performed when the
+ variable is assigned a value.
+
+ ‘-l’
+ When the variable is assigned a value, all upper-case
+ characters are converted to lower-case. The upper-case
+ attribute is disabled.
+
+ ‘-n’
+ Give each NAME the ‘nameref’ attribute, making it a name
+ reference to another variable. That other variable is defined
+ by the value of NAME. All references, assignments, and
+ attribute modifications to NAME, except for those using or
+ changing the ‘-n’ attribute itself, are performed on the
+ variable referenced by NAME's value. The nameref attribute
+ cannot be applied to array variables.
+
+ ‘-r’
+ Make NAMEs readonly. These names cannot then be assigned
+ values by subsequent assignment statements or unset.
+
+ ‘-t’
+ Give each NAME the ‘trace’ attribute. Traced functions
+ inherit the ‘DEBUG’ and ‘RETURN’ traps from the calling shell.
+ The trace attribute has no special meaning for variables.
+
+ ‘-u’
+ When the variable is assigned a value, all lower-case
+ characters are converted to upper-case. The lower-case
+ attribute is disabled.
+
+ ‘-x’
+ Mark each NAME for export to subsequent commands via the
+ environment.
+
+ Using ‘+’ instead of ‘-’ turns off the specified attribute instead,
+ with the exceptions that ‘+a’ and ‘+A’ may not be used to destroy
+ array variables and ‘+r’ will not remove the readonly attribute.
+
+ When used in a function, ‘declare’ makes each NAME local, as with
+ the ‘local’ command, unless the ‘-g’ option is supplied. If a
+ variable name is followed by =VALUE, the value of the variable is
+ set to VALUE.
+
+ When using ‘-a’ or ‘-A’ and the compound assignment syntax to
+ create array variables, additional attributes do not take effect
+ until subsequent assignments.
+
+ The return status is zero unless an invalid option is encountered,
+ an attempt is made to define a function using ‘-f foo=bar’, an
+ attempt is made to assign a value to a readonly variable, an
+ attempt is made to assign a value to an array variable without
+ using the compound assignment syntax (*note Arrays::), one of the
+ NAMEs is not a valid shell variable name, an attempt is made to
+ turn off readonly status for a readonly variable, an attempt is
+ made to turn off array status for an array variable, or an attempt
+ is made to display a non-existent function with ‘-f’.
+
+‘echo’
+ echo [-neE] [ARG ...]
+
+ Output the ARGs, separated by spaces, terminated with a newline.
+ The return status is 0 unless a write error occurs. If ‘-n’ is
+ specified, the trailing newline is not printed.
+
+ If the ‘-e’ option is given, ‘echo’ interprets the following
+ backslash-escaped characters. The ‘-E’ option disables
+ interpretation of these escape characters, even on systems where
+ they are interpreted by default. The ‘xpg_echo’ shell option
+ determines whether or not ‘echo’ interprets any options and expands
+ these escape characters. ‘echo’ does not interpret ‘--’ to mean
+ the end of options.
+
+ ‘echo’ interprets the following escape sequences:
+ ‘\a’
+ alert (bell)
+ ‘\b’
+ backspace
+ ‘\c’
+ suppress further output
+ ‘\e’
+ ‘\E’
+ escape
+ ‘\f’
+ form feed
+ ‘\n’
+ new line
+ ‘\r’
+ carriage return
+ ‘\t’
+ horizontal tab
+ ‘\v’
+ vertical tab
+ ‘\\’
+ backslash
+ ‘\0NNN’
+ The eight-bit character whose value is the octal value NNN
+ (zero to three octal digits).
+ ‘\xHH’
+ The eight-bit character whose value is the hexadecimal value
+ HH (one or two hex digits).
+ ‘\uHHHH’
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHH (one to four hex digits).
+ ‘\UHHHHHHHH’
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHHHHHH (one to eight hex digits).
+
+ ‘echo’ writes any unrecognized backslash-escaped characters
+ unchanged.
+
+‘enable’
+ enable [-a] [-dnps] [-f FILENAME] [NAME ...]
+
+ Enable and disable builtin shell commands. Disabling a builtin
+ allows an executable file which has the same name as a shell
+ builtin to be executed without specifying a full pathname, even
+ though the shell normally searches for builtins before files.
+
+ If ‘-n’ is supplied, the NAMEs are disabled. Otherwise NAMEs are
+ enabled. For example, to use the ‘test’ binary found using ‘$PATH’
+ instead of the shell builtin version, type ‘enable -n test’.
+
+ If the ‘-p’ option is supplied, or no NAME arguments are supplied,
+ print a list of shell builtins. With no other arguments, the list
+ consists of all enabled shell builtins. The ‘-n’ option means to
+ print only disabled builtins. The ‘-a’ option means to list each
+ builtin with an indication of whether or not it is enabled. The
+ ‘-s’ option means to restrict ‘enable’ to the POSIX special
+ builtins.
+
+ The ‘-f’ option means to load the new builtin command NAME from
+ shared object FILENAME, on systems that support dynamic loading.
+ If FILENAME does not contain a slash. Bash will use the value of
+ the ‘BASH_LOADABLES_PATH’ variable as a colon-separated list of
+ directories in which to search for FILENAME. The default for
+ ‘BASH_LOADABLES_PATH’ is system-dependent, and may include "." to
+ force a search of the current directory. The ‘-d’ option will
+ delete a builtin loaded with ‘-f’. If ‘-s’ is used with ‘-f’, the
+ new builtin becomes a POSIX special builtin (*note Special
+ Builtins::).
+
+ If no options are supplied and a NAME is not a shell builtin,
+ ‘enable’ will attempt to load NAME from a shared object named NAME,
+ as if the command were ‘enable -f NAME NAME’.
+
+ The return status is zero unless a NAME is not a shell builtin or
+ there is an error loading a new builtin from a shared object.
+
+‘help’
+ help [-dms] [PATTERN]
+
+ Display helpful information about builtin commands. If PATTERN is
+ specified, ‘help’ gives detailed help on all commands matching
+ PATTERN as described below; otherwise it displays a list of all
+ builtins and shell compound commands.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-d’
+ Display a short description of each PATTERN
+ ‘-m’
+ Display the description of each PATTERN in a manpage-like
+ format
+ ‘-s’
+ Display only a short usage synopsis for each PATTERN
+
+ If PATTERN contains pattern matching characters (*note Pattern
+ Matching::) it's treated as a shell pattern and ‘help’ prints the
+ description of each help topic matching PATTERN.
+
+ If not, and PATTERN exactly matches the name of a help topic,
+ ‘help’ prints the description associated with that topic.
+ Otherwise, ‘help’ performs prefix matching and prints the
+ descriptions of all matching help topics.
+
+ The return status is zero unless no command matches PATTERN.
+
+‘let’
+ let EXPRESSION [EXPRESSION ...]
+
+ The ‘let’ builtin allows arithmetic to be performed on shell
+ variables. Each EXPRESSION is evaluated as an arithmetic
+ expression according to the rules given below in *note Shell
+ Arithmetic::. If the last EXPRESSION evaluates to 0, ‘let’ returns
+ 1; otherwise ‘let’ returns 0.
+
+‘local’
+ local [OPTION] NAME[=VALUE] ...
+
+ For each argument, create a local variable named NAME, and assign
+ it VALUE. The OPTION can be any of the options accepted by
+ ‘declare’. ‘local’ can only be used within a function; it makes
+ the variable NAME have a visible scope restricted to that function
+ and its children. It is an error to use ‘local’ when not within a
+ function.
+
+ If NAME is ‘-’, it makes the set of shell options local to the
+ function in which ‘local’ is invoked: any shell options changed
+ using the ‘set’ builtin inside the function after the call to
+ ‘local’ are restored to their original values when the function
+ returns. The restore is performed as if a series of ‘set’ commands
+ were executed to restore the values that were in place before the
+ function.
+
+ With no operands, ‘local’ writes a list of local variables to the
+ standard output.
+
+ The return status is zero unless ‘local’ is used outside a
+ function, an invalid NAME is supplied, or NAME is a readonly
+ variable.
+
+‘logout’
+ logout [N]
+
+ Exit a login shell, returning a status of N to the shell's parent.
+
+‘mapfile’
+ mapfile [-d DELIM] [-n COUNT] [-O ORIGIN] [-s COUNT]
+ [-t] [-u FD] [-C CALLBACK] [-c QUANTUM] [ARRAY]
+
+ Read lines from the standard input, or from file descriptor FD if
+ the ‘-u’ option is supplied, into the indexed array variable ARRAY.
+ The variable ‘MAPFILE’ is the default ARRAY. Options, if supplied,
+ have the following meanings:
+
+ ‘-d’
+ Use the first character of DELIM to terminate each input line,
+ rather than newline. If DELIM is the empty string, ‘mapfile’
+ will terminate a line when it reads a NUL character.
+ ‘-n’
+ Copy at most COUNT lines. If COUNT is 0, copy all lines.
+ ‘-O’
+ Begin assigning to ARRAY at index ORIGIN. The default index
+ is 0.
+ ‘-s’
+ Discard the first COUNT lines read.
+ ‘-t’
+ Remove a trailing DELIM (default newline) from each line read.
+ ‘-u’
+ Read lines from file descriptor FD instead of the standard
+ input.
+ ‘-C’
+ Evaluate CALLBACK each time QUANTUM lines are read. The ‘-c’
+ option specifies QUANTUM.
+ ‘-c’
+ Specify the number of lines read between each call to
+ CALLBACK.
+
+ If ‘-C’ is specified without ‘-c’, the default quantum is 5000.
+ When CALLBACK is evaluated, it is supplied the index of the next
+ array element to be assigned and the line to be assigned to that
+ element as additional arguments. CALLBACK is evaluated after the
+ line is read but before the array element is assigned.
+
+ If not supplied with an explicit origin, ‘mapfile’ will clear ARRAY
+ before assigning to it.
+
+ ‘mapfile’ returns zero unless an invalid option or option argument
+ is supplied, ARRAY is invalid or unassignable, or if ARRAY is not
+ an indexed array.
+
+‘printf’
+ printf [-v VAR] FORMAT [ARGUMENTS]
+
+ Write the formatted ARGUMENTS to the standard output under the
+ control of the FORMAT. The ‘-v’ option assigns the output to the
+ variable VAR rather than printing it to the standard output.
+
+ The FORMAT is a character string which contains three types of
+ objects: plain characters, which are simply copied to standard
+ output, character escape sequences, which are converted and copied
+ to the standard output, and format specifications, each of which
+ causes printing of the next successive ARGUMENT. In addition to
+ the standard ‘printf(3)’ format characters ‘cCsSndiouxXeEfFgGaA’,
+ ‘printf’ interprets the following additional format specifiers:
+
+ ‘%b’
+ Causes ‘printf’ to expand backslash escape sequences in the
+ corresponding ARGUMENT in the same way as ‘echo -e’ (*note
+ Bash Builtins::).
+ ‘%q’
+ Causes ‘printf’ to output the corresponding ARGUMENT in a
+ format that can be reused as shell input. ‘%q’ and ‘%Q’P use
+ the ANSI-C quoting style (*note ANSI-C Quoting::) if any
+ characters in the argument string require it, and backslash
+ quoting otherwise. If the format string uses the ‘printf’
+ _alternate form_, these two formats quote the argument string
+ using single quotes.
+
+ ‘%Q’
+ like ‘%q’, but applies any supplied precision to the ARGUMENT
+ before quoting it.
+
+ ‘%(DATEFMT)T’
+ Causes ‘printf’ to output the date-time string resulting from
+ using DATEFMT as a format string for ‘strftime’(3). The
+ corresponding ARGUMENT is an integer representing the number
+ of seconds since the epoch. This format specifier recognizes
+ Two special argument values: -1 represents the current time,
+ and -2 represents the time the shell was invoked. If no
+ argument is specified, conversion behaves as if -1 had been
+ supplied. This is an exception to the usual ‘printf’
+ behavior.
+
+ The %b, %q, and %T format specifiers all use the field width and
+ precision arguments from the format specification and write that
+ many bytes from (or use that wide a field for) the expanded
+ argument, which usually contains more characters than the original.
+
+ The %n format specifier accepts a corresponding argument that is
+ treated as a shell variable name.
+
+ The %s and %c format specifiers accept an l (long) modifier, which
+ forces them to convert the argument string to a wide-character
+ string and apply any supplied field width and precision in terms of
+ characters, not bytes. The %S and %C format specifiers are
+ equivalent to %ls and %lc, respectively.
+
+ Arguments to non-string format specifiers are treated as C language
+ constants, except that a leading plus or minus sign is allowed, and
+ if the leading character is a single or double quote, the value is
+ the numeric value of the following character, using the current
+ locale.
+
+ The FORMAT is reused as necessary to consume all of the ARGUMENTS.
+ If the FORMAT requires more ARGUMENTS than are supplied, the extra
+ format specifications behave as if a zero value or null string, as
+ appropriate, had been supplied. The return value is zero on
+ success, non-zero if an invalid option is supplied or a write or
+ assignment error occurs.
+
+‘read’
+ read [-Eers] [-a ANAME] [-d DELIM] [-i TEXT] [-n NCHARS]
+ [-N NCHARS] [-p PROMPT] [-t TIMEOUT] [-u FD] [NAME ...]
+
+ Read one line from the standard input, or from the file descriptor
+ FD supplied as an argument to the ‘-u’ option, split it into words
+ as described above in *note Word Splitting::, and assign the first
+ word to the first NAME, the second word to the second NAME, and so
+ on. If there are more words than names, the remaining words and
+ their intervening delimiters are assigned to the last NAME. If
+ there are fewer words read from the input stream than names, the
+ remaining names are assigned empty values. The characters in the
+ value of the ‘IFS’ variable are used to split the line into words
+ using the same rules the shell uses for expansion (described above
+ in *note Word Splitting::). The backslash character ‘\’ removes
+ any special meaning for the next character read and is used for
+ line continuation.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-a ANAME’
+ The words are assigned to sequential indices of the array
+ variable ANAME, starting at 0. All elements are removed from
+ ANAME before the assignment. Other NAME arguments are
+ ignored.
+
+ ‘-d DELIM’
+ The first character of DELIM terminates the input line, rather
+ than newline. If DELIM is the empty string, ‘read’ will
+ terminate a line when it reads a NUL character.
+
+ ‘-e’
+ If the standard input is coming from a terminal, ‘read’ uses
+ Readline (*note Command Line Editing::) to obtain the line.
+ Readline uses the current (or default, if line editing was not
+ previously active) editing settings, but uses Readline's
+ default filename completion.
+
+ ‘-E’
+ If the standard input is coming from a terminal, ‘read’ uses
+ Readline (*note Command Line Editing::) to obtain the line.
+ Readline uses the current (or default, if line editing was not
+ previously active) editing settings, but uses Bash's default
+ completion, including programmable completion.
+
+ ‘-i TEXT’
+ If Readline is being used to read the line, ‘read’ places TEXT
+ into the editing buffer before editing begins.
+
+ ‘-n NCHARS’
+ ‘read’ returns after reading NCHARS characters rather than
+ waiting for a complete line of input, unless it encounters EOF
+ or ‘read’ times out, but honors a delimiter if it reads fewer
+ than NCHARS characters before the delimiter.
+
+ ‘-N NCHARS’
+ ‘read’ returns after reading exactly NCHARS characters rather
+ than waiting for a complete line of input, unless it
+ encounters EOF or ‘read’ times out. Delimiter characters in
+ the input are not treated specially and do not cause ‘read’ to
+ return until it has read NCHARS characters. The result is not
+ split on the characters in ‘IFS’; the intent is that the
+ variable is assigned exactly the characters read (with the
+ exception of backslash; see the ‘-r’ option below).
+
+ ‘-p PROMPT’
+ Display PROMPT, without a trailing newline, before attempting
+ to read any input, but only if input is coming from a
+ terminal.
+
+ ‘-r’
+ If this option is given, backslash does not act as an escape
+ character. The backslash is considered to be part of the
+ line. In particular, a backslash-newline pair may not then be
+ used as a line continuation.
+
+ ‘-s’
+ Silent mode. If input is coming from a terminal, characters
+ are not echoed.
+
+ ‘-t TIMEOUT’
+ Cause ‘read’ to time out and return failure if it does not
+ read a complete line of input (or a specified number of
+ characters) within TIMEOUT seconds. TIMEOUT may be a decimal
+ number with a fractional portion following the decimal point.
+ This option is only effective if ‘read’ is reading input from
+ a terminal, pipe, or other special file; it has no effect when
+ reading from regular files. If ‘read’ times out, it saves any
+ partial input read into the specified variable NAME, and
+ returns a status greater than 128. If TIMEOUT is 0, ‘read’
+ returns immediately, without trying to read any data. In this
+ case, the exit status is 0 if input is available on the
+ specified file descriptor, or the read will return EOF,
+ non-zero otherwise.
+
+ ‘-u FD’
+ Read input from file descriptor FD instead of the standard
+ input.
+
+ Other than the case where DELIM is the empty string, ‘read’ ignores
+ any NUL characters in the input.
+
+ If no NAMEs are supplied, ‘read’ assigns the line read, without the
+ ending delimiter but otherwise unmodified, to the variable ‘REPLY’.
+
+ The exit status is zero, unless end-of-file is encountered, ‘read’
+ times out (in which case the status is greater than 128), a
+ variable assignment error (such as assigning to a readonly
+ variable) occurs, or an invalid file descriptor is supplied as the
+ argument to ‘-u’.
+
+‘readarray’
+ readarray [-d DELIM] [-n COUNT] [-O ORIGIN] [-s COUNT]
+ [-t] [-u FD] [-C CALLBACK] [-c QUANTUM] [ARRAY]
+
+ Read lines from the standard input into the indexed array variable
+ ARRAY, or from file descriptor FD if the ‘-u’ option is supplied.
+
+ A synonym for ‘mapfile’.
+
+‘source’
+ source [-p PATH] FILENAME [ARGUMENTS]
+
+ A synonym for ‘.’ (*note Bourne Shell Builtins::).
+
+‘type’
+ type [-afptP] [NAME ...]
+
+ Indicate how each NAME would be interpreted if used as a command
+ name.
+
+ If the ‘-t’ option is used, ‘type’ prints a single word which is
+ one of ‘alias’, ‘keyword’, ‘function’, ‘builtin’, or ‘file’, if
+ NAME is an alias, shell reserved word, shell function, shell
+ builtin, or executable file, respectively. If the NAME is not
+ found, ‘type’ prints nothing and returns a failure status.
+
+ If the ‘-p’ option is used, ‘type’ either returns the name of the
+ executable file that would be found by searching ‘$PATH’ for
+ ‘name’, or nothing if ‘-t’ would not return ‘file’.
+
+ The ‘-P’ option forces a path search for each NAME, even if ‘-t’
+ would not return ‘file’.
+
+ If a NAME is present in the table of hashed commands, options ‘-p’
+ and ‘-P’ print the hashed value, which is not necessarily the file
+ that appears first in ‘$PATH’.
+
+ If the ‘-a’ option is used, ‘type’ returns all of the places that
+ contain a command named NAME. This includes aliases, reserved
+ words, functions, and builtins, but the path search options (‘-p’
+ and ‘-P’) can be supplied to restrict the output to executable
+ files. If ‘-a’ is supplied with ‘-p’, ‘type’ does not look in the
+ table of hashed commands, and only performs a ‘PATH’ search for
+ NAME.
+
+ If the ‘-f’ option is used, ‘type’ does not attempt to find shell
+ functions, as with the ‘command’ builtin.
+
+ The return status is zero if all of the NAMEs are found, non-zero
+ if any are not found.
+
+‘typeset’
+ typeset [-afFgrxilnrtux] [-p] [NAME[=VALUE] ...]
+
+ The ‘typeset’ command is supplied for compatibility with the Korn
+ shell. It is a synonym for the ‘declare’ builtin command.
+
+‘ulimit’
+ ulimit [-HS] -a
+ ulimit [-HS] [-bcdefiklmnpqrstuvxPRT] [LIMIT]
+
+ ‘ulimit’ provides control over the resources available to the shell
+ and to processes it starts, on systems that allow such control. If
+ an option is given, it is interpreted as follows:
+
+ ‘-S’
+ Change and report the soft limit associated with a resource.
+
+ ‘-H’
+ Change and report the hard limit associated with a resource.
+
+ ‘-a’
+ Report all current limits; no limits are set.
+
+ ‘-b’
+ The maximum socket buffer size.
+
+ ‘-c’
+ The maximum size of core files created.
+
+ ‘-d’
+ The maximum size of a process's data segment.
+
+ ‘-e’
+ The maximum scheduling priority ("nice").
+
+ ‘-f’
+ The maximum size of files written by the shell and its
+ children.
+
+ ‘-i’
+ The maximum number of pending signals.
+
+ ‘-k’
+ The maximum number of kqueues that may be allocated.
+
+ ‘-l’
+ The maximum size that may be locked into memory.
+
+ ‘-m’
+ The maximum resident set size (many systems do not honor this
+ limit).
+
+ ‘-n’
+ The maximum number of open file descriptors (most systems do
+ not allow this value to be set).
+
+ ‘-p’
+ The pipe buffer size.
+
+ ‘-q’
+ The maximum number of bytes in POSIX message queues.
+
+ ‘-r’
+ The maximum real-time scheduling priority.
+
+ ‘-s’
+ The maximum stack size.
+
+ ‘-t’
+ The maximum amount of cpu time in seconds.
+
+ ‘-u’
+ The maximum number of processes available to a single user.
+
+ ‘-v’
+ The maximum amount of virtual memory available to the shell,
+ and, on some systems, to its children.
+
+ ‘-x’
+ The maximum number of file locks.
+
+ ‘-P’
+ The maximum number of pseudoterminals.
+
+ ‘-R’
+ The maximum time a real-time process can run before blocking,
+ in microseconds.
+
+ ‘-T’
+ The maximum number of threads.
+
+ If LIMIT is supplied, and the ‘-a’ option is not used, LIMIT is the
+ new value of the specified resource. The special LIMIT values
+ ‘hard’, ‘soft’, and ‘unlimited’ stand for the current hard limit,
+ the current soft limit, and no limit, respectively. A hard limit
+ cannot be increased by a non-root user once it is set; a soft limit
+ may be increased up to the value of the hard limit. Otherwise,
+ ‘ulimit’ prints the current value of the soft limit for the
+ specified resource, unless the ‘-H’ option is supplied. When more
+ than one resource is specified, the limit name and unit, if
+ appropriate, are printed before the value. When setting new
+ limits, if neither ‘-H’ nor ‘-S’ is supplied, ‘ulimit’ sets both
+ the hard and soft limits. If no option is supplied, then ‘-f’ is
+ assumed.
+
+ Values are in 1024-byte increments, except for ‘-t’, which is in
+ seconds; ‘-R’, which is in microseconds; ‘-p’, which is in units of
+ 512-byte blocks; ‘-P’, ‘-T’, ‘-b’, ‘-k’, ‘-n’ and ‘-u’, which are
+ unscaled values; and, when in POSIX mode (*note Bash POSIX Mode::),
+ ‘-c’ and ‘-f’, which are in 512-byte increments.
+
+ The return status is zero unless an invalid option or argument is
+ supplied, or an error occurs while setting a new limit.
+
+‘unalias’
+ unalias [-a] [NAME ... ]
+
+ Remove each NAME from the list of aliases. If ‘-a’ is supplied,
+ remove all aliases. The return value is true unless a supplied
+ NAME is not a defined alias. Aliases are described in *note
+ Aliases::.
+
+\1f
+File: bash.info, Node: Modifying Shell Behavior, Next: Special Builtins, Prev: Bash Builtins, Up: Shell Builtin Commands
+
+4.3 Modifying Shell Behavior
+============================
+
+* Menu:
+
+* The Set Builtin:: Change the values of shell attributes and
+ positional parameters.
+* The Shopt Builtin:: Modify shell optional behavior.
+
+\1f
+File: bash.info, Node: The Set Builtin, Next: The Shopt Builtin, Up: Modifying Shell Behavior
+
+4.3.1 The Set Builtin
+---------------------
+
+This builtin is so complicated that it deserves its own section. ‘set’
+allows you to change the values of shell options and set the positional
+parameters, or to display the names and values of shell variables.
+
+‘set’
+ set [-abefhkmnptuvxBCEHPT] [-o OPTION-NAME] [--] [-] [ARGUMENT ...]
+ set [+abefhkmnptuvxBCEHPT] [+o OPTION-NAME] [--] [-] [ARGUMENT ...]
+ set -o
+ set +o
+
+ If no options or arguments are supplied, ‘set’ displays the names
+ and values of all shell variables and functions, sorted according
+ to the current locale, in a format that may be reused as input for
+ setting or resetting the currently-set variables. Read-only
+ variables cannot be reset. In POSIX mode, only shell variables are
+ listed.
+
+ When options are supplied, they set or unset shell attributes. Any
+ arguments remaining after option processing replace the positional
+ parameters.
+
+ Options, if specified, have the following meanings:
+
+ ‘-a’
+ Each variable or function that is created or modified is given
+ the export attribute and marked for export to the environment
+ of subsequent commands.
+
+ ‘-b’
+ Cause the status of terminated background jobs to be reported
+ immediately, rather than before printing the next primary
+ prompt or, under some circumstances, when a foreground command
+ exits. This is effective only when job control is enabled.
+
+ ‘-e’
+ Exit immediately if a pipeline (*note Pipelines::), which may
+ consist of a single simple command (*note Simple Commands::),
+ a list (*note Lists::), or a compound command (*note Compound
+ Commands::) returns a non-zero status. The shell does not
+ exit if the command that fails is part of the command list
+ immediately following a ‘while’ or ‘until’ reserved word, part
+ of the test in an ‘if’ statement, part of any command executed
+ in a ‘&&’ or ‘||’ list except the command following the final
+ ‘&&’ or ‘||’, any command in a pipeline but the last (subject
+ to the state of the ‘pipefail’ shell option), or if the
+ command's return status is being inverted with ‘!’. If a
+ compound command other than a subshell returns a non-zero
+ status because a command failed while ‘-e’ was being ignored,
+ the shell does not exit. A trap on ‘ERR’, if set, is executed
+ before the shell exits.
+
+ This option applies to the shell environment and each subshell
+ environment separately (*note Command Execution
+ Environment::), and may cause subshells to exit before
+ executing all the commands in the subshell.
+
+ If a compound command or shell function executes in a context
+ where ‘-e’ is being ignored, none of the commands executed
+ within the compound command or function body will be affected
+ by the ‘-e’ setting, even if ‘-e’ is set and a command returns
+ a failure status. If a compound command or shell function
+ sets ‘-e’ while executing in a context where ‘-e’ is ignored,
+ that setting will not have any effect until the compound
+ command or the command containing the function call completes.
+
+ ‘-f’
+ Disable filename expansion (globbing).
+
+ ‘-h’
+ Locate and remember (hash) commands as they are looked up for
+ execution. This option is enabled by default.
+
+ ‘-k’
+ All arguments in the form of assignment statements are placed
+ in the environment for a command, not just those that precede
+ the command name.
+
+ ‘-m’
+ Job control is enabled (*note Job Control::). All processes
+ run in a separate process group. When a background job
+ completes, the shell prints a line containing its exit status.
+
+ ‘-n’
+ Read commands but do not execute them. This may be used to
+ check a script for syntax errors. This option is ignored by
+ interactive shells.
+
+ ‘-o OPTION-NAME’
+
+ Set the option corresponding to OPTION-NAME. If ‘-o’ is
+ supplied with no OPTION-NAME, ‘set’ prints the current shell
+ options settings. If ‘+o’ is supplied with no OPTION-NAME,
+ ‘set’ prints a series of ‘set’ commands to recreate the
+ current option settings on the standard output. Valid option
+ names are:
+
+ ‘allexport’
+ Same as ‘-a’.
+
+ ‘braceexpand’
+ Same as ‘-B’.
+
+ ‘emacs’
+ Use an ‘emacs’-style line editing interface (*note
+ Command Line Editing::). This also affects the editing
+ interface used for ‘read -e’.
+
+ ‘errexit’
+ Same as ‘-e’.
+
+ ‘errtrace’
+ Same as ‘-E’.
+
+ ‘functrace’
+ Same as ‘-T’.
+
+ ‘hashall’
+ Same as ‘-h’.
+
+ ‘histexpand’
+ Same as ‘-H’.
+
+ ‘history’
+ Enable command history, as described in *note Bash
+ History Facilities::. This option is on by default in
+ interactive shells.
+
+ ‘ignoreeof’
+ An interactive shell will not exit upon reading EOF.
+
+ ‘keyword’
+ Same as ‘-k’.
+
+ ‘monitor’
+ Same as ‘-m’.
+
+ ‘noclobber’
+ Same as ‘-C’.
+
+ ‘noexec’
+ Same as ‘-n’.
+
+ ‘noglob’
+ Same as ‘-f’.
+
+ ‘nolog’
+ Currently ignored.
+
+ ‘notify’
+ Same as ‘-b’.
+
+ ‘nounset’
+ Same as ‘-u’.
+
+ ‘onecmd’
+ Same as ‘-t’.
+
+ ‘physical’
+ Same as ‘-P’.
+
+ ‘pipefail’
+ If set, the return value of a pipeline is the value of
+ the last (rightmost) command to exit with a non-zero
+ status, or zero if all commands in the pipeline exit
+ successfully. This option is disabled by default.
+
+ ‘posix’
+ Enable POSIX mode; change the behavior of Bash where the
+ default operation differs from the POSIX standard to
+ match the standard (*note Bash POSIX Mode::). This is
+ intended to make Bash behave as a strict superset of that
+ standard.
+
+ ‘privileged’
+ Same as ‘-p’.
+
+ ‘verbose’
+ Same as ‘-v’.
+
+ ‘vi’
+ Use a ‘vi’-style line editing interface. This also
+ affects the editing interface used for ‘read -e’.
+
+ ‘xtrace’
+ Same as ‘-x’.
+
+ ‘-p’
+ Turn on privileged mode. In this mode, the ‘$BASH_ENV’ and
+ ‘$ENV’ files are not processed, shell functions are not
+ inherited from the environment, and the ‘SHELLOPTS’,
+ ‘BASHOPTS’, ‘CDPATH’ and ‘GLOBIGNORE’ variables, if they
+ appear in the environment, are ignored. If the shell is
+ started with the effective user (group) id not equal to the
+ real user (group) id, and the ‘-p’ option is not supplied,
+ these actions are taken and the effective user id is set to
+ the real user id. If the ‘-p’ option is supplied at startup,
+ the effective user id is not reset. Turning this option off
+ causes the effective user and group ids to be set to the real
+ user and group ids.
+
+ ‘-r’
+ Enable restricted shell mode (*note The Restricted Shell::).
+ This option cannot be unset once it has been set.
+
+ ‘-t’
+ Exit after reading and executing one command.
+
+ ‘-u’
+ Treat unset variables and parameters other than the special
+ parameters ‘@’ or ‘*’, or array variables subscripted with ‘@’
+ or ‘*’, as an error when performing parameter expansion. An
+ error message will be written to the standard error, and a
+ non-interactive shell will exit.
+
+ ‘-v’
+ Print shell input lines to standard error as they are read.
+
+ ‘-x’
+ Print a trace of simple commands, ‘for’ commands, ‘case’
+ commands, ‘select’ commands, and arithmetic ‘for’ commands and
+ their arguments or associated word lists to the standard error
+ after they are expanded and before they are executed. The
+ shell prints the expanded value of the ‘PS4’ variable before
+ the command and its expanded arguments.
+
+ ‘-B’
+ The shell will perform brace expansion (*note Brace
+ Expansion::). This option is on by default.
+
+ ‘-C’
+ Prevent output redirection using ‘>’, ‘>&’, and ‘<>’ from
+ overwriting existing files. Using the redirection operator
+ ‘>|’ instead of ‘>’ will override this and force the creation
+ of an output file.
+
+ ‘-E’
+ If set, any trap on ‘ERR’ is inherited by shell functions,
+ command substitutions, and commands executed in a subshell
+ environment. The ‘ERR’ trap is normally not inherited in such
+ cases.
+
+ ‘-H’
+ Enable ‘!’ style history substitution (*note History
+ Interaction::). This option is on by default for interactive
+ shells.
+
+ ‘-P’
+ If set, Bash does not resolve symbolic links when executing
+ commands such as ‘cd’ which change the current directory. It
+ uses the physical directory structure instead. By default,
+ Bash follows the logical chain of directories when performing
+ commands which change the current directory.
+
+ For example, if ‘/usr/sys’ is a symbolic link to
+ ‘/usr/local/sys’ then:
+ $ cd /usr/sys; echo $PWD
+ /usr/sys
+ $ cd ..; pwd
+ /usr
+
+ If ‘set -P’ is on, then:
+ $ cd /usr/sys; echo $PWD
+ /usr/local/sys
+ $ cd ..; pwd
+ /usr/local
+
+ ‘-T’
+ If set, any traps on ‘DEBUG’ and ‘RETURN’ are inherited by
+ shell functions, command substitutions, and commands executed
+ in a subshell environment. The ‘DEBUG’ and ‘RETURN’ traps are
+ normally not inherited in such cases.
+
+ ‘--’
+ If no arguments follow this option, unset the positional
+ parameters. Otherwise, the positional parameters are set to
+ the ARGUMENTS, even if some of them begin with a ‘-’.
+
+ ‘-’
+ Signal the end of options, and assign all remaining ARGUMENTS
+ to the positional parameters. The ‘-x’ and ‘-v’ options are
+ turned off. If there are no arguments, the positional
+ parameters remain unchanged.
+
+ Using ‘+’ rather than ‘-’ causes these options to be turned off.
+ The options can also be used upon invocation of the shell. The
+ current set of options may be found in ‘$-’.
+
+ The remaining N ARGUMENTS are positional parameters and are
+ assigned, in order, to ‘$1’, ‘$2’, ... ‘$N’. The special parameter
+ ‘#’ is set to N.
+
+ The return status is always zero unless an invalid option is
+ supplied.
+
+\1f
+File: bash.info, Node: The Shopt Builtin, Prev: The Set Builtin, Up: Modifying Shell Behavior
+
+4.3.2 The Shopt Builtin
+-----------------------
+
+This builtin allows you to change additional optional shell behavior.
+
+‘shopt’
+ shopt [-pqsu] [-o] [OPTNAME ...]
+
+ Toggle the values of settings controlling optional shell behavior.
+ The settings can be either those listed below, or, if the ‘-o’
+ option is used, those available with the ‘-o’ option to the ‘set’
+ builtin command (*note The Set Builtin::).
+
+ With no options, or with the ‘-p’ option, display a list of all
+ settable options, with an indication of whether or not each is set;
+ if any OPTNAMEs are supplied, the output is restricted to those
+ options. The ‘-p’ option displays output in a form that may be
+ reused as input.
+
+ Other options have the following meanings:
+
+ ‘-s’
+ Enable (set) each OPTNAME.
+
+ ‘-u’
+ Disable (unset) each OPTNAME.
+
+ ‘-q’
+ Suppresses normal output; the return status indicates whether
+ the OPTNAME is set or unset. If multiple OPTNAME arguments
+ are supplied with ‘-q’, the return status is zero if all
+ OPTNAMEs are enabled; non-zero otherwise.
+
+ ‘-o’
+ Restricts the values of OPTNAME to be those defined for the
+ ‘-o’ option to the ‘set’ builtin (*note The Set Builtin::).
+
+ If either ‘-s’ or ‘-u’ is used with no OPTNAME arguments, ‘shopt’
+ shows only those options which are set or unset, respectively.
+
+ Unless otherwise noted, the ‘shopt’ options are disabled (off) by
+ default.
+
+ The return status when listing options is zero if all OPTNAMEs are
+ enabled, non-zero otherwise. When setting or unsetting options,
+ the return status is zero unless an OPTNAME is not a valid shell
+ option.
+
+ The list of ‘shopt’ options is:
+
+ ‘array_expand_once’
+ If set, the shell suppresses multiple evaluation of
+ associative and indexed array subscripts during arithmetic
+ expression evaluation, while executing builtins that can
+ perform variable assignments, and while executing builtins
+ that perform array dereferencing.
+
+ ‘assoc_expand_once’
+ Deprecated; a synonym for ‘array_expand_once’.
+
+ ‘autocd’
+ If set, a command name that is the name of a directory is
+ executed as if it were the argument to the ‘cd’ command. This
+ option is only used by interactive shells.
+
+ ‘bash_source_fullpath’
+ If set, filenames added to the ‘BASH_SOURCE’ array variable
+ are converted to full pathnames (*note Bash Variables::).
+
+ ‘cdable_vars’
+ If this is set, an argument to the ‘cd’ builtin command that
+ is not a directory is assumed to be the name of a variable
+ whose value is the directory to change to.
+
+ ‘cdspell’
+ If set, the ‘cd’ command attempts to correct minor errors in
+ the spelling of a directory component. Minor errors include
+ transposed characters, a missing character, and one extra
+ character. If ‘cd’ corrects the directory name, it prints the
+ corrected filename, and the command proceeds. This option is
+ only used by interactive shells.
+
+ ‘checkhash’
+ If this is set, Bash checks that a command found in the hash
+ table exists before trying to execute it. If a hashed command
+ no longer exists, Bash performs a normal path search.
+
+ ‘checkjobs’
+ If set, Bash lists the status of any stopped and running jobs
+ before exiting an interactive shell. If any jobs are running,
+ Bash defers the exit until a second exit is attempted without
+ an intervening command (*note Job Control::). The shell
+ always postpones exiting if any jobs are stopped.
+
+ ‘checkwinsize’
+ If set, Bash checks the window size after each external
+ (non-builtin) command and, if necessary, updates the values of
+ ‘LINES’ and ‘COLUMNS’, using the file descriptor associated
+ with stderr if it is a terminal. This option is enabled by
+ default.
+
+ ‘cmdhist’
+ If set, Bash attempts to save all lines of a multiple-line
+ command in the same history entry. This allows easy
+ re-editing of multi-line commands. This option is enabled by
+ default, but only has an effect if command history is enabled
+ (*note Bash History Facilities::).
+
+ ‘compat31’
+ ‘compat32’
+ ‘compat40’
+ ‘compat41’
+ ‘compat42’
+ ‘compat43’
+ ‘compat44’
+ These control aspects of the shell's compatibility mode (*note
+ Shell Compatibility Mode::).
+
+ ‘complete_fullquote’
+ If set, Bash quotes all shell metacharacters in filenames and
+ directory names when performing completion. If not set, Bash
+ removes metacharacters such as the dollar sign from the set of
+ characters that will be quoted in completed filenames when
+ these metacharacters appear in shell variable references in
+ words to be completed. This means that dollar signs in
+ variable names that expand to directories will not be quoted;
+ however, any dollar signs appearing in filenames will not be
+ quoted, either. This is active only when Bash is using
+ backslashes to quote completed filenames. This variable is
+ set by default, which is the default Bash behavior in versions
+ through 4.2.
+
+ ‘direxpand’
+ If set, Bash replaces directory names with the results of word
+ expansion when performing filename completion. This changes
+ the contents of the Readline editing buffer. If not set, Bash
+ attempts to preserve what the user typed.
+
+ ‘dirspell’
+ If set, Bash attempts spelling correction on directory names
+ during word completion if the directory name initially
+ supplied does not exist.
+
+ ‘dotglob’
+ If set, Bash includes filenames beginning with a ‘.’ in the
+ results of filename expansion. The filenames ‘.’ and ‘..’
+ must always be matched explicitly, even if ‘dotglob’ is set.
+
+ ‘execfail’
+ If this is set, a non-interactive shell will not exit if it
+ cannot execute the file specified as an argument to the ‘exec’
+ builtin. An interactive shell does not exit if ‘exec’ fails.
+
+ ‘expand_aliases’
+ If set, aliases are expanded as described below under Aliases,
+ *note Aliases::. This option is enabled by default for
+ interactive shells.
+
+ ‘extdebug’
+ If set at shell invocation, or in a shell startup file,
+ arrange to execute the debugger profile before the shell
+ starts, identical to the ‘--debugger’ option. If set after
+ invocation, behavior intended for use by debuggers is enabled:
+
+ 1. The ‘-F’ option to the ‘declare’ builtin (*note Bash
+ Builtins::) displays the source file name and line number
+ corresponding to each function name supplied as an
+ argument.
+
+ 2. If the command run by the ‘DEBUG’ trap returns a non-zero
+ value, the next command is skipped and not executed.
+
+ 3. If the command run by the ‘DEBUG’ trap returns a value of
+ 2, and the shell is executing in a subroutine (a shell
+ function or a shell script executed by the ‘.’ or
+ ‘source’ builtins), the shell simulates a call to
+ ‘return’.
+
+ 4. ‘BASH_ARGC’ and ‘BASH_ARGV’ are updated as described in
+ their descriptions (*note Bash Variables::).
+
+ 5. Function tracing is enabled: command substitution, shell
+ functions, and subshells invoked with ‘( COMMAND )’
+ inherit the ‘DEBUG’ and ‘RETURN’ traps.
+
+ 6. Error tracing is enabled: command substitution, shell
+ functions, and subshells invoked with ‘( COMMAND )’
+ inherit the ‘ERR’ trap.
+
+ ‘extglob’
+ If set, enable the extended pattern matching features
+ described above (*note Pattern Matching::).
+
+ ‘extquote’
+ If set, ‘$'STRING'’ and ‘$"STRING"’ quoting is performed
+ within ‘${PARAMETER}’ expansions enclosed in double quotes.
+ This option is enabled by default.
+
+ ‘failglob’
+ If set, patterns which fail to match filenames during filename
+ expansion result in an expansion error.
+
+ ‘force_fignore’
+ If set, the suffixes specified by the ‘FIGNORE’ shell variable
+ cause words to be ignored when performing word completion even
+ if the ignored words are the only possible completions. *Note
+ Bash Variables::, for a description of ‘FIGNORE’. This option
+ is enabled by default.
+
+ ‘globasciiranges’
+ If set, range expressions used in pattern matching bracket
+ expressions (*note Pattern Matching::) behave as if in the
+ traditional C locale when performing comparisons. That is,
+ pattern matching does not take the current locale's collating
+ sequence into account, so ‘b’ will not collate between ‘A’ and
+ ‘B’, and upper-case and lower-case ASCII characters will
+ collate together.
+
+ ‘globskipdots’
+ If set, filename expansion will never match the filenames ‘.’
+ and ‘..’, even if the pattern begins with a ‘.’. This option
+ is enabled by default.
+
+ ‘globstar’
+ If set, the pattern ‘**’ used in a filename expansion context
+ will match all files and zero or more directories and
+ subdirectories. If the pattern is followed by a ‘/’, only
+ directories and subdirectories match.
+
+ ‘gnu_errfmt’
+ If set, shell error messages are written in the standard GNU
+ error message format.
+
+ ‘histappend’
+ If set, the history list is appended to the file named by the
+ value of the ‘HISTFILE’ variable when the shell exits, rather
+ than overwriting the file.
+
+ ‘histreedit’
+ If set, and Readline is being used, the user is given the
+ opportunity to re-edit a failed history substitution.
+
+ ‘histverify’
+ If set, and Readline is being used, the results of history
+ substitution are not immediately passed to the shell parser.
+ Instead, the resulting line is loaded into the Readline
+ editing buffer, allowing further modification.
+
+ ‘hostcomplete’
+ If set, and Readline is being used, Bash will attempt to
+ perform hostname completion when a word containing a ‘@’ is
+ being completed (*note Commands For Completion::). This
+ option is enabled by default.
+
+ ‘huponexit’
+ If set, Bash will send ‘SIGHUP’ to all jobs when an
+ interactive login shell exits (*note Signals::).
+
+ ‘inherit_errexit’
+ If set, command substitution inherits the value of the
+ ‘errexit’ option, instead of unsetting it in the subshell
+ environment. This option is enabled when POSIX mode is
+ enabled.
+
+ ‘interactive_comments’
+ In an interactive shell, a word beginning with ‘#’ causes that
+ word and all remaining characters on that line to be ignored,
+ as in a non-interactive shell. This option is enabled by
+ default.
+
+ ‘lastpipe’
+ If set, and job control is not active, the shell runs the last
+ command of a pipeline not executed in the background in the
+ current shell environment.
+
+ ‘lithist’
+ If enabled, and the ‘cmdhist’ option is enabled, multi-line
+ commands are saved to the history with embedded newlines
+ rather than using semicolon separators where possible.
+
+ ‘localvar_inherit’
+ If set, local variables inherit the value and attributes of a
+ variable of the same name that exists at a previous scope
+ before any new value is assigned. The ‘nameref’ attribute is
+ not inherited.
+
+ ‘localvar_unset’
+ If set, calling ‘unset’ on local variables in previous
+ function scopes marks them so subsequent lookups find them
+ unset until that function returns. This is identical to the
+ behavior of unsetting local variables at the current function
+ scope.
+
+ ‘login_shell’
+ The shell sets this option if it is started as a login shell
+ (*note Invoking Bash::). The value may not be changed.
+
+ ‘mailwarn’
+ If set, and a file that Bash is checking for mail has been
+ accessed since the last time it was checked, Bash displays the
+ message ‘"The mail in MAILFILE has been read"’.
+
+ ‘no_empty_cmd_completion’
+ If set, and Readline is being used, Bash does not search the
+ ‘PATH’ for possible completions when completion is attempted
+ on an empty line.
+
+ ‘nocaseglob’
+ If set, Bash matches filenames in a case-insensitive fashion
+ when performing filename expansion.
+
+ ‘nocasematch’
+ If set, Bash matches patterns in a case-insensitive fashion
+ when performing matching while executing ‘case’ or ‘[[’
+ conditional commands (*note Conditional Constructs::), when
+ performing pattern substitution word expansions, or when
+ filtering possible completions as part of programmable
+ completion.
+
+ ‘noexpand_translation’
+ If set, Bash encloses the translated results of $"..." quoting
+ in single quotes instead of double quotes. If the string is
+ not translated, this has no effect.
+
+ ‘nullglob’
+ If set, filename expansion patterns which match no files
+ (*note Filename Expansion::) expand to nothing and are
+ removed, rather than expanding to themselves.
+
+ ‘patsub_replacement’
+ If set, Bash expands occurrences of ‘&’ in the replacement
+ string of pattern substitution to the text matched by the
+ pattern, as described above (*note Shell Parameter
+ Expansion::). This option is enabled by default.
+
+ ‘progcomp’
+ If set, enable the programmable completion facilities (*note
+ Programmable Completion::). This option is enabled by
+ default.
+
+ ‘progcomp_alias’
+ If set, and programmable completion is enabled, Bash treats a
+ command name that doesn't have any completions as a possible
+ alias and attempts alias expansion. If it has an alias, Bash
+ attempts programmable completion using the command word
+ resulting from the expanded alias.
+
+ ‘promptvars’
+ If set, prompt strings undergo parameter expansion, command
+ substitution, arithmetic expansion, and quote removal after
+ being expanded as described below (*note Controlling the
+ Prompt::). This option is enabled by default.
+
+ ‘restricted_shell’
+ The shell sets this option if it is started in restricted mode
+ (*note The Restricted Shell::). The value may not be changed.
+ This is not reset when the startup files are executed,
+ allowing the startup files to discover whether or not a shell
+ is restricted.
+
+ ‘shift_verbose’
+ If this is set, the ‘shift’ builtin prints an error message
+ when the shift count exceeds the number of positional
+ parameters.
+
+ ‘sourcepath’
+ If set, the ‘.’ (‘source’) builtin uses the value of ‘PATH’ to
+ find the directory containing the file supplied as an argument
+ when the ‘-p’ option is not supplied. This option is enabled
+ by default.
+
+ ‘varredir_close’
+ If set, the shell automatically closes file descriptors
+ assigned using the ‘{varname}’ redirection syntax (*note
+ Redirections::) instead of leaving them open when the command
+ completes.
+
+ ‘xpg_echo’
+ If set, the ‘echo’ builtin expands backslash-escape sequences
+ by default. If the ‘posix’ shell option (*note The Set
+ Builtin::) is also enabled, ‘echo’ does not interpret any
+ options.
+
+\1f
+File: bash.info, Node: Special Builtins, Prev: Modifying Shell Behavior, Up: Shell Builtin Commands
+
+4.4 Special Builtins
+====================
+
+For historical reasons, the POSIX standard has classified several
+builtin commands as _special_. When Bash is executing in POSIX mode,
+the special builtins differ from other builtin commands in three
+respects:
+
+ 1. Special builtins are found before shell functions during command
+ lookup.
+
+ 2. If a special builtin returns an error status, a non-interactive
+ shell exits.
+
+ 3. Assignment statements preceding the command stay in effect in the
+ shell environment after the command completes.
+
+ When Bash is not executing in POSIX mode, these builtins behave no
+differently than the rest of the Bash builtin commands. The Bash POSIX
+mode is described in *note Bash POSIX Mode::.
+
+ These are the POSIX special builtins:
+ break : . source continue eval exec exit export readonly return set
+ shift times trap unset
+
+\1f
+File: bash.info, Node: Shell Variables, Next: Bash Features, Prev: Shell Builtin Commands, Up: Top
+
+5 Shell Variables
+*****************
+
+* Menu:
+
+* Bourne Shell Variables:: Variables which Bash uses in the same way
+ as the Bourne Shell.
+* Bash Variables:: List of variables that exist in Bash.
+
+This chapter describes the shell variables that Bash uses. Bash
+automatically assigns default values to a number of variables.
+
+\1f
+File: bash.info, Node: Bourne Shell Variables, Next: Bash Variables, Up: Shell Variables
+
+5.1 Bourne Shell Variables
+==========================
+
+Bash uses certain shell variables in the same way as the Bourne shell.
+In some cases, Bash assigns a default value to the variable.
+
+‘CDPATH’
+ A colon-separated list of directories used as a search path for the
+ ‘cd’ builtin command.
+
+‘HOME’
+ The current user's home directory; the default for the ‘cd’ builtin
+ command. The value of this variable is also used by tilde
+ expansion (*note Tilde Expansion::).
+
+‘IFS’
+ A list of characters that separate fields; used when the shell
+ splits words as part of expansion and by the ‘read’ builtin to
+ split lines into words. *Note Word Splitting::, for a description
+ of word splitting.
+
+‘MAIL’
+ If the value is set to a filename or directory name and the
+ ‘MAILPATH’ variable is not set, Bash informs the user of the
+ arrival of mail in the specified file or Maildir-format directory.
+
+‘MAILPATH’
+ A colon-separated list of filenames which the shell periodically
+ checks for new mail. Each list entry can specify the message that
+ is printed when new mail arrives in the mail file by separating the
+ filename from the message with a ‘?’. When used in the text of the
+ message, ‘$_’ expands to the name of the current mail file.
+
+‘OPTARG’
+ The value of the last option argument processed by the ‘getopts’
+ builtin.
+
+‘OPTIND’
+ The index of the next argument to be processed by the ‘getopts’
+ builtin.
+
+‘PATH’
+ A colon-separated list of directories in which the shell looks for
+ commands. A zero-length (null) directory name in the value of
+ ‘PATH’ indicates the current directory. A null directory name may
+ appear as two adjacent colons, or as an initial or trailing colon.
+ The default path is system-dependent, and is set by the
+ administrator who installs ‘bash’. A common value is
+ "/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin".
+
+‘PS1’
+ The primary prompt string. The default value is ‘\s-\v\$ ’. *Note
+ Controlling the Prompt::, for the complete list of escape sequences
+ that are expanded before ‘PS1’ is displayed.
+
+‘PS2’
+ The secondary prompt string. The default value is ‘> ’. ‘PS2’ is
+ expanded in the same way as ‘PS1’ before being displayed.
+
+\1f
+File: bash.info, Node: Bash Variables, Prev: Bourne Shell Variables, Up: Shell Variables
+
+5.2 Bash Variables
+==================
+
+These variables are set or used by Bash, but other shells do not
+normally treat them specially.
+
+ A few variables used by Bash are described in different chapters:
+variables for controlling the job control facilities (*note Job Control
+Variables::).
+
+‘_’
+ ($_, an underscore.) This has a number of meanings depending on
+ context. At shell startup, $_ set to the pathname used to invoke
+ the shell or shell script being executed as passed in the
+ environment or argument list. Subsequently, it expands to the last
+ argument to the previous simple command executed in the foreground,
+ after expansion. It is also set to the full pathname used to
+ invoke each command executed and placed in the environment exported
+ to that command. When checking mail, $_ expands to the name of the
+ mail file.
+
+‘BASH’
+ The full pathname used to execute the current instance of Bash.
+
+‘BASHOPTS’
+ A colon-separated list of enabled shell options. Each word in the
+ list is a valid argument for the ‘-s’ option to the ‘shopt’ builtin
+ command (*note The Shopt Builtin::). The options appearing in
+ ‘BASHOPTS’ are those reported as ‘on’ by ‘shopt’. If this variable
+ is in the environment when Bash starts up, the shell enables each
+ option in the list before reading any startup files. If this
+ variable is exported, child shells will enable each option in the
+ list. This variable is readonly.
+
+‘BASHPID’
+ Expands to the process ID of the current Bash process. This
+ differs from ‘$$’ under certain circumstances, such as subshells
+ that do not require Bash to be re-initialized. Assignments to
+ ‘BASHPID’ have no effect. If ‘BASHPID’ is unset, it loses its
+ special properties, even if it is subsequently reset.
+
+‘BASH_ALIASES’
+ An associative array variable whose members correspond to the
+ internal list of aliases as maintained by the ‘alias’ builtin.
+ (*note Bourne Shell Builtins::). Elements added to this array
+ appear in the alias list; however, unsetting array elements
+ currently does not cause aliases to be removed from the alias list.
+ If ‘BASH_ALIASES’ is unset, it loses its special properties, even
+ if it is subsequently reset.
+
+‘BASH_ARGC’
+ An array variable whose values are the number of parameters in each
+ frame of the current Bash execution call stack. The number of
+ parameters to the current subroutine (shell function or script
+ executed with ‘.’ or ‘source’) is at the top of the stack. When a
+ subroutine is executed, the number of parameters passed is pushed
+ onto ‘BASH_ARGC’. The shell sets ‘BASH_ARGC’ only when in extended
+ debugging mode (see *note The Shopt Builtin:: for a description of
+ the ‘extdebug’ option to the ‘shopt’ builtin). Setting ‘extdebug’
+ after the shell has started to execute a subroutine, or referencing
+ this variable when ‘extdebug’ is not set, may result in
+ inconsistent values. Assignments to ‘BASH_ARGC’ have no effect,
+ and it may not be unset.
+
+‘BASH_ARGV’
+ An array variable containing all of the parameters in the current
+ Bash execution call stack. The final parameter of the last
+ subroutine call is at the top of the stack; the first parameter of
+ the initial call is at the bottom. When a subroutine is executed,
+ the shell pushes the supplied parameters onto ‘BASH_ARGV’. The
+ shell sets ‘BASH_ARGV’ only when in extended debugging mode (see
+ *note The Shopt Builtin:: for a description of the ‘extdebug’
+ option to the ‘shopt’ builtin). Setting ‘extdebug’ after the shell
+ has started to execute a script, or referencing this variable when
+ ‘extdebug’ is not set, may result in inconsistent values.
+ Assignments to ‘BASH_ARGV’ have no effect, and it may not be unset.
+
+‘BASH_ARGV0’
+ When referenced, this variable expands to the name of the shell or
+ shell script (identical to ‘$0’; *Note Special Parameters::, for
+ the description of special parameter 0). Assigning a value to
+ ‘BASH_ARGV0’ sets ‘$0’ to the same value. If ‘BASH_ARGV0’ is
+ unset, it loses its special properties, even if it is subsequently
+ reset.
+
+‘BASH_CMDS’
+ An associative array variable whose members correspond to the
+ internal hash table of commands as maintained by the ‘hash’ builtin
+ (*note Bourne Shell Builtins::). Adding elements to this array
+ makes them appear in the hash table; however, unsetting array
+ elements currently does not remove command names from the hash
+ table. If ‘BASH_CMDS’ is unset, it loses its special properties,
+ even if it is subsequently reset.
+
+‘BASH_COMMAND’
+ Expands to the command currently being executed or about to be
+ executed, unless the shell is executing a command as the result of
+ a trap, in which case it is the command executing at the time of
+ the trap. If ‘BASH_COMMAND’ is unset, it loses its special
+ properties, even if it is subsequently reset.
+
+‘BASH_COMPAT’
+ The value is used to set the shell's compatibility level. *Note
+ Shell Compatibility Mode::, for a description of the various
+ compatibility levels and their effects. The value may be a decimal
+ number (e.g., 4.2) or an integer (e.g., 42) corresponding to the
+ desired compatibility level. If ‘BASH_COMPAT’ is unset or set to
+ the empty string, the compatibility level is set to the default for
+ the current version. If ‘BASH_COMPAT’ is set to a value that is
+ not one of the valid compatibility levels, the shell prints an
+ error message and sets the compatibility level to the default for
+ the current version. A subset of the valid values correspond to
+ the compatibility levels described below (*note Shell Compatibility
+ Mode::). For example, 4.2 and 42 are valid values that correspond
+ to the ‘compat42’ ‘shopt’ option and set the compatibility level to
+ 42. The current version is also a valid value.
+
+‘BASH_ENV’
+ If this variable is set when Bash is invoked to execute a shell
+ script, its value is expanded and used as the name of a startup
+ file to read before executing the script. Bash does not use ‘PATH’
+ to search for the resultant filename. *Note Bash Startup Files::.
+
+‘BASH_EXECUTION_STRING’
+ The command argument to the ‘-c’ invocation option.
+
+‘BASH_LINENO’
+ An array variable whose members are the line numbers in source
+ files where each corresponding member of ‘FUNCNAME’ was invoked.
+ ‘${BASH_LINENO[$i]}’ is the line number in the source file
+ (‘${BASH_SOURCE[$i+1]}’) where ‘${FUNCNAME[$i]}’ was called (or
+ ‘${BASH_LINENO[$i-1]}’ if referenced within another shell
+ function). Use ‘LINENO’ to obtain the current line number.
+ Assignments to ‘BASH_LINENO’ have no effect, and it may not be
+ unset.
+
+‘BASH_LOADABLES_PATH’
+ A colon-separated list of directories in which the ‘enable’ command
+ looks for dynamically loadable builtins.
+
+‘BASH_MONOSECONDS’
+ Each time this variable is referenced, it expands to the value
+ returned by the system's monotonic clock, if one is available. If
+ there is no monotonic clock, this is equivalent to ‘EPOCHSECONDS’.
+ If ‘BASH_MONOSECONDS’ is unset, it loses its special properties,
+ even if it is subsequently reset.
+
+‘BASH_REMATCH’
+ An array variable whose members are assigned by the ‘=~’ binary
+ operator to the ‘[[’ conditional command (*note Conditional
+ Constructs::). The element with index 0 is the portion of the
+ string matching the entire regular expression. The element with
+ index N is the portion of the string matching the Nth parenthesized
+ subexpression.
+
+‘BASH_SOURCE’
+ An array variable whose members are the source filenames where the
+ corresponding shell function names in the ‘FUNCNAME’ array variable
+ are defined. The shell function ‘${FUNCNAME[$i]}’ is defined in
+ the file ‘${BASH_SOURCE[$i]}’ and called from
+ ‘${BASH_SOURCE[$i+1]}’ Assignments to ‘BASH_SOURCE’ have no effect,
+ and it may not be unset.
+
+‘BASH_SUBSHELL’
+ Incremented by one within each subshell or subshell environment
+ when the shell begins executing in that environment. The initial
+ value is 0. If ‘BASH_SUBSHELL’ is unset, it loses its special
+ properties, even if it is subsequently reset.
+
+‘BASH_TRAPSIG’
+ Set to the signal number corresponding to the trap action being
+ executed during its execution. See the description of ‘trap’
+ (*note Bourne Shell Builtins::) for information about signal
+ numbers and trap execution.
+
+‘BASH_VERSINFO’
+ A readonly array variable (*note Arrays::) whose members hold
+ version information for this instance of Bash. The values assigned
+ to the array members are as follows:
+
+ ‘BASH_VERSINFO[0]’
+ The major version number (the “release”).
+
+ ‘BASH_VERSINFO[1]’
+ The minor version number (the “version”).
+
+ ‘BASH_VERSINFO[2]’
+ The patch level.
+
+ ‘BASH_VERSINFO[3]’
+ The build version.
+
+ ‘BASH_VERSINFO[4]’
+ The release status (e.g., ‘beta’).
+
+ ‘BASH_VERSINFO[5]’
+ The value of ‘MACHTYPE’.
+
+‘BASH_VERSION’
+ Expands to a string describing the version of this instance of Bash
+ (e.g., 5.2.37(3)-release).
+
+‘BASH_XTRACEFD’
+ If set to an integer corresponding to a valid file descriptor, Bash
+ writes the trace output generated when ‘set -x’ is enabled to that
+ file descriptor, instead of the standard error. This allows
+ tracing output to be separated from diagnostic and error messages.
+ The file descriptor is closed when ‘BASH_XTRACEFD’ is unset or
+ assigned a new value. Unsetting ‘BASH_XTRACEFD’ or assigning it
+ the empty string causes the trace output to be sent to the standard
+ error. Note that setting ‘BASH_XTRACEFD’ to 2 (the standard error
+ file descriptor) and then unsetting it will result in the standard
+ error being closed.
+
+‘CHILD_MAX’
+ Set the number of exited child status values for the shell to
+ remember. Bash will not allow this value to be decreased below a
+ POSIX-mandated minimum, and there is a maximum value (currently
+ 8192) that this may not exceed. The minimum value is
+ system-dependent.
+
+‘COLUMNS’
+ Used by the ‘select’ command to determine the terminal width when
+ printing selection lists. Automatically set if the ‘checkwinsize’
+ option is enabled (*note The Shopt Builtin::), or in an interactive
+ shell upon receipt of a ‘SIGWINCH’.
+
+‘COMP_CWORD’
+ An index into ‘${COMP_WORDS}’ of the word containing the current
+ cursor position. This variable is available only in shell
+ functions invoked by the programmable completion facilities (*note
+ Programmable Completion::).
+
+‘COMP_KEY’
+ The key (or final key of a key sequence) used to invoke the current
+ completion function. This variable is available only in shell
+ functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMP_LINE’
+ The current command line. This variable is available only in shell
+ functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMP_POINT’
+ The index of the current cursor position relative to the beginning
+ of the current command. If the current cursor position is at the
+ end of the current command, the value of this variable is equal to
+ ‘${#COMP_LINE}’. This variable is available only in shell
+ functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMP_TYPE’
+ Set to an integer value corresponding to the type of attempted
+ completion that caused a completion function to be called: <TAB>,
+ for normal completion, ‘?’, for listing completions after
+ successive tabs, ‘!’, for listing alternatives on partial word
+ completion, ‘@’, to list completions if the word is not unmodified,
+ or ‘%’, for menu completion. This variable is available only in
+ shell functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMP_WORDBREAKS’
+ The set of characters that the Readline library treats as word
+ separators when performing word completion. If ‘COMP_WORDBREAKS’
+ is unset, it loses its special properties, even if it is
+ subsequently reset.
+
+‘COMP_WORDS’
+ An array variable consisting of the individual words in the current
+ command line. The line is split into words as Readline would split
+ it, using ‘COMP_WORDBREAKS’ as described above. This variable is
+ available only in shell functions invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMPREPLY’
+ An array variable from which Bash reads the possible completions
+ generated by a shell function invoked by the programmable
+ completion facility (*note Programmable Completion::). Each array
+ element contains one possible completion.
+
+‘COPROC’
+ An array variable created to hold the file descriptors for output
+ from and input to an unnamed coprocess (*note Coprocesses::).
+
+‘DIRSTACK’
+ An array variable containing the current contents of the directory
+ stack. Directories appear in the stack in the order they are
+ displayed by the ‘dirs’ builtin. Assigning to members of this
+ array variable may be used to modify directories already in the
+ stack, but the ‘pushd’ and ‘popd’ builtins must be used to add and
+ remove directories. Assigning to this variable does not change the
+ current directory. If ‘DIRSTACK’ is unset, it loses its special
+ properties, even if it is subsequently reset.
+
+‘EMACS’
+ If Bash finds this variable in the environment when the shell
+ starts, and its value is ‘t’, Bash assumes that the shell is
+ running in an Emacs shell buffer and disables line editing.
+
+‘ENV’
+ Expanded and executed similarly to ‘BASH_ENV’ (*note Bash Startup
+ Files::) when an interactive shell is invoked in POSIX mode (*note
+ Bash POSIX Mode::).
+
+‘EPOCHREALTIME’
+ Each time this parameter is referenced, it expands to the number of
+ seconds since the Unix Epoch as a floating-point value with
+ micro-second granularity (see the documentation for the C library
+ function ‘time’ for the definition of Epoch). Assignments to
+ ‘EPOCHREALTIME’ are ignored. If ‘EPOCHREALTIME’ is unset, it loses
+ its special properties, even if it is subsequently reset.
+
+‘EPOCHSECONDS’
+ Each time this parameter is referenced, it expands to the number of
+ seconds since the Unix Epoch (see the documentation for the C
+ library function ‘time’ for the definition of Epoch). Assignments
+ to ‘EPOCHSECONDS’ are ignored. If ‘EPOCHSECONDS’ is unset, it
+ loses its special properties, even if it is subsequently reset.
+
+‘EUID’
+ The numeric effective user id of the current user. This variable
+ is readonly.
+
+‘EXECIGNORE’
+ A colon-separated list of shell patterns (*note Pattern Matching::)
+ defining the set of filenames to be ignored by command search using
+ ‘PATH’. Files whose full pathnames match one of these patterns are
+ not considered executable files for the purposes of completion and
+ command execution via ‘PATH’ lookup. This does not affect the
+ behavior of the ‘[’, ‘test’, and ‘[[’ commands. Full pathnames in
+ the command hash table are not subject to ‘EXECIGNORE’. Use this
+ variable to ignore shared library files that have the executable
+ bit set, but are not executable files. The pattern matching honors
+ the setting of the ‘extglob’ shell option.
+
+‘FCEDIT’
+ The editor used as a default by the ‘fc’ builtin command.
+
+‘FIGNORE’
+ A colon-separated list of suffixes to ignore when performing
+ filename completion. A filename whose suffix matches one of the
+ entries in ‘FIGNORE’ is excluded from the list of matched
+ filenames. A sample value is ‘.o:~’
+
+‘FUNCNAME’
+ An array variable containing the names of all shell functions
+ currently in the execution call stack. The element with index 0 is
+ the name of any currently-executing shell function. The
+ bottom-most element (the one with the highest index) is ‘"main"’.
+ This variable exists only when a shell function is executing.
+ Assignments to ‘FUNCNAME’ have no effect. If ‘FUNCNAME’ is unset,
+ it loses its special properties, even if it is subsequently reset.
+
+ This variable can be used with ‘BASH_LINENO’ and ‘BASH_SOURCE’.
+ Each element of ‘FUNCNAME’ has corresponding elements in
+ ‘BASH_LINENO’ and ‘BASH_SOURCE’ to describe the call stack. For
+ instance, ‘${FUNCNAME[$i]}’ was called from the file
+ ‘${BASH_SOURCE[$i+1]}’ at line number ‘${BASH_LINENO[$i]}’. The
+ ‘caller’ builtin displays the current call stack using this
+ information.
+
+‘FUNCNEST’
+ A numeric value greater than 0 defines a maximum function nesting
+ level. Function invocations that exceed this nesting level cause
+ the current command to abort.
+
+‘GLOBIGNORE’
+ A colon-separated list of patterns defining the set of file names
+ to be ignored by filename expansion. If a file name matched by a
+ filename expansion pattern also matches one of the patterns in
+ ‘GLOBIGNORE’, it is removed from the list of matches. The pattern
+ matching honors the setting of the ‘extglob’ shell option.
+
+‘GLOBSORT’
+ Controls how the results of filename expansion are sorted. The
+ value of this variable specifies the sort criteria and sort order
+ for the results of filename expansion. If this variable is unset
+ or set to the null string, filename expansion uses the historical
+ behavior of sorting by name, in ascending lexicographic order as
+ determined by the ‘LC_COLLATE’ shell variable.
+
+ If set, a valid value begins with an optional ‘+’, which is
+ ignored, or ‘-’, which reverses the sort order from ascending to
+ descending, followed by a sort specifier. The valid sort
+ specifiers are ‘name’, ‘numeric’, ‘size’, ‘mtime’, ‘atime’,
+ ‘ctime’, and ‘blocks’, which sort the files on name, names in
+ numeric rather than lexicographic order, file size, modification
+ time, access time, inode change time, and number of blocks,
+ respectively. If any of the non-name keys compare as equal (e.g.,
+ if two files are the same size), sorting uses the name as a
+ secondary sort key.
+
+ For example, a value of ‘-mtime’ sorts the results in descending
+ order by modification time (newest first).
+
+ The ‘numeric’ specifier treats names consisting solely of digits as
+ numbers and sorts them using their numeric value (so "2" sorts
+ before "10", for example). When using ‘numeric’, names containing
+ non-digits sort after all the all-digit names and are sorted by
+ name using the traditional behavior.
+
+ A sort specifier of ‘nosort’ disables sorting completely; Bash
+ returns the results in the order they are read from the file
+ system, ignoring any leading ‘-’.
+
+ If the sort specifier is missing, it defaults to NAME, so a value
+ of ‘+’ is equivalent to the null string, and a value of ‘-’ sorts
+ by name in descending order.
+
+ Any invalid value restores the historical sorting behavior.
+
+‘GROUPS’
+ An array variable containing the list of groups of which the
+ current user is a member. Assignments to ‘GROUPS’ have no effect.
+ If ‘GROUPS’ is unset, it loses its special properties, even if it
+ is subsequently reset.
+
+‘histchars’
+ The two or three characters which control history expansion, quick
+ substitution, and tokenization (*note History Interaction::). The
+ first character is the “history expansion” character, the character
+ which begins a history expansion, normally ‘!’. The second
+ character is the “quick substitution” character, normally ‘^’.
+ When it appears as the first character on the line, history
+ substitution repeats the previous command, replacing one string
+ with another. The optional third character is the “history
+ comment” character, normally ‘#’, which indicates that the
+ remainder of the line is a comment when it appears as the first
+ character of a word. The history comment character disables
+ history substitution for the remaining words on the line. It does
+ not necessarily cause the shell parser to treat the rest of the
+ line as a comment.
+
+‘HISTCMD’
+ The history number, or index in the history list, of the current
+ command. Assignments to ‘HISTCMD’ have no effect. If ‘HISTCMD’ is
+ unset, it loses its special properties, even if it is subsequently
+ reset.
+
+‘HISTCONTROL’
+ A colon-separated list of values controlling how commands are saved
+ on the history list. If the list of values includes ‘ignorespace’,
+ lines which begin with a space character are not saved in the
+ history list. A value of ‘ignoredups’ causes lines which match the
+ previous history entry not to be saved. A value of ‘ignoreboth’ is
+ shorthand for ‘ignorespace’ and ‘ignoredups’. A value of
+ ‘erasedups’ causes all previous lines matching the current line to
+ be removed from the history list before that line is saved. Any
+ value not in the above list is ignored. If ‘HISTCONTROL’ is unset,
+ or does not include a valid value, Bash saves all lines read by the
+ shell parser on the history list, subject to the value of
+ ‘HISTIGNORE’. If the first line of a multi-line compound command
+ was saved, the second and subsequent lines are not tested, and are
+ added to the history regardless of the value of ‘HISTCONTROL’. If
+ the first line was not saved, the second and subsequent lines of
+ the command are not saved either.
+
+‘HISTFILE’
+ The name of the file to which the command history is saved. Bash
+ assigns a default value of ‘~/.bash_history’. If ‘HISTFILE’ is
+ unset or null, the shell does not save the command history when it
+ exits.
+
+‘HISTFILESIZE’
+ The maximum number of lines contained in the history file. When
+ this variable is assigned a value, the history file is truncated,
+ if necessary, to contain no more than the number of history entries
+ that total no more than that number of lines by removing the oldest
+ entries. If the history list contains multi-line entries, the
+ history file may contain more lines than this maximum to avoid
+ leaving partial history entries. The history file is also
+ truncated to this size after writing it when a shell exits or by
+ the ‘history’ builtin. If the value is 0, the history file is
+ truncated to zero size. Non-numeric values and numeric values less
+ than zero inhibit truncation. The shell sets the default value to
+ the value of ‘HISTSIZE’ after reading any startup files.
+
+‘HISTIGNORE’
+ A colon-separated list of patterns used to decide which command
+ lines should be saved on the history list. If a command line
+ matches one of the patterns in the value of ‘HISTIGNORE’, it is not
+ saved on the history list. Each pattern is anchored at the
+ beginning of the line and must match the complete line (Bash does
+ not implicitly append a ‘*’). Each pattern is tested against the
+ line after the checks specified by ‘HISTCONTROL’ are applied. In
+ addition to the normal shell pattern matching characters, ‘&’
+ matches the previous history line. A backslash escapes the ‘&’;
+ the backslash is removed before attempting a match. If the first
+ line of a multi-line compound command was saved, the second and
+ subsequent lines are not tested, and are added to the history
+ regardless of the value of ‘HISTIGNORE’. If the first line was not
+ saved, the second and subsequent lines of the command are not saved
+ either. The pattern matching honors the setting of the ‘extglob’
+ shell option.
+
+ ‘HISTIGNORE’ subsumes some of the function of ‘HISTCONTROL’. A
+ pattern of ‘&’ is identical to ‘ignoredups’, and a pattern of ‘[
+ ]*’ is identical to ‘ignorespace’. Combining these two patterns,
+ separating them with a colon, provides the functionality of
+ ‘ignoreboth’.
+
+‘HISTSIZE’
+ The maximum number of commands to remember on the history list. If
+ the value is 0, commands are not saved in the history list.
+ Numeric values less than zero result in every command being saved
+ on the history list (there is no limit). The shell sets the
+ default value to 500 after reading any startup files.
+
+‘HISTTIMEFORMAT’
+ If this variable is set and not null, its value is used as a format
+ string for ‘strftime’(3) to print the time stamp associated with
+ each history entry displayed by the ‘history’ builtin. If this
+ variable is set, the shell writes time stamps to the history file
+ so they may be preserved across shell sessions. This uses the
+ history comment character to distinguish timestamps from other
+ history lines.
+
+‘HOSTFILE’
+ Contains the name of a file in the same format as ‘/etc/hosts’ that
+ should be read when the shell needs to complete a hostname. The
+ list of possible hostname completions may be changed while the
+ shell is running; the next time hostname completion is attempted
+ after the value is changed, Bash adds the contents of the new file
+ to the existing list. If ‘HOSTFILE’ is set, but has no value, or
+ does not name a readable file, Bash attempts to read ‘/etc/hosts’
+ to obtain the list of possible hostname completions. When
+ ‘HOSTFILE’ is unset, Bash clears the hostname list.
+
+‘HOSTNAME’
+ The name of the current host.
+
+‘HOSTTYPE’
+ A string describing the machine Bash is running on.
+
+‘IGNOREEOF’
+ Controls the action of the shell on receipt of an ‘EOF’ character
+ as the sole input. If set, the value is the number of consecutive
+ ‘EOF’ characters that can be read as the first character on an
+ input line before Bash exits. If the variable is set but does not
+ have a numeric value, or the value is null, then the default is 10.
+ If the variable is unset, then ‘EOF’ signifies the end of input to
+ the shell. This is only in effect for interactive shells.
+
+‘INPUTRC’
+ The name of the Readline initialization file, overriding the
+ default of ‘~/.inputrc’.
+
+‘INSIDE_EMACS’
+ If Bash finds this variable in the environment when the shell
+ starts, it assumes that the shell is running in an Emacs shell
+ buffer and may disable line editing depending on the value of
+ ‘TERM’.
+
+‘LANG’
+ Used to determine the locale category for any category not
+ specifically selected with a variable starting with ‘LC_’.
+
+‘LC_ALL’
+ This variable overrides the value of ‘LANG’ and any other ‘LC_’
+ variable specifying a locale category.
+
+‘LC_COLLATE’
+ This variable determines the collation order used when sorting the
+ results of filename expansion, and determines the behavior of range
+ expressions, equivalence classes, and collating sequences within
+ filename expansion and pattern matching (*note Filename
+ Expansion::).
+
+‘LC_CTYPE’
+ This variable determines the interpretation of characters and the
+ behavior of character classes within filename expansion and pattern
+ matching (*note Filename Expansion::).
+
+‘LC_MESSAGES’
+ This variable determines the locale used to translate double-quoted
+ strings preceded by a ‘$’ (*note Locale Translation::).
+
+‘LC_NUMERIC’
+ This variable determines the locale category used for number
+ formatting.
+
+‘LC_TIME’
+ This variable determines the locale category used for data and time
+ formatting.
+
+‘LINENO’
+ The line number in the script or shell function currently
+ executing. Line numbers start with 1. When not in a script or
+ function, the value is not guaranteed to be meaningful. If
+ ‘LINENO’ is unset, it loses its special properties, even if it is
+ subsequently reset.
+
+‘LINES’
+ Used by the ‘select’ command to determine the column length for
+ printing selection lists. Automatically set if the ‘checkwinsize’
+ option is enabled (*note The Shopt Builtin::), or in an interactive
+ shell upon receipt of a ‘SIGWINCH’.
+
+‘MACHTYPE’
+ A string that fully describes the system type on which Bash is
+ executing, in the standard GNU CPU-COMPANY-SYSTEM format.
+
+‘MAILCHECK’
+ How often (in seconds) that the shell should check for mail in the
+ files specified in the ‘MAILPATH’ or ‘MAIL’ variables. The default
+ is 60 seconds. When it is time to check for mail, the shell does
+ so before displaying the primary prompt. If this variable is
+ unset, or set to a value that is not a number greater than or equal
+ to zero, the shell disables mail checking.
+
+‘MAPFILE’
+ An array variable created to hold the text read by the ‘mapfile’
+ builtin when no variable name is supplied.
+
+‘OLDPWD’
+ The previous working directory as set by the ‘cd’ builtin.
+
+‘OPTERR’
+ If set to the value 1, Bash displays error messages generated by
+ the ‘getopts’ builtin command. ‘OPTERR’ is initialized to 1 each
+ time the shell is invoked.
+
+‘OSTYPE’
+ A string describing the operating system Bash is running on.
+
+‘PIPESTATUS’
+ An array variable (*note Arrays::) containing a list of exit status
+ values from the commands in the most-recently-executed foreground
+ pipeline, which may consist of only a simple command (*note Shell
+ Commands::). Bash sets ‘PIPESTATUS’ after executing multi-element
+ pipelines, timed and negated pipelines, simple commands, subshells
+ created with the ‘(’ operator, the ‘[[’ and ‘((’ compound commands,
+ and after error conditions that result in the shell aborting
+ command execution.
+
+‘POSIXLY_CORRECT’
+ If this variable is in the environment when Bash starts, the shell
+ enters POSIX mode (*note Bash POSIX Mode::) before reading the
+ startup files, as if the ‘--posix’ invocation option had been
+ supplied. If it is set while the shell is running, Bash enables
+ POSIX mode, as if the command
+ set -o posix
+ had been executed. When the shell enters POSIX mode, it sets this
+ variable if it was not already set.
+
+‘PPID’
+ The process ID of the shell's parent process. This variable is
+ readonly.
+
+‘PROMPT_COMMAND’
+ If this variable is set, and is an array, the value of each set
+ element is interpreted as a command to execute before printing the
+ primary prompt (‘$PS1’). If this is set but not an array variable,
+ its value is used as a command to execute instead.
+
+‘PROMPT_DIRTRIM’
+ If set to a number greater than zero, the value is used as the
+ number of trailing directory components to retain when expanding
+ the ‘\w’ and ‘\W’ prompt string escapes (*note Controlling the
+ Prompt::). Characters removed are replaced with an ellipsis.
+
+‘PS0’
+ The value of this parameter is expanded like ‘PS1’ and displayed by
+ interactive shells after reading a command and before the command
+ is executed.
+
+‘PS3’
+ The value of this variable is used as the prompt for the ‘select’
+ command. If this variable is not set, the ‘select’ command prompts
+ with ‘#? ’
+
+‘PS4’
+ The value of this parameter is expanded like ‘PS1’ and the expanded
+ value is the prompt printed before the command line is echoed when
+ the ‘-x’ option is set (*note The Set Builtin::). The first
+ character of the expanded value is replicated multiple times, as
+ necessary, to indicate multiple levels of indirection. The default
+ is ‘+ ’.
+
+‘PWD’
+ The current working directory as set by the ‘cd’ builtin.
+
+‘RANDOM’
+ Each time this parameter is referenced, it expands to a random
+ integer between 0 and 32767. Assigning a value to ‘RANDOM’
+ initializes (seeds) the sequence of random numbers. Seeding the
+ random number generator with the same constant value produces the
+ same sequence of values. If ‘RANDOM’ is unset, it loses its
+ special properties, even if it is subsequently reset.
+
+‘READLINE_ARGUMENT’
+ Any numeric argument given to a Readline command that was defined
+ using ‘bind -x’ (*note Bash Builtins::) when it was invoked.
+
+‘READLINE_LINE’
+ The contents of the Readline line buffer, for use with ‘bind -x’
+ (*note Bash Builtins::).
+
+‘READLINE_MARK’
+ The position of the “mark” (saved insertion point) in the Readline
+ line buffer, for use with ‘bind -x’ (*note Bash Builtins::). The
+ characters between the insertion point and the mark are often
+ called the “region”.
+
+‘READLINE_POINT’
+ The position of the insertion point in the Readline line buffer,
+ for use with ‘bind -x’ (*note Bash Builtins::).
+
+‘REPLY’
+ The default variable for the ‘read’ builtin; set to the line read
+ when ‘read’ is not supplied a variable name argument.
+
+‘SECONDS’
+ This variable expands to the number of seconds since the shell was
+ started. Assignment to this variable resets the count to the value
+ assigned, and the expanded value becomes the value assigned plus
+ the number of seconds since the assignment. The number of seconds
+ at shell invocation and the current time are always determined by
+ querying the system clock at one-second resolution. If ‘SECONDS’
+ is unset, it loses its special properties, even if it is
+ subsequently reset.
+
+‘SHELL’
+ This environment variable expands to the full pathname to the
+ shell. If it is not set when the shell starts, Bash assigns to it
+ the full pathname of the current user's login shell.
+
+‘SHELLOPTS’
+ A colon-separated list of enabled shell options. Each word in the
+ list is a valid argument for the ‘-o’ option to the ‘set’ builtin
+ command (*note The Set Builtin::). The options appearing in
+ ‘SHELLOPTS’ are those reported as ‘on’ by ‘set -o’. If this
+ variable is in the environment when Bash starts up, the shell
+ enables each option in the list before reading any startup files.
+ If this variable is exported, child shells will enable each option
+ in the list. This variable is readonly.
+
+‘SHLVL’
+ Incremented by one each time a new instance of Bash is started.
+ This is intended to be a count of how deeply your Bash shells are
+ nested.
+
+‘SRANDOM’
+ This variable expands to a 32-bit pseudo-random number each time it
+ is referenced. The random number generator is not linear on
+ systems that support ‘/dev/urandom’ or ‘arc4random’, so each
+ returned number has no relationship to the numbers preceding it.
+ The random number generator cannot be seeded, so assignments to
+ this variable have no effect. If ‘SRANDOM’ is unset, it loses its
+ special properties, even if it is subsequently reset.
+
+‘TIMEFORMAT’
+ The value of this parameter is used as a format string specifying
+ how the timing information for pipelines prefixed with the ‘time’
+ reserved word should be displayed. The ‘%’ character introduces an
+ escape sequence that is expanded to a time value or other
+ information. The escape sequences and their meanings are as
+ follows; the brackets denote optional portions.
+
+ ‘%%’
+ A literal ‘%’.
+
+ ‘%[P][l]R’
+ The elapsed time in seconds.
+
+ ‘%[P][l]U’
+ The number of CPU seconds spent in user mode.
+
+ ‘%[P][l]S’
+ The number of CPU seconds spent in system mode.
+
+ ‘%P’
+ The CPU percentage, computed as (%U + %S) / %R.
+
+ The optional P is a digit specifying the precision, the number of
+ fractional digits after a decimal point. A value of 0 causes no
+ decimal point or fraction to be output. ‘time’ prints at most six
+ digits after the decimal point; values of P greater than 6 are
+ changed to 6. If P is not specified, ‘time’ prints three digits
+ after the decimal point.
+
+ The optional ‘l’ specifies a longer format, including minutes, of
+ the form MMmSS.FFs. The value of P determines whether or not the
+ fraction is included.
+
+ If this variable is not set, Bash acts as if it had the value
+ $'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'
+ If the value is null, Bash does not display any timing information.
+ A trailing newline is added when the format string is displayed.
+
+‘TMOUT’
+ If set to a value greater than zero, the ‘read’ builtin uses the
+ value as its default timeout (*note Bash Builtins::). The ‘select’
+ command (*note Conditional Constructs::) terminates if input does
+ not arrive after ‘TMOUT’ seconds when input is coming from a
+ terminal.
+
+ In an interactive shell, the value is interpreted as the number of
+ seconds to wait for a line of input after issuing the primary
+ prompt. Bash terminates after waiting for that number of seconds
+ if a complete line of input does not arrive.
+
+‘TMPDIR’
+ If set, Bash uses its value as the name of a directory in which
+ Bash creates temporary files for the shell's use.
+
+‘UID’
+ The numeric real user id of the current user. This variable is
+ readonly.
+
+\1f
+File: bash.info, Node: Bash Features, Next: Job Control, Prev: Shell Variables, Up: Top
+
+6 Bash Features
+***************
+
+This chapter describes features unique to Bash.
+
+* Menu:
+
+* Invoking Bash:: Command line options that you can give
+ to Bash.
+* Bash Startup Files:: When and how Bash executes scripts.
+* Interactive Shells:: What an interactive shell is.
+* Bash Conditional Expressions:: Primitives used in composing expressions for
+ the ‘test’ builtin.
+* Shell Arithmetic:: Arithmetic on shell variables.
+* Aliases:: Substituting one command for another.
+* Arrays:: Array Variables.
+* The Directory Stack:: History of visited directories.
+* Controlling the Prompt:: Customizing the various prompt strings.
+* The Restricted Shell:: A more controlled mode of shell execution.
+* Bash POSIX Mode:: Making Bash behave more closely to what
+ the POSIX standard specifies.
+* Shell Compatibility Mode:: How Bash supports behavior that was present
+ in earlier versions and has changed.
+
+\1f
+File: bash.info, Node: Invoking Bash, Next: Bash Startup Files, Up: Bash Features
+
+6.1 Invoking Bash
+=================
+
+ bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o OPTION]
+ [-O SHOPT_OPTION] [ARGUMENT ...]
+ bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o OPTION]
+ [-O SHOPT_OPTION] -c STRING [ARGUMENT ...]
+ bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o OPTION]
+ [-O SHOPT_OPTION] [ARGUMENT ...]
+
+ All of the single-character options used with the ‘set’ builtin
+(*note The Set Builtin::) can be used as options when the shell is
+invoked. In addition, there are several multi-character options that
+you can use. These options must appear on the command line before the
+single-character options to be recognized.
+
+‘--debugger’
+ Arrange for the debugger profile to be executed before the shell
+ starts. Turns on extended debugging mode (see *note The Shopt
+ Builtin:: for a description of the ‘extdebug’ option to the ‘shopt’
+ builtin).
+
+‘--dump-po-strings’
+ Print a list of all double-quoted strings preceded by ‘$’ on the
+ standard output in the GNU ‘gettext’ PO (portable object) file
+ format. Equivalent to ‘-D’ except for the output format.
+
+‘--dump-strings’
+ Equivalent to ‘-D’.
+
+‘--help’
+ Display a usage message on standard output and exit successfully.
+
+‘--init-file FILENAME’
+‘--rcfile FILENAME’
+ Execute commands from FILENAME (instead of ‘~/.bashrc’) in an
+ interactive shell.
+
+‘--login’
+ Equivalent to ‘-l’.
+
+‘--noediting’
+ Do not use the GNU Readline library (*note Command Line Editing::)
+ to read command lines when the shell is interactive.
+
+‘--noprofile’
+ Don't load the system-wide startup file ‘/etc/profile’ or any of
+ the personal initialization files ‘~/.bash_profile’,
+ ‘~/.bash_login’, or ‘~/.profile’ when Bash is invoked as a login
+ shell.
+
+‘--norc’
+ Don't read the ‘~/.bashrc’ initialization file in an interactive
+ shell. This is on by default if the shell is invoked as ‘sh’.
+
+‘--posix’
+ Enable POSIX mode; change the behavior of Bash where the default
+ operation differs from the POSIX standard to match the standard.
+ This is intended to make Bash behave as a strict superset of that
+ standard. *Note Bash POSIX Mode::, for a description of the Bash
+ POSIX mode.
+
+‘--restricted’
+ Equivalent to ‘-r’. Make the shell a restricted shell (*note The
+ Restricted Shell::).
+
+‘--verbose’
+ Equivalent to ‘-v’. Print shell input lines as they're read.
+
+‘--version’
+ Show version information for this instance of Bash on the standard
+ output and exit successfully.
+
+ There are several single-character options that may be supplied at
+invocation which are not available with the ‘set’ builtin.
+
+‘-c’
+ Read and execute commands from the first non-option argument
+ COMMAND_STRING, then exit. If there are arguments after the
+ COMMAND_STRING, the first argument is assigned to ‘$0’ and any
+ remaining arguments are assigned to the positional parameters. The
+ assignment to ‘$0’ sets the name of the shell, which is used in
+ warning and error messages.
+
+‘-i’
+ Force the shell to run interactively. Interactive shells are
+ described in *note Interactive Shells::.
+
+‘-l’
+ Make this shell act as if it had been directly invoked by login.
+ When the shell is interactive, this is equivalent to starting a
+ login shell with ‘exec -l bash’. When the shell is not
+ interactive, it will read and execute the login shell startup
+ files. ‘exec bash -l’ or ‘exec bash --login’ will replace the
+ current shell with a Bash login shell. *Note Bash Startup Files::,
+ for a description of the special behavior of a login shell.
+
+‘-r’
+ Make the shell a restricted shell (*note The Restricted Shell::).
+
+‘-s’
+ If this option is present, or if no arguments remain after option
+ processing, then Bash reads commands from the standard input. This
+ option allows the positional parameters to be set when invoking an
+ interactive shell or when reading input through a pipe.
+
+‘-D’
+ Print a list of all double-quoted strings preceded by ‘$’ on the
+ standard output. These are the strings that are subject to
+ language translation when the current locale is not ‘C’ or ‘POSIX’
+ (*note Locale Translation::). This implies the ‘-n’ option; no
+ commands will be executed.
+
+‘[-+]O [SHOPT_OPTION]’
+ SHOPT_OPTION is one of the shell options accepted by the ‘shopt’
+ builtin (*note The Shopt Builtin::). If SHOPT_OPTION is present,
+ ‘-O’ sets the value of that option; ‘+O’ unsets it. If
+ SHOPT_OPTION is not supplied, Bash prints the names and values of
+ the shell options accepted by ‘shopt’ on the standard output. If
+ the invocation option is ‘+O’, the output is displayed in a format
+ that may be reused as input.
+
+‘--’
+ A ‘--’ signals the end of options and disables further option
+ processing. Any arguments after the ‘--’ are treated as a shell
+ script filename (*note Shell Scripts::) and arguments passed to
+ that script.
+
+‘-’
+ Equivalent to ‘--’.
+
+ A “login shell” is one whose first character of argument zero is ‘-’,
+or one invoked with the ‘--login’ option.
+
+ An “interactive shell” is one started without non-option arguments,
+unless ‘-s’ is specified, without specifying the ‘-c’ option, and whose
+standard input and standard error are both connected to terminals (as
+determined by isatty(3)), or one started with the ‘-i’ option. *Note
+Interactive Shells::, for more information.
+
+ If arguments remain after option processing, and neither the ‘-c’ nor
+the ‘-s’ option has been supplied, the first argument is treated as the
+name of a file containing shell commands (*note Shell Scripts::). When
+Bash is invoked in this fashion, ‘$0’ is set to the name of the file,
+and the positional parameters are set to the remaining arguments. Bash
+reads and executes commands from this file, then exits. Bash's exit
+status is the exit status of the last command executed in the script.
+If no commands are executed, the exit status is 0. Bash first attempts
+to open the file in the current directory, and, if no file is found,
+searches the directories in ‘PATH’ for the script.
+
+\1f
+File: bash.info, Node: Bash Startup Files, Next: Interactive Shells, Prev: Invoking Bash, Up: Bash Features
+
+6.2 Bash Startup Files
+======================
+
+This section describes how Bash executes its startup files. If any of
+the files exist but cannot be read, Bash reports an error. Tildes are
+expanded in filenames as described above under Tilde Expansion (*note
+Tilde Expansion::).
+
+ Interactive shells are described in *note Interactive Shells::.
+
+Invoked as an interactive login shell, or with ‘--login’
+........................................................
+
+When Bash is invoked as an interactive login shell, or as a
+non-interactive shell with the ‘--login’ option, it first reads and
+executes commands from the file ‘/etc/profile’, if that file exists.
+After reading that file, it looks for ‘~/.bash_profile’,
+‘~/.bash_login’, and ‘~/.profile’, in that order, and reads and executes
+commands from the first one that exists and is readable. The
+‘--noprofile’ option inhibits this behavior.
+
+ When an interactive login shell exits, or a non-interactive login
+shell executes the ‘exit’ builtin command, Bash reads and executes
+commands from the file ‘~/.bash_logout’, if it exists.
+
+Invoked as an interactive non-login shell
+.........................................
+
+When Bash runs as an interactive shell that is not a login shell, it
+reads and executes commands from ‘~/.bashrc’, if that file exists. The
+‘--norc’ option inhibits this behavior. The ‘--rcfile FILE’ option
+causes Bash to use FILE instead of ‘~/.bashrc’.
+
+ So, typically, your ‘~/.bash_profile’ contains the line
+ if [ -f ~/.bashrc ]; then . ~/.bashrc; fi
+after (or before) any login-specific initializations.
+
+Invoked non-interactively
+.........................
+
+When Bash is started non-interactively, to run a shell script, for
+example, it looks for the variable ‘BASH_ENV’ in the environment,
+expands its value if it appears there, and uses the expanded value as
+the name of a file to read and execute. Bash behaves as if the
+following command were executed:
+ if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
+but does not the value of the ‘PATH’ variable to search for the
+filename.
+
+ As noted above, if a non-interactive shell is invoked with the
+‘--login’ option, Bash attempts to read and execute commands from the
+login shell startup files.
+
+Invoked with name ‘sh’
+......................
+
+If Bash is invoked with the name ‘sh’, it tries to mimic the startup
+behavior of historical versions of ‘sh’ as closely as possible, while
+conforming to the POSIX standard as well.
+
+ When invoked as an interactive login shell, or as a non-interactive
+shell with the ‘--login’ option, it first attempts to read and execute
+commands from ‘/etc/profile’ and ‘~/.profile’, in that order. The
+‘--noprofile’ option inhibits this behavior.
+
+ When invoked as an interactive shell with the name ‘sh’, Bash looks
+for the variable ‘ENV’, expands its value if it is defined, and uses the
+expanded value as the name of a file to read and execute. Since a shell
+invoked as ‘sh’ does not attempt to read and execute commands from any
+other startup files, the ‘--rcfile’ option has no effect.
+
+ A non-interactive shell invoked with the name ‘sh’ does not attempt
+to read any other startup files.
+
+ When invoked as ‘sh’, Bash enters POSIX mode after reading the
+startup files.
+
+Invoked in POSIX mode
+.....................
+
+When Bash is started in POSIX mode, as with the ‘--posix’ command line
+option, it follows the POSIX standard for startup files. In this mode,
+interactive shells expand the ‘ENV’ variable and read and execute
+commands from the file whose name is the expanded value. No other
+startup files are read.
+
+Invoked by remote shell daemon
+..............................
+
+Bash attempts to determine when it is being run with its standard input
+connected to a network connection, as when executed by the historical
+and rarely-seen remote shell daemon, usually ‘rshd’, or the secure shell
+daemon ‘sshd’. If Bash determines it is being run non-interactively in
+this fashion, it reads and executes commands from ‘~/.bashrc’, if that
+file exists and is readable. Bash does not read this file if invoked as
+‘sh’. The ‘--norc’ option inhibits this behavior, and the ‘--rcfile’
+option makes Bash use a different file instead of ‘~/.bashrc’, but
+neither ‘rshd’ nor ‘sshd’ generally invoke the shell with those options
+or allow them to be specified.
+
+Invoked with unequal effective and real UID/GIDs
+................................................
+
+If Bash is started with the effective user (group) id not equal to the
+real user (group) id, and the ‘-p’ option is not supplied, no startup
+files are read, shell functions are not inherited from the environment,
+the ‘SHELLOPTS’, ‘BASHOPTS’, ‘CDPATH’, and ‘GLOBIGNORE’ variables, if
+they appear in the environment, are ignored, and the effective user id
+is set to the real user id. If the ‘-p’ option is supplied at
+invocation, the startup behavior is the same, but the effective user id
+is not reset.
+
+\1f
+File: bash.info, Node: Interactive Shells, Next: Bash Conditional Expressions, Prev: Bash Startup Files, Up: Bash Features
+
+6.3 Interactive Shells
+======================
+
+* Menu:
+
+* What is an Interactive Shell?:: What determines whether a shell is Interactive.
+* Is this Shell Interactive?:: How to tell if a shell is interactive.
+* Interactive Shell Behavior:: What changes in an interactive shell?
+
+\1f
+File: bash.info, Node: What is an Interactive Shell?, Next: Is this Shell Interactive?, Up: Interactive Shells
+
+6.3.1 What is an Interactive Shell?
+-----------------------------------
+
+An interactive shell is one started without non-option arguments (unless
+‘-s’ is specified) and without specifying the ‘-c’ option, whose input
+and error output are both connected to terminals (as determined by
+‘isatty(3)’), or one started with the ‘-i’ option.
+
+ An interactive shell generally reads from and writes to a user's
+terminal.
+
+ The ‘-s’ invocation option may be used to set the positional
+parameters when an interactive shell starts.
+
+\1f
+File: bash.info, Node: Is this Shell Interactive?, Next: Interactive Shell Behavior, Prev: What is an Interactive Shell?, Up: Interactive Shells
+
+6.3.2 Is this Shell Interactive?
+--------------------------------
+
+To determine within a startup script whether or not Bash is running
+interactively, test the value of the ‘-’ special parameter. It contains
+‘i’ when the shell is interactive. For example:
+
+ case "$-" in
+ *i*) echo This shell is interactive ;;
+ *) echo This shell is not interactive ;;
+ esac
+
+ Alternatively, startup scripts may examine the variable ‘PS1’; it is
+unset in non-interactive shells, and set in interactive shells. Thus:
+
+ if [ -z "$PS1" ]; then
+ echo This shell is not interactive
+ else
+ echo This shell is interactive
+ fi
+
+\1f
+File: bash.info, Node: Interactive Shell Behavior, Prev: Is this Shell Interactive?, Up: Interactive Shells
+
+6.3.3 Interactive Shell Behavior
+--------------------------------
+
+When the shell is running interactively, it changes its behavior in
+several ways.
+
+ 1. Bash reads and executes startup files as described in *note Bash
+ Startup Files::.
+
+ 2. Job Control (*note Job Control::) is enabled by default. When job
+ control is in effect, Bash ignores the keyboard-generated job
+ control signals ‘SIGTTIN’, ‘SIGTTOU’, and ‘SIGTSTP’.
+
+ 3. Bash executes the values of the set elements of the
+ ‘PROMPT_COMMAND’ array variable as commands before printing the
+ primary prompt, ‘$PS1’ (*note Bash Variables::).
+
+ 4. Bash expands and displays ‘PS1’ before reading the first line of a
+ command, and expands and displays ‘PS2’ before reading the second
+ and subsequent lines of a multi-line command. Bash expands and
+ displays ‘PS0’ after it reads a command but before executing it.
+ See *note Controlling the Prompt::, for a complete list of prompt
+ string escape sequences.
+
+ 5. Bash uses Readline (*note Command Line Editing::) to read commands
+ from the user's terminal.
+
+ 6. Bash inspects the value of the ‘ignoreeof’ option to ‘set -o’
+ instead of exiting immediately when it receives an ‘EOF’ on its
+ standard input when reading a command (*note The Set Builtin::).
+
+ 7. Bash enables Command history (*note Bash History Facilities::) and
+ history expansion (*note History Interaction::) by default. When a
+ shell with history enabled exits, Bash saves the command history to
+ the file named by ‘$HISTFILE’.
+
+ 8. Alias expansion (*note Aliases::) is performed by default.
+
+ 9. In the absence of any traps, Bash ignores ‘SIGTERM’ (*note
+ Signals::).
+
+ 10. In the absence of any traps, ‘SIGINT’ is caught and handled (*note
+ Signals::). ‘SIGINT’ will interrupt some shell builtins.
+
+ 11. An interactive login shell sends a ‘SIGHUP’ to all jobs on exit if
+ the ‘huponexit’ shell option has been enabled (*note Signals::).
+
+ 12. The ‘-n’ option has no effect, whether at invocation or when using
+ ‘set -n’ (*note The Set Builtin::).
+
+ 13. Bash will check for mail periodically, depending on the values of
+ the ‘MAIL’, ‘MAILPATH’, and ‘MAILCHECK’ shell variables (*note Bash
+ Variables::).
+
+ 14. The shell will not exit on expansion errors due to references to
+ unbound shell variables after ‘set -u’ has been enabled (*note The
+ Set Builtin::).
+
+ 15. The shell will not exit on expansion errors caused by VAR being
+ unset or null in ‘${VAR:?WORD}’ expansions (*note Shell Parameter
+ Expansion::).
+
+ 16. Redirection errors encountered by shell builtins will not cause
+ the shell to exit.
+
+ 17. When running in POSIX mode, a special builtin returning an error
+ status will not cause the shell to exit (*note Bash POSIX Mode::).
+
+ 18. A failed ‘exec’ will not cause the shell to exit (*note Bourne
+ Shell Builtins::).
+
+ 19. Parser syntax errors will not cause the shell to exit.
+
+ 20. If the ‘cdspell’ shell option is enabled, the shell will attempt
+ simple spelling correction for directory arguments to the ‘cd’
+ builtin (see the description of the ‘cdspell’ option to the ‘shopt’
+ builtin in *note The Shopt Builtin::). The ‘cdspell’ option is
+ only effective in interactive shells.
+
+ 21. The shell will check the value of the ‘TMOUT’ variable and exit if
+ a command is not read within the specified number of seconds after
+ printing ‘$PS1’ (*note Bash Variables::).
+
+\1f
+File: bash.info, Node: Bash Conditional Expressions, Next: Shell Arithmetic, Prev: Interactive Shells, Up: Bash Features
+
+6.4 Bash Conditional Expressions
+================================
+
+Conditional expressions are used by the ‘[[’ compound command (*note
+Conditional Constructs::) and the ‘test’ and ‘[’ builtin commands (*note
+Bourne Shell Builtins::). The ‘test’ and ‘[’ commands determine their
+behavior based on the number of arguments; see the descriptions of those
+commands for any other command-specific actions.
+
+ Expressions may be unary or binary, and are formed from the primaries
+listed below. Unary expressions are often used to examine the status of
+a file or shell variable. Binary operators are used for string,
+numeric, and file attribute comparisons.
+
+ Bash handles several filenames specially when they are used in
+expressions. If the operating system on which Bash is running provides
+these special files, Bash uses them; otherwise it emulates them
+internally with this behavior: If the FILE argument to one of the
+primaries is of the form ‘/dev/fd/N’, then Bash checks file descriptor
+N. If the FILE argument to one of the primaries is one of ‘/dev/stdin’,
+‘/dev/stdout’, or ‘/dev/stderr’, Bash checks file descriptor 0, 1, or 2,
+respectively.
+
+ When used with ‘[[’, the ‘<’ and ‘>’ operators sort lexicographically
+using the current locale. The ‘test’ command uses ASCII ordering.
+
+ Unless otherwise specified, primaries that operate on files follow
+symbolic links and operate on the target of the link, rather than the
+link itself.
+
+‘-a FILE’
+ True if FILE exists.
+
+‘-b FILE’
+ True if FILE exists and is a block special file.
+
+‘-c FILE’
+ True if FILE exists and is a character special file.
+
+‘-d FILE’
+ True if FILE exists and is a directory.
+
+‘-e FILE’
+ True if FILE exists.
+
+‘-f FILE’
+ True if FILE exists and is a regular file.
+
+‘-g FILE’
+ True if FILE exists and its set-group-id bit is set.
+
+‘-h FILE’
+ True if FILE exists and is a symbolic link.
+
+‘-k FILE’
+ True if FILE exists and its "sticky" bit is set.
+
+‘-p FILE’
+ True if FILE exists and is a named pipe (FIFO).
+
+‘-r FILE’
+ True if FILE exists and is readable.
+
+‘-s FILE’
+ True if FILE exists and has a size greater than zero.
+
+‘-t FD’
+ True if file descriptor FD is open and refers to a terminal.
+
+‘-u FILE’
+ True if FILE exists and its set-user-id bit is set.
+
+‘-w FILE’
+ True if FILE exists and is writable.
+
+‘-x FILE’
+ True if FILE exists and is executable.
+
+‘-G FILE’
+ True if FILE exists and is owned by the effective group id.
+
+‘-L FILE’
+ True if FILE exists and is a symbolic link.
+
+‘-N FILE’
+ True if FILE exists and has been modified since it was last
+ accessed.
+
+‘-O FILE’
+ True if FILE exists and is owned by the effective user id.
+
+‘-S FILE’
+ True if FILE exists and is a socket.
+
+‘FILE1 -ef FILE2’
+ True if FILE1 and FILE2 refer to the same device and inode numbers.
+
+‘FILE1 -nt FILE2’
+ True if FILE1 is newer (according to modification date) than FILE2,
+ or if FILE1 exists and FILE2 does not.
+
+‘FILE1 -ot FILE2’
+ True if FILE1 is older than FILE2, or if FILE2 exists and FILE1
+ does not.
+
+‘-o OPTNAME’
+ True if the shell option OPTNAME is enabled. The list of options
+ appears in the description of the ‘-o’ option to the ‘set’ builtin
+ (*note The Set Builtin::).
+
+‘-v VARNAME’
+ True if the shell variable VARNAME is set (has been assigned a
+ value). If VARNAME is an indexed array variable name subscripted
+ by ‘@’ or ‘*’, this returns true if the array has any set elements.
+ If VARNAME is an associative array variable name subscripted by ‘@’
+ or ‘*’, this returns true if an element with that key is set.
+
+‘-R VARNAME’
+ True if the shell variable VARNAME is set and is a name reference.
+
+‘-z STRING’
+ True if the length of STRING is zero.
+
+‘-n STRING’
+‘STRING’
+ True if the length of STRING is non-zero.
+
+‘STRING1 == STRING2’
+‘STRING1 = STRING2’
+ True if the strings are equal. When used with the ‘[[’ command,
+ this performs pattern matching as described above (*note
+ Conditional Constructs::).
+
+ ‘=’ should be used with the ‘test’ command for POSIX conformance.
+
+‘STRING1 != STRING2’
+ True if the strings are not equal.
+
+‘STRING1 < STRING2’
+ True if STRING1 sorts before STRING2 lexicographically.
+
+‘STRING1 > STRING2’
+ True if STRING1 sorts after STRING2 lexicographically.
+
+‘ARG1 OP ARG2’
+ ‘OP’ is one of ‘-eq’, ‘-ne’, ‘-lt’, ‘-le’, ‘-gt’, or ‘-ge’. These
+ arithmetic binary operators return true if ARG1 is equal to, not
+ equal to, less than, less than or equal to, greater than, or
+ greater than or equal to ARG2, respectively. ARG1 and ARG2 may be
+ positive or negative integers. When used with the ‘[[’ command,
+ ARG1 and ARG2 are evaluated as arithmetic expressions (*note Shell
+ Arithmetic::). Since the expansions the ‘[[’ command performs on
+ ARG1 and ARG2 can potentially result in empty strings, arithmetic
+ expression evaluation treats those as expressions that evaluate to
+ 0.
+
+\1f
+File: bash.info, Node: Shell Arithmetic, Next: Aliases, Prev: Bash Conditional Expressions, Up: Bash Features
+
+6.5 Shell Arithmetic
+====================
+
+The shell allows arithmetic expressions to be evaluated, as one of the
+shell expansions or by using the ‘((’ compound command, the ‘let’ and
+‘declare’ builtins, the arithmetic ‘for’ command, the ‘[[’ conditional
+command, or the ‘-i’ option to the ‘declare’ builtin.
+
+ Evaluation is done in the largest fixed-width integers available,
+with no check for overflow, though division by 0 is trapped and flagged
+as an error. The operators and their precedence, associativity, and
+values are the same as in the C language. The following list of
+operators is grouped into levels of equal-precedence operators. The
+levels are listed in order of decreasing precedence.
+
+‘ID++ ID--’
+ variable post-increment and post-decrement
+
+‘++ID --ID’
+ variable pre-increment and pre-decrement
+
+‘- +’
+ unary minus and plus
+
+‘! ~’
+ logical and bitwise negation
+
+‘**’
+ exponentiation
+
+‘* / %’
+ multiplication, division, remainder
+
+‘+ -’
+ addition, subtraction
+
+‘<< >>’
+ left and right bitwise shifts
+
+‘<= >= < >’
+ comparison
+
+‘== !=’
+ equality and inequality
+
+‘&’
+ bitwise AND
+
+‘^’
+ bitwise exclusive OR
+
+‘|’
+ bitwise OR
+
+‘&&’
+ logical AND
+
+‘||’
+ logical OR
+
+‘expr ? if-true-expr : if-false-expr’
+ conditional operator
+
+‘= *= /= %= += -= <<= >>= &= ^= |=’
+ assignment
+
+‘expr1 , expr2’
+ comma
+
+ Shell variables are allowed as operands; parameter expansion is
+performed before the expression is evaluated. Within an expression,
+shell variables may also be referenced by name without using the
+parameter expansion syntax. This means you can use X, where X is a
+shell variable name, in an arithmetic expression, and the shell will
+evaluate its value as an expression and use the result. A shell
+variable that is null or unset evaluates to 0 when referenced by name in
+an expression.
+
+ The value of a variable is evaluated as an arithmetic expression when
+it is referenced, or when a variable which has been given the ‘integer’
+attribute using ‘declare -i’ is assigned a value. A null value
+evaluates to 0. A shell variable need not have its ‘integer’ attribute
+enabled to be used in an expression.
+
+ Integer constants follow the C language definition, without suffixes
+or character constants. Constants with a leading 0 are interpreted as
+octal numbers. A leading ‘0x’ or ‘0X’ denotes hexadecimal. Otherwise,
+numbers take the form [BASE‘#’]N, where the optional BASE is a decimal
+number between 2 and 64 representing the arithmetic base, and N is a
+number in that base. If BASE‘#’ is omitted, then base 10 is used. When
+specifying N, if a non-digit is required, the digits greater than 9 are
+represented by the lowercase letters, the uppercase letters, ‘@’, and
+‘_’, in that order. If BASE is less than or equal to 36, lowercase and
+uppercase letters may be used interchangeably to represent numbers
+between 10 and 35.
+
+ Operators are evaluated in precedence order. Sub-expressions in
+parentheses are evaluated first and may override the precedence rules
+above.
+
+\1f
+File: bash.info, Node: Aliases, Next: Arrays, Prev: Shell Arithmetic, Up: Bash Features
+
+6.6 Aliases
+===========
+
+“Aliases” allow a string to be substituted for a word that is in a
+position in the input where it can be the first word of a simple
+command. Aliases have names and corresponding values that are set and
+unset using the ‘alias’ and ‘unalias’ builtin commands (*note Shell
+Builtin Commands::).
+
+ If the shell reads an unquoted word in the right position, it checks
+the word to see if it matches an alias name. If it matches, the shell
+replaces the word with the alias value, and reads that value as if it
+had been read instead of the word. The shell doesn't look at any
+characters following the word before attempting alias substitution.
+
+ The characters ‘/’, ‘$’, ‘`’, ‘=’ and any of the shell metacharacters
+or quoting characters listed above may not appear in an alias name. The
+replacement text may contain any valid shell input, including shell
+metacharacters. The first word of the replacement text is tested for
+aliases, but a word that is identical to an alias being expanded is not
+expanded a second time. This means that one may alias ‘ls’ to ‘"ls
+-F"’, for instance, and Bash does not try to recursively expand the
+replacement text.
+
+ If the last character of the alias value is a ‘blank’, then the shell
+checks the next command word following the alias for alias expansion.
+
+ Aliases are created and listed with the ‘alias’ command, and removed
+with the ‘unalias’ command.
+
+ There is no mechanism for using arguments in the replacement text, as
+in ‘csh’. If arguments are needed, use a shell function (*note Shell
+Functions::) instead.
+
+ Aliases are not expanded when the shell is not interactive, unless
+the ‘expand_aliases’ shell option is set using ‘shopt’ (*note The Shopt
+Builtin::).
+
+ The rules concerning the definition and use of aliases are somewhat
+confusing. Bash always reads at least one complete line of input, and
+all lines that make up a compound command, before executing any of the
+commands on that line or the compound command. Aliases are expanded
+when a command is read, not when it is executed. Therefore, an alias
+definition appearing on the same line as another command does not take
+effect until the shell reads the next line of input, and an alias
+definition in a compound command does not take effect until the shell
+parses and executes the entire compound command. The commands following
+the alias definition on that line, or in the rest of a compound command,
+are not affected by the new alias. This behavior is also an issue when
+functions are executed. Aliases are expanded when a function definition
+is read, not when the function is executed, because a function
+definition is itself a command. As a consequence, aliases defined in a
+function are not available until after that function is executed. To be
+safe, always put alias definitions on a separate line, and do not use
+‘alias’ in compound commands.
+
+ For almost every purpose, shell functions are preferable to aliases.
+
+\1f
+File: bash.info, Node: Arrays, Next: The Directory Stack, Prev: Aliases, Up: Bash Features
+
+6.7 Arrays
+==========
+
+Bash provides one-dimensional indexed and associative array variables.
+Any variable may be used as an indexed array; the ‘declare’ builtin
+explicitly declares an array. There is no maximum limit on the size of
+an array, nor any requirement that members be indexed or assigned
+contiguously. Indexed arrays are referenced using arithmetic
+expressions that must expand to an integer (*note Shell Arithmetic::))
+and are zero-based; associative arrays use arbitrary strings. Unless
+otherwise noted, indexed array indices must be non-negative integers.
+
+ The shell performs parameter and variable expansion, arithmetic
+expansion, command substitution, and quote removal on indexed array
+subscripts. Since this can potentially result in empty strings,
+subscript indexing treats those as expressions that evaluate to 0.
+
+ The shell performs tilde expansion, parameter and variable expansion,
+arithmetic expansion, command substitution, and quote removal on
+associative array subscripts. Empty strings cannot be used as
+associative array keys.
+
+ Bash automatically creates an indexed array if any variable is
+assigned to using the syntax
+ NAME[SUBSCRIPT]=VALUE
+
+The SUBSCRIPT is treated as an arithmetic expression that must evaluate
+to a number greater than or equal to zero. To explicitly declare an
+indexed array, use
+ declare -a NAME
+(*note Bash Builtins::). The syntax
+ declare -a NAME[SUBSCRIPT]
+is also accepted; the SUBSCRIPT is ignored.
+
+Associative arrays are created using
+ declare -A NAME
+
+ Attributes may be specified for an array variable using the ‘declare’
+and ‘readonly’ builtins. Each attribute applies to all members of an
+array.
+
+ Arrays are assigned using compound assignments of the form
+ NAME=(VALUE1 VALUE2 ... )
+where each VALUE may be of the form ‘[SUBSCRIPT]=’STRING. Indexed array
+assignments do not require anything but STRING.
+
+ Each VALUE in the list undergoes the shell expansions described above
+(*note Shell Expansions::), but VALUEs that are valid variable
+assignments including the brackets and subscript do not undergo brace
+expansion and word splitting, as with individual variable assignments.
+
+ When assigning to indexed arrays, if the optional subscript is
+supplied, that index is assigned to; otherwise the index of the element
+assigned is the last index assigned to by the statement plus one.
+Indexing starts at zero.
+
+ When assigning to an associative array, the words in a compound
+assignment may be either assignment statements, for which the subscript
+is required, or a list of words that is interpreted as a sequence of
+alternating keys and values: NAME=(KEY1 VALUE1 KEY2 VALUE2 ... ). These
+are treated identically to NAME=( [KEY1]=VALUE1 [KEY2]=VALUE2 ... ).
+The first word in the list determines how the remaining words are
+interpreted; all assignments in a list must be of the same type. When
+using key/value pairs, the keys may not be missing or empty; a final
+missing value is treated like the empty string.
+
+ This syntax is also accepted by the ‘declare’ builtin. Individual
+array elements may be assigned to using the ‘NAME[SUBSCRIPT]=VALUE’
+syntax introduced above.
+
+ When assigning to an indexed array, if NAME is subscripted by a
+negative number, that number is interpreted as relative to one greater
+than the maximum index of NAME, so negative indices count back from the
+end of the array, and an index of -1 references the last element.
+
+ The ‘+=’ operator appends to an array variable when assigning using
+the compound assignment syntax; see *note Shell Parameters:: above.
+
+ An array element is referenced using ‘${NAME[SUBSCRIPT]}’. The
+braces are required to avoid conflicts with the shell's filename
+expansion operators. If the SUBSCRIPT is ‘@’ or ‘*’, the word expands
+to all members of the array NAME, unless otherwise noted in the
+description of a builtin or word expansion. These subscripts differ
+only when the word appears within double quotes. If the word is
+double-quoted, ‘${NAME[*]}’ expands to a single word with the value of
+each array member separated by the first character of the ‘IFS’
+variable, and ‘${NAME[@]}’ expands each element of NAME to a separate
+word. When there are no array members, ‘${NAME[@]}’ expands to nothing.
+If the double-quoted expansion occurs within a word, the expansion of
+the first parameter is joined with the beginning part of the expansion
+of the original word, and the expansion of the last parameter is joined
+with the last part of the expansion of the original word. This is
+analogous to the expansion of the special parameters ‘@’ and ‘*’.
+
+ ‘${#NAME[SUBSCRIPT]}’ expands to the length of ‘${NAME[SUBSCRIPT]}’.
+If SUBSCRIPT is ‘@’ or ‘*’, the expansion is the number of elements in
+the array.
+
+ If the SUBSCRIPT used to reference an element of an indexed array
+evaluates to a number less than zero, it is interpreted as relative to
+one greater than the maximum index of the array, so negative indices
+count back from the end of the array, and an index of -1 refers to the
+last element.
+
+ Referencing an array variable without a subscript is equivalent to
+referencing with a subscript of 0. Any reference to a variable using a
+valid subscript is valid; Bash creates an array if necessary.
+
+ An array variable is considered set if a subscript has been assigned
+a value. The null string is a valid value.
+
+ It is possible to obtain the keys (indices) of an array as well as
+the values. ${!NAME[@]} and ${!NAME[*]} expand to the indices assigned
+in array variable NAME. The treatment when in double quotes is similar
+to the expansion of the special parameters ‘@’ and ‘*’ within double
+quotes.
+
+ The ‘unset’ builtin is used to destroy arrays. ‘unset
+NAME[SUBSCRIPT]’ unsets the array element at index SUBSCRIPT. Negative
+subscripts to indexed arrays are interpreted as described above.
+Unsetting the last element of an array variable does not unset the
+variable. ‘unset NAME’, where NAME is an array, removes the entire
+array. ‘unset NAME[SUBSCRIPT]’ behaves differently depending on the
+array type when SUBSCRIPT is ‘*’ or ‘@’. When NAME is an associative
+array, it removes the element with key ‘*’ or ‘@’. If NAME is an
+indexed array, ‘unset’ removes all of the elements, but does not remove
+the array itself.
+
+ When using a variable name with a subscript as an argument to a
+command, such as with ‘unset’, without using the word expansion syntax
+described above (e.g., unset a[4]), the argument is subject to the
+shell's filename expansion. Quote the argument if pathname expansion is
+not desired (e.g., unset 'a[4]').
+
+ The ‘declare’, ‘local’, and ‘readonly’ builtins each accept a ‘-a’
+option to specify an indexed array and a ‘-A’ option to specify an
+associative array. If both options are supplied, ‘-A’ takes precedence.
+The ‘read’ builtin accepts a ‘-a’ option to assign a list of words read
+from the standard input to an array, and can read values from the
+standard input into individual array elements. The ‘set’ and ‘declare’
+builtins display array values in a way that allows them to be reused as
+input. Other builtins accept array name arguments as well (e.g.,
+‘mapfile’); see the descriptions of individual builtins for details.
+The shell provides a number of builtin array variables.
+
+\1f
+File: bash.info, Node: The Directory Stack, Next: Controlling the Prompt, Prev: Arrays, Up: Bash Features
+
+6.8 The Directory Stack
+=======================
+
+* Menu:
+
+* Directory Stack Builtins:: Bash builtin commands to manipulate
+ the directory stack.
+
+The directory stack is a list of recently-visited directories. The
+‘pushd’ builtin adds directories to the stack as it changes the current
+directory, and the ‘popd’ builtin removes specified directories from the
+stack and changes the current directory to the directory removed. The
+‘dirs’ builtin displays the contents of the directory stack. The
+current directory is always the "top" of the directory stack.
+
+ The contents of the directory stack are also visible as the value of
+the ‘DIRSTACK’ shell variable.
+
+\1f
+File: bash.info, Node: Directory Stack Builtins, Up: The Directory Stack
+
+6.8.1 Directory Stack Builtins
+------------------------------
+
+‘dirs’
+ dirs [-clpv] [+N | -N]
+
+ Without options, display the list of currently remembered
+ directories. Directories are added to the list with the ‘pushd’
+ command; the ‘popd’ command removes directories from the list. The
+ current directory is always the first directory in the stack.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-c’
+ Clears the directory stack by deleting all of the elements.
+ ‘-l’
+ Produces a listing using full pathnames; the default listing
+ format uses a tilde to denote the home directory.
+ ‘-p’
+ Causes ‘dirs’ to print the directory stack with one entry per
+ line.
+ ‘-v’
+ Causes ‘dirs’ to print the directory stack with one entry per
+ line, prefixing each entry with its index in the stack.
+ ‘+N’
+ Displays the Nth directory (counting from the left of the list
+ printed by ‘dirs’ when invoked without options), starting with
+ zero.
+ ‘-N’
+ Displays the Nth directory (counting from the right of the
+ list printed by ‘dirs’ when invoked without options), starting
+ with zero.
+
+‘popd’
+ popd [-n] [+N | -N]
+
+ Remove elements from the directory stack. The elements are
+ numbered from 0 starting at the first directory listed by ‘dirs’;
+ that is, ‘popd’ is equivalent to ‘popd +0’.
+
+ When no arguments are given, ‘popd’ removes the top directory from
+ the stack and changes to the new top directory.
+
+ Arguments, if supplied, have the following meanings:
+
+ ‘-n’
+ Suppress the normal change of directory when removing
+ directories from the stack, only manipulate the stack.
+ ‘+N’
+ Remove the Nth directory (counting from the left of the list
+ printed by ‘dirs’), starting with zero, from the stack.
+ ‘-N’
+ Remove the Nth directory (counting from the right of the list
+ printed by ‘dirs’), starting with zero, from the stack.
+
+ If the top element of the directory stack is modified, and the ‘-n’
+ option was not supplied, ‘popd’ uses the ‘cd’ builtin to change to
+ the directory at the top of the stack. If the ‘cd’ fails, ‘popd’
+ returns a non-zero value.
+
+ Otherwise, ‘popd’ returns an unsuccessful status if an invalid
+ option is specified, the directory stack is empty, or N specifies a
+ non-existent directory stack entry.
+
+ If the ‘popd’ command is successful, Bash runs ‘dirs’ to show the
+ final contents of the directory stack, and the return status is 0.
+
+‘pushd’
+ pushd [-n] [+N | -N | DIR]
+
+ Add a directory to the top of the directory stack, or rotate the
+ stack, making the new top of the stack the current working
+ directory. With no arguments, ‘pushd’ exchanges the top two
+ elements of the directory stack.
+
+ Arguments, if supplied, have the following meanings:
+
+ ‘-n’
+ Suppress the normal change of directory when rotating or
+ adding directories to the stack, only manipulate the stack.
+ ‘+N’
+ Rotate the stack so that the Nth directory (counting from the
+ left of the list printed by ‘dirs’, starting with zero) is at
+ the top.
+ ‘-N’
+ Rotate the stack so that the Nth directory (counting from the
+ right of the list printed by ‘dirs’, starting with zero) is at
+ the top.
+ ‘DIR’
+ Make DIR be the top of the stack.
+
+ After the stack has been modified, if the ‘-n’ option was not
+ supplied, ‘pushd’ uses the ‘cd’ builtin to change to the directory
+ at the top of the stack. If the ‘cd’ fails, ‘pushd’ returns a
+ non-zero value.
+
+ Otherwise, if no arguments are supplied, ‘pushd’ returns zero
+ unless the directory stack is empty. When rotating the directory
+ stack, ‘pushd’ returns zero unless the directory stack is empty or
+ N specifies a non-existent directory stack element.
+
+ If the ‘pushd’ command is successful, Bash runs ‘dirs’ to show the
+ final contents of the directory stack.
+
+\1f
+File: bash.info, Node: Controlling the Prompt, Next: The Restricted Shell, Prev: The Directory Stack, Up: Bash Features
+
+6.9 Controlling the Prompt
+==========================
+
+In addition, the following table describes the special characters which
+can appear in the prompt variables ‘PS0’, ‘PS1’, ‘PS2’, and ‘PS4’:
+
+‘\a’
+ A bell character.
+‘\d’
+ The date, in "Weekday Month Date" format (e.g., "Tue May 26").
+‘\D{FORMAT}’
+ The FORMAT is passed to ‘strftime’(3) and the result is inserted
+ into the prompt string; an empty FORMAT results in a
+ locale-specific time representation. The braces are required.
+‘\e’
+ An escape character.
+‘\h’
+ The hostname, up to the first ‘.’.
+‘\H’
+ The hostname.
+‘\j’
+ The number of jobs currently managed by the shell.
+‘\l’
+ The basename of the shell's terminal device name (e.g., "ttys0").
+‘\n’
+ A newline.
+‘\r’
+ A carriage return.
+‘\s’
+ The name of the shell: the basename of ‘$0’ (the portion following
+ the final slash).
+‘\t’
+ The time, in 24-hour HH:MM:SS format.
+‘\T’
+ The time, in 12-hour HH:MM:SS format.
+‘\@’
+ The time, in 12-hour am/pm format.
+‘\A’
+ The time, in 24-hour HH:MM format.
+‘\u’
+ The username of the current user.
+‘\v’
+ The Bash version (e.g., 2.00).
+‘\V’
+ The Bash release, version + patchlevel (e.g., 2.00.0).
+‘\w’
+ The value of the ‘PWD’ shell variable (‘$PWD’), with ‘$HOME’
+ abbreviated with a tilde (uses the ‘$PROMPT_DIRTRIM’ variable).
+‘\W’
+ The basename of ‘$PWD’, with ‘$HOME’ abbreviated with a tilde.
+‘\!’
+ The history number of this command.
+‘\#’
+ The command number of this command.
+‘\$’
+ If the effective uid is 0, ‘#’, otherwise ‘$’.
+‘\NNN’
+ The character whose ASCII code is the octal value NNN.
+‘\\’
+ A backslash.
+‘\[’
+ Begin a sequence of non-printing characters. Thiss could be used
+ to embed a terminal control sequence into the prompt.
+‘\]’
+ End a sequence of non-printing characters.
+
+ The command number and the history number are usually different: the
+history number of a command is its position in the history list, which
+may include commands restored from the history file (*note Bash History
+Facilities::), while the command number is the position in the sequence
+of commands executed during the current shell session.
+
+ After the string is decoded, it is expanded via parameter expansion,
+command substitution, arithmetic expansion, and quote removal, subject
+to the value of the ‘promptvars’ shell option (*note The Shopt
+Builtin::). This can have unwanted side effects if escaped portions of
+the string appear within command substitution or contain characters
+special to word expansion.
+
+\1f
+File: bash.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Controlling the Prompt, Up: Bash Features
+
+6.10 The Restricted Shell
+=========================
+
+If Bash is started with the name ‘rbash’, or the ‘--restricted’ or ‘-r’
+option is supplied at invocation, the shell becomes RESTRICTED. A
+restricted shell is used to set up an environment more controlled than
+the standard shell. A restricted shell behaves identically to ‘bash’
+with the exception that the following are disallowed or not performed:
+
+ • Changing directories with the ‘cd’ builtin.
+ • Setting or unsetting the values of the ‘SHELL’, ‘PATH’, ‘HISTFILE’,
+ ‘ENV’, or ‘BASH_ENV’ variables.
+ • Specifying command names containing slashes.
+ • Specifying a filename containing a slash as an argument to the ‘.’
+ builtin command.
+ • Using the ‘-p’ option to the ‘.’ builtin command to specify a
+ search path.
+ • Specifying a filename containing a slash as an argument to the
+ ‘history’ builtin command.
+ • Specifying a filename containing a slash as an argument to the ‘-p’
+ option to the ‘hash’ builtin command.
+ • Importing function definitions from the shell environment at
+ startup.
+ • Parsing the value of ‘SHELLOPTS’ from the shell environment at
+ startup.
+ • Redirecting output using the ‘>’, ‘>|’, ‘<>’, ‘>&’, ‘&>’, and ‘>>’
+ redirection operators.
+ • Using the ‘exec’ builtin to replace the shell with another command.
+ • Adding or deleting builtin commands with the ‘-f’ and ‘-d’ options
+ to the ‘enable’ builtin.
+ • Using the ‘enable’ builtin command to enable disabled shell
+ builtins.
+ • Specifying the ‘-p’ option to the ‘command’ builtin.
+ • Turning off restricted mode with ‘set +r’ or ‘shopt -u
+ restricted_shell’.
+
+ These restrictions are enforced after any startup files are read.
+
+ When a command that is found to be a shell script is executed (*note
+Shell Scripts::), ‘rbash’ turns off any restrictions in the shell
+spawned to execute the script.
+
+ The restricted shell mode is only one component of a useful
+restricted environment. It should be accompanied by setting ‘PATH’ to a
+value that allows execution of only a few verified commands (commands
+that allow shell escapes are particularly vulnerable), changing the
+current directory to a non-writable directory other than ‘$HOME’ after
+login, not allowing the restricted shell to execute shell scripts, and
+cleaning the environment of variables that cause some commands to modify
+their behavior (e.g., ‘VISUAL’ or ‘PAGER’).
+
+ Modern systems provide more secure ways to implement a restricted
+environment, such as ‘jails’, ‘zones’, or ‘containers’.
+
+\1f
+File: bash.info, Node: Bash POSIX Mode, Next: Shell Compatibility Mode, Prev: The Restricted Shell, Up: Bash Features
+
+6.11 Bash and POSIX
+===================
+
+6.11.1 What is POSIX?
+---------------------
+
+POSIX is the name for a family of standards based on Unix. A number of
+Unix services, tools, and functions are part of the standard, ranging
+from the basic system calls and C library functions to common
+applications and tools to system administration and management.
+
+ The POSIX Shell and Utilities standard was originally developed by
+IEEE Working Group 1003.2 (POSIX.2). The first edition of the 1003.2
+standard was published in 1992. It was merged with the original IEEE
+1003.1 Working Group and is currently maintained by the Austin Group (a
+joint working group of the IEEE, The Open Group and ISO/IEC SC22/WG15).
+Today the Shell and Utilities are a volume within the set of documents
+that make up IEEE Std 1003.1-2024, and thus the former POSIX.2 (from
+1992) is now part of the current unified POSIX standard.
+
+ The Shell and Utilities volume concentrates on the command
+interpreter interface and utility programs commonly executed from the
+command line or by other programs. The standard is freely available on
+the web at
+<https://pubs.opengroup.org/onlinepubs/9799919799/utilities/contents.html>.
+
+ Bash is concerned with the aspects of the shell's behavior defined by
+the POSIX Shell and Utilities volume. The shell command language has of
+course been standardized, including the basic flow control and program
+execution constructs, I/O redirection and pipelines, argument handling,
+variable expansion, and quoting.
+
+ The special builtins, which must be implemented as part of the shell
+to provide the desired functionality, are specified as being part of the
+shell; examples of these are ‘eval’ and ‘export’. Other utilities
+appear in the sections of POSIX not devoted to the shell which are
+commonly (and in some cases must be) implemented as builtin commands,
+such as ‘read’ and ‘test’. POSIX also specifies aspects of the shell's
+interactive behavior, including job control and command line editing.
+Only vi-style line editing commands have been standardized; emacs
+editing commands were left out due to objections.
+
+6.11.2 Bash POSIX Mode
+----------------------
+
+Although Bash is an implementation of the POSIX shell specification,
+there are areas where the Bash default behavior differs from the
+specification. The Bash “posix mode” changes the Bash behavior in these
+areas so that it conforms more strictly to the standard.
+
+ Starting Bash with the ‘--posix’ command-line option or executing
+‘set -o posix’ while Bash is running will cause Bash to conform more
+closely to the POSIX standard by changing the behavior to match that
+specified by POSIX in areas where the Bash default differs.
+
+ When invoked as ‘sh’, Bash enters POSIX mode after reading the
+startup files.
+
+ The following list is what's changed when POSIX mode is in effect:
+
+ 1. Bash ensures that the ‘POSIXLY_CORRECT’ variable is set.
+
+ 2. Bash reads and executes the POSIX startup files (‘$ENV’) rather
+ than the normal Bash files (*note Bash Startup Files::).
+
+ 3. Alias expansion is always enabled, even in non-interactive shells.
+
+ 4. Reserved words appearing in a context where reserved words are
+ recognized do not undergo alias expansion.
+
+ 5. Alias expansion is performed when initially parsing a command
+ substitution. The default (non-posix) mode generally defers it,
+ when enabled, until the command substitution is executed. This
+ means that command substitution will not expand aliases that are
+ defined after the command substitution is initially parsed (e.g.,
+ as part of a function definition).
+
+ 6. The ‘time’ reserved word may be used by itself as a simple command.
+ When used in this way, it displays timing statistics for the shell
+ and its completed children. The ‘TIMEFORMAT’ variable controls the
+ format of the timing information.
+
+ 7. The parser does not recognize ‘time’ as a reserved word if the next
+ token begins with a ‘-’.
+
+ 8. When parsing and expanding a ${...} expansion that appears within
+ double quotes, single quotes are no longer special and cannot be
+ used to quote a closing brace or other special character, unless
+ the operator is one of those defined to perform pattern removal.
+ In this case, they do not have to appear as matched pairs.
+
+ 9. Redirection operators do not perform filename expansion on the word
+ in a redirection unless the shell is interactive.
+
+ 10. Redirection operators do not perform word splitting on the word in
+ a redirection.
+
+ 11. Function names may not be the same as one of the POSIX special
+ builtins.
+
+ 12. Tilde expansion is only performed on assignments preceding a
+ command name, rather than on all assignment statements on the line.
+
+ 13. While variable indirection is available, it may not be applied to
+ the ‘#’ and ‘?’ special parameters.
+
+ 14. Expanding the ‘*’ special parameter in a pattern context where the
+ expansion is double-quoted does not treat the ‘$*’ as if it were
+ double-quoted.
+
+ 15. A double quote character (‘"’) is treated specially when it
+ appears in a backquoted command substitution in the body of a
+ here-document that undergoes expansion. That means, for example,
+ that a backslash preceding a double quote character will escape it
+ and the backslash will be removed.
+
+ 16. Command substitutions don't set the ‘?’ special parameter. The
+ exit status of a simple command without a command word is still the
+ exit status of the last command substitution that occurred while
+ evaluating the variable assignments and redirections in that
+ command, but that does not happen until after all of the
+ assignments and redirections.
+
+ 17. Literal tildes that appear as the first character in elements of
+ the ‘PATH’ variable are not expanded as described above under *note
+ Tilde Expansion::.
+
+ 18. Command lookup finds POSIX special builtins before shell
+ functions, including output printed by the ‘type’ and ‘command’
+ builtins.
+
+ 19. Even if a shell function whose name contains a slash was defined
+ before entering POSIX mode, the shell will not execute a function
+ whose name contains one or more slashes.
+
+ 20. When a command in the hash table no longer exists, Bash will
+ re-search ‘$PATH’ to find the new location. This is also available
+ with ‘shopt -s checkhash’.
+
+ 21. Bash will not insert a command without the execute bit set into
+ the command hash table, even if it returns it as a (last-ditch)
+ result from a ‘$PATH’ search.
+
+ 22. The message printed by the job control code and builtins when a
+ job exits with a non-zero status is "Done(status)".
+
+ 23. The message printed by the job control code and builtins when a
+ job is stopped is "Stopped(SIGNAME)", where SIGNAME is, for
+ example, ‘SIGTSTP’.
+
+ 24. If the shell is interactive, Bash does not perform job
+ notifications between executing commands in lists separated by ‘;’
+ or newline. Non-interactive shells print status messages after a
+ foreground job in a list completes.
+
+ 25. If the shell is interactive, Bash waits until the next prompt
+ before printing the status of a background job that changes status
+ or a foreground job that terminates due to a signal.
+ Non-interactive shells print status messages after a foreground job
+ completes.
+
+ 26. Bash permanently removes jobs from the jobs table after notifying
+ the user of their termination via the ‘wait’ or ‘jobs’ builtins.
+ It removes the job from the jobs list after notifying the user of
+ its termination, but the status is still available via ‘wait’, as
+ long as ‘wait’ is supplied a PID argument.
+
+ 27. The ‘vi’ editing mode will invoke the ‘vi’ editor directly when
+ the ‘v’ command is run, instead of checking ‘$VISUAL’ and
+ ‘$EDITOR’.
+
+ 28. Prompt expansion enables the POSIX ‘PS1’ and ‘PS2’ expansions of
+ ‘!’ to the history number and ‘!!’ to ‘!’, and Bash performs
+ parameter expansion on the values of ‘PS1’ and ‘PS2’ regardless of
+ the setting of the ‘promptvars’ option.
+
+ 29. The default history file is ‘~/.sh_history’ (this is the default
+ value the shell assigns to ‘$HISTFILE’).
+
+ 30. The ‘!’ character does not introduce history expansion within a
+ double-quoted string, even if the ‘histexpand’ option is enabled.
+
+ 31. When printing shell function definitions (e.g., by ‘type’), Bash
+ does not print the ‘function’ reserved word unless necessary.
+
+ 32. Non-interactive shells exit if a syntax error in an arithmetic
+ expansion results in an invalid expression.
+
+ 33. Non-interactive shells exit if a parameter expansion error occurs.
+
+ 34. If a POSIX special builtin returns an error status, a
+ non-interactive shell exits. The fatal errors are those listed in
+ the POSIX standard, and include things like passing incorrect
+ options, redirection errors, variable assignment errors for
+ assignments preceding the command name, and so on.
+
+ 35. A non-interactive shell exits with an error status if a variable
+ assignment error occurs when no command name follows the assignment
+ statements. A variable assignment error occurs, for example, when
+ trying to assign a value to a readonly variable.
+
+ 36. A non-interactive shell exits with an error status if a variable
+ assignment error occurs in an assignment statement preceding a
+ special builtin, but not with any other simple command. For any
+ other simple command, the shell aborts execution of that command,
+ and execution continues at the top level ("the shell shall not
+ perform any further processing of the command in which the error
+ occurred").
+
+ 37. A non-interactive shell exits with an error status if the
+ iteration variable in a ‘for’ statement or the selection variable
+ in a ‘select’ statement is a readonly variable or has an invalid
+ name.
+
+ 38. Non-interactive shells exit if FILENAME in ‘.’ FILENAME is not
+ found.
+
+ 39. Non-interactive shells exit if there is a syntax error in a script
+ read with the ‘.’ or ‘source’ builtins, or in a string processed by
+ the ‘eval’ builtin.
+
+ 40. Non-interactive shells exit if the ‘export’, ‘readonly’ or ‘unset’
+ builtin commands get an argument that is not a valid identifier,
+ and they are not operating on shell functions. These errors force
+ an exit because these are special builtins.
+
+ 41. Assignment statements preceding POSIX special builtins persist in
+ the shell environment after the builtin completes.
+
+ 42. The ‘command’ builtin does not prevent builtins that take
+ assignment statements as arguments from expanding them as
+ assignment statements; when not in POSIX mode, declaration commands
+ lose their assignment statement expansion properties when preceded
+ by ‘command’.
+
+ 43. Enabling POSIX mode has the effect of setting the
+ ‘inherit_errexit’ option, so subshells spawned to execute command
+ substitutions inherit the value of the ‘-e’ option from the parent
+ shell. When the ‘inherit_errexit’ option is not enabled, Bash
+ clears the ‘-e’ option in such subshells.
+
+ 44. Enabling POSIX mode has the effect of setting the ‘shift_verbose’
+ option, so numeric arguments to ‘shift’ that exceed the number of
+ positional parameters will result in an error message.
+
+ 45. Enabling POSIX mode has the effect of setting the
+ ‘interactive_comments’ option (*note Comments::).
+
+ 46. The ‘.’ and ‘source’ builtins do not search the current directory
+ for the filename argument if it is not found by searching ‘PATH’.
+
+ 47. When the ‘alias’ builtin displays alias definitions, it does not
+ display them with a leading ‘alias ’ unless the ‘-p’ option is
+ supplied.
+
+ 48. The ‘bg’ builtin uses the required format to describe each job
+ placed in the background, which does not include an indication of
+ whether the job is the current or previous job.
+
+ 49. When the ‘cd’ builtin is invoked in logical mode, and the pathname
+ constructed from ‘$PWD’ and the directory name supplied as an
+ argument does not refer to an existing directory, ‘cd’ will fail
+ instead of falling back to physical mode.
+
+ 50. When the ‘cd’ builtin cannot change a directory because the length
+ of the pathname constructed from ‘$PWD’ and the directory name
+ supplied as an argument exceeds ‘PATH_MAX’ when canonicalized, ‘cd’
+ will attempt to use the supplied directory name.
+
+ 51. When the ‘xpg_echo’ option is enabled, Bash does not attempt to
+ interpret any arguments to ‘echo’ as options. ‘echo’ displays each
+ argument after converting escape sequences.
+
+ 52. The ‘export’ and ‘readonly’ builtin commands display their output
+ in the format required by POSIX.
+
+ 53. When listing the history, the ‘fc’ builtin does not include an
+ indication of whether or not a history entry has been modified.
+
+ 54. The default editor used by ‘fc’ is ‘ed’.
+
+ 55. ‘fc’ treats extra arguments as an error instead of ignoring them.
+
+ 56. If there are too many arguments supplied to ‘fc -s’, ‘fc’ prints
+ an error message and returns failure.
+
+ 57. The output of ‘kill -l’ prints all the signal names on a single
+ line, separated by spaces, without the ‘SIG’ prefix.
+
+ 58. The ‘kill’ builtin does not accept signal names with a ‘SIG’
+ prefix.
+
+ 59. The ‘kill’ builtin returns a failure status if any of the pid or
+ job arguments are invalid or if sending the specified signal to any
+ of them fails. In default mode, ‘kill’ returns success if the
+ signal was successfully sent to any of the specified processes.
+
+ 60. The ‘printf’ builtin uses ‘double’ (via ‘strtod’) to convert
+ arguments corresponding to floating point conversion specifiers,
+ instead of ‘long double’ if it's available. The ‘L’ length
+ modifier forces ‘printf’ to use ‘long double’ if it's available.
+
+ 61. The ‘pwd’ builtin verifies that the value it prints is the same as
+ the current directory, even if it is not asked to check the file
+ system with the ‘-P’ option.
+
+ 62. The ‘read’ builtin may be interrupted by a signal for which a trap
+ has been set. If Bash receives a trapped signal while executing
+ ‘read’, the trap handler executes and ‘read’ returns an exit status
+ greater than 128.
+
+ 63. When the ‘set’ builtin is invoked without options, it does not
+ display shell function names and definitions.
+
+ 64. When the ‘set’ builtin is invoked without options, it displays
+ variable values without quotes, unless they contain shell
+ metacharacters, even if the result contains nonprinting characters.
+
+ 65. The ‘test’ builtin compares strings using the current locale when
+ evaluating the ‘<’ and ‘>’ binary operators.
+
+ 66. The ‘test’ builtin's ‘-t’ unary primary requires an argument.
+ Historical versions of ‘test’ made the argument optional in certain
+ cases, and Bash attempts to accommodate those for backwards
+ compatibility.
+
+ 67. The ‘trap’ builtin displays signal names without the leading
+ ‘SIG’.
+
+ 68. The ‘trap’ builtin doesn't check the first argument for a possible
+ signal specification and revert the signal handling to the original
+ disposition if it is, unless that argument consists solely of
+ digits and is a valid signal number. If users want to reset the
+ handler for a given signal to the original disposition, they should
+ use ‘-’ as the first argument.
+
+ 69. ‘trap -p’ without arguments displays signals whose dispositions
+ are set to SIG_DFL and those that were ignored when the shell
+ started, not just trapped signals.
+
+ 70. The ‘type’ and ‘command’ builtins will not report a non-executable
+ file as having been found, though the shell will attempt to execute
+ such a file if it is the only so-named file found in ‘$PATH’.
+
+ 71. The ‘ulimit’ builtin uses a block size of 512 bytes for the ‘-c’
+ and ‘-f’ options.
+
+ 72. The ‘unset’ builtin with the ‘-v’ option specified returns a fatal
+ error if it attempts to unset a ‘readonly’ or ‘non-unsettable’
+ variable, which causes a non-interactive shell to exit.
+
+ 73. When asked to unset a variable that appears in an assignment
+ statement preceding the command, the ‘unset’ builtin attempts to
+ unset a variable of the same name in the current or previous scope
+ as well. This implements the required "if an assigned variable is
+ further modified by the utility, the modifications made by the
+ utility shall persist" behavior.
+
+ 74. The arrival of ‘SIGCHLD’ when a trap is set on ‘SIGCHLD’ does not
+ interrupt the ‘wait’ builtin and cause it to return immediately.
+ The trap command is run once for each child that exits.
+
+ 75. Bash removes an exited background process's status from the list
+ of such statuses after the ‘wait’ builtin returns it.
+
+ There is additional POSIX behavior that Bash does not implement by
+default even when in POSIX mode. Specifically:
+
+ 1. POSIX requires that word splitting be byte-oriented. That is, each
+ _byte_ in the value of ‘IFS’ potentially splits a word, even if
+ that byte is part of a multibyte character in ‘IFS’ or part of
+ multibyte character in the word. Bash allows multibyte characters
+ in the value of ‘IFS’, treating a valid multibyte character as a
+ single delimiter, and will not split a valid multibyte character
+ even if one of the bytes composing that character appears in ‘IFS’.
+ This is POSIX interpretation 1560, further modified by issue 1924.
+
+ 2. The ‘fc’ builtin checks ‘$EDITOR’ as a program to edit history
+ entries if ‘FCEDIT’ is unset, rather than defaulting directly to
+ ‘ed’. ‘fc’ uses ‘ed’ if ‘EDITOR’ is unset.
+
+ 3. As noted above, Bash requires the ‘xpg_echo’ option to be enabled
+ for the ‘echo’ builtin to be fully conformant.
+
+ Bash can be configured to be POSIX-conformant by default, by
+specifying the ‘--enable-strict-posix-default’ to ‘configure’ when
+building (*note Optional Features::).
+
+\1f
+File: bash.info, Node: Shell Compatibility Mode, Prev: Bash POSIX Mode, Up: Bash Features
+
+6.12 Shell Compatibility Mode
+=============================
+
+Bash-4.0 introduced the concept of a “shell compatibility level”,
+specified as a set of options to the shopt builtin (‘compat31’,
+‘compat32’, ‘compat40’, ‘compat41’, and so on). There is only one
+current compatibility level - each option is mutually exclusive. The
+compatibility level is intended to allow users to select behavior from
+previous versions that is incompatible with newer versions while they
+migrate scripts to use current features and behavior. It's intended to
+be a temporary solution.
+
+ This section does not mention behavior that is standard for a
+particular version (e.g., setting ‘compat32’ means that quoting the
+right hand side of the regexp matching operator quotes special regexp
+characters in the word, which is default behavior in bash-3.2 and
+subsequent versions).
+
+ If a user enables, say, ‘compat32’, it may affect the behavior of
+other compatibility levels up to and including the current compatibility
+level. The idea is that each compatibility level controls behavior that
+changed in that version of Bash, but that behavior may have been present
+in earlier versions. For instance, the change to use locale-based
+comparisons with the ‘[[’ command came in bash-4.1, and earlier versions
+used ASCII-based comparisons, so enabling ‘compat32’ will enable
+ASCII-based comparisons as well. That granularity may not be sufficient
+for all uses, and as a result users should employ compatibility levels
+carefully. Read the documentation for a particular feature to find out
+the current behavior.
+
+ Bash-4.3 introduced a new shell variable: ‘BASH_COMPAT’. The value
+assigned to this variable (a decimal version number like 4.2, or an
+integer corresponding to the ‘compat’NN option, like 42) determines the
+compatibility level.
+
+ Starting with bash-4.4, Bash began deprecating older compatibility
+levels. Eventually, the options will be removed in favor of
+‘BASH_COMPAT’.
+
+ Bash-5.0 was the final version for which there was an individual
+shopt option for the previous version. ‘BASH_COMPAT’ is the only
+mechanism to control the compatibility level in versions newer than
+bash-5.0.
+
+ The following table describes the behavior changes controlled by each
+compatibility level setting. The ‘compat’NN tag is used as shorthand
+for setting the compatibility level to NN using one of the following
+mechanisms. For versions prior to bash-5.0, the compatibility level may
+be set using the corresponding ‘compat’NN shopt option. For bash-4.3
+and later versions, the ‘BASH_COMPAT’ variable is preferred, and it is
+required for bash-5.1 and later versions.
+
+‘compat31’
+ • Quoting the rhs of the ‘[[’ command's regexp matching operator
+ (=~) has no special effect
+
+‘compat40’
+ • The ‘<’ and ‘>’ operators to the ‘[[’ command do not consider
+ the current locale when comparing strings; they use ASCII
+ ordering. Bash versions prior to bash-4.1 use ASCII collation
+ and strcmp(3); bash-4.1 and later use the current locale's
+ collation sequence and strcoll(3).
+
+‘compat41’
+ • In POSIX mode, ‘time’ may be followed by options and still be
+ recognized as a reserved word (this is POSIX interpretation
+ 267).
+ • In POSIX mode, the parser requires that an even number of
+ single quotes occur in the WORD portion of a double-quoted
+ ${...} parameter expansion and treats them specially, so that
+ characters within the single quotes are considered quoted
+ (this is POSIX interpretation 221).
+
+‘compat42’
+ • The replacement string in double-quoted pattern substitution
+ does not undergo quote removal, as it does in versions after
+ bash-4.2.
+ • In POSIX mode, single quotes are considered special when
+ expanding the WORD portion of a double-quoted ${...} parameter
+ expansion and can be used to quote a closing brace or other
+ special character (this is part of POSIX interpretation 221);
+ in later versions, single quotes are not special within
+ double-quoted word expansions.
+
+‘compat43’
+ • Word expansion errors are considered non-fatal errors that
+ cause the current command to fail, even in POSIX mode (the
+ default behavior is to make them fatal errors that cause the
+ shell to exit).
+ • When executing a shell function, the loop state
+ (while/until/etc.) is not reset, so ‘break’ or ‘continue’ in
+ that function will break or continue loops in the calling
+ context. Bash-4.4 and later reset the loop state to prevent
+ this.
+
+‘compat44’
+ • The shell sets up the values used by ‘BASH_ARGV’ and
+ ‘BASH_ARGC’ so they can expand to the shell's positional
+ parameters even if extended debugging mode is not enabled.
+ • A subshell inherits loops from its parent context, so ‘break’
+ or ‘continue’ will cause the subshell to exit. Bash-5.0 and
+ later reset the loop state to prevent the exit.
+ • Variable assignments preceding builtins like ‘export’ and
+ ‘readonly’ that set attributes continue to affect variables
+ with the same name in the calling environment even if the
+ shell is not in POSIX mode.
+
+‘compat50 (set using BASH_COMPAT)’
+ • Bash-5.1 changed the way ‘$RANDOM’ is generated to introduce
+ slightly more randomness. If the shell compatibility level is
+ set to 50 or lower, it reverts to the method from bash-5.0 and
+ previous versions, so seeding the random number generator by
+ assigning a value to ‘RANDOM’ will produce the same sequence
+ as in bash-5.0.
+ • If the command hash table is empty, Bash versions prior to
+ bash-5.1 printed an informational message to that effect, even
+ when producing output that can be reused as input. Bash-5.1
+ suppresses that message when the ‘-l’ option is supplied.
+
+‘compat51 (set using BASH_COMPAT)’
+ • The ‘unset’ builtin will unset the array ‘a’ given an argument
+ like ‘a[@]’. Bash-5.2 will unset an element with key ‘@’
+ (associative arrays) or remove all the elements without
+ unsetting the array (indexed arrays).
+ • Arithmetic commands ( ((...)) ) and the expressions in an
+ arithmetic for statement can be expanded more than once.
+ • Expressions used as arguments to arithmetic operators in the
+ ‘[[’ conditional command can be expanded more than once.
+ • The expressions in substring parameter brace expansion can be
+ expanded more than once.
+ • The expressions in the $(( ... )) word expansion can be
+ expanded more than once.
+ • Arithmetic expressions used as indexed array subscripts can be
+ expanded more than once.
+ • ‘test -v’, when given an argument of ‘A[@]’, where A is an
+ existing associative array, will return true if the array has
+ any set elements. Bash-5.2 will look for and report on a key
+ named ‘@’.
+ • the ${PARAMETER[:]=VALUE} word expansion will return VALUE,
+ before any variable-specific transformations have been
+ performed (e.g., converting to lowercase). Bash-5.2 will
+ return the final value assigned to the variable.
+ • Parsing command substitutions will behave as if extended
+ globbing (*note The Shopt Builtin::) is enabled, so that
+ parsing a command substitution containing an extglob pattern
+ (say, as part of a shell function) will not fail. This
+ assumes the intent is to enable extglob before the command is
+ executed and word expansions are performed. It will fail at
+ word expansion time if extglob hasn't been enabled by the time
+ the command is executed.
+
+‘compat52 (set using BASH_COMPAT)’
+ • The ‘test’ builtin uses its historical algorithm to parse
+ parenthesized subexpressions when given five or more
+ arguments.
+ • If the ‘-p’ or ‘-P’ option is supplied to the ‘bind’ builtin,
+ ‘bind’ treats any arguments remaining after option processing
+ as bindable command names, and displays any key sequences
+ bound to those commands, instead of treating the arguments as
+ key sequences to bind.
+ • Interactive shells will notify the user of completed jobs
+ while sourcing a script. Newer versions defer notification
+ until script execution completes.
+
+\1f
+File: bash.info, Node: Job Control, Next: Command Line Editing, Prev: Bash Features, Up: Top
+
+7 Job Control
+*************
+
+This chapter discusses what job control is, how it works, and how Bash
+allows you to access its facilities.
+
+* Menu:
+
+* Job Control Basics:: How job control works.
+* Job Control Builtins:: Bash builtin commands used to interact
+ with job control.
+* Job Control Variables:: Variables Bash uses to customize job
+ control.
+
+\1f
+File: bash.info, Node: Job Control Basics, Next: Job Control Builtins, Up: Job Control
+
+7.1 Job Control Basics
+======================
+
+Job control refers to the ability to selectively stop (suspend) the
+execution of processes and continue (resume) their execution at a later
+point. A user typically employs this facility via an interactive
+interface supplied jointly by the operating system kernel's terminal
+driver and Bash.
+
+ The shell associates a JOB with each pipeline. It keeps a table of
+currently executing jobs, which the ‘jobs’ command will display. Each
+job has a “job number”, which ‘jobs’ displays between brackets. Job
+numbers start at 1. When Bash starts a job asynchronously, it prints a
+line that looks like:
+ [1] 25647
+indicating that this job is job number 1 and that the process ID of the
+last process in the pipeline associated with this job is 25647. All of
+the processes in a single pipeline are members of the same job. Bash
+uses the JOB abstraction as the basis for job control.
+
+ To facilitate the implementation of the user interface to job
+control, each process has a “process group ID”, and the operating system
+maintains the notion of a current terminal process group ID. This
+terminal process group ID is associated with the “controlling terminal”.
