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 b\bba\bas\bsh\bh does not reset the effective
- user id.
+ the real user (group) id, and the -\b-p\bp option is not supplied, bash does
+ not attempt to read any startup files or _\b~_\b/_\b._\bb_\ba_\bs_\bh_\b__\bl_\bo_\bg_\bo_\bu_\bt, does not in-
+ herit shell functions from the environment, ignores 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 appear in the envi-
+ ronment, and sets the effective user id to the real user id. If the -\b-p\bp
+ option is supplied at invocation, the startup behavior is the same, but
+ b\bba\bas\bsh\bh does not reset the effective user id.
D\bDE\bEF\bFI\bIN\bNI\bIT\bTI\bIO\bON\bNS\bS
- The following definitions are used throughout the rest of this docu-
+ 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-
+ 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
+ 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-
+ 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
+ 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
+\bo the first word of a command (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR below);
- +\bo the first word following a reserved word other than c\bca\bas\bse\be, f\bfo\bor\br,
+ +\bo the first word following a reserved word other than c\bca\bas\bse\be, f\bfo\bor\br,
s\bse\bel\ble\bec\bct\bt, or i\bin\bn;
+\bo the third word of a c\bca\bas\bse\be command (only i\bin\bn is valid);
- +\bo the third word of a f\bfo\bor\br or s\bse\bel\ble\bec\bct\bt command (only i\bin\bn and d\bdo\bo are
+ +\bo the third word of a f\bfo\bor\br or s\bse\bel\ble\bec\bct\bt command (only i\bin\bn and d\bdo\bo are
valid);
+\bo following a control operator.
The following are reserved words:
- !\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
+ !\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-
+ 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
+ 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-
+ 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 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
+ 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-
+ 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-
+ 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
+ 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
+ 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
+ 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,
+ 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 AND or OR lists separated by one of
- the operators ;\b;, &\b&, or <\b<n\bne\bew\bwl\bli\bin\bne\be>\b>, and optionally terminated by one of
+ the operators ;\b;, &\b&, or <\b<n\bne\bew\bwl\bli\bin\bne\be>\b>, and optionally terminated by one of
those three characters.
- 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
+ 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
+ _\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
+ _\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.
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
+ 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 asynchronously in a subshell. This is known as exe-
- cuting a command in the _\bb_\ba_\bc_\bk_\bg_\br_\bo_\bu_\bn_\bd, and these are referred to as _\ba_\bs_\by_\bn_\b-
- _\bc_\bh_\br_\bo_\bn_\bo_\bu_\bs commands. The shell does not wait for the command to finish,
- and the return status is 0. When job control is not active, the stan-
- dard input for asynchronous commands, in the absence of any explicit
- redirections involving the standard input, is redirected from
+ If a command is terminated by the control operator &\b&, the shell exe-
+ cutes the command asynchronously in a subshell. This is known as exe-
+ cuting a command in the _\bb_\ba_\bc_\bk_\bg_\br_\bo_\bu_\bn_\bd, and these are referred to as _\ba_\bs_\by_\bn_\b-
+ _\bc_\bh_\br_\bo_\bn_\bo_\bu_\bs commands. The shell does not wait for the command to finish,
+ and the return status is 0. When job control is not active, the stan-
+ dard input for asynchronous commands, in the absence of any explicit
+ redirections involving the standard input, is redirected from
_\b/_\bd_\be_\bv_\b/_\bn_\bu_\bl_\bl.
- Commands separated or terminated by ;\b; (or an equivalent <\b<n\bne\bew\bwl\bli\bin\bne\be>\b>) are
+ Commands separated or terminated by ;\b; (or an equivalent <\b<n\bne\bew\bwl\bli\bin\bne\be>\b>) are
executed sequentially; the shell waits for each command to terminate in
turn.
cuted.
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
+ 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
+ (_\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
+ 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
+ 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-
+ 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
+ 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-
+ 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-
+ 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
+ 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
+ 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
+ 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:
+ =\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
+ 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.
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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. B\bBa\bas\bsh\bh unsets B\bBA\bAS\bSH\bH_\b_R\bRE\bEM\bMA\bAT\bTC\bCH\bH before at-
- tempting the match, so if there is no match, it remains unset.
+ tempting the match, so if there is no match, it remains unset.
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 subexpressions within the regular ex-
- pression are saved in the remaining 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 index _\bn is the portion of the
- string matching the _\bnth parenthesized 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 if it is not set; if it is de-
- clared as a local variable before running [\b[[\b[, b\bba\bas\bsh\bh keeps it a
+ the string matching the entire regular expression. Substrings
+ matched by parenthesized subexpressions within the regular ex-
+ pression are saved in the remaining 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 index _\bn is the portion of the
+ string matching the _\bnth parenthesized 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 if it is not set; if it is de-
+ clared as a local variable before running [\b[[\b[, b\bba\bas\bsh\bh keeps it a
local variable.