+
+ Processes that have the same process group ID are said to be part of
+the same “process group”. Members of the foreground process group
+(processes whose process group ID is equal to the current terminal
+process group ID) receive keyboard-generated signals such as ‘SIGINT’.
+Processes in the foreground process group are said to be foreground
+processes. Background processes are those whose process group ID
+differs from the controlling terminal's; such processes are immune to
+keyboard-generated signals. Only foreground processes are allowed to
+read from or, if the user so specifies with ‘stty tostop’, write to the
+controlling terminal. The system sends a ‘SIGTTIN’ (‘SIGTTOU’) signal
+to background processes which attempt to read from (write to when
+‘tostop’ is in effect) the terminal, which, unless caught, suspends the
+process.
+
+ If the operating system on which Bash is running supports job
+control, Bash contains facilities to use it. Typing the “suspend”
+character (typically ‘^Z’, Control-Z) while a process is running stops
+that process and returns control to Bash. Typing the “delayed suspend”
+character (typically ‘^Y’, Control-Y) causes the process to stop when it
+attempts to read input from the terminal, and returns control to Bash.
+The user then manipulates the state of this job, using the ‘bg’ command
+to continue it in the background, the ‘fg’ command to continue it in the
+foreground, or the ‘kill’ command to kill it. The suspend character
+takes effect immediately, and has the additional side effect of
+discarding any pending output and typeahead. If you want to force a
+background process to stop, or stop a process that's not associated with
+your terminal session, send it the ‘SIGSTOP’ signal using ‘kill’.
+
+ There are a number of ways to refer to a job in the shell. The ‘%’
+character introduces a “job specification” (jobspec).
+
+ Job number ‘n’ may be referred to as ‘%n’. A job may also be
+referred to using a prefix of the name used to start it, or using a
+substring that appears in its command line. For example, ‘%ce’ refers
+to a job whose command name begins with ‘ce’. Using ‘%?ce’, on the
+other hand, refers to any job containing the string ‘ce’ in its command
+line. If the prefix or substring matches more than one job, Bash
+reports an error.
+
+ The symbols ‘%%’ and ‘%+’ refer to the shell's notion of the “current
+job”. A single ‘%’ (with no accompanying job specification) also refers
+to the current job. ‘%-’ refers to the “previous job”. When a job
+starts in the background, a job stops while in the foreground, or a job
+is resumed in the background, it becomes the current job. The job that
+was the current job becomes the previous job. When the current job
+terminates, the previous job becomes the current job. If there is only
+a single job, ‘%+’ and ‘%-’ can both be used to refer to that job. In
+output pertaining to jobs (e.g., the output of the ‘jobs’ command), the
+current job is always marked with a ‘+’, and the previous job with a
+‘-’.
+
+ Simply naming a job can be used to bring it into the foreground: ‘%1’
+is a synonym for ‘fg %1’, bringing job 1 from the background into the
+foreground. Similarly, ‘%1 &’ resumes job 1 in the background,
+equivalent to ‘bg %1’.
+
+ The shell learns immediately whenever a job changes state. Normally,
+Bash waits until it is about to print a prompt before notifying the user
+about changes in a job's status so as to not interrupt any other output,
+though it will notify of changes in a job's status after a foreground
+command in a list completes, before executing the next command in the
+list. If the ‘-b’ option to the ‘set’ builtin is enabled, Bash reports
+status changes immediately (*note The Set Builtin::). Bash executes any
+trap on ‘SIGCHLD’ for each child process that terminates.
+
+ When a job terminates and Bash notifies the user about it, Bash
+removes the job from the jobs table. It will not appear in ‘jobs’
+output, but ‘wait’ will report its exit status, as long as it's supplied
+the process ID associated with the job as an argument. When the table
+is empty, job numbers start over at 1.
+
+ If a user attempts to exit Bash while jobs are stopped, (or running,
+if the ‘checkjobs’ option is enabled - see *note The Shopt Builtin::),
+the shell prints a warning message, and if the ‘checkjobs’ option is
+enabled, lists the jobs and their statuses. The ‘jobs’ command may then
+be used to inspect their status. If the user immediately attempts to
+exit again, without an intervening command, Bash does not print another
+warning, and terminates any stopped jobs.
+
+ When the shell is waiting for a job or process using the ‘wait’
+builtin, and job control is enabled, ‘wait’ will return when the job
+changes state. The ‘-f’ option causes ‘wait’ to wait until the job or
+process terminates before returning.
+
+\1f
+File: bash.info, Node: Job Control Builtins, Next: Job Control Variables, Prev: Job Control Basics, Up: Job Control
+
+7.2 Job Control Builtins
+========================
+
+‘bg’
+ bg [JOBSPEC ...]
+
+ Resume each suspended job JOBSPEC in the background, as if it had
+ been started with ‘&’. If JOBSPEC is not supplied, the shell uses
+ its notion of the current job. ‘bg’ returns zero unless it is run
+ when job control is not enabled, or, when run with job control
+ enabled, any JOBSPEC was not found or specifies a job that was
+ started without job control.
+
+‘fg’
+ fg [JOBSPEC]
+
+ Resume the job JOBSPEC in the foreground and make it the current
+ job. If JOBSPEC is not supplied, ‘fg’ resumes the current job.
+ The return status is that of the command placed into the
+ foreground, or non-zero if run when job control is disabled or,
+ when run with job control enabled, JOBSPEC does not specify a valid
+ job or JOBSPEC specifies a job that was started without job
+ control.
+
+‘jobs’
+ jobs [-lnprs] [JOBSPEC]
+ jobs -x COMMAND [ARGUMENTS]
+
+ The first form lists the active jobs. The options have the
+ following meanings:
+
+ ‘-l’
+ List process IDs in addition to the normal information.
+
+ ‘-n’
+ Display information only about jobs that have changed status
+ since the user was last notified of their status.
+
+ ‘-p’
+ List only the process ID of the job's process group leader.
+
+ ‘-r’
+ Display only running jobs.
+
+ ‘-s’
+ Display only stopped jobs.
+
+ If JOBSPEC is supplied, ‘jobs’ restricts output to information
+ about that job. If JOBSPEC is not supplied, ‘jobs’ lists the
+ status of all jobs. The return status is zero unless an invalid
+ option is encountered or an invalid JOBSPEC is supplied.
+
+ If the ‘-x’ option is supplied, ‘jobs’ replaces any JOBSPEC found
+ in COMMAND or ARGUMENTS with the corresponding process group ID,
+ and executes COMMAND, passing it ARGUMENTs, returning its exit
+ status.
+
+‘kill’
+ kill [-s SIGSPEC] [-n SIGNUM] [-SIGSPEC] ID [...]
+ kill -l|-L [EXIT_STATUS]
+
+ Send a signal specified by SIGSPEC or SIGNUM to the processes named
+ by each ID. Each ID may be a job specification JOBSPEC or process
+ ID PID. SIGSPEC is either a case-insensitive signal name such as
+ ‘SIGINT’ (with or without the ‘SIG’ prefix) or a signal number;
+ SIGNUM is a signal number. If SIGSPEC and SIGNUM are not present,
+ ‘kill’ sends ‘SIGTERM’.
+
+ The ‘-l’ option lists the signal names. If any arguments are
+ supplied when ‘-l’ is supplied, ‘kill’ lists the names of the
+ signals corresponding to the arguments, and the return status is
+ zero. EXIT_STATUS is a number specifying a signal number or the
+ exit status of a process terminated by a signal; if it is supplied,
+ ‘kill’ prints the name of the signal that caused the process to
+ terminate. ‘kill’ assumes that process exit statuses are greater
+ than 128; anything less than that is a signal number. The ‘-L’
+ option is equivalent to ‘-l’.
+
+ The return status is zero if at least one signal was successfully
+ sent, or non-zero if an error occurs or an invalid option is
+ encountered.
+
+‘wait’
+ wait [-fn] [-p VARNAME] [ID ...]
+
+ Wait until the child process specified by each ID exits and return
+ the exit status of the last ID. Each ID may be a process ID PID or
+ a job specification JOBSPEC; if a jobspec is supplied, ‘wait’ waits
+ for all processes in the job.
+
+ If no options or IDs are supplied, ‘wait’ waits for all running
+ background jobs and the last-executed process substitution, if its
+ process id is the same as $!, and the return status is zero.
+
+ If the ‘-n’ option is supplied, ‘wait’ waits for any one of the IDs
+ or, if no IDs are supplied, any job or process substitution, to
+ complete and returns its exit status. If none of the supplied IDs
+ is a child of the shell, or if no arguments are supplied and the
+ shell has no unwaited-for children, the exit status is 127.
+
+ If the ‘-p’ option is supplied, ‘wait’ assigns the process or job
+ identifier of the job for which the exit status is returned to the
+ variable VARNAME named by the option argument. The variable, which
+ cannot be readonly, will be unset initially, before any assignment.
+ This is useful only when used with the ‘-n’ option.
+
+ Supplying the ‘-f’ option, when job control is enabled, forces
+ ‘wait’ to wait for each ID to terminate before returning its
+ status, instead of returning when it changes status.
+
+ If none of the IDs specify one of the shell's an active child
+ processes, the return status is 127. If ‘wait’ is interrupted by a
+ signal, any VARNAME will remain unset, and the return status will
+ be greater than 128, as described above (*note Signals::).
+ Otherwise, the return status is the exit status of the last ID.
+
+‘disown’
+ disown [-ar] [-h] [ID ...]
+
+ Without options, remove each ID from the table of active jobs.
+ Each ID may be a job specification JOBSPEC or a process ID PID; if
+ ID is a PID, ‘disown’ uses the job containing PID as JOBSPEC.
+
+ If the ‘-h’ option is supplied, ‘disown’ does not remove the jobs
+ corresponding to each ‘id’ from the jobs table, but rather marks
+ them so the shell does not send ‘SIGHUP’ to the job if the shell
+ receives a ‘SIGHUP’.
+
+ If no ID is supplied, the ‘-a’ option means to remove or mark all
+ jobs; the ‘-r’ option without an ID argument removes or marks
+ running jobs. If no ID is supplied, and neither the ‘-a’ nor the
+ ‘-r’ option is supplied, ‘disown’ removes or marks the current job.
+
+ The return value is 0 unless an ID does not specify a valid job.
+
+‘suspend’
+ suspend [-f]
+
+ Suspend the execution of this shell until it receives a ‘SIGCONT’
+ signal. A login shell, or a shell without job control enabled,
+ cannot be suspended; the ‘-f’ option will override this and force
+ the suspension. The return status is 0 unless the shell is a login
+ shell or job control is not enabled and ‘-f’ is not supplied.
+
+ When job control is not active, the ‘kill’ and ‘wait’ builtins do not
+accept JOBSPEC arguments. They must be supplied process IDs.
+
+\1f
+File: bash.info, Node: Job Control Variables, Prev: Job Control Builtins, Up: Job Control
+
+7.3 Job Control Variables
+=========================
+
+‘auto_resume’
+ This variable controls how the shell interacts with the user and
+ job control. If this variable exists then simple commands
+ consisting of only a single word, without redirections, are treated
+ as candidates for resumption of an existing job. There is no
+ ambiguity allowed; if there is more than one job beginning with or
+ containing the word, then this selects the most recently accessed
+ job. The name of a stopped job, in this context, is the command
+ line used to start it, as displayed by ‘jobs’. If this variable is
+ set to the value ‘exact’, the word must match the name of a stopped
+ job exactly; if set to ‘substring’, the word needs to match a
+ substring of the name of a stopped job. The ‘substring’ value
+ provides functionality analogous to the ‘%?string’ job ID (*note
+ Job Control Basics::). If set to any other value (e.g., ‘prefix’),
+ the word must be a prefix of a stopped job's name; this provides
+ functionality analogous to the ‘%string’ job ID.
+
+\1f
+File: bash.info, Node: Command Line Editing, Next: Using History Interactively, Prev: Job Control, Up: Top
+
+8 Command Line Editing
+**********************
+
+This chapter describes the basic features of the GNU command line
+editing interface. Command line editing is provided by the Readline
+library, which is used by several different programs, including Bash.
+Command line editing is enabled by default when using an interactive
+shell, unless the ‘--noediting’ option is supplied at shell invocation.
+Line editing is also used when using the ‘-e’ option to the ‘read’
+builtin command (*note Bash Builtins::). By default, the line editing
+commands are similar to those of Emacs; a vi-style line editing
+interface is also available. Line editing can be enabled at any time
+using the ‘-o emacs’ or ‘-o vi’ options to the ‘set’ builtin command
+(*note The Set Builtin::), or disabled using the ‘+o emacs’ or ‘+o vi’
+options to ‘set’.
+
+* Menu:
+
+* Introduction and Notation:: Notation used in this text.
+* Readline Interaction:: The minimum set of commands for editing a line.
+* Readline Init File:: Customizing Readline from a user's view.
+* Bindable Readline Commands:: A description of most of the Readline commands
+ available for binding
+* Readline vi Mode:: A short description of how to make Readline
+ behave like the vi editor.
+* Programmable Completion:: How to specify the possible completions for
+ a specific command.
+* Programmable Completion Builtins:: Builtin commands to specify how to
+ complete arguments for a particular command.
+* A Programmable Completion Example:: An example shell function for
+ generating possible completions.
+
+\1f
+File: bash.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
+
+8.1 Introduction to Line Editing
+================================
+
+The following paragraphs use Emacs style to describe the notation used
+to represent keystrokes.
+
+ The text ‘C-k’ is read as "Control-K" and describes the character
+produced when the <k> key is pressed while the Control key is depressed.
+
+ The text ‘M-k’ is read as "Meta-K" and describes the character
+produced when the Meta key (if you have one) is depressed, and the <k>
+key is pressed (a “meta character”), then both are released. The Meta
+key is labeled <ALT> or <Option> on many keyboards. On keyboards with
+two keys labeled <ALT> (usually to either side of the space bar), the
+<ALT> on the left side is generally set to work as a Meta key. One of
+the <ALT> keys may also be configured as some other modifier, such as a
+Compose key for typing accented characters.
+
+ On some keyboards, the Meta key modifier produces characters with the
+eighth bit (0200) set. You can use the ‘enable-meta-key’ variable to
+control whether or not it does this, if the keyboard allows it. On many
+others, the terminal or terminal emulator converts the metafied key to a
+key sequence beginning with <ESC> as described in the next paragraph.
+
+ If you do not have a Meta or <ALT> key, or another key working as a
+Meta key, you can generally achieve the latter effect by typing <ESC>
+_first_, and then typing <k>. The <ESC> character is known as the “meta
+prefix”).
+
+ Either process is known as “metafying” the <k> key.
+
+ If your Meta key produces a key sequence with the <ESC> meta prefix,
+you can make ‘M-key’ key bindings you specify (see ‘Key Bindings’ in
+*note Readline Init File Syntax::) do the same thing by setting the
+‘force-meta-prefix’ variable.
+
+ The text ‘M-C-k’ is read as "Meta-Control-k" and describes the
+character produced by metafying ‘C-k’.
+
+ In addition, several keys have their own names. Specifically, <DEL>,
+<ESC>, <LFD>, <SPC>, <RET>, and <TAB> all stand for themselves when seen
+in this text, or in an init file (*note Readline Init File::). If your
+keyboard lacks a <LFD> key, typing <C-j> will output the appropriate
+character. The <RET> key may be labeled <Return> or <Enter> on some
+keyboards.
+
+\1f
+File: bash.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
+
+8.2 Readline Interaction
+========================
+
+Often during an interactive session you type in a long line of text,
+only to notice that the first word on the line is misspelled. The
+Readline library gives you a set of commands for manipulating the text
+as you type it in, allowing you to just fix your typo, and not forcing
+you to retype the majority of the line. Using these editing commands,
+you move the cursor to the place that needs correction, and delete or
+insert the text of the corrections. Then, when you are satisfied with
+the line, you simply press <RET>. You do not have to be at the end of
+the line to press <RET>; the entire line is accepted regardless of the
+location of the cursor within the line.
+
+* Menu:
+
+* Readline Bare Essentials:: The least you need to know about Readline.
+* Readline Movement Commands:: Moving about the input line.
+* Readline Killing Commands:: How to delete text, and how to get it back!
+* Readline Arguments:: Giving numeric arguments to commands.
+* Searching:: Searching through previous lines.
+
+\1f
+File: bash.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
+
+8.2.1 Readline Bare Essentials
+------------------------------
+
+In order to enter characters into the line, simply type them. The typed
+character appears where the cursor was, and then the cursor moves one
+space to the right. If you mistype a character, you can use your erase
+character to back up and delete the mistyped character.
+
+ Sometimes you may mistype a character, and not notice the error until
+you have typed several other characters. In that case, you can type
+‘C-b’ to move the cursor to the left, and then correct your mistake.
+Afterwards, you can move the cursor to the right with ‘C-f’.
+
+ When you add text in the middle of a line, you will notice that
+characters to the right of the cursor are "pushed over" to make room for
+the text that you have inserted. Likewise, when you delete text behind
+the cursor, characters to the right of the cursor are "pulled back" to
+fill in the blank space created by the removal of the text. These are
+the bare essentials for editing the text of an input line:
+
+‘C-b’
+ Move back one character.
+‘C-f’
+ Move forward one character.
+<DEL> or <Backspace>
+ Delete the character to the left of the cursor.
+‘C-d’
+ Delete the character underneath the cursor.
+Printing characters
+ Insert the character into the line at the cursor.
+‘C-_’ or ‘C-x C-u’
+ Undo the last editing command. You can undo all the way back to an
+ empty line.
+
+Depending on your configuration, the <Backspace> key might be set to
+delete the character to the left of the cursor and the <DEL> key set to
+delete the character underneath the cursor, like ‘C-d’, rather than the
+character to the left of the cursor.
+
+\1f
+File: bash.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
+
+8.2.2 Readline Movement Commands
+--------------------------------
+
+The above table describes the most basic keystrokes that you need in
+order to do editing of the input line. For your convenience, many other
+commands are available in addition to ‘C-b’, ‘C-f’, ‘C-d’, and <DEL>.
+Here are some commands for moving more rapidly within the line.
+
+‘C-a’
+ Move to the start of the line.
+‘C-e’
+ Move to the end of the line.
+‘M-f’
+ Move forward a word, where a word is composed of letters and
+ digits.
+‘M-b’
+ Move backward a word.
+‘C-l’
+ Clear the screen, reprinting the current line at the top.
+
+ Notice how ‘C-f’ moves forward a character, while ‘M-f’ moves forward
+a word. It is a loose convention that control keystrokes operate on
+characters while meta keystrokes operate on words.
+
+\1f
+File: bash.info, Node: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
+
+8.2.3 Readline Killing Commands
+-------------------------------
+
+“Killing” text means to delete the text from the line, but to save it
+away for later use, usually by “yanking” (re-inserting) it back into the
+line. ("Cut" and "paste" are more recent jargon for "kill" and "yank".)
+
+ If the description for a command says that it "kills" text, then you
+can be sure that you can get the text back in a different (or the same)
+place later.
+
+ When you use a kill command, the text is saved in a “kill-ring”. Any
+number of consecutive kills save all of the killed text together, so
+that when you yank it back, you get it all. The kill ring is not line
+specific; the text that you killed on a previously typed line is
+available to be yanked back later, when you are typing another line.
+
+ Here is the list of commands for killing text.
+
+‘C-k’
+ Kill the text from the current cursor position to the end of the
+ line.
+
+‘M-d’
+ Kill from the cursor to the end of the current word, or, if between
+ words, to the end of the next word. Word boundaries are the same
+ as those used by ‘M-f’.
+
+‘M-<DEL>’
+ Kill from the cursor to the start of the current word, or, if
+ between words, to the start of the previous word. Word boundaries
+ are the same as those used by ‘M-b’.
+
+‘C-w’
+ Kill from the cursor to the previous whitespace. This is different
+ than ‘M-<DEL>’ because the word boundaries differ.
+
+ Here is how to “yank” the text back into the line. Yanking means to
+copy the most-recently-killed text from the kill buffer into the line at
+the current cursor position.
+
+‘C-y’
+ Yank the most recently killed text back into the buffer at the
+ cursor.
+
+‘M-y’
+ Rotate the kill-ring, and yank the new top. You can only do this
+ if the prior command is ‘C-y’ or ‘M-y’.
+
+\1f
+File: bash.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
+
+8.2.4 Readline Arguments
+------------------------
+
+You can pass numeric arguments to Readline commands. Sometimes the
+argument acts as a repeat count, other times it is the sign of the
+argument that is significant. If you pass a negative argument to a
+command which normally acts in a forward direction, that command will
+act in a backward direction. For example, to kill text back to the
+start of the line, you might type ‘M-- C-k’.
+
+ The general way to pass numeric arguments to a command is to type the
+Meta key and then digits ("meta digits") before the command. If the
+first "digit" typed is a minus sign (‘-’), then the sign of the argument
+will be negative. Once you have typed one meta digit to get the
+argument started, you can type the remainder of the digits, and then the
+command. For example, to give the ‘C-d’ command an argument of 10, you
+could type ‘M-1 0 C-d’, which will delete the next ten characters on the
+input line.
+
+\1f
+File: bash.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
+
+8.2.5 Searching for Commands in the History
+-------------------------------------------
+
+Readline provides commands for searching through the command history
+(*note Bash History Facilities::) for lines containing a specified
+string. There are two search modes: “incremental” and
+“non-incremental”.
+
+ Incremental searches begin before the user has finished typing the
+search string. As each character of the search string is typed,
+Readline displays the next entry from the history matching the string
+typed so far. An incremental search requires only as many characters as
+needed to find the desired history entry. When using emacs editing
+mode, type ‘C-r’ to search backward in the history for a particular
+string. Typing ‘C-s’ searches forward through the history. The
+characters present in the value of the ‘isearch-terminators’ variable
+are used to terminate an incremental search. If that variable has not
+been assigned a value, the <ESC> and ‘C-j’ characters terminate an
+incremental search. ‘C-g’ aborts an incremental search and restores the
+original line. When the search is terminated, the history entry
+containing the search string becomes the current line.
+
+ To find other matching entries in the history list, type ‘C-r’ or
+‘C-s’ as appropriate. This searches backward or forward in the history
+for the next entry matching the search string typed so far. Any other
+key sequence bound to a Readline command terminates the search and
+executes that command. For instance, a <RET> terminates the search and
+accepts the line, thereby executing the command from the history list.
+A movement command will terminate the search, make the last line found
+the current line, and begin editing.
+
+ Readline remembers the last incremental search string. If two ‘C-r’s
+are typed without any intervening characters defining a new search
+string, Readline uses any remembered search string.
+
+ Non-incremental searches read the entire search string before
+starting to search for matching history entries. The search string may
+be typed by the user or be part of the contents of the current line.
+
+\1f
+File: bash.info, Node: Readline Init File, Next: Bindable Readline Commands, Prev: Readline Interaction, Up: Command Line Editing
+
+8.3 Readline Init File
+======================
+
+Although the Readline library comes with a set of Emacs-like keybindings
+installed by default, it is possible to use a different set of
+keybindings. Any user can customize programs that use Readline by
+putting commands in an “inputrc” file, conventionally in their home
+directory. The name of this file is taken from the value of the shell
+variable ‘INPUTRC’. If that variable is unset, the default is
+‘~/.inputrc’. If that file does not exist or cannot be read, Readline
+looks for ‘/etc/inputrc’. The ‘bind’ builtin command can also be used
+to set Readline keybindings and variables. *Note Bash Builtins::.
+
+ When a program that uses the Readline library starts up, Readline
+reads the init file and sets any variables and key bindings it contains.
+
+ In addition, the ‘C-x C-r’ command re-reads this init file, thus
+incorporating any changes that you might have made to it.
+
+* Menu:
+
+* Readline Init File Syntax:: Syntax for the commands in the inputrc file.
+* Conditional Init Constructs:: Conditional key bindings in the inputrc file.
+* Sample Init File:: An example inputrc file.
+
+\1f
+File: bash.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
+
+8.3.1 Readline Init File Syntax
+-------------------------------
+
+There are only a few basic constructs allowed in the Readline init file.
+Blank lines are ignored. Lines beginning with a ‘#’ are comments.
+Lines beginning with a ‘$’ indicate conditional constructs (*note
+Conditional Init Constructs::). Other lines denote variable settings
+and key bindings.
+
+Variable Settings
+ You can modify the run-time behavior of Readline by altering the
+ values of variables in Readline using the ‘set’ command within the
+ init file. The syntax is simple:
+
+ set VARIABLE VALUE
+
+ Here, for example, is how to change from the default Emacs-like key
+ binding to use ‘vi’ line editing commands:
+
+ set editing-mode vi
+
+ Variable names and values, where appropriate, are recognized
+ without regard to case. Unrecognized variable names are ignored.
+
+ Boolean variables (those that can be set to on or off) are set to
+ on if the value is null or empty, ON (case-insensitive), or 1. Any
+ other value results in the variable being set to off.
+
+ The ‘bind -V’ command lists the current Readline variable names and
+ values. *Note Bash Builtins::.
+
+ A great deal of run-time behavior is changeable with the following
+ variables.
+
+ ‘active-region-start-color’
+ A string variable that controls the text color and background
+ when displaying the text in the active region (see the
+ description of ‘enable-active-region’ below). This string
+ must not take up any physical character positions on the
+ display, so it should consist only of terminal escape
+ sequences. It is output to the terminal before displaying the
+ text in the active region. This variable is reset to the
+ default value whenever the terminal type changes. The default
+ value is the string that puts the terminal in standout mode,
+ as obtained from the terminal's terminfo description. A
+ sample value might be ‘\e[01;33m’.
+
+ ‘active-region-end-color’
+ A string variable that "undoes" the effects of
+ ‘active-region-start-color’ and restores "normal" terminal
+ display appearance after displaying text in the active region.
+ This string must not take up any physical character positions
+ on the display, so it should consist only of terminal escape
+ sequences. It is output to the terminal after displaying the
+ text in the active region. This variable is reset to the
+ default value whenever the terminal type changes. The default
+ value is the string that restores the terminal from standout
+ mode, as obtained from the terminal's terminfo description. A
+ sample value might be ‘\e[0m’.
+
+ ‘bell-style’
+ Controls what happens when Readline wants to ring the terminal
+ bell. If set to ‘none’, Readline never rings the bell. If
+ set to ‘visible’, Readline uses a visible bell if one is
+ available. If set to ‘audible’ (the default), Readline
+ attempts to ring the terminal's bell.
+
+ ‘bind-tty-special-chars’
+ If set to ‘on’ (the default), Readline attempts to bind the
+ control characters that are treated specially by the kernel's
+ terminal driver to their Readline equivalents. These override
+ the default Readline bindings described here. Type ‘stty -a’
+ at a Bash prompt to see your current terminal settings,
+ including the special control characters (usually ‘cchars’).
+ This binding takes place on each call to ‘readline()’, so
+ changes made by ‘stty’ can take effect.
+
+ ‘blink-matching-paren’
+ If set to ‘on’, Readline attempts to briefly move the cursor
+ to an opening parenthesis when a closing parenthesis is
+ inserted. The default is ‘off’.
+
+ ‘colored-completion-prefix’
+ If set to ‘on’, when listing completions, Readline displays
+ the common prefix of the set of possible completions using a
+ different color. The color definitions are taken from the
+ value of the ‘LS_COLORS’ environment variable. If there is a
+ color definition in ‘LS_COLORS’ for the custom suffix
+ ‘readline-colored-completion-prefix’, Readline uses this color
+ for the common prefix instead of its default. The default is
+ ‘off’.
+
+ ‘colored-stats’
+ If set to ‘on’, Readline displays possible completions using
+ different colors to indicate their file type. The color
+ definitions are taken from the value of the ‘LS_COLORS’
+ environment variable. The default is ‘off’.
+
+ ‘comment-begin’
+ The string to insert at the beginning of the line by the
+ ‘insert-comment’ command. The default value is ‘"#"’.
+
+ ‘completion-display-width’
+ The number of screen columns used to display possible matches
+ when performing completion. The value is ignored if it is
+ less than 0 or greater than the terminal screen width. A
+ value of 0 causes matches to be displayed one per line. The
+ default value is -1.
+
+ ‘completion-ignore-case’
+ If set to ‘on’, Readline performs filename matching and
+ completion in a case-insensitive fashion. The default value
+ is ‘off’.
+
+ ‘completion-map-case’
+ If set to ‘on’, and COMPLETION-IGNORE-CASE is enabled,
+ Readline treats hyphens (‘-’) and underscores (‘_’) as
+ equivalent when performing case-insensitive filename matching
+ and completion. The default value is ‘off’.
+
+ ‘completion-prefix-display-length’
+ The maximum length in characters of the common prefix of a
+ list of possible completions that is displayed without
+ modification. When set to a value greater than zero, Readline
+ replaces common prefixes longer than this value with an
+ ellipsis when displaying possible completions. If a
+ completion begins with a period, and Readline is completing
+ filenames, it uses three underscores instead of an ellipsis.
+
+ ‘completion-query-items’
+ The number of possible completions that determines when the
+ user is asked whether the list of possibilities should be
+ displayed. If the number of possible completions is greater
+ than or equal to this value, Readline asks whether or not the
+ user wishes to view them; otherwise, Readline simply lists the
+ completions. This variable must be set to an integer value
+ greater than or equal to zero. A zero value means Readline
+ should never ask; negative values are treated as zero. The
+ default limit is ‘100’.
+
+ ‘convert-meta’
+ If set to ‘on’, Readline converts characters it reads that
+ have the eighth bit set to an ASCII key sequence by clearing
+ the eighth bit and prefixing an <ESC> character, converting
+ them to a meta-prefixed key sequence. The default value is
+ ‘on’, but Readline sets it to ‘off’ if the locale contains
+ characters whose encodings may include bytes with the eighth
+ bit set. This variable is dependent on the ‘LC_CTYPE’ locale
+ category, and may change if the locale changes. This variable
+ also affects key bindings; see the description of
+ ‘force-meta-prefix’ below.
+
+ ‘disable-completion’
+ If set to ‘On’, Readline inhibits word completion. Completion
+ characters are inserted into the line as if they had been
+ mapped to ‘self-insert’. The default is ‘off’.
+
+ ‘echo-control-characters’
+ When set to ‘on’, on operating systems that indicate they
+ support it, Readline echoes a character corresponding to a
+ signal generated from the keyboard. The default is ‘on’.
+
+ ‘editing-mode’
+ The ‘editing-mode’ variable controls the default set of key
+ bindings. By default, Readline starts up in emacs editing
+ mode, where the keystrokes are most similar to Emacs. This
+ variable can be set to either ‘emacs’ or ‘vi’.
+
+ ‘emacs-mode-string’
+ If the SHOW-MODE-IN-PROMPT variable is enabled, this string is
+ displayed immediately before the last line of the primary
+ prompt when emacs editing mode is active. The value is
+ expanded like a key binding, so the standard set of meta- and
+ control- prefixes and backslash escape sequences is available.
+ The ‘\1’ and ‘\2’ escapes begin and end sequences of
+ non-printing characters, which can be used to embed a terminal
+ control sequence into the mode string. The default is ‘@’.
+
+ ‘enable-active-region’
+ “point” is the current cursor position, and “mark” refers to a
+ saved cursor position (*note Commands For Moving::). The text
+ between the point and mark is referred to as the “region”.
+ When this variable is set to ‘On’, Readline allows certain
+ commands to designate the region as “active”. When the region
+ is active, Readline highlights the text in the region using
+ the value of the ‘active-region-start-color’, which defaults
+ to the string that enables the terminal's standout mode. The
+ active region shows the text inserted by bracketed-paste and
+ any matching text found by incremental and non-incremental
+ history searches. The default is ‘On’.
+
+ ‘enable-bracketed-paste’
+ When set to ‘On’, Readline configures the terminal to insert
+ each paste into the editing buffer as a single string of
+ characters, instead of treating each character as if it had
+ been read from the keyboard. This is called putting the
+ terminal into “bracketed paste mode”; it prevents Readline
+ from executing any editing commands bound to key sequences
+ appearing in the pasted text. The default is ‘On’.
+
+ ‘enable-keypad’
+ When set to ‘on’, Readline tries to enable the application
+ keypad when it is called. Some systems need this to enable
+ the arrow keys. The default is ‘off’.
+
+ ‘enable-meta-key’
+ When set to ‘on’, Readline tries to enable any meta modifier
+ key the terminal claims to support when it is called. On many
+ terminals, the Meta key is used to send eight-bit characters;
+ this variable checks for the terminal capability that
+ indicates the terminal can enable and disable a mode that sets
+ the eighth bit of a character (0200) if the Meta key is held
+ down when the character is typed (a meta character). The
+ default is ‘on’.
+
+ ‘expand-tilde’
+ If set to ‘on’, Readline attempts tilde expansion when it
+ attempts word completion. The default is ‘off’.
+
+ ‘force-meta-prefix’
+ If set to ‘on’, Readline modifies its behavior when binding
+ key sequences containing ‘\M-’ or ‘Meta-’ (see ‘Key Bindings’
+ in *note Readline Init File Syntax::) by converting a key
+ sequence of the form ‘\M-’C or ‘Meta-’C to the two-character
+ sequence ‘ESC’ C (adding the meta prefix). If
+ ‘force-meta-prefix’ is set to ‘off’ (the default), Readline
+ uses the value of the ‘convert-meta’ variable to determine
+ whether to perform this conversion: if ‘convert-meta’ is ‘on’,
+ Readline performs the conversion described above; if it is
+ ‘off’, Readline converts C to a meta character by setting the
+ eighth bit (0200). The default is ‘off’.
+
+ ‘history-preserve-point’
+ If set to ‘on’, the history code attempts to place the point
+ (the current cursor position) at the same location on each
+ history line retrieved with ‘previous-history’ or
+ ‘next-history’. The default is ‘off’.
+
+ ‘history-size’
+ Set the maximum number of history entries saved in the history
+ list. If set to zero, any existing history entries are
+ deleted and no new entries are saved. If set to a value less
+ than zero, the number of history entries is not limited. By
+ default, Bash sets the maximum number of history entries to
+ the value of the ‘HISTSIZE’ shell variable. If you try to set
+ HISTORY-SIZE to a non-numeric value, the maximum number of
+ history entries will be set to 500.
+
+ ‘horizontal-scroll-mode’
+ Setting this variable to ‘on’ means that the text of the lines
+ being edited will scroll horizontally on a single screen line
+ when the lines are longer than the width of the screen,
+ instead of wrapping onto a new screen line. This variable is
+ automatically set to ‘on’ for terminals of height 1. By
+ default, this variable is set to ‘off’.
+
+ ‘input-meta’
+ If set to ‘on’, Readline enables eight-bit input (that is, it
+ does not clear the eighth bit in the characters it reads),
+ regardless of what the terminal claims it can support. The
+ default value is ‘off’, but Readline sets it to ‘on’ if the
+ locale contains characters whose encodings may include bytes
+ with the eighth bit set. This variable is dependent on the
+ ‘LC_CTYPE’ locale category, and its value may change if the
+ locale changes. The name ‘meta-flag’ is a synonym for
+ ‘input-meta’.
+
+ ‘isearch-terminators’
+ The string of characters that should terminate an incremental
+ search without subsequently executing the character as a
+ command (*note Searching::). If this variable has not been
+ given a value, the characters <ESC> and ‘C-j’ terminate an
+ incremental search.
+
+ ‘keymap’
+ Sets Readline's idea of the current keymap for key binding
+ commands. Built-in ‘keymap’ names are ‘emacs’,
+ ‘emacs-standard’, ‘emacs-meta’, ‘emacs-ctlx’, ‘vi’, ‘vi-move’,
+ ‘vi-command’, and ‘vi-insert’. ‘vi’ is equivalent to
+ ‘vi-command’ (‘vi-move’ is also a synonym); ‘emacs’ is
+ equivalent to ‘emacs-standard’. Applications may add
+ additional names. The default value is ‘emacs’; the value of
+ the ‘editing-mode’ variable also affects the default keymap.
+
+ ‘keyseq-timeout’
+ Specifies the duration Readline will wait for a character when
+ reading an ambiguous key sequence (one that can form a
+ complete key sequence using the input read so far, or can take
+ additional input to complete a longer key sequence). If
+ Readline doesn't receive any input within the timeout, it uses
+ the shorter but complete key sequence. Readline uses this
+ value to determine whether or not input is available on the
+ current input source (‘rl_instream’ by default). The value is
+ specified in milliseconds, so a value of 1000 means that
+ Readline will wait one second for additional input. If this
+ variable is set to a value less than or equal to zero, or to a
+ non-numeric value, Readline waits until another key is pressed
+ to decide which key sequence to complete. The default value
+ is ‘500’.
+
+ ‘mark-directories’
+ If set to ‘on’, completed directory names have a slash
+ appended. The default is ‘on’.
+
+ ‘mark-modified-lines’
+ When this variable is set to ‘on’, Readline displays an
+ asterisk (‘*’) at the start of history lines which have been
+ modified. This variable is ‘off’ by default.
+
+ ‘mark-symlinked-directories’
+ If set to ‘on’, completed names which are symbolic links to
+ directories have a slash appended, subject to the value of
+ ‘mark-directories’. The default is ‘off’.
+
+ ‘match-hidden-files’
+ This variable, when set to ‘on’, forces Readline to match
+ files whose names begin with a ‘.’ (hidden files) when
+ performing filename completion. If set to ‘off’, the user
+ must include the leading ‘.’ in the filename to be completed.
+ This variable is ‘on’ by default.
+
+ ‘menu-complete-display-prefix’
+ If set to ‘on’, menu completion displays the common prefix of
+ the list of possible completions (which may be empty) before
+ cycling through the list. The default is ‘off’.
+
+ ‘output-meta’
+ If set to ‘on’, Readline displays characters with the eighth
+ bit set directly rather than as a meta-prefixed escape
+ sequence. The default is ‘off’, but Readline sets it to ‘on’
+ if the locale contains characters whose encodings may include
+ bytes with the eighth bit set. This variable is dependent on
+ the ‘LC_CTYPE’ locale category, and its value may change if
+ the locale changes.
+
+ ‘page-completions’
+ If set to ‘on’, Readline uses an internal pager resembling
+ more(1) to display a screenful of possible completions at a
+ time. This variable is ‘on’ by default.
+
+ ‘prefer-visible-bell’
+ See ‘bell-style’.
+
+ ‘print-completions-horizontally’
+ If set to ‘on’, Readline displays completions with matches
+ sorted horizontally in alphabetical order, rather than down
+ the screen. The default is ‘off’.
+
+ ‘revert-all-at-newline’
+ If set to ‘on’, Readline will undo all changes to history
+ lines before returning when executing ‘accept-line’. By
+ default, history lines may be modified and retain individual
+ undo lists across calls to ‘readline()’. The default is
+ ‘off’.
+
+ ‘search-ignore-case’
+ If set to ‘on’, Readline performs incremental and
+ non-incremental history list searches in a case-insensitive
+ fashion. The default value is ‘off’.
+
+ ‘show-all-if-ambiguous’
+ This alters the default behavior of the completion functions.
+ If set to ‘on’, words which have more than one possible
+ completion cause the matches to be listed immediately instead
+ of ringing the bell. The default value is ‘off’.
+
+ ‘show-all-if-unmodified’
+ This alters the default behavior of the completion functions
+ in a fashion similar to SHOW-ALL-IF-AMBIGUOUS. If set to
+ ‘on’, words which have more than one possible completion
+ without any possible partial completion (the possible
+ completions don't share a common prefix) cause the matches to
+ be listed immediately instead of ringing the bell. The
+ default value is ‘off’.
+
+ ‘show-mode-in-prompt’
+ If set to ‘on’, add a string to the beginning of the prompt
+ indicating the editing mode: emacs, vi command, or vi
+ insertion. The mode strings are user-settable (e.g.,
+ EMACS-MODE-STRING). The default value is ‘off’.
+
+ ‘skip-completed-text’
+ If set to ‘on’, this alters the default completion behavior
+ when inserting a single match into the line. It's only active
+ when performing completion in the middle of a word. If
+ enabled, Readline does not insert characters from the
+ completion that match characters after point in the word being
+ completed, so portions of the word following the cursor are
+ not duplicated. For instance, if this is enabled, attempting
+ completion when the cursor is after the first ‘e’ in
+ ‘Makefile’ will result in ‘Makefile’ rather than
+ ‘Makefilefile’, assuming there is a single possible
+ completion. The default value is ‘off’.
+
+ ‘vi-cmd-mode-string’
+ If the SHOW-MODE-IN-PROMPT variable is enabled, this string is
+ displayed immediately before the last line of the primary
+ prompt when vi editing mode is active and in command mode.
+ The value is expanded like a key binding, so the standard set
+ of meta- and control- prefixes and backslash escape sequences
+ is available. The ‘\1’ and ‘\2’ escapes begin and end
+ sequences of non-printing characters, which can be used to
+ embed a terminal control sequence into the mode string. The
+ default is ‘(cmd)’.
+
+ ‘vi-ins-mode-string’
+ If the SHOW-MODE-IN-PROMPT variable is enabled, this string is
+ displayed immediately before the last line of the primary
+ prompt when vi editing mode is active and in insertion mode.
+ The value is expanded like a key binding, so the standard set
+ of meta- and control- prefixes and backslash escape sequences
+ is available. The ‘\1’ and ‘\2’ escapes begin and end
+ sequences of non-printing characters, which can be used to
+ embed a terminal control sequence into the mode string. The
+ default is ‘(ins)’.
+
+ ‘visible-stats’
+ If set to ‘on’, a character denoting a file's type is appended
+ to the filename when listing possible completions. The
+ default is ‘off’.
+
+Key Bindings
+ The syntax for controlling key bindings in the init file is simple.
+ First you need to find the name of the command that you want to
+ change. The following sections contain tables of the command name,
+ the default keybinding, if any, and a short description of what the
+ command does.
+
+ Once you know the name of the command, simply place on a line in
+ the init file the name of the key you wish to bind the command to,
+ a colon, and then the name of the command. There can be no space
+ between the key name and the colon - that will be interpreted as
+ part of the key name. The name of the key can be expressed in
+ different ways, depending on what you find most comfortable.
+
+ In addition to command names, Readline allows keys to be bound to a
+ string that is inserted when the key is pressed (a MACRO). The
+ difference between a macro and a command is that a macro is
+ enclosed in single or double quotes.
+
+ The ‘bind -p’ command displays Readline function names and bindings
+ in a format that can be put directly into an initialization file.
+ *Note Bash Builtins::.
+
+ KEYNAME: FUNCTION-NAME or MACRO
+ KEYNAME is the name of a key spelled out in English. For
+ example:
+ Control-u: universal-argument
+ Meta-Rubout: backward-kill-word
+ Control-o: "> output"
+
+ In the example above, ‘C-u’ is bound to the function
+ ‘universal-argument’, ‘M-DEL’ is bound to the function
+ ‘backward-kill-word’, and ‘C-o’ is bound to run the macro
+ expressed on the right hand side (that is, to insert the text
+ ‘> output’ into the line).
+
+ This key binding syntax recognizes a number of symbolic
+ character names: DEL, ESC, ESCAPE, LFD, NEWLINE, RET, RETURN,
+ RUBOUT (a destructive backspace), SPACE, SPC, and TAB.
+
+ "KEYSEQ": FUNCTION-NAME or MACRO
+ KEYSEQ differs from KEYNAME above in that strings denoting an
+ entire key sequence can be specified, by placing the key
+ sequence in double quotes. Some GNU Emacs style key escapes
+ can be used, as in the following example, but none of the
+ special character names are recognized.
+
+ "\C-u": universal-argument
+ "\C-x\C-r": re-read-init-file
+ "\e[11~": "Function Key 1"
+
+ In the above example, ‘C-u’ is again bound to the function
+ ‘universal-argument’ (just as it was in the first example),
+ ‘‘C-x’ ‘C-r’’ is bound to the function ‘re-read-init-file’,
+ and ‘<ESC> <[> <1> <1> <~>’ is bound to insert the text
+ ‘Function Key 1’.
+
+ The following GNU Emacs style escape sequences are available when
+ specifying key sequences:
+
+ ‘\C-’
+ A control prefix.
+ ‘\M-’
+ Adding the meta prefix or converting the following character
+ to a meta character, as described above under
+ ‘force-meta-prefix’ (see ‘Variable Settings’ in *note Readline
+ Init File Syntax::).
+ ‘\e’
+ An escape character.
+ ‘\\’
+ Backslash.
+ ‘\"’
+ <">, a double quotation mark.
+ ‘\'’
+ <'>, a single quote or apostrophe.
+
+ In addition to the GNU Emacs style escape sequences, a second set
+ of backslash escapes is available:
+
+ ‘\a’
+ alert (bell)
+ ‘\b’
+ backspace
+ ‘\d’
+ delete
+ ‘\f’
+ form feed
+ ‘\n’
+ newline
+ ‘\r’
+ carriage return
+ ‘\t’
+ horizontal tab
+ ‘\v’
+ vertical tab
+ ‘\NNN’
+ The eight-bit character whose value is the octal value NNN
+ (one to three digits).
+ ‘\xHH’
+ The eight-bit character whose value is the hexadecimal value
+ HH (one or two hex digits).
+
+ When entering the text of a macro, single or double quotes must be
+ used to indicate a macro definition. Unquoted text is assumed to
+ be a function name. The backslash escapes described above are
+ expanded in the macro body. Backslash will quote any other
+ character in the macro text, including ‘"’ and ‘'’. For example,
+ the following binding will make ‘‘C-x’ \’ insert a single ‘\’ into
+ the line:
+ "\C-x\\": "\\"
+
+\1f
+File: bash.info, Node: Conditional Init Constructs, Next: Sample Init File, Prev: Readline Init File Syntax, Up: Readline Init File
+
+8.3.2 Conditional Init Constructs
+---------------------------------
+
+Readline implements a facility similar in spirit to the conditional
+compilation features of the C preprocessor which allows key bindings and
+variable settings to be performed as the result of tests. There are
+four parser directives available.
+
+‘$if’
+ The ‘$if’ construct allows bindings to be made based on the editing
+ mode, the terminal being used, or the application using Readline.
+ The text of the test, after any comparison operator, extends to the
+ end of the line; unless otherwise noted, no characters are required
+ to isolate it.
+
+ ‘mode’
+ The ‘mode=’ form of the ‘$if’ directive is used to test
+ whether Readline is in ‘emacs’ or ‘vi’ mode. This may be used
+ in conjunction with the ‘set keymap’ command, for instance, to
+ set bindings in the ‘emacs-standard’ and ‘emacs-ctlx’ keymaps
+ only if Readline is starting out in ‘emacs’ mode.
+
+ ‘term’
+ The ‘term=’ form may be used to include terminal-specific key
+ bindings, perhaps to bind the key sequences output by the
+ terminal's function keys. The word on the right side of the
+ ‘=’ is tested against both the full name of the terminal and
+ the portion of the terminal name before the first ‘-’. This
+ allows ‘xterm’ to match both ‘xterm’ and ‘xterm-256color’, for
+ instance.
+
+ ‘version’
+ The ‘version’ test may be used to perform comparisons against
+ specific Readline versions. The ‘version’ expands to the
+ current Readline version. The set of comparison operators
+ includes ‘=’ (and ‘==’), ‘!=’, ‘<=’, ‘>=’, ‘<’, and ‘>’. The
+ version number supplied on the right side of the operator
+ consists of a major version number, an optional decimal point,
+ and an optional minor version (e.g., ‘7.1’). If the minor
+ version is omitted, it defaults to ‘0’. The operator may be
+ separated from the string ‘version’ and from the version
+ number argument by whitespace. The following example sets a
+ variable if the Readline version being used is 7.0 or newer:
+ $if version >= 7.0
+ set show-mode-in-prompt on
+ $endif
+
+ ‘application’
+ The APPLICATION construct is used to include
+ application-specific settings. Each program using the
+ Readline library sets the APPLICATION NAME, and you can test
+ for a particular value. This could be used to bind key
+ sequences to functions useful for a specific program. For
+ instance, the following command adds a key sequence that
+ quotes the current or previous word in Bash:
+ $if Bash
+ # Quote the current or previous word
+ "\C-xq": "\eb\"\ef\""
+ $endif
+
+ ‘variable’
+ The VARIABLE construct provides simple equality tests for
+ Readline variables and values. The permitted comparison
+ operators are ‘=’, ‘==’, and ‘!=’. The variable name must be
+ separated from the comparison operator by whitespace; the
+ operator may be separated from the value on the right hand
+ side by whitespace. String and boolean variables may be
+ tested. Boolean variables must be tested against the values
+ ON and OFF. The following example is equivalent to the
+ ‘mode=emacs’ test described above:
+ $if editing-mode == emacs
+ set show-mode-in-prompt on
+ $endif
+
+‘$else’
+ Commands in this branch of the ‘$if’ directive are executed if the
+ test fails.
+
+‘$endif’
+ This command, as seen in the previous example, terminates an ‘$if’
+ command.
+
+‘$include’
+ This directive takes a single filename as an argument and reads
+ commands and key bindings from that file. For example, the
+ following directive reads from ‘/etc/inputrc’:
+ $include /etc/inputrc
+
+\1f
+File: bash.info, Node: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
+
+8.3.3 Sample Init File
+----------------------
+
+Here is an example of an INPUTRC file. This illustrates key binding,
+variable assignment, and conditional syntax.
+
+ # This file controls the behavior of line input editing for
+ # programs that use the GNU Readline library. Existing
+ # programs include FTP, Bash, and GDB.
+ #
+ # You can re-read the inputrc file with C-x C-r.
+ # Lines beginning with '#' are comments.
+ #
+ # First, include any system-wide bindings and variable
+ # assignments from /etc/Inputrc
+ $include /etc/Inputrc
+
+ #
+ # Set various bindings for emacs mode.
+
+ set editing-mode emacs
+
+ $if mode=emacs
+
+ Meta-Control-h: backward-kill-word Text after the function name is ignored
+
+ #
+ # Arrow keys in keypad mode
+ #
+ #"\M-OD": backward-char
+ #"\M-OC": forward-char
+ #"\M-OA": previous-history
+ #"\M-OB": next-history
+ #
+ # Arrow keys in ANSI mode
+ #
+ "\M-[D": backward-char
+ "\M-[C": forward-char
+ "\M-[A": previous-history
+ "\M-[B": next-history
+ #
+ # Arrow keys in 8 bit keypad mode
+ #
+ #"\M-\C-OD": backward-char
+ #"\M-\C-OC": forward-char
+ #"\M-\C-OA": previous-history
+ #"\M-\C-OB": next-history
+ #
+ # Arrow keys in 8 bit ANSI mode
+ #
+ #"\M-\C-[D": backward-char
+ #"\M-\C-[C": forward-char
+ #"\M-\C-[A": previous-history
+ #"\M-\C-[B": next-history
+
+ C-q: quoted-insert
+
+ $endif
+
+ # An old-style binding. This happens to be the default.
+ TAB: complete
+
+ # Macros that are convenient for shell interaction
+ $if Bash
+ # edit the path
+ "\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
+ # prepare to type a quoted word --
+ # insert open and close double quotes
+ # and move to just after the open quote
+ "\C-x\"": "\"\"\C-b"
+ # insert a backslash (testing backslash escapes
+ # in sequences and macros)
+ "\C-x\\": "\\"
+ # Quote the current or previous word
+ "\C-xq": "\eb\"\ef\""
+ # Add a binding to refresh the line, which is unbound
+ "\C-xr": redraw-current-line
+ # Edit variable on current line.
+ "\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
+ $endif
+
+ # use a visible bell if one is available
+ set bell-style visible
+
+ # don't strip characters to 7 bits when reading
+ set input-meta on
+
+ # allow iso-latin1 characters to be inserted rather
+ # than converted to prefix-meta sequences
+ set convert-meta off
+
+ # display characters with the eighth bit set directly
+ # rather than as meta-prefixed characters
+ set output-meta on
+
+ # if there are 150 or more possible completions for a word,
+ # ask whether or not the user wants to see all of them
+ set completion-query-items 150
+
+ # For FTP
+ $if Ftp
+ "\C-xg": "get \M-?"
+ "\C-xt": "put \M-?"
+ "\M-.": yank-last-arg
+ $endif
+
+\1f
+File: bash.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
+
+8.4 Bindable Readline Commands
+==============================
+
+* Menu:
+
+* Commands For Moving:: Moving about the line.
+* Commands For History:: Getting at previous lines.
+* Commands For Text:: Commands for changing text.
+* Commands For Killing:: Commands for killing and yanking.
+* Numeric Arguments:: Specifying numeric arguments, repeat counts.
+* Commands For Completion:: Getting Readline to do the typing for you.
+* Keyboard Macros:: Saving and re-executing typed characters
+* Miscellaneous Commands:: Other miscellaneous commands.
+
+This section describes Readline commands that may be bound to key
+sequences. You can list your key bindings by executing ‘bind -P’ or,
+for a more terse format, suitable for an INPUTRC file, ‘bind -p’.
+(*Note Bash Builtins::.) Command names without an accompanying key
+sequence are unbound by default.
+
+ In the following descriptions, “point” refers to the current cursor
+position, and “mark” refers to a cursor position saved by the ‘set-mark’
+command. The text between the point and mark is referred to as the
+“region”. Readline has the concept of an _active region_: when the
+region is active, Readline redisplay highlights the region using the
+value of the ‘active-region-start-color’ variable. The
+‘enable-active-region’ variable turns this on and off. Several commands
+set the region to active; those are noted below.
+
+\1f
+File: bash.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
+
+8.4.1 Commands For Moving
+-------------------------
+
+‘beginning-of-line (C-a)’
+ Move to the start of the current line. This may also be bound to
+ the Home key on some keyboards.
+
+‘end-of-line (C-e)’
+ Move to the end of the line. This may also be bound to the End key
+ on some keyboards.
+
+‘forward-char (C-f)’
+ Move forward a character. This may also be bound to the right
+ arrow key on some keyboards.
+
+‘backward-char (C-b)’
+ Move back a character. This may also be bound to the left arrow
+ key on some keyboards.
+
+‘forward-word (M-f)’
+ Move forward to the end of the next word. Words are composed of
+ letters and digits.
+
+‘backward-word (M-b)’
+ Move back to the start of the current or previous word. Words are
+ composed of letters and digits.
+
+‘shell-forward-word (M-C-f)’
+ Move forward to the end of the next word. Words are delimited by
+ non-quoted shell metacharacters.
+
+‘shell-backward-word (M-C-b)’
+ Move back to the start of the current or previous word. Words are
+ delimited by non-quoted shell metacharacters.
+
+‘previous-screen-line ()’
+ Attempt to move point to the same physical screen column on the
+ previous physical screen line. This will not have the desired
+ effect if the current Readline line does not take up more than one
+ physical line or if point is not greater than the length of the
+ prompt plus the screen width.
+
+‘next-screen-line ()’
+ Attempt to move point to the same physical screen column on the
+ next physical screen line. This will not have the desired effect
+ if the current Readline line does not take up more than one
+ physical line or if the length of the current Readline line is not
+ greater than the length of the prompt plus the screen width.
+
+‘clear-display (M-C-l)’
+ Clear the screen and, if possible, the terminal's scrollback
+ buffer, then redraw the current line, leaving the current line at
+ the top of the screen.
+
+‘clear-screen (C-l)’
+ Clear the screen, then redraw the current line, leaving the current
+ line at the top of the screen. If given a numeric argument, this
+ refreshes the current line without clearing the screen.
+
+‘redraw-current-line ()’
+ Refresh the current line. By default, this is unbound.
+
+\1f
+File: bash.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
+
+8.4.2 Commands For Manipulating The History
+-------------------------------------------
+
+‘accept-line (Newline or Return)’
+ Accept the line regardless of where the cursor is. If this line is
+ non-empty, add it to the history list according to the setting of
+ the ‘HISTCONTROL’ and ‘HISTIGNORE’ variables. If this line is a
+ modified history line, then restore the history line to its
+ original state.
+
+‘previous-history (C-p)’
+ Move "back" through the history list, fetching the previous
+ command. This may also be bound to the up arrow key on some
+ keyboards.
+
+‘next-history (C-n)’
+ Move "forward" through the history list, fetching the next command.
+ This may also be bound to the down arrow key on some keyboards.
+
+‘beginning-of-history (M-<)’
+ Move to the first line in the history.
+
+‘end-of-history (M->)’
+ Move to the end of the input history, i.e., the line currently
+ being entered.
+
+‘reverse-search-history (C-r)’
+ Search backward starting at the current line and moving "up"
+ through the history as necessary. This is an incremental search.
+ This command sets the region to the matched text and activates the
+ region.
+
+‘forward-search-history (C-s)’
+ Search forward starting at the current line and moving "down"
+ through the history as necessary. This is an incremental search.
+ This command sets the region to the matched text and activates the
+ region.
+
+‘non-incremental-reverse-search-history (M-p)’
+ Search backward starting at the current line and moving "up"
+
+ through the history as necessary using a non-incremental search for
+ a string supplied by the user. The search string may match
+ anywhere in a history line.
+
+‘non-incremental-forward-search-history (M-n)’
+ Search forward starting at the current line and moving "down"
+ through the history as necessary using a non-incremental search for
+ a string supplied by the user. The search string may match
+ anywhere in a history line.
+
+‘history-search-backward ()’
+ Search backward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string must match at the beginning of a history line. This is a
+ non-incremental search. By default, this command is unbound, but
+ may be bound to the Page Down key on some keyboards.
+
+‘history-search-forward ()’
+ Search forward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string must match at the beginning of a history line. This is a
+ non-incremental search. By default, this command is unbound, but
+ may be bound to the Page Up key on some keyboards.
+
+‘history-substring-search-backward ()’
+ Search backward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string may match anywhere in a history line. This is a
+ non-incremental search. By default, this command is unbound.
+
+‘history-substring-search-forward ()’
+ Search forward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string may match anywhere in a history line. This is a
+ non-incremental search. By default, this command is unbound.
+
+‘yank-nth-arg (M-C-y)’
+ Insert the first argument to the previous command (usually the
+ second word on the previous line) at point. With an argument N,
+ insert the Nth word from the previous command (the words in the
+ previous command begin with word 0). A negative argument inserts
+ the Nth word from the end of the previous command. Once the
+ argument N is computed, this uses the history expansion facilities
+ to extract the Nth word, as if the ‘!N’ history expansion had been
+ specified.
+
+‘yank-last-arg (M-. or M-_)’
+ Insert last argument to the previous command (the last word of the
+ previous history entry). With a numeric argument, behave exactly
+ like ‘yank-nth-arg’. Successive calls to ‘yank-last-arg’ move back
+ through the history list, inserting the last word (or the word
+ specified by the argument to the first call) of each line in turn.
+ Any numeric argument supplied to these successive calls determines
+ the direction to move through the history. A negative argument
+ switches the direction through the history (back or forward). This
+ uses the history expansion facilities to extract the last word, as
+ if the ‘!$’ history expansion had been specified.
+
+‘operate-and-get-next (C-o)’
+ Accept the current line for return to the calling application as if
+ a newline had been entered, and fetch the next line relative to the
+ current line from the history for editing. A numeric argument, if
+ supplied, specifies the history entry to use instead of the current
+ line.
+
+‘fetch-history ()’
+ With a numeric argument, fetch that entry from the history list and
+ make it the current line. Without an argument, move back to the
+ first entry in the history list.
+
+\1f
+File: bash.info, Node: Commands For Text, Next: Commands For Killing, Prev: Commands For History, Up: Bindable Readline Commands
+
+8.4.3 Commands For Changing Text
+--------------------------------
+
+‘end-of-file (usually C-d)’
+ The character indicating end-of-file as set, for example, by
+ ‘stty’. If this character is read when there are no characters on
+ the line, and point is at the beginning of the line, Readline
+ interprets it as the end of input and returns EOF.
+
+‘delete-char (C-d)’
+ Delete the character at point. If this function is bound to the
+ same character as the tty EOF character, as ‘C-d’ commonly is, see
+ above for the effects. This may also be bound to the Delete key on
+ some keyboards.
+
+‘backward-delete-char (Rubout)’
+ Delete the character behind the cursor. A numeric argument means
+ to kill the characters, saving them on the kill ring, instead of
+ deleting them.
+
+‘forward-backward-delete-char ()’
+ Delete the character under the cursor, unless the cursor is at the
+ end of the line, in which case the character behind the cursor is
+ deleted. By default, this is not bound to a key.
+
+‘quoted-insert (C-q or C-v)’
+ Add the next character typed to the line verbatim. This is how to
+ insert key sequences like ‘C-q’, for example.
+
+‘self-insert (a, b, A, 1, !, ...)’
+ Insert the character typed.
+
+‘bracketed-paste-begin ()’
+ This function is intended to be bound to the "bracketed paste"
+ escape sequence sent by some terminals, and such a binding is
+ assigned by default. It allows Readline to insert the pasted text
+ as a single unit without treating each character as if it had been
+ read from the keyboard. The characters are inserted as if each one
+ was bound to ‘self-insert’ instead of executing any editing
+ commands.
+
+ Bracketed paste sets the region (the characters between point and
+ the mark) to the inserted text. It sets the _active region_.
+
+‘transpose-chars (C-t)’
+ Drag the character before the cursor forward over the character at
+ the cursor, moving the cursor forward as well. If the insertion
+ point is at the end of the line, then this transposes the last two
+ characters of the line. Negative arguments have no effect.
+
+‘transpose-words (M-t)’
+ Drag the word before point past the word after point, moving point
+ past that word as well. If the insertion point is at the end of
+ the line, this transposes the last two words on the line.
+
+‘shell-transpose-words (M-C-t)’
+ Drag the word before point past the word after point, moving point
+ past that word as well. If the insertion point is at the end of
+ the line, this transposes the last two words on the line. Word
+ boundaries are the same as ‘shell-forward-word’ and
+ ‘shell-backward-word’.
+
+‘upcase-word (M-u)’
+ Uppercase the current (or following) word. With a negative
+ argument, uppercase the previous word, but do not move the cursor.
+
+‘downcase-word (M-l)’
+ Lowercase the current (or following) word. With a negative
+ argument, lowercase the previous word, but do not move the cursor.
+
+‘capitalize-word (M-c)’
+ Capitalize the current (or following) word. With a negative
+ argument, capitalize the previous word, but do not move the cursor.
+
+‘overwrite-mode ()’
+ Toggle overwrite mode. With an explicit positive numeric argument,
+ switches to overwrite mode. With an explicit non-positive numeric
+ argument, switches to insert mode. This command affects only
+ ‘emacs’ mode; ‘vi’ mode does overwrite differently. Each call to
+ ‘readline()’ starts in insert mode.
+
+ In overwrite mode, characters bound to ‘self-insert’ replace the
+ text at point rather than pushing the text to the right.
+ Characters bound to ‘backward-delete-char’ replace the character
+ before point with a space.
+
+ By default, this command is unbound, but may be bound to the Insert
+ key on some keyboards.
+
+\1f
+File: bash.info, Node: Commands For Killing, Next: Numeric Arguments, Prev: Commands For Text, Up: Bindable Readline Commands
+
+8.4.4 Killing And Yanking
+-------------------------
+
+‘kill-line (C-k)’
+ Kill the text from point to the end of the current line. With a
+ negative numeric argument, kill backward from the cursor to the
+ beginning of the line.
+
+‘backward-kill-line (C-x Rubout)’
+ Kill backward from the cursor to the beginning of the current line.
+ With a negative numeric argument, kill forward from the cursor to
+ the end of the line.
+
+‘unix-line-discard (C-u)’
+ Kill backward from the cursor to the beginning of the current line.
+
+‘kill-whole-line ()’
+ Kill all characters on the current line, no matter where point is.
+ By default, this is unbound.
+
+‘kill-word (M-d)’
+ Kill from point to the end of the current word, or if between
+ words, to the end of the next word. Word boundaries are the same
+ as ‘forward-word’.
+
+‘backward-kill-word (M-<DEL>)’
+ Kill the word behind point. Word boundaries are the same as
+ ‘backward-word’.
+
+‘shell-kill-word (M-C-d)’
+ Kill from point to the end of the current word, or if between
+ words, to the end of the next word. Word boundaries are the same
+ as ‘shell-forward-word’.
+
+‘shell-backward-kill-word ()’
+ Kill the word behind point. Word boundaries are the same as
+ ‘shell-backward-word’.
+
+‘unix-word-rubout (C-w)’
+ Kill the word behind point, using white space as a word boundary,
+ saving the killed text on the kill-ring.
+
+‘unix-filename-rubout ()’
+ Kill the word behind point, using white space and the slash
+ character as the word boundaries, saving the killed text on the
+ kill-ring.
+
+‘delete-horizontal-space ()’
+ Delete all spaces and tabs around point. By default, this is
+ unbound.
+
+‘kill-region ()’
+ Kill the text in the current region. By default, this command is
+ unbound.
+
+‘copy-region-as-kill ()’
+ Copy the text in the region to the kill buffer, so it can be yanked
+ right away. By default, this command is unbound.
+
+‘copy-backward-word ()’
+ Copy the word before point to the kill buffer. The word boundaries
+ are the same as ‘backward-word’. By default, this command is
+ unbound.
+
+‘copy-forward-word ()’
+ Copy the word following point to the kill buffer. The word
+ boundaries are the same as ‘forward-word’. By default, this
+ command is unbound.
+
+‘yank (C-y)’
+ Yank the top of the kill ring into the buffer at point.
+
+‘yank-pop (M-y)’
+ Rotate the kill-ring, and yank the new top. You can only do this
+ if the prior command is ‘yank’ or ‘yank-pop’.
+
+\1f
+File: bash.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
+
+8.4.5 Specifying Numeric Arguments
+----------------------------------
+
+‘digit-argument (M-0, M-1, ... M--)’
+ Add this digit to the argument already accumulating, or start a new
+ argument. ‘M--’ starts a negative argument.
+
+‘universal-argument ()’
+ This is another way to specify an argument. If this command is
+ followed by one or more digits, optionally with a leading minus
+ sign, those digits define the argument. If the command is followed
+ by digits, executing ‘universal-argument’ again ends the numeric
+ argument, but is otherwise ignored. As a special case, if this
+ command is immediately followed by a character that is neither a
+ digit nor minus sign, the argument count for the next command is
+ multiplied by four. The argument count is initially one, so
+ executing this function the first time makes the argument count
+ four, a second time makes the argument count sixteen, and so on.
+ By default, this is not bound to a key.
+
+\1f
+File: bash.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
+
+8.4.6 Letting Readline Type For You
+-----------------------------------
+
+‘complete (<TAB>)’
+ Attempt to perform completion on the text before point. The actual
+ completion performed is application-specific. Bash attempts
+ completion by first checking for any programmable completions for
+ the command word (*note Programmable Completion::), otherwise
+ treating the text as a variable (if the text begins with ‘$’),
+ username (if the text begins with ‘~’), hostname (if the text
+ begins with ‘@’), or command (including aliases, functions, and
+ builtins) in turn. If none of these produces a match, it falls
+ back to filename completion.
+
+‘possible-completions (M-?)’
+ List the possible completions of the text before point. When
+ displaying completions, Readline sets the number of columns used
+ for display to the value of ‘completion-display-width’, the value
+ of the environment variable ‘COLUMNS’, or the screen width, in that
+ order.
+
+‘insert-completions (M-*)’
+ Insert all completions of the text before point that would have
+ been generated by ‘possible-completions’, separated by a space.
+
+‘menu-complete ()’
+ Similar to ‘complete’, but replaces the word to be completed with a
+ single match from the list of possible completions. Repeatedly
+ executing ‘menu-complete’ steps through the list of possible
+ completions, inserting each match in turn. At the end of the list
+ of completions, ‘menu-complete’ rings the bell (subject to the
+ setting of ‘bell-style’) and restores the original text. An
+ argument of N moves N positions forward in the list of matches; a
+ negative argument moves backward through the list. This command is
+ intended to be bound to <TAB>, but is unbound by default.
+
+‘menu-complete-backward ()’
+ Identical to ‘menu-complete’, but moves backward through the list
+ of possible completions, as if ‘menu-complete’ had been given a
+ negative argument. This command is unbound by default.
+
+‘export-completions ()’
+ Perform completion on the word before point as described above and
+ write the list of possible completions to Readline's output stream
+ using the following format, writing information on separate lines:
+
+ • the number of matches N;
+ • the word being completed;
+ • S:E, where S and E are the start and end offsets of the word
+ in the Readline line buffer; then
+ • each match, one per line
+
+ If there are no matches, the first line will be "0", and this
+ command does not print any output after the S:E. If there is only
+ a single match, this prints a single line containing it. If there
+ is more than one match, this prints the common prefix of the
+ matches, which may be empty, on the first line after the S:E, then
+ the matches on subsequent lines. In this case, N will include the
+ first line with the common prefix.
+
+ The user or application should be able to accommodate the
+ possibility of a blank line. The intent is that the user or
+ application reads N lines after the line containing S:E to obtain
+ the match list. This command is unbound by default.
+
+‘delete-char-or-list ()’
+ Deletes the character under the cursor if not at the beginning or
+ end of the line (like ‘delete-char’). At the end of the line, it
+ behaves identically to ‘possible-completions’. This command is
+ unbound by default.
+
+‘complete-filename (M-/)’
+ Attempt filename completion on the text before point.
+
+‘possible-filename-completions (C-x /)’
+ List the possible completions of the text before point, treating it
+ as a filename.
+
+‘complete-username (M-~)’
+ Attempt completion on the text before point, treating it as a
+ username.
+
+‘possible-username-completions (C-x ~)’
+ List the possible completions of the text before point, treating it
+ as a username.
+
+‘complete-variable (M-$)’
+ Attempt completion on the text before point, treating it as a shell
+ variable.
+
+‘possible-variable-completions (C-x $)’
+ List the possible completions of the text before point, treating it
+ as a shell variable.
+
+‘complete-hostname (M-@)’
+ Attempt completion on the text before point, treating it as a
+ hostname.
+
+‘possible-hostname-completions (C-x @)’
+ List the possible completions of the text before point, treating it
+ as a hostname.
+
+‘complete-command (M-!)’
+ Attempt completion on the text before point, treating it as a
+ command name. Command completion attempts to match the text
+ against aliases, reserved words, shell functions, shell builtins,
+ and finally executable filenames, in that order.
+
+‘possible-command-completions (C-x !)’
+ List the possible completions of the text before point, treating it
+ as a command name.
+
+‘dynamic-complete-history (M-<TAB>)’
+ Attempt completion on the text before point, comparing the text
+ against history list entries for possible completion matches.
+
+‘dabbrev-expand ()’
+ Attempt menu completion on the text before point, comparing the
+ text against lines from the history list for possible completion
+ matches.
+
+‘complete-into-braces (M-{)’
+ Perform filename completion and insert the list of possible
+ completions enclosed within braces so the list is available to the
+ shell (*note Brace Expansion::).
+
+\1f
+File: bash.info, Node: Keyboard Macros, Next: Miscellaneous Commands, Prev: Commands For Completion, Up: Bindable Readline Commands
+
+8.4.7 Keyboard Macros
+---------------------
+
+‘start-kbd-macro (C-x ()’
+ Begin saving the characters typed into the current keyboard macro.
+
+‘end-kbd-macro (C-x ))’
+ Stop saving the characters typed into the current keyboard macro
+ and save the definition.
+
+‘call-last-kbd-macro (C-x e)’
+ Re-execute the last keyboard macro defined, by making the
+ characters in the macro appear as if typed at the keyboard.
+
+‘print-last-kbd-macro ()’
+ Print the last keyboard macro defined in a format suitable for the
+ INPUTRC file.
+
+\1f
+File: bash.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
+
+8.4.8 Some Miscellaneous Commands
+---------------------------------
+
+‘re-read-init-file (C-x C-r)’
+ Read in the contents of the INPUTRC file, and incorporate any
+ bindings or variable assignments found there.
+
+‘abort (C-g)’
+ Abort the current editing command and ring the terminal's bell
+ (subject to the setting of ‘bell-style’).
+
+‘do-lowercase-version (M-A, M-B, M-X, ...)’
+ If the metafied character X is upper case, run the command that is
+ bound to the corresponding metafied lower case character. The
+ behavior is undefined if X is already lower case.
+
+‘prefix-meta (<ESC>)’
+ Metafy the next character typed. Typing ‘<ESC> f’ is equivalent to
+ typing ‘M-f’.
+
+‘undo (C-_ or C-x C-u)’
+ Incremental undo, separately remembered for each line.
+
+‘revert-line (M-r)’
+ Undo all changes made to this line. This is like executing the
+ ‘undo’ command enough times to get back to the initial state.
+
+‘tilde-expand (M-&)’
+ Perform tilde expansion on the current word.
+
+‘set-mark (C-@)’
+ Set the mark to the point. If a numeric argument is supplied, set
+ the mark to that position.
+
+‘exchange-point-and-mark (C-x C-x)’
+ Swap the point with the mark. Set the current cursor position to
+ the saved position, then set the mark to the old cursor position.
+
+‘character-search (C-])’
+ Read a character and move point to the next occurrence of that
+ character. A negative argument searches for previous occurrences.
+
+‘character-search-backward (M-C-])’
+ Read a character and move point to the previous occurrence of that
+ character. A negative argument searches for subsequent
+ occurrences.
+
+‘skip-csi-sequence ()’
+ Read enough characters to consume a multi-key sequence such as
+ those defined for keys like Home and End. CSI sequences begin with
+ a Control Sequence Indicator (CSI), usually ‘ESC [’. If this
+ sequence is bound to "\e[", keys producing CSI sequences have no
+ effect unless explicitly bound to a Readline command, instead of
+ inserting stray characters into the editing buffer. This is
+ unbound by default, but usually bound to ‘ESC [’.
+
+‘insert-comment (M-#)’
+ Without a numeric argument, insert the value of the ‘comment-begin’
+ variable at the beginning of the current line. If a numeric
+ argument is supplied, this command acts as a toggle: if the
+ characters at the beginning of the line do not match the value of
+ ‘comment-begin’, insert the value; otherwise delete the characters
+ in ‘comment-begin’ from the beginning of the line. In either case,
+ the line is accepted as if a newline had been typed. The default
+ value of ‘comment-begin’ causes this command to make the current
+ line a shell comment. If a numeric argument causes the comment
+ character to be removed, the line will be executed by the shell.
+
+‘dump-functions ()’
+ Print all of the functions and their key bindings to the Readline
+ output stream. If a numeric argument is supplied, the output is
+ formatted in such a way that it can be made part of an INPUTRC
+ file. This command is unbound by default.
+
+‘dump-variables ()’
+ Print all of the settable variables and their values to the
+ Readline output stream. If a numeric argument is supplied, the
+ output is formatted in such a way that it can be made part of an
+ INPUTRC file. This command is unbound by default.
+
+‘dump-macros ()’
+ Print all of the Readline key sequences bound to macros and the
+ strings they output to the Readline output stream. If a numeric
+ argument is supplied, the output is formatted in such a way that it
+ can be made part of an INPUTRC file. This command is unbound by
+ default.
+
+‘execute-named-command (M-x)’
+ Read a bindable Readline command name from the input and execute
+ the function to which it's bound, as if the key sequence to which
+ it was bound appeared in the input. If this function is supplied
+ with a numeric argument, it passes that argument to the function it
+ executes.
+
+‘spell-correct-word (C-x s)’
+ Perform spelling correction on the current word, treating it as a
+ directory or filename, in the same way as the ‘cdspell’ shell
+ option. Word boundaries are the same as those used by
+ ‘shell-forward-word’.
+
+‘glob-complete-word (M-g)’
+ Treat the word before point as a pattern for pathname expansion,
+ with an asterisk implicitly appended, then use the pattern to
+ generate a list of matching file names for possible completions.
+
+‘glob-expand-word (C-x *)’
+ Treat the word before point as a pattern for pathname expansion,
+ and insert the list of matching file names, replacing the word. If
+ a numeric argument is supplied, append a ‘*’ before pathname
+ expansion.
+
+‘glob-list-expansions (C-x g)’
+ Display the list of expansions that would have been generated by
+ ‘glob-expand-word’, and redisplay the line. If a numeric argument
+ is supplied, append a ‘*’ before pathname expansion.
+
+‘shell-expand-line (M-C-e)’
+ Expand the line by performing shell word expansions. This performs
+ alias and history expansion, $'STRING' and $"STRING" quoting, tilde
+ expansion, parameter and variable expansion, arithmetic expansion,
+ command and process substitution, word splitting, and quote
+ removal. An explicit argument suppresses command and process
+ substitution.
+
+‘history-expand-line (M-^)’
+ Perform history expansion on the current line.
+
+‘magic-space ()’
+ Perform history expansion on the current line and insert a space
+ (*note History Interaction::).
+
+‘alias-expand-line ()’
+ Perform alias expansion on the current line (*note Aliases::).
+
+‘history-and-alias-expand-line ()’
+ Perform history and alias expansion on the current line.
+
+‘insert-last-argument (M-. or M-_)’
+ A synonym for ‘yank-last-arg’.
+
+‘edit-and-execute-command (C-x C-e)’
+ Invoke an editor on the current command line, and execute the
+ result as shell commands. Bash attempts to invoke ‘$VISUAL’,
+ ‘$EDITOR’, and ‘emacs’ as the editor, in that order.
+
+‘display-shell-version (C-x C-v)’
+ Display version information about the current instance of Bash.
+
+\1f
+File: bash.info, Node: Readline vi Mode, Next: Programmable Completion, Prev: Bindable Readline Commands, Up: Command Line Editing
+
+8.5 Readline vi Mode
+====================
+
+While the Readline library does not have a full set of ‘vi’ editing
+functions, it does contain enough to allow simple editing of the line.
+The Readline ‘vi’ mode behaves as specified in the ‘sh’ description in
+the POSIX standard.
+
+ You can use the ‘set -o emacs’ and ‘set -o vi’ commands (*note The
+Set Builtin::) to switch interactively between ‘emacs’ and ‘vi’ editing
+modes, The Readline default is ‘emacs’ mode.
+
+ When you enter a line in ‘vi’ mode, you are already placed in
+"insertion" mode, as if you had typed an ‘i’. Pressing <ESC> switches
+you into "command" mode, where you can edit the text of the line with
+the standard ‘vi’ movement keys, move to previous history lines with ‘k’
+and subsequent lines with ‘j’, and so forth.
+
+\1f
+File: bash.info, Node: Programmable Completion, Next: Programmable Completion Builtins, Prev: Readline vi Mode, Up: Command Line Editing
+
+8.6 Programmable Completion
+===========================
+
+When the user attempts word completion for a command or an argument to a
+command for which a completion specification (a “compspec”) has been
+defined using the ‘complete’ builtin (*note Programmable Completion
+Builtins::), Readline invokes the programmable completion facilities.
+
+ First, Bash identifies the command name. If a compspec has been
+defined for that command, the compspec is used to generate the list of
+possible completions for the word. If the command word is the empty
+string (completion attempted at the beginning of an empty line), Bash
+uses any compspec defined with the ‘-E’ option to ‘complete’. The ‘-I’
+option to ‘complete’ indicates that the command word is the first
+non-assignment word on the line, or after a command delimiter such as
+‘;’ or ‘|’. This usually indicates command name completion.
+
+ If the command word is a full pathname, Bash searches for a compspec
+for the full pathname first. If there is no compspec for the full
+pathname, Bash attempts to find a compspec for the portion following the
+final slash. If those searches do not result in a compspec, or if there
+is no compspec for the command word, Bash uses any compspec defined with
+the ‘-D’ option to ‘complete’ as the default. If there is no default
+compspec, Bash performs alias expansion on the command word as a final
+resort, and attempts to find a compspec for the command word resulting
+from any successful expansion.
+
+ If a compspec is not found, Bash performs its default completion
+described above (*note Commands For Completion::). Otherwise, once a
+compspec has been found, Bash uses it to generate the list of matching
+words.
+
+ First, Bash performs the ACTIONS specified by the compspec. This
+only returns matches which are prefixes of the word being completed.
+When the ‘-f’ or ‘-d’ option is used for filename or directory name
+completion, Bash uses shell the variable ‘FIGNORE’ to filter the
+matches. *Note Bash Variables::, for a description of ‘FIGNORE’.
+
+ Next, programmable completion generates matches specified by a
+pathname expansion pattern supplied as an argument to the ‘-G’ option.
+The words generated by the pattern need not match the word being
+completed. Bash uses the ‘FIGNORE’ variable to filter the matches, but
+does not use the ‘GLOBIGNORE’ shell variable.
+
+ Next, completion considers the string specified as the argument to
+the ‘-W’ option. The string is first split using the characters in the
+‘IFS’ special variable as delimiters. This honors shell quoting within
+the string, in order to provide a mechanism for the words to contain
+shell metacharacters or characters in the value of ‘IFS’. Each word is
+then expanded using brace expansion, tilde expansion, parameter and
+variable expansion, command substitution, and arithmetic expansion, as
+described above (*note Shell Expansions::). The results are split using
+the rules described above (*note Word Splitting::). The results of the
+expansion are prefix-matched against the word being completed, and the
+matching words become possible completions.
+
+ After these matches have been generated, Bash executes any shell
+function or command specified with the ‘-F’ and ‘-C’ options. When the
+command or function is invoked, Bash assigns values to the ‘COMP_LINE’,
+‘COMP_POINT’, ‘COMP_KEY’, and ‘COMP_TYPE’ variables as described above
+(*note Bash Variables::). If a shell function is being invoked, Bash
+also sets the ‘COMP_WORDS’ and ‘COMP_CWORD’ variables. When the
+function or command is invoked, the first argument ($1) is the name of
+the command whose arguments are being completed, the second argument
+($2) is the word being completed, and the third argument ($3) is the
+word preceding the word being completed on the current command line.
+There is no filtering of the generated completions against the word
+being completed; the function or command has complete freedom in
+generating the matches and they do not need to match a prefix of the
+word.
+
+ Any function specified with ‘-F’ is invoked first. The function may
+use any of the shell facilities, including the ‘compgen’ and ‘compopt’
+builtins described below (*note Programmable Completion Builtins::), to
+generate the matches. It must put the possible completions in the
+‘COMPREPLY’ array variable, one per array element.
+
+ Next, any command specified with the ‘-C’ option is invoked in an
+environment equivalent to command substitution. It should print a list
+of completions, one per line, to the standard output. Backslash will
+escape a newline, if necessary. These are added to the set of possible
+completions.
+
+ External commands that are invoked to generate completions ("external
+completers") receive the word preceding the completion word as an
+argument, as described above. This provides context that is sometimes
+useful, but may include information that is considered sensitive or part
+of a word expansion that will not appear in the command line after
+expansion. That word may be visible in process listings or in audit
+logs. This may be a concern to users and completion specification
+authors if there is sensitive information on the command line before
+expansion, since completion takes place before words are expanded. If
+this is an issue, completion authors should use functions as wrappers
+around external commands and pass context information to the external
+command in a different way. External completers can infer context from
+the COMP_LINE and COMP_POINT environment variables, but they need to
+ensure they break words in the same way Readline does, using the
+COMP_WORDBREAKS variable.
+
+ After generating all of the possible completions, Bash applies any
+filter specified with the ‘-X’ option to the completions in the list.
+The filter is a pattern as used for pathname expansion; a ‘&’ in the
+pattern is replaced with the text of the word being completed. A
+literal ‘&’ may be escaped with a backslash; the backslash is removed
+before attempting a match. Any completion that matches the pattern is
+removed from the list. A leading ‘!’ negates the pattern; in this case
+Bash removes any completion that does not match the pattern. If the
+‘nocasematch’ shell option is enabled (see the description of ‘shopt’ in
+*note The Shopt Builtin::), Bash performs the match without regard to
+the case of alphabetic characters.
+
+ Finally, programmable completion adds any prefix and suffix specified
+with the ‘-P’ and ‘-S’ options, respectively, to each completion, and
+returns the result to Readline as the list of possible completions.
+
+ If the previously-applied actions do not generate any matches, and
+the ‘-o dirnames’ option was supplied to ‘complete’ when the compspec
+was defined, Bash attempts directory name completion.
+
+ If the ‘-o plusdirs’ option was supplied to ‘complete’ when the
+compspec was defined, Bash attempts directory name completion and adds
+any matches to the set of possible completions.
+
+ By default, if a compspec is found, whatever it generates is returned
+to the completion code as the full set of possible completions. The
+default Bash completions and the Readline default of filename completion
+are disabled. If the ‘-o bashdefault’ option was supplied to ‘complete’
+when the compspec was defined, and the compspec generates no matches,
+Bash attempts its default completions. If the compspec and, if
+attempted, the default Bash completions generate no matches, and the ‘-o
+default’ option was supplied to ‘complete’ when the compspec was
+defined, programmable completion performs Readline's default completion.
+
+ The options supplied to ‘complete’ and ‘compopt’ can control how
+Readline treats the completions. For instance, the ‘-o fullquote’
+option tells Readline to quote the matches as if they were filenames.
+See the description of ‘complete’ (*note Programmable Completion
+Builtins::) for details.
+
+ When a compspec indicates that it wants directory name completion,
+the programmable completion functions force Readline to append a slash
+to completed names which are symbolic links to directories, subject to
+the value of the MARK-DIRECTORIES Readline variable, regardless of the
+setting of the MARK-SYMLINKED-DIRECTORIES Readline variable.
+
+ There is some support for dynamically modifying completions. This is
+most useful when used in combination with a default completion specified
+with ‘-D’. It's possible for shell functions executed as completion
+functions to indicate that completion should be retried by returning an
+exit status of 124. If a shell function returns 124, and changes the
+compspec associated with the command on which completion is being
+attempted (supplied as the first argument when the function is
+executed), programmable completion restarts from the beginning, with an
+attempt to find a new compspec for that command. This can be used to
+build a set of completions dynamically as completion is attempted,
+rather than loading them all at once.
+
+ For instance, assuming that there is a library of compspecs, each
+kept in a file corresponding to the name of the command, the following
+default completion function would load completions dynamically:
+
+ _completion_loader()
+ {
+ . "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
+ }
+ complete -D -F _completion_loader -o bashdefault -o default
+
+\1f
+File: bash.info, Node: Programmable Completion Builtins, Next: A Programmable Completion Example, Prev: Programmable Completion, Up: Command Line Editing
+
+8.7 Programmable Completion Builtins
+====================================
+
+Three builtin commands are available to manipulate the programmable
+completion facilities: one to specify how the arguments to a particular
+command are to be completed, and two to modify the completion as it is
+happening.
+
+‘compgen’
+ compgen [-V VARNAME] [OPTION] [WORD]
+
+ Generate possible completion matches for WORD according to the
+ OPTIONs, which may be any option accepted by the ‘complete’ builtin
+ with the exceptions of ‘-p’, ‘-r’, ‘-D’, ‘-E’, and ‘-I’, and write
+ the matches to the standard output.
+
+ If the ‘-V’ option is supplied, ‘compgen’ stores the generated
+ completions into the indexed array variable VARNAME instead of
+ writing them to the standard output.
+
+ When using the ‘-F’ or ‘-C’ options, the various shell variables
+ set by the programmable completion facilities, while available,
+ will not have useful values.
+
+ The matches will be generated in the same way as if the
+ programmable completion code had generated them directly from a
+ completion specification with the same flags. If WORD is
+ specified, only those completions matching WORD will be displayed
+ or stored.
+
+ The return value is true unless an invalid option is supplied, or
+ no matches were generated.
+
+‘complete’
+ complete [-abcdefgjksuv] [-o COMP-OPTION] [-DEI] [-A ACTION]
+ [-G GLOBPAT] [-W WORDLIST] [-F FUNCTION] [-C COMMAND]
+ [-X FILTERPAT] [-P PREFIX] [-S SUFFIX] NAME [NAME ...]
+ complete -pr [-DEI] [NAME ...]
+
+ Specify how arguments to each NAME should be completed.
+
+ If the ‘-p’ option is supplied, or if no options or NAMEs are
+ supplied, print existing completion specifications in a way that
+ allows them to be reused as input. The ‘-r’ option removes a
+ completion specification for each NAME, or, if no NAMEs are
+ supplied, all completion specifications.
+
+ The ‘-D’ option indicates that other supplied options and actions
+ should apply to the "default" command completion; that is,
+ completion attempted on a command for which no completion has
+ previously been defined. The ‘-E’ option indicates that other
+ supplied options and actions should apply to "empty" command
+ completion; that is, completion attempted on a blank line. The
+ ‘-I’ option indicates that other supplied options and actions
+ should apply to completion on the initial non-assignment word on
+ the line, or after a command delimiter such as ‘;’ or ‘|’, which is
+ usually command name completion. If multiple options are supplied,
+ the ‘-D’ option takes precedence over ‘-E’, and both take
+ precedence over ‘-I’. If any of ‘-D’, ‘-E’, or ‘-I’ are supplied,
+ any other NAME arguments are ignored; these completions only apply
+ to the case specified by the option.
+
+ The process of applying these completion specifications when word
+ completion is attempted is described above (*note Programmable
+ Completion::).
+
+ Other options, if specified, have the following meanings. The
+ arguments to the ‘-G’, ‘-W’, and ‘-X’ options (and, if necessary,
+ the ‘-P’ and ‘-S’ options) should be quoted to protect them from
+ expansion before the ‘complete’ builtin is invoked.
+
+ ‘-o COMP-OPTION’
+ The COMP-OPTION controls several aspects of the compspec's
+ behavior beyond the simple generation of completions.
+ COMP-OPTION may be one of:
+
+ ‘bashdefault’
+ Perform the rest of the default Bash completions if the
+ compspec generates no matches.
+
+ ‘default’
+ Use Readline's default filename completion if the
+ compspec generates no matches.
+
+ ‘dirnames’
+ Perform directory name completion if the compspec
+ generates no matches.
+
+ ‘filenames’
+ Tell Readline that the compspec generates filenames, so
+ it can perform any filename-specific processing (such as
+ adding a slash to directory names, quoting special
+ characters, or suppressing trailing spaces). This option
+ is intended to be used with shell functions specified
+ with ‘-F’.
+
+ ‘fullquote’
+ Tell Readline to quote all the completed words even if
+ they are not filenames.
+
+ ‘noquote’
+ Tell Readline not to quote the completed words if they
+ are filenames (quoting filenames is the default).
+
+ ‘nosort’
+ Tell Readline not to sort the list of possible
+ completions alphabetically.
+
+ ‘nospace’
+ Tell Readline not to append a space (the default) to
+ words completed at the end of the line.
+
+ ‘plusdirs’
+ After generating any matches defined by the compspec,
+ attempt directory name completion and add any matches to
+ the results of the other actions.
+
+ ‘-A ACTION’
+ The ACTION may be one of the following to generate a list of
+ possible completions:
+
+ ‘alias’
+ Alias names. May also be specified as ‘-a’.
+
+ ‘arrayvar’
+ Array variable names.
+
+ ‘binding’
+ Readline key binding names (*note Bindable Readline
+ Commands::).
+
+ ‘builtin’
+ Names of shell builtin commands. May also be specified
+ as ‘-b’.
+
+ ‘command’
+ Command names. May also be specified as ‘-c’.
+
+ ‘directory’
+ Directory names. May also be specified as ‘-d’.
+
+ ‘disabled’
+ Names of disabled shell builtins.
+
+ ‘enabled’
+ Names of enabled shell builtins.
+
+ ‘export’
+ Names of exported shell variables. May also be specified
+ as ‘-e’.
+
+ ‘file’
+ File and directory names, similar to Readline's filename
+ completion. May also be specified as ‘-f’.
+
+ ‘function’
+ Names of shell functions.
+
+ ‘group’
+ Group names. May also be specified as ‘-g’.
+
+ ‘helptopic’
+ Help topics as accepted by the ‘help’ builtin (*note Bash
+ Builtins::).
+
+ ‘hostname’
+ Hostnames, as taken from the file specified by the
+ ‘HOSTFILE’ shell variable (*note Bash Variables::).
+
+ ‘job’
+ Job names, if job control is active. May also be
+ specified as ‘-j’.
+
+ ‘keyword’
+ Shell reserved words. May also be specified as ‘-k’.
+
+ ‘running’
+ Names of running jobs, if job control is active.
+
+ ‘service’
+ Service names. May also be specified as ‘-s’.
+
+ ‘setopt’
+ Valid arguments for the ‘-o’ option to the ‘set’ builtin
+ (*note The Set Builtin::).
+
+ ‘shopt’
+ Shell option names as accepted by the ‘shopt’ builtin
+ (*note Bash Builtins::).
+
+ ‘signal’
+ Signal names.
+
+ ‘stopped’
+ Names of stopped jobs, if job control is active.
+
+ ‘user’
+ User names. May also be specified as ‘-u’.
+
+ ‘variable’
+ Names of all shell variables. May also be specified as
+ ‘-v’.
+
+ ‘-C COMMAND’
+ COMMAND is executed in a subshell environment, and its output
+ is used as the possible completions. Arguments are passed as
+ with the ‘-F’ option.
+
+ ‘-F FUNCTION’
+ The shell function FUNCTION is executed in the current shell
+ environment. When it is executed, the first argument ($1) is
+ the name of the command whose arguments are being completed,
+ the second argument ($2) is the word being completed, and the
+ third argument ($3) is the word preceding the word being
+ completed, as described above (*note Programmable
+ Completion::). When ‘function’ finishes, programmable
+ completion retrieves the possible completions from the value
+ of the ‘COMPREPLY’ array variable.
+
+ ‘-G GLOBPAT’
+ Expand the filename expansion pattern GLOBPAT to generate the
+ possible completions.
+
+ ‘-P PREFIX’
+ Add PREFIX to the beginning of each possible completion after
+ all other options have been applied.
+
+ ‘-S SUFFIX’
+ Append SUFFIX to each possible completion after all other
+ options have been applied.
+
+ ‘-W WORDLIST’
+ Split the WORDLIST using the characters in the ‘IFS’ special
+ variable as delimiters, and expand each resulting word. Shell
+ quoting is honored within WORDLIST in order to provide a
+ mechanism for the words to contain shell metacharacters or
+ characters in the value of ‘IFS’. The possible completions
+ are the members of the resultant list which match a prefix of
+ the word being completed.
+
+ ‘-X FILTERPAT’
+ FILTERPAT is a pattern as used for filename expansion. It is
+ applied to the list of possible completions generated by the
+ preceding options and arguments, and each completion matching
+ FILTERPAT is removed from the list. A leading ‘!’ in
+ FILTERPAT negates the pattern; in this case, any completion
+ not matching FILTERPAT is removed.
+
+ The return value is true unless an invalid option is supplied, an
+ option other than ‘-p’, ‘-r’, ‘-D’, ‘-E’, or ‘-I’ is supplied
+ without a NAME argument, an attempt is made to remove a completion
+ specification for a NAME for which no specification exists, or an
+ error occurs adding a completion specification.
+
+‘compopt’
+ compopt [-o OPTION] [-DEI] [+o OPTION] [NAME]
+ Modify completion options for each NAME according to the OPTIONs,
+ or for the currently-executing completion if no NAMEs are supplied.
+ If no OPTIONs are given, display the completion options for each
+ NAME or the current completion. The possible values of OPTION are
+ those valid for the ‘complete’ builtin described above.
+
+ The ‘-D’ option indicates that other supplied options should apply
+ to the "default" command completion; the ‘-E’ option indicates that
+ other supplied options should apply to "empty" command completion;
+ and the ‘-I’ option indicates that other supplied options should
+ apply to completion on the initial word on the line. These are
+ determined in the same way as the ‘complete’ builtin.
+
+ If multiple options are supplied, the ‘-D’ option takes precedence
+ over ‘-E’, and both take precedence over ‘-I’
+
+ The return value is true unless an invalid option is supplied, an
+ attempt is made to modify the options for a NAME for which no
+ completion specification exists, or an output error occurs.
+
+\1f
+File: bash.info, Node: A Programmable Completion Example, Prev: Programmable Completion Builtins, Up: Command Line Editing
+
+8.8 A Programmable Completion Example
+=====================================
+
+The most common way to obtain additional completion functionality beyond
+the default actions ‘complete’ and ‘compgen’ provide is to use a shell
+function and bind it to a particular command using ‘complete -F’.
+
+ The following function provides completions for the ‘cd’ builtin. It
+is a reasonably good example of what shell functions must do when used
+for completion. This function uses the word passed as ‘$2’ to determine
+the directory name to complete. You can also use the ‘COMP_WORDS’ array
+variable; the current word is indexed by the ‘COMP_CWORD’ variable.
+
+ The function relies on the ‘complete’ and ‘compgen’ builtins to do
+much of the work, adding only the things that the Bash ‘cd’ does beyond
+accepting basic directory names: tilde expansion (*note Tilde
+Expansion::), searching directories in $CDPATH, which is described above
+(*note Bourne Shell Builtins::), and basic support for the ‘cdable_vars’
+shell option (*note The Shopt Builtin::). ‘_comp_cd’ modifies the value
+of IFS so that it contains only a newline to accommodate file names
+containing spaces and tabs - ‘compgen’ prints the possible completions
+it generates one per line.
+
+ Possible completions go into the COMPREPLY array variable, one
+completion per array element. The programmable completion system
+retrieves the completions from there when the function returns.
+
+ # A completion function for the cd builtin
+ # based on the cd completion function from the bash_completion package
+ _comp_cd()
+ {
+ local IFS=$' \t\n' # normalize IFS
+ local cur _skipdot _cdpath
+ local i j k
+
+ # Tilde expansion, which also expands tilde to full pathname
+ case "$2" in
+ \~*) eval cur="$2" ;;
+ *) cur=$2 ;;
+ esac
+
+ # no cdpath or absolute pathname -- straight directory completion
+ if [[ -z "${CDPATH:-}" ]] || [[ "$cur" == @(./*|../*|/*) ]]; then
+ # compgen prints paths one per line; could also use while loop
+ IFS=$'\n'
+ COMPREPLY=( $(compgen -d -- "$cur") )
+ IFS=$' \t\n'
+ # CDPATH+directories in the current directory if not in CDPATH
+ else
+ IFS=$'\n'
+ _skipdot=false
+ # preprocess CDPATH to convert null directory names to .
+ _cdpath=${CDPATH/#:/.:}
+ _cdpath=${_cdpath//::/:.:}
+ _cdpath=${_cdpath/%:/:.}
+ for i in ${_cdpath//:/$'\n'}; do
+ if [[ $i -ef . ]]; then _skipdot=true; fi
+ k="${#COMPREPLY[@]}"
+ for j in $( compgen -d -- "$i/$cur" ); do
+ COMPREPLY[k++]=${j#$i/} # cut off directory
+ done
+ done
+ $_skipdot || COMPREPLY+=( $(compgen -d -- "$cur") )
+ IFS=$' \t\n'
+ fi
+
+ # variable names if appropriate shell option set and no completions
+ if shopt -q cdable_vars && [[ ${#COMPREPLY[@]} -eq 0 ]]; then
+ COMPREPLY=( $(compgen -v -- "$cur") )
+ fi
+
+ return 0
+ }
+
+ We install the completion function using the ‘-F’ option to
+‘complete’:
+
+ # Tell readline to quote appropriate and append slashes to directories;
+ # use the bash default completion for other arguments
+ complete -o filenames -o nospace -o bashdefault -F _comp_cd cd
+
+Since we'd like Bash and Readline to take care of some of the other
+details for us, we use several other options to tell Bash and Readline
+what to do. The ‘-o filenames’ option tells Readline that the possible
+completions should be treated as filenames, and quoted appropriately.
+That option will also cause Readline to append a slash to filenames it
+can determine are directories (which is why we might want to extend
+‘_comp_cd’ to append a slash if we're using directories found via
+CDPATH: Readline can't tell those completions are directories). The ‘-o
+nospace’ option tells Readline to not append a space character to the
+directory name, in case we want to append to it. The ‘-o bashdefault’
+option brings in the rest of the "Bash default" completions - possible
+completions that Bash adds to the default Readline set. These include
+things like command name completion, variable completion for words
+beginning with ‘$’ or ‘${’, completions containing pathname expansion
+patterns (*note Filename Expansion::), and so on.
+
+ Once installed using ‘complete’, ‘_comp_cd’ will be called every time
+we attempt word completion for a ‘cd’ command.
+
+ Many more examples - an extensive collection of completions for most
+of the common GNU, Unix, and Linux commands - are available as part of
+the bash_completion project. This is installed by default on many
+GNU/Linux distributions. Originally written by Ian Macdonald, the
+project now lives at <https://github.com/scop/bash-completion/>. There
+are ports for other systems such as Solaris and Mac OS X.
+
+ An older version of the bash_completion package is distributed with
+bash in the ‘examples/complete’ subdirectory.
+
+\1f
+File: bash.info, Node: Using History Interactively, Next: Installing Bash, Prev: Command Line Editing, Up: Top
+
+9 Using History Interactively
+*****************************
+
+This chapter describes how to use the GNU History Library interactively,
+from a user's standpoint. It should be considered a user's guide. For
+information on using the GNU History Library in other programs, see the
+GNU Readline Library Manual.
+
+* Menu:
+
+* Bash History Facilities:: How Bash lets you manipulate your command
+ history.
+* Bash History Builtins:: The Bash builtin commands that manipulate
+ the command history.
+* History Interaction:: What it feels like using History as a user.
+
+\1f
+File: bash.info, Node: Bash History Facilities, Next: Bash History Builtins, Up: Using History Interactively
+
+9.1 Bash History Facilities
+===========================
+
+When the ‘-o history’ option to the ‘set’ builtin is enabled (*note The
+Set Builtin::), the shell provides access to the “command history”, the
+list of commands previously typed. The value of the ‘HISTSIZE’ shell
+variable is used as the number of commands to save in a history list:
+the shell saves the text of the last ‘$HISTSIZE’ commands (default 500).
+The shell stores each command in the history list prior to parameter and
+variable expansion but after history expansion is performed, subject to
+the values of the shell variables ‘HISTIGNORE’ and ‘HISTCONTROL’.
+
+ When the shell starts up, Bash initializes the history list by
+reading history entries from the file named by the ‘HISTFILE’ variable
+(default ‘~/.bash_history’). This is referred to as the “history file”.
+The history file is truncated, if necessary, to contain no more than the
+number of history entries specified by the value of the ‘HISTFILESIZE’
+variable. If ‘HISTFILESIZE’ is unset, or set to null, a non-numeric
+value, or a numeric value less than zero, the history file is not
+truncated.
+
+ When the history file is read, lines beginning with the history
+comment character followed immediately by a digit are interpreted as
+timestamps for the following history entry. These timestamps are
+optionally displayed depending on the value of the ‘HISTTIMEFORMAT’
+variable (*note Bash Variables::). When present, history timestamps
+delimit history entries, making multi-line entries possible.
+
+ When a shell with history enabled exits, Bash copies the last
+‘$HISTSIZE’ entries from the history list to the file named by
+‘$HISTFILE’. If the ‘histappend’ shell option is set (*note Bash
+Builtins::), Bash appends the entries to the history file, otherwise it
+overwrites the history file. If ‘HISTFILE’ is unset or null, or if the
+history file is unwritable, the history is not saved. After saving the
+history, Bash truncates the history file to contain no more than
+‘$HISTFILESIZE’ lines as described above.
+
+ If the ‘HISTTIMEFORMAT’ variable is set, the shell writes the
+timestamp information associated with each history entry to the history
+file, marked with the history comment character, so timestamps are
+preserved across shell sessions. When the history file is read, lines
+beginning with the history comment character followed immediately by a
+digit are interpreted as timestamps for the following history entry. As
+above, when using ‘HISTTIMEFORMAT’, the timestamps delimit multi-line
+history entries.
+
+ The ‘fc’ builtin command will list or edit and re-execute a portion
+of the history list. The ‘history’ builtin can display or modify the
+history list and manipulate the history file. When using command-line
+editing, search commands are available in each editing mode that provide
+access to the history list (*note Commands For History::).
+
+ The shell allows control over which commands are saved on the history
+list. The ‘HISTCONTROL’ and ‘HISTIGNORE’ variables are used to save
+only a subset of the commands entered. If the ‘cmdhist’ shell option is
+enabled, the shell attempts to save each line of a multi-line command in
+the same history entry, adding semicolons where necessary to preserve
+syntactic correctness. The ‘lithist’ shell option modifies ‘cmdhist’ by
+saving the command with embedded newlines instead of semicolons. The
+‘shopt’ builtin is used to set these options. *Note The Shopt
+Builtin::, for a description of ‘shopt’.
+
+\1f
+File: bash.info, Node: Bash History Builtins, Next: History Interaction, Prev: Bash History Facilities, Up: Using History Interactively
+
+9.2 Bash History Builtins
+=========================
+
+Bash provides two builtin commands which manipulate the history list and
+history file.
+
+‘fc’
+ fc [-e ENAME] [-lnr] [FIRST] [LAST]
+ fc -s [PAT=REP] [COMMAND]
+
+ The first form selects a range of commands from FIRST to LAST from
+ the history list and displays or edits and re-executes them. Both
+ FIRST and LAST may be specified as a string (to locate the most
+ recent command beginning with that string) or as a number (an index
+ into the history list, where a negative number is used as an offset
+ from the current command number).
+
+ When listing, a FIRST or LAST of 0 is equivalent to -1 and -0 is
+ equivalent to the current command (usually the ‘fc’ command);
+ otherwise 0 is equivalent to -1 and -0 is invalid.
+
+ If LAST is not specified, it is set to the current command for
+ listing and to FIRST otherwise. If FIRST is not specified, it is
+ set to the previous command for editing and −16 for listing.
+
+ If the ‘-l’ flag is supplied, the commands are listed on standard
+ output. The ‘-n’ flag suppresses the command numbers when listing.
+ The ‘-r’ flag reverses the order of the listing.
+
+ Otherwise, ‘fc’ invokes the editor named by ENAME on a file
+ containing those commands. If ENAME is not supplied, ‘fc’ uses the
+ value of the following variable expansion:
+ ‘${FCEDIT:-${EDITOR:-vi}}’. This says to use the value of the
+ ‘FCEDIT’ variable if set, or the value of the ‘EDITOR’ variable if
+ that is set, or ‘vi’ if neither is set. When editing is complete,
+ ‘fc’ reads the file of edited commands and echoes and executes
+ them.
+
+ In the second form, ‘fc’ re-executes COMMAND after replacing each
+ instance of PAT in the selected command with REP. COMMAND is
+ interpreted the same as FIRST above.
+
+ A useful alias to use with the ‘fc’ command is ‘r='fc -s'’, so that
+ typing ‘r cc’ runs the last command beginning with ‘cc’ and typing
+ ‘r’ re-executes the last command (*note Aliases::).
+
+ If the first form is used, the return value is zero unless an
+ invalid option is encountered or FIRST or LAST specify history
+ lines out of range. When editing and re-executing a file of
+ commands, the return value is the value of the last command
+ executed or failure if an error occurs with the temporary file. If
+ the second form is used, the return status is that of the
+ re-executed command, unless COMMAND does not specify a valid
+ history entry, in which case ‘fc’ returns a non-zero status.
+
+‘history’
+ history [N]
+ history -c
+ history -d OFFSET
+ history -d START-END
+ history [-anrw] [FILENAME]
+ history -ps ARG
+
+ With no options, display the history list with numbers. Entries
+ prefixed with a ‘*’ have been modified. An argument of N lists
+ only the last N entries. If the shell variable ‘HISTTIMEFORMAT’ is
+ set and not null, it is used as a format string for ‘strftime’(3)
+ to display the time stamp associated with each displayed history
+ entry. If ‘history’ uses ‘HISTTIMEFORMAT’, it does not print an
+ intervening space between the formatted time stamp and the history
+ entry.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-c’
+ Clear the history list. This may be combined with the other
+ options to replace the history list.
+
+ ‘-d OFFSET’
+ Delete the history entry at position OFFSET. If OFFSET is
+ positive, it should be specified as it appears when the
+ history is displayed. If OFFSET is negative, it is
+ interpreted as relative to one greater than the last history
+ position, so negative indices count back from the end of the
+ history, and an index of ‘-1’ refers to the current ‘history
+ -d’ command.
+
+ ‘-d START-END’
+ Delete the range of history entries between positions START
+ and END, inclusive. Positive and negative values for START
+ and END are interpreted as described above.
+
+ ‘-a’
+ Append the "new" history lines to the history file. These are
+ history lines entered since the beginning of the current Bash
+ session, but not already appended to the history file.
+
+ ‘-n’
+ Read the history lines not already read from the history file
+ and add them to the current history list. These are lines
+ appended to the history file since the beginning of the
+ current Bash session.
+
+ ‘-r’
+ Read the history file and append its contents to the history
+ list.
+
+ ‘-w’
+ Write the current history list to the history file,
+ overwriting the history file.
+
+ ‘-p’
+ Perform history substitution on the ARGs and display the
+ result on the standard output, without storing the results in
+ the history list.
+
+ ‘-s’
+ Add the ARGs to the end of the history list as a single entry.
+ The last command in the history list is removed before adding
+ the ARGs.
+
+ If a FILENAME argument is supplied with any of the ‘-w’, ‘-r’,
+ ‘-a’, or ‘-n’ options, Bash uses FILENAME as the history file. If
+ not, it uses the value of the ‘HISTFILE’ variable. If ‘HISTFILE’
+ is unset or null, these options have no effect.
+
+ If the ‘HISTTIMEFORMAT’ variable is set, ‘history’ writes the time
+ stamp information associated with each history entry to the history
+ file, marked with the history comment character as described above.
+ When the history file is read, lines beginning with the history
+ comment character followed immediately by a digit are interpreted
+ as timestamps for the following history entry.
+
+ The return value is 0 unless an invalid option is encountered, an
+ error occurs while reading or writing the history file, an invalid
+ OFFSET or range is supplied as an argument to ‘-d’, or the history
+ expansion supplied as an argument to ‘-p’ fails.
+
+\1f
+File: bash.info, Node: History Interaction, Prev: Bash History Builtins, Up: Using History Interactively
+
+9.3 History Expansion
+=====================
+
+The shell provides a history expansion feature that is similar to the
+history expansion provided by ‘csh’ (also referred to as history
+substitution where appropriate). This section describes the syntax used
+to manipulate the history information.
+
+ History expansion is enabled by default for interactive shells, and
+can be disabled using the ‘+H’ option to the ‘set’ builtin command
+(*note The Set Builtin::). Non-interactive shells do not perform
+history expansion by default, but it can be enabled with ‘set -H’.
+
+ History expansions introduce words from the history list into the
+input stream, making it easy to repeat commands, insert the arguments to
+a previous command into the current input line, or fix errors in
+previous commands quickly.
+
+ History expansion is performed immediately after a complete line is
+read, before the shell breaks it into words, and is performed on each
+line individually. Bash attempts to inform the history expansion
+functions about quoting still in effect from previous lines.
+
+ History expansion takes place in two parts. The first is to
+determine which entry from the history list should be used during
+substitution. The second is to select portions of that entry to include
+into the current one.
+
+ The entry selected from the history is called the “event”, and the
+portions of that entry that are acted upon are “words”. Various
+“modifiers” are available to manipulate the selected words. The entry
+is split into words in the same fashion that Bash does when reading
+input, so that several words surrounded by quotes are considered one
+word. The “event designator” selects the event, the optional “word
+designator” selects words from the event, and various optional
+“modifiers” are available to manipulate the selected words.
+
+ History expansions are introduced by the appearance of the history
+expansion character, which is ‘!’ by default. History expansions may
+appear anywhere in the input, but do not nest.
+
+ History expansion implements shell-like quoting conventions: a
+backslash can be used to remove the special handling for the next
+character; single quotes enclose verbatim sequences of characters, and
+can be used to inhibit history expansion; and characters enclosed within
+double quotes may be subject to history expansion, since backslash can
+escape the history expansion character, but single quotes may not, since
+they are not treated specially within double quotes.
+
+ When using the shell, only ‘\’ and ‘'’ may be used to escape the
+history expansion character, but the history expansion character is also
+treated as quoted if it immediately precedes the closing double quote in
+a double-quoted string.
+
+ Several characters inhibit history expansion if found immediately
+following the history expansion character, even if it is unquoted:
+space, tab, newline, carriage return, ‘=’, and the other shell
+metacharacters.
+
+ There is a special abbreviation for substitution, active when the
+QUICK SUBSTITUTION character (described above under ‘histchars’) is the
+first character on the line. It selects the previous history list
+entry, using an event designator equivalent to ‘!!’, and substitutes one
+string for another in that entry. It is described below (*note Event
+Designators::). This is the only history expansion that does not begin
+with the history expansion character.
+
+ Several shell options settable with the ‘shopt’ builtin (*note The
+Shopt Builtin::) modify history expansion behavior If the ‘histverify’
+shell option is enabled, and Readline is being used, history
+substitutions are not immediately passed to the shell parser. Instead,
+the expanded line is reloaded into the Readline editing buffer for
+further modification. If Readline is being used, and the ‘histreedit’
+shell option is enabled, a failed history expansion is reloaded into the
+Readline editing buffer for correction.
+
+ The ‘-p’ option to the ‘history’ builtin command shows what a history
+expansion will do before using it. The ‘-s’ option to the ‘history’
+builtin may be used to add commands to the end of the history list
+without actually executing them, so that they are available for
+subsequent recall. This is most useful in conjunction with Readline.
+
+ The shell allows control of the various characters used by the
+history expansion mechanism with the ‘histchars’ variable, as explained
+above (*note Bash Variables::). The shell uses the history comment
+character to mark history timestamps when writing the history file.
+
+* Menu:
+
+* Event Designators:: How to specify which history line to use.
+* Word Designators:: Specifying which words are of interest.
+* Modifiers:: Modifying the results of substitution.
+
+\1f
+File: bash.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
+
+9.3.1 Event Designators
+-----------------------
+
+An event designator is a reference to an entry in the history list. The
+event designator consists of the portion of the word beginning with the
+history expansion character, and ending with the word designator if one
+is present, or the end of the word. Unless the reference is absolute,
+events are relative to the current position in the history list.
+
+‘!’
+ Start a history substitution, except when followed by a space, tab,
+ the end of the line, ‘=’, or the rest of the shell metacharacters
+ defined above (*note Definitions::).
+
+‘!N’
+ Refer to history list entry N.
+
+‘!-N’
+ Refer to the history entry minus N.
+
+‘!!’
+ Refer to the previous entry. This is a synonym for ‘!-1’.
+
+‘!STRING’
+ Refer to the most recent command preceding the current position in
+ the history list starting with STRING.
+
+‘!?STRING[?]’
+ Refer to the most recent command preceding the current position in
+ the history list containing STRING. The trailing ‘?’ may be
+ omitted if the STRING is followed immediately by a newline. If
+ STRING is missing, this uses the string from the most recent
+ search; it is an error if there is no previous search string.
+
+‘^STRING1^STRING2^’
+ Quick Substitution. Repeat the last command, replacing STRING1
+ with STRING2. Equivalent to ‘!!:s^STRING1^STRING2^’.
+
+‘!#’
+ The entire command line typed so far.
+
+\1f
+File: bash.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
+
+9.3.2 Word Designators
+----------------------
+
+Word designators are used to select desired words from the event. They
+are optional; if the word designator isn't supplied, the history
+expansion uses the entire event. A ‘:’ separates the event
+specification from the word designator. It may be omitted if the word
+designator begins with a ‘^’, ‘$’, ‘*’, ‘-’, or ‘%’. Words are numbered
+from the beginning of the line, with the first word being denoted by 0
+(zero). That first word is usually the command word, and the arguments
+begin with the second word. Words are inserted into the current line
+separated by single spaces.
+
+ For example,
+
+‘!!’
+ designates the preceding command. When you type this, the
+ preceding command is repeated in toto.
+
+‘!!:$’
+ designates the last word of the preceding command. This may be
+ shortened to ‘!$’.
+
+‘!fi:2’
+ designates the second argument of the most recent command starting
+ with the letters ‘fi’.
+
+ Here are the word designators:
+
+‘0 (zero)’
+ The ‘0’th word. For the shell, and many other, applications, this
+ is the command word.
+
+‘N’
+ The Nth word.
+
+‘^’
+ The first argument: word 1.
+
+‘$’
+ The last word. This is usually the last argument, but expands to
+ the zeroth word if there is only one word in the line.
+
+‘%’
+ The first word matched by the most recent ‘?STRING?’ search, if the
+ search string begins with a character that is part of a word. By
+ default, searches begin at the end of each line and proceed to the
+ beginning, so the first word matched is the one closest to the end
+ of the line.
+
+‘X-Y’
+ A range of words; ‘-Y’ abbreviates ‘0-Y’.
+
+‘*’
+ All of the words, except the ‘0’th. This is a synonym for ‘1-$’.
+ It is not an error to use ‘*’ if there is just one word in the
+ event; it expands to the empty string in that case.
+
+‘X*’
+ Abbreviates ‘X-$’.
+
+‘X-’
+ Abbreviates ‘X-$’ like ‘X*’, but omits the last word. If ‘x’ is
+ missing, it defaults to 0.
+
+ If a word designator is supplied without an event specification, the
+previous command is used as the event, equivalent to ‘!!’.
+
+\1f
+File: bash.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
+
+9.3.3 Modifiers
+---------------
+
+After the optional word designator, you can add a sequence of one or
+more of the following modifiers, each preceded by a ‘:’. These modify,
+or edit, the word or words selected from the history event.
+
+‘h’
+ Remove a trailing filename component, leaving only the head.
+
+‘t’
+ Remove all leading filename components, leaving the tail.
+
+‘r’
+ Remove a trailing suffix of the form ‘.SUFFIX’, leaving the
+ basename.
+
+‘e’
+ Remove all but the trailing suffix.
+
+‘p’
+ Print the new command but do not execute it.
+
+‘q’
+ Quote the substituted words, escaping further substitutions.
+
+‘x’
+ Quote the substituted words as with ‘q’, but break into words at
+ spaces, tabs, and newlines. The ‘q’ and ‘x’ modifiers are mutually
+ exclusive; expansion uses the last one supplied.
+
+‘s/OLD/NEW/’
+ Substitute NEW for the first occurrence of OLD in the event line.
+ Any character may be used as the delimiter in place of ‘/’. The
+ delimiter may be quoted in OLD and NEW with a single backslash. If
+ ‘&’ appears in NEW, it is replaced with OLD. A single backslash
+ quotes the ‘&’ in OLD and NEW. If OLD is null, it is set to the
+ last OLD substituted, or, if no previous history substitutions took
+ place, the last STRING in a !?STRING‘[?]’ search. If NEW is null,
+ each matching OLD is deleted. The final delimiter is optional if
+ it is the last character on the input line.
+
+‘&’
+ Repeat the previous substitution.
+
+‘g’
+‘a’
+ Cause changes to be applied over the entire event line. This is
+ used in conjunction with ‘s’, as in ‘gs/OLD/NEW/’, or with ‘&’.
+
+‘G’
+ Apply the following ‘s’ or ‘&’ modifier once to each word in the
+ event.
+
+\1f
+File: bash.info, Node: Installing Bash, Next: Reporting Bugs, Prev: Using History Interactively, Up: Top
+
+10 Installing Bash
+******************
+
+This chapter provides basic instructions for installing Bash on the
+various supported platforms. The distribution supports the GNU
+operating systems, nearly every version of Unix, and several non-Unix
+systems such as BeOS and Interix. Other independent ports exist for
+Windows platforms.
+
+* Menu:
+
+* Basic Installation:: Installation instructions.
+* Compilers and Options:: How to set special options for various
+ systems.
+* Compiling For Multiple Architectures:: How to compile Bash for more
+ than one kind of system from
+ the same source tree.
+* Installation Names:: How to set the various paths used by the installation.
+* Specifying the System Type:: How to configure Bash for a particular system.
+* Sharing Defaults:: How to share default configuration values among GNU
+ programs.
+* Operation Controls:: Options recognized by the configuration program.
+* Optional Features:: How to enable and disable optional features when
+ building Bash.
+
+\1f
+File: bash.info, Node: Basic Installation, Next: Compilers and Options, Up: Installing Bash
+
+10.1 Basic Installation
+=======================
+
+These are installation instructions for Bash.
+
+ The simplest way to compile Bash is:
+
+ 1. ‘cd’ to the directory containing the source code and type
+ ‘./configure’ to configure Bash for your system. If you're using
+ ‘csh’ on an old version of System V, you might need to type ‘sh
+ ./configure’ instead to prevent ‘csh’ from trying to execute
+ ‘configure’ itself.
+
+ Running ‘configure’ takes some time. While running, it prints
+ messages telling which features it is checking for.
+
+ 2. Type ‘make’ to compile Bash and build the ‘bashbug’ bug reporting
+ script.
+
+ 3. Optionally, type ‘make tests’ to run the Bash test suite.
+
+ 4. Type ‘make install’ to install ‘bash’ and ‘bashbug’. This will
+ also install the manual pages and Info file, message translation
+ files, some supplemental documentation, a number of example
+ loadable builtin commands, and a set of header files for developing
+ loadable builtins. You may need additional privileges to install
+ ‘bash’ to your desired destination, which may require ‘sudo make
+ install’. More information about controlling the locations where
+ ‘bash’ and other files are installed is below (*note Installation
+ Names::).
+
+ The ‘configure’ shell script attempts to guess correct values for
+various system-dependent variables used during compilation. It uses
+those values to create a ‘Makefile’ in each directory of the package
+(the top directory, the ‘builtins’, ‘doc’, ‘po’, and ‘support’
+directories, each directory under ‘lib’, and several others). It also
+creates a ‘config.h’ file containing system-dependent definitions.
+Finally, it creates a shell script named ‘config.status’ that you can
+run in the future to recreate the current configuration, a file
+‘config.cache’ that saves the results of its tests to speed up
+reconfiguring, and a file ‘config.log’ containing compiler output
+(useful mainly for debugging ‘configure’). If at some point
+‘config.cache’ contains results you don't want to keep, you may remove
+or edit it.
+
+ To find out more about the options and arguments that the ‘configure’
+script understands, type
+
+ bash-4.2$ ./configure --help
+
+at the Bash prompt in your Bash source directory.
+
+ If you want to build Bash in a directory separate from the source
+directory - to build for multiple architectures, for example - just use
+the full path to the configure script. The following commands will
+build Bash in a directory under ‘/usr/local/build’ from the source code
+in ‘/usr/local/src/bash-4.4’:
+
+ mkdir /usr/local/build/bash-4.4
+ cd /usr/local/build/bash-4.4
+ bash /usr/local/src/bash-4.4/configure
+ make
+
+ See *note Compiling For Multiple Architectures:: for more information
+about building in a directory separate from the source.
+
+ If you need to do unusual things to compile Bash, please try to
+figure out how ‘configure’ could check whether or not to do them, and
+mail diffs or instructions to <bash-maintainers@gnu.org> so they can be
+considered for the next release.
+
+ The file ‘configure.ac’ is used to create ‘configure’ by a program
+called Autoconf. You only need ‘configure.ac’ if you want to change it
+or regenerate ‘configure’ using a newer version of Autoconf. If you do
+this, make sure you are using Autoconf version 2.69 or newer.
+
+ You can remove the program binaries and object files from the source
+code directory by typing ‘make clean’. To also remove the files that
+‘configure’ created (so you can compile Bash for a different kind of
+computer), type ‘make distclean’.
+
+\1f
+File: bash.info, Node: Compilers and Options, Next: Compiling For Multiple Architectures, Prev: Basic Installation, Up: Installing Bash
+
+10.2 Compilers and Options
+==========================
+
+Some systems require unusual options for compilation or linking that the
+‘configure’ script does not know about. You can give ‘configure’
+initial values for variables by setting them in the environment. Using
+a Bourne-compatible shell, you can do that on the command line like
+this:
+
+ CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure
+
+ On systems that have the ‘env’ program, you can do it like this:
+
+ env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure
+
+ The configuration process uses GCC to build Bash if it is available.
+
+\1f
+File: bash.info, Node: Compiling For Multiple Architectures, Next: Installation Names, Prev: Compilers and Options, Up: Installing Bash
+
+10.3 Compiling For Multiple Architectures
+=========================================
+
+You can compile Bash for more than one kind of computer at the same
+time, by placing the object files for each architecture in their own
+directory. To do this, you must use a version of ‘make’ that supports
+the ‘VPATH’ variable, such as GNU ‘make’. ‘cd’ to the directory where
+you want the object files and executables to go and run the ‘configure’
+script from the source directory (*note Basic Installation::). You may
+need to supply the ‘--srcdir=PATH’ argument to tell ‘configure’ where
+the source files are. ‘configure’ automatically checks for the source
+code in the directory that ‘configure’ is in and in ‘..’.
+
+ If you have to use a ‘make’ that does not support the ‘VPATH’
+variable, you can compile Bash for one architecture at a time in the
+source code directory. After you have installed Bash for one
+architecture, use ‘make distclean’ before reconfiguring for another
+architecture.
+
+ Alternatively, if your system supports symbolic links, you can use
+the ‘support/mkclone’ script to create a build tree which has symbolic
+links back to each file in the source directory. Here's an example that
+creates a build directory in the current directory from a source
+directory ‘/usr/gnu/src/bash-2.0’:
+
+ bash /usr/gnu/src/bash-2.0/support/mkclone -s /usr/gnu/src/bash-2.0 .
+
+The ‘mkclone’ script requires Bash, so you must have already built Bash
+for at least one architecture before you can create build directories
+for other architectures.
+
+\1f
+File: bash.info, Node: Installation Names, Next: Specifying the System Type, Prev: Compiling For Multiple Architectures, Up: Installing Bash
+
+10.4 Installation Names
+=======================
+
+By default, ‘make install’ will install into ‘/usr/local/bin’,
+‘/usr/local/man’, etc.; that is, the “installation prefix” defaults to
+‘/usr/local’. You can specify an installation prefix other than
+‘/usr/local’ by giving ‘configure’ the option ‘--prefix=PATH’, or by
+specifying a value for the ‘prefix’ ‘make’ variable when running ‘make
+install’ (e.g., ‘make install prefix=PATH’). The ‘prefix’ variable
+provides a default for ‘exec_prefix’ and other variables used when
+installing Bash.
+
+ You can specify separate installation prefixes for
+architecture-specific files and architecture-independent files. If you
+give ‘configure’ the option ‘--exec-prefix=PATH’, ‘make install’ will
+use PATH as the prefix for installing programs and libraries.
+Documentation and other data files will still use the regular prefix.
+
+ If you would like to change the installation locations for a single
+run, you can specify these variables as arguments to ‘make’: ‘make
+install exec_prefix=/’ will install ‘bash’ and ‘bashbug’ into ‘/bin’
+instead of the default ‘/usr/local/bin’.
+
+ If you want to see the files Bash will install and where it will
+install them without changing anything on your system, specify the
+variable ‘DESTDIR’ as an argument to ‘make’. Its value should be the
+absolute directory path you'd like to use as the root of your sample
+installation tree. For example,
+
+ mkdir /fs1/bash-install
+ make install DESTDIR=/fs1/bash-install
+
+will install ‘bash’ into ‘/fs1/bash-install/usr/local/bin/bash’, the
+documentation into directories within
+‘/fs1/bash-install/usr/local/share’, the example loadable builtins into
+‘/fs1/bash-install/usr/local/lib/bash’, and so on. You can use the
+usual ‘exec_prefix’ and ‘prefix’ variables to alter the directory paths
+beneath the value of ‘DESTDIR’.
+
+ The GNU Makefile standards provide a more complete description of
+these variables and their effects.
+
+\1f
+File: bash.info, Node: Specifying the System Type, Next: Sharing Defaults, Prev: Installation Names, Up: Installing Bash
+
+10.5 Specifying the System Type
+===============================
+
+There may be some features ‘configure’ can not figure out automatically,
+but needs to determine by the type of host Bash will run on. Usually
+‘configure’ can figure that out, but if it prints a message saying it
+can not guess the host type, give it the ‘--host=TYPE’ option. ‘TYPE’
+can either be a short name for the system type, such as ‘sun4’, or a
+canonical name with three fields: ‘CPU-COMPANY-SYSTEM’ (e.g.,
+‘i386-unknown-freebsd4.2’).
+
+ See the file ‘support/config.sub’ for the possible values of each
+field.
+
+\1f
+File: bash.info, Node: Sharing Defaults, Next: Operation Controls, Prev: Specifying the System Type, Up: Installing Bash
+
+10.6 Sharing Defaults
+=====================
+
+If you want to set default values for ‘configure’ scripts to share, you
+can create a site shell script called ‘config.site’ that gives default
+values for variables like ‘CC’, ‘cache_file’, and ‘prefix’. ‘configure’
+looks for ‘PREFIX/share/config.site’ if it exists, then
+‘PREFIX/etc/config.site’ if it exists. Or, you can set the
+‘CONFIG_SITE’ environment variable to the location of the site script.
+A warning: the Bash ‘configure’ looks for a site script, but not all
+‘configure’ scripts do.
+
+\1f
+File: bash.info, Node: Operation Controls, Next: Optional Features, Prev: Sharing Defaults, Up: Installing Bash
+
+10.7 Operation Controls
+=======================
+
+‘configure’ recognizes the following options to control how it operates.
+
+‘--cache-file=FILE’
+ Use and save the results of the tests in FILE instead of
+ ‘./config.cache’. Set FILE to ‘/dev/null’ to disable caching, for
+ debugging ‘configure’.
+
+‘--help’
+ Print a summary of the options to ‘configure’, and exit.
+
+‘--quiet’
+‘--silent’
+‘-q’
+ Do not print messages saying which checks are being made.
+
+‘--srcdir=DIR’
+ Look for the Bash source code in directory DIR. Usually
+ ‘configure’ can determine that directory automatically.
+
+‘--version’
+ Print the version of Autoconf used to generate the ‘configure’
+ script, and exit.
+
+ ‘configure’ also accepts some other, not widely used, boilerplate
+options. ‘configure --help’ prints the complete list.
+
+\1f
+File: bash.info, Node: Optional Features, Prev: Operation Controls, Up: Installing Bash
+
+10.8 Optional Features
+======================
+
+The Bash ‘configure’ has a number of ‘--enable-FEATURE’ options, where
+FEATURE indicates an optional part of Bash. There are also several
+‘--with-PACKAGE’ options, where PACKAGE is something like ‘bash-malloc’
+or ‘afs’. To turn off the default use of a package, use
+‘--without-PACKAGE’. To configure Bash without a feature that is
+enabled by default, use ‘--disable-FEATURE’.
+
+ Here is a complete list of the ‘--enable-’ and ‘--with-’ options that
+the Bash ‘configure’ recognizes.
+
+‘--with-afs’
+ Define if you are using the Andrew File System from Transarc.
+
+‘--with-bash-malloc’
+ Use the Bash version of ‘malloc’ in the directory ‘lib/malloc’.
+ This is not the same ‘malloc’ that appears in GNU libc, but a
+ custom version originally derived from the 4.2 BSD ‘malloc’. This
+ ‘malloc’ is very fast, but wastes some space on each allocation,
+ though it uses several techniques to minimize the waste. This
+ option is enabled by default. The ‘NOTES’ file contains a list of
+ systems for which this should be turned off, and ‘configure’
+ disables this option automatically for a number of systems.
+
+‘--with-curses[=LIBNAME]’
+ Use the curses library instead of the termcap library as the
+ library where the linker can find the termcap functions.
+ ‘configure’ usually chooses this automatically, since most systems
+ include the termcap functions in the curses library. If LIBNAME is
+ supplied, ‘configure’ does not search for an appropriate library
+ and uses LIBNAME instead. LIBNAME should be either an argument for
+ the linker (e.g., ‘-lLIBNAME’) or a filename (e.g.,
+ ‘/opt/local/lib/libncursesw.so’).
+
+‘--with-gnu-malloc’
+ A synonym for ‘--with-bash-malloc’.
+
+‘--with-installed-readline[=PREFIX]’
+ Define this to make Bash link with a locally-installed version of
+ Readline rather than the version in ‘lib/readline’. This works
+ only with Readline 5.0 and later versions. If PREFIX is ‘yes’ or
+ not supplied, ‘configure’ uses the values of the make variables
+ ‘includedir’ and ‘libdir’, which are subdirectories of ‘prefix’ by
+ default, to find the installed version of Readline if it is not in
+ the standard system include and library directories. If PREFIX is
+ ‘no’, Bash links with the version in ‘lib/readline’. If PREFIX is
+ set to any other value, ‘configure’ treats it as a directory
+ pathname and looks for the installed version of Readline in
+ subdirectories of that directory (include files in PREFIX/‘include’
+ and the library in PREFIX/‘lib’). The Bash default is to link with
+ a static library built in the ‘lib/readline’ subdirectory of the
+ build directory.
+
+‘--with-libintl-prefix[=PREFIX]’
+ Define this to make Bash link with a locally-installed version of
+ the libintl library instead of the version in ‘lib/intl’.
+
+‘--with-libiconv-prefix[=PREFIX]’
+ Define this to make Bash look for libiconv in PREFIX instead of the
+ standard system locations. The Bash distribution does not include
+ this library.
+
+‘--enable-minimal-config’
+ This produces a shell with minimal features, closer to the
+ historical Bourne shell.
+
+ There are several ‘--enable-’ options that alter how Bash is
+compiled, linked, and installed, rather than changing run-time features.
+
+‘--enable-largefile’
+ Enable support for large files
+ (http://www.unix.org/version2/whatsnew/lfs20mar.html) if the
+ operating system requires special compiler options to build
+ programs which can access large files. This is enabled by default,
+ if the operating system provides large file support.
+
+‘--enable-profiling’
+ This builds a Bash binary that produces profiling information to be
+ processed by ‘gprof’ each time it is executed.
+
+‘--enable-separate-helpfiles’
+ Use external files for the documentation displayed by the ‘help’
+ builtin instead of storing the text internally.
+
+‘--enable-static-link’
+ This causes Bash to be linked statically, if ‘gcc’ is being used.
+ This could be used to build a version to use as root's shell.
+
+ The ‘minimal-config’ option can be used to disable all of the
+following options, but it is processed first, so individual options may
+be enabled using ‘enable-FEATURE’.
+
+ All of the following options except for ‘alt-array-implementation’,
+‘disabled-builtins’, ‘direxpand-default’, ‘strict-posix-default’, and
+‘xpg-echo-default’ are enabled by default, unless the operating system
+does not provide the necessary support.
+
+‘--enable-alias’
+ Allow alias expansion and include the ‘alias’ and ‘unalias’
+ builtins (*note Aliases::).
+
+‘--enable-alt-array-implementation’
+ This builds Bash using an alternate implementation of arrays (*note
+ Arrays::) that provides faster access at the expense of using more
+ memory (sometimes many times more, depending on how sparse an array
+ is).
+
+‘--enable-arith-for-command’
+ Include support for the alternate form of the ‘for’ command that
+ behaves like the C language ‘for’ statement (*note Looping
+ Constructs::).
+
+‘--enable-array-variables’
+ Include support for one-dimensional array shell variables (*note
+ Arrays::).
+
+‘--enable-bang-history’
+ Include support for ‘csh’-like history substitution (*note History
+ Interaction::).
+
+‘--enable-bash-source-fullpath-default’
+ Set the default value of the ‘bash_source_fullpath’ shell option
+ described above under *note The Shopt Builtin:: to be enabled.
+ This controls how filenames are assigned to the ‘BASH_SOURCE’ array
+ variable.
+
+‘--enable-brace-expansion’
+ Include ‘csh’-like brace expansion ( ‘b{a,b}c’ ↦ ‘bac bbc’ ). See
+ *note Brace Expansion::, for a complete description.
+
+‘--enable-casemod-attributes’
+ Include support for case-modifying attributes in the ‘declare’
+ builtin and assignment statements. Variables with the ‘uppercase’
+ attribute, for example, will have their values converted to
+ uppercase upon assignment.
+
+‘--enable-casemod-expansion’
+ Include support for case-modifying word expansions.
+
+‘--enable-command-timing’
+ Include support for recognizing ‘time’ as a reserved word and for
+ displaying timing statistics for the pipeline following ‘time’
+ (*note Pipelines::). This allows timing pipelines, shell compound
+ commands, shell builtins, and shell functions, which an external
+ command cannot do easily.
+
+‘--enable-cond-command’
+ Include support for the ‘[[’ conditional command. (*note
+ Conditional Constructs::).
+
+‘--enable-cond-regexp’
+ Include support for matching POSIX regular expressions using the
+ ‘=~’ binary operator in the ‘[[’ conditional command. (*note
+ Conditional Constructs::).
+
+‘--enable-coprocesses’
+ Include support for coprocesses and the ‘coproc’ reserved word
+ (*note Pipelines::).
+
+‘--enable-debugger’
+ Include support for the Bash debugger (distributed separately).
+
+‘--enable-dev-fd-stat-broken’
+ If calling ‘stat’ on /dev/fd/N returns different results than
+ calling ‘fstat’ on file descriptor N, supply this option to enable
+ a workaround. This has implications for conditional commands that
+ test file attributes.
+
+‘--enable-direxpand-default’
+ Cause the ‘direxpand’ shell option (*note The Shopt Builtin::) to
+ be enabled by default when the shell starts. It is normally
+ disabled by default.
+
+‘--enable-directory-stack’
+ Include support for a ‘csh’-like directory stack and the ‘pushd’,
+ ‘popd’, and ‘dirs’ builtins (*note The Directory Stack::).
+
+‘--enable-disabled-builtins’
+ Allow builtin commands to be invoked via ‘builtin xxx’ even after
+ ‘xxx’ has been disabled using ‘enable -n xxx’. See *note Bash
+ Builtins::, for details of the ‘builtin’ and ‘enable’ builtin
+ commands.
+
+‘--enable-dparen-arithmetic’
+ Include support for the ‘((...))’ command (*note Conditional
+ Constructs::).
+
+‘--enable-extended-glob’
+ Include support for the extended pattern matching features
+ described above under *note Pattern Matching::.
+
+‘--enable-extended-glob-default’
+ Set the default value of the ‘extglob’ shell option described above
+ under *note The Shopt Builtin:: to be enabled.
+
+‘--enable-function-import’
+ Include support for importing function definitions exported by
+ another instance of the shell from the environment. This option is
+ enabled by default.
+
+‘--enable-glob-asciiranges-default’
+ Set the default value of the ‘globasciiranges’ shell option
+ described above under *note The Shopt Builtin:: to be enabled.
+ This controls the behavior of character ranges when used in pattern
+ matching bracket expressions.
+
+‘--enable-help-builtin’
+ Include the ‘help’ builtin, which displays help on shell builtins
+ and variables (*note Bash Builtins::).
+
+‘--enable-history’
+ Include command history and the ‘fc’ and ‘history’ builtin commands
+ (*note Bash History Facilities::).
+
+‘--enable-job-control’
+ This enables the job control features (*note Job Control::), if the
+ operating system supports them.
+
+‘--enable-multibyte’
+ This enables support for multibyte characters if the operating
+ system provides the necessary support.
+
+‘--enable-net-redirections’
+ This enables the special handling of filenames of the form
+ ‘/dev/tcp/HOST/PORT’ and ‘/dev/udp/HOST/PORT’ when used in
+ redirections (*note Redirections::).
+
+‘--enable-process-substitution’
+ This enables process substitution (*note Process Substitution::) if
+ the operating system provides the necessary support.
+
+‘--enable-progcomp’
+ Enable the programmable completion facilities (*note Programmable
+ Completion::). If Readline is not enabled, this option has no
+ effect.
+
+‘--enable-prompt-string-decoding’
+ Turn on the interpretation of a number of backslash-escaped
+ characters in the ‘$PS0’, ‘$PS1’, ‘$PS2’, and ‘$PS4’ prompt
+ strings. See *note Controlling the Prompt::, for a complete list
+ of prompt string escape sequences.
+
+‘--enable-readline’
+ Include support for command-line editing and history with the Bash
+ version of the Readline library (*note Command Line Editing::).
+
+‘--enable-restricted’
+ Include support for a “restricted shell”. If this is enabled, Bash
+ enters a restricted mode when called as ‘rbash’. See *note The
+ Restricted Shell::, for a description of restricted mode.
+
+‘--enable-select’
+ Include the ‘select’ compound command, which allows generation of
+ simple menus (*note Conditional Constructs::).
+
+‘--enable-single-help-strings’
+ Store the text displayed by the ‘help’ builtin as a single string
+ for each help topic. This aids in translating the text to
+ different languages. You may need to disable this if your compiler
+ cannot handle very long string literals.
+
+‘--enable-strict-posix-default’
+ Make Bash POSIX-conformant by default (*note Bash POSIX Mode::).
+
+‘--enable-translatable-strings’
+ Enable support for ‘$"STRING"’ translatable strings (*note Locale
+ Translation::).
+
+‘--enable-usg-echo-default’
+ A synonym for ‘--enable-xpg-echo-default’.
+
+‘--enable-xpg-echo-default’
+ Make the ‘echo’ builtin expand backslash-escaped characters by
+ default, without requiring the ‘-e’ option. This sets the default
+ value of the ‘xpg_echo’ shell option to ‘on’, which makes the Bash
+ ‘echo’ behave more like the version specified in the Single Unix
+ Specification, version 3. *Note Bash Builtins::, for a description
+ of the escape sequences that ‘echo’ recognizes.
+
+ The file ‘config-top.h’ contains C Preprocessor ‘#define’ statements
+for options which are not settable from ‘configure’. Some of these are
+not meant to be changed; beware of the consequences if you do. Read the
+comments associated with each definition for more information about its
+effect.
+
+\1f
+File: bash.info, Node: Reporting Bugs, Next: Major Differences From The Bourne Shell, Prev: Installing Bash, Up: Top
+
+Appendix A Reporting Bugs
+*************************
+
+Please report all bugs you find in Bash. But first, you should make
+sure that it really is a bug, and that it appears in the latest version
+of Bash. The latest released version of Bash is always available for
+FTP from <ftp://ftp.gnu.org/pub/gnu/bash/> and from
+<http://git.savannah.gnu.org/cgit/bash.git/snapshot/bash-master.tar.gz>.
+
+ Once you have determined that a bug actually exists, use the
+‘bashbug’ command to submit a bug report or use the form at the Bash
+project page (https://savannah.gnu.org/projects/bash/). If you have a
+fix, you are encouraged to submit that as well! Suggestions and
+"philosophical" bug reports may be mailed to <bug-bash@gnu.org> or
+<help-bash@gnu.org>.
+
+ All bug reports should include:
+ • The version number of Bash.
+ • The hardware and operating system.
+ • The compiler used to compile Bash.
+ • A description of the bug behavior.
+ • A short script or "recipe" which exercises the bug and may be used
+ to reproduce it.
+
+‘bashbug’ inserts the first three items automatically into the template
+it provides for filing a bug report.
+
+ Please send all reports concerning this manual to <bug-bash@gnu.org>.
+
+\1f
+File: bash.info, Node: Major Differences From The Bourne Shell, Next: GNU Free Documentation License, Prev: Reporting Bugs, Up: Top
+
+Appendix B Major Differences From The Bourne Shell
+**************************************************
+
+Bash implements essentially the same grammar, parameter and variable
+expansion, redirection, and quoting as the Bourne Shell. Bash uses the
+POSIX standard as the specification of how these features are to be
+implemented and how they should behave. There are some differences
+between the traditional Bourne shell and Bash; this section quickly
+details the differences of significance. A number of these differences
+are explained in greater depth in previous sections. This section uses
+the version of ‘sh’ included in SVR4.2 (the last version of the
+historical Bourne shell) as the baseline reference.
+
+ • Bash is POSIX-conformant, even where the POSIX specification
+ differs from traditional ‘sh’ behavior (*note Bash POSIX Mode::).
+
+ • Bash has multi-character invocation options (*note Invoking
+ Bash::).
+
+ • The Bash restricted mode is more useful (*note The Restricted
+ Shell::); the SVR4.2 shell restricted mode is too limited.
+
+ • Bash has command-line editing (*note Command Line Editing::) and
+ the ‘bind’ builtin.
+
+ • Bash provides a programmable word completion mechanism (*note
+ Programmable Completion::), and builtin commands ‘complete’,
+ ‘compgen’, and ‘compopt’, to manipulate it.
+
+ • Bash decodes a number of backslash-escape sequences in the prompt
+ string variables (‘PS0’, ‘PS1’, ‘PS2’, and ‘PS4’) (*note
+ Controlling the Prompt::).
+
+ • Bash expands and displays the ‘PS0’ prompt string variable.
+
+ • Bash runs commands from the ‘PROMPT_COMMAND’ array variable before
+ issuing each primary prompt.
+
+ • Bash has command history (*note Bash History Facilities::) and the
+ ‘history’ and ‘fc’ builtins to manipulate it. The Bash history
+ list maintains timestamp information and uses the value of the
+ ‘HISTTIMEFORMAT’ variable to display it.
+
+ • Bash implements ‘csh’-like history expansion (*note History
+ Interaction::).
+
+ • Bash supports the ‘$'...'’ quoting syntax, which expands ANSI-C
+ backslash-escaped characters in the text between the single quotes
+ (*note ANSI-C Quoting::).
+
+ • Bash supports the ‘$"..."’ quoting syntax and performs
+ locale-specific translation of the characters between the double
+ quotes. The ‘-D’, ‘--dump-strings’, and ‘--dump-po-strings’
+ invocation options list the translatable strings found in a script
+ (*note Locale Translation::).
+
+ • Bash includes brace expansion (*note Brace Expansion::) and tilde
+ expansion (*note Tilde Expansion::).
+
+ • Bash implements command aliases and the ‘alias’ and ‘unalias’
+ builtins (*note Aliases::).
+
+ • Bash implements the ‘!’ reserved word to negate the return value of
+ a pipeline (*note Pipelines::). This is very useful when an ‘if’
+ statement needs to act only if a test fails. The Bash ‘-o
+ pipefail’ option to ‘set’ will cause a pipeline to return a failure
+ status if any command fails (*note The Set Builtin::).
+
+ • Bash has the ‘time’ reserved word and command timing (*note
+ Pipelines::). The display of the timing statistics may be
+ controlled with the ‘TIMEFORMAT’ variable.
+
+ • Bash provides coprocesses and the ‘coproc’ reserved word (*note
+ Coprocesses::).
+
+ • Bash implements the ‘for (( EXPR1 ; EXPR2 ; EXPR3 ))’ arithmetic
+ for command, similar to the C language (*note Looping
+ Constructs::).
+
+ • Bash includes the ‘select’ compound command, which allows the
+ generation of simple menus (*note Conditional Constructs::).
+
+ • Bash includes the ‘[[’ compound command, which makes conditional
+ testing part of the shell grammar (*note Conditional Constructs::),
+ including optional regular expression matching.
+
+ • Bash provides optional case-insensitive matching for the ‘case’ and
+ ‘[[’ constructs (*note Conditional Constructs::).
+
+ • Bash provides additional ‘case’ statement action list terminators:
+ ‘;&’ and ‘;;&’ (*note Conditional Constructs::).
+
+ • Bash provides shell arithmetic, the ‘((’ compound command (*note
+ Conditional Constructs::), the ‘let’ builtin, and arithmetic
+ expansion (*note Shell Arithmetic::).
+
+ • Bash has one-dimensional array variables (*note Arrays::), and the
+ appropriate variable expansions and assignment syntax to use them.
+ Several of the Bash builtins take options to act on arrays. Bash
+ provides a number of built-in array variables.
+
+ • Variables present in the shell's initial environment are
+ automatically exported to child processes (*note Command Execution
+ Environment::). The Bourne shell does not normally do this unless
+ the variables are explicitly marked using the ‘export’ command.
+
+ • Bash can expand positional parameters beyond ‘$9’ using ‘${NUM}’
+ (*note Shell Parameter Expansion::).
+
+ • Bash supports the ‘+=’ assignment operator, which appends to the
+ value of the variable named on the left hand side (*note Shell
+ Parameters::).
+
+ • Bash includes the POSIX pattern removal ‘%’, ‘#’, ‘%%’ and ‘##’
+ expansions to remove leading or trailing substrings from variable
+ values (*note Shell Parameter Expansion::).
+
+ • The expansion ‘${#xx}’, which returns the length of ‘${xx}’, is
+ supported (*note Shell Parameter Expansion::).
+
+ • The expansion ‘${var:’OFFSET‘[:’LENGTH‘]}’, which expands to the
+ substring of ‘var’'s value of length LENGTH, beginning at OFFSET,
+ is present (*note Shell Parameter Expansion::).
+
+ • The expansion ‘${VAR/[/]’PATTERN‘[/’REPLACEMENT‘]}’, which matches
+ PATTERN and replaces it with REPLACEMENT in the value of VAR, is
+ available (*note Shell Parameter Expansion::), with a mechanism to
+ use the matched text in REPLACEMENT.
+
+ • The expansion ‘${!PREFIX*}’ expansion, which expands to the names
+ of all shell variables whose names begin with PREFIX, is available
+ (*note Shell Parameter Expansion::).
+
+ • Bash has indirect variable expansion using ‘${!word}’ (*note Shell
+ Parameter Expansion::) and implements the ‘nameref’ variable
+ attribute for automatic indirect variable expansion.
+
+ • Bash includes a set of parameter transformation word expansions of
+ the form ‘${var@X}’, where ‘X’ specifies the transformation (*note
+ Shell Parameter Expansion::).
+
+ • The POSIX ‘$()’ form of command substitution is implemented (*note
+ Command Substitution::), and preferred to the Bourne shell's ‘``’
+ (which is also implemented for backwards compatibility).
+
+ • Bash implements a variant of command substitution that runs the
+ enclosed command in the current shell execution environment: ‘${
+ COMMAND;}’ or ‘${|COMMAND;}’ (*note Command Substitution::).
+
+ • Bash has process substitution (*note Process Substitution::).
+
+ • Bash automatically assigns variables that provide information about
+ the current user (‘UID’, ‘EUID’, and ‘GROUPS’), the current host
+ (‘HOSTTYPE’, ‘OSTYPE’, ‘MACHTYPE’, and ‘HOSTNAME’), and the
+ instance of Bash that is running (‘BASH’, ‘BASH_VERSION’, and
+ ‘BASH_VERSINFO’). *Note Bash Variables::, for details.
+
+ • Bash uses many variables to provide functionality and customize
+ shell behavior that the Bourne shell does not. Examples include
+ ‘RANDOM’, ‘SRANDOM’, ‘EPOCHSECONDS’, ‘EPOCHREALTIME’, ‘TIMEFORMAT’,
+ ‘BASHPID’, ‘BASH_XTRACEFD’, ‘GLOBIGNORE’, ‘HISTIGNORE’, and
+ ‘BASH_VERSION’. *Note Bash Variables::, for a complete list.
+
+ • Bash uses the ‘GLOBSORT’ shell variable to control how to sort the
+ results of filename expansion (*note Filename Expansion::).
+
+ • Bash uses the ‘IFS’ variable to split only the results of
+ expansion, not all words (*note Word Splitting::). This closes a
+ longstanding shell security hole.
+
+ • The filename expansion bracket expression code uses ‘!’ and ‘^’ to
+ negate the set of characters between the brackets (*note Filename
+ Expansion::). The Bourne shell uses only ‘!’.
+
+ • Bash implements the full set of POSIX filename expansion operators,
+ including character classes, equivalence classes, and collating
+ symbols (*note Filename Expansion::).
+
+ • Bash implements extended pattern matching features when the
+ ‘extglob’ shell option is enabled (*note Pattern Matching::).
+
+ • The ‘globstar’ shell option extends filename expansion to
+ recursively scan directories and subdirectories for matching
+ filenames (*note Pattern Matching::).
+
+ • It is possible to have a variable and a function with the same
+ name; ‘sh’ does not separate the two name spaces.
+
+ • Bash functions are permitted to have local variables using the
+ ‘local’ builtin, and thus users can write useful recursive
+ functions (*note Bash Builtins::).
+
+ • Bash performs filename expansion on filenames specified as operands
+ to input and output redirection operators (*note Redirections::).
+
+ • Bash contains the ‘<>’ redirection operator, allowing a file to be
+ opened for both reading and writing, and the ‘&>’ redirection
+ operator, for directing standard output and standard error to the
+ same file (*note Redirections::).
+
+ • Bash includes the ‘<<<’ redirection operator, allowing a string to
+ be used as the standard input to a command (*note Redirections::).
+
+ • Bash implements the ‘[n]<&WORD’ and ‘[n]>&WORD’ redirection
+ operators, which move one file descriptor to another.
+
+ • Bash treats a number of filenames specially when they are used in
+ redirection operators (*note Redirections::).
+
+ • Bash provides the {VAR}<WORD capability to have the shell allocate
+ file descriptors for redirections and assign them to VAR (*note
+ Redirections::). This works with multiple redirection operators.
+
+ • Bash can open network connections to arbitrary machines and
+ services with the redirection operators (*note Redirections::).
+
+ • The ‘noclobber’ option is available to avoid overwriting existing
+ files with output redirection (*note The Set Builtin::). The ‘>|’
+ redirection operator may be used to override ‘noclobber’.
+
+ • Variable assignments preceding commands affect only that command,
+ even builtins and functions (*note Environment::). In ‘sh’, all
+ variable assignments preceding commands are global unless the
+ command is executed from the file system.
+
+ • Bash includes a number of features to support a separate debugger
+ for shell scripts: variables (‘BASH_ARGC’, ‘BASH_ARGV’,
+ ‘BASH_LINENO’, ‘BASH_SOURCE’), the ‘DEBUG’, ‘RETURN’, and ‘ERR’
+ traps, ‘declare -F’, and the ‘caller’ builtin.
+
+ • Bash implements a ‘csh’-like directory stack, and provides the
+ ‘pushd’, ‘popd’, and ‘dirs’ builtins to manipulate it (*note The
+ Directory Stack::). Bash also makes the directory stack visible as
+ the value of the ‘DIRSTACK’ shell variable.
+
+ • Bash allows a function to override a builtin with the same name,
+ and provides access to that builtin's functionality within the
+ function via the ‘builtin’ and ‘command’ builtins (*note Bash
+ Builtins::).
+
+ • Bash includes the ‘caller’ builtin (*note Bash Builtins::), which
+ displays the context of any active subroutine call (a shell
+ function or a script executed with the ‘.’ or ‘source’ builtins).
+ This supports the Bash debugger.
+
+ • The Bash ‘cd’ and ‘pwd’ builtins (*note Bourne Shell Builtins::)
+ each take ‘-L’ and ‘-P’ options to switch between logical and
+ physical modes.
+
+ • The ‘command’ builtin allows selectively skipping shell functions
+ when performing command lookup (*note Bash Builtins::).
+
+ • Bash uses the ‘declare’ builtin to modify the full set of variable
+ and function attributes, and to assign values to variables.
+
+ • The ‘disown’ builtin can remove a job from the internal shell job
+ table (*note Job Control Builtins::) or suppress sending ‘SIGHUP’
+ to a job when the shell exits as the result of a ‘SIGHUP’.
+
+ • The ‘enable’ builtin (*note Bash Builtins::) can enable or disable
+ individual builtins and implements support for dynamically loading
+ builtin commands from shared objects.
+
+ • The Bash ‘exec’ builtin takes additional options that allow users
+ to control the contents of the environment passed to the executed
+ command, and what the zeroth argument to the command is to be
+ (*note Bourne Shell Builtins::).
+
+ • Shell functions may be exported to children via the environment
+ using ‘export -f’ (*note Shell Functions::).
+
+ • The Bash ‘export’ and ‘readonly’ builtins (*note Bourne Shell
+ Builtins::) can take a ‘-f’ option to act on shell functions, a
+ ‘-p’ option to display variables with various attributes set in a
+ format that can be used as shell input, a ‘-n’ option to remove
+ various variable attributes, and ‘name=value’ arguments to set
+ variable attributes and values simultaneously.
+
+ • The Bash ‘hash’ builtin allows a name to be associated with an
+ arbitrary filename, even when that filename cannot be found by
+ searching the ‘$PATH’, using ‘hash -p’ (*note Bourne Shell
+ Builtins::).
+
+ • Bash includes a ‘help’ builtin for quick reference to shell
+ facilities (*note Bash Builtins::).
+
+ • Bash includes the ‘mapfile’ builtin to quickly read the contents of
+ a file into an indexed array variable (*note Bash Builtins::).
+
+ • The ‘printf’ builtin is available to display formatted output
+ (*note Bash Builtins::), and has additional custom format
+ specifiers and an option to assign the formatted output directly to
+ a shell variable.
+
+ • The Bash ‘read’ builtin (*note Bash Builtins::) will read a line
+ ending in ‘\’ with the ‘-r’ option, and will use the ‘REPLY’
+ variable as a default if no non-option arguments are supplied.
+
+ • The ‘read’ builtin (*note Bash Builtins::) accepts a prompt string
+ with the ‘-p’ option and will use Readline to obtain the line when
+ given the ‘-e’ or ‘-E’ options, with the ability to insert text
+ into the line using the ‘-i’ option. The ‘read’ builtin also has
+ additional options to control input: the ‘-s’ option will turn off
+ echoing of input characters as they are read, the ‘-t’ option will
+ allow ‘read’ to time out if input does not arrive within a
+ specified number of seconds, the ‘-n’ option will allow reading
+ only a specified number of characters rather than a full line, and
+ the ‘-d’ option will read until a particular character rather than
+ newline.
+
+ • The ‘return’ builtin may be used to abort execution of scripts
+ executed with the ‘.’ or ‘source’ builtins (*note Bourne Shell
+ Builtins::).
+
+ • Bash has much more optional behavior controllable with the ‘set’
+ builtin (*note The Set Builtin::).
+
+ • The ‘-x’ (‘xtrace’) option displays commands other than simple
+ commands when performing an execution trace (*note The Set
+ Builtin::).
+
+ • Bash includes the ‘shopt’ builtin, for finer control of shell
+ optional capabilities (*note The Shopt Builtin::), and allows these
+ options to be set and unset at shell invocation (*note Invoking
+ Bash::).
+
+ • The ‘test’ builtin (*note Bourne Shell Builtins::) is slightly
+ different, as it implements the POSIX algorithm, which specifies
+ the behavior based on the number of arguments.
+
+ • The ‘trap’ builtin (*note Bourne Shell Builtins::) allows a ‘DEBUG’
+ pseudo-signal specification, similar to ‘EXIT’. Commands specified
+ with a ‘DEBUG’ trap are executed before every simple command, ‘for’
+ command, ‘case’ command, ‘select’ command, every arithmetic ‘for’
+ command, and before the first command executes in a shell function.
+ The ‘DEBUG’ trap is not inherited by shell functions unless the
+ function has been given the ‘trace’ attribute or the ‘functrace’
+ option has been enabled using the ‘shopt’ builtin. The ‘extdebug’
+ shell option has additional effects on the ‘DEBUG’ trap.
+
+ The ‘trap’ builtin (*note Bourne Shell Builtins::) allows an ‘ERR’
+ pseudo-signal specification, similar to ‘EXIT’ and ‘DEBUG’.
+ Commands specified with an ‘ERR’ trap are executed after a simple
+ command fails, with a few exceptions. The ‘ERR’ trap is not
+ inherited by shell functions unless the ‘-o errtrace’ option to the
+ ‘set’ builtin is enabled.
+
+ The ‘trap’ builtin (*note Bourne Shell Builtins::) allows a
+ ‘RETURN’ pseudo-signal specification, similar to ‘EXIT’ and
+ ‘DEBUG’. Commands specified with a ‘RETURN’ trap are executed
+ before execution resumes after a shell function or a shell script
+ executed with ‘.’ or ‘source’ returns. The ‘RETURN’ trap is not
+ inherited by shell functions unless the function has been given the
+ ‘trace’ attribute or the ‘functrace’ option has been enabled using
+ the ‘shopt’ builtin.
+
+ • The Bash ‘type’ builtin is more extensive and gives more
+ information about the names it finds (*note Bash Builtins::).
+
+ • The ‘ulimit’ builtin provides control over many more per-process
+ resources (*note Bash Builtins::).
+
+ • The Bash ‘umask’ builtin uses the ‘-p’ option to display the output
+ in the form of a ‘umask’ command that may be reused as input (*note
+ Bourne Shell Builtins::).
+
+ • The Bash ‘wait’ builtin has a ‘-n’ option to wait for the next
+ child to exit, possibly selecting from a list of supplied jobs, and
+ the ‘-p’ option to store information about a terminated child
+ process in a shell variable.
+
+ • The SVR4.2 shell behaves differently when invoked as ‘jsh’ (it
+ turns on job control).
+
+ • The SVR4.2 shell has two privilege-related builtins (‘mldmode’ and
+ ‘priv’) not present in Bash.
+
+ • Bash does not have the ‘stop’ or ‘newgrp’ builtins.
+
+ • Bash does not use the ‘SHACCT’ variable or perform shell
+ accounting.
+
+ • The SVR4.2 ‘sh’ uses a ‘TIMEOUT’ variable like Bash uses ‘TMOUT’.
+
+More features unique to Bash may be found in *note Bash Features::.
+
+B.1 Implementation Differences From The SVR4.2 Shell
+====================================================
+
+Since Bash is a completely new implementation, it does not suffer from
+many of the limitations of the SVR4.2 shell. For instance:
+
+ • Bash does not fork a subshell when redirecting into or out of a
+ shell control structure such as an ‘if’ or ‘while’ statement.
+
+ • Bash does not allow unbalanced quotes. The SVR4.2 shell will
+ silently insert a needed closing quote at ‘EOF’ under certain
+ circumstances. This can be the cause of some hard-to-find errors.
+
+ • The SVR4.2 shell uses a baroque memory management scheme based on
+ trapping ‘SIGSEGV’. If the shell is started from a process with
+ ‘SIGSEGV’ blocked (e.g., by using the ‘system()’ C library function
+ call), it misbehaves badly.
+
+ • In a questionable attempt at security, the SVR4.2 shell, when
+ invoked without the ‘-p’ option, will alter its real and effective
+ UID and GID if they are less than some magic threshold value,
+ commonly 100. This can lead to unexpected results.
+
+ • The SVR4.2 shell does not allow users to trap ‘SIGSEGV’, ‘SIGALRM’,
+ or ‘SIGCHLD’.
+
+ • The SVR4.2 shell does not allow the ‘IFS’, ‘MAILCHECK’, ‘PATH’,
+ ‘PS1’, or ‘PS2’ variables to be unset.
+
+ • The SVR4.2 shell treats ‘^’ as the undocumented equivalent of ‘|’.
+
+ • Bash allows multiple option arguments when it is invoked (‘-x -v’);
+ the SVR4.2 shell allows only one option argument (‘-xv’). In fact,
+ some versions of the shell dump core if the second argument begins
+ with a ‘-’.
+
+ • The SVR4.2 shell exits a script if any builtin fails; Bash exits a
+ script only if one of the POSIX special builtins fails, and only
+ for certain failures, as enumerated in the POSIX standard.
+
+ • If the ‘lastpipe’ option is enabled, and job control is not active,
+ Bash runs the last element of a pipeline in the current shell
+ execution environment.
+
+\1f
+File: bash.info, Node: GNU Free Documentation License, Next: Indexes, Prev: Major Differences From The Bourne Shell, Up: Top
+
+Appendix C GNU Free Documentation License
+*****************************************
+
+ Version 1.3, 3 November 2008
+
+ Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
+ <http://fsf.org/>
+
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+ 0. PREAMBLE
+
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+ functional and useful document “free” in the sense of freedom: to
+ assure everyone the effective freedom to copy and redistribute it,
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+ being considered responsible for modifications made by others.
+
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+ It complements the GNU General Public License, which is a copyleft
+ license designed for free software.
+
+ We have designed this License in order to use it for manuals for
+ free software, because free software needs free documentation: a
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+
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+
+ If you publish or distribute Opaque copies of the Document
+ numbering more than 100, you must either include a machine-readable
+ Transparent copy along with each Opaque copy, or state in or with
+ each Opaque copy a computer-network location from which the general
+ network-using public has access to download using public-standard
+ network protocols a complete Transparent copy of the Document, free
+ of added material. If you use the latter option, you must take
+ reasonably prudent steps, when you begin distribution of Opaque
+ copies in quantity, to ensure that this Transparent copy will
+ remain thus accessible at the stated location until at least one
+ year after the last time you distribute an Opaque copy (directly or
+ through your agents or retailers) of that edition to the public.
+
+ It is requested, but not required, that you contact the authors of
+ the Document well before redistributing any large number of copies,
+ to give them a chance to provide you with an updated version of the
+ Document.
+
+ 4. MODIFICATIONS
+
+ You may copy and distribute a Modified Version of the Document
+ under the conditions of sections 2 and 3 above, provided that you
+ release the Modified Version under precisely this License, with the
+ Modified Version filling the role of the Document, thus licensing
+ distribution and modification of the Modified Version to whoever
+ possesses a copy of it. In addition, you must do these things in
+ the Modified Version:
+
+ A. Use in the Title Page (and on the covers, if any) a title
+ distinct from that of the Document, and from those of previous
+ versions (which should, if there were any, be listed in the
+ History section of the Document). You may use the same title
+ as a previous version if the original publisher of that
+ version gives permission.
+
+ B. List on the Title Page, as authors, one or more persons or
+ entities responsible for authorship of the modifications in
+ the Modified Version, together with at least five of the
+ principal authors of the Document (all of its principal
+ authors, if it has fewer than five), unless they release you
+ from this requirement.
+
+ C. State on the Title page the name of the publisher of the
+ Modified Version, as the publisher.
+
+ D. Preserve all the copyright notices of the Document.
+
+ E. Add an appropriate copyright notice for your modifications
+ adjacent to the other copyright notices.
+
+ F. Include, immediately after the copyright notices, a license
+ notice giving the public permission to use the Modified
+ Version under the terms of this License, in the form shown in
+ the Addendum below.
+
+ G. Preserve in that license notice the full lists of Invariant
+ Sections and required Cover Texts given in the Document's
+ license notice.
+
+ H. Include an unaltered copy of this License.
+
+ I. Preserve the section Entitled "History", Preserve its Title,
+ and add to it an item stating at least the title, year, new
+ authors, and publisher of the Modified Version as given on the
+ Title Page. If there is no section Entitled "History" in the
+ Document, create one stating the title, year, authors, and
+ publisher of the Document as given on its Title Page, then add
+ an item describing the Modified Version as stated in the
+ previous sentence.
+
+ J. Preserve the network location, if any, given in the Document
+ for public access to a Transparent copy of the Document, and
+ likewise the network locations given in the Document for
+ previous versions it was based on. These may be placed in the
+ "History" section. You may omit a network location for a work
+ that was published at least four years before the Document
+ itself, or if the original publisher of the version it refers
+ to gives permission.
+
+ K. For any section Entitled "Acknowledgements" or "Dedications",
+ Preserve the Title of the section, and preserve in the section
+ all the substance and tone of each of the contributor
+ acknowledgements and/or dedications given therein.
+
+ L. Preserve all the Invariant Sections of the Document, unaltered
+ in their text and in their titles. Section numbers or the
+ equivalent are not considered part of the section titles.
+
+ M. Delete any section Entitled "Endorsements". Such a section
+ may not be included in the Modified Version.
+
+ N. Do not retitle any existing section to be Entitled
+ "Endorsements" or to conflict in title with any Invariant
+ Section.
+
+ O. Preserve any Warranty Disclaimers.
+
+ If the Modified Version includes new front-matter sections or
+ appendices that qualify as Secondary Sections and contain no
+ material copied from the Document, you may at your option designate
+ some or all of these sections as invariant. To do this, add their
+ titles to the list of Invariant Sections in the Modified Version's
+ license notice. These titles must be distinct from any other
+ section titles.
+
+ You may add a section Entitled "Endorsements", provided it contains
+ nothing but endorsements of your Modified Version by various
+ parties--for example, statements of peer review or that the text
+ has been approved by an organization as the authoritative
+ definition of a standard.
+
+ You may add a passage of up to five words as a Front-Cover Text,
+ and a passage of up to 25 words as a Back-Cover Text, to the end of
+ the list of Cover Texts in the Modified Version. Only one passage
+ of Front-Cover Text and one of Back-Cover Text may be added by (or
+ through arrangements made by) any one entity. If the Document
+ already includes a cover text for the same cover, previously added
+ by you or by arrangement made by the same entity you are acting on
+ behalf of, you may not add another; but you may replace the old
+ one, on explicit permission from the previous publisher that added
+ the old one.
+
+ The author(s) and publisher(s) of the Document do not by this
+ License give permission to use their names for publicity for or to
+ assert or imply endorsement of any Modified Version.
+
+ 5. COMBINING DOCUMENTS
+
+ You may combine the Document with other documents released under
+ this License, under the terms defined in section 4 above for
+ modified versions, provided that you include in the combination all
+ of the Invariant Sections of all of the original documents,
+ unmodified, and list them all as Invariant Sections of your
+ combined work in its license notice, and that you preserve all
+ their Warranty Disclaimers.
+
+ The combined work need only contain one copy of this License, and
+ multiple identical Invariant Sections may be replaced with a single
+ copy. If there are multiple Invariant Sections with the same name
+ but different contents, make the title of each such section unique
+ by adding at the end of it, in parentheses, the name of the
+ original author or publisher of that section if known, or else a
+ unique number. Make the same adjustment to the section titles in
+ the list of Invariant Sections in the license notice of the
+ combined work.
+
+ In the combination, you must combine any sections Entitled
+ "History" in the various original documents, forming one section
+ Entitled "History"; likewise combine any sections Entitled
+ "Acknowledgements", and any sections Entitled "Dedications". You
+ must delete all sections Entitled "Endorsements."
+
+ 6. COLLECTIONS OF DOCUMENTS
+
+ You may make a collection consisting of the Document and other
+ documents released under this License, and replace the individual
+ copies of this License in the various documents with a single copy
+ that is included in the collection, provided that you follow the
+ rules of this License for verbatim copying of each of the documents
+ in all other respects.
+
+ You may extract a single document from such a collection, and
+ distribute it individually under this License, provided you insert
+ a copy of this License into the extracted document, and follow this
+ License in all other respects regarding verbatim copying of that
+ document.
+
+ 7. AGGREGATION WITH INDEPENDENT WORKS
+
+ A compilation of the Document or its derivatives with other
+ separate and independent documents or works, in or on a volume of a
+ storage or distribution medium, is called an "aggregate" if the
+ copyright resulting from the compilation is not used to limit the
+ legal rights of the compilation's users beyond what the individual
+ works permit. When the Document is included in an aggregate, this
+ License does not apply to the other works in the aggregate which
+ are not themselves derivative works of the Document.
+
+ If the Cover Text requirement of section 3 is applicable to these
+ copies of the Document, then if the Document is less than one half
+ of the entire aggregate, the Document's Cover Texts may be placed
+ on covers that bracket the Document within the aggregate, or the
+ electronic equivalent of covers if the Document is in electronic
+ form. Otherwise they must appear on printed covers that bracket
+ the whole aggregate.
+
+ 8. TRANSLATION
+
+ Translation is considered a kind of modification, so you may
+ distribute translations of the Document under the terms of section
+ 4. Replacing Invariant Sections with translations requires special
+ permission from their copyright holders, but you may include
+ translations of some or all Invariant Sections in addition to the
+ original versions of these Invariant Sections. You may include a
+ translation of this License, and all the license notices in the
+ Document, and any Warranty Disclaimers, provided that you also
+ include the original English version of this License and the
+ original versions of those notices and disclaimers. In case of a
+ disagreement between the translation and the original version of
+ this License or a notice or disclaimer, the original version will
+ prevail.
+
+ If a section in the Document is Entitled "Acknowledgements",
+ "Dedications", or "History", the requirement (section 4) to
+ Preserve its Title (section 1) will typically require changing the
+ actual title.
+
+ 9. TERMINATION
+
+ You may not copy, modify, sublicense, or distribute the Document
+ except as expressly provided under this License. Any attempt
+ otherwise to copy, modify, sublicense, or distribute it is void,
+ and will automatically terminate your rights under this License.
+
+ However, if you cease all violation of this License, then your
+ license from a particular copyright holder is reinstated (a)
+ provisionally, unless and until the copyright holder explicitly and
+ finally terminates your license, and (b) permanently, if the
+ copyright holder fails to notify you of the violation by some
+ reasonable means prior to 60 days after the cessation.
+
+ Moreover, your license from a particular copyright holder is
+ reinstated permanently if the copyright holder notifies you of the
+ violation by some reasonable means, this is the first time you have
+ received notice of violation of this License (for any work) from
+ that copyright holder, and you cure the violation prior to 30 days
+ after your receipt of the notice.
+
+ Termination of your rights under this section does not terminate
+ the licenses of parties who have received copies or rights from you
+ under this License. If your rights have been terminated and not
+ permanently reinstated, receipt of a copy of some or all of the
+ same material does not give you any rights to use it.
+
+ 10. FUTURE REVISIONS OF THIS LICENSE
+
+ The Free Software Foundation may publish new, revised versions of
+ the GNU Free Documentation License from time to time. Such new
+ versions will be similar in spirit to the present version, but may
+ differ in detail to address new problems or concerns. See
+ <http://www.gnu.org/copyleft/>.
+
+ Each version of the License is given a distinguishing version
+ number. If the Document specifies that a particular numbered
+ version of this License "or any later version" applies to it, you
+ have the option of following the terms and conditions either of
+ that specified version or of any later version that has been
+ published (not as a draft) by the Free Software Foundation. If the
+ Document does not specify a version number of this License, you may
+ choose any version ever published (not as a draft) by the Free
+ Software Foundation. If the Document specifies that a proxy can
+ decide which future versions of this License can be used, that
+ proxy's public statement of acceptance of a version permanently
+ authorizes you to choose that version for the Document.
+
+ 11. RELICENSING
+
+ "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
+ World Wide Web server that publishes copyrightable works and also
+ provides prominent facilities for anybody to edit those works. A
+ public wiki that anybody can edit is an example of such a server.
+ A "Massive Multiauthor Collaboration" (or "MMC") contained in the
+ site means any set of copyrightable works thus published on the MMC
+ site.
+
+ "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
+ license published by Creative Commons Corporation, a not-for-profit
+ corporation with a principal place of business in San Francisco,
+ California, as well as future copyleft versions of that license
+ published by that same organization.
+
+ "Incorporate" means to publish or republish a Document, in whole or
+ in part, as part of another Document.
+
+ An MMC is "eligible for relicensing" if it is licensed under this
+ License, and if all works that were first published under this
+ License somewhere other than this MMC, and subsequently
+ incorporated in whole or in part into the MMC, (1) had no cover
+ texts or invariant sections, and (2) were thus incorporated prior
+ to November 1, 2008.
+
+ The operator of an MMC Site may republish an MMC contained in the
+ site under CC-BY-SA on the same site at any time before August 1,
+ 2009, provided the MMC is eligible for relicensing.
+
+ADDENDUM: How to use this License for your documents
+====================================================
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and license
+notices just after the title page:
+
+ Copyright (C) YEAR YOUR NAME.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
+ Texts. A copy of the license is included in the section entitled ``GNU
+ Free Documentation License''.
+
+ If you have Invariant Sections, Front-Cover Texts and Back-Cover
+Texts, replace the "with...Texts." line with this:
+
+ with the Invariant Sections being LIST THEIR TITLES, with
+ the Front-Cover Texts being LIST, and with the Back-Cover Texts
+ being LIST.
+
+ If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+
+ If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of free
+software license, such as the GNU General Public License, to permit
+their use in free software.
+
+\1f
+File: bash.info, Node: Indexes, Prev: GNU Free Documentation License, Up: Top
+
+Appendix D Indexes
+******************
+
+* Menu:
+
+* Builtin Index:: Index of Bash builtin commands.
+* Reserved Word Index:: Index of Bash reserved words.
+* Variable Index:: Quick reference helps you find the
+ variable you want.
+* Function Index:: Index of bindable Readline functions.
+* Concept Index:: General index for concepts described in
+ this manual.
+
+\1f
+File: bash.info, Node: Builtin Index, Next: Reserved Word Index, Up: Indexes
+
+D.1 Index of Shell Builtin Commands
+===================================
+
+\0\b[index\0\b]
+* Menu:
+
+* :: Bourne Shell Builtins.
+ (line 11)
+* .: Bourne Shell Builtins.
+ (line 17)
+* [: Bourne Shell Builtins.
+ (line 340)
+* alias: Bash Builtins. (line 11)
+* bg: Job Control Builtins.
+ (line 7)
+* bind: Bash Builtins. (line 24)
+* break: Bourne Shell Builtins.
+ (line 47)
+* builtin: Bash Builtins. (line 133)
+* caller: Bash Builtins. (line 142)
+* cd: Bourne Shell Builtins.
+ (line 55)
+* command: Bash Builtins. (line 159)
+* compgen: Programmable Completion Builtins.
+ (line 12)
+* complete: Programmable Completion Builtins.
+ (line 37)
+* compopt: Programmable Completion Builtins.
+ (line 258)
+* continue: Bourne Shell Builtins.
+ (line 107)
+* declare: Bash Builtins. (line 179)
+* dirs: Directory Stack Builtins.
+ (line 7)
+* disown: Job Control Builtins.
+ (line 120)
+* echo: Bash Builtins. (line 284)
+* enable: Bash Builtins. (line 337)
+* eval: Bourne Shell Builtins.
+ (line 116)
+* exec: Bourne Shell Builtins.
+ (line 124)
+* exit: Bourne Shell Builtins.
+ (line 146)
+* export: Bourne Shell Builtins.
+ (line 153)
+* false: Bourne Shell Builtins.
+ (line 176)
+* fc: Bash History Builtins.
+ (line 10)
+* fg: Job Control Builtins.
+ (line 17)
+* getopts: Bourne Shell Builtins.
+ (line 181)
+* hash: Bourne Shell Builtins.
+ (line 233)
+* help: Bash Builtins. (line 375)
+* history: Bash History Builtins.
+ (line 59)
+* jobs: Job Control Builtins.
+ (line 28)
+* kill: Job Control Builtins.
+ (line 61)
+* let: Bash Builtins. (line 404)
+* local: Bash Builtins. (line 413)
+* logout: Bash Builtins. (line 438)
+* mapfile: Bash Builtins. (line 443)
+* popd: Directory Stack Builtins.
+ (line 37)
+* printf: Bash Builtins. (line 488)
+* pushd: Directory Stack Builtins.
+ (line 71)
+* pwd: Bourne Shell Builtins.
+ (line 265)
+* read: Bash Builtins. (line 558)
+* readarray: Bash Builtins. (line 669)
+* readonly: Bourne Shell Builtins.
+ (line 277)
+* return: Bourne Shell Builtins.
+ (line 302)
+* set: The Set Builtin. (line 11)
+* shift: Bourne Shell Builtins.
+ (line 327)
+* shopt: The Shopt Builtin. (line 9)
+* source: Bash Builtins. (line 678)
+* suspend: Job Control Builtins.
+ (line 139)
+* test: Bourne Shell Builtins.
+ (line 340)
+* times: Bourne Shell Builtins.
+ (line 440)
+* trap: Bourne Shell Builtins.
+ (line 446)
+* true: Bourne Shell Builtins.
+ (line 512)
+* type: Bash Builtins. (line 683)
+* typeset: Bash Builtins. (line 720)
+* ulimit: Bash Builtins. (line 726)
+* umask: Bourne Shell Builtins.
+ (line 517)
+* unalias: Bash Builtins. (line 834)
+* unset: Bourne Shell Builtins.
+ (line 535)
+* wait: Job Control Builtins.
+ (line 86)
+
+\1f
+File: bash.info, Node: Reserved Word Index, Next: Variable Index, Prev: Builtin Index, Up: Indexes
+
+D.2 Index of Shell Reserved Words
+=================================
+
+\0\b[index\0\b]
+* Menu:
+
+* !: Pipelines. (line 9)
+* [[: Conditional Constructs.
+ (line 128)
+* ]]: Conditional Constructs.
+ (line 128)
+* {: Command Grouping. (line 21)
+* }: Command Grouping. (line 21)
+* case: Conditional Constructs.
+ (line 28)
+* do: Looping Constructs. (line 12)
+* done: Looping Constructs. (line 12)
+* elif: Conditional Constructs.
+ (line 7)
+* else: Conditional Constructs.
+ (line 7)
+* esac: Conditional Constructs.
+ (line 28)
+* fi: Conditional Constructs.
+ (line 7)
+* for: Looping Constructs. (line 32)
+* function: Shell Functions. (line 13)
+* if: Conditional Constructs.
+ (line 7)
+* in: Conditional Constructs.
+ (line 28)
+* select: Conditional Constructs.
+ (line 84)
+* then: Conditional Constructs.
+ (line 7)
+* time: Pipelines. (line 9)
+* until: Looping Constructs. (line 12)
+* while: Looping Constructs. (line 22)
+
+\1f
+File: bash.info, Node: Variable Index, Next: Function Index, Prev: Reserved Word Index, Up: Indexes
+
+D.3 Parameter and Variable Index
+================================
+
+\0\b[index\0\b]
+* Menu:
+
+* _: Bash Variables. (line 13)
+* -: Special Parameters. (line 48)
+* !: Special Parameters. (line 57)
+* ?: Special Parameters. (line 44)
+* @: Special Parameters. (line 23)
+* *: Special Parameters. (line 10)
+* #: Special Parameters. (line 41)
+* $: Special Parameters. (line 53)
+* $_: Bash Variables. (line 14)
+* $-: Special Parameters. (line 49)
+* $!: Special Parameters. (line 58)
+* $?: Special Parameters. (line 45)
+* $@: Special Parameters. (line 24)
+* $*: Special Parameters. (line 11)
+* $#: Special Parameters. (line 42)
+* $$: Special Parameters. (line 54)
+* $0: Special Parameters. (line 63)
+* 0: Special Parameters. (line 62)
+* active-region-end-color: Readline Init File Syntax.
+ (line 51)
+* active-region-start-color: Readline Init File Syntax.
+ (line 38)
+* auto_resume: Job Control Variables.
+ (line 6)
+* BASH: Bash Variables. (line 24)
+* BASH_ALIASES: Bash Variables. (line 44)
+* BASH_ARGC: Bash Variables. (line 53)
+* BASH_ARGV: Bash Variables. (line 67)
+* BASH_ARGV0: Bash Variables. (line 80)
+* BASH_CMDS: Bash Variables. (line 88)
+* BASH_COMMAND: Bash Variables. (line 97)
+* BASH_COMPAT: Bash Variables. (line 104)
+* BASH_ENV: Bash Variables. (line 120)
+* BASH_EXECUTION_STRING: Bash Variables. (line 126)
+* BASH_LINENO: Bash Variables. (line 129)
+* BASH_LOADABLES_PATH: Bash Variables. (line 139)
+* BASH_MONOSECONDS: Bash Variables. (line 143)
+* BASH_REMATCH: Bash Variables. (line 150)
+* BASH_SOURCE: Bash Variables. (line 158)
+* BASH_SUBSHELL: Bash Variables. (line 166)
+* BASH_TRAPSIG: Bash Variables. (line 172)
+* BASH_VERSINFO: Bash Variables. (line 178)
+* BASH_VERSION: Bash Variables. (line 201)
+* BASH_XTRACEFD: Bash Variables. (line 205)
+* BASHOPTS: Bash Variables. (line 27)
+* BASHPID: Bash Variables. (line 37)
+* bell-style: Readline Init File Syntax.
+ (line 64)
+* bind-tty-special-chars: Readline Init File Syntax.
+ (line 71)
+* blink-matching-paren: Readline Init File Syntax.
+ (line 81)
+* CDPATH: Bourne Shell Variables.
+ (line 9)
+* CHILD_MAX: Bash Variables. (line 217)
+* colored-completion-prefix: Readline Init File Syntax.
+ (line 86)
+* colored-stats: Readline Init File Syntax.
+ (line 96)
+* COLUMNS: Bash Variables. (line 224)
+* comment-begin: Readline Init File Syntax.
+ (line 102)
+* COMP_CWORD: Bash Variables. (line 230)
+* COMP_KEY: Bash Variables. (line 236)
+* COMP_LINE: Bash Variables. (line 242)
+* COMP_POINT: Bash Variables. (line 247)
+* COMP_TYPE: Bash Variables. (line 255)
+* COMP_WORDBREAKS: Bash Variables. (line 265)
+* COMP_WORDS: Bash Variables. (line 271)
+* completion-display-width: Readline Init File Syntax.
+ (line 106)
+* completion-ignore-case: Readline Init File Syntax.
+ (line 113)
+* completion-map-case: Readline Init File Syntax.
+ (line 118)
+* completion-prefix-display-length: Readline Init File Syntax.
+ (line 124)
+* completion-query-items: Readline Init File Syntax.
+ (line 133)
+* COMPREPLY: Bash Variables. (line 278)
+* convert-meta: Readline Init File Syntax.
+ (line 144)
+* COPROC: Bash Variables. (line 284)
+* DIRSTACK: Bash Variables. (line 288)
+* disable-completion: Readline Init File Syntax.
+ (line 156)
+* echo-control-characters: Readline Init File Syntax.
+ (line 161)
+* editing-mode: Readline Init File Syntax.
+ (line 166)
+* EMACS: Bash Variables. (line 298)
+* emacs-mode-string: Readline Init File Syntax.
+ (line 172)
+* enable-active-region The: Readline Init File Syntax.
+ (line 182)
+* enable-bracketed-paste: Readline Init File Syntax.
+ (line 195)
+* enable-keypad: Readline Init File Syntax.
+ (line 204)
+* enable-meta-key: Readline Init File Syntax.
+ (line 209)
+* ENV: Bash Variables. (line 303)
+* EPOCHREALTIME: Bash Variables. (line 308)
+* EPOCHSECONDS: Bash Variables. (line 316)
+* EUID: Bash Variables. (line 323)
+* EXECIGNORE: Bash Variables. (line 327)
+* expand-tilde: Readline Init File Syntax.
+ (line 219)
+* FCEDIT: Bash Variables. (line 339)
+* FIGNORE: Bash Variables. (line 342)
+* force-meta-prefix: Readline Init File Syntax.
+ (line 223)
+* FUNCNAME: Bash Variables. (line 348)
+* FUNCNEST: Bash Variables. (line 365)
+* GLOBIGNORE: Bash Variables. (line 370)
+* GLOBSORT: Bash Variables. (line 377)
+* GROUPS: Bash Variables. (line 415)
+* histchars: Bash Variables. (line 421)
+* HISTCMD: Bash Variables. (line 437)
+* HISTCONTROL: Bash Variables. (line 443)
+* HISTFILE: Bash Variables. (line 461)
+* HISTFILESIZE: Bash Variables. (line 467)
+* HISTIGNORE: Bash Variables. (line 481)
+* history-preserve-point: Readline Init File Syntax.
+ (line 236)
+* history-size: Readline Init File Syntax.
+ (line 242)
+* HISTSIZE: Bash Variables. (line 505)
+* HISTTIMEFORMAT: Bash Variables. (line 512)
+* HOME: Bourne Shell Variables.
+ (line 13)
+* horizontal-scroll-mode: Readline Init File Syntax.
+ (line 252)
+* HOSTFILE: Bash Variables. (line 521)
+* HOSTNAME: Bash Variables. (line 532)
+* HOSTTYPE: Bash Variables. (line 535)
+* IFS: Bourne Shell Variables.
+ (line 18)
+* IGNOREEOF: Bash Variables. (line 538)
+* input-meta: Readline Init File Syntax.
+ (line 260)
+* INPUTRC: Bash Variables. (line 547)
+* INSIDE_EMACS: Bash Variables. (line 551)
+* isearch-terminators: Readline Init File Syntax.
+ (line 271)
+* keymap: Readline Init File Syntax.
+ (line 278)
+* LANG: Creating Internationalized Scripts.
+ (line 51)
+* LANG <1>: Bash Variables. (line 557)
+* LC_ALL: Bash Variables. (line 561)
+* LC_COLLATE: Bash Variables. (line 565)
+* LC_CTYPE: Bash Variables. (line 572)
+* LC_MESSAGES: Creating Internationalized Scripts.
+ (line 51)
+* LC_MESSAGES <1>: Bash Variables. (line 577)
+* LC_NUMERIC: Bash Variables. (line 581)
+* LC_TIME: Bash Variables. (line 585)
+* LINENO: Bash Variables. (line 589)
+* LINES: Bash Variables. (line 596)
+* MACHTYPE: Bash Variables. (line 602)
+* MAIL: Bourne Shell Variables.
+ (line 24)
+* MAILCHECK: Bash Variables. (line 606)
+* MAILPATH: Bourne Shell Variables.
+ (line 29)
+* MAPFILE: Bash Variables. (line 614)
+* mark-modified-lines: Readline Init File Syntax.
+ (line 308)
+* mark-symlinked-directories: Readline Init File Syntax.
+ (line 313)
+* match-hidden-files: Readline Init File Syntax.
+ (line 318)
+* menu-complete-display-prefix: Readline Init File Syntax.
+ (line 325)
+* meta-flag: Readline Init File Syntax.
+ (line 260)
+* OLDPWD: Bash Variables. (line 618)
+* OPTARG: Bourne Shell Variables.
+ (line 36)
+* OPTERR: Bash Variables. (line 621)
+* OPTIND: Bourne Shell Variables.
+ (line 40)
+* OSTYPE: Bash Variables. (line 626)
+* output-meta: Readline Init File Syntax.
+ (line 330)
+* page-completions: Readline Init File Syntax.
+ (line 339)
+* PATH: Bourne Shell Variables.
+ (line 44)
+* PIPESTATUS: Bash Variables. (line 629)
+* POSIXLY_CORRECT: Bash Variables. (line 639)
+* PPID: Bash Variables. (line 649)
+* PROMPT_COMMAND: Bash Variables. (line 653)
+* PROMPT_DIRTRIM: Bash Variables. (line 659)
+* PS0: Bash Variables. (line 665)
+* PS1: Bourne Shell Variables.
+ (line 53)
+* PS2: Bourne Shell Variables.
+ (line 58)
+* PS3: Bash Variables. (line 670)
+* PS4: Bash Variables. (line 675)
+* PWD: Bash Variables. (line 683)
+* RANDOM: Bash Variables. (line 686)
+* READLINE_ARGUMENT: Bash Variables. (line 694)
+* READLINE_LINE: Bash Variables. (line 698)
+* READLINE_MARK: Bash Variables. (line 702)
+* READLINE_POINT: Bash Variables. (line 708)
+* REPLY: Bash Variables. (line 712)
+* revert-all-at-newline: Readline Init File Syntax.
+ (line 352)
+* search-ignore-case: Readline Init File Syntax.
+ (line 359)
+* SECONDS: Bash Variables. (line 716)
+* SHELL: Bash Variables. (line 726)
+* SHELLOPTS: Bash Variables. (line 731)
+* SHLVL: Bash Variables. (line 741)
+* show-all-if-ambiguous: Readline Init File Syntax.
+ (line 364)
+* show-all-if-unmodified: Readline Init File Syntax.
+ (line 370)
+* show-mode-in-prompt: Readline Init File Syntax.
+ (line 379)
+* skip-completed-text: Readline Init File Syntax.
+ (line 385)
+* SRANDOM: Bash Variables. (line 746)
+* TEXTDOMAIN: Creating Internationalized Scripts.
+ (line 51)
+* TEXTDOMAINDIR: Creating Internationalized Scripts.
+ (line 51)
+* TIMEFORMAT: Bash Variables. (line 755)
+* TMOUT: Bash Variables. (line 794)
+* TMPDIR: Bash Variables. (line 806)
+* UID: Bash Variables. (line 810)
+* vi-cmd-mode-string: Readline Init File Syntax.
+ (line 398)
+* vi-ins-mode-string: Readline Init File Syntax.
+ (line 409)
+* visible-stats: Readline Init File Syntax.
+ (line 420)
+
+\1f
+File: bash.info, Node: Function Index, Next: Concept Index, Prev: Variable Index, Up: Indexes
+
+D.4 Function Index
+==================
+
+\0\b[index\0\b]
+* Menu:
+
+* abort (C-g): Miscellaneous Commands.
+ (line 10)
+* accept-line (Newline or Return): Commands For History.
+ (line 6)
+* alias-expand-line (): Miscellaneous Commands.
+ (line 134)
+* backward-char (C-b): Commands For Moving. (line 18)
+* backward-delete-char (Rubout): Commands For Text. (line 18)
+* backward-kill-line (C-x Rubout): Commands For Killing.
+ (line 11)
+* backward-kill-word (M-<DEL>): Commands For Killing.
+ (line 28)
+* backward-word (M-b): Commands For Moving. (line 26)
+* beginning-of-history (M-<): Commands For History.
+ (line 22)
+* beginning-of-line (C-a): Commands For Moving. (line 6)
+* bracketed-paste-begin (): Commands For Text. (line 35)
+* call-last-kbd-macro (C-x e): Keyboard Macros. (line 13)
+* capitalize-word (M-c): Commands For Text. (line 73)
+* character-search (C-]): Miscellaneous Commands.
+ (line 41)
+* character-search-backward (M-C-]): Miscellaneous Commands.
+ (line 45)
+* clear-display (M-C-l): Commands For Moving. (line 52)
+* clear-screen (C-l): Commands For Moving. (line 57)
+* complete (<TAB>): Commands For Completion.
+ (line 6)
+* complete-command (M-!): Commands For Completion.
+ (line 105)
+* complete-filename (M-/): Commands For Completion.
+ (line 74)
+* complete-hostname (M-@): Commands For Completion.
+ (line 97)
+* complete-into-braces (M-{): Commands For Completion.
+ (line 124)
+* complete-username (M-~): Commands For Completion.
+ (line 81)
+* complete-variable (M-$): Commands For Completion.
+ (line 89)
+* copy-backward-word (): Commands For Killing.
+ (line 62)
+* copy-forward-word (): Commands For Killing.
+ (line 67)
+* copy-region-as-kill (): Commands For Killing.
+ (line 58)
+* dabbrev-expand (): Commands For Completion.
+ (line 119)
+* delete-char (C-d): Commands For Text. (line 12)
+* delete-char-or-list (): Commands For Completion.
+ (line 68)
+* delete-horizontal-space (): Commands For Killing.
+ (line 50)
+* digit-argument (M-0, M-1, ... M--): Numeric Arguments. (line 6)
+* display-shell-version (C-x C-v): Miscellaneous Commands.
+ (line 148)
+* do-lowercase-version (M-A, M-B, M-X, ...): Miscellaneous Commands.
+ (line 14)
+* downcase-word (M-l): Commands For Text. (line 69)
+* dump-functions (): Miscellaneous Commands.
+ (line 71)
+* dump-macros (): Miscellaneous Commands.
+ (line 83)
+* dump-variables (): Miscellaneous Commands.
+ (line 77)
+* dynamic-complete-history (M-<TAB>): Commands For Completion.
+ (line 115)
+* edit-and-execute-command (C-x C-e): Miscellaneous Commands.
+ (line 143)
+* end-kbd-macro (C-x )): Keyboard Macros. (line 9)
+* end-of-file (usually C-d): Commands For Text. (line 6)
+* end-of-history (M->): Commands For History.
+ (line 25)
+* end-of-line (C-e): Commands For Moving. (line 10)
+* exchange-point-and-mark (C-x C-x): Miscellaneous Commands.
+ (line 37)
+* execute-named-command (M-x): Miscellaneous Commands.
+ (line 90)
+* export-completions (): Commands For Completion.
+ (line 44)
+* fetch-history (): Commands For History.
+ (line 109)
+* forward-backward-delete-char (): Commands For Text. (line 23)
+* forward-char (C-f): Commands For Moving. (line 14)
+* forward-search-history (C-s): Commands For History.
+ (line 35)
+* forward-word (M-f): Commands For Moving. (line 22)
+* glob-complete-word (M-g): Miscellaneous Commands.
+ (line 103)
+* glob-expand-word (C-x *): Miscellaneous Commands.
+ (line 108)
+* glob-list-expansions (C-x g): Miscellaneous Commands.
+ (line 114)
+* history-and-alias-expand-line (): Miscellaneous Commands.
+ (line 137)
+* history-expand-line (M-^): Miscellaneous Commands.
+ (line 127)
+* history-search-backward (): Commands For History.
+ (line 54)
+* history-search-forward (): Commands For History.
+ (line 61)
+* history-substring-search-backward (): Commands For History.
+ (line 68)
+* history-substring-search-forward (): Commands For History.
+ (line 74)
+* insert-comment (M-#): Miscellaneous Commands.
+ (line 59)
+* insert-completions (M-*): Commands For Completion.
+ (line 24)
+* insert-last-argument (M-. or M-_): Miscellaneous Commands.
+ (line 140)
+* kill-line (C-k): Commands For Killing.
+ (line 6)
+* kill-region (): Commands For Killing.
+ (line 54)
+* kill-whole-line (): Commands For Killing.
+ (line 19)
+* kill-word (M-d): Commands For Killing.
+ (line 23)
+* magic-space (): Miscellaneous Commands.
+ (line 130)
+* menu-complete (): Commands For Completion.
+ (line 28)
+* menu-complete-backward (): Commands For Completion.
+ (line 39)
+* next-history (C-n): Commands For History.
+ (line 18)
+* next-screen-line (): Commands For Moving. (line 45)
+* non-incremental-forward-search-history (M-n): Commands For History.
+ (line 48)
+* non-incremental-reverse-search-history (M-p): Commands For History.
+ (line 41)
+* operate-and-get-next (C-o): Commands For History.
+ (line 102)
+* overwrite-mode (): Commands For Text. (line 77)
+* possible-command-completions (C-x !): Commands For Completion.
+ (line 111)
+* possible-completions (M-?): Commands For Completion.
+ (line 17)
+* possible-filename-completions (C-x /): Commands For Completion.
+ (line 77)
+* possible-hostname-completions (C-x @): Commands For Completion.
+ (line 101)
+* possible-username-completions (C-x ~): Commands For Completion.
+ (line 85)
+* possible-variable-completions (C-x $): Commands For Completion.
+ (line 93)
+* prefix-meta (<ESC>): Miscellaneous Commands.
+ (line 19)
+* previous-history (C-p): Commands For History.
+ (line 13)
+* previous-screen-line (): Commands For Moving. (line 38)
+* print-last-kbd-macro (): Keyboard Macros. (line 17)
+* quoted-insert (C-q or C-v): Commands For Text. (line 28)
+* re-read-init-file (C-x C-r): Miscellaneous Commands.
+ (line 6)
+* redraw-current-line (): Commands For Moving. (line 62)
+* reverse-search-history (C-r): Commands For History.
+ (line 29)
+* revert-line (M-r): Miscellaneous Commands.
+ (line 26)
+* self-insert (a, b, A, 1, !, ...): Commands For Text. (line 32)
+* set-mark (C-@): Miscellaneous Commands.
+ (line 33)
+* shell-backward-kill-word (): Commands For Killing.
+ (line 37)
+* shell-backward-word (M-C-b): Commands For Moving. (line 34)
+* shell-expand-line (M-C-e): Miscellaneous Commands.
+ (line 119)
+* shell-forward-word (M-C-f): Commands For Moving. (line 30)
+* shell-kill-word (M-C-d): Commands For Killing.
+ (line 32)
+* shell-transpose-words (M-C-t): Commands For Text. (line 58)
+* skip-csi-sequence (): Miscellaneous Commands.
+ (line 50)
+* spell-correct-word (C-x s): Miscellaneous Commands.
+ (line 97)
+* start-kbd-macro (C-x (): Keyboard Macros. (line 6)
+* tilde-expand (M-&): Miscellaneous Commands.
+ (line 30)
+* transpose-chars (C-t): Commands For Text. (line 47)
+* transpose-words (M-t): Commands For Text. (line 53)
+* undo (C-_ or C-x C-u): Miscellaneous Commands.
+ (line 23)
+* universal-argument (): Numeric Arguments. (line 10)
+* unix-filename-rubout (): Commands For Killing.
+ (line 45)
+* unix-line-discard (C-u): Commands For Killing.
+ (line 16)
+* unix-word-rubout (C-w): Commands For Killing.
+ (line 41)
+* upcase-word (M-u): Commands For Text. (line 65)
+* yank (C-y): Commands For Killing.
+ (line 72)
+* yank-last-arg (M-. or M-_): Commands For History.
+ (line 90)
+* yank-nth-arg (M-C-y): Commands For History.
+ (line 80)
+* yank-pop (M-y): Commands For Killing.
+ (line 75)
+
+\1f
+File: bash.info, Node: Concept Index, Prev: Function Index, Up: Indexes
+
+D.5 Concept Index
+=================
+
+\0\b[index\0\b]
+* Menu:
+
+* alias expansion: Aliases. (line 6)
+* arithmetic evaluation: Shell Arithmetic. (line 6)
+* arithmetic expansion: Arithmetic Expansion.
+ (line 6)
+* arithmetic operators: Shell Arithmetic. (line 18)
+* arithmetic, shell: Shell Arithmetic. (line 6)
+* arrays: Arrays. (line 6)
+* background: Job Control Basics. (line 6)
+* Bash configuration: Basic Installation. (line 6)
+* Bash installation: Basic Installation. (line 6)
+* binary arithmetic operators: Shell Arithmetic. (line 18)
+* bitwise arithmetic operators: Shell Arithmetic. (line 18)
+* Bourne shell: Basic Shell Features.
+ (line 6)
+* brace expansion: Brace Expansion. (line 6)
+* builtin: Definitions. (line 21)
+* command editing: Readline Bare Essentials.
+ (line 6)
+* command execution: Command Search and Execution.
+ (line 6)
+* command expansion: Simple Command Expansion.
+ (line 6)
+* command history: Bash History Facilities.
+ (line 6)
+* command search: Command Search and Execution.
+ (line 6)
+* command substitution: Command Substitution.
+ (line 6)
+* command timing: Pipelines. (line 9)
+* commands, compound: Compound Commands. (line 6)
+* commands, conditional: Conditional Constructs.
+ (line 6)
+* commands, grouping: Command Grouping. (line 6)
+* commands, lists: Lists. (line 6)
+* commands, looping: Looping Constructs. (line 6)
+* commands, pipelines: Pipelines. (line 6)
+* commands, shell: Shell Commands. (line 6)
+* commands, simple: Simple Commands. (line 6)
+* comments, shell: Comments. (line 6)
+* Compatibility Level: Shell Compatibility Mode.
+ (line 6)
+* Compatibility Mode: Shell Compatibility Mode.
+ (line 6)
+* completion builtins: Programmable Completion Builtins.
+ (line 6)
+* conditional arithmetic operator: Shell Arithmetic. (line 18)
+* configuration: Basic Installation. (line 6)
+* control operator: Definitions. (line 25)
+* coprocess: Coprocesses. (line 6)
+* directory stack: The Directory Stack. (line 6)
+* dollar-single quote quoting: ANSI-C Quoting. (line 6)
+* editing command lines: Readline Bare Essentials.
+ (line 6)
+* environment: Environment. (line 6)
+* evaluation, arithmetic: Shell Arithmetic. (line 6)
+* event designators: Event Designators. (line 6)
+* execution environment: Command Execution Environment.
+ (line 6)
+* exit status: Definitions. (line 30)
+* exit status <1>: Exit Status. (line 6)
+* expansion: Shell Expansions. (line 6)
+* expansion, arithmetic: Arithmetic Expansion.
+ (line 6)
+* expansion, brace: Brace Expansion. (line 6)
+* expansion, filename: Filename Expansion. (line 9)
+* expansion, parameter: Shell Parameter Expansion.
+ (line 6)
+* expansion, pathname: Filename Expansion. (line 9)
+* expansion, tilde: Tilde Expansion. (line 6)
+* expressions, arithmetic: Shell Arithmetic. (line 6)
+* expressions, conditional: Bash Conditional Expressions.
+ (line 6)
+* field: Definitions. (line 34)
+* filename: Definitions. (line 39)
+* filename expansion: Filename Expansion. (line 9)
+* foreground: Job Control Basics. (line 6)
+* functions, shell: Shell Functions. (line 6)
+* history builtins: Bash History Builtins.
+ (line 6)
+* history events: Event Designators. (line 10)
+* history expansion: History Interaction. (line 6)
+* history list: Bash History Facilities.
+ (line 6)
+* History, how to use: A Programmable Completion Example.
+ (line 113)
+* identifier: Definitions. (line 55)
+* initialization file, readline: Readline Init File. (line 6)
+* installation: Basic Installation. (line 6)
+* interaction, readline: Readline Interaction.
+ (line 6)
+* interactive shell: Invoking Bash. (line 137)
+* interactive shell <1>: Interactive Shells. (line 6)
+* internationalization: Locale Translation. (line 6)
+* internationalized scripts: Creating Internationalized Scripts.
+ (line 3)
+* job: Definitions. (line 42)
+* job control: Definitions. (line 46)
+* job control <1>: Job Control Basics. (line 6)
+* kill ring: Readline Killing Commands.
+ (line 18)
+* killing text: Readline Killing Commands.
+ (line 6)
+* localization: Locale Translation. (line 6)
+* login shell: Invoking Bash. (line 134)
+* matching, pattern: Pattern Matching. (line 6)
+* metacharacter: Definitions. (line 50)
+* name: Definitions. (line 55)
+* native languages: Locale Translation. (line 6)
+* notation, readline: Readline Bare Essentials.
+ (line 6)
+* operator, shell: Definitions. (line 61)
+* parameter expansion: Shell Parameter Expansion.
+ (line 6)
+* parameters: Shell Parameters. (line 6)
+* parameters, positional: Positional Parameters.
+ (line 6)
+* parameters, special: Special Parameters. (line 6)
+* pathname expansion: Filename Expansion. (line 9)
+* pattern matching: Pattern Matching. (line 6)
+* pipeline: Pipelines. (line 6)
+* POSIX: Definitions. (line 9)
+* POSIX description: Bash POSIX Mode. (line 9)
+* POSIX Mode: Bash POSIX Mode. (line 48)
+* process group: Definitions. (line 66)
+* process group ID: Definitions. (line 70)
+* process substitution: Process Substitution.
+ (line 6)
+* programmable completion: Programmable Completion.
+ (line 6)
+* prompting: Controlling the Prompt.
+ (line 6)
+* quoting: Quoting. (line 6)
+* quoting, ANSI: ANSI-C Quoting. (line 6)
+* Readline, how to use: Job Control Variables.
+ (line 23)
+* redirection: Redirections. (line 6)
+* reserved word: Definitions. (line 74)
+* reserved words: Reserved Words. (line 6)
+* restricted shell: The Restricted Shell.
+ (line 6)
+* return status: Definitions. (line 79)
+* shell arithmetic: Shell Arithmetic. (line 6)
+* shell function: Shell Functions. (line 6)
+* shell script: Shell Scripts. (line 6)
+* shell variable: Shell Parameters. (line 6)
+* shell, interactive: Interactive Shells. (line 6)
+* signal: Definitions. (line 82)
+* signal handling: Signals. (line 6)
+* special builtin: Definitions. (line 86)
+* special builtin <1>: Special Builtins. (line 6)
+* startup files: Bash Startup Files. (line 6)
+* string translations: Creating Internationalized Scripts.
+ (line 3)
+* suspending jobs: Job Control Basics. (line 6)
+* tilde expansion: Tilde Expansion. (line 6)
+* token: Definitions. (line 90)
+* translation, native languages: Locale Translation. (line 6)
+* unary arithmetic operators: Shell Arithmetic. (line 18)
+* variable, shell: Shell Parameters. (line 6)
+* variables, readline: Readline Init File Syntax.
+ (line 37)
+* word: Definitions. (line 94)
+* word splitting: Word Splitting. (line 6)
+* yanking text: Readline Killing Commands.
+ (line 6)
+
+\1f
+Tag Table:
+Node: Top\7f895
+Node: Introduction\7f2830
+Node: What is Bash?\7f3043
+Node: What is a shell?\7f4176
+Node: Definitions\7f6786
+Node: Basic Shell Features\7f10113
+Node: Shell Syntax\7f11337
+Node: Shell Operation\7f12364
+Node: Quoting\7f13655
+Node: Escape Character\7f14993
+Node: Single Quotes\7f15528
+Node: Double Quotes\7f15877
+Node: ANSI-C Quoting\7f17222
+Node: Locale Translation\7f18616
+Node: Creating Internationalized Scripts\7f20019
+Node: Comments\7f24217
+Node: Shell Commands\7f24984
+Node: Reserved Words\7f25923
+Node: Simple Commands\7f26788
+Node: Pipelines\7f27450
+Node: Lists\7f30706
+Node: Compound Commands\7f32578
+Node: Looping Constructs\7f33587
+Node: Conditional Constructs\7f36136
+Node: Command Grouping\7f51206
+Node: Coprocesses\7f52698
+Node: GNU Parallel\7f55384
+Node: Shell Functions\7f56302
+Node: Shell Parameters\7f64750
+Node: Positional Parameters\7f69651
+Node: Special Parameters\7f70741
+Node: Shell Expansions\7f74202
+Node: Brace Expansion\7f76391
+Node: Tilde Expansion\7f79727
+Node: Shell Parameter Expansion\7f82682
+Node: Command Substitution\7f103325
+Node: Arithmetic Expansion\7f106854
+Node: Process Substitution\7f108030
+Node: Word Splitting\7f109138
+Node: Filename Expansion\7f111582
+Node: Pattern Matching\7f114806
+Node: Quote Removal\7f120529
+Node: Redirections\7f120833
+Node: Executing Commands\7f131089
+Node: Simple Command Expansion\7f131756
+Node: Command Search and Execution\7f133864
+Node: Command Execution Environment\7f136308
+Node: Environment\7f139756
+Node: Exit Status\7f141659
+Node: Signals\7f143718
+Node: Shell Scripts\7f148648
+Node: Shell Builtin Commands\7f151946
+Node: Bourne Shell Builtins\7f154057
+Node: Bash Builtins\7f180776
+Node: Modifying Shell Behavior\7f217700
+Node: The Set Builtin\7f218042
+Node: The Shopt Builtin\7f230036
+Node: Special Builtins\7f247089
+Node: Shell Variables\7f248078
+Node: Bourne Shell Variables\7f248512
+Node: Bash Variables\7f251020
+Node: Bash Features\7f290145
+Node: Invoking Bash\7f291159
+Node: Bash Startup Files\7f297743
+Node: Interactive Shells\7f302985
+Node: What is an Interactive Shell?\7f303393
+Node: Is this Shell Interactive?\7f304055
+Node: Interactive Shell Behavior\7f304879
+Node: Bash Conditional Expressions\7f308640
+Node: Shell Arithmetic\7f314057
+Node: Aliases\7f317384
+Node: Arrays\7f320518
+Node: The Directory Stack\7f328106
+Node: Directory Stack Builtins\7f328903
+Node: Controlling the Prompt\7f333348
+Node: The Restricted Shell\7f336233
+Node: Bash POSIX Mode\7f339115
+Node: Shell Compatibility Mode\7f358062
+Node: Job Control\7f367069
+Node: Job Control Basics\7f367526
+Node: Job Control Builtins\7f373894
+Node: Job Control Variables\7f380576
+Node: Command Line Editing\7f381807
+Node: Introduction and Notation\7f383510
+Node: Readline Interaction\7f385862
+Node: Readline Bare Essentials\7f387050
+Node: Readline Movement Commands\7f388858
+Node: Readline Killing Commands\7f389854
+Node: Readline Arguments\7f391877
+Node: Searching\7f392967
+Node: Readline Init File\7f395210
+Node: Readline Init File Syntax\7f396513
+Node: Conditional Init Constructs\7f423464
+Node: Sample Init File\7f427849
+Node: Bindable Readline Commands\7f430969
+Node: Commands For Moving\7f432507
+Node: Commands For History\7f434971
+Node: Commands For Text\7f440362
+Node: Commands For Killing\7f444487
+Node: Numeric Arguments\7f447275
+Node: Commands For Completion\7f448427
+Node: Keyboard Macros\7f454123
+Node: Miscellaneous Commands\7f454824
+Node: Readline vi Mode\7f461391
+Node: Programmable Completion\7f462368
+Node: Programmable Completion Builtins\7f472104
+Node: A Programmable Completion Example\7f483841
+Node: Using History Interactively\7f489186
+Node: Bash History Facilities\7f489867
+Node: Bash History Builtins\7f493602
+Node: History Interaction\7f500073
+Node: Event Designators\7f505023
+Node: Word Designators\7f506601
+Node: Modifiers\7f508993
+Node: Installing Bash\7f510930
+Node: Basic Installation\7f512046
+Node: Compilers and Options\7f515922
+Node: Compiling For Multiple Architectures\7f516672
+Node: Installation Names\7f518425
+Node: Specifying the System Type\7f520659
+Node: Sharing Defaults\7f521405
+Node: Operation Controls\7f522119
+Node: Optional Features\7f523138
+Node: Reporting Bugs\7f535861
+Node: Major Differences From The Bourne Shell\7f537218
+Node: GNU Free Documentation License\7f558645
+Node: Indexes\7f583822
+Node: Builtin Index\7f584273
+Node: Reserved Word Index\7f591371
+Node: Variable Index\7f593816
+Node: Function Index\7f611229
+Node: Concept Index\7f625224
+\1f
+End Tag Table
+
+\1f
+Local Variables:
+coding: utf-8
+End:
--- /dev/null
+This is bashref.info, produced by makeinfo version 7.2 from
+bashref.texi.
+
+This text is a brief description of the features that are present in the
+Bash shell (version 5.3, 7 August 2025).
+
+ This is Edition 5.3, last updated 7 August 2025, of ‘The GNU Bash
+Reference Manual’, for ‘Bash’, Version 5.3.
+
+ Copyright © 1988-2025 Free Software Foundation, Inc.
+
+ Permission is granted to copy, distribute and/or modify this
+ document under the terms of the GNU Free Documentation License,
+ Version 1.3 or any later version published by the Free Software
+ Foundation; with no Invariant Sections, no Front-Cover Texts, and
+ no Back-Cover Texts. A copy of the license is included in the
+ section entitled "GNU Free Documentation License".
+INFO-DIR-SECTION Basics
+START-INFO-DIR-ENTRY
+* Bash: (bash). The GNU Bourne-Again SHell.
+END-INFO-DIR-ENTRY
+
+\1f
+File: bashref.info, Node: Top, Next: Introduction, Prev: (dir), Up: (dir)
+
+Bash Features
+*************
+
+This text is a brief description of the features that are present in the
+Bash shell (version 5.3, 7 August 2025). The Bash home page is
+<http://www.gnu.org/software/bash/>.
+
+ This is Edition 5.3, last updated 7 August 2025, of ‘The GNU Bash
+Reference Manual’, for ‘Bash’, Version 5.3.
+
+ Bash contains features that appear in other popular shells, and some
+features that only appear in Bash. Some of the shells that Bash has
+borrowed concepts from are the Bourne Shell (‘sh’), the Korn Shell
+(‘ksh’), and the C-shell (‘csh’ and its successor, ‘tcsh’). The
+following menu breaks the features up into categories, noting which
+features were inspired by other shells and which are specific to Bash.
+
+ This manual is meant as a brief introduction to features found in
+Bash. The Bash manual page should be used as the definitive reference
+on shell behavior.
+
+* Menu:
+
+* Introduction:: An introduction to the shell.
+* Definitions:: Some definitions used in the rest of this
+ manual.
+* Basic Shell Features:: The shell "building blocks".
+* Shell Builtin Commands:: Commands that are a part of the shell.
+* Shell Variables:: Variables used or set by Bash.
+* Bash Features:: Features found only in Bash.
+* Job Control:: What job control is and how Bash allows you
+ to use it.
+* Command Line Editing:: Chapter describing the command line
+ editing features.
+* Using History Interactively:: Command History Expansion
+* Installing Bash:: How to build and install Bash on your system.
+* Reporting Bugs:: How to report bugs in Bash.
+* Major Differences From The Bourne Shell:: A terse list of the differences
+ between Bash and historical
+ versions of /bin/sh.
+* GNU Free Documentation License:: Copying and sharing this documentation.
+* Indexes:: Various indexes for this manual.
+
+\1f
+File: bashref.info, Node: Introduction, Next: Definitions, Up: Top
+
+1 Introduction
+**************
+
+* Menu:
+
+* What is Bash?:: A short description of Bash.
+* What is a shell?:: A brief introduction to shells.
+
+\1f
+File: bashref.info, Node: What is Bash?, Next: What is a shell?, Up: Introduction
+
+1.1 What is Bash?
+=================
+
+Bash is the shell, or command language interpreter, for the GNU
+operating system. The name is an acronym for the ‘Bourne-Again SHell’,
+a pun on Stephen Bourne, the author of the direct ancestor of the
+current Unix shell ‘sh’, which appeared in the Seventh Edition Bell Labs
+Research version of Unix.
+
+ Bash is largely compatible with ‘sh’ and incorporates useful features
+from the Korn shell ‘ksh’ and the C shell ‘csh’. It is intended to be a
+conformant implementation of the IEEE POSIX Shell and Tools portion of
+the IEEE POSIX specification (IEEE Standard 1003.1). It offers
+functional improvements over ‘sh’ for both interactive and programming
+use.
+
+ While the GNU operating system provides other shells, including a
+version of ‘csh’, Bash is the default shell. Like other GNU software,
+Bash is quite portable. It currently runs on nearly every version of
+Unix and a few other operating systems − independently-supported ports
+exist for Windows and other platforms.
+
+\1f
+File: bashref.info, Node: What is a shell?, Prev: What is Bash?, Up: Introduction
+
+1.2 What is a shell?
+====================
+
+At its base, a shell is simply a macro processor that executes commands.
+The term macro processor means functionality where text and symbols are
+expanded to create larger expressions.
+
+ A Unix shell is both a command interpreter and a programming
+language. As a command interpreter, the shell provides the user
+interface to the rich set of GNU utilities. The programming language
+features allow these utilities to be combined. Users can create files
+containing commands, and these become commands themselves. These new
+commands have the same status as system commands in directories such as
+‘/bin’, allowing users or groups to establish custom environments to
+automate their common tasks.
+
+ Shells may be used interactively or non-interactively. In
+interactive mode, they accept input typed from the keyboard. When
+executing non-interactively, shells execute commands read from a file or
+a string.
+
+ A shell allows execution of GNU commands, both synchronously and
+asynchronously. The shell waits for synchronous commands to complete
+before accepting more input; asynchronous commands continue to execute
+in parallel with the shell while it reads and executes additional
+commands. The “redirection” constructs permit fine-grained control of
+the input and output of those commands. Moreover, the shell allows
+control over the contents of commands' environments.
+
+ Shells also provide a small set of built-in commands (“builtins”)
+implementing functionality impossible or inconvenient to obtain via
+separate utilities. For example, ‘cd’, ‘break’, ‘continue’, and ‘exec’
+cannot be implemented outside of the shell because they directly
+manipulate the shell itself. The ‘history’, ‘getopts’, ‘kill’, or ‘pwd’
+builtins, among others, could be implemented in separate utilities, but
+they are more convenient to use as builtin commands. All of the shell
+builtins are described in subsequent sections.
+
+ While executing commands is essential, most of the power (and
+complexity) of shells is due to their embedded programming languages.
+Like any high-level language, the shell provides variables, flow control
+constructs, quoting, and functions.
+
+ Shells offer features geared specifically for interactive use rather
+than to augment the programming language. These interactive features
+include job control, command line editing, command history and aliases.
+This manual describes how Bash provides all of these features.
+
+\1f
+File: bashref.info, Node: Definitions, Next: Basic Shell Features, Prev: Introduction, Up: Top
+
+2 Definitions
+*************
+
+These definitions are used throughout the remainder of this manual.
+
+‘POSIX’
+ A family of open system standards based on Unix. Bash is primarily
+ concerned with the Shell and Utilities portion of the POSIX 1003.1
+ standard.
+
+‘blank’
+ A space or tab character.
+
+‘whitespace’
+ A character belonging to the ‘space’ character class in the current
+ locale, or for which ‘isspace()’ returns true.
+
+‘builtin’
+ A command that is implemented internally by the shell itself,
+ rather than by an executable program somewhere in the file system.
+
+‘control operator’
+ A ‘token’ that performs a control function. It is a ‘newline’ or
+ one of the following: ‘||’, ‘&&’, ‘&’, ‘;’, ‘;;’, ‘;&’, ‘;;&’, ‘|’,
+ ‘|&’, ‘(’, or ‘)’.
+
+‘exit status’
+ The value returned by a command to its caller. The value is
+ restricted to eight bits, so the maximum value is 255.
+
+‘field’
+ A unit of text that is the result of one of the shell expansions.
+ After expansion, when executing a command, the resulting fields are
+ used as the command name and arguments.
+
+‘filename’
+ A string of characters used to identify a file.
+
+‘job’
+ A set of processes comprising a pipeline, and any processes
+ descended from it, that are all in the same process group.
+
+‘job control’
+ A mechanism by which users can selectively stop (suspend) and
+ restart (resume) execution of processes.
+
+‘metacharacter’
+ A character that, when unquoted, separates words. A metacharacter
+ is a ‘space’, ‘tab’, ‘newline’, or one of the following characters:
+ ‘|’, ‘&’, ‘;’, ‘(’, ‘)’, ‘<’, or ‘>’.
+
+‘name’
+ A ‘word’ consisting solely of letters, numbers, and underscores,
+ and beginning with a letter or underscore. ‘Name’s are used as
+ shell variable and function names. Also referred to as an
+ ‘identifier’.
+
+‘operator’
+ A ‘control operator’ or a ‘redirection operator’. *Note
+ Redirections::, for a list of redirection operators. Operators
+ contain at least one unquoted ‘metacharacter’.
+
+‘process group’
+ A collection of related processes each having the same process
+ group ID.
+
+‘process group ID’
+ A unique identifier that represents a ‘process group’ during its
+ lifetime.
+
+‘reserved word’
+ A ‘word’ that has a special meaning to the shell. Most reserved
+ words introduce shell flow control constructs, such as ‘for’ and
+ ‘while’.
+
+‘return status’
+ A synonym for ‘exit status’.
+
+‘signal’
+ A mechanism by which a process may be notified by the kernel of an
+ event occurring in the system.
+
+‘special builtin’
+ A shell builtin command that has been classified as special by the
+ POSIX standard.
+
+‘token’
+ A sequence of characters considered a single unit by the shell. It
+ is either a ‘word’ or an ‘operator’.
+
+‘word’
+ A sequence of characters treated as a unit by the shell. Words may
+ not include unquoted ‘metacharacters’.
+
+\1f
+File: bashref.info, Node: Basic Shell Features, Next: Shell Builtin Commands, Prev: Definitions, Up: Top
+
+3 Basic Shell Features
+**********************
+
+Bash is an acronym for ‘Bourne-Again SHell’. The Bourne shell is the
+traditional Unix shell originally written by Stephen Bourne. All of the
+Bourne shell builtin commands are available in Bash, and the rules for
+evaluation and quoting are taken from the POSIX specification for the
+"standard" Unix shell.
+
+ This chapter briefly summarizes the shell's "building blocks":
+commands, control structures, shell functions, shell parameters, shell
+expansions, redirections, which are a way to direct input and output
+from and to named files, and how the shell executes commands.
+
+* Menu:
+
+* Shell Syntax:: What your input means to the shell.
+* Shell Commands:: The types of commands you can use.
+* Shell Functions:: Grouping commands by name.
+* Shell Parameters:: How the shell stores values.
+* Shell Expansions:: How Bash expands parameters and the various
+ expansions available.
+* Redirections:: A way to control where input and output go.
+* Executing Commands:: What happens when you run a command.
+* Shell Scripts:: Executing files of shell commands.
+
+\1f
+File: bashref.info, Node: Shell Syntax, Next: Shell Commands, Up: Basic Shell Features
+
+3.1 Shell Syntax
+================
+
+* Menu:
+
+* Shell Operation:: The basic operation of the shell.
+* Quoting:: How to remove the special meaning from characters.
+* Comments:: How to specify comments.
+
+When the shell reads input, it proceeds through a sequence of
+operations. If the input indicates the beginning of a comment, the
+shell ignores the comment symbol (‘#’), and the rest of that line.
+
+ Otherwise, roughly speaking, the shell reads its input and divides
+the input into words and operators, employing the quoting rules to
+select which meanings to assign various words and characters.
+
+ The shell then parses these tokens into commands and other
+constructs, removes the special meaning of certain words or characters,
+expands others, redirects input and output as needed, executes the
+specified command, waits for the command's exit status, and makes that
+exit status available for further inspection or processing.
+
+\1f
+File: bashref.info, Node: Shell Operation, Next: Quoting, Up: Shell Syntax
+
+3.1.1 Shell Operation
+---------------------
+
+The following is a brief description of the shell's operation when it
+reads and executes a command. Basically, the shell does the following:
+
+ 1. Reads its input from a file (*note Shell Scripts::), from a string
+ supplied as an argument to the ‘-c’ invocation option (*note
+ Invoking Bash::), or from the user's terminal.
+
+ 2. Breaks the input into words and operators, obeying the quoting
+ rules described in *note Quoting::. These tokens are separated by
+ ‘metacharacters’. This step performs alias expansion (*note
+ Aliases::).
+
+ 3. Parses the tokens into simple and compound commands (*note Shell
+ Commands::).
+
+ 4. Performs the various shell expansions (*note Shell Expansions::),
+ breaking the expanded tokens into lists of filenames (*note
+ Filename Expansion::) and commands and arguments.
+
+ 5. Performs any necessary redirections (*note Redirections::) and
+ removes the redirection operators and their operands from the
+ argument list.
+
+ 6. Executes the command (*note Executing Commands::).
+
+ 7. Optionally waits for the command to complete and collects its exit
+ status (*note Exit Status::).
+
+\1f
+File: bashref.info, Node: Quoting, Next: Comments, Prev: Shell Operation, Up: Shell Syntax
+
+3.1.2 Quoting
+-------------
+
+* Menu:
+
+* Escape Character:: How to remove the special meaning from a single
+ character.
+* Single Quotes:: How to inhibit all interpretation of a sequence
+ of characters.
+* Double Quotes:: How to suppress most of the interpretation of a
+ sequence of characters.
+* ANSI-C Quoting:: How to expand ANSI-C sequences in quoted strings.
+* Locale Translation:: How to translate strings into different languages.
+
+Quoting is used to remove the special meaning of certain characters or
+words to the shell. Quoting can be used to disable special treatment
+for special characters, to prevent reserved words from being recognized
+as such, and to prevent parameter expansion.
+
+ Each of the shell metacharacters (*note Definitions::) has special
+meaning to the shell and must be quoted if it is to represent itself.
+
+ When the command history expansion facilities are being used (*note
+History Interaction::), the “history expansion” character, usually ‘!’,
+must be quoted to prevent history expansion. *Note Bash History
+Facilities::, for more details concerning history expansion.
+
+ There are four quoting mechanisms: the “escape character”, single
+quotes, double quotes, and dollar-single quotes.
+
+\1f
+File: bashref.info, Node: Escape Character, Next: Single Quotes, Up: Quoting
+
+3.1.2.1 Escape Character
+........................
+
+A non-quoted backslash ‘\’ is the Bash escape character. It preserves
+the literal value of the next character that follows, removing any
+special meaning it has, with the exception of ‘newline’. If a
+‘\newline’ pair appears, and the backslash itself is not quoted, the
+‘\newline’ is treated as a line continuation (that is, it is removed
+from the input stream and effectively ignored).
+
+\1f
+File: bashref.info, Node: Single Quotes, Next: Double Quotes, Prev: Escape Character, Up: Quoting
+
+3.1.2.2 Single Quotes
+.....................
+
+Enclosing characters in single quotes (‘'’) preserves the literal value
+of each character within the quotes. A single quote may not occur
+between single quotes, even when preceded by a backslash.
+
+\1f
+File: bashref.info, Node: Double Quotes, Next: ANSI-C Quoting, Prev: Single Quotes, Up: Quoting
+
+3.1.2.3 Double Quotes
+.....................
+
+Enclosing characters in double quotes (‘"’) preserves the literal value
+of all characters within the quotes, with the exception of ‘$’, ‘`’,
+‘\’, and, when history expansion is enabled, ‘!’. When the shell is in
+POSIX mode (*note Bash POSIX Mode::), the ‘!’ has no special meaning
+within double quotes, even when history expansion is enabled. The
+characters ‘$’ and ‘`’ retain their special meaning within double quotes
+(*note Shell Expansions::). The backslash retains its special meaning
+only when followed by one of the following characters: ‘$’, ‘`’, ‘"’,
+‘\’, or ‘newline’. Within double quotes, backslashes that are followed
+by one of these characters are removed. Backslashes preceding
+characters without a special meaning are left unmodified.
+
+ A double quote may be quoted within double quotes by preceding it
+with a backslash. If enabled, history expansion will be performed
+unless an ‘!’ appearing in double quotes is escaped using a backslash.
+The backslash preceding the ‘!’ is not removed.
+
+ The special parameters ‘*’ and ‘@’ have special meaning when in
+double quotes (*note Shell Parameter Expansion::).
+
+\1f
+File: bashref.info, Node: ANSI-C Quoting, Next: Locale Translation, Prev: Double Quotes, Up: Quoting
+
+3.1.2.4 ANSI-C Quoting
+......................
+
+Character sequences of the form ‘$'STRING'’ are treated as a special
+kind of single quotes. The sequence expands to STRING, with
+backslash-escaped characters in STRING replaced as specified by the ANSI
+C standard. Backslash escape sequences, if present, are decoded as
+follows:
+
+‘\a’
+ alert (bell)
+‘\b’
+ backspace
+‘\e’
+‘\E’
+ An escape character (not in ANSI C).
+‘\f’
+ form feed
+‘\n’
+ newline
+‘\r’
+ carriage return
+‘\t’
+ horizontal tab
+‘\v’
+ vertical tab
+‘\\’
+ backslash
+‘\'’
+ single quote
+‘\"’
+ double quote
+‘\?’
+ question mark
+‘\NNN’
+ The eight-bit character whose value is the octal value NNN (one to
+ three octal digits).
+‘\xHH’
+ The eight-bit character whose value is the hexadecimal value HH
+ (one or two hex digits).
+‘\uHHHH’
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHH (one to four hex digits).
+‘\UHHHHHHHH’
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHHHHHH (one to eight hex digits).
+‘\cX’
+ A control-X character.
+
+The expanded result is single-quoted, as if the dollar sign had not been
+present.
+
+\1f
+File: bashref.info, Node: Locale Translation, Prev: ANSI-C Quoting, Up: Quoting
+
+3.1.2.5 Locale-Specific Translation
+...................................
+
+* Menu:
+
+* Creating Internationalized Scripts:: How to use translations and different
+ languages in your scripts.
+
+Prefixing a double-quoted string with a dollar sign (‘$’), such as
+$"hello, world", causes the string to be translated according to the
+current locale. The ‘gettext’ infrastructure performs the lookup and
+translation, using the ‘LC_MESSAGES’, ‘TEXTDOMAINDIR’, and ‘TEXTDOMAIN’
+shell variables, as explained below. See the gettext documentation for
+additional details not covered here. If the current locale is ‘C’ or
+‘POSIX’, if there are no translations available, or if the string is not
+translated, the dollar sign is ignored, and the string is treated as
+double-quoted as described above. Since this is a form of double
+quoting, the string remains double-quoted by default, whether or not it
+is translated and replaced. If the ‘noexpand_translation’ option is
+enabled using the ‘shopt’ builtin (*note The Shopt Builtin::),
+translated strings are single-quoted instead of double-quoted.
+
+ The rest of this section is a brief overview of how you use gettext
+to create translations for strings in a shell script named SCRIPTNAME.
+There are more details in the gettext documentation.
+
+\1f
+File: bashref.info, Node: Creating Internationalized Scripts, Up: Locale Translation
+
+Once you've marked the strings in your script that you want to translate
+using $"...", you create a gettext "template" file using the command
+
+ bash --dump-po-strings SCRIPTNAME > DOMAIN.pot
+
+The DOMAIN is your “message domain”. It's just an arbitrary string
+that's used to identify the files gettext needs, like a package or
+script name. It needs to be unique among all the message domains on
+systems where you install the translations, so gettext knows which
+translations correspond to your script. You'll use the template file to
+create translations for each target language. The template file
+conventionally has the suffix ‘.pot’.
+
+ You copy this template file to a separate file for each target
+language you want to support (called "PO" files, which use the suffix
+‘.po’). PO files use various naming conventions, but when you are
+working to translate a template file into a particular language, you
+first copy the template file to a file whose name is the language you
+want to target, with the ‘.po’ suffix. For instance, the Spanish
+translations of your strings would be in a file named ‘es.po’, and to
+get started using a message domain named "example," you would run
+
+ cp example.pot es.po
+
+Ultimately, PO files are often named DOMAIN.po and installed in
+directories that contain multiple translation files for a particular
+language.
+
+ Whichever naming convention you choose, you will need to translate
+the strings in the PO files into the appropriate languages. This has to
+be done manually.
+
+ When you have the translations and PO files complete, you'll use the
+gettext tools to produce what are called "MO" files, which are compiled
+versions of the PO files the gettext tools use to look up translations
+efficiently. MO files are also called "message catalog" files. You use
+the ‘msgfmt’ program to do this. For instance, if you had a file with
+Spanish translations, you could run
+
+ msgfmt -o es.mo es.po
+
+to produce the corresponding MO file.
+
+ Once you have the MO files, you decide where to install them and use
+the ‘TEXTDOMAINDIR’ shell variable to tell the gettext tools where they
+are. Make sure to use the same message domain to name the MO files as
+you did for the PO files when you install them.
+
+ Your users will use the ‘LANG’ or ‘LC_MESSAGES’ shell variables to
+select the desired language.
+
+ You set the ‘TEXTDOMAIN’ variable to the script's message domain. As
+above, you use the message domain to name your translation files.
+
+ You, or possibly your users, set the ‘TEXTDOMAINDIR’ variable to the
+name of a directory where the message catalog files are stored. If you
+install the message files into the system's standard message catalog
+directory, you don't need to worry about this variable.
+
+ The directory where the message catalog files are stored varies
+between systems. Some use the message catalog selected by the
+‘LC_MESSAGES’ shell variable. Others create the name of the message
+catalog from the value of the ‘TEXTDOMAIN’ shell variable, possibly
+adding the ‘.mo’ suffix. If you use the ‘TEXTDOMAIN’ variable, you may
+need to set the ‘TEXTDOMAINDIR’ variable to the location of the message
+catalog files, as above. It's common to use both variables in this
+fashion: ‘$TEXTDOMAINDIR’/‘$LC_MESSAGES’/LC_MESSAGES/‘$TEXTDOMAIN’.mo.
+
+ If you used that last convention, and you wanted to store the message
+catalog files with Spanish (es) and Esperanto (eo) translations into a
+local directory you use for custom translation files, you could run
+
+ TEXTDOMAIN=example
+ TEXTDOMAINDIR=/usr/local/share/locale
+
+ cp es.mo ${TEXTDOMAINDIR}/es/LC_MESSAGES/${TEXTDOMAIN}.mo
+ cp eo.mo ${TEXTDOMAINDIR}/eo/LC_MESSAGES/${TEXTDOMAIN}.mo
+
+ When all of this is done, and the message catalog files containing
+the compiled translations are installed in the correct location, your
+users will be able to see translated strings in any of the supported
+languages by setting the ‘LANG’ or ‘LC_MESSAGES’ environment variables
+before running your script.
+
+\1f
+File: bashref.info, Node: Comments, Prev: Quoting, Up: Shell Syntax
+
+3.1.3 Comments
+--------------
+
+In a non-interactive shell, or an interactive shell in which the
+‘interactive_comments’ option to the ‘shopt’ builtin is enabled (*note
+The Shopt Builtin::), a word beginning with ‘#’ introduces a comment. A
+word begins at the beginning of a line, after unquoted whitespace, or
+after an operator. The comment causes that word and all remaining
+characters on that line to be ignored. An interactive shell without the
+‘interactive_comments’ option enabled does not allow comments. The
+‘interactive_comments’ option is enabled by default in interactive
+shells. *Note Interactive Shells::, for a description of what makes a
+shell interactive.
+
+\1f
+File: bashref.info, Node: Shell Commands, Next: Shell Functions, Prev: Shell Syntax, Up: Basic Shell Features
+
+3.2 Shell Commands
+==================
+
+A simple shell command such as ‘echo a b c’ consists of the command
+itself followed by arguments, separated by spaces.
+
+ More complex shell commands are composed of simple commands arranged
+together in a variety of ways: in a pipeline in which the output of one
+command becomes the input of a second, in a loop or conditional
+construct, or in some other grouping.
+
+* Menu:
+
+* Reserved Words:: Words that have special meaning to the shell.
+* Simple Commands:: The most common type of command.
+* Pipelines:: Connecting the input and output of several
+ commands.
+* Lists:: How to execute commands sequentially.
+* Compound Commands:: Shell commands for control flow.
+* Coprocesses:: Two-way communication between commands.
+* GNU Parallel:: Running commands in parallel.
+
+\1f
+File: bashref.info, Node: Reserved Words, Next: Simple Commands, Up: Shell Commands
+
+3.2.1 Reserved Words
+--------------------
+
+Reserved words are words that have special meaning to the shell. They
+are used to begin and end the shell's compound commands.
+
+ The following words are recognized as reserved when unquoted and the
+first word of a command (see below for exceptions):
+
+‘if’ ‘then’ ‘elif’ ‘else’ ‘fi’ ‘time’
+‘for’ ‘in’ ‘until’ ‘while’ ‘do’ ‘done’
+‘case’ ‘esac’ ‘coproc’‘select’‘function’
+‘{’ ‘}’ ‘[[’ ‘]]’ ‘!’
+
+‘in’ is recognized as a reserved word if it is the third word of a
+‘case’ or ‘select’ command. ‘in’ and ‘do’ are recognized as reserved
+words if they are the third word in a ‘for’ command.
+
+\1f
+File: bashref.info, Node: Simple Commands, Next: Pipelines, Prev: Reserved Words, Up: Shell Commands
+
+3.2.2 Simple Commands
+---------------------
+
+A simple command is the kind of command that's executed most often.
+It's just a sequence of words separated by ‘blank’s, terminated by one
+of the shell's control operators (*note Definitions::). The first word
+generally specifies a command to be executed, with the rest of the words
+being that command's arguments.
+
+ The return status (*note Exit Status::) of a simple command is its
+exit status as provided by the POSIX 1003.1 ‘waitpid’ function, or 128+N
+if the command was terminated by signal N.
+
+\1f
+File: bashref.info, Node: Pipelines, Next: Lists, Prev: Simple Commands, Up: Shell Commands
+
+3.2.3 Pipelines
+---------------
+
+A ‘pipeline’ is a sequence of one or more commands separated by one of
+the control operators ‘|’ or ‘|&’.
+
+ The format for a pipeline is
+ [time [-p]] [!] COMMAND1 [ | or |& COMMAND2 ] ...
+
+The output of each command in the pipeline is connected via a pipe to
+the input of the next command. That is, each command reads the previous
+command's output. This connection is performed before any redirections
+specified by COMMAND1.
+
+ If ‘|&’ is the pipeline operator, COMMAND1's standard error, in
+addition to its standard output, is connected to COMMAND2's standard
+input through the pipe; it is shorthand for ‘2>&1 |’. This implicit
+redirection of the standard error to the standard output is performed
+after any redirections specified by COMMAND1, consistent with that
+shorthand.
+
+ If the reserved word ‘time’ precedes the pipeline, Bash prints timing
+statistics for the pipeline once it finishes. The statistics currently
+consist of elapsed (wall-clock) time and user and system time consumed
+by the command's execution. The ‘-p’ option changes the output format
+to that specified by POSIX. When the shell is in POSIX mode (*note Bash
+POSIX Mode::), it does not recognize ‘time’ as a reserved word if the
+next token begins with a ‘-’. The value of the ‘TIMEFORMAT’ variable is
+a format string that specifies how the timing information should be
+displayed. *Note Bash Variables::, for a description of the available
+formats. Providing ‘time’ as a reserved word permits the timing of
+shell builtins, shell functions, and pipelines. An external ‘time’
+command cannot time these easily.
+
+ When the shell is in POSIX mode (*note Bash POSIX Mode::), you can
+use ‘time’ by itself as a simple command. In this case, the shell
+displays the total user and system time consumed by the shell and its
+children. The ‘TIMEFORMAT’ variable specifies the format of the time
+information.
+
+ If a pipeline is not executed asynchronously (*note Lists::), the
+shell waits for all commands in the pipeline to complete.
+
+ Each command in a multi-command pipeline, where pipes are created, is
+executed in its own “subshell”, which is a separate process (*note
+Command Execution Environment::). If the ‘lastpipe’ option is enabled
+using the ‘shopt’ builtin (*note The Shopt Builtin::), and job control
+is not active, the last element of a pipeline may be run by the shell
+process.
+
+ The exit status of a pipeline is the exit status of the last command
+in the pipeline, unless the ‘pipefail’ option is enabled (*note The Set
+Builtin::). If ‘pipefail’ is enabled, the pipeline's return status is
+the value of the last (rightmost) command to exit with a non-zero
+status, or zero if all commands exit successfully. If the reserved word
+‘!’ precedes the pipeline, the exit status is the logical negation of
+the exit status as described above. If a pipeline is not executed
+asynchronously (*note Lists::), the shell waits for all commands in the
+pipeline to terminate before returning a value. The return status of an
+asynchronous pipeline is 0.
+
+\1f
+File: bashref.info, Node: Lists, Next: Compound Commands, Prev: Pipelines, Up: Shell Commands
+
+3.2.4 Lists of Commands
+-----------------------
+
+A ‘list’ is a sequence of one or more pipelines separated by one of the
+operators ‘;’, ‘&’, ‘&&’, or ‘||’, and optionally terminated by one of
+‘;’, ‘&’, or a ‘newline’.
+
+ Of these list operators, ‘&&’ and ‘||’ have equal precedence,
+followed by ‘;’ and ‘&’, which have equal precedence.
+
+ A sequence of one or more newlines may appear in a ‘list’ to delimit
+commands, equivalent to a semicolon.
+
+ If a command is terminated by the control operator ‘&’, the shell
+executes the command asynchronously in a subshell. This is known as
+executing the command in the “background”, and these are referred to as
+“asynchronous” commands. The shell does not wait for the command to
+finish, and the return status is 0 (true). When job control is not
+active (*note Job Control::), the standard input for asynchronous
+commands, in the absence of any explicit redirections, is redirected
+from ‘/dev/null’.
+
+ Commands separated by a ‘;’ are executed sequentially; the shell
+waits for each command to terminate in turn. The return status is the
+exit status of the last command executed.
+
+ AND and OR lists are sequences of one or more pipelines separated by
+the control operators ‘&&’ and ‘||’, respectively. AND and OR lists are
+executed with left associativity.
+
+ An AND list has the form
+ COMMAND1 && COMMAND2
+
+COMMAND2 is executed if, and only if, COMMAND1 returns an exit status of
+zero (success).
+
+ An OR list has the form
+ COMMAND1 || COMMAND2
+
+COMMAND2 is executed if, and only if, COMMAND1 returns a non-zero exit
+status.
+
+ The return status of AND and OR lists is the exit status of the last
+command executed in the list.
+
+\1f
+File: bashref.info, Node: Compound Commands, Next: Coprocesses, Prev: Lists, Up: Shell Commands
+
+3.2.5 Compound Commands
+-----------------------
+
+* Menu:
+
+* Looping Constructs:: Shell commands for iterative action.
+* Conditional Constructs:: Shell commands for conditional execution.
+* Command Grouping:: Ways to group commands.
+
+Compound commands are the shell programming language constructs. Each
+construct begins with a reserved word or control operator and is
+terminated by a corresponding reserved word or operator. Any
+redirections (*note Redirections::) associated with a compound command
+apply to all commands within that compound command unless explicitly
+overridden.
+
+ In most cases a list of commands in a compound command's description
+may be separated from the rest of the command by one or more newlines,
+and may be followed by a newline in place of a semicolon.
+
+ Bash provides looping constructs, conditional commands, and
+mechanisms to group commands and execute them as a unit.
+
+\1f
+File: bashref.info, Node: Looping Constructs, Next: Conditional Constructs, Up: Compound Commands
+
+3.2.5.1 Looping Constructs
+..........................
+
+Bash supports the following looping constructs.
+
+ Note that wherever a ‘;’ appears in the description of a command's
+syntax, it may be replaced with one or more newlines.
+
+‘until’
+ The syntax of the ‘until’ command is:
+
+ until TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
+
+ Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
+ status which is not zero. The return status is the exit status of
+ the last command executed in CONSEQUENT-COMMANDS, or zero if none
+ was executed.
+
+‘while’
+ The syntax of the ‘while’ command is:
+
+ while TEST-COMMANDS; do CONSEQUENT-COMMANDS; done
+
+ Execute CONSEQUENT-COMMANDS as long as TEST-COMMANDS has an exit
+ status of zero. The return status is the exit status of the last
+ command executed in CONSEQUENT-COMMANDS, or zero if none was
+ executed.
+
+‘for’
+ The syntax of the ‘for’ command is:
+
+ for NAME [ [in WORDS ...] ; ] do COMMANDS; done
+
+ Expand WORDS (*note Shell Expansions::), and then execute COMMANDS
+ once for each word in the resultant list, with NAME bound to the
+ current word. If ‘in WORDS’ is not present, the ‘for’ command
+ executes the COMMANDS once for each positional parameter that is
+ set, as if ‘in "$@"’ had been specified (*note Special
+ Parameters::).
+
+ The return status is the exit status of the last command that
+ executes. If there are no items in the expansion of WORDS, no
+ commands are executed, and the return status is zero.
+
+ There is an alternate form of the ‘for’ command which is similar to
+ the C language:
+
+ for (( EXPR1 ; EXPR2 ; EXPR3 )) [;] do COMMANDS ; done
+
+ First, evaluate the arithmetic expression EXPR1 according to the
+ rules described below (*note Shell Arithmetic::). Then, repeatedly
+ evaluate the arithmetic expression EXPR2 until it evaluates to
+ zero. Each time EXPR2 evaluates to a non-zero value, execute
+ COMMANDS and evaluate the arithmetic expression EXPR3. If any
+ expression is omitted, it behaves as if it evaluates to 1. The
+ return value is the exit status of the last command in COMMANDS
+ that is executed, or non-zero if any of the expressions is invalid.
+
+ Use the ‘break’ and ‘continue’ builtins (*note Bourne Shell
+Builtins::) to control loop execution.
+
+\1f
+File: bashref.info, Node: Conditional Constructs, Next: Command Grouping, Prev: Looping Constructs, Up: Compound Commands
+
+3.2.5.2 Conditional Constructs
+..............................
+
+‘if’
+ The syntax of the ‘if’ command is:
+
+ if TEST-COMMANDS; then
+ CONSEQUENT-COMMANDS;
+ [elif MORE-TEST-COMMANDS; then
+ MORE-CONSEQUENTS;]
+ [else ALTERNATE-CONSEQUENTS;]
+ fi
+
+ The TEST-COMMANDS list is executed, and if its return status is
+ zero, the CONSEQUENT-COMMANDS list is executed. If TEST-COMMANDS
+ returns a non-zero status, each ‘elif’ list is executed in turn,
+ and if its exit status is zero, the corresponding MORE-CONSEQUENTS
+ is executed and the command completes. If ‘else
+ ALTERNATE-CONSEQUENTS’ is present, and the final command in the
+ final ‘if’ or ‘elif’ clause has a non-zero exit status, then
+ ALTERNATE-CONSEQUENTS is executed. The return status is the exit
+ status of the last command executed, or zero if no condition tested
+ true.
+
+‘case’
+ The syntax of the ‘case’ command is:
+
+ case WORD in
+ [ [(] PATTERN [| PATTERN]...) COMMAND-LIST ;;]...
+ esac
+
+ ‘case’ will selectively execute the COMMAND-LIST corresponding to
+ the first PATTERN that matches WORD, proceeding from the first
+ pattern to the last. The match is performed according to the rules
+ described below in *note Pattern Matching::. If the ‘nocasematch’
+ shell option (see the description of ‘shopt’ in *note The Shopt
+ Builtin::) is enabled, the match is performed without regard to the
+ case of alphabetic characters. The ‘|’ is used to separate
+ multiple patterns in a pattern list, and the ‘)’ operator
+ terminates the pattern list. A pattern list and an associated
+ COMMAND-LIST is known as a CLAUSE.
+
+ Each clause must be terminated with ‘;;’, ‘;&’, or ‘;;&’. The WORD
+ undergoes tilde expansion, parameter expansion, command
+ substitution, process substitution, arithmetic expansion, and quote
+ removal (*note Shell Parameter Expansion::) before the shell
+ attempts to match the pattern. Each PATTERN undergoes tilde
+ expansion, parameter expansion, command substitution, arithmetic
+ expansion, process substitution, and quote removal.
+
+ There may be an arbitrary number of ‘case’ clauses, each terminated
+ by a ‘;;’, ‘;&’, or ‘;;&’. The first pattern that matches
+ determines the command-list that is executed. It's a common idiom
+ to use ‘*’ as the final pattern to define the default case, since
+ that pattern will always match.
+
+ Here is an example using ‘case’ in a script that could be used to
+ describe one interesting feature of an animal:
+
+ echo -n "Enter the name of an animal: "
+ read ANIMAL
+ echo -n "The $ANIMAL has "
+ case $ANIMAL in
+ horse | dog | cat) echo -n "four";;
+ man | kangaroo ) echo -n "two";;
+ *) echo -n "an unknown number of";;
+ esac
+ echo " legs."
+
+ If the ‘;;’ operator is used, the ‘case’ command completes after
+ the first pattern match. Using ‘;&’ in place of ‘;;’ causes
+ execution to continue with the COMMAND-LIST associated with the
+ next clause, if any. Using ‘;;&’ in place of ‘;;’ causes the shell
+ to test the patterns in the next clause, if any, and execute any
+ associated COMMAND-LIST if the match succeeds, continuing the case
+ statement execution as if the pattern list had not matched.
+
+ The return status is zero if no PATTERN matches. Otherwise, the
+ return status is the exit status of the last COMMAND-LIST executed.
+
+‘select’
+
+ The ‘select’ construct allows the easy generation of menus. It has
+ almost the same syntax as the ‘for’ command:
+
+ select NAME [in WORDS ...]; do COMMANDS; done
+
+ First, expand the list of words following ‘in’, generating a list
+ of items, and print the set of expanded words on the standard error
+ stream, each preceded by a number. If the ‘in WORDS’ is omitted,
+ print the positional parameters, as if ‘in "$@"’ had been
+ specified. ‘select’ then displays the ‘PS3’ prompt and reads a
+ line from the standard input. If the line consists of a number
+ corresponding to one of the displayed words, then ‘select’ sets the
+ value of NAME to that word. If the line is empty, ‘select’
+ displays the words and prompt again. If ‘EOF’ is read, ‘select’
+ completes and returns 1. Any other value read causes NAME to be
+ set to null. The line read is saved in the variable ‘REPLY’.
+
+ The COMMANDS are executed after each selection until a ‘break’
+ command is executed, at which point the ‘select’ command completes.
+
+ Here is an example that allows the user to pick a filename from the
+ current directory, and displays the name and index of the file
+ selected.
+
+ select fname in *;
+ do
+ echo you picked $fname \($REPLY\)
+ break;
+ done
+
+‘((...))’
+ (( EXPRESSION ))
+
+ The arithmetic EXPRESSION is evaluated according to the rules
+ described below (*note Shell Arithmetic::). The EXPRESSION
+ undergoes the same expansions as if it were within double quotes,
+ but unescaped double quote characters in EXPRESSION are not treated
+ specially and are removed. Since this can potentially result in
+ empty strings, this command treats those as expressions that
+ evaluate to 0. If the value of the expression is non-zero, the
+ return status is 0; otherwise the return status is 1.
+
+‘[[...]]’
+ [[ EXPRESSION ]]
+
+ Evaluate the conditional expression EXPRESSION and return a status
+ of zero (true) or non-zero (false). Expressions are composed of
+ the primaries described below in *note Bash Conditional
+ Expressions::. The words between the ‘[[’ and ‘]]’ do not undergo
+ word splitting and filename expansion. The shell performs tilde
+ expansion, parameter and variable expansion, arithmetic expansion,
+ command substitution, process substitution, and quote removal on
+ those words. Conditional operators such as ‘-f’ must be unquoted
+ to be recognized as primaries.
+
+ When used with ‘[[’, the ‘<’ and ‘>’ operators sort
+ lexicographically using the current locale.
+
+ When the ‘==’ and ‘!=’ operators are used, the string to the right
+ of the operator is considered a pattern and matched according to
+ the rules described below in *note Pattern Matching::, as if the
+ ‘extglob’ shell option were enabled. The ‘=’ operator is identical
+ to ‘==’. If the ‘nocasematch’ shell option (see the description of
+ ‘shopt’ in *note The Shopt Builtin::) is enabled, the match is
+ performed without regard to the case of alphabetic characters. The
+ return value is 0 if the string matches (‘==’) or does not match
+ (‘!=’) the pattern, and 1 otherwise.
+
+ If you quote any part of the pattern, using any of the shell's
+ quoting mechanisms, the quoted portion is matched literally. This
+ means every character in the quoted portion matches itself, instead
+ of having any special pattern matching meaning.
+
+ An additional binary operator, ‘=~’, is available, with the same
+ precedence as ‘==’ and ‘!=’. When you use ‘=~’, the string to the
+ right of the operator is considered a POSIX extended regular
+ expression pattern and matched accordingly (using the POSIX
+ ‘regcomp’ and ‘regexec’ interfaces usually described in regex(3)).
+ The return value is 0 if the string matches the pattern, and 1 if
+ it does not. If the regular expression is syntactically incorrect,
+ the conditional expression returns 2. If the ‘nocasematch’ shell
+ option (see the description of ‘shopt’ in *note The Shopt
+ Builtin::) is enabled, the match is performed without regard to the
+ case of alphabetic characters.
+
+ You can quote any part of the pattern to force the quoted portion
+ to be matched literally instead of as a regular expression (see
+ above). If the pattern is stored in a shell variable, quoting the
+ variable expansion forces the entire pattern to be matched
+ literally.
+
+ The match succeeds if the pattern matches any part of the string.
+ If you want to force the pattern to match the entire string, anchor
+ the pattern using the ‘^’ and ‘$’ regular expression operators.
+
+ For example, the following will match a line (stored in the shell
+ variable ‘line’) if there is a sequence of characters anywhere in
+ the value consisting of any number, including zero, of characters
+ in the ‘space’ character class, immediately followed by zero or one
+ instances of ‘a’, then a ‘b’:
+
+ [[ $line =~ [[:space:]]*(a)?b ]]
+
+ That means values for ‘line’ like ‘aab’, ‘ aaaaaab’, ‘xaby’, and ‘
+ ab’ will all match, as will a line containing a ‘b’ anywhere in its
+ value.
+
+ If you want to match a character that's special to the regular
+ expression grammar (‘^$|[]()\.*+?’), it has to be quoted to remove
+ its special meaning. This means that in the pattern ‘xxx.txt’, the
+ ‘.’ matches any character in the string (its usual regular
+ expression meaning), but in the pattern ‘"xxx.txt"’, it can only
+ match a literal ‘.’.
+
+ Likewise, if you want to include a character in your pattern that
+ has a special meaning to the regular expression grammar, you must
+ make sure it's not quoted. If you want to anchor a pattern at the
+ beginning or end of the string, for instance, you cannot quote the
+ ‘^’ or ‘$’ characters using any form of shell quoting.
+
+ If you want to match ‘initial string’ at the start of a line, the
+ following will work:
+ [[ $line =~ ^"initial string" ]]
+ but this will not:
+ [[ $line =~ "^initial string" ]]
+ because in the second example the ‘^’ is quoted and doesn't have
+ its usual special meaning.
+
+ It is sometimes difficult to specify a regular expression properly
+ without using quotes, or to keep track of the quoting used by
+ regular expressions while paying attention to shell quoting and the
+ shell's quote removal. Storing the regular expression in a shell
+ variable is often a useful way to avoid problems with quoting
+ characters that are special to the shell. For example, the
+ following is equivalent to the pattern used above:
+
+ pattern='[[:space:]]*(a)?b'
+ [[ $line =~ $pattern ]]
+
+ Shell programmers should take special care with backslashes, since
+ backslashes are used by both the shell and regular expressions to
+ remove the special meaning from the following character. This
+ means that after the shell's word expansions complete (*note Shell
+ Expansions::), any backslashes remaining in parts of the pattern
+ that were originally not quoted can remove the special meaning of
+ pattern characters. If any part of the pattern is quoted, the
+ shell does its best to ensure that the regular expression treats
+ those remaining backslashes as literal, if they appeared in a
+ quoted portion.
+
+ The following two sets of commands are _not_ equivalent:
+
+ pattern='\.'
+
+ [[ . =~ $pattern ]]
+ [[ . =~ \. ]]
+
+ [[ . =~ "$pattern" ]]
+ [[ . =~ '\.' ]]
+
+ The first two matches will succeed, but the second two will not,
+ because in the second two the backslash will be part of the pattern
+ to be matched. In the first two examples, the pattern passed to
+ the regular expression parser is ‘\.’. The backslash removes the
+ special meaning from ‘.’, so the literal ‘.’ matches. In the
+ second two examples, the pattern passed to the regular expression
+ parser has the backslash quoted (e.g., ‘\\\.’), which will not
+ match the string, since it does not contain a backslash. If the
+ string in the first examples were anything other than ‘.’, say ‘a’,
+ the pattern would not match, because the quoted ‘.’ in the pattern
+ loses its special meaning of matching any single character.
+
+ Bracket expressions in regular expressions can be sources of errors
+ as well, since characters that are normally special in regular
+ expressions lose their special meanings between brackets. However,
+ you can use bracket expressions to match special pattern characters
+ without quoting them, so they are sometimes useful for this
+ purpose.
+
+ Though it might seem like a strange way to write it, the following
+ pattern will match a ‘.’ in the string:
+
+ [[ . =~ [.] ]]
+
+ The shell performs any word expansions before passing the pattern
+ to the regular expression functions, so you can assume that the
+ shell's quoting takes precedence. As noted above, the regular
+ expression parser will interpret any unquoted backslashes remaining
+ in the pattern after shell expansion according to its own rules.
+ The intention is to avoid making shell programmers quote things
+ twice as much as possible, so shell quoting should be sufficient to
+ quote special pattern characters where that's necessary.
+
+ The array variable ‘BASH_REMATCH’ records which parts of the string
+ matched the pattern. The element of ‘BASH_REMATCH’ with index 0
+ contains the portion of the string matching the entire regular
+ expression. Substrings matched by parenthesized subexpressions
+ within the regular expression are saved in the remaining
+ ‘BASH_REMATCH’ indices. The element of ‘BASH_REMATCH’ with index N
+ is the portion of the string matching the Nth parenthesized
+ subexpression.
+
+ Bash sets ‘BASH_REMATCH’ in the global scope; declaring it as a
+ local variable will lead to unexpected results.
+
+ Expressions may be combined using the following operators, listed
+ in decreasing order of precedence:
+
+ ‘( EXPRESSION )’
+ Returns the value of EXPRESSION. This may be used to override
+ the normal precedence of operators.
+
+ ‘! EXPRESSION’
+ True if EXPRESSION is false.
+
+ ‘EXPRESSION1 && EXPRESSION2’
+ True if both EXPRESSION1 and EXPRESSION2 are true.
+
+ ‘EXPRESSION1 || EXPRESSION2’
+ True if either EXPRESSION1 or EXPRESSION2 is true.
+
+ The ‘&&’ and ‘||’ operators do not evaluate EXPRESSION2 if the
+ value of EXPRESSION1 is sufficient to determine the return value of
+ the entire conditional expression.
+
+\1f
+File: bashref.info, Node: Command Grouping, Prev: Conditional Constructs, Up: Compound Commands
+
+3.2.5.3 Grouping Commands
+.........................
+
+Bash provides two ways to group a list of commands to be executed as a
+unit. When commands are grouped, redirections may be applied to the
+entire command list. For example, the output of all the commands in the
+list may be redirected to a single stream.
+
+‘()’
+ ( LIST )
+
+ Placing a list of commands between parentheses forces the shell to
+ create a subshell (*note Command Execution Environment::), and each
+ of the commands in LIST is executed in that subshell environment.
+ Since the LIST is executed in a subshell, variable assignments do
+ not remain in effect after the subshell completes.
+
+‘{}’
+ { LIST; }
+
+ Placing a list of commands between curly braces causes the list to
+ be executed in the current shell environment. No subshell is
+ created. The semicolon (or newline) following LIST is required.
+
+ In addition to the creation of a subshell, there is a subtle
+difference between these two constructs due to historical reasons. The
+braces are reserved words, so they must be separated from the LIST by
+‘blank’s or other shell metacharacters. The parentheses are operators,
+and are recognized as separate tokens by the shell even if they are not
+separated from the LIST by whitespace.
+
+ The exit status of both of these constructs is the exit status of
+LIST.
+
+\1f
+File: bashref.info, Node: Coprocesses, Next: GNU Parallel, Prev: Compound Commands, Up: Shell Commands
+
+3.2.6 Coprocesses
+-----------------
+
+A ‘coprocess’ is a shell command preceded by the ‘coproc’ reserved word.
+A coprocess is executed asynchronously in a subshell, as if the command
+had been terminated with the ‘&’ control operator, with a two-way pipe
+established between the executing shell and the coprocess.
+
+ The syntax for a coprocess is:
+
+ coproc [NAME] COMMAND [REDIRECTIONS]
+
+This creates a coprocess named NAME. COMMAND may be either a simple
+command (*note Simple Commands::) or a compound command (*note Compound
+Commands::). NAME is a shell variable name. If NAME is not supplied,
+the default name is ‘COPROC’.
+
+ The recommended form to use for a coprocess is
+
+ coproc NAME { COMMAND; }
+
+This form is preferred because simple commands result in the coprocess
+always being named ‘COPROC’, and it is simpler to use and more complete
+than the other compound commands.
+
+ There are other forms of coprocesses:
+
+ coproc NAME COMPOUND-COMMAND
+ coproc COMPOUND-COMMAND
+ coproc SIMPLE-COMMAND
+
+If COMMAND is a compound command, NAME is optional. The word following
+‘coproc’ determines whether that word is interpreted as a variable name:
+it is interpreted as NAME if it is not a reserved word that introduces a
+compound command. If COMMAND is a simple command, NAME is not allowed;
+this is to avoid confusion between NAME and the first word of the simple
+command.
+
+ When the coprocess is executed, the shell creates an array variable
+(*note Arrays::) named NAME in the context of the executing shell. The
+standard output of COMMAND is connected via a pipe to a file descriptor
+in the executing shell, and that file descriptor is assigned to NAME[0].
+The standard input of COMMAND is connected via a pipe to a file
+descriptor in the executing shell, and that file descriptor is assigned
+to NAME[1]. This pipe is established before any redirections specified
+by the command (*note Redirections::). The file descriptors can be
+utilized as arguments to shell commands and redirections using standard
+word expansions. Other than those created to execute command and
+process substitutions, the file descriptors are not available in
+subshells.
+
+ The process ID of the shell spawned to execute the coprocess is
+available as the value of the variable ‘NAME_PID’. The ‘wait’ builtin
+may be used to wait for the coprocess to terminate.
+
+ Since the coprocess is created as an asynchronous command, the
+‘coproc’ command always returns success. The return status of a
+coprocess is the exit status of COMMAND.
+
+\1f
+File: bashref.info, Node: GNU Parallel, Prev: Coprocesses, Up: Shell Commands
+
+3.2.7 GNU Parallel
+------------------
+
+There are ways to run commands in parallel that are not built into Bash.
+GNU Parallel is a tool to do just that.
+
+ GNU Parallel, as its name suggests, can be used to build and run
+commands in parallel. You may run the same command with different
+arguments, whether they are filenames, usernames, hostnames, or lines
+read from files. GNU Parallel provides shorthand references to many of
+the most common operations (input lines, various portions of the input
+line, different ways to specify the input source, and so on). Parallel
+can replace ‘xargs’ or feed commands from its input sources to several
+different instances of Bash.
+
+ For a complete description, refer to the GNU Parallel documentation,
+which is available at
+<https://www.gnu.org/software/parallel/parallel_tutorial.html>.
+
+\1f
+File: bashref.info, Node: Shell Functions, Next: Shell Parameters, Prev: Shell Commands, Up: Basic Shell Features
+
+3.3 Shell Functions
+===================
+
+Shell functions are a way to group commands for later execution using a
+single name for the group. They are executed just like a "regular"
+simple command. When the name of a shell function is used as a simple
+command name, the shell executes the list of commands associated with
+that function name. Shell functions are executed in the current shell
+context; there is no new process created to interpret them.
+
+ Functions are declared using this syntax:
+ FNAME () COMPOUND-COMMAND [ REDIRECTIONS ]
+
+ or
+
+ function FNAME [()] COMPOUND-COMMAND [ REDIRECTIONS ]
+
+ This defines a shell function named FNAME. The reserved word
+‘function’ is optional. If the ‘function’ reserved word is supplied,
+the parentheses are optional. The “body” of the function is the
+compound command COMPOUND-COMMAND (*note Compound Commands::). That
+command is usually a LIST enclosed between { and }, but may be any
+compound command listed above. If the ‘function’ reserved word is used,
+but the parentheses are not supplied, the braces are recommended. When
+the shell is in POSIX mode (*note Bash POSIX Mode::), FNAME must be a
+valid shell name and may not be the same as one of the special builtins
+(*note Special Builtins::). When not in POSIX mode, a function name can
+be any unquoted shell word that does not contain ‘$’.
+
+ Any redirections (*note Redirections::) associated with the shell
+function are performed when the function is executed. Function
+definitions are deleted using the ‘-f’ option to the ‘unset’ builtin
+(*note Bourne Shell Builtins::).
+
+ The exit status of a function definition is zero unless a syntax
+error occurs or a readonly function with the same name already exists.
+When executed, the exit status of a function is the exit status of the
+last command executed in the body.
+
+ Note that for historical reasons, in the most common usage the curly
+braces that surround the body of the function must be separated from the
+body by ‘blank’s or newlines. This is because the braces are reserved
+words and are only recognized as such when they are separated from the
+command list by whitespace or another shell metacharacter. When using
+the braces, the LIST must be terminated by a semicolon, a ‘&’, or a
+newline.
+
+ COMPOUND-COMMAND is executed whenever FNAME is specified as the name
+of a simple command. Functions are executed in the context of the
+calling shell; there is no new process created to interpret them
+(contrast this with the execution of a shell script).
+
+ When a function is executed, the arguments to the function become the
+positional parameters during its execution (*note Positional
+Parameters::). The special parameter ‘#’ that expands to the number of
+positional parameters is updated to reflect the new set of positional
+parameters. Special parameter ‘0’ is unchanged. The first element of
+the ‘FUNCNAME’ variable is set to the name of the function while the
+function is executing.
+
+ All other aspects of the shell execution environment are identical
+between a function and its caller with these exceptions: the ‘DEBUG’ and
+‘RETURN’ traps are not inherited unless the function has been given the
+‘trace’ attribute using the ‘declare’ builtin or the ‘-o functrace’
+option has been enabled with the ‘set’ builtin, (in which case all
+functions inherit the ‘DEBUG’ and ‘RETURN’ traps), and the ‘ERR’ trap is
+not inherited unless the ‘-o errtrace’ shell option has been enabled.
+*Note Bourne Shell Builtins::, for the description of the ‘trap’
+builtin.
+
+ The ‘FUNCNEST’ variable, if set to a numeric value greater than 0,
+defines a maximum function nesting level. Function invocations that
+exceed the limit cause the entire command to abort.
+
+ If the builtin command ‘return’ is executed in a function, the
+function completes and execution resumes with the next command after the
+function call. Any command associated with the ‘RETURN’ trap is
+executed before execution resumes. When a function completes, the
+values of the positional parameters and the special parameter ‘#’ are
+restored to the values they had prior to the function's execution. If
+‘return’ is supplied a numeric argument, that is the function's return
+status; otherwise the function's return status is the exit status of the
+last command executed before the ‘return’.
+
+ Variables local to the function are declared with the ‘local’ builtin
+(“local variables”). Ordinarily, variables and their values are shared
+between a function and its caller. These variables are visible only to
+the function and the commands it invokes. This is particularly
+important when a shell function calls other functions.
+
+ In the following description, the “current scope” is a currently-
+executing function. Previous scopes consist of that function's caller
+and so on, back to the "global" scope, where the shell is not executing
+any shell function. A local variable at the current local scope is a
+variable declared using the ‘local’ or ‘declare’ builtins in the
+function that is currently executing.
+
+ Local variables "shadow" variables with the same name declared at
+previous scopes. For instance, a local variable declared in a function
+hides variables with the same name declared at previous scopes,
+including global variables: references and assignments refer to the
+local variable, leaving the variables at previous scopes unmodified.
+When the function returns, the global variable is once again visible.
+
+ The shell uses “dynamic scoping” to control a variable's visibility
+within functions. With dynamic scoping, visible variables and their
+values are a result of the sequence of function calls that caused
+execution to reach the current function. The value of a variable that a
+function sees depends on its value within its caller, if any, whether
+that caller is the global scope or another shell function. This is also
+the value that a local variable declaration shadows, and the value that
+is restored when the function returns.
+
+ For example, if a variable ‘var’ is declared as local in function
+‘func1’, and ‘func1’ calls another function ‘func2’, references to ‘var’
+made from within ‘func2’ resolve to the local variable ‘var’ from
+‘func1’, shadowing any global variable named ‘var’.
+
+ The following script demonstrates this behavior. When executed, the
+script displays
+
+ In func2, var = func1 local
+
+ func1()
+ {
+ local var='func1 local'
+ func2
+ }
+
+ func2()
+ {
+ echo "In func2, var = $var"
+ }
+
+ var=global
+ func1
+
+ The ‘unset’ builtin also acts using the same dynamic scope: if a
+variable is local to the current scope, ‘unset’ unsets it; otherwise the
+unset will refer to the variable found in any calling scope as described
+above. If a variable at the current local scope is unset, it remains so
+(appearing as unset) until it is reset in that scope or until the
+function returns. Once the function returns, any instance of the
+variable at a previous scope becomes visible. If the unset acts on a
+variable at a previous scope, any instance of a variable with that name
+that had been shadowed becomes visible (see below how the
+‘localvar_unset’ shell option changes this behavior).
+
+ The ‘-f’ option to the ‘declare’ (‘typeset’) builtin command (*note
+Bash Builtins::) lists function names and definitions. The ‘-F’ option
+to ‘declare’ or ‘typeset’ lists the function names only (and optionally
+the source file and line number, if the ‘extdebug’ shell option is
+enabled). Functions may be exported so that child shell processes
+(those created when executing a separate shell invocation) automatically
+have them defined with the ‘-f’ option to the ‘export’ builtin (*note
+Bourne Shell Builtins::). The ‘-f’ option to the ‘unset’ builtin (*note
+Bourne Shell Builtins::) deletes a function definition.
+
+ Functions may be recursive. The ‘FUNCNEST’ variable may be used to
+limit the depth of the function call stack and restrict the number of
+function invocations. By default, Bash places no limit on the number of
+recursive calls.
+
+\1f
+File: bashref.info, Node: Shell Parameters, Next: Shell Expansions, Prev: Shell Functions, Up: Basic Shell Features
+
+3.4 Shell Parameters
+====================
+
+* Menu:
+
+* Positional Parameters:: The shell's command-line arguments.
+* Special Parameters:: Parameters denoted by special characters.
+
+A “parameter” is an entity that stores values. It can be a ‘name’, a
+number, or one of the special characters listed below. A “variable” is
+a parameter denoted by a ‘name’. A variable has a ‘value’ and zero or
+more ‘attributes’. Attributes are assigned using the ‘declare’ builtin
+command (see the description of the ‘declare’ builtin in *note Bash
+Builtins::). The ‘export’ and ‘readonly’ builtins assign specific
+attributes.
+
+ A parameter is set if it has been assigned a value. The null string
+is a valid value. Once a variable is set, it may be unset only by using
+the ‘unset’ builtin command.
+
+ A variable is assigned to using a statement of the form
+ NAME=[VALUE]
+If VALUE is not given, the variable is assigned the null string. All
+VALUEs undergo tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote removal (*note
+Shell Parameter Expansion::). If the variable has its ‘integer’
+attribute set, then VALUE is evaluated as an arithmetic expression even
+if the ‘$((...))’ expansion is not used (*note Arithmetic Expansion::).
+Word splitting and filename expansion are not performed. Assignment
+statements may also appear as arguments to the ‘alias’, ‘declare’,
+‘typeset’, ‘export’, ‘readonly’, and ‘local’ builtin commands
+(“declaration commands”). When in POSIX mode (*note Bash POSIX Mode::),
+these builtins may appear in a command after one or more instances of
+the ‘command’ builtin and retain these assignment statement properties.
+For example,
+ command export var=value
+
+ In the context where an assignment statement is assigning a value to
+a shell variable or array index (*note Arrays::), the ‘+=’ operator
+appends to or adds to the variable's previous value. This includes
+arguments to declaration commands such as ‘declare’ that accept
+assignment statements. When ‘+=’ is applied to a variable for which the
+‘integer’ attribute has been set, the variable's current value and VALUE
+are each evaluated as arithmetic expressions, and the sum of the results
+is assigned as the variable's value. The current value is usually an
+integer constant, but may be an expression. When ‘+=’ is applied to an
+array variable using compound assignment (*note Arrays::), the
+variable's value is not unset (as it is when using ‘=’), and new values
+are appended to the array beginning at one greater than the array's
+maximum index (for indexed arrays), or added as additional key-value
+pairs in an associative array. When applied to a string-valued
+variable, VALUE is expanded and appended to the variable's value.
+
+ A variable can be assigned the ‘nameref’ attribute using the ‘-n’
+option to the ‘declare’ or ‘local’ builtin commands (*note Bash
+Builtins::) to create a “nameref”, or a reference to another variable.
+This allows variables to be manipulated indirectly. Whenever the
+nameref variable is referenced, assigned to, unset, or has its
+attributes modified (other than using or changing the nameref attribute
+itself), the operation is actually performed on the variable specified
+by the nameref variable's value. A nameref is commonly used within
+shell functions to refer to a variable whose name is passed as an
+argument to the function. For instance, if a variable name is passed to
+a shell function as its first argument, running
+ declare -n ref=$1
+inside the function creates a local nameref variable ‘ref’ whose value
+is the variable name passed as the first argument. References and
+assignments to ‘ref’, and changes to its attributes, are treated as
+references, assignments, and attribute modifications to the variable
+whose name was passed as ‘$1’.
+
+ If the control variable in a ‘for’ loop has the nameref attribute,
+the list of words can be a list of shell variables, and a name reference
+is established for each word in the list, in turn, when the loop is
+executed. Array variables cannot be given the nameref attribute.
+However, nameref variables can reference array variables and subscripted
+array variables. Namerefs can be unset using the ‘-n’ option to the
+‘unset’ builtin (*note Bourne Shell Builtins::). Otherwise, if ‘unset’
+is executed with the name of a nameref variable as an argument, the
+variable referenced by the nameref variable is unset.
+
+ When the shell starts, it reads its environment and creates a shell
+variable from each environment variable that has a valid name, as
+described below (*note Environment::).
+
+\1f
+File: bashref.info, Node: Positional Parameters, Next: Special Parameters, Up: Shell Parameters
+
+3.4.1 Positional Parameters
+---------------------------
+
+A “positional parameter” is a parameter denoted by one or more digits,
+other than the single digit ‘0’. Positional parameters are assigned
+from the shell's arguments when it is invoked, and may be reassigned
+using the ‘set’ builtin command. Positional parameter ‘N’ may be
+referenced as ‘${N}’, or as ‘$N’ when ‘N’ consists of a single digit.
+Positional parameters may not be assigned to with assignment statements.
+The ‘set’ and ‘shift’ builtins are used to set and unset them (*note
+Shell Builtin Commands::). The positional parameters are temporarily
+replaced when a shell function is executed (*note Shell Functions::).
+
+ When a positional parameter consisting of more than a single digit is
+expanded, it must be enclosed in braces. Without braces, a digit
+following ‘$’ can only refer to one of the first nine positional
+parameters ($1\-$9) or the special parameter $0 (see below).
+
+\1f
+File: bashref.info, Node: Special Parameters, Prev: Positional Parameters, Up: Shell Parameters
+
+3.4.2 Special Parameters
+------------------------
+
+The shell treats several parameters specially. These parameters may
+only be referenced; assignment to them is not allowed. Special
+parameters are denoted by one of the following characters.
+
+‘*’
+ ($*) Expands to the positional parameters, starting from one. When
+ the expansion is not within double quotes, each positional
+ parameter expands to a separate word. In contexts where word
+ expansions are performed, those words are subject to further word
+ splitting and filename expansion. When the expansion occurs within
+ double quotes, it expands to a single word with the value of each
+ parameter separated by the first character of the ‘IFS’ variable.
+ That is, ‘"$*"’ is equivalent to ‘"$1C$2C..."’, where C is the
+ first character of the value of the ‘IFS’ variable. If ‘IFS’ is
+ unset, the parameters are separated by spaces. If ‘IFS’ is null,
+ the parameters are joined without intervening separators.
+
+‘@’
+ ($@) Expands to the positional parameters, starting from one. In
+ contexts where word splitting is performed, this expands each
+ positional parameter to a separate word; if not within double
+ quotes, these words are subject to word splitting. In contexts
+ where word splitting is not performed, such as the value portion of
+ an assignment statement, this expands to a single word with each
+ positional parameter separated by a space. When the expansion
+ occurs within double quotes, and word splitting is performed, each
+ parameter expands to a separate word. That is, ‘"$@"’ is
+ equivalent to ‘"$1" "$2" ...’. If the double-quoted expansion
+ occurs within a word, the expansion of the first parameter is
+ joined with the expansion of the beginning part of the original
+ word, and the expansion of the last parameter is joined with the
+ expansion of the last part of the original word. When there are no
+ positional parameters, ‘"$@"’ and ‘$@’ expand to nothing (i.e.,
+ they are removed).
+
+‘#’
+ ($#) Expands to the number of positional parameters in decimal.
+
+‘?’
+ ($?) Expands to the exit status of the most recently executed
+ command.
+
+‘-’
+ ($-, a hyphen.) Expands to the current option flags as specified
+ upon invocation, by the ‘set’ builtin command, or those set by the
+ shell itself (such as the ‘-i’ option).
+
+‘$’
+ ($$) Expands to the process ID of the shell. In a subshell, it
+ expands to the process ID of the invoking shell, not the subshell.
+
+‘!’
+ ($!) Expands to the process ID of the job most recently placed
+ into the background, whether executed as an asynchronous command or
+ using the ‘bg’ builtin (*note Job Control Builtins::).
+
+‘0’
+ ($0) Expands to the name of the shell or shell script. This is set
+ at shell initialization. If Bash is invoked with a file of
+ commands (*note Shell Scripts::), ‘$0’ is set to the name of that
+ file. If Bash is started with the ‘-c’ option (*note Invoking
+ Bash::), then ‘$0’ is set to the first argument after the string to
+ be executed, if one is present. Otherwise, it is set to the
+ filename used to invoke Bash, as given by argument zero.
+
+\1f
+File: bashref.info, Node: Shell Expansions, Next: Redirections, Prev: Shell Parameters, Up: Basic Shell Features
+
+3.5 Shell Expansions
+====================
+
+Expansion is performed on the command line after it has been split into
+‘token’s. Bash performs these expansions:
+
+ • brace expansion
+ • tilde expansion
+ • parameter and variable expansion
+ • command substitution
+ • arithmetic expansion
+ • word splitting
+ • filename expansion
+ • quote removal
+
+* Menu:
+
+* Brace Expansion:: Expansion of expressions within braces.
+* Tilde Expansion:: Expansion of the ~ character.
+* Shell Parameter Expansion:: How Bash expands variables to their values.
+* Command Substitution:: Using the output of a command as an argument.
+* Arithmetic Expansion:: How to use arithmetic in shell expansions.
+* Process Substitution:: A way to write and read to and from a
+ command.
+* Word Splitting:: How the results of expansion are split into separate
+ arguments.
+* Filename Expansion:: A shorthand for specifying filenames matching patterns.
+* Quote Removal:: How and when quote characters are removed from
+ words.
+
+ The order of expansions is: brace expansion; tilde expansion,
+parameter and variable expansion, arithmetic expansion, and command
+substitution (done in a left-to-right fashion); word splitting; filename
+expansion; and quote removal.
+
+ On systems that can support it, there is an additional expansion
+available: “process substitution”. This is performed at the same time
+as tilde, parameter, variable, and arithmetic expansion and command
+substitution.
+
+ “Quote removal” is always performed last. It removes quote
+characters present in the original word, not ones resulting from one of
+the other expansions, unless they have been quoted themselves. *Note
+Quote Removal:: for more details.
+
+ Only brace expansion, word splitting, and filename expansion can
+increase the number of words of the expansion; other expansions expand a
+single word to a single word. The only exceptions to this are the
+expansions of ‘"$@"’ and ‘$*’ (*note Special Parameters::), and
+‘"${NAME[@]}"’ and ‘${NAME[*]}’ (*note Arrays::).
+
+\1f
+File: bashref.info, Node: Brace Expansion, Next: Tilde Expansion, Up: Shell Expansions
+
+3.5.1 Brace Expansion
+---------------------
+
+Brace expansion is a mechanism to generate arbitrary strings sharing a
+common prefix and suffix, either of which can be empty. This mechanism
+is similar to “filename expansion” (*note Filename Expansion::), but the
+filenames generated need not exist. Patterns to be brace expanded are
+formed from an optional PREAMBLE, followed by either a series of
+comma-separated strings or a sequence expression between a pair of
+braces, followed by an optional POSTSCRIPT. The preamble is prefixed to
+each string contained within the braces, and the postscript is then
+appended to each resulting string, expanding left to right.
+
+ Brace expansions may be nested. The results of each expanded string
+are not sorted; brace expansion preserves left to right order. For
+example,
+ bash$ echo a{d,c,b}e
+ ade ace abe
+
+ A sequence expression takes the form ‘X..Y[..INCR]’, where X and Y
+are either integers or letters, and INCR, an optional increment, is an
+integer. When integers are supplied, the expression expands to each
+number between X and Y, inclusive. If either X or Y begins with a zero,
+each generated term will contain the same number of digits, zero-padding
+where necessary. When letters are supplied, the expression expands to
+each character lexicographically between X and Y, inclusive, using the C
+locale. Note that both X and Y must be of the same type (integer or
+letter). When the increment is supplied, it is used as the difference
+between each term. The default increment is 1 or -1 as appropriate.
+
+ Brace expansion is performed before any other expansions, and any
+characters special to other expansions are preserved in the result. It
+is strictly textual. Bash does not apply any syntactic interpretation
+to the context of the expansion or the text between the braces.
+
+ A correctly-formed brace expansion must contain unquoted opening and
+closing braces, and at least one unquoted comma or a valid sequence
+expression. Any incorrectly formed brace expansion is left unchanged.
+
+ A ‘{’ or ‘,’ may be quoted with a backslash to prevent its being
+considered part of a brace expression. To avoid conflicts with
+parameter expansion, the string ‘${’ is not considered eligible for
+brace expansion, and inhibits brace expansion until the closing ‘}’.
+
+ This construct is typically used as shorthand when the common prefix
+of the strings to be generated is longer than in the above example:
+ mkdir /usr/local/src/bash/{old,new,dist,bugs}
+ or
+ chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
+
+ Brace expansion introduces a slight incompatibility with historical
+versions of ‘sh’. ‘sh’ does not treat opening or closing braces
+specially when they appear as part of a word, and preserves them in the
+output. Bash removes braces from words as a consequence of brace
+expansion. For example, a word entered to ‘sh’ as ‘file{1,2}’ appears
+identically in the output. Bash outputs that word as ‘file1 file2’
+after brace expansion. Start Bash with the ‘+B’ option or disable brace
+expansion with the ‘+B’ option to the ‘set’ command (*note Shell Builtin
+Commands::) for strict ‘sh’ compatibility.
+
+\1f
+File: bashref.info, Node: Tilde Expansion, Next: Shell Parameter Expansion, Prev: Brace Expansion, Up: Shell Expansions
+
+3.5.2 Tilde Expansion
+---------------------
+
+If a word begins with an unquoted tilde character (‘~’), all of the
+characters up to the first unquoted slash (or all characters, if there
+is no unquoted slash) are considered a “tilde-prefix”. If none of the
+characters in the tilde-prefix are quoted, the characters in the
+tilde-prefix following the tilde are treated as a possible “login name”.
+If this login name is the null string, the tilde is replaced with the
+value of the ‘HOME’ shell variable. If ‘HOME’ is unset, the tilde
+expands to the home directory of the user executing the shell instead.
+Otherwise, the tilde-prefix is replaced with the home directory
+associated with the specified login name.
+
+ If the tilde-prefix is ‘~+’, the value of the shell variable ‘PWD’
+replaces the tilde-prefix. If the tilde-prefix is ‘~-’, the shell
+substitutes the value of the shell variable ‘OLDPWD’, if it is set.
+
+ If the characters following the tilde in the tilde-prefix consist of
+a number N, optionally prefixed by a ‘+’ or a ‘-’, the tilde-prefix is
+replaced with the corresponding element from the directory stack, as it
+would be displayed by the ‘dirs’ builtin invoked with the characters
+following tilde in the tilde-prefix as an argument (*note The Directory
+Stack::). If the tilde-prefix, sans the tilde, consists of a number
+without a leading ‘+’ or ‘-’, tilde expansion assumes ‘+’.
+
+ The results of tilde expansion are treated as if they were quoted, so
+the replacement is not subject to word splitting and filename expansion.
+
+ If the login name is invalid, or the tilde expansion fails, the
+tilde-prefix is left unchanged.
+
+ Bash checks each variable assignment for unquoted tilde-prefixes
+immediately following a ‘:’ or the first ‘=’, and performs tilde
+expansion in these cases. Consequently, one may use filenames with
+tildes in assignments to ‘PATH’, ‘MAILPATH’, and ‘CDPATH’, and the shell
+assigns the expanded value.
+
+ The following table shows how Bash treats unquoted tilde-prefixes:
+
+‘~’
+ The value of ‘$HOME’.
+‘~/foo’
+ ‘$HOME/foo’
+
+‘~fred/foo’
+ The directory or file ‘foo’ in the home directory of the user
+ ‘fred’.
+
+‘~+/foo’
+ ‘$PWD/foo’
+
+‘~-/foo’
+ ‘${OLDPWD-'~-'}/foo’
+
+‘~N’
+ The string that would be displayed by ‘dirs +N’.
+
+‘~+N’
+ The string that would be displayed by ‘dirs +N’.
+
+‘~-N’
+ The string that would be displayed by ‘dirs -N’.
+
+ Bash also performs tilde expansion on words satisfying the conditions
+of variable assignments (*note Shell Parameters::) when they appear as
+arguments to simple commands. Bash does not do this, except for the
+declaration commands listed above, when in POSIX mode.
+
+\1f
+File: bashref.info, Node: Shell Parameter Expansion, Next: Command Substitution, Prev: Tilde Expansion, Up: Shell Expansions
+
+3.5.3 Shell Parameter Expansion
+-------------------------------
+
+The ‘$’ character introduces parameter expansion, command substitution,
+or arithmetic expansion. The parameter name or symbol to be expanded
+may be enclosed in braces, which are optional but serve to protect the
+variable to be expanded from characters immediately following it which
+could be interpreted as part of the name. For example, if the first
+positional parameter has the value ‘a’, then ‘${11}’ expands to the
+value of the eleventh positional parameter, while ‘$11’ expands to ‘a1’.
+
+ When braces are used, the matching ending brace is the first ‘}’ not
+escaped by a backslash or within a quoted string, and not within an
+embedded arithmetic expansion, command substitution, or parameter
+expansion.
+
+ The basic form of parameter expansion is ${PARAMETER}, which
+substitutes the value of PARAMETER. The PARAMETER is a shell parameter
+as described above (*note Shell Parameters::) or an array reference
+(*note Arrays::). The braces are required when PARAMETER is a
+positional parameter with more than one digit, or when PARAMETER is
+followed by a character that is not to be interpreted as part of its
+name.
+
+ If the first character of PARAMETER is an exclamation point (!), and
+PARAMETER is not a nameref, it introduces a level of indirection. Bash
+uses the value formed by expanding the rest of PARAMETER as the new
+PARAMETER; this new parameter is then expanded and that value is used in
+the rest of the expansion, rather than the expansion of the original
+PARAMETER. This is known as ‘indirect expansion’. The value is subject
+to tilde expansion, parameter expansion, command substitution, and
+arithmetic expansion. If PARAMETER is a nameref, this expands to the
+name of the variable referenced by PARAMETER instead of performing the
+complete indirect expansion, for compatibility. The exceptions to this
+are the expansions of ${!PREFIX*} and ${!NAME[@]} described below. The
+exclamation point must immediately follow the left brace in order to
+introduce indirection.
+
+ In each of the cases below, WORD is subject to tilde expansion,
+parameter expansion, command substitution, and arithmetic expansion.
+
+ When not performing substring expansion, using the forms described
+below (e.g., ‘:-’), Bash tests for a parameter that is unset or null.
+Omitting the colon results in a test only for a parameter that is unset.
+Put another way, if the colon is included, the operator tests for both
+PARAMETER's existence and that its value is not null; if the colon is
+omitted, the operator tests only for existence.
+
+‘${PARAMETER:−WORD}’
+ If PARAMETER is unset or null, the expansion of WORD is
+ substituted. Otherwise, the value of PARAMETER is substituted.
+
+ $ v=123
+ $ echo ${v-unset}
+ 123
+ $ echo ${v:-unset-or-null}
+ 123
+ $ unset v
+ $ echo ${v-unset}
+ unset
+ $ v=
+ $ echo ${v-unset}
+
+ $ echo ${v:-unset-or-null}
+ unset-or-null
+
+‘${PARAMETER:=WORD}’
+ If PARAMETER is unset or null, the expansion of WORD is assigned to
+ PARAMETER, and the result of the expansion is the final value of
+ PARAMETER. Positional parameters and special parameters may not be
+ assigned in this way.
+
+ $ unset var
+ $ : ${var=DEFAULT}
+ $ echo $var
+ DEFAULT
+ $ var=
+ $ : ${var=DEFAULT}
+ $ echo $var
+
+ $ var=
+ $ : ${var:=DEFAULT}
+ $ echo $var
+ DEFAULT
+ $ unset var
+ $ : ${var:=DEFAULT}
+ $ echo $var
+ DEFAULT
+
+‘${PARAMETER:?WORD}’
+ If PARAMETER is null or unset, the shell writes the expansion of
+ WORD (or a message to that effect if WORD is not present) to the
+ standard error and, if it is not interactive, exits with a non-zero
+ status. An interactive shell does not exit, but does not execute
+ the command associated with the expansion. Otherwise, the value of
+ PARAMETER is substituted.
+
+ $ var=
+ $ : ${var:?var is unset or null}
+ bash: var: var is unset or null
+ $ echo ${var?var is unset}
+
+ $ unset var
+ $ : ${var?var is unset}
+ bash: var: var is unset
+ $ : ${var:?var is unset or null}
+ bash: var: var is unset or null
+ $ var=123
+ $ echo ${var:?var is unset or null}
+ 123
+
+‘${PARAMETER:+WORD}’
+ If PARAMETER is null or unset, nothing is substituted, otherwise
+ the expansion of WORD is substituted. The value of PARAMETER is
+ not used.
+
+ $ var=123
+ $ echo ${var:+var is set and not null}
+ var is set and not null
+ $ echo ${var+var is set}
+ var is set
+ $ var=
+ $ echo ${var:+var is set and not null}
+
+ $ echo ${var+var is set}
+ var is set
+ $ unset var
+ $ echo ${var+var is set}
+
+ $ echo ${var:+var is set and not null}
+
+ $
+
+‘${PARAMETER:OFFSET}’
+‘${PARAMETER:OFFSET:LENGTH}’
+ This is referred to as Substring Expansion. It expands to up to
+ LENGTH characters of the value of PARAMETER starting at the
+ character specified by OFFSET. If PARAMETER is ‘@’ or ‘*’, an
+ indexed array subscripted by ‘@’ or ‘*’, or an associative array
+ name, the results differ as described below. If :LENGTH is omitted
+ (the first form above), this expands to the substring of the value
+ of PARAMETER starting at the character specified by OFFSET and
+ extending to the end of the value. If OFFSET is omitted, it is
+ treated as 0. If LENGTH is omitted, but the colon after OFFSET is
+ present, it is treated as 0. LENGTH and OFFSET are arithmetic
+ expressions (*note Shell Arithmetic::).
+
+ If OFFSET evaluates to a number less than zero, the value is used
+ as an offset in characters from the end of the value of PARAMETER.
+ If LENGTH evaluates to a number less than zero, it is interpreted
+ as an offset in characters from the end of the value of PARAMETER
+ rather than a number of characters, and the expansion is the
+ characters between OFFSET and that result.
+
+ Note that a negative offset must be separated from the colon by at
+ least one space to avoid being confused with the ‘:-’ expansion.
+
+ Here are some examples illustrating substring expansion on
+ parameters and subscripted arrays:
+
+ $ string=01234567890abcdefgh
+ $ echo ${string:7}
+ 7890abcdefgh
+ $ echo ${string:7:0}
+
+ $ echo ${string:7:2}
+ 78
+ $ echo ${string:7:-2}
+ 7890abcdef
+ $ echo ${string: -7}
+ bcdefgh
+ $ echo ${string: -7:0}
+
+ $ echo ${string: -7:2}
+ bc
+ $ echo ${string: -7:-2}
+ bcdef
+ $ set -- 01234567890abcdefgh
+ $ echo ${1:7}
+ 7890abcdefgh
+ $ echo ${1:7:0}
+
+ $ echo ${1:7:2}
+ 78
+ $ echo ${1:7:-2}
+ 7890abcdef
+ $ echo ${1: -7}
+ bcdefgh
+ $ echo ${1: -7:0}
+
+ $ echo ${1: -7:2}
+ bc
+ $ echo ${1: -7:-2}
+ bcdef
+ $ array[0]=01234567890abcdefgh
+ $ echo ${array[0]:7}
+ 7890abcdefgh
+ $ echo ${array[0]:7:0}
+
+ $ echo ${array[0]:7:2}
+ 78
+ $ echo ${array[0]:7:-2}
+ 7890abcdef
+ $ echo ${array[0]: -7}
+ bcdefgh
+ $ echo ${array[0]: -7:0}
+
+ $ echo ${array[0]: -7:2}
+ bc
+ $ echo ${array[0]: -7:-2}
+ bcdef
+
+ If PARAMETER is ‘@’ or ‘*’, the result is LENGTH positional
+ parameters beginning at OFFSET. A negative OFFSET is taken
+ relative to one greater than the greatest positional parameter, so
+ an offset of -1 evaluates to the last positional parameter (or 0 if
+ there are no positional parameters). It is an expansion error if
+ LENGTH evaluates to a number less than zero.
+
+ The following examples illustrate substring expansion using
+ positional parameters:
+
+ $ set -- 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+ $ echo ${@:7}
+ 7 8 9 0 a b c d e f g h
+ $ echo ${@:7:0}
+
+ $ echo ${@:7:2}
+ 7 8
+ $ echo ${@:7:-2}
+ bash: -2: substring expression < 0
+ $ echo ${@: -7:2}
+ b c
+ $ echo ${@:0}
+ ./bash 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+ $ echo ${@:0:2}
+ ./bash 1
+ $ echo ${@: -7:0}
+
+
+ If PARAMETER is an indexed array name subscripted by ‘@’ or ‘*’,
+ the result is the LENGTH members of the array beginning with
+ ‘${PARAMETER[OFFSET]}’. A negative OFFSET is taken relative to one
+ greater than the maximum index of the specified array. It is an
+ expansion error if LENGTH evaluates to a number less than zero.
+
+ These examples show how you can use substring expansion with
+ indexed arrays:
+
+ $ array=(0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h)
+ $ echo ${array[@]:7}
+ 7 8 9 0 a b c d e f g h
+ $ echo ${array[@]:7:2}
+ 7 8
+ $ echo ${array[@]: -7:2}
+ b c
+ $ echo ${array[@]: -7:-2}
+ bash: -2: substring expression < 0
+ $ echo ${array[@]:0}
+ 0 1 2 3 4 5 6 7 8 9 0 a b c d e f g h
+ $ echo ${array[@]:0:2}
+ 0 1
+ $ echo ${array[@]: -7:0}
+
+
+ Substring expansion applied to an associative array produces
+ undefined results.
+
+ Substring indexing is zero-based unless the positional parameters
+ are used, in which case the indexing starts at 1 by default. If
+ OFFSET is 0, and the positional parameters are used, ‘$0’ is
+ prefixed to the list.
+
+‘${!PREFIX*}’
+‘${!PREFIX@}’
+ Expands to the names of variables whose names begin with PREFIX,
+ separated by the first character of the ‘IFS’ special variable.
+ When ‘@’ is used and the expansion appears within double quotes,
+ each variable name expands to a separate word.
+
+‘${!NAME[@]}’
+‘${!NAME[*]}’
+ If NAME is an array variable, expands to the list of array indices
+ (keys) assigned in NAME. If NAME is not an array, expands to 0 if
+ NAME is set and null otherwise. When ‘@’ is used and the expansion
+ appears within double quotes, each key expands to a separate word.
+
+‘${#PARAMETER}’
+ Substitutes the length in characters of the value of PARAMETER. If
+ PARAMETER is ‘*’ or ‘@’, the value substituted is the number of
+ positional parameters. If PARAMETER is an array name subscripted
+ by ‘*’ or ‘@’, the value substituted is the number of elements in
+ the array. If PARAMETER is an indexed array name subscripted by a
+ negative number, that number is interpreted as relative to one
+ greater than the maximum index of PARAMETER, so negative indices
+ count back from the end of the array, and an index of -1 references
+ the last element.
+
+‘${PARAMETER#WORD}’
+‘${PARAMETER##WORD}’
+ The WORD is expanded to produce a pattern and matched against the
+ expanded value of PARAMETER according to the rules described below
+ (*note Pattern Matching::). If the pattern matches the beginning
+ of the expanded value of PARAMETER, then the result of the
+ expansion is the expanded value of PARAMETER with the shortest
+ matching pattern (the ‘#’ case) or the longest matching pattern
+ (the ‘##’ case) deleted. If PARAMETER is ‘@’ or ‘*’, the pattern
+ removal operation is applied to each positional parameter in turn,
+ and the expansion is the resultant list. If PARAMETER is an array
+ variable subscripted with ‘@’ or ‘*’, the pattern removal operation
+ is applied to each member of the array in turn, and the expansion
+ is the resultant list.
+
+‘${PARAMETER%WORD}’
+‘${PARAMETER%%WORD}’
+ The WORD is expanded to produce a pattern and matched against the
+ expanded value of PARAMETER according to the rules described below
+ (*note Pattern Matching::). If the pattern matches a trailing
+ portion of the expanded value of PARAMETER, then the result of the
+ expansion is the value of PARAMETER with the shortest matching
+ pattern (the ‘%’ case) or the longest matching pattern (the ‘%%’
+ case) deleted. If PARAMETER is ‘@’ or ‘*’, the pattern removal
+ operation is applied to each positional parameter in turn, and the
+ expansion is the resultant list. If PARAMETER is an array variable
+ subscripted with ‘@’ or ‘*’, the pattern removal operation is
+ applied to each member of the array in turn, and the expansion is
+ the resultant list.
+
+‘${PARAMETER/PATTERN/STRING}’
+‘${PARAMETER//PATTERN/STRING}’
+‘${PARAMETER/#PATTERN/STRING}’
+‘${PARAMETER/%PATTERN/STRING}’
+ The PATTERN is expanded to produce a pattern and matched against
+ the expanded value of PARAMETER as described below (*note Pattern
+ Matching::). The longest match of PATTERN in the expanded value is
+ replaced with STRING. STRING undergoes tilde expansion, parameter
+ and variable expansion, arithmetic expansion, command and process
+ substitution, and quote removal.
+
+ In the first form above, only the first match is replaced. If
+ there are two slashes separating PARAMETER and PATTERN (the second
+ form above), all matches of PATTERN are replaced with STRING. If
+ PATTERN is preceded by ‘#’ (the third form above), it must match at
+ the beginning of the expanded value of PARAMETER. If PATTERN is
+ preceded by ‘%’ (the fourth form above), it must match at the end
+ of the expanded value of PARAMETER.
+
+ If the expansion of STRING is null, matches of PATTERN are deleted
+ and the ‘/’ following PATTERN may be omitted.
+
+ If the ‘patsub_replacement’ shell option is enabled using ‘shopt’
+ (*note The Shopt Builtin::), any unquoted instances of ‘&’ in
+ STRING are replaced with the matching portion of PATTERN. This is
+ intended to duplicate a common ‘sed’ idiom.
+
+ Quoting any part of STRING inhibits replacement in the expansion of
+ the quoted portion, including replacement strings stored in shell
+ variables. Backslash escapes ‘&’ in STRING; the backslash is
+ removed in order to permit a literal ‘&’ in the replacement string.
+ Users should take care if STRING is double-quoted to avoid unwanted
+ interactions between the backslash and double-quoting, since
+ backslash has special meaning within double quotes. Pattern
+ substitution performs the check for unquoted ‘&’ after expanding
+ STRING, so users should ensure to properly quote any occurrences of
+ ‘&’ they want to be taken literally in the replacement and ensure
+ any instances of ‘&’ they want to be replaced are unquoted.
+
+ For instance,
+
+ var=abcdef
+ rep='& '
+ echo ${var/abc/& }
+ echo "${var/abc/& }"
+ echo ${var/abc/$rep}
+ echo "${var/abc/$rep}"
+
+ will display four lines of "abc def", while
+
+ var=abcdef
+ rep='& '
+ echo ${var/abc/\& }
+ echo "${var/abc/\& }"
+ echo ${var/abc/"& "}
+ echo ${var/abc/"$rep"}
+
+ will display four lines of "& def". Like the pattern removal
+ operators, double quotes surrounding the replacement string quote
+ the expanded characters, while double quotes enclosing the entire
+ parameter substitution do not, since the expansion is performed in
+ a context that doesn't take any enclosing double quotes into
+ account.
+
+ Since backslash can escape ‘&’, it can also escape a backslash in
+ the replacement string. This means that ‘\\’ will insert a literal
+ backslash into the replacement, so these two ‘echo’ commands
+
+ var=abcdef
+ rep='\\&xyz'
+ echo ${var/abc/\\&xyz}
+ echo ${var/abc/$rep}
+
+ will both output ‘\abcxyzdef’.
+
+ It should rarely be necessary to enclose only STRING in double
+ quotes.
+
+ If the ‘nocasematch’ shell option (see the description of ‘shopt’
+ in *note The Shopt Builtin::) is enabled, the match is performed
+ without regard to the case of alphabetic characters.
+
+ If PARAMETER is ‘@’ or ‘*’, the substitution operation is applied
+ to each positional parameter in turn, and the expansion is the
+ resultant list. If PARAMETER is an array variable subscripted with
+ ‘@’ or ‘*’, the substitution operation is applied to each member of
+ the array in turn, and the expansion is the resultant list.
+
+‘${PARAMETER^PATTERN}’
+‘${PARAMETER^^PATTERN}’
+‘${PARAMETER,PATTERN}’
+‘${PARAMETER,,PATTERN}’
+ This expansion modifies the case of alphabetic characters in
+ PARAMETER. First, the PATTERN is expanded to produce a pattern as
+ described below in *note Pattern Matching::.
+
+ ‘Bash’ then examines characters in the expanded value of PARAMETER
+ against PATTERN as described below. If a character matches the
+ pattern, its case is converted. The pattern should not attempt to
+ match more than one character.
+
+ Using ‘^’ converts lowercase letters matching PATTERN to uppercase;
+ ‘,’ converts matching uppercase letters to lowercase. The ‘^’ and
+ ‘,’ variants examine the first character in the expanded value and
+ convert its case if it matches PATTERN; the ‘^^’ and ‘,,’ variants
+ examine all characters in the expanded value and convert each one
+ that matches PATTERN. If PATTERN is omitted, it is treated like a
+ ‘?’, which matches every character.
+
+ If PARAMETER is ‘@’ or ‘*’, the case modification operation is
+ applied to each positional parameter in turn, and the expansion is
+ the resultant list. If PARAMETER is an array variable subscripted
+ with ‘@’ or ‘*’, the case modification operation is applied to each
+ member of the array in turn, and the expansion is the resultant
+ list.
+
+‘${PARAMETER@OPERATOR}’
+ The expansion is either a transformation of the value of PARAMETER
+ or information about PARAMETER itself, depending on the value of
+ OPERATOR. Each OPERATOR is a single letter:
+
+ ‘U’
+ The expansion is a string that is the value of PARAMETER with
+ lowercase alphabetic characters converted to uppercase.
+ ‘u’
+ The expansion is a string that is the value of PARAMETER with
+ the first character converted to uppercase, if it is
+ alphabetic.
+ ‘L’
+ The expansion is a string that is the value of PARAMETER with
+ uppercase alphabetic characters converted to lowercase.
+ ‘Q’
+ The expansion is a string that is the value of PARAMETER
+ quoted in a format that can be reused as input.
+ ‘E’
+ The expansion is a string that is the value of PARAMETER with
+ backslash escape sequences expanded as with the ‘$'...'’
+ quoting mechanism.
+ ‘P’
+ The expansion is a string that is the result of expanding the
+ value of PARAMETER as if it were a prompt string (*note
+ Controlling the Prompt::).
+ ‘A’
+ The expansion is a string in the form of an assignment
+ statement or ‘declare’ command that, if evaluated, recreates
+ PARAMETER with its attributes and value.
+ ‘K’
+ Produces a possibly-quoted version of the value of PARAMETER,
+ except that it prints the values of indexed and associative
+ arrays as a sequence of quoted key-value pairs (*note
+ Arrays::). The keys and values are quoted in a format that
+ can be reused as input.
+ ‘a’
+ The expansion is a string consisting of flag values
+ representing PARAMETER's attributes.
+ ‘k’
+ Like the ‘K’ transformation, but expands the keys and values
+ of indexed and associative arrays to separate words after word
+ splitting.
+
+ If PARAMETER is ‘@’ or ‘*’, the operation is applied to each
+ positional parameter in turn, and the expansion is the resultant
+ list. If PARAMETER is an array variable subscripted with ‘@’ or
+ ‘*’, the operation is applied to each member of the array in turn,
+ and the expansion is the resultant list.
+
+ The result of the expansion is subject to word splitting and
+ filename expansion as described below.
+
+\1f
+File: bashref.info, Node: Command Substitution, Next: Arithmetic Expansion, Prev: Shell Parameter Expansion, Up: Shell Expansions
+
+3.5.4 Command Substitution
+--------------------------
+
+Command substitution allows the output of a command to replace the
+command itself. The standard form of command substitution occurs when a
+command is enclosed as follows:
+ $(COMMAND)
+or (deprecated)
+ `COMMAND`.
+
+Bash performs command substitution by executing COMMAND in a subshell
+environment and replacing the command substitution with the standard
+output of the command, with any trailing newlines deleted. Embedded
+newlines are not deleted, but they may be removed during word splitting.
+The command substitution ‘$(cat FILE)’ can be replaced by the equivalent
+but faster ‘$(< FILE)’.
+
+ With the old-style backquote form of substitution, backslash retains
+its literal meaning except when followed by ‘$’, ‘`’, or ‘\’. The first
+backquote not preceded by a backslash terminates the command
+substitution. When using the ‘$(COMMAND)’ form, all characters between
+the parentheses make up the command; none are treated specially.
+
+ There is an alternate form of command substitution:
+
+ ${C COMMAND; }
+
+which executes COMMAND in the current execution environment and captures
+its output, again with trailing newlines removed.
+
+ The character C following the open brace must be a space, tab,
+newline, or ‘|’, and the close brace must be in a position where a
+reserved word may appear (i.e., preceded by a command terminator such as
+semicolon). Bash allows the close brace to be joined to the remaining
+characters in the word without being followed by a shell metacharacter
+as a reserved word would usually require.
+
+ Any side effects of COMMAND take effect immediately in the current
+execution environment and persist in the current environment after the
+command completes (e.g., the ‘exit’ builtin exits the shell).
+
+ This type of command substitution superficially resembles executing
+an unnamed shell function: local variables are created as when a shell
+function is executing, and the ‘return’ builtin forces COMMAND to
+complete; however, the rest of the execution environment, including the
+positional parameters, is shared with the caller.
+
+ If the first character following the open brace is a ‘|’, the
+construct expands to the value of the ‘REPLY’ shell variable after
+COMMAND executes, without removing any trailing newlines, and the
+standard output of COMMAND remains the same as in the calling shell.
+Bash creates ‘REPLY’ as an initially-unset local variable when COMMAND
+executes, and restores ‘REPLY’ to the value it had before the command
+substitution after COMMAND completes, as with any local variable.
+
+ For example, this construct expands to ‘12345’, and leaves the shell
+variable ‘X’ unchanged in the current execution environment:
+
+
+ ${ local X=12345 ; echo $X; }
+
+(not declaring ‘X’ as local would modify its value in the current
+environment, as with normal shell function execution), while this
+construct does not require any output to expand to ‘12345’:
+
+ ${| REPLY=12345; }
+
+and restores ‘REPLY’ to the value it had before the command
+substitution.
+
+ Command substitutions may be nested. To nest when using the
+backquoted form, escape the inner backquotes with backslashes.
+
+ If the substitution appears within double quotes, Bash does not
+perform word splitting and filename expansion on the results.
+
+\1f
+File: bashref.info, Node: Arithmetic Expansion, Next: Process Substitution, Prev: Command Substitution, Up: Shell Expansions
+
+3.5.5 Arithmetic Expansion
+--------------------------
+
+Arithmetic expansion evaluates an arithmetic expression and substitutes
+the result. The format for arithmetic expansion is:
+
+ $(( EXPRESSION ))
+
+ The EXPRESSION undergoes the same expansions as if it were within
+double quotes, but unescaped double quote characters in EXPRESSION are
+not treated specially and are removed. All tokens in the expression
+undergo parameter and variable expansion, command substitution, and
+quote removal. The result is treated as the arithmetic expression to be
+evaluated. Since the way Bash handles double quotes can potentially
+result in empty strings, arithmetic expansion treats those as
+expressions that evaluate to 0. Arithmetic expansions may be nested.
+
+ The evaluation is performed according to the rules listed below
+(*note Shell Arithmetic::). If the expression is invalid, Bash prints a
+message indicating failure to the standard error, does not perform the
+substitution, and does not execute the command associated with the
+expansion.
+
+\1f
+File: bashref.info, Node: Process Substitution, Next: Word Splitting, Prev: Arithmetic Expansion, Up: Shell Expansions
+
+3.5.6 Process Substitution
+--------------------------
+
+Process substitution allows a process's input or output to be referred
+to using a filename. It takes the form of
+ <(LIST)
+or
+ >(LIST)
+The process LIST is run asynchronously, and its input or output appears
+as a filename. This filename is passed as an argument to the current
+command as the result of the expansion.
+
+ If the ‘>(LIST)’ form is used, writing to the file provides input for
+LIST. If the ‘<(LIST)’ form is used, reading the file obtains the
+output of LIST. Note that no space may appear between the ‘<’ or ‘>’
+and the left parenthesis, otherwise the construct would be interpreted
+as a redirection.
+
+ Process substitution is supported on systems that support named pipes
+(FIFOs) or the ‘/dev/fd’ method of naming open files.
+
+ When available, process substitution is performed simultaneously with
+parameter and variable expansion, command substitution, and arithmetic
+expansion.
+
+\1f
+File: bashref.info, Node: Word Splitting, Next: Filename Expansion, Prev: Process Substitution, Up: Shell Expansions
+
+3.5.7 Word Splitting
+--------------------
+
+The shell scans the results of parameter expansion, command
+substitution, and arithmetic expansion that did not occur within double
+quotes for word splitting. Words that were not expanded are not split.
+
+ The shell treats each character of ‘$IFS’ as a delimiter, and splits
+the results of the other expansions into fields using these characters
+as field terminators.
+
+ An “IFS whitespace” character is whitespace as defined above (*note
+Definitions::) that appears in the value of ‘IFS’. Space, tab, and
+newline are always considered IFS whitespace, even if they don't appear
+in the locale's ‘space’ category.
+
+ If ‘IFS’ is unset, word splitting behaves as if its value were
+‘<space><tab><newline>’, and treats these characters as IFS whitespace.
+If the value of ‘IFS’ is null, no word splitting occurs, but implicit
+null arguments (see below) are still removed.
+
+ Word splitting begins by removing sequences of IFS whitespace
+characters from the beginning and end of the results of the previous
+expansions, then splits the remaining words.
+
+ If the value of ‘IFS’ consists solely of IFS whitespace, any sequence
+of IFS whitespace characters delimits a field, so a field consists of
+characters that are not unquoted IFS whitespace, and null fields result
+only from quoting.
+
+ If ‘IFS’ contains a non-whitespace character, then any character in
+the value of ‘IFS’ that is not IFS whitespace, along with any adjacent
+IFS whitespace characters, delimits a field. This means that adjacent
+non-IFS-whitespace delimiters produce a null field. A sequence of IFS
+whitespace characters also delimits a field.
+
+ Explicit null arguments (‘""’ or ‘''’) are retained and passed to
+commands as empty strings. Unquoted implicit null arguments, resulting
+from the expansion of parameters that have no values, are removed.
+Expanding a parameter with no value within double quotes produces a null
+field, which is retained and passed to a command as an empty string.
+
+ When a quoted null argument appears as part of a word whose expansion
+is non-null, word splitting removes the null argument portion, leaving
+the non-null expansion. That is, the word ‘-d''’ becomes ‘-d’ after
+word splitting and null argument removal.
+
+\1f
+File: bashref.info, Node: Filename Expansion, Next: Quote Removal, Prev: Word Splitting, Up: Shell Expansions
+
+3.5.8 Filename Expansion
+------------------------
+
+* Menu:
+
+* Pattern Matching:: How the shell matches patterns.
+
+After word splitting, unless the ‘-f’ option has been set (*note The Set
+Builtin::), Bash scans each word for the characters ‘*’, ‘?’, and ‘[’.
+If one of these characters appears, and is not quoted, then the word is
+regarded as a PATTERN, and replaced with a sorted list of filenames
+matching the pattern (*note Pattern Matching::), subject to the value of
+the ‘GLOBSORT’ shell variable (*note Bash Variables::).
+
+ If no matching filenames are found, and the shell option ‘nullglob’
+is disabled, the word is left unchanged. If the ‘nullglob’ option is
+set, and no matches are found, the word is removed. If the ‘failglob’
+shell option is set, and no matches are found, Bash prints an error
+message and does not execute the command. If the shell option
+‘nocaseglob’ is enabled, the match is performed without regard to the
+case of alphabetic characters.
+
+ When a pattern is used for filename expansion, the character ‘.’ at
+the start of a filename or immediately following a slash must be matched
+explicitly, unless the shell option ‘dotglob’ is set. In order to match
+the filenames ‘.’ and ‘..’, the pattern must begin with ‘.’ (for
+example, ‘.?’), even if ‘dotglob’ is set. If the ‘globskipdots’ shell
+option is enabled, the filenames ‘.’ and ‘..’ never match, even if the
+pattern begins with a ‘.’. When not matching filenames, the ‘.’
+character is not treated specially.
+
+ When matching a filename, the slash character must always be matched
+explicitly by a slash in the pattern, but in other matching contexts it
+can be matched by a special pattern character as described below (*note
+Pattern Matching::).
+
+ See the description of ‘shopt’ in *note The Shopt Builtin::, for a
+description of the ‘nocaseglob’, ‘nullglob’, ‘globskipdots’, ‘failglob’,
+and ‘dotglob’ options.
+
+ The ‘GLOBIGNORE’ shell variable may be used to restrict the set of
+file names matching a pattern. If ‘GLOBIGNORE’ is set, each matching
+file name that also matches one of the patterns in ‘GLOBIGNORE’ is
+removed from the list of matches. If the ‘nocaseglob’ option is set,
+the matching against the patterns in ‘GLOBIGNORE’ is performed without
+regard to case. The filenames ‘.’ and ‘..’ are always ignored when
+‘GLOBIGNORE’ is set and not null. However, setting ‘GLOBIGNORE’ to a
+non-null value has the effect of enabling the ‘dotglob’ shell option, so
+all other filenames beginning with a ‘.’ match. To get the old behavior
+of ignoring filenames beginning with a ‘.’, make ‘.*’ one of the
+patterns in ‘GLOBIGNORE’. The ‘dotglob’ option is disabled when
+‘GLOBIGNORE’ is unset. The ‘GLOBIGNORE’ pattern matching honors the
+setting of the ‘extglob’ shell option.
+
+ The value of the ‘GLOBSORT’ shell variable controls how the results
+of pathname expansion are sorted, as described below (*note Bash
+Variables::).
+
+\1f
+File: bashref.info, Node: Pattern Matching, Up: Filename Expansion
+
+3.5.8.1 Pattern Matching
+........................
+
+Any character that appears in a pattern, other than the special pattern
+characters described below, matches itself. The NUL character may not
+occur in a pattern. A backslash escapes the following character; the
+escaping backslash is discarded when matching. The special pattern
+characters must be quoted if they are to be matched literally.
+
+ The special pattern characters have the following meanings:
+‘*’
+ Matches any string, including the null string. When the ‘globstar’
+ shell option is enabled, and ‘*’ is used in a filename expansion
+ context, two adjacent ‘*’s used as a single pattern match all files
+ and zero or more directories and subdirectories. If followed by a
+ ‘/’, two adjacent ‘*’s match only directories and subdirectories.
+‘?’
+ Matches any single character.
+‘[...]’
+ Matches any one of the characters enclosed between the brackets.
+ This is known as a “bracket expression” and matches a single
+ character. A pair of characters separated by a hyphen denotes a
+ “range expression”; any character that falls between those two
+ characters, inclusive, using the current locale's collating
+ sequence and character set, matches. If the first character
+ following the ‘[’ is a ‘!’ or a ‘^’ then any character not within
+ the range matches. To match a ‘−’, include it as the first or last
+ character in the set. To match a ‘]’, include it as the first
+ character in the set.
+
+ The sorting order of characters in range expressions, and the
+ characters included in the range, are determined by the current
+ locale and the values of the ‘LC_COLLATE’ and ‘LC_ALL’ shell
+ variables, if set.
+
+ For example, in the default C locale, ‘[a-dx-z]’ is equivalent to
+ ‘[abcdxyz]’. Many locales sort characters in dictionary order, and
+ in these locales ‘[a-dx-z]’ is typically not equivalent to
+ ‘[abcdxyz]’; it might be equivalent to ‘[aBbCcDdxYyZz]’, for
+ example. To obtain the traditional interpretation of ranges in
+ bracket expressions, you can force the use of the C locale by
+ setting the ‘LC_COLLATE’ or ‘LC_ALL’ environment variable to the
+ value ‘C’, or enable the ‘globasciiranges’ shell option.
+
+ Within a bracket expression, “character classes” can be specified
+ using the syntax ‘[:’CLASS‘:]’, where CLASS is one of the following
+ classes defined in the POSIX standard:
+ alnum alpha ascii blank cntrl digit graph lower
+ print punct space upper word xdigit
+ A character class matches any character belonging to that class.
+ The ‘word’ character class matches letters, digits, and the
+ character ‘_’.
+
+ For instance, the following pattern will match any character
+ belonging to the ‘space’ character class in the current locale,
+ then any upper case letter or ‘!’, a dot, and finally any lower
+ case letter or a hyphen.
+
+ [[:space:]][[:upper:]!].[-[:lower:]]
+
+ Within a bracket expression, an “equivalence class” can be
+ specified using the syntax ‘[=’C‘=]’, which matches all characters
+ with the same collation weight (as defined by the current locale)
+ as the character C.
+
+ Within a bracket expression, the syntax ‘[.’SYMBOL‘.]’ matches the
+ collating symbol SYMBOL.
+
+ If the ‘extglob’ shell option is enabled using the ‘shopt’ builtin,
+the shell recognizes several extended pattern matching operators. In
+the following description, a PATTERN-LIST is a list of one or more
+patterns separated by a ‘|’. When matching filenames, the ‘dotglob’
+shell option determines the set of filenames that are tested, as
+described above. Composite patterns may be formed using one or more of
+the following sub-patterns:
+
+‘?(PATTERN-LIST)’
+ Matches zero or one occurrence of the given patterns.
+
+‘*(PATTERN-LIST)’
+ Matches zero or more occurrences of the given patterns.
+
+‘+(PATTERN-LIST)’
+ Matches one or more occurrences of the given patterns.
+
+‘@(PATTERN-LIST)’
+ Matches one of the given patterns.
+
+‘!(PATTERN-LIST)’
+ Matches anything except one of the given patterns.
+
+ The ‘extglob’ option changes the behavior of the parser, since the
+parentheses are normally treated as operators with syntactic meaning.
+To ensure that extended matching patterns are parsed correctly, make
+sure that ‘extglob’ is enabled before parsing constructs containing the
+patterns, including shell functions and command substitutions.
+
+ When matching filenames, the ‘dotglob’ shell option determines the
+set of filenames that are tested: when ‘dotglob’ is enabled, the set of
+filenames includes all files beginning with ‘.’, but the filenames ‘.’
+and ‘..’ must be matched by a pattern or sub-pattern that begins with a
+dot; when it is disabled, the set does not include any filenames
+beginning with ‘.’ unless the pattern or sub-pattern begins with a ‘.’.
+If the ‘globskipdots’ shell option is enabled, the filenames ‘.’ and
+‘..’ never appear in the set. As above, ‘.’ only has a special meaning
+when matching filenames.
+
+ Complicated extended pattern matching against long strings is slow,
+especially when the patterns contain alternations and the strings
+contain multiple matches. Using separate matches against shorter
+strings, or using arrays of strings instead of a single long string, may
+be faster.
+
+\1f
+File: bashref.info, Node: Quote Removal, Prev: Filename Expansion, Up: Shell Expansions
+
+3.5.9 Quote Removal
+-------------------
+
+After the preceding expansions, all unquoted occurrences of the
+characters ‘\’, ‘'’, and ‘"’ that did not result from one of the above
+expansions are removed.
+
+\1f
+File: bashref.info, Node: Redirections, Next: Executing Commands, Prev: Shell Expansions, Up: Basic Shell Features
+
+3.6 Redirections
+================
+
+Before a command is executed, its input and output may be “redirected”
+using a special notation interpreted by the shell. “Redirection” allows
+commands' file handles to be duplicated, opened, closed, made to refer
+to different files, and can change the files the command reads from and
+writes to. When used with the ‘exec’ builtin, redirections modify file
+handles in the current shell execution environment. The following
+redirection operators may precede or appear anywhere within a simple
+command or may follow a command. Redirections are processed in the
+order they appear, from left to right.
+
+ Each redirection that may be preceded by a file descriptor number may
+instead be preceded by a word of the form {VARNAME}. In this case, for
+each redirection operator except ‘>&-’ and ‘<&-’, the shell allocates a
+file descriptor greater than or equal to 10 and assigns it to {VARNAME}.
+If {VARNAME} precedes ‘>&-’ or ‘<&-’, the value of VARNAME defines the
+file descriptor to close. If {VARNAME} is supplied, the redirection
+persists beyond the scope of the command, which allows the shell
+programmer to manage the file descriptor's lifetime manually without
+using the ‘exec’ builtin. The ‘varredir_close’ shell option manages
+this behavior (*note The Shopt Builtin::).
+
+ In the following descriptions, if the file descriptor number is
+omitted, and the first character of the redirection operator is ‘<’, the
+redirection refers to the standard input (file descriptor 0). If the
+first character of the redirection operator is ‘>’, the redirection
+refers to the standard output (file descriptor 1).
+
+ The WORD following the redirection operator in the following
+descriptions, unless otherwise noted, is subjected to brace expansion,
+tilde expansion, parameter and variable expansion, command substitution,
+arithmetic expansion, quote removal, filename expansion, and word
+splitting. If it expands to more than one word, Bash reports an error.
+
+ The order of redirections is significant. For example, the command
+ ls > DIRLIST 2>&1
+directs both standard output (file descriptor 1) and standard error
+(file descriptor 2) to the file DIRLIST, while the command
+ ls 2>&1 > DIRLIST
+directs only the standard output to file DIRLIST, because the standard
+error was made a copy of the standard output before the standard output
+was redirected to DIRLIST.
+
+ Bash handles several filenames specially when they are used in
+redirections, as described in the following table. If the operating
+system on which Bash is running provides these special files, Bash uses
+them; otherwise it emulates them internally with the behavior described
+below.
+
+‘/dev/fd/FD’
+ If FD is a valid integer, duplicate file descriptor FD.
+
+‘/dev/stdin’
+ File descriptor 0 is duplicated.
+
+‘/dev/stdout’
+ File descriptor 1 is duplicated.
+
+‘/dev/stderr’
+ File descriptor 2 is duplicated.
+
+‘/dev/tcp/HOST/PORT’
+ If HOST is a valid hostname or Internet address, and PORT is an
+ integer port number or service name, Bash attempts to open the
+ corresponding TCP socket.
+
+‘/dev/udp/HOST/PORT’
+ If HOST is a valid hostname or Internet address, and PORT is an
+ integer port number or service name, Bash attempts to open the
+ corresponding UDP socket.
+
+ A failure to open or create a file causes the redirection to fail.
+
+ Redirections using file descriptors greater than 9 should be used
+with care, as they may conflict with file descriptors the shell uses
+internally.
+
+3.6.1 Redirecting Input
+-----------------------
+
+Redirecting input opens the file whose name results from the expansion
+of WORD for reading on file descriptor ‘n’, or the standard input (file
+descriptor 0) if ‘n’ is not specified.
+
+ The general format for redirecting input is:
+ [N]<WORD
+
+3.6.2 Redirecting Output
+------------------------
+
+Redirecting output opens the file whose name results from the expansion
+of WORD for writing on file descriptor N, or the standard output (file
+descriptor 1) if N is not specified. If the file does not exist it is
+created; if it does exist it is truncated to zero size.
+
+ The general format for redirecting output is:
+ [N]>[|]WORD
+
+ If the redirection operator is ‘>’, and the ‘noclobber’ option to the
+‘set’ builtin command has been enabled, the redirection fails if the
+file whose name results from the expansion of WORD exists and is a
+regular file. If the redirection operator is ‘>|’, or the redirection
+operator is ‘>’ and the ‘noclobber’ option to the ‘set’ builtin is not
+enabled, Bash attempts the redirection even if the file named by WORD
+exists.
+
+3.6.3 Appending Redirected Output
+---------------------------------
+
+Redirecting output in this fashion opens the file whose name results
+from the expansion of WORD for appending on file descriptor N, or the
+standard output (file descriptor 1) if N is not specified. If the file
+does not exist it is created.
+
+ The general format for appending output is:
+ [N]>>WORD
+
+3.6.4 Redirecting Standard Output and Standard Error
+----------------------------------------------------
+
+This construct redirects both the standard output (file descriptor 1)
+and the standard error output (file descriptor 2) to the file whose name
+is the expansion of WORD.
+
+ There are two formats for redirecting standard output and standard
+error:
+ &>WORD
+and
+ >&WORD
+Of the two forms, the first is preferred. This is semantically
+equivalent to
+ >WORD 2>&1
+ When using the second form, WORD may not expand to a number or ‘-’.
+If it does, other redirection operators apply (see Duplicating File
+Descriptors below) for compatibility reasons.
+
+3.6.5 Appending Standard Output and Standard Error
+--------------------------------------------------
+
+This construct appends both the standard output (file descriptor 1) and
+the standard error output (file descriptor 2) to the file whose name is
+the expansion of WORD.
+
+ The format for appending standard output and standard error is:
+ &>>WORD
+This is semantically equivalent to
+ >>WORD 2>&1
+ (see Duplicating File Descriptors below).
+
+3.6.6 Here Documents
+--------------------
+
+This type of redirection instructs the shell to read input from the
+current source until it reads a line containing only DELIMITER (with no
+trailing blanks). All of the lines read up to that point then become
+the standard input (or file descriptor N if N is specified) for a
+command.
+
+ The format of here-documents is:
+ [N]<<[−]WORD
+ HERE-DOCUMENT
+ DELIMITER
+
+ The shell does not perform parameter and variable expansion, command
+substitution, arithmetic expansion, or filename expansion on WORD.
+
+ If any part of WORD is quoted, the DELIMITER is the result of quote
+removal on WORD, and the lines in the here-document are not expanded.
+If WORD is unquoted, DELIMITER is WORD itself, and the here-document
+text is treated similarly to a double-quoted string: all lines of the
+here-document are subjected to parameter expansion, command
+substitution, and arithmetic expansion, the character sequence
+‘\newline’ is treated literally, and ‘\’ must be used to quote the
+characters ‘\’, ‘$’, and ‘`’; however, double quote characters have no
+special meaning.
+
+ If the redirection operator is ‘<<-’, the shell strips leading tab
+characters from input lines and the line containing DELIMITER. This
+allows here-documents within shell scripts to be indented in a natural
+fashion.
+
+ If the delimiter is not quoted, the shell treats the ‘\<newline>’
+sequence as a line continuation: the two lines are joined and the
+backslash-newline is removed. This happens while reading the
+here-document, before the check for the ending delimiter, so joined
+lines can form the end delimiter.
+
+3.6.7 Here Strings
+------------------
+
+A variant of here documents, the format is:
+ [N]<<< WORD
+
+ The WORD undergoes tilde expansion, parameter and variable expansion,
+command substitution, arithmetic expansion, and quote removal. Filename
+expansion and word splitting are not performed. The result is supplied
+as a single string, with a newline appended, to the command on its
+standard input (or file descriptor N if N is specified).
+
+3.6.8 Duplicating File Descriptors
+----------------------------------
+
+The redirection operator
+ [N]<&WORD
+is used to duplicate input file descriptors. If WORD expands to one or
+more digits, file descriptor N is made to be a copy of that file
+descriptor. It is a redirection error if the digits in WORD do not
+specify a file descriptor open for input. If WORD evaluates to ‘-’,
+file descriptor N is closed. If N is not specified, this uses the
+standard input (file descriptor 0).
+
+ The operator
+ [N]>&WORD
+is used similarly to duplicate output file descriptors. If N is not
+specified, this uses the standard output (file descriptor 1). It is a
+redirection error if the digits in WORD do not specify a file descriptor
+open for output. If WORD evaluates to ‘-’, file descriptor N is closed.
+As a special case, if N is omitted, and WORD does not expand to one or
+more digits or ‘-’, this redirects the standard output and standard
+error as described previously.
+
+3.6.9 Moving File Descriptors
+-----------------------------
+
+The redirection operator
+ [N]<&DIGIT-
+moves the file descriptor DIGIT to file descriptor N, or the standard
+input (file descriptor 0) if N is not specified. DIGIT is closed after
+being duplicated to N.
+
+ Similarly, the redirection operator
+ [N]>&DIGIT-
+moves the file descriptor DIGIT to file descriptor N, or the standard
+output (file descriptor 1) if N is not specified.
+
+3.6.10 Opening File Descriptors for Reading and Writing
+-------------------------------------------------------
+
+The redirection operator
+ [N]<>WORD
+opens the file whose name is the expansion of WORD for both reading and
+writing on file descriptor N, or on file descriptor 0 if N is not
+specified. If the file does not exist, it is created.
+
+\1f
+File: bashref.info, Node: Executing Commands, Next: Shell Scripts, Prev: Redirections, Up: Basic Shell Features
+
+3.7 Executing Commands
+======================
+
+* Menu:
+
+* Simple Command Expansion:: How Bash expands simple commands before
+ executing them.
+* Command Search and Execution:: How Bash finds commands and runs them.
+* Command Execution Environment:: The environment in which Bash
+ executes commands that are not
+ shell builtins.
+* Environment:: The environment given to a command.
+* Exit Status:: The status returned by commands and how Bash
+ interprets it.
+* Signals:: What happens when Bash or a command it runs
+ receives a signal.
+
+\1f
+File: bashref.info, Node: Simple Command Expansion, Next: Command Search and Execution, Up: Executing Commands
+
+3.7.1 Simple Command Expansion
+------------------------------
+
+When the shell executes a simple command, it performs the following
+expansions, assignments, and redirections, from left to right, in the
+following order.
+
+ 1. The words that the parser has marked as variable assignments (those
+ preceding the command name) and redirections are saved for later
+ processing.
+
+ 2. The words that are not variable assignments or redirections are
+ expanded (*note Shell Expansions::). If any words remain after
+ expansion, the first word is taken to be the name of the command
+ and the remaining words are the arguments.
+
+ 3. Redirections are performed as described above (*note
+ Redirections::).
+
+ 4. The text after the ‘=’ in each variable assignment undergoes tilde
+ expansion, parameter expansion, command substitution, arithmetic
+ expansion, and quote removal before being assigned to the variable.
+
+ If no command name results, the variable assignments affect the
+current shell environment. In the case of such a command (one that
+consists only of assignment statements and redirections), assignment
+statements are performed before redirections. Otherwise, the variables
+are added to the environment of the executed command and do not affect
+the current shell environment. If any of the assignments attempts to
+assign a value to a readonly variable, an error occurs, and the command
+exits with a non-zero status.
+
+ If no command name results, redirections are performed, but do not
+affect the current shell environment. A redirection error causes the
+command to exit with a non-zero status.
+
+ If there is a command name left after expansion, execution proceeds
+as described below. Otherwise, the command exits. If one of the
+expansions contained a command substitution, the exit status of the
+command is the exit status of the last command substitution performed.
+If there were no command substitutions, the command exits with a zero
+status.
+
+\1f
+File: bashref.info, Node: Command Search and Execution, Next: Command Execution Environment, Prev: Simple Command Expansion, Up: Executing Commands
+
+3.7.2 Command Search and Execution
+----------------------------------
+
+After a command has been split into words, if it results in a simple
+command and an optional list of arguments, the shell performs the
+following actions.
+
+ 1. If the command name contains no slashes, the shell attempts to
+ locate it. If there exists a shell function by that name, that
+ function is invoked as described in *note Shell Functions::.
+
+ 2. If the name does not match a function, the shell searches for it in
+ the list of shell builtins. If a match is found, that builtin is
+ invoked.
+
+ 3. If the name is neither a shell function nor a builtin, and contains
+ no slashes, Bash searches each element of ‘$PATH’ for a directory
+ containing an executable file by that name. Bash uses a hash table
+ to remember the full pathnames of executable files to avoid
+ multiple ‘PATH’ searches (see the description of ‘hash’ in *note
+ Bourne Shell Builtins::). Bash performs a full search of the
+ directories in ‘$PATH’ only if the command is not found in the hash
+ table. If the search is unsuccessful, the shell searches for a
+ defined shell function named ‘command_not_found_handle’. If that
+ function exists, it is invoked in a separate execution environment
+ with the original command and the original command's arguments as
+ its arguments, and the function's exit status becomes the exit
+ status of that subshell. If that function is not defined, the
+ shell prints an error message and returns an exit status of 127.
+
+ 4. If the search is successful, or if the command name contains one or
+ more slashes, the shell executes the named program in a separate
+ execution environment. Argument 0 is set to the name given, and
+ the remaining arguments to the command are set to the arguments
+ supplied, if any.
+
+ 5. If this execution fails because the file is not in executable
+ format, and the file is not a directory, it is assumed to be a
+ “shell script”, a file containing shell commands, and the shell
+ executes it as described in *note Shell Scripts::.
+
+ 6. If the command was not begun asynchronously, the shell waits for
+ the command to complete and collects its exit status.
+
+\1f
+File: bashref.info, Node: Command Execution Environment, Next: Environment, Prev: Command Search and Execution, Up: Executing Commands
+
+3.7.3 Command Execution Environment
+-----------------------------------
+
+The shell has an “execution environment”, which consists of the
+following:
+
+ • Open files inherited by the shell at invocation, as modified by
+ redirections supplied to the ‘exec’ builtin.
+
+ • The current working directory as set by ‘cd’, ‘pushd’, or ‘popd’,
+ or inherited by the shell at invocation.
+
+ • The file creation mode mask as set by ‘umask’ or inherited from the
+ shell's parent.
+
+ • Current traps set by ‘trap’.
+
+ • Shell parameters that are set by variable assignment or with ‘set’
+ or inherited from the shell's parent in the environment.
+
+ • Shell functions defined during execution or inherited from the
+ shell's parent in the environment.
+
+ • Options enabled at invocation (either by default or with
+ command-line arguments) or by ‘set’.
+
+ • Options enabled by ‘shopt’ (*note The Shopt Builtin::).
+
+ • Shell aliases defined with ‘alias’ (*note Aliases::).
+
+ • Various process IDs, including those of background jobs (*note
+ Lists::), the value of ‘$$’, and the value of ‘$PPID’.
+
+ When a simple command other than a builtin or shell function is to be
+executed, it is invoked in a separate execution environment that
+consists of the following. Unless otherwise noted, the values are
+inherited from the shell.
+
+ • The shell's open files, plus any modifications and additions
+ specified by redirections to the command.
+
+ • The current working directory.
+
+ • The file creation mode mask.
+
+ • Shell variables and functions marked for export, along with
+ variables exported for the command, passed in the environment
+ (*note Environment::).
+
+ • Traps caught by the shell are reset to the values inherited from
+ the shell's parent, and traps ignored by the shell are ignored.
+
+ A command invoked in this separate environment cannot affect the
+shell's execution environment.
+
+ A “subshell” is a copy of the shell process.
+
+ Command substitution, commands grouped with parentheses, and
+asynchronous commands are invoked in a subshell environment that is a
+duplicate of the shell environment, except that traps caught by the
+shell are reset to the values that the shell inherited from its parent
+at invocation. Builtin commands that are invoked as part of a pipeline,
+except possibly in the last element depending on the value of the
+‘lastpipe’ shell option (*note The Shopt Builtin::), are also executed
+in a subshell environment. Changes made to the subshell environment
+cannot affect the shell's execution environment.
+
+ When the shell is in POSIX mode, subshells spawned to execute command
+substitutions inherit the value of the ‘-e’ option from the parent
+shell. When not in POSIX mode, Bash clears the ‘-e’ option in such
+subshells See the description of the ‘inherit_errexit’ shell option
+(*note Bash Builtins::) for how to control this behavior when not in
+POSIX mode.
+
+ If a command is followed by a ‘&’ and job control is not active, the
+default standard input for the command is the empty file ‘/dev/null’.
+Otherwise, the invoked command inherits the file descriptors of the
+calling shell as modified by redirections.
+
+\1f
+File: bashref.info, Node: Environment, Next: Exit Status, Prev: Command Execution Environment, Up: Executing Commands
+
+3.7.4 Environment
+-----------------
+
+When a program is invoked it is given an array of strings called the
+“environment”. This is a list of name-value pairs, of the form
+‘name=value’.
+
+ Bash provides several ways to manipulate the environment. On
+invocation, the shell scans its own environment and creates a parameter
+for each name found, automatically marking it for ‘export’ to child
+processes. Executed commands inherit the environment. The ‘export’,
+‘declare -x’, and ‘unset’ commands modify the environment by adding and
+deleting parameters and functions. If the value of a parameter in the
+environment is modified, the new value automatically becomes part of the
+environment, replacing the old. The environment inherited by any
+executed command consists of the shell's initial environment, whose
+values may be modified in the shell, less any pairs removed by the
+‘unset’ and ‘export -n’ commands, plus any additions via the ‘export’
+and ‘declare -x’ commands.
+
+ If any parameter assignment statements, as described in *note Shell
+Parameters::, appear before a simple command, the variable assignments
+are part of that command's environment for as long as it executes.
+These assignment statements affect only the environment seen by that
+command. If these assignments precede a call to a shell function, the
+variables are local to the function and exported to that function's
+children.
+
+ If the ‘-k’ option is set (*note The Set Builtin::), then all
+parameter assignments are placed in the environment for a command, not
+just those that precede the command name.
+
+ When Bash invokes an external command, the variable ‘$_’ is set to
+the full pathname of the command and passed to that command in its
+environment.
+
+\1f
+File: bashref.info, Node: Exit Status, Next: Signals, Prev: Environment, Up: Executing Commands
+
+3.7.5 Exit Status
+-----------------
+
+The exit status of an executed command is the value returned by the
+‘waitpid’ system call or equivalent function. Exit statuses fall
+between 0 and 255, though, as explained below, the shell may use values
+above 125 specially. Exit statuses from shell builtins and compound
+commands are also limited to this range. Under certain circumstances,
+the shell will use special values to indicate specific failure modes.
+
+ For the shell's purposes, a command which exits with a zero exit
+status has succeeded. So while an exit status of zero indicates
+success, a non-zero exit status indicates failure. This seemingly
+counter-intuitive scheme is used so there is one well-defined way to
+indicate success and a variety of ways to indicate various failure
+modes.
+
+ When a command terminates on a fatal signal whose number is N, Bash
+uses the value 128+N as the exit status.
+
+ If a command is not found, the child process created to execute it
+returns a status of 127. If a command is found but is not executable,
+the return status is 126.
+
+ If a command fails because of an error during expansion or
+redirection, the exit status is greater than zero.
+
+ The exit status is used by the Bash conditional commands (*note
+Conditional Constructs::) and some of the list constructs (*note
+Lists::).
+
+ All of the Bash builtins return an exit status of zero if they
+succeed and a non-zero status on failure, so they may be used by the
+conditional and list constructs. All builtins return an exit status of
+2 to indicate incorrect usage, generally invalid options or missing
+arguments.
+
+ The exit status of the last command is available in the special
+parameter $? (*note Special Parameters::).
+
+ Bash itself returns the exit status of the last command executed,
+unless a syntax error occurs, in which case it exits with a non-zero
+value. See also the ‘exit’ builtin command (*note Bourne Shell
+Builtins::).
+
+\1f
+File: bashref.info, Node: Signals, Prev: Exit Status, Up: Executing Commands
+
+3.7.6 Signals
+-------------
+
+When Bash is interactive, in the absence of any traps, it ignores
+‘SIGTERM’ (so that ‘kill 0’ does not kill an interactive shell), and
+catches and handles ‘SIGINT’ (so that the ‘wait’ builtin is
+interruptible). When Bash receives a ‘SIGINT’, it breaks out of any
+executing loops. In all cases, Bash ignores ‘SIGQUIT’. If job control
+is in effect (*note Job Control::), Bash ignores ‘SIGTTIN’, ‘SIGTTOU’,
+and ‘SIGTSTP’.
+
+ The ‘trap’ builtin modifies the shell's signal handling, as described
+below (*note Bourne Shell Builtins::).
+
+ Non-builtin commands Bash executes have signal handlers set to the
+values inherited by the shell from its parent, unless ‘trap’ sets them
+to be ignored, in which case the child process will ignore them as well.
+When job control is not in effect, asynchronous commands ignore ‘SIGINT’
+and ‘SIGQUIT’ in addition to these inherited handlers. Commands run as
+a result of command substitution ignore the keyboard-generated job
+control signals ‘SIGTTIN’, ‘SIGTTOU’, and ‘SIGTSTP’.
+
+ The shell exits by default upon receipt of a ‘SIGHUP’. Before
+exiting, an interactive shell resends the ‘SIGHUP’ to all jobs, running
+or stopped. The shell sends ‘SIGCONT’ to stopped jobs to ensure that
+they receive the ‘SIGHUP’ (*Note Job Control::, for more information
+about running and stopped jobs). To prevent the shell from sending the
+‘SIGHUP’ signal to a particular job, remove it from the jobs table with
+the ‘disown’ builtin (*note Job Control Builtins::) or mark it not to
+receive ‘SIGHUP’ using ‘disown -h’.
+
+ If the ‘huponexit’ shell option has been set using ‘shopt’ (*note The
+Shopt Builtin::), Bash sends a ‘SIGHUP’ to all jobs when an interactive
+login shell exits.
+
+ If Bash is waiting for a command to complete and receives a signal
+for which a trap has been set, it will not execute the trap until the
+command completes. If Bash is waiting for an asynchronous command via
+the ‘wait’ builtin, and it receives a signal for which a trap has been
+set, the ‘wait’ builtin will return immediately with an exit status
+greater than 128, immediately after which the shell executes the trap.
+
+ When job control is not enabled, and Bash is waiting for a foreground
+command to complete, the shell receives keyboard-generated signals such
+as ‘SIGINT’ (usually generated by ‘^C’) that users commonly intend to
+send to that command. This happens because the shell and the command
+are in the same process group as the terminal, and ‘^C’ sends ‘SIGINT’
+to all processes in that process group. Since Bash does not enable job
+control by default when the shell is not interactive, this scenario is
+most common in non-interactive shells.
+
+ When job control is enabled, and Bash is waiting for a foreground
+command to complete, the shell does not receive keyboard-generated
+signals, because it is not in the same process group as the terminal.
+This scenario is most common in interactive shells, where Bash attempts
+to enable job control by default. See *note Job Control::, for a more
+in-depth discussion of process groups.
+
+ When job control is not enabled, and Bash receives ‘SIGINT’ while
+waiting for a foreground command, it waits until that foreground command
+terminates and then decides what to do about the ‘SIGINT’:
+
+ 1. If the command terminates due to the ‘SIGINT’, Bash concludes that
+ the user meant to send the ‘SIGINT’ to the shell as well, and acts
+ on the ‘SIGINT’ (e.g., by running a ‘SIGINT’ trap, exiting a
+ non-interactive shell, or returning to the top level to read a new
+ command).
+
+ 2. If the command does not terminate due to ‘SIGINT’, the program
+ handled the ‘SIGINT’ itself and did not treat it as a fatal signal.
+ In that case, Bash does not treat ‘SIGINT’ as a fatal signal,
+ either, instead assuming that the ‘SIGINT’ was used as part of the
+ program's normal operation (e.g., ‘emacs’ uses it to abort editing
+ commands) or deliberately discarded. However, Bash will run any
+ trap set on ‘SIGINT’, as it does with any other trapped signal it
+ receives while it is waiting for the foreground command to
+ complete, for compatibility.
+
+ When job control is enabled, Bash does not receive keyboard-generated
+signals such as ‘SIGINT’ while it is waiting for a foreground command.
+An interactive shell does not pay attention to the ‘SIGINT’, even if the
+foreground command terminates as a result, other than noting its exit
+status. If the shell is not interactive, and the foreground command
+terminates due to the ‘SIGINT’, Bash pretends it received the ‘SIGINT’
+itself (scenario 1 above), for compatibility.
+
+\1f
+File: bashref.info, Node: Shell Scripts, Prev: Executing Commands, Up: Basic Shell Features
+
+3.8 Shell Scripts
+=================
+
+A shell script is a text file containing shell commands. When such a
+file is used as the first non-option argument when invoking Bash, and
+neither the ‘-c’ nor ‘-s’ option is supplied (*note Invoking Bash::),
+Bash reads and executes commands from the file, then exits. This mode
+of operation creates a non-interactive shell. If the filename does not
+contain any slashes, the shell first searches for the file in the
+current directory, and looks in the directories in ‘$PATH’ if not found
+there.
+
+ Bash tries to determine whether the file is a text file or a binary,
+and will not execute files it determines to be binaries.
+
+ When Bash runs a shell script, it sets the special parameter ‘0’ to
+the name of the file, rather than the name of the shell, and the
+positional parameters are set to the remaining arguments, if any are
+given. If no additional arguments are supplied, the positional
+parameters are unset.
+
+ A shell script may be made executable by using the ‘chmod’ command to
+turn on the execute bit. When Bash finds such a file while searching
+the ‘$PATH’ for a command, it creates a new instance of itself to
+execute it. In other words, executing
+ filename ARGUMENTS
+is equivalent to executing
+ bash filename ARGUMENTS
+
+if ‘filename’ is an executable shell script. This subshell
+reinitializes itself, so that the effect is as if a new shell had been
+invoked to interpret the script, with the exception that the locations
+of commands remembered by the parent (see the description of ‘hash’ in
+*note Bourne Shell Builtins::) are retained by the child.
+
+ The GNU operating system, and most versions of Unix, make this a part
+of the operating system's command execution mechanism. If the first
+line of a script begins with the two characters ‘#!’, the remainder of
+the line specifies an interpreter for the program and, depending on the
+operating system, one or more optional arguments for that interpreter.
+Thus, you can specify Bash, ‘awk’, Perl, or some other interpreter and
+write the rest of the script file in that language.
+
+ The arguments to the interpreter consist of one or more optional
+arguments following the interpreter name on the first line of the script
+file, followed by the name of the script file, followed by the rest of
+the arguments supplied to the script. The details of how the
+interpreter line is split into an interpreter name and a set of
+arguments vary across systems. Bash will perform this action on
+operating systems that do not handle it themselves. Note that some
+older versions of Unix limit the interpreter name and a single argument
+to a maximum of 32 characters, so it's not portable to assume that using
+more than one argument will work.
+
+ Bash scripts often begin with ‘#! /bin/bash’ (assuming that Bash has
+been installed in ‘/bin’), since this ensures that Bash will be used to
+interpret the script, even if it is executed under another shell. It's
+a common idiom to use ‘env’ to find ‘bash’ even if it's been installed
+in another directory: ‘#!/usr/bin/env bash’ will find the first
+occurrence of ‘bash’ in ‘$PATH’.
+
+\1f
+File: bashref.info, Node: Shell Builtin Commands, Next: Shell Variables, Prev: Basic Shell Features, Up: Top
+
+4 Shell Builtin Commands
+************************
+
+* Menu:
+
+* Bourne Shell Builtins:: Builtin commands inherited from the Bourne
+ Shell.
+* Bash Builtins:: Table of builtins specific to Bash.
+* Modifying Shell Behavior:: Builtins to modify shell attributes and
+ optional behavior.
+* Special Builtins:: Builtin commands classified specially by
+ POSIX.
+
+Builtin commands are contained within the shell itself. When the name
+of a builtin command is used as the first word of a simple command
+(*note Simple Commands::), the shell executes the command directly,
+without invoking another program. Builtin commands are necessary to
+implement functionality impossible or inconvenient to obtain with
+separate utilities.
+
+ This section briefly describes the builtins which Bash inherits from
+the Bourne Shell, as well as the builtin commands which are unique to or
+have been extended in Bash.
+
+ Several builtin commands are described in other chapters: builtin
+commands which provide the Bash interface to the job control facilities
+(*note Job Control Builtins::), the directory stack (*note Directory
+Stack Builtins::), the command history (*note Bash History Builtins::),
+and the programmable completion facilities (*note Programmable
+Completion Builtins::).
+
+ Many of the builtins have been extended by POSIX or Bash.
+
+ Unless otherwise noted, each builtin command documented as accepting
+options preceded by ‘-’ accepts ‘--’ to signify the end of the options.
+The ‘:’, ‘true’, ‘false’, and ‘test’/‘[’ builtins do not accept options
+and do not treat ‘--’ specially. The ‘exit’, ‘logout’, ‘return’,
+‘break’, ‘continue’, ‘let’, and ‘shift’ builtins accept and process
+arguments beginning with ‘-’ without requiring ‘--’. Other builtins
+that accept arguments but are not specified as accepting options
+interpret arguments beginning with ‘-’ as invalid options and require
+‘--’ to prevent this interpretation.
+
+\1f
+File: bashref.info, Node: Bourne Shell Builtins, Next: Bash Builtins, Up: Shell Builtin Commands
+
+4.1 Bourne Shell Builtins
+=========================
+
+The following shell builtin commands are inherited from the Bourne
+Shell. These commands are implemented as specified by the POSIX
+standard.
+
+‘: (a colon)’
+ : [ARGUMENTS]
+
+ Do nothing beyond expanding ARGUMENTS and performing redirections.
+ The return status is zero.
+
+‘. (a period)’
+ . [-p PATH] FILENAME [ARGUMENTS]
+
+ The ‘.’ command reads and execute commands from the FILENAME
+ argument in the current shell context.
+
+ If FILENAME does not contain a slash, ‘.’ searches for it. If ‘-p’
+ is supplied, ‘.’ treats PATH as a colon-separated list of
+ directories in which to find FILENAME; otherwise, ‘.’ uses the
+ directories in ‘PATH’ to find FILENAME. FILENAME does not need to
+ be executable. When Bash is not in POSIX mode, it searches the
+ current directory if FILENAME is not found in ‘$PATH’, but does not
+ search the current directory if ‘-p’ is supplied. If the
+ ‘sourcepath’ option (*note The Shopt Builtin::) is turned off, ‘.’
+ does not search ‘PATH’.
+
+ If any ARGUMENTS are supplied, they become the positional
+ parameters when FILENAME is executed. Otherwise the positional
+ parameters are unchanged.
+
+ If the ‘-T’ option is enabled, ‘.’ inherits any trap on ‘DEBUG’; if
+ it is not, any ‘DEBUG’ trap string is saved and restored around the
+ call to ‘.’, and ‘.’ unsets the ‘DEBUG’ trap while it executes. If
+ ‘-T’ is not set, and the sourced file changes the ‘DEBUG’ trap, the
+ new value persists after ‘.’ completes. The return status is the
+ exit status of the last command executed from FILENAME, or zero if
+ no commands are executed. If FILENAME is not found, or cannot be
+ read, the return status is non-zero. This builtin is equivalent to
+ ‘source’.
+
+‘break’
+ break [N]
+
+ Exit from a ‘for’, ‘while’, ‘until’, or ‘select’ loop. If N is
+ supplied, ‘break’ exits the Nth enclosing loop. N must be greater
+ than or equal to 1. The return status is zero unless N is not
+ greater than or equal to 1.
+
+‘cd’
+ cd [-L] [-@] [DIRECTORY]
+ cd -P [-e] [-@] [DIRECTORY]
+
+ Change the current working directory to DIRECTORY. If DIRECTORY is
+ not supplied, the value of the ‘HOME’ shell variable is used as
+ DIRECTORY. If DIRECTORY is the empty string, ‘cd’ treats it as an
+ error. If the shell variable ‘CDPATH’ exists, and DIRECTORY does
+ not begin with a slash, ‘cd’ uses it as a search path: ‘cd’
+ searches each directory name in ‘CDPATH’ for DIRECTORY, with
+ alternative directory names in ‘CDPATH’ separated by a colon (‘:’).
+ A null directory name in ‘CDPATH’ means the same thing as the
+ current directory.
+
+ The ‘-P’ option means not to follow symbolic links: symbolic links
+ are resolved while ‘cd’ is traversing DIRECTORY and before
+ processing an instance of ‘..’ in DIRECTORY.
+
+ By default, or when the ‘-L’ option is supplied, symbolic links in
+ DIRECTORY are resolved after ‘cd’ processes an instance of ‘..’ in
+ DIRECTORY.
+
+ If ‘..’ appears in DIRECTORY, ‘cd’ processes it by removing the
+ immediately preceding pathname component, back to a slash or the
+ beginning of DIRECTORY, and verifying that the portion of DIRECTORY
+ it has processed to that point is still a valid directory name
+ after removing the pathname component. If it is not a valid
+ directory name, ‘cd’ returns a non-zero status.
+
+ If the ‘-e’ option is supplied with ‘-P’ and ‘cd’ cannot
+ successfully determine the current working directory after a
+ successful directory change, it returns a non-zero status.
+
+ On systems that support it, the ‘-@’ option presents the extended
+ attributes associated with a file as a directory.
+
+ If DIRECTORY is ‘-’, it is converted to ‘$OLDPWD’ before attempting
+ the directory change.
+
+ If ‘cd’ uses a non-empty directory name from ‘CDPATH’, or if ‘-’ is
+ the first argument, and the directory change is successful, ‘cd’
+ writes the absolute pathname of the new working directory to the
+ standard output.
+
+ If the directory change is successful, ‘cd’ sets the value of the
+ ‘PWD’ environment variable to the new directory name, and sets the
+ ‘OLDPWD’ environment variable to the value of the current working
+ directory before the change.
+
+ The return status is zero if the directory is successfully changed,
+ non-zero otherwise.
+
+‘continue’
+ continue [N]
+
+ ‘continue’ resumes the next iteration of an enclosing ‘for’,
+ ‘while’, ‘until’, or ‘select’ loop. If N is supplied, Bash resumes
+ the execution of the Nth enclosing loop. N must be greater than or
+ equal to 1. The return status is zero unless N is not greater than
+ or equal to 1.
+
+‘eval’
+ eval [ARGUMENTS]
+
+ The ARGUMENTS are concatenated together into a single command,
+ separated by spaces. Bash then reads and executes this command and
+ returns its exit status as the exit status of ‘eval’. If there are
+ no arguments or only empty arguments, the return status is zero.
+
+‘exec’
+ exec [-cl] [-a NAME] [COMMAND [ARGUMENTS]]
+
+ If COMMAND is supplied, it replaces the shell without creating a
+ new process. COMMAND cannot be a shell builtin or function. The
+ ARGUMENTS become the arguments to COMMAND If the ‘-l’ option is
+ supplied, the shell places a dash at the beginning of the zeroth
+ argument passed to COMMAND. This is what the ‘login’ program does.
+ The ‘-c’ option causes COMMAND to be executed with an empty
+ environment. If ‘-a’ is supplied, the shell passes NAME as the
+ zeroth argument to COMMAND.
+
+ If COMMAND cannot be executed for some reason, a non-interactive
+ shell exits, unless the ‘execfail’ shell option is enabled. In
+ that case, it returns a non-zero status. An interactive shell
+ returns a non-zero status if the file cannot be executed. A
+ subshell exits unconditionally if ‘exec’ fails.
+
+ If COMMAND is not specified, redirections may be used to affect the
+ current shell environment. If there are no redirection errors, the
+ return status is zero; otherwise the return status is non-zero.
+
+‘exit’
+ exit [N]
+
+ Exit the shell, returning a status of N to the shell's parent. If
+ N is omitted, the exit status is that of the last command executed.
+ Any trap on ‘EXIT’ is executed before the shell terminates.
+
+‘export’
+ export [-fn] [-p] [NAME[=VALUE]]
+
+ Mark each NAME to be passed to subsequently executed commands in
+ the environment. If the ‘-f’ option is supplied, the NAMEs refer
+ to shell functions; otherwise the names refer to shell variables.
+
+ The ‘-n’ option means to unexport each name: no longer mark it for
+ export. If no NAMEs are supplied, or if only the ‘-p’ option is
+ given, ‘export’ displays a list of names of all exported variables
+ on the standard output. Using ‘-p’ and ‘-f’ together displays
+ exported functions. The ‘-p’ option displays output in a form that
+ may be reused as input.
+
+ ‘export’ allows the value of a variable to be set at the same time
+ it is exported or unexported by following the variable name with
+ =VALUE. This sets the value of the variable is to VALUE while
+ modifying the export attribute.
+
+ The return status is zero unless an invalid option is supplied, one
+ of the names is not a valid shell variable name, or ‘-f’ is
+ supplied with a name that is not a shell function.
+
+‘false’
+ false
+
+ Does nothing; returns a non-zero status.
+
+‘getopts’
+ getopts OPTSTRING NAME [ARG ...]
+
+ ‘getopts’ is used by shell scripts or functions to parse positional
+ parameters and obtain options and their arguments. OPTSTRING
+ contains the option characters to be recognized; if a character is
+ followed by a colon, the option is expected to have an argument,
+ which should be separated from it by whitespace. The colon (‘:’)
+ and question mark (‘?’) may not be used as option characters.
+
+ Each time it is invoked, ‘getopts’ places the next option in the
+ shell variable NAME, initializing NAME if it does not exist, and
+ the index of the next argument to be processed into the variable
+ ‘OPTIND’. ‘OPTIND’ is initialized to 1 each time the shell or a
+ shell script is invoked. When an option requires an argument,
+ ‘getopts’ places that argument into the variable ‘OPTARG’.
+
+ The shell does not reset ‘OPTIND’ automatically; it must be
+ manually reset between multiple calls to ‘getopts’ within the same
+ shell invocation to use a new set of parameters.
+
+ When it reaches the end of options, ‘getopts’ exits with a return
+ value greater than zero. ‘OPTIND’ is set to the index of the first
+ non-option argument, and NAME is set to ‘?’.
+
+ ‘getopts’ normally parses the positional parameters, but if more
+ arguments are supplied as ARG values, ‘getopts’ parses those
+ instead.
+
+ ‘getopts’ can report errors in two ways. If the first character of
+ OPTSTRING is a colon, ‘getopts’ uses _silent_ error reporting. In
+ normal operation, ‘getopts’ prints diagnostic messages when it
+ encounters invalid options or missing option arguments. If the
+ variable ‘OPTERR’ is set to 0, ‘getopts’ does not display any error
+ messages, even if the first character of ‘optstring’ is not a
+ colon.
+
+ If ‘getopts’ detects an invalid option, it places ‘?’ into NAME
+ and, if not silent, prints an error message and unsets ‘OPTARG’.
+ If ‘getopts’ is silent, it assigns the option character found to
+ ‘OPTARG’ and does not print a diagnostic message.
+
+ If a required argument is not found, and ‘getopts’ is not silent,
+ it sets the value of NAME to a question mark (‘?’), unsets
+ ‘OPTARG’, and prints a diagnostic message. If ‘getopts’ is silent,
+ it sets the value of NAME to a colon (‘:’), and sets ‘OPTARG’ to
+ the option character found.
+
+ ‘getopts’ returns true if an option, specified or unspecified, is
+ found. It returns false when it encounters the end of options or
+ if an error occurs.
+
+‘hash’
+ hash [-r] [-p FILENAME] [-dt] [NAME]
+
+ Each time ‘hash’ is invoked, it remembers the full filenames of the
+ commands specified as NAME arguments, so they need not be searched
+ for on subsequent invocations. The commands are found by searching
+ through the directories listed in ‘$PATH’. Any
+ previously-remembered filename associated with NAME is discarded.
+ The ‘-p’ option inhibits the path search, and ‘hash’ uses FILENAME
+ as the location of NAME.
+
+ The ‘-r’ option causes the shell to forget all remembered
+ locations. Assigning to the ‘PATH’ variable also clears all hashed
+ filenames. The ‘-d’ option causes the shell to forget the
+ remembered location of each NAME.
+
+ If the ‘-t’ option is supplied, ‘hash’ prints the full pathname
+ corresponding to each NAME. If multiple NAME arguments are
+ supplied with ‘-t’, ‘hash’ prints each NAME before the
+ corresponding hashed full path. The ‘-l’ option displays output in
+ a format that may be reused as input.
+
+ If no arguments are given, or if only ‘-l’ is supplied, ‘hash’
+ prints information about remembered commands. The ‘-t’, ‘-d’, and
+ ‘-p’ options (the options that act on the NAME arguments) are
+ mutually exclusive. Only one will be active. If more than one is
+ supplied, ‘-t’ has higher priority than ‘-p’, and both have higher
+ priority than ‘-d’.
+
+ The return status is zero unless a NAME is not found or an invalid
+ option is supplied.
+
+‘pwd’
+ pwd [-LP]
+
+ Print the absolute pathname of the current working directory. If
+ the ‘-P’ option is supplied, or the ‘-o physical’ option to the
+ ‘set’ builtin (*note The Set Builtin::) is enabled, the pathname
+ printed will not contain symbolic links. If the ‘-L’ option is
+ supplied, the pathname printed may contain symbolic links. The
+ return status is zero unless an error is encountered while
+ determining the name of the current directory or an invalid option
+ is supplied.
+
+‘readonly’
+ readonly [-aAf] [-p] [NAME[=VALUE]] ...
+
+ Mark each NAME as readonly. The values of these names may not be
+ changed by subsequent assignment or unset. If the ‘-f’ option is
+ supplied, each NAME refers to a shell function. The ‘-a’ option
+ means each NAME refers to an indexed array variable; the ‘-A’
+ option means each NAME refers to an associative array variable. If
+ both options are supplied, ‘-A’ takes precedence. If no NAME
+ arguments are supplied, or if the ‘-p’ option is supplied, print a
+ list of all readonly names. The other options may be used to
+ restrict the output to a subset of the set of readonly names. The
+ ‘-p’ option displays output in a format that may be reused as
+ input.
+
+ ‘readonly’ allows the value of a variable to be set at the same
+ time the readonly attribute is changed by following the variable
+ name with =VALUE. This sets the value of the variable is to VALUE
+ while modifying the readonly attribute.
+
+ The return status is zero unless an invalid option is supplied, one
+ of the NAME arguments is not a valid shell variable or function
+ name, or the ‘-f’ option is supplied with a name that is not a
+ shell function.
+
+‘return’
+ return [N]
+
+ Stop executing a shell function or sourced file and return the
+ value N to its caller. If N is not supplied, the return value is
+ the exit status of the last command executed. If ‘return’ is
+ executed by a trap handler, the last command used to determine the
+ status is the last command executed before the trap handler. If
+ ‘return’ is executed during a ‘DEBUG’ trap, the last command used
+ to determine the status is the last command executed by the trap
+ handler before ‘return’ was invoked.
+
+ When ‘return’ is used to terminate execution of a script being
+ executed with the ‘.’ (‘source’) builtin, it returns either N or
+ the exit status of the last command executed within the script as
+ the exit status of the script. If N is supplied, the return value
+ is its least significant 8 bits.
+
+ Any command associated with the ‘RETURN’ trap is executed before
+ execution resumes after the function or script.
+
+ The return status is non-zero if ‘return’ is supplied a non-numeric
+ argument or is used outside a function and not during the execution
+ of a script by ‘.’ or ‘source’.
+
+‘shift’
+ shift [N]
+
+ Shift the positional parameters to the left by N: the positional
+ parameters from N+1 ... ‘$#’ are renamed to ‘$1’ ... ‘$#’-N.
+ Parameters represented by the numbers ‘$#’ down to ‘$#’-N+1 are
+ unset. N must be a non-negative number less than or equal to ‘$#’.
+ If N is not supplied, it is assumed to be 1. If N is zero or
+ greater than ‘$#’, the positional parameters are not changed. The
+ return status is zero unless N is greater than ‘$#’ or less than
+ zero, non-zero otherwise.
+
+‘test’
+‘[’
+ test EXPR
+
+ Evaluate a conditional expression EXPR and return a status of 0
+ (true) or 1 (false). Each operator and operand must be a separate
+ argument. Expressions are composed of the primaries described
+ below in *note Bash Conditional Expressions::. ‘test’ does not
+ accept any options, nor does it accept and ignore an argument of
+ ‘--’ as signifying the end of options. When using the ‘[’ form,
+ the last argument to the command must be a ‘]’.
+
+ Expressions may be combined using the following operators, listed
+ in decreasing order of precedence. The evaluation depends on the
+ number of arguments; see below. ‘test’ uses operator precedence
+ when there are five or more arguments.
+
+ ‘! EXPR’
+ True if EXPR is false.
+
+ ‘( EXPR )’
+ Returns the value of EXPR. This may be used to override
+ normal operator precedence.
+
+ ‘EXPR1 -a EXPR2’
+ True if both EXPR1 and EXPR2 are true.
+
+ ‘EXPR1 -o EXPR2’
+ True if either EXPR1 or EXPR2 is true.
+
+ The ‘test’ and ‘[’ builtins evaluate conditional expressions using
+ a set of rules based on the number of arguments.
+
+ 0 arguments
+ The expression is false.
+
+ 1 argument
+ The expression is true if, and only if, the argument is not
+ null.
+
+ 2 arguments
+ If the first argument is ‘!’, the expression is true if and
+ only if the second argument is null. If the first argument is
+ one of the unary conditional operators (*note Bash Conditional
+ Expressions::), the expression is true if the unary test is
+ true. If the first argument is not a valid unary operator,
+ the expression is false.
+
+ 3 arguments
+ The following conditions are applied in the order listed.
+
+ 1. If the second argument is one of the binary conditional
+ operators (*note Bash Conditional Expressions::), the
+ result of the expression is the result of the binary test
+ using the first and third arguments as operands. The
+ ‘-a’ and ‘-o’ operators are considered binary operators
+ when there are three arguments.
+ 2. If the first argument is ‘!’, the value is the negation
+ of the two-argument test using the second and third
+ arguments.
+ 3. If the first argument is exactly ‘(’ and the third
+ argument is exactly ‘)’, the result is the one-argument
+ test of the second argument.
+ 4. Otherwise, the expression is false.
+
+ 4 arguments
+ The following conditions are applied in the order listed.
+
+ 1. If the first argument is ‘!’, the result is the negation
+ of the three-argument expression composed of the
+ remaining arguments.
+ 2. If the first argument is exactly ‘(’ and the fourth
+ argument is exactly ‘)’, the result is the two-argument
+ test of the second and third arguments.
+ 3. Otherwise, the expression is parsed and evaluated
+ according to precedence using the rules listed above.
+
+ 5 or more arguments
+ The expression is parsed and evaluated according to precedence
+ using the rules listed above.
+
+ If the shell is in POSIX mode, or if the expression is part of the
+ ‘[[’ command, the ‘<’ and ‘>’ operators sort using the current
+ locale. If the shell is not in POSIX mode, the ‘test’ and ‘[’
+ commands sort lexicographically using ASCII ordering.
+
+ The historical operator-precedence parsing with 4 or more arguments
+ can lead to ambiguities when it encounters strings that look like
+ primaries. The POSIX standard has deprecated the ‘-a’ and ‘-o’
+ primaries and enclosing expressions within parentheses. Scripts
+ should no longer use them. It's much more reliable to restrict
+ test invocations to a single primary, and to replace uses of ‘-a’
+ and ‘-o’ with the shell's ‘&&’ and ‘||’ list operators. For
+ example, use
+
+ test -n string1 && test -n string2
+
+ instead of
+
+ test -n string1 -a -n string2
+
+‘times’
+ times
+
+ Print out the user and system times used by the shell and its
+ children. The return status is zero.
+
+‘trap’
+ trap [-lpP] [ACTION] [SIGSPEC ...]
+
+ The ACTION is a command that is read and executed when the shell
+ receives any of the signals SIGSPEC. If ACTION is absent (and
+ there is a single SIGSPEC) or equal to ‘-’, each specified
+ SIGSPEC's disposition is reset to the value it had when the shell
+ was started. If ACTION is the null string, then the signal
+ specified by each SIGSPEC is ignored by the shell and commands it
+ invokes.
+
+ If no arguments are supplied, ‘trap’ prints the actions associated
+ with each trapped signal as a set of ‘trap’ commands that can be
+ reused as shell input to restore the current signal dispositions.
+
+ If ACTION is not present and ‘-p’ has been supplied, ‘trap’
+ displays the trap commands associated with each SIGSPEC, or, if no
+ SIGSPECs are supplied, for all trapped signals, as a set of ‘trap’
+ commands that can be reused as shell input to restore the current
+ signal dispositions. The ‘-P’ option behaves similarly, but
+ displays only the actions associated with each SIGSPEC argument.
+ ‘-P’ requires at least one SIGSPEC argument. The ‘-P’ or ‘-p’
+ options may be used in a subshell environment (e.g., command
+ substitution) and, as long as they are used before ‘trap’ is used
+ to change a signal's handling, will display the state of its
+ parent's traps.
+
+ The ‘-l’ option prints a list of signal names and their
+ corresponding numbers. Each SIGSPEC is either a signal name or a
+ signal number. Signal names are case insensitive and the ‘SIG’
+ prefix is optional. If ‘-l’ is supplied with no SIGSPEC arguments,
+ it prints a list of valid signal names.
+
+ If a SIGSPEC is ‘0’ or ‘EXIT’, ACTION is executed when the shell
+ exits. If a SIGSPEC is ‘DEBUG’, ACTION is executed before every
+ simple command, ‘for’ command, ‘case’ command, ‘select’ command, ((
+ arithmetic command, [[ conditional command, arithmetic ‘for’
+ command, and before the first command executes in a shell function.
+ Refer to the description of the ‘extdebug’ shell option (*note The
+ Shopt Builtin::) for details of its effect on the ‘DEBUG’ trap. If
+ a SIGSPEC is ‘RETURN’, ACTION is executed each time a shell
+ function or a script executed with the ‘.’ or ‘source’ builtins
+ finishes executing.
+
+ If a SIGSPEC is ‘ERR’, ACTION is executed whenever a pipeline
+ (which may consist of a single simple command), a list, or a
+ compound command returns a non-zero exit status, subject to the
+ following conditions. The ‘ERR’ trap is not executed if the failed
+ command is part of the command list immediately following an
+ ‘until’ or ‘while’ reserved word, part of the test following the
+ ‘if’ or ‘elif’ reserved words, part of a command executed in a ‘&&’
+ or ‘||’ list except the command following the final ‘&&’ or ‘||’,
+ any command in a pipeline but the last, (subject to the state of
+ the ‘pipefail’ shell option), or if the command's return status is
+ being inverted using ‘!’. These are the same conditions obeyed by
+ the ‘errexit’ (‘-e’) option.
+
+ When the shell is not interactive, signals ignored upon entry to a
+ non-interactive shell cannot be trapped or reset. Interactive
+ shells permit trapping signals ignored on entry. Trapped signals
+ that are not being ignored are reset to their original values in a
+ subshell or subshell environment when one is created.
+
+ The return status is zero unless a SIGSPEC does not specify a valid
+ signal; non-zero otherwise.
+
+‘true’
+ true
+
+ Does nothing, returns a 0 status.
+
+‘umask’
+ umask [-p] [-S] [MODE]
+
+ Set the shell process's file creation mask to MODE. If MODE begins
+ with a digit, it is interpreted as an octal number; if not, it is
+ interpreted as a symbolic mode mask similar to that accepted by the
+ ‘chmod’ command. If MODE is omitted, ‘umask’ prints the current
+ value of the mask. If the ‘-S’ option is supplied without a MODE
+ argument, ‘umask’ prints the mask in a symbolic format; the default
+ output is an octal number. If the ‘-p’ option is supplied, and
+ MODE is omitted, the output is in a form that may be reused as
+ input. The return status is zero if the mode is successfully
+ changed or if no MODE argument is supplied, and non-zero otherwise.
+
+ Note that when the mode is interpreted as an octal number, each
+ number of the umask is subtracted from ‘7’. Thus, a umask of ‘022’
+ results in permissions of ‘755’.
+
+‘unset’
+ unset [-fnv] [NAME]
+
+ Remove each variable or function NAME. If the ‘-v’ option is
+ given, each NAME refers to a shell variable and that variable is
+ removed. If the ‘-f’ option is given, the NAMEs refer to shell
+ functions, and the function definition is removed. If the ‘-n’
+ option is supplied, and NAME is a variable with the ‘nameref’
+ attribute, NAME will be unset rather than the variable it
+ references. ‘-n’ has no effect if the ‘-f’ option is supplied. If
+ no options are supplied, each NAME refers to a variable; if there
+ is no variable by that name, a function with that name, if any, is
+ unset. Readonly variables and functions may not be unset. When
+ variables or functions are removed, they are also removed from the
+ environment passed to subsequent commands. Some shell variables
+ may not be unset. Some shell variables lose their special behavior
+ if they are unset; such behavior is noted in the description of the
+ individual variables. The return status is zero unless a NAME is
+ readonly or may not be unset.
+
+\1f
+File: bashref.info, Node: Bash Builtins, Next: Modifying Shell Behavior, Prev: Bourne Shell Builtins, Up: Shell Builtin Commands
+
+4.2 Bash Builtin Commands
+=========================
+
+This section describes builtin commands which are unique to or have been
+extended in Bash. Some of these commands are specified in the POSIX
+standard.
+
+‘alias’
+ alias [-p] [NAME[=VALUE] ...]
+
+ Without arguments or with the ‘-p’ option, ‘alias’ prints the list
+ of aliases on the standard output in a form that allows them to be
+ reused as input. If arguments are supplied, define an alias for
+ each NAME whose VALUE is given. If no VALUE is given, print the
+ name and value of the alias NAME. A trailing space in VALUE causes
+ the next word to be checked for alias substitution when the alias
+ is expanded during command parsing. ‘alias’ returns true unless a
+ NAME is given (without a corresponding =VALUE) for which no alias
+ has been defined. Aliases are described in *note Aliases::.
+
+‘bind’
+ bind [-m KEYMAP] [-lsvSVX]
+ bind [-m KEYMAP] [-q FUNCTION] [-u FUNCTION] [-r KEYSEQ]
+ bind [-m KEYMAP] -f FILENAME
+ bind [-m KEYMAP] -x KEYSEQ[: ]SHELL-COMMAND
+ bind [-m KEYMAP] KEYSEQ:FUNCTION-NAME
+ bind [-m KEYMAP] KEYSEQ:READLINE-COMMAND
+ bind [-m KEYMAP] -p|-P [READLINE-COMMAND]
+ bind READLINE-COMMAND-LINE
+
+ Display current Readline (*note Command Line Editing::) key and
+ function bindings, bind a key sequence to a Readline function or
+ macro or to a shell command, or set a Readline variable. Each
+ non-option argument is a key binding or command as it would appear
+ in a Readline initialization file (*note Readline Init File::), but
+ each binding or command must be passed as a separate argument;
+ e.g., ‘"\C-x\C-r":re-read-init-file’.
+
+ In the following descriptions, options that display output in a
+ form available to be re-read format their output as commands that
+ would appear in a Readline initialization file or that would be
+ supplied as individual arguments to a ‘bind’ command.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-m KEYMAP’
+ Use KEYMAP as the keymap to be affected by the subsequent
+ bindings. Acceptable KEYMAP names are ‘emacs’,
+ ‘emacs-standard’, ‘emacs-meta’, ‘emacs-ctlx’, ‘vi’, ‘vi-move’,
+ ‘vi-command’, and ‘vi-insert’. ‘vi’ is equivalent to
+ ‘vi-command’ (‘vi-move’ is also a synonym); ‘emacs’ is
+ equivalent to ‘emacs-standard’.
+
+ ‘-l’
+ List the names of all Readline functions.
+
+ ‘-p’
+ Display Readline function names and bindings in such a way
+ that they can be used as an argument to a subsequent ‘bind’
+ command or in a Readline initialization file. If arguments
+ remain after option processing, ‘bind’ treats them as readline
+ command names and restricts output to those names.
+
+ ‘-P’
+ List current Readline function names and bindings. If
+ arguments remain after option processing, ‘bind’ treats them
+ as readline command names and restricts output to those names.
+
+ ‘-s’
+ Display Readline key sequences bound to macros and the strings
+ they output in such a way that they can be used as an argument
+ to a subsequent ‘bind’ command or in a Readline initialization
+ file.
+
+ ‘-S’
+ Display Readline key sequences bound to macros and the strings
+ they output.
+
+ ‘-v’
+ Display Readline variable names and values in such a way that
+ they can be used as an argument to a subsequent ‘bind’ command
+ or in a Readline initialization file.
+
+ ‘-V’
+ List current Readline variable names and values.
+
+ ‘-f FILENAME’
+ Read key bindings from FILENAME.
+
+ ‘-q FUNCTION’
+ Display key sequences that invoke the named Readline FUNCTION.
+
+ ‘-u FUNCTION’
+ Unbind all key sequences bound to the named Readline FUNCTION.
+
+ ‘-r KEYSEQ’
+ Remove any current binding for KEYSEQ.
+
+ ‘-x KEYSEQ:SHELL-COMMAND’
+ Cause SHELL-COMMAND to be executed whenever KEYSEQ is entered.
+ The separator between KEYSEQ and SHELL-COMMAND is either
+ whitespace or a colon optionally followed by whitespace. If
+ the separator is whitespace, SHELL-COMMAND must be enclosed in
+ double quotes and Readline expands any of its special
+ backslash-escapes in SHELL-COMMAND before saving it. If the
+ separator is a colon, any enclosing double quotes are
+ optional, and Readline does not expand the command string
+ before saving it. Since the entire key binding expression
+ must be a single argument, it should be enclosed in single
+ quotes. When SHELL-COMMAND is executed, the shell sets the
+ ‘READLINE_LINE’ variable to the contents of the Readline line
+ buffer and the ‘READLINE_POINT’ and ‘READLINE_MARK’ variables
+ to the current location of the insertion point and the saved
+ insertion point (the MARK), respectively. The shell assigns
+ any numeric argument the user supplied to the
+ ‘READLINE_ARGUMENT’ variable. If there was no argument, that
+ variable is not set. If the executed command changes the
+ value of any of ‘READLINE_LINE’, ‘READLINE_POINT’, or
+ ‘READLINE_MARK’, those new values will be reflected in the
+ editing state.
+
+ ‘-X’
+ List all key sequences bound to shell commands and the
+ associated commands in a format that can be reused as an
+ argument to a subsequent ‘bind’ command.
+
+ The return status is zero unless an invalid option is supplied or
+ an error occurs.
+
+‘builtin’
+ builtin [SHELL-BUILTIN [ARGS]]
+
+ Execute the specified shell builtin SHELL-BUILTIN, passing it ARGS,
+ and return its exit status. This is useful when defining a shell
+ function with the same name as a shell builtin, retaining the
+ functionality of the builtin within the function. The return
+ status is non-zero if SHELL-BUILTIN is not a shell builtin command.
+
+‘caller’
+ caller [EXPR]
+
+ Returns the context of any active subroutine call (a shell function
+ or a script executed with the ‘.’ or ‘source’ builtins).
+
+ Without EXPR, ‘caller’ displays the line number and source filename
+ of the current subroutine call. If a non-negative integer is
+ supplied as EXPR, ‘caller’ displays the line number, subroutine
+ name, and source file corresponding to that position in the current
+ execution call stack. This extra information may be used, for
+ example, to print a stack trace. The current frame is frame 0.
+
+ The return value is 0 unless the shell is not executing a
+ subroutine call or EXPR does not correspond to a valid position in
+ the call stack.
+
+‘command’
+ command [-pVv] COMMAND [ARGUMENTS ...]
+
+ The ‘command’ builtin runs COMMAND with ARGUMENTS ignoring any
+ shell function named COMMAND. Only shell builtin commands or
+ commands found by searching the ‘PATH’ are executed. If there is a
+ shell function named ‘ls’, running ‘command ls’ within the function
+ will execute the external command ‘ls’ instead of calling the
+ function recursively. The ‘-p’ option means to use a default value
+ for ‘PATH’ that is guaranteed to find all of the standard
+ utilities. The return status in this case is 127 if COMMAND cannot
+ be found or an error occurred, and the exit status of COMMAND
+ otherwise.
+
+ If either the ‘-V’ or ‘-v’ option is supplied, ‘command’ prints a
+ description of COMMAND. The ‘-v’ option displays a single word
+ indicating the command or file name used to invoke COMMAND; the
+ ‘-V’ option produces a more verbose description. In this case, the
+ return status is zero if COMMAND is found, and non-zero if not.
+
+‘declare’
+ declare [-aAfFgiIlnrtux] [-p] [NAME[=VALUE] ...]
+
+ Declare variables and give them attributes. If no NAMEs are given,
+ then display the values of variables or shell functions instead.
+
+ The ‘-p’ option will display the attributes and values of each
+ NAME. When ‘-p’ is used with NAME arguments, additional options,
+ other than ‘-f’ and ‘-F’, are ignored.
+
+ When ‘-p’ is supplied without NAME arguments, ‘declare’ will
+ display the attributes and values of all variables having the
+ attributes specified by the additional options. If no other
+ options are supplied with ‘-p’, ‘declare’ will display the
+ attributes and values of all shell variables. The ‘-f’ option
+ restricts the display to shell functions.
+
+ The ‘-F’ option inhibits the display of function definitions; only
+ the function name and attributes are printed. If the ‘extdebug’
+ shell option is enabled using ‘shopt’ (*note The Shopt Builtin::),
+ the source file name and line number where each NAME is defined are
+ displayed as well. ‘-F’ implies ‘-f’.
+
+ The ‘-g’ option forces variables to be created or modified at the
+ global scope, even when ‘declare’ is executed in a shell function.
+ It is ignored in when ‘declare’ is not executed in a shell
+ function.
+
+ The ‘-I’ option causes local variables to inherit the attributes
+ (except the ‘nameref’ attribute) and value of any existing variable
+ with the same NAME at a surrounding scope. If there is no existing
+ variable, the local variable is initially unset.
+
+ The following options can be used to restrict output to variables
+ with the specified attributes or to give variables attributes:
+
+ ‘-a’
+ Each NAME is an indexed array variable (*note Arrays::).
+
+ ‘-A’
+ Each NAME is an associative array variable (*note Arrays::).
+
+ ‘-f’
+ Each NAME refers to a shell function.
+
+ ‘-i’
+ The variable is to be treated as an integer; arithmetic
+ evaluation (*note Shell Arithmetic::) is performed when the
+ variable is assigned a value.
+
+ ‘-l’
+ When the variable is assigned a value, all upper-case
+ characters are converted to lower-case. The upper-case
+ attribute is disabled.
+
+ ‘-n’
+ Give each NAME the ‘nameref’ attribute, making it a name
+ reference to another variable. That other variable is defined
+ by the value of NAME. All references, assignments, and
+ attribute modifications to NAME, except for those using or
+ changing the ‘-n’ attribute itself, are performed on the
+ variable referenced by NAME's value. The nameref attribute
+ cannot be applied to array variables.
+
+ ‘-r’
+ Make NAMEs readonly. These names cannot then be assigned
+ values by subsequent assignment statements or unset.
+
+ ‘-t’
+ Give each NAME the ‘trace’ attribute. Traced functions
+ inherit the ‘DEBUG’ and ‘RETURN’ traps from the calling shell.
+ The trace attribute has no special meaning for variables.
+
+ ‘-u’
+ When the variable is assigned a value, all lower-case
+ characters are converted to upper-case. The lower-case
+ attribute is disabled.
+
+ ‘-x’
+ Mark each NAME for export to subsequent commands via the
+ environment.
+
+ Using ‘+’ instead of ‘-’ turns off the specified attribute instead,
+ with the exceptions that ‘+a’ and ‘+A’ may not be used to destroy
+ array variables and ‘+r’ will not remove the readonly attribute.
+
+ When used in a function, ‘declare’ makes each NAME local, as with
+ the ‘local’ command, unless the ‘-g’ option is supplied. If a
+ variable name is followed by =VALUE, the value of the variable is
+ set to VALUE.
+
+ When using ‘-a’ or ‘-A’ and the compound assignment syntax to
+ create array variables, additional attributes do not take effect
+ until subsequent assignments.
+
+ The return status is zero unless an invalid option is encountered,
+ an attempt is made to define a function using ‘-f foo=bar’, an
+ attempt is made to assign a value to a readonly variable, an
+ attempt is made to assign a value to an array variable without
+ using the compound assignment syntax (*note Arrays::), one of the
+ NAMEs is not a valid shell variable name, an attempt is made to
+ turn off readonly status for a readonly variable, an attempt is
+ made to turn off array status for an array variable, or an attempt
+ is made to display a non-existent function with ‘-f’.
+
+‘echo’
+ echo [-neE] [ARG ...]
+
+ Output the ARGs, separated by spaces, terminated with a newline.
+ The return status is 0 unless a write error occurs. If ‘-n’ is
+ specified, the trailing newline is not printed.
+
+ If the ‘-e’ option is given, ‘echo’ interprets the following
+ backslash-escaped characters. The ‘-E’ option disables
+ interpretation of these escape characters, even on systems where
+ they are interpreted by default. The ‘xpg_echo’ shell option
+ determines whether or not ‘echo’ interprets any options and expands
+ these escape characters. ‘echo’ does not interpret ‘--’ to mean
+ the end of options.
+
+ ‘echo’ interprets the following escape sequences:
+ ‘\a’
+ alert (bell)
+ ‘\b’
+ backspace
+ ‘\c’
+ suppress further output
+ ‘\e’
+ ‘\E’
+ escape
+ ‘\f’
+ form feed
+ ‘\n’
+ new line
+ ‘\r’
+ carriage return
+ ‘\t’
+ horizontal tab
+ ‘\v’
+ vertical tab
+ ‘\\’
+ backslash
+ ‘\0NNN’
+ The eight-bit character whose value is the octal value NNN
+ (zero to three octal digits).
+ ‘\xHH’
+ The eight-bit character whose value is the hexadecimal value
+ HH (one or two hex digits).
+ ‘\uHHHH’
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHH (one to four hex digits).
+ ‘\UHHHHHHHH’
+ The Unicode (ISO/IEC 10646) character whose value is the
+ hexadecimal value HHHHHHHH (one to eight hex digits).
+
+ ‘echo’ writes any unrecognized backslash-escaped characters
+ unchanged.
+
+‘enable’
+ enable [-a] [-dnps] [-f FILENAME] [NAME ...]
+
+ Enable and disable builtin shell commands. Disabling a builtin
+ allows an executable file which has the same name as a shell
+ builtin to be executed without specifying a full pathname, even
+ though the shell normally searches for builtins before files.
+
+ If ‘-n’ is supplied, the NAMEs are disabled. Otherwise NAMEs are
+ enabled. For example, to use the ‘test’ binary found using ‘$PATH’
+ instead of the shell builtin version, type ‘enable -n test’.
+
+ If the ‘-p’ option is supplied, or no NAME arguments are supplied,
+ print a list of shell builtins. With no other arguments, the list
+ consists of all enabled shell builtins. The ‘-n’ option means to
+ print only disabled builtins. The ‘-a’ option means to list each
+ builtin with an indication of whether or not it is enabled. The
+ ‘-s’ option means to restrict ‘enable’ to the POSIX special
+ builtins.
+
+ The ‘-f’ option means to load the new builtin command NAME from
+ shared object FILENAME, on systems that support dynamic loading.
+ If FILENAME does not contain a slash. Bash will use the value of
+ the ‘BASH_LOADABLES_PATH’ variable as a colon-separated list of
+ directories in which to search for FILENAME. The default for
+ ‘BASH_LOADABLES_PATH’ is system-dependent, and may include "." to
+ force a search of the current directory. The ‘-d’ option will
+ delete a builtin loaded with ‘-f’. If ‘-s’ is used with ‘-f’, the
+ new builtin becomes a POSIX special builtin (*note Special
+ Builtins::).
+
+ If no options are supplied and a NAME is not a shell builtin,
+ ‘enable’ will attempt to load NAME from a shared object named NAME,
+ as if the command were ‘enable -f NAME NAME’.
+
+ The return status is zero unless a NAME is not a shell builtin or
+ there is an error loading a new builtin from a shared object.
+
+‘help’
+ help [-dms] [PATTERN]
+
+ Display helpful information about builtin commands. If PATTERN is
+ specified, ‘help’ gives detailed help on all commands matching
+ PATTERN as described below; otherwise it displays a list of all
+ builtins and shell compound commands.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-d’
+ Display a short description of each PATTERN
+ ‘-m’
+ Display the description of each PATTERN in a manpage-like
+ format
+ ‘-s’
+ Display only a short usage synopsis for each PATTERN
+
+ If PATTERN contains pattern matching characters (*note Pattern
+ Matching::) it's treated as a shell pattern and ‘help’ prints the
+ description of each help topic matching PATTERN.
+
+ If not, and PATTERN exactly matches the name of a help topic,
+ ‘help’ prints the description associated with that topic.
+ Otherwise, ‘help’ performs prefix matching and prints the
+ descriptions of all matching help topics.
+
+ The return status is zero unless no command matches PATTERN.
+
+‘let’
+ let EXPRESSION [EXPRESSION ...]
+
+ The ‘let’ builtin allows arithmetic to be performed on shell
+ variables. Each EXPRESSION is evaluated as an arithmetic
+ expression according to the rules given below in *note Shell
+ Arithmetic::. If the last EXPRESSION evaluates to 0, ‘let’ returns
+ 1; otherwise ‘let’ returns 0.
+
+‘local’
+ local [OPTION] NAME[=VALUE] ...
+
+ For each argument, create a local variable named NAME, and assign
+ it VALUE. The OPTION can be any of the options accepted by
+ ‘declare’. ‘local’ can only be used within a function; it makes
+ the variable NAME have a visible scope restricted to that function
+ and its children. It is an error to use ‘local’ when not within a
+ function.
+
+ If NAME is ‘-’, it makes the set of shell options local to the
+ function in which ‘local’ is invoked: any shell options changed
+ using the ‘set’ builtin inside the function after the call to
+ ‘local’ are restored to their original values when the function
+ returns. The restore is performed as if a series of ‘set’ commands
+ were executed to restore the values that were in place before the
+ function.
+
+ With no operands, ‘local’ writes a list of local variables to the
+ standard output.
+
+ The return status is zero unless ‘local’ is used outside a
+ function, an invalid NAME is supplied, or NAME is a readonly
+ variable.
+
+‘logout’
+ logout [N]
+
+ Exit a login shell, returning a status of N to the shell's parent.
+
+‘mapfile’
+ mapfile [-d DELIM] [-n COUNT] [-O ORIGIN] [-s COUNT]
+ [-t] [-u FD] [-C CALLBACK] [-c QUANTUM] [ARRAY]
+
+ Read lines from the standard input, or from file descriptor FD if
+ the ‘-u’ option is supplied, into the indexed array variable ARRAY.
+ The variable ‘MAPFILE’ is the default ARRAY. Options, if supplied,
+ have the following meanings:
+
+ ‘-d’
+ Use the first character of DELIM to terminate each input line,
+ rather than newline. If DELIM is the empty string, ‘mapfile’
+ will terminate a line when it reads a NUL character.
+ ‘-n’
+ Copy at most COUNT lines. If COUNT is 0, copy all lines.
+ ‘-O’
+ Begin assigning to ARRAY at index ORIGIN. The default index
+ is 0.
+ ‘-s’
+ Discard the first COUNT lines read.
+ ‘-t’
+ Remove a trailing DELIM (default newline) from each line read.
+ ‘-u’
+ Read lines from file descriptor FD instead of the standard
+ input.
+ ‘-C’
+ Evaluate CALLBACK each time QUANTUM lines are read. The ‘-c’
+ option specifies QUANTUM.
+ ‘-c’
+ Specify the number of lines read between each call to
+ CALLBACK.
+
+ If ‘-C’ is specified without ‘-c’, the default quantum is 5000.
+ When CALLBACK is evaluated, it is supplied the index of the next
+ array element to be assigned and the line to be assigned to that
+ element as additional arguments. CALLBACK is evaluated after the
+ line is read but before the array element is assigned.
+
+ If not supplied with an explicit origin, ‘mapfile’ will clear ARRAY
+ before assigning to it.
+
+ ‘mapfile’ returns zero unless an invalid option or option argument
+ is supplied, ARRAY is invalid or unassignable, or if ARRAY is not
+ an indexed array.
+
+‘printf’
+ printf [-v VAR] FORMAT [ARGUMENTS]
+
+ Write the formatted ARGUMENTS to the standard output under the
+ control of the FORMAT. The ‘-v’ option assigns the output to the
+ variable VAR rather than printing it to the standard output.
+
+ The FORMAT is a character string which contains three types of
+ objects: plain characters, which are simply copied to standard
+ output, character escape sequences, which are converted and copied
+ to the standard output, and format specifications, each of which
+ causes printing of the next successive ARGUMENT. In addition to
+ the standard ‘printf(3)’ format characters ‘cCsSndiouxXeEfFgGaA’,
+ ‘printf’ interprets the following additional format specifiers:
+
+ ‘%b’
+ Causes ‘printf’ to expand backslash escape sequences in the
+ corresponding ARGUMENT in the same way as ‘echo -e’ (*note
+ Bash Builtins::).
+ ‘%q’
+ Causes ‘printf’ to output the corresponding ARGUMENT in a
+ format that can be reused as shell input. ‘%q’ and ‘%Q’P use
+ the ANSI-C quoting style (*note ANSI-C Quoting::) if any
+ characters in the argument string require it, and backslash
+ quoting otherwise. If the format string uses the ‘printf’
+ _alternate form_, these two formats quote the argument string
+ using single quotes.
+
+ ‘%Q’
+ like ‘%q’, but applies any supplied precision to the ARGUMENT
+ before quoting it.
+
+ ‘%(DATEFMT)T’
+ Causes ‘printf’ to output the date-time string resulting from
+ using DATEFMT as a format string for ‘strftime’(3). The
+ corresponding ARGUMENT is an integer representing the number
+ of seconds since the epoch. This format specifier recognizes
+ Two special argument values: -1 represents the current time,
+ and -2 represents the time the shell was invoked. If no
+ argument is specified, conversion behaves as if -1 had been
+ supplied. This is an exception to the usual ‘printf’
+ behavior.
+
+ The %b, %q, and %T format specifiers all use the field width and
+ precision arguments from the format specification and write that
+ many bytes from (or use that wide a field for) the expanded
+ argument, which usually contains more characters than the original.
+
+ The %n format specifier accepts a corresponding argument that is
+ treated as a shell variable name.
+
+ The %s and %c format specifiers accept an l (long) modifier, which
+ forces them to convert the argument string to a wide-character
+ string and apply any supplied field width and precision in terms of
+ characters, not bytes. The %S and %C format specifiers are
+ equivalent to %ls and %lc, respectively.
+
+ Arguments to non-string format specifiers are treated as C language
+ constants, except that a leading plus or minus sign is allowed, and
+ if the leading character is a single or double quote, the value is
+ the numeric value of the following character, using the current
+ locale.
+
+ The FORMAT is reused as necessary to consume all of the ARGUMENTS.
+ If the FORMAT requires more ARGUMENTS than are supplied, the extra
+ format specifications behave as if a zero value or null string, as
+ appropriate, had been supplied. The return value is zero on
+ success, non-zero if an invalid option is supplied or a write or
+ assignment error occurs.
+
+‘read’
+ read [-Eers] [-a ANAME] [-d DELIM] [-i TEXT] [-n NCHARS]
+ [-N NCHARS] [-p PROMPT] [-t TIMEOUT] [-u FD] [NAME ...]
+
+ Read one line from the standard input, or from the file descriptor
+ FD supplied as an argument to the ‘-u’ option, split it into words
+ as described above in *note Word Splitting::, and assign the first
+ word to the first NAME, the second word to the second NAME, and so
+ on. If there are more words than names, the remaining words and
+ their intervening delimiters are assigned to the last NAME. If
+ there are fewer words read from the input stream than names, the
+ remaining names are assigned empty values. The characters in the
+ value of the ‘IFS’ variable are used to split the line into words
+ using the same rules the shell uses for expansion (described above
+ in *note Word Splitting::). The backslash character ‘\’ removes
+ any special meaning for the next character read and is used for
+ line continuation.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-a ANAME’
+ The words are assigned to sequential indices of the array
+ variable ANAME, starting at 0. All elements are removed from
+ ANAME before the assignment. Other NAME arguments are
+ ignored.
+
+ ‘-d DELIM’
+ The first character of DELIM terminates the input line, rather
+ than newline. If DELIM is the empty string, ‘read’ will
+ terminate a line when it reads a NUL character.
+
+ ‘-e’
+ If the standard input is coming from a terminal, ‘read’ uses
+ Readline (*note Command Line Editing::) to obtain the line.
+ Readline uses the current (or default, if line editing was not
+ previously active) editing settings, but uses Readline's
+ default filename completion.
+
+ ‘-E’
+ If the standard input is coming from a terminal, ‘read’ uses
+ Readline (*note Command Line Editing::) to obtain the line.
+ Readline uses the current (or default, if line editing was not
+ previously active) editing settings, but uses Bash's default
+ completion, including programmable completion.
+
+ ‘-i TEXT’
+ If Readline is being used to read the line, ‘read’ places TEXT
+ into the editing buffer before editing begins.
+
+ ‘-n NCHARS’
+ ‘read’ returns after reading NCHARS characters rather than
+ waiting for a complete line of input, unless it encounters EOF
+ or ‘read’ times out, but honors a delimiter if it reads fewer
+ than NCHARS characters before the delimiter.
+
+ ‘-N NCHARS’
+ ‘read’ returns after reading exactly NCHARS characters rather
+ than waiting for a complete line of input, unless it
+ encounters EOF or ‘read’ times out. Delimiter characters in
+ the input are not treated specially and do not cause ‘read’ to
+ return until it has read NCHARS characters. The result is not
+ split on the characters in ‘IFS’; the intent is that the
+ variable is assigned exactly the characters read (with the
+ exception of backslash; see the ‘-r’ option below).
+
+ ‘-p PROMPT’
+ Display PROMPT, without a trailing newline, before attempting
+ to read any input, but only if input is coming from a
+ terminal.
+
+ ‘-r’
+ If this option is given, backslash does not act as an escape
+ character. The backslash is considered to be part of the
+ line. In particular, a backslash-newline pair may not then be
+ used as a line continuation.
+
+ ‘-s’
+ Silent mode. If input is coming from a terminal, characters
+ are not echoed.
+
+ ‘-t TIMEOUT’
+ Cause ‘read’ to time out and return failure if it does not
+ read a complete line of input (or a specified number of
+ characters) within TIMEOUT seconds. TIMEOUT may be a decimal
+ number with a fractional portion following the decimal point.
+ This option is only effective if ‘read’ is reading input from
+ a terminal, pipe, or other special file; it has no effect when
+ reading from regular files. If ‘read’ times out, it saves any
+ partial input read into the specified variable NAME, and
+ returns a status greater than 128. If TIMEOUT is 0, ‘read’
+ returns immediately, without trying to read any data. In this
+ case, the exit status is 0 if input is available on the
+ specified file descriptor, or the read will return EOF,
+ non-zero otherwise.
+
+ ‘-u FD’
+ Read input from file descriptor FD instead of the standard
+ input.
+
+ Other than the case where DELIM is the empty string, ‘read’ ignores
+ any NUL characters in the input.
+
+ If no NAMEs are supplied, ‘read’ assigns the line read, without the
+ ending delimiter but otherwise unmodified, to the variable ‘REPLY’.
+
+ The exit status is zero, unless end-of-file is encountered, ‘read’
+ times out (in which case the status is greater than 128), a
+ variable assignment error (such as assigning to a readonly
+ variable) occurs, or an invalid file descriptor is supplied as the
+ argument to ‘-u’.
+
+‘readarray’
+ readarray [-d DELIM] [-n COUNT] [-O ORIGIN] [-s COUNT]
+ [-t] [-u FD] [-C CALLBACK] [-c QUANTUM] [ARRAY]
+
+ Read lines from the standard input into the indexed array variable
+ ARRAY, or from file descriptor FD if the ‘-u’ option is supplied.
+
+ A synonym for ‘mapfile’.
+
+‘source’
+ source [-p PATH] FILENAME [ARGUMENTS]
+
+ A synonym for ‘.’ (*note Bourne Shell Builtins::).
+
+‘type’
+ type [-afptP] [NAME ...]
+
+ Indicate how each NAME would be interpreted if used as a command
+ name.
+
+ If the ‘-t’ option is used, ‘type’ prints a single word which is
+ one of ‘alias’, ‘keyword’, ‘function’, ‘builtin’, or ‘file’, if
+ NAME is an alias, shell reserved word, shell function, shell
+ builtin, or executable file, respectively. If the NAME is not
+ found, ‘type’ prints nothing and returns a failure status.
+
+ If the ‘-p’ option is used, ‘type’ either returns the name of the
+ executable file that would be found by searching ‘$PATH’ for
+ ‘name’, or nothing if ‘-t’ would not return ‘file’.
+
+ The ‘-P’ option forces a path search for each NAME, even if ‘-t’
+ would not return ‘file’.
+
+ If a NAME is present in the table of hashed commands, options ‘-p’
+ and ‘-P’ print the hashed value, which is not necessarily the file
+ that appears first in ‘$PATH’.
+
+ If the ‘-a’ option is used, ‘type’ returns all of the places that
+ contain a command named NAME. This includes aliases, reserved
+ words, functions, and builtins, but the path search options (‘-p’
+ and ‘-P’) can be supplied to restrict the output to executable
+ files. If ‘-a’ is supplied with ‘-p’, ‘type’ does not look in the
+ table of hashed commands, and only performs a ‘PATH’ search for
+ NAME.
+
+ If the ‘-f’ option is used, ‘type’ does not attempt to find shell
+ functions, as with the ‘command’ builtin.
+
+ The return status is zero if all of the NAMEs are found, non-zero
+ if any are not found.
+
+‘typeset’
+ typeset [-afFgrxilnrtux] [-p] [NAME[=VALUE] ...]
+
+ The ‘typeset’ command is supplied for compatibility with the Korn
+ shell. It is a synonym for the ‘declare’ builtin command.
+
+‘ulimit’
+ ulimit [-HS] -a
+ ulimit [-HS] [-bcdefiklmnpqrstuvxPRT] [LIMIT]
+
+ ‘ulimit’ provides control over the resources available to the shell
+ and to processes it starts, on systems that allow such control. If
+ an option is given, it is interpreted as follows:
+
+ ‘-S’
+ Change and report the soft limit associated with a resource.
+
+ ‘-H’
+ Change and report the hard limit associated with a resource.
+
+ ‘-a’
+ Report all current limits; no limits are set.
+
+ ‘-b’
+ The maximum socket buffer size.
+
+ ‘-c’
+ The maximum size of core files created.
+
+ ‘-d’
+ The maximum size of a process's data segment.
+
+ ‘-e’
+ The maximum scheduling priority ("nice").
+
+ ‘-f’
+ The maximum size of files written by the shell and its
+ children.
+
+ ‘-i’
+ The maximum number of pending signals.
+
+ ‘-k’
+ The maximum number of kqueues that may be allocated.
+
+ ‘-l’
+ The maximum size that may be locked into memory.
+
+ ‘-m’
+ The maximum resident set size (many systems do not honor this
+ limit).
+
+ ‘-n’
+ The maximum number of open file descriptors (most systems do
+ not allow this value to be set).
+
+ ‘-p’
+ The pipe buffer size.
+
+ ‘-q’
+ The maximum number of bytes in POSIX message queues.
+
+ ‘-r’
+ The maximum real-time scheduling priority.
+
+ ‘-s’
+ The maximum stack size.
+
+ ‘-t’
+ The maximum amount of cpu time in seconds.
+
+ ‘-u’
+ The maximum number of processes available to a single user.
+
+ ‘-v’
+ The maximum amount of virtual memory available to the shell,
+ and, on some systems, to its children.
+
+ ‘-x’
+ The maximum number of file locks.
+
+ ‘-P’
+ The maximum number of pseudoterminals.
+
+ ‘-R’
+ The maximum time a real-time process can run before blocking,
+ in microseconds.
+
+ ‘-T’
+ The maximum number of threads.
+
+ If LIMIT is supplied, and the ‘-a’ option is not used, LIMIT is the
+ new value of the specified resource. The special LIMIT values
+ ‘hard’, ‘soft’, and ‘unlimited’ stand for the current hard limit,
+ the current soft limit, and no limit, respectively. A hard limit
+ cannot be increased by a non-root user once it is set; a soft limit
+ may be increased up to the value of the hard limit. Otherwise,
+ ‘ulimit’ prints the current value of the soft limit for the
+ specified resource, unless the ‘-H’ option is supplied. When more
+ than one resource is specified, the limit name and unit, if
+ appropriate, are printed before the value. When setting new
+ limits, if neither ‘-H’ nor ‘-S’ is supplied, ‘ulimit’ sets both
+ the hard and soft limits. If no option is supplied, then ‘-f’ is
+ assumed.
+
+ Values are in 1024-byte increments, except for ‘-t’, which is in
+ seconds; ‘-R’, which is in microseconds; ‘-p’, which is in units of
+ 512-byte blocks; ‘-P’, ‘-T’, ‘-b’, ‘-k’, ‘-n’ and ‘-u’, which are
+ unscaled values; and, when in POSIX mode (*note Bash POSIX Mode::),
+ ‘-c’ and ‘-f’, which are in 512-byte increments.
+
+ The return status is zero unless an invalid option or argument is
+ supplied, or an error occurs while setting a new limit.
+
+‘unalias’
+ unalias [-a] [NAME ... ]
+
+ Remove each NAME from the list of aliases. If ‘-a’ is supplied,
+ remove all aliases. The return value is true unless a supplied
+ NAME is not a defined alias. Aliases are described in *note
+ Aliases::.
+
+\1f
+File: bashref.info, Node: Modifying Shell Behavior, Next: Special Builtins, Prev: Bash Builtins, Up: Shell Builtin Commands
+
+4.3 Modifying Shell Behavior
+============================
+
+* Menu:
+
+* The Set Builtin:: Change the values of shell attributes and
+ positional parameters.
+* The Shopt Builtin:: Modify shell optional behavior.
+
+\1f
+File: bashref.info, Node: The Set Builtin, Next: The Shopt Builtin, Up: Modifying Shell Behavior
+
+4.3.1 The Set Builtin
+---------------------
+
+This builtin is so complicated that it deserves its own section. ‘set’
+allows you to change the values of shell options and set the positional
+parameters, or to display the names and values of shell variables.
+
+‘set’
+ set [-abefhkmnptuvxBCEHPT] [-o OPTION-NAME] [--] [-] [ARGUMENT ...]
+ set [+abefhkmnptuvxBCEHPT] [+o OPTION-NAME] [--] [-] [ARGUMENT ...]
+ set -o
+ set +o
+
+ If no options or arguments are supplied, ‘set’ displays the names
+ and values of all shell variables and functions, sorted according
+ to the current locale, in a format that may be reused as input for
+ setting or resetting the currently-set variables. Read-only
+ variables cannot be reset. In POSIX mode, only shell variables are
+ listed.
+
+ When options are supplied, they set or unset shell attributes. Any
+ arguments remaining after option processing replace the positional
+ parameters.
+
+ Options, if specified, have the following meanings:
+
+ ‘-a’
+ Each variable or function that is created or modified is given
+ the export attribute and marked for export to the environment
+ of subsequent commands.
+
+ ‘-b’
+ Cause the status of terminated background jobs to be reported
+ immediately, rather than before printing the next primary
+ prompt or, under some circumstances, when a foreground command
+ exits. This is effective only when job control is enabled.
+
+ ‘-e’
+ Exit immediately if a pipeline (*note Pipelines::), which may
+ consist of a single simple command (*note Simple Commands::),
+ a list (*note Lists::), or a compound command (*note Compound
+ Commands::) returns a non-zero status. The shell does not
+ exit if the command that fails is part of the command list
+ immediately following a ‘while’ or ‘until’ reserved word, part
+ of the test in an ‘if’ statement, part of any command executed
+ in a ‘&&’ or ‘||’ list except the command following the final
+ ‘&&’ or ‘||’, any command in a pipeline but the last (subject
+ to the state of the ‘pipefail’ shell option), or if the
+ command's return status is being inverted with ‘!’. If a
+ compound command other than a subshell returns a non-zero
+ status because a command failed while ‘-e’ was being ignored,
+ the shell does not exit. A trap on ‘ERR’, if set, is executed
+ before the shell exits.
+
+ This option applies to the shell environment and each subshell
+ environment separately (*note Command Execution
+ Environment::), and may cause subshells to exit before
+ executing all the commands in the subshell.
+
+ If a compound command or shell function executes in a context
+ where ‘-e’ is being ignored, none of the commands executed
+ within the compound command or function body will be affected
+ by the ‘-e’ setting, even if ‘-e’ is set and a command returns
+ a failure status. If a compound command or shell function
+ sets ‘-e’ while executing in a context where ‘-e’ is ignored,
+ that setting will not have any effect until the compound
+ command or the command containing the function call completes.
+
+ ‘-f’
+ Disable filename expansion (globbing).
+
+ ‘-h’
+ Locate and remember (hash) commands as they are looked up for
+ execution. This option is enabled by default.
+
+ ‘-k’
+ All arguments in the form of assignment statements are placed
+ in the environment for a command, not just those that precede
+ the command name.
+
+ ‘-m’
+ Job control is enabled (*note Job Control::). All processes
+ run in a separate process group. When a background job
+ completes, the shell prints a line containing its exit status.
+
+ ‘-n’
+ Read commands but do not execute them. This may be used to
+ check a script for syntax errors. This option is ignored by
+ interactive shells.
+
+ ‘-o OPTION-NAME’
+
+ Set the option corresponding to OPTION-NAME. If ‘-o’ is
+ supplied with no OPTION-NAME, ‘set’ prints the current shell
+ options settings. If ‘+o’ is supplied with no OPTION-NAME,
+ ‘set’ prints a series of ‘set’ commands to recreate the
+ current option settings on the standard output. Valid option
+ names are:
+
+ ‘allexport’
+ Same as ‘-a’.
+
+ ‘braceexpand’
+ Same as ‘-B’.
+
+ ‘emacs’
+ Use an ‘emacs’-style line editing interface (*note
+ Command Line Editing::). This also affects the editing
+ interface used for ‘read -e’.
+
+ ‘errexit’
+ Same as ‘-e’.
+
+ ‘errtrace’
+ Same as ‘-E’.
+
+ ‘functrace’
+ Same as ‘-T’.
+
+ ‘hashall’
+ Same as ‘-h’.
+
+ ‘histexpand’
+ Same as ‘-H’.
+
+ ‘history’
+ Enable command history, as described in *note Bash
+ History Facilities::. This option is on by default in
+ interactive shells.
+
+ ‘ignoreeof’
+ An interactive shell will not exit upon reading EOF.
+
+ ‘keyword’
+ Same as ‘-k’.
+
+ ‘monitor’
+ Same as ‘-m’.
+
+ ‘noclobber’
+ Same as ‘-C’.
+
+ ‘noexec’
+ Same as ‘-n’.
+
+ ‘noglob’
+ Same as ‘-f’.
+
+ ‘nolog’
+ Currently ignored.
+
+ ‘notify’
+ Same as ‘-b’.
+
+ ‘nounset’
+ Same as ‘-u’.
+
+ ‘onecmd’
+ Same as ‘-t’.
+
+ ‘physical’
+ Same as ‘-P’.
+
+ ‘pipefail’
+ If set, the return value of a pipeline is the value of
+ the last (rightmost) command to exit with a non-zero
+ status, or zero if all commands in the pipeline exit
+ successfully. This option is disabled by default.
+
+ ‘posix’
+ Enable POSIX mode; change the behavior of Bash where the
+ default operation differs from the POSIX standard to
+ match the standard (*note Bash POSIX Mode::). This is
+ intended to make Bash behave as a strict superset of that
+ standard.
+
+ ‘privileged’
+ Same as ‘-p’.
+
+ ‘verbose’
+ Same as ‘-v’.
+
+ ‘vi’
+ Use a ‘vi’-style line editing interface. This also
+ affects the editing interface used for ‘read -e’.
+
+ ‘xtrace’
+ Same as ‘-x’.
+
+ ‘-p’
+ Turn on privileged mode. In this mode, the ‘$BASH_ENV’ and
+ ‘$ENV’ files are not processed, shell functions are not
+ inherited from the environment, and the ‘SHELLOPTS’,
+ ‘BASHOPTS’, ‘CDPATH’ and ‘GLOBIGNORE’ variables, if they
+ appear in the environment, are ignored. If the shell is
+ started with the effective user (group) id not equal to the
+ real user (group) id, and the ‘-p’ option is not supplied,
+ these actions are taken and the effective user id is set to
+ the real user id. If the ‘-p’ option is supplied at startup,
+ the effective user id is not reset. Turning this option off
+ causes the effective user and group ids to be set to the real
+ user and group ids.
+
+ ‘-r’
+ Enable restricted shell mode (*note The Restricted Shell::).
+ This option cannot be unset once it has been set.
+
+ ‘-t’
+ Exit after reading and executing one command.
+
+ ‘-u’
+ Treat unset variables and parameters other than the special
+ parameters ‘@’ or ‘*’, or array variables subscripted with ‘@’
+ or ‘*’, as an error when performing parameter expansion. An
+ error message will be written to the standard error, and a
+ non-interactive shell will exit.
+
+ ‘-v’
+ Print shell input lines to standard error as they are read.
+
+ ‘-x’
+ Print a trace of simple commands, ‘for’ commands, ‘case’
+ commands, ‘select’ commands, and arithmetic ‘for’ commands and
+ their arguments or associated word lists to the standard error
+ after they are expanded and before they are executed. The
+ shell prints the expanded value of the ‘PS4’ variable before
+ the command and its expanded arguments.
+
+ ‘-B’
+ The shell will perform brace expansion (*note Brace
+ Expansion::). This option is on by default.
+
+ ‘-C’
+ Prevent output redirection using ‘>’, ‘>&’, and ‘<>’ from
+ overwriting existing files. Using the redirection operator
+ ‘>|’ instead of ‘>’ will override this and force the creation
+ of an output file.
+
+ ‘-E’
+ If set, any trap on ‘ERR’ is inherited by shell functions,
+ command substitutions, and commands executed in a subshell
+ environment. The ‘ERR’ trap is normally not inherited in such
+ cases.
+
+ ‘-H’
+ Enable ‘!’ style history substitution (*note History
+ Interaction::). This option is on by default for interactive
+ shells.
+
+ ‘-P’
+ If set, Bash does not resolve symbolic links when executing
+ commands such as ‘cd’ which change the current directory. It
+ uses the physical directory structure instead. By default,
+ Bash follows the logical chain of directories when performing
+ commands which change the current directory.
+
+ For example, if ‘/usr/sys’ is a symbolic link to
+ ‘/usr/local/sys’ then:
+ $ cd /usr/sys; echo $PWD
+ /usr/sys
+ $ cd ..; pwd
+ /usr
+
+ If ‘set -P’ is on, then:
+ $ cd /usr/sys; echo $PWD
+ /usr/local/sys
+ $ cd ..; pwd
+ /usr/local
+
+ ‘-T’
+ If set, any traps on ‘DEBUG’ and ‘RETURN’ are inherited by
+ shell functions, command substitutions, and commands executed
+ in a subshell environment. The ‘DEBUG’ and ‘RETURN’ traps are
+ normally not inherited in such cases.
+
+ ‘--’
+ If no arguments follow this option, unset the positional
+ parameters. Otherwise, the positional parameters are set to
+ the ARGUMENTS, even if some of them begin with a ‘-’.
+
+ ‘-’
+ Signal the end of options, and assign all remaining ARGUMENTS
+ to the positional parameters. The ‘-x’ and ‘-v’ options are
+ turned off. If there are no arguments, the positional
+ parameters remain unchanged.
+
+ Using ‘+’ rather than ‘-’ causes these options to be turned off.
+ The options can also be used upon invocation of the shell. The
+ current set of options may be found in ‘$-’.
+
+ The remaining N ARGUMENTS are positional parameters and are
+ assigned, in order, to ‘$1’, ‘$2’, ... ‘$N’. The special parameter
+ ‘#’ is set to N.
+
+ The return status is always zero unless an invalid option is
+ supplied.
+
+\1f
+File: bashref.info, Node: The Shopt Builtin, Prev: The Set Builtin, Up: Modifying Shell Behavior
+
+4.3.2 The Shopt Builtin
+-----------------------
+
+This builtin allows you to change additional optional shell behavior.
+
+‘shopt’
+ shopt [-pqsu] [-o] [OPTNAME ...]
+
+ Toggle the values of settings controlling optional shell behavior.
+ The settings can be either those listed below, or, if the ‘-o’
+ option is used, those available with the ‘-o’ option to the ‘set’
+ builtin command (*note The Set Builtin::).
+
+ With no options, or with the ‘-p’ option, display a list of all
+ settable options, with an indication of whether or not each is set;
+ if any OPTNAMEs are supplied, the output is restricted to those
+ options. The ‘-p’ option displays output in a form that may be
+ reused as input.
+
+ Other options have the following meanings:
+
+ ‘-s’
+ Enable (set) each OPTNAME.
+
+ ‘-u’
+ Disable (unset) each OPTNAME.
+
+ ‘-q’
+ Suppresses normal output; the return status indicates whether
+ the OPTNAME is set or unset. If multiple OPTNAME arguments
+ are supplied with ‘-q’, the return status is zero if all
+ OPTNAMEs are enabled; non-zero otherwise.
+
+ ‘-o’
+ Restricts the values of OPTNAME to be those defined for the
+ ‘-o’ option to the ‘set’ builtin (*note The Set Builtin::).
+
+ If either ‘-s’ or ‘-u’ is used with no OPTNAME arguments, ‘shopt’
+ shows only those options which are set or unset, respectively.
+
+ Unless otherwise noted, the ‘shopt’ options are disabled (off) by
+ default.
+
+ The return status when listing options is zero if all OPTNAMEs are
+ enabled, non-zero otherwise. When setting or unsetting options,
+ the return status is zero unless an OPTNAME is not a valid shell
+ option.
+
+ The list of ‘shopt’ options is:
+
+ ‘array_expand_once’
+ If set, the shell suppresses multiple evaluation of
+ associative and indexed array subscripts during arithmetic
+ expression evaluation, while executing builtins that can
+ perform variable assignments, and while executing builtins
+ that perform array dereferencing.
+
+ ‘assoc_expand_once’
+ Deprecated; a synonym for ‘array_expand_once’.
+
+ ‘autocd’
+ If set, a command name that is the name of a directory is
+ executed as if it were the argument to the ‘cd’ command. This
+ option is only used by interactive shells.
+
+ ‘bash_source_fullpath’
+ If set, filenames added to the ‘BASH_SOURCE’ array variable
+ are converted to full pathnames (*note Bash Variables::).
+
+ ‘cdable_vars’
+ If this is set, an argument to the ‘cd’ builtin command that
+ is not a directory is assumed to be the name of a variable
+ whose value is the directory to change to.
+
+ ‘cdspell’
+ If set, the ‘cd’ command attempts to correct minor errors in
+ the spelling of a directory component. Minor errors include
+ transposed characters, a missing character, and one extra
+ character. If ‘cd’ corrects the directory name, it prints the
+ corrected filename, and the command proceeds. This option is
+ only used by interactive shells.
+
+ ‘checkhash’
+ If this is set, Bash checks that a command found in the hash
+ table exists before trying to execute it. If a hashed command
+ no longer exists, Bash performs a normal path search.
+
+ ‘checkjobs’
+ If set, Bash lists the status of any stopped and running jobs
+ before exiting an interactive shell. If any jobs are running,
+ Bash defers the exit until a second exit is attempted without
+ an intervening command (*note Job Control::). The shell
+ always postpones exiting if any jobs are stopped.
+
+ ‘checkwinsize’
+ If set, Bash checks the window size after each external
+ (non-builtin) command and, if necessary, updates the values of
+ ‘LINES’ and ‘COLUMNS’, using the file descriptor associated
+ with stderr if it is a terminal. This option is enabled by
+ default.
+
+ ‘cmdhist’
+ If set, Bash attempts to save all lines of a multiple-line
+ command in the same history entry. This allows easy
+ re-editing of multi-line commands. This option is enabled by
+ default, but only has an effect if command history is enabled
+ (*note Bash History Facilities::).
+
+ ‘compat31’
+ ‘compat32’
+ ‘compat40’
+ ‘compat41’
+ ‘compat42’
+ ‘compat43’
+ ‘compat44’
+ These control aspects of the shell's compatibility mode (*note
+ Shell Compatibility Mode::).
+
+ ‘complete_fullquote’
+ If set, Bash quotes all shell metacharacters in filenames and
+ directory names when performing completion. If not set, Bash
+ removes metacharacters such as the dollar sign from the set of
+ characters that will be quoted in completed filenames when
+ these metacharacters appear in shell variable references in
+ words to be completed. This means that dollar signs in
+ variable names that expand to directories will not be quoted;
+ however, any dollar signs appearing in filenames will not be
+ quoted, either. This is active only when Bash is using
+ backslashes to quote completed filenames. This variable is
+ set by default, which is the default Bash behavior in versions
+ through 4.2.
+
+ ‘direxpand’
+ If set, Bash replaces directory names with the results of word
+ expansion when performing filename completion. This changes
+ the contents of the Readline editing buffer. If not set, Bash
+ attempts to preserve what the user typed.
+
+ ‘dirspell’
+ If set, Bash attempts spelling correction on directory names
+ during word completion if the directory name initially
+ supplied does not exist.
+
+ ‘dotglob’
+ If set, Bash includes filenames beginning with a ‘.’ in the
+ results of filename expansion. The filenames ‘.’ and ‘..’
+ must always be matched explicitly, even if ‘dotglob’ is set.
+
+ ‘execfail’
+ If this is set, a non-interactive shell will not exit if it
+ cannot execute the file specified as an argument to the ‘exec’
+ builtin. An interactive shell does not exit if ‘exec’ fails.
+
+ ‘expand_aliases’
+ If set, aliases are expanded as described below under Aliases,
+ *note Aliases::. This option is enabled by default for
+ interactive shells.
+
+ ‘extdebug’
+ If set at shell invocation, or in a shell startup file,
+ arrange to execute the debugger profile before the shell
+ starts, identical to the ‘--debugger’ option. If set after
+ invocation, behavior intended for use by debuggers is enabled:
+
+ 1. The ‘-F’ option to the ‘declare’ builtin (*note Bash
+ Builtins::) displays the source file name and line number
+ corresponding to each function name supplied as an
+ argument.
+
+ 2. If the command run by the ‘DEBUG’ trap returns a non-zero
+ value, the next command is skipped and not executed.
+
+ 3. If the command run by the ‘DEBUG’ trap returns a value of
+ 2, and the shell is executing in a subroutine (a shell
+ function or a shell script executed by the ‘.’ or
+ ‘source’ builtins), the shell simulates a call to
+ ‘return’.
+
+ 4. ‘BASH_ARGC’ and ‘BASH_ARGV’ are updated as described in
+ their descriptions (*note Bash Variables::).
+
+ 5. Function tracing is enabled: command substitution, shell
+ functions, and subshells invoked with ‘( COMMAND )’
+ inherit the ‘DEBUG’ and ‘RETURN’ traps.
+
+ 6. Error tracing is enabled: command substitution, shell
+ functions, and subshells invoked with ‘( COMMAND )’
+ inherit the ‘ERR’ trap.
+
+ ‘extglob’
+ If set, enable the extended pattern matching features
+ described above (*note Pattern Matching::).
+
+ ‘extquote’
+ If set, ‘$'STRING'’ and ‘$"STRING"’ quoting is performed
+ within ‘${PARAMETER}’ expansions enclosed in double quotes.
+ This option is enabled by default.
+
+ ‘failglob’
+ If set, patterns which fail to match filenames during filename
+ expansion result in an expansion error.
+
+ ‘force_fignore’
+ If set, the suffixes specified by the ‘FIGNORE’ shell variable
+ cause words to be ignored when performing word completion even
+ if the ignored words are the only possible completions. *Note
+ Bash Variables::, for a description of ‘FIGNORE’. This option
+ is enabled by default.
+
+ ‘globasciiranges’
+ If set, range expressions used in pattern matching bracket
+ expressions (*note Pattern Matching::) behave as if in the
+ traditional C locale when performing comparisons. That is,
+ pattern matching does not take the current locale's collating
+ sequence into account, so ‘b’ will not collate between ‘A’ and
+ ‘B’, and upper-case and lower-case ASCII characters will
+ collate together.
+
+ ‘globskipdots’
+ If set, filename expansion will never match the filenames ‘.’
+ and ‘..’, even if the pattern begins with a ‘.’. This option
+ is enabled by default.
+
+ ‘globstar’
+ If set, the pattern ‘**’ used in a filename expansion context
+ will match all files and zero or more directories and
+ subdirectories. If the pattern is followed by a ‘/’, only
+ directories and subdirectories match.
+
+ ‘gnu_errfmt’
+ If set, shell error messages are written in the standard GNU
+ error message format.
+
+ ‘histappend’
+ If set, the history list is appended to the file named by the
+ value of the ‘HISTFILE’ variable when the shell exits, rather
+ than overwriting the file.
+
+ ‘histreedit’
+ If set, and Readline is being used, the user is given the
+ opportunity to re-edit a failed history substitution.
+
+ ‘histverify’
+ If set, and Readline is being used, the results of history
+ substitution are not immediately passed to the shell parser.
+ Instead, the resulting line is loaded into the Readline
+ editing buffer, allowing further modification.
+
+ ‘hostcomplete’
+ If set, and Readline is being used, Bash will attempt to
+ perform hostname completion when a word containing a ‘@’ is
+ being completed (*note Commands For Completion::). This
+ option is enabled by default.
+
+ ‘huponexit’
+ If set, Bash will send ‘SIGHUP’ to all jobs when an
+ interactive login shell exits (*note Signals::).
+
+ ‘inherit_errexit’
+ If set, command substitution inherits the value of the
+ ‘errexit’ option, instead of unsetting it in the subshell
+ environment. This option is enabled when POSIX mode is
+ enabled.
+
+ ‘interactive_comments’
+ In an interactive shell, a word beginning with ‘#’ causes that
+ word and all remaining characters on that line to be ignored,
+ as in a non-interactive shell. This option is enabled by
+ default.
+
+ ‘lastpipe’
+ If set, and job control is not active, the shell runs the last
+ command of a pipeline not executed in the background in the
+ current shell environment.
+
+ ‘lithist’
+ If enabled, and the ‘cmdhist’ option is enabled, multi-line
+ commands are saved to the history with embedded newlines
+ rather than using semicolon separators where possible.
+
+ ‘localvar_inherit’
+ If set, local variables inherit the value and attributes of a
+ variable of the same name that exists at a previous scope
+ before any new value is assigned. The ‘nameref’ attribute is
+ not inherited.
+
+ ‘localvar_unset’
+ If set, calling ‘unset’ on local variables in previous
+ function scopes marks them so subsequent lookups find them
+ unset until that function returns. This is identical to the
+ behavior of unsetting local variables at the current function
+ scope.
+
+ ‘login_shell’
+ The shell sets this option if it is started as a login shell
+ (*note Invoking Bash::). The value may not be changed.
+
+ ‘mailwarn’
+ If set, and a file that Bash is checking for mail has been
+ accessed since the last time it was checked, Bash displays the
+ message ‘"The mail in MAILFILE has been read"’.
+
+ ‘no_empty_cmd_completion’
+ If set, and Readline is being used, Bash does not search the
+ ‘PATH’ for possible completions when completion is attempted
+ on an empty line.
+
+ ‘nocaseglob’
+ If set, Bash matches filenames in a case-insensitive fashion
+ when performing filename expansion.
+
+ ‘nocasematch’
+ If set, Bash matches patterns in a case-insensitive fashion
+ when performing matching while executing ‘case’ or ‘[[’
+ conditional commands (*note Conditional Constructs::), when
+ performing pattern substitution word expansions, or when
+ filtering possible completions as part of programmable
+ completion.
+
+ ‘noexpand_translation’
+ If set, Bash encloses the translated results of $"..." quoting
+ in single quotes instead of double quotes. If the string is
+ not translated, this has no effect.
+
+ ‘nullglob’
+ If set, filename expansion patterns which match no files
+ (*note Filename Expansion::) expand to nothing and are
+ removed, rather than expanding to themselves.
+
+ ‘patsub_replacement’
+ If set, Bash expands occurrences of ‘&’ in the replacement
+ string of pattern substitution to the text matched by the
+ pattern, as described above (*note Shell Parameter
+ Expansion::). This option is enabled by default.
+
+ ‘progcomp’
+ If set, enable the programmable completion facilities (*note
+ Programmable Completion::). This option is enabled by
+ default.
+
+ ‘progcomp_alias’
+ If set, and programmable completion is enabled, Bash treats a
+ command name that doesn't have any completions as a possible
+ alias and attempts alias expansion. If it has an alias, Bash
+ attempts programmable completion using the command word
+ resulting from the expanded alias.
+
+ ‘promptvars’
+ If set, prompt strings undergo parameter expansion, command
+ substitution, arithmetic expansion, and quote removal after
+ being expanded as described below (*note Controlling the
+ Prompt::). This option is enabled by default.
+
+ ‘restricted_shell’
+ The shell sets this option if it is started in restricted mode
+ (*note The Restricted Shell::). The value may not be changed.
+ This is not reset when the startup files are executed,
+ allowing the startup files to discover whether or not a shell
+ is restricted.
+
+ ‘shift_verbose’
+ If this is set, the ‘shift’ builtin prints an error message
+ when the shift count exceeds the number of positional
+ parameters.
+
+ ‘sourcepath’
+ If set, the ‘.’ (‘source’) builtin uses the value of ‘PATH’ to
+ find the directory containing the file supplied as an argument
+ when the ‘-p’ option is not supplied. This option is enabled
+ by default.
+
+ ‘varredir_close’
+ If set, the shell automatically closes file descriptors
+ assigned using the ‘{varname}’ redirection syntax (*note
+ Redirections::) instead of leaving them open when the command
+ completes.
+
+ ‘xpg_echo’
+ If set, the ‘echo’ builtin expands backslash-escape sequences
+ by default. If the ‘posix’ shell option (*note The Set
+ Builtin::) is also enabled, ‘echo’ does not interpret any
+ options.
+
+\1f
+File: bashref.info, Node: Special Builtins, Prev: Modifying Shell Behavior, Up: Shell Builtin Commands
+
+4.4 Special Builtins
+====================
+
+For historical reasons, the POSIX standard has classified several
+builtin commands as _special_. When Bash is executing in POSIX mode,
+the special builtins differ from other builtin commands in three
+respects:
+
+ 1. Special builtins are found before shell functions during command
+ lookup.
+
+ 2. If a special builtin returns an error status, a non-interactive
+ shell exits.
+
+ 3. Assignment statements preceding the command stay in effect in the
+ shell environment after the command completes.
+
+ When Bash is not executing in POSIX mode, these builtins behave no
+differently than the rest of the Bash builtin commands. The Bash POSIX
+mode is described in *note Bash POSIX Mode::.
+
+ These are the POSIX special builtins:
+ break : . source continue eval exec exit export readonly return set
+ shift times trap unset
+
+\1f
+File: bashref.info, Node: Shell Variables, Next: Bash Features, Prev: Shell Builtin Commands, Up: Top
+
+5 Shell Variables
+*****************
+
+* Menu:
+
+* Bourne Shell Variables:: Variables which Bash uses in the same way
+ as the Bourne Shell.
+* Bash Variables:: List of variables that exist in Bash.
+
+This chapter describes the shell variables that Bash uses. Bash
+automatically assigns default values to a number of variables.
+
+\1f
+File: bashref.info, Node: Bourne Shell Variables, Next: Bash Variables, Up: Shell Variables
+
+5.1 Bourne Shell Variables
+==========================
+
+Bash uses certain shell variables in the same way as the Bourne shell.
+In some cases, Bash assigns a default value to the variable.
+
+‘CDPATH’
+ A colon-separated list of directories used as a search path for the
+ ‘cd’ builtin command.
+
+‘HOME’
+ The current user's home directory; the default for the ‘cd’ builtin
+ command. The value of this variable is also used by tilde
+ expansion (*note Tilde Expansion::).
+
+‘IFS’
+ A list of characters that separate fields; used when the shell
+ splits words as part of expansion and by the ‘read’ builtin to
+ split lines into words. *Note Word Splitting::, for a description
+ of word splitting.
+
+‘MAIL’
+ If the value is set to a filename or directory name and the
+ ‘MAILPATH’ variable is not set, Bash informs the user of the
+ arrival of mail in the specified file or Maildir-format directory.
+
+‘MAILPATH’
+ A colon-separated list of filenames which the shell periodically
+ checks for new mail. Each list entry can specify the message that
+ is printed when new mail arrives in the mail file by separating the
+ filename from the message with a ‘?’. When used in the text of the
+ message, ‘$_’ expands to the name of the current mail file.
+
+‘OPTARG’
+ The value of the last option argument processed by the ‘getopts’
+ builtin.
+
+‘OPTIND’
+ The index of the next argument to be processed by the ‘getopts’
+ builtin.
+
+‘PATH’
+ A colon-separated list of directories in which the shell looks for
+ commands. A zero-length (null) directory name in the value of
+ ‘PATH’ indicates the current directory. A null directory name may
+ appear as two adjacent colons, or as an initial or trailing colon.
+ The default path is system-dependent, and is set by the
+ administrator who installs ‘bash’. A common value is
+ "/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin".
+
+‘PS1’
+ The primary prompt string. The default value is ‘\s-\v\$ ’. *Note
+ Controlling the Prompt::, for the complete list of escape sequences
+ that are expanded before ‘PS1’ is displayed.
+
+‘PS2’
+ The secondary prompt string. The default value is ‘> ’. ‘PS2’ is
+ expanded in the same way as ‘PS1’ before being displayed.
+
+\1f
+File: bashref.info, Node: Bash Variables, Prev: Bourne Shell Variables, Up: Shell Variables
+
+5.2 Bash Variables
+==================
+
+These variables are set or used by Bash, but other shells do not
+normally treat them specially.
+
+ A few variables used by Bash are described in different chapters:
+variables for controlling the job control facilities (*note Job Control
+Variables::).
+
+‘_’
+ ($_, an underscore.) This has a number of meanings depending on
+ context. At shell startup, $_ set to the pathname used to invoke
+ the shell or shell script being executed as passed in the
+ environment or argument list. Subsequently, it expands to the last
+ argument to the previous simple command executed in the foreground,
+ after expansion. It is also set to the full pathname used to
+ invoke each command executed and placed in the environment exported
+ to that command. When checking mail, $_ expands to the name of the
+ mail file.
+
+‘BASH’
+ The full pathname used to execute the current instance of Bash.
+
+‘BASHOPTS’
+ A colon-separated list of enabled shell options. Each word in the
+ list is a valid argument for the ‘-s’ option to the ‘shopt’ builtin
+ command (*note The Shopt Builtin::). The options appearing in
+ ‘BASHOPTS’ are those reported as ‘on’ by ‘shopt’. If this variable
+ is in the environment when Bash starts up, the shell enables each
+ option in the list before reading any startup files. If this
+ variable is exported, child shells will enable each option in the
+ list. This variable is readonly.
+
+‘BASHPID’
+ Expands to the process ID of the current Bash process. This
+ differs from ‘$$’ under certain circumstances, such as subshells
+ that do not require Bash to be re-initialized. Assignments to
+ ‘BASHPID’ have no effect. If ‘BASHPID’ is unset, it loses its
+ special properties, even if it is subsequently reset.
+
+‘BASH_ALIASES’
+ An associative array variable whose members correspond to the
+ internal list of aliases as maintained by the ‘alias’ builtin.
+ (*note Bourne Shell Builtins::). Elements added to this array
+ appear in the alias list; however, unsetting array elements
+ currently does not cause aliases to be removed from the alias list.
+ If ‘BASH_ALIASES’ is unset, it loses its special properties, even
+ if it is subsequently reset.
+
+‘BASH_ARGC’
+ An array variable whose values are the number of parameters in each
+ frame of the current Bash execution call stack. The number of
+ parameters to the current subroutine (shell function or script
+ executed with ‘.’ or ‘source’) is at the top of the stack. When a
+ subroutine is executed, the number of parameters passed is pushed
+ onto ‘BASH_ARGC’. The shell sets ‘BASH_ARGC’ only when in extended
+ debugging mode (see *note The Shopt Builtin:: for a description of
+ the ‘extdebug’ option to the ‘shopt’ builtin). Setting ‘extdebug’
+ after the shell has started to execute a subroutine, or referencing
+ this variable when ‘extdebug’ is not set, may result in
+ inconsistent values. Assignments to ‘BASH_ARGC’ have no effect,
+ and it may not be unset.
+
+‘BASH_ARGV’
+ An array variable containing all of the parameters in the current
+ Bash execution call stack. The final parameter of the last
+ subroutine call is at the top of the stack; the first parameter of
+ the initial call is at the bottom. When a subroutine is executed,
+ the shell pushes the supplied parameters onto ‘BASH_ARGV’. The
+ shell sets ‘BASH_ARGV’ only when in extended debugging mode (see
+ *note The Shopt Builtin:: for a description of the ‘extdebug’
+ option to the ‘shopt’ builtin). Setting ‘extdebug’ after the shell
+ has started to execute a script, or referencing this variable when
+ ‘extdebug’ is not set, may result in inconsistent values.
+ Assignments to ‘BASH_ARGV’ have no effect, and it may not be unset.
+
+‘BASH_ARGV0’
+ When referenced, this variable expands to the name of the shell or
+ shell script (identical to ‘$0’; *Note Special Parameters::, for
+ the description of special parameter 0). Assigning a value to
+ ‘BASH_ARGV0’ sets ‘$0’ to the same value. If ‘BASH_ARGV0’ is
+ unset, it loses its special properties, even if it is subsequently
+ reset.
+
+‘BASH_CMDS’
+ An associative array variable whose members correspond to the
+ internal hash table of commands as maintained by the ‘hash’ builtin
+ (*note Bourne Shell Builtins::). Adding elements to this array
+ makes them appear in the hash table; however, unsetting array
+ elements currently does not remove command names from the hash
+ table. If ‘BASH_CMDS’ is unset, it loses its special properties,
+ even if it is subsequently reset.
+
+‘BASH_COMMAND’
+ Expands to the command currently being executed or about to be
+ executed, unless the shell is executing a command as the result of
+ a trap, in which case it is the command executing at the time of
+ the trap. If ‘BASH_COMMAND’ is unset, it loses its special
+ properties, even if it is subsequently reset.
+
+‘BASH_COMPAT’
+ The value is used to set the shell's compatibility level. *Note
+ Shell Compatibility Mode::, for a description of the various
+ compatibility levels and their effects. The value may be a decimal
+ number (e.g., 4.2) or an integer (e.g., 42) corresponding to the
+ desired compatibility level. If ‘BASH_COMPAT’ is unset or set to
+ the empty string, the compatibility level is set to the default for
+ the current version. If ‘BASH_COMPAT’ is set to a value that is
+ not one of the valid compatibility levels, the shell prints an
+ error message and sets the compatibility level to the default for
+ the current version. A subset of the valid values correspond to
+ the compatibility levels described below (*note Shell Compatibility
+ Mode::). For example, 4.2 and 42 are valid values that correspond
+ to the ‘compat42’ ‘shopt’ option and set the compatibility level to
+ 42. The current version is also a valid value.
+
+‘BASH_ENV’
+ If this variable is set when Bash is invoked to execute a shell
+ script, its value is expanded and used as the name of a startup
+ file to read before executing the script. Bash does not use ‘PATH’
+ to search for the resultant filename. *Note Bash Startup Files::.
+
+‘BASH_EXECUTION_STRING’
+ The command argument to the ‘-c’ invocation option.
+
+‘BASH_LINENO’
+ An array variable whose members are the line numbers in source
+ files where each corresponding member of ‘FUNCNAME’ was invoked.
+ ‘${BASH_LINENO[$i]}’ is the line number in the source file
+ (‘${BASH_SOURCE[$i+1]}’) where ‘${FUNCNAME[$i]}’ was called (or
+ ‘${BASH_LINENO[$i-1]}’ if referenced within another shell
+ function). Use ‘LINENO’ to obtain the current line number.
+ Assignments to ‘BASH_LINENO’ have no effect, and it may not be
+ unset.
+
+‘BASH_LOADABLES_PATH’
+ A colon-separated list of directories in which the ‘enable’ command
+ looks for dynamically loadable builtins.
+
+‘BASH_MONOSECONDS’
+ Each time this variable is referenced, it expands to the value
+ returned by the system's monotonic clock, if one is available. If
+ there is no monotonic clock, this is equivalent to ‘EPOCHSECONDS’.
+ If ‘BASH_MONOSECONDS’ is unset, it loses its special properties,
+ even if it is subsequently reset.
+
+‘BASH_REMATCH’
+ An array variable whose members are assigned by the ‘=~’ binary
+ operator to the ‘[[’ conditional command (*note Conditional
+ Constructs::). The element with index 0 is the portion of the
+ string matching the entire regular expression. The element with
+ index N is the portion of the string matching the Nth parenthesized
+ subexpression.
+
+‘BASH_SOURCE’
+ An array variable whose members are the source filenames where the
+ corresponding shell function names in the ‘FUNCNAME’ array variable
+ are defined. The shell function ‘${FUNCNAME[$i]}’ is defined in
+ the file ‘${BASH_SOURCE[$i]}’ and called from
+ ‘${BASH_SOURCE[$i+1]}’ Assignments to ‘BASH_SOURCE’ have no effect,
+ and it may not be unset.
+
+‘BASH_SUBSHELL’
+ Incremented by one within each subshell or subshell environment
+ when the shell begins executing in that environment. The initial
+ value is 0. If ‘BASH_SUBSHELL’ is unset, it loses its special
+ properties, even if it is subsequently reset.
+
+‘BASH_TRAPSIG’
+ Set to the signal number corresponding to the trap action being
+ executed during its execution. See the description of ‘trap’
+ (*note Bourne Shell Builtins::) for information about signal
+ numbers and trap execution.
+
+‘BASH_VERSINFO’
+ A readonly array variable (*note Arrays::) whose members hold
+ version information for this instance of Bash. The values assigned
+ to the array members are as follows:
+
+ ‘BASH_VERSINFO[0]’
+ The major version number (the “release”).
+
+ ‘BASH_VERSINFO[1]’
+ The minor version number (the “version”).
+
+ ‘BASH_VERSINFO[2]’
+ The patch level.
+
+ ‘BASH_VERSINFO[3]’
+ The build version.
+
+ ‘BASH_VERSINFO[4]’
+ The release status (e.g., ‘beta’).
+
+ ‘BASH_VERSINFO[5]’
+ The value of ‘MACHTYPE’.
+
+‘BASH_VERSION’
+ Expands to a string describing the version of this instance of Bash
+ (e.g., 5.2.37(3)-release).
+
+‘BASH_XTRACEFD’
+ If set to an integer corresponding to a valid file descriptor, Bash
+ writes the trace output generated when ‘set -x’ is enabled to that
+ file descriptor, instead of the standard error. This allows
+ tracing output to be separated from diagnostic and error messages.
+ The file descriptor is closed when ‘BASH_XTRACEFD’ is unset or
+ assigned a new value. Unsetting ‘BASH_XTRACEFD’ or assigning it
+ the empty string causes the trace output to be sent to the standard
+ error. Note that setting ‘BASH_XTRACEFD’ to 2 (the standard error
+ file descriptor) and then unsetting it will result in the standard
+ error being closed.
+
+‘CHILD_MAX’
+ Set the number of exited child status values for the shell to
+ remember. Bash will not allow this value to be decreased below a
+ POSIX-mandated minimum, and there is a maximum value (currently
+ 8192) that this may not exceed. The minimum value is
+ system-dependent.
+
+‘COLUMNS’
+ Used by the ‘select’ command to determine the terminal width when
+ printing selection lists. Automatically set if the ‘checkwinsize’
+ option is enabled (*note The Shopt Builtin::), or in an interactive
+ shell upon receipt of a ‘SIGWINCH’.
+
+‘COMP_CWORD’
+ An index into ‘${COMP_WORDS}’ of the word containing the current
+ cursor position. This variable is available only in shell
+ functions invoked by the programmable completion facilities (*note
+ Programmable Completion::).
+
+‘COMP_KEY’
+ The key (or final key of a key sequence) used to invoke the current
+ completion function. This variable is available only in shell
+ functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMP_LINE’
+ The current command line. This variable is available only in shell
+ functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMP_POINT’
+ The index of the current cursor position relative to the beginning
+ of the current command. If the current cursor position is at the
+ end of the current command, the value of this variable is equal to
+ ‘${#COMP_LINE}’. This variable is available only in shell
+ functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMP_TYPE’
+ Set to an integer value corresponding to the type of attempted
+ completion that caused a completion function to be called: <TAB>,
+ for normal completion, ‘?’, for listing completions after
+ successive tabs, ‘!’, for listing alternatives on partial word
+ completion, ‘@’, to list completions if the word is not unmodified,
+ or ‘%’, for menu completion. This variable is available only in
+ shell functions and external commands invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMP_WORDBREAKS’
+ The set of characters that the Readline library treats as word
+ separators when performing word completion. If ‘COMP_WORDBREAKS’
+ is unset, it loses its special properties, even if it is
+ subsequently reset.
+
+‘COMP_WORDS’
+ An array variable consisting of the individual words in the current
+ command line. The line is split into words as Readline would split
+ it, using ‘COMP_WORDBREAKS’ as described above. This variable is
+ available only in shell functions invoked by the programmable
+ completion facilities (*note Programmable Completion::).
+
+‘COMPREPLY’
+ An array variable from which Bash reads the possible completions
+ generated by a shell function invoked by the programmable
+ completion facility (*note Programmable Completion::). Each array
+ element contains one possible completion.
+
+‘COPROC’
+ An array variable created to hold the file descriptors for output
+ from and input to an unnamed coprocess (*note Coprocesses::).
+
+‘DIRSTACK’
+ An array variable containing the current contents of the directory
+ stack. Directories appear in the stack in the order they are
+ displayed by the ‘dirs’ builtin. Assigning to members of this
+ array variable may be used to modify directories already in the
+ stack, but the ‘pushd’ and ‘popd’ builtins must be used to add and
+ remove directories. Assigning to this variable does not change the
+ current directory. If ‘DIRSTACK’ is unset, it loses its special
+ properties, even if it is subsequently reset.
+
+‘EMACS’
+ If Bash finds this variable in the environment when the shell
+ starts, and its value is ‘t’, Bash assumes that the shell is
+ running in an Emacs shell buffer and disables line editing.
+
+‘ENV’
+ Expanded and executed similarly to ‘BASH_ENV’ (*note Bash Startup
+ Files::) when an interactive shell is invoked in POSIX mode (*note
+ Bash POSIX Mode::).
+
+‘EPOCHREALTIME’
+ Each time this parameter is referenced, it expands to the number of
+ seconds since the Unix Epoch as a floating-point value with
+ micro-second granularity (see the documentation for the C library
+ function ‘time’ for the definition of Epoch). Assignments to
+ ‘EPOCHREALTIME’ are ignored. If ‘EPOCHREALTIME’ is unset, it loses
+ its special properties, even if it is subsequently reset.
+
+‘EPOCHSECONDS’
+ Each time this parameter is referenced, it expands to the number of
+ seconds since the Unix Epoch (see the documentation for the C
+ library function ‘time’ for the definition of Epoch). Assignments
+ to ‘EPOCHSECONDS’ are ignored. If ‘EPOCHSECONDS’ is unset, it
+ loses its special properties, even if it is subsequently reset.
+
+‘EUID’
+ The numeric effective user id of the current user. This variable
+ is readonly.
+
+‘EXECIGNORE’
+ A colon-separated list of shell patterns (*note Pattern Matching::)
+ defining the set of filenames to be ignored by command search using
+ ‘PATH’. Files whose full pathnames match one of these patterns are
+ not considered executable files for the purposes of completion and
+ command execution via ‘PATH’ lookup. This does not affect the
+ behavior of the ‘[’, ‘test’, and ‘[[’ commands. Full pathnames in
+ the command hash table are not subject to ‘EXECIGNORE’. Use this
+ variable to ignore shared library files that have the executable
+ bit set, but are not executable files. The pattern matching honors
+ the setting of the ‘extglob’ shell option.
+
+‘FCEDIT’
+ The editor used as a default by the ‘fc’ builtin command.
+
+‘FIGNORE’
+ A colon-separated list of suffixes to ignore when performing
+ filename completion. A filename whose suffix matches one of the
+ entries in ‘FIGNORE’ is excluded from the list of matched
+ filenames. A sample value is ‘.o:~’
+
+‘FUNCNAME’
+ An array variable containing the names of all shell functions
+ currently in the execution call stack. The element with index 0 is
+ the name of any currently-executing shell function. The
+ bottom-most element (the one with the highest index) is ‘"main"’.
+ This variable exists only when a shell function is executing.
+ Assignments to ‘FUNCNAME’ have no effect. If ‘FUNCNAME’ is unset,
+ it loses its special properties, even if it is subsequently reset.
+
+ This variable can be used with ‘BASH_LINENO’ and ‘BASH_SOURCE’.
+ Each element of ‘FUNCNAME’ has corresponding elements in
+ ‘BASH_LINENO’ and ‘BASH_SOURCE’ to describe the call stack. For
+ instance, ‘${FUNCNAME[$i]}’ was called from the file
+ ‘${BASH_SOURCE[$i+1]}’ at line number ‘${BASH_LINENO[$i]}’. The
+ ‘caller’ builtin displays the current call stack using this
+ information.
+
+‘FUNCNEST’
+ A numeric value greater than 0 defines a maximum function nesting
+ level. Function invocations that exceed this nesting level cause
+ the current command to abort.
+
+‘GLOBIGNORE’
+ A colon-separated list of patterns defining the set of file names
+ to be ignored by filename expansion. If a file name matched by a
+ filename expansion pattern also matches one of the patterns in
+ ‘GLOBIGNORE’, it is removed from the list of matches. The pattern
+ matching honors the setting of the ‘extglob’ shell option.
+
+‘GLOBSORT’
+ Controls how the results of filename expansion are sorted. The
+ value of this variable specifies the sort criteria and sort order
+ for the results of filename expansion. If this variable is unset
+ or set to the null string, filename expansion uses the historical
+ behavior of sorting by name, in ascending lexicographic order as
+ determined by the ‘LC_COLLATE’ shell variable.
+
+ If set, a valid value begins with an optional ‘+’, which is
+ ignored, or ‘-’, which reverses the sort order from ascending to
+ descending, followed by a sort specifier. The valid sort
+ specifiers are ‘name’, ‘numeric’, ‘size’, ‘mtime’, ‘atime’,
+ ‘ctime’, and ‘blocks’, which sort the files on name, names in
+ numeric rather than lexicographic order, file size, modification
+ time, access time, inode change time, and number of blocks,
+ respectively. If any of the non-name keys compare as equal (e.g.,
+ if two files are the same size), sorting uses the name as a
+ secondary sort key.
+
+ For example, a value of ‘-mtime’ sorts the results in descending
+ order by modification time (newest first).
+
+ The ‘numeric’ specifier treats names consisting solely of digits as
+ numbers and sorts them using their numeric value (so "2" sorts
+ before "10", for example). When using ‘numeric’, names containing
+ non-digits sort after all the all-digit names and are sorted by
+ name using the traditional behavior.
+
+ A sort specifier of ‘nosort’ disables sorting completely; Bash
+ returns the results in the order they are read from the file
+ system, ignoring any leading ‘-’.
+
+ If the sort specifier is missing, it defaults to NAME, so a value
+ of ‘+’ is equivalent to the null string, and a value of ‘-’ sorts
+ by name in descending order.
+
+ Any invalid value restores the historical sorting behavior.
+
+‘GROUPS’
+ An array variable containing the list of groups of which the
+ current user is a member. Assignments to ‘GROUPS’ have no effect.
+ If ‘GROUPS’ is unset, it loses its special properties, even if it
+ is subsequently reset.
+
+‘histchars’
+ The two or three characters which control history expansion, quick
+ substitution, and tokenization (*note History Interaction::). The
+ first character is the “history expansion” character, the character
+ which begins a history expansion, normally ‘!’. The second
+ character is the “quick substitution” character, normally ‘^’.
+ When it appears as the first character on the line, history
+ substitution repeats the previous command, replacing one string
+ with another. The optional third character is the “history
+ comment” character, normally ‘#’, which indicates that the
+ remainder of the line is a comment when it appears as the first
+ character of a word. The history comment character disables
+ history substitution for the remaining words on the line. It does
+ not necessarily cause the shell parser to treat the rest of the
+ line as a comment.
+
+‘HISTCMD’
+ The history number, or index in the history list, of the current
+ command. Assignments to ‘HISTCMD’ have no effect. If ‘HISTCMD’ is
+ unset, it loses its special properties, even if it is subsequently
+ reset.
+
+‘HISTCONTROL’
+ A colon-separated list of values controlling how commands are saved
+ on the history list. If the list of values includes ‘ignorespace’,
+ lines which begin with a space character are not saved in the
+ history list. A value of ‘ignoredups’ causes lines which match the
+ previous history entry not to be saved. A value of ‘ignoreboth’ is
+ shorthand for ‘ignorespace’ and ‘ignoredups’. A value of
+ ‘erasedups’ causes all previous lines matching the current line to
+ be removed from the history list before that line is saved. Any
+ value not in the above list is ignored. If ‘HISTCONTROL’ is unset,
+ or does not include a valid value, Bash saves all lines read by the
+ shell parser on the history list, subject to the value of
+ ‘HISTIGNORE’. If the first line of a multi-line compound command
+ was saved, the second and subsequent lines are not tested, and are
+ added to the history regardless of the value of ‘HISTCONTROL’. If
+ the first line was not saved, the second and subsequent lines of
+ the command are not saved either.
+
+‘HISTFILE’
+ The name of the file to which the command history is saved. Bash
+ assigns a default value of ‘~/.bash_history’. If ‘HISTFILE’ is
+ unset or null, the shell does not save the command history when it
+ exits.
+
+‘HISTFILESIZE’
+ The maximum number of lines contained in the history file. When
+ this variable is assigned a value, the history file is truncated,
+ if necessary, to contain no more than the number of history entries
+ that total no more than that number of lines by removing the oldest
+ entries. If the history list contains multi-line entries, the
+ history file may contain more lines than this maximum to avoid
+ leaving partial history entries. The history file is also
+ truncated to this size after writing it when a shell exits or by
+ the ‘history’ builtin. If the value is 0, the history file is
+ truncated to zero size. Non-numeric values and numeric values less
+ than zero inhibit truncation. The shell sets the default value to
+ the value of ‘HISTSIZE’ after reading any startup files.
+
+‘HISTIGNORE’
+ A colon-separated list of patterns used to decide which command
+ lines should be saved on the history list. If a command line
+ matches one of the patterns in the value of ‘HISTIGNORE’, it is not
+ saved on the history list. Each pattern is anchored at the
+ beginning of the line and must match the complete line (Bash does
+ not implicitly append a ‘*’). Each pattern is tested against the
+ line after the checks specified by ‘HISTCONTROL’ are applied. In
+ addition to the normal shell pattern matching characters, ‘&’
+ matches the previous history line. A backslash escapes the ‘&’;
+ the backslash is removed before attempting a match. If the first
+ line of a multi-line compound command was saved, the second and
+ subsequent lines are not tested, and are added to the history
+ regardless of the value of ‘HISTIGNORE’. If the first line was not
+ saved, the second and subsequent lines of the command are not saved
+ either. The pattern matching honors the setting of the ‘extglob’
+ shell option.
+
+ ‘HISTIGNORE’ subsumes some of the function of ‘HISTCONTROL’. A
+ pattern of ‘&’ is identical to ‘ignoredups’, and a pattern of ‘[
+ ]*’ is identical to ‘ignorespace’. Combining these two patterns,
+ separating them with a colon, provides the functionality of
+ ‘ignoreboth’.
+
+‘HISTSIZE’
+ The maximum number of commands to remember on the history list. If
+ the value is 0, commands are not saved in the history list.
+ Numeric values less than zero result in every command being saved
+ on the history list (there is no limit). The shell sets the
+ default value to 500 after reading any startup files.
+
+‘HISTTIMEFORMAT’
+ If this variable is set and not null, its value is used as a format
+ string for ‘strftime’(3) to print the time stamp associated with
+ each history entry displayed by the ‘history’ builtin. If this
+ variable is set, the shell writes time stamps to the history file
+ so they may be preserved across shell sessions. This uses the
+ history comment character to distinguish timestamps from other
+ history lines.
+
+‘HOSTFILE’
+ Contains the name of a file in the same format as ‘/etc/hosts’ that
+ should be read when the shell needs to complete a hostname. The
+ list of possible hostname completions may be changed while the
+ shell is running; the next time hostname completion is attempted
+ after the value is changed, Bash adds the contents of the new file
+ to the existing list. If ‘HOSTFILE’ is set, but has no value, or
+ does not name a readable file, Bash attempts to read ‘/etc/hosts’
+ to obtain the list of possible hostname completions. When
+ ‘HOSTFILE’ is unset, Bash clears the hostname list.
+
+‘HOSTNAME’
+ The name of the current host.
+
+‘HOSTTYPE’
+ A string describing the machine Bash is running on.
+
+‘IGNOREEOF’
+ Controls the action of the shell on receipt of an ‘EOF’ character
+ as the sole input. If set, the value is the number of consecutive
+ ‘EOF’ characters that can be read as the first character on an
+ input line before Bash exits. If the variable is set but does not
+ have a numeric value, or the value is null, then the default is 10.
+ If the variable is unset, then ‘EOF’ signifies the end of input to
+ the shell. This is only in effect for interactive shells.
+
+‘INPUTRC’
+ The name of the Readline initialization file, overriding the
+ default of ‘~/.inputrc’.
+
+‘INSIDE_EMACS’
+ If Bash finds this variable in the environment when the shell
+ starts, it assumes that the shell is running in an Emacs shell
+ buffer and may disable line editing depending on the value of
+ ‘TERM’.
+
+‘LANG’
+ Used to determine the locale category for any category not
+ specifically selected with a variable starting with ‘LC_’.
+
+‘LC_ALL’
+ This variable overrides the value of ‘LANG’ and any other ‘LC_’
+ variable specifying a locale category.
+
+‘LC_COLLATE’
+ This variable determines the collation order used when sorting the
+ results of filename expansion, and determines the behavior of range
+ expressions, equivalence classes, and collating sequences within
+ filename expansion and pattern matching (*note Filename
+ Expansion::).
+
+‘LC_CTYPE’
+ This variable determines the interpretation of characters and the
+ behavior of character classes within filename expansion and pattern
+ matching (*note Filename Expansion::).
+
+‘LC_MESSAGES’
+ This variable determines the locale used to translate double-quoted
+ strings preceded by a ‘$’ (*note Locale Translation::).
+
+‘LC_NUMERIC’
+ This variable determines the locale category used for number
+ formatting.
+
+‘LC_TIME’
+ This variable determines the locale category used for data and time
+ formatting.
+
+‘LINENO’
+ The line number in the script or shell function currently
+ executing. Line numbers start with 1. When not in a script or
+ function, the value is not guaranteed to be meaningful. If
+ ‘LINENO’ is unset, it loses its special properties, even if it is
+ subsequently reset.
+
+‘LINES’
+ Used by the ‘select’ command to determine the column length for
+ printing selection lists. Automatically set if the ‘checkwinsize’
+ option is enabled (*note The Shopt Builtin::), or in an interactive
+ shell upon receipt of a ‘SIGWINCH’.
+
+‘MACHTYPE’
+ A string that fully describes the system type on which Bash is
+ executing, in the standard GNU CPU-COMPANY-SYSTEM format.
+
+‘MAILCHECK’
+ How often (in seconds) that the shell should check for mail in the
+ files specified in the ‘MAILPATH’ or ‘MAIL’ variables. The default
+ is 60 seconds. When it is time to check for mail, the shell does
+ so before displaying the primary prompt. If this variable is
+ unset, or set to a value that is not a number greater than or equal
+ to zero, the shell disables mail checking.
+
+‘MAPFILE’
+ An array variable created to hold the text read by the ‘mapfile’
+ builtin when no variable name is supplied.
+
+‘OLDPWD’
+ The previous working directory as set by the ‘cd’ builtin.
+
+‘OPTERR’
+ If set to the value 1, Bash displays error messages generated by
+ the ‘getopts’ builtin command. ‘OPTERR’ is initialized to 1 each
+ time the shell is invoked.
+
+‘OSTYPE’
+ A string describing the operating system Bash is running on.
+
+‘PIPESTATUS’
+ An array variable (*note Arrays::) containing a list of exit status
+ values from the commands in the most-recently-executed foreground
+ pipeline, which may consist of only a simple command (*note Shell
+ Commands::). Bash sets ‘PIPESTATUS’ after executing multi-element
+ pipelines, timed and negated pipelines, simple commands, subshells
+ created with the ‘(’ operator, the ‘[[’ and ‘((’ compound commands,
+ and after error conditions that result in the shell aborting
+ command execution.
+
+‘POSIXLY_CORRECT’
+ If this variable is in the environment when Bash starts, the shell
+ enters POSIX mode (*note Bash POSIX Mode::) before reading the
+ startup files, as if the ‘--posix’ invocation option had been
+ supplied. If it is set while the shell is running, Bash enables
+ POSIX mode, as if the command
+ set -o posix
+ had been executed. When the shell enters POSIX mode, it sets this
+ variable if it was not already set.
+
+‘PPID’
+ The process ID of the shell's parent process. This variable is
+ readonly.
+
+‘PROMPT_COMMAND’
+ If this variable is set, and is an array, the value of each set
+ element is interpreted as a command to execute before printing the
+ primary prompt (‘$PS1’). If this is set but not an array variable,
+ its value is used as a command to execute instead.
+
+‘PROMPT_DIRTRIM’
+ If set to a number greater than zero, the value is used as the
+ number of trailing directory components to retain when expanding
+ the ‘\w’ and ‘\W’ prompt string escapes (*note Controlling the
+ Prompt::). Characters removed are replaced with an ellipsis.
+
+‘PS0’
+ The value of this parameter is expanded like ‘PS1’ and displayed by
+ interactive shells after reading a command and before the command
+ is executed.
+
+‘PS3’
+ The value of this variable is used as the prompt for the ‘select’
+ command. If this variable is not set, the ‘select’ command prompts
+ with ‘#? ’
+
+‘PS4’
+ The value of this parameter is expanded like ‘PS1’ and the expanded
+ value is the prompt printed before the command line is echoed when
+ the ‘-x’ option is set (*note The Set Builtin::). The first
+ character of the expanded value is replicated multiple times, as
+ necessary, to indicate multiple levels of indirection. The default
+ is ‘+ ’.
+
+‘PWD’
+ The current working directory as set by the ‘cd’ builtin.
+
+‘RANDOM’
+ Each time this parameter is referenced, it expands to a random
+ integer between 0 and 32767. Assigning a value to ‘RANDOM’
+ initializes (seeds) the sequence of random numbers. Seeding the
+ random number generator with the same constant value produces the
+ same sequence of values. If ‘RANDOM’ is unset, it loses its
+ special properties, even if it is subsequently reset.
+
+‘READLINE_ARGUMENT’
+ Any numeric argument given to a Readline command that was defined
+ using ‘bind -x’ (*note Bash Builtins::) when it was invoked.
+
+‘READLINE_LINE’
+ The contents of the Readline line buffer, for use with ‘bind -x’
+ (*note Bash Builtins::).
+
+‘READLINE_MARK’
+ The position of the “mark” (saved insertion point) in the Readline
+ line buffer, for use with ‘bind -x’ (*note Bash Builtins::). The
+ characters between the insertion point and the mark are often
+ called the “region”.
+
+‘READLINE_POINT’
+ The position of the insertion point in the Readline line buffer,
+ for use with ‘bind -x’ (*note Bash Builtins::).
+
+‘REPLY’
+ The default variable for the ‘read’ builtin; set to the line read
+ when ‘read’ is not supplied a variable name argument.
+
+‘SECONDS’
+ This variable expands to the number of seconds since the shell was
+ started. Assignment to this variable resets the count to the value
+ assigned, and the expanded value becomes the value assigned plus
+ the number of seconds since the assignment. The number of seconds
+ at shell invocation and the current time are always determined by
+ querying the system clock at one-second resolution. If ‘SECONDS’
+ is unset, it loses its special properties, even if it is
+ subsequently reset.
+
+‘SHELL’
+ This environment variable expands to the full pathname to the
+ shell. If it is not set when the shell starts, Bash assigns to it
+ the full pathname of the current user's login shell.
+
+‘SHELLOPTS’
+ A colon-separated list of enabled shell options. Each word in the
+ list is a valid argument for the ‘-o’ option to the ‘set’ builtin
+ command (*note The Set Builtin::). The options appearing in
+ ‘SHELLOPTS’ are those reported as ‘on’ by ‘set -o’. If this
+ variable is in the environment when Bash starts up, the shell
+ enables each option in the list before reading any startup files.
+ If this variable is exported, child shells will enable each option
+ in the list. This variable is readonly.
+
+‘SHLVL’
+ Incremented by one each time a new instance of Bash is started.
+ This is intended to be a count of how deeply your Bash shells are
+ nested.
+
+‘SRANDOM’
+ This variable expands to a 32-bit pseudo-random number each time it
+ is referenced. The random number generator is not linear on
+ systems that support ‘/dev/urandom’ or ‘arc4random’, so each
+ returned number has no relationship to the numbers preceding it.
+ The random number generator cannot be seeded, so assignments to
+ this variable have no effect. If ‘SRANDOM’ is unset, it loses its
+ special properties, even if it is subsequently reset.
+
+‘TIMEFORMAT’
+ The value of this parameter is used as a format string specifying
+ how the timing information for pipelines prefixed with the ‘time’
+ reserved word should be displayed. The ‘%’ character introduces an
+ escape sequence that is expanded to a time value or other
+ information. The escape sequences and their meanings are as
+ follows; the brackets denote optional portions.
+
+ ‘%%’
+ A literal ‘%’.
+
+ ‘%[P][l]R’
+ The elapsed time in seconds.
+
+ ‘%[P][l]U’
+ The number of CPU seconds spent in user mode.
+
+ ‘%[P][l]S’
+ The number of CPU seconds spent in system mode.
+
+ ‘%P’
+ The CPU percentage, computed as (%U + %S) / %R.
+
+ The optional P is a digit specifying the precision, the number of
+ fractional digits after a decimal point. A value of 0 causes no
+ decimal point or fraction to be output. ‘time’ prints at most six
+ digits after the decimal point; values of P greater than 6 are
+ changed to 6. If P is not specified, ‘time’ prints three digits
+ after the decimal point.
+
+ The optional ‘l’ specifies a longer format, including minutes, of
+ the form MMmSS.FFs. The value of P determines whether or not the
+ fraction is included.
+
+ If this variable is not set, Bash acts as if it had the value
+ $'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'
+ If the value is null, Bash does not display any timing information.
+ A trailing newline is added when the format string is displayed.
+
+‘TMOUT’
+ If set to a value greater than zero, the ‘read’ builtin uses the
+ value as its default timeout (*note Bash Builtins::). The ‘select’
+ command (*note Conditional Constructs::) terminates if input does
+ not arrive after ‘TMOUT’ seconds when input is coming from a
+ terminal.
+
+ In an interactive shell, the value is interpreted as the number of
+ seconds to wait for a line of input after issuing the primary
+ prompt. Bash terminates after waiting for that number of seconds
+ if a complete line of input does not arrive.
+
+‘TMPDIR’
+ If set, Bash uses its value as the name of a directory in which
+ Bash creates temporary files for the shell's use.
+
+‘UID’
+ The numeric real user id of the current user. This variable is
+ readonly.
+
+\1f
+File: bashref.info, Node: Bash Features, Next: Job Control, Prev: Shell Variables, Up: Top
+
+6 Bash Features
+***************
+
+This chapter describes features unique to Bash.
+
+* Menu:
+
+* Invoking Bash:: Command line options that you can give
+ to Bash.
+* Bash Startup Files:: When and how Bash executes scripts.
+* Interactive Shells:: What an interactive shell is.
+* Bash Conditional Expressions:: Primitives used in composing expressions for
+ the ‘test’ builtin.
+* Shell Arithmetic:: Arithmetic on shell variables.
+* Aliases:: Substituting one command for another.
+* Arrays:: Array Variables.
+* The Directory Stack:: History of visited directories.
+* Controlling the Prompt:: Customizing the various prompt strings.
+* The Restricted Shell:: A more controlled mode of shell execution.
+* Bash POSIX Mode:: Making Bash behave more closely to what
+ the POSIX standard specifies.
+* Shell Compatibility Mode:: How Bash supports behavior that was present
+ in earlier versions and has changed.
+
+\1f
+File: bashref.info, Node: Invoking Bash, Next: Bash Startup Files, Up: Bash Features
+
+6.1 Invoking Bash
+=================
+
+ bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o OPTION]
+ [-O SHOPT_OPTION] [ARGUMENT ...]
+ bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o OPTION]
+ [-O SHOPT_OPTION] -c STRING [ARGUMENT ...]
+ bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o OPTION]
+ [-O SHOPT_OPTION] [ARGUMENT ...]
+
+ All of the single-character options used with the ‘set’ builtin
+(*note The Set Builtin::) can be used as options when the shell is
+invoked. In addition, there are several multi-character options that
+you can use. These options must appear on the command line before the
+single-character options to be recognized.
+
+‘--debugger’
+ Arrange for the debugger profile to be executed before the shell
+ starts. Turns on extended debugging mode (see *note The Shopt
+ Builtin:: for a description of the ‘extdebug’ option to the ‘shopt’
+ builtin).
+
+‘--dump-po-strings’
+ Print a list of all double-quoted strings preceded by ‘$’ on the
+ standard output in the GNU ‘gettext’ PO (portable object) file
+ format. Equivalent to ‘-D’ except for the output format.
+
+‘--dump-strings’
+ Equivalent to ‘-D’.
+
+‘--help’
+ Display a usage message on standard output and exit successfully.
+
+‘--init-file FILENAME’
+‘--rcfile FILENAME’
+ Execute commands from FILENAME (instead of ‘~/.bashrc’) in an
+ interactive shell.
+
+‘--login’
+ Equivalent to ‘-l’.
+
+‘--noediting’
+ Do not use the GNU Readline library (*note Command Line Editing::)
+ to read command lines when the shell is interactive.
+
+‘--noprofile’
+ Don't load the system-wide startup file ‘/etc/profile’ or any of
+ the personal initialization files ‘~/.bash_profile’,
+ ‘~/.bash_login’, or ‘~/.profile’ when Bash is invoked as a login
+ shell.
+
+‘--norc’
+ Don't read the ‘~/.bashrc’ initialization file in an interactive
+ shell. This is on by default if the shell is invoked as ‘sh’.
+
+‘--posix’
+ Enable POSIX mode; change the behavior of Bash where the default
+ operation differs from the POSIX standard to match the standard.
+ This is intended to make Bash behave as a strict superset of that
+ standard. *Note Bash POSIX Mode::, for a description of the Bash
+ POSIX mode.
+
+‘--restricted’
+ Equivalent to ‘-r’. Make the shell a restricted shell (*note The
+ Restricted Shell::).
+
+‘--verbose’
+ Equivalent to ‘-v’. Print shell input lines as they're read.
+
+‘--version’
+ Show version information for this instance of Bash on the standard
+ output and exit successfully.
+
+ There are several single-character options that may be supplied at
+invocation which are not available with the ‘set’ builtin.
+
+‘-c’
+ Read and execute commands from the first non-option argument
+ COMMAND_STRING, then exit. If there are arguments after the
+ COMMAND_STRING, the first argument is assigned to ‘$0’ and any
+ remaining arguments are assigned to the positional parameters. The
+ assignment to ‘$0’ sets the name of the shell, which is used in
+ warning and error messages.
+
+‘-i’
+ Force the shell to run interactively. Interactive shells are
+ described in *note Interactive Shells::.
+
+‘-l’
+ Make this shell act as if it had been directly invoked by login.
+ When the shell is interactive, this is equivalent to starting a
+ login shell with ‘exec -l bash’. When the shell is not
+ interactive, it will read and execute the login shell startup
+ files. ‘exec bash -l’ or ‘exec bash --login’ will replace the
+ current shell with a Bash login shell. *Note Bash Startup Files::,
+ for a description of the special behavior of a login shell.
+
+‘-r’
+ Make the shell a restricted shell (*note The Restricted Shell::).
+
+‘-s’
+ If this option is present, or if no arguments remain after option
+ processing, then Bash reads commands from the standard input. This
+ option allows the positional parameters to be set when invoking an
+ interactive shell or when reading input through a pipe.
+
+‘-D’
+ Print a list of all double-quoted strings preceded by ‘$’ on the
+ standard output. These are the strings that are subject to
+ language translation when the current locale is not ‘C’ or ‘POSIX’
+ (*note Locale Translation::). This implies the ‘-n’ option; no
+ commands will be executed.
+
+‘[-+]O [SHOPT_OPTION]’
+ SHOPT_OPTION is one of the shell options accepted by the ‘shopt’
+ builtin (*note The Shopt Builtin::). If SHOPT_OPTION is present,
+ ‘-O’ sets the value of that option; ‘+O’ unsets it. If
+ SHOPT_OPTION is not supplied, Bash prints the names and values of
+ the shell options accepted by ‘shopt’ on the standard output. If
+ the invocation option is ‘+O’, the output is displayed in a format
+ that may be reused as input.
+
+‘--’
+ A ‘--’ signals the end of options and disables further option
+ processing. Any arguments after the ‘--’ are treated as a shell
+ script filename (*note Shell Scripts::) and arguments passed to
+ that script.
+
+‘-’
+ Equivalent to ‘--’.
+
+ A “login shell” is one whose first character of argument zero is ‘-’,
+or one invoked with the ‘--login’ option.
+
+ An “interactive shell” is one started without non-option arguments,
+unless ‘-s’ is specified, without specifying the ‘-c’ option, and whose
+standard input and standard error are both connected to terminals (as
+determined by isatty(3)), or one started with the ‘-i’ option. *Note
+Interactive Shells::, for more information.
+
+ If arguments remain after option processing, and neither the ‘-c’ nor
+the ‘-s’ option has been supplied, the first argument is treated as the
+name of a file containing shell commands (*note Shell Scripts::). When
+Bash is invoked in this fashion, ‘$0’ is set to the name of the file,
+and the positional parameters are set to the remaining arguments. Bash
+reads and executes commands from this file, then exits. Bash's exit
+status is the exit status of the last command executed in the script.
+If no commands are executed, the exit status is 0. Bash first attempts
+to open the file in the current directory, and, if no file is found,
+searches the directories in ‘PATH’ for the script.
+
+\1f
+File: bashref.info, Node: Bash Startup Files, Next: Interactive Shells, Prev: Invoking Bash, Up: Bash Features
+
+6.2 Bash Startup Files
+======================
+
+This section describes how Bash executes its startup files. If any of
+the files exist but cannot be read, Bash reports an error. Tildes are
+expanded in filenames as described above under Tilde Expansion (*note
+Tilde Expansion::).
+
+ Interactive shells are described in *note Interactive Shells::.
+
+Invoked as an interactive login shell, or with ‘--login’
+........................................................
+
+When Bash is invoked as an interactive login shell, or as a
+non-interactive shell with the ‘--login’ option, it first reads and
+executes commands from the file ‘/etc/profile’, if that file exists.
+After reading that file, it looks for ‘~/.bash_profile’,
+‘~/.bash_login’, and ‘~/.profile’, in that order, and reads and executes
+commands from the first one that exists and is readable. The
+‘--noprofile’ option inhibits this behavior.
+
+ When an interactive login shell exits, or a non-interactive login
+shell executes the ‘exit’ builtin command, Bash reads and executes
+commands from the file ‘~/.bash_logout’, if it exists.
+
+Invoked as an interactive non-login shell
+.........................................
+
+When Bash runs as an interactive shell that is not a login shell, it
+reads and executes commands from ‘~/.bashrc’, if that file exists. The
+‘--norc’ option inhibits this behavior. The ‘--rcfile FILE’ option
+causes Bash to use FILE instead of ‘~/.bashrc’.
+
+ So, typically, your ‘~/.bash_profile’ contains the line
+ if [ -f ~/.bashrc ]; then . ~/.bashrc; fi
+after (or before) any login-specific initializations.
+
+Invoked non-interactively
+.........................
+
+When Bash is started non-interactively, to run a shell script, for
+example, it looks for the variable ‘BASH_ENV’ in the environment,
+expands its value if it appears there, and uses the expanded value as
+the name of a file to read and execute. Bash behaves as if the
+following command were executed:
+ if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
+but does not the value of the ‘PATH’ variable to search for the
+filename.
+
+ As noted above, if a non-interactive shell is invoked with the
+‘--login’ option, Bash attempts to read and execute commands from the
+login shell startup files.
+
+Invoked with name ‘sh’
+......................
+
+If Bash is invoked with the name ‘sh’, it tries to mimic the startup
+behavior of historical versions of ‘sh’ as closely as possible, while
+conforming to the POSIX standard as well.
+
+ When invoked as an interactive login shell, or as a non-interactive
+shell with the ‘--login’ option, it first attempts to read and execute
+commands from ‘/etc/profile’ and ‘~/.profile’, in that order. The
+‘--noprofile’ option inhibits this behavior.
+
+ When invoked as an interactive shell with the name ‘sh’, Bash looks
+for the variable ‘ENV’, expands its value if it is defined, and uses the
+expanded value as the name of a file to read and execute. Since a shell
+invoked as ‘sh’ does not attempt to read and execute commands from any
+other startup files, the ‘--rcfile’ option has no effect.
+
+ A non-interactive shell invoked with the name ‘sh’ does not attempt
+to read any other startup files.
+
+ When invoked as ‘sh’, Bash enters POSIX mode after reading the
+startup files.
+
+Invoked in POSIX mode
+.....................
+
+When Bash is started in POSIX mode, as with the ‘--posix’ command line
+option, it follows the POSIX standard for startup files. In this mode,
+interactive shells expand the ‘ENV’ variable and read and execute
+commands from the file whose name is the expanded value. No other
+startup files are read.
+
+Invoked by remote shell daemon
+..............................
+
+Bash attempts to determine when it is being run with its standard input
+connected to a network connection, as when executed by the historical
+and rarely-seen remote shell daemon, usually ‘rshd’, or the secure shell
+daemon ‘sshd’. If Bash determines it is being run non-interactively in
+this fashion, it reads and executes commands from ‘~/.bashrc’, if that
+file exists and is readable. Bash does not read this file if invoked as
+‘sh’. The ‘--norc’ option inhibits this behavior, and the ‘--rcfile’
+option makes Bash use a different file instead of ‘~/.bashrc’, but
+neither ‘rshd’ nor ‘sshd’ generally invoke the shell with those options
+or allow them to be specified.
+
+Invoked with unequal effective and real UID/GIDs
+................................................
+
+If Bash is started with the effective user (group) id not equal to the
+real user (group) id, and the ‘-p’ option is not supplied, no startup
+files are read, shell functions are not inherited from the environment,
+the ‘SHELLOPTS’, ‘BASHOPTS’, ‘CDPATH’, and ‘GLOBIGNORE’ variables, if
+they appear in the environment, are ignored, and the effective user id
+is set to the real user id. If the ‘-p’ option is supplied at
+invocation, the startup behavior is the same, but the effective user id
+is not reset.
+
+\1f
+File: bashref.info, Node: Interactive Shells, Next: Bash Conditional Expressions, Prev: Bash Startup Files, Up: Bash Features
+
+6.3 Interactive Shells
+======================
+
+* Menu:
+
+* What is an Interactive Shell?:: What determines whether a shell is Interactive.
+* Is this Shell Interactive?:: How to tell if a shell is interactive.
+* Interactive Shell Behavior:: What changes in an interactive shell?
+
+\1f
+File: bashref.info, Node: What is an Interactive Shell?, Next: Is this Shell Interactive?, Up: Interactive Shells
+
+6.3.1 What is an Interactive Shell?
+-----------------------------------
+
+An interactive shell is one started without non-option arguments (unless
+‘-s’ is specified) and without specifying the ‘-c’ option, whose input
+and error output are both connected to terminals (as determined by
+‘isatty(3)’), or one started with the ‘-i’ option.
+
+ An interactive shell generally reads from and writes to a user's
+terminal.
+
+ The ‘-s’ invocation option may be used to set the positional
+parameters when an interactive shell starts.
+
+\1f
+File: bashref.info, Node: Is this Shell Interactive?, Next: Interactive Shell Behavior, Prev: What is an Interactive Shell?, Up: Interactive Shells
+
+6.3.2 Is this Shell Interactive?
+--------------------------------
+
+To determine within a startup script whether or not Bash is running
+interactively, test the value of the ‘-’ special parameter. It contains
+‘i’ when the shell is interactive. For example:
+
+ case "$-" in
+ *i*) echo This shell is interactive ;;
+ *) echo This shell is not interactive ;;
+ esac
+
+ Alternatively, startup scripts may examine the variable ‘PS1’; it is
+unset in non-interactive shells, and set in interactive shells. Thus:
+
+ if [ -z "$PS1" ]; then
+ echo This shell is not interactive
+ else
+ echo This shell is interactive
+ fi
+
+\1f
+File: bashref.info, Node: Interactive Shell Behavior, Prev: Is this Shell Interactive?, Up: Interactive Shells
+
+6.3.3 Interactive Shell Behavior
+--------------------------------
+
+When the shell is running interactively, it changes its behavior in
+several ways.
+
+ 1. Bash reads and executes startup files as described in *note Bash
+ Startup Files::.
+
+ 2. Job Control (*note Job Control::) is enabled by default. When job
+ control is in effect, Bash ignores the keyboard-generated job
+ control signals ‘SIGTTIN’, ‘SIGTTOU’, and ‘SIGTSTP’.
+
+ 3. Bash executes the values of the set elements of the
+ ‘PROMPT_COMMAND’ array variable as commands before printing the
+ primary prompt, ‘$PS1’ (*note Bash Variables::).
+
+ 4. Bash expands and displays ‘PS1’ before reading the first line of a
+ command, and expands and displays ‘PS2’ before reading the second
+ and subsequent lines of a multi-line command. Bash expands and
+ displays ‘PS0’ after it reads a command but before executing it.
+ See *note Controlling the Prompt::, for a complete list of prompt
+ string escape sequences.
+
+ 5. Bash uses Readline (*note Command Line Editing::) to read commands
+ from the user's terminal.
+
+ 6. Bash inspects the value of the ‘ignoreeof’ option to ‘set -o’
+ instead of exiting immediately when it receives an ‘EOF’ on its
+ standard input when reading a command (*note The Set Builtin::).
+
+ 7. Bash enables Command history (*note Bash History Facilities::) and
+ history expansion (*note History Interaction::) by default. When a
+ shell with history enabled exits, Bash saves the command history to
+ the file named by ‘$HISTFILE’.
+
+ 8. Alias expansion (*note Aliases::) is performed by default.
+
+ 9. In the absence of any traps, Bash ignores ‘SIGTERM’ (*note
+ Signals::).
+
+ 10. In the absence of any traps, ‘SIGINT’ is caught and handled (*note
+ Signals::). ‘SIGINT’ will interrupt some shell builtins.
+
+ 11. An interactive login shell sends a ‘SIGHUP’ to all jobs on exit if
+ the ‘huponexit’ shell option has been enabled (*note Signals::).
+
+ 12. The ‘-n’ option has no effect, whether at invocation or when using
+ ‘set -n’ (*note The Set Builtin::).
+
+ 13. Bash will check for mail periodically, depending on the values of
+ the ‘MAIL’, ‘MAILPATH’, and ‘MAILCHECK’ shell variables (*note Bash
+ Variables::).
+
+ 14. The shell will not exit on expansion errors due to references to
+ unbound shell variables after ‘set -u’ has been enabled (*note The
+ Set Builtin::).
+
+ 15. The shell will not exit on expansion errors caused by VAR being
+ unset or null in ‘${VAR:?WORD}’ expansions (*note Shell Parameter
+ Expansion::).
+
+ 16. Redirection errors encountered by shell builtins will not cause
+ the shell to exit.
+
+ 17. When running in POSIX mode, a special builtin returning an error
+ status will not cause the shell to exit (*note Bash POSIX Mode::).
+
+ 18. A failed ‘exec’ will not cause the shell to exit (*note Bourne
+ Shell Builtins::).
+
+ 19. Parser syntax errors will not cause the shell to exit.
+
+ 20. If the ‘cdspell’ shell option is enabled, the shell will attempt
+ simple spelling correction for directory arguments to the ‘cd’
+ builtin (see the description of the ‘cdspell’ option to the ‘shopt’
+ builtin in *note The Shopt Builtin::). The ‘cdspell’ option is
+ only effective in interactive shells.
+
+ 21. The shell will check the value of the ‘TMOUT’ variable and exit if
+ a command is not read within the specified number of seconds after
+ printing ‘$PS1’ (*note Bash Variables::).
+
+\1f
+File: bashref.info, Node: Bash Conditional Expressions, Next: Shell Arithmetic, Prev: Interactive Shells, Up: Bash Features
+
+6.4 Bash Conditional Expressions
+================================
+
+Conditional expressions are used by the ‘[[’ compound command (*note
+Conditional Constructs::) and the ‘test’ and ‘[’ builtin commands (*note
+Bourne Shell Builtins::). The ‘test’ and ‘[’ commands determine their
+behavior based on the number of arguments; see the descriptions of those
+commands for any other command-specific actions.
+
+ Expressions may be unary or binary, and are formed from the primaries
+listed below. Unary expressions are often used to examine the status of
+a file or shell variable. Binary operators are used for string,
+numeric, and file attribute comparisons.
+
+ Bash handles several filenames specially when they are used in
+expressions. If the operating system on which Bash is running provides
+these special files, Bash uses them; otherwise it emulates them
+internally with this behavior: If the FILE argument to one of the
+primaries is of the form ‘/dev/fd/N’, then Bash checks file descriptor
+N. If the FILE argument to one of the primaries is one of ‘/dev/stdin’,
+‘/dev/stdout’, or ‘/dev/stderr’, Bash checks file descriptor 0, 1, or 2,
+respectively.
+
+ When used with ‘[[’, the ‘<’ and ‘>’ operators sort lexicographically
+using the current locale. The ‘test’ command uses ASCII ordering.
+
+ Unless otherwise specified, primaries that operate on files follow
+symbolic links and operate on the target of the link, rather than the
+link itself.
+
+‘-a FILE’
+ True if FILE exists.
+
+‘-b FILE’
+ True if FILE exists and is a block special file.
+
+‘-c FILE’
+ True if FILE exists and is a character special file.
+
+‘-d FILE’
+ True if FILE exists and is a directory.
+
+‘-e FILE’
+ True if FILE exists.
+
+‘-f FILE’
+ True if FILE exists and is a regular file.
+
+‘-g FILE’
+ True if FILE exists and its set-group-id bit is set.
+
+‘-h FILE’
+ True if FILE exists and is a symbolic link.
+
+‘-k FILE’
+ True if FILE exists and its "sticky" bit is set.
+
+‘-p FILE’
+ True if FILE exists and is a named pipe (FIFO).
+
+‘-r FILE’
+ True if FILE exists and is readable.
+
+‘-s FILE’
+ True if FILE exists and has a size greater than zero.
+
+‘-t FD’
+ True if file descriptor FD is open and refers to a terminal.
+
+‘-u FILE’
+ True if FILE exists and its set-user-id bit is set.
+
+‘-w FILE’
+ True if FILE exists and is writable.
+
+‘-x FILE’
+ True if FILE exists and is executable.
+
+‘-G FILE’
+ True if FILE exists and is owned by the effective group id.
+
+‘-L FILE’
+ True if FILE exists and is a symbolic link.
+
+‘-N FILE’
+ True if FILE exists and has been modified since it was last
+ accessed.
+
+‘-O FILE’
+ True if FILE exists and is owned by the effective user id.
+
+‘-S FILE’
+ True if FILE exists and is a socket.
+
+‘FILE1 -ef FILE2’
+ True if FILE1 and FILE2 refer to the same device and inode numbers.
+
+‘FILE1 -nt FILE2’
+ True if FILE1 is newer (according to modification date) than FILE2,
+ or if FILE1 exists and FILE2 does not.
+
+‘FILE1 -ot FILE2’
+ True if FILE1 is older than FILE2, or if FILE2 exists and FILE1
+ does not.
+
+‘-o OPTNAME’
+ True if the shell option OPTNAME is enabled. The list of options
+ appears in the description of the ‘-o’ option to the ‘set’ builtin
+ (*note The Set Builtin::).
+
+‘-v VARNAME’
+ True if the shell variable VARNAME is set (has been assigned a
+ value). If VARNAME is an indexed array variable name subscripted
+ by ‘@’ or ‘*’, this returns true if the array has any set elements.
+ If VARNAME is an associative array variable name subscripted by ‘@’
+ or ‘*’, this returns true if an element with that key is set.
+
+‘-R VARNAME’
+ True if the shell variable VARNAME is set and is a name reference.
+
+‘-z STRING’
+ True if the length of STRING is zero.
+
+‘-n STRING’
+‘STRING’
+ True if the length of STRING is non-zero.
+
+‘STRING1 == STRING2’
+‘STRING1 = STRING2’
+ True if the strings are equal. When used with the ‘[[’ command,
+ this performs pattern matching as described above (*note
+ Conditional Constructs::).
+
+ ‘=’ should be used with the ‘test’ command for POSIX conformance.
+
+‘STRING1 != STRING2’
+ True if the strings are not equal.
+
+‘STRING1 < STRING2’
+ True if STRING1 sorts before STRING2 lexicographically.
+
+‘STRING1 > STRING2’
+ True if STRING1 sorts after STRING2 lexicographically.
+
+‘ARG1 OP ARG2’
+ ‘OP’ is one of ‘-eq’, ‘-ne’, ‘-lt’, ‘-le’, ‘-gt’, or ‘-ge’. These
+ arithmetic binary operators return true if ARG1 is equal to, not
+ equal to, less than, less than or equal to, greater than, or
+ greater than or equal to ARG2, respectively. ARG1 and ARG2 may be
+ positive or negative integers. When used with the ‘[[’ command,
+ ARG1 and ARG2 are evaluated as arithmetic expressions (*note Shell
+ Arithmetic::). Since the expansions the ‘[[’ command performs on
+ ARG1 and ARG2 can potentially result in empty strings, arithmetic
+ expression evaluation treats those as expressions that evaluate to
+ 0.
+
+\1f
+File: bashref.info, Node: Shell Arithmetic, Next: Aliases, Prev: Bash Conditional Expressions, Up: Bash Features
+
+6.5 Shell Arithmetic
+====================
+
+The shell allows arithmetic expressions to be evaluated, as one of the
+shell expansions or by using the ‘((’ compound command, the ‘let’ and
+‘declare’ builtins, the arithmetic ‘for’ command, the ‘[[’ conditional
+command, or the ‘-i’ option to the ‘declare’ builtin.
+
+ Evaluation is done in the largest fixed-width integers available,
+with no check for overflow, though division by 0 is trapped and flagged
+as an error. The operators and their precedence, associativity, and
+values are the same as in the C language. The following list of
+operators is grouped into levels of equal-precedence operators. The
+levels are listed in order of decreasing precedence.
+
+‘ID++ ID--’
+ variable post-increment and post-decrement
+
+‘++ID --ID’
+ variable pre-increment and pre-decrement
+
+‘- +’
+ unary minus and plus
+
+‘! ~’
+ logical and bitwise negation
+
+‘**’
+ exponentiation
+
+‘* / %’
+ multiplication, division, remainder
+
+‘+ -’
+ addition, subtraction
+
+‘<< >>’
+ left and right bitwise shifts
+
+‘<= >= < >’
+ comparison
+
+‘== !=’
+ equality and inequality
+
+‘&’
+ bitwise AND
+
+‘^’
+ bitwise exclusive OR
+
+‘|’
+ bitwise OR
+
+‘&&’
+ logical AND
+
+‘||’
+ logical OR
+
+‘expr ? if-true-expr : if-false-expr’
+ conditional operator
+
+‘= *= /= %= += -= <<= >>= &= ^= |=’
+ assignment
+
+‘expr1 , expr2’
+ comma
+
+ Shell variables are allowed as operands; parameter expansion is
+performed before the expression is evaluated. Within an expression,
+shell variables may also be referenced by name without using the
+parameter expansion syntax. This means you can use X, where X is a
+shell variable name, in an arithmetic expression, and the shell will
+evaluate its value as an expression and use the result. A shell
+variable that is null or unset evaluates to 0 when referenced by name in
+an expression.
+
+ The value of a variable is evaluated as an arithmetic expression when
+it is referenced, or when a variable which has been given the ‘integer’
+attribute using ‘declare -i’ is assigned a value. A null value
+evaluates to 0. A shell variable need not have its ‘integer’ attribute
+enabled to be used in an expression.
+
+ Integer constants follow the C language definition, without suffixes
+or character constants. Constants with a leading 0 are interpreted as
+octal numbers. A leading ‘0x’ or ‘0X’ denotes hexadecimal. Otherwise,
+numbers take the form [BASE‘#’]N, where the optional BASE is a decimal
+number between 2 and 64 representing the arithmetic base, and N is a
+number in that base. If BASE‘#’ is omitted, then base 10 is used. When
+specifying N, if a non-digit is required, the digits greater than 9 are
+represented by the lowercase letters, the uppercase letters, ‘@’, and
+‘_’, in that order. If BASE is less than or equal to 36, lowercase and
+uppercase letters may be used interchangeably to represent numbers
+between 10 and 35.
+
+ Operators are evaluated in precedence order. Sub-expressions in
+parentheses are evaluated first and may override the precedence rules
+above.
+
+\1f
+File: bashref.info, Node: Aliases, Next: Arrays, Prev: Shell Arithmetic, Up: Bash Features
+
+6.6 Aliases
+===========
+
+“Aliases” allow a string to be substituted for a word that is in a
+position in the input where it can be the first word of a simple
+command. Aliases have names and corresponding values that are set and
+unset using the ‘alias’ and ‘unalias’ builtin commands (*note Shell
+Builtin Commands::).
+
+ If the shell reads an unquoted word in the right position, it checks
+the word to see if it matches an alias name. If it matches, the shell
+replaces the word with the alias value, and reads that value as if it
+had been read instead of the word. The shell doesn't look at any
+characters following the word before attempting alias substitution.
+
+ The characters ‘/’, ‘$’, ‘`’, ‘=’ and any of the shell metacharacters
+or quoting characters listed above may not appear in an alias name. The
+replacement text may contain any valid shell input, including shell
+metacharacters. The first word of the replacement text is tested for
+aliases, but a word that is identical to an alias being expanded is not
+expanded a second time. This means that one may alias ‘ls’ to ‘"ls
+-F"’, for instance, and Bash does not try to recursively expand the
+replacement text.
+
+ If the last character of the alias value is a ‘blank’, then the shell
+checks the next command word following the alias for alias expansion.
+
+ Aliases are created and listed with the ‘alias’ command, and removed
+with the ‘unalias’ command.
+
+ There is no mechanism for using arguments in the replacement text, as
+in ‘csh’. If arguments are needed, use a shell function (*note Shell
+Functions::) instead.
+
+ Aliases are not expanded when the shell is not interactive, unless
+the ‘expand_aliases’ shell option is set using ‘shopt’ (*note The Shopt
+Builtin::).
+
+ The rules concerning the definition and use of aliases are somewhat
+confusing. Bash always reads at least one complete line of input, and
+all lines that make up a compound command, before executing any of the
+commands on that line or the compound command. Aliases are expanded
+when a command is read, not when it is executed. Therefore, an alias
+definition appearing on the same line as another command does not take
+effect until the shell reads the next line of input, and an alias
+definition in a compound command does not take effect until the shell
+parses and executes the entire compound command. The commands following
+the alias definition on that line, or in the rest of a compound command,
+are not affected by the new alias. This behavior is also an issue when
+functions are executed. Aliases are expanded when a function definition
+is read, not when the function is executed, because a function
+definition is itself a command. As a consequence, aliases defined in a
+function are not available until after that function is executed. To be
+safe, always put alias definitions on a separate line, and do not use
+‘alias’ in compound commands.
+
+ For almost every purpose, shell functions are preferable to aliases.
+
+\1f
+File: bashref.info, Node: Arrays, Next: The Directory Stack, Prev: Aliases, Up: Bash Features
+
+6.7 Arrays
+==========
+
+Bash provides one-dimensional indexed and associative array variables.
+Any variable may be used as an indexed array; the ‘declare’ builtin
+explicitly declares an array. There is no maximum limit on the size of
+an array, nor any requirement that members be indexed or assigned
+contiguously. Indexed arrays are referenced using arithmetic
+expressions that must expand to an integer (*note Shell Arithmetic::))
+and are zero-based; associative arrays use arbitrary strings. Unless
+otherwise noted, indexed array indices must be non-negative integers.
+
+ The shell performs parameter and variable expansion, arithmetic
+expansion, command substitution, and quote removal on indexed array
+subscripts. Since this can potentially result in empty strings,
+subscript indexing treats those as expressions that evaluate to 0.
+
+ The shell performs tilde expansion, parameter and variable expansion,
+arithmetic expansion, command substitution, and quote removal on
+associative array subscripts. Empty strings cannot be used as
+associative array keys.
+
+ Bash automatically creates an indexed array if any variable is
+assigned to using the syntax
+ NAME[SUBSCRIPT]=VALUE
+
+The SUBSCRIPT is treated as an arithmetic expression that must evaluate
+to a number greater than or equal to zero. To explicitly declare an
+indexed array, use
+ declare -a NAME
+(*note Bash Builtins::). The syntax
+ declare -a NAME[SUBSCRIPT]
+is also accepted; the SUBSCRIPT is ignored.
+
+Associative arrays are created using
+ declare -A NAME
+
+ Attributes may be specified for an array variable using the ‘declare’
+and ‘readonly’ builtins. Each attribute applies to all members of an
+array.
+
+ Arrays are assigned using compound assignments of the form
+ NAME=(VALUE1 VALUE2 ... )
+where each VALUE may be of the form ‘[SUBSCRIPT]=’STRING. Indexed array
+assignments do not require anything but STRING.
+
+ Each VALUE in the list undergoes the shell expansions described above
+(*note Shell Expansions::), but VALUEs that are valid variable
+assignments including the brackets and subscript do not undergo brace
+expansion and word splitting, as with individual variable assignments.
+
+ When assigning to indexed arrays, if the optional subscript is
+supplied, that index is assigned to; otherwise the index of the element
+assigned is the last index assigned to by the statement plus one.
+Indexing starts at zero.
+
+ When assigning to an associative array, the words in a compound
+assignment may be either assignment statements, for which the subscript
+is required, or a list of words that is interpreted as a sequence of
+alternating keys and values: NAME=(KEY1 VALUE1 KEY2 VALUE2 ... ). These
+are treated identically to NAME=( [KEY1]=VALUE1 [KEY2]=VALUE2 ... ).
+The first word in the list determines how the remaining words are
+interpreted; all assignments in a list must be of the same type. When
+using key/value pairs, the keys may not be missing or empty; a final
+missing value is treated like the empty string.
+
+ This syntax is also accepted by the ‘declare’ builtin. Individual
+array elements may be assigned to using the ‘NAME[SUBSCRIPT]=VALUE’
+syntax introduced above.
+
+ When assigning to an indexed array, if NAME is subscripted by a
+negative number, that number is interpreted as relative to one greater
+than the maximum index of NAME, so negative indices count back from the
+end of the array, and an index of -1 references the last element.
+
+ The ‘+=’ operator appends to an array variable when assigning using
+the compound assignment syntax; see *note Shell Parameters:: above.
+
+ An array element is referenced using ‘${NAME[SUBSCRIPT]}’. The
+braces are required to avoid conflicts with the shell's filename
+expansion operators. If the SUBSCRIPT is ‘@’ or ‘*’, the word expands
+to all members of the array NAME, unless otherwise noted in the
+description of a builtin or word expansion. These subscripts differ
+only when the word appears within double quotes. If the word is
+double-quoted, ‘${NAME[*]}’ expands to a single word with the value of
+each array member separated by the first character of the ‘IFS’
+variable, and ‘${NAME[@]}’ expands each element of NAME to a separate
+word. When there are no array members, ‘${NAME[@]}’ expands to nothing.
+If the double-quoted expansion occurs within a word, the expansion of
+the first parameter is joined with the beginning part of the expansion
+of the original word, and the expansion of the last parameter is joined
+with the last part of the expansion of the original word. This is
+analogous to the expansion of the special parameters ‘@’ and ‘*’.
+
+ ‘${#NAME[SUBSCRIPT]}’ expands to the length of ‘${NAME[SUBSCRIPT]}’.
+If SUBSCRIPT is ‘@’ or ‘*’, the expansion is the number of elements in
+the array.
+
+ If the SUBSCRIPT used to reference an element of an indexed array
+evaluates to a number less than zero, it is interpreted as relative to
+one greater than the maximum index of the array, so negative indices
+count back from the end of the array, and an index of -1 refers to the
+last element.
+
+ Referencing an array variable without a subscript is equivalent to
+referencing with a subscript of 0. Any reference to a variable using a
+valid subscript is valid; Bash creates an array if necessary.
+
+ An array variable is considered set if a subscript has been assigned
+a value. The null string is a valid value.
+
+ It is possible to obtain the keys (indices) of an array as well as
+the values. ${!NAME[@]} and ${!NAME[*]} expand to the indices assigned
+in array variable NAME. The treatment when in double quotes is similar
+to the expansion of the special parameters ‘@’ and ‘*’ within double
+quotes.
+
+ The ‘unset’ builtin is used to destroy arrays. ‘unset
+NAME[SUBSCRIPT]’ unsets the array element at index SUBSCRIPT. Negative
+subscripts to indexed arrays are interpreted as described above.
+Unsetting the last element of an array variable does not unset the
+variable. ‘unset NAME’, where NAME is an array, removes the entire
+array. ‘unset NAME[SUBSCRIPT]’ behaves differently depending on the
+array type when SUBSCRIPT is ‘*’ or ‘@’. When NAME is an associative
+array, it removes the element with key ‘*’ or ‘@’. If NAME is an
+indexed array, ‘unset’ removes all of the elements, but does not remove
+the array itself.
+
+ When using a variable name with a subscript as an argument to a
+command, such as with ‘unset’, without using the word expansion syntax
+described above (e.g., unset a[4]), the argument is subject to the
+shell's filename expansion. Quote the argument if pathname expansion is
+not desired (e.g., unset 'a[4]').
+
+ The ‘declare’, ‘local’, and ‘readonly’ builtins each accept a ‘-a’
+option to specify an indexed array and a ‘-A’ option to specify an
+associative array. If both options are supplied, ‘-A’ takes precedence.
+The ‘read’ builtin accepts a ‘-a’ option to assign a list of words read
+from the standard input to an array, and can read values from the
+standard input into individual array elements. The ‘set’ and ‘declare’
+builtins display array values in a way that allows them to be reused as
+input. Other builtins accept array name arguments as well (e.g.,
+‘mapfile’); see the descriptions of individual builtins for details.
+The shell provides a number of builtin array variables.
+
+\1f
+File: bashref.info, Node: The Directory Stack, Next: Controlling the Prompt, Prev: Arrays, Up: Bash Features
+
+6.8 The Directory Stack
+=======================
+
+* Menu:
+
+* Directory Stack Builtins:: Bash builtin commands to manipulate
+ the directory stack.
+
+The directory stack is a list of recently-visited directories. The
+‘pushd’ builtin adds directories to the stack as it changes the current
+directory, and the ‘popd’ builtin removes specified directories from the
+stack and changes the current directory to the directory removed. The
+‘dirs’ builtin displays the contents of the directory stack. The
+current directory is always the "top" of the directory stack.
+
+ The contents of the directory stack are also visible as the value of
+the ‘DIRSTACK’ shell variable.
+
+\1f
+File: bashref.info, Node: Directory Stack Builtins, Up: The Directory Stack
+
+6.8.1 Directory Stack Builtins
+------------------------------
+
+‘dirs’
+ dirs [-clpv] [+N | -N]
+
+ Without options, display the list of currently remembered
+ directories. Directories are added to the list with the ‘pushd’
+ command; the ‘popd’ command removes directories from the list. The
+ current directory is always the first directory in the stack.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-c’
+ Clears the directory stack by deleting all of the elements.
+ ‘-l’
+ Produces a listing using full pathnames; the default listing
+ format uses a tilde to denote the home directory.
+ ‘-p’
+ Causes ‘dirs’ to print the directory stack with one entry per
+ line.
+ ‘-v’
+ Causes ‘dirs’ to print the directory stack with one entry per
+ line, prefixing each entry with its index in the stack.
+ ‘+N’
+ Displays the Nth directory (counting from the left of the list
+ printed by ‘dirs’ when invoked without options), starting with
+ zero.
+ ‘-N’
+ Displays the Nth directory (counting from the right of the
+ list printed by ‘dirs’ when invoked without options), starting
+ with zero.
+
+‘popd’
+ popd [-n] [+N | -N]
+
+ Remove elements from the directory stack. The elements are
+ numbered from 0 starting at the first directory listed by ‘dirs’;
+ that is, ‘popd’ is equivalent to ‘popd +0’.
+
+ When no arguments are given, ‘popd’ removes the top directory from
+ the stack and changes to the new top directory.
+
+ Arguments, if supplied, have the following meanings:
+
+ ‘-n’
+ Suppress the normal change of directory when removing
+ directories from the stack, only manipulate the stack.
+ ‘+N’
+ Remove the Nth directory (counting from the left of the list
+ printed by ‘dirs’), starting with zero, from the stack.
+ ‘-N’
+ Remove the Nth directory (counting from the right of the list
+ printed by ‘dirs’), starting with zero, from the stack.
+
+ If the top element of the directory stack is modified, and the ‘-n’
+ option was not supplied, ‘popd’ uses the ‘cd’ builtin to change to
+ the directory at the top of the stack. If the ‘cd’ fails, ‘popd’
+ returns a non-zero value.
+
+ Otherwise, ‘popd’ returns an unsuccessful status if an invalid
+ option is specified, the directory stack is empty, or N specifies a
+ non-existent directory stack entry.
+
+ If the ‘popd’ command is successful, Bash runs ‘dirs’ to show the
+ final contents of the directory stack, and the return status is 0.
+
+‘pushd’
+ pushd [-n] [+N | -N | DIR]
+
+ Add a directory to the top of the directory stack, or rotate the
+ stack, making the new top of the stack the current working
+ directory. With no arguments, ‘pushd’ exchanges the top two
+ elements of the directory stack.
+
+ Arguments, if supplied, have the following meanings:
+
+ ‘-n’
+ Suppress the normal change of directory when rotating or
+ adding directories to the stack, only manipulate the stack.
+ ‘+N’
+ Rotate the stack so that the Nth directory (counting from the
+ left of the list printed by ‘dirs’, starting with zero) is at
+ the top.
+ ‘-N’
+ Rotate the stack so that the Nth directory (counting from the
+ right of the list printed by ‘dirs’, starting with zero) is at
+ the top.
+ ‘DIR’
+ Make DIR be the top of the stack.
+
+ After the stack has been modified, if the ‘-n’ option was not
+ supplied, ‘pushd’ uses the ‘cd’ builtin to change to the directory
+ at the top of the stack. If the ‘cd’ fails, ‘pushd’ returns a
+ non-zero value.
+
+ Otherwise, if no arguments are supplied, ‘pushd’ returns zero
+ unless the directory stack is empty. When rotating the directory
+ stack, ‘pushd’ returns zero unless the directory stack is empty or
+ N specifies a non-existent directory stack element.
+
+ If the ‘pushd’ command is successful, Bash runs ‘dirs’ to show the
+ final contents of the directory stack.
+
+\1f
+File: bashref.info, Node: Controlling the Prompt, Next: The Restricted Shell, Prev: The Directory Stack, Up: Bash Features
+
+6.9 Controlling the Prompt
+==========================
+
+In addition, the following table describes the special characters which
+can appear in the prompt variables ‘PS0’, ‘PS1’, ‘PS2’, and ‘PS4’:
+
+‘\a’
+ A bell character.
+‘\d’
+ The date, in "Weekday Month Date" format (e.g., "Tue May 26").
+‘\D{FORMAT}’
+ The FORMAT is passed to ‘strftime’(3) and the result is inserted
+ into the prompt string; an empty FORMAT results in a
+ locale-specific time representation. The braces are required.
+‘\e’
+ An escape character.
+‘\h’
+ The hostname, up to the first ‘.’.
+‘\H’
+ The hostname.
+‘\j’
+ The number of jobs currently managed by the shell.
+‘\l’
+ The basename of the shell's terminal device name (e.g., "ttys0").
+‘\n’
+ A newline.
+‘\r’
+ A carriage return.
+‘\s’
+ The name of the shell: the basename of ‘$0’ (the portion following
+ the final slash).
+‘\t’
+ The time, in 24-hour HH:MM:SS format.
+‘\T’
+ The time, in 12-hour HH:MM:SS format.
+‘\@’
+ The time, in 12-hour am/pm format.
+‘\A’
+ The time, in 24-hour HH:MM format.
+‘\u’
+ The username of the current user.
+‘\v’
+ The Bash version (e.g., 2.00).
+‘\V’
+ The Bash release, version + patchlevel (e.g., 2.00.0).
+‘\w’
+ The value of the ‘PWD’ shell variable (‘$PWD’), with ‘$HOME’
+ abbreviated with a tilde (uses the ‘$PROMPT_DIRTRIM’ variable).
+‘\W’
+ The basename of ‘$PWD’, with ‘$HOME’ abbreviated with a tilde.
+‘\!’
+ The history number of this command.
+‘\#’
+ The command number of this command.
+‘\$’
+ If the effective uid is 0, ‘#’, otherwise ‘$’.
+‘\NNN’
+ The character whose ASCII code is the octal value NNN.
+‘\\’
+ A backslash.
+‘\[’
+ Begin a sequence of non-printing characters. Thiss could be used
+ to embed a terminal control sequence into the prompt.
+‘\]’
+ End a sequence of non-printing characters.
+
+ The command number and the history number are usually different: the
+history number of a command is its position in the history list, which
+may include commands restored from the history file (*note Bash History
+Facilities::), while the command number is the position in the sequence
+of commands executed during the current shell session.
+
+ After the string is decoded, it is expanded via parameter expansion,
+command substitution, arithmetic expansion, and quote removal, subject
+to the value of the ‘promptvars’ shell option (*note The Shopt
+Builtin::). This can have unwanted side effects if escaped portions of
+the string appear within command substitution or contain characters
+special to word expansion.
+
+\1f
+File: bashref.info, Node: The Restricted Shell, Next: Bash POSIX Mode, Prev: Controlling the Prompt, Up: Bash Features
+
+6.10 The Restricted Shell
+=========================
+
+If Bash is started with the name ‘rbash’, or the ‘--restricted’ or ‘-r’
+option is supplied at invocation, the shell becomes RESTRICTED. A
+restricted shell is used to set up an environment more controlled than
+the standard shell. A restricted shell behaves identically to ‘bash’
+with the exception that the following are disallowed or not performed:
+
+ • Changing directories with the ‘cd’ builtin.
+ • Setting or unsetting the values of the ‘SHELL’, ‘PATH’, ‘HISTFILE’,
+ ‘ENV’, or ‘BASH_ENV’ variables.
+ • Specifying command names containing slashes.
+ • Specifying a filename containing a slash as an argument to the ‘.’
+ builtin command.
+ • Using the ‘-p’ option to the ‘.’ builtin command to specify a
+ search path.
+ • Specifying a filename containing a slash as an argument to the
+ ‘history’ builtin command.
+ • Specifying a filename containing a slash as an argument to the ‘-p’
+ option to the ‘hash’ builtin command.
+ • Importing function definitions from the shell environment at
+ startup.
+ • Parsing the value of ‘SHELLOPTS’ from the shell environment at
+ startup.
+ • Redirecting output using the ‘>’, ‘>|’, ‘<>’, ‘>&’, ‘&>’, and ‘>>’
+ redirection operators.
+ • Using the ‘exec’ builtin to replace the shell with another command.
+ • Adding or deleting builtin commands with the ‘-f’ and ‘-d’ options
+ to the ‘enable’ builtin.
+ • Using the ‘enable’ builtin command to enable disabled shell
+ builtins.
+ • Specifying the ‘-p’ option to the ‘command’ builtin.
+ • Turning off restricted mode with ‘set +r’ or ‘shopt -u
+ restricted_shell’.
+
+ These restrictions are enforced after any startup files are read.
+
+ When a command that is found to be a shell script is executed (*note
+Shell Scripts::), ‘rbash’ turns off any restrictions in the shell
+spawned to execute the script.
+
+ The restricted shell mode is only one component of a useful
+restricted environment. It should be accompanied by setting ‘PATH’ to a
+value that allows execution of only a few verified commands (commands
+that allow shell escapes are particularly vulnerable), changing the
+current directory to a non-writable directory other than ‘$HOME’ after
+login, not allowing the restricted shell to execute shell scripts, and
+cleaning the environment of variables that cause some commands to modify
+their behavior (e.g., ‘VISUAL’ or ‘PAGER’).
+
+ Modern systems provide more secure ways to implement a restricted
+environment, such as ‘jails’, ‘zones’, or ‘containers’.
+
+\1f
+File: bashref.info, Node: Bash POSIX Mode, Next: Shell Compatibility Mode, Prev: The Restricted Shell, Up: Bash Features
+
+6.11 Bash and POSIX
+===================
+
+6.11.1 What is POSIX?
+---------------------
+
+POSIX is the name for a family of standards based on Unix. A number of
+Unix services, tools, and functions are part of the standard, ranging
+from the basic system calls and C library functions to common
+applications and tools to system administration and management.
+
+ The POSIX Shell and Utilities standard was originally developed by
+IEEE Working Group 1003.2 (POSIX.2). The first edition of the 1003.2
+standard was published in 1992. It was merged with the original IEEE
+1003.1 Working Group and is currently maintained by the Austin Group (a
+joint working group of the IEEE, The Open Group and ISO/IEC SC22/WG15).
+Today the Shell and Utilities are a volume within the set of documents
+that make up IEEE Std 1003.1-2024, and thus the former POSIX.2 (from
+1992) is now part of the current unified POSIX standard.
+
+ The Shell and Utilities volume concentrates on the command
+interpreter interface and utility programs commonly executed from the
+command line or by other programs. The standard is freely available on
+the web at
+<https://pubs.opengroup.org/onlinepubs/9799919799/utilities/contents.html>.
+
+ Bash is concerned with the aspects of the shell's behavior defined by
+the POSIX Shell and Utilities volume. The shell command language has of
+course been standardized, including the basic flow control and program
+execution constructs, I/O redirection and pipelines, argument handling,
+variable expansion, and quoting.
+
+ The special builtins, which must be implemented as part of the shell
+to provide the desired functionality, are specified as being part of the
+shell; examples of these are ‘eval’ and ‘export’. Other utilities
+appear in the sections of POSIX not devoted to the shell which are
+commonly (and in some cases must be) implemented as builtin commands,
+such as ‘read’ and ‘test’. POSIX also specifies aspects of the shell's
+interactive behavior, including job control and command line editing.
+Only vi-style line editing commands have been standardized; emacs
+editing commands were left out due to objections.
+
+6.11.2 Bash POSIX Mode
+----------------------
+
+Although Bash is an implementation of the POSIX shell specification,
+there are areas where the Bash default behavior differs from the
+specification. The Bash “posix mode” changes the Bash behavior in these
+areas so that it conforms more strictly to the standard.
+
+ Starting Bash with the ‘--posix’ command-line option or executing
+‘set -o posix’ while Bash is running will cause Bash to conform more
+closely to the POSIX standard by changing the behavior to match that
+specified by POSIX in areas where the Bash default differs.
+
+ When invoked as ‘sh’, Bash enters POSIX mode after reading the
+startup files.
+
+ The following list is what's changed when POSIX mode is in effect:
+
+ 1. Bash ensures that the ‘POSIXLY_CORRECT’ variable is set.
+
+ 2. Bash reads and executes the POSIX startup files (‘$ENV’) rather
+ than the normal Bash files (*note Bash Startup Files::).
+
+ 3. Alias expansion is always enabled, even in non-interactive shells.
+
+ 4. Reserved words appearing in a context where reserved words are
+ recognized do not undergo alias expansion.
+
+ 5. Alias expansion is performed when initially parsing a command
+ substitution. The default (non-posix) mode generally defers it,
+ when enabled, until the command substitution is executed. This
+ means that command substitution will not expand aliases that are
+ defined after the command substitution is initially parsed (e.g.,
+ as part of a function definition).
+
+ 6. The ‘time’ reserved word may be used by itself as a simple command.
+ When used in this way, it displays timing statistics for the shell
+ and its completed children. The ‘TIMEFORMAT’ variable controls the
+ format of the timing information.
+
+ 7. The parser does not recognize ‘time’ as a reserved word if the next
+ token begins with a ‘-’.
+
+ 8. When parsing and expanding a ${...} expansion that appears within
+ double quotes, single quotes are no longer special and cannot be
+ used to quote a closing brace or other special character, unless
+ the operator is one of those defined to perform pattern removal.
+ In this case, they do not have to appear as matched pairs.
+
+ 9. Redirection operators do not perform filename expansion on the word
+ in a redirection unless the shell is interactive.
+
+ 10. Redirection operators do not perform word splitting on the word in
+ a redirection.
+
+ 11. Function names may not be the same as one of the POSIX special
+ builtins.
+
+ 12. Tilde expansion is only performed on assignments preceding a
+ command name, rather than on all assignment statements on the line.
+
+ 13. While variable indirection is available, it may not be applied to
+ the ‘#’ and ‘?’ special parameters.
+
+ 14. Expanding the ‘*’ special parameter in a pattern context where the
+ expansion is double-quoted does not treat the ‘$*’ as if it were
+ double-quoted.
+
+ 15. A double quote character (‘"’) is treated specially when it
+ appears in a backquoted command substitution in the body of a
+ here-document that undergoes expansion. That means, for example,
+ that a backslash preceding a double quote character will escape it
+ and the backslash will be removed.
+
+ 16. Command substitutions don't set the ‘?’ special parameter. The
+ exit status of a simple command without a command word is still the
+ exit status of the last command substitution that occurred while
+ evaluating the variable assignments and redirections in that
+ command, but that does not happen until after all of the
+ assignments and redirections.
+
+ 17. Literal tildes that appear as the first character in elements of
+ the ‘PATH’ variable are not expanded as described above under *note
+ Tilde Expansion::.
+
+ 18. Command lookup finds POSIX special builtins before shell
+ functions, including output printed by the ‘type’ and ‘command’
+ builtins.
+
+ 19. Even if a shell function whose name contains a slash was defined
+ before entering POSIX mode, the shell will not execute a function
+ whose name contains one or more slashes.
+
+ 20. When a command in the hash table no longer exists, Bash will
+ re-search ‘$PATH’ to find the new location. This is also available
+ with ‘shopt -s checkhash’.
+
+ 21. Bash will not insert a command without the execute bit set into
+ the command hash table, even if it returns it as a (last-ditch)
+ result from a ‘$PATH’ search.
+
+ 22. The message printed by the job control code and builtins when a
+ job exits with a non-zero status is "Done(status)".
+
+ 23. The message printed by the job control code and builtins when a
+ job is stopped is "Stopped(SIGNAME)", where SIGNAME is, for
+ example, ‘SIGTSTP’.
+
+ 24. If the shell is interactive, Bash does not perform job
+ notifications between executing commands in lists separated by ‘;’
+ or newline. Non-interactive shells print status messages after a
+ foreground job in a list completes.
+
+ 25. If the shell is interactive, Bash waits until the next prompt
+ before printing the status of a background job that changes status
+ or a foreground job that terminates due to a signal.
+ Non-interactive shells print status messages after a foreground job
+ completes.
+
+ 26. Bash permanently removes jobs from the jobs table after notifying
+ the user of their termination via the ‘wait’ or ‘jobs’ builtins.
+ It removes the job from the jobs list after notifying the user of
+ its termination, but the status is still available via ‘wait’, as
+ long as ‘wait’ is supplied a PID argument.
+
+ 27. The ‘vi’ editing mode will invoke the ‘vi’ editor directly when
+ the ‘v’ command is run, instead of checking ‘$VISUAL’ and
+ ‘$EDITOR’.
+
+ 28. Prompt expansion enables the POSIX ‘PS1’ and ‘PS2’ expansions of
+ ‘!’ to the history number and ‘!!’ to ‘!’, and Bash performs
+ parameter expansion on the values of ‘PS1’ and ‘PS2’ regardless of
+ the setting of the ‘promptvars’ option.
+
+ 29. The default history file is ‘~/.sh_history’ (this is the default
+ value the shell assigns to ‘$HISTFILE’).
+
+ 30. The ‘!’ character does not introduce history expansion within a
+ double-quoted string, even if the ‘histexpand’ option is enabled.
+
+ 31. When printing shell function definitions (e.g., by ‘type’), Bash
+ does not print the ‘function’ reserved word unless necessary.
+
+ 32. Non-interactive shells exit if a syntax error in an arithmetic
+ expansion results in an invalid expression.
+
+ 33. Non-interactive shells exit if a parameter expansion error occurs.
+
+ 34. If a POSIX special builtin returns an error status, a
+ non-interactive shell exits. The fatal errors are those listed in
+ the POSIX standard, and include things like passing incorrect
+ options, redirection errors, variable assignment errors for
+ assignments preceding the command name, and so on.
+
+ 35. A non-interactive shell exits with an error status if a variable
+ assignment error occurs when no command name follows the assignment
+ statements. A variable assignment error occurs, for example, when
+ trying to assign a value to a readonly variable.
+
+ 36. A non-interactive shell exits with an error status if a variable
+ assignment error occurs in an assignment statement preceding a
+ special builtin, but not with any other simple command. For any
+ other simple command, the shell aborts execution of that command,
+ and execution continues at the top level ("the shell shall not
+ perform any further processing of the command in which the error
+ occurred").
+
+ 37. A non-interactive shell exits with an error status if the
+ iteration variable in a ‘for’ statement or the selection variable
+ in a ‘select’ statement is a readonly variable or has an invalid
+ name.
+
+ 38. Non-interactive shells exit if FILENAME in ‘.’ FILENAME is not
+ found.
+
+ 39. Non-interactive shells exit if there is a syntax error in a script
+ read with the ‘.’ or ‘source’ builtins, or in a string processed by
+ the ‘eval’ builtin.
+
+ 40. Non-interactive shells exit if the ‘export’, ‘readonly’ or ‘unset’
+ builtin commands get an argument that is not a valid identifier,
+ and they are not operating on shell functions. These errors force
+ an exit because these are special builtins.
+
+ 41. Assignment statements preceding POSIX special builtins persist in
+ the shell environment after the builtin completes.
+
+ 42. The ‘command’ builtin does not prevent builtins that take
+ assignment statements as arguments from expanding them as
+ assignment statements; when not in POSIX mode, declaration commands
+ lose their assignment statement expansion properties when preceded
+ by ‘command’.
+
+ 43. Enabling POSIX mode has the effect of setting the
+ ‘inherit_errexit’ option, so subshells spawned to execute command
+ substitutions inherit the value of the ‘-e’ option from the parent
+ shell. When the ‘inherit_errexit’ option is not enabled, Bash
+ clears the ‘-e’ option in such subshells.
+
+ 44. Enabling POSIX mode has the effect of setting the ‘shift_verbose’
+ option, so numeric arguments to ‘shift’ that exceed the number of
+ positional parameters will result in an error message.
+
+ 45. Enabling POSIX mode has the effect of setting the
+ ‘interactive_comments’ option (*note Comments::).
+
+ 46. The ‘.’ and ‘source’ builtins do not search the current directory
+ for the filename argument if it is not found by searching ‘PATH’.
+
+ 47. When the ‘alias’ builtin displays alias definitions, it does not
+ display them with a leading ‘alias ’ unless the ‘-p’ option is
+ supplied.
+
+ 48. The ‘bg’ builtin uses the required format to describe each job
+ placed in the background, which does not include an indication of
+ whether the job is the current or previous job.
+
+ 49. When the ‘cd’ builtin is invoked in logical mode, and the pathname
+ constructed from ‘$PWD’ and the directory name supplied as an
+ argument does not refer to an existing directory, ‘cd’ will fail
+ instead of falling back to physical mode.
+
+ 50. When the ‘cd’ builtin cannot change a directory because the length
+ of the pathname constructed from ‘$PWD’ and the directory name
+ supplied as an argument exceeds ‘PATH_MAX’ when canonicalized, ‘cd’
+ will attempt to use the supplied directory name.
+
+ 51. When the ‘xpg_echo’ option is enabled, Bash does not attempt to
+ interpret any arguments to ‘echo’ as options. ‘echo’ displays each
+ argument after converting escape sequences.
+
+ 52. The ‘export’ and ‘readonly’ builtin commands display their output
+ in the format required by POSIX.
+
+ 53. When listing the history, the ‘fc’ builtin does not include an
+ indication of whether or not a history entry has been modified.
+
+ 54. The default editor used by ‘fc’ is ‘ed’.
+
+ 55. ‘fc’ treats extra arguments as an error instead of ignoring them.
+
+ 56. If there are too many arguments supplied to ‘fc -s’, ‘fc’ prints
+ an error message and returns failure.
+
+ 57. The output of ‘kill -l’ prints all the signal names on a single
+ line, separated by spaces, without the ‘SIG’ prefix.
+
+ 58. The ‘kill’ builtin does not accept signal names with a ‘SIG’
+ prefix.
+
+ 59. The ‘kill’ builtin returns a failure status if any of the pid or
+ job arguments are invalid or if sending the specified signal to any
+ of them fails. In default mode, ‘kill’ returns success if the
+ signal was successfully sent to any of the specified processes.
+
+ 60. The ‘printf’ builtin uses ‘double’ (via ‘strtod’) to convert
+ arguments corresponding to floating point conversion specifiers,
+ instead of ‘long double’ if it's available. The ‘L’ length
+ modifier forces ‘printf’ to use ‘long double’ if it's available.
+
+ 61. The ‘pwd’ builtin verifies that the value it prints is the same as
+ the current directory, even if it is not asked to check the file
+ system with the ‘-P’ option.
+
+ 62. The ‘read’ builtin may be interrupted by a signal for which a trap
+ has been set. If Bash receives a trapped signal while executing
+ ‘read’, the trap handler executes and ‘read’ returns an exit status
+ greater than 128.
+
+ 63. When the ‘set’ builtin is invoked without options, it does not
+ display shell function names and definitions.
+
+ 64. When the ‘set’ builtin is invoked without options, it displays
+ variable values without quotes, unless they contain shell
+ metacharacters, even if the result contains nonprinting characters.
+
+ 65. The ‘test’ builtin compares strings using the current locale when
+ evaluating the ‘<’ and ‘>’ binary operators.
+
+ 66. The ‘test’ builtin's ‘-t’ unary primary requires an argument.
+ Historical versions of ‘test’ made the argument optional in certain
+ cases, and Bash attempts to accommodate those for backwards
+ compatibility.
+
+ 67. The ‘trap’ builtin displays signal names without the leading
+ ‘SIG’.
+
+ 68. The ‘trap’ builtin doesn't check the first argument for a possible
+ signal specification and revert the signal handling to the original
+ disposition if it is, unless that argument consists solely of
+ digits and is a valid signal number. If users want to reset the
+ handler for a given signal to the original disposition, they should
+ use ‘-’ as the first argument.
+
+ 69. ‘trap -p’ without arguments displays signals whose dispositions
+ are set to SIG_DFL and those that were ignored when the shell
+ started, not just trapped signals.
+
+ 70. The ‘type’ and ‘command’ builtins will not report a non-executable
+ file as having been found, though the shell will attempt to execute
+ such a file if it is the only so-named file found in ‘$PATH’.
+
+ 71. The ‘ulimit’ builtin uses a block size of 512 bytes for the ‘-c’
+ and ‘-f’ options.
+
+ 72. The ‘unset’ builtin with the ‘-v’ option specified returns a fatal
+ error if it attempts to unset a ‘readonly’ or ‘non-unsettable’
+ variable, which causes a non-interactive shell to exit.
+
+ 73. When asked to unset a variable that appears in an assignment
+ statement preceding the command, the ‘unset’ builtin attempts to
+ unset a variable of the same name in the current or previous scope
+ as well. This implements the required "if an assigned variable is
+ further modified by the utility, the modifications made by the
+ utility shall persist" behavior.
+
+ 74. The arrival of ‘SIGCHLD’ when a trap is set on ‘SIGCHLD’ does not
+ interrupt the ‘wait’ builtin and cause it to return immediately.
+ The trap command is run once for each child that exits.
+
+ 75. Bash removes an exited background process's status from the list
+ of such statuses after the ‘wait’ builtin returns it.
+
+ There is additional POSIX behavior that Bash does not implement by
+default even when in POSIX mode. Specifically:
+
+ 1. POSIX requires that word splitting be byte-oriented. That is, each
+ _byte_ in the value of ‘IFS’ potentially splits a word, even if
+ that byte is part of a multibyte character in ‘IFS’ or part of
+ multibyte character in the word. Bash allows multibyte characters
+ in the value of ‘IFS’, treating a valid multibyte character as a
+ single delimiter, and will not split a valid multibyte character
+ even if one of the bytes composing that character appears in ‘IFS’.
+ This is POSIX interpretation 1560, further modified by issue 1924.
+
+ 2. The ‘fc’ builtin checks ‘$EDITOR’ as a program to edit history
+ entries if ‘FCEDIT’ is unset, rather than defaulting directly to
+ ‘ed’. ‘fc’ uses ‘ed’ if ‘EDITOR’ is unset.
+
+ 3. As noted above, Bash requires the ‘xpg_echo’ option to be enabled
+ for the ‘echo’ builtin to be fully conformant.
+
+ Bash can be configured to be POSIX-conformant by default, by
+specifying the ‘--enable-strict-posix-default’ to ‘configure’ when
+building (*note Optional Features::).
+
+\1f
+File: bashref.info, Node: Shell Compatibility Mode, Prev: Bash POSIX Mode, Up: Bash Features
+
+6.12 Shell Compatibility Mode
+=============================
+
+Bash-4.0 introduced the concept of a “shell compatibility level”,
+specified as a set of options to the shopt builtin (‘compat31’,
+‘compat32’, ‘compat40’, ‘compat41’, and so on). There is only one
+current compatibility level - each option is mutually exclusive. The
+compatibility level is intended to allow users to select behavior from
+previous versions that is incompatible with newer versions while they
+migrate scripts to use current features and behavior. It's intended to
+be a temporary solution.
+
+ This section does not mention behavior that is standard for a
+particular version (e.g., setting ‘compat32’ means that quoting the
+right hand side of the regexp matching operator quotes special regexp
+characters in the word, which is default behavior in bash-3.2 and
+subsequent versions).
+
+ If a user enables, say, ‘compat32’, it may affect the behavior of
+other compatibility levels up to and including the current compatibility
+level. The idea is that each compatibility level controls behavior that
+changed in that version of Bash, but that behavior may have been present
+in earlier versions. For instance, the change to use locale-based
+comparisons with the ‘[[’ command came in bash-4.1, and earlier versions
+used ASCII-based comparisons, so enabling ‘compat32’ will enable
+ASCII-based comparisons as well. That granularity may not be sufficient
+for all uses, and as a result users should employ compatibility levels
+carefully. Read the documentation for a particular feature to find out
+the current behavior.
+
+ Bash-4.3 introduced a new shell variable: ‘BASH_COMPAT’. The value
+assigned to this variable (a decimal version number like 4.2, or an
+integer corresponding to the ‘compat’NN option, like 42) determines the
+compatibility level.
+
+ Starting with bash-4.4, Bash began deprecating older compatibility
+levels. Eventually, the options will be removed in favor of
+‘BASH_COMPAT’.
+
+ Bash-5.0 was the final version for which there was an individual
+shopt option for the previous version. ‘BASH_COMPAT’ is the only
+mechanism to control the compatibility level in versions newer than
+bash-5.0.
+
+ The following table describes the behavior changes controlled by each
+compatibility level setting. The ‘compat’NN tag is used as shorthand
+for setting the compatibility level to NN using one of the following
+mechanisms. For versions prior to bash-5.0, the compatibility level may
+be set using the corresponding ‘compat’NN shopt option. For bash-4.3
+and later versions, the ‘BASH_COMPAT’ variable is preferred, and it is
+required for bash-5.1 and later versions.
+
+‘compat31’
+ • Quoting the rhs of the ‘[[’ command's regexp matching operator
+ (=~) has no special effect
+
+‘compat40’
+ • The ‘<’ and ‘>’ operators to the ‘[[’ command do not consider
+ the current locale when comparing strings; they use ASCII
+ ordering. Bash versions prior to bash-4.1 use ASCII collation
+ and strcmp(3); bash-4.1 and later use the current locale's
+ collation sequence and strcoll(3).
+
+‘compat41’
+ • In POSIX mode, ‘time’ may be followed by options and still be
+ recognized as a reserved word (this is POSIX interpretation
+ 267).
+ • In POSIX mode, the parser requires that an even number of
+ single quotes occur in the WORD portion of a double-quoted
+ ${...} parameter expansion and treats them specially, so that
+ characters within the single quotes are considered quoted
+ (this is POSIX interpretation 221).
+
+‘compat42’
+ • The replacement string in double-quoted pattern substitution
+ does not undergo quote removal, as it does in versions after
+ bash-4.2.
+ • In POSIX mode, single quotes are considered special when
+ expanding the WORD portion of a double-quoted ${...} parameter
+ expansion and can be used to quote a closing brace or other
+ special character (this is part of POSIX interpretation 221);
+ in later versions, single quotes are not special within
+ double-quoted word expansions.
+
+‘compat43’
+ • Word expansion errors are considered non-fatal errors that
+ cause the current command to fail, even in POSIX mode (the
+ default behavior is to make them fatal errors that cause the
+ shell to exit).
+ • When executing a shell function, the loop state
+ (while/until/etc.) is not reset, so ‘break’ or ‘continue’ in
+ that function will break or continue loops in the calling
+ context. Bash-4.4 and later reset the loop state to prevent
+ this.
+
+‘compat44’
+ • The shell sets up the values used by ‘BASH_ARGV’ and
+ ‘BASH_ARGC’ so they can expand to the shell's positional
+ parameters even if extended debugging mode is not enabled.
+ • A subshell inherits loops from its parent context, so ‘break’
+ or ‘continue’ will cause the subshell to exit. Bash-5.0 and
+ later reset the loop state to prevent the exit.
+ • Variable assignments preceding builtins like ‘export’ and
+ ‘readonly’ that set attributes continue to affect variables
+ with the same name in the calling environment even if the
+ shell is not in POSIX mode.
+
+‘compat50 (set using BASH_COMPAT)’
+ • Bash-5.1 changed the way ‘$RANDOM’ is generated to introduce
+ slightly more randomness. If the shell compatibility level is
+ set to 50 or lower, it reverts to the method from bash-5.0 and
+ previous versions, so seeding the random number generator by
+ assigning a value to ‘RANDOM’ will produce the same sequence
+ as in bash-5.0.
+ • If the command hash table is empty, Bash versions prior to
+ bash-5.1 printed an informational message to that effect, even
+ when producing output that can be reused as input. Bash-5.1
+ suppresses that message when the ‘-l’ option is supplied.
+
+‘compat51 (set using BASH_COMPAT)’
+ • The ‘unset’ builtin will unset the array ‘a’ given an argument
+ like ‘a[@]’. Bash-5.2 will unset an element with key ‘@’
+ (associative arrays) or remove all the elements without
+ unsetting the array (indexed arrays).
+ • Arithmetic commands ( ((...)) ) and the expressions in an
+ arithmetic for statement can be expanded more than once.
+ • Expressions used as arguments to arithmetic operators in the
+ ‘[[’ conditional command can be expanded more than once.
+ • The expressions in substring parameter brace expansion can be
+ expanded more than once.
+ • The expressions in the $(( ... )) word expansion can be
+ expanded more than once.
+ • Arithmetic expressions used as indexed array subscripts can be
+ expanded more than once.
+ • ‘test -v’, when given an argument of ‘A[@]’, where A is an
+ existing associative array, will return true if the array has
+ any set elements. Bash-5.2 will look for and report on a key
+ named ‘@’.
+ • the ${PARAMETER[:]=VALUE} word expansion will return VALUE,
+ before any variable-specific transformations have been
+ performed (e.g., converting to lowercase). Bash-5.2 will
+ return the final value assigned to the variable.
+ • Parsing command substitutions will behave as if extended
+ globbing (*note The Shopt Builtin::) is enabled, so that
+ parsing a command substitution containing an extglob pattern
+ (say, as part of a shell function) will not fail. This
+ assumes the intent is to enable extglob before the command is
+ executed and word expansions are performed. It will fail at
+ word expansion time if extglob hasn't been enabled by the time
+ the command is executed.
+
+‘compat52 (set using BASH_COMPAT)’
+ • The ‘test’ builtin uses its historical algorithm to parse
+ parenthesized subexpressions when given five or more
+ arguments.
+ • If the ‘-p’ or ‘-P’ option is supplied to the ‘bind’ builtin,
+ ‘bind’ treats any arguments remaining after option processing
+ as bindable command names, and displays any key sequences
+ bound to those commands, instead of treating the arguments as
+ key sequences to bind.
+ • Interactive shells will notify the user of completed jobs
+ while sourcing a script. Newer versions defer notification
+ until script execution completes.
+
+\1f
+File: bashref.info, Node: Job Control, Next: Command Line Editing, Prev: Bash Features, Up: Top
+
+7 Job Control
+*************
+
+This chapter discusses what job control is, how it works, and how Bash
+allows you to access its facilities.
+
+* Menu:
+
+* Job Control Basics:: How job control works.
+* Job Control Builtins:: Bash builtin commands used to interact
+ with job control.
+* Job Control Variables:: Variables Bash uses to customize job
+ control.
+
+\1f
+File: bashref.info, Node: Job Control Basics, Next: Job Control Builtins, Up: Job Control
+
+7.1 Job Control Basics
+======================
+
+Job control refers to the ability to selectively stop (suspend) the
+execution of processes and continue (resume) their execution at a later
+point. A user typically employs this facility via an interactive
+interface supplied jointly by the operating system kernel's terminal
+driver and Bash.
+
+ The shell associates a JOB with each pipeline. It keeps a table of
+currently executing jobs, which the ‘jobs’ command will display. Each
+job has a “job number”, which ‘jobs’ displays between brackets. Job
+numbers start at 1. When Bash starts a job asynchronously, it prints a
+line that looks like:
+ [1] 25647
+indicating that this job is job number 1 and that the process ID of the
+last process in the pipeline associated with this job is 25647. All of
+the processes in a single pipeline are members of the same job. Bash
+uses the JOB abstraction as the basis for job control.
+
+ To facilitate the implementation of the user interface to job
+control, each process has a “process group ID”, and the operating system
+maintains the notion of a current terminal process group ID. This
+terminal process group ID is associated with the “controlling terminal”.
+
+ Processes that have the same process group ID are said to be part of
+the same “process group”. Members of the foreground process group
+(processes whose process group ID is equal to the current terminal
+process group ID) receive keyboard-generated signals such as ‘SIGINT’.
+Processes in the foreground process group are said to be foreground
+processes. Background processes are those whose process group ID
+differs from the controlling terminal's; such processes are immune to
+keyboard-generated signals. Only foreground processes are allowed to
+read from or, if the user so specifies with ‘stty tostop’, write to the
+controlling terminal. The system sends a ‘SIGTTIN’ (‘SIGTTOU’) signal
+to background processes which attempt to read from (write to when
+‘tostop’ is in effect) the terminal, which, unless caught, suspends the
+process.
+
+ If the operating system on which Bash is running supports job
+control, Bash contains facilities to use it. Typing the “suspend”
+character (typically ‘^Z’, Control-Z) while a process is running stops
+that process and returns control to Bash. Typing the “delayed suspend”
+character (typically ‘^Y’, Control-Y) causes the process to stop when it
+attempts to read input from the terminal, and returns control to Bash.
+The user then manipulates the state of this job, using the ‘bg’ command
+to continue it in the background, the ‘fg’ command to continue it in the
+foreground, or the ‘kill’ command to kill it. The suspend character
+takes effect immediately, and has the additional side effect of
+discarding any pending output and typeahead. If you want to force a
+background process to stop, or stop a process that's not associated with
+your terminal session, send it the ‘SIGSTOP’ signal using ‘kill’.
+
+ There are a number of ways to refer to a job in the shell. The ‘%’
+character introduces a “job specification” (jobspec).
+
+ Job number ‘n’ may be referred to as ‘%n’. A job may also be
+referred to using a prefix of the name used to start it, or using a
+substring that appears in its command line. For example, ‘%ce’ refers
+to a job whose command name begins with ‘ce’. Using ‘%?ce’, on the
+other hand, refers to any job containing the string ‘ce’ in its command
+line. If the prefix or substring matches more than one job, Bash
+reports an error.
+
+ The symbols ‘%%’ and ‘%+’ refer to the shell's notion of the “current
+job”. A single ‘%’ (with no accompanying job specification) also refers
+to the current job. ‘%-’ refers to the “previous job”. When a job
+starts in the background, a job stops while in the foreground, or a job
+is resumed in the background, it becomes the current job. The job that
+was the current job becomes the previous job. When the current job
+terminates, the previous job becomes the current job. If there is only
+a single job, ‘%+’ and ‘%-’ can both be used to refer to that job. In
+output pertaining to jobs (e.g., the output of the ‘jobs’ command), the
+current job is always marked with a ‘+’, and the previous job with a
+‘-’.
+
+ Simply naming a job can be used to bring it into the foreground: ‘%1’
+is a synonym for ‘fg %1’, bringing job 1 from the background into the
+foreground. Similarly, ‘%1 &’ resumes job 1 in the background,
+equivalent to ‘bg %1’.
+
+ The shell learns immediately whenever a job changes state. Normally,
+Bash waits until it is about to print a prompt before notifying the user
+about changes in a job's status so as to not interrupt any other output,
+though it will notify of changes in a job's status after a foreground
+command in a list completes, before executing the next command in the
+list. If the ‘-b’ option to the ‘set’ builtin is enabled, Bash reports
+status changes immediately (*note The Set Builtin::). Bash executes any
+trap on ‘SIGCHLD’ for each child process that terminates.
+
+ When a job terminates and Bash notifies the user about it, Bash
+removes the job from the jobs table. It will not appear in ‘jobs’
+output, but ‘wait’ will report its exit status, as long as it's supplied
+the process ID associated with the job as an argument. When the table
+is empty, job numbers start over at 1.
+
+ If a user attempts to exit Bash while jobs are stopped, (or running,
+if the ‘checkjobs’ option is enabled - see *note The Shopt Builtin::),
+the shell prints a warning message, and if the ‘checkjobs’ option is
+enabled, lists the jobs and their statuses. The ‘jobs’ command may then
+be used to inspect their status. If the user immediately attempts to
+exit again, without an intervening command, Bash does not print another
+warning, and terminates any stopped jobs.
+
+ When the shell is waiting for a job or process using the ‘wait’
+builtin, and job control is enabled, ‘wait’ will return when the job
+changes state. The ‘-f’ option causes ‘wait’ to wait until the job or
+process terminates before returning.
+
+\1f
+File: bashref.info, Node: Job Control Builtins, Next: Job Control Variables, Prev: Job Control Basics, Up: Job Control
+
+7.2 Job Control Builtins
+========================
+
+‘bg’
+ bg [JOBSPEC ...]
+
+ Resume each suspended job JOBSPEC in the background, as if it had
+ been started with ‘&’. If JOBSPEC is not supplied, the shell uses
+ its notion of the current job. ‘bg’ returns zero unless it is run
+ when job control is not enabled, or, when run with job control
+ enabled, any JOBSPEC was not found or specifies a job that was
+ started without job control.
+
+‘fg’
+ fg [JOBSPEC]
+
+ Resume the job JOBSPEC in the foreground and make it the current
+ job. If JOBSPEC is not supplied, ‘fg’ resumes the current job.
+ The return status is that of the command placed into the
+ foreground, or non-zero if run when job control is disabled or,
+ when run with job control enabled, JOBSPEC does not specify a valid
+ job or JOBSPEC specifies a job that was started without job
+ control.
+
+‘jobs’
+ jobs [-lnprs] [JOBSPEC]
+ jobs -x COMMAND [ARGUMENTS]
+
+ The first form lists the active jobs. The options have the
+ following meanings:
+
+ ‘-l’
+ List process IDs in addition to the normal information.
+
+ ‘-n’
+ Display information only about jobs that have changed status
+ since the user was last notified of their status.
+
+ ‘-p’
+ List only the process ID of the job's process group leader.
+
+ ‘-r’
+ Display only running jobs.
+
+ ‘-s’
+ Display only stopped jobs.
+
+ If JOBSPEC is supplied, ‘jobs’ restricts output to information
+ about that job. If JOBSPEC is not supplied, ‘jobs’ lists the
+ status of all jobs. The return status is zero unless an invalid
+ option is encountered or an invalid JOBSPEC is supplied.
+
+ If the ‘-x’ option is supplied, ‘jobs’ replaces any JOBSPEC found
+ in COMMAND or ARGUMENTS with the corresponding process group ID,
+ and executes COMMAND, passing it ARGUMENTs, returning its exit
+ status.
+
+‘kill’
+ kill [-s SIGSPEC] [-n SIGNUM] [-SIGSPEC] ID [...]
+ kill -l|-L [EXIT_STATUS]
+
+ Send a signal specified by SIGSPEC or SIGNUM to the processes named
+ by each ID. Each ID may be a job specification JOBSPEC or process
+ ID PID. SIGSPEC is either a case-insensitive signal name such as
+ ‘SIGINT’ (with or without the ‘SIG’ prefix) or a signal number;
+ SIGNUM is a signal number. If SIGSPEC and SIGNUM are not present,
+ ‘kill’ sends ‘SIGTERM’.
+
+ The ‘-l’ option lists the signal names. If any arguments are
+ supplied when ‘-l’ is supplied, ‘kill’ lists the names of the
+ signals corresponding to the arguments, and the return status is
+ zero. EXIT_STATUS is a number specifying a signal number or the
+ exit status of a process terminated by a signal; if it is supplied,
+ ‘kill’ prints the name of the signal that caused the process to
+ terminate. ‘kill’ assumes that process exit statuses are greater
+ than 128; anything less than that is a signal number. The ‘-L’
+ option is equivalent to ‘-l’.
+
+ The return status is zero if at least one signal was successfully
+ sent, or non-zero if an error occurs or an invalid option is
+ encountered.
+
+‘wait’
+ wait [-fn] [-p VARNAME] [ID ...]
+
+ Wait until the child process specified by each ID exits and return
+ the exit status of the last ID. Each ID may be a process ID PID or
+ a job specification JOBSPEC; if a jobspec is supplied, ‘wait’ waits
+ for all processes in the job.
+
+ If no options or IDs are supplied, ‘wait’ waits for all running
+ background jobs and the last-executed process substitution, if its
+ process id is the same as $!, and the return status is zero.
+
+ If the ‘-n’ option is supplied, ‘wait’ waits for any one of the IDs
+ or, if no IDs are supplied, any job or process substitution, to
+ complete and returns its exit status. If none of the supplied IDs
+ is a child of the shell, or if no arguments are supplied and the
+ shell has no unwaited-for children, the exit status is 127.
+
+ If the ‘-p’ option is supplied, ‘wait’ assigns the process or job
+ identifier of the job for which the exit status is returned to the
+ variable VARNAME named by the option argument. The variable, which
+ cannot be readonly, will be unset initially, before any assignment.
+ This is useful only when used with the ‘-n’ option.
+
+ Supplying the ‘-f’ option, when job control is enabled, forces
+ ‘wait’ to wait for each ID to terminate before returning its
+ status, instead of returning when it changes status.
+
+ If none of the IDs specify one of the shell's an active child
+ processes, the return status is 127. If ‘wait’ is interrupted by a
+ signal, any VARNAME will remain unset, and the return status will
+ be greater than 128, as described above (*note Signals::).
+ Otherwise, the return status is the exit status of the last ID.
+
+‘disown’
+ disown [-ar] [-h] [ID ...]
+
+ Without options, remove each ID from the table of active jobs.
+ Each ID may be a job specification JOBSPEC or a process ID PID; if
+ ID is a PID, ‘disown’ uses the job containing PID as JOBSPEC.
+
+ If the ‘-h’ option is supplied, ‘disown’ does not remove the jobs
+ corresponding to each ‘id’ from the jobs table, but rather marks
+ them so the shell does not send ‘SIGHUP’ to the job if the shell
+ receives a ‘SIGHUP’.
+
+ If no ID is supplied, the ‘-a’ option means to remove or mark all
+ jobs; the ‘-r’ option without an ID argument removes or marks
+ running jobs. If no ID is supplied, and neither the ‘-a’ nor the
+ ‘-r’ option is supplied, ‘disown’ removes or marks the current job.
+
+ The return value is 0 unless an ID does not specify a valid job.
+
+‘suspend’
+ suspend [-f]
+
+ Suspend the execution of this shell until it receives a ‘SIGCONT’
+ signal. A login shell, or a shell without job control enabled,
+ cannot be suspended; the ‘-f’ option will override this and force
+ the suspension. The return status is 0 unless the shell is a login
+ shell or job control is not enabled and ‘-f’ is not supplied.
+
+ When job control is not active, the ‘kill’ and ‘wait’ builtins do not
+accept JOBSPEC arguments. They must be supplied process IDs.
+
+\1f
+File: bashref.info, Node: Job Control Variables, Prev: Job Control Builtins, Up: Job Control
+
+7.3 Job Control Variables
+=========================
+
+‘auto_resume’
+ This variable controls how the shell interacts with the user and
+ job control. If this variable exists then simple commands
+ consisting of only a single word, without redirections, are treated
+ as candidates for resumption of an existing job. There is no
+ ambiguity allowed; if there is more than one job beginning with or
+ containing the word, then this selects the most recently accessed
+ job. The name of a stopped job, in this context, is the command
+ line used to start it, as displayed by ‘jobs’. If this variable is
+ set to the value ‘exact’, the word must match the name of a stopped
+ job exactly; if set to ‘substring’, the word needs to match a
+ substring of the name of a stopped job. The ‘substring’ value
+ provides functionality analogous to the ‘%?string’ job ID (*note
+ Job Control Basics::). If set to any other value (e.g., ‘prefix’),
+ the word must be a prefix of a stopped job's name; this provides
+ functionality analogous to the ‘%string’ job ID.
+
+\1f
+File: bashref.info, Node: Command Line Editing, Next: Using History Interactively, Prev: Job Control, Up: Top
+
+8 Command Line Editing
+**********************
+
+This chapter describes the basic features of the GNU command line
+editing interface. Command line editing is provided by the Readline
+library, which is used by several different programs, including Bash.
+Command line editing is enabled by default when using an interactive
+shell, unless the ‘--noediting’ option is supplied at shell invocation.
+Line editing is also used when using the ‘-e’ option to the ‘read’
+builtin command (*note Bash Builtins::). By default, the line editing
+commands are similar to those of Emacs; a vi-style line editing
+interface is also available. Line editing can be enabled at any time
+using the ‘-o emacs’ or ‘-o vi’ options to the ‘set’ builtin command
+(*note The Set Builtin::), or disabled using the ‘+o emacs’ or ‘+o vi’
+options to ‘set’.
+
+* Menu:
+
+* Introduction and Notation:: Notation used in this text.
+* Readline Interaction:: The minimum set of commands for editing a line.
+* Readline Init File:: Customizing Readline from a user's view.
+* Bindable Readline Commands:: A description of most of the Readline commands
+ available for binding
+* Readline vi Mode:: A short description of how to make Readline
+ behave like the vi editor.
+* Programmable Completion:: How to specify the possible completions for
+ a specific command.
+* Programmable Completion Builtins:: Builtin commands to specify how to
+ complete arguments for a particular command.
+* A Programmable Completion Example:: An example shell function for
+ generating possible completions.
+
+\1f
+File: bashref.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
+
+8.1 Introduction to Line Editing
+================================
+
+The following paragraphs use Emacs style to describe the notation used
+to represent keystrokes.
+
+ The text ‘C-k’ is read as "Control-K" and describes the character
+produced when the <k> key is pressed while the Control key is depressed.
+
+ The text ‘M-k’ is read as "Meta-K" and describes the character
+produced when the Meta key (if you have one) is depressed, and the <k>
+key is pressed (a “meta character”), then both are released. The Meta
+key is labeled <ALT> or <Option> on many keyboards. On keyboards with
+two keys labeled <ALT> (usually to either side of the space bar), the
+<ALT> on the left side is generally set to work as a Meta key. One of
+the <ALT> keys may also be configured as some other modifier, such as a
+Compose key for typing accented characters.
+
+ On some keyboards, the Meta key modifier produces characters with the
+eighth bit (0200) set. You can use the ‘enable-meta-key’ variable to
+control whether or not it does this, if the keyboard allows it. On many
+others, the terminal or terminal emulator converts the metafied key to a
+key sequence beginning with <ESC> as described in the next paragraph.
+
+ If you do not have a Meta or <ALT> key, or another key working as a
+Meta key, you can generally achieve the latter effect by typing <ESC>
+_first_, and then typing <k>. The <ESC> character is known as the “meta
+prefix”).
+
+ Either process is known as “metafying” the <k> key.
+
+ If your Meta key produces a key sequence with the <ESC> meta prefix,
+you can make ‘M-key’ key bindings you specify (see ‘Key Bindings’ in
+*note Readline Init File Syntax::) do the same thing by setting the
+‘force-meta-prefix’ variable.
+
+ The text ‘M-C-k’ is read as "Meta-Control-k" and describes the
+character produced by metafying ‘C-k’.
+
+ In addition, several keys have their own names. Specifically, <DEL>,
+<ESC>, <LFD>, <SPC>, <RET>, and <TAB> all stand for themselves when seen
+in this text, or in an init file (*note Readline Init File::). If your
+keyboard lacks a <LFD> key, typing <C-j> will output the appropriate
+character. The <RET> key may be labeled <Return> or <Enter> on some
+keyboards.
+
+\1f
+File: bashref.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
+
+8.2 Readline Interaction
+========================
+
+Often during an interactive session you type in a long line of text,
+only to notice that the first word on the line is misspelled. The
+Readline library gives you a set of commands for manipulating the text
+as you type it in, allowing you to just fix your typo, and not forcing
+you to retype the majority of the line. Using these editing commands,
+you move the cursor to the place that needs correction, and delete or
+insert the text of the corrections. Then, when you are satisfied with
+the line, you simply press <RET>. You do not have to be at the end of
+the line to press <RET>; the entire line is accepted regardless of the
+location of the cursor within the line.
+
+* Menu:
+
+* Readline Bare Essentials:: The least you need to know about Readline.
+* Readline Movement Commands:: Moving about the input line.
+* Readline Killing Commands:: How to delete text, and how to get it back!
+* Readline Arguments:: Giving numeric arguments to commands.
+* Searching:: Searching through previous lines.
+
+\1f
+File: bashref.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
+
+8.2.1 Readline Bare Essentials
+------------------------------
+
+In order to enter characters into the line, simply type them. The typed
+character appears where the cursor was, and then the cursor moves one
+space to the right. If you mistype a character, you can use your erase
+character to back up and delete the mistyped character.
+
+ Sometimes you may mistype a character, and not notice the error until
+you have typed several other characters. In that case, you can type
+‘C-b’ to move the cursor to the left, and then correct your mistake.
+Afterwards, you can move the cursor to the right with ‘C-f’.
+
+ When you add text in the middle of a line, you will notice that
+characters to the right of the cursor are "pushed over" to make room for
+the text that you have inserted. Likewise, when you delete text behind
+the cursor, characters to the right of the cursor are "pulled back" to
+fill in the blank space created by the removal of the text. These are
+the bare essentials for editing the text of an input line:
+
+‘C-b’
+ Move back one character.
+‘C-f’
+ Move forward one character.
+<DEL> or <Backspace>
+ Delete the character to the left of the cursor.
+‘C-d’
+ Delete the character underneath the cursor.
+Printing characters
+ Insert the character into the line at the cursor.
+‘C-_’ or ‘C-x C-u’
+ Undo the last editing command. You can undo all the way back to an
+ empty line.
+
+Depending on your configuration, the <Backspace> key might be set to
+delete the character to the left of the cursor and the <DEL> key set to
+delete the character underneath the cursor, like ‘C-d’, rather than the
+character to the left of the cursor.
+
+\1f
+File: bashref.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
+
+8.2.2 Readline Movement Commands
+--------------------------------
+
+The above table describes the most basic keystrokes that you need in
+order to do editing of the input line. For your convenience, many other
+commands are available in addition to ‘C-b’, ‘C-f’, ‘C-d’, and <DEL>.
+Here are some commands for moving more rapidly within the line.
+
+‘C-a’
+ Move to the start of the line.
+‘C-e’
+ Move to the end of the line.
+‘M-f’
+ Move forward a word, where a word is composed of letters and
+ digits.
+‘M-b’
+ Move backward a word.
+‘C-l’
+ Clear the screen, reprinting the current line at the top.
+
+ Notice how ‘C-f’ moves forward a character, while ‘M-f’ moves forward
+a word. It is a loose convention that control keystrokes operate on
+characters while meta keystrokes operate on words.
+
+\1f
+File: bashref.info, Node: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
+
+8.2.3 Readline Killing Commands
+-------------------------------
+
+“Killing” text means to delete the text from the line, but to save it
+away for later use, usually by “yanking” (re-inserting) it back into the
+line. ("Cut" and "paste" are more recent jargon for "kill" and "yank".)
+
+ If the description for a command says that it "kills" text, then you
+can be sure that you can get the text back in a different (or the same)
+place later.
+
+ When you use a kill command, the text is saved in a “kill-ring”. Any
+number of consecutive kills save all of the killed text together, so
+that when you yank it back, you get it all. The kill ring is not line
+specific; the text that you killed on a previously typed line is
+available to be yanked back later, when you are typing another line.
+
+ Here is the list of commands for killing text.
+
+‘C-k’
+ Kill the text from the current cursor position to the end of the
+ line.
+
+‘M-d’
+ Kill from the cursor to the end of the current word, or, if between
+ words, to the end of the next word. Word boundaries are the same
+ as those used by ‘M-f’.
+
+‘M-<DEL>’
+ Kill from the cursor to the start of the current word, or, if
+ between words, to the start of the previous word. Word boundaries
+ are the same as those used by ‘M-b’.
+
+‘C-w’
+ Kill from the cursor to the previous whitespace. This is different
+ than ‘M-<DEL>’ because the word boundaries differ.
+
+ Here is how to “yank” the text back into the line. Yanking means to
+copy the most-recently-killed text from the kill buffer into the line at
+the current cursor position.
+
+‘C-y’
+ Yank the most recently killed text back into the buffer at the
+ cursor.
+
+‘M-y’
+ Rotate the kill-ring, and yank the new top. You can only do this
+ if the prior command is ‘C-y’ or ‘M-y’.
+
+\1f
+File: bashref.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
+
+8.2.4 Readline Arguments
+------------------------
+
+You can pass numeric arguments to Readline commands. Sometimes the
+argument acts as a repeat count, other times it is the sign of the
+argument that is significant. If you pass a negative argument to a
+command which normally acts in a forward direction, that command will
+act in a backward direction. For example, to kill text back to the
+start of the line, you might type ‘M-- C-k’.
+
+ The general way to pass numeric arguments to a command is to type the
+Meta key and then digits ("meta digits") before the command. If the
+first "digit" typed is a minus sign (‘-’), then the sign of the argument
+will be negative. Once you have typed one meta digit to get the
+argument started, you can type the remainder of the digits, and then the
+command. For example, to give the ‘C-d’ command an argument of 10, you
+could type ‘M-1 0 C-d’, which will delete the next ten characters on the
+input line.
+
+\1f
+File: bashref.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
+
+8.2.5 Searching for Commands in the History
+-------------------------------------------
+
+Readline provides commands for searching through the command history
+(*note Bash History Facilities::) for lines containing a specified
+string. There are two search modes: “incremental” and
+“non-incremental”.
+
+ Incremental searches begin before the user has finished typing the
+search string. As each character of the search string is typed,
+Readline displays the next entry from the history matching the string
+typed so far. An incremental search requires only as many characters as
+needed to find the desired history entry. When using emacs editing
+mode, type ‘C-r’ to search backward in the history for a particular
+string. Typing ‘C-s’ searches forward through the history. The
+characters present in the value of the ‘isearch-terminators’ variable
+are used to terminate an incremental search. If that variable has not
+been assigned a value, the <ESC> and ‘C-j’ characters terminate an
+incremental search. ‘C-g’ aborts an incremental search and restores the
+original line. When the search is terminated, the history entry
+containing the search string becomes the current line.
+
+ To find other matching entries in the history list, type ‘C-r’ or
+‘C-s’ as appropriate. This searches backward or forward in the history
+for the next entry matching the search string typed so far. Any other
+key sequence bound to a Readline command terminates the search and
+executes that command. For instance, a <RET> terminates the search and
+accepts the line, thereby executing the command from the history list.
+A movement command will terminate the search, make the last line found
+the current line, and begin editing.
+
+ Readline remembers the last incremental search string. If two ‘C-r’s
+are typed without any intervening characters defining a new search
+string, Readline uses any remembered search string.
+
+ Non-incremental searches read the entire search string before
+starting to search for matching history entries. The search string may
+be typed by the user or be part of the contents of the current line.
+
+\1f
+File: bashref.info, Node: Readline Init File, Next: Bindable Readline Commands, Prev: Readline Interaction, Up: Command Line Editing
+
+8.3 Readline Init File
+======================
+
+Although the Readline library comes with a set of Emacs-like keybindings
+installed by default, it is possible to use a different set of
+keybindings. Any user can customize programs that use Readline by
+putting commands in an “inputrc” file, conventionally in their home
+directory. The name of this file is taken from the value of the shell
+variable ‘INPUTRC’. If that variable is unset, the default is
+‘~/.inputrc’. If that file does not exist or cannot be read, Readline
+looks for ‘/etc/inputrc’. The ‘bind’ builtin command can also be used
+to set Readline keybindings and variables. *Note Bash Builtins::.
+
+ When a program that uses the Readline library starts up, Readline
+reads the init file and sets any variables and key bindings it contains.
+
+ In addition, the ‘C-x C-r’ command re-reads this init file, thus
+incorporating any changes that you might have made to it.
+
+* Menu:
+
+* Readline Init File Syntax:: Syntax for the commands in the inputrc file.
+* Conditional Init Constructs:: Conditional key bindings in the inputrc file.
+* Sample Init File:: An example inputrc file.
+
+\1f
+File: bashref.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
+
+8.3.1 Readline Init File Syntax
+-------------------------------
+
+There are only a few basic constructs allowed in the Readline init file.
+Blank lines are ignored. Lines beginning with a ‘#’ are comments.
+Lines beginning with a ‘$’ indicate conditional constructs (*note
+Conditional Init Constructs::). Other lines denote variable settings
+and key bindings.
+
+Variable Settings
+ You can modify the run-time behavior of Readline by altering the
+ values of variables in Readline using the ‘set’ command within the
+ init file. The syntax is simple:
+
+ set VARIABLE VALUE
+
+ Here, for example, is how to change from the default Emacs-like key
+ binding to use ‘vi’ line editing commands:
+
+ set editing-mode vi
+
+ Variable names and values, where appropriate, are recognized
+ without regard to case. Unrecognized variable names are ignored.
+
+ Boolean variables (those that can be set to on or off) are set to
+ on if the value is null or empty, ON (case-insensitive), or 1. Any
+ other value results in the variable being set to off.
+
+ The ‘bind -V’ command lists the current Readline variable names and
+ values. *Note Bash Builtins::.
+
+ A great deal of run-time behavior is changeable with the following
+ variables.
+
+ ‘active-region-start-color’
+ A string variable that controls the text color and background
+ when displaying the text in the active region (see the
+ description of ‘enable-active-region’ below). This string
+ must not take up any physical character positions on the
+ display, so it should consist only of terminal escape
+ sequences. It is output to the terminal before displaying the
+ text in the active region. This variable is reset to the
+ default value whenever the terminal type changes. The default
+ value is the string that puts the terminal in standout mode,
+ as obtained from the terminal's terminfo description. A
+ sample value might be ‘\e[01;33m’.
+
+ ‘active-region-end-color’
+ A string variable that "undoes" the effects of
+ ‘active-region-start-color’ and restores "normal" terminal
+ display appearance after displaying text in the active region.
+ This string must not take up any physical character positions
+ on the display, so it should consist only of terminal escape
+ sequences. It is output to the terminal after displaying the
+ text in the active region. This variable is reset to the
+ default value whenever the terminal type changes. The default
+ value is the string that restores the terminal from standout
+ mode, as obtained from the terminal's terminfo description. A
+ sample value might be ‘\e[0m’.
+
+ ‘bell-style’
+ Controls what happens when Readline wants to ring the terminal
+ bell. If set to ‘none’, Readline never rings the bell. If
+ set to ‘visible’, Readline uses a visible bell if one is
+ available. If set to ‘audible’ (the default), Readline
+ attempts to ring the terminal's bell.
+
+ ‘bind-tty-special-chars’
+ If set to ‘on’ (the default), Readline attempts to bind the
+ control characters that are treated specially by the kernel's
+ terminal driver to their Readline equivalents. These override
+ the default Readline bindings described here. Type ‘stty -a’
+ at a Bash prompt to see your current terminal settings,
+ including the special control characters (usually ‘cchars’).
+ This binding takes place on each call to ‘readline()’, so
+ changes made by ‘stty’ can take effect.
+
+ ‘blink-matching-paren’
+ If set to ‘on’, Readline attempts to briefly move the cursor
+ to an opening parenthesis when a closing parenthesis is
+ inserted. The default is ‘off’.
+
+ ‘colored-completion-prefix’
+ If set to ‘on’, when listing completions, Readline displays
+ the common prefix of the set of possible completions using a
+ different color. The color definitions are taken from the
+ value of the ‘LS_COLORS’ environment variable. If there is a
+ color definition in ‘LS_COLORS’ for the custom suffix
+ ‘readline-colored-completion-prefix’, Readline uses this color
+ for the common prefix instead of its default. The default is
+ ‘off’.
+
+ ‘colored-stats’
+ If set to ‘on’, Readline displays possible completions using
+ different colors to indicate their file type. The color
+ definitions are taken from the value of the ‘LS_COLORS’
+ environment variable. The default is ‘off’.
+
+ ‘comment-begin’
+ The string to insert at the beginning of the line by the
+ ‘insert-comment’ command. The default value is ‘"#"’.
+
+ ‘completion-display-width’
+ The number of screen columns used to display possible matches
+ when performing completion. The value is ignored if it is
+ less than 0 or greater than the terminal screen width. A
+ value of 0 causes matches to be displayed one per line. The
+ default value is -1.
+
+ ‘completion-ignore-case’
+ If set to ‘on’, Readline performs filename matching and
+ completion in a case-insensitive fashion. The default value
+ is ‘off’.
+
+ ‘completion-map-case’
+ If set to ‘on’, and COMPLETION-IGNORE-CASE is enabled,
+ Readline treats hyphens (‘-’) and underscores (‘_’) as
+ equivalent when performing case-insensitive filename matching
+ and completion. The default value is ‘off’.
+
+ ‘completion-prefix-display-length’
+ The maximum length in characters of the common prefix of a
+ list of possible completions that is displayed without
+ modification. When set to a value greater than zero, Readline
+ replaces common prefixes longer than this value with an
+ ellipsis when displaying possible completions. If a
+ completion begins with a period, and Readline is completing
+ filenames, it uses three underscores instead of an ellipsis.
+
+ ‘completion-query-items’
+ The number of possible completions that determines when the
+ user is asked whether the list of possibilities should be
+ displayed. If the number of possible completions is greater
+ than or equal to this value, Readline asks whether or not the
+ user wishes to view them; otherwise, Readline simply lists the
+ completions. This variable must be set to an integer value
+ greater than or equal to zero. A zero value means Readline
+ should never ask; negative values are treated as zero. The
+ default limit is ‘100’.
+
+ ‘convert-meta’
+ If set to ‘on’, Readline converts characters it reads that
+ have the eighth bit set to an ASCII key sequence by clearing
+ the eighth bit and prefixing an <ESC> character, converting
+ them to a meta-prefixed key sequence. The default value is
+ ‘on’, but Readline sets it to ‘off’ if the locale contains
+ characters whose encodings may include bytes with the eighth
+ bit set. This variable is dependent on the ‘LC_CTYPE’ locale
+ category, and may change if the locale changes. This variable
+ also affects key bindings; see the description of
+ ‘force-meta-prefix’ below.
+
+ ‘disable-completion’
+ If set to ‘On’, Readline inhibits word completion. Completion
+ characters are inserted into the line as if they had been
+ mapped to ‘self-insert’. The default is ‘off’.
+
+ ‘echo-control-characters’
+ When set to ‘on’, on operating systems that indicate they
+ support it, Readline echoes a character corresponding to a
+ signal generated from the keyboard. The default is ‘on’.
+
+ ‘editing-mode’
+ The ‘editing-mode’ variable controls the default set of key
+ bindings. By default, Readline starts up in emacs editing
+ mode, where the keystrokes are most similar to Emacs. This
+ variable can be set to either ‘emacs’ or ‘vi’.
+
+ ‘emacs-mode-string’
+ If the SHOW-MODE-IN-PROMPT variable is enabled, this string is
+ displayed immediately before the last line of the primary
+ prompt when emacs editing mode is active. The value is
+ expanded like a key binding, so the standard set of meta- and
+ control- prefixes and backslash escape sequences is available.
+ The ‘\1’ and ‘\2’ escapes begin and end sequences of
+ non-printing characters, which can be used to embed a terminal
+ control sequence into the mode string. The default is ‘@’.
+
+ ‘enable-active-region’
+ “point” is the current cursor position, and “mark” refers to a
+ saved cursor position (*note Commands For Moving::). The text
+ between the point and mark is referred to as the “region”.
+ When this variable is set to ‘On’, Readline allows certain
+ commands to designate the region as “active”. When the region
+ is active, Readline highlights the text in the region using
+ the value of the ‘active-region-start-color’, which defaults
+ to the string that enables the terminal's standout mode. The
+ active region shows the text inserted by bracketed-paste and
+ any matching text found by incremental and non-incremental
+ history searches. The default is ‘On’.
+
+ ‘enable-bracketed-paste’
+ When set to ‘On’, Readline configures the terminal to insert
+ each paste into the editing buffer as a single string of
+ characters, instead of treating each character as if it had
+ been read from the keyboard. This is called putting the
+ terminal into “bracketed paste mode”; it prevents Readline
+ from executing any editing commands bound to key sequences
+ appearing in the pasted text. The default is ‘On’.
+
+ ‘enable-keypad’
+ When set to ‘on’, Readline tries to enable the application
+ keypad when it is called. Some systems need this to enable
+ the arrow keys. The default is ‘off’.
+
+ ‘enable-meta-key’
+ When set to ‘on’, Readline tries to enable any meta modifier
+ key the terminal claims to support when it is called. On many
+ terminals, the Meta key is used to send eight-bit characters;
+ this variable checks for the terminal capability that
+ indicates the terminal can enable and disable a mode that sets
+ the eighth bit of a character (0200) if the Meta key is held
+ down when the character is typed (a meta character). The
+ default is ‘on’.
+
+ ‘expand-tilde’
+ If set to ‘on’, Readline attempts tilde expansion when it
+ attempts word completion. The default is ‘off’.
+
+ ‘force-meta-prefix’
+ If set to ‘on’, Readline modifies its behavior when binding
+ key sequences containing ‘\M-’ or ‘Meta-’ (see ‘Key Bindings’
+ in *note Readline Init File Syntax::) by converting a key
+ sequence of the form ‘\M-’C or ‘Meta-’C to the two-character
+ sequence ‘ESC’ C (adding the meta prefix). If
+ ‘force-meta-prefix’ is set to ‘off’ (the default), Readline
+ uses the value of the ‘convert-meta’ variable to determine
+ whether to perform this conversion: if ‘convert-meta’ is ‘on’,
+ Readline performs the conversion described above; if it is
+ ‘off’, Readline converts C to a meta character by setting the
+ eighth bit (0200). The default is ‘off’.
+
+ ‘history-preserve-point’
+ If set to ‘on’, the history code attempts to place the point
+ (the current cursor position) at the same location on each
+ history line retrieved with ‘previous-history’ or
+ ‘next-history’. The default is ‘off’.
+
+ ‘history-size’
+ Set the maximum number of history entries saved in the history
+ list. If set to zero, any existing history entries are
+ deleted and no new entries are saved. If set to a value less
+ than zero, the number of history entries is not limited. By
+ default, Bash sets the maximum number of history entries to
+ the value of the ‘HISTSIZE’ shell variable. If you try to set
+ HISTORY-SIZE to a non-numeric value, the maximum number of
+ history entries will be set to 500.
+
+ ‘horizontal-scroll-mode’
+ Setting this variable to ‘on’ means that the text of the lines
+ being edited will scroll horizontally on a single screen line
+ when the lines are longer than the width of the screen,
+ instead of wrapping onto a new screen line. This variable is
+ automatically set to ‘on’ for terminals of height 1. By
+ default, this variable is set to ‘off’.
+
+ ‘input-meta’
+ If set to ‘on’, Readline enables eight-bit input (that is, it
+ does not clear the eighth bit in the characters it reads),
+ regardless of what the terminal claims it can support. The
+ default value is ‘off’, but Readline sets it to ‘on’ if the
+ locale contains characters whose encodings may include bytes
+ with the eighth bit set. This variable is dependent on the
+ ‘LC_CTYPE’ locale category, and its value may change if the
+ locale changes. The name ‘meta-flag’ is a synonym for
+ ‘input-meta’.
+
+ ‘isearch-terminators’
+ The string of characters that should terminate an incremental
+ search without subsequently executing the character as a
+ command (*note Searching::). If this variable has not been
+ given a value, the characters <ESC> and ‘C-j’ terminate an
+ incremental search.
+
+ ‘keymap’
+ Sets Readline's idea of the current keymap for key binding
+ commands. Built-in ‘keymap’ names are ‘emacs’,
+ ‘emacs-standard’, ‘emacs-meta’, ‘emacs-ctlx’, ‘vi’, ‘vi-move’,
+ ‘vi-command’, and ‘vi-insert’. ‘vi’ is equivalent to
+ ‘vi-command’ (‘vi-move’ is also a synonym); ‘emacs’ is
+ equivalent to ‘emacs-standard’. Applications may add
+ additional names. The default value is ‘emacs’; the value of
+ the ‘editing-mode’ variable also affects the default keymap.
+
+ ‘keyseq-timeout’
+ Specifies the duration Readline will wait for a character when
+ reading an ambiguous key sequence (one that can form a
+ complete key sequence using the input read so far, or can take
+ additional input to complete a longer key sequence). If
+ Readline doesn't receive any input within the timeout, it uses
+ the shorter but complete key sequence. Readline uses this
+ value to determine whether or not input is available on the
+ current input source (‘rl_instream’ by default). The value is
+ specified in milliseconds, so a value of 1000 means that
+ Readline will wait one second for additional input. If this
+ variable is set to a value less than or equal to zero, or to a
+ non-numeric value, Readline waits until another key is pressed
+ to decide which key sequence to complete. The default value
+ is ‘500’.
+
+ ‘mark-directories’
+ If set to ‘on’, completed directory names have a slash
+ appended. The default is ‘on’.
+
+ ‘mark-modified-lines’
+ When this variable is set to ‘on’, Readline displays an
+ asterisk (‘*’) at the start of history lines which have been
+ modified. This variable is ‘off’ by default.
+
+ ‘mark-symlinked-directories’
+ If set to ‘on’, completed names which are symbolic links to
+ directories have a slash appended, subject to the value of
+ ‘mark-directories’. The default is ‘off’.
+
+ ‘match-hidden-files’
+ This variable, when set to ‘on’, forces Readline to match
+ files whose names begin with a ‘.’ (hidden files) when
+ performing filename completion. If set to ‘off’, the user
+ must include the leading ‘.’ in the filename to be completed.
+ This variable is ‘on’ by default.
+
+ ‘menu-complete-display-prefix’
+ If set to ‘on’, menu completion displays the common prefix of
+ the list of possible completions (which may be empty) before
+ cycling through the list. The default is ‘off’.
+
+ ‘output-meta’
+ If set to ‘on’, Readline displays characters with the eighth
+ bit set directly rather than as a meta-prefixed escape
+ sequence. The default is ‘off’, but Readline sets it to ‘on’
+ if the locale contains characters whose encodings may include
+ bytes with the eighth bit set. This variable is dependent on
+ the ‘LC_CTYPE’ locale category, and its value may change if
+ the locale changes.
+
+ ‘page-completions’
+ If set to ‘on’, Readline uses an internal pager resembling
+ more(1) to display a screenful of possible completions at a
+ time. This variable is ‘on’ by default.
+
+ ‘prefer-visible-bell’
+ See ‘bell-style’.
+
+ ‘print-completions-horizontally’
+ If set to ‘on’, Readline displays completions with matches
+ sorted horizontally in alphabetical order, rather than down
+ the screen. The default is ‘off’.
+
+ ‘revert-all-at-newline’
+ If set to ‘on’, Readline will undo all changes to history
+ lines before returning when executing ‘accept-line’. By
+ default, history lines may be modified and retain individual
+ undo lists across calls to ‘readline()’. The default is
+ ‘off’.
+
+ ‘search-ignore-case’
+ If set to ‘on’, Readline performs incremental and
+ non-incremental history list searches in a case-insensitive
+ fashion. The default value is ‘off’.
+
+ ‘show-all-if-ambiguous’
+ This alters the default behavior of the completion functions.
+ If set to ‘on’, words which have more than one possible
+ completion cause the matches to be listed immediately instead
+ of ringing the bell. The default value is ‘off’.
+
+ ‘show-all-if-unmodified’
+ This alters the default behavior of the completion functions
+ in a fashion similar to SHOW-ALL-IF-AMBIGUOUS. If set to
+ ‘on’, words which have more than one possible completion
+ without any possible partial completion (the possible
+ completions don't share a common prefix) cause the matches to
+ be listed immediately instead of ringing the bell. The
+ default value is ‘off’.
+
+ ‘show-mode-in-prompt’
+ If set to ‘on’, add a string to the beginning of the prompt
+ indicating the editing mode: emacs, vi command, or vi
+ insertion. The mode strings are user-settable (e.g.,
+ EMACS-MODE-STRING). The default value is ‘off’.
+
+ ‘skip-completed-text’
+ If set to ‘on’, this alters the default completion behavior
+ when inserting a single match into the line. It's only active
+ when performing completion in the middle of a word. If
+ enabled, Readline does not insert characters from the
+ completion that match characters after point in the word being
+ completed, so portions of the word following the cursor are
+ not duplicated. For instance, if this is enabled, attempting
+ completion when the cursor is after the first ‘e’ in
+ ‘Makefile’ will result in ‘Makefile’ rather than
+ ‘Makefilefile’, assuming there is a single possible
+ completion. The default value is ‘off’.
+
+ ‘vi-cmd-mode-string’
+ If the SHOW-MODE-IN-PROMPT variable is enabled, this string is
+ displayed immediately before the last line of the primary
+ prompt when vi editing mode is active and in command mode.
+ The value is expanded like a key binding, so the standard set
+ of meta- and control- prefixes and backslash escape sequences
+ is available. The ‘\1’ and ‘\2’ escapes begin and end
+ sequences of non-printing characters, which can be used to
+ embed a terminal control sequence into the mode string. The
+ default is ‘(cmd)’.
+
+ ‘vi-ins-mode-string’
+ If the SHOW-MODE-IN-PROMPT variable is enabled, this string is
+ displayed immediately before the last line of the primary
+ prompt when vi editing mode is active and in insertion mode.
+ The value is expanded like a key binding, so the standard set
+ of meta- and control- prefixes and backslash escape sequences
+ is available. The ‘\1’ and ‘\2’ escapes begin and end
+ sequences of non-printing characters, which can be used to
+ embed a terminal control sequence into the mode string. The
+ default is ‘(ins)’.
+
+ ‘visible-stats’
+ If set to ‘on’, a character denoting a file's type is appended
+ to the filename when listing possible completions. The
+ default is ‘off’.
+
+Key Bindings
+ The syntax for controlling key bindings in the init file is simple.
+ First you need to find the name of the command that you want to
+ change. The following sections contain tables of the command name,
+ the default keybinding, if any, and a short description of what the
+ command does.
+
+ Once you know the name of the command, simply place on a line in
+ the init file the name of the key you wish to bind the command to,
+ a colon, and then the name of the command. There can be no space
+ between the key name and the colon - that will be interpreted as
+ part of the key name. The name of the key can be expressed in
+ different ways, depending on what you find most comfortable.
+
+ In addition to command names, Readline allows keys to be bound to a
+ string that is inserted when the key is pressed (a MACRO). The
+ difference between a macro and a command is that a macro is
+ enclosed in single or double quotes.
+
+ The ‘bind -p’ command displays Readline function names and bindings
+ in a format that can be put directly into an initialization file.
+ *Note Bash Builtins::.
+
+ KEYNAME: FUNCTION-NAME or MACRO
+ KEYNAME is the name of a key spelled out in English. For
+ example:
+ Control-u: universal-argument
+ Meta-Rubout: backward-kill-word
+ Control-o: "> output"
+
+ In the example above, ‘C-u’ is bound to the function
+ ‘universal-argument’, ‘M-DEL’ is bound to the function
+ ‘backward-kill-word’, and ‘C-o’ is bound to run the macro
+ expressed on the right hand side (that is, to insert the text
+ ‘> output’ into the line).
+
+ This key binding syntax recognizes a number of symbolic
+ character names: DEL, ESC, ESCAPE, LFD, NEWLINE, RET, RETURN,
+ RUBOUT (a destructive backspace), SPACE, SPC, and TAB.
+
+ "KEYSEQ": FUNCTION-NAME or MACRO
+ KEYSEQ differs from KEYNAME above in that strings denoting an
+ entire key sequence can be specified, by placing the key
+ sequence in double quotes. Some GNU Emacs style key escapes
+ can be used, as in the following example, but none of the
+ special character names are recognized.
+
+ "\C-u": universal-argument
+ "\C-x\C-r": re-read-init-file
+ "\e[11~": "Function Key 1"
+
+ In the above example, ‘C-u’ is again bound to the function
+ ‘universal-argument’ (just as it was in the first example),
+ ‘‘C-x’ ‘C-r’’ is bound to the function ‘re-read-init-file’,
+ and ‘<ESC> <[> <1> <1> <~>’ is bound to insert the text
+ ‘Function Key 1’.
+
+ The following GNU Emacs style escape sequences are available when
+ specifying key sequences:
+
+ ‘\C-’
+ A control prefix.
+ ‘\M-’
+ Adding the meta prefix or converting the following character
+ to a meta character, as described above under
+ ‘force-meta-prefix’ (see ‘Variable Settings’ in *note Readline
+ Init File Syntax::).
+ ‘\e’
+ An escape character.
+ ‘\\’
+ Backslash.
+ ‘\"’
+ <">, a double quotation mark.
+ ‘\'’
+ <'>, a single quote or apostrophe.
+
+ In addition to the GNU Emacs style escape sequences, a second set
+ of backslash escapes is available:
+
+ ‘\a’
+ alert (bell)
+ ‘\b’
+ backspace
+ ‘\d’
+ delete
+ ‘\f’
+ form feed
+ ‘\n’
+ newline
+ ‘\r’
+ carriage return
+ ‘\t’
+ horizontal tab
+ ‘\v’
+ vertical tab
+ ‘\NNN’
+ The eight-bit character whose value is the octal value NNN
+ (one to three digits).
+ ‘\xHH’
+ The eight-bit character whose value is the hexadecimal value
+ HH (one or two hex digits).
+
+ When entering the text of a macro, single or double quotes must be
+ used to indicate a macro definition. Unquoted text is assumed to
+ be a function name. The backslash escapes described above are
+ expanded in the macro body. Backslash will quote any other
+ character in the macro text, including ‘"’ and ‘'’. For example,
+ the following binding will make ‘‘C-x’ \’ insert a single ‘\’ into
+ the line:
+ "\C-x\\": "\\"
+
+\1f
+File: bashref.info, Node: Conditional Init Constructs, Next: Sample Init File, Prev: Readline Init File Syntax, Up: Readline Init File
+
+8.3.2 Conditional Init Constructs
+---------------------------------
+
+Readline implements a facility similar in spirit to the conditional
+compilation features of the C preprocessor which allows key bindings and
+variable settings to be performed as the result of tests. There are
+four parser directives available.
+
+‘$if’
+ The ‘$if’ construct allows bindings to be made based on the editing
+ mode, the terminal being used, or the application using Readline.
+ The text of the test, after any comparison operator, extends to the
+ end of the line; unless otherwise noted, no characters are required
+ to isolate it.
+
+ ‘mode’
+ The ‘mode=’ form of the ‘$if’ directive is used to test
+ whether Readline is in ‘emacs’ or ‘vi’ mode. This may be used
+ in conjunction with the ‘set keymap’ command, for instance, to
+ set bindings in the ‘emacs-standard’ and ‘emacs-ctlx’ keymaps
+ only if Readline is starting out in ‘emacs’ mode.
+
+ ‘term’
+ The ‘term=’ form may be used to include terminal-specific key
+ bindings, perhaps to bind the key sequences output by the
+ terminal's function keys. The word on the right side of the
+ ‘=’ is tested against both the full name of the terminal and
+ the portion of the terminal name before the first ‘-’. This
+ allows ‘xterm’ to match both ‘xterm’ and ‘xterm-256color’, for
+ instance.
+
+ ‘version’
+ The ‘version’ test may be used to perform comparisons against
+ specific Readline versions. The ‘version’ expands to the
+ current Readline version. The set of comparison operators
+ includes ‘=’ (and ‘==’), ‘!=’, ‘<=’, ‘>=’, ‘<’, and ‘>’. The
+ version number supplied on the right side of the operator
+ consists of a major version number, an optional decimal point,
+ and an optional minor version (e.g., ‘7.1’). If the minor
+ version is omitted, it defaults to ‘0’. The operator may be
+ separated from the string ‘version’ and from the version
+ number argument by whitespace. The following example sets a
+ variable if the Readline version being used is 7.0 or newer:
+ $if version >= 7.0
+ set show-mode-in-prompt on
+ $endif
+
+ ‘application’
+ The APPLICATION construct is used to include
+ application-specific settings. Each program using the
+ Readline library sets the APPLICATION NAME, and you can test
+ for a particular value. This could be used to bind key
+ sequences to functions useful for a specific program. For
+ instance, the following command adds a key sequence that
+ quotes the current or previous word in Bash:
+ $if Bash
+ # Quote the current or previous word
+ "\C-xq": "\eb\"\ef\""
+ $endif
+
+ ‘variable’
+ The VARIABLE construct provides simple equality tests for
+ Readline variables and values. The permitted comparison
+ operators are ‘=’, ‘==’, and ‘!=’. The variable name must be
+ separated from the comparison operator by whitespace; the
+ operator may be separated from the value on the right hand
+ side by whitespace. String and boolean variables may be
+ tested. Boolean variables must be tested against the values
+ ON and OFF. The following example is equivalent to the
+ ‘mode=emacs’ test described above:
+ $if editing-mode == emacs
+ set show-mode-in-prompt on
+ $endif
+
+‘$else’
+ Commands in this branch of the ‘$if’ directive are executed if the
+ test fails.
+
+‘$endif’
+ This command, as seen in the previous example, terminates an ‘$if’
+ command.
+
+‘$include’
+ This directive takes a single filename as an argument and reads
+ commands and key bindings from that file. For example, the
+ following directive reads from ‘/etc/inputrc’:
+ $include /etc/inputrc
+
+\1f
+File: bashref.info, Node: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
+
+8.3.3 Sample Init File
+----------------------
+
+Here is an example of an INPUTRC file. This illustrates key binding,
+variable assignment, and conditional syntax.
+
+ # This file controls the behavior of line input editing for
+ # programs that use the GNU Readline library. Existing
+ # programs include FTP, Bash, and GDB.
+ #
+ # You can re-read the inputrc file with C-x C-r.
+ # Lines beginning with '#' are comments.
+ #
+ # First, include any system-wide bindings and variable
+ # assignments from /etc/Inputrc
+ $include /etc/Inputrc
+
+ #
+ # Set various bindings for emacs mode.
+
+ set editing-mode emacs
+
+ $if mode=emacs
+
+ Meta-Control-h: backward-kill-word Text after the function name is ignored
+
+ #
+ # Arrow keys in keypad mode
+ #
+ #"\M-OD": backward-char
+ #"\M-OC": forward-char
+ #"\M-OA": previous-history
+ #"\M-OB": next-history
+ #
+ # Arrow keys in ANSI mode
+ #
+ "\M-[D": backward-char
+ "\M-[C": forward-char
+ "\M-[A": previous-history
+ "\M-[B": next-history
+ #
+ # Arrow keys in 8 bit keypad mode
+ #
+ #"\M-\C-OD": backward-char
+ #"\M-\C-OC": forward-char
+ #"\M-\C-OA": previous-history
+ #"\M-\C-OB": next-history
+ #
+ # Arrow keys in 8 bit ANSI mode
+ #
+ #"\M-\C-[D": backward-char
+ #"\M-\C-[C": forward-char
+ #"\M-\C-[A": previous-history
+ #"\M-\C-[B": next-history
+
+ C-q: quoted-insert
+
+ $endif
+
+ # An old-style binding. This happens to be the default.
+ TAB: complete
+
+ # Macros that are convenient for shell interaction
+ $if Bash
+ # edit the path
+ "\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
+ # prepare to type a quoted word --
+ # insert open and close double quotes
+ # and move to just after the open quote
+ "\C-x\"": "\"\"\C-b"
+ # insert a backslash (testing backslash escapes
+ # in sequences and macros)
+ "\C-x\\": "\\"
+ # Quote the current or previous word
+ "\C-xq": "\eb\"\ef\""
+ # Add a binding to refresh the line, which is unbound
+ "\C-xr": redraw-current-line
+ # Edit variable on current line.
+ "\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
+ $endif
+
+ # use a visible bell if one is available
+ set bell-style visible
+
+ # don't strip characters to 7 bits when reading
+ set input-meta on
+
+ # allow iso-latin1 characters to be inserted rather
+ # than converted to prefix-meta sequences
+ set convert-meta off
+
+ # display characters with the eighth bit set directly
+ # rather than as meta-prefixed characters
+ set output-meta on
+
+ # if there are 150 or more possible completions for a word,
+ # ask whether or not the user wants to see all of them
+ set completion-query-items 150
+
+ # For FTP
+ $if Ftp
+ "\C-xg": "get \M-?"
+ "\C-xt": "put \M-?"
+ "\M-.": yank-last-arg
+ $endif
+
+\1f
+File: bashref.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
+
+8.4 Bindable Readline Commands
+==============================
+
+* Menu:
+
+* Commands For Moving:: Moving about the line.
+* Commands For History:: Getting at previous lines.
+* Commands For Text:: Commands for changing text.
+* Commands For Killing:: Commands for killing and yanking.
+* Numeric Arguments:: Specifying numeric arguments, repeat counts.
+* Commands For Completion:: Getting Readline to do the typing for you.
+* Keyboard Macros:: Saving and re-executing typed characters
+* Miscellaneous Commands:: Other miscellaneous commands.
+
+This section describes Readline commands that may be bound to key
+sequences. You can list your key bindings by executing ‘bind -P’ or,
+for a more terse format, suitable for an INPUTRC file, ‘bind -p’.
+(*Note Bash Builtins::.) Command names without an accompanying key
+sequence are unbound by default.
+
+ In the following descriptions, “point” refers to the current cursor
+position, and “mark” refers to a cursor position saved by the ‘set-mark’
+command. The text between the point and mark is referred to as the
+“region”. Readline has the concept of an _active region_: when the
+region is active, Readline redisplay highlights the region using the
+value of the ‘active-region-start-color’ variable. The
+‘enable-active-region’ variable turns this on and off. Several commands
+set the region to active; those are noted below.
+
+\1f
+File: bashref.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
+
+8.4.1 Commands For Moving
+-------------------------
+
+‘beginning-of-line (C-a)’
+ Move to the start of the current line. This may also be bound to
+ the Home key on some keyboards.
+
+‘end-of-line (C-e)’
+ Move to the end of the line. This may also be bound to the End key
+ on some keyboards.
+
+‘forward-char (C-f)’
+ Move forward a character. This may also be bound to the right
+ arrow key on some keyboards.
+
+‘backward-char (C-b)’
+ Move back a character. This may also be bound to the left arrow
+ key on some keyboards.
+
+‘forward-word (M-f)’
+ Move forward to the end of the next word. Words are composed of
+ letters and digits.
+
+‘backward-word (M-b)’
+ Move back to the start of the current or previous word. Words are
+ composed of letters and digits.
+
+‘shell-forward-word (M-C-f)’
+ Move forward to the end of the next word. Words are delimited by
+ non-quoted shell metacharacters.
+
+‘shell-backward-word (M-C-b)’
+ Move back to the start of the current or previous word. Words are
+ delimited by non-quoted shell metacharacters.
+
+‘previous-screen-line ()’
+ Attempt to move point to the same physical screen column on the
+ previous physical screen line. This will not have the desired
+ effect if the current Readline line does not take up more than one
+ physical line or if point is not greater than the length of the
+ prompt plus the screen width.
+
+‘next-screen-line ()’
+ Attempt to move point to the same physical screen column on the
+ next physical screen line. This will not have the desired effect
+ if the current Readline line does not take up more than one
+ physical line or if the length of the current Readline line is not
+ greater than the length of the prompt plus the screen width.
+
+‘clear-display (M-C-l)’
+ Clear the screen and, if possible, the terminal's scrollback
+ buffer, then redraw the current line, leaving the current line at
+ the top of the screen.
+
+‘clear-screen (C-l)’
+ Clear the screen, then redraw the current line, leaving the current
+ line at the top of the screen. If given a numeric argument, this
+ refreshes the current line without clearing the screen.
+
+‘redraw-current-line ()’
+ Refresh the current line. By default, this is unbound.
+
+\1f
+File: bashref.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
+
+8.4.2 Commands For Manipulating The History
+-------------------------------------------
+
+‘accept-line (Newline or Return)’
+ Accept the line regardless of where the cursor is. If this line is
+ non-empty, add it to the history list according to the setting of
+ the ‘HISTCONTROL’ and ‘HISTIGNORE’ variables. If this line is a
+ modified history line, then restore the history line to its
+ original state.
+
+‘previous-history (C-p)’
+ Move "back" through the history list, fetching the previous
+ command. This may also be bound to the up arrow key on some
+ keyboards.
+
+‘next-history (C-n)’
+ Move "forward" through the history list, fetching the next command.
+ This may also be bound to the down arrow key on some keyboards.
+
+‘beginning-of-history (M-<)’
+ Move to the first line in the history.
+
+‘end-of-history (M->)’
+ Move to the end of the input history, i.e., the line currently
+ being entered.
+
+‘reverse-search-history (C-r)’
+ Search backward starting at the current line and moving "up"
+ through the history as necessary. This is an incremental search.
+ This command sets the region to the matched text and activates the
+ region.
+
+‘forward-search-history (C-s)’
+ Search forward starting at the current line and moving "down"
+ through the history as necessary. This is an incremental search.
+ This command sets the region to the matched text and activates the
+ region.
+
+‘non-incremental-reverse-search-history (M-p)’
+ Search backward starting at the current line and moving "up"
+
+ through the history as necessary using a non-incremental search for
+ a string supplied by the user. The search string may match
+ anywhere in a history line.
+
+‘non-incremental-forward-search-history (M-n)’
+ Search forward starting at the current line and moving "down"
+ through the history as necessary using a non-incremental search for
+ a string supplied by the user. The search string may match
+ anywhere in a history line.
+
+‘history-search-backward ()’
+ Search backward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string must match at the beginning of a history line. This is a
+ non-incremental search. By default, this command is unbound, but
+ may be bound to the Page Down key on some keyboards.
+
+‘history-search-forward ()’
+ Search forward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string must match at the beginning of a history line. This is a
+ non-incremental search. By default, this command is unbound, but
+ may be bound to the Page Up key on some keyboards.
+
+‘history-substring-search-backward ()’
+ Search backward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string may match anywhere in a history line. This is a
+ non-incremental search. By default, this command is unbound.
+
+‘history-substring-search-forward ()’
+ Search forward through the history for the string of characters
+ between the start of the current line and the point. The search
+ string may match anywhere in a history line. This is a
+ non-incremental search. By default, this command is unbound.
+
+‘yank-nth-arg (M-C-y)’
+ Insert the first argument to the previous command (usually the
+ second word on the previous line) at point. With an argument N,
+ insert the Nth word from the previous command (the words in the
+ previous command begin with word 0). A negative argument inserts
+ the Nth word from the end of the previous command. Once the
+ argument N is computed, this uses the history expansion facilities
+ to extract the Nth word, as if the ‘!N’ history expansion had been
+ specified.
+
+‘yank-last-arg (M-. or M-_)’
+ Insert last argument to the previous command (the last word of the
+ previous history entry). With a numeric argument, behave exactly
+ like ‘yank-nth-arg’. Successive calls to ‘yank-last-arg’ move back
+ through the history list, inserting the last word (or the word
+ specified by the argument to the first call) of each line in turn.
+ Any numeric argument supplied to these successive calls determines
+ the direction to move through the history. A negative argument
+ switches the direction through the history (back or forward). This
+ uses the history expansion facilities to extract the last word, as
+ if the ‘!$’ history expansion had been specified.
+
+‘operate-and-get-next (C-o)’
+ Accept the current line for return to the calling application as if
+ a newline had been entered, and fetch the next line relative to the
+ current line from the history for editing. A numeric argument, if
+ supplied, specifies the history entry to use instead of the current
+ line.
+
+‘fetch-history ()’
+ With a numeric argument, fetch that entry from the history list and
+ make it the current line. Without an argument, move back to the
+ first entry in the history list.
+
+\1f
+File: bashref.info, Node: Commands For Text, Next: Commands For Killing, Prev: Commands For History, Up: Bindable Readline Commands
+
+8.4.3 Commands For Changing Text
+--------------------------------
+
+‘end-of-file (usually C-d)’
+ The character indicating end-of-file as set, for example, by
+ ‘stty’. If this character is read when there are no characters on
+ the line, and point is at the beginning of the line, Readline
+ interprets it as the end of input and returns EOF.
+
+‘delete-char (C-d)’
+ Delete the character at point. If this function is bound to the
+ same character as the tty EOF character, as ‘C-d’ commonly is, see
+ above for the effects. This may also be bound to the Delete key on
+ some keyboards.
+
+‘backward-delete-char (Rubout)’
+ Delete the character behind the cursor. A numeric argument means
+ to kill the characters, saving them on the kill ring, instead of
+ deleting them.
+
+‘forward-backward-delete-char ()’
+ Delete the character under the cursor, unless the cursor is at the
+ end of the line, in which case the character behind the cursor is
+ deleted. By default, this is not bound to a key.
+
+‘quoted-insert (C-q or C-v)’
+ Add the next character typed to the line verbatim. This is how to
+ insert key sequences like ‘C-q’, for example.
+
+‘self-insert (a, b, A, 1, !, ...)’
+ Insert the character typed.
+
+‘bracketed-paste-begin ()’
+ This function is intended to be bound to the "bracketed paste"
+ escape sequence sent by some terminals, and such a binding is
+ assigned by default. It allows Readline to insert the pasted text
+ as a single unit without treating each character as if it had been
+ read from the keyboard. The characters are inserted as if each one
+ was bound to ‘self-insert’ instead of executing any editing
+ commands.
+
+ Bracketed paste sets the region (the characters between point and
+ the mark) to the inserted text. It sets the _active region_.
+
+‘transpose-chars (C-t)’
+ Drag the character before the cursor forward over the character at
+ the cursor, moving the cursor forward as well. If the insertion
+ point is at the end of the line, then this transposes the last two
+ characters of the line. Negative arguments have no effect.
+
+‘transpose-words (M-t)’
+ Drag the word before point past the word after point, moving point
+ past that word as well. If the insertion point is at the end of
+ the line, this transposes the last two words on the line.
+
+‘shell-transpose-words (M-C-t)’
+ Drag the word before point past the word after point, moving point
+ past that word as well. If the insertion point is at the end of
+ the line, this transposes the last two words on the line. Word
+ boundaries are the same as ‘shell-forward-word’ and
+ ‘shell-backward-word’.
+
+‘upcase-word (M-u)’
+ Uppercase the current (or following) word. With a negative
+ argument, uppercase the previous word, but do not move the cursor.
+
+‘downcase-word (M-l)’
+ Lowercase the current (or following) word. With a negative
+ argument, lowercase the previous word, but do not move the cursor.
+
+‘capitalize-word (M-c)’
+ Capitalize the current (or following) word. With a negative
+ argument, capitalize the previous word, but do not move the cursor.
+
+‘overwrite-mode ()’
+ Toggle overwrite mode. With an explicit positive numeric argument,
+ switches to overwrite mode. With an explicit non-positive numeric
+ argument, switches to insert mode. This command affects only
+ ‘emacs’ mode; ‘vi’ mode does overwrite differently. Each call to
+ ‘readline()’ starts in insert mode.
+
+ In overwrite mode, characters bound to ‘self-insert’ replace the
+ text at point rather than pushing the text to the right.
+ Characters bound to ‘backward-delete-char’ replace the character
+ before point with a space.
+
+ By default, this command is unbound, but may be bound to the Insert
+ key on some keyboards.
+
+\1f
+File: bashref.info, Node: Commands For Killing, Next: Numeric Arguments, Prev: Commands For Text, Up: Bindable Readline Commands
+
+8.4.4 Killing And Yanking
+-------------------------
+
+‘kill-line (C-k)’
+ Kill the text from point to the end of the current line. With a
+ negative numeric argument, kill backward from the cursor to the
+ beginning of the line.
+
+‘backward-kill-line (C-x Rubout)’
+ Kill backward from the cursor to the beginning of the current line.
+ With a negative numeric argument, kill forward from the cursor to
+ the end of the line.
+
+‘unix-line-discard (C-u)’
+ Kill backward from the cursor to the beginning of the current line.
+
+‘kill-whole-line ()’
+ Kill all characters on the current line, no matter where point is.
+ By default, this is unbound.
+
+‘kill-word (M-d)’
+ Kill from point to the end of the current word, or if between
+ words, to the end of the next word. Word boundaries are the same
+ as ‘forward-word’.
+
+‘backward-kill-word (M-<DEL>)’
+ Kill the word behind point. Word boundaries are the same as
+ ‘backward-word’.
+
+‘shell-kill-word (M-C-d)’
+ Kill from point to the end of the current word, or if between
+ words, to the end of the next word. Word boundaries are the same
+ as ‘shell-forward-word’.
+
+‘shell-backward-kill-word ()’
+ Kill the word behind point. Word boundaries are the same as
+ ‘shell-backward-word’.
+
+‘unix-word-rubout (C-w)’
+ Kill the word behind point, using white space as a word boundary,
+ saving the killed text on the kill-ring.
+
+‘unix-filename-rubout ()’
+ Kill the word behind point, using white space and the slash
+ character as the word boundaries, saving the killed text on the
+ kill-ring.
+
+‘delete-horizontal-space ()’
+ Delete all spaces and tabs around point. By default, this is
+ unbound.
+
+‘kill-region ()’
+ Kill the text in the current region. By default, this command is
+ unbound.
+
+‘copy-region-as-kill ()’
+ Copy the text in the region to the kill buffer, so it can be yanked
+ right away. By default, this command is unbound.
+
+‘copy-backward-word ()’
+ Copy the word before point to the kill buffer. The word boundaries
+ are the same as ‘backward-word’. By default, this command is
+ unbound.
+
+‘copy-forward-word ()’
+ Copy the word following point to the kill buffer. The word
+ boundaries are the same as ‘forward-word’. By default, this
+ command is unbound.
+
+‘yank (C-y)’
+ Yank the top of the kill ring into the buffer at point.
+
+‘yank-pop (M-y)’
+ Rotate the kill-ring, and yank the new top. You can only do this
+ if the prior command is ‘yank’ or ‘yank-pop’.
+
+\1f
+File: bashref.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
+
+8.4.5 Specifying Numeric Arguments
+----------------------------------
+
+‘digit-argument (M-0, M-1, ... M--)’
+ Add this digit to the argument already accumulating, or start a new
+ argument. ‘M--’ starts a negative argument.
+
+‘universal-argument ()’
+ This is another way to specify an argument. If this command is
+ followed by one or more digits, optionally with a leading minus
+ sign, those digits define the argument. If the command is followed
+ by digits, executing ‘universal-argument’ again ends the numeric
+ argument, but is otherwise ignored. As a special case, if this
+ command is immediately followed by a character that is neither a
+ digit nor minus sign, the argument count for the next command is
+ multiplied by four. The argument count is initially one, so
+ executing this function the first time makes the argument count
+ four, a second time makes the argument count sixteen, and so on.
+ By default, this is not bound to a key.
+
+\1f
+File: bashref.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
+
+8.4.6 Letting Readline Type For You
+-----------------------------------
+
+‘complete (<TAB>)’
+ Attempt to perform completion on the text before point. The actual
+ completion performed is application-specific. Bash attempts
+ completion by first checking for any programmable completions for
+ the command word (*note Programmable Completion::), otherwise
+ treating the text as a variable (if the text begins with ‘$’),
+ username (if the text begins with ‘~’), hostname (if the text
+ begins with ‘@’), or command (including aliases, functions, and
+ builtins) in turn. If none of these produces a match, it falls
+ back to filename completion.
+
+‘possible-completions (M-?)’
+ List the possible completions of the text before point. When
+ displaying completions, Readline sets the number of columns used
+ for display to the value of ‘completion-display-width’, the value
+ of the environment variable ‘COLUMNS’, or the screen width, in that
+ order.
+
+‘insert-completions (M-*)’
+ Insert all completions of the text before point that would have
+ been generated by ‘possible-completions’, separated by a space.
+
+‘menu-complete ()’
+ Similar to ‘complete’, but replaces the word to be completed with a
+ single match from the list of possible completions. Repeatedly
+ executing ‘menu-complete’ steps through the list of possible
+ completions, inserting each match in turn. At the end of the list
+ of completions, ‘menu-complete’ rings the bell (subject to the
+ setting of ‘bell-style’) and restores the original text. An
+ argument of N moves N positions forward in the list of matches; a
+ negative argument moves backward through the list. This command is
+ intended to be bound to <TAB>, but is unbound by default.
+
+‘menu-complete-backward ()’
+ Identical to ‘menu-complete’, but moves backward through the list
+ of possible completions, as if ‘menu-complete’ had been given a
+ negative argument. This command is unbound by default.
+
+‘export-completions ()’
+ Perform completion on the word before point as described above and
+ write the list of possible completions to Readline's output stream
+ using the following format, writing information on separate lines:
+
+ • the number of matches N;
+ • the word being completed;
+ • S:E, where S and E are the start and end offsets of the word
+ in the Readline line buffer; then
+ • each match, one per line
+
+ If there are no matches, the first line will be "0", and this
+ command does not print any output after the S:E. If there is only
+ a single match, this prints a single line containing it. If there
+ is more than one match, this prints the common prefix of the
+ matches, which may be empty, on the first line after the S:E, then
+ the matches on subsequent lines. In this case, N will include the
+ first line with the common prefix.
+
+ The user or application should be able to accommodate the
+ possibility of a blank line. The intent is that the user or
+ application reads N lines after the line containing S:E to obtain
+ the match list. This command is unbound by default.
+
+‘delete-char-or-list ()’
+ Deletes the character under the cursor if not at the beginning or
+ end of the line (like ‘delete-char’). At the end of the line, it
+ behaves identically to ‘possible-completions’. This command is
+ unbound by default.
+
+‘complete-filename (M-/)’
+ Attempt filename completion on the text before point.
+
+‘possible-filename-completions (C-x /)’
+ List the possible completions of the text before point, treating it
+ as a filename.
+
+‘complete-username (M-~)’
+ Attempt completion on the text before point, treating it as a
+ username.
+
+‘possible-username-completions (C-x ~)’
+ List the possible completions of the text before point, treating it
+ as a username.
+
+‘complete-variable (M-$)’
+ Attempt completion on the text before point, treating it as a shell
+ variable.
+
+‘possible-variable-completions (C-x $)’
+ List the possible completions of the text before point, treating it
+ as a shell variable.
+
+‘complete-hostname (M-@)’
+ Attempt completion on the text before point, treating it as a
+ hostname.
+
+‘possible-hostname-completions (C-x @)’
+ List the possible completions of the text before point, treating it
+ as a hostname.
+
+‘complete-command (M-!)’
+ Attempt completion on the text before point, treating it as a
+ command name. Command completion attempts to match the text
+ against aliases, reserved words, shell functions, shell builtins,
+ and finally executable filenames, in that order.
+
+‘possible-command-completions (C-x !)’
+ List the possible completions of the text before point, treating it
+ as a command name.
+
+‘dynamic-complete-history (M-<TAB>)’
+ Attempt completion on the text before point, comparing the text
+ against history list entries for possible completion matches.
+
+‘dabbrev-expand ()’
+ Attempt menu completion on the text before point, comparing the
+ text against lines from the history list for possible completion
+ matches.
+
+‘complete-into-braces (M-{)’
+ Perform filename completion and insert the list of possible
+ completions enclosed within braces so the list is available to the
+ shell (*note Brace Expansion::).
+
+\1f
+File: bashref.info, Node: Keyboard Macros, Next: Miscellaneous Commands, Prev: Commands For Completion, Up: Bindable Readline Commands
+
+8.4.7 Keyboard Macros
+---------------------
+
+‘start-kbd-macro (C-x ()’
+ Begin saving the characters typed into the current keyboard macro.
+
+‘end-kbd-macro (C-x ))’
+ Stop saving the characters typed into the current keyboard macro
+ and save the definition.
+
+‘call-last-kbd-macro (C-x e)’
+ Re-execute the last keyboard macro defined, by making the
+ characters in the macro appear as if typed at the keyboard.
+
+‘print-last-kbd-macro ()’
+ Print the last keyboard macro defined in a format suitable for the
+ INPUTRC file.
+
+\1f
+File: bashref.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
+
+8.4.8 Some Miscellaneous Commands
+---------------------------------
+
+‘re-read-init-file (C-x C-r)’
+ Read in the contents of the INPUTRC file, and incorporate any
+ bindings or variable assignments found there.
+
+‘abort (C-g)’
+ Abort the current editing command and ring the terminal's bell
+ (subject to the setting of ‘bell-style’).
+
+‘do-lowercase-version (M-A, M-B, M-X, ...)’
+ If the metafied character X is upper case, run the command that is
+ bound to the corresponding metafied lower case character. The
+ behavior is undefined if X is already lower case.
+
+‘prefix-meta (<ESC>)’
+ Metafy the next character typed. Typing ‘<ESC> f’ is equivalent to
+ typing ‘M-f’.
+
+‘undo (C-_ or C-x C-u)’
+ Incremental undo, separately remembered for each line.
+
+‘revert-line (M-r)’
+ Undo all changes made to this line. This is like executing the
+ ‘undo’ command enough times to get back to the initial state.
+
+‘tilde-expand (M-&)’
+ Perform tilde expansion on the current word.
+
+‘set-mark (C-@)’
+ Set the mark to the point. If a numeric argument is supplied, set
+ the mark to that position.
+
+‘exchange-point-and-mark (C-x C-x)’
+ Swap the point with the mark. Set the current cursor position to
+ the saved position, then set the mark to the old cursor position.
+
+‘character-search (C-])’
+ Read a character and move point to the next occurrence of that
+ character. A negative argument searches for previous occurrences.
+
+‘character-search-backward (M-C-])’
+ Read a character and move point to the previous occurrence of that
+ character. A negative argument searches for subsequent
+ occurrences.
+
+‘skip-csi-sequence ()’
+ Read enough characters to consume a multi-key sequence such as
+ those defined for keys like Home and End. CSI sequences begin with
+ a Control Sequence Indicator (CSI), usually ‘ESC [’. If this
+ sequence is bound to "\e[", keys producing CSI sequences have no
+ effect unless explicitly bound to a Readline command, instead of
+ inserting stray characters into the editing buffer. This is
+ unbound by default, but usually bound to ‘ESC [’.
+
+‘insert-comment (M-#)’
+ Without a numeric argument, insert the value of the ‘comment-begin’
+ variable at the beginning of the current line. If a numeric
+ argument is supplied, this command acts as a toggle: if the
+ characters at the beginning of the line do not match the value of
+ ‘comment-begin’, insert the value; otherwise delete the characters
+ in ‘comment-begin’ from the beginning of the line. In either case,
+ the line is accepted as if a newline had been typed. The default
+ value of ‘comment-begin’ causes this command to make the current
+ line a shell comment. If a numeric argument causes the comment
+ character to be removed, the line will be executed by the shell.
+
+‘dump-functions ()’
+ Print all of the functions and their key bindings to the Readline
+ output stream. If a numeric argument is supplied, the output is
+ formatted in such a way that it can be made part of an INPUTRC
+ file. This command is unbound by default.
+
+‘dump-variables ()’
+ Print all of the settable variables and their values to the
+ Readline output stream. If a numeric argument is supplied, the
+ output is formatted in such a way that it can be made part of an
+ INPUTRC file. This command is unbound by default.
+
+‘dump-macros ()’
+ Print all of the Readline key sequences bound to macros and the
+ strings they output to the Readline output stream. If a numeric
+ argument is supplied, the output is formatted in such a way that it
+ can be made part of an INPUTRC file. This command is unbound by
+ default.
+
+‘execute-named-command (M-x)’
+ Read a bindable Readline command name from the input and execute
+ the function to which it's bound, as if the key sequence to which
+ it was bound appeared in the input. If this function is supplied
+ with a numeric argument, it passes that argument to the function it
+ executes.
+
+‘spell-correct-word (C-x s)’
+ Perform spelling correction on the current word, treating it as a
+ directory or filename, in the same way as the ‘cdspell’ shell
+ option. Word boundaries are the same as those used by
+ ‘shell-forward-word’.
+
+‘glob-complete-word (M-g)’
+ Treat the word before point as a pattern for pathname expansion,
+ with an asterisk implicitly appended, then use the pattern to
+ generate a list of matching file names for possible completions.
+
+‘glob-expand-word (C-x *)’
+ Treat the word before point as a pattern for pathname expansion,
+ and insert the list of matching file names, replacing the word. If
+ a numeric argument is supplied, append a ‘*’ before pathname
+ expansion.
+
+‘glob-list-expansions (C-x g)’
+ Display the list of expansions that would have been generated by
+ ‘glob-expand-word’, and redisplay the line. If a numeric argument
+ is supplied, append a ‘*’ before pathname expansion.
+
+‘shell-expand-line (M-C-e)’
+ Expand the line by performing shell word expansions. This performs
+ alias and history expansion, $'STRING' and $"STRING" quoting, tilde
+ expansion, parameter and variable expansion, arithmetic expansion,
+ command and process substitution, word splitting, and quote
+ removal. An explicit argument suppresses command and process
+ substitution.
+
+‘history-expand-line (M-^)’
+ Perform history expansion on the current line.
+
+‘magic-space ()’
+ Perform history expansion on the current line and insert a space
+ (*note History Interaction::).
+
+‘alias-expand-line ()’
+ Perform alias expansion on the current line (*note Aliases::).
+
+‘history-and-alias-expand-line ()’
+ Perform history and alias expansion on the current line.
+
+‘insert-last-argument (M-. or M-_)’
+ A synonym for ‘yank-last-arg’.
+
+‘edit-and-execute-command (C-x C-e)’
+ Invoke an editor on the current command line, and execute the
+ result as shell commands. Bash attempts to invoke ‘$VISUAL’,
+ ‘$EDITOR’, and ‘emacs’ as the editor, in that order.
+
+‘display-shell-version (C-x C-v)’
+ Display version information about the current instance of Bash.
+
+\1f
+File: bashref.info, Node: Readline vi Mode, Next: Programmable Completion, Prev: Bindable Readline Commands, Up: Command Line Editing
+
+8.5 Readline vi Mode
+====================
+
+While the Readline library does not have a full set of ‘vi’ editing
+functions, it does contain enough to allow simple editing of the line.
+The Readline ‘vi’ mode behaves as specified in the ‘sh’ description in
+the POSIX standard.
+
+ You can use the ‘set -o emacs’ and ‘set -o vi’ commands (*note The
+Set Builtin::) to switch interactively between ‘emacs’ and ‘vi’ editing
+modes, The Readline default is ‘emacs’ mode.
+
+ When you enter a line in ‘vi’ mode, you are already placed in
+"insertion" mode, as if you had typed an ‘i’. Pressing <ESC> switches
+you into "command" mode, where you can edit the text of the line with
+the standard ‘vi’ movement keys, move to previous history lines with ‘k’
+and subsequent lines with ‘j’, and so forth.
+
+\1f
+File: bashref.info, Node: Programmable Completion, Next: Programmable Completion Builtins, Prev: Readline vi Mode, Up: Command Line Editing
+
+8.6 Programmable Completion
+===========================
+
+When the user attempts word completion for a command or an argument to a
+command for which a completion specification (a “compspec”) has been
+defined using the ‘complete’ builtin (*note Programmable Completion
+Builtins::), Readline invokes the programmable completion facilities.
+
+ First, Bash identifies the command name. If a compspec has been
+defined for that command, the compspec is used to generate the list of
+possible completions for the word. If the command word is the empty
+string (completion attempted at the beginning of an empty line), Bash
+uses any compspec defined with the ‘-E’ option to ‘complete’. The ‘-I’
+option to ‘complete’ indicates that the command word is the first
+non-assignment word on the line, or after a command delimiter such as
+‘;’ or ‘|’. This usually indicates command name completion.
+
+ If the command word is a full pathname, Bash searches for a compspec
+for the full pathname first. If there is no compspec for the full
+pathname, Bash attempts to find a compspec for the portion following the
+final slash. If those searches do not result in a compspec, or if there
+is no compspec for the command word, Bash uses any compspec defined with
+the ‘-D’ option to ‘complete’ as the default. If there is no default
+compspec, Bash performs alias expansion on the command word as a final
+resort, and attempts to find a compspec for the command word resulting
+from any successful expansion.
+
+ If a compspec is not found, Bash performs its default completion
+described above (*note Commands For Completion::). Otherwise, once a
+compspec has been found, Bash uses it to generate the list of matching
+words.
+
+ First, Bash performs the ACTIONS specified by the compspec. This
+only returns matches which are prefixes of the word being completed.
+When the ‘-f’ or ‘-d’ option is used for filename or directory name
+completion, Bash uses shell the variable ‘FIGNORE’ to filter the
+matches. *Note Bash Variables::, for a description of ‘FIGNORE’.
+
+ Next, programmable completion generates matches specified by a
+pathname expansion pattern supplied as an argument to the ‘-G’ option.
+The words generated by the pattern need not match the word being
+completed. Bash uses the ‘FIGNORE’ variable to filter the matches, but
+does not use the ‘GLOBIGNORE’ shell variable.
+
+ Next, completion considers the string specified as the argument to
+the ‘-W’ option. The string is first split using the characters in the
+‘IFS’ special variable as delimiters. This honors shell quoting within
+the string, in order to provide a mechanism for the words to contain
+shell metacharacters or characters in the value of ‘IFS’. Each word is
+then expanded using brace expansion, tilde expansion, parameter and
+variable expansion, command substitution, and arithmetic expansion, as
+described above (*note Shell Expansions::). The results are split using
+the rules described above (*note Word Splitting::). The results of the
+expansion are prefix-matched against the word being completed, and the
+matching words become possible completions.
+
+ After these matches have been generated, Bash executes any shell
+function or command specified with the ‘-F’ and ‘-C’ options. When the
+command or function is invoked, Bash assigns values to the ‘COMP_LINE’,
+‘COMP_POINT’, ‘COMP_KEY’, and ‘COMP_TYPE’ variables as described above
+(*note Bash Variables::). If a shell function is being invoked, Bash
+also sets the ‘COMP_WORDS’ and ‘COMP_CWORD’ variables. When the
+function or command is invoked, the first argument ($1) is the name of
+the command whose arguments are being completed, the second argument
+($2) is the word being completed, and the third argument ($3) is the
+word preceding the word being completed on the current command line.
+There is no filtering of the generated completions against the word
+being completed; the function or command has complete freedom in
+generating the matches and they do not need to match a prefix of the
+word.
+
+ Any function specified with ‘-F’ is invoked first. The function may
+use any of the shell facilities, including the ‘compgen’ and ‘compopt’
+builtins described below (*note Programmable Completion Builtins::), to
+generate the matches. It must put the possible completions in the
+‘COMPREPLY’ array variable, one per array element.
+
+ Next, any command specified with the ‘-C’ option is invoked in an
+environment equivalent to command substitution. It should print a list
+of completions, one per line, to the standard output. Backslash will
+escape a newline, if necessary. These are added to the set of possible
+completions.
+
+ External commands that are invoked to generate completions ("external
+completers") receive the word preceding the completion word as an
+argument, as described above. This provides context that is sometimes
+useful, but may include information that is considered sensitive or part
+of a word expansion that will not appear in the command line after
+expansion. That word may be visible in process listings or in audit
+logs. This may be a concern to users and completion specification
+authors if there is sensitive information on the command line before
+expansion, since completion takes place before words are expanded. If
+this is an issue, completion authors should use functions as wrappers
+around external commands and pass context information to the external
+command in a different way. External completers can infer context from
+the COMP_LINE and COMP_POINT environment variables, but they need to
+ensure they break words in the same way Readline does, using the
+COMP_WORDBREAKS variable.
+
+ After generating all of the possible completions, Bash applies any
+filter specified with the ‘-X’ option to the completions in the list.
+The filter is a pattern as used for pathname expansion; a ‘&’ in the
+pattern is replaced with the text of the word being completed. A
+literal ‘&’ may be escaped with a backslash; the backslash is removed
+before attempting a match. Any completion that matches the pattern is
+removed from the list. A leading ‘!’ negates the pattern; in this case
+Bash removes any completion that does not match the pattern. If the
+‘nocasematch’ shell option is enabled (see the description of ‘shopt’ in
+*note The Shopt Builtin::), Bash performs the match without regard to
+the case of alphabetic characters.
+
+ Finally, programmable completion adds any prefix and suffix specified
+with the ‘-P’ and ‘-S’ options, respectively, to each completion, and
+returns the result to Readline as the list of possible completions.
+
+ If the previously-applied actions do not generate any matches, and
+the ‘-o dirnames’ option was supplied to ‘complete’ when the compspec
+was defined, Bash attempts directory name completion.
+
+ If the ‘-o plusdirs’ option was supplied to ‘complete’ when the
+compspec was defined, Bash attempts directory name completion and adds
+any matches to the set of possible completions.
+
+ By default, if a compspec is found, whatever it generates is returned
+to the completion code as the full set of possible completions. The
+default Bash completions and the Readline default of filename completion
+are disabled. If the ‘-o bashdefault’ option was supplied to ‘complete’
+when the compspec was defined, and the compspec generates no matches,
+Bash attempts its default completions. If the compspec and, if
+attempted, the default Bash completions generate no matches, and the ‘-o
+default’ option was supplied to ‘complete’ when the compspec was
+defined, programmable completion performs Readline's default completion.
+
+ The options supplied to ‘complete’ and ‘compopt’ can control how
+Readline treats the completions. For instance, the ‘-o fullquote’
+option tells Readline to quote the matches as if they were filenames.
+See the description of ‘complete’ (*note Programmable Completion
+Builtins::) for details.
+
+ When a compspec indicates that it wants directory name completion,
+the programmable completion functions force Readline to append a slash
+to completed names which are symbolic links to directories, subject to
+the value of the MARK-DIRECTORIES Readline variable, regardless of the
+setting of the MARK-SYMLINKED-DIRECTORIES Readline variable.
+
+ There is some support for dynamically modifying completions. This is
+most useful when used in combination with a default completion specified
+with ‘-D’. It's possible for shell functions executed as completion
+functions to indicate that completion should be retried by returning an
+exit status of 124. If a shell function returns 124, and changes the
+compspec associated with the command on which completion is being
+attempted (supplied as the first argument when the function is
+executed), programmable completion restarts from the beginning, with an
+attempt to find a new compspec for that command. This can be used to
+build a set of completions dynamically as completion is attempted,
+rather than loading them all at once.
+
+ For instance, assuming that there is a library of compspecs, each
+kept in a file corresponding to the name of the command, the following
+default completion function would load completions dynamically:
+
+ _completion_loader()
+ {
+ . "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
+ }
+ complete -D -F _completion_loader -o bashdefault -o default
+
+\1f
+File: bashref.info, Node: Programmable Completion Builtins, Next: A Programmable Completion Example, Prev: Programmable Completion, Up: Command Line Editing
+
+8.7 Programmable Completion Builtins
+====================================
+
+Three builtin commands are available to manipulate the programmable
+completion facilities: one to specify how the arguments to a particular
+command are to be completed, and two to modify the completion as it is
+happening.
+
+‘compgen’
+ compgen [-V VARNAME] [OPTION] [WORD]
+
+ Generate possible completion matches for WORD according to the
+ OPTIONs, which may be any option accepted by the ‘complete’ builtin
+ with the exceptions of ‘-p’, ‘-r’, ‘-D’, ‘-E’, and ‘-I’, and write
+ the matches to the standard output.
+
+ If the ‘-V’ option is supplied, ‘compgen’ stores the generated
+ completions into the indexed array variable VARNAME instead of
+ writing them to the standard output.
+
+ When using the ‘-F’ or ‘-C’ options, the various shell variables
+ set by the programmable completion facilities, while available,
+ will not have useful values.
+
+ The matches will be generated in the same way as if the
+ programmable completion code had generated them directly from a
+ completion specification with the same flags. If WORD is
+ specified, only those completions matching WORD will be displayed
+ or stored.
+
+ The return value is true unless an invalid option is supplied, or
+ no matches were generated.
+
+‘complete’
+ complete [-abcdefgjksuv] [-o COMP-OPTION] [-DEI] [-A ACTION]
+ [-G GLOBPAT] [-W WORDLIST] [-F FUNCTION] [-C COMMAND]
+ [-X FILTERPAT] [-P PREFIX] [-S SUFFIX] NAME [NAME ...]
+ complete -pr [-DEI] [NAME ...]
+
+ Specify how arguments to each NAME should be completed.
+
+ If the ‘-p’ option is supplied, or if no options or NAMEs are
+ supplied, print existing completion specifications in a way that
+ allows them to be reused as input. The ‘-r’ option removes a
+ completion specification for each NAME, or, if no NAMEs are
+ supplied, all completion specifications.
+
+ The ‘-D’ option indicates that other supplied options and actions
+ should apply to the "default" command completion; that is,
+ completion attempted on a command for which no completion has
+ previously been defined. The ‘-E’ option indicates that other
+ supplied options and actions should apply to "empty" command
+ completion; that is, completion attempted on a blank line. The
+ ‘-I’ option indicates that other supplied options and actions
+ should apply to completion on the initial non-assignment word on
+ the line, or after a command delimiter such as ‘;’ or ‘|’, which is
+ usually command name completion. If multiple options are supplied,
+ the ‘-D’ option takes precedence over ‘-E’, and both take
+ precedence over ‘-I’. If any of ‘-D’, ‘-E’, or ‘-I’ are supplied,
+ any other NAME arguments are ignored; these completions only apply
+ to the case specified by the option.
+
+ The process of applying these completion specifications when word
+ completion is attempted is described above (*note Programmable
+ Completion::).
+
+ Other options, if specified, have the following meanings. The
+ arguments to the ‘-G’, ‘-W’, and ‘-X’ options (and, if necessary,
+ the ‘-P’ and ‘-S’ options) should be quoted to protect them from
+ expansion before the ‘complete’ builtin is invoked.
+
+ ‘-o COMP-OPTION’
+ The COMP-OPTION controls several aspects of the compspec's
+ behavior beyond the simple generation of completions.
+ COMP-OPTION may be one of:
+
+ ‘bashdefault’
+ Perform the rest of the default Bash completions if the
+ compspec generates no matches.
+
+ ‘default’
+ Use Readline's default filename completion if the
+ compspec generates no matches.
+
+ ‘dirnames’
+ Perform directory name completion if the compspec
+ generates no matches.
+
+ ‘filenames’
+ Tell Readline that the compspec generates filenames, so
+ it can perform any filename-specific processing (such as
+ adding a slash to directory names, quoting special
+ characters, or suppressing trailing spaces). This option
+ is intended to be used with shell functions specified
+ with ‘-F’.
+
+ ‘fullquote’
+ Tell Readline to quote all the completed words even if
+ they are not filenames.
+
+ ‘noquote’
+ Tell Readline not to quote the completed words if they
+ are filenames (quoting filenames is the default).
+
+ ‘nosort’
+ Tell Readline not to sort the list of possible
+ completions alphabetically.
+
+ ‘nospace’
+ Tell Readline not to append a space (the default) to
+ words completed at the end of the line.
+
+ ‘plusdirs’
+ After generating any matches defined by the compspec,
+ attempt directory name completion and add any matches to
+ the results of the other actions.
+
+ ‘-A ACTION’
+ The ACTION may be one of the following to generate a list of
+ possible completions:
+
+ ‘alias’
+ Alias names. May also be specified as ‘-a’.
+
+ ‘arrayvar’
+ Array variable names.
+
+ ‘binding’
+ Readline key binding names (*note Bindable Readline
+ Commands::).
+
+ ‘builtin’
+ Names of shell builtin commands. May also be specified
+ as ‘-b’.
+
+ ‘command’
+ Command names. May also be specified as ‘-c’.
+
+ ‘directory’
+ Directory names. May also be specified as ‘-d’.
+
+ ‘disabled’
+ Names of disabled shell builtins.
+
+ ‘enabled’
+ Names of enabled shell builtins.
+
+ ‘export’
+ Names of exported shell variables. May also be specified
+ as ‘-e’.
+
+ ‘file’
+ File and directory names, similar to Readline's filename
+ completion. May also be specified as ‘-f’.
+
+ ‘function’
+ Names of shell functions.
+
+ ‘group’
+ Group names. May also be specified as ‘-g’.
+
+ ‘helptopic’
+ Help topics as accepted by the ‘help’ builtin (*note Bash
+ Builtins::).
+
+ ‘hostname’
+ Hostnames, as taken from the file specified by the
+ ‘HOSTFILE’ shell variable (*note Bash Variables::).
+
+ ‘job’
+ Job names, if job control is active. May also be
+ specified as ‘-j’.
+
+ ‘keyword’
+ Shell reserved words. May also be specified as ‘-k’.
+
+ ‘running’
+ Names of running jobs, if job control is active.
+
+ ‘service’
+ Service names. May also be specified as ‘-s’.
+
+ ‘setopt’
+ Valid arguments for the ‘-o’ option to the ‘set’ builtin
+ (*note The Set Builtin::).
+
+ ‘shopt’
+ Shell option names as accepted by the ‘shopt’ builtin
+ (*note Bash Builtins::).
+
+ ‘signal’
+ Signal names.
+
+ ‘stopped’
+ Names of stopped jobs, if job control is active.
+
+ ‘user’
+ User names. May also be specified as ‘-u’.
+
+ ‘variable’
+ Names of all shell variables. May also be specified as
+ ‘-v’.
+
+ ‘-C COMMAND’
+ COMMAND is executed in a subshell environment, and its output
+ is used as the possible completions. Arguments are passed as
+ with the ‘-F’ option.
+
+ ‘-F FUNCTION’
+ The shell function FUNCTION is executed in the current shell
+ environment. When it is executed, the first argument ($1) is
+ the name of the command whose arguments are being completed,
+ the second argument ($2) is the word being completed, and the
+ third argument ($3) is the word preceding the word being
+ completed, as described above (*note Programmable
+ Completion::). When ‘function’ finishes, programmable
+ completion retrieves the possible completions from the value
+ of the ‘COMPREPLY’ array variable.
+
+ ‘-G GLOBPAT’
+ Expand the filename expansion pattern GLOBPAT to generate the
+ possible completions.
+
+ ‘-P PREFIX’
+ Add PREFIX to the beginning of each possible completion after
+ all other options have been applied.
+
+ ‘-S SUFFIX’
+ Append SUFFIX to each possible completion after all other
+ options have been applied.
+
+ ‘-W WORDLIST’
+ Split the WORDLIST using the characters in the ‘IFS’ special
+ variable as delimiters, and expand each resulting word. Shell
+ quoting is honored within WORDLIST in order to provide a
+ mechanism for the words to contain shell metacharacters or
+ characters in the value of ‘IFS’. The possible completions
+ are the members of the resultant list which match a prefix of
+ the word being completed.
+
+ ‘-X FILTERPAT’
+ FILTERPAT is a pattern as used for filename expansion. It is
+ applied to the list of possible completions generated by the
+ preceding options and arguments, and each completion matching
+ FILTERPAT is removed from the list. A leading ‘!’ in
+ FILTERPAT negates the pattern; in this case, any completion
+ not matching FILTERPAT is removed.
+
+ The return value is true unless an invalid option is supplied, an
+ option other than ‘-p’, ‘-r’, ‘-D’, ‘-E’, or ‘-I’ is supplied
+ without a NAME argument, an attempt is made to remove a completion
+ specification for a NAME for which no specification exists, or an
+ error occurs adding a completion specification.
+
+‘compopt’
+ compopt [-o OPTION] [-DEI] [+o OPTION] [NAME]
+ Modify completion options for each NAME according to the OPTIONs,
+ or for the currently-executing completion if no NAMEs are supplied.
+ If no OPTIONs are given, display the completion options for each
+ NAME or the current completion. The possible values of OPTION are
+ those valid for the ‘complete’ builtin described above.
+
+ The ‘-D’ option indicates that other supplied options should apply
+ to the "default" command completion; the ‘-E’ option indicates that
+ other supplied options should apply to "empty" command completion;
+ and the ‘-I’ option indicates that other supplied options should
+ apply to completion on the initial word on the line. These are
+ determined in the same way as the ‘complete’ builtin.
+
+ If multiple options are supplied, the ‘-D’ option takes precedence
+ over ‘-E’, and both take precedence over ‘-I’
+
+ The return value is true unless an invalid option is supplied, an
+ attempt is made to modify the options for a NAME for which no
+ completion specification exists, or an output error occurs.
+
+\1f
+File: bashref.info, Node: A Programmable Completion Example, Prev: Programmable Completion Builtins, Up: Command Line Editing
+
+8.8 A Programmable Completion Example
+=====================================
+
+The most common way to obtain additional completion functionality beyond
+the default actions ‘complete’ and ‘compgen’ provide is to use a shell
+function and bind it to a particular command using ‘complete -F’.
+
+ The following function provides completions for the ‘cd’ builtin. It
+is a reasonably good example of what shell functions must do when used
+for completion. This function uses the word passed as ‘$2’ to determine
+the directory name to complete. You can also use the ‘COMP_WORDS’ array
+variable; the current word is indexed by the ‘COMP_CWORD’ variable.
+
+ The function relies on the ‘complete’ and ‘compgen’ builtins to do
+much of the work, adding only the things that the Bash ‘cd’ does beyond
+accepting basic directory names: tilde expansion (*note Tilde
+Expansion::), searching directories in $CDPATH, which is described above
+(*note Bourne Shell Builtins::), and basic support for the ‘cdable_vars’
+shell option (*note The Shopt Builtin::). ‘_comp_cd’ modifies the value
+of IFS so that it contains only a newline to accommodate file names
+containing spaces and tabs - ‘compgen’ prints the possible completions
+it generates one per line.
+
+ Possible completions go into the COMPREPLY array variable, one
+completion per array element. The programmable completion system
+retrieves the completions from there when the function returns.
+
+ # A completion function for the cd builtin
+ # based on the cd completion function from the bash_completion package
+ _comp_cd()
+ {
+ local IFS=$' \t\n' # normalize IFS
+ local cur _skipdot _cdpath
+ local i j k
+
+ # Tilde expansion, which also expands tilde to full pathname
+ case "$2" in
+ \~*) eval cur="$2" ;;
+ *) cur=$2 ;;
+ esac
+
+ # no cdpath or absolute pathname -- straight directory completion
+ if [[ -z "${CDPATH:-}" ]] || [[ "$cur" == @(./*|../*|/*) ]]; then
+ # compgen prints paths one per line; could also use while loop
+ IFS=$'\n'
+ COMPREPLY=( $(compgen -d -- "$cur") )
+ IFS=$' \t\n'
+ # CDPATH+directories in the current directory if not in CDPATH
+ else
+ IFS=$'\n'
+ _skipdot=false
+ # preprocess CDPATH to convert null directory names to .
+ _cdpath=${CDPATH/#:/.:}
+ _cdpath=${_cdpath//::/:.:}
+ _cdpath=${_cdpath/%:/:.}
+ for i in ${_cdpath//:/$'\n'}; do
+ if [[ $i -ef . ]]; then _skipdot=true; fi
+ k="${#COMPREPLY[@]}"
+ for j in $( compgen -d -- "$i/$cur" ); do
+ COMPREPLY[k++]=${j#$i/} # cut off directory
+ done
+ done
+ $_skipdot || COMPREPLY+=( $(compgen -d -- "$cur") )
+ IFS=$' \t\n'
+ fi
+
+ # variable names if appropriate shell option set and no completions
+ if shopt -q cdable_vars && [[ ${#COMPREPLY[@]} -eq 0 ]]; then
+ COMPREPLY=( $(compgen -v -- "$cur") )
+ fi
+
+ return 0
+ }
+
+ We install the completion function using the ‘-F’ option to
+‘complete’:
+
+ # Tell readline to quote appropriate and append slashes to directories;
+ # use the bash default completion for other arguments
+ complete -o filenames -o nospace -o bashdefault -F _comp_cd cd
+
+Since we'd like Bash and Readline to take care of some of the other
+details for us, we use several other options to tell Bash and Readline
+what to do. The ‘-o filenames’ option tells Readline that the possible
+completions should be treated as filenames, and quoted appropriately.
+That option will also cause Readline to append a slash to filenames it
+can determine are directories (which is why we might want to extend
+‘_comp_cd’ to append a slash if we're using directories found via
+CDPATH: Readline can't tell those completions are directories). The ‘-o
+nospace’ option tells Readline to not append a space character to the
+directory name, in case we want to append to it. The ‘-o bashdefault’
+option brings in the rest of the "Bash default" completions - possible
+completions that Bash adds to the default Readline set. These include
+things like command name completion, variable completion for words
+beginning with ‘$’ or ‘${’, completions containing pathname expansion
+patterns (*note Filename Expansion::), and so on.
+
+ Once installed using ‘complete’, ‘_comp_cd’ will be called every time
+we attempt word completion for a ‘cd’ command.
+
+ Many more examples - an extensive collection of completions for most
+of the common GNU, Unix, and Linux commands - are available as part of
+the bash_completion project. This is installed by default on many
+GNU/Linux distributions. Originally written by Ian Macdonald, the
+project now lives at <https://github.com/scop/bash-completion/>. There
+are ports for other systems such as Solaris and Mac OS X.
+
+ An older version of the bash_completion package is distributed with
+bash in the ‘examples/complete’ subdirectory.
+
+\1f
+File: bashref.info, Node: Using History Interactively, Next: Installing Bash, Prev: Command Line Editing, Up: Top
+
+9 Using History Interactively
+*****************************
+
+This chapter describes how to use the GNU History Library interactively,
+from a user's standpoint. It should be considered a user's guide. For
+information on using the GNU History Library in other programs, see the
+GNU Readline Library Manual.
+
+* Menu:
+
+* Bash History Facilities:: How Bash lets you manipulate your command
+ history.
+* Bash History Builtins:: The Bash builtin commands that manipulate
+ the command history.
+* History Interaction:: What it feels like using History as a user.
+
+\1f
+File: bashref.info, Node: Bash History Facilities, Next: Bash History Builtins, Up: Using History Interactively
+
+9.1 Bash History Facilities
+===========================
+
+When the ‘-o history’ option to the ‘set’ builtin is enabled (*note The
+Set Builtin::), the shell provides access to the “command history”, the
+list of commands previously typed. The value of the ‘HISTSIZE’ shell
+variable is used as the number of commands to save in a history list:
+the shell saves the text of the last ‘$HISTSIZE’ commands (default 500).
+The shell stores each command in the history list prior to parameter and
+variable expansion but after history expansion is performed, subject to
+the values of the shell variables ‘HISTIGNORE’ and ‘HISTCONTROL’.
+
+ When the shell starts up, Bash initializes the history list by
+reading history entries from the file named by the ‘HISTFILE’ variable
+(default ‘~/.bash_history’). This is referred to as the “history file”.
+The history file is truncated, if necessary, to contain no more than the
+number of history entries specified by the value of the ‘HISTFILESIZE’
+variable. If ‘HISTFILESIZE’ is unset, or set to null, a non-numeric
+value, or a numeric value less than zero, the history file is not
+truncated.
+
+ When the history file is read, lines beginning with the history
+comment character followed immediately by a digit are interpreted as
+timestamps for the following history entry. These timestamps are
+optionally displayed depending on the value of the ‘HISTTIMEFORMAT’
+variable (*note Bash Variables::). When present, history timestamps
+delimit history entries, making multi-line entries possible.
+
+ When a shell with history enabled exits, Bash copies the last
+‘$HISTSIZE’ entries from the history list to the file named by
+‘$HISTFILE’. If the ‘histappend’ shell option is set (*note Bash
+Builtins::), Bash appends the entries to the history file, otherwise it
+overwrites the history file. If ‘HISTFILE’ is unset or null, or if the
+history file is unwritable, the history is not saved. After saving the
+history, Bash truncates the history file to contain no more than
+‘$HISTFILESIZE’ lines as described above.
+
+ If the ‘HISTTIMEFORMAT’ variable is set, the shell writes the
+timestamp information associated with each history entry to the history
+file, marked with the history comment character, so timestamps are
+preserved across shell sessions. When the history file is read, lines
+beginning with the history comment character followed immediately by a
+digit are interpreted as timestamps for the following history entry. As
+above, when using ‘HISTTIMEFORMAT’, the timestamps delimit multi-line
+history entries.
+
+ The ‘fc’ builtin command will list or edit and re-execute a portion
+of the history list. The ‘history’ builtin can display or modify the
+history list and manipulate the history file. When using command-line
+editing, search commands are available in each editing mode that provide
+access to the history list (*note Commands For History::).
+
+ The shell allows control over which commands are saved on the history
+list. The ‘HISTCONTROL’ and ‘HISTIGNORE’ variables are used to save
+only a subset of the commands entered. If the ‘cmdhist’ shell option is
+enabled, the shell attempts to save each line of a multi-line command in
+the same history entry, adding semicolons where necessary to preserve
+syntactic correctness. The ‘lithist’ shell option modifies ‘cmdhist’ by
+saving the command with embedded newlines instead of semicolons. The
+‘shopt’ builtin is used to set these options. *Note The Shopt
+Builtin::, for a description of ‘shopt’.
+
+\1f
+File: bashref.info, Node: Bash History Builtins, Next: History Interaction, Prev: Bash History Facilities, Up: Using History Interactively
+
+9.2 Bash History Builtins
+=========================
+
+Bash provides two builtin commands which manipulate the history list and
+history file.
+
+‘fc’
+ fc [-e ENAME] [-lnr] [FIRST] [LAST]
+ fc -s [PAT=REP] [COMMAND]
+
+ The first form selects a range of commands from FIRST to LAST from
+ the history list and displays or edits and re-executes them. Both
+ FIRST and LAST may be specified as a string (to locate the most
+ recent command beginning with that string) or as a number (an index
+ into the history list, where a negative number is used as an offset
+ from the current command number).
+
+ When listing, a FIRST or LAST of 0 is equivalent to -1 and -0 is
+ equivalent to the current command (usually the ‘fc’ command);
+ otherwise 0 is equivalent to -1 and -0 is invalid.
+
+ If LAST is not specified, it is set to the current command for
+ listing and to FIRST otherwise. If FIRST is not specified, it is
+ set to the previous command for editing and −16 for listing.
+
+ If the ‘-l’ flag is supplied, the commands are listed on standard
+ output. The ‘-n’ flag suppresses the command numbers when listing.
+ The ‘-r’ flag reverses the order of the listing.
+
+ Otherwise, ‘fc’ invokes the editor named by ENAME on a file
+ containing those commands. If ENAME is not supplied, ‘fc’ uses the
+ value of the following variable expansion:
+ ‘${FCEDIT:-${EDITOR:-vi}}’. This says to use the value of the
+ ‘FCEDIT’ variable if set, or the value of the ‘EDITOR’ variable if
+ that is set, or ‘vi’ if neither is set. When editing is complete,
+ ‘fc’ reads the file of edited commands and echoes and executes
+ them.
+
+ In the second form, ‘fc’ re-executes COMMAND after replacing each
+ instance of PAT in the selected command with REP. COMMAND is
+ interpreted the same as FIRST above.
+
+ A useful alias to use with the ‘fc’ command is ‘r='fc -s'’, so that
+ typing ‘r cc’ runs the last command beginning with ‘cc’ and typing
+ ‘r’ re-executes the last command (*note Aliases::).
+
+ If the first form is used, the return value is zero unless an
+ invalid option is encountered or FIRST or LAST specify history
+ lines out of range. When editing and re-executing a file of
+ commands, the return value is the value of the last command
+ executed or failure if an error occurs with the temporary file. If
+ the second form is used, the return status is that of the
+ re-executed command, unless COMMAND does not specify a valid
+ history entry, in which case ‘fc’ returns a non-zero status.
+
+‘history’
+ history [N]
+ history -c
+ history -d OFFSET
+ history -d START-END
+ history [-anrw] [FILENAME]
+ history -ps ARG
+
+ With no options, display the history list with numbers. Entries
+ prefixed with a ‘*’ have been modified. An argument of N lists
+ only the last N entries. If the shell variable ‘HISTTIMEFORMAT’ is
+ set and not null, it is used as a format string for ‘strftime’(3)
+ to display the time stamp associated with each displayed history
+ entry. If ‘history’ uses ‘HISTTIMEFORMAT’, it does not print an
+ intervening space between the formatted time stamp and the history
+ entry.
+
+ Options, if supplied, have the following meanings:
+
+ ‘-c’
+ Clear the history list. This may be combined with the other
+ options to replace the history list.
+
+ ‘-d OFFSET’
+ Delete the history entry at position OFFSET. If OFFSET is
+ positive, it should be specified as it appears when the
+ history is displayed. If OFFSET is negative, it is
+ interpreted as relative to one greater than the last history
+ position, so negative indices count back from the end of the
+ history, and an index of ‘-1’ refers to the current ‘history
+ -d’ command.
+
+ ‘-d START-END’
+ Delete the range of history entries between positions START
+ and END, inclusive. Positive and negative values for START
+ and END are interpreted as described above.
+
+ ‘-a’
+ Append the "new" history lines to the history file. These are
+ history lines entered since the beginning of the current Bash
+ session, but not already appended to the history file.
+
+ ‘-n’
+ Read the history lines not already read from the history file
+ and add them to the current history list. These are lines
+ appended to the history file since the beginning of the
+ current Bash session.
+
+ ‘-r’
+ Read the history file and append its contents to the history
+ list.
+
+ ‘-w’
+ Write the current history list to the history file,
+ overwriting the history file.
+
+ ‘-p’
+ Perform history substitution on the ARGs and display the
+ result on the standard output, without storing the results in
+ the history list.
+
+ ‘-s’
+ Add the ARGs to the end of the history list as a single entry.
+ The last command in the history list is removed before adding
+ the ARGs.
+
+ If a FILENAME argument is supplied with any of the ‘-w’, ‘-r’,
+ ‘-a’, or ‘-n’ options, Bash uses FILENAME as the history file. If
+ not, it uses the value of the ‘HISTFILE’ variable. If ‘HISTFILE’
+ is unset or null, these options have no effect.
+
+ If the ‘HISTTIMEFORMAT’ variable is set, ‘history’ writes the time
+ stamp information associated with each history entry to the history
+ file, marked with the history comment character as described above.
+ When the history file is read, lines beginning with the history
+ comment character followed immediately by a digit are interpreted
+ as timestamps for the following history entry.
+
+ The return value is 0 unless an invalid option is encountered, an
+ error occurs while reading or writing the history file, an invalid
+ OFFSET or range is supplied as an argument to ‘-d’, or the history
+ expansion supplied as an argument to ‘-p’ fails.
+
+\1f
+File: bashref.info, Node: History Interaction, Prev: Bash History Builtins, Up: Using History Interactively
+
+9.3 History Expansion
+=====================
+
+The shell provides a history expansion feature that is similar to the
+history expansion provided by ‘csh’ (also referred to as history
+substitution where appropriate). This section describes the syntax used
+to manipulate the history information.
+
+ History expansion is enabled by default for interactive shells, and
+can be disabled using the ‘+H’ option to the ‘set’ builtin command
+(*note The Set Builtin::). Non-interactive shells do not perform
+history expansion by default, but it can be enabled with ‘set -H’.
+
+ History expansions introduce words from the history list into the
+input stream, making it easy to repeat commands, insert the arguments to
+a previous command into the current input line, or fix errors in
+previous commands quickly.
+
+ History expansion is performed immediately after a complete line is
+read, before the shell breaks it into words, and is performed on each
+line individually. Bash attempts to inform the history expansion
+functions about quoting still in effect from previous lines.
+
+ History expansion takes place in two parts. The first is to
+determine which entry from the history list should be used during
+substitution. The second is to select portions of that entry to include
+into the current one.
+
+ The entry selected from the history is called the “event”, and the
+portions of that entry that are acted upon are “words”. Various
+“modifiers” are available to manipulate the selected words. The entry
+is split into words in the same fashion that Bash does when reading
+input, so that several words surrounded by quotes are considered one
+word. The “event designator” selects the event, the optional “word
+designator” selects words from the event, and various optional
+“modifiers” are available to manipulate the selected words.
+
+ History expansions are introduced by the appearance of the history
+expansion character, which is ‘!’ by default. History expansions may
+appear anywhere in the input, but do not nest.
+
+ History expansion implements shell-like quoting conventions: a
+backslash can be used to remove the special handling for the next
+character; single quotes enclose verbatim sequences of characters, and
+can be used to inhibit history expansion; and characters enclosed within
+double quotes may be subject to history expansion, since backslash can
+escape the history expansion character, but single quotes may not, since
+they are not treated specially within double quotes.
+
+ When using the shell, only ‘\’ and ‘'’ may be used to escape the
+history expansion character, but the history expansion character is also
+treated as quoted if it immediately precedes the closing double quote in
+a double-quoted string.
+
+ Several characters inhibit history expansion if found immediately
+following the history expansion character, even if it is unquoted:
+space, tab, newline, carriage return, ‘=’, and the other shell
+metacharacters.
+
+ There is a special abbreviation for substitution, active when the
+QUICK SUBSTITUTION character (described above under ‘histchars’) is the
+first character on the line. It selects the previous history list
+entry, using an event designator equivalent to ‘!!’, and substitutes one
+string for another in that entry. It is described below (*note Event
+Designators::). This is the only history expansion that does not begin
+with the history expansion character.
+
+ Several shell options settable with the ‘shopt’ builtin (*note The
+Shopt Builtin::) modify history expansion behavior If the ‘histverify’
+shell option is enabled, and Readline is being used, history
+substitutions are not immediately passed to the shell parser. Instead,
+the expanded line is reloaded into the Readline editing buffer for
+further modification. If Readline is being used, and the ‘histreedit’
+shell option is enabled, a failed history expansion is reloaded into the
+Readline editing buffer for correction.
+
+ The ‘-p’ option to the ‘history’ builtin command shows what a history
+expansion will do before using it. The ‘-s’ option to the ‘history’
+builtin may be used to add commands to the end of the history list
+without actually executing them, so that they are available for
+subsequent recall. This is most useful in conjunction with Readline.
+
+ The shell allows control of the various characters used by the
+history expansion mechanism with the ‘histchars’ variable, as explained
+above (*note Bash Variables::). The shell uses the history comment
+character to mark history timestamps when writing the history file.
+
+* Menu:
+
+* Event Designators:: How to specify which history line to use.
+* Word Designators:: Specifying which words are of interest.
+* Modifiers:: Modifying the results of substitution.
+
+\1f
+File: bashref.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
+
+9.3.1 Event Designators
+-----------------------
+
+An event designator is a reference to an entry in the history list. The
+event designator consists of the portion of the word beginning with the
+history expansion character, and ending with the word designator if one
+is present, or the end of the word. Unless the reference is absolute,
+events are relative to the current position in the history list.
+
+‘!’
+ Start a history substitution, except when followed by a space, tab,
+ the end of the line, ‘=’, or the rest of the shell metacharacters
+ defined above (*note Definitions::).
+
+‘!N’
+ Refer to history list entry N.
+
+‘!-N’
+ Refer to the history entry minus N.
+
+‘!!’
+ Refer to the previous entry. This is a synonym for ‘!-1’.
+
+‘!STRING’
+ Refer to the most recent command preceding the current position in
+ the history list starting with STRING.
+
+‘!?STRING[?]’
+ Refer to the most recent command preceding the current position in
+ the history list containing STRING. The trailing ‘?’ may be
+ omitted if the STRING is followed immediately by a newline. If
+ STRING is missing, this uses the string from the most recent
+ search; it is an error if there is no previous search string.
+
+‘^STRING1^STRING2^’
+ Quick Substitution. Repeat the last command, replacing STRING1
+ with STRING2. Equivalent to ‘!!:s^STRING1^STRING2^’.
+
+‘!#’
+ The entire command line typed so far.
+
+\1f
+File: bashref.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
+
+9.3.2 Word Designators
+----------------------
+
+Word designators are used to select desired words from the event. They
+are optional; if the word designator isn't supplied, the history
+expansion uses the entire event. A ‘:’ separates the event
+specification from the word designator. It may be omitted if the word
+designator begins with a ‘^’, ‘$’, ‘*’, ‘-’, or ‘%’. Words are numbered
+from the beginning of the line, with the first word being denoted by 0
+(zero). That first word is usually the command word, and the arguments
+begin with the second word. Words are inserted into the current line
+separated by single spaces.
+
+ For example,
+
+‘!!’
+ designates the preceding command. When you type this, the
+ preceding command is repeated in toto.
+
+‘!!:$’
+ designates the last word of the preceding command. This may be
+ shortened to ‘!$’.
+
+‘!fi:2’
+ designates the second argument of the most recent command starting
+ with the letters ‘fi’.
+
+ Here are the word designators:
+
+‘0 (zero)’
+ The ‘0’th word. For the shell, and many other, applications, this
+ is the command word.
+
+‘N’
+ The Nth word.
+
+‘^’
+ The first argument: word 1.
+
+‘$’
+ The last word. This is usually the last argument, but expands to
+ the zeroth word if there is only one word in the line.
+
+‘%’
+ The first word matched by the most recent ‘?STRING?’ search, if the
+ search string begins with a character that is part of a word. By
+ default, searches begin at the end of each line and proceed to the
+ beginning, so the first word matched is the one closest to the end
+ of the line.
+
+‘X-Y’
+ A range of words; ‘-Y’ abbreviates ‘0-Y’.
+
+‘*’
+ All of the words, except the ‘0’th. This is a synonym for ‘1-$’.
+ It is not an error to use ‘*’ if there is just one word in the
+ event; it expands to the empty string in that case.
+
+‘X*’
+ Abbreviates ‘X-$’.
+
+‘X-’
+ Abbreviates ‘X-$’ like ‘X*’, but omits the last word. If ‘x’ is
+ missing, it defaults to 0.
+
+ If a word designator is supplied without an event specification, the
+previous command is used as the event, equivalent to ‘!!’.
+
+\1f
+File: bashref.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
+
+9.3.3 Modifiers
+---------------
+
+After the optional word designator, you can add a sequence of one or
+more of the following modifiers, each preceded by a ‘:’. These modify,
+or edit, the word or words selected from the history event.
+
+‘h’
+ Remove a trailing filename component, leaving only the head.
+
+‘t’
+ Remove all leading filename components, leaving the tail.
+
+‘r’
+ Remove a trailing suffix of the form ‘.SUFFIX’, leaving the
+ basename.
+
+‘e’
+ Remove all but the trailing suffix.
+
+‘p’
+ Print the new command but do not execute it.
+
+‘q’
+ Quote the substituted words, escaping further substitutions.
+
+‘x’
+ Quote the substituted words as with ‘q’, but break into words at
+ spaces, tabs, and newlines. The ‘q’ and ‘x’ modifiers are mutually
+ exclusive; expansion uses the last one supplied.
+
+‘s/OLD/NEW/’
+ Substitute NEW for the first occurrence of OLD in the event line.
+ Any character may be used as the delimiter in place of ‘/’. The
+ delimiter may be quoted in OLD and NEW with a single backslash. If
+ ‘&’ appears in NEW, it is replaced with OLD. A single backslash
+ quotes the ‘&’ in OLD and NEW. If OLD is null, it is set to the
+ last OLD substituted, or, if no previous history substitutions took
+ place, the last STRING in a !?STRING‘[?]’ search. If NEW is null,
+ each matching OLD is deleted. The final delimiter is optional if
+ it is the last character on the input line.
+
+‘&’
+ Repeat the previous substitution.
+
+‘g’
+‘a’
+ Cause changes to be applied over the entire event line. This is
+ used in conjunction with ‘s’, as in ‘gs/OLD/NEW/’, or with ‘&’.
+
+‘G’
+ Apply the following ‘s’ or ‘&’ modifier once to each word in the
+ event.
+
+\1f
+File: bashref.info, Node: Installing Bash, Next: Reporting Bugs, Prev: Using History Interactively, Up: Top
+
+10 Installing Bash
+******************
+
+This chapter provides basic instructions for installing Bash on the
+various supported platforms. The distribution supports the GNU
+operating systems, nearly every version of Unix, and several non-Unix
+systems such as BeOS and Interix. Other independent ports exist for
+Windows platforms.
+
+* Menu:
+
+* Basic Installation:: Installation instructions.
+* Compilers and Options:: How to set special options for various
+ systems.
+* Compiling For Multiple Architectures:: How to compile Bash for more
+ than one kind of system from
+ the same source tree.
+* Installation Names:: How to set the various paths used by the installation.
+* Specifying the System Type:: How to configure Bash for a particular system.
+* Sharing Defaults:: How to share default configuration values among GNU
+ programs.
+* Operation Controls:: Options recognized by the configuration program.
+* Optional Features:: How to enable and disable optional features when
+ building Bash.
+
+\1f
+File: bashref.info, Node: Basic Installation, Next: Compilers and Options, Up: Installing Bash
+
+10.1 Basic Installation
+=======================
+
+These are installation instructions for Bash.
+
+ The simplest way to compile Bash is:
+
+ 1. ‘cd’ to the directory containing the source code and type
+ ‘./configure’ to configure Bash for your system. If you're using
+ ‘csh’ on an old version of System V, you might need to type ‘sh
+ ./configure’ instead to prevent ‘csh’ from trying to execute
+ ‘configure’ itself.
+
+ Running ‘configure’ takes some time. While running, it prints
+ messages telling which features it is checking for.
+
+ 2. Type ‘make’ to compile Bash and build the ‘bashbug’ bug reporting
+ script.
+
+ 3. Optionally, type ‘make tests’ to run the Bash test suite.
+
+ 4. Type ‘make install’ to install ‘bash’ and ‘bashbug’. This will
+ also install the manual pages and Info file, message translation
+ files, some supplemental documentation, a number of example
+ loadable builtin commands, and a set of header files for developing
+ loadable builtins. You may need additional privileges to install
+ ‘bash’ to your desired destination, which may require ‘sudo make
+ install’. More information about controlling the locations where
+ ‘bash’ and other files are installed is below (*note Installation
+ Names::).
+
+ The ‘configure’ shell script attempts to guess correct values for
+various system-dependent variables used during compilation. It uses
+those values to create a ‘Makefile’ in each directory of the package
+(the top directory, the ‘builtins’, ‘doc’, ‘po’, and ‘support’
+directories, each directory under ‘lib’, and several others). It also
+creates a ‘config.h’ file containing system-dependent definitions.
+Finally, it creates a shell script named ‘config.status’ that you can
+run in the future to recreate the current configuration, a file
+‘config.cache’ that saves the results of its tests to speed up
+reconfiguring, and a file ‘config.log’ containing compiler output
+(useful mainly for debugging ‘configure’). If at some point
+‘config.cache’ contains results you don't want to keep, you may remove
+or edit it.
+
+ To find out more about the options and arguments that the ‘configure’
+script understands, type
+
+ bash-4.2$ ./configure --help
+
+at the Bash prompt in your Bash source directory.
+
+ If you want to build Bash in a directory separate from the source
+directory - to build for multiple architectures, for example - just use
+the full path to the configure script. The following commands will
+build Bash in a directory under ‘/usr/local/build’ from the source code
+in ‘/usr/local/src/bash-4.4’:
+
+ mkdir /usr/local/build/bash-4.4
+ cd /usr/local/build/bash-4.4
+ bash /usr/local/src/bash-4.4/configure
+ make
+
+ See *note Compiling For Multiple Architectures:: for more information
+about building in a directory separate from the source.
+
+ If you need to do unusual things to compile Bash, please try to
+figure out how ‘configure’ could check whether or not to do them, and
+mail diffs or instructions to <bash-maintainers@gnu.org> so they can be
+considered for the next release.
+
+ The file ‘configure.ac’ is used to create ‘configure’ by a program
+called Autoconf. You only need ‘configure.ac’ if you want to change it
+or regenerate ‘configure’ using a newer version of Autoconf. If you do
+this, make sure you are using Autoconf version 2.69 or newer.
+
+ You can remove the program binaries and object files from the source
+code directory by typing ‘make clean’. To also remove the files that
+‘configure’ created (so you can compile Bash for a different kind of
+computer), type ‘make distclean’.
+
+\1f
+File: bashref.info, Node: Compilers and Options, Next: Compiling For Multiple Architectures, Prev: Basic Installation, Up: Installing Bash
+
+10.2 Compilers and Options
+==========================
+
+Some systems require unusual options for compilation or linking that the
+‘configure’ script does not know about. You can give ‘configure’
+initial values for variables by setting them in the environment. Using
+a Bourne-compatible shell, you can do that on the command line like
+this:
+
+ CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure
+
+ On systems that have the ‘env’ program, you can do it like this:
+
+ env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure
+
+ The configuration process uses GCC to build Bash if it is available.
+
+\1f
+File: bashref.info, Node: Compiling For Multiple Architectures, Next: Installation Names, Prev: Compilers and Options, Up: Installing Bash
+
+10.3 Compiling For Multiple Architectures
+=========================================
+
+You can compile Bash for more than one kind of computer at the same
+time, by placing the object files for each architecture in their own
+directory. To do this, you must use a version of ‘make’ that supports
+the ‘VPATH’ variable, such as GNU ‘make’. ‘cd’ to the directory where
+you want the object files and executables to go and run the ‘configure’
+script from the source directory (*note Basic Installation::). You may
+need to supply the ‘--srcdir=PATH’ argument to tell ‘configure’ where
+the source files are. ‘configure’ automatically checks for the source
+code in the directory that ‘configure’ is in and in ‘..’.
+
+ If you have to use a ‘make’ that does not support the ‘VPATH’
+variable, you can compile Bash for one architecture at a time in the
+source code directory. After you have installed Bash for one
+architecture, use ‘make distclean’ before reconfiguring for another
+architecture.
+
+ Alternatively, if your system supports symbolic links, you can use
+the ‘support/mkclone’ script to create a build tree which has symbolic
+links back to each file in the source directory. Here's an example that
+creates a build directory in the current directory from a source
+directory ‘/usr/gnu/src/bash-2.0’:
+
+ bash /usr/gnu/src/bash-2.0/support/mkclone -s /usr/gnu/src/bash-2.0 .
+
+The ‘mkclone’ script requires Bash, so you must have already built Bash
+for at least one architecture before you can create build directories
+for other architectures.
+
+\1f
+File: bashref.info, Node: Installation Names, Next: Specifying the System Type, Prev: Compiling For Multiple Architectures, Up: Installing Bash
+
+10.4 Installation Names
+=======================
+
+By default, ‘make install’ will install into ‘/usr/local/bin’,
+‘/usr/local/man’, etc.; that is, the “installation prefix” defaults to
+‘/usr/local’. You can specify an installation prefix other than
+‘/usr/local’ by giving ‘configure’ the option ‘--prefix=PATH’, or by
+specifying a value for the ‘prefix’ ‘make’ variable when running ‘make
+install’ (e.g., ‘make install prefix=PATH’). The ‘prefix’ variable
+provides a default for ‘exec_prefix’ and other variables used when
+installing Bash.
+
+ You can specify separate installation prefixes for
+architecture-specific files and architecture-independent files. If you
+give ‘configure’ the option ‘--exec-prefix=PATH’, ‘make install’ will
+use PATH as the prefix for installing programs and libraries.
+Documentation and other data files will still use the regular prefix.
+
+ If you would like to change the installation locations for a single
+run, you can specify these variables as arguments to ‘make’: ‘make
+install exec_prefix=/’ will install ‘bash’ and ‘bashbug’ into ‘/bin’
+instead of the default ‘/usr/local/bin’.
+
+ If you want to see the files Bash will install and where it will
+install them without changing anything on your system, specify the
+variable ‘DESTDIR’ as an argument to ‘make’. Its value should be the
+absolute directory path you'd like to use as the root of your sample
+installation tree. For example,
+
+ mkdir /fs1/bash-install
+ make install DESTDIR=/fs1/bash-install
+
+will install ‘bash’ into ‘/fs1/bash-install/usr/local/bin/bash’, the
+documentation into directories within
+‘/fs1/bash-install/usr/local/share’, the example loadable builtins into
+‘/fs1/bash-install/usr/local/lib/bash’, and so on. You can use the
+usual ‘exec_prefix’ and ‘prefix’ variables to alter the directory paths
+beneath the value of ‘DESTDIR’.
+
+ The GNU Makefile standards provide a more complete description of
+these variables and their effects.
+
+\1f
+File: bashref.info, Node: Specifying the System Type, Next: Sharing Defaults, Prev: Installation Names, Up: Installing Bash
+
+10.5 Specifying the System Type
+===============================
+
+There may be some features ‘configure’ can not figure out automatically,
+but needs to determine by the type of host Bash will run on. Usually
+‘configure’ can figure that out, but if it prints a message saying it
+can not guess the host type, give it the ‘--host=TYPE’ option. ‘TYPE’
+can either be a short name for the system type, such as ‘sun4’, or a
+canonical name with three fields: ‘CPU-COMPANY-SYSTEM’ (e.g.,
+‘i386-unknown-freebsd4.2’).
+
+ See the file ‘support/config.sub’ for the possible values of each
+field.
+
+\1f
+File: bashref.info, Node: Sharing Defaults, Next: Operation Controls, Prev: Specifying the System Type, Up: Installing Bash
+
+10.6 Sharing Defaults
+=====================
+
+If you want to set default values for ‘configure’ scripts to share, you
+can create a site shell script called ‘config.site’ that gives default
+values for variables like ‘CC’, ‘cache_file’, and ‘prefix’. ‘configure’
+looks for ‘PREFIX/share/config.site’ if it exists, then
+‘PREFIX/etc/config.site’ if it exists. Or, you can set the
+‘CONFIG_SITE’ environment variable to the location of the site script.
+A warning: the Bash ‘configure’ looks for a site script, but not all
+‘configure’ scripts do.
+
+\1f
+File: bashref.info, Node: Operation Controls, Next: Optional Features, Prev: Sharing Defaults, Up: Installing Bash
+
+10.7 Operation Controls
+=======================
+
+‘configure’ recognizes the following options to control how it operates.
+
+‘--cache-file=FILE’
+ Use and save the results of the tests in FILE instead of
+ ‘./config.cache’. Set FILE to ‘/dev/null’ to disable caching, for
+ debugging ‘configure’.
+
+‘--help’
+ Print a summary of the options to ‘configure’, and exit.
+
+‘--quiet’
+‘--silent’
+‘-q’
+ Do not print messages saying which checks are being made.
+
+‘--srcdir=DIR’
+ Look for the Bash source code in directory DIR. Usually
+ ‘configure’ can determine that directory automatically.
+
+‘--version’
+ Print the version of Autoconf used to generate the ‘configure’
+ script, and exit.
+
+ ‘configure’ also accepts some other, not widely used, boilerplate
+options. ‘configure --help’ prints the complete list.
+
+\1f
+File: bashref.info, Node: Optional Features, Prev: Operation Controls, Up: Installing Bash
+
+10.8 Optional Features
+======================
+
+The Bash ‘configure’ has a number of ‘--enable-FEATURE’ options, where
+FEATURE indicates an optional part of Bash. There are also several
+‘--with-PACKAGE’ options, where PACKAGE is something like ‘bash-malloc’
+or ‘afs’. To turn off the default use of a package, use
+‘--without-PACKAGE’. To configure Bash without a feature that is
+enabled by default, use ‘--disable-FEATURE’.
+
+ Here is a complete list of the ‘--enable-’ and ‘--with-’ options that
+the Bash ‘configure’ recognizes.
+
+‘--with-afs’
+ Define if you are using the Andrew File System from Transarc.
+
+‘--with-bash-malloc’
+ Use the Bash version of ‘malloc’ in the directory ‘lib/malloc’.
+ This is not the same ‘malloc’ that appears in GNU libc, but a
+ custom version originally derived from the 4.2 BSD ‘malloc’. This
+ ‘malloc’ is very fast, but wastes some space on each allocation,
+ though it uses several techniques to minimize the waste. This
+ option is enabled by default. The ‘NOTES’ file contains a list of
+ systems for which this should be turned off, and ‘configure’
+ disables this option automatically for a number of systems.
+
+‘--with-curses[=LIBNAME]’
+ Use the curses library instead of the termcap library as the
+ library where the linker can find the termcap functions.
+ ‘configure’ usually chooses this automatically, since most systems
+ include the termcap functions in the curses library. If LIBNAME is
+ supplied, ‘configure’ does not search for an appropriate library
+ and uses LIBNAME instead. LIBNAME should be either an argument for
+ the linker (e.g., ‘-lLIBNAME’) or a filename (e.g.,
+ ‘/opt/local/lib/libncursesw.so’).
+
+‘--with-gnu-malloc’
+ A synonym for ‘--with-bash-malloc’.
+
+‘--with-installed-readline[=PREFIX]’
+ Define this to make Bash link with a locally-installed version of
+ Readline rather than the version in ‘lib/readline’. This works
+ only with Readline 5.0 and later versions. If PREFIX is ‘yes’ or
+ not supplied, ‘configure’ uses the values of the make variables
+ ‘includedir’ and ‘libdir’, which are subdirectories of ‘prefix’ by
+ default, to find the installed version of Readline if it is not in
+ the standard system include and library directories. If PREFIX is
+ ‘no’, Bash links with the version in ‘lib/readline’. If PREFIX is
+ set to any other value, ‘configure’ treats it as a directory
+ pathname and looks for the installed version of Readline in
+ subdirectories of that directory (include files in PREFIX/‘include’
+ and the library in PREFIX/‘lib’). The Bash default is to link with
+ a static library built in the ‘lib/readline’ subdirectory of the
+ build directory.
+
+‘--with-libintl-prefix[=PREFIX]’
+ Define this to make Bash link with a locally-installed version of
+ the libintl library instead of the version in ‘lib/intl’.
+
+‘--with-libiconv-prefix[=PREFIX]’
+ Define this to make Bash look for libiconv in PREFIX instead of the
+ standard system locations. The Bash distribution does not include
+ this library.
+
+‘--enable-minimal-config’
+ This produces a shell with minimal features, closer to the
+ historical Bourne shell.
+
+ There are several ‘--enable-’ options that alter how Bash is
+compiled, linked, and installed, rather than changing run-time features.
+
+‘--enable-largefile’
+ Enable support for large files
+ (http://www.unix.org/version2/whatsnew/lfs20mar.html) if the
+ operating system requires special compiler options to build
+ programs which can access large files. This is enabled by default,
+ if the operating system provides large file support.
+
+‘--enable-profiling’
+ This builds a Bash binary that produces profiling information to be
+ processed by ‘gprof’ each time it is executed.
+
+‘--enable-separate-helpfiles’
+ Use external files for the documentation displayed by the ‘help’
+ builtin instead of storing the text internally.
+
+‘--enable-static-link’
+ This causes Bash to be linked statically, if ‘gcc’ is being used.
+ This could be used to build a version to use as root's shell.
+
+ The ‘minimal-config’ option can be used to disable all of the
+following options, but it is processed first, so individual options may
+be enabled using ‘enable-FEATURE’.
+
+ All of the following options except for ‘alt-array-implementation’,
+‘disabled-builtins’, ‘direxpand-default’, ‘strict-posix-default’, and
+‘xpg-echo-default’ are enabled by default, unless the operating system
+does not provide the necessary support.
+
+‘--enable-alias’
+ Allow alias expansion and include the ‘alias’ and ‘unalias’
+ builtins (*note Aliases::).
+
+‘--enable-alt-array-implementation’
+ This builds Bash using an alternate implementation of arrays (*note
+ Arrays::) that provides faster access at the expense of using more
+ memory (sometimes many times more, depending on how sparse an array
+ is).
+
+‘--enable-arith-for-command’
+ Include support for the alternate form of the ‘for’ command that
+ behaves like the C language ‘for’ statement (*note Looping
+ Constructs::).
+
+‘--enable-array-variables’
+ Include support for one-dimensional array shell variables (*note
+ Arrays::).
+
+‘--enable-bang-history’
+ Include support for ‘csh’-like history substitution (*note History
+ Interaction::).
+
+‘--enable-bash-source-fullpath-default’
+ Set the default value of the ‘bash_source_fullpath’ shell option
+ described above under *note The Shopt Builtin:: to be enabled.
+ This controls how filenames are assigned to the ‘BASH_SOURCE’ array
+ variable.
+
+‘--enable-brace-expansion’
+ Include ‘csh’-like brace expansion ( ‘b{a,b}c’ ↦ ‘bac bbc’ ). See
+ *note Brace Expansion::, for a complete description.
+
+‘--enable-casemod-attributes’
+ Include support for case-modifying attributes in the ‘declare’
+ builtin and assignment statements. Variables with the ‘uppercase’
+ attribute, for example, will have their values converted to
+ uppercase upon assignment.
+
+‘--enable-casemod-expansion’
+ Include support for case-modifying word expansions.
+
+‘--enable-command-timing’
+ Include support for recognizing ‘time’ as a reserved word and for
+ displaying timing statistics for the pipeline following ‘time’
+ (*note Pipelines::). This allows timing pipelines, shell compound
+ commands, shell builtins, and shell functions, which an external
+ command cannot do easily.
+
+‘--enable-cond-command’
+ Include support for the ‘[[’ conditional command. (*note
+ Conditional Constructs::).
+
+‘--enable-cond-regexp’
+ Include support for matching POSIX regular expressions using the
+ ‘=~’ binary operator in the ‘[[’ conditional command. (*note
+ Conditional Constructs::).
+
+‘--enable-coprocesses’
+ Include support for coprocesses and the ‘coproc’ reserved word
+ (*note Pipelines::).
+
+‘--enable-debugger’
+ Include support for the Bash debugger (distributed separately).
+
+‘--enable-dev-fd-stat-broken’
+ If calling ‘stat’ on /dev/fd/N returns different results than
+ calling ‘fstat’ on file descriptor N, supply this option to enable
+ a workaround. This has implications for conditional commands that
+ test file attributes.
+
+‘--enable-direxpand-default’
+ Cause the ‘direxpand’ shell option (*note The Shopt Builtin::) to
+ be enabled by default when the shell starts. It is normally
+ disabled by default.
+
+‘--enable-directory-stack’
+ Include support for a ‘csh’-like directory stack and the ‘pushd’,
+ ‘popd’, and ‘dirs’ builtins (*note The Directory Stack::).
+
+‘--enable-disabled-builtins’
+ Allow builtin commands to be invoked via ‘builtin xxx’ even after
+ ‘xxx’ has been disabled using ‘enable -n xxx’. See *note Bash
+ Builtins::, for details of the ‘builtin’ and ‘enable’ builtin
+ commands.
+
+‘--enable-dparen-arithmetic’
+ Include support for the ‘((...))’ command (*note Conditional
+ Constructs::).
+
+‘--enable-extended-glob’
+ Include support for the extended pattern matching features
+ described above under *note Pattern Matching::.
+
+‘--enable-extended-glob-default’
+ Set the default value of the ‘extglob’ shell option described above
+ under *note The Shopt Builtin:: to be enabled.
+
+‘--enable-function-import’
+ Include support for importing function definitions exported by
+ another instance of the shell from the environment. This option is
+ enabled by default.
+
+‘--enable-glob-asciiranges-default’
+ Set the default value of the ‘globasciiranges’ shell option
+ described above under *note The Shopt Builtin:: to be enabled.
+ This controls the behavior of character ranges when used in pattern
+ matching bracket expressions.
+
+‘--enable-help-builtin’
+ Include the ‘help’ builtin, which displays help on shell builtins
+ and variables (*note Bash Builtins::).
+
+‘--enable-history’
+ Include command history and the ‘fc’ and ‘history’ builtin commands
+ (*note Bash History Facilities::).
+
+‘--enable-job-control’
+ This enables the job control features (*note Job Control::), if the
+ operating system supports them.
+
+‘--enable-multibyte’
+ This enables support for multibyte characters if the operating
+ system provides the necessary support.
+
+‘--enable-net-redirections’
+ This enables the special handling of filenames of the form
+ ‘/dev/tcp/HOST/PORT’ and ‘/dev/udp/HOST/PORT’ when used in
+ redirections (*note Redirections::).
+
+‘--enable-process-substitution’
+ This enables process substitution (*note Process Substitution::) if
+ the operating system provides the necessary support.
+
+‘--enable-progcomp’
+ Enable the programmable completion facilities (*note Programmable
+ Completion::). If Readline is not enabled, this option has no
+ effect.
+
+‘--enable-prompt-string-decoding’
+ Turn on the interpretation of a number of backslash-escaped
+ characters in the ‘$PS0’, ‘$PS1’, ‘$PS2’, and ‘$PS4’ prompt
+ strings. See *note Controlling the Prompt::, for a complete list
+ of prompt string escape sequences.
+
+‘--enable-readline’
+ Include support for command-line editing and history with the Bash
+ version of the Readline library (*note Command Line Editing::).
+
+‘--enable-restricted’
+ Include support for a “restricted shell”. If this is enabled, Bash
+ enters a restricted mode when called as ‘rbash’. See *note The
+ Restricted Shell::, for a description of restricted mode.
+
+‘--enable-select’
+ Include the ‘select’ compound command, which allows generation of
+ simple menus (*note Conditional Constructs::).
+
+‘--enable-single-help-strings’
+ Store the text displayed by the ‘help’ builtin as a single string
+ for each help topic. This aids in translating the text to
+ different languages. You may need to disable this if your compiler
+ cannot handle very long string literals.
+
+‘--enable-strict-posix-default’
+ Make Bash POSIX-conformant by default (*note Bash POSIX Mode::).
+
+‘--enable-translatable-strings’
+ Enable support for ‘$"STRING"’ translatable strings (*note Locale
+ Translation::).
+
+‘--enable-usg-echo-default’
+ A synonym for ‘--enable-xpg-echo-default’.
+
+‘--enable-xpg-echo-default’
+ Make the ‘echo’ builtin expand backslash-escaped characters by
+ default, without requiring the ‘-e’ option. This sets the default
+ value of the ‘xpg_echo’ shell option to ‘on’, which makes the Bash
+ ‘echo’ behave more like the version specified in the Single Unix
+ Specification, version 3. *Note Bash Builtins::, for a description
+ of the escape sequences that ‘echo’ recognizes.
+
+ The file ‘config-top.h’ contains C Preprocessor ‘#define’ statements
+for options which are not settable from ‘configure’. Some of these are
+not meant to be changed; beware of the consequences if you do. Read the
+comments associated with each definition for more information about its
+effect.
+
+\1f
+File: bashref.info, Node: Reporting Bugs, Next: Major Differences From The Bourne Shell, Prev: Installing Bash, Up: Top
+
+Appendix A Reporting Bugs
+*************************
+
+Please report all bugs you find in Bash. But first, you should make
+sure that it really is a bug, and that it appears in the latest version
+of Bash. The latest released version of Bash is always available for
+FTP from <ftp://ftp.gnu.org/pub/gnu/bash/> and from
+<http://git.savannah.gnu.org/cgit/bash.git/snapshot/bash-master.tar.gz>.
+
+ Once you have determined that a bug actually exists, use the
+‘bashbug’ command to submit a bug report or use the form at the Bash
+project page (https://savannah.gnu.org/projects/bash/). If you have a
+fix, you are encouraged to submit that as well! Suggestions and
+"philosophical" bug reports may be mailed to <bug-bash@gnu.org> or
+<help-bash@gnu.org>.
+
+ All bug reports should include:
+ • The version number of Bash.
+ • The hardware and operating system.
+ • The compiler used to compile Bash.
+ • A description of the bug behavior.
+ • A short script or "recipe" which exercises the bug and may be used
+ to reproduce it.
+
+‘bashbug’ inserts the first three items automatically into the template
+it provides for filing a bug report.
+
+ Please send all reports concerning this manual to <bug-bash@gnu.org>.
+
+\1f
+File: bashref.info, Node: Major Differences From The Bourne Shell, Next: GNU Free Documentation License, Prev: Reporting Bugs, Up: Top
+
+Appendix B Major Differences From The Bourne Shell
+**************************************************
+
+Bash implements essentially the same grammar, parameter and variable
+expansion, redirection, and quoting as the Bourne Shell. Bash uses the
+POSIX standard as the specification of how these features are to be
+implemented and how they should behave. There are some differences
+between the traditional Bourne shell and Bash; this section quickly
+details the differences of significance. A number of these differences
+are explained in greater depth in previous sections. This section uses
+the version of ‘sh’ included in SVR4.2 (the last version of the
+historical Bourne shell) as the baseline reference.
+
+ • Bash is POSIX-conformant, even where the POSIX specification
+ differs from traditional ‘sh’ behavior (*note Bash POSIX Mode::).
+
+ • Bash has multi-character invocation options (*note Invoking
+ Bash::).
+
+ • The Bash restricted mode is more useful (*note The Restricted
+ Shell::); the SVR4.2 shell restricted mode is too limited.
+
+ • Bash has command-line editing (*note Command Line Editing::) and
+ the ‘bind’ builtin.
+
+ • Bash provides a programmable word completion mechanism (*note
+ Programmable Completion::), and builtin commands ‘complete’,
+ ‘compgen’, and ‘compopt’, to manipulate it.
+
+ • Bash decodes a number of backslash-escape sequences in the prompt
+ string variables (‘PS0’, ‘PS1’, ‘PS2’, and ‘PS4’) (*note
+ Controlling the Prompt::).
+
+ • Bash expands and displays the ‘PS0’ prompt string variable.
+
+ • Bash runs commands from the ‘PROMPT_COMMAND’ array variable before
+ issuing each primary prompt.
+
+ • Bash has command history (*note Bash History Facilities::) and the
+ ‘history’ and ‘fc’ builtins to manipulate it. The Bash history
+ list maintains timestamp information and uses the value of the
+ ‘HISTTIMEFORMAT’ variable to display it.
+
+ • Bash implements ‘csh’-like history expansion (*note History
+ Interaction::).
+
+ • Bash supports the ‘$'...'’ quoting syntax, which expands ANSI-C
+ backslash-escaped characters in the text between the single quotes
+ (*note ANSI-C Quoting::).
+
+ • Bash supports the ‘$"..."’ quoting syntax and performs
+ locale-specific translation of the characters between the double
+ quotes. The ‘-D’, ‘--dump-strings’, and ‘--dump-po-strings’
+ invocation options list the translatable strings found in a script
+ (*note Locale Translation::).
+
+ • Bash includes brace expansion (*note Brace Expansion::) and tilde
+ expansion (*note Tilde Expansion::).
+
+ • Bash implements command aliases and the ‘alias’ and ‘unalias’
+ builtins (*note Aliases::).
+
+ • Bash implements the ‘!’ reserved word to negate the return value of
+ a pipeline (*note Pipelines::). This is very useful when an ‘if’
+ statement needs to act only if a test fails. The Bash ‘-o
+ pipefail’ option to ‘set’ will cause a pipeline to return a failure
+ status if any command fails (*note The Set Builtin::).
+
+ • Bash has the ‘time’ reserved word and command timing (*note
+ Pipelines::). The display of the timing statistics may be
+ controlled with the ‘TIMEFORMAT’ variable.
+
+ • Bash provides coprocesses and the ‘coproc’ reserved word (*note
+ Coprocesses::).
+
+ • Bash implements the ‘for (( EXPR1 ; EXPR2 ; EXPR3 ))’ arithmetic
+ for command, similar to the C language (*note Looping
+ Constructs::).
+
+ • Bash includes the ‘select’ compound command, which allows the
+ generation of simple menus (*note Conditional Constructs::).
+
+ • Bash includes the ‘[[’ compound command, which makes conditional
+ testing part of the shell grammar (*note Conditional Constructs::),
+ including optional regular expression matching.
+
+ • Bash provides optional case-insensitive matching for the ‘case’ and
+ ‘[[’ constructs (*note Conditional Constructs::).
+
+ • Bash provides additional ‘case’ statement action list terminators:
+ ‘;&’ and ‘;;&’ (*note Conditional Constructs::).
+
+ • Bash provides shell arithmetic, the ‘((’ compound command (*note
+ Conditional Constructs::), the ‘let’ builtin, and arithmetic
+ expansion (*note Shell Arithmetic::).
+
+ • Bash has one-dimensional array variables (*note Arrays::), and the
+ appropriate variable expansions and assignment syntax to use them.
+ Several of the Bash builtins take options to act on arrays. Bash
+ provides a number of built-in array variables.
+
+ • Variables present in the shell's initial environment are
+ automatically exported to child processes (*note Command Execution
+ Environment::). The Bourne shell does not normally do this unless
+ the variables are explicitly marked using the ‘export’ command.
+
+ • Bash can expand positional parameters beyond ‘$9’ using ‘${NUM}’
+ (*note Shell Parameter Expansion::).
+
+ • Bash supports the ‘+=’ assignment operator, which appends to the
+ value of the variable named on the left hand side (*note Shell
+ Parameters::).
+
+ • Bash includes the POSIX pattern removal ‘%’, ‘#’, ‘%%’ and ‘##’
+ expansions to remove leading or trailing substrings from variable
+ values (*note Shell Parameter Expansion::).
+
+ • The expansion ‘${#xx}’, which returns the length of ‘${xx}’, is
+ supported (*note Shell Parameter Expansion::).
+
+ • The expansion ‘${var:’OFFSET‘[:’LENGTH‘]}’, which expands to the
+ substring of ‘var’'s value of length LENGTH, beginning at OFFSET,
+ is present (*note Shell Parameter Expansion::).
+
+ • The expansion ‘${VAR/[/]’PATTERN‘[/’REPLACEMENT‘]}’, which matches
+ PATTERN and replaces it with REPLACEMENT in the value of VAR, is
+ available (*note Shell Parameter Expansion::), with a mechanism to
+ use the matched text in REPLACEMENT.
+
+ • The expansion ‘${!PREFIX*}’ expansion, which expands to the names
+ of all shell variables whose names begin with PREFIX, is available
+ (*note Shell Parameter Expansion::).
+
+ • Bash has indirect variable expansion using ‘${!word}’ (*note Shell
+ Parameter Expansion::) and implements the ‘nameref’ variable
+ attribute for automatic indirect variable expansion.
+
+ • Bash includes a set of parameter transformation word expansions of
+ the form ‘${var@X}’, where ‘X’ specifies the transformation (*note
+ Shell Parameter Expansion::).
+
+ • The POSIX ‘$()’ form of command substitution is implemented (*note
+ Command Substitution::), and preferred to the Bourne shell's ‘``’
+ (which is also implemented for backwards compatibility).
+
+ • Bash implements a variant of command substitution that runs the
+ enclosed command in the current shell execution environment: ‘${
+ COMMAND;}’ or ‘${|COMMAND;}’ (*note Command Substitution::).
+
+ • Bash has process substitution (*note Process Substitution::).
+
+ • Bash automatically assigns variables that provide information about
+ the current user (‘UID’, ‘EUID’, and ‘GROUPS’), the current host
+ (‘HOSTTYPE’, ‘OSTYPE’, ‘MACHTYPE’, and ‘HOSTNAME’), and the
+ instance of Bash that is running (‘BASH’, ‘BASH_VERSION’, and
+ ‘BASH_VERSINFO’). *Note Bash Variables::, for details.
+
+ • Bash uses many variables to provide functionality and customize
+ shell behavior that the Bourne shell does not. Examples include
+ ‘RANDOM’, ‘SRANDOM’, ‘EPOCHSECONDS’, ‘EPOCHREALTIME’, ‘TIMEFORMAT’,
+ ‘BASHPID’, ‘BASH_XTRACEFD’, ‘GLOBIGNORE’, ‘HISTIGNORE’, and
+ ‘BASH_VERSION’. *Note Bash Variables::, for a complete list.
+
+ • Bash uses the ‘GLOBSORT’ shell variable to control how to sort the
+ results of filename expansion (*note Filename Expansion::).
+
+ • Bash uses the ‘IFS’ variable to split only the results of
+ expansion, not all words (*note Word Splitting::). This closes a
+ longstanding shell security hole.
+
+ • The filename expansion bracket expression code uses ‘!’ and ‘^’ to
+ negate the set of characters between the brackets (*note Filename
+ Expansion::). The Bourne shell uses only ‘!’.
+
+ • Bash implements the full set of POSIX filename expansion operators,
+ including character classes, equivalence classes, and collating
+ symbols (*note Filename Expansion::).
+
+ • Bash implements extended pattern matching features when the
+ ‘extglob’ shell option is enabled (*note Pattern Matching::).
+
+ • The ‘globstar’ shell option extends filename expansion to
+ recursively scan directories and subdirectories for matching
+ filenames (*note Pattern Matching::).
+
+ • It is possible to have a variable and a function with the same
+ name; ‘sh’ does not separate the two name spaces.
+
+ • Bash functions are permitted to have local variables using the
+ ‘local’ builtin, and thus users can write useful recursive
+ functions (*note Bash Builtins::).
+
+ • Bash performs filename expansion on filenames specified as operands
+ to input and output redirection operators (*note Redirections::).
+
+ • Bash contains the ‘<>’ redirection operator, allowing a file to be
+ opened for both reading and writing, and the ‘&>’ redirection
+ operator, for directing standard output and standard error to the
+ same file (*note Redirections::).
+
+ • Bash includes the ‘<<<’ redirection operator, allowing a string to
+ be used as the standard input to a command (*note Redirections::).
+
+ • Bash implements the ‘[n]<&WORD’ and ‘[n]>&WORD’ redirection
+ operators, which move one file descriptor to another.
+
+ • Bash treats a number of filenames specially when they are used in
+ redirection operators (*note Redirections::).
+
+ • Bash provides the {VAR}<WORD capability to have the shell allocate
+ file descriptors for redirections and assign them to VAR (*note
+ Redirections::). This works with multiple redirection operators.
+
+ • Bash can open network connections to arbitrary machines and
+ services with the redirection operators (*note Redirections::).
+
+ • The ‘noclobber’ option is available to avoid overwriting existing
+ files with output redirection (*note The Set Builtin::). The ‘>|’
+ redirection operator may be used to override ‘noclobber’.
+
+ • Variable assignments preceding commands affect only that command,
+ even builtins and functions (*note Environment::). In ‘sh’, all
+ variable assignments preceding commands are global unless the
+ command is executed from the file system.
+
+ • Bash includes a number of features to support a separate debugger
+ for shell scripts: variables (‘BASH_ARGC’, ‘BASH_ARGV’,
+ ‘BASH_LINENO’, ‘BASH_SOURCE’), the ‘DEBUG’, ‘RETURN’, and ‘ERR’
+ traps, ‘declare -F’, and the ‘caller’ builtin.
+
+ • Bash implements a ‘csh’-like directory stack, and provides the
+ ‘pushd’, ‘popd’, and ‘dirs’ builtins to manipulate it (*note The
+ Directory Stack::). Bash also makes the directory stack visible as
+ the value of the ‘DIRSTACK’ shell variable.
+
+ • Bash allows a function to override a builtin with the same name,
+ and provides access to that builtin's functionality within the
+ function via the ‘builtin’ and ‘command’ builtins (*note Bash
+ Builtins::).
+
+ • Bash includes the ‘caller’ builtin (*note Bash Builtins::), which
+ displays the context of any active subroutine call (a shell
+ function or a script executed with the ‘.’ or ‘source’ builtins).
+ This supports the Bash debugger.
+
+ • The Bash ‘cd’ and ‘pwd’ builtins (*note Bourne Shell Builtins::)
+ each take ‘-L’ and ‘-P’ options to switch between logical and
+ physical modes.
+
+ • The ‘command’ builtin allows selectively skipping shell functions
+ when performing command lookup (*note Bash Builtins::).
+
+ • Bash uses the ‘declare’ builtin to modify the full set of variable
+ and function attributes, and to assign values to variables.
+
+ • The ‘disown’ builtin can remove a job from the internal shell job
+ table (*note Job Control Builtins::) or suppress sending ‘SIGHUP’
+ to a job when the shell exits as the result of a ‘SIGHUP’.
+
+ • The ‘enable’ builtin (*note Bash Builtins::) can enable or disable
+ individual builtins and implements support for dynamically loading
+ builtin commands from shared objects.
+
+ • The Bash ‘exec’ builtin takes additional options that allow users
+ to control the contents of the environment passed to the executed
+ command, and what the zeroth argument to the command is to be
+ (*note Bourne Shell Builtins::).
+
+ • Shell functions may be exported to children via the environment
+ using ‘export -f’ (*note Shell Functions::).
+
+ • The Bash ‘export’ and ‘readonly’ builtins (*note Bourne Shell
+ Builtins::) can take a ‘-f’ option to act on shell functions, a
+ ‘-p’ option to display variables with various attributes set in a
+ format that can be used as shell input, a ‘-n’ option to remove
+ various variable attributes, and ‘name=value’ arguments to set
+ variable attributes and values simultaneously.
+
+ • The Bash ‘hash’ builtin allows a name to be associated with an
+ arbitrary filename, even when that filename cannot be found by
+ searching the ‘$PATH’, using ‘hash -p’ (*note Bourne Shell
+ Builtins::).
+
+ • Bash includes a ‘help’ builtin for quick reference to shell
+ facilities (*note Bash Builtins::).
+
+ • Bash includes the ‘mapfile’ builtin to quickly read the contents of
+ a file into an indexed array variable (*note Bash Builtins::).
+
+ • The ‘printf’ builtin is available to display formatted output
+ (*note Bash Builtins::), and has additional custom format
+ specifiers and an option to assign the formatted output directly to
+ a shell variable.
+
+ • The Bash ‘read’ builtin (*note Bash Builtins::) will read a line
+ ending in ‘\’ with the ‘-r’ option, and will use the ‘REPLY’
+ variable as a default if no non-option arguments are supplied.
+
+ • The ‘read’ builtin (*note Bash Builtins::) accepts a prompt string
+ with the ‘-p’ option and will use Readline to obtain the line when
+ given the ‘-e’ or ‘-E’ options, with the ability to insert text
+ into the line using the ‘-i’ option. The ‘read’ builtin also has
+ additional options to control input: the ‘-s’ option will turn off
+ echoing of input characters as they are read, the ‘-t’ option will
+ allow ‘read’ to time out if input does not arrive within a
+ specified number of seconds, the ‘-n’ option will allow reading
+ only a specified number of characters rather than a full line, and
+ the ‘-d’ option will read until a particular character rather than
+ newline.
+
+ • The ‘return’ builtin may be used to abort execution of scripts
+ executed with the ‘.’ or ‘source’ builtins (*note Bourne Shell
+ Builtins::).
+
+ • Bash has much more optional behavior controllable with the ‘set’
+ builtin (*note The Set Builtin::).
+
+ • The ‘-x’ (‘xtrace’) option displays commands other than simple
+ commands when performing an execution trace (*note The Set
+ Builtin::).
+
+ • Bash includes the ‘shopt’ builtin, for finer control of shell
+ optional capabilities (*note The Shopt Builtin::), and allows these
+ options to be set and unset at shell invocation (*note Invoking
+ Bash::).
+
+ • The ‘test’ builtin (*note Bourne Shell Builtins::) is slightly
+ different, as it implements the POSIX algorithm, which specifies
+ the behavior based on the number of arguments.
+
+ • The ‘trap’ builtin (*note Bourne Shell Builtins::) allows a ‘DEBUG’
+ pseudo-signal specification, similar to ‘EXIT’. Commands specified
+ with a ‘DEBUG’ trap are executed before every simple command, ‘for’
+ command, ‘case’ command, ‘select’ command, every arithmetic ‘for’
+ command, and before the first command executes in a shell function.
+ The ‘DEBUG’ trap is not inherited by shell functions unless the
+ function has been given the ‘trace’ attribute or the ‘functrace’
+ option has been enabled using the ‘shopt’ builtin. The ‘extdebug’
+ shell option has additional effects on the ‘DEBUG’ trap.
+
+ The ‘trap’ builtin (*note Bourne Shell Builtins::) allows an ‘ERR’
+ pseudo-signal specification, similar to ‘EXIT’ and ‘DEBUG’.
+ Commands specified with an ‘ERR’ trap are executed after a simple
+ command fails, with a few exceptions. The ‘ERR’ trap is not
+ inherited by shell functions unless the ‘-o errtrace’ option to the
+ ‘set’ builtin is enabled.
+
+ The ‘trap’ builtin (*note Bourne Shell Builtins::) allows a
+ ‘RETURN’ pseudo-signal specification, similar to ‘EXIT’ and
+ ‘DEBUG’. Commands specified with a ‘RETURN’ trap are executed
+ before execution resumes after a shell function or a shell script
+ executed with ‘.’ or ‘source’ returns. The ‘RETURN’ trap is not
+ inherited by shell functions unless the function has been given the
+ ‘trace’ attribute or the ‘functrace’ option has been enabled using
+ the ‘shopt’ builtin.
+
+ • The Bash ‘type’ builtin is more extensive and gives more
+ information about the names it finds (*note Bash Builtins::).
+
+ • The ‘ulimit’ builtin provides control over many more per-process
+ resources (*note Bash Builtins::).
+
+ • The Bash ‘umask’ builtin uses the ‘-p’ option to display the output
+ in the form of a ‘umask’ command that may be reused as input (*note
+ Bourne Shell Builtins::).
+
+ • The Bash ‘wait’ builtin has a ‘-n’ option to wait for the next
+ child to exit, possibly selecting from a list of supplied jobs, and
+ the ‘-p’ option to store information about a terminated child
+ process in a shell variable.
+
+ • The SVR4.2 shell behaves differently when invoked as ‘jsh’ (it
+ turns on job control).
+
+ • The SVR4.2 shell has two privilege-related builtins (‘mldmode’ and
+ ‘priv’) not present in Bash.
+
+ • Bash does not have the ‘stop’ or ‘newgrp’ builtins.
+
+ • Bash does not use the ‘SHACCT’ variable or perform shell
+ accounting.
+
+ • The SVR4.2 ‘sh’ uses a ‘TIMEOUT’ variable like Bash uses ‘TMOUT’.
+
+More features unique to Bash may be found in *note Bash Features::.
+
+B.1 Implementation Differences From The SVR4.2 Shell
+====================================================
+
+Since Bash is a completely new implementation, it does not suffer from
+many of the limitations of the SVR4.2 shell. For instance:
+
+ • Bash does not fork a subshell when redirecting into or out of a
+ shell control structure such as an ‘if’ or ‘while’ statement.
+
+ • Bash does not allow unbalanced quotes. The SVR4.2 shell will
+ silently insert a needed closing quote at ‘EOF’ under certain
+ circumstances. This can be the cause of some hard-to-find errors.
+
+ • The SVR4.2 shell uses a baroque memory management scheme based on
+ trapping ‘SIGSEGV’. If the shell is started from a process with
+ ‘SIGSEGV’ blocked (e.g., by using the ‘system()’ C library function
+ call), it misbehaves badly.
+
+ • In a questionable attempt at security, the SVR4.2 shell, when
+ invoked without the ‘-p’ option, will alter its real and effective
+ UID and GID if they are less than some magic threshold value,
+ commonly 100. This can lead to unexpected results.
+
+ • The SVR4.2 shell does not allow users to trap ‘SIGSEGV’, ‘SIGALRM’,
+ or ‘SIGCHLD’.
+
+ • The SVR4.2 shell does not allow the ‘IFS’, ‘MAILCHECK’, ‘PATH’,
+ ‘PS1’, or ‘PS2’ variables to be unset.
+
+ • The SVR4.2 shell treats ‘^’ as the undocumented equivalent of ‘|’.
+
+ • Bash allows multiple option arguments when it is invoked (‘-x -v’);
+ the SVR4.2 shell allows only one option argument (‘-xv’). In fact,
+ some versions of the shell dump core if the second argument begins
+ with a ‘-’.
+
+ • The SVR4.2 shell exits a script if any builtin fails; Bash exits a
+ script only if one of the POSIX special builtins fails, and only
+ for certain failures, as enumerated in the POSIX standard.
+
+ • If the ‘lastpipe’ option is enabled, and job control is not active,
+ Bash runs the last element of a pipeline in the current shell
+ execution environment.
+
+\1f
+File: bashref.info, Node: GNU Free Documentation License, Next: Indexes, Prev: Major Differences From The Bourne Shell, Up: Top
+
+Appendix C GNU Free Documentation License
+*****************************************
+
+ Version 1.3, 3 November 2008
+
+ Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
+ <http://fsf.org/>
+
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+ 0. PREAMBLE
+
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+ functional and useful document “free” in the sense of freedom: to
+ assure everyone the effective freedom to copy and redistribute it,
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+ being considered responsible for modifications made by others.
+
+ This License is a kind of "copyleft", which means that derivative
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+ It complements the GNU General Public License, which is a copyleft
+ license designed for free software.
+
+ We have designed this License in order to use it for manuals for
+ free software, because free software needs free documentation: a
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+ recommend this License principally for works whose purpose is
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+
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+
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+ If the required texts for either cover are too voluminous to fit
+ legibly, you should put the first ones listed (as many as fit
+ reasonably) on the actual cover, and continue the rest onto
+ adjacent pages.
+
+ If you publish or distribute Opaque copies of the Document
+ numbering more than 100, you must either include a machine-readable
+ Transparent copy along with each Opaque copy, or state in or with
+ each Opaque copy a computer-network location from which the general
+ network-using public has access to download using public-standard
+ network protocols a complete Transparent copy of the Document, free
+ of added material. If you use the latter option, you must take
+ reasonably prudent steps, when you begin distribution of Opaque
+ copies in quantity, to ensure that this Transparent copy will
+ remain thus accessible at the stated location until at least one
+ year after the last time you distribute an Opaque copy (directly or
+ through your agents or retailers) of that edition to the public.
+
+ It is requested, but not required, that you contact the authors of
+ the Document well before redistributing any large number of copies,
+ to give them a chance to provide you with an updated version of the
+ Document.
+
+ 4. MODIFICATIONS
+
+ You may copy and distribute a Modified Version of the Document
+ under the conditions of sections 2 and 3 above, provided that you
+ release the Modified Version under precisely this License, with the
+ Modified Version filling the role of the Document, thus licensing
+ distribution and modification of the Modified Version to whoever
+ possesses a copy of it. In addition, you must do these things in
+ the Modified Version:
+
+ A. Use in the Title Page (and on the covers, if any) a title
+ distinct from that of the Document, and from those of previous
+ versions (which should, if there were any, be listed in the
+ History section of the Document). You may use the same title
+ as a previous version if the original publisher of that
+ version gives permission.
+
+ B. List on the Title Page, as authors, one or more persons or
+ entities responsible for authorship of the modifications in
+ the Modified Version, together with at least five of the
+ principal authors of the Document (all of its principal
+ authors, if it has fewer than five), unless they release you
+ from this requirement.
+
+ C. State on the Title page the name of the publisher of the
+ Modified Version, as the publisher.
+
+ D. Preserve all the copyright notices of the Document.
+
+ E. Add an appropriate copyright notice for your modifications
+ adjacent to the other copyright notices.
+
+ F. Include, immediately after the copyright notices, a license
+ notice giving the public permission to use the Modified
+ Version under the terms of this License, in the form shown in
+ the Addendum below.
+
+ G. Preserve in that license notice the full lists of Invariant
+ Sections and required Cover Texts given in the Document's
+ license notice.
+
+ H. Include an unaltered copy of this License.
+
+ I. Preserve the section Entitled "History", Preserve its Title,
+ and add to it an item stating at least the title, year, new
+ authors, and publisher of the Modified Version as given on the
+ Title Page. If there is no section Entitled "History" in the
+ Document, create one stating the title, year, authors, and
+ publisher of the Document as given on its Title Page, then add
+ an item describing the Modified Version as stated in the
+ previous sentence.
+
+ J. Preserve the network location, if any, given in the Document
+ for public access to a Transparent copy of the Document, and
+ likewise the network locations given in the Document for
+ previous versions it was based on. These may be placed in the
+ "History" section. You may omit a network location for a work
+ that was published at least four years before the Document
+ itself, or if the original publisher of the version it refers
+ to gives permission.
+
+ K. For any section Entitled "Acknowledgements" or "Dedications",
+ Preserve the Title of the section, and preserve in the section
+ all the substance and tone of each of the contributor
+ acknowledgements and/or dedications given therein.
+
+ L. Preserve all the Invariant Sections of the Document, unaltered
+ in their text and in their titles. Section numbers or the
+ equivalent are not considered part of the section titles.
+
+ M. Delete any section Entitled "Endorsements". Such a section
+ may not be included in the Modified Version.
+
+ N. Do not retitle any existing section to be Entitled
+ "Endorsements" or to conflict in title with any Invariant
+ Section.
+
+ O. Preserve any Warranty Disclaimers.
+
+ If the Modified Version includes new front-matter sections or
+ appendices that qualify as Secondary Sections and contain no
+ material copied from the Document, you may at your option designate
+ some or all of these sections as invariant. To do this, add their
+ titles to the list of Invariant Sections in the Modified Version's
+ license notice. These titles must be distinct from any other
+ section titles.
+
+ You may add a section Entitled "Endorsements", provided it contains
+ nothing but endorsements of your Modified Version by various
+ parties--for example, statements of peer review or that the text
+ has been approved by an organization as the authoritative
+ definition of a standard.
+
+ You may add a passage of up to five words as a Front-Cover Text,
+ and a passage of up to 25 words as a Back-Cover Text, to the end of
+ the list of Cover Texts in the Modified Version. Only one passage
+ of Front-Cover Text and one of Back-Cover Text may be added by (or
+ through arrangements made by) any one entity. If the Document
+ already includes a cover text for the same cover, previously added
+ by you or by arrangement made by the same entity you are acting on
+ behalf of, you may not add another; but you may replace the old
+ one, on explicit permission from the previous publisher that added
+ the old one.
+
+ The author(s) and publisher(s) of the Document do not by this
+ License give permission to use their names for publicity for or to
+ assert or imply endorsement of any Modified Version.
+
+ 5. COMBINING DOCUMENTS
+
+ You may combine the Document with other documents released under
+ this License, under the terms defined in section 4 above for
+ modified versions, provided that you include in the combination all
+ of the Invariant Sections of all of the original documents,
+ unmodified, and list them all as Invariant Sections of your
+ combined work in its license notice, and that you preserve all
+ their Warranty Disclaimers.
+
+ The combined work need only contain one copy of this License, and
+ multiple identical Invariant Sections may be replaced with a single
+ copy. If there are multiple Invariant Sections with the same name
+ but different contents, make the title of each such section unique
+ by adding at the end of it, in parentheses, the name of the
+ original author or publisher of that section if known, or else a
+ unique number. Make the same adjustment to the section titles in
+ the list of Invariant Sections in the license notice of the
+ combined work.
+
+ In the combination, you must combine any sections Entitled
+ "History" in the various original documents, forming one section
+ Entitled "History"; likewise combine any sections Entitled
+ "Acknowledgements", and any sections Entitled "Dedications". You
+ must delete all sections Entitled "Endorsements."
+
+ 6. COLLECTIONS OF DOCUMENTS
+
+ You may make a collection consisting of the Document and other
+ documents released under this License, and replace the individual
+ copies of this License in the various documents with a single copy
+ that is included in the collection, provided that you follow the
+ rules of this License for verbatim copying of each of the documents
+ in all other respects.
+
+ You may extract a single document from such a collection, and
+ distribute it individually under this License, provided you insert
+ a copy of this License into the extracted document, and follow this
+ License in all other respects regarding verbatim copying of that
+ document.
+
+ 7. AGGREGATION WITH INDEPENDENT WORKS
+
+ A compilation of the Document or its derivatives with other
+ separate and independent documents or works, in or on a volume of a
+ storage or distribution medium, is called an "aggregate" if the
+ copyright resulting from the compilation is not used to limit the
+ legal rights of the compilation's users beyond what the individual
+ works permit. When the Document is included in an aggregate, this
+ License does not apply to the other works in the aggregate which
+ are not themselves derivative works of the Document.
+
+ If the Cover Text requirement of section 3 is applicable to these
+ copies of the Document, then if the Document is less than one half
+ of the entire aggregate, the Document's Cover Texts may be placed
+ on covers that bracket the Document within the aggregate, or the
+ electronic equivalent of covers if the Document is in electronic
+ form. Otherwise they must appear on printed covers that bracket
+ the whole aggregate.
+
+ 8. TRANSLATION
+
+ Translation is considered a kind of modification, so you may
+ distribute translations of the Document under the terms of section
+ 4. Replacing Invariant Sections with translations requires special
+ permission from their copyright holders, but you may include
+ translations of some or all Invariant Sections in addition to the
+ original versions of these Invariant Sections. You may include a
+ translation of this License, and all the license notices in the
+ Document, and any Warranty Disclaimers, provided that you also
+ include the original English version of this License and the
+ original versions of those notices and disclaimers. In case of a
+ disagreement between the translation and the original version of
+ this License or a notice or disclaimer, the original version will
+ prevail.
+
+ If a section in the Document is Entitled "Acknowledgements",
+ "Dedications", or "History", the requirement (section 4) to
+ Preserve its Title (section 1) will typically require changing the
+ actual title.
+
+ 9. TERMINATION
+
+ You may not copy, modify, sublicense, or distribute the Document
+ except as expressly provided under this License. Any attempt
+ otherwise to copy, modify, sublicense, or distribute it is void,
+ and will automatically terminate your rights under this License.
+
+ However, if you cease all violation of this License, then your
+ license from a particular copyright holder is reinstated (a)
+ provisionally, unless and until the copyright holder explicitly and
+ finally terminates your license, and (b) permanently, if the
+ copyright holder fails to notify you of the violation by some
+ reasonable means prior to 60 days after the cessation.
+
+ Moreover, your license from a particular copyright holder is
+ reinstated permanently if the copyright holder notifies you of the
+ violation by some reasonable means, this is the first time you have
+ received notice of violation of this License (for any work) from
+ that copyright holder, and you cure the violation prior to 30 days
+ after your receipt of the notice.
+
+ Termination of your rights under this section does not terminate
+ the licenses of parties who have received copies or rights from you
+ under this License. If your rights have been terminated and not
+ permanently reinstated, receipt of a copy of some or all of the
+ same material does not give you any rights to use it.
+
+ 10. FUTURE REVISIONS OF THIS LICENSE
+
+ The Free Software Foundation may publish new, revised versions of
+ the GNU Free Documentation License from time to time. Such new
+ versions will be similar in spirit to the present version, but may
+ differ in detail to address new problems or concerns. See
+ <http://www.gnu.org/copyleft/>.
+
+ Each version of the License is given a distinguishing version
+ number. If the Document specifies that a particular numbered
+ version of this License "or any later version" applies to it, you
+ have the option of following the terms and conditions either of
+ that specified version or of any later version that has been
+ published (not as a draft) by the Free Software Foundation. If the
+ Document does not specify a version number of this License, you may
+ choose any version ever published (not as a draft) by the Free
+ Software Foundation. If the Document specifies that a proxy can
+ decide which future versions of this License can be used, that
+ proxy's public statement of acceptance of a version permanently
+ authorizes you to choose that version for the Document.
+
+ 11. RELICENSING
+
+ "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
+ World Wide Web server that publishes copyrightable works and also
+ provides prominent facilities for anybody to edit those works. A
+ public wiki that anybody can edit is an example of such a server.
+ A "Massive Multiauthor Collaboration" (or "MMC") contained in the
+ site means any set of copyrightable works thus published on the MMC
+ site.
+
+ "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
+ license published by Creative Commons Corporation, a not-for-profit
+ corporation with a principal place of business in San Francisco,
+ California, as well as future copyleft versions of that license
+ published by that same organization.
+
+ "Incorporate" means to publish or republish a Document, in whole or
+ in part, as part of another Document.
+
+ An MMC is "eligible for relicensing" if it is licensed under this
+ License, and if all works that were first published under this
+ License somewhere other than this MMC, and subsequently
+ incorporated in whole or in part into the MMC, (1) had no cover
+ texts or invariant sections, and (2) were thus incorporated prior
+ to November 1, 2008.
+
+ The operator of an MMC Site may republish an MMC contained in the
+ site under CC-BY-SA on the same site at any time before August 1,
+ 2009, provided the MMC is eligible for relicensing.
+
+ADDENDUM: How to use this License for your documents
+====================================================
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and license
+notices just after the title page:
+
+ Copyright (C) YEAR YOUR NAME.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
+ Texts. A copy of the license is included in the section entitled ``GNU
+ Free Documentation License''.
+
+ If you have Invariant Sections, Front-Cover Texts and Back-Cover
+Texts, replace the "with...Texts." line with this:
+
+ with the Invariant Sections being LIST THEIR TITLES, with
+ the Front-Cover Texts being LIST, and with the Back-Cover Texts
+ being LIST.
+
+ If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+
+ If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of free
+software license, such as the GNU General Public License, to permit
+their use in free software.
+
+\1f
+File: bashref.info, Node: Indexes, Prev: GNU Free Documentation License, Up: Top
+
+Appendix D Indexes
+******************
+
+* Menu:
+
+* Builtin Index:: Index of Bash builtin commands.
+* Reserved Word Index:: Index of Bash reserved words.
+* Variable Index:: Quick reference helps you find the
+ variable you want.
+* Function Index:: Index of bindable Readline functions.
+* Concept Index:: General index for concepts described in
+ this manual.
+
+\1f
+File: bashref.info, Node: Builtin Index, Next: Reserved Word Index, Up: Indexes
+
+D.1 Index of Shell Builtin Commands
+===================================
+
+\0\b[index\0\b]
+* Menu:
+
+* :: Bourne Shell Builtins.
+ (line 11)
+* .: Bourne Shell Builtins.
+ (line 17)
+* [: Bourne Shell Builtins.
+ (line 340)
+* alias: Bash Builtins. (line 11)
+* bg: Job Control Builtins.
+ (line 7)
+* bind: Bash Builtins. (line 24)
+* break: Bourne Shell Builtins.
+ (line 47)
+* builtin: Bash Builtins. (line 133)
+* caller: Bash Builtins. (line 142)
+* cd: Bourne Shell Builtins.
+ (line 55)
+* command: Bash Builtins. (line 159)
+* compgen: Programmable Completion Builtins.
+ (line 12)
+* complete: Programmable Completion Builtins.
+ (line 37)
+* compopt: Programmable Completion Builtins.
+ (line 258)
+* continue: Bourne Shell Builtins.
+ (line 107)
+* declare: Bash Builtins. (line 179)
+* dirs: Directory Stack Builtins.
+ (line 7)
+* disown: Job Control Builtins.
+ (line 120)
+* echo: Bash Builtins. (line 284)
+* enable: Bash Builtins. (line 337)
+* eval: Bourne Shell Builtins.
+ (line 116)
+* exec: Bourne Shell Builtins.
+ (line 124)
+* exit: Bourne Shell Builtins.
+ (line 146)
+* export: Bourne Shell Builtins.
+ (line 153)
+* false: Bourne Shell Builtins.
+ (line 176)
+* fc: Bash History Builtins.
+ (line 10)
+* fg: Job Control Builtins.
+ (line 17)
+* getopts: Bourne Shell Builtins.
+ (line 181)
+* hash: Bourne Shell Builtins.
+ (line 233)
+* help: Bash Builtins. (line 375)
+* history: Bash History Builtins.
+ (line 59)
+* jobs: Job Control Builtins.
+ (line 28)
+* kill: Job Control Builtins.
+ (line 61)
+* let: Bash Builtins. (line 404)
+* local: Bash Builtins. (line 413)
+* logout: Bash Builtins. (line 438)
+* mapfile: Bash Builtins. (line 443)
+* popd: Directory Stack Builtins.
+ (line 37)
+* printf: Bash Builtins. (line 488)
+* pushd: Directory Stack Builtins.
+ (line 71)
+* pwd: Bourne Shell Builtins.
+ (line 265)
+* read: Bash Builtins. (line 558)
+* readarray: Bash Builtins. (line 669)
+* readonly: Bourne Shell Builtins.
+ (line 277)
+* return: Bourne Shell Builtins.
+ (line 302)
+* set: The Set Builtin. (line 11)
+* shift: Bourne Shell Builtins.
+ (line 327)
+* shopt: The Shopt Builtin. (line 9)
+* source: Bash Builtins. (line 678)
+* suspend: Job Control Builtins.
+ (line 139)
+* test: Bourne Shell Builtins.
+ (line 340)
+* times: Bourne Shell Builtins.
+ (line 440)
+* trap: Bourne Shell Builtins.
+ (line 446)
+* true: Bourne Shell Builtins.
+ (line 512)
+* type: Bash Builtins. (line 683)
+* typeset: Bash Builtins. (line 720)
+* ulimit: Bash Builtins. (line 726)
+* umask: Bourne Shell Builtins.
+ (line 517)
+* unalias: Bash Builtins. (line 834)
+* unset: Bourne Shell Builtins.
+ (line 535)
+* wait: Job Control Builtins.
+ (line 86)
+
+\1f
+File: bashref.info, Node: Reserved Word Index, Next: Variable Index, Prev: Builtin Index, Up: Indexes
+
+D.2 Index of Shell Reserved Words
+=================================
+
+\0\b[index\0\b]
+* Menu:
+
+* !: Pipelines. (line 9)
+* [[: Conditional Constructs.
+ (line 128)
+* ]]: Conditional Constructs.
+ (line 128)
+* {: Command Grouping. (line 21)
+* }: Command Grouping. (line 21)
+* case: Conditional Constructs.
+ (line 28)
+* do: Looping Constructs. (line 12)
+* done: Looping Constructs. (line 12)
+* elif: Conditional Constructs.
+ (line 7)
+* else: Conditional Constructs.
+ (line 7)
+* esac: Conditional Constructs.
+ (line 28)
+* fi: Conditional Constructs.
+ (line 7)
+* for: Looping Constructs. (line 32)
+* function: Shell Functions. (line 13)
+* if: Conditional Constructs.
+ (line 7)
+* in: Conditional Constructs.
+ (line 28)
+* select: Conditional Constructs.
+ (line 84)
+* then: Conditional Constructs.
+ (line 7)
+* time: Pipelines. (line 9)
+* until: Looping Constructs. (line 12)
+* while: Looping Constructs. (line 22)
+
+\1f
+File: bashref.info, Node: Variable Index, Next: Function Index, Prev: Reserved Word Index, Up: Indexes
+
+D.3 Parameter and Variable Index
+================================
+
+\0\b[index\0\b]
+* Menu:
+
+* _: Bash Variables. (line 13)
+* -: Special Parameters. (line 48)
+* !: Special Parameters. (line 57)
+* ?: Special Parameters. (line 44)
+* @: Special Parameters. (line 23)
+* *: Special Parameters. (line 10)
+* #: Special Parameters. (line 41)
+* $: Special Parameters. (line 53)
+* $_: Bash Variables. (line 14)
+* $-: Special Parameters. (line 49)
+* $!: Special Parameters. (line 58)
+* $?: Special Parameters. (line 45)
+* $@: Special Parameters. (line 24)
+* $*: Special Parameters. (line 11)
+* $#: Special Parameters. (line 42)
+* $$: Special Parameters. (line 54)
+* $0: Special Parameters. (line 63)
+* 0: Special Parameters. (line 62)
+* active-region-end-color: Readline Init File Syntax.
+ (line 51)
+* active-region-start-color: Readline Init File Syntax.
+ (line 38)
+* auto_resume: Job Control Variables.
+ (line 6)
+* BASH: Bash Variables. (line 24)
+* BASH_ALIASES: Bash Variables. (line 44)
+* BASH_ARGC: Bash Variables. (line 53)
+* BASH_ARGV: Bash Variables. (line 67)
+* BASH_ARGV0: Bash Variables. (line 80)
+* BASH_CMDS: Bash Variables. (line 88)
+* BASH_COMMAND: Bash Variables. (line 97)
+* BASH_COMPAT: Bash Variables. (line 104)
+* BASH_ENV: Bash Variables. (line 120)
+* BASH_EXECUTION_STRING: Bash Variables. (line 126)
+* BASH_LINENO: Bash Variables. (line 129)
+* BASH_LOADABLES_PATH: Bash Variables. (line 139)
+* BASH_MONOSECONDS: Bash Variables. (line 143)
+* BASH_REMATCH: Bash Variables. (line 150)
+* BASH_SOURCE: Bash Variables. (line 158)
+* BASH_SUBSHELL: Bash Variables. (line 166)
+* BASH_TRAPSIG: Bash Variables. (line 172)
+* BASH_VERSINFO: Bash Variables. (line 178)
+* BASH_VERSION: Bash Variables. (line 201)
+* BASH_XTRACEFD: Bash Variables. (line 205)
+* BASHOPTS: Bash Variables. (line 27)
+* BASHPID: Bash Variables. (line 37)
+* bell-style: Readline Init File Syntax.
+ (line 64)
+* bind-tty-special-chars: Readline Init File Syntax.
+ (line 71)
+* blink-matching-paren: Readline Init File Syntax.
+ (line 81)
+* CDPATH: Bourne Shell Variables.
+ (line 9)
+* CHILD_MAX: Bash Variables. (line 217)
+* colored-completion-prefix: Readline Init File Syntax.
+ (line 86)
+* colored-stats: Readline Init File Syntax.
+ (line 96)
+* COLUMNS: Bash Variables. (line 224)
+* comment-begin: Readline Init File Syntax.
+ (line 102)
+* COMP_CWORD: Bash Variables. (line 230)
+* COMP_KEY: Bash Variables. (line 236)
+* COMP_LINE: Bash Variables. (line 242)
+* COMP_POINT: Bash Variables. (line 247)
+* COMP_TYPE: Bash Variables. (line 255)
+* COMP_WORDBREAKS: Bash Variables. (line 265)
+* COMP_WORDS: Bash Variables. (line 271)
+* completion-display-width: Readline Init File Syntax.
+ (line 106)
+* completion-ignore-case: Readline Init File Syntax.
+ (line 113)
+* completion-map-case: Readline Init File Syntax.
+ (line 118)
+* completion-prefix-display-length: Readline Init File Syntax.
+ (line 124)
+* completion-query-items: Readline Init File Syntax.
+ (line 133)
+* COMPREPLY: Bash Variables. (line 278)
+* convert-meta: Readline Init File Syntax.
+ (line 144)
+* COPROC: Bash Variables. (line 284)
+* DIRSTACK: Bash Variables. (line 288)
+* disable-completion: Readline Init File Syntax.
+ (line 156)
+* echo-control-characters: Readline Init File Syntax.
+ (line 161)
+* editing-mode: Readline Init File Syntax.
+ (line 166)
+* EMACS: Bash Variables. (line 298)
+* emacs-mode-string: Readline Init File Syntax.
+ (line 172)
+* enable-active-region The: Readline Init File Syntax.
+ (line 182)
+* enable-bracketed-paste: Readline Init File Syntax.
+ (line 195)
+* enable-keypad: Readline Init File Syntax.
+ (line 204)
+* enable-meta-key: Readline Init File Syntax.
+ (line 209)
+* ENV: Bash Variables. (line 303)
+* EPOCHREALTIME: Bash Variables. (line 308)
+* EPOCHSECONDS: Bash Variables. (line 316)
+* EUID: Bash Variables. (line 323)
+* EXECIGNORE: Bash Variables. (line 327)
+* expand-tilde: Readline Init File Syntax.
+ (line 219)
+* FCEDIT: Bash Variables. (line 339)
+* FIGNORE: Bash Variables. (line 342)
+* force-meta-prefix: Readline Init File Syntax.
+ (line 223)
+* FUNCNAME: Bash Variables. (line 348)
+* FUNCNEST: Bash Variables. (line 365)
+* GLOBIGNORE: Bash Variables. (line 370)
+* GLOBSORT: Bash Variables. (line 377)
+* GROUPS: Bash Variables. (line 415)
+* histchars: Bash Variables. (line 421)
+* HISTCMD: Bash Variables. (line 437)
+* HISTCONTROL: Bash Variables. (line 443)
+* HISTFILE: Bash Variables. (line 461)
+* HISTFILESIZE: Bash Variables. (line 467)
+* HISTIGNORE: Bash Variables. (line 481)
+* history-preserve-point: Readline Init File Syntax.
+ (line 236)
+* history-size: Readline Init File Syntax.
+ (line 242)
+* HISTSIZE: Bash Variables. (line 505)
+* HISTTIMEFORMAT: Bash Variables. (line 512)
+* HOME: Bourne Shell Variables.
+ (line 13)
+* horizontal-scroll-mode: Readline Init File Syntax.
+ (line 252)
+* HOSTFILE: Bash Variables. (line 521)
+* HOSTNAME: Bash Variables. (line 532)
+* HOSTTYPE: Bash Variables. (line 535)
+* IFS: Bourne Shell Variables.
+ (line 18)
+* IGNOREEOF: Bash Variables. (line 538)
+* input-meta: Readline Init File Syntax.
+ (line 260)
+* INPUTRC: Bash Variables. (line 547)
+* INSIDE_EMACS: Bash Variables. (line 551)
+* isearch-terminators: Readline Init File Syntax.
+ (line 271)
+* keymap: Readline Init File Syntax.
+ (line 278)
+* LANG: Creating Internationalized Scripts.
+ (line 51)
+* LANG <1>: Bash Variables. (line 557)
+* LC_ALL: Bash Variables. (line 561)
+* LC_COLLATE: Bash Variables. (line 565)
+* LC_CTYPE: Bash Variables. (line 572)
+* LC_MESSAGES: Creating Internationalized Scripts.
+ (line 51)
+* LC_MESSAGES <1>: Bash Variables. (line 577)
+* LC_NUMERIC: Bash Variables. (line 581)
+* LC_TIME: Bash Variables. (line 585)
+* LINENO: Bash Variables. (line 589)
+* LINES: Bash Variables. (line 596)
+* MACHTYPE: Bash Variables. (line 602)
+* MAIL: Bourne Shell Variables.
+ (line 24)
+* MAILCHECK: Bash Variables. (line 606)
+* MAILPATH: Bourne Shell Variables.
+ (line 29)
+* MAPFILE: Bash Variables. (line 614)
+* mark-modified-lines: Readline Init File Syntax.
+ (line 308)
+* mark-symlinked-directories: Readline Init File Syntax.
+ (line 313)
+* match-hidden-files: Readline Init File Syntax.
+ (line 318)
+* menu-complete-display-prefix: Readline Init File Syntax.
+ (line 325)
+* meta-flag: Readline Init File Syntax.
+ (line 260)
+* OLDPWD: Bash Variables. (line 618)
+* OPTARG: Bourne Shell Variables.
+ (line 36)
+* OPTERR: Bash Variables. (line 621)
+* OPTIND: Bourne Shell Variables.
+ (line 40)
+* OSTYPE: Bash Variables. (line 626)
+* output-meta: Readline Init File Syntax.
+ (line 330)
+* page-completions: Readline Init File Syntax.
+ (line 339)
+* PATH: Bourne Shell Variables.
+ (line 44)
+* PIPESTATUS: Bash Variables. (line 629)
+* POSIXLY_CORRECT: Bash Variables. (line 639)
+* PPID: Bash Variables. (line 649)
+* PROMPT_COMMAND: Bash Variables. (line 653)
+* PROMPT_DIRTRIM: Bash Variables. (line 659)
+* PS0: Bash Variables. (line 665)
+* PS1: Bourne Shell Variables.
+ (line 53)
+* PS2: Bourne Shell Variables.
+ (line 58)
+* PS3: Bash Variables. (line 670)
+* PS4: Bash Variables. (line 675)
+* PWD: Bash Variables. (line 683)
+* RANDOM: Bash Variables. (line 686)
+* READLINE_ARGUMENT: Bash Variables. (line 694)
+* READLINE_LINE: Bash Variables. (line 698)
+* READLINE_MARK: Bash Variables. (line 702)
+* READLINE_POINT: Bash Variables. (line 708)
+* REPLY: Bash Variables. (line 712)
+* revert-all-at-newline: Readline Init File Syntax.
+ (line 352)
+* search-ignore-case: Readline Init File Syntax.
+ (line 359)
+* SECONDS: Bash Variables. (line 716)
+* SHELL: Bash Variables. (line 726)
+* SHELLOPTS: Bash Variables. (line 731)
+* SHLVL: Bash Variables. (line 741)
+* show-all-if-ambiguous: Readline Init File Syntax.
+ (line 364)
+* show-all-if-unmodified: Readline Init File Syntax.
+ (line 370)
+* show-mode-in-prompt: Readline Init File Syntax.
+ (line 379)
+* skip-completed-text: Readline Init File Syntax.
+ (line 385)
+* SRANDOM: Bash Variables. (line 746)
+* TEXTDOMAIN: Creating Internationalized Scripts.
+ (line 51)
+* TEXTDOMAINDIR: Creating Internationalized Scripts.
+ (line 51)
+* TIMEFORMAT: Bash Variables. (line 755)
+* TMOUT: Bash Variables. (line 794)
+* TMPDIR: Bash Variables. (line 806)
+* UID: Bash Variables. (line 810)
+* vi-cmd-mode-string: Readline Init File Syntax.
+ (line 398)
+* vi-ins-mode-string: Readline Init File Syntax.
+ (line 409)
+* visible-stats: Readline Init File Syntax.
+ (line 420)
+
+\1f
+File: bashref.info, Node: Function Index, Next: Concept Index, Prev: Variable Index, Up: Indexes
+
+D.4 Function Index
+==================
+
+\0\b[index\0\b]
+* Menu:
+
+* abort (C-g): Miscellaneous Commands.
+ (line 10)
+* accept-line (Newline or Return): Commands For History.
+ (line 6)
+* alias-expand-line (): Miscellaneous Commands.
+ (line 134)
+* backward-char (C-b): Commands For Moving. (line 18)
+* backward-delete-char (Rubout): Commands For Text. (line 18)
+* backward-kill-line (C-x Rubout): Commands For Killing.
+ (line 11)
+* backward-kill-word (M-<DEL>): Commands For Killing.
+ (line 28)
+* backward-word (M-b): Commands For Moving. (line 26)
+* beginning-of-history (M-<): Commands For History.
+ (line 22)
+* beginning-of-line (C-a): Commands For Moving. (line 6)
+* bracketed-paste-begin (): Commands For Text. (line 35)
+* call-last-kbd-macro (C-x e): Keyboard Macros. (line 13)
+* capitalize-word (M-c): Commands For Text. (line 73)
+* character-search (C-]): Miscellaneous Commands.
+ (line 41)
+* character-search-backward (M-C-]): Miscellaneous Commands.
+ (line 45)
+* clear-display (M-C-l): Commands For Moving. (line 52)
+* clear-screen (C-l): Commands For Moving. (line 57)
+* complete (<TAB>): Commands For Completion.
+ (line 6)
+* complete-command (M-!): Commands For Completion.
+ (line 105)
+* complete-filename (M-/): Commands For Completion.
+ (line 74)
+* complete-hostname (M-@): Commands For Completion.
+ (line 97)
+* complete-into-braces (M-{): Commands For Completion.
+ (line 124)
+* complete-username (M-~): Commands For Completion.
+ (line 81)
+* complete-variable (M-$): Commands For Completion.
+ (line 89)
+* copy-backward-word (): Commands For Killing.
+ (line 62)
+* copy-forward-word (): Commands For Killing.
+ (line 67)
+* copy-region-as-kill (): Commands For Killing.
+ (line 58)
+* dabbrev-expand (): Commands For Completion.
+ (line 119)
+* delete-char (C-d): Commands For Text. (line 12)
+* delete-char-or-list (): Commands For Completion.
+ (line 68)
+* delete-horizontal-space (): Commands For Killing.
+ (line 50)
+* digit-argument (M-0, M-1, ... M--): Numeric Arguments. (line 6)
+* display-shell-version (C-x C-v): Miscellaneous Commands.
+ (line 148)
+* do-lowercase-version (M-A, M-B, M-X, ...): Miscellaneous Commands.
+ (line 14)
+* downcase-word (M-l): Commands For Text. (line 69)
+* dump-functions (): Miscellaneous Commands.
+ (line 71)
+* dump-macros (): Miscellaneous Commands.
+ (line 83)
+* dump-variables (): Miscellaneous Commands.
+ (line 77)
+* dynamic-complete-history (M-<TAB>): Commands For Completion.
+ (line 115)
+* edit-and-execute-command (C-x C-e): Miscellaneous Commands.
+ (line 143)
+* end-kbd-macro (C-x )): Keyboard Macros. (line 9)
+* end-of-file (usually C-d): Commands For Text. (line 6)
+* end-of-history (M->): Commands For History.
+ (line 25)
+* end-of-line (C-e): Commands For Moving. (line 10)
+* exchange-point-and-mark (C-x C-x): Miscellaneous Commands.
+ (line 37)
+* execute-named-command (M-x): Miscellaneous Commands.
+ (line 90)
+* export-completions (): Commands For Completion.
+ (line 44)
+* fetch-history (): Commands For History.
+ (line 109)
+* forward-backward-delete-char (): Commands For Text. (line 23)
+* forward-char (C-f): Commands For Moving. (line 14)
+* forward-search-history (C-s): Commands For History.
+ (line 35)
+* forward-word (M-f): Commands For Moving. (line 22)
+* glob-complete-word (M-g): Miscellaneous Commands.
+ (line 103)
+* glob-expand-word (C-x *): Miscellaneous Commands.
+ (line 108)
+* glob-list-expansions (C-x g): Miscellaneous Commands.
+ (line 114)
+* history-and-alias-expand-line (): Miscellaneous Commands.
+ (line 137)
+* history-expand-line (M-^): Miscellaneous Commands.
+ (line 127)
+* history-search-backward (): Commands For History.
+ (line 54)
+* history-search-forward (): Commands For History.
+ (line 61)
+* history-substring-search-backward (): Commands For History.
+ (line 68)
+* history-substring-search-forward (): Commands For History.
+ (line 74)
+* insert-comment (M-#): Miscellaneous Commands.
+ (line 59)
+* insert-completions (M-*): Commands For Completion.
+ (line 24)
+* insert-last-argument (M-. or M-_): Miscellaneous Commands.
+ (line 140)
+* kill-line (C-k): Commands For Killing.
+ (line 6)
+* kill-region (): Commands For Killing.
+ (line 54)
+* kill-whole-line (): Commands For Killing.
+ (line 19)
+* kill-word (M-d): Commands For Killing.
+ (line 23)
+* magic-space (): Miscellaneous Commands.
+ (line 130)
+* menu-complete (): Commands For Completion.
+ (line 28)
+* menu-complete-backward (): Commands For Completion.
+ (line 39)
+* next-history (C-n): Commands For History.
+ (line 18)
+* next-screen-line (): Commands For Moving. (line 45)
+* non-incremental-forward-search-history (M-n): Commands For History.
+ (line 48)
+* non-incremental-reverse-search-history (M-p): Commands For History.
+ (line 41)
+* operate-and-get-next (C-o): Commands For History.
+ (line 102)
+* overwrite-mode (): Commands For Text. (line 77)
+* possible-command-completions (C-x !): Commands For Completion.
+ (line 111)
+* possible-completions (M-?): Commands For Completion.
+ (line 17)
+* possible-filename-completions (C-x /): Commands For Completion.
+ (line 77)
+* possible-hostname-completions (C-x @): Commands For Completion.
+ (line 101)
+* possible-username-completions (C-x ~): Commands For Completion.
+ (line 85)
+* possible-variable-completions (C-x $): Commands For Completion.
+ (line 93)
+* prefix-meta (<ESC>): Miscellaneous Commands.
+ (line 19)
+* previous-history (C-p): Commands For History.
+ (line 13)
+* previous-screen-line (): Commands For Moving. (line 38)
+* print-last-kbd-macro (): Keyboard Macros. (line 17)
+* quoted-insert (C-q or C-v): Commands For Text. (line 28)
+* re-read-init-file (C-x C-r): Miscellaneous Commands.
+ (line 6)
+* redraw-current-line (): Commands For Moving. (line 62)
+* reverse-search-history (C-r): Commands For History.
+ (line 29)
+* revert-line (M-r): Miscellaneous Commands.
+ (line 26)
+* self-insert (a, b, A, 1, !, ...): Commands For Text. (line 32)
+* set-mark (C-@): Miscellaneous Commands.
+ (line 33)
+* shell-backward-kill-word (): Commands For Killing.
+ (line 37)
+* shell-backward-word (M-C-b): Commands For Moving. (line 34)
+* shell-expand-line (M-C-e): Miscellaneous Commands.
+ (line 119)
+* shell-forward-word (M-C-f): Commands For Moving. (line 30)
+* shell-kill-word (M-C-d): Commands For Killing.
+ (line 32)
+* shell-transpose-words (M-C-t): Commands For Text. (line 58)
+* skip-csi-sequence (): Miscellaneous Commands.
+ (line 50)
+* spell-correct-word (C-x s): Miscellaneous Commands.
+ (line 97)
+* start-kbd-macro (C-x (): Keyboard Macros. (line 6)
+* tilde-expand (M-&): Miscellaneous Commands.
+ (line 30)
+* transpose-chars (C-t): Commands For Text. (line 47)
+* transpose-words (M-t): Commands For Text. (line 53)
+* undo (C-_ or C-x C-u): Miscellaneous Commands.
+ (line 23)
+* universal-argument (): Numeric Arguments. (line 10)
+* unix-filename-rubout (): Commands For Killing.
+ (line 45)
+* unix-line-discard (C-u): Commands For Killing.
+ (line 16)
+* unix-word-rubout (C-w): Commands For Killing.
+ (line 41)
+* upcase-word (M-u): Commands For Text. (line 65)
+* yank (C-y): Commands For Killing.
+ (line 72)
+* yank-last-arg (M-. or M-_): Commands For History.
+ (line 90)
+* yank-nth-arg (M-C-y): Commands For History.
+ (line 80)
+* yank-pop (M-y): Commands For Killing.
+ (line 75)
+
+\1f
+File: bashref.info, Node: Concept Index, Prev: Function Index, Up: Indexes
+
+D.5 Concept Index
+=================
+
+\0\b[index\0\b]
+* Menu:
+
+* alias expansion: Aliases. (line 6)
+* arithmetic evaluation: Shell Arithmetic. (line 6)
+* arithmetic expansion: Arithmetic Expansion.
+ (line 6)
+* arithmetic operators: Shell Arithmetic. (line 18)
+* arithmetic, shell: Shell Arithmetic. (line 6)
+* arrays: Arrays. (line 6)
+* background: Job Control Basics. (line 6)
+* Bash configuration: Basic Installation. (line 6)
+* Bash installation: Basic Installation. (line 6)
+* binary arithmetic operators: Shell Arithmetic. (line 18)
+* bitwise arithmetic operators: Shell Arithmetic. (line 18)
+* Bourne shell: Basic Shell Features.
+ (line 6)
+* brace expansion: Brace Expansion. (line 6)
+* builtin: Definitions. (line 21)
+* command editing: Readline Bare Essentials.
+ (line 6)
+* command execution: Command Search and Execution.
+ (line 6)
+* command expansion: Simple Command Expansion.
+ (line 6)
+* command history: Bash History Facilities.
+ (line 6)
+* command search: Command Search and Execution.
+ (line 6)
+* command substitution: Command Substitution.
+ (line 6)
+* command timing: Pipelines. (line 9)
+* commands, compound: Compound Commands. (line 6)
+* commands, conditional: Conditional Constructs.
+ (line 6)
+* commands, grouping: Command Grouping. (line 6)
+* commands, lists: Lists. (line 6)
+* commands, looping: Looping Constructs. (line 6)
+* commands, pipelines: Pipelines. (line 6)
+* commands, shell: Shell Commands. (line 6)
+* commands, simple: Simple Commands. (line 6)
+* comments, shell: Comments. (line 6)
+* Compatibility Level: Shell Compatibility Mode.
+ (line 6)
+* Compatibility Mode: Shell Compatibility Mode.
+ (line 6)
+* completion builtins: Programmable Completion Builtins.
+ (line 6)
+* conditional arithmetic operator: Shell Arithmetic. (line 18)
+* configuration: Basic Installation. (line 6)
+* control operator: Definitions. (line 25)
+* coprocess: Coprocesses. (line 6)
+* directory stack: The Directory Stack. (line 6)
+* dollar-single quote quoting: ANSI-C Quoting. (line 6)
+* editing command lines: Readline Bare Essentials.
+ (line 6)
+* environment: Environment. (line 6)
+* evaluation, arithmetic: Shell Arithmetic. (line 6)
+* event designators: Event Designators. (line 6)
+* execution environment: Command Execution Environment.
+ (line 6)
+* exit status: Definitions. (line 30)
+* exit status <1>: Exit Status. (line 6)
+* expansion: Shell Expansions. (line 6)
+* expansion, arithmetic: Arithmetic Expansion.
+ (line 6)
+* expansion, brace: Brace Expansion. (line 6)
+* expansion, filename: Filename Expansion. (line 9)
+* expansion, parameter: Shell Parameter Expansion.
+ (line 6)
+* expansion, pathname: Filename Expansion. (line 9)
+* expansion, tilde: Tilde Expansion. (line 6)
+* expressions, arithmetic: Shell Arithmetic. (line 6)
+* expressions, conditional: Bash Conditional Expressions.
+ (line 6)
+* field: Definitions. (line 34)
+* filename: Definitions. (line 39)
+* filename expansion: Filename Expansion. (line 9)
+* foreground: Job Control Basics. (line 6)
+* functions, shell: Shell Functions. (line 6)
+* history builtins: Bash History Builtins.
+ (line 6)
+* history events: Event Designators. (line 10)
+* history expansion: History Interaction. (line 6)
+* history list: Bash History Facilities.
+ (line 6)
+* History, how to use: A Programmable Completion Example.
+ (line 113)
+* identifier: Definitions. (line 55)
+* initialization file, readline: Readline Init File. (line 6)
+* installation: Basic Installation. (line 6)
+* interaction, readline: Readline Interaction.
+ (line 6)
+* interactive shell: Invoking Bash. (line 137)
+* interactive shell <1>: Interactive Shells. (line 6)
+* internationalization: Locale Translation. (line 6)
+* internationalized scripts: Creating Internationalized Scripts.
+ (line 3)
+* job: Definitions. (line 42)
+* job control: Definitions. (line 46)
+* job control <1>: Job Control Basics. (line 6)
+* kill ring: Readline Killing Commands.
+ (line 18)
+* killing text: Readline Killing Commands.
+ (line 6)
+* localization: Locale Translation. (line 6)
+* login shell: Invoking Bash. (line 134)
+* matching, pattern: Pattern Matching. (line 6)
+* metacharacter: Definitions. (line 50)
+* name: Definitions. (line 55)
+* native languages: Locale Translation. (line 6)
+* notation, readline: Readline Bare Essentials.
+ (line 6)
+* operator, shell: Definitions. (line 61)
+* parameter expansion: Shell Parameter Expansion.
+ (line 6)
+* parameters: Shell Parameters. (line 6)
+* parameters, positional: Positional Parameters.
+ (line 6)
+* parameters, special: Special Parameters. (line 6)
+* pathname expansion: Filename Expansion. (line 9)
+* pattern matching: Pattern Matching. (line 6)
+* pipeline: Pipelines. (line 6)
+* POSIX: Definitions. (line 9)
+* POSIX description: Bash POSIX Mode. (line 9)
+* POSIX Mode: Bash POSIX Mode. (line 48)
+* process group: Definitions. (line 66)
+* process group ID: Definitions. (line 70)
+* process substitution: Process Substitution.
+ (line 6)
+* programmable completion: Programmable Completion.
+ (line 6)
+* prompting: Controlling the Prompt.
+ (line 6)
+* quoting: Quoting. (line 6)
+* quoting, ANSI: ANSI-C Quoting. (line 6)
+* Readline, how to use: Job Control Variables.
+ (line 23)
+* redirection: Redirections. (line 6)
+* reserved word: Definitions. (line 74)
+* reserved words: Reserved Words. (line 6)
+* restricted shell: The Restricted Shell.
+ (line 6)
+* return status: Definitions. (line 79)
+* shell arithmetic: Shell Arithmetic. (line 6)
+* shell function: Shell Functions. (line 6)
+* shell script: Shell Scripts. (line 6)
+* shell variable: Shell Parameters. (line 6)
+* shell, interactive: Interactive Shells. (line 6)
+* signal: Definitions. (line 82)
+* signal handling: Signals. (line 6)
+* special builtin: Definitions. (line 86)
+* special builtin <1>: Special Builtins. (line 6)
+* startup files: Bash Startup Files. (line 6)
+* string translations: Creating Internationalized Scripts.
+ (line 3)
+* suspending jobs: Job Control Basics. (line 6)
+* tilde expansion: Tilde Expansion. (line 6)
+* token: Definitions. (line 90)
+* translation, native languages: Locale Translation. (line 6)
+* unary arithmetic operators: Shell Arithmetic. (line 18)
+* variable, shell: Shell Parameters. (line 6)
+* variables, readline: Readline Init File Syntax.
+ (line 37)
+* word: Definitions. (line 94)
+* word splitting: Word Splitting. (line 6)
+* yanking text: Readline Killing Commands.
+ (line 6)
+
+\1f
+Tag Table:
+Node: Top\7f898
+Node: Introduction\7f2836
+Node: What is Bash?\7f3052
+Node: What is a shell?\7f4188
+Node: Definitions\7f6801
+Node: Basic Shell Features\7f10131
+Node: Shell Syntax\7f11358
+Node: Shell Operation\7f12388
+Node: Quoting\7f13682
+Node: Escape Character\7f15023
+Node: Single Quotes\7f15561
+Node: Double Quotes\7f15913
+Node: ANSI-C Quoting\7f17261
+Node: Locale Translation\7f18658
+Node: Creating Internationalized Scripts\7f20064
+Node: Comments\7f24265
+Node: Shell Commands\7f25035
+Node: Reserved Words\7f25977
+Node: Simple Commands\7f26845
+Node: Pipelines\7f27510
+Node: Lists\7f30769
+Node: Compound Commands\7f32644
+Node: Looping Constructs\7f33656
+Node: Conditional Constructs\7f36208
+Node: Command Grouping\7f51281
+Node: Coprocesses\7f52776
+Node: GNU Parallel\7f55465
+Node: Shell Functions\7f56386
+Node: Shell Parameters\7f64837
+Node: Positional Parameters\7f69741
+Node: Special Parameters\7f70834
+Node: Shell Expansions\7f74298
+Node: Brace Expansion\7f76490
+Node: Tilde Expansion\7f79829
+Node: Shell Parameter Expansion\7f82787
+Node: Command Substitution\7f103433
+Node: Arithmetic Expansion\7f106965
+Node: Process Substitution\7f108144
+Node: Word Splitting\7f109255
+Node: Filename Expansion\7f111702
+Node: Pattern Matching\7f114929
+Node: Quote Removal\7f120655
+Node: Redirections\7f120962
+Node: Executing Commands\7f131221
+Node: Simple Command Expansion\7f131891
+Node: Command Search and Execution\7f134002
+Node: Command Execution Environment\7f136449
+Node: Environment\7f139900
+Node: Exit Status\7f141806
+Node: Signals\7f143868
+Node: Shell Scripts\7f148801
+Node: Shell Builtin Commands\7f152102
+Node: Bourne Shell Builtins\7f154216
+Node: Bash Builtins\7f180938
+Node: Modifying Shell Behavior\7f217865
+Node: The Set Builtin\7f218210
+Node: The Shopt Builtin\7f230207
+Node: Special Builtins\7f247263
+Node: Shell Variables\7f248255
+Node: Bourne Shell Variables\7f248692
+Node: Bash Variables\7f251203
+Node: Bash Features\7f290331
+Node: Invoking Bash\7f291348
+Node: Bash Startup Files\7f297935
+Node: Interactive Shells\7f303180
+Node: What is an Interactive Shell?\7f303591
+Node: Is this Shell Interactive?\7f304256
+Node: Interactive Shell Behavior\7f305083
+Node: Bash Conditional Expressions\7f308847
+Node: Shell Arithmetic\7f314267
+Node: Aliases\7f317597
+Node: Arrays\7f320734
+Node: The Directory Stack\7f328325
+Node: Directory Stack Builtins\7f329125
+Node: Controlling the Prompt\7f333573
+Node: The Restricted Shell\7f336461
+Node: Bash POSIX Mode\7f339346
+Node: Shell Compatibility Mode\7f358296
+Node: Job Control\7f367306
+Node: Job Control Basics\7f367766
+Node: Job Control Builtins\7f374137
+Node: Job Control Variables\7f380822
+Node: Command Line Editing\7f382056
+Node: Introduction and Notation\7f383762
+Node: Readline Interaction\7f386117
+Node: Readline Bare Essentials\7f387308
+Node: Readline Movement Commands\7f389119
+Node: Readline Killing Commands\7f390118
+Node: Readline Arguments\7f392144
+Node: Searching\7f393237
+Node: Readline Init File\7f395483
+Node: Readline Init File Syntax\7f396789
+Node: Conditional Init Constructs\7f423743
+Node: Sample Init File\7f428131
+Node: Bindable Readline Commands\7f431254
+Node: Commands For Moving\7f432795
+Node: Commands For History\7f435262
+Node: Commands For Text\7f440656
+Node: Commands For Killing\7f444784
+Node: Numeric Arguments\7f447575
+Node: Commands For Completion\7f448730
+Node: Keyboard Macros\7f454429
+Node: Miscellaneous Commands\7f455133
+Node: Readline vi Mode\7f461703
+Node: Programmable Completion\7f462683
+Node: Programmable Completion Builtins\7f472422
+Node: A Programmable Completion Example\7f484162
+Node: Using History Interactively\7f489510
+Node: Bash History Facilities\7f490194
+Node: Bash History Builtins\7f493932
+Node: History Interaction\7f500406
+Node: Event Designators\7f505359
+Node: Word Designators\7f506940
+Node: Modifiers\7f509335
+Node: Installing Bash\7f511275
+Node: Basic Installation\7f512394
+Node: Compilers and Options\7f516273
+Node: Compiling For Multiple Architectures\7f517026
+Node: Installation Names\7f518782
+Node: Specifying the System Type\7f521019
+Node: Sharing Defaults\7f521768
+Node: Operation Controls\7f522485
+Node: Optional Features\7f523507
+Node: Reporting Bugs\7f536233
+Node: Major Differences From The Bourne Shell\7f537593
+Node: GNU Free Documentation License\7f559023
+Node: Indexes\7f584203
+Node: Builtin Index\7f584657
+Node: Reserved Word Index\7f591758
+Node: Variable Index\7f594206
+Node: Function Index\7f611622
+Node: Concept Index\7f625620
+\1f
+End Tag Table
+
+\1f
+Local Variables:
+coding: utf-8
+End:
sh_invalidopt ("-a");
return (EX_BADUSAGE);
}
+ /* Ineffective, since you can't have namerefs referencing positional parameters */
+ else if ((flags_on & att_nameref) && (flags_on & att_integer))
+ {
+ builtin_error ("cannot use -n with -i");
+ return (EX_BADUSAGE);
+ }
return 0;
}
cape a newline, if necessary. These are added to the set of possible
completions.
+ External commands that are invoked to generate completions ( "external
+ completers") receive the word preceding the completion word as an argu-
+ ment, as described above. This provides context that is sometimes use-
+ ful, but may include information that is considered sensitive or part
+ of a word expansion that will not appear in the command line after ex-
+ pansion. That word may be visible in process listings or in audit
+ logs. This may be a concern to users and completion specification au-
+ thors if there is sensitive information on the command line before ex-
+ pansion, since completion takes place before words are expanded. If
+ this is an issue, completion authors should use functions as wrappers
+ around external commands and pass context information to the external
+ command in a different way. External completers can infer context from
+ the C\bCO\bOM\bMP\bP_\b_L\bLI\bIN\bNE\bE and C\bCO\bOM\bMP\bP_\b_P\bPO\bOI\bIN\bNT\bT environment variables, but they need to
+ ensure they break words in the same way r\bre\bea\bad\bdl\bli\bin\bne\be does, using the
+ C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS variable.
+
After generating all of the possible completions, b\bba\bas\bsh\bh applies any fil-
- ter specified with the -\b-X\bX option to the completions in the list. The
- filter is a pattern as used for pathname expansion; a &\b& in the pattern
+ ter specified with the -\b-X\bX option to the completions in the list. The
+ filter is a pattern as used for pathname expansion; a &\b& in the pattern
is replaced with the text of the word being completed. A literal &\b& may
be escaped with a backslash; the backslash is removed before attempting
- a match. Any completion that matches the pattern is removed from the
- list. A leading !\b! negates the pattern; in this case b\bba\bas\bsh\bh removes any
- completion that does not match the pattern. If the n\bno\boc\bca\bas\bse\bem\bma\bat\btc\bch\bh shell
- option is enabled, b\bba\bas\bsh\bh performs the match without regard to the case
+ a match. Any completion that matches the pattern is removed from the
+ list. A leading !\b! negates the pattern; in this case b\bba\bas\bsh\bh removes any
+ completion that does not match the pattern. If the n\bno\boc\bca\bas\bse\bem\bma\bat\btc\bch\bh shell
+ option is enabled, b\bba\bas\bsh\bh performs the match without regard to the case
of alphabetic characters.
- Finally, programmable completion adds any prefix and suffix specified
- with the -\b-P\bP and -\b-S\bS options, respectively, to each completion, and re-
+ Finally, programmable completion adds any prefix and suffix specified
+ with the -\b-P\bP and -\b-S\bS options, respectively, to each completion, and re-
turns the result to r\bre\bea\bad\bdl\bli\bin\bne\be as the list of possible completions.
- If the previously-applied actions do not generate any matches, and the
- -\b-o\bo d\bdi\bir\brn\bna\bam\bme\bes\bs option was supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be when the compspec was de-
+ If the previously-applied actions do not generate any matches, and the
+ -\b-o\bo d\bdi\bir\brn\bna\bam\bme\bes\bs option was supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be when the compspec was de-
fined, b\bba\bas\bsh\bh attempts directory name completion.
- If the -\b-o\bo p\bpl\blu\bus\bsd\bdi\bir\brs\bs option was supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be when the compspec
- was defined, b\bba\bas\bsh\bh attempts directory name completion and adds any
+ If the -\b-o\bo p\bpl\blu\bus\bsd\bdi\bir\brs\bs option was supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be when the compspec
+ was defined, b\bba\bas\bsh\bh attempts directory name completion and adds any
matches to the set of possible completions.
- By default, if a compspec is found, whatever it generates is returned
- to the completion code as the full set of possible completions. The
- default b\bba\bas\bsh\bh completions and the r\bre\bea\bad\bdl\bli\bin\bne\be default of filename comple-
- tion are disabled. If the -\b-o\bo b\bba\bas\bsh\bhd\bde\bef\bfa\bau\bul\blt\bt option was supplied to c\bco\bom\bm-\b-
- p\bpl\ble\bet\bte\be when the compspec was defined, and the compspec generates no
- matches, b\bba\bas\bsh\bh attempts its default completions. If the compspec and,
+ By default, if a compspec is found, whatever it generates is returned
+ to the completion code as the full set of possible completions. The
+ default b\bba\bas\bsh\bh completions and the r\bre\bea\bad\bdl\bli\bin\bne\be default of filename comple-
+ tion are disabled. If the -\b-o\bo b\bba\bas\bsh\bhd\bde\bef\bfa\bau\bul\blt\bt option was supplied to c\bco\bom\bm-\b-
+ p\bpl\ble\bet\bte\be when the compspec was defined, and the compspec generates no
+ matches, b\bba\bas\bsh\bh attempts its default completions. If the compspec and,
if attempted, the default b\bba\bas\bsh\bh completions generate no matches, and the
- -\b-o\bo d\bde\bef\bfa\bau\bul\blt\bt option was supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be when the compspec was de-
+ -\b-o\bo d\bde\bef\bfa\bau\bul\blt\bt option was supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be when the compspec was de-
fined, programmable completion performs r\bre\bea\bad\bdl\bli\bin\bne\be's default completion.
- The options supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be and c\bco\bom\bmp\bpo\bop\bpt\bt can control how r\bre\bea\bad\bdl\bli\bin\bne\be
- treats the completions. For instance, the _\b-_\bo _\bf_\bu_\bl_\bl_\bq_\bu_\bo_\bt_\be option tells
- r\bre\bea\bad\bdl\bli\bin\bne\be to quote the matches as if they were filenames. See the de-
+ The options supplied to c\bco\bom\bmp\bpl\ble\bet\bte\be and c\bco\bom\bmp\bpo\bop\bpt\bt can control how r\bre\bea\bad\bdl\bli\bin\bne\be
+ treats the completions. For instance, the _\b-_\bo _\bf_\bu_\bl_\bl_\bq_\bu_\bo_\bt_\be option tells
+ r\bre\bea\bad\bdl\bli\bin\bne\be to quote the matches as if they were filenames. See the de-
scription of c\bco\bom\bmp\bpl\ble\bet\bte\be below for details.
- When a compspec indicates that it wants directory name completion, the
- programmable completion functions force r\bre\bea\bad\bdl\bli\bin\bne\be to append a slash to
+ When a compspec indicates that it wants directory name completion, the
+ programmable completion functions force r\bre\bea\bad\bdl\bli\bin\bne\be to append a slash to
completed names which are symbolic links to directories, subject to the
value of the m\bma\bar\brk\bk-\b-d\bdi\bir\bre\bec\bct\bto\bor\bri\bie\bes\bs r\bre\bea\bad\bdl\bli\bin\bne\be variable, regardless of the set-
ting of the m\bma\bar\brk\bk-\b-s\bsy\bym\bml\bli\bin\bnk\bke\bed\bd-\b-d\bdi\bir\bre\bec\bct\bto\bor\bri\bie\bes\bs r\bre\bea\bad\bdl\bli\bin\bne\be variable.
- There is some support for dynamically modifying completions. This is
- most useful when used in combination with a default completion speci-
- fied with c\bco\bom\bmp\bpl\ble\bet\bte\be -\b-D\bD. It's possible for shell functions executed as
- completion functions to indicate that completion should be retried by
- returning an exit status of 124. If a shell function returns 124, and
+ There is some support for dynamically modifying completions. This is
+ most useful when used in combination with a default completion speci-
+ fied with c\bco\bom\bmp\bpl\ble\bet\bte\be -\b-D\bD. It's possible for shell functions executed as
+ completion functions to indicate that completion should be retried by
+ returning an exit status of 124. If a shell function returns 124, and
changes the compspec associated with the command on which completion is
- being attempted (supplied as the first argument when the function is
+ being attempted (supplied as the first argument when the function is
executed), programmable completion restarts from the beginning, with an
- attempt to find a new compspec for that command. This can be used to
- build a set of completions dynamically as completion is attempted,
+ attempt to find a new compspec for that command. This can be used to
+ build a set of completions dynamically as completion is attempted,
rather than loading them all at once.
- For instance, assuming that there is a library of compspecs, each kept
- in a file corresponding to the name of the command, the following de-
+ For instance, assuming that there is a library of compspecs, each kept
+ in a file corresponding to the name of the command, the following de-
fault completion function would load completions dynamically:
_completion_loader()
{
-o bashdefault -o default
H\bHI\bIS\bST\bTO\bOR\bRY\bY
- When the -\b-o\bo h\bhi\bis\bst\bto\bor\bry\by option to the s\bse\bet\bt builtin is enabled, the shell
+ When the -\b-o\bo h\bhi\bis\bst\bto\bor\bry\by option to the s\bse\bet\bt builtin is enabled, the shell
provides access to the _\bc_\bo_\bm_\bm_\ba_\bn_\bd _\bh_\bi_\bs_\bt_\bo_\br_\by, the list of commands previously
- typed. The value of the H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE variable is used as the number of
- commands to save in a history list: the shell saves the text of the
+ typed. The value of the H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE variable is used as the number of
+ commands to save in a history list: the shell saves the text of the
last H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE commands (default 500). The shell stores each command in
- the history list prior to parameter and variable expansion (see E\bEX\bXP\bPA\bAN\bN-\b-
- S\bSI\bIO\bON\bN above) but after history expansion is performed, subject to the
+ the history list prior to parameter and variable expansion (see E\bEX\bXP\bPA\bAN\bN-\b-
+ S\bSI\bIO\bON\bN above) but after history expansion is performed, subject to the
values of the shell variables H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE and H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL.
- On startup, b\bba\bas\bsh\bh initializes the history list by reading history en-
- tries from the file named by the H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE variable (default
- _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bh_\bi_\bs_\bt_\bo_\br_\by). That file is referred to as the _\bh_\bi_\bs_\bt_\bo_\br_\by _\bf_\bi_\bl_\be. The
- history file is truncated, if necessary, to contain no more than the
- number of history entries specified by the value of the H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bES\bSI\bIZ\bZE\bE
- variable. If H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bES\bSI\bIZ\bZE\bE is unset, or set to null, a non-numeric
+ On startup, b\bba\bas\bsh\bh initializes the history list by reading history en-
+ tries from the file named by the H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE variable (default
+ _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bh_\bi_\bs_\bt_\bo_\br_\by). That file is referred to as the _\bh_\bi_\bs_\bt_\bo_\br_\by _\bf_\bi_\bl_\be. The
+ history file is truncated, if necessary, to contain no more than the
+ number of history entries specified by the value of the H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bES\bSI\bIZ\bZE\bE
+ variable. If H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bES\bSI\bIZ\bZE\bE is unset, or set to null, a non-numeric
value, or a numeric value less than zero, the history file is not trun-
cated.
When the history file is read, lines beginning with the history comment
character followed immediately by a digit are interpreted as timestamps
- for the following history line. These timestamps are optionally dis-
- played depending on the value of the H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable. When
- present, history timestamps delimit history entries, making multi-line
+ for the following history line. These timestamps are optionally dis-
+ played depending on the value of the H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable. When
+ present, history timestamps delimit history entries, making multi-line
entries possible.
When a shell with history enabled exits, b\bba\bas\bsh\bh copies the last $\b$H\bHI\bIS\bST\bTS\bSI\bIZ\bZE\bE
- entries from the history list to $\b$H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE. If the h\bhi\bis\bst\bta\bap\bpp\bpe\ben\bnd\bd shell
- option is enabled (see the description of s\bsh\bho\bop\bpt\bt under S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN
- C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below), b\bba\bas\bsh\bh appends the entries to the history file, other-
- wise it overwrites the history file. If H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE is unset or null, or
- if the history file is unwritable, the history is not saved. After
- saving the history, b\bba\bas\bsh\bh truncates the history file to contain no more
+ entries from the history list to $\b$H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE. If the h\bhi\bis\bst\bta\bap\bpp\bpe\ben\bnd\bd shell
+ option is enabled (see the description of s\bsh\bho\bop\bpt\bt under S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN
+ C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below), b\bba\bas\bsh\bh appends the entries to the history file, other-
+ wise it overwrites the history file. If H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE is unset or null, or
+ if the history file is unwritable, the history is not saved. After
+ saving the history, b\bba\bas\bsh\bh truncates the history file to contain no more
than H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bES\bSI\bIZ\bZE\bE lines as described above.
- If the H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable is set, the shell writes the timestamp
- information associated with each history entry to the history file,
- marked with the history comment character, so timestamps are preserved
+ If the H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable is set, the shell writes the timestamp
+ information associated with each history entry to the history file,
+ marked with the history comment character, so timestamps are preserved
across shell sessions. This uses the history comment character to dis-
- tinguish timestamps from other history lines. As above, when using
+ tinguish timestamps from other history lines. As above, when using
H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT, the timestamps delimit multi-line history entries.
- The f\bfc\bc builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below) will list or
+ The f\bfc\bc builtin command (see S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below) will list or
edit and re-execute a portion of the history list. The h\bhi\bis\bst\bto\bor\bry\by builtin
can display or modify the history list and manipulate the history file.
- When using command-line editing, search commands are available in each
+ When using command-line editing, search commands are available in each
editing mode that provide access to the history list.
- The shell allows control over which commands are saved on the history
+ The shell allows control over which commands are saved on the history
list. The H\bHI\bIS\bST\bTC\bCO\bON\bNT\bTR\bRO\bOL\bL and H\bHI\bIS\bST\bTI\bIG\bGN\bNO\bOR\bRE\bE variables are used to save only a
- subset of the commands entered. If the c\bcm\bmd\bdh\bhi\bis\bst\bt shell option is en-
- abled, the shell attempts to save each line of a multi-line command in
- the same history entry, adding semicolons where necessary to preserve
- syntactic correctness. The l\bli\bit\bth\bhi\bis\bst\bt shell option modifies c\bcm\bmd\bdh\bhi\bis\bst\bt by
- saving the command with embedded newlines instead of semicolons. See
+ subset of the commands entered. If the c\bcm\bmd\bdh\bhi\bis\bst\bt shell option is en-
+ abled, the shell attempts to save each line of a multi-line command in
+ the same history entry, adding semicolons where necessary to preserve
+ syntactic correctness. The l\bli\bit\bth\bhi\bis\bst\bt shell option modifies c\bcm\bmd\bdh\bhi\bis\bst\bt by
+ saving the command with embedded newlines instead of semicolons. See
the description of the s\bsh\bho\bop\bpt\bt builtin below under S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS
for information on setting and unsetting shell options.
H\bHI\bIS\bST\bTO\bOR\bRY\bY E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN
- The shell supports a history expansion feature that is similar to the
- history expansion in c\bcs\bsh\bh. This section describes what syntax features
+ The shell supports a history expansion feature that is similar to the
+ history expansion in c\bcs\bsh\bh. This section describes what syntax features
are available.
History expansion is enabled by default for interactive shells, and can
- be disabled using the +\b+H\bH option to the s\bse\bet\bt builtin command (see S\bSH\bHE\bEL\bLL\bL
+ be disabled using the +\b+H\bH option to the s\bse\bet\bt builtin command (see S\bSH\bHE\bEL\bLL\bL
B\bBU\bUI\bIL\bLT\bTI\bIN\bN C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS below). Non-interactive shells do not perform history
expansion by default, but it can be enabled with "set -H".
History expansions introduce words from the history list into the input
- stream, making it easy to repeat commands, insert the arguments to a
+ stream, making it easy to repeat commands, insert the arguments to a
previous command into the current input line, or fix errors in previous
commands quickly.
- History expansion is performed immediately after a complete line is
- read, before the shell breaks it into words, and is performed on each
- line individually. The shell attempts to inform the history expansion
+ History expansion is performed immediately after a complete line is
+ read, before the shell breaks it into words, and is performed on each
+ line individually. The shell attempts to inform the history expansion
functions about quoting still in effect from previous lines.
- It takes place in two parts. The first is to determine which history
- list entry to use during substitution. The second is to select por-
+ It takes place in two parts. The first is to determine which history
+ list entry to use during substitution. The second is to select por-
tions of that entry to include into the current one.
- The entry selected from the history is the _\be_\bv_\be_\bn_\bt, and the portions of
+ The entry selected from the history is the _\be_\bv_\be_\bn_\bt, and the portions of
that entry that are acted upon are _\bw_\bo_\br_\bd_\bs. Various _\bm_\bo_\bd_\bi_\bf_\bi_\be_\br_\bs are avail-
- able to manipulate the selected words. The entry is split into words
- in the same fashion as when reading input, so that several _\bm_\be_\bt_\ba_\bc_\bh_\ba_\br_\ba_\bc_\b-
- _\bt_\be_\br-separated words surrounded by quotes are considered one word. The
- _\be_\bv_\be_\bn_\bt _\bd_\be_\bs_\bi_\bg_\bn_\ba_\bt_\bo_\br selects the event, the optional _\bw_\bo_\br_\bd _\bd_\be_\bs_\bi_\bg_\bn_\ba_\bt_\bo_\br se-
- lects words from the event, and various optional _\bm_\bo_\bd_\bi_\bf_\bi_\be_\br_\bs are avail-
+ able to manipulate the selected words. The entry is split into words
+ in the same fashion as when reading input, so that several _\bm_\be_\bt_\ba_\bc_\bh_\ba_\br_\ba_\bc_\b-
+ _\bt_\be_\br-separated words surrounded by quotes are considered one word. The
+ _\be_\bv_\be_\bn_\bt _\bd_\be_\bs_\bi_\bg_\bn_\ba_\bt_\bo_\br selects the event, the optional _\bw_\bo_\br_\bd _\bd_\be_\bs_\bi_\bg_\bn_\ba_\bt_\bo_\br se-
+ lects words from the event, and various optional _\bm_\bo_\bd_\bi_\bf_\bi_\be_\br_\bs are avail-
able to manipulate the selected words.
- History expansions are introduced by the appearance of the history ex-
- pansion character, which is !\b! by default. History expansions may ap-
+ History expansions are introduced by the appearance of the history ex-
+ pansion character, which is !\b! by default. History expansions may ap-
pear anywhere in the input, but do not nest.
- Only backslash (\\b\) and single quotes can quote the history expansion
- character, but the history expansion character is also treated as
+ Only backslash (\\b\) and single quotes can quote the history expansion
+ character, but the history expansion character is also treated as
quoted if it immediately precedes the closing double quote in a double-
quoted string.
- Several characters inhibit history expansion if found immediately fol-
- lowing the history expansion character, even if it is unquoted: space,
- tab, newline, carriage return, =\b=, and the other shell metacharacters
+ Several characters inhibit history expansion if found immediately fol-
+ lowing the history expansion character, even if it is unquoted: space,
+ tab, newline, carriage return, =\b=, and the other shell metacharacters
defined above.
There is a special abbreviation for substitution, active when the _\bq_\bu_\bi_\bc_\bk
- _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\bt_\bi_\bo_\bn character (described above under h\bhi\bis\bst\btc\bch\bha\bar\brs\bs) is the first
+ _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\bt_\bi_\bo_\bn character (described above under h\bhi\bis\bst\btc\bch\bha\bar\brs\bs) is the first
character on the line. It selects the previous history list entry, us-
- ing an event designator equivalent to !\b!!\b!, and substitutes one string
- for another in that entry. It is described below under E\bEv\bve\ben\bnt\bt D\bDe\bes\bsi\big\bgn\bna\ba-\b-
- t\bto\bor\brs\bs. This is the only history expansion that does not begin with the
+ ing an event designator equivalent to !\b!!\b!, and substitutes one string
+ for another in that entry. It is described below under E\bEv\bve\ben\bnt\bt D\bDe\bes\bsi\big\bgn\bna\ba-\b-
+ t\bto\bor\brs\bs. This is the only history expansion that does not begin with the
history expansion character.
- Several shell options settable with the s\bsh\bho\bop\bpt\bt builtin will modify his-
- tory expansion behavior (see the description of the s\bsh\bho\bop\bpt\bt builtin be-
+ Several shell options settable with the s\bsh\bho\bop\bpt\bt builtin will modify his-
+ tory expansion behavior (see the description of the s\bsh\bho\bop\bpt\bt builtin be-
low).and If the h\bhi\bis\bst\btv\bve\ber\bri\bif\bfy\by shell option is enabled, and r\bre\bea\bad\bdl\bli\bin\bne\be is be-
ing used, history substitutions are not immediately passed to the shell
parser. Instead, the expanded line is reloaded into the r\bre\bea\bad\bdl\bli\bin\bne\be edit-
- ing buffer for further modification. If r\bre\bea\bad\bdl\bli\bin\bne\be is being used, and
- the h\bhi\bis\bst\btr\bre\bee\bed\bdi\bit\bt shell option is enabled, a failed history substitution
+ ing buffer for further modification. If r\bre\bea\bad\bdl\bli\bin\bne\be is being used, and
+ the h\bhi\bis\bst\btr\bre\bee\bed\bdi\bit\bt shell option is enabled, a failed history substitution
is reloaded into the r\bre\bea\bad\bdl\bli\bin\bne\be editing buffer for correction.
- The -\b-p\bp option to the h\bhi\bis\bst\bto\bor\bry\by builtin command shows what a history ex-
- pansion will do before using it. The -\b-s\bs option to the h\bhi\bis\bst\bto\bor\bry\by builtin
- will add commands to the end of the history list without actually exe-
+ The -\b-p\bp option to the h\bhi\bis\bst\bto\bor\bry\by builtin command shows what a history ex-
+ pansion will do before using it. The -\b-s\bs option to the h\bhi\bis\bst\bto\bor\bry\by builtin
+ will add commands to the end of the history list without actually exe-
cuting them, so that they are available for subsequent recall.
- The shell allows control of the various characters used by the history
+ The shell allows control of the various characters used by the history
expansion mechanism (see the description of h\bhi\bis\bst\btc\bch\bha\bar\brs\bs above under S\bSh\bhe\bel\bll\bl
- V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs). The shell uses the history comment character to mark his-
+ V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs). The shell uses the history comment character to mark his-
tory timestamps when writing the history file.
E\bEv\bve\ben\bnt\bt D\bDe\bes\bsi\big\bgn\bna\bat\bto\bor\brs\bs
- An event designator is a reference to an entry in the history list.
+ An event designator is a reference to an entry in the history list.
The event designator consists of the portion of the word beginning with
- the history expansion character and ending with the word designator if
- present, or the end of the word. Unless the reference is absolute,
+ the history expansion character and ending with the word designator if
+ present, or the end of the word. Unless the reference is absolute,
events are relative to the current position in the history list.
- !\b! Start a history substitution, except when followed by a b\bbl\bla\ban\bnk\bk,
- newline, carriage return, =, or, when the e\bex\bxt\btg\bgl\blo\bob\bb shell option
+ !\b! Start a history substitution, except when followed by a b\bbl\bla\ban\bnk\bk,
+ newline, carriage return, =, or, when the e\bex\bxt\btg\bgl\blo\bob\bb shell option
is enabled using the s\bsh\bho\bop\bpt\bt builtin, (.
!\b!_\bn Refer to history list entry _\bn.
!\b!-\b-_\bn Refer to the current entry minus _\bn.
!\b!!\b! Refer to the previous entry. This is a synonym for "!-1".
!\b!_\bs_\bt_\br_\bi_\bn_\bg
- Refer to the most recent command preceding the current position
+ Refer to the most recent command preceding the current position
in the history list starting with _\bs_\bt_\br_\bi_\bn_\bg.
!\b!?\b?_\bs_\bt_\br_\bi_\bn_\bg[\b[?\b?]\b]
- Refer to the most recent command preceding the current position
- in the history list containing _\bs_\bt_\br_\bi_\bn_\bg. The trailing ?\b? may be
- omitted if _\bs_\bt_\br_\bi_\bn_\bg is followed immediately by a newline. If
- _\bs_\bt_\br_\bi_\bn_\bg is missing, this uses the string from the most recent
+ Refer to the most recent command preceding the current position
+ in the history list containing _\bs_\bt_\br_\bi_\bn_\bg. The trailing ?\b? may be
+ omitted if _\bs_\bt_\br_\bi_\bn_\bg is followed immediately by a newline. If
+ _\bs_\bt_\br_\bi_\bn_\bg is missing, this uses the string from the most recent
search; it is an error if there is no previous search string.
^\b^_\bs_\bt_\br_\bi_\bn_\bg_\b1^\b^_\bs_\bt_\br_\bi_\bn_\bg_\b2^\b^
- Quick substitution. Repeat the previous command, replacing
- _\bs_\bt_\br_\bi_\bn_\bg_\b1 with _\bs_\bt_\br_\bi_\bn_\bg_\b2. Equivalent to "!!:s^_\bs_\bt_\br_\bi_\bn_\bg_\b1^_\bs_\bt_\br_\bi_\bn_\bg_\b2^"
+ Quick substitution. Repeat the previous command, replacing
+ _\bs_\bt_\br_\bi_\bn_\bg_\b1 with _\bs_\bt_\br_\bi_\bn_\bg_\b2. Equivalent to "!!:s^_\bs_\bt_\br_\bi_\bn_\bg_\b1^_\bs_\bt_\br_\bi_\bn_\bg_\b2^"
(see M\bMo\bod\bdi\bif\bfi\bie\ber\brs\bs below).
!\b!#\b# The entire command line typed so far.
Word designators are used to select desired words from the event. They
are optional; if the word designator isn't supplied, the history expan-
sion uses the entire event. A :\b: separates the event specification from
- the word designator. It may be omitted if the word designator begins
- with a ^\b^, $\b$, *\b*, -\b-, or %\b%. Words are numbered from the beginning of the
- line, with the first word being denoted by 0 (zero). Words are in-
+ the word designator. It may be omitted if the word designator begins
+ with a ^\b^, $\b$, *\b*, -\b-, or %\b%. Words are numbered from the beginning of the
+ line, with the first word being denoted by 0 (zero). Words are in-
serted into the current line separated by single spaces.
0\b0 (\b(z\bze\ber\bro\bo)\b)
The zeroth word. For the shell, this is the command word.
_\bn The _\bnth word.
^\b^ The first argument: word 1.
- $\b$ The last word. This is usually the last argument, but will ex-
+ $\b$ The last word. This is usually the last argument, but will ex-
pand to the zeroth word if there is only one word in the line.
%\b% The first word matched by the most recent "?_\bs_\bt_\br_\bi_\bn_\bg?" search, if
- the search string begins with a character that is part of a
- word. By default, searches begin at the end of each line and
- proceed to the beginning, so the first word matched is the one
+ the search string begins with a character that is part of a
+ word. By default, searches begin at the end of each line and
+ proceed to the beginning, so the first word matched is the one
closest to the end of the line.
_\bx-\b-_\by A range of words; "-_\by" abbreviates "0-_\by".
- *\b* All of the words but the zeroth. This is a synonym for "_\b1_\b-_\b$".
- It is not an error to use *\b* if there is just one word in the
+ *\b* All of the words but the zeroth. This is a synonym for "_\b1_\b-_\b$".
+ It is not an error to use *\b* if there is just one word in the
event; it expands to the empty string in that case.
x\bx*\b* Abbreviates _\bx_\b-_\b$.
x\bx-\b- Abbreviates _\bx_\b-_\b$ like x\bx*\b*, but omits the last word. If x\bx is miss-
ing, it defaults to 0.
- If a word designator is supplied without an event specification, the
+ If a word designator is supplied without an event specification, the
previous command is used as the event, equivalent to !\b!!\b!.
M\bMo\bod\bdi\bif\bfi\bie\ber\brs\bs
- After the optional word designator, the expansion may include a se-
- quence of one or more of the following modifiers, each preceded by a
- ":". These modify, or edit, the word or words selected from the his-
+ After the optional word designator, the expansion may include a se-
+ quence of one or more of the following modifiers, each preceded by a
+ ":". These modify, or edit, the word or words selected from the his-
tory event.
h\bh Remove a trailing pathname component, leaving only the head.
e\be Remove all but the trailing suffix.
p\bp Print the new command but do not execute it.
q\bq Quote the substituted words, escaping further substitutions.
- x\bx Quote the substituted words as with q\bq, but break into words at
- b\bbl\bla\ban\bnk\bks\bs and newlines. The q\bq and x\bx modifiers are mutually exclu-
+ x\bx Quote the substituted words as with q\bq, but break into words at
+ b\bbl\bla\ban\bnk\bks\bs and newlines. The q\bq and x\bx modifiers are mutually exclu-
sive; expansion uses the last one supplied.
s\bs/\b/_\bo_\bl_\bd/\b/_\bn_\be_\bw/\b/
- Substitute _\bn_\be_\bw for the first occurrence of _\bo_\bl_\bd in the event
+ Substitute _\bn_\be_\bw for the first occurrence of _\bo_\bl_\bd in the event
line. Any character may be used as the delimiter in place of /.
- The final delimiter is optional if it is the last character of
- the event line. A single backslash quotes the delimiter in _\bo_\bl_\bd
- and _\bn_\be_\bw. If & appears in _\bn_\be_\bw, it is replaced with _\bo_\bl_\bd. A sin-
- gle backslash quotes the &. If _\bo_\bl_\bd is null, it is set to the
- last _\bo_\bl_\bd substituted, or, if no previous history substitutions
+ The final delimiter is optional if it is the last character of
+ the event line. A single backslash quotes the delimiter in _\bo_\bl_\bd
+ and _\bn_\be_\bw. If & appears in _\bn_\be_\bw, it is replaced with _\bo_\bl_\bd. A sin-
+ gle backslash quotes the &. If _\bo_\bl_\bd is null, it is set to the
+ last _\bo_\bl_\bd substituted, or, if no previous history substitutions
took place, the last _\bs_\bt_\br_\bi_\bn_\bg in a !\b!?\b?_\bs_\bt_\br_\bi_\bn_\bg[\b[?\b?]\b] search. If _\bn_\be_\bw is
null, each matching _\bo_\bl_\bd is deleted.
&\b& Repeat the previous substitution.
g\bg Cause changes to be applied over the entire event line. This is
- used in conjunction with ":\b:s\bs" (e.g., ":\b:g\bgs\bs/\b/_\bo_\bl_\bd/\b/_\bn_\be_\bw/\b/") or ":\b:&\b&".
- If used with ":\b:s\bs", any delimiter can be used in place of /, and
- the final delimiter is optional if it is the last character of
+ used in conjunction with ":\b:s\bs" (e.g., ":\b:g\bgs\bs/\b/_\bo_\bl_\bd/\b/_\bn_\be_\bw/\b/") or ":\b:&\b&".
+ If used with ":\b:s\bs", any delimiter can be used in place of /, and
+ the final delimiter is optional if it is the last character of
the event line. An a\ba may be used as a synonym for g\bg.
G\bG Apply the following "s\bs" or "&\b&" modifier once to each word in the
event line.
Unless otherwise noted, each builtin command documented in this section
as accepting options preceded by -\b- accepts -\b--\b- to signify the end of the
options. The :\b:, t\btr\bru\bue\be, f\bfa\bal\bls\bse\be, and t\bte\bes\bst\bt/[\b[ builtins do not accept options
- and do not treat -\b--\b- specially. The e\bex\bxi\bit\bt, l\blo\bog\bgo\bou\but\bt, r\bre\bet\btu\bur\brn\bn, b\bbr\bre\bea\bak\bk, c\bco\bon\bn-\b-
- t\bti\bin\bnu\bue\be, l\ble\bet\bt, and s\bsh\bhi\bif\bft\bt builtins accept and process arguments beginning
- with -\b- without requiring -\b--\b-. Other builtins that accept arguments but
- are not specified as accepting options interpret arguments beginning
- with -\b- as invalid options and require -\b--\b- to prevent this interpreta-
+ and do not treat -\b--\b- specially. The e\bex\bxi\bit\bt, l\blo\bog\bgo\bou\but\bt, r\bre\bet\btu\bur\brn\bn, b\bbr\bre\bea\bak\bk, c\bco\bon\bn-\b-
+ t\bti\bin\bnu\bue\be, l\ble\bet\bt, and s\bsh\bhi\bif\bft\bt builtins accept and process arguments beginning
+ with -\b- without requiring -\b--\b-. Other builtins that accept arguments but
+ are not specified as accepting options interpret arguments beginning
+ with -\b- as invalid options and require -\b--\b- to prevent this interpreta-
tion.
:\b: [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
- No effect; the command does nothing beyond expanding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs
+ No effect; the command does nothing beyond expanding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs
and performing any specified redirections. The return status is
zero.
.\b. [-\b-p\bp _\bp_\ba_\bt_\bh] _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
s\bso\bou\bur\brc\bce\be [-\b-p\bp _\bp_\ba_\bt_\bh] _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
- The .\b. command (s\bso\bou\bur\brc\bce\be) reads and execute commands from _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
- in the current shell environment and returns the exit status of
+ The .\b. command (s\bso\bou\bur\brc\bce\be) reads and execute commands from _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
+ in the current shell environment and returns the exit status of
the last command executed from _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be.
If _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be does not contain a slash, .\b. searches for it. If the
- -\b-p\bp option is supplied, .\b. treats _\bp_\ba_\bt_\bh as a colon-separated list
- of directories in which to find _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be; otherwise, .\b. uses the
- entries in P\bPA\bAT\bTH\bH to find the directory containing _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be.
- _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be does not need to be executable. When b\bba\bas\bsh\bh is not in
+ -\b-p\bp option is supplied, .\b. treats _\bp_\ba_\bt_\bh as a colon-separated list
+ of directories in which to find _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be; otherwise, .\b. uses the
+ entries in P\bPA\bAT\bTH\bH to find the directory containing _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be.
+ _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be does not need to be executable. When b\bba\bas\bsh\bh is not in
posix mode, it searches the current directory if _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is not
- found in P\bPA\bAT\bTH\bH, but does not search the current directory if -\b-p\bp
+ found in P\bPA\bAT\bTH\bH, but does not search the current directory if -\b-p\bp
is supplied. If the s\bso\bou\bur\brc\bce\bep\bpa\bat\bth\bh option to the s\bsh\bho\bop\bpt\bt builtin com-
mand is turned off, .\b. does not search P\bPA\bAT\bTH\bH.
- If any _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs are supplied, they become the positional para-
- meters when _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is executed. Otherwise the positional pa-
+ If any _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs are supplied, they become the positional para-
+ meters when _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is executed. Otherwise the positional pa-
rameters are unchanged.
If the -\b-T\bT option is enabled, .\b. inherits any trap on D\bDE\bEB\bBU\bUG\bG; if it
- is not, any D\bDE\bEB\bBU\bUG\bG trap string is saved and restored around the
+ is not, any D\bDE\bEB\bBU\bUG\bG trap string is saved and restored around the
call to .\b., and .\b. unsets the D\bDE\bEB\bBU\bUG\bG trap while it executes. If -\b-T\bT
is not set, and the sourced file changes the D\bDE\bEB\bBU\bUG\bG trap, the new
value persists after .\b. completes. The return status is the sta-
tus of the last command executed from _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be (0 if no commands
- are executed), and non-zero if _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is not found or cannot
+ are executed), and non-zero if _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is not found or cannot
be read.
a\bal\bli\bia\bas\bs [-\b-p\bp] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be] ...]
- With no arguments or with the -\b-p\bp option, a\bal\bli\bia\bas\bs prints the list
- of aliases in the form a\bal\bli\bia\bas\bs _\bn_\ba_\bm_\be=_\bv_\ba_\bl_\bu_\be on standard output.
+ With no arguments or with the -\b-p\bp option, a\bal\bli\bia\bas\bs prints the list
+ of aliases in the form a\bal\bli\bia\bas\bs _\bn_\ba_\bm_\be=_\bv_\ba_\bl_\bu_\be on standard output.
When arguments are supplied, define an alias for each _\bn_\ba_\bm_\be whose
- _\bv_\ba_\bl_\bu_\be is given. A trailing space in _\bv_\ba_\bl_\bu_\be causes the next word
- to be checked for alias substitution when the alias is expanded
- during command parsing. For each _\bn_\ba_\bm_\be in the argument list for
- which no _\bv_\ba_\bl_\bu_\be is supplied, print the name and value of the
- alias _\bn_\ba_\bm_\be. a\bal\bli\bia\bas\bs returns true unless a _\bn_\ba_\bm_\be is given (without
+ _\bv_\ba_\bl_\bu_\be is given. A trailing space in _\bv_\ba_\bl_\bu_\be causes the next word
+ to be checked for alias substitution when the alias is expanded
+ during command parsing. For each _\bn_\ba_\bm_\be in the argument list for
+ which no _\bv_\ba_\bl_\bu_\be is supplied, print the name and value of the
+ alias _\bn_\ba_\bm_\be. a\bal\bli\bia\bas\bs returns true unless a _\bn_\ba_\bm_\be is given (without
a corresponding =_\bv_\ba_\bl_\bu_\be) for which no alias has been defined.
b\bbg\bg [_\bj_\bo_\bb_\bs_\bp_\be_\bc ...]
- Resume each suspended job _\bj_\bo_\bb_\bs_\bp_\be_\bc in the background, as if it
- had been started with &\b&. If _\bj_\bo_\bb_\bs_\bp_\be_\bc is not present, the shell
+ Resume each suspended job _\bj_\bo_\bb_\bs_\bp_\be_\bc in the background, as if it
+ had been started with &\b&. If _\bj_\bo_\bb_\bs_\bp_\be_\bc is not present, the shell
uses its notion of the _\bc_\bu_\br_\br_\be_\bn_\bt _\bj_\bo_\bb. b\bbg\bg _\bj_\bo_\bb_\bs_\bp_\be_\bc returns 0 unless
- run when job control is disabled or, when run with job control
- enabled, any specified _\bj_\bo_\bb_\bs_\bp_\be_\bc was not found or was started
+ run when job control is disabled or, when run with job control
+ enabled, any specified _\bj_\bo_\bb_\bs_\bp_\be_\bc was not found or was started
without job control.
b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] [-\b-l\bls\bsv\bvS\bSV\bVX\bX]
b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] -\b-p\bp|-\b-P\bP [_\br_\be_\ba_\bd_\bl_\bi_\bn_\be_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd]
b\bbi\bin\bnd\bd [-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp] _\bk_\be_\by_\bs_\be_\bq:_\br_\be_\ba_\bd_\bl_\bi_\bn_\be_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd
b\bbi\bin\bnd\bd _\br_\be_\ba_\bd_\bl_\bi_\bn_\be_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd_\b-_\bl_\bi_\bn_\be
- Display current r\bre\bea\bad\bdl\bli\bin\bne\be key and function bindings, bind a key
- sequence to a r\bre\bea\bad\bdl\bli\bin\bne\be function or macro or to a shell command,
- or set a r\bre\bea\bad\bdl\bli\bin\bne\be variable. Each non-option argument is a key
- binding or command as it would appear in a r\bre\bea\bad\bdl\bli\bin\bne\be initializa-
- tion file such as _\b._\bi_\bn_\bp_\bu_\bt_\br_\bc, but each binding or command must be
- passed as a separate argument; e.g., '"\C-x\C-r":
- re-read-init-file'. In the following descriptions, output
- available to be re-read is formatted as commands that would ap-
+ Display current r\bre\bea\bad\bdl\bli\bin\bne\be key and function bindings, bind a key
+ sequence to a r\bre\bea\bad\bdl\bli\bin\bne\be function or macro or to a shell command,
+ or set a r\bre\bea\bad\bdl\bli\bin\bne\be variable. Each non-option argument is a key
+ binding or command as it would appear in a r\bre\bea\bad\bdl\bli\bin\bne\be initializa-
+ tion file such as _\b._\bi_\bn_\bp_\bu_\bt_\br_\bc, but each binding or command must be
+ passed as a separate argument; e.g., '"\C-x\C-r":
+ re-read-init-file'. In the following descriptions, output
+ available to be re-read is formatted as commands that would ap-
pear in a r\bre\bea\bad\bdl\bli\bin\bne\be initialization file or that would be supplied
- as individual arguments to a b\bbi\bin\bnd\bd command. Options, if sup-
+ as individual arguments to a b\bbi\bin\bnd\bd command. Options, if sup-
plied, have the following meanings:
-\b-m\bm _\bk_\be_\by_\bm_\ba_\bp
Use _\bk_\be_\by_\bm_\ba_\bp as the keymap to be affected by the subsequent
bindings. Acceptable _\bk_\be_\by_\bm_\ba_\bp names are _\be_\bm_\ba_\bc_\bs_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bs_\bt_\ba_\bn_\b-
- _\bd_\ba_\br_\bd_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bm_\be_\bt_\ba_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bc_\bt_\bl_\bx_\b, _\bv_\bi_\b, _\bv_\bi_\b-_\bm_\bo_\bv_\be_\b, _\bv_\bi_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd,
- and _\bv_\bi_\b-_\bi_\bn_\bs_\be_\br_\bt. _\bv_\bi is equivalent to _\bv_\bi_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd (_\bv_\bi_\b-_\bm_\bo_\bv_\be
- is also a synonym); _\be_\bm_\ba_\bc_\bs is equivalent to _\be_\bm_\ba_\bc_\bs_\b-_\bs_\bt_\ba_\bn_\b-
+ _\bd_\ba_\br_\bd_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bm_\be_\bt_\ba_\b, _\be_\bm_\ba_\bc_\bs_\b-_\bc_\bt_\bl_\bx_\b, _\bv_\bi_\b, _\bv_\bi_\b-_\bm_\bo_\bv_\be_\b, _\bv_\bi_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd,
+ and _\bv_\bi_\b-_\bi_\bn_\bs_\be_\br_\bt. _\bv_\bi is equivalent to _\bv_\bi_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd (_\bv_\bi_\b-_\bm_\bo_\bv_\be
+ is also a synonym); _\be_\bm_\ba_\bc_\bs is equivalent to _\be_\bm_\ba_\bc_\bs_\b-_\bs_\bt_\ba_\bn_\b-
_\bd_\ba_\br_\bd.
-\b-l\bl List the names of all r\bre\bea\bad\bdl\bli\bin\bne\be functions.
- -\b-p\bp Display r\bre\bea\bad\bdl\bli\bin\bne\be function names and bindings in such a
- way that they can be used as an argument to a subsequent
- b\bbi\bin\bnd\bd command or in a r\bre\bea\bad\bdl\bli\bin\bne\be initialization file. If
- arguments remain after option processing, b\bbi\bin\bnd\bd treats
- them as r\bre\bea\bad\bdl\bli\bin\bne\be command names and restricts output to
- those names.
- -\b-P\bP List current r\bre\bea\bad\bdl\bli\bin\bne\be function names and bindings. If
+ -\b-p\bp Display r\bre\bea\bad\bdl\bli\bin\bne\be function names and bindings in such a
+ way that they can be used as an argument to a subsequent
+ b\bbi\bin\bnd\bd command or in a r\bre\bea\bad\bdl\bli\bin\bne\be initialization file. If
arguments remain after option processing, b\bbi\bin\bnd\bd treats
them as r\bre\bea\bad\bdl\bli\bin\bne\be command names and restricts output to
those names.
- -\b-s\bs Display r\bre\bea\bad\bdl\bli\bin\bne\be key sequences bound to macros and the
- strings they output in such a way that they can be used
+ -\b-P\bP List current r\bre\bea\bad\bdl\bli\bin\bne\be function names and bindings. If
+ arguments remain after option processing, b\bbi\bin\bnd\bd treats
+ them as r\bre\bea\bad\bdl\bli\bin\bne\be command names and restricts output to
+ those names.
+ -\b-s\bs Display r\bre\bea\bad\bdl\bli\bin\bne\be key sequences bound to macros and the
+ strings they output in such a way that they can be used
as an argument to a subsequent b\bbi\bin\bnd\bd command or in a r\bre\bea\bad\bd-\b-
l\bli\bin\bne\be initialization file.
- -\b-S\bS Display r\bre\bea\bad\bdl\bli\bin\bne\be key sequences bound to macros and the
+ -\b-S\bS Display r\bre\bea\bad\bdl\bli\bin\bne\be key sequences bound to macros and the
strings they output.
- -\b-v\bv Display r\bre\bea\bad\bdl\bli\bin\bne\be variable names and values in such a way
+ -\b-v\bv Display r\bre\bea\bad\bdl\bli\bin\bne\be variable names and values in such a way
that they can be used as an argument to a subsequent b\bbi\bin\bnd\bd
command or in a r\bre\bea\bad\bdl\bli\bin\bne\be initialization file.
-\b-V\bV List current r\bre\bea\bad\bdl\bli\bin\bne\be variable names and values.
-\b-f\bf _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
Read key bindings from _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be.
-\b-q\bq _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn
- Display key sequences that invoke the named r\bre\bea\bad\bdl\bli\bin\bne\be
+ Display key sequences that invoke the named r\bre\bea\bad\bdl\bli\bin\bne\be
_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn.
-\b-u\bu _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn
- Unbind all key sequences bound to the named r\bre\bea\bad\bdl\bli\bin\bne\be
+ Unbind all key sequences bound to the named r\bre\bea\bad\bdl\bli\bin\bne\be
_\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn.
-\b-r\br _\bk_\be_\by_\bs_\be_\bq
Remove any current binding for _\bk_\be_\by_\bs_\be_\bq.
-\b-x\bx _\bk_\be_\by_\bs_\be_\bq[\b[:\b: ]\b]_\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd
Cause _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd to be executed whenever _\bk_\be_\by_\bs_\be_\bq is en-
tered. The separator between _\bk_\be_\by_\bs_\be_\bq and _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd is
- either whitespace or a colon optionally followed by
- whitespace. If the separator is whitespace, _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\b-
- _\bm_\ba_\bn_\bd must be enclosed in double quotes and r\bre\bea\bad\bdl\bli\bin\bne\be ex-
- pands any of its special backslash-escapes in _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\b-
- _\bm_\ba_\bn_\bd before saving it. If the separator is a colon, any
- enclosing double quotes are optional, and r\bre\bea\bad\bdl\bli\bin\bne\be does
- not expand the command string before saving it. Since
- the entire key binding expression must be a single argu-
- ment, it should be enclosed in single quotes. When
- _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd is executed, the shell sets the R\bRE\bEA\bAD\bD-\b-
- L\bLI\bIN\bNE\bE_\b_L\bLI\bIN\bNE\bE variable to the contents of the r\bre\bea\bad\bdl\bli\bin\bne\be line
+ either whitespace or a colon optionally followed by
+ whitespace. If the separator is whitespace, _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\b-
+ _\bm_\ba_\bn_\bd must be enclosed in double quotes and r\bre\bea\bad\bdl\bli\bin\bne\be ex-
+ pands any of its special backslash-escapes in _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\b-
+ _\bm_\ba_\bn_\bd before saving it. If the separator is a colon, any
+ enclosing double quotes are optional, and r\bre\bea\bad\bdl\bli\bin\bne\be does
+ not expand the command string before saving it. Since
+ the entire key binding expression must be a single argu-
+ ment, it should be enclosed in single quotes. When
+ _\bs_\bh_\be_\bl_\bl_\b-_\bc_\bo_\bm_\bm_\ba_\bn_\bd is executed, the shell sets the R\bRE\bEA\bAD\bD-\b-
+ L\bLI\bIN\bNE\bE_\b_L\bLI\bIN\bNE\bE variable to the contents of the r\bre\bea\bad\bdl\bli\bin\bne\be line
buffer and the R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_P\bPO\bOI\bIN\bNT\bT and R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_M\bMA\bAR\bRK\bK variables
- to the current location of the insertion point and the
- saved insertion point (the mark), respectively. The
- shell assigns any numeric argument the user supplied to
- the R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_A\bAR\bRG\bGU\bUM\bME\bEN\bNT\bT variable. If there was no argu-
- ment, that variable is not set. If the executed command
- changes the value of any of R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_L\bLI\bIN\bNE\bE, R\bRE\bEA\bAD\bD-\b-
- L\bLI\bIN\bNE\bE_\b_P\bPO\bOI\bIN\bNT\bT, or R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_M\bMA\bAR\bRK\bK, those new values will be
+ to the current location of the insertion point and the
+ saved insertion point (the mark), respectively. The
+ shell assigns any numeric argument the user supplied to
+ the R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_A\bAR\bRG\bGU\bUM\bME\bEN\bNT\bT variable. If there was no argu-
+ ment, that variable is not set. If the executed command
+ changes the value of any of R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_L\bLI\bIN\bNE\bE, R\bRE\bEA\bAD\bD-\b-
+ L\bLI\bIN\bNE\bE_\b_P\bPO\bOI\bIN\bNT\bT, or R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE_\b_M\bMA\bAR\bRK\bK, those new values will be
reflected in the editing state.
- -\b-X\bX List all key sequences bound to shell commands and the
- associated commands in a format that can be reused as an
+ -\b-X\bX List all key sequences bound to shell commands and the
+ associated commands in a format that can be reused as an
argument to a subsequent b\bbi\bin\bnd\bd command.
- The return value is 0 unless an unrecognized option is supplied
+ The return value is 0 unless an unrecognized option is supplied
or an error occurred.
b\bbr\bre\bea\bak\bk [_\bn]
- Exit from within a f\bfo\bor\br, w\bwh\bhi\bil\ble\be, u\bun\bnt\bti\bil\bl, or s\bse\bel\ble\bec\bct\bt loop. If _\bn is
+ Exit from within a f\bfo\bor\br, w\bwh\bhi\bil\ble\be, u\bun\bnt\bti\bil\bl, or s\bse\bel\ble\bec\bct\bt loop. If _\bn is
specified, b\bbr\bre\bea\bak\bk exits _\bn enclosing loops. _\bn must be >= 1. If _\bn
- is greater than the number of enclosing loops, all enclosing
+ is greater than the number of enclosing loops, all enclosing
loops are exited. The return value is 0 unless _\bn is not greater
than or equal to 1.
b\bbu\bui\bil\blt\bti\bin\bn _\bs_\bh_\be_\bl_\bl_\b-_\bb_\bu_\bi_\bl_\bt_\bi_\bn [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
- Execute the specified shell builtin _\bs_\bh_\be_\bl_\bl_\b-_\bb_\bu_\bi_\bl_\bt_\bi_\bn, passing it
- _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs, and return its exit status. This is useful when
- defining a function whose name is the same as a shell builtin,
- retaining the functionality of the builtin within the function.
- The c\bcd\bd builtin is commonly redefined this way. The return sta-
+ Execute the specified shell builtin _\bs_\bh_\be_\bl_\bl_\b-_\bb_\bu_\bi_\bl_\bt_\bi_\bn, passing it
+ _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs, and return its exit status. This is useful when
+ defining a function whose name is the same as a shell builtin,
+ retaining the functionality of the builtin within the function.
+ The c\bcd\bd builtin is commonly redefined this way. The return sta-
tus is false if _\bs_\bh_\be_\bl_\bl_\b-_\bb_\bu_\bi_\bl_\bt_\bi_\bn is not a shell builtin command.
c\bca\bal\bll\ble\ber\br [_\be_\bx_\bp_\br]
Returns the context of any active subroutine call (a shell func-
tion or a script executed with the .\b. or s\bso\bou\bur\brc\bce\be builtins).
- Without _\be_\bx_\bp_\br, c\bca\bal\bll\ble\ber\br displays the line number and source file-
- name of the current subroutine call. If a non-negative integer
+ Without _\be_\bx_\bp_\br, c\bca\bal\bll\ble\ber\br displays the line number and source file-
+ name of the current subroutine call. If a non-negative integer
is supplied as _\be_\bx_\bp_\br, c\bca\bal\bll\ble\ber\br displays the line number, subroutine
name, and source file corresponding to that position in the cur-
- rent execution call stack. This extra information may be used,
+ rent execution call stack. This extra information may be used,
for example, to print a stack trace. The current frame is frame
0.
- The return value is 0 unless the shell is not executing a sub-
- routine call or _\be_\bx_\bp_\br does not correspond to a valid position in
+ The return value is 0 unless the shell is not executing a sub-
+ routine call or _\be_\bx_\bp_\br does not correspond to a valid position in
the call stack.
c\bcd\bd [-\b-L\bL] [-\b-@\b@] [_\bd_\bi_\br]
c\bcd\bd -\b-P\bP [-\b-e\be] [-\b-@\b@] [_\bd_\bi_\br]
- Change the current directory to _\bd_\bi_\br. if _\bd_\bi_\br is not supplied,
- the value of the H\bHO\bOM\bME\bE shell variable is used as _\bd_\bi_\br. If _\bd_\bi_\br is
+ Change the current directory to _\bd_\bi_\br. if _\bd_\bi_\br is not supplied,
+ the value of the H\bHO\bOM\bME\bE shell variable is used as _\bd_\bi_\br. If _\bd_\bi_\br is
the empty string, c\bcd\bd treats it as an error. The variable C\bCD\bDP\bPA\bAT\bTH\bH
exists, and _\bd_\bi_\br does not begin with a slash (/), c\bcd\bd uses it as a
- search path: the shell searches each directory name in C\bCD\bDP\bPA\bAT\bTH\bH
+ search path: the shell searches each directory name in C\bCD\bDP\bPA\bAT\bTH\bH
for _\bd_\bi_\br. Alternative directory names in C\bCD\bDP\bPA\bAT\bTH\bH are separated by
a colon (:). A null directory name in C\bCD\bDP\bPA\bAT\bTH\bH is the same as the
current directory, i.e., ".".
- The -\b-P\bP option causes c\bcd\bd to use the physical directory structure
+ The -\b-P\bP option causes c\bcd\bd to use the physical directory structure
by resolving symbolic links while traversing _\bd_\bi_\br and before pro-
- cessing instances of _\b._\b. in _\bd_\bi_\br (see also the -\b-P\bP option to the
+ cessing instances of _\b._\b. in _\bd_\bi_\br (see also the -\b-P\bP option to the
s\bse\bet\bt builtin command).
- The -\b-L\bL option forces c\bcd\bd to follow symbolic links by resolving
+ The -\b-L\bL option forces c\bcd\bd to follow symbolic links by resolving
the link after processing instances of _\b._\b. in _\bd_\bi_\br. If _\b._\b. appears
- in _\bd_\bi_\br, c\bcd\bd processes it by removing the immediately previous
+ in _\bd_\bi_\br, c\bcd\bd processes it by removing the immediately previous
pathname component from _\bd_\bi_\br, back to a slash or the beginning of
- _\bd_\bi_\br, and verifying that the portion of _\bd_\bi_\br it has processed to
- that point is still a valid directory name after removing the
+ _\bd_\bi_\br, and verifying that the portion of _\bd_\bi_\br it has processed to
+ that point is still a valid directory name after removing the
pathname component. If it is not a valid directory name, c\bcd\bd re-
- turns a non-zero status. If neither -\b-L\bL nor -\b-P\bP is supplied, c\bcd\bd
+ turns a non-zero status. If neither -\b-L\bL nor -\b-P\bP is supplied, c\bcd\bd
behaves as if -\b-L\bL had been supplied.
If the -\b-e\be option is supplied with -\b-P\bP, and c\bcd\bd cannot successfully
- determine the current working directory after a successful di-
+ determine the current working directory after a successful di-
rectory change, it returns a non-zero status.
- On systems that support it, the -\b-@\b@ option presents the extended
+ On systems that support it, the -\b-@\b@ option presents the extended
attributes associated with a file as a directory.
- An argument of -\b- is converted to $\b$O\bOL\bLD\bDP\bPW\bWD\bD before attempting the
+ An argument of -\b- is converted to $\b$O\bOL\bLD\bDP\bPW\bWD\bD before attempting the
directory change.
- If c\bcd\bd uses a non-empty directory name from C\bCD\bDP\bPA\bAT\bTH\bH, or if -\b- is
- the first argument, and the directory change is successful, c\bcd\bd
+ If c\bcd\bd uses a non-empty directory name from C\bCD\bDP\bPA\bAT\bTH\bH, or if -\b- is
+ the first argument, and the directory change is successful, c\bcd\bd
writes the absolute pathname of the new working directory to the
standard output.
- If the directory change is successful, c\bcd\bd sets the value of the
+ If the directory change is successful, c\bcd\bd sets the value of the
P\bPW\bWD\bD environment variable to the new directory name, and sets the
- O\bOL\bLD\bDP\bPW\bWD\bD environment variable to the value of the current working
+ O\bOL\bLD\bDP\bPW\bWD\bD environment variable to the value of the current working
directory before the change.
- The return value is true if the directory was successfully
+ The return value is true if the directory was successfully
changed; false otherwise.
c\bco\bom\bmm\bma\ban\bnd\bd [-\b-p\bpV\bVv\bv] _\bc_\bo_\bm_\bm_\ba_\bn_\bd [_\ba_\br_\bg ...]
- The c\bco\bom\bmm\bma\ban\bnd\bd builtin runs _\bc_\bo_\bm_\bm_\ba_\bn_\bd with _\ba_\br_\bg_\bs suppressing the nor-
+ The c\bco\bom\bmm\bma\ban\bnd\bd builtin runs _\bc_\bo_\bm_\bm_\ba_\bn_\bd with _\ba_\br_\bg_\bs suppressing the nor-
mal shell function lookup for _\bc_\bo_\bm_\bm_\ba_\bn_\bd. Only builtin commands or
- commands found in the P\bPA\bAT\bTH\bH named _\bc_\bo_\bm_\bm_\ba_\bn_\bd are executed. If the
+ commands found in the P\bPA\bAT\bTH\bH named _\bc_\bo_\bm_\bm_\ba_\bn_\bd are executed. If the
-\b-p\bp option is supplied, the search for _\bc_\bo_\bm_\bm_\ba_\bn_\bd is performed using
- a default value for P\bPA\bAT\bTH\bH that is guaranteed to find all of the
+ a default value for P\bPA\bAT\bTH\bH that is guaranteed to find all of the
standard utilities.
- If either the -\b-V\bV or -\b-v\bv option is supplied, c\bco\bom\bmm\bma\ban\bnd\bd prints a de-
- scription of _\bc_\bo_\bm_\bm_\ba_\bn_\bd. The -\b-v\bv option displays a single word in-
- dicating the command or filename used to invoke _\bc_\bo_\bm_\bm_\ba_\bn_\bd; the -\b-V\bV
+ If either the -\b-V\bV or -\b-v\bv option is supplied, c\bco\bom\bmm\bma\ban\bnd\bd prints a de-
+ scription of _\bc_\bo_\bm_\bm_\ba_\bn_\bd. The -\b-v\bv option displays a single word in-
+ dicating the command or filename used to invoke _\bc_\bo_\bm_\bm_\ba_\bn_\bd; the -\b-V\bV
option produces a more verbose description.
- If the -\b-V\bV or -\b-v\bv option is supplied, the exit status is zero if
- _\bc_\bo_\bm_\bm_\ba_\bn_\bd was found, and non-zero if not. If neither option is
- supplied and an error occurred or _\bc_\bo_\bm_\bm_\ba_\bn_\bd cannot be found, the
- exit status is 127. Otherwise, the exit status of the c\bco\bom\bmm\bma\ban\bnd\bd
+ If the -\b-V\bV or -\b-v\bv option is supplied, the exit status is zero if
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd was found, and non-zero if not. If neither option is
+ supplied and an error occurred or _\bc_\bo_\bm_\bm_\ba_\bn_\bd cannot be found, the
+ exit status is 127. Otherwise, the exit status of the c\bco\bom\bmm\bma\ban\bnd\bd
builtin is the exit status of _\bc_\bo_\bm_\bm_\ba_\bn_\bd.
c\bco\bom\bmp\bpg\bge\ben\bn [-\b-V\bV _\bv_\ba_\br_\bn_\ba_\bm_\be] [_\bo_\bp_\bt_\bi_\bo_\bn] [_\bw_\bo_\br_\bd]
- Generate possible completion matches for _\bw_\bo_\br_\bd according to the
- _\bo_\bp_\bt_\bi_\bo_\bns, which may be any option accepted by the c\bco\bom\bmp\bpl\ble\bet\bte\be
+ Generate possible completion matches for _\bw_\bo_\br_\bd according to the
+ _\bo_\bp_\bt_\bi_\bo_\bns, which may be any option accepted by the c\bco\bom\bmp\bpl\ble\bet\bte\be
builtin with the exceptions of -\b-p\bp, -\b-r\br, -\b-D\bD, -\b-E\bE, and -\b-I\bI, and write
the matches to the standard output.
- If the -\b-V\bV option is supplied, c\bco\bom\bmp\bpg\bge\ben\bn stores the generated com-
- pletions into the indexed array variable _\bv_\ba_\br_\bn_\ba_\bm_\be instead of
+ If the -\b-V\bV option is supplied, c\bco\bom\bmp\bpg\bge\ben\bn stores the generated com-
+ pletions into the indexed array variable _\bv_\ba_\br_\bn_\ba_\bm_\be instead of
writing them to the standard output.
When using the -\b-F\bF or -\b-C\bC options, the various shell variables set
The matches will be generated in the same way as if the program-
mable completion code had generated them directly from a comple-
- tion specification with the same flags. If _\bw_\bo_\br_\bd is specified,
- only those completions matching _\bw_\bo_\br_\bd will be displayed or
+ tion specification with the same flags. If _\bw_\bo_\br_\bd is specified,
+ only those completions matching _\bw_\bo_\br_\bd will be displayed or
stored.
- The return value is true unless an invalid option is supplied,
+ The return value is true unless an invalid option is supplied,
or no matches were generated.
c\bco\bom\bmp\bpl\ble\bet\bte\be [-\b-a\bab\bbc\bcd\bde\bef\bfg\bgj\bjk\bks\bsu\buv\bv] [-\b-o\bo _\bc_\bo_\bm_\bp_\b-_\bo_\bp_\bt_\bi_\bo_\bn] [-\b-D\bDE\bEI\bI] [-\b-A\bA _\ba_\bc_\bt_\bi_\bo_\bn]
Specify how arguments to each _\bn_\ba_\bm_\be should be completed.
If the -\b-p\bp option is supplied, or if no options or _\bn_\ba_\bm_\bes are sup-
- plied, print existing completion specifications in a way that
+ plied, print existing completion specifications in a way that
allows them to be reused as input. The -\b-r\br option removes a com-
- pletion specification for each _\bn_\ba_\bm_\be, or, if no _\bn_\ba_\bm_\bes are sup-
+ pletion specification for each _\bn_\ba_\bm_\be, or, if no _\bn_\ba_\bm_\bes are sup-
plied, all completion specifications.
- The -\b-D\bD option indicates that other supplied options and actions
- should apply to the "default" command completion; that is, com-
- pletion attempted on a command for which no completion has pre-
- viously been defined. The -\b-E\bE option indicates that other sup-
- plied options and actions should apply to "empty" command com-
- pletion; that is, completion attempted on a blank line. The -\b-I\bI
- option indicates that other supplied options and actions should
- apply to completion on the initial non-assignment word on the
+ The -\b-D\bD option indicates that other supplied options and actions
+ should apply to the "default" command completion; that is, com-
+ pletion attempted on a command for which no completion has pre-
+ viously been defined. The -\b-E\bE option indicates that other sup-
+ plied options and actions should apply to "empty" command com-
+ pletion; that is, completion attempted on a blank line. The -\b-I\bI
+ option indicates that other supplied options and actions should
+ apply to completion on the initial non-assignment word on the
line, or after a command delimiter such as ;\b; or |\b|, which is usu-
ally command name completion. If multiple options are supplied,
the -\b-D\bD option takes precedence over -\b-E\bE, and both take precedence
- over -\b-I\bI. If any of -\b-D\bD, -\b-E\bE, or -\b-I\bI are supplied, any other _\bn_\ba_\bm_\be
- arguments are ignored; these completions only apply to the case
+ over -\b-I\bI. If any of -\b-D\bD, -\b-E\bE, or -\b-I\bI are supplied, any other _\bn_\ba_\bm_\be
+ arguments are ignored; these completions only apply to the case
specified by the option.
The process of applying these completion specifications when at-
- tempting word completion is described above under P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be
+ tempting word completion is described above under P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be
C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn.
- Other options, if specified, have the following meanings. The
- arguments to the -\b-G\bG, -\b-W\bW, and -\b-X\bX options (and, if necessary, the
- -\b-P\bP and -\b-S\bS options) should be quoted to protect them from expan-
+ Other options, if specified, have the following meanings. The
+ arguments to the -\b-G\bG, -\b-W\bW, and -\b-X\bX options (and, if necessary, the
+ -\b-P\bP and -\b-S\bS options) should be quoted to protect them from expan-
sion before the c\bco\bom\bmp\bpl\ble\bet\bte\be builtin is invoked.
-\b-o\bo _\bc_\bo_\bm_\bp_\b-_\bo_\bp_\bt_\bi_\bo_\bn
- The _\bc_\bo_\bm_\bp_\b-_\bo_\bp_\bt_\bi_\bo_\bn controls several aspects of the comp-
- spec's behavior beyond the simple generation of comple-
+ The _\bc_\bo_\bm_\bp_\b-_\bo_\bp_\bt_\bi_\bo_\bn controls several aspects of the comp-
+ spec's behavior beyond the simple generation of comple-
tions. _\bc_\bo_\bm_\bp_\b-_\bo_\bp_\bt_\bi_\bo_\bn may be one of:
b\bba\bas\bsh\bhd\bde\bef\bfa\bau\bul\blt\bt
Perform the rest of the default b\bba\bas\bsh\bh completions
if the compspec generates no matches.
- d\bde\bef\bfa\bau\bul\blt\bt Use r\bre\bea\bad\bdl\bli\bin\bne\be's default filename completion if
+ d\bde\bef\bfa\bau\bul\blt\bt Use r\bre\bea\bad\bdl\bli\bin\bne\be's default filename completion if
the compspec generates no matches.
d\bdi\bir\brn\bna\bam\bme\bes\bs
- Perform directory name completion if the comp-
+ Perform directory name completion if the comp-
spec generates no matches.
f\bfi\bil\ble\ben\bna\bam\bme\bes\bs
- Tell r\bre\bea\bad\bdl\bli\bin\bne\be that the compspec generates file-
- names, so it can perform any filename-specific
- processing (such as adding a slash to directory
- names, quoting special characters, or suppress-
- ing trailing spaces). This is intended to be
+ Tell r\bre\bea\bad\bdl\bli\bin\bne\be that the compspec generates file-
+ names, so it can perform any filename-specific
+ processing (such as adding a slash to directory
+ names, quoting special characters, or suppress-
+ ing trailing spaces). This is intended to be
used with shell functions.
f\bfu\bul\bll\blq\bqu\buo\bot\bte\be
- Tell r\bre\bea\bad\bdl\bli\bin\bne\be to quote all the completed words
+ Tell r\bre\bea\bad\bdl\bli\bin\bne\be to quote all the completed words
even if they are not filenames.
- n\bno\boq\bqu\buo\bot\bte\be Tell r\bre\bea\bad\bdl\bli\bin\bne\be not to quote the completed words
- if they are filenames (quoting filenames is the
+ n\bno\boq\bqu\buo\bot\bte\be Tell r\bre\bea\bad\bdl\bli\bin\bne\be not to quote the completed words
+ if they are filenames (quoting filenames is the
default).
- n\bno\bos\bso\bor\brt\bt Tell r\bre\bea\bad\bdl\bli\bin\bne\be not to sort the list of possible
+ n\bno\bos\bso\bor\brt\bt Tell r\bre\bea\bad\bdl\bli\bin\bne\be not to sort the list of possible
completions alphabetically.
- n\bno\bos\bsp\bpa\bac\bce\be Tell r\bre\bea\bad\bdl\bli\bin\bne\be not to append a space (the de-
- fault) to words completed at the end of the
+ n\bno\bos\bsp\bpa\bac\bce\be Tell r\bre\bea\bad\bdl\bli\bin\bne\be not to append a space (the de-
+ fault) to words completed at the end of the
line.
p\bpl\blu\bus\bsd\bdi\bir\brs\bs
- After generating any matches defined by the
- compspec, attempt directory name completion and
- add any matches to the results of the other ac-
+ After generating any matches defined by the
+ compspec, attempt directory name completion and
+ add any matches to the results of the other ac-
tions.
-\b-A\bA _\ba_\bc_\bt_\bi_\bo_\bn
- The _\ba_\bc_\bt_\bi_\bo_\bn may be one of the following to generate a
+ The _\ba_\bc_\bt_\bi_\bo_\bn may be one of the following to generate a
list of possible completions:
a\bal\bli\bia\bas\bs Alias names. May also be specified as -\b-a\ba.
a\bar\brr\bra\bay\byv\bva\bar\br
Array variable names.
b\bbi\bin\bnd\bdi\bin\bng\bg R\bRe\bea\bad\bdl\bli\bin\bne\be key binding names.
- b\bbu\bui\bil\blt\bti\bin\bn Names of shell builtin commands. May also be
+ b\bbu\bui\bil\blt\bti\bin\bn Names of shell builtin commands. May also be
specified as -\b-b\bb.
c\bco\bom\bmm\bma\ban\bnd\bd Command names. May also be specified as -\b-c\bc.
d\bdi\bir\bre\bec\bct\bto\bor\bry\by
d\bdi\bis\bsa\bab\bbl\ble\bed\bd
Names of disabled shell builtins.
e\ben\bna\bab\bbl\ble\bed\bd Names of enabled shell builtins.
- e\bex\bxp\bpo\bor\brt\bt Names of exported shell variables. May also be
+ e\bex\bxp\bpo\bor\brt\bt Names of exported shell variables. May also be
specified as -\b-e\be.
- f\bfi\bil\ble\be File and directory names, similar to r\bre\bea\bad\bdl\bli\bin\bne\be's
- filename completion. May also be specified as
+ f\bfi\bil\ble\be File and directory names, similar to r\bre\bea\bad\bdl\bli\bin\bne\be's
+ filename completion. May also be specified as
-\b-f\bf.
f\bfu\bun\bnc\bct\bti\bio\bon\bn
Names of shell functions.
h\bhe\bel\blp\bpt\bto\bop\bpi\bic\bc
Help topics as accepted by the h\bhe\bel\blp\bp builtin.
h\bho\bos\bst\btn\bna\bam\bme\be
- Hostnames, as taken from the file specified by
+ Hostnames, as taken from the file specified by
the H\bHO\bOS\bST\bTF\bFI\bIL\bLE\bE shell variable.
- j\bjo\bob\bb Job names, if job control is active. May also
+ j\bjo\bob\bb Job names, if job control is active. May also
be specified as -\b-j\bj.
- k\bke\bey\byw\bwo\bor\brd\bd Shell reserved words. May also be specified as
+ k\bke\bey\byw\bwo\bor\brd\bd Shell reserved words. May also be specified as
-\b-k\bk.
r\bru\bun\bnn\bni\bin\bng\bg Names of running jobs, if job control is active.
s\bse\ber\brv\bvi\bic\bce\be Service names. May also be specified as -\b-s\bs.
- s\bse\bet\bto\bop\bpt\bt Valid arguments for the -\b-o\bo option to the s\bse\bet\bt
+ s\bse\bet\bto\bop\bpt\bt Valid arguments for the -\b-o\bo option to the s\bse\bet\bt
builtin.
- s\bsh\bho\bop\bpt\bt Shell option names as accepted by the s\bsh\bho\bop\bpt\bt
+ s\bsh\bho\bop\bpt\bt Shell option names as accepted by the s\bsh\bho\bop\bpt\bt
builtin.
s\bsi\big\bgn\bna\bal\bl Signal names.
s\bst\bto\bop\bpp\bpe\bed\bd Names of stopped jobs, if job control is active.
Names of all shell variables. May also be spec-
ified as -\b-v\bv.
-\b-C\bC _\bc_\bo_\bm_\bm_\ba_\bn_\bd
- _\bc_\bo_\bm_\bm_\ba_\bn_\bd is executed in a subshell environment, and its
- output is used as the possible completions. Arguments
+ _\bc_\bo_\bm_\bm_\ba_\bn_\bd is executed in a subshell environment, and its
+ output is used as the possible completions. Arguments
are passed as with the -\b-F\bF option.
-\b-F\bF _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn
- The shell function _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn is executed in the current
- shell environment. When the function is executed, the
+ The shell function _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn is executed in the current
+ shell environment. When the function is executed, the
first argument ($\b$1\b1) is the name of the command whose ar-
guments are being completed, the second argument ($\b$2\b2) is
the word being completed, and the third argument ($\b$3\b3) is
- the word preceding the word being completed on the cur-
+ the word preceding the word being completed on the cur-
rent command line. When _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn finishes, programmable
- completion retrieves the possible completions from the
+ completion retrieves the possible completions from the
value of the C\bCO\bOM\bMP\bPR\bRE\bEP\bPL\bLY\bY array variable.
-\b-G\bG _\bg_\bl_\bo_\bb_\bp_\ba_\bt
- Expand the pathname expansion pattern _\bg_\bl_\bo_\bb_\bp_\ba_\bt to gener-
+ Expand the pathname expansion pattern _\bg_\bl_\bo_\bb_\bp_\ba_\bt to gener-
ate the possible completions.
-\b-P\bP _\bp_\br_\be_\bf_\bi_\bx
- Add _\bp_\br_\be_\bf_\bi_\bx to the beginning of each possible completion
+ Add _\bp_\br_\be_\bf_\bi_\bx to the beginning of each possible completion
after all other options have been applied.
-\b-S\bS _\bs_\bu_\bf_\bf_\bi_\bx
- Append _\bs_\bu_\bf_\bf_\bi_\bx to each possible completion after all
+ Append _\bs_\bu_\bf_\bf_\bi_\bx to each possible completion after all
other options have been applied.
-\b-W\bW _\bw_\bo_\br_\bd_\bl_\bi_\bs_\bt
- Split the _\bw_\bo_\br_\bd_\bl_\bi_\bs_\bt using the characters in the I\bIF\bFS\bS spe-
- cial variable as delimiters, and expand each resulting
- word. Shell quoting is honored within _\bw_\bo_\br_\bd_\bl_\bi_\bs_\bt, in or-
- der to provide a mechanism for the words to contain
- shell metacharacters or characters in the value of I\bIF\bFS\bS.
- The possible completions are the members of the resul-
- tant list which match a prefix of the word being com-
+ Split the _\bw_\bo_\br_\bd_\bl_\bi_\bs_\bt using the characters in the I\bIF\bFS\bS spe-
+ cial variable as delimiters, and expand each resulting
+ word. Shell quoting is honored within _\bw_\bo_\br_\bd_\bl_\bi_\bs_\bt, in or-
+ der to provide a mechanism for the words to contain
+ shell metacharacters or characters in the value of I\bIF\bFS\bS.
+ The possible completions are the members of the resul-
+ tant list which match a prefix of the word being com-
pleted.
-\b-X\bX _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt
- _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt is a pattern as used for pathname expansion.
+ _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt is a pattern as used for pathname expansion.
It is applied to the list of possible completions gener-
- ated by the preceding options and arguments, and each
- completion matching _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt is removed from the list.
- A leading !\b! in _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt negates the pattern; in this
+ ated by the preceding options and arguments, and each
+ completion matching _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt is removed from the list.
+ A leading !\b! in _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt negates the pattern; in this
case, any completion not matching _\bf_\bi_\bl_\bt_\be_\br_\bp_\ba_\bt is removed.
- The return value is true unless an invalid option is supplied,
+ The return value is true unless an invalid option is supplied,
an option other than -\b-p\bp, -\b-r\br, -\b-D\bD, -\b-E\bE, or -\b-I\bI is supplied without a
- _\bn_\ba_\bm_\be argument, an attempt is made to remove a completion speci-
+ _\bn_\ba_\bm_\be argument, an attempt is made to remove a completion speci-
fication for a _\bn_\ba_\bm_\be for which no specification exists, or an er-
ror occurs adding a completion specification.
c\bco\bom\bmp\bpo\bop\bpt\bt [-\b-o\bo _\bo_\bp_\bt_\bi_\bo_\bn] [-\b-D\bDE\bEI\bI] [+\b+o\bo _\bo_\bp_\bt_\bi_\bo_\bn] [_\bn_\ba_\bm_\be]
- Modify completion options for each _\bn_\ba_\bm_\be according to the _\bo_\bp_\b-
+ Modify completion options for each _\bn_\ba_\bm_\be according to the _\bo_\bp_\b-
_\bt_\bi_\bo_\bns, or for the currently-executing completion if no _\bn_\ba_\bm_\bes are
- supplied. If no _\bo_\bp_\bt_\bi_\bo_\bns are supplied, display the completion
- options for each _\bn_\ba_\bm_\be or the current completion. The possible
- values of _\bo_\bp_\bt_\bi_\bo_\bn are those valid for the c\bco\bom\bmp\bpl\ble\bet\bte\be builtin de-
+ supplied. If no _\bo_\bp_\bt_\bi_\bo_\bns are supplied, display the completion
+ options for each _\bn_\ba_\bm_\be or the current completion. The possible
+ values of _\bo_\bp_\bt_\bi_\bo_\bn are those valid for the c\bco\bom\bmp\bpl\ble\bet\bte\be builtin de-
scribed above.
The -\b-D\bD option indicates that other supplied options should apply
- to the "default" command completion; the -\b-E\bE option indicates
+ to the "default" command completion; the -\b-E\bE option indicates
that other supplied options should apply to "empty" command com-
pletion; and the -\b-I\bI option indicates that other supplied options
- should apply to completion on the initial word on the line.
+ should apply to completion on the initial word on the line.
These are determined in the same way as the c\bco\bom\bmp\bpl\ble\bet\bte\be builtin.
If multiple options are supplied, the -\b-D\bD option takes precedence
over -\b-E\bE, and both take precedence over -\b-I\bI.
- The return value is true unless an invalid option is supplied,
+ The return value is true unless an invalid option is supplied,
an attempt is made to modify the options for a _\bn_\ba_\bm_\be for which no
completion specification exists, or an output error occurs.
c\bco\bon\bnt\bti\bin\bnu\bue\be [_\bn]
c\bco\bon\bnt\bti\bin\bnu\bue\be resumes the next iteration of the enclosing f\bfo\bor\br, w\bwh\bhi\bil\ble\be,
- u\bun\bnt\bti\bil\bl, or s\bse\bel\ble\bec\bct\bt loop. If _\bn is specified, b\bba\bas\bsh\bh resumes the _\bnth
- enclosing loop. _\bn must be >= 1. If _\bn is greater than the num-
- ber of enclosing loops, the shell resumes the last enclosing
- loop (the "top-level" loop). The return value is 0 unless _\bn is
+ u\bun\bnt\bti\bil\bl, or s\bse\bel\ble\bec\bct\bt loop. If _\bn is specified, b\bba\bas\bsh\bh resumes the _\bnth
+ enclosing loop. _\bn must be >= 1. If _\bn is greater than the num-
+ ber of enclosing loops, the shell resumes the last enclosing
+ loop (the "top-level" loop). The return value is 0 unless _\bn is
not greater than or equal to 1.
d\bde\bec\bcl\bla\bar\bre\be [-\b-a\baA\bAf\bfF\bFg\bgi\biI\bIl\bln\bnr\brt\btu\bux\bx] [-\b-p\bp] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be] ...]
t\bty\byp\bpe\bes\bse\bet\bt [-\b-a\baA\bAf\bfF\bFg\bgi\biI\bIl\bln\bnr\brt\btu\bux\bx] [-\b-p\bp] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be] ...]
- Declare variables and/or give them attributes. If no _\bn_\ba_\bm_\bes are
+ Declare variables and/or give them attributes. If no _\bn_\ba_\bm_\bes are
given then display the values of variables or functions. The -\b-p\bp
- option will display the attributes and values of each _\bn_\ba_\bm_\be.
- When -\b-p\bp is used with _\bn_\ba_\bm_\be arguments, additional options, other
+ option will display the attributes and values of each _\bn_\ba_\bm_\be.
+ When -\b-p\bp is used with _\bn_\ba_\bm_\be arguments, additional options, other
than -\b-f\bf and -\b-F\bF, are ignored.
When -\b-p\bp is supplied without _\bn_\ba_\bm_\be arguments, d\bde\bec\bcl\bla\bar\bre\be will display
the attributes and values of all variables having the attributes
- specified by the additional options. If no other options are
+ specified by the additional options. If no other options are
supplied with -\b-p\bp, d\bde\bec\bcl\bla\bar\bre\be will display the attributes and values
- of all shell variables. The -\b-f\bf option restricts the display to
+ of all shell variables. The -\b-f\bf option restricts the display to
shell functions.
The -\b-F\bF option inhibits the display of function definitions; only
- the function name and attributes are printed. If the e\bex\bxt\btd\bde\beb\bbu\bug\bg
- shell option is enabled using s\bsh\bho\bop\bpt\bt, the source file name and
- line number where each _\bn_\ba_\bm_\be is defined are displayed as well.
+ the function name and attributes are printed. If the e\bex\bxt\btd\bde\beb\bbu\bug\bg
+ shell option is enabled using s\bsh\bho\bop\bpt\bt, the source file name and
+ line number where each _\bn_\ba_\bm_\be is defined are displayed as well.
The -\b-F\bF option implies -\b-f\bf.
- The -\b-g\bg option forces variables to be created or modified at the
+ The -\b-g\bg option forces variables to be created or modified at the
global scope, even when d\bde\bec\bcl\bla\bar\bre\be is executed in a shell function.
It is ignored when d\bde\bec\bcl\bla\bar\bre\be is not executed in a shell function.
- The -\b-I\bI option causes local variables to inherit the attributes
- (except the _\bn_\ba_\bm_\be_\br_\be_\bf attribute) and value of any existing vari-
- able with the same _\bn_\ba_\bm_\be at a surrounding scope. If there is no
+ The -\b-I\bI option causes local variables to inherit the attributes
+ (except the _\bn_\ba_\bm_\be_\br_\be_\bf attribute) and value of any existing vari-
+ able with the same _\bn_\ba_\bm_\be at a surrounding scope. If there is no
existing variable, the local variable is initially unset.
- The following options can be used to restrict output to vari-
- ables with the specified attribute or to give variables attrib-
+ The following options can be used to restrict output to vari-
+ ables with the specified attribute or to give variables attrib-
utes:
- -\b-a\ba Each _\bn_\ba_\bm_\be is an indexed array variable (see A\bAr\brr\bra\bay\bys\bs
+ -\b-a\ba Each _\bn_\ba_\bm_\be is an indexed array variable (see A\bAr\brr\bra\bay\bys\bs
above).
- -\b-A\bA Each _\bn_\ba_\bm_\be is an associative array variable (see A\bAr\brr\bra\bay\bys\bs
+ -\b-A\bA Each _\bn_\ba_\bm_\be is an associative array variable (see A\bAr\brr\bra\bay\bys\bs
above).
-\b-f\bf Each _\bn_\ba_\bm_\be refers to a shell function.
-\b-i\bi The variable is treated as an integer; arithmetic evalua-
- tion (see A\bAR\bRI\bIT\bTH\bHM\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN above) is performed when
+ tion (see A\bAR\bRI\bIT\bTH\bHM\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN above) is performed when
the variable is assigned a value.
- -\b-l\bl When the variable is assigned a value, all upper-case
- characters are converted to lower-case. The upper-case
+ -\b-l\bl When the variable is assigned a value, all upper-case
+ characters are converted to lower-case. The upper-case
attribute is disabled.
- -\b-n\bn Give each _\bn_\ba_\bm_\be the _\bn_\ba_\bm_\be_\br_\be_\bf attribute, making it a name
- reference to another variable. That other variable is
- defined by the value of _\bn_\ba_\bm_\be. All references, assign-
- ments, and attribute modifications to _\bn_\ba_\bm_\be, except those
- using or changing the -\b-n\bn attribute itself, are performed
- on the variable referenced by _\bn_\ba_\bm_\be's value. The nameref
+ -\b-n\bn Give each _\bn_\ba_\bm_\be the _\bn_\ba_\bm_\be_\br_\be_\bf attribute, making it a name
+ reference to another variable. That other variable is
+ defined by the value of _\bn_\ba_\bm_\be. All references, assign-
+ ments, and attribute modifications to _\bn_\ba_\bm_\be, except those
+ using or changing the -\b-n\bn attribute itself, are performed
+ on the variable referenced by _\bn_\ba_\bm_\be's value. The nameref
attribute cannot be applied to array variables.
-\b-r\br Make _\bn_\ba_\bm_\bes readonly. These names cannot then be assigned
values by subsequent assignment statements or unset.
-\b-t\bt Give each _\bn_\ba_\bm_\be the _\bt_\br_\ba_\bc_\be attribute. Traced functions in-
- herit the D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN traps from the calling shell.
+ herit the D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN traps from the calling shell.
The trace attribute has no special meaning for variables.
- -\b-u\bu When the variable is assigned a value, all lower-case
- characters are converted to upper-case. The lower-case
+ -\b-u\bu When the variable is assigned a value, all lower-case
+ characters are converted to upper-case. The lower-case
attribute is disabled.
- -\b-x\bx Mark each _\bn_\ba_\bm_\be for export to subsequent commands via the
+ -\b-x\bx Mark each _\bn_\ba_\bm_\be for export to subsequent commands via the
environment.
- Using "+" instead of "-" turns off the specified attribute in-
+ Using "+" instead of "-" turns off the specified attribute in-
stead, with the exceptions that +\b+a\ba and +\b+A\bA may not be used to de-
- stroy array variables and +\b+r\br will not remove the readonly at-
+ stroy array variables and +\b+r\br will not remove the readonly at-
tribute.
- When used in a function, d\bde\bec\bcl\bla\bar\bre\be and t\bty\byp\bpe\bes\bse\bet\bt make each _\bn_\ba_\bm_\be lo-
- cal, as with the l\blo\boc\bca\bal\bl command, unless the -\b-g\bg option is sup-
- plied. If a variable name is followed by =_\bv_\ba_\bl_\bu_\be, the value of
- the variable is set to _\bv_\ba_\bl_\bu_\be. When using -\b-a\ba or -\b-A\bA and the com-
- pound assignment syntax to create array variables, additional
+ When used in a function, d\bde\bec\bcl\bla\bar\bre\be and t\bty\byp\bpe\bes\bse\bet\bt make each _\bn_\ba_\bm_\be lo-
+ cal, as with the l\blo\boc\bca\bal\bl command, unless the -\b-g\bg option is sup-
+ plied. If a variable name is followed by =_\bv_\ba_\bl_\bu_\be, the value of
+ the variable is set to _\bv_\ba_\bl_\bu_\be. When using -\b-a\ba or -\b-A\bA and the com-
+ pound assignment syntax to create array variables, additional
attributes do not take effect until subsequent assignments.
- The return value is 0 unless an invalid option is encountered,
- an attempt is made to define a function using "-f foo=bar", an
+ The return value is 0 unless an invalid option is encountered,
+ an attempt is made to define a function using "-f foo=bar", an
attempt is made to assign a value to a readonly variable, an at-
tempt is made to assign a value to an array variable without us-
- ing the compound assignment syntax (see A\bAr\brr\bra\bay\bys\bs above), one of
+ ing the compound assignment syntax (see A\bAr\brr\bra\bay\bys\bs above), one of
the _\bn_\ba_\bm_\be_\bs is not a valid shell variable name, an attempt is made
- to turn off readonly status for a readonly variable, an attempt
- is made to turn off array status for an array variable, or an
+ to turn off readonly status for a readonly variable, an attempt
+ is made to turn off array status for an array variable, or an
attempt is made to display a non-existent function with -\b-f\bf.
d\bdi\bir\brs\bs [\b[-\b-c\bcl\blp\bpv\bv]\b] [\b[+\b+_\bn]\b] [\b[-\b-_\bn]\b]
Without options, display the list of currently remembered direc-
- tories. The default display is on a single line with directory
- names separated by spaces. Directories are added to the list
- with the p\bpu\bus\bsh\bhd\bd command; the p\bpo\bop\bpd\bd command removes entries from
- the list. The current directory is always the first directory
+ tories. The default display is on a single line with directory
+ names separated by spaces. Directories are added to the list
+ with the p\bpu\bus\bsh\bhd\bd command; the p\bpo\bop\bpd\bd command removes entries from
+ the list. The current directory is always the first directory
in the stack.
Options, if supplied, have the following meanings:
- -\b-c\bc Clears the directory stack by deleting all of the en-
+ -\b-c\bc Clears the directory stack by deleting all of the en-
tries.
- -\b-l\bl Produces a listing using full pathnames; the default
+ -\b-l\bl Produces a listing using full pathnames; the default
listing format uses a tilde to denote the home directory.
-\b-p\bp Print the directory stack with one entry per line.
- -\b-v\bv Print the directory stack with one entry per line, pre-
+ -\b-v\bv Print the directory stack with one entry per line, pre-
fixing each entry with its index in the stack.
+\b+_\bn Displays the _\bnth entry counting from the left of the list
shown by d\bdi\bir\brs\bs when invoked without options, starting with
zero.
- -\b-_\bn Displays the _\bnth entry counting from the right of the
+ -\b-_\bn Displays the _\bnth entry counting from the right of the
list shown by d\bdi\bir\brs\bs when invoked without options, starting
with zero.
- The return value is 0 unless an invalid option is supplied or _\bn
+ The return value is 0 unless an invalid option is supplied or _\bn
indexes beyond the end of the directory stack.
d\bdi\bis\bso\bow\bwn\bn [-\b-a\bar\br] [-\b-h\bh] [_\bi_\bd ...]
- Without options, remove each _\bi_\bd from the table of active jobs.
- Each _\bi_\bd may be a job specification _\bj_\bo_\bb_\bs_\bp_\be_\bc or a process ID _\bp_\bi_\bd;
+ Without options, remove each _\bi_\bd from the table of active jobs.
+ Each _\bi_\bd may be a job specification _\bj_\bo_\bb_\bs_\bp_\be_\bc or a process ID _\bp_\bi_\bd;
if _\bi_\bd is a _\bp_\bi_\bd, d\bdi\bis\bso\bow\bwn\bn uses the job containing _\bp_\bi_\bd as _\bj_\bo_\bb_\bs_\bp_\be_\bc.
- If the -\b-h\bh option is supplied, d\bdi\bis\bso\bow\bwn\bn does not remove the jobs
- corresponding to each _\bi_\bd from the jobs table, but rather marks
- them so the shell does not send S\bSI\bIG\bGH\bHU\bUP\bP to the job if the shell
+ If the -\b-h\bh option is supplied, d\bdi\bis\bso\bow\bwn\bn does not remove the jobs
+ corresponding to each _\bi_\bd from the jobs table, but rather marks
+ them so the shell does not send S\bSI\bIG\bGH\bHU\bUP\bP to the job if the shell
receives a S\bSI\bIG\bGH\bHU\bUP\bP.
- If no _\bi_\bd is supplied, the -\b-a\ba option means to remove or mark all
+ If no _\bi_\bd is supplied, the -\b-a\ba option means to remove or mark all
jobs; the -\b-r\br option without an _\bi_\bd argument removes or marks run-
- ning jobs. If no _\bi_\bd is supplied, and neither the -\b-a\ba nor the -\b-r\br
+ ning jobs. If no _\bi_\bd is supplied, and neither the -\b-a\ba nor the -\b-r\br
option is supplied, d\bdi\bis\bso\bow\bwn\bn removes or marks the current job.
The return value is 0 unless an _\bi_\bd does not specify a valid job.
e\bec\bch\bho\bo [-\b-n\bne\beE\bE] [_\ba_\br_\bg ...]
- Output the _\ba_\br_\bgs, separated by spaces, followed by a newline.
- The return status is 0 unless a write error occurs. If -\b-n\bn is
+ Output the _\ba_\br_\bgs, separated by spaces, followed by a newline.
+ The return status is 0 unless a write error occurs. If -\b-n\bn is
specified, the trailing newline is not printed.
- If the -\b-e\be option is given, e\bec\bch\bho\bo interprets the following back-
+ If the -\b-e\be option is given, e\bec\bch\bho\bo interprets the following back-
slash-escaped characters. The -\b-E\bE option disables interpretation
- of these escape characters, even on systems where they are in-
- terpreted by default. The x\bxp\bpg\bg_\b_e\bec\bch\bho\bo shell option determines
+ of these escape characters, even on systems where they are in-
+ terpreted by default. The x\bxp\bpg\bg_\b_e\bec\bch\bho\bo shell option determines
whether or not e\bec\bch\bho\bo interprets any options and expands these es-
- cape characters. e\bec\bch\bho\bo does not interpret -\b--\b- to mean the end of
+ cape characters. e\bec\bch\bho\bo does not interpret -\b--\b- to mean the end of
options.
e\bec\bch\bho\bo interprets the following escape sequences:
\\b\t\bt horizontal tab
\\b\v\bv vertical tab
\\b\\\b\ backslash
- \\b\0\b0_\bn_\bn_\bn The eight-bit character whose value is the octal value
+ \\b\0\b0_\bn_\bn_\bn The eight-bit character whose value is the octal value
_\bn_\bn_\bn (zero to three octal digits).
- \\b\x\bx_\bH_\bH The eight-bit character whose value is the hexadecimal
+ \\b\x\bx_\bH_\bH The eight-bit character whose value is the hexadecimal
value _\bH_\bH (one or two hex digits).
- \\b\u\bu_\bH_\bH_\bH_\bH The Unicode (ISO/IEC 10646) character whose value is the
+ \\b\u\bu_\bH_\bH_\bH_\bH The Unicode (ISO/IEC 10646) character whose value is the
hexadecimal value _\bH_\bH_\bH_\bH (one to four hex digits).
\\b\U\bU_\bH_\bH_\bH_\bH_\bH_\bH_\bH_\bH
- The Unicode (ISO/IEC 10646) character whose value is the
+ The Unicode (ISO/IEC 10646) character whose value is the
hexadecimal value _\bH_\bH_\bH_\bH_\bH_\bH_\bH_\bH (one to eight hex digits).
- e\bec\bch\bho\bo writes any unrecognized backslash-escaped characters un-
+ e\bec\bch\bho\bo writes any unrecognized backslash-escaped characters un-
changed.
e\ben\bna\bab\bbl\ble\be [-\b-a\ba] [-\b-d\bdn\bnp\bps\bs] [-\b-f\bf _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be] [_\bn_\ba_\bm_\be ...]
- Enable and disable builtin shell commands. Disabling a builtin
- allows an executable file which has the same name as a shell
- builtin to be executed without specifying a full pathname, even
+ Enable and disable builtin shell commands. Disabling a builtin
+ allows an executable file which has the same name as a shell
+ builtin to be executed without specifying a full pathname, even
though the shell normally searches for builtins before files.
- If -\b-n\bn is supplied, each _\bn_\ba_\bm_\be is disabled; otherwise, _\bn_\ba_\bm_\bes are
- enabled. For example, to use the t\bte\bes\bst\bt binary found using P\bPA\bAT\bTH\bH
+ If -\b-n\bn is supplied, each _\bn_\ba_\bm_\be is disabled; otherwise, _\bn_\ba_\bm_\bes are
+ enabled. For example, to use the t\bte\bes\bst\bt binary found using P\bPA\bAT\bTH\bH
instead of the shell builtin version, run "enable -n test".
- If no _\bn_\ba_\bm_\be arguments are supplied, or if the -\b-p\bp option is sup-
+ If no _\bn_\ba_\bm_\be arguments are supplied, or if the -\b-p\bp option is sup-
plied, print a list of shell builtins. With no other option ar-
guments, the list consists of all enabled shell builtins. If -\b-n\bn
- is supplied, print only disabled builtins. If -\b-a\ba is supplied,
- the list printed includes all builtins, with an indication of
+ is supplied, print only disabled builtins. If -\b-a\ba is supplied,
+ the list printed includes all builtins, with an indication of
whether or not each is enabled. The -\b-s\bs option means to restrict
the output to the POSIX _\bs_\bp_\be_\bc_\bi_\ba_\bl builtins.
- The -\b-f\bf option means to load the new builtin command _\bn_\ba_\bm_\be from
+ The -\b-f\bf option means to load the new builtin command _\bn_\ba_\bm_\be from
shared object _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be, on systems that support dynamic loading.
If _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be does not contain a slash, B\bBa\bas\bsh\bh will use the value of
- the B\bBA\bAS\bSH\bH_\b_L\bLO\bOA\bAD\bDA\bAB\bBL\bLE\bES\bS_\b_P\bPA\bAT\bTH\bH variable as a colon-separated list of
- directories in which to search for _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be. The default for
- B\bBA\bAS\bSH\bH_\b_L\bLO\bOA\bAD\bDA\bAB\bBL\bLE\bES\bS_\b_P\bPA\bAT\bTH\bH is system-dependent, and may include "." to
- force a search of the current directory. The -\b-d\bd option will
- delete a builtin previously loaded with -\b-f\bf. If _\b-_\bs is used with
+ the B\bBA\bAS\bSH\bH_\b_L\bLO\bOA\bAD\bDA\bAB\bBL\bLE\bES\bS_\b_P\bPA\bAT\bTH\bH variable as a colon-separated list of
+ directories in which to search for _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be. The default for
+ B\bBA\bAS\bSH\bH_\b_L\bLO\bOA\bAD\bDA\bAB\bBL\bLE\bES\bS_\b_P\bPA\bAT\bTH\bH is system-dependent, and may include "." to
+ force a search of the current directory. The -\b-d\bd option will
+ delete a builtin previously loaded with -\b-f\bf. If _\b-_\bs is used with
_\b-_\bf, the new builtin becomes a POSIX special builtin.
- If no options are supplied and a _\bn_\ba_\bm_\be is not a shell builtin,
- e\ben\bna\bab\bbl\ble\be will attempt to load _\bn_\ba_\bm_\be from a shared object named
+ If no options are supplied and a _\bn_\ba_\bm_\be is not a shell builtin,
+ e\ben\bna\bab\bbl\ble\be will attempt to load _\bn_\ba_\bm_\be from a shared object named
_\bn_\ba_\bm_\be, as if the command were "enable -f _\bn_\ba_\bm_\be _\bn_\ba_\bm_\be".
- The return value is 0 unless a _\bn_\ba_\bm_\be is not a shell builtin or
+ The return value is 0 unless a _\bn_\ba_\bm_\be is not a shell builtin or
there is an error loading a new builtin from a shared object.
e\bev\bva\bal\bl [_\ba_\br_\bg ...]
- Concatenate the _\ba_\br_\bgs together into a single command, separating
+ Concatenate the _\ba_\br_\bgs together into a single command, separating
them with spaces. B\bBa\bas\bsh\bh then reads and execute this command, and
- returns its exit status as the return status of e\bev\bva\bal\bl. If there
+ returns its exit status as the return status of e\bev\bva\bal\bl. If there
are no _\ba_\br_\bg_\bs, or only null arguments, e\bev\bva\bal\bl returns 0.
e\bex\bxe\bec\bc [-\b-c\bcl\bl] [-\b-a\ba _\bn_\ba_\bm_\be] [_\bc_\bo_\bm_\bm_\ba_\bn_\bd [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]]
- If _\bc_\bo_\bm_\bm_\ba_\bn_\bd is specified, it replaces the shell without creating
- a new process. _\bc_\bo_\bm_\bm_\ba_\bn_\bd cannot be a shell builtin or function.
+ If _\bc_\bo_\bm_\bm_\ba_\bn_\bd is specified, it replaces the shell without creating
+ a new process. _\bc_\bo_\bm_\bm_\ba_\bn_\bd cannot be a shell builtin or function.
The _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs become the arguments to _\bc_\bo_\bm_\bm_\ba_\bn_\bd. If the -\b-l\bl option
is supplied, the shell places a dash at the beginning of the ze-
- roth argument passed to _\bc_\bo_\bm_\bm_\ba_\bn_\bd. This is what _\bl_\bo_\bg_\bi_\bn(1) does.
- The -\b-c\bc option causes _\bc_\bo_\bm_\bm_\ba_\bn_\bd to be executed with an empty envi-
+ roth argument passed to _\bc_\bo_\bm_\bm_\ba_\bn_\bd. This is what _\bl_\bo_\bg_\bi_\bn(1) does.
+ The -\b-c\bc option causes _\bc_\bo_\bm_\bm_\ba_\bn_\bd to be executed with an empty envi-
ronment. If -\b-a\ba is supplied, the shell passes _\bn_\ba_\bm_\be as the zeroth
argument to the executed command.
If _\bc_\bo_\bm_\bm_\ba_\bn_\bd cannot be executed for some reason, a non-interactive
- shell exits, unless the e\bex\bxe\bec\bcf\bfa\bai\bil\bl shell option is enabled. In
- that case, it returns a non-zero status. An interactive shell
- returns a non-zero status if the file cannot be executed. A
+ shell exits, unless the e\bex\bxe\bec\bcf\bfa\bai\bil\bl shell option is enabled. In
+ that case, it returns a non-zero status. An interactive shell
+ returns a non-zero status if the file cannot be executed. A
subshell exits unconditionally if e\bex\bxe\bec\bc fails.
If _\bc_\bo_\bm_\bm_\ba_\bn_\bd is not specified, any redirections take effect in the
- current shell, and the return status is 0. If there is a redi-
+ current shell, and the return status is 0. If there is a redi-
rection error, the return status is 1.
e\bex\bxi\bit\bt [_\bn]
- Cause the shell to exit with a status of _\bn. If _\bn is omitted,
- the exit status is that of the last command executed. Any trap
+ Cause the shell to exit with a status of _\bn. If _\bn is omitted,
+ the exit status is that of the last command executed. Any trap
on E\bEX\bXI\bIT\bT is executed before the shell terminates.
e\bex\bxp\bpo\bor\brt\bt [-\b-f\bfn\bn] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be]] ...
e\bex\bxp\bpo\bor\brt\bt -\b-p\bp [\b[-\b-f\bf]\b]
- The supplied _\bn_\ba_\bm_\be_\bs are marked for automatic export to the envi-
- ronment of subsequently executed commands. If the -\b-f\bf option is
+ The supplied _\bn_\ba_\bm_\be_\bs are marked for automatic export to the envi-
+ ronment of subsequently executed commands. If the -\b-f\bf option is
given, the _\bn_\ba_\bm_\be_\bs refer to functions.
- The -\b-n\bn option unexports, or removes the export attribute, from
- each _\bn_\ba_\bm_\be. If no _\bn_\ba_\bm_\be_\bs are given, or if only the -\b-p\bp option is
- supplied, e\bex\bxp\bpo\bor\brt\bt displays a list of names of all exported vari-
+ The -\b-n\bn option unexports, or removes the export attribute, from
+ each _\bn_\ba_\bm_\be. If no _\bn_\ba_\bm_\be_\bs are given, or if only the -\b-p\bp option is
+ supplied, e\bex\bxp\bpo\bor\brt\bt displays a list of names of all exported vari-
ables on the standard output. Using -\b-p\bp and -\b-f\bf together displays
- exported functions. The -\b-p\bp option displays output in a form
+ exported functions. The -\b-p\bp option displays output in a form
that may be reused as input.
- e\bex\bxp\bpo\bor\brt\bt allows the value of a variable to be set when it is ex-
+ e\bex\bxp\bpo\bor\brt\bt allows the value of a variable to be set when it is ex-
ported or unexported by following the variable name with =_\bv_\ba_\bl_\bu_\be.
This sets the value of the variable to _\bv_\ba_\bl_\bu_\be while modifying the
- export attribute. e\bex\bxp\bpo\bor\brt\bt returns an exit status of 0 unless an
- invalid option is encountered, one of the _\bn_\ba_\bm_\be_\bs is not a valid
+ export attribute. e\bex\bxp\bpo\bor\brt\bt returns an exit status of 0 unless an
+ invalid option is encountered, one of the _\bn_\ba_\bm_\be_\bs is not a valid
shell variable name, or -\b-f\bf is supplied with a _\bn_\ba_\bm_\be that is not a
function.
f\bfc\bc [-\b-e\be _\be_\bn_\ba_\bm_\be] [-\b-l\bln\bnr\br] [_\bf_\bi_\br_\bs_\bt] [_\bl_\ba_\bs_\bt]
f\bfc\bc -\b-s\bs [_\bp_\ba_\bt=_\br_\be_\bp] [_\bc_\bm_\bd]
- The first form selects a range of commands from _\bf_\bi_\br_\bs_\bt to _\bl_\ba_\bs_\bt
- from the history list and displays or edits and re-executes
- them. _\bF_\bi_\br_\bs_\bt and _\bl_\ba_\bs_\bt may be specified as a string (to locate
- the last command beginning with that string) or as a number (an
- index into the history list, where a negative number is used as
+ The first form selects a range of commands from _\bf_\bi_\br_\bs_\bt to _\bl_\ba_\bs_\bt
+ from the history list and displays or edits and re-executes
+ them. _\bF_\bi_\br_\bs_\bt and _\bl_\ba_\bs_\bt may be specified as a string (to locate
+ the last command beginning with that string) or as a number (an
+ index into the history list, where a negative number is used as
an offset from the current command number).
When listing, a _\bf_\bi_\br_\bs_\bt or _\bl_\ba_\bs_\bt of 0 is equivalent to -1 and -0 is
equivalent to the current command (usually the f\bfc\bc command); oth-
- erwise 0 is equivalent to -1 and -0 is invalid. If _\bl_\ba_\bs_\bt is not
+ erwise 0 is equivalent to -1 and -0 is invalid. If _\bl_\ba_\bs_\bt is not
specified, it is set to the current command for listing (so that
"fc -l -10" prints the last 10 commands) and to _\bf_\bi_\br_\bs_\bt otherwise.
If _\bf_\bi_\br_\bs_\bt is not specified, it is set to the previous command for
editing and -16 for listing.
- If the -\b-l\bl option is supplied, the commands are listed on the
- standard output. The -\b-n\bn option suppresses the command numbers
+ If the -\b-l\bl option is supplied, the commands are listed on the
+ standard output. The -\b-n\bn option suppresses the command numbers
when listing. The -\b-r\br option reverses the order of the commands.
- Otherwise, f\bfc\bc invokes the editor named by _\be_\bn_\ba_\bm_\be on a file con-
- taining those commands. If _\be_\bn_\ba_\bm_\be is not supplied, f\bfc\bc uses the
- value of the F\bFC\bCE\bED\bDI\bIT\bT variable, and the value of E\bED\bDI\bIT\bTO\bOR\bR if F\bFC\bCE\bED\bDI\bIT\bT
- is not set. If neither variable is set, f\bfc\bc uses _\bv_\bi_\b. When edit-
- ing is complete, f\bfc\bc reads the file containing the edited com-
+ Otherwise, f\bfc\bc invokes the editor named by _\be_\bn_\ba_\bm_\be on a file con-
+ taining those commands. If _\be_\bn_\ba_\bm_\be is not supplied, f\bfc\bc uses the
+ value of the F\bFC\bCE\bED\bDI\bIT\bT variable, and the value of E\bED\bDI\bIT\bTO\bOR\bR if F\bFC\bCE\bED\bDI\bIT\bT
+ is not set. If neither variable is set, f\bfc\bc uses _\bv_\bi_\b. When edit-
+ ing is complete, f\bfc\bc reads the file containing the edited com-
mands and echoes and executes them.
- In the second form, f\bfc\bc re-executes _\bc_\bo_\bm_\bm_\ba_\bn_\bd after replacing each
- instance of _\bp_\ba_\bt with _\br_\be_\bp. _\bC_\bo_\bm_\bm_\ba_\bn_\bd is interpreted the same as
+ In the second form, f\bfc\bc re-executes _\bc_\bo_\bm_\bm_\ba_\bn_\bd after replacing each
+ instance of _\bp_\ba_\bt with _\br_\be_\bp. _\bC_\bo_\bm_\bm_\ba_\bn_\bd is interpreted the same as
_\bf_\bi_\br_\bs_\bt above.
- A useful alias to use with f\bfc\bc is "r="fc -s"", so that typing "r
+ A useful alias to use with f\bfc\bc is "r="fc -s"", so that typing "r
cc" runs the last command beginning with "cc" and typing "r" re-
executes the last command.
- If the first form is used, the return value is zero unless an
- invalid option is encountered or _\bf_\bi_\br_\bs_\bt or _\bl_\ba_\bs_\bt specify history
- lines out of range. When editing and re-executing a file of
+ If the first form is used, the return value is zero unless an
+ invalid option is encountered or _\bf_\bi_\br_\bs_\bt or _\bl_\ba_\bs_\bt specify history
+ lines out of range. When editing and re-executing a file of
commands, the return value is the value of the last command exe-
cuted or failure if an error occurs with the temporary file. If
the second form is used, the return status is that of the re-ex-
- ecuted command, unless _\bc_\bm_\bd does not specify a valid history en-
+ ecuted command, unless _\bc_\bm_\bd does not specify a valid history en-
try, in which case f\bfc\bc returns a non-zero status.
f\bfg\bg [_\bj_\bo_\bb_\bs_\bp_\be_\bc]
- Resume _\bj_\bo_\bb_\bs_\bp_\be_\bc in the foreground, and make it the current job.
- If _\bj_\bo_\bb_\bs_\bp_\be_\bc is not present, f\bfg\bg uses the shell's notion of the
- _\bc_\bu_\br_\br_\be_\bn_\bt _\bj_\bo_\bb. The return value is that of the command placed
- into the foreground, or failure if run when job control is dis-
+ Resume _\bj_\bo_\bb_\bs_\bp_\be_\bc in the foreground, and make it the current job.
+ If _\bj_\bo_\bb_\bs_\bp_\be_\bc is not present, f\bfg\bg uses the shell's notion of the
+ _\bc_\bu_\br_\br_\be_\bn_\bt _\bj_\bo_\bb. The return value is that of the command placed
+ into the foreground, or failure if run when job control is dis-
abled or, when run with job control enabled, if _\bj_\bo_\bb_\bs_\bp_\be_\bc does not
- specify a valid job or _\bj_\bo_\bb_\bs_\bp_\be_\bc specifies a job that was started
+ specify a valid job or _\bj_\bo_\bb_\bs_\bp_\be_\bc specifies a job that was started
without job control.
g\bge\bet\bto\bop\bpt\bts\bs _\bo_\bp_\bt_\bs_\bt_\br_\bi_\bn_\bg _\bn_\ba_\bm_\be [_\ba_\br_\bg ...]
- g\bge\bet\bto\bop\bpt\bts\bs is used by shell scripts and functions to parse posi-
- tional parameters and obtain options and their arguments. _\bo_\bp_\bt_\b-
- _\bs_\bt_\br_\bi_\bn_\bg contains the option characters to be recognized; if a
+ g\bge\bet\bto\bop\bpt\bts\bs is used by shell scripts and functions to parse posi-
+ tional parameters and obtain options and their arguments. _\bo_\bp_\bt_\b-
+ _\bs_\bt_\br_\bi_\bn_\bg contains the option characters to be recognized; if a
character is followed by a colon, the option is expected to have
- an argument, which should be separated from it by white space.
+ an argument, which should be separated from it by white space.
The colon and question mark characters may not be used as option
characters.
- Each time it is invoked, g\bge\bet\bto\bop\bpt\bts\bs places the next option in the
+ Each time it is invoked, g\bge\bet\bto\bop\bpt\bts\bs places the next option in the
shell variable _\bn_\ba_\bm_\be, initializing _\bn_\ba_\bm_\be if it does not exist, and
the index of the next argument to be processed into the variable
- O\bOP\bPT\bTI\bIN\bND\bD. O\bOP\bPT\bTI\bIN\bND\bD is initialized to 1 each time the shell or a
- shell script is invoked. When an option requires an argument,
+ O\bOP\bPT\bTI\bIN\bND\bD. O\bOP\bPT\bTI\bIN\bND\bD is initialized to 1 each time the shell or a
+ shell script is invoked. When an option requires an argument,
g\bge\bet\bto\bop\bpt\bts\bs places that argument into the variable O\bOP\bPT\bTA\bAR\bRG\bG.
- The shell does not reset O\bOP\bPT\bTI\bIN\bND\bD automatically; it must be manu-
- ally reset between multiple calls to g\bge\bet\bto\bop\bpt\bts\bs within the same
+ The shell does not reset O\bOP\bPT\bTI\bIN\bND\bD automatically; it must be manu-
+ ally reset between multiple calls to g\bge\bet\bto\bop\bpt\bts\bs within the same
shell invocation to use a new set of parameters.
- When it reaches the end of options, g\bge\bet\bto\bop\bpt\bts\bs exits with a return
- value greater than zero. O\bOP\bPT\bTI\bIN\bND\bD is set to the index of the
+ When it reaches the end of options, g\bge\bet\bto\bop\bpt\bts\bs exits with a return
+ value greater than zero. O\bOP\bPT\bTI\bIN\bND\bD is set to the index of the
first non-option argument, and _\bn_\ba_\bm_\be is set to ?.
- g\bge\bet\bto\bop\bpt\bts\bs normally parses the positional parameters, but if more
- arguments are supplied as _\ba_\br_\bg values, g\bge\bet\bto\bop\bpt\bts\bs parses those in-
+ g\bge\bet\bto\bop\bpt\bts\bs normally parses the positional parameters, but if more
+ arguments are supplied as _\ba_\br_\bg values, g\bge\bet\bto\bop\bpt\bts\bs parses those in-
stead.
- g\bge\bet\bto\bop\bpt\bts\bs can report errors in two ways. If the first character
- of _\bo_\bp_\bt_\bs_\bt_\br_\bi_\bn_\bg is a colon, g\bge\bet\bto\bop\bpt\bts\bs uses _\bs_\bi_\bl_\be_\bn_\bt error reporting.
- In normal operation, g\bge\bet\bto\bop\bpt\bts\bs prints diagnostic messages when it
- encounters invalid options or missing option arguments. If the
- variable O\bOP\bPT\bTE\bER\bRR\bR is set to 0, g\bge\bet\bto\bop\bpt\bts\bs does not display any error
- messages, even if the first character of _\bo_\bp_\bt_\bs_\bt_\br_\bi_\bn_\bg is not a
+ g\bge\bet\bto\bop\bpt\bts\bs can report errors in two ways. If the first character
+ of _\bo_\bp_\bt_\bs_\bt_\br_\bi_\bn_\bg is a colon, g\bge\bet\bto\bop\bpt\bts\bs uses _\bs_\bi_\bl_\be_\bn_\bt error reporting.
+ In normal operation, g\bge\bet\bto\bop\bpt\bts\bs prints diagnostic messages when it
+ encounters invalid options or missing option arguments. If the
+ variable O\bOP\bPT\bTE\bER\bRR\bR is set to 0, g\bge\bet\bto\bop\bpt\bts\bs does not display any error
+ messages, even if the first character of _\bo_\bp_\bt_\bs_\bt_\br_\bi_\bn_\bg is not a
colon.
If g\bge\bet\bto\bop\bpt\bts\bs detects an invalid option, it places ? into _\bn_\ba_\bm_\be and,
- if not silent, prints an error message and unsets O\bOP\bPT\bTA\bAR\bRG\bG. If
- g\bge\bet\bto\bop\bpt\bts\bs is silent, it assigns the option character found to O\bOP\bP-\b-
+ if not silent, prints an error message and unsets O\bOP\bPT\bTA\bAR\bRG\bG. If
+ g\bge\bet\bto\bop\bpt\bts\bs is silent, it assigns the option character found to O\bOP\bP-\b-
T\bTA\bAR\bRG\bG and does not print a diagnostic message.
- If a required argument is not found, and g\bge\bet\bto\bop\bpt\bts\bs is not silent,
+ If a required argument is not found, and g\bge\bet\bto\bop\bpt\bts\bs is not silent,
it sets the value of _\bn_\ba_\bm_\be to a question mark (?\b?), unsets O\bOP\bPT\bTA\bAR\bRG\bG,
- and prints a diagnostic message. If g\bge\bet\bto\bop\bpt\bts\bs is silent, it sets
- the value of _\bn_\ba_\bm_\be to a colon (:\b:) and sets O\bOP\bPT\bTA\bAR\bRG\bG to the option
+ and prints a diagnostic message. If g\bge\bet\bto\bop\bpt\bts\bs is silent, it sets
+ the value of _\bn_\ba_\bm_\be to a colon (:\b:) and sets O\bOP\bPT\bTA\bAR\bRG\bG to the option
character found.
- g\bge\bet\bto\bop\bpt\bts\bs returns true if an option, specified or unspecified, is
+ g\bge\bet\bto\bop\bpt\bts\bs returns true if an option, specified or unspecified, is
found. It returns false if the end of options is encountered or
an error occurs.
h\bha\bas\bsh\bh [-\b-l\blr\br] [-\b-p\bp _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be] [-\b-d\bdt\bt] [_\bn_\ba_\bm_\be]
Each time h\bha\bas\bsh\bh is invoked, it remembers the full pathname of the
- command _\bn_\ba_\bm_\be as determined by searching the directories in
- $\b$P\bPA\bAT\bTH\bH. Any previously-remembered pathname associated with _\bn_\ba_\bm_\be
- is discarded. If the -\b-p\bp option is supplied, h\bha\bas\bsh\bh uses _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
+ command _\bn_\ba_\bm_\be as determined by searching the directories in
+ $\b$P\bPA\bAT\bTH\bH. Any previously-remembered pathname associated with _\bn_\ba_\bm_\be
+ is discarded. If the -\b-p\bp option is supplied, h\bha\bas\bsh\bh uses _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
as the full pathname of the command.
- The -\b-r\br option causes the shell to forget all remembered loca-
- tions. Assigning to the P\bPA\bAT\bTH\bH variable also clears all hashed
- filenames. The -\b-d\bd option causes the shell to forget the remem-
+ The -\b-r\br option causes the shell to forget all remembered loca-
+ tions. Assigning to the P\bPA\bAT\bTH\bH variable also clears all hashed
+ filenames. The -\b-d\bd option causes the shell to forget the remem-
bered location of each _\bn_\ba_\bm_\be.
If the -\b-t\bt option is supplied, h\bha\bas\bsh\bh prints the full pathname cor-
- responding to each _\bn_\ba_\bm_\be. If multiple _\bn_\ba_\bm_\be arguments are sup-
- plied with -\b-t\bt, h\bha\bas\bsh\bh prints the _\bn_\ba_\bm_\be before the corresponding
+ responding to each _\bn_\ba_\bm_\be. If multiple _\bn_\ba_\bm_\be arguments are sup-
+ plied with -\b-t\bt, h\bha\bas\bsh\bh prints the _\bn_\ba_\bm_\be before the corresponding
hashed full pathname. The -\b-l\bl option displays output in a format
that may be reused as input.
- If no arguments are given, or if only -\b-l\bl is supplied, h\bha\bas\bsh\bh
- prints information about remembered commands. The -\b-t\bt, -\b-d\bd, and
- -\b-p\bp options (the options that act on the _\bn_\ba_\bm_\be arguments) are mu-
+ If no arguments are given, or if only -\b-l\bl is supplied, h\bha\bas\bsh\bh
+ prints information about remembered commands. The -\b-t\bt, -\b-d\bd, and
+ -\b-p\bp options (the options that act on the _\bn_\ba_\bm_\be arguments) are mu-
tually exclusive. Only one will be active. If more than one is
- supplied, -\b-t\bt has higher priority than -\b-p\bp, and both have higher
+ supplied, -\b-t\bt has higher priority than -\b-p\bp, and both have higher
priority than -\b-d\bd.
- The return status is zero unless a _\bn_\ba_\bm_\be is not found or an in-
+ The return status is zero unless a _\bn_\ba_\bm_\be is not found or an in-
valid option is supplied.
h\bhe\bel\blp\bp [-\b-d\bdm\bms\bs] [_\bp_\ba_\bt_\bt_\be_\br_\bn]
- Display helpful information about builtin commands. If _\bp_\ba_\bt_\bt_\be_\br_\bn
- is specified, h\bhe\bel\blp\bp gives detailed help on all commands matching
- _\bp_\ba_\bt_\bt_\be_\br_\bn as described below; otherwise it displays a list of all
+ Display helpful information about builtin commands. If _\bp_\ba_\bt_\bt_\be_\br_\bn
+ is specified, h\bhe\bel\blp\bp gives detailed help on all commands matching
+ _\bp_\ba_\bt_\bt_\be_\br_\bn as described below; otherwise it displays a list of all
the builtins and shell compound commands.
Options, if supplied, have the follow meanings:
format
-\b-s\bs Display only a short usage synopsis for each _\bp_\ba_\bt_\bt_\be_\br_\bn
- If _\bp_\ba_\bt_\bt_\be_\br_\bn contains pattern matching characters (see P\bPa\bat\btt\bte\ber\brn\bn
- M\bMa\bat\btc\bch\bhi\bin\bng\bg above) it's treated as a shell pattern and h\bhe\bel\blp\bp prints
+ If _\bp_\ba_\bt_\bt_\be_\br_\bn contains pattern matching characters (see P\bPa\bat\btt\bte\ber\brn\bn
+ M\bMa\bat\btc\bch\bhi\bin\bng\bg above) it's treated as a shell pattern and h\bhe\bel\blp\bp prints
the description of each help topic matching _\bp_\ba_\bt_\bt_\be_\br_\bn.
- If not, and _\bp_\ba_\bt_\bt_\be_\br_\bn exactly matches the name of a help topic,
- h\bhe\bel\blp\bp prints the description associated with that topic. Other-
- wise, h\bhe\bel\blp\bp performs prefix matching and prints the descriptions
+ If not, and _\bp_\ba_\bt_\bt_\be_\br_\bn exactly matches the name of a help topic,
+ h\bhe\bel\blp\bp prints the description associated with that topic. Other-
+ wise, h\bhe\bel\blp\bp performs prefix matching and prints the descriptions
of all matching help topics.
The return status is 0 unless no command matches _\bp_\ba_\bt_\bt_\be_\br_\bn.
h\bhi\bis\bst\bto\bor\bry\by -\b-a\ban\bnr\brw\bw [_\bf_\bi_\bl_\be_\bn_\ba_\bm_\be]
h\bhi\bis\bst\bto\bor\bry\by -\b-p\bp _\ba_\br_\bg [_\ba_\br_\bg ...]
h\bhi\bis\bst\bto\bor\bry\by -\b-s\bs _\ba_\br_\bg [_\ba_\br_\bg ...]
- With no options, display the command history list with numbers.
- Entries prefixed with a *\b* have been modified. An argument of _\bn
- lists only the last _\bn entries. If the shell variable H\bHI\bIS\bST\bTT\bTI\bIM\bME\bE-\b-
- F\bFO\bOR\bRM\bMA\bAT\bT is set and not null, it is used as a format string for
- _\bs_\bt_\br_\bf_\bt_\bi_\bm_\be(3) to display the time stamp associated with each dis-
- played history entry. If h\bhi\bis\bst\bto\bor\bry\by uses H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT, it does
- not print an intervening space between the formatted time stamp
+ With no options, display the command history list with numbers.
+ Entries prefixed with a *\b* have been modified. An argument of _\bn
+ lists only the last _\bn entries. If the shell variable H\bHI\bIS\bST\bTT\bTI\bIM\bME\bE-\b-
+ F\bFO\bOR\bRM\bMA\bAT\bT is set and not null, it is used as a format string for
+ _\bs_\bt_\br_\bf_\bt_\bi_\bm_\be(3) to display the time stamp associated with each dis-
+ played history entry. If h\bhi\bis\bst\bto\bor\bry\by uses H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT, it does
+ not print an intervening space between the formatted time stamp
and the history entry.
If _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be is supplied, h\bhi\bis\bst\bto\bor\bry\by uses it as the name of the his-
- tory file; if not, it uses the value of H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE. If _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
- is not supplied and H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE is unset or null, the -\b-a\ba,\b, -\b-n\bn,\b, -\b-r\br,\b,
+ tory file; if not, it uses the value of H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE. If _\bf_\bi_\bl_\be_\bn_\ba_\bm_\be
+ is not supplied and H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE is unset or null, the -\b-a\ba,\b, -\b-n\bn,\b, -\b-r\br,\b,
and -\b-w\bw options have no effect.
Options, if supplied, have the following meanings:
can be used with the other options to replace the history
list.
-\b-d\bd _\bo_\bf_\bf_\bs_\be_\bt
- Delete the history entry at position _\bo_\bf_\bf_\bs_\be_\bt. If _\bo_\bf_\bf_\bs_\be_\bt
+ Delete the history entry at position _\bo_\bf_\bf_\bs_\be_\bt. If _\bo_\bf_\bf_\bs_\be_\bt
is negative, it is interpreted as relative to one greater
than the last history position, so negative indices count
- back from the end of the history, and an index of -1
+ back from the end of the history, and an index of -1
refers to the current h\bhi\bis\bst\bto\bor\bry\by -\b-d\bd command.
-\b-d\bd _\bs_\bt_\ba_\br_\bt-_\be_\bn_\bd
- Delete the range of history entries between positions
- _\bs_\bt_\ba_\br_\bt and _\be_\bn_\bd, inclusive. Positive and negative values
+ Delete the range of history entries between positions
+ _\bs_\bt_\ba_\br_\bt and _\be_\bn_\bd, inclusive. Positive and negative values
for _\bs_\bt_\ba_\br_\bt and _\be_\bn_\bd are interpreted as described above.
- -\b-a\ba Append the "new" history lines to the history file.
- These are history lines entered since the beginning of
+ -\b-a\ba Append the "new" history lines to the history file.
+ These are history lines entered since the beginning of
the current b\bba\bas\bsh\bh session, but not already appended to the
history file.
- -\b-n\bn Read the history lines not already read from the history
+ -\b-n\bn Read the history lines not already read from the history
file and add them to the current history list. These are
lines appended to the history file since the beginning of
the current b\bba\bas\bsh\bh session.
rent history list.
-\b-w\bw Write the current history list to the history file, over-
writing the history file.
- -\b-p\bp Perform history substitution on the following _\ba_\br_\bg_\bs and
- display the result on the standard output, without stor-
- ing the results in the history list. Each _\ba_\br_\bg must be
+ -\b-p\bp Perform history substitution on the following _\ba_\br_\bg_\bs and
+ display the result on the standard output, without stor-
+ ing the results in the history list. Each _\ba_\br_\bg must be
quoted to disable normal history expansion.
- -\b-s\bs Store the _\ba_\br_\bg_\bs in the history list as a single entry.
- The last command in the history list is removed before
+ -\b-s\bs Store the _\ba_\br_\bg_\bs in the history list as a single entry.
+ The last command in the history list is removed before
adding the _\ba_\br_\bg_\bs.
- If the H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable is set, h\bhi\bis\bst\bto\bor\bry\by writes the time
+ If the H\bHI\bIS\bST\bTT\bTI\bIM\bME\bEF\bFO\bOR\bRM\bMA\bAT\bT variable is set, h\bhi\bis\bst\bto\bor\bry\by writes the time
stamp information associated with each history entry to the his-
- tory file, marked with the history comment character as de-
- scribed above. When the history file is read, lines beginning
- with the history comment character followed immediately by a
- digit are interpreted as timestamps for the following history
+ tory file, marked with the history comment character as de-
+ scribed above. When the history file is read, lines beginning
+ with the history comment character followed immediately by a
+ digit are interpreted as timestamps for the following history
entry.
- The return value is 0 unless an invalid option is encountered,
- an error occurs while reading or writing the history file, an
+ The return value is 0 unless an invalid option is encountered,
+ an error occurs while reading or writing the history file, an
invalid _\bo_\bf_\bf_\bs_\be_\bt or range is supplied as an argument to -\b-d\bd, or the
history expansion supplied as an argument to -\b-p\bp fails.
The first form lists the active jobs. The options have the fol-
lowing meanings:
-\b-l\bl List process IDs in addition to the normal information.
- -\b-n\bn Display information only about jobs that have changed
+ -\b-n\bn Display information only about jobs that have changed
status since the user was last notified of their status.
- -\b-p\bp List only the process ID of the job's process group
+ -\b-p\bp List only the process ID of the job's process group
leader.
-\b-r\br Display only running jobs.
-\b-s\bs Display only stopped jobs.
- If _\bj_\bo_\bb_\bs_\bp_\be_\bc is supplied, j\bjo\bob\bbs\bs restricts output to information
+ If _\bj_\bo_\bb_\bs_\bp_\be_\bc is supplied, j\bjo\bob\bbs\bs restricts output to information
about that job. The return status is 0 unless an invalid option
is encountered or an invalid _\bj_\bo_\bb_\bs_\bp_\be_\bc is supplied.
k\bki\bil\bll\bl [-\b-s\bs _\bs_\bi_\bg_\bs_\bp_\be_\bc | -\b-n\bn _\bs_\bi_\bg_\bn_\bu_\bm | -\b-_\bs_\bi_\bg_\bs_\bp_\be_\bc] _\bi_\bd [ ... ]
k\bki\bil\bll\bl -\b-l\bl|-\b-L\bL [_\bs_\bi_\bg_\bs_\bp_\be_\bc | _\be_\bx_\bi_\bt_\b__\bs_\bt_\ba_\bt_\bu_\bs]
- Send the signal specified by _\bs_\bi_\bg_\bs_\bp_\be_\bc or _\bs_\bi_\bg_\bn_\bu_\bm to the processes
+ Send the signal specified by _\bs_\bi_\bg_\bs_\bp_\be_\bc or _\bs_\bi_\bg_\bn_\bu_\bm to the processes
named by each _\bi_\bd. Each _\bi_\bd may be a job specification _\bj_\bo_\bb_\bs_\bp_\be_\bc or
- a process ID _\bp_\bi_\bd. _\bs_\bi_\bg_\bs_\bp_\be_\bc is either a case-insensitive signal
- name such as S\bSI\bIG\bGK\bKI\bIL\bLL\bL (with or without the S\bSI\bIG\bG prefix) or a sig-
- nal number; _\bs_\bi_\bg_\bn_\bu_\bm is a signal number. If _\bs_\bi_\bg_\bs_\bp_\be_\bc is not sup-
+ a process ID _\bp_\bi_\bd. _\bs_\bi_\bg_\bs_\bp_\be_\bc is either a case-insensitive signal
+ name such as S\bSI\bIG\bGK\bKI\bIL\bLL\bL (with or without the S\bSI\bIG\bG prefix) or a sig-
+ nal number; _\bs_\bi_\bg_\bn_\bu_\bm is a signal number. If _\bs_\bi_\bg_\bs_\bp_\be_\bc is not sup-
plied, then k\bki\bil\bll\bl sends S\bSI\bIG\bGT\bTE\bER\bRM\bM.
The -\b-l\bl option lists the signal names. If any arguments are sup-
plied when -\b-l\bl is given, k\bki\bil\bll\bl lists the names of the signals cor-
- responding to the arguments, and the return status is 0. The
- _\be_\bx_\bi_\bt_\b__\bs_\bt_\ba_\bt_\bu_\bs argument to -\b-l\bl is a number specifying either a sig-
- nal number or the exit status of a process terminated by a sig-
- nal; if it is supplied, k\bki\bil\bll\bl prints the name of the signal that
+ responding to the arguments, and the return status is 0. The
+ _\be_\bx_\bi_\bt_\b__\bs_\bt_\ba_\bt_\bu_\bs argument to -\b-l\bl is a number specifying either a sig-
+ nal number or the exit status of a process terminated by a sig-
+ nal; if it is supplied, k\bki\bil\bll\bl prints the name of the signal that
caused the process to terminate. k\bki\bil\bll\bl assumes that process exit
statuses are greater than 128; anything less than that is a sig-
nal number. The -\b-L\bL option is equivalent to -\b-l\bl.
- k\bki\bil\bll\bl returns true if at least one signal was successfully sent,
+ k\bki\bil\bll\bl returns true if at least one signal was successfully sent,
or false if an error occurs or an invalid option is encountered.
l\ble\bet\bt _\ba_\br_\bg [_\ba_\br_\bg ...]
- Each _\ba_\br_\bg is evaluated as an arithmetic expression (see A\bAR\bRI\bIT\bTH\bH-\b-
- M\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN above). If the last _\ba_\br_\bg evaluates to 0, l\ble\bet\bt
+ Each _\ba_\br_\bg is evaluated as an arithmetic expression (see A\bAR\bRI\bIT\bTH\bH-\b-
+ M\bME\bET\bTI\bIC\bC E\bEV\bVA\bAL\bLU\bUA\bAT\bTI\bIO\bON\bN above). If the last _\ba_\br_\bg evaluates to 0, l\ble\bet\bt
returns 1; otherwise l\ble\bet\bt returns 0.
l\blo\boc\bca\bal\bl [_\bo_\bp_\bt_\bi_\bo_\bn] [_\bn_\ba_\bm_\be[=_\bv_\ba_\bl_\bu_\be] ... | - ]
For each argument, create a local variable named _\bn_\ba_\bm_\be and assign
- it _\bv_\ba_\bl_\bu_\be. The _\bo_\bp_\bt_\bi_\bo_\bn can be any of the options accepted by d\bde\be-\b-
- c\bcl\bla\bar\bre\be. When l\blo\boc\bca\bal\bl is used within a function, it causes the
- variable _\bn_\ba_\bm_\be to have a visible scope restricted to that func-
- tion and its children. It is an error to use l\blo\boc\bca\bal\bl when not
+ it _\bv_\ba_\bl_\bu_\be. The _\bo_\bp_\bt_\bi_\bo_\bn can be any of the options accepted by d\bde\be-\b-
+ c\bcl\bla\bar\bre\be. When l\blo\boc\bca\bal\bl is used within a function, it causes the
+ variable _\bn_\ba_\bm_\be to have a visible scope restricted to that func-
+ tion and its children. It is an error to use l\blo\boc\bca\bal\bl when not
within a function.
- If _\bn_\ba_\bm_\be is -, it makes the set of shell options local to the
- function in which l\blo\boc\bca\bal\bl is invoked: any shell options changed
- using the s\bse\bet\bt builtin inside the function after the call to l\blo\bo-\b-
- c\bca\bal\bl are restored to their original values when the function re-
- turns. The restore is performed as if a series of s\bse\bet\bt commands
- were executed to restore the values that were in place before
+ If _\bn_\ba_\bm_\be is -, it makes the set of shell options local to the
+ function in which l\blo\boc\bca\bal\bl is invoked: any shell options changed
+ using the s\bse\bet\bt builtin inside the function after the call to l\blo\bo-\b-
+ c\bca\bal\bl are restored to their original values when the function re-
+ turns. The restore is performed as if a series of s\bse\bet\bt commands
+ were executed to restore the values that were in place before
the function.
- With no operands, l\blo\boc\bca\bal\bl writes a list of local variables to the
+ With no operands, l\blo\boc\bca\bal\bl writes a list of local variables to the
standard output.
- The return status is 0 unless l\blo\boc\bca\bal\bl is used outside a function,
+ The return status is 0 unless l\blo\boc\bca\bal\bl is used outside a function,
an invalid _\bn_\ba_\bm_\be is supplied, or _\bn_\ba_\bm_\be is a readonly variable.
l\blo\bog\bgo\bou\but\bt [\b[_\bn]\b]
- Exit a login shell, returning a status of _\bn to the shell's par-
+ Exit a login shell, returning a status of _\bn to the shell's par-
ent.
m\bma\bap\bpf\bfi\bil\ble\be [-\b-d\bd _\bd_\be_\bl_\bi_\bm] [-\b-n\bn _\bc_\bo_\bu_\bn_\bt] [-\b-O\bO _\bo_\br_\bi_\bg_\bi_\bn] [-\b-s\bs _\bc_\bo_\bu_\bn_\bt] [-\b-t\bt] [-\b-u\bu _\bf_\bd] [-\b-C\bC
_\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk] [-\b-c\bc _\bq_\bu_\ba_\bn_\bt_\bu_\bm] [_\ba_\br_\br_\ba_\by]
r\bre\bea\bad\bda\bar\brr\bra\bay\by [-\b-d\bd _\bd_\be_\bl_\bi_\bm] [-\b-n\bn _\bc_\bo_\bu_\bn_\bt] [-\b-O\bO _\bo_\br_\bi_\bg_\bi_\bn] [-\b-s\bs _\bc_\bo_\bu_\bn_\bt] [-\b-t\bt] [-\b-u\bu _\bf_\bd] [-\b-C\bC
_\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk] [-\b-c\bc _\bq_\bu_\ba_\bn_\bt_\bu_\bm] [_\ba_\br_\br_\ba_\by]
- Read lines from the standard input, or from file descriptor _\bf_\bd
- if the -\b-u\bu option is supplied, into the indexed array variable
- _\ba_\br_\br_\ba_\by. The variable M\bMA\bAP\bPF\bFI\bIL\bLE\bE is the default _\ba_\br_\br_\ba_\by. Options, if
+ Read lines from the standard input, or from file descriptor _\bf_\bd
+ if the -\b-u\bu option is supplied, into the indexed array variable
+ _\ba_\br_\br_\ba_\by. The variable M\bMA\bAP\bPF\bFI\bIL\bLE\bE is the default _\ba_\br_\br_\ba_\by. Options, if
supplied, have the following meanings:
- -\b-d\bd Use the first character of _\bd_\be_\bl_\bi_\bm to terminate each input
+ -\b-d\bd Use the first character of _\bd_\be_\bl_\bi_\bm to terminate each input
line, rather than newline. If _\bd_\be_\bl_\bi_\bm is the empty string,
m\bma\bap\bpf\bfi\bil\ble\be will terminate a line when it reads a NUL charac-
ter.
-\b-n\bn Copy at most _\bc_\bo_\bu_\bn_\bt lines. If _\bc_\bo_\bu_\bn_\bt is 0, copy all lines.
- -\b-O\bO Begin assigning to _\ba_\br_\br_\ba_\by at index _\bo_\br_\bi_\bg_\bi_\bn. The default
+ -\b-O\bO Begin assigning to _\ba_\br_\br_\ba_\by at index _\bo_\br_\bi_\bg_\bi_\bn. The default
index is 0.
-\b-s\bs Discard the first _\bc_\bo_\bu_\bn_\bt lines read.
- -\b-t\bt Remove a trailing _\bd_\be_\bl_\bi_\bm (default newline) from each line
+ -\b-t\bt Remove a trailing _\bd_\be_\bl_\bi_\bm (default newline) from each line
read.
- -\b-u\bu Read lines from file descriptor _\bf_\bd instead of the stan-
+ -\b-u\bu Read lines from file descriptor _\bf_\bd instead of the stan-
dard input.
- -\b-C\bC Evaluate _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk each time _\bq_\bu_\ba_\bn_\bt_\bu_\bm lines are read. The
+ -\b-C\bC Evaluate _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk each time _\bq_\bu_\ba_\bn_\bt_\bu_\bm lines are read. The
-\b-c\bc option specifies _\bq_\bu_\ba_\bn_\bt_\bu_\bm.
- -\b-c\bc Specify the number of lines read between each call to
+ -\b-c\bc Specify the number of lines read between each call to
_\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk.
- If -\b-C\bC is specified without -\b-c\bc, the default quantum is 5000.
+ If -\b-C\bC is specified without -\b-c\bc, the default quantum is 5000.
When _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk is evaluated, it is supplied the index of the next
array element to be assigned and the line to be assigned to that
- element as additional arguments. _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk is evaluated after
+ element as additional arguments. _\bc_\ba_\bl_\bl_\bb_\ba_\bc_\bk is evaluated after
the line is read but before the array element is assigned.
- If not supplied with an explicit origin, m\bma\bap\bpf\bfi\bil\ble\be will clear _\ba_\br_\b-
+ If not supplied with an explicit origin, m\bma\bap\bpf\bfi\bil\ble\be will clear _\ba_\br_\b-
_\br_\ba_\by before assigning to it.
m\bma\bap\bpf\bfi\bil\ble\be returns zero unless an invalid option or option argument
- is supplied, _\ba_\br_\br_\ba_\by is invalid or unassignable, or if _\ba_\br_\br_\ba_\by is
+ is supplied, _\ba_\br_\br_\ba_\by is invalid or unassignable, or if _\ba_\br_\br_\ba_\by is
not an indexed array.
p\bpo\bop\bpd\bd [-n\bn] [+_\bn] [-_\bn]
- Remove entries from the directory stack. The elements are num-
- bered from 0 starting at the first directory listed by d\bdi\bir\brs\bs, so
- p\bpo\bop\bpd\bd is equivalent to "popd +0." With no arguments, p\bpo\bop\bpd\bd re-
- moves the top directory from the stack, and changes to the new
+ Remove entries from the directory stack. The elements are num-
+ bered from 0 starting at the first directory listed by d\bdi\bir\brs\bs, so
+ p\bpo\bop\bpd\bd is equivalent to "popd +0." With no arguments, p\bpo\bop\bpd\bd re-
+ moves the top directory from the stack, and changes to the new
top directory. Arguments, if supplied, have the following mean-
ings:
-\b-n\bn Suppress the normal change of directory when removing di-
rectories from the stack, only manipulate the stack.
- +\b+_\bn Remove the _\bnth entry counting from the left of the list
- shown by d\bdi\bir\brs\bs, starting with zero, from the stack. For
+ +\b+_\bn Remove the _\bnth entry counting from the left of the list
+ shown by d\bdi\bir\brs\bs, starting with zero, from the stack. For
example: "popd +0" removes the first directory, "popd +1"
the second.
- -\b-_\bn Remove the _\bnth entry counting from the right of the list
- shown by d\bdi\bir\brs\bs, starting with zero. For example: "popd
- -0" removes the last directory, "popd -1" the next to
+ -\b-_\bn Remove the _\bnth entry counting from the right of the list
+ shown by d\bdi\bir\brs\bs, starting with zero. For example: "popd
+ -0" removes the last directory, "popd -1" the next to
last.
- If the top element of the directory stack is modified, and the
- _\b-_\bn option was not supplied, p\bpo\bop\bpd\bd uses the c\bcd\bd builtin to change
+ If the top element of the directory stack is modified, and the
+ _\b-_\bn option was not supplied, p\bpo\bop\bpd\bd uses the c\bcd\bd builtin to change
to the directory at the top of the stack. If the c\bcd\bd fails, p\bpo\bop\bpd\bd
returns a non-zero value.
- Otherwise, p\bpo\bop\bpd\bd returns false if an invalid option is supplied,
- the directory stack is empty, or _\bn specifies a non-existent di-
+ Otherwise, p\bpo\bop\bpd\bd returns false if an invalid option is supplied,
+ the directory stack is empty, or _\bn specifies a non-existent di-
rectory stack entry.
- If the p\bpo\bop\bpd\bd command is successful, b\bba\bas\bsh\bh runs d\bdi\bir\brs\bs to show the
- final contents of the directory stack, and the return status is
+ If the p\bpo\bop\bpd\bd command is successful, b\bba\bas\bsh\bh runs d\bdi\bir\brs\bs to show the
+ final contents of the directory stack, and the return status is
0.
p\bpr\bri\bin\bnt\btf\bf [-\b-v\bv _\bv_\ba_\br] _\bf_\bo_\br_\bm_\ba_\bt [_\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs]
- Write the formatted _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs to the standard output under the
- control of the _\bf_\bo_\br_\bm_\ba_\bt. The -\b-v\bv option assigns the output to the
+ Write the formatted _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs to the standard output under the
+ control of the _\bf_\bo_\br_\bm_\ba_\bt. The -\b-v\bv option assigns the output to the
variable _\bv_\ba_\br rather than printing it to the standard output.
- The _\bf_\bo_\br_\bm_\ba_\bt is a character string which contains three types of
- objects: plain characters, which are simply copied to standard
- output, character escape sequences, which are converted and
- copied to the standard output, and format specifications, each
- of which causes printing of the next successive _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt. In
- addition to the standard _\bp_\br_\bi_\bn_\bt_\bf(3) format characters c\bcC\bCs\bsS\bS-\b-
+ The _\bf_\bo_\br_\bm_\ba_\bt is a character string which contains three types of
+ objects: plain characters, which are simply copied to standard
+ output, character escape sequences, which are converted and
+ copied to the standard output, and format specifications, each
+ of which causes printing of the next successive _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt. In
+ addition to the standard _\bp_\br_\bi_\bn_\bt_\bf(3) format characters c\bcC\bCs\bsS\bS-\b-
n\bnd\bdi\bio\bou\bux\bxX\bXe\beE\bEf\bfF\bFg\bgG\bGa\baA\bA, p\bpr\bri\bin\bnt\btf\bf interprets the following additional for-
mat specifiers:
%\b%b\bb causes p\bpr\bri\bin\bnt\btf\bf to expand backslash escape sequences in the
corresponding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt in the same way as e\bec\bch\bho\bo -\b-e\be.
- %\b%q\bq causes p\bpr\bri\bin\bnt\btf\bf to output the corresponding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt in a
- format that can be reused as shell input. %\b%q\bq and %\b%Q\bQ use
- the $\b$'\b''\b' quoting style if any characters in the argument
- string require it, and backslash quoting otherwise. If
- the format string uses the _\bp_\br_\bi_\bn_\bt_\bf alternate form, these
+ %\b%q\bq causes p\bpr\bri\bin\bnt\btf\bf to output the corresponding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt in a
+ format that can be reused as shell input. %\b%q\bq and %\b%Q\bQ use
+ the $\b$'\b''\b' quoting style if any characters in the argument
+ string require it, and backslash quoting otherwise. If
+ the format string uses the _\bp_\br_\bi_\bn_\bt_\bf alternate form, these
two formats quote the argument string using single
quotes.
- %\b%Q\bQ like %\b%q\bq, but applies any supplied precision to the _\ba_\br_\bg_\bu_\b-
+ %\b%Q\bQ like %\b%q\bq, but applies any supplied precision to the _\ba_\br_\bg_\bu_\b-
_\bm_\be_\bn_\bt before quoting it.
%\b%(\b(_\bd_\ba_\bt_\be_\bf_\bm_\bt)\b)T\bT
- causes p\bpr\bri\bin\bnt\btf\bf to output the date-time string resulting
- from using _\bd_\ba_\bt_\be_\bf_\bm_\bt as a format string for _\bs_\bt_\br_\bf_\bt_\bi_\bm_\be(3).
+ causes p\bpr\bri\bin\bnt\btf\bf to output the date-time string resulting
+ from using _\bd_\ba_\bt_\be_\bf_\bm_\bt as a format string for _\bs_\bt_\br_\bf_\bt_\bi_\bm_\be(3).
The corresponding _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt is an integer representing the
number of seconds since the epoch. This format specifier
recognizes two special argument values: -1 represents the
- current time, and -2 represents the time the shell was
+ current time, and -2 represents the time the shell was
invoked. If no argument is specified, conversion behaves
- as if -1 had been supplied. This is an exception to the
+ as if -1 had been supplied. This is an exception to the
usual p\bpr\bri\bin\bnt\btf\bf behavior.
The %b, %q, and %T format specifiers all use the field width and
precision arguments from the format specification and write that
- many bytes from (or use that wide a field for) the expanded ar-
- gument, which usually contains more characters than the origi-
+ many bytes from (or use that wide a field for) the expanded ar-
+ gument, which usually contains more characters than the origi-
nal.
The %n format specifier accepts a corresponding argument that is
treated as a shell variable name.
- The %s and %c format specifiers accept an l (long) modifier,
+ The %s and %c format specifiers accept an l (long) modifier,
which forces them to convert the argument string to a wide-char-
acter string and apply any supplied field width and precision in
terms of characters, not bytes. The %S and %C format specifiers
are equivalent to %ls and %lc, respectively.
- Arguments to non-string format specifiers are treated as C con-
+ Arguments to non-string format specifiers are treated as C con-
stants, except that a leading plus or minus sign is allowed, and
- if the leading character is a single or double quote, the value
- is the numeric value of the following character, using the cur-
+ if the leading character is a single or double quote, the value
+ is the numeric value of the following character, using the cur-
rent locale.
- The _\bf_\bo_\br_\bm_\ba_\bt is reused as necessary to consume all of the _\ba_\br_\bg_\bu_\b-
+ The _\bf_\bo_\br_\bm_\ba_\bt is reused as necessary to consume all of the _\ba_\br_\bg_\bu_\b-
_\bm_\be_\bn_\bt_\bs. If the _\bf_\bo_\br_\bm_\ba_\bt requires more _\ba_\br_\bg_\bu_\bm_\be_\bn_\bt_\bs than are supplied,
- the extra format specifications behave as if a zero value or
- null string, as appropriate, had been supplied. The return
- value is zero on success, non-zero if an invalid option is sup-
+ the extra format specifications behave as if a zero value or
+ null string, as appropriate, had been supplied. The return
+ value is zero on success, non-zero if an invalid option is sup-
plied or a write or assignment error occurs.
p\bpu\bus\bsh\bhd\bd [-\b-n\bn] [+_\bn] [-_\bn]
p\bpu\bus\bsh\bhd\bd [-\b-n\bn] [_\bd_\bi_\br]
Add a directory to the top of the directory stack, or rotate the
- stack, making the new top of the stack the current working di-
- rectory. With no arguments, p\bpu\bus\bsh\bhd\bd exchanges the top two ele-
- ments of the directory stack. Arguments, if supplied, have the
+ stack, making the new top of the stack the current working di-
+ rectory. With no arguments, p\bpu\bus\bsh\bhd\bd exchanges the top two ele-
+ ments of the directory stack. Arguments, if supplied, have the
following meanings:
- -\b-n\bn Suppress the normal change of directory when rotating or
- adding directories to the stack, only manipulate the
+ -\b-n\bn Suppress the normal change of directory when rotating or
+ adding directories to the stack, only manipulate the
stack.
+\b+_\bn Rotate the stack so that the _\bnth directory (counting from
- the left of the list shown by d\bdi\bir\brs\bs, starting with zero)
+ the left of the list shown by d\bdi\bir\brs\bs, starting with zero)
is at the top.
- -\b-_\bn Rotates the stack so that the _\bnth directory (counting
- from the right of the list shown by d\bdi\bir\brs\bs, starting with
+ -\b-_\bn Rotates the stack so that the _\bnth directory (counting
+ from the right of the list shown by d\bdi\bir\brs\bs, starting with
zero) is at the top.
_\bd_\bi_\br Adds _\bd_\bi_\br to the directory stack at the top.
After the stack has been modified, if the -\b-n\bn option was not sup-
- plied, p\bpu\bus\bsh\bhd\bd uses the c\bcd\bd builtin to change to the directory at
+ plied, p\bpu\bus\bsh\bhd\bd uses the c\bcd\bd builtin to change to the directory at
the top of the stack. If the c\bcd\bd fails, p\bpu\bus\bsh\bhd\bd returns a non-zero
value.
- Otherwise, if no arguments are supplied, p\bpu\bus\bsh\bhd\bd returns zero un-
- less the directory stack is empty. When rotating the directory
+ Otherwise, if no arguments are supplied, p\bpu\bus\bsh\bhd\bd returns zero un-
+ less the directory stack is empty. When rotating the directory
stack, p\bpu\bus\bsh\bhd\bd returns zero unless the directory stack is empty or
_\bn specifies a non-existent directory stack element.
- If the p\bpu\bus\bsh\bhd\bd command is successful, b\bba\bas\bsh\bh runs d\bdi\bir\brs\bs to show the
+ If the p\bpu\bus\bsh\bhd\bd command is successful, b\bba\bas\bsh\bh runs d\bdi\bir\brs\bs to show the
final contents of the directory stack.
p\bpw\bwd\bd [-\b-L\bLP\bP]
- Print the absolute pathname of the current working directory.
+ Print the absolute pathname of the current working directory.
The pathname printed contains no symbolic links if the -\b-P\bP option
is supplied or the -\b-o\bo p\bph\bhy\bys\bsi\bic\bca\bal\bl option to the s\bse\bet\bt builtin command
- is enabled. If the -\b-L\bL option is used, the pathname printed may
- contain symbolic links. The return status is 0 unless an error
+ is enabled. If the -\b-L\bL option is used, the pathname printed may
+ contain symbolic links. The return status is 0 unless an error
occurs while reading the name of the current directory or an in-
valid option is supplied.
r\bre\bea\bad\bd [-\b-E\bEe\ber\brs\bs] [-\b-a\ba _\ba_\bn_\ba_\bm_\be] [-\b-d\bd _\bd_\be_\bl_\bi_\bm] [-\b-i\bi _\bt_\be_\bx_\bt] [-\b-n\bn _\bn_\bc_\bh_\ba_\br_\bs] [-\b-N\bN _\bn_\bc_\bh_\ba_\br_\bs]
[-\b-p\bp _\bp_\br_\bo_\bm_\bp_\bt] [-\b-t\bt _\bt_\bi_\bm_\be_\bo_\bu_\bt] [-\b-u\bu _\bf_\bd] [_\bn_\ba_\bm_\be ...]
Read one line from the standard input, or from the file descrip-
- tor _\bf_\bd supplied as an argument to the -\b-u\bu option, split it into
- words as described above under W\bWo\bor\brd\bd S\bSp\bpl\bli\bit\btt\bti\bin\bng\bg, and assign the
- first word to the first _\bn_\ba_\bm_\be, the second word to the second
- _\bn_\ba_\bm_\be, and so on. If there are more words than names, the re-
- maining words and their intervening delimiters are assigned to
- the last _\bn_\ba_\bm_\be. If there are fewer words read from the input
- stream than names, the remaining names are assigned empty val-
- ues. The characters in the value of the I\bIF\bFS\bS variable are used
+ tor _\bf_\bd supplied as an argument to the -\b-u\bu option, split it into
+ words as described above under W\bWo\bor\brd\bd S\bSp\bpl\bli\bit\btt\bti\bin\bng\bg, and assign the
+ first word to the first _\bn_\ba_\bm_\be, the second word to the second
+ _\bn_\ba_\bm_\be, and so on. If there are more words than names, the re-
+ maining words and their intervening delimiters are assigned to
+ the last _\bn_\ba_\bm_\be. If there are fewer words read from the input
+ stream than names, the remaining names are assigned empty val-
+ ues. The characters in the value of the I\bIF\bFS\bS variable are used
to split the line into words using the same rules the shell uses
for expansion (described above under W\bWo\bor\brd\bd S\bSp\bpl\bli\bit\btt\bti\bin\bng\bg). The back-
- slash character (\\b\) removes any special meaning for the next
+ slash character (\\b\) removes any special meaning for the next
character read and is used for line continuation.
Options, if supplied, have the following meanings:
-\b-a\ba _\ba_\bn_\ba_\bm_\be
The words are assigned to sequential indices of the array
variable _\ba_\bn_\ba_\bm_\be, starting at 0. _\ba_\bn_\ba_\bm_\be is unset before any
- new values are assigned. Other _\bn_\ba_\bm_\be arguments are ig-
+ new values are assigned. Other _\bn_\ba_\bm_\be arguments are ig-
nored.
-\b-d\bd _\bd_\be_\bl_\bi_\bm
- The first character of _\bd_\be_\bl_\bi_\bm terminates the input line,
- rather than newline. If _\bd_\be_\bl_\bi_\bm is the empty string, r\bre\bea\bad\bd
+ The first character of _\bd_\be_\bl_\bi_\bm terminates the input line,
+ rather than newline. If _\bd_\be_\bl_\bi_\bm is the empty string, r\bre\bea\bad\bd
will terminate a line when it reads a NUL character.
- -\b-e\be If the standard input is coming from a terminal, r\bre\bea\bad\bd
- uses r\bre\bea\bad\bdl\bli\bin\bne\be (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE above) to obtain the line.
- R\bRe\bea\bad\bdl\bli\bin\bne\be uses the current (or default, if line editing
- was not previously active) editing settings, but uses
+ -\b-e\be If the standard input is coming from a terminal, r\bre\bea\bad\bd
+ uses r\bre\bea\bad\bdl\bli\bin\bne\be (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE above) to obtain the line.
+ R\bRe\bea\bad\bdl\bli\bin\bne\be uses the current (or default, if line editing
+ was not previously active) editing settings, but uses
r\bre\bea\bad\bdl\bli\bin\bne\be's default filename completion.
- -\b-E\bE If the standard input is coming from a terminal, r\bre\bea\bad\bd
- uses r\bre\bea\bad\bdl\bli\bin\bne\be (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE above) to obtain the line.
- R\bRe\bea\bad\bdl\bli\bin\bne\be uses the current (or default, if line editing
- was not previously active) editing settings, but uses
+ -\b-E\bE If the standard input is coming from a terminal, r\bre\bea\bad\bd
+ uses r\bre\bea\bad\bdl\bli\bin\bne\be (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE above) to obtain the line.
+ R\bRe\bea\bad\bdl\bli\bin\bne\be uses the current (or default, if line editing
+ was not previously active) editing settings, but uses
bash's default completion, including programmable comple-
tion.
-\b-i\bi _\bt_\be_\bx_\bt
- If r\bre\bea\bad\bdl\bli\bin\bne\be is being used to read the line, r\bre\bea\bad\bd places
+ If r\bre\bea\bad\bdl\bli\bin\bne\be is being used to read the line, r\bre\bea\bad\bd places
_\bt_\be_\bx_\bt into the editing buffer before editing begins.
-\b-n\bn _\bn_\bc_\bh_\ba_\br_\bs
- r\bre\bea\bad\bd returns after reading _\bn_\bc_\bh_\ba_\br_\bs characters rather than
- waiting for a complete line of input, unless it encoun-
- ters EOF or r\bre\bea\bad\bd times out, but honors a delimiter if it
+ r\bre\bea\bad\bd returns after reading _\bn_\bc_\bh_\ba_\br_\bs characters rather than
+ waiting for a complete line of input, unless it encoun-
+ ters EOF or r\bre\bea\bad\bd times out, but honors a delimiter if it
reads fewer than _\bn_\bc_\bh_\ba_\br_\bs characters before the delimiter.
-\b-N\bN _\bn_\bc_\bh_\ba_\br_\bs
- r\bre\bea\bad\bd returns after reading exactly _\bn_\bc_\bh_\ba_\br_\bs characters
- rather than waiting for a complete line of input, unless
+ r\bre\bea\bad\bd returns after reading exactly _\bn_\bc_\bh_\ba_\br_\bs characters
+ rather than waiting for a complete line of input, unless
it encounters EOF or r\bre\bea\bad\bd times out. Any delimiter char-
- acters in the input are not treated specially and do not
+ acters in the input are not treated specially and do not
cause r\bre\bea\bad\bd to return until it has read _\bn_\bc_\bh_\ba_\br_\bs characters.
The result is not split on the characters in I\bIF\bFS\bS; the in-
tent is that the variable is assigned exactly the charac-
- ters read (with the exception of backslash; see the -\b-r\br
+ ters read (with the exception of backslash; see the -\b-r\br
option below).
-\b-p\bp _\bp_\br_\bo_\bm_\bp_\bt
Display _\bp_\br_\bo_\bm_\bp_\bt on standard error, without a trailing new-
- line, before attempting to read any input, but only if
+ line, before attempting to read any input, but only if
input is coming from a terminal.
-\b-r\br Backslash does not act as an escape character. The back-
- slash is considered to be part of the line. In particu-
- lar, a backslash-newline pair may not then be used as a
+ slash is considered to be part of the line. In particu-
+ lar, a backslash-newline pair may not then be used as a
line continuation.
-\b-s\bs Silent mode. If input is coming from a terminal, charac-
ters are not echoed.
-\b-t\bt _\bt_\bi_\bm_\be_\bo_\bu_\bt
- Cause r\bre\bea\bad\bd to time out and return failure if it does not
- read a complete line of input (or a specified number of
- characters) within _\bt_\bi_\bm_\be_\bo_\bu_\bt seconds. _\bt_\bi_\bm_\be_\bo_\bu_\bt may be a
- decimal number with a fractional portion following the
- decimal point. This option is only effective if r\bre\bea\bad\bd is
- reading input from a terminal, pipe, or other special
- file; it has no effect when reading from regular files.
- If r\bre\bea\bad\bd times out, it saves any partial input read into
- the specified variable _\bn_\ba_\bm_\be, and the exit status is
- greater than 128. If _\bt_\bi_\bm_\be_\bo_\bu_\bt is 0, r\bre\bea\bad\bd returns immedi-
- ately, without trying to read any data. In this case,
- the exit status is 0 if input is available on the speci-
- fied file descriptor, or the read will return EOF, non-
+ Cause r\bre\bea\bad\bd to time out and return failure if it does not
+ read a complete line of input (or a specified number of
+ characters) within _\bt_\bi_\bm_\be_\bo_\bu_\bt seconds. _\bt_\bi_\bm_\be_\bo_\bu_\bt may be a
+ decimal number with a fractional portion following the
+ decimal point. This option is only effective if r\bre\bea\bad\bd is
+ reading input from a terminal, pipe, or other special
+ file; it has no effect when reading from regular files.
+ If r\bre\bea\bad\bd times out, it saves any partial input read into
+ the specified variable _\bn_\ba_\bm_\be, and the exit status is
+ greater than 128. If _\bt_\bi_\bm_\be_\bo_\bu_\bt is 0, r\bre\bea\bad\bd returns immedi-
+ ately, without trying to read any data. In this case,
+ the exit status is 0 if input is available on the speci-
+ fied file descriptor, or the read will return EOF, non-
zero otherwise.
- -\b-u\bu _\bf_\bd Read input from file descriptor _\bf_\bd instead of the stan-
+ -\b-u\bu _\bf_\bd Read input from file descriptor _\bf_\bd instead of the stan-
dard input.
- Other than the case where _\bd_\be_\bl_\bi_\bm is the empty string, r\bre\bea\bad\bd ig-
+ Other than the case where _\bd_\be_\bl_\bi_\bm is the empty string, r\bre\bea\bad\bd ig-
nores any NUL characters in the input.
- If no _\bn_\ba_\bm_\be_\bs are supplied, r\bre\bea\bad\bd assigns the line read, without
- the ending delimiter but otherwise unmodified, to the variable
+ If no _\bn_\ba_\bm_\be_\bs are supplied, r\bre\bea\bad\bd assigns the line read, without
+ the ending delimiter but otherwise unmodified, to the variable
R\bRE\bEP\bPL\bLY\bY.
The exit status is zero, unless end-of-file is encountered, r\bre\bea\bad\bd
- times out (in which case the status is greater than 128), a
+ times out (in which case the status is greater than 128), a
variable assignment error (such as assigning to a readonly vari-
- able) occurs, or an invalid file descriptor is supplied as the
+ able) occurs, or an invalid file descriptor is supplied as the
argument to -\b-u\bu.
r\bre\bea\bad\bdo\bon\bnl\bly\by [-\b-a\baA\bAf\bf] [-\b-p\bp] [_\bn_\ba_\bm_\be[=_\bw_\bo_\br_\bd] ...]
- The given _\bn_\ba_\bm_\be_\bs are marked readonly; the values of these _\bn_\ba_\bm_\be_\bs
+ The given _\bn_\ba_\bm_\be_\bs are marked readonly; the values of these _\bn_\ba_\bm_\be_\bs
may not be changed by subsequent assignment or unset. If the -\b-f\bf
- option is supplied, each _\bn_\ba_\bm_\be refers to a shell function. The
- -\b-a\ba option restricts the variables to indexed arrays; the -\b-A\bA op-
+ option is supplied, each _\bn_\ba_\bm_\be refers to a shell function. The
+ -\b-a\ba option restricts the variables to indexed arrays; the -\b-A\bA op-
tion restricts the variables to associative arrays. If both op-
- tions are supplied, -\b-A\bA takes precedence. If no _\bn_\ba_\bm_\be arguments
- are supplied, or if the -\b-p\bp option is supplied, print a list of
- all readonly names. The other options may be used to restrict
+ tions are supplied, -\b-A\bA takes precedence. If no _\bn_\ba_\bm_\be arguments
+ are supplied, or if the -\b-p\bp option is supplied, print a list of
+ all readonly names. The other options may be used to restrict
the output to a subset of the set of readonly names. The -\b-p\bp op-
tion displays output in a format that may be reused as input.
- r\bre\bea\bad\bdo\bon\bnl\bly\by allows the value of a variable to be set at the same
+ r\bre\bea\bad\bdo\bon\bnl\bly\by allows the value of a variable to be set at the same
time the readonly attribute is changed by following the variable
- name with =_\bv_\ba_\bl_\bu_\be. This sets the value of the variable is to
+ name with =_\bv_\ba_\bl_\bu_\be. This sets the value of the variable is to
_\bv_\ba_\bl_\bu_\be while modifying the readonly attribute.
- The return status is 0 unless an invalid option is encountered,
- one of the _\bn_\ba_\bm_\be_\bs is not a valid shell variable name, or -\b-f\bf is
+ The return status is 0 unless an invalid option is encountered,
+ one of the _\bn_\ba_\bm_\be_\bs is not a valid shell variable name, or -\b-f\bf is
supplied with a _\bn_\ba_\bm_\be that is not a function.
r\bre\bet\btu\bur\brn\bn [_\bn]
- Stop executing a shell function or sourced file and return the
+ Stop executing a shell function or sourced file and return the
value specified by _\bn to its caller. If _\bn is omitted, the return
- status is that of the last command executed. If r\bre\bet\btu\bur\brn\bn is exe-
- cuted by a trap handler, the last command used to determine the
+ status is that of the last command executed. If r\bre\bet\btu\bur\brn\bn is exe-
+ cuted by a trap handler, the last command used to determine the
status is the last command executed before the trap handler. If
r\bre\bet\btu\bur\brn\bn is executed during a D\bDE\bEB\bBU\bUG\bG trap, the last command used to
- determine the status is the last command executed by the trap
+ determine the status is the last command executed by the trap
handler before r\bre\bet\btu\bur\brn\bn was invoked.
When r\bre\bet\btu\bur\brn\bn is used to terminate execution of a script being ex-
- ecuted by the .\b. (s\bso\bou\bur\brc\bce\be) command, it causes the shell to stop
- executing that script and return either _\bn or the exit status of
- the last command executed within the script as the exit status
- of the script. If _\bn is supplied, the return value is its least
+ ecuted by the .\b. (s\bso\bou\bur\brc\bce\be) command, it causes the shell to stop
+ executing that script and return either _\bn or the exit status of
+ the last command executed within the script as the exit status
+ of the script. If _\bn is supplied, the return value is its least
significant 8 bits.
- Any command associated with the R\bRE\bET\bTU\bUR\bRN\bN trap is executed before
+ Any command associated with the R\bRE\bET\bTU\bUR\bRN\bN trap is executed before
execution resumes after the function or script.
- The return status is non-zero if r\bre\bet\btu\bur\brn\bn is supplied a non-nu-
+ The return status is non-zero if r\bre\bet\btu\bur\brn\bn is supplied a non-nu-
meric argument, or is used outside a function and not during ex-
ecution of a script by .\b. or s\bso\bou\bur\brc\bce\be.
s\bse\bet\bt [-\b-a\bab\bbe\bef\bfh\bhk\bkm\bmn\bnp\bpt\btu\buv\bvx\bxB\bBC\bCE\bEH\bHP\bPT\bT] [-\b-o\bo _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be] [-\b--\b-] [-\b-] [_\ba_\br_\bg ...]
s\bse\bet\bt [+\b+a\bab\bbe\bef\bfh\bhk\bkm\bmn\bnp\bpt\btu\buv\bvx\bxB\bBC\bCE\bEH\bHP\bPT\bT] [+\b+o\bo _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be] [-\b--\b-] [-\b-] [_\ba_\br_\bg ...]
s\bse\bet\bt -\b-o\bo
- s\bse\bet\bt +\b+o\bo Without options, display the name and value of each shell vari-
- able in a format that can be reused as input for setting or re-
+ s\bse\bet\bt +\b+o\bo Without options, display the name and value of each shell vari-
+ able in a format that can be reused as input for setting or re-
setting the currently-set variables. Read-only variables cannot
- be reset. In posix mode, only shell variables are listed. The
- output is sorted according to the current locale. When options
- are specified, they set or unset shell attributes. Any argu-
- ments remaining after option processing are treated as values
+ be reset. In posix mode, only shell variables are listed. The
+ output is sorted according to the current locale. When options
+ are specified, they set or unset shell attributes. Any argu-
+ ments remaining after option processing are treated as values
for the positional parameters and are assigned, in order, to $\b$1\b1,
- $\b$2\b2, ..., $\b$_\bn. Options, if specified, have the following mean-
+ $\b$2\b2, ..., $\b$_\bn. Options, if specified, have the following mean-
ings:
-\b-a\ba Each variable or function that is created or modified is
- given the export attribute and marked for export to the
+ given the export attribute and marked for export to the
environment of subsequent commands.
- -\b-b\bb Report the status of terminated background jobs immedi-
+ -\b-b\bb Report the status of terminated background jobs immedi-
ately, rather than before the next primary prompt or af-
- ter a foreground command terminates. This is effective
+ ter a foreground command terminates. This is effective
only when job control is enabled.
- -\b-e\be Exit immediately if a _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be (which may consist of a
- single _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd), a _\bl_\bi_\bs_\bt, or a _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd _\bc_\bo_\bm_\bm_\ba_\bn_\bd
+ -\b-e\be Exit immediately if a _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be (which may consist of a
+ single _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd), a _\bl_\bi_\bs_\bt, or a _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd _\bc_\bo_\bm_\bm_\ba_\bn_\bd
(see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR above), exits with a non-zero status.
- The shell does not exit if the command that fails is
- part of the command list immediately following a w\bwh\bhi\bil\ble\be
- or u\bun\bnt\bti\bil\bl reserved word, part of the test following the
- i\bif\bf or e\bel\bli\bif\bf reserved words, part of any command executed
- in a &\b&&\b& or |\b||\b| list except the command following the fi-
- nal &\b&&\b& or |\b||\b|, any command in a pipeline but the last
- (subject to the state of the p\bpi\bip\bpe\bef\bfa\bai\bil\bl shell option), or
- if the command's return value is being inverted with !\b!.
- If a compound command other than a subshell returns a
- non-zero status because a command failed while -\b-e\be was
- being ignored, the shell does not exit. A trap on E\bER\bRR\bR,
+ The shell does not exit if the command that fails is
+ part of the command list immediately following a w\bwh\bhi\bil\ble\be
+ or u\bun\bnt\bti\bil\bl reserved word, part of the test following the
+ i\bif\bf or e\bel\bli\bif\bf reserved words, part of any command executed
+ in a &\b&&\b& or |\b||\b| list except the command following the fi-
+ nal &\b&&\b& or |\b||\b|, any command in a pipeline but the last
+ (subject to the state of the p\bpi\bip\bpe\bef\bfa\bai\bil\bl shell option), or
+ if the command's return value is being inverted with !\b!.
+ If a compound command other than a subshell returns a
+ non-zero status because a command failed while -\b-e\be was
+ being ignored, the shell does not exit. A trap on E\bER\bRR\bR,
if set, is executed before the shell exits. This option
applies to the shell environment and each subshell envi-
- ronment separately (see C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN E\bEN\bNV\bVI\bIR\bRO\bON\bNM\bME\bEN\bNT\bT
+ ronment separately (see C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN E\bEN\bNV\bVI\bIR\bRO\bON\bNM\bME\bEN\bNT\bT
above), and may cause subshells to exit before executing
all the commands in the subshell.
- If a compound command or shell function executes in a
- context where -\b-e\be is being ignored, none of the commands
- executed within the compound command or function body
- will be affected by the -\b-e\be setting, even if -\b-e\be is set
- and a command returns a failure status. If a compound
- command or shell function sets -\b-e\be while executing in a
- context where -\b-e\be is ignored, that setting will not have
- any effect until the compound command or the command
+ If a compound command or shell function executes in a
+ context where -\b-e\be is being ignored, none of the commands
+ executed within the compound command or function body
+ will be affected by the -\b-e\be setting, even if -\b-e\be is set
+ and a command returns a failure status. If a compound
+ command or shell function sets -\b-e\be while executing in a
+ context where -\b-e\be is ignored, that setting will not have
+ any effect until the compound command or the command
containing the function call completes.
-\b-f\bf Disable pathname expansion.
- -\b-h\bh Remember the location of commands as they are looked up
+ -\b-h\bh Remember the location of commands as they are looked up
for execution. This is enabled by default.
- -\b-k\bk All arguments in the form of assignment statements are
- placed in the environment for a command, not just those
+ -\b-k\bk All arguments in the form of assignment statements are
+ placed in the environment for a command, not just those
that precede the command name.
- -\b-m\bm Monitor mode. Job control is enabled. This option is
- on by default for interactive shells on systems that
- support it (see J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL above). All processes run
+ -\b-m\bm Monitor mode. Job control is enabled. This option is
+ on by default for interactive shells on systems that
+ support it (see J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL above). All processes run
in a separate process group. When a background job com-
pletes, the shell prints a line containing its exit sta-
tus.
-\b-n\bn Read commands but do not execute them. This may be used
- to check a shell script for syntax errors. This is ig-
+ to check a shell script for syntax errors. This is ig-
nored by interactive shells.
-\b-o\bo _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be
The _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be can be one of the following:
Same as -\b-a\ba.
b\bbr\bra\bac\bce\bee\bex\bxp\bpa\ban\bnd\bd
Same as -\b-B\bB.
- e\bem\bma\bac\bcs\bs Use an emacs-style command line editing inter-
+ e\bem\bma\bac\bcs\bs Use an emacs-style command line editing inter-
face. This is enabled by default when the shell
is interactive, unless the shell is started with
- the -\b--\b-n\bno\boe\bed\bdi\bit\bti\bin\bng\bg option. This also affects the
+ the -\b--\b-n\bno\boe\bed\bdi\bit\bti\bin\bng\bg option. This also affects the
editing interface used for r\bre\bea\bad\bd -\b-e\be.
e\ber\brr\bre\bex\bxi\bit\bt Same as -\b-e\be.
e\ber\brr\brt\btr\bra\bac\bce\be
H\bHI\bIS\bST\bTO\bOR\bRY\bY. This option is on by default in inter-
active shells.
i\big\bgn\bno\bor\bre\bee\beo\bof\bf
- The effect is as if the shell command
+ The effect is as if the shell command
"IGNOREEOF=10" had been executed (see S\bSh\bhe\bel\bll\bl
V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs above).
k\bke\bey\byw\bwo\bor\brd\bd Same as -\b-k\bk.
p\bph\bhy\bys\bsi\bic\bca\bal\bl
Same as -\b-P\bP.
p\bpi\bip\bpe\bef\bfa\bai\bil\bl
- If set, the return value of a pipeline is the
- value of the last (rightmost) command to exit
- with a non-zero status, or zero if all commands
- in the pipeline exit successfully. This option
+ If set, the return value of a pipeline is the
+ value of the last (rightmost) command to exit
+ with a non-zero status, or zero if all commands
+ in the pipeline exit successfully. This option
is disabled by default.
- p\bpo\bos\bsi\bix\bx Enable posix mode; change the behavior of b\bba\bas\bsh\bh
- where the default operation differs from the
- POSIX standard to match the standard. See S\bSE\bEE\bE
- A\bAL\bLS\bSO\bO below for a reference to a document that
+ p\bpo\bos\bsi\bix\bx Enable posix mode; change the behavior of b\bba\bas\bsh\bh
+ where the default operation differs from the
+ POSIX standard to match the standard. See S\bSE\bEE\bE
+ A\bAL\bLS\bSO\bO below for a reference to a document that
details how posix mode affects bash's behavior.
p\bpr\bri\biv\bvi\bil\ble\beg\bge\bed\bd
Same as -\b-p\bp.
v\bve\ber\brb\bbo\bos\bse\be Same as -\b-v\bv.
- v\bvi\bi Use a vi-style command line editing interface.
+ v\bvi\bi Use a vi-style command line editing interface.
This also affects the editing interface used for
r\bre\bea\bad\bd -\b-e\be.
x\bxt\btr\bra\bac\bce\be Same as -\b-x\bx.
- If -\b-o\bo is supplied with no _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be, s\bse\bet\bt prints the
- current shell option settings. If +\b+o\bo is supplied with
- no _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be, s\bse\bet\bt prints a series of s\bse\bet\bt commands to
- recreate the current option settings on the standard
+ If -\b-o\bo is supplied with no _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be, s\bse\bet\bt prints the
+ current shell option settings. If +\b+o\bo is supplied with
+ no _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be, s\bse\bet\bt prints a series of s\bse\bet\bt commands to
+ recreate the current option settings on the standard
output.
- -\b-p\bp Turn on _\bp_\br_\bi_\bv_\bi_\bl_\be_\bg_\be_\bd mode. In this mode, the shell does
- not read the $\b$E\bEN\bNV\bV and $\b$B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV files, shell functions
- are not inherited from the environment, and the S\bSH\bHE\bEL\bL-\b-
- L\bLO\bOP\bPT\bTS\bS, B\bBA\bAS\bSH\bHO\bOP\bPT\bTS\bS, C\bCD\bDP\bPA\bAT\bTH\bH, and G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE variables, if
- they appear in the environment, are ignored. If the
- shell is started with the effective user (group) id not
- equal to the real user (group) id, and the -\b-p\bp option is
- not supplied, these actions are taken and the effective
+ -\b-p\bp Turn on _\bp_\br_\bi_\bv_\bi_\bl_\be_\bg_\be_\bd mode. In this mode, the shell does
+ not read the $\b$E\bEN\bNV\bV and $\b$B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV files, shell functions
+ are not inherited from the environment, and the S\bSH\bHE\bEL\bL-\b-
+ L\bLO\bOP\bPT\bTS\bS, B\bBA\bAS\bSH\bHO\bOP\bPT\bTS\bS, C\bCD\bDP\bPA\bAT\bTH\bH, and G\bGL\bLO\bOB\bBI\bIG\bGN\bNO\bOR\bRE\bE variables, if
+ they appear in the environment, are ignored. If the
+ shell is started with the effective user (group) id not
+ equal to the real user (group) id, and the -\b-p\bp option is
+ not supplied, these actions are taken and the effective
user id is set to the real user id. If the -\b-p\bp option is
supplied at startup, the effective user id is not reset.
- Turning this option off causes the effective user and
+ Turning this option off causes the effective user and
group ids to be set to the real user and group ids.
-\b-r\br Enable restricted shell mode. This option cannot be un-
set once it has been set.
-\b-t\bt Exit after reading and executing one command.
-\b-u\bu Treat unset variables and parameters other than the spe-
- cial parameters "@" and "*", or array variables sub-
- scripted with "@" or "*", as an error when performing
- parameter expansion. If expansion is attempted on an
- unset variable or parameter, the shell prints an error
- message, and, if not interactive, exits with a non-zero
+ cial parameters "@" and "*", or array variables sub-
+ scripted with "@" or "*", as an error when performing
+ parameter expansion. If expansion is attempted on an
+ unset variable or parameter, the shell prints an error
+ message, and, if not interactive, exits with a non-zero
status.
-\b-v\bv Print shell input lines as they are read.
- -\b-x\bx After expanding each _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd, f\bfo\bor\br command, c\bca\bas\bse\be
+ -\b-x\bx After expanding each _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd, f\bfo\bor\br command, c\bca\bas\bse\be
command, s\bse\bel\ble\bec\bct\bt command, or arithmetic f\bfo\bor\br command, dis-
- play the expanded value of P\bPS\bS4\b4, followed by the command
- and its expanded arguments or associated word list, to
+ play the expanded value of P\bPS\bS4\b4, followed by the command
+ and its expanded arguments or associated word list, to
the standard error.
- -\b-B\bB The shell performs brace expansion (see B\bBr\bra\bac\bce\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
+ -\b-B\bB The shell performs brace expansion (see B\bBr\bra\bac\bce\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
above). This is on by default.
- -\b-C\bC If set, b\bba\bas\bsh\bh does not overwrite an existing file with
- the >\b>, >\b>&\b&, and <\b<>\b> redirection operators. Using the
- redirection operator >\b>|\b| instead of >\b> will override this
+ -\b-C\bC If set, b\bba\bas\bsh\bh does not overwrite an existing file with
+ the >\b>, >\b>&\b&, and <\b<>\b> redirection operators. Using the
+ redirection operator >\b>|\b| instead of >\b> will override this
and force the creation of an output file.
-\b-E\bE If set, any trap on E\bER\bRR\bR is inherited by shell functions,
- command substitutions, and commands executed in a sub-
- shell environment. The E\bER\bRR\bR trap is normally not inher-
+ command substitutions, and commands executed in a sub-
+ shell environment. The E\bER\bRR\bR trap is normally not inher-
ited in such cases.
-\b-H\bH Enable !\b! style history substitution. This option is on
by default when the shell is interactive.
- -\b-P\bP If set, the shell does not resolve symbolic links when
- executing commands such as c\bcd\bd that change the current
+ -\b-P\bP If set, the shell does not resolve symbolic links when
+ executing commands such as c\bcd\bd that change the current
working directory. It uses the physical directory
structure instead. By default, b\bba\bas\bsh\bh follows the logical
- chain of directories when performing commands which
+ chain of directories when performing commands which
change the current directory.
- -\b-T\bT If set, any traps on D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN are inherited by
+ -\b-T\bT If set, any traps on D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN are inherited by
shell functions, command substitutions, and commands ex-
- ecuted in a subshell environment. The D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN
+ ecuted in a subshell environment. The D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN
traps are normally not inherited in such cases.
-\b--\b- If no arguments follow this option, unset the positional
parameters. Otherwise, set the positional parameters to
the _\ba_\br_\bgs, even if some of them begin with a -\b-.
-\b- Signal the end of options, and assign all remaining _\ba_\br_\bgs
to the positional parameters. The -\b-x\bx and -\b-v\bv options are
- turned off. If there are no _\ba_\br_\bgs, the positional para-
+ turned off. If there are no _\ba_\br_\bgs, the positional para-
meters remain unchanged.
- The options are off by default unless otherwise noted. Using +
- rather than - causes these options to be turned off. The op-
+ The options are off by default unless otherwise noted. Using +
+ rather than - causes these options to be turned off. The op-
tions can also be specified as arguments to an invocation of the
- shell. The current set of options may be found in $\b$-\b-. The re-
- turn status is always zero unless an invalid option is encoun-
+ shell. The current set of options may be found in $\b$-\b-. The re-
+ turn status is always zero unless an invalid option is encoun-
tered.
s\bsh\bhi\bif\bft\bt [_\bn]
Rename positional parameters from _\bn+1 ... to $\b$1\b1 .\b..\b..\b..\b. Parameters
- represented by the numbers $\b$#\b# down to $\b$#\b#-_\bn+1 are unset. _\bn must
- be a non-negative number less than or equal to $\b$#\b#. If _\bn is 0,
- no parameters are changed. If _\bn is not given, it is assumed to
- be 1. If _\bn is greater than $\b$#\b#, the positional parameters are
- not changed. The return status is greater than zero if _\bn is
+ represented by the numbers $\b$#\b# down to $\b$#\b#-_\bn+1 are unset. _\bn must
+ be a non-negative number less than or equal to $\b$#\b#. If _\bn is 0,
+ no parameters are changed. If _\bn is not given, it is assumed to
+ be 1. If _\bn is greater than $\b$#\b#, the positional parameters are
+ not changed. The return status is greater than zero if _\bn is
greater than $\b$#\b# or less than zero; otherwise 0.
s\bsh\bho\bop\bpt\bt [-\b-p\bpq\bqs\bsu\bu] [-\b-o\bo] [_\bo_\bp_\bt_\bn_\ba_\bm_\be ...]
- Toggle the values of settings controlling optional shell behav-
- ior. The settings can be either those listed below, or, if the
+ Toggle the values of settings controlling optional shell behav-
+ ior. The settings can be either those listed below, or, if the
-\b-o\bo option is used, those available with the -\b-o\bo option to the s\bse\bet\bt
builtin command.
- With no options, or with the -\b-p\bp option, display a list of all
- settable options, with an indication of whether or not each is
- set; if any _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs are supplied, the output is restricted to
+ With no options, or with the -\b-p\bp option, display a list of all
+ settable options, with an indication of whether or not each is
+ set; if any _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs are supplied, the output is restricted to
those options. The -\b-p\bp option displays output in a form that may
be reused as input.
Other options have the following meanings:
-\b-s\bs Enable (set) each _\bo_\bp_\bt_\bn_\ba_\bm_\be.
-\b-u\bu Disable (unset) each _\bo_\bp_\bt_\bn_\ba_\bm_\be.
- -\b-q\bq Suppresses normal output (quiet mode); the return status
+ -\b-q\bq Suppresses normal output (quiet mode); the return status
indicates whether the _\bo_\bp_\bt_\bn_\ba_\bm_\be is set or unset. If multi-
- ple _\bo_\bp_\bt_\bn_\ba_\bm_\be arguments are supplied with -\b-q\bq, the return
+ ple _\bo_\bp_\bt_\bn_\ba_\bm_\be arguments are supplied with -\b-q\bq, the return
status is zero if all _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs are enabled; non-zero oth-
erwise.
- -\b-o\bo Restricts the values of _\bo_\bp_\bt_\bn_\ba_\bm_\be to be those defined for
+ -\b-o\bo Restricts the values of _\bo_\bp_\bt_\bn_\ba_\bm_\be to be those defined for
the -\b-o\bo option to the s\bse\bet\bt builtin.
- If either -\b-s\bs or -\b-u\bu is used with no _\bo_\bp_\bt_\bn_\ba_\bm_\be arguments, s\bsh\bho\bop\bpt\bt
- shows only those options which are set or unset, respectively.
- Unless otherwise noted, the s\bsh\bho\bop\bpt\bt options are disabled (unset)
+ If either -\b-s\bs or -\b-u\bu is used with no _\bo_\bp_\bt_\bn_\ba_\bm_\be arguments, s\bsh\bho\bop\bpt\bt
+ shows only those options which are set or unset, respectively.
+ Unless otherwise noted, the s\bsh\bho\bop\bpt\bt options are disabled (unset)
by default.
- The return status when listing options is zero if all _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs
- are enabled, non-zero otherwise. When setting or unsetting op-
- tions, the return status is zero unless an _\bo_\bp_\bt_\bn_\ba_\bm_\be is not a
+ The return status when listing options is zero if all _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs
+ are enabled, non-zero otherwise. When setting or unsetting op-
+ tions, the return status is zero unless an _\bo_\bp_\bt_\bn_\ba_\bm_\be is not a
valid shell option.
The list of s\bsh\bho\bop\bpt\bt options is:
a\bar\brr\bra\bay\by_\b_e\bex\bxp\bpa\ban\bnd\bd_\b_o\bon\bnc\bce\be
- If set, the shell suppresses multiple evaluation of as-
+ If set, the shell suppresses multiple evaluation of as-
sociative and indexed array subscripts during arithmetic
expression evaluation, while executing builtins that can
- perform variable assignments, and while executing
+ perform variable assignments, and while executing
builtins that perform array dereferencing.
a\bas\bss\bso\boc\bc_\b_e\bex\bxp\bpa\ban\bnd\bd_\b_o\bon\bnc\bce\be
Deprecated; a synonym for a\bar\brr\bra\bay\by_\b_e\bex\bxp\bpa\ban\bnd\bd_\b_o\bon\bnc\bce\be.
- a\bau\but\bto\boc\bcd\bd If set, a command name that is the name of a directory
- is executed as if it were the argument to the c\bcd\bd com-
+ a\bau\but\bto\boc\bcd\bd If set, a command name that is the name of a directory
+ is executed as if it were the argument to the c\bcd\bd com-
mand. This option is only used by interactive shells.
b\bba\bas\bsh\bh_\b_s\bso\bou\bur\brc\bce\be_\b_f\bfu\bul\bll\blp\bpa\bat\bth\bh
- If set, filenames added to the B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE array vari-
- able are converted to full pathnames (see S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bi-\b-
+ If set, filenames added to the B\bBA\bAS\bSH\bH_\b_S\bSO\bOU\bUR\bRC\bCE\bE array vari-
+ able are converted to full pathnames (see S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bi-\b-
a\bab\bbl\ble\bes\bs above).
c\bcd\bda\bab\bbl\ble\be_\b_v\bva\bar\brs\bs
- If set, an argument to the c\bcd\bd builtin command that is
- not a directory is assumed to be the name of a variable
+ If set, an argument to the c\bcd\bd builtin command that is
+ not a directory is assumed to be the name of a variable
whose value is the directory to change to.
- c\bcd\bds\bsp\bpe\bel\bll\bl If set, the c\bcd\bd command attempts to correct minor errors
- in the spelling of a directory component. Minor errors
- include transposed characters, a missing character, and
+ c\bcd\bds\bsp\bpe\bel\bll\bl If set, the c\bcd\bd command attempts to correct minor errors
+ in the spelling of a directory component. Minor errors
+ include transposed characters, a missing character, and
one extra character. If c\bcd\bd corrects the directory name,
- it prints the corrected filename, and the command pro-
+ it prints the corrected filename, and the command pro-
ceeds. This option is only used by interactive shells.
c\bch\bhe\bec\bck\bkh\bha\bas\bsh\bh
If set, b\bba\bas\bsh\bh checks that a command found in the hash ta-
- ble exists before trying to execute it. If a hashed
- command no longer exists, b\bba\bas\bsh\bh performs a normal path
+ ble exists before trying to execute it. If a hashed
+ command no longer exists, b\bba\bas\bsh\bh performs a normal path
search.
c\bch\bhe\bec\bck\bkj\bjo\bob\bbs\bs
If set, b\bba\bas\bsh\bh lists the status of any stopped and running
- jobs before exiting an interactive shell. If any jobs
+ jobs before exiting an interactive shell. If any jobs
are running, b\bba\bas\bsh\bh defers the exit until a second exit is
- attempted without an intervening command (see J\bJO\bOB\bB C\bCO\bON\bN-\b-
- T\bTR\bRO\bOL\bL above). The shell always postpones exiting if any
+ attempted without an intervening command (see J\bJO\bOB\bB C\bCO\bON\bN-\b-
+ T\bTR\bRO\bOL\bL above). The shell always postpones exiting if any
jobs are stopped.
c\bch\bhe\bec\bck\bkw\bwi\bin\bns\bsi\biz\bze\be
- If set, b\bba\bas\bsh\bh checks the window size after each external
- (non-builtin) command and, if necessary, updates the
- values of L\bLI\bIN\bNE\bES\bS and C\bCO\bOL\bLU\bUM\bMN\bNS\bS, using the file descriptor
- associated with the standard error if it is a terminal.
+ If set, b\bba\bas\bsh\bh checks the window size after each external
+ (non-builtin) command and, if necessary, updates the
+ values of L\bLI\bIN\bNE\bES\bS and C\bCO\bOL\bLU\bUM\bMN\bNS\bS, using the file descriptor
+ associated with the standard error if it is a terminal.
This option is enabled by default.
- c\bcm\bmd\bdh\bhi\bis\bst\bt If set, b\bba\bas\bsh\bh attempts to save all lines of a multiple-
- line command in the same history entry. This allows
- easy re-editing of multi-line commands. This option is
- enabled by default, but only has an effect if command
+ c\bcm\bmd\bdh\bhi\bis\bst\bt If set, b\bba\bas\bsh\bh attempts to save all lines of a multiple-
+ line command in the same history entry. This allows
+ easy re-editing of multi-line commands. This option is
+ enabled by default, but only has an effect if command
history is enabled, as described above under H\bHI\bIS\bST\bTO\bOR\bRY\bY.
c\bco\bom\bmp\bpa\bat\bt3\b31\b1
c\bco\bom\bmp\bpa\bat\bt3\b32\b2
c\bco\bom\bmp\bpa\bat\bt4\b42\b2
c\bco\bom\bmp\bpa\bat\bt4\b43\b3
c\bco\bom\bmp\bpa\bat\bt4\b44\b4
- These control aspects of the shell's compatibility mode
+ These control aspects of the shell's compatibility mode
(see S\bSH\bHE\bEL\bLL\bL C\bCO\bOM\bMP\bPA\bAT\bTI\bIB\bBI\bIL\bLI\bIT\bTY\bY M\bMO\bOD\bDE\bE below).
c\bco\bom\bmp\bpl\ble\bet\bte\be_\b_f\bfu\bul\bll\blq\bqu\buo\bot\bte\be
- If set, b\bba\bas\bsh\bh quotes all shell metacharacters in file-
- names and directory names when performing completion.
+ If set, b\bba\bas\bsh\bh quotes all shell metacharacters in file-
+ names and directory names when performing completion.
If not set, b\bba\bas\bsh\bh removes metacharacters such as the dol-
- lar sign from the set of characters that will be quoted
- in completed filenames when these metacharacters appear
- in shell variable references in words to be completed.
- This means that dollar signs in variable names that ex-
- pand to directories will not be quoted; however, any
- dollar signs appearing in filenames will not be quoted,
- either. This is active only when bash is using back-
- slashes to quote completed filenames. This variable is
- set by default, which is the default bash behavior in
+ lar sign from the set of characters that will be quoted
+ in completed filenames when these metacharacters appear
+ in shell variable references in words to be completed.
+ This means that dollar signs in variable names that ex-
+ pand to directories will not be quoted; however, any
+ dollar signs appearing in filenames will not be quoted,
+ either. This is active only when bash is using back-
+ slashes to quote completed filenames. This variable is
+ set by default, which is the default bash behavior in
versions through 4.2.
d\bdi\bir\bre\bex\bxp\bpa\ban\bnd\bd
- If set, b\bba\bas\bsh\bh replaces directory names with the results
- of word expansion when performing filename completion.
+ If set, b\bba\bas\bsh\bh replaces directory names with the results
+ of word expansion when performing filename completion.
This changes the contents of the r\bre\bea\bad\bdl\bli\bin\bne\be editing
- buffer. If not set, b\bba\bas\bsh\bh attempts to preserve what the
+ buffer. If not set, b\bba\bas\bsh\bh attempts to preserve what the
user typed.
d\bdi\bir\brs\bsp\bpe\bel\bll\bl
- If set, b\bba\bas\bsh\bh attempts spelling correction on directory
- names during word completion if the directory name ini-
+ If set, b\bba\bas\bsh\bh attempts spelling correction on directory
+ names during word completion if the directory name ini-
tially supplied does not exist.
- d\bdo\bot\btg\bgl\blo\bob\bb If set, b\bba\bas\bsh\bh includes filenames beginning with a "." in
- the results of pathname expansion. The filenames _\b. and
+ d\bdo\bot\btg\bgl\blo\bob\bb If set, b\bba\bas\bsh\bh includes filenames beginning with a "." in
+ the results of pathname expansion. The filenames _\b. and
_\b._\b. must always be matched explicitly, even if d\bdo\bot\btg\bgl\blo\bob\bb is
set.
e\bex\bxe\bec\bcf\bfa\bai\bil\bl
If set, a non-interactive shell will not exit if it can-
- not execute the file specified as an argument to the
- e\bex\bxe\bec\bc builtin. An interactive shell does not exit if
+ not execute the file specified as an argument to the
+ e\bex\bxe\bec\bc builtin. An interactive shell does not exit if
e\bex\bxe\bec\bc fails.
e\bex\bxp\bpa\ban\bnd\bd_\b_a\bal\bli\bia\bas\bse\bes\bs
- If set, aliases are expanded as described above under
+ If set, aliases are expanded as described above under
A\bAL\bLI\bIA\bAS\bSE\bES\bS. This option is enabled by default for interac-
tive shells.
e\bex\bxt\btd\bde\beb\bbu\bug\bg
- If set at shell invocation, or in a shell startup file,
+ If set at shell invocation, or in a shell startup file,
arrange to execute the debugger profile before the shell
- starts, identical to the -\b--\b-d\bde\beb\bbu\bug\bgg\bge\ber\br option. If set af-
- ter invocation, behavior intended for use by debuggers
+ starts, identical to the -\b--\b-d\bde\beb\bbu\bug\bgg\bge\ber\br option. If set af-
+ ter invocation, behavior intended for use by debuggers
is enabled:
1\b1.\b. The -\b-F\bF option to the d\bde\bec\bcl\bla\bar\bre\be builtin displays the
source file name and line number corresponding to
each function name supplied as an argument.
- 2\b2.\b. If the command run by the D\bDE\bEB\bBU\bUG\bG trap returns a
- non-zero value, the next command is skipped and
+ 2\b2.\b. If the command run by the D\bDE\bEB\bBU\bUG\bG trap returns a
+ non-zero value, the next command is skipped and
not executed.
- 3\b3.\b. If the command run by the D\bDE\bEB\bBU\bUG\bG trap returns a
- value of 2, and the shell is executing in a sub-
- routine (a shell function or a shell script exe-
- cuted by the .\b. or s\bso\bou\bur\brc\bce\be builtins), the shell
+ 3\b3.\b. If the command run by the D\bDE\bEB\bBU\bUG\bG trap returns a
+ value of 2, and the shell is executing in a sub-
+ routine (a shell function or a shell script exe-
+ cuted by the .\b. or s\bso\bou\bur\brc\bce\be builtins), the shell
simulates a call to r\bre\bet\btu\bur\brn\bn.
- 4\b4.\b. B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC and B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV are updated as described
+ 4\b4.\b. B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC and B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV are updated as described
in their descriptions above).
- 5\b5.\b. Function tracing is enabled: command substitu-
+ 5\b5.\b. Function tracing is enabled: command substitu-
tion, shell functions, and subshells invoked with
(\b( _\bc_\bo_\bm_\bm_\ba_\bn_\bd )\b) inherit the D\bDE\bEB\bBU\bUG\bG and R\bRE\bET\bTU\bUR\bRN\bN traps.
- 6\b6.\b. Error tracing is enabled: command substitution,
- shell functions, and subshells invoked with (\b(
+ 6\b6.\b. Error tracing is enabled: command substitution,
+ shell functions, and subshells invoked with (\b(
_\bc_\bo_\bm_\bm_\ba_\bn_\bd )\b) inherit the E\bER\bRR\bR trap.
- e\bex\bxt\btg\bgl\blo\bob\bb If set, enable the extended pattern matching features
+ e\bex\bxt\btg\bgl\blo\bob\bb If set, enable the extended pattern matching features
described above under P\bPa\bat\bth\bhn\bna\bam\bme\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn.
e\bex\bxt\btq\bqu\buo\bot\bte\be
- If set, $\b$'_\bs_\bt_\br_\bi_\bn_\bg' and $\b$"_\bs_\bt_\br_\bi_\bn_\bg" quoting is performed
- within $\b${\b{_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br}\b} expansions enclosed in double
+ If set, $\b$'_\bs_\bt_\br_\bi_\bn_\bg' and $\b$"_\bs_\bt_\br_\bi_\bn_\bg" quoting is performed
+ within $\b${\b{_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br}\b} expansions enclosed in double
quotes. This option is enabled by default.
f\bfa\bai\bil\blg\bgl\blo\bob\bb
- If set, patterns which fail to match filenames during
+ If set, patterns which fail to match filenames during
pathname expansion result in an expansion error.
f\bfo\bor\brc\bce\be_\b_f\bfi\big\bgn\bno\bor\bre\be
- If set, the suffixes specified by the F\bFI\bIG\bGN\bNO\bOR\bRE\bE shell
- variable cause words to be ignored when performing word
+ If set, the suffixes specified by the F\bFI\bIG\bGN\bNO\bOR\bRE\bE shell
+ variable cause words to be ignored when performing word
completion even if the ignored words are the only possi-
- ble completions. See S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs above for a de-
- scription of F\bFI\bIG\bGN\bNO\bOR\bRE\bE. This option is enabled by de-
+ ble completions. See S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs above for a de-
+ scription of F\bFI\bIG\bGN\bNO\bOR\bRE\bE. This option is enabled by de-
fault.
g\bgl\blo\bob\bba\bas\bsc\bci\bii\bir\bra\ban\bng\bge\bes\bs
- If set, range expressions used in pattern matching
- bracket expressions (see P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg above) behave
- as if in the traditional C locale when performing com-
- parisons. That is, pattern matching does not take the
- current locale's collating sequence into account, so b\bb
- will not collate between A\bA and B\bB, and upper-case and
+ If set, range expressions used in pattern matching
+ bracket expressions (see P\bPa\bat\btt\bte\ber\brn\bn M\bMa\bat\btc\bch\bhi\bin\bng\bg above) behave
+ as if in the traditional C locale when performing com-
+ parisons. That is, pattern matching does not take the
+ current locale's collating sequence into account, so b\bb
+ will not collate between A\bA and B\bB, and upper-case and
lower-case ASCII characters will collate together.
g\bgl\blo\bob\bbs\bsk\bki\bip\bpd\bdo\bot\bts\bs
- If set, pathname expansion will never match the file-
- names _\b. and _\b._\b., even if the pattern begins with a ".".
+ If set, pathname expansion will never match the file-
+ names _\b. and _\b._\b., even if the pattern begins with a ".".
This option is enabled by default.
g\bgl\blo\bob\bbs\bst\bta\bar\br
If set, the pattern *\b**\b* used in a pathname expansion con-
- text will match all files and zero or more directories
- and subdirectories. If the pattern is followed by a /\b/,
+ text will match all files and zero or more directories
+ and subdirectories. If the pattern is followed by a /\b/,
only directories and subdirectories match.
g\bgn\bnu\bu_\b_e\ber\brr\brf\bfm\bmt\bt
If set, shell error messages are written in the standard
GNU error message format.
h\bhi\bis\bst\bta\bap\bpp\bpe\ben\bnd\bd
- If set, the history list is appended to the file named
+ If set, the history list is appended to the file named
by the value of the H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE variable when the shell ex-
its, rather than overwriting the file.
h\bhi\bis\bst\btr\bre\bee\bed\bdi\bit\bt
- If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, the user is given
- the opportunity to re-edit a failed history substitu-
+ If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, the user is given
+ the opportunity to re-edit a failed history substitu-
tion.
h\bhi\bis\bst\btv\bve\ber\bri\bif\bfy\by
- If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, the results of his-
- tory substitution are not immediately passed to the
- shell parser. Instead, the resulting line is loaded
+ If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, the results of his-
+ tory substitution are not immediately passed to the
+ shell parser. Instead, the resulting line is loaded
into the r\bre\bea\bad\bdl\bli\bin\bne\be editing buffer, allowing further modi-
fication.
h\bho\bos\bst\btc\bco\bom\bmp\bpl\ble\bet\bte\be
If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, b\bba\bas\bsh\bh will attempt to
- perform hostname completion when a word containing a @\b@
- is being completed (see C\bCo\bom\bmp\bpl\ble\bet\bti\bin\bng\bg under R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE
+ perform hostname completion when a word containing a @\b@
+ is being completed (see C\bCo\bom\bmp\bpl\ble\bet\bti\bin\bng\bg under R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE
above). This is enabled by default.
h\bhu\bup\bpo\bon\bne\bex\bxi\bit\bt
If set, b\bba\bas\bsh\bh will send S\bSI\bIG\bGH\bHU\bUP\bP to all jobs when an inter-
active login shell exits.
i\bin\bnh\bhe\ber\bri\bit\bt_\b_e\ber\brr\bre\bex\bxi\bit\bt
- If set, command substitution inherits the value of the
- e\ber\brr\bre\bex\bxi\bit\bt option, instead of unsetting it in the subshell
- environment. This option is enabled when posix mode is
+ If set, command substitution inherits the value of the
+ e\ber\brr\bre\bex\bxi\bit\bt option, instead of unsetting it in the subshell
+ environment. This option is enabled when posix mode is
enabled.
i\bin\bnt\bte\ber\bra\bac\bct\bti\biv\bve\be_\b_c\bco\bom\bmm\bme\ben\bnt\bts\bs
- In an interactive shell, a word beginning with #\b# causes
- that word and all remaining characters on that line to
- be ignored, as in a non-interactive shell (see C\bCO\bOM\bMM\bME\bEN\bNT\bTS\bS
+ In an interactive shell, a word beginning with #\b# causes
+ that word and all remaining characters on that line to
+ be ignored, as in a non-interactive shell (see C\bCO\bOM\bMM\bME\bEN\bNT\bTS\bS
above). This option is enabled by default.
l\bla\bas\bst\btp\bpi\bip\bpe\be
- If set, and job control is not active, the shell runs
+ If set, and job control is not active, the shell runs
the last command of a pipeline not executed in the back-
ground in the current shell environment.
- l\bli\bit\bth\bhi\bis\bst\bt If set, and the c\bcm\bmd\bdh\bhi\bis\bst\bt option is enabled, multi-line
+ l\bli\bit\bth\bhi\bis\bst\bt If set, and the c\bcm\bmd\bdh\bhi\bis\bst\bt option is enabled, multi-line
commands are saved to the history with embedded newlines
rather than using semicolon separators where possible.
l\blo\boc\bca\bal\blv\bva\bar\br_\b_i\bin\bnh\bhe\ber\bri\bit\bt
scope before any new value is assigned. The nameref at-
tribute is not inherited.
l\blo\boc\bca\bal\blv\bva\bar\br_\b_u\bun\bns\bse\bet\bt
- If set, calling u\bun\bns\bse\bet\bt on local variables in previous
- function scopes marks them so subsequent lookups find
+ If set, calling u\bun\bns\bse\bet\bt on local variables in previous
+ function scopes marks them so subsequent lookups find
them unset until that function returns. This is identi-
- cal to the behavior of unsetting local variables at the
+ cal to the behavior of unsetting local variables at the
current function scope.
l\blo\bog\bgi\bin\bn_\b_s\bsh\bhe\bel\bll\bl
- The shell sets this option if it is started as a login
- shell (see I\bIN\bNV\bVO\bOC\bCA\bAT\bTI\bIO\bON\bN above). The value may not be
+ The shell sets this option if it is started as a login
+ shell (see I\bIN\bNV\bVO\bOC\bCA\bAT\bTI\bIO\bON\bN above). The value may not be
changed.
m\bma\bai\bil\blw\bwa\bar\brn\bn
- If set, and a file that b\bba\bas\bsh\bh is checking for mail has
- been accessed since the last time it was checked, b\bba\bas\bsh\bh
- displays the message "The mail in _\bm_\ba_\bi_\bl_\bf_\bi_\bl_\be has been
+ If set, and a file that b\bba\bas\bsh\bh is checking for mail has
+ been accessed since the last time it was checked, b\bba\bas\bsh\bh
+ displays the message "The mail in _\bm_\ba_\bi_\bl_\bf_\bi_\bl_\be has been
read".
n\bno\bo_\b_e\bem\bmp\bpt\bty\by_\b_c\bcm\bmd\bd_\b_c\bco\bom\bmp\bpl\ble\bet\bti\bio\bon\bn
If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, b\bba\bas\bsh\bh does not search
- P\bPA\bAT\bTH\bH for possible completions when completion is at-
+ P\bPA\bAT\bTH\bH for possible completions when completion is at-
tempted on an empty line.
n\bno\boc\bca\bas\bse\beg\bgl\blo\bob\bb
- If set, b\bba\bas\bsh\bh matches filenames in a case-insensitive
+ If set, b\bba\bas\bsh\bh matches filenames in a case-insensitive
fashion when performing pathname expansion (see P\bPa\bat\bth\bhn\bna\bam\bme\be
E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn above).
n\bno\boc\bca\bas\bse\bem\bma\bat\btc\bch\bh
- If set, b\bba\bas\bsh\bh matches patterns in a case-insensitive
+ If set, b\bba\bas\bsh\bh matches patterns in a case-insensitive
fashion when performing matching while executing c\bca\bas\bse\be or
[\b[[\b[ conditional commands, when performing pattern substi-
- tution word expansions, or when filtering possible com-
+ tution word expansions, or when filtering possible com-
pletions as part of programmable completion.
n\bno\boe\bex\bxp\bpa\ban\bnd\bd_\b_t\btr\bra\ban\bns\bsl\bla\bat\bti\bio\bon\bn
- If set, b\bba\bas\bsh\bh encloses the translated results of $\b$"\b"..."\b"
- quoting in single quotes instead of double quotes. If
+ If set, b\bba\bas\bsh\bh encloses the translated results of $\b$"\b"..."\b"
+ quoting in single quotes instead of double quotes. If
the string is not translated, this has no effect.
n\bnu\bul\bll\blg\bgl\blo\bob\bb
If set, pathname expansion patterns which match no files
removed, rather than expanding to themselves.
p\bpa\bat\bts\bsu\bub\bb_\b_r\bre\bep\bpl\bla\bac\bce\bem\bme\ben\bnt\bt
If set, b\bba\bas\bsh\bh expands occurrences of &\b& in the replacement
- string of pattern substitution to the text matched by
- the pattern, as described under P\bPa\bar\bra\bam\bme\bet\bte\ber\br E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
+ string of pattern substitution to the text matched by
+ the pattern, as described under P\bPa\bar\bra\bam\bme\bet\bte\ber\br E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
above. This option is enabled by default.
p\bpr\bro\bog\bgc\bco\bom\bmp\bp
- If set, enable the programmable completion facilities
+ If set, enable the programmable completion facilities
(see P\bPr\bro\bog\bgr\bra\bam\bmm\bma\bab\bbl\ble\be C\bCo\bom\bmp\bpl\ble\bet\bti\bio\bon\bn above). This option is en-
abled by default.
p\bpr\bro\bog\bgc\bco\bom\bmp\bp_\b_a\bal\bli\bia\bas\bs
- If set, and programmable completion is enabled, b\bba\bas\bsh\bh
- treats a command name that doesn't have any completions
+ If set, and programmable completion is enabled, b\bba\bas\bsh\bh
+ treats a command name that doesn't have any completions
as a possible alias and attempts alias expansion. If it
- has an alias, b\bba\bas\bsh\bh attempts programmable completion us-
+ has an alias, b\bba\bas\bsh\bh attempts programmable completion us-
ing the command word resulting from the expanded alias.
p\bpr\bro\bom\bmp\bpt\btv\bva\bar\brs\bs
If set, prompt strings undergo parameter expansion, com-
- mand substitution, arithmetic expansion, and quote re-
- moval after being expanded as described in P\bPR\bRO\bOM\bMP\bPT\bTI\bIN\bNG\bG
+ mand substitution, arithmetic expansion, and quote re-
+ moval after being expanded as described in P\bPR\bRO\bOM\bMP\bPT\bTI\bIN\bNG\bG
above. This option is enabled by default.
r\bre\bes\bst\btr\bri\bic\bct\bte\bed\bd_\b_s\bsh\bhe\bel\bll\bl
- The shell sets this option if it is started in re-
- stricted mode (see R\bRE\bES\bST\bTR\bRI\bIC\bCT\bTE\bED\bD S\bSH\bHE\bEL\bLL\bL below). The value
- may not be changed. This is not reset when the startup
- files are executed, allowing the startup files to dis-
+ The shell sets this option if it is started in re-
+ stricted mode (see R\bRE\bES\bST\bTR\bRI\bIC\bCT\bTE\bED\bD S\bSH\bHE\bEL\bLL\bL below). The value
+ may not be changed. This is not reset when the startup
+ files are executed, allowing the startup files to dis-
cover whether or not a shell is restricted.
s\bsh\bhi\bif\bft\bt_\b_v\bve\ber\brb\bbo\bos\bse\be
- If set, the s\bsh\bhi\bif\bft\bt builtin prints an error message when
+ If set, the s\bsh\bhi\bif\bft\bt builtin prints an error message when
the shift count exceeds the number of positional parame-
ters.
s\bso\bou\bur\brc\bce\bep\bpa\bat\bth\bh
If set, the .\b. (s\bso\bou\bur\brc\bce\be) builtin uses the value of P\bPA\bAT\bTH\bH to
- find the directory containing the file supplied as an
- argument when the -\b-p\bp option is not supplied. This op-
+ find the directory containing the file supplied as an
+ argument when the -\b-p\bp option is not supplied. This op-
tion is enabled by default.
v\bva\bar\brr\bre\bed\bdi\bir\br_\b_c\bcl\blo\bos\bse\be
- If set, the shell automatically closes file descriptors
- assigned using the _\b{_\bv_\ba_\br_\bn_\ba_\bm_\be_\b} redirection syntax (see
+ If set, the shell automatically closes file descriptors
+ assigned using the _\b{_\bv_\ba_\br_\bn_\ba_\bm_\be_\b} redirection syntax (see
R\bRE\bED\bDI\bIR\bRE\bEC\bCT\bTI\bIO\bON\bN above) instead of leaving them open when the
command completes.
x\bxp\bpg\bg_\b_e\bec\bch\bho\bo
- If set, the e\bec\bch\bho\bo builtin expands backslash-escape se-
- quences by default. If the p\bpo\bos\bsi\bix\bx shell option is also
+ If set, the e\bec\bch\bho\bo builtin expands backslash-escape se-
+ quences by default. If the p\bpo\bos\bsi\bix\bx shell option is also
enabled, e\bec\bch\bho\bo does not interpret any options.
s\bsu\bus\bsp\bpe\ben\bnd\bd [-\b-f\bf]
- Suspend the execution of this shell until it receives a S\bSI\bIG\bGC\bCO\bON\bNT\bT
- signal. A login shell, or a shell without job control enabled,
- cannot be suspended; the -\b-f\bf option will override this and force
- the suspension. The return status is 0 unless the shell is a
- login shell or job control is not enabled and -\b-f\bf is not sup-
+ Suspend the execution of this shell until it receives a S\bSI\bIG\bGC\bCO\bON\bNT\bT
+ signal. A login shell, or a shell without job control enabled,
+ cannot be suspended; the -\b-f\bf option will override this and force
+ the suspension. The return status is 0 unless the shell is a
+ login shell or job control is not enabled and -\b-f\bf is not sup-
plied.
t\bte\bes\bst\bt _\be_\bx_\bp_\br
[\b[ _\be_\bx_\bp_\br ]\b]
Return a status of 0 (true) or 1 (false) depending on the evalu-
- ation of the conditional expression _\be_\bx_\bp_\br. Each operator and
- operand must be a separate argument. Expressions are composed
- of the primaries described above under C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bSS\bSI\bIO\bON\bNS\bS.
- t\bte\bes\bst\bt does not accept any options, nor does it accept and ignore
+ ation of the conditional expression _\be_\bx_\bp_\br. Each operator and
+ operand must be a separate argument. Expressions are composed
+ of the primaries described above under C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bSS\bSI\bIO\bON\bNS\bS.
+ t\bte\bes\bst\bt does not accept any options, nor does it accept and ignore
an argument of -\b--\b- as signifying the end of options.
- Expressions may be combined using the following operators,
- listed in decreasing order of precedence. The evaluation de-
+ Expressions may be combined using the following operators,
+ listed in decreasing order of precedence. The evaluation de-
pends on the number of arguments; see below. t\bte\bes\bst\bt uses operator
precedence when there are five or more arguments.
!\b! _\be_\bx_\bp_\br True if _\be_\bx_\bp_\br is false.
(\b( _\be_\bx_\bp_\br )\b)
- Returns the value of _\be_\bx_\bp_\br. This may be used to override
+ Returns the value of _\be_\bx_\bp_\br. This may be used to override
normal operator precedence.
_\be_\bx_\bp_\br_\b1 -a\ba _\be_\bx_\bp_\br_\b2
True if both _\be_\bx_\bp_\br_\b1 and _\be_\bx_\bp_\br_\b2 are true.
null.
2 arguments
If the first argument is !\b!, the expression is true if and
- only if the second argument is null. If the first argu-
- ment is one of the unary conditional operators listed
- above under C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bSS\bSI\bIO\bON\bNS\bS, the expression is
+ only if the second argument is null. If the first argu-
+ ment is one of the unary conditional operators listed
+ above under C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bSS\bSI\bIO\bON\bNS\bS, the expression is
true if the unary test is true. If the first argument is
not a valid unary conditional operator, the expression is
false.
3 arguments
The following conditions are applied in the order listed.
- If the second argument is one of the binary conditional
+ If the second argument is one of the binary conditional
operators listed above under C\bCO\bON\bND\bDI\bIT\bTI\bIO\bON\bNA\bAL\bL E\bEX\bXP\bPR\bRE\bES\bSS\bSI\bIO\bON\bNS\bS, the
result of the expression is the result of the binary test
- using the first and third arguments as operands. The -\b-a\ba
- and -\b-o\bo operators are considered binary operators when
- there are three arguments. If the first argument is !\b!,
- the value is the negation of the two-argument test using
+ using the first and third arguments as operands. The -\b-a\ba
+ and -\b-o\bo operators are considered binary operators when
+ there are three arguments. If the first argument is !\b!,
+ the value is the negation of the two-argument test using
the second and third arguments. If the first argument is
exactly (\b( and the third argument is exactly )\b), the result
- is the one-argument test of the second argument. Other-
+ is the one-argument test of the second argument. Other-
wise, the expression is false.
4 arguments
The following conditions are applied in the order listed.
If the first argument is !\b!, the result is the negation of
- the three-argument expression composed of the remaining
- arguments. If the first argument is exactly (\b( and the
+ the three-argument expression composed of the remaining
+ arguments. If the first argument is exactly (\b( and the
fourth argument is exactly )\b), the result is the two-argu-
- ment test of the second and third arguments. Otherwise,
- the expression is parsed and evaluated according to
+ ment test of the second and third arguments. Otherwise,
+ the expression is parsed and evaluated according to
precedence using the rules listed above.
5 or more arguments
- The expression is parsed and evaluated according to
+ The expression is parsed and evaluated according to
precedence using the rules listed above.
When the shell is in posix mode, or if the expression is part of
the [\b[[\b[ command, the <\b< and >\b> operators sort using the current lo-
- cale. If the shell is not in posix mode, the t\bte\bes\bst\bt and [\b[ com-
+ cale. If the shell is not in posix mode, the t\bte\bes\bst\bt and [\b[ com-
mands sort lexicographically using ASCII ordering.
- The historical operator-precedence parsing with 4 or more argu-
- ments can lead to ambiguities when it encounters strings that
- look like primaries. The POSIX standard has deprecated the -\b-a\ba
- and -\b-o\bo primaries and enclosing expressions within parentheses.
- Scripts should no longer use them. It's much more reliable to
- restrict test invocations to a single primary, and to replace
+ The historical operator-precedence parsing with 4 or more argu-
+ ments can lead to ambiguities when it encounters strings that
+ look like primaries. The POSIX standard has deprecated the -\b-a\ba
+ and -\b-o\bo primaries and enclosing expressions within parentheses.
+ Scripts should no longer use them. It's much more reliable to
+ restrict test invocations to a single primary, and to replace
uses of -\b-a\ba and -\b-o\bo with the shell's &\b&&\b& and |\b||\b| list operators.
- t\bti\bim\bme\bes\bs Print the accumulated user and system times for the shell and
+ t\bti\bim\bme\bes\bs Print the accumulated user and system times for the shell and
for processes run from the shell. The return status is 0.
t\btr\bra\bap\bp [-\b-l\blp\bpP\bP] [[_\ba_\bc_\bt_\bi_\bo_\bn] _\bs_\bi_\bg_\bs_\bp_\be_\bc ...]
The _\ba_\bc_\bt_\bi_\bo_\bn is a command that is read and executed when the shell
- receives any of the signals _\bs_\bi_\bg_\bs_\bp_\be_\bc. If _\ba_\bc_\bt_\bi_\bo_\bn is absent (and
+ receives any of the signals _\bs_\bi_\bg_\bs_\bp_\be_\bc. If _\ba_\bc_\bt_\bi_\bo_\bn is absent (and
there is a single _\bs_\bi_\bg_\bs_\bp_\be_\bc) or -\b-, each specified _\bs_\bi_\bg_\bs_\bp_\be_\bc is reset
- to the value it had when the shell was started. If _\ba_\bc_\bt_\bi_\bo_\bn is
- the null string the signal specified by each _\bs_\bi_\bg_\bs_\bp_\be_\bc is ignored
+ to the value it had when the shell was started. If _\ba_\bc_\bt_\bi_\bo_\bn is
+ the null string the signal specified by each _\bs_\bi_\bg_\bs_\bp_\be_\bc is ignored
by the shell and by the commands it invokes.
- If no arguments are supplied, t\btr\bra\bap\bp displays the actions associ-
+ If no arguments are supplied, t\btr\bra\bap\bp displays the actions associ-
ated with each trapped signal as a set of t\btr\bra\bap\bp commands that can
- be reused as shell input to restore the current signal disposi-
- tions. If -\b-p\bp is given, and _\ba_\bc_\bt_\bi_\bo_\bn is not present, then t\btr\bra\bap\bp
- displays the actions associated with each _\bs_\bi_\bg_\bs_\bp_\be_\bc or, if none
+ be reused as shell input to restore the current signal disposi-
+ tions. If -\b-p\bp is given, and _\ba_\bc_\bt_\bi_\bo_\bn is not present, then t\btr\bra\bap\bp
+ displays the actions associated with each _\bs_\bi_\bg_\bs_\bp_\be_\bc or, if none
are supplied, for all trapped signals, as a set of t\btr\bra\bap\bp commands
- that can be reused as shell input to restore the current signal
- dispositions. The -\b-P\bP option behaves similarly, but displays
- only the actions associated with each _\bs_\bi_\bg_\bs_\bp_\be_\bc argument. -\b-P\bP re-
- quires at least one _\bs_\bi_\bg_\bs_\bp_\be_\bc argument. The -\b-P\bP or -\b-p\bp options may
- be used in a subshell environment (e.g., command substitution)
- and, as long as they are used before t\btr\bra\bap\bp is used to change a
+ that can be reused as shell input to restore the current signal
+ dispositions. The -\b-P\bP option behaves similarly, but displays
+ only the actions associated with each _\bs_\bi_\bg_\bs_\bp_\be_\bc argument. -\b-P\bP re-
+ quires at least one _\bs_\bi_\bg_\bs_\bp_\be_\bc argument. The -\b-P\bP or -\b-p\bp options may
+ be used in a subshell environment (e.g., command substitution)
+ and, as long as they are used before t\btr\bra\bap\bp is used to change a
signal's handling, will display the state of its parent's traps.
- The -\b-l\bl option prints a list of signal names and their corre-
- sponding numbers. Each _\bs_\bi_\bg_\bs_\bp_\be_\bc is either a signal name defined
+ The -\b-l\bl option prints a list of signal names and their corre-
+ sponding numbers. Each _\bs_\bi_\bg_\bs_\bp_\be_\bc is either a signal name defined
in <_\bs_\bi_\bg_\bn_\ba_\bl_\b._\bh>, or a signal number. Signal names are case insen-
- sitive and the S\bSI\bIG\bG prefix is optional. If -\b-l\bl is supplied with
+ sitive and the S\bSI\bIG\bG prefix is optional. If -\b-l\bl is supplied with
no _\bs_\bi_\bg_\bs_\bp_\be_\bc arguments, it prints a list of valid signal names.
- If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bEX\bXI\bIT\bT (0), _\ba_\bc_\bt_\bi_\bo_\bn is executed on exit from the
- shell. If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is D\bDE\bEB\bBU\bUG\bG, _\ba_\bc_\bt_\bi_\bo_\bn is executed before every
- _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd, _\bf_\bo_\br command, _\bc_\ba_\bs_\be command, _\bs_\be_\bl_\be_\bc_\bt command, ((
- arithmetic command, [[ conditional command, arithmetic _\bf_\bo_\br com-
- mand, and before the first command executes in a shell function
- (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR above). Refer to the description of the
- e\bex\bxt\btd\bde\beb\bbu\bug\bg shell option (see s\bsh\bho\bop\bpt\bt above) for details of its ef-
- fect on the D\bDE\bEB\bBU\bUG\bG trap. If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is R\bRE\bET\bTU\bUR\bRN\bN, _\ba_\bc_\bt_\bi_\bo_\bn is exe-
+ If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bEX\bXI\bIT\bT (0), _\ba_\bc_\bt_\bi_\bo_\bn is executed on exit from the
+ shell. If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is D\bDE\bEB\bBU\bUG\bG, _\ba_\bc_\bt_\bi_\bo_\bn is executed before every
+ _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd, _\bf_\bo_\br command, _\bc_\ba_\bs_\be command, _\bs_\be_\bl_\be_\bc_\bt command, ((
+ arithmetic command, [[ conditional command, arithmetic _\bf_\bo_\br com-
+ mand, and before the first command executes in a shell function
+ (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR above). Refer to the description of the
+ e\bex\bxt\btd\bde\beb\bbu\bug\bg shell option (see s\bsh\bho\bop\bpt\bt above) for details of its ef-
+ fect on the D\bDE\bEB\bBU\bUG\bG trap. If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is R\bRE\bET\bTU\bUR\bRN\bN, _\ba_\bc_\bt_\bi_\bo_\bn is exe-
cuted each time a shell function or a script executed with the .\b.
or s\bso\bou\bur\brc\bce\be builtins finishes executing.
- If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bER\bRR\bR, _\ba_\bc_\bt_\bi_\bo_\bn is executed whenever a pipeline
- (which may consist of a single simple command), a list, or a
- compound command returns a non-zero exit status, subject to the
- following conditions. The E\bER\bRR\bR trap is not executed if the
+ If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bER\bRR\bR, _\ba_\bc_\bt_\bi_\bo_\bn is executed whenever a pipeline
+ (which may consist of a single simple command), a list, or a
+ compound command returns a non-zero exit status, subject to the
+ following conditions. The E\bER\bRR\bR trap is not executed if the
failed command is part of the command list immediately following
a w\bwh\bhi\bil\ble\be or u\bun\bnt\bti\bil\bl reserved word, part of the test in an _\bi_\bf state-
- ment, part of a command executed in a &\b&&\b& or |\b||\b| list except the
- command following the final &\b&&\b& or |\b||\b|, any command in a pipeline
- but the last (subject to the state of the p\bpi\bip\bpe\bef\bfa\bai\bil\bl shell op-
- tion), or if the command's return value is being inverted using
+ ment, part of a command executed in a &\b&&\b& or |\b||\b| list except the
+ command following the final &\b&&\b& or |\b||\b|, any command in a pipeline
+ but the last (subject to the state of the p\bpi\bip\bpe\bef\bfa\bai\bil\bl shell op-
+ tion), or if the command's return value is being inverted using
!\b!. These are the same conditions obeyed by the e\ber\brr\bre\bex\bxi\bit\bt (-\b-e\be) op-
tion.
When the shell is not interactive, signals ignored upon entry to
the shell cannot be trapped or reset. Interactive shells permit
trapping signals ignored on entry. Trapped signals that are not
- being ignored are reset to their original values in a subshell
- or subshell environment when one is created. The return status
+ being ignored are reset to their original values in a subshell
+ or subshell environment when one is created. The return status
is false if any _\bs_\bi_\bg_\bs_\bp_\be_\bc is invalid; otherwise t\btr\bra\bap\bp returns true.
t\btr\bru\bue\be Does nothing, returns a 0 status.
Indicate how each _\bn_\ba_\bm_\be would be interpreted if used as a command
name.
- If the -\b-t\bt option is used, t\bty\byp\bpe\be prints a string which is one of
- _\ba_\bl_\bi_\ba_\bs, _\bk_\be_\by_\bw_\bo_\br_\bd, _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn, _\bb_\bu_\bi_\bl_\bt_\bi_\bn, or _\bf_\bi_\bl_\be if _\bn_\ba_\bm_\be is an alias,
- shell reserved word, function, builtin, or executable file, re-
- spectively. If the _\bn_\ba_\bm_\be is not found, t\bty\byp\bpe\be prints nothing and
+ If the -\b-t\bt option is used, t\bty\byp\bpe\be prints a string which is one of
+ _\ba_\bl_\bi_\ba_\bs, _\bk_\be_\by_\bw_\bo_\br_\bd, _\bf_\bu_\bn_\bc_\bt_\bi_\bo_\bn, _\bb_\bu_\bi_\bl_\bt_\bi_\bn, or _\bf_\bi_\bl_\be if _\bn_\ba_\bm_\be is an alias,
+ shell reserved word, function, builtin, or executable file, re-
+ spectively. If the _\bn_\ba_\bm_\be is not found, t\bty\byp\bpe\be prints nothing and
returns a non-zero exit status.
- If the -\b-p\bp option is used, t\bty\byp\bpe\be either returns the pathname of
- the executable file that would be found by searching $\b$P\bPA\bAT\bTH\bH for
+ If the -\b-p\bp option is used, t\bty\byp\bpe\be either returns the pathname of
+ the executable file that would be found by searching $\b$P\bPA\bAT\bTH\bH for
_\bn_\ba_\bm_\be or nothing if "type -t name" would not return _\bf_\bi_\bl_\be. The -\b-P\bP
- option forces a P\bPA\bAT\bTH\bH search for each _\bn_\ba_\bm_\be, even if "type -t
+ option forces a P\bPA\bAT\bTH\bH search for each _\bn_\ba_\bm_\be, even if "type -t
name" would not return _\bf_\bi_\bl_\be. If _\bn_\ba_\bm_\be is present in the table of
- hashed commands, -\b-p\bp and -\b-P\bP print the hashed value, which is not
+ hashed commands, -\b-p\bp and -\b-P\bP print the hashed value, which is not
necessarily the file that appears first in P\bPA\bAT\bTH\bH.
- If the -\b-a\ba option is used, t\bty\byp\bpe\be prints all of the places that
- contain a command named _\bn_\ba_\bm_\be. This includes aliases, reserved
- words, functions, and builtins, but the path search options (-\b-p\bp
- and -\b-P\bP) can be supplied to restrict the output to executable
- files. t\bty\byp\bpe\be does not consult the table of hashed commands when
+ If the -\b-a\ba option is used, t\bty\byp\bpe\be prints all of the places that
+ contain a command named _\bn_\ba_\bm_\be. This includes aliases, reserved
+ words, functions, and builtins, but the path search options (-\b-p\bp
+ and -\b-P\bP) can be supplied to restrict the output to executable
+ files. t\bty\byp\bpe\be does not consult the table of hashed commands when
using -\b-a\ba with -\b-p\bp, and only performs a P\bPA\bAT\bTH\bH search for _\bn_\ba_\bm_\be.
The -\b-f\bf option suppresses shell function lookup, as with the c\bco\bom\bm-\b-
- m\bma\ban\bnd\bd builtin. t\bty\byp\bpe\be returns true if all of the arguments are
+ m\bma\ban\bnd\bd builtin. t\bty\byp\bpe\be returns true if all of the arguments are
found, false if any are not found.
u\bul\bli\bim\bmi\bit\bt [-\b-H\bHS\bS] -\b-a\ba
u\bul\bli\bim\bmi\bit\bt [-\b-H\bHS\bS] [-\b-b\bbc\bcd\bde\bef\bfi\bik\bkl\blm\bmn\bnp\bpq\bqr\brs\bst\btu\buv\bvx\bxP\bPR\bRT\bT [_\bl_\bi_\bm_\bi_\bt]]
- Provides control over the resources available to the shell and
+ Provides control over the resources available to the shell and
to processes it starts, on systems that allow such control.
- The -\b-H\bH and -\b-S\bS options specify whether the hard or soft limit is
+ The -\b-H\bH and -\b-S\bS options specify whether the hard or soft limit is
set for the given resource. A hard limit cannot be increased by
a non-root user once it is set; a soft limit may be increased up
- to the value of the hard limit. If neither -\b-H\bH nor -\b-S\bS is speci-
+ to the value of the hard limit. If neither -\b-H\bH nor -\b-S\bS is speci-
fied, u\bul\bli\bim\bmi\bit\bt sets both the soft and hard limits.
The value of _\bl_\bi_\bm_\bi_\bt can be a number in the unit specified for the
- resource or one of the special values h\bha\bar\brd\bd, s\bso\bof\bft\bt, or u\bun\bnl\bli\bim\bmi\bit\bte\bed\bd,
- which stand for the current hard limit, the current soft limit,
- and no limit, respectively. If _\bl_\bi_\bm_\bi_\bt is omitted, u\bul\bli\bim\bmi\bit\bt prints
- the current value of the soft limit of the resource, unless the
- -\b-H\bH option is given. When more than one resource is specified,
- the limit name and unit, if appropriate, are printed before the
+ resource or one of the special values h\bha\bar\brd\bd, s\bso\bof\bft\bt, or u\bun\bnl\bli\bim\bmi\bit\bte\bed\bd,
+ which stand for the current hard limit, the current soft limit,
+ and no limit, respectively. If _\bl_\bi_\bm_\bi_\bt is omitted, u\bul\bli\bim\bmi\bit\bt prints
+ the current value of the soft limit of the resource, unless the
+ -\b-H\bH option is given. When more than one resource is specified,
+ the limit name and unit, if appropriate, are printed before the
value. Other options are interpreted as follows:
-\b-a\ba Report all current limits; no limits are set.
-\b-b\bb The maximum socket buffer size.
-\b-c\bc The maximum size of core files created.
-\b-d\bd The maximum size of a process's data segment.
-\b-e\be The maximum scheduling priority ("nice").
- -\b-f\bf The maximum size of files written by the shell and its
+ -\b-f\bf The maximum size of files written by the shell and its
children.
-\b-i\bi The maximum number of pending signals.
-\b-k\bk The maximum number of kqueues that may be allocated.
-\b-l\bl The maximum size that may be locked into memory.
- -\b-m\bm The maximum resident set size (many systems do not honor
+ -\b-m\bm The maximum resident set size (many systems do not honor
this limit).
-\b-n\bn The maximum number of open file descriptors (most systems
do not allow this value to be set).
-\b-r\br The maximum real-time scheduling priority.
-\b-s\bs The maximum stack size.
-\b-t\bt The maximum amount of cpu time in seconds.
- -\b-u\bu The maximum number of processes available to a single
+ -\b-u\bu The maximum number of processes available to a single
user.
- -\b-v\bv The maximum amount of virtual memory available to the
+ -\b-v\bv The maximum amount of virtual memory available to the
shell and, on some systems, to its children.
-\b-x\bx The maximum number of file locks.
-\b-P\bP The maximum number of pseudoterminals.
- -\b-R\bR The maximum time a real-time process can run before
+ -\b-R\bR The maximum time a real-time process can run before
blocking, in microseconds.
-\b-T\bT The maximum number of threads.
- If _\bl_\bi_\bm_\bi_\bt is supplied, and the -\b-a\ba option is not used, _\bl_\bi_\bm_\bi_\bt is
- the new value of the specified resource. If no option is sup-
+ If _\bl_\bi_\bm_\bi_\bt is supplied, and the -\b-a\ba option is not used, _\bl_\bi_\bm_\bi_\bt is
+ the new value of the specified resource. If no option is sup-
plied, then -\b-f\bf is assumed.
- Values are in 1024-byte increments, except for -\b-t\bt, which is in
- seconds; -\b-R\bR, which is in microseconds; -\b-p\bp, which is in units of
- 512-byte blocks; -\b-P\bP, -\b-T\bT, -\b-b\bb, -\b-k\bk, -\b-n\bn, and -\b-u\bu, which are unscaled
- values; and, when in posix mode, -\b-c\bc and -\b-f\bf, which are in
- 512-byte increments. The return status is 0 unless an invalid
+ Values are in 1024-byte increments, except for -\b-t\bt, which is in
+ seconds; -\b-R\bR, which is in microseconds; -\b-p\bp, which is in units of
+ 512-byte blocks; -\b-P\bP, -\b-T\bT, -\b-b\bb, -\b-k\bk, -\b-n\bn, and -\b-u\bu, which are unscaled
+ values; and, when in posix mode, -\b-c\bc and -\b-f\bf, which are in
+ 512-byte increments. The return status is 0 unless an invalid
option or argument is supplied, or an error occurs while setting
a new limit.
u\bum\bma\bas\bsk\bk [-\b-p\bp] [-\b-S\bS] [_\bm_\bo_\bd_\be]
- Set the user file-creation mask to _\bm_\bo_\bd_\be. If _\bm_\bo_\bd_\be begins with a
+ Set the user file-creation mask to _\bm_\bo_\bd_\be. If _\bm_\bo_\bd_\be begins with a
digit, it is interpreted as an octal number; otherwise it is in-
- terpreted as a symbolic mode mask similar to that accepted by
+ terpreted as a symbolic mode mask similar to that accepted by
_\bc_\bh_\bm_\bo_\bd(1). If _\bm_\bo_\bd_\be is omitted, u\bum\bma\bas\bsk\bk prints the current value of
the mask. The -\b-S\bS option without a _\bm_\bo_\bd_\be argument prints the mask
in a symbolic format; the default output is an octal number. If
the -\b-p\bp option is supplied, and _\bm_\bo_\bd_\be is omitted, the output is in
- a form that may be reused as input. The return status is zero
- if the mode was successfully changed or if no _\bm_\bo_\bd_\be argument was
+ a form that may be reused as input. The return status is zero
+ if the mode was successfully changed or if no _\bm_\bo_\bd_\be argument was
supplied, and non-zero otherwise.
u\bun\bna\bal\bli\bia\bas\bs [-a\ba] [_\bn_\ba_\bm_\be ...]
- Remove each _\bn_\ba_\bm_\be from the list of defined aliases. If -\b-a\ba is
- supplied, remove all alias definitions. The return value is
+ Remove each _\bn_\ba_\bm_\be from the list of defined aliases. If -\b-a\ba is
+ supplied, remove all alias definitions. The return value is
true unless a supplied _\bn_\ba_\bm_\be is not a defined alias.
u\bun\bns\bse\bet\bt [-f\bfv\bv] [-n\bn] [_\bn_\ba_\bm_\be ...]
- For each _\bn_\ba_\bm_\be, remove the corresponding variable or function.
+ For each _\bn_\ba_\bm_\be, remove the corresponding variable or function.
If the -\b-v\bv option is given, each _\bn_\ba_\bm_\be refers to a shell variable,
- and that variable is removed. If -\b-f\bf is specified, each _\bn_\ba_\bm_\be
- refers to a shell function, and the function definition is re-
- moved. If the -\b-n\bn option is supplied, and _\bn_\ba_\bm_\be is a variable
- with the _\bn_\ba_\bm_\be_\br_\be_\bf attribute, _\bn_\ba_\bm_\be will be unset rather than the
- variable it references. -\b-n\bn has no effect if the -\b-f\bf option is
- supplied. Read-only variables and functions may not be unset.
- When variables or functions are removed, they are also removed
- from the environment passed to subsequent commands. If no op-
- tions are supplied, each _\bn_\ba_\bm_\be refers to a variable; if there is
- no variable by that name, a function with that name, if any, is
- unset. Some shell variables may not be unset. If any of
+ and that variable is removed. If -\b-f\bf is specified, each _\bn_\ba_\bm_\be
+ refers to a shell function, and the function definition is re-
+ moved. If the -\b-n\bn option is supplied, and _\bn_\ba_\bm_\be is a variable
+ with the _\bn_\ba_\bm_\be_\br_\be_\bf attribute, _\bn_\ba_\bm_\be will be unset rather than the
+ variable it references. -\b-n\bn has no effect if the -\b-f\bf option is
+ supplied. Read-only variables and functions may not be unset.
+ When variables or functions are removed, they are also removed
+ from the environment passed to subsequent commands. If no op-
+ tions are supplied, each _\bn_\ba_\bm_\be refers to a variable; if there is
+ no variable by that name, a function with that name, if any, is
+ unset. Some shell variables may not be unset. If any of
B\bBA\bAS\bSH\bH_\b_A\bAL\bLI\bIA\bAS\bSE\bES\bS, B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV0\b0, B\bBA\bAS\bSH\bH_\b_C\bCM\bMD\bDS\bS, B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMM\bMA\bAN\bND\bD, B\bBA\bAS\bSH\bH_\b_S\bSU\bUB\bB-\b-
- S\bSH\bHE\bEL\bLL\bL, B\bBA\bAS\bSH\bHP\bPI\bID\bD, C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS, D\bDI\bIR\bRS\bST\bTA\bAC\bCK\bK, E\bEP\bPO\bOC\bCH\bHR\bRE\bEA\bAL\bLT\bTI\bIM\bME\bE,
- E\bEP\bPO\bOC\bCH\bHS\bSE\bEC\bCO\bON\bND\bDS\bS, F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE, G\bGR\bRO\bOU\bUP\bPS\bS, H\bHI\bIS\bST\bTC\bCM\bMD\bD, L\bLI\bIN\bNE\bEN\bNO\bO, R\bRA\bAN\bND\bDO\bOM\bM, S\bSE\bEC\bC-\b-
- O\bON\bND\bDS\bS, or S\bSR\bRA\bAN\bND\bDO\bOM\bM are unset, they lose their special properties,
- even if they are subsequently reset. The exit status is true
+ S\bSH\bHE\bEL\bLL\bL, B\bBA\bAS\bSH\bHP\bPI\bID\bD, C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS, D\bDI\bIR\bRS\bST\bTA\bAC\bCK\bK, E\bEP\bPO\bOC\bCH\bHR\bRE\bEA\bAL\bLT\bTI\bIM\bME\bE,
+ E\bEP\bPO\bOC\bCH\bHS\bSE\bEC\bCO\bON\bND\bDS\bS, F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE, G\bGR\bRO\bOU\bUP\bPS\bS, H\bHI\bIS\bST\bTC\bCM\bMD\bD, L\bLI\bIN\bNE\bEN\bNO\bO, R\bRA\bAN\bND\bDO\bOM\bM, S\bSE\bEC\bC-\b-
+ O\bON\bND\bDS\bS, or S\bSR\bRA\bAN\bND\bDO\bOM\bM are unset, they lose their special properties,
+ even if they are subsequently reset. The exit status is true
unless a _\bn_\ba_\bm_\be is readonly or may not be unset.
w\bwa\bai\bit\bt [-\b-f\bfn\bn] [-\b-p\bp _\bv_\ba_\br_\bn_\ba_\bm_\be] [_\bi_\bd ...]
Wait for each specified child process _\bi_\bd and return the termina-
- tion status of the last _\bi_\bd. Each _\bi_\bd may be a process ID _\bp_\bi_\bd or
- a job specification _\bj_\bo_\bb_\bs_\bp_\be_\bc; if a jobspec is supplied, w\bwa\bai\bit\bt
+ tion status of the last _\bi_\bd. Each _\bi_\bd may be a process ID _\bp_\bi_\bd or
+ a job specification _\bj_\bo_\bb_\bs_\bp_\be_\bc; if a jobspec is supplied, w\bwa\bai\bit\bt
waits for all processes in the job.
- If no options or _\bi_\bds are supplied, w\bwa\bai\bit\bt waits for all running
- background jobs and the last-executed process substitution, if
+ If no options or _\bi_\bds are supplied, w\bwa\bai\bit\bt waits for all running
+ background jobs and the last-executed process substitution, if
its process id is the same as $\b$!\b!, and the return status is zero.
- If the -\b-n\bn option is supplied, w\bwa\bai\bit\bt waits for any one of the
+ If the -\b-n\bn option is supplied, w\bwa\bai\bit\bt waits for any one of the
given _\bi_\bds or, if no _\bi_\bds are supplied, any job or process substi-
tution, to complete and returns its exit status. If none of the
- supplied _\bi_\bds is a child of the shell, or if no _\bi_\bds are supplied
- and the shell has no unwaited-for children, the exit status is
+ supplied _\bi_\bds is a child of the shell, or if no _\bi_\bds are supplied
+ and the shell has no unwaited-for children, the exit status is
127.
- If the -\b-p\bp option is supplied, w\bwa\bai\bit\bt assigns the process or job
- identifier of the job for which the exit status is returned to
- the variable _\bv_\ba_\br_\bn_\ba_\bm_\be named by the option argument. The vari-
- able, which cannot be readonly, will be unset initially, before
- any assignment. This is useful only when used with the -\b-n\bn op-
+ If the -\b-p\bp option is supplied, w\bwa\bai\bit\bt assigns the process or job
+ identifier of the job for which the exit status is returned to
+ the variable _\bv_\ba_\br_\bn_\ba_\bm_\be named by the option argument. The vari-
+ able, which cannot be readonly, will be unset initially, before
+ any assignment. This is useful only when used with the -\b-n\bn op-
tion.
- Supplying the -\b-f\bf option, when job control is enabled, forces
- w\bwa\bai\bit\bt to wait for each _\bi_\bd to terminate before returning its sta-
+ Supplying the -\b-f\bf option, when job control is enabled, forces
+ w\bwa\bai\bit\bt to wait for each _\bi_\bd to terminate before returning its sta-
tus, instead of returning when it changes status.
- If none of the _\bi_\bds specify one of the shell's active child
- processes, the return status is 127. If w\bwa\bai\bit\bt is interrupted by
- a signal, any _\bv_\ba_\br_\bn_\ba_\bm_\be will remain unset, and the return status
- will be greater than 128, as described under S\bSI\bIG\bGN\bNA\bAL\bLS\bS above.
+ If none of the _\bi_\bds specify one of the shell's active child
+ processes, the return status is 127. If w\bwa\bai\bit\bt is interrupted by
+ a signal, any _\bv_\ba_\br_\bn_\ba_\bm_\be will remain unset, and the return status
+ will be greater than 128, as described under S\bSI\bIG\bGN\bNA\bAL\bLS\bS above.
Otherwise, the return status is the exit status of the last _\bi_\bd.
S\bSH\bHE\bEL\bLL\bL C\bCO\bOM\bMP\bPA\bAT\bTI\bIB\bBI\bIL\bLI\bIT\bTY\bY M\bMO\bOD\bDE\bE
- Bash-4.0 introduced the concept of a _\bs_\bh_\be_\bl_\bl _\bc_\bo_\bm_\bp_\ba_\bt_\bi_\bb_\bi_\bl_\bi_\bt_\by _\bl_\be_\bv_\be_\bl, speci-
+ Bash-4.0 introduced the concept of a _\bs_\bh_\be_\bl_\bl _\bc_\bo_\bm_\bp_\ba_\bt_\bi_\bb_\bi_\bl_\bi_\bt_\by _\bl_\be_\bv_\be_\bl, speci-
fied as a set of options to the shopt builtin (c\bco\bom\bmp\bpa\bat\bt3\b31\b1, c\bco\bom\bmp\bpa\bat\bt3\b32\b2, c\bco\bom\bm-\b-
- p\bpa\bat\bt4\b40\b0, c\bco\bom\bmp\bpa\bat\bt4\b41\b1, and so on). There is only one current compatibility
+ p\bpa\bat\bt4\b40\b0, c\bco\bom\bmp\bpa\bat\bt4\b41\b1, and so on). There is only one current compatibility
level -- each option is mutually exclusive. The compatibility level is
- intended to allow users to select behavior from previous versions that
- is incompatible with newer versions while they migrate scripts to use
- current features and behavior. It's intended to be a temporary solu-
+ intended to allow users to select behavior from previous versions that
+ is incompatible with newer versions while they migrate scripts to use
+ current features and behavior. It's intended to be a temporary solu-
tion.
- This section does not mention behavior that is standard for a particu-
- lar version (e.g., setting c\bco\bom\bmp\bpa\bat\bt3\b32\b2 means that quoting the right hand
- side of the regexp matching operator quotes special regexp characters
- in the word, which is default behavior in bash-3.2 and subsequent ver-
+ This section does not mention behavior that is standard for a particu-
+ lar version (e.g., setting c\bco\bom\bmp\bpa\bat\bt3\b32\b2 means that quoting the right hand
+ side of the regexp matching operator quotes special regexp characters
+ in the word, which is default behavior in bash-3.2 and subsequent ver-
sions).
- If a user enables, say, c\bco\bom\bmp\bpa\bat\bt3\b32\b2, it may affect the behavior of other
- compatibility levels up to and including the current compatibility
- level. The idea is that each compatibility level controls behavior
- that changed in that version of b\bba\bas\bsh\bh, but that behavior may have been
- present in earlier versions. For instance, the change to use locale-
- based comparisons with the [\b[[\b[ command came in bash-4.1, and earlier
+ If a user enables, say, c\bco\bom\bmp\bpa\bat\bt3\b32\b2, it may affect the behavior of other
+ compatibility levels up to and including the current compatibility
+ level. The idea is that each compatibility level controls behavior
+ that changed in that version of b\bba\bas\bsh\bh, but that behavior may have been
+ present in earlier versions. For instance, the change to use locale-
+ based comparisons with the [\b[[\b[ command came in bash-4.1, and earlier
versions used ASCII-based comparisons, so enabling c\bco\bom\bmp\bpa\bat\bt3\b32\b2 will enable
- ASCII-based comparisons as well. That granularity may not be suffi-
- cient for all uses, and as a result users should employ compatibility
- levels carefully. Read the documentation for a particular feature to
+ ASCII-based comparisons as well. That granularity may not be suffi-
+ cient for all uses, and as a result users should employ compatibility
+ levels carefully. Read the documentation for a particular feature to
find out the current behavior.
- Bash-4.3 introduced a new shell variable: B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT. The value as-
+ Bash-4.3 introduced a new shell variable: B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT. The value as-
signed to this variable (a decimal version number like 4.2, or an inte-
- ger corresponding to the c\bco\bom\bmp\bpa\bat\bt_\bN_\bN option, like 42) determines the com-
+ ger corresponding to the c\bco\bom\bmp\bpa\bat\bt_\bN_\bN option, like 42) determines the com-
patibility level.
Starting with bash-4.4, b\bba\bas\bsh\bh began deprecating older compatibility lev-
els. Eventually, the options will be removed in favor of B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT.
- Bash-5.0 was the final version for which there was an individual shopt
- option for the previous version. B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT is the only mechanism to
+ Bash-5.0 was the final version for which there was an individual shopt
+ option for the previous version. B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT is the only mechanism to
control the compatibility level in versions newer than bash-5.0.
- The following table describes the behavior changes controlled by each
+ The following table describes the behavior changes controlled by each
compatibility level setting. The c\bco\bom\bmp\bpa\bat\bt_\bN_\bN tag is used as shorthand for
setting the compatibility level to _\bN_\bN using one of the following mecha-
- nisms. For versions prior to bash-5.0, the compatibility level may be
- set using the corresponding c\bco\bom\bmp\bpa\bat\bt_\bN_\bN shopt option. For bash-4.3 and
- later versions, the B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT variable is preferred, and it is re-
+ nisms. For versions prior to bash-5.0, the compatibility level may be
+ set using the corresponding c\bco\bom\bmp\bpa\bat\bt_\bN_\bN shopt option. For bash-4.3 and
+ later versions, the B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT variable is preferred, and it is re-
quired for bash-5.1 and later versions.
c\bco\bom\bmp\bpa\bat\bt3\b31\b1
ator (=~) has no special effect.
c\bco\bom\bmp\bpa\bat\bt3\b32\b2
- +\bo The <\b< and >\b> operators to the [\b[[\b[ command do not consider
+ +\bo The <\b< and >\b> operators to the [\b[[\b[ command do not consider
the current locale when comparing strings; they use ASCII
ordering.
c\bco\bom\bmp\bpa\bat\bt4\b40\b0
- +\bo The <\b< and >\b> operators to the [\b[[\b[ command do not consider
+ +\bo The <\b< and >\b> operators to the [\b[[\b[ command do not consider
the current locale when comparing strings; they use ASCII
ordering. B\bBa\bas\bsh\bh versions prior to bash-4.1 use ASCII col-
- lation and _\bs_\bt_\br_\bc_\bm_\bp(3); bash-4.1 and later use the current
+ lation and _\bs_\bt_\br_\bc_\bm_\bp(3); bash-4.1 and later use the current
locale's collation sequence and _\bs_\bt_\br_\bc_\bo_\bl_\bl(3).
c\bco\bom\bmp\bpa\bat\bt4\b41\b1
- +\bo In posix mode, t\bti\bim\bme\be may be followed by options and still
+ +\bo In posix mode, t\bti\bim\bme\be may be followed by options and still
be recognized as a reserved word (this is POSIX interpre-
tation 267).
+\bo In _\bp_\bo_\bs_\bi_\bx mode, the parser requires that an even number of
- single quotes occur in the _\bw_\bo_\br_\bd portion of a double-
- quoted parameter expansion and treats them specially, so
- that characters within the single quotes are considered
+ single quotes occur in the _\bw_\bo_\br_\bd portion of a double-
+ quoted parameter expansion and treats them specially, so
+ that characters within the single quotes are considered
quoted (this is POSIX interpretation 221).
c\bco\bom\bmp\bpa\bat\bt4\b42\b2
+\bo The replacement string in double-quoted pattern substitu-
- tion does not undergo quote removal, as it does in ver-
+ tion does not undergo quote removal, as it does in ver-
sions after bash-4.2.
- +\bo In posix mode, single quotes are considered special when
- expanding the _\bw_\bo_\br_\bd portion of a double-quoted parameter
- expansion and can be used to quote a closing brace or
- other special character (this is part of POSIX interpre-
- tation 221); in later versions, single quotes are not
+ +\bo In posix mode, single quotes are considered special when
+ expanding the _\bw_\bo_\br_\bd portion of a double-quoted parameter
+ expansion and can be used to quote a closing brace or
+ other special character (this is part of POSIX interpre-
+ tation 221); in later versions, single quotes are not
special within double-quoted word expansions.
c\bco\bom\bmp\bpa\bat\bt4\b43\b3
- +\bo Word expansion errors are considered non-fatal errors
- that cause the current command to fail, even in posix
- mode (the default behavior is to make them fatal errors
+ +\bo Word expansion errors are considered non-fatal errors
+ that cause the current command to fail, even in posix
+ mode (the default behavior is to make them fatal errors
that cause the shell to exit).
- +\bo When executing a shell function, the loop state
+ +\bo When executing a shell function, the loop state
(while/until/etc.) is not reset, so b\bbr\bre\bea\bak\bk or c\bco\bon\bnt\bti\bin\bnu\bue\be in
that function will break or continue loops in the calling
context. Bash-4.4 and later reset the loop state to pre-
vent this.
c\bco\bom\bmp\bpa\bat\bt4\b44\b4
- +\bo The shell sets up the values used by B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV and
- B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC so they can expand to the shell's positional
- parameters even if extended debugging mode is not en-
+ +\bo The shell sets up the values used by B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGV\bV and
+ B\bBA\bAS\bSH\bH_\b_A\bAR\bRG\bGC\bC so they can expand to the shell's positional
+ parameters even if extended debugging mode is not en-
abled.
- +\bo A subshell inherits loops from its parent context, so
- b\bbr\bre\bea\bak\bk or c\bco\bon\bnt\bti\bin\bnu\bue\be will cause the subshell to exit.
- Bash-5.0 and later reset the loop state to prevent the
+ +\bo A subshell inherits loops from its parent context, so
+ b\bbr\bre\bea\bak\bk or c\bco\bon\bnt\bti\bin\bnu\bue\be will cause the subshell to exit.
+ Bash-5.0 and later reset the loop state to prevent the
exit
- +\bo Variable assignments preceding builtins like e\bex\bxp\bpo\bor\brt\bt and
+ +\bo Variable assignments preceding builtins like e\bex\bxp\bpo\bor\brt\bt and
r\bre\bea\bad\bdo\bon\bnl\bly\by that set attributes continue to affect variables
with the same name in the calling environment even if the
shell is not in posix mode.
c\bco\bom\bmp\bpa\bat\bt5\b50\b0
- +\bo Bash-5.1 changed the way $\b$R\bRA\bAN\bND\bDO\bOM\bM is generated to intro-
- duce slightly more randomness. If the shell compatibil-
+ +\bo Bash-5.1 changed the way $\b$R\bRA\bAN\bND\bDO\bOM\bM is generated to intro-
+ duce slightly more randomness. If the shell compatibil-
ity level is set to 50 or lower, it reverts to the method
- from bash-5.0 and previous versions, so seeding the ran-
- dom number generator by assigning a value to R\bRA\bAN\bND\bDO\bOM\bM will
+ from bash-5.0 and previous versions, so seeding the ran-
+ dom number generator by assigning a value to R\bRA\bAN\bND\bDO\bOM\bM will
produce the same sequence as in bash-5.0.
- +\bo If the command hash table is empty, bash versions prior
- to bash-5.1 printed an informational message to that ef-
- fect, even when producing output that can be reused as
- input. Bash-5.1 suppresses that message when the -\b-l\bl op-
+ +\bo If the command hash table is empty, bash versions prior
+ to bash-5.1 printed an informational message to that ef-
+ fect, even when producing output that can be reused as
+ input. Bash-5.1 suppresses that message when the -\b-l\bl op-
tion is supplied.
c\bco\bom\bmp\bpa\bat\bt5\b51\b1
- +\bo The u\bun\bns\bse\bet\bt builtin treats attempts to unset array sub-
- scripts @\b@ and *\b* differently depending on whether the ar-
- ray is indexed or associative, and differently than in
+ +\bo The u\bun\bns\bse\bet\bt builtin treats attempts to unset array sub-
+ scripts @\b@ and *\b* differently depending on whether the ar-
+ ray is indexed or associative, and differently than in
previous versions.
+\bo Arithmetic commands ( (\b((\b(...)\b))\b) ) and the expressions in an
arithmetic for statement can be expanded more than once.
- +\bo Expressions used as arguments to arithmetic operators in
- the [\b[[\b[ conditional command can be expanded more than
+ +\bo Expressions used as arguments to arithmetic operators in
+ the [\b[[\b[ conditional command can be expanded more than
once.
- +\bo The expressions in substring parameter brace expansion
+ +\bo The expressions in substring parameter brace expansion
can be expanded more than once.
+\bo The expressions in the $\b$(\b((\b(...)\b))\b) word expansion can be ex-
panded more than once.
- +\bo Arithmetic expressions used as indexed array subscripts
+ +\bo Arithmetic expressions used as indexed array subscripts
can be expanded more than once.
- +\bo t\bte\bes\bst\bt -\b-v\bv, when given an argument of A\bA[\b[@\b@]\b], where A\bA is an
+ +\bo t\bte\bes\bst\bt -\b-v\bv, when given an argument of A\bA[\b[@\b@]\b], where A\bA is an
existing associative array, will return true if the array
- has any set elements. Bash-5.2 will look for and report
+ has any set elements. Bash-5.2 will look for and report
on a key named @\b@.
+\bo The ${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br[\b[:\b:]\b]=\b=_\bv_\ba_\bl_\bu_\be} word expansion will return
- _\bv_\ba_\bl_\bu_\be, before any variable-specific transformations have
+ _\bv_\ba_\bl_\bu_\be, before any variable-specific transformations have
been performed (e.g., converting to lowercase). Bash-5.2
will return the final value assigned to the variable.
- +\bo Parsing command substitutions will behave as if extended
+ +\bo Parsing command substitutions will behave as if extended
globbing (see the description of the s\bsh\bho\bop\bpt\bt builtin above)
- is enabled, so that parsing a command substitution con-
+ is enabled, so that parsing a command substitution con-
taining an extglob pattern (say, as part of a shell func-
- tion) will not fail. This assumes the intent is to en-
- able extglob before the command is executed and word ex-
- pansions are performed. It will fail at word expansion
- time if extglob hasn't been enabled by the time the com-
+ tion) will not fail. This assumes the intent is to en-
+ able extglob before the command is executed and word ex-
+ pansions are performed. It will fail at word expansion
+ time if extglob hasn't been enabled by the time the com-
mand is executed.
c\bco\bom\bmp\bpa\bat\bt5\b52\b2
- +\bo The t\bte\bes\bst\bt builtin uses its historical algorithm to parse
- parenthesized subexpressions when given five or more ar-
+ +\bo The t\bte\bes\bst\bt builtin uses its historical algorithm to parse
+ parenthesized subexpressions when given five or more ar-
guments.
- +\bo If the -\b-p\bp or -\b-P\bP option is supplied to the b\bbi\bin\bnd\bd builtin,
+ +\bo If the -\b-p\bp or -\b-P\bP option is supplied to the b\bbi\bin\bnd\bd builtin,
b\bbi\bin\bnd\bd treats any arguments remaining after option process-
- ing as bindable command names, and displays any key se-
- quences bound to those commands, instead of treating the
+ ing as bindable command names, and displays any key se-
+ quences bound to those commands, instead of treating the
arguments as key sequences to bind.
R\bRE\bES\bST\bTR\bRI\bIC\bCT\bTE\bED\bD S\bSH\bHE\bEL\bLL\bL
If b\bba\bas\bsh\bh is started with the name r\brb\bba\bas\bsh\bh, or the -\b-r\br option is supplied at
- invocation, the shell becomes _\br_\be_\bs_\bt_\br_\bi_\bc_\bt_\be_\bd. A restricted shell is used
- to set up an environment more controlled than the standard shell. It
- behaves identically to b\bba\bas\bsh\bh with the exception that the following are
+ invocation, the shell becomes _\br_\be_\bs_\bt_\br_\bi_\bc_\bt_\be_\bd. A restricted shell is used
+ to set up an environment more controlled than the standard shell. It
+ behaves identically to b\bba\bas\bsh\bh with the exception that the following are
disallowed or not performed:
+\bo Changing directories with c\bcd\bd.
- +\bo Setting or unsetting the values of S\bSH\bHE\bEL\bLL\bL, P\bPA\bAT\bTH\bH, H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE, E\bEN\bNV\bV,
+ +\bo Setting or unsetting the values of S\bSH\bHE\bEL\bLL\bL, P\bPA\bAT\bTH\bH, H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE, E\bEN\bNV\bV,
or B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV.
+\bo Specifying command names containing /\b/.
- +\bo Specifying a filename containing a /\b/ as an argument to the .\b.
+ +\bo Specifying a filename containing a /\b/ as an argument to the .\b.
builtin command.
- +\bo Using the -\b-p\bp option to the .\b. builtin command to specify a
+ +\bo Using the -\b-p\bp option to the .\b. builtin command to specify a
search path.
- +\bo Specifying a filename containing a slash as an argument to the
+ +\bo Specifying a filename containing a slash as an argument to the
h\bhi\bis\bst\bto\bor\bry\by builtin command.
- +\bo Specifying a filename containing a slash as an argument to the
+ +\bo Specifying a filename containing a slash as an argument to the
-\b-p\bp option to the h\bha\bas\bsh\bh builtin command.
- +\bo Importing function definitions from the shell environment at
+ +\bo Importing function definitions from the shell environment at
startup.
- +\bo Parsing the values of B\bBA\bAS\bSH\bHO\bOP\bPT\bTS\bS and S\bSH\bHE\bEL\bLL\bLO\bOP\bPT\bTS\bS from the shell en-
+ +\bo Parsing the values of B\bBA\bAS\bSH\bHO\bOP\bPT\bTS\bS and S\bSH\bHE\bEL\bLL\bLO\bOP\bPT\bTS\bS from the shell en-
vironment at startup.
- +\bo Redirecting output using the >, >|, <>, >&, &>, and >> redirec-
+ +\bo Redirecting output using the >, >|, <>, >&, &>, and >> redirec-
tion operators.
+\bo Using the e\bex\bxe\bec\bc builtin command to replace the shell with another
command.
- +\bo Adding or deleting builtin commands with the -\b-f\bf and -\b-d\bd options
+ +\bo Adding or deleting builtin commands with the -\b-f\bf and -\b-d\bd options
to the e\ben\bna\bab\bbl\ble\be builtin command.
- +\bo Using the e\ben\bna\bab\bbl\ble\be builtin command to enable disabled shell
+ +\bo Using the e\ben\bna\bab\bbl\ble\be builtin command to enable disabled shell
builtins.
+\bo Specifying the -\b-p\bp option to the c\bco\bom\bmm\bma\ban\bnd\bd builtin command.
- +\bo Turning off restricted mode with s\bse\bet\bt +\b+r\br or s\bsh\bho\bop\bpt\bt -\b-u\bu r\bre\be-\b-
+ +\bo Turning off restricted mode with s\bse\bet\bt +\b+r\br or s\bsh\bho\bop\bpt\bt -\b-u\bu r\bre\be-\b-
s\bst\btr\bri\bic\bct\bte\bed\bd_\b_s\bsh\bhe\bel\bll\bl.
These restrictions are enforced after any startup files are read.
When a command that is found to be a shell script is executed (see C\bCO\bOM\bM-\b-
- M\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN above), r\brb\bba\bas\bsh\bh turns off any restrictions in the shell
+ M\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN above), r\brb\bba\bas\bsh\bh turns off any restrictions in the shell
spawned to execute the script.
S\bSE\bEE\bE A\bAL\bLS\bSO\bO
_\b~_\b/_\b._\bb_\ba_\bs_\bh_\br_\bc
The individual per-interactive-shell startup file
_\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bl_\bo_\bg_\bo_\bu_\bt
- The individual login shell cleanup file, executed when a login
+ The individual login shell cleanup file, executed when a login
shell exits
_\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bh_\bi_\bs_\bt_\bo_\br_\by
- The default value of H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE, the file in which bash saves the
+ The default value of H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE, the file in which bash saves the
command history
_\b~_\b/_\b._\bi_\bn_\bp_\bu_\bt_\br_\bc
Individual _\br_\be_\ba_\bd_\bl_\bi_\bn_\be initialization file
B\bBU\bUG\bG R\bRE\bEP\bPO\bOR\bRT\bTS\bS
If you find a bug in b\bba\bas\bsh\bh, you should report it. But first, you should
- make sure that it really is a bug, and that it appears in the latest
- version of b\bba\bas\bsh\bh. The latest version is always available from
+ make sure that it really is a bug, and that it appears in the latest
+ version of b\bba\bas\bsh\bh. The latest version is always available from
_\bf_\bt_\bp_\b:_\b/_\b/_\bf_\bt_\bp_\b._\bg_\bn_\bu_\b._\bo_\br_\bg_\b/_\bp_\bu_\bb_\b/_\bg_\bn_\bu_\b/_\bb_\ba_\bs_\bh_\b/ and _\bh_\bt_\bt_\bp_\b:_\b/_\b/_\bg_\bi_\bt_\b._\bs_\ba_\bv_\ba_\bn_\b-
_\bn_\ba_\bh_\b._\bg_\bn_\bu_\b._\bo_\br_\bg_\b/_\bc_\bg_\bi_\bt_\b/_\bb_\ba_\bs_\bh_\b._\bg_\bi_\bt_\b/_\bs_\bn_\ba_\bp_\bs_\bh_\bo_\bt_\b/_\bb_\ba_\bs_\bh_\b-_\bm_\ba_\bs_\bt_\be_\br_\b._\bt_\ba_\br_\b._\bg_\bz.
- Once you have determined that a bug actually exists, use the _\bb_\ba_\bs_\bh_\bb_\bu_\bg
- command to submit a bug report. If you have a fix, you are encouraged
+ Once you have determined that a bug actually exists, use the _\bb_\ba_\bs_\bh_\bb_\bu_\bg
+ command to submit a bug report. If you have a fix, you are encouraged
to mail that as well! You may send suggestions and "philosophical" bug
- reports to _\bb_\bu_\bg_\b-_\bb_\ba_\bs_\bh_\b@_\bg_\bn_\bu_\b._\bo_\br_\bg or post them to the Usenet newsgroup
+ reports to _\bb_\bu_\bg_\b-_\bb_\ba_\bs_\bh_\b@_\bg_\bn_\bu_\b._\bo_\br_\bg or post them to the Usenet newsgroup
g\bgn\bnu\bu.\b.b\bba\bas\bsh\bh.\b.b\bbu\bug\bg.
ALL bug reports should include:
A description of the bug behavior
A short script or "recipe" which exercises the bug
- _\bb_\ba_\bs_\bh_\bb_\bu_\bg inserts the first three items automatically into the template
+ _\bb_\ba_\bs_\bh_\bb_\bu_\bg inserts the first three items automatically into the template
it provides for filing a bug report.
Comments and bug reports concerning this manual page should be directed
Shell builtin commands and functions are not stoppable/restartable.
- Compound commands and command lists of the form "a ; b ; c" are not
- handled gracefully when combined with process suspension. When a
- process is stopped, the shell immediately executes the next command in
- the list or breaks out of any existing loops. It suffices to enclose
- the command in parentheses to force it into a subshell, which may be
- stopped as a unit, or to start the command in the background and imme-
+ Compound commands and command lists of the form "a ; b ; c" are not
+ handled gracefully when combined with process suspension. When a
+ process is stopped, the shell immediately executes the next command in
+ the list or breaks out of any existing loops. It suffices to enclose
+ the command in parentheses to force it into a subshell, which may be
+ stopped as a unit, or to start the command in the background and imme-
diately bring it into the foreground.
Array variables may not (yet) be exported.
-GNU Bash 5.3 2025 July 30 _\bB_\bA_\bS_\bH(1)
+GNU Bash 5.3 2025 August 25 _\bB_\bA_\bS_\bH(1)
.\" Case Western Reserve University
.\" chet.ramey@case.edu
.\"
-.\" Last Change: Wed Jul 30 14:47:58 EDT 2025
+.\" Last Change: Mon Aug 25 11:35:58 EDT 2025
.\"
.\" For bash_builtins, strip all but "SHELL BUILTIN COMMANDS" section
.\" For rbash, strip all but "RESTRICTED SHELL" section
.ds zY \" empty
.if \n(zZ=1 .ig zZ
.if \n(zY=1 .ig zY
-.TH BASH 1 "2025 July 30" "GNU Bash 5.3"
+.TH BASH 1 "2025 August 25" "GNU Bash 5.3"
.\"
.ie \n(.g \{\
.ds ' \(aq
here-documents within shell scripts to be indented in a
natural fashion.
.PP
-If the delimiter is not quoted, the
+If the delimiter is not quoted, the shell treats the
.B \e<newline>
-sequence is treated as a line continuation: the two lines are joined
+sequence as a line continuation: the two lines are joined
and the backslash-newline is removed.
This happens while reading the here-document, before the check for
the ending delimiter, so joined lines can form the end delimiter.
Backslash will escape a newline, if necessary.
These are added to the set of possible completions.
.PP
+External commands that are invoked to generate completions (
+.Q "external completers" )
+receive the word preceding the completion word as an argument,
+as described above.
+This provides context that is sometimes useful, but may include
+information that is considered sensitive or part of a word expansion
+that will not appear in the command line after expansion.
+That word may be visible in process listings or in audit logs.
+This may be a concern to users and completion specification authors
+if there is sensitive information on the command line before
+expansion, since completion takes place before words are expanded.
+If this is an issue, completion authors should use functions as
+wrappers around external commands and pass context information to the
+external command in a different way.
+External completers can infer context from the
+.SM
+.B COMP_LINE
+and
+.SM
+.B COMP_POINT
+environment variables, but they need to ensure
+they break words in the same way \fBreadline\fP does, using the
+.SM
+.B COMP_WORDBREAKS
+variable.
+.PP
After generating all of the possible completions,
\fBbash\fP applies any filter
specified with the \fB\-X\fP option to the completions in the list.
</HEAD>
<BODY><TABLE WIDTH=100%>
<TR>
-<TH ALIGN=LEFT width=33%>BASH(1)<TH ALIGN=CENTER width=33%>2025 April 7<TH ALIGN=RIGHT width=33%>BASH(1)
+<TH ALIGN=LEFT width=33%>BASH(1)<TH ALIGN=CENTER width=33%>2025 August 25<TH ALIGN=RIGHT width=33%>BASH(1)
</TR>
</TABLE>
<BR><A HREF="#index">Index</A>
<I>integer</I> attribute using <B>declare -i</B> is assigned a value.
A null value evaluates to 0.
A shell variable need not have its <I>integer</I> attribute
-turned on to be used in an expression.
+enabled to be used in an expression.
<P>
Integer constants follow the C language definition, without suffixes or
at a <B>bash</B> prompt to see your current terminal settings,
including the special control characters (usually <B>cchars</B>).
+This binding takes place on each call to <B>readline</B>,
+so changes made by
+
+can take effect.
<DT><B>blink-matching-paren (Off)</B>
<DD>
These are added to the set of possible completions.
<P>
+External commands that are invoked to generate completions (
+
+receive the word preceding the completion word as an argument,
+as described above.
+This provides context that is sometimes useful, but may include
+information that is considered sensitive or part of a word expansion
+that will not appear in the command line after expansion.
+That word may be visible in process listings or in audit logs.
+This may be a concern to users and completion specification authors
+if there is sensitive information on the command line before
+expansion, since completion takes place before words are expanded.
+If this is an issue, completion authors should use functions as
+wrappers around external commands and pass context information to the
+external command in a different way.
+External completers can infer context from the
+<FONT SIZE=-1><B>COMP_LINE</B>
+
+</FONT>
+and
+<FONT SIZE=-1><B>COMP_POINT</B>
+
+</FONT>
+environment variables, but they need to ensure
+they break words in the same way <B>readline</B> does, using the
+<FONT SIZE=-1><B>COMP_WORDBREAKS</B>
+
+</FONT>
+variable.
+<P>
+
After generating all of the possible completions,
<B>bash</B> applies any filter
specified with the <B>-X</B> option to the completions in the list.
</FONT>
shell variable is used as <I>dir</I>.
+If <I>dir</I> is the empty string, <B>cd</B> treats it as an error.
The variable
<FONT SIZE=-1><B>CDPATH</B>
<HR>
<TABLE WIDTH=100%>
<TR>
-<TH ALIGN=LEFT width=33%>GNU Bash 5.3<TH ALIGN=CENTER width=33%>2025 April 7<TH ALIGN=RIGHT width=33%>BASH(1)
+<TH ALIGN=LEFT width=33%>GNU Bash 5.3<TH ALIGN=CENTER width=33%>2025 August 25<TH ALIGN=RIGHT width=33%>BASH(1)
</TR>
</TABLE>
<HR>
<DT><A HREF="#lbDJ">BUGS</A><DD>
</DL>
<HR>
-This document was created by man2html from /usr/local/src/bash/bash-20250502/doc/bash.1.<BR>
-Time: 04 May 2025 17:25:09 EDT
+This document was created by man2html from /usr/local/src/bash/bash-20250822/doc/bash.1.<BR>
+Time: 25 August 2025 11:45:48 EDT
</BODY>
</HTML>
escape a newline, if necessary. These are added to the set of possible
completions.
+ External commands that are invoked to generate completions ("external
+completers") receive the word preceding the completion word as an
+argument, as described above. This provides context that is sometimes
+useful, but may include information that is considered sensitive or part
+of a word expansion that will not appear in the command line after
+expansion. That word may be visible in process listings or in audit
+logs. This may be a concern to users and completion specification
+authors if there is sensitive information on the command line before
+expansion, since completion takes place before words are expanded. If
+this is an issue, completion authors should use functions as wrappers
+around external commands and pass context information to the external
+command in a different way. External completers can infer context from
+the COMP_LINE and COMP_POINT environment variables, but they need to
+ensure they break words in the same way Readline does, using the
+COMP_WORDBREAKS variable.
+
After generating all of the possible completions, Bash applies any
filter specified with the ‘-X’ option to the completions in the list.
The filter is a pattern as used for pathname expansion; a ‘&’ in the
Node: Miscellaneous Commands\7f454797
Node: Readline vi Mode\7f461364
Node: Programmable Completion\7f462341
-Node: Programmable Completion Builtins\7f471078
-Node: A Programmable Completion Example\7f482815
-Node: Using History Interactively\7f488160
-Node: Bash History Facilities\7f488841
-Node: Bash History Builtins\7f492576
-Node: History Interaction\7f499047
-Node: Event Designators\7f503997
-Node: Word Designators\7f505575
-Node: Modifiers\7f507967
-Node: Installing Bash\7f509904
-Node: Basic Installation\7f511020
-Node: Compilers and Options\7f514896
-Node: Compiling For Multiple Architectures\7f515646
-Node: Installation Names\7f517399
-Node: Specifying the System Type\7f519633
-Node: Sharing Defaults\7f520379
-Node: Operation Controls\7f521093
-Node: Optional Features\7f522112
-Node: Reporting Bugs\7f534835
-Node: Major Differences From The Bourne Shell\7f536192
-Node: GNU Free Documentation License\7f557619
-Node: Indexes\7f582796
-Node: Builtin Index\7f583247
-Node: Reserved Word Index\7f590345
-Node: Variable Index\7f592790
-Node: Function Index\7f610203
-Node: Concept Index\7f624198
+Node: Programmable Completion Builtins\7f472077
+Node: A Programmable Completion Example\7f483814
+Node: Using History Interactively\7f489159
+Node: Bash History Facilities\7f489840
+Node: Bash History Builtins\7f493575
+Node: History Interaction\7f500046
+Node: Event Designators\7f504996
+Node: Word Designators\7f506574
+Node: Modifiers\7f508966
+Node: Installing Bash\7f510903
+Node: Basic Installation\7f512019
+Node: Compilers and Options\7f515895
+Node: Compiling For Multiple Architectures\7f516645
+Node: Installation Names\7f518398
+Node: Specifying the System Type\7f520632
+Node: Sharing Defaults\7f521378
+Node: Operation Controls\7f522092
+Node: Optional Features\7f523111
+Node: Reporting Bugs\7f535834
+Node: Major Differences From The Bourne Shell\7f537191
+Node: GNU Free Documentation License\7f558618
+Node: Indexes\7f583795
+Node: Builtin Index\7f584246
+Node: Reserved Word Index\7f591344
+Node: Variable Index\7f593789
+Node: Function Index\7f611202
+Node: Concept Index\7f625197
\1f
End Tag Table
\entry{suspend}{128}{\code {suspend}}
\entry{compgen}{161}{\code {compgen}}
\entry{complete}{161}{\code {complete}}
-\entry{compopt}{164}{\code {compopt}}
+\entry{compopt}{165}{\code {compopt}}
\entry{fc}{169}{\code {fc}}
\entry{history}{169}{\code {history}}
\entry{\code {command}}{63}
\entry{\code {compgen}}{161}
\entry{\code {complete}}{161}
-\entry{\code {compopt}}{164}
+\entry{\code {compopt}}{165}
\entry{\code {continue}}{54}
\initial {D}
\entry{\code {declare}}{64}
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<!-- This text is a brief description of the features that are present in
-the Bash shell (version 5.3, 18 May 2025).
+the Bash shell (version 5.3, 7 August 2025).
-This is Edition 5.3, last updated 18 May 2025,
+This is Edition 5.3, last updated 7 August 2025,
of The GNU Bash Reference Manual,
for Bash, Version 5.3.
<h1 class="top" id="Bash-Features-1"><span>Bash Features<a class="copiable-link" href="#Bash-Features-1"> ¶</a></span></h1>
<p>This text is a brief description of the features that are present in
-the Bash shell (version 5.3, 18 May 2025).
+the Bash shell (version 5.3, 7 August 2025).
The Bash home page is <a class="url" href="http://www.gnu.org/software/bash/">http://www.gnu.org/software/bash/</a>.
</p>
-<p>This is Edition 5.3, last updated 18 May 2025,
+<p>This is Edition 5.3, last updated 7 August 2025,
of <cite class="cite">The GNU Bash Reference Manual</cite>,
for <code class="code">Bash</code>, Version 5.3.
</p>
<p>Bash itself returns the exit status of the last command
executed, unless a syntax error occurs, in which case it exits
with a non-zero value.
-See also the <code class="code">exit</code> builtin command (see <a class="pxref" href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>.
+See also the <code class="code">exit</code> builtin command (see <a class="pxref" href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
</p>
<hr>
</div>
ignores <code class="code">SIGTTIN</code>, <code class="code">SIGTTOU</code>, and <code class="code">SIGTSTP</code>.
</p>
<p>The <code class="code">trap</code> builtin modifies the shell’s signal handling, as
-described below (see <a class="pxref" href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>.
+described below (see <a class="pxref" href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>).
</p>
<p>Non-builtin commands Bash executes have signal handlers set to the
values inherited by the shell from its parent,
<p>Change the current working directory to <var class="var">directory</var>.
If <var class="var">directory</var> is not supplied, the value of the <code class="env">HOME</code>
shell variable is used as <var class="var">directory</var>.
+If <var class="var">directory</var> is the empty string, <code class="code">cd</code> treats it as an error.
If the shell variable
<code class="env">CDPATH</code> exists,
and <var class="var">directory</var> does not begin with a slash,
<dt><code class="code">nocasematch</code></dt>
<dd><p>If set, Bash matches patterns in a case-insensitive fashion when
performing matching while executing <code class="code">case</code> or <code class="code">[[</code>
-conditional commands (see <a class="pxref" href="#Conditional-Constructs">Conditional Constructs</a>,
+conditional commands (see <a class="pxref" href="#Conditional-Constructs">Conditional Constructs</a>),
when performing pattern substitution word expansions,
or when filtering possible completions as part of programmable completion.
</p>
<dt><a id="index-READLINE_005fARGUMENT"></a><span><code class="code">READLINE_ARGUMENT</code><a class="copiable-link" href="#index-READLINE_005fARGUMENT"> ¶</a></span></dt>
<dd><p>Any numeric argument given to a Readline
command that was defined using
-‘<samp class="samp">bind -x</samp>’ (see <a class="pxref" href="#Bash-Builtins">Bash Builtin Commands</a>
+‘<samp class="samp">bind -x</samp>’ (see <a class="pxref" href="#Bash-Builtins">Bash Builtin Commands</a>)
when it was invoked.
</p>
</dd>
when it is referenced, or when a variable which has been given the
<code class="code">integer</code> attribute using ‘<samp class="samp">declare -i</samp>’ is assigned a value.
A null value evaluates to 0.
-A shell variable need not have its <code class="code">integer</code> attribute turned on
+A shell variable need not have its <code class="code">integer</code> attribute enabled
to be used in an expression.
</p>
<p>Integer constants follow the C language definition, without suffixes or
</li><li> Bash reads and executes the <small class="sc">POSIX</small> startup files
(<code class="env">$ENV</code>) rather than
-the normal Bash files (see <a class="pxref" href="#Bash-Startup-Files">Bash Startup Files</a>.
+the normal Bash files (see <a class="pxref" href="#Bash-Startup-Files">Bash Startup Files</a>).
</li><li> Alias expansion is always enabled, even in non-interactive shells.
These override the default Readline bindings described here.
Type ‘<samp class="samp">stty -a</samp>’ at a Bash prompt to see your current terminal settings,
including the special control characters (usually <code class="code">cchars</code>).
+This binding takes place on each call to <code class="code">readline()</code>,
+so changes made by
+‘<samp class="samp">stty</samp>’
+can take effect.
</p>
</dd>
<dt><a id="index-blink_002dmatching_002dparen"></a><span><code class="code">blink-matching-paren</code><a class="copiable-link" href="#index-blink_002dmatching_002dparen"> ¶</a></span></dt>
Backslash will escape a newline, if necessary.
These are added to the set of possible completions.
</p>
+<p>External commands that are invoked to generate completions
+("external completers")
+receive the word preceding the completion word as an argument,
+as described above.
+This provides context that is sometimes useful, but may include
+information that is considered sensitive or part of a word expansion
+that will not appear in the command line after expansion.
+That word may be visible in process listings or in audit logs.
+This may be a concern to users and completion specification authors
+if there is sensitive information on the command line before
+expansion, since completion takes place before words are expanded.
+If this is an issue, completion authors should use functions as
+wrappers around external commands and pass context information to the
+external command in a different way.
+External completers can infer context from the <var class="var">COMP_LINE</var>
+and <var class="var">COMP_POINT</var> environment variables, but they need to ensure
+they break words in the same way Readline does, using the
+<var class="var">COMP_WORDBREAKS</var> variable.
+</p>
<p>After generating all of the possible completions,
Bash applies any filter
specified with the <samp class="option">-X</samp> option to the completions in the list.
option automatically for a number of systems.
</p>
</dd>
-<dt><code class="code">--with-curses</code></dt>
-<dd><p>Use the curses library instead of the termcap library.
+<dt><code class="code">--with-curses[=<var class="var">LIBNAME</var>]</code></dt>
+<dd><p>Use the curses library instead of the termcap library as the library
+where the linker can find the termcap functions.
<code class="code">configure</code> usually chooses this automatically, since most systems
include the termcap functions in the curses library.
+If <var class="var">LIBNAME</var> is supplied, <code class="code">configure</code> does not search for an
+appropriate library and uses <var class="var">LIBNAME</var> instead.
+<var class="var">LIBNAME</var> should be either an argument for the linker
+(e.g., <samp class="option">-l<var class="var">libname</var></samp>)
+or a filename
+(e.g., <samp class="file">/opt/local/lib/libncursesw.so</samp>).
</p>
</dd>
<dt><code class="code">--with-gnu-malloc</code></dt>
using <code class="code">export -f</code> (see <a class="pxref" href="#Shell-Functions">Shell Functions</a>).
</li><li>The Bash <code class="code">export</code> and <code class="code">readonly</code> builtins
-(see <a class="pxref" href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a> can
+(see <a class="pxref" href="#Bourne-Shell-Builtins">Bourne Shell Builtins</a>) can
take a <samp class="option">-f</samp> option to act on shell functions, a <samp class="option">-p</samp> option to
display variables with various attributes set in a format that can be
used as shell input, a <samp class="option">-n</samp> option to remove various variable
escape a newline, if necessary. These are added to the set of possible
completions.
+ External commands that are invoked to generate completions ("external
+completers") receive the word preceding the completion word as an
+argument, as described above. This provides context that is sometimes
+useful, but may include information that is considered sensitive or part
+of a word expansion that will not appear in the command line after
+expansion. That word may be visible in process listings or in audit
+logs. This may be a concern to users and completion specification
+authors if there is sensitive information on the command line before
+expansion, since completion takes place before words are expanded. If
+this is an issue, completion authors should use functions as wrappers
+around external commands and pass context information to the external
+command in a different way. External completers can infer context from
+the COMP_LINE and COMP_POINT environment variables, but they need to
+ensure they break words in the same way Readline does, using the
+COMP_WORDBREAKS variable.
+
After generating all of the possible completions, Bash applies any
filter specified with the ‘-X’ option to the completions in the list.
The filter is a pattern as used for pathname expansion; a ‘&’ in the
Node: Miscellaneous Commands\7f455106
Node: Readline vi Mode\7f461676
Node: Programmable Completion\7f462656
-Node: Programmable Completion Builtins\7f471396
-Node: A Programmable Completion Example\7f483136
-Node: Using History Interactively\7f488484
-Node: Bash History Facilities\7f489168
-Node: Bash History Builtins\7f492906
-Node: History Interaction\7f499380
-Node: Event Designators\7f504333
-Node: Word Designators\7f505914
-Node: Modifiers\7f508309
-Node: Installing Bash\7f510249
-Node: Basic Installation\7f511368
-Node: Compilers and Options\7f515247
-Node: Compiling For Multiple Architectures\7f516000
-Node: Installation Names\7f517756
-Node: Specifying the System Type\7f519993
-Node: Sharing Defaults\7f520742
-Node: Operation Controls\7f521459
-Node: Optional Features\7f522481
-Node: Reporting Bugs\7f535207
-Node: Major Differences From The Bourne Shell\7f536567
-Node: GNU Free Documentation License\7f557997
-Node: Indexes\7f583177
-Node: Builtin Index\7f583631
-Node: Reserved Word Index\7f590732
-Node: Variable Index\7f593180
-Node: Function Index\7f610596
-Node: Concept Index\7f624594
+Node: Programmable Completion Builtins\7f472395
+Node: A Programmable Completion Example\7f484135
+Node: Using History Interactively\7f489483
+Node: Bash History Facilities\7f490167
+Node: Bash History Builtins\7f493905
+Node: History Interaction\7f500379
+Node: Event Designators\7f505332
+Node: Word Designators\7f506913
+Node: Modifiers\7f509308
+Node: Installing Bash\7f511248
+Node: Basic Installation\7f512367
+Node: Compilers and Options\7f516246
+Node: Compiling For Multiple Architectures\7f516999
+Node: Installation Names\7f518755
+Node: Specifying the System Type\7f520992
+Node: Sharing Defaults\7f521741
+Node: Operation Controls\7f522458
+Node: Optional Features\7f523480
+Node: Reporting Bugs\7f536206
+Node: Major Differences From The Bourne Shell\7f537566
+Node: GNU Free Documentation License\7f558996
+Node: Indexes\7f584176
+Node: Builtin Index\7f584630
+Node: Reserved Word Index\7f591731
+Node: Variable Index\7f594179
+Node: Function Index\7f611595
+Node: Concept Index\7f625593
\1f
End Tag Table
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[1] Chapter 2 [2]
[52]
[53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67]
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the traditional Unix shell originally written by Stephen Bourne.
All of the Bourne shell builtin commands are available in Bash, and
the rules for evaluation and quoting are taken from the @sc{posix}
-specification for the `standard' Unix shell.
+specification for the ``standard'' Unix shell.
-This chapter briefly summarizes the shell's `building blocks':
+This chapter briefly summarizes the shell's ``building blocks'':
commands, control structures, shell functions, shell @i{parameters},
shell expansions,
@i{redirections}, which are a way to direct input and output from
however, double quote characters have no special meaning.
If the redirection operator is @samp{<<-},
-the shell strips leading tab characters are stripped from input lines
+the shell strips leading tab characters from input lines
and the line containing @var{delimiter}.
This allows here-documents within shell scripts to be indented in a
natural fashion.
-If the delimiter is not quoted, the
+If the delimiter is not quoted, the shell treats the
@code{\<newline>}
-sequence is treated as a line continuation: the two lines are joined
+sequence as a line continuation: the two lines are joined
and the backslash-newline is removed.
This happens while reading the here-document, before the check for
the ending delimiter, so joined lines can form the end delimiter.
@item
The message printed by the job control code and builtins when a job
-exits with a non-zero status is `Done(status)'.
+exits with a non-zero status is ``Done(status)''.
@item
The message printed by the job control code and builtins when a job
-is stopped is `Stopped(@var{signame})', where @var{signame} is, for
+is stopped is ``Stopped(@var{signame})'', where @var{signame} is, for
example, @code{SIGTSTP}.
@item
@code{bashbug} command to submit a bug report or use the form at the
@uref{https://savannah.gnu.org/projects/bash/,Bash project page}.
If you have a fix, you are encouraged to submit that as well!
-Suggestions and `philosophical' bug reports may be mailed
+Suggestions and ``philosophical'' bug reports may be mailed
to @email{bug-bash@@gnu.org} or @email{help-bash@@gnu.org}.
All bug reports should include:
@item
A description of the bug behavior.
@item
-A short script or `recipe' which exercises the bug and may be used
+A short script or ``recipe'' which exercises the bug and may be used
to reproduce it.
@end itemize
c\bcd\bd [-\b-L\bL] [-\b-@\b@] [_\bd_\bi_\br]
c\bcd\bd -\b-P\bP [-\b-e\be] [-\b-@\b@] [_\bd_\bi_\br]
Change the current directory to _\bd_\bi_\br. if _\bd_\bi_\br is not supplied,
- the value of the H\bHO\bOM\bME\bE shell variable is used as _\bd_\bi_\br. The vari-
- able C\bCD\bDP\bPA\bAT\bTH\bH exists, and _\bd_\bi_\br does not begin with a slash (/), c\bcd\bd
- uses it as a search path: the shell searches each directory name
- in C\bCD\bDP\bPA\bAT\bTH\bH for _\bd_\bi_\br. Alternative directory names in C\bCD\bDP\bPA\bAT\bTH\bH are
- separated by a colon (:). A null directory name in C\bCD\bDP\bPA\bAT\bTH\bH is
- the same as the current directory, i.e.,
+ the value of the H\bHO\bOM\bME\bE shell variable is used as _\bd_\bi_\br. If _\bd_\bi_\br is
+ the empty string, c\bcd\bd treats it as an error. The variable C\bCD\bDP\bPA\bAT\bTH\bH
+ exists, and _\bd_\bi_\br does not begin with a slash (/), c\bcd\bd uses it as a
+ search path: the shell searches each directory name in C\bCD\bDP\bPA\bAT\bTH\bH
+ for _\bd_\bi_\br. Alternative directory names in C\bCD\bDP\bPA\bAT\bTH\bH are separated by
+ a colon (:). A null directory name in C\bCD\bDP\bPA\bAT\bTH\bH is the same as the
+ current directory, i.e.,
The -\b-P\bP option causes c\bcd\bd to use the physical directory structure
by resolving symbolic links while traversing _\bd_\bi_\br and before pro-
USE_VAR(asynchronous);
subshell_level++;
+ /* should_redir_stdin reflects whether we are executing an asynchronous
+ command terminated by a `&'. */
should_redir_stdin = (asynchronous && (command->flags & CMD_STDIN_REDIR) &&
pipe_in == NO_PIPE &&
+#if 0 /*TAG:bash-5.4 POSIX interp 1913 */
+ /* POSIX interp 1913 says that the redirection of fd 0
+ from /dev/null is unconditional. */
+ (posixly_correct || stdin_redirects (command->redirects) == 0));
+#else
stdin_redirects (command->redirects) == 0);
+#endif
invert = (command->flags & CMD_INVERT_RETURN) != 0;
user_subshell = command->type == cm_subshell || ((command->flags & CMD_WANT_SUBSHELL) != 0);
if we are currently in a subshell via `( xxx )', or if job
control is not active then the standard input for an
asynchronous command is forced to /dev/null. */
+ /* If we want to make this /dev/null redirection unconditional in posix
+ mode, change this to check posixly_correct */
#if defined (JOB_CONTROL)
+#if 0 /*TAG:bash-5.4 POSIX interp 1913 */
+ if (((subshell_environment || !job_control) && !stdin_redir) || posixly_correct)
+#else
if ((subshell_environment || !job_control) && !stdin_redir)
+#endif
+#else
+#if 0 /*TAG:bash-5.4 POSIX interp 1913 */
+ if (!stdin_redir || posixly_correct)
#else
if (!stdin_redir)
+#endif
#endif /* JOB_CONTROL */
tc->flags |= CMD_STDIN_REDIR;
{
if ((cmdflags & CMD_STDIN_REDIR) &&
pipe_in == NO_PIPE &&
+#if 0 /*TAG:bash-5.4 POSIX interp 1913 */
+ /* POSIX interp 1913 says that the redirection of fd 0
+ from /dev/null is unconditional. */
+ (posixly_correct || stdin_redirects (simple_command->redirects) == 0))
+#else
(stdin_redirects (simple_command->redirects) == 0))
+#endif
async_redirect_stdin ();
setup_async_signals ();
}
{
if ((cmdflags & CMD_STDIN_REDIR) &&
pipe_in == NO_PIPE &&
+#if 0 /*TAG:bash-5.4 POSIX interp 1913 */
+ /* POSIX interp 1913 says that the redirection of fd 0
+ from /dev/null is unconditional. */
+ (posixly_correct || stdin_redirects (redirects) == 0))
+#else
(stdin_redirects (redirects) == 0))
+#endif
async_redirect_stdin ();
setup_async_signals ();
}
if (_rl_echoing_p == 0)
return;
+ RL_SETSTATE (RL_STATE_REDISPLAYING);
/* Block keyboard interrupts because this function manipulates global
data structures. */
_rl_block_sigint ();
- RL_SETSTATE (RL_STATE_REDISPLAYING);
cur_face = FACE_NORMAL;
/* Can turn this into an array for multiple highlighted objects in addition
_rl_quick_redisplay = 0;
}
- RL_UNSETSTATE (RL_STATE_REDISPLAYING);
_rl_release_sigint ();
+ RL_UNSETSTATE (RL_STATE_REDISPLAYING);
}
static void
* Terminal Management:: Functions to manage terminal settings.
* Utility Functions:: Generally useful functions and hooks.
* Miscellaneous Functions:: Functions that don't fall into any category.
-* Alternate Interface:: Using Readline in a `callback' fashion.
+* Alternate Interface:: Using Readline in a ``callback'' fashion.
* A Readline Example:: An example Readline function.
* Alternate Interface Example:: An example program using the alternate interface.
@end menu
or window system I/O, typically by using a main loop to @code{select()}
on various file descriptors.
To accommodate this use case, Readline can
-also be invoked as a `callback' function from an event loop.
+also be invoked as a ``callback'' function from an event loop.
There are functions available to make this easy.
@deftypefun void rl_callback_handler_install (const char *prompt, rl_vcpfunc_t *line_handler)
The following paragraphs use Emacs style to
describe the notation used to represent keystrokes.
-The text @kbd{C-k} is read as `Control-K' and describes the character
+The text @kbd{C-k} is read as ``Control-K'' and describes the character
produced when the @key{k} key is pressed while the Control key
is depressed.
-The text @kbd{M-k} is read as `Meta-K' and describes the character
+The text @kbd{M-k} is read as ``Meta-K'' and describes the character
produced when the Meta key (if you have one) is depressed, and the @key{k}
key is pressed (a @dfn{meta character}), then both are released.
The Meta key is labeled @key{ALT} or @key{Option} on many keyboards.
(see @code{Key Bindings} in @ref{Readline Init File Syntax})
do the same thing by setting the @code{force-meta-prefix} variable.
-The text @kbd{M-C-k} is read as `Meta-Control-k' and describes the
+The text @kbd{M-C-k} is read as ``Meta-Control-k'' and describes the
character produced by metafying @kbd{C-k}.
In addition, several keys have their own names.
Afterwards, you can move the cursor to the right with @kbd{C-f}.
When you add text in the middle of a line, you will notice that characters
-to the right of the cursor are `pushed over' to make room for the text
+to the right of the cursor are ``pushed over'' to make room for the text
that you have inserted.
Likewise, when you delete text behind the cursor,
-characters to the right of the cursor are `pulled back' to fill in the
+characters to the right of the cursor are ``pulled back'' to fill in the
blank space created by the removal of the text.
These are the bare
essentials for editing the text of an input line:
@dfn{Killing} text means to delete the text from the line, but to save
it away for later use, usually by @dfn{yanking} (re-inserting)
it back into the line.
-(`Cut' and `paste' are more recent jargon for `kill' and `yank'.)
+(``Cut'' and ``paste'' are more recent jargon for ``kill'' and ``yank''.)
-If the description for a command says that it `kills' text, then you can
+If the description for a command says that it ``kills'' text, then you can
be sure that you can get the text back in a different (or the same)
place later.
For example, to kill text back to the
start of the line, you might type @samp{M-- C-k}.
-The general way to pass numeric arguments to a command is to type meta
-digits before the command.
-If the first `digit' typed is a minus
+The general way to pass numeric arguments to a command is to type
+the Meta key and then digits (``meta digits'')
+before the command.
+If the first ``digit'' typed is a minus
sign (@samp{-}), then the sign of the argument will be negative.
Once you have typed one meta digit to get the argument started, you can
type the remainder of the digits, and then the command.
to its original state.
@item previous-history (C-p)
-Move `back' through the history list, fetching the previous command.
+Move ``back'' through the history list, fetching the previous command.
This may also be bound to the up arrow key on some keyboards.
@item next-history (C-n)
-Move `forward' through the history list, fetching the next command.
+Move ``forward'' through the history list, fetching the next command.
This may also be bound to the down arrow key on some keyboards.
@item beginning-of-history (M-<)
being entered.
@item reverse-search-history (C-r)
-Search backward starting at the current line and moving `up' through
+Search backward starting at the current line and moving ``up'' through
the history as necessary.
This is an incremental search.
This command sets the region to the matched text and activates the region.
@item forward-search-history (C-s)
-Search forward starting at the current line and moving `down' through
+Search forward starting at the current line and moving ``down'' through
the history as necessary.
This is an incremental search.
This command sets the region to the matched text and activates the region.
@item non-incremental-reverse-search-history (M-p)
-Search backward starting at the current line and moving `up'
+Search backward starting at the current line and moving ``up''
+
through the history as necessary using a non-incremental search
for a string supplied by the user.
The search string may match anywhere in a history line.
@item non-incremental-forward-search-history (M-n)
-Search forward starting at the current line and moving `down'
+Search forward starting at the current line and moving ``down''
through the history as necessary using a non-incremental search
for a string supplied by the user.
The search string may match anywhere in a history line.
The Readline default is @code{emacs} mode.
When you enter a line in @code{vi} mode, you are already placed in
-`insertion' mode, as if you had typed an @samp{i}. Pressing @key{ESC}
-switches you into `command' mode, where you can edit the text of the
+``insertion'' mode, as if you had typed an @samp{i}. Pressing @key{ESC}
+switches you into ``command'' mode, where you can edit the text of the
line with the standard @code{vi} movement keys, move to previous
history lines with @samp{k} and subsequent lines with @samp{j}, and
so forth.
Backslash will escape a newline, if necessary.
These are added to the set of possible completions.
+External commands that are invoked to generate completions
+("external completers")
+receive the word preceding the completion word as an argument,
+as described above.
+This provides context that is sometimes useful, but may include
+information that is considered sensitive or part of a word expansion
+that will not appear in the command line after expansion.
+That word may be visible in process listings or in audit logs.
+This may be a concern to users and completion specification authors
+if there is sensitive information on the command line before
+expansion, since completion takes place before words are expanded.
+If this is an issue, completion authors should use functions as
+wrappers around external commands and pass context information to the
+external command in a different way.
+External completers can infer context from the @var{COMP_LINE}
+and @var{COMP_POINT} environment variables, but they need to ensure
+they break words in the same way Readline does, using the
+@var{COMP_WORDBREAKS} variable.
+
After generating all of the possible completions,
Bash applies any filter
specified with the @option{-X} option to the completions in the list.
@set EDITION 8.3
@set VERSION 8.3
-@set UPDATED 15 July 2025
-@set UPDATED-MONTH July 2025
+@set UPDATED 25 August 2025
+@set UPDATED-MONTH August 2025
-@set LASTCHANGE Tue Jul 15 10:18:40 EDT 2025
+@set LASTCHANGE Mon Aug 25 11:33:46 EDT 2025
{
if (rl_get_char (&c) == 0)
c = (*rl_getc_function) (rl_instream);
-if (_rl_caught_signal)
- {
-fprintf(stderr, "rl_read_key: calling RL_CHECK_SIGNALS: c = %d _rl_caught_signal = %d\r\n", c, _rl_caught_signal);
- if (c > 0)
- rl_stuff_char (c);
- c = -1;
- RL_CHECK_SIGNALS ();
- }
+ /* This can happen if rl_getc_function != rl_getc */
+ if (_rl_caught_signal)
+ {
+ if (c > 0)
+ rl_stuff_char (c);
+ c = -1;
+ RL_CHECK_SIGNALS ();
+ }
}
}
(*rl_signal_event_hook) ();
/* If the application's SIGINT handler returns, make sure we abort out of
searches and numeric arguments because we've freed necessary state. */
- if (osig == SIGINT && (ostate & (RL_STATE_ISEARCH|RL_STATE_NSEARCH|RL_STATE_NUMERICARG)))
+ if (osig == SIGINT && (ostate & (RL_STATE_ISEARCH|RL_STATE_NSEARCH|RL_STATE_NUMERICARG|RL_STATE_MOREINPUT)))
/* just these cases for now */
_rl_abort_internal ();
}
{
char *message;
size_t msglen, searchlen;
+ unsigned char c;
searchlen = (search_string && *search_string) ? strlen (search_string) : 0;
- message = (char *)xmalloc (searchlen + 64);
+ message = (char *)xmalloc (searchlen * 2 + 64);
msglen = 0;
#if defined (NOTDEF)
if (search_string && *search_string)
{
- strcpy (message + msglen, search_string);
- msglen += searchlen;
+ for ( ; c = *search_string; search_string++)
+ {
+ if (CTRL_CHAR (c) || c == RUBOUT)
+ {
+ message[msglen++] = '^';
+ c = CTRL_CHAR (c) ? UNCTRL (c) : '?';
+ }
+ message[msglen++] = c;
+ }
}
else
_rl_optimize_redisplay ();
/* Read a key and decide how to proceed. */
RL_SETSTATE(RL_STATE_MOREINPUT);
- c = cxt->lastc = rl_read_key ();
+ c = cxt->lastc = rl_read_key (); /* XXX */
RL_UNSETSTATE(RL_STATE_MOREINPUT);
#if defined (HANDLE_MULTIBYTE)
void
_rl_release_sigint (void)
{
+ int osig, ostate;
+
if (sigint_blocked == 0)
return;
sigint_blocked = 0;
+ osig = _rl_caught_signal;
+ ostate = rl_readline_state;
if (RL_ISSTATE (RL_STATE_SIGHANDLER) == 0)
RL_CHECK_SIGNALS ();
+ /* These are basically all the places that call rl_message() */
+ if (osig == SIGINT && (ostate & (RL_STATE_ISEARCH|RL_STATE_NSEARCH|RL_STATE_NUMERICARG|RL_STATE_MOREINPUT|RL_STATE_READSTR)))
+ _rl_abort_internal ();
}
int
rl_end = rl_point = 0;
p = _rl_make_prompt_for_search (pchar ? pchar : '@');
+
+ RL_SETSTATE (RL_STATE_READSTR);
cxt->flags |= READSTR_FREEPMT;
rl_message ("%s", p);
xfree (p);
- RL_SETSTATE (RL_STATE_READSTR);
-
_rl_rscxt = cxt;
return cxt;
alias: 0
alias: 0
-./alias.tests: line 38: qfoo: command not found
-./alias.tests: line 44: unalias: foo: not found
+./alias.tests: line 40: qfoo: command not found
+./alias.tests: line 46: unalias: foo: not found
quux
hi
declare -a m=([0]="x")
-./alias.tests: line 66: alias: `\$': invalid alias name
-./alias.tests: line 67: `\$': invalid alias name
+./alias.tests: line 68: alias: `\$': invalid alias name
+./alias.tests: line 69: `\$': invalid alias name
+ alias1.sub
bar
value
bar
OK
OK
OK
+ alias2.sub
one
two
three
two
three
four
+ alias3.sub
+ alias4.sub
Error: bar
ok 1
ok 2
bad
0
<|cat>
+ alias5.sub
foo
bar
baz
foo
bar
baz
+ alias6.sub
<áa>
<aá>
+ alias7.sub
bar
foo bar x
foo
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# place holder for future alias testing
+. ./test-aux-functions
+
shopt -s expand_aliases
# alias/unalias tests originally in builtins.tests
alias '\$'=xx
BASH_ALIASES['\$']=xx
-${THIS_SH} ./alias1.sub
-${THIS_SH} ./alias2.sub
-${THIS_SH} ./alias3.sub
-${THIS_SH} ./alias4.sub
-${THIS_SH} ./alias5.sub
-${THIS_SH} ./alias6.sub
-${THIS_SH} ./alias7.sub
+test_runsub ./alias1.sub
+test_runsub ./alias2.sub
+test_runsub ./alias3.sub
+test_runsub ./alias4.sub
+test_runsub ./alias5.sub
+test_runsub ./alias6.sub
+test_runsub ./alias7.sub
4
9
16
-./appendop.tests: line 97: x: readonly variable
+./appendop.tests: line 99: x: readonly variable
+ appendop1.sub
declare -A foo=([two]="baz" [three]="quux" [one]="bar" )
declare -A foo=([0]="zero" [two]="baz" [three]="quux" [one]="bar" )
declare -A foo=([four]="four" [0]="zero" [two]="baz" [three]="quux" [one]="bar" )
declare -ai iarr=([0]="3" [1]="2" [2]="3")
declare -ai iarr=([0]="3" [1]="2" [2]="3" [3]="4" [4]="5" [5]="6")
+ appendop2.sub
25 25
7 7
14
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
+. ./test-aux-functions
+
# basic cases
a=1
a+=4
x+=5
-${THIS_SH} ./appendop1.sub
-${THIS_SH} ./appendop2.sub
+test_runsub ./appendop1.sub
+test_runsub ./appendop2.sub
1,i+=2
30
1,j+=2
-./arith.tests: line 129: 1 ? 20 : x+=2: attempted assignment to non-variable (error token is "+=2")
+./arith.tests: line 131: 1 ? 20 : x+=2: attempted assignment to non-variable (error token is "+=2")
20
6
6,5,3
36
62
63
-./arith.tests: line 168: 3425#56: invalid arithmetic base (error token is "3425#56")
-./arith.tests: line 171: 2#: invalid integer constant (error token is "2#")
-./arith.tests: line 174: 7 = 43 : attempted assignment to non-variable (error token is "= 43 ")
-./arith.tests: line 175: 2#44: value too great for base (error token is "2#44")
-./arith.tests: line 176: 44 / 0 : division by 0 (error token is "0 ")
-./arith.tests: line 177: let: jv += $iv: arithmetic syntax error: operand expected (error token is "$iv")
-./arith.tests: line 178: jv += $iv : arithmetic syntax error: operand expected (error token is "$iv ")
-./arith.tests: line 179: let: rv = 7 + (43 * 6: missing `)' (error token is "6")
-./arith.tests: line 182: b / 0 : division by 0 (error token is "0 ")
-./arith.tests: line 183: b /= 0 : division by 0 (error token is "0 ")
-./arith.tests: line 188: 0#4: invalid number (error token is "0#4")
-./arith.tests: line 189: 2#110#11: invalid number (error token is "2#110#11")
+./arith.tests: line 170: 3425#56: invalid arithmetic base (error token is "3425#56")
+./arith.tests: line 173: 2#: invalid integer constant (error token is "2#")
+./arith.tests: line 176: 7 = 43 : attempted assignment to non-variable (error token is "= 43 ")
+./arith.tests: line 177: 2#44: value too great for base (error token is "2#44")
+./arith.tests: line 178: 44 / 0 : division by 0 (error token is "0 ")
+./arith.tests: line 179: let: jv += $iv: arithmetic syntax error: operand expected (error token is "$iv")
+./arith.tests: line 180: jv += $iv : arithmetic syntax error: operand expected (error token is "$iv ")
+./arith.tests: line 181: let: rv = 7 + (43 * 6: missing `)' (error token is "6")
+./arith.tests: line 184: b / 0 : division by 0 (error token is "0 ")
+./arith.tests: line 185: b /= 0 : division by 0 (error token is "0 ")
+./arith.tests: line 190: 0#4: invalid number (error token is "0#4")
+./arith.tests: line 191: 2#110#11: invalid number (error token is "2#110#11")
abc
def
ghi
6
1
0
-./arith.tests: line 207: 4 + : arithmetic syntax error: operand expected (error token is "+ ")
+./arith.tests: line 209: 4 + : arithmetic syntax error: operand expected (error token is "+ ")
16
-./arith.tests: line 212: 4 ? : 3 + 5 : expression expected (error token is ": 3 + 5 ")
-./arith.tests: line 213: 1 ? 20 : `:' expected for conditional expression (error token is "20 ")
-./arith.tests: line 214: 4 ? 20 : : expression expected (error token is ": ")
+./arith.tests: line 214: 4 ? : 3 + 5 : expression expected (error token is ": 3 + 5 ")
+./arith.tests: line 215: 1 ? 20 : `:' expected for conditional expression (error token is "20 ")
+./arith.tests: line 216: 4 ? 20 : : expression expected (error token is ": ")
9
-./arith.tests: line 220: 0 && B=42 : attempted assignment to non-variable (error token is "=42 ")
+./arith.tests: line 222: 0 && B=42 : attempted assignment to non-variable (error token is "=42 ")
9
-./arith.tests: line 223: 1 || B=88 : attempted assignment to non-variable (error token is "=88 ")
+./arith.tests: line 225: 1 || B=88 : attempted assignment to non-variable (error token is "=88 ")
9
0
9
131072
2147483647
1
-./arith.tests: line 255: 2**-1 : exponent less than 0 (error token is "1 ")
+./arith.tests: line 257: 2**-1 : exponent less than 0 (error token is "1 ")
4
4
5
4
4
7
-./arith.tests: line 274: 7-- : arithmetic syntax error: operand expected (error token is "- ")
-./arith.tests: line 276: --x=7 : attempted assignment to non-variable (error token is "=7 ")
-./arith.tests: line 277: ++x=7 : attempted assignment to non-variable (error token is "=7 ")
-./arith.tests: line 279: x++=7 : attempted assignment to non-variable (error token is "=7 ")
-./arith.tests: line 280: x--=7 : attempted assignment to non-variable (error token is "=7 ")
+./arith.tests: line 276: 7-- : arithmetic syntax error: operand expected (error token is "- ")
+./arith.tests: line 278: --x=7 : attempted assignment to non-variable (error token is "=7 ")
+./arith.tests: line 279: ++x=7 : attempted assignment to non-variable (error token is "=7 ")
+./arith.tests: line 281: x++=7 : attempted assignment to non-variable (error token is "=7 ")
+./arith.tests: line 282: x--=7 : attempted assignment to non-variable (error token is "=7 ")
4
7
-7
7
7
-./arith.tests: line 292: --x++ : ++: assignment requires lvalue (error token is "++ ")
+./arith.tests: line 294: --x++ : ++: assignment requires lvalue (error token is "++ ")
2
2
+ arith1.sub
./arith1.sub: line 15: 4-- : arithmetic syntax error: operand expected (error token is "- ")
./arith1.sub: line 16: 4++ : arithmetic syntax error: operand expected (error token is "+ ")
./arith1.sub: line 17: 4 -- : arithmetic syntax error: operand expected (error token is "- ")
7
7
./arith1.sub: line 51: ((: -- : arithmetic syntax error: operand expected (error token is "- ")
+ arith2.sub
7
7
7
-7
7
7
+ arith3.sub
1
1
4
4
5000
5000
+ arith4.sub
1
0
0
1
2147483649
+ arith5.sub
0
0
0
-9223372036854775808
-9223372036854775808
9223372036854775805 9223372036854775806 9223372036854775807
+ arith6.sub
123 456
123 456
123 456
0
0, 0
0, 1
+ arith7.sub
efg
e
efg
e
abcdefg
efg
+ arith8.sub
0
0
0
0
0
0
+ arith9.sub
./arith9.sub: line 4: a: unbound variable
./arith9.sub: line 5: a: unbound variable
0
+ set +x
./arith9.sub: line 37: 4+: arithmetic syntax error: operand expected (error token is "+")
x = 4+ y =
+ arith10.sub
== arraysub ==
=== assoc_expand_once unset ===
declare -a a=([0]="10")
3 1
./arith10.sub: line 95: let: 0 - "": arithmetic syntax error: operand expected (error token is """")
4 1
+ arith11.sub
0
declare -a yy=([0]="10")
Y
./arith11.sub: line 65: 'foo' : arithmetic syntax error: operand expected (error token is "'foo' ")
8 12
-./arith.tests: line 338: ((: x=9 y=41 : arithmetic syntax error in expression (error token is "y=41 ")
-./arith.tests: line 342: a b: arithmetic syntax error in expression (error token is "b")
-./arith.tests: line 343: ((: a b: arithmetic syntax error in expression (error token is "b")
+./arith.tests: line 340: ((: x=9 y=41 : arithmetic syntax error in expression (error token is "y=41 ")
+./arith.tests: line 344: a b: arithmetic syntax error in expression (error token is "b")
+./arith.tests: line 345: ((: a b: arithmetic syntax error in expression (error token is "b")
42
42
42
42
42
42
-./arith.tests: line 358: 'foo' : arithmetic syntax error: operand expected (error token is "'foo' ")
-./arith.tests: line 361: b[c]d: arithmetic syntax error in expression (error token is "d")
+./arith.tests: line 360: 'foo' : arithmetic syntax error: operand expected (error token is "'foo' ")
+./arith.tests: line 363: b[c]d: arithmetic syntax error in expression (error token is "d")
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
+. ./test-aux-functions
+
set +o posix
declare -i iv jv
echo $(( "`echo 1+1`" ))
echo $(( `echo 1+1` ))
-${THIS_SH} ./arith1.sub
-${THIS_SH} ./arith2.sub
-${THIS_SH} ./arith3.sub
-${THIS_SH} ./arith4.sub
+test_runsub ./arith1.sub
+test_runsub ./arith2.sub
+test_runsub ./arith3.sub
+test_runsub ./arith4.sub
# make sure arithmetic expansion handles ints > 2**31 - 1 using intmax_t
echo $(( 2147483645 + 4 ))
# other tests using INTMAX_MIN and INTMAX_MAX that cause exceptions if not
# handled correctly -- problem through bash-4.2
-${THIS_SH} ./arith5.sub
+test_runsub ./arith5.sub
# problems with suppressing evaluation present through bash-4.2
-${THIS_SH} ./arith6.sub
+test_runsub ./arith6.sub
# problems with parsing arithmetic expressions containing colons that are
# part of word expansions such as substring extraction
-${THIS_SH} ./arith7.sub
+test_runsub ./arith7.sub
# problems with evaluation of conditional expressions
-${THIS_SH} ./arith8.sub
+test_runsub ./arith8.sub
# expressions with unset variables and nounset enabled
-${THIS_SH} ./arith9.sub
+test_runsub ./arith9.sub
# empty expressions in various arithmetic evaluation contexts
-${THIS_SH} ./arith10.sub
+test_runsub ./arith10.sub
# internal quoting for array subscripts
-${THIS_SH} ./arith11.sub
+test_runsub ./arith11.sub
x=4
y=7
-./array.tests: line 34: syntax error near unexpected token `&'
-./array.tests: line 34: `test=(first & second)'
+./array.tests: line 35: syntax error near unexpected token `&'
+./array.tests: line 35: `test=(first & second)'
1
abcde
abcde
abcde bdef
abcde bdef
-declare -a BASH_ARGC=()
+declare -a BASH_ARGC=([0]="0")
declare -a BASH_ARGV=()
declare -a BASH_LINENO=([0]="0")
declare -a BASH_SOURCE=([0]="./array.tests")
11
3
bdef hello world test expression test 2
-./array.tests: line 98: readonly: `a[5]': not a valid identifier
+./array.tests: line 99: readonly: `a[5]': not a valid identifier
declare -ar a=([1]="" [2]="bdef" [5]="hello world" [6]="test expression" [15]="test 2")
declare -ar c
declare -ar a=([1]="" [2]="bdef" [5]="hello world" [6]="test expression" [15]="test 2")
readonly -a a=([1]="" [2]="bdef" [5]="hello world" [6]="test expression" [15]="test 2")
readonly -a c
a test
-declare -a BASH_ARGC=()
+declare -a BASH_ARGC=([0]="0")
declare -a BASH_ARGV=()
declare -a BASH_LINENO=([0]="0")
declare -a BASH_SOURCE=([0]="./array.tests")
declare -a d=([1]="" [2]="bdef" [5]="hello world" [6]="test" [9]="ninth element")
declare -a e=([0]="test")
declare -a f=([0]="" [1]="bdef" [2]="hello world" [3]="test" [4]="ninth element")
-./array.tests: line 122: a: readonly variable
-./array.tests: line 124: b[]: bad array subscript
-./array.tests: line 125: b[*]: bad array subscript
+./array.tests: line 123: a: readonly variable
+./array.tests: line 125: b[]: bad array subscript
+./array.tests: line 126: b[*]: bad array subscript
this
-./array.tests: line 128: c[-2]: bad array subscript
-./array.tests: line 129: c: bad array subscript
+./array.tests: line 129: c[-2]: bad array subscript
+./array.tests: line 130: c: bad array subscript
-./array.tests: line 131: d[7]: cannot assign list to array member
-./array.tests: line 133: []=abcde: bad array subscript
-./array.tests: line 134: [*]=last: cannot assign to non-numeric index
-./array.tests: line 135: [-65]=negative: bad array subscript
-declare -a BASH_ARGC=()
+./array.tests: line 132: d[7]: cannot assign list to array member
+./array.tests: line 134: []=abcde: bad array subscript
+./array.tests: line 135: [*]=last: cannot assign to non-numeric index
+./array.tests: line 136: [-65]=negative: bad array subscript
+declare -a BASH_ARGC=([0]="0")
declare -a BASH_ARGV=()
declare -a BASH_LINENO=([0]="0")
declare -a BASH_SOURCE=([0]="./array.tests")
declare -a d=([1]="test test")
declare -a e=()
declare -a f=([0]="" [1]="bdef" [2]="hello world" [3]="test" [4]="ninth element")
-./array.tests: line 143: unset: ps1: not an array variable
-./array.tests: line 147: declare: c: readonly variable
+./array.tests: line 144: unset: ps1: not an array variable
+./array.tests: line 148: declare: c: readonly variable
this of
this is a test of read using arrays
this test
this is a test of arrays
-declare -a BASH_ARGC=()
+declare -a BASH_ARGC=([0]="0")
declare -a BASH_ARGV=()
declare -a BASH_LINENO=([0]="0")
declare -a BASH_SOURCE=([0]="./array.tests")
55
49
6 -- 6
-./array.tests: line 238: [-10]: bad array subscript
+./array.tests: line 239: [-10]: bad array subscript
0
42 14 44
grep [ 123 ] *
6 7 9 5
length = 3
value = new1 new2 new3
-./array.tests: line 267: syntax error near unexpected token `&'
-./array.tests: line 267: `badarray=( metacharacters like & need to be quoted in compound assignments)'
-./array.tests: line 271: narray[4]: unbound variable
+./array.tests: line 268: syntax error near unexpected token `&'
+./array.tests: line 268: `badarray=( metacharacters like & need to be quoted in compound assignments)'
+./array.tests: line 272: narray[4]: unbound variable
+ array1.sub
./array1.sub: line 1: syntax error near unexpected token `('
./array1.sub: line 1: `printf "%s\n" -a a=(a 'b c')'
+ array2.sub
./array2.sub: line 1: declare: `[]=asdf': not a valid identifier
./array2.sub: line 2: a[]: bad array subscript
./array2.sub: line 4: syntax error near unexpected token `('
./array2.sub: line 4: `declare -a ''=(a 'b c')'
+ array3.sub
9
9
7 8 9
+ array4.sub
8 11
8 11
6
12 14 16 18 20
4414758999202
aaa bbb
-./array.tests: line 321: syntax error near unexpected token `<>'
-./array.tests: line 321: `metas=( <> < > ! )'
./array.tests: line 322: syntax error near unexpected token `<>'
-./array.tests: line 322: `metas=( [1]=<> [2]=< [3]=> [4]=! )'
+./array.tests: line 322: `metas=( <> < > ! )'
+./array.tests: line 323: syntax error near unexpected token `<>'
+./array.tests: line 323: `metas=( [1]=<> [2]=< [3]=> [4]=! )'
abc 3
case 4
abc case if then else 5
FIN4:0
FIN5:0
FIN6:0
+ array5.sub
t
[3]=abcde r s t u v
e
9
2
+ array6.sub
a b c
argv[1] = <-iname 'a>
argv[2] = <-iname 'b>
argv[2] = <element2 with spaces>
argv[1] = <element1 with spaces>
argv[2] = <element2 with spaces>
+ array7.sub
nord!olz
rdholz
rdho
+ array8.sub
argv[1] = <fooq//barq/>
argv[1] = <fooq>
argv[2] = <>
argv[2] = <>
argv[3] = <BARQ>
argv[4] = <>
+ array9.sub
126
127
128
argv[1] = <~>
argv[2] = <^?>
argv[3] = <\80>
+ array10.sub
Monday Tuesday Wednesday Thursday Friday Saturday Sunday
Monday
Monday
onday
uesday
ednesday
+ array11.sub
version[agent]
version.agent
version[agent]
bleh bbb bleh
ab]
bar
+ array12.sub
1
1
1
1
1
1
+ array13.sub
main main
function function
function function
+ array14.sub
declare -a x=([0]="0" [1]="1" [2]="2" [3]="3" [4]="4" [5]="5")
declare -a x=([0]="0" [1]="1" [2]="2" [3]="3" [4]="4")
declare -a x=([0]="0" [1]="1" [2]="2" [4]="4")
declare -a x=([0]="0" [1]="1" [2]="2" [3]="3" [4]="4" [5]="5")
declare -a x=([0]="0" [1]="1" [2]="2" [3]="3" [4]="4four" [5]="5")
strlen(4four) = 5
+ array15.sub
1 2 0 3
1 2 0 3
1 2 0 3
1 2 0 3
declare -ai arr=([0]="2" [1]="4" [2]="6")
declare -a arr=([0]="hello" [1]="world")
+ array16.sub
foo index 1: ok
foo index 2: ok
foo: implicit reference to element 0: ok
0
0
0
+ array17.sub
2
2
2
two
two
./array17.sub: line 89: ~ : arithmetic syntax error: operand expected (error token is "~ ")
+ array18.sub
1
argv[1] = <>
argv[2] = <>
argv[1] = <->
argv[2] = <->
argv[1] = < >
+ array19.sub
declare -a foo=([0]="( zeroind )")
declare -a foo=([0]="zeroind")
declare -a foo=([0]="zeroind")
declare -A c=([1]="2" )
declare -A d=(["a b"]="" )
declare -A e=([Darwin]="" )
+ array20.sub
a+b+c
x+b+c
a+b+c
x b c
a b c
x b c
+ array21.sub
declare -a a=([1]="2" [2]="3" [3]="4")
abcd
unset
declare -a a=()
declare -A A=()
declare -a foo=([0]="1" [1]="(4 5 6)" [2]="3")
+ array22.sub
a1
argv[1] = <>
argv[2] = <>
argv[1] = <y>
<X> <X> <X> <X>
<X> <X> <X> <X>
+ array23.sub
./array23.sub: line 22: $( echo >&2 foo ) : arithmetic syntax error: operand expected (error token is "$( echo >&2 foo ) ")
./array23.sub: line 23: $( echo >&2 foo ) : arithmetic syntax error: operand expected (error token is "$( echo >&2 foo ) ")
./array23.sub: line 24: $( echo >&2 foo ) : arithmetic syntax error: operand expected (error token is "$( echo >&2 foo ) ")
0
0
0
+ array24.sub
IFS=: ${var-$*}
abc
def ghi
abc
def ghi
jkl
+ array25.sub
1. indexed:
reference:
1. 0
6.declare -A a=([1]="1" [0]="0" [" "]="10" ["\" \""]="11" )
7.declare -A a=([1]="1" [0]="0" [" "]="12" ["\" \""]="11" )
8.declare -A a=([1]="1" [0]="0" [" "]="12" ["\" \""]="13" )
+ array26.sub
argv[1] = <aa>
argv[2] = <bb>
argv[1] = <aa>
argv[1] = <b>
argv[2] = <a>
argv[1] = <b+a>
+ array27.sub
7
7
declare -A A=([$'\t']="2" [" "]="2" )
declare -A A=(["*"]="X" ["@"]="X" )
./array27.sub: line 81: y[]: bad array subscript
./array27.sub: line 81: y[]: bad array subscript
+ array28.sub
declare -a bug4=([0]="" [1]="5" [2]="" [3]="1" [4]="")
declare -a bug=([0]="" [1]="5" [2]="" [3]="1" [4]="")
declare -a bug2=([0]="")
declare -a bug3=([0]="" [1]="5" [2]="" [3]="1" [4]="")
declare -a not_bug=([0]="no" [1]="nulls")
declare -a workaround=([0]="")
+ array29.sub
declare -a var=([0]=$'\001\001\001\001')
declare -A v2=([$'\001']=$'ab\001c' )
declare -a foo=([0]=$'\001\001\001\001')
declare -A foo=([v]=$'\001\001\001\001' )
declare -A foo=([$'\001']=$'ab\001c' )
declare -A foo=([$'\001']=$'ab\001c' )
+ array30.sub
foo
declare -a a=([42]="foo")
foo
declare -Au A=([Darwin]="FOO" )
FOO
declare -Au A=(["@"]="FOO" )
+ array31.sub
declare -a aa=([0]="/homes/cj/Desktop")
declare -a aa=([0]="/homes/cj/Desktop")
declare -a aa=([0]="/homes/cj/Desktop:/homes/cj/Library:/homes/cj/Documents")
declare -a aa=([0]="/homes/cj/Desktop:/homes/cj/Library:/homes/cj/Documents")
declare -a aa=([0]="/homes/cj/Desktop:/homes/cj/Library:/homes/cj/Documents" [1]="/homes/cj/Applications")
declare -a aa=([0]="/homes/cj/Desktop:/homes/cj/Library:/homes/cj/Documents" [1]="/homes/cj/Applications")
+ array32.sub
./array32.sub: line 20: $(echo INJECTION! >&2 ; echo 0): arithmetic syntax error: operand expected (error token is "$(echo INJECTION! >&2 ; echo 0)")
./array32.sub: line 21: declare: a: not found
./array32.sub: line 24: $(echo INJECTION! >&2 ; echo 0): arithmetic syntax error: operand expected (error token is "$(echo INJECTION! >&2 ; echo 0)")
declare -a a=()
./array32.sub: line 95: $(echo INJECTION! >&2 ; echo 0): arithmetic syntax error: operand expected (error token is "$(echo INJECTION! >&2 ; echo 0)")
declare -a a=()
+ array33.sub
declare -A A=([x]="x" )
declare -A A=([1]="1" )
./array33.sub: line 27: f: A: cannot convert associative to indexed array
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
+. ./test-aux-functions
# Filter stdin to remove builtin array variables that are
# automatically set and possibly contain values that vary.
set -u
( echo ${#narray[4]} )
-${THIS_SH} ./array1.sub
-${THIS_SH} ./array2.sub
+test_runsub ./array1.sub
+test_runsub ./array2.sub
# some old bugs and ksh93 compatibility tests
-${THIS_SH} ./array3.sub
+test_runsub ./array3.sub
# some compound assignment parsing problems that showed up in bash-3.1-release
-${THIS_SH} ./array4.sub
+test_runsub ./array4.sub
set +u
cd ${TMPDIR:=/tmp}
declare BASH_ARGV[1]=foo ; echo FIN6:$?
# tests for bash-3.1 problems
-${THIS_SH} ./array5.sub
+test_runsub ./array5.sub
# tests for post-bash-3.2 problems, most fixed in bash-3.2 patches
-${THIS_SH} ./array6.sub
-${THIS_SH} ./array7.sub
-
-${THIS_SH} ./array8.sub
-${THIS_SH} ./array9.sub
-${THIS_SH} ./array10.sub
-${THIS_SH} ./array11.sub
-${THIS_SH} ./array12.sub
-${THIS_SH} ./array13.sub
-${THIS_SH} ./array14.sub
-${THIS_SH} ./array15.sub
-${THIS_SH} ./array16.sub
-${THIS_SH} ./array17.sub
-${THIS_SH} ./array18.sub
-${THIS_SH} ./array19.sub
-${THIS_SH} ./array20.sub
-${THIS_SH} ./array21.sub
-${THIS_SH} ./array22.sub
-${THIS_SH} ./array23.sub
-${THIS_SH} ./array24.sub
-${THIS_SH} ./array25.sub
-${THIS_SH} ./array26.sub
-${THIS_SH} ./array27.sub
-${THIS_SH} ./array28.sub
-${THIS_SH} ./array29.sub
-${THIS_SH} ./array30.sub
-${THIS_SH} ./array31.sub
-${THIS_SH} ./array32.sub
-${THIS_SH} ./array33.sub
+test_runsub ./array6.sub
+test_runsub ./array7.sub
+
+test_runsub ./array8.sub
+test_runsub ./array9.sub
+test_runsub ./array10.sub
+test_runsub ./array11.sub
+test_runsub ./array12.sub
+test_runsub ./array13.sub
+test_runsub ./array14.sub
+test_runsub ./array15.sub
+test_runsub ./array16.sub
+test_runsub ./array17.sub
+test_runsub ./array18.sub
+test_runsub ./array19.sub
+test_runsub ./array20.sub
+test_runsub ./array21.sub
+test_runsub ./array22.sub
+test_runsub ./array23.sub
+test_runsub ./array24.sub
+test_runsub ./array25.sub
+test_runsub ./array26.sub
+test_runsub ./array27.sub
+test_runsub ./array28.sub
+test_runsub ./array29.sub
+test_runsub ./array30.sub
+test_runsub ./array31.sub
+test_runsub ./array32.sub
+test_runsub ./array33.sub
declare -A fluff=([foo]="one" [bar]="two" )
declare -A fluff=([bar]="two" )
declare -A fluff=([qux]="assigned" [bar]="newval" )
-./assoc.tests: line 39: chaff: four: must use subscript when assigning associative array
+./assoc.tests: line 41: chaff: four: must use subscript when assigning associative array
declare -A BASH_ALIASES=()
declare -A BASH_CMDS=()
declare -Ai chaff=([one]="10" [zero]="5" )
-declare -Ar waste=([pid]="42134" [lineno]="41" [source]="./assoc.tests" [version]="4.0-devel" )
+declare -Ar waste=([pid]="42134" [lineno]="43" [source]="./assoc.tests" [version]="4.0-devel" )
declare -A wheat=([two]="b" [three]="c" [one]="a" [zero]="0" )
declare -A chaff=(["hello world"]="flip" [one]="10" [zero]="5" )
-./assoc.tests: line 51: waste: readonly variable
-./assoc.tests: line 52: unset: waste: cannot unset: readonly variable
+./assoc.tests: line 53: waste: readonly variable
+./assoc.tests: line 54: unset: waste: cannot unset: readonly variable
declare -A chaff=(["*"]="12" ["hello world"]="flip" [one]="a" )
flip
argv[1] = <multiple>
argv[4] = <flip>
argv[5] = <a>
argv[1] = <multiple words 12 flip a>
-./assoc.tests: line 71: declare: chaff: cannot destroy array variables in this way
+./assoc.tests: line 73: declare: chaff: cannot destroy array variables in this way
declare -A wheat=([six]="6" ["foo bar"]="qux qix" )
argv[1] = <qux>
argv[2] = <qix>
argv[1] = <qux qix>
declare -A wheat=([six]="6" ["foo bar"]="qux qix" )
argv[1] = <2>
-./assoc.tests: line 99: [$unset]: bad array subscript
+./assoc.tests: line 101: [$unset]: bad array subscript
0
argv[1] = <7>
argv[1] = <qux>
\usr\local\bin \bin . \usr\bin \usr\ucb \usr\sbin \bin \sbin
\usr\local\bin \bin . \usr\bin \usr\ucb \usr\sbin \bin \sbin
([a]=1)
+ assoc1.sub
foo qux
/usr/sbin/foo /usr/local/bin/qux
0 /usr/local/bin/qux
foo sh blat qux
/usr/sbin/foo /bin/sh /sbin/blat /usr/local/bin/qux
+ assoc2.sub
foo qux
argv[1] = </usr/sbin/foo>
argv[2] = </usr/sbin/foo>
argv[3] = </bin/bash --login -o posix>
argv[4] = </usr/local/bin/qux -l>
+ assoc3.sub
outside: outside
declare -A BASH_ALIASES=()
declare -A BASH_CMDS=()
argv[2] = <six>
argv[3] = <foo quux>
outside 2: outside
+ assoc4.sub
argv[1] = </barq//fooq>
argv[1] = <>
argv[2] = <barq>
argv[2] = <BARQ>
argv[3] = <>
argv[4] = <FOOQ>
+ assoc5.sub
abc
def
def
123
myarray=(["]"]="def" ["a]=test2;#a"]="def" [foo]="bleh" ["a]a"]="abc" ["a]=test1;#a"]="123" )
+ assoc6.sub
bar"bie
doll
declare -A foo=(["bar\"bie"]="doll" )
bar${foo}bie
doll
declare -A foo=(["bar\${foo}bie"]="doll" )
+ assoc7.sub
bar
after printf
after use: 0
declare -Ar assoc=([two]="twoless" [three]="three" [one]="onemore" )
declare -A hash=([key]="value1" )
declare -A hash=([key]="value1 value2" )
+ assoc8.sub
+ assoc9.sub
declare -A b=([")"]="" ["\""]="" ["]"]="" ["\\"]="" ["\`"]="" )
declare -A b=(["]"]="" ["\`"]="" )
declare -A dict=(["'"]="3" ["\""]="1" ["\\"]="4" ["\`"]="2" )
foo]bar
bip
declare -A foo=(["foo]bar"]="bip" )
+ assoc10.sub
./assoc10.sub: line 14: declare: a: cannot convert indexed to associative array
f: declare -a a
./assoc10.sub: line 17: declare: a: cannot convert associative to indexed array
main: declare -- a="7"
f: declare -A a
main: declare -- a="42"
+ assoc11.sub
declare -A a=([3]="" [1]="2" )
declare -A foo=([d]="4" [c]="3" [b]="2" [a]="1" )
foo=( d "4" c "3" b "2" a "1" )
declare -A a=([")"]="rparen" ["\""]="dquote" ["]"]="rbracket" ["\\"]="bs" )
declare -Arx foo=([two]="2" [three]="3" [one]="1" )
./assoc11.sub: line 90: foo: readonly variable
+ assoc12.sub
declare -A v1=(["1 2"]="3" )
declare -A v2=(["1 2"]="3" )
declare -A v3=(["1 2"]="3" )
declare -A v1=(["20 40 80"]="new xtra" ["1 2"]="3 4 5" )
declare -A v2=(["20 40 80"]="new xtra" ["1 2"]="3 4 5" )
declare -A v3=(["1 2"]="3 4 5" ["\$xtra"]="new xtra" )
+ assoc13.sub
declare -A assoc=(["*"]="star" ["!"]="bang" ["@"]="at" )
at
star
declare -A a=(["@"]="at2" )
declare -A a=(["@"]=" string" )
declare -A a=(["*"]="star2" ["@"]="at" )
+ assoc14.sub
declare -A assoc=([hello]="world" ["key with spaces"]="value with spaces" [foo]="bar" [one]="1" )
argv[1] = <world>
argv[2] = <value with spaces>
argv[8] = <'bar'>
declare -A clone=([hello]="world" ["key with spaces"]="value with spaces" [foo]="bar" [one]="1" )
declare -A posparams=([hello]="world" ["key with spaces"]="value with spaces" [foo]="bar" [one]="1" )
+ assoc15.sub
declare -A var=([$'\001']=$'\001\001\001\001' )
declare -A v2=([$'\001']=$'\001\001\001\001' )
argv[1] = <^A>
declare -A foo=([two]=$'ab\001cd' [one]=$'\001\001\001\001' )
declare -A foo=([$'\001']=$'ab\001cd' )
declare -A foo=([$'\001']=$'\001\001\001\001' )
+ assoc16.sub
declare -A A=(["\$(echo Darwin ; echo stderr>&2)"]="darjeeling" [Darwin]="darjeeling" )
stderr
darjsharking
stderr
42
42
+ assoc17.sub
declare -A A=(["]"]="rbracket" ["["]="lbracket" )
declare -A A=()
declare -A A=(["]"]="rbracket" ["["]="lbracket" )
declare -A A=()
declare -A A=(["]"]="rbracket" ["["]="lbracket" )
declare -A A=()
+ assoc18.sub
declare -A A=(["]"]="rbracket" ["["]="lbracket" )
declare -A A=()
declare -A A=(["]"]="rbracket" ["["]="lbracket" )
declare -A A=()
5: ok 1
+ assoc19.sub
declare -A aa=([key]="/homes/cj/Desktop" )
declare -A aa=([key]="/homes/cj/Desktop" )
declare -A aa=([k2]="/homes/cj/Library" [key]="/homes/cj/Desktop" )
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
+. ./test-aux-functions
+
# TEST - basic declaration and assignment
typeset -A fluff
declare -A
echo 'assoc.tests: $T and ${T[0]} mismatch'
fi
-${THIS_SH} ./assoc1.sub
+test_runsub ./assoc1.sub
-${THIS_SH} ./assoc2.sub
+test_runsub ./assoc2.sub
-${THIS_SH} ./assoc3.sub
+test_runsub ./assoc3.sub
-${THIS_SH} ./assoc4.sub
+test_runsub ./assoc4.sub
-${THIS_SH} ./assoc5.sub
+test_runsub ./assoc5.sub
-${THIS_SH} ./assoc6.sub
+test_runsub ./assoc6.sub
-${THIS_SH} ./assoc7.sub
+test_runsub ./assoc7.sub
# test converting between scalars and assoc arrays
unset assoc
unset hash
-${THIS_SH} ./assoc8.sub
+test_runsub ./assoc8.sub
# new shopt option to prevent multiple expansion of assoc array subscripts
-${THIS_SH} ./assoc9.sub
+test_runsub ./assoc9.sub
-${THIS_SH} ./assoc10.sub
+test_runsub ./assoc10.sub
# test assigning associative arrays using compound key/value pair assignments
-${THIS_SH} ./assoc11.sub
+test_runsub ./assoc11.sub
# more kvpair associative array assignment tests
-${THIS_SH} ./assoc12.sub
+test_runsub ./assoc12.sub
# assignment to @ and *
-${THIS_SH} ./assoc13.sub
+test_runsub ./assoc13.sub
# tests of the @k transformation on associative arrays
-${THIS_SH} ./assoc14.sub
+test_runsub ./assoc14.sub
# tests with subscripts and values containing 0x01 (some indexed array tests too)
-${THIS_SH} ./assoc15.sub
+test_runsub ./assoc15.sub
# tests with subscripts being expanded more than one in ${xxx} word expansions
-${THIS_SH} ./assoc16.sub
+test_runsub ./assoc16.sub
# tests with `[' and `]' subscripts and `unset'
-${THIS_SH} ./assoc17.sub
+test_runsub ./assoc17.sub
# tests with `[' and `]' subscripts and printf/read/wait builtins
-${THIS_SH} ./assoc18.sub
+test_runsub ./assoc18.sub
# tests with tilde expansion in keys and values post-bash-5.2
-${THIS_SH} ./assoc19.sub
+test_runsub ./assoc19.sub
after f1:declare -ar a=([0]="1")
-./attr.tests: line 17: f2: a: readonly variable
+./attr.tests: line 19: f2: a: readonly variable
after f2:declare -ar a=([0]="1")
-./attr.tests: line 18: a: readonly variable
+./attr.tests: line 20: a: readonly variable
after f3:declare -ar a=([0]="1")
-./attr.tests: line 19: readonly: a: readonly variable
+./attr.tests: line 21: readonly: a: readonly variable
after f4:declare -ar a=([0]="1")
after f2:declare -ar b=([0]="2")
after f3:declare -ar c=([0]="(3)")
after f4:declare -ar d=([0]="4")
+ attr1.sub
declare -r m="4"
in func:declare -r n="4"
declare -r n="4"
declare -ar y1=([0]="4")
in func:declare -ar z1=([0]="4")
declare -ar z1=([0]="4")
+ attr2.sub
declare -x p="4"
declare -ax r=([0]="4")
declare -ax r=([0]="(5)")
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
+. ./test-aux-functions
+
a=(outside)
f1() { readonly a=(1) ; }
echo -n after f4:
declare -p d
-${THIS_SH} ./attr1.sub
-${THIS_SH} ./attr2.sub
-
+test_runsub ./attr1.sub
+test_runsub ./attr2.sub
unset x
set -- 'a[${ break;}]'
-declare -in x
+declare -n x
for x do :; done
echo after for
# checks for properly deciding what constitutes an executable file
${THIS_SH} ./exec7.sub
-${THIS_SH} -i ${PWD}/exec8.sub
+HISTFILE= ${THIS_SH} --norc -i ${PWD}/exec8.sub
${THIS_SH} ./exec9.sub
declare -ai a=([0]="5")
declare -ai a=([0]="6")
declare -ai a=([0]="42")
-./nameref23.sub: line 28: declare: a[0]: expands to invalid variable name for name reference
+./nameref23.sub: line 28: declare: cannot use -n with -i
declare -ai a=([0]="1")
./nameref23.sub: line 29: declare: b: not found
declare -ai a=([0]="1")
./nameref23.sub: line 39: declare: `1': invalid variable name for name reference
declare -ai a=([0]="1")
./nameref23.sub: line 41: declare: b: not found
+./nameref23.sub: line 48: declare: cannot use -n with -i
declare -ai a=([0]="4")
-declare -in b="a[0]"
+declare -n b="a[0]"
declare -ai a=([0]="6")
-declare -in b="a[0]"
+declare -n b="a[0]"
foo
foo bar
declare -a a=([0]="" [1]="foo bar")
#####
declare -ai a=('4');
declare -n b='a[0]';
-declare -ni b; # this should maybe not be allowed, but it is for now
+declare -ni b; # this is now disallowed; doesn't change attributes
declare -p a b
b+=2;
projects / thirdparty / bash.git / commitdiff