- Expressions may be combined using the following operators,
+ 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
+ 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.
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
+ 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
+ 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-
+ 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
+ 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-
+ 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-
+ 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
+ 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 _\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, 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
+ 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
+ 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
+ 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. The _\bw_\bo_\br_\bd
is expanded using tilde expansion, parameter and variable expan-
- sion, arithmetic expansion, command substitution, process sub-
- stitution and quote removal. Each _\bp_\ba_\bt_\bt_\be_\br_\bn examined is expanded
- using tilde expansion, parameter and variable expansion, arith-
+ sion, arithmetic expansion, command substitution, process sub-
+ stitution and quote removal. Each _\bp_\ba_\bt_\bt_\be_\br_\bn examined is expanded
+ using tilde expansion, parameter and variable expansion, arith-
metic 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
+ 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
characters.
- A _\bp_\ba_\bt_\bt_\be_\br_\bn _\bl_\bi_\bs_\bt is a set of one or more patterns separated by |\b|,
- and terminated by the )\b) operator. A case _\bc_\bl_\ba_\bu_\bs_\be is a pattern
- list and an associated _\bl_\bi_\bs_\bt, terminated by ;\b;;\b;, ;\b;&\b&, or ;\b;;\b;&\b&. The
- terminator is optional for the last clause preceding e\bes\bsa\bac\bc.
- There may be an arbitrary number of case clauses. The first
+ A _\bp_\ba_\bt_\bt_\be_\br_\bn _\bl_\bi_\bs_\bt is a set of one or more patterns separated by |\b|,
+ and terminated by the )\b) operator. A case _\bc_\bl_\ba_\bu_\bs_\be is a pattern
+ list and an associated _\bl_\bi_\bs_\bt, terminated by ;\b;;\b;, ;\b;&\b&, or ;\b;;\b;&\b&. The
+ terminator is optional for the last clause preceding e\bes\bsa\bac\bc.
+ There may be an arbitrary number of case clauses. The first
pattern that matches determines the _\bl_\bi_\bs_\bt that is executed.
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 the ;\b;&\b& terminator con-
- tinues execution with the _\bl_\bi_\bs_\bt associated with the next clause,
- if any. Using the ;\b;;\b;&\b& terminator causes the shell to test the
+ the ;\b;;\b; operator terminates the case clause, the c\bca\bas\bse\be command
+ completes after the first match. Using the ;\b;&\b& terminator con-
+ tinues execution with the _\bl_\bi_\bs_\bt associated with the next clause,
+ if any. Using the ;\b;;\b;&\b& terminator causes the shell to test the
pattern list in the next clause, if any, and execute any associ-
- ated _\bl_\bi_\bs_\bt if the match succeeds, continuing the case statement
+ ated _\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
+ 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
+ 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-
+ _\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
+ 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-
+ 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
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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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.
+ 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
+ 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.
+ 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
+ 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
+ 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
+ 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\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
+ 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
+ _\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
+ 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-
+ 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
+ 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
+ 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,
+ 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\,
+ 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 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-
+ !\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
+ 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-
+ 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\'\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
+ \\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
+ \\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).
\\b\c\bc_\bx A control-_\bx character.
- The expanded result is single-quoted, as if the dollar sign had not
+ 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
+ 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
+ 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
+ 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-
+ 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).
+ _\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
+ 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-
+ 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-
+ 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
+ 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,
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
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
+ 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
+ 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-
+ 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,
+ 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
+ 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
+ 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$0\b0 (see the next
+ sitional parameters ($\b$1\b1-\b-$\b$9\b9) or the special parameter $\b$0\b0 (see the next
section).
S\bSp\bpe\bec\bci\bia\bal\bl P\bPa\bar\bra\bam\bme\bet\bte\ber\brs\bs
- The shell treats several parameters specially. These parameters may
+ The shell treats several parameters specially. These parameters may
only be referenced; assignment to them is not allowed. Special parame-
ters are denoted by one of the following characters.
- *\b* ($\b$*\b*) Expands to the positional parameters, starting from one.
- When the expansion is not within double quotes, each positional
- parameter expands to a separate word. In contexts where word
- expansions are performed, those words are subject to further
- word splitting and pathname expansion. When the expansion oc-
- curs within double quotes, it expands to a single word with the
- value of each parameter separated by the first character of the
+ *\b* ($\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$2\b2_\bc.\b..\b..\b."\b", where
- _\bc is the first character of the value of the I\bIF\bFS\bS variable. If
+ _\bc is the first character of the value of the I\bIF\bFS\bS variable. If
I\bIF\bFS\bS is unset, the parameters are separated by spaces. If I\bIF\bFS\bS is
null, the parameters are joined without intervening separators.
- @\b@ ($\b$@\b@) Expands to the positional parameters, starting from one.
+ @\b@ ($\b$@\b@) Expands to the positional parameters, starting from one.
In contexts where word splitting is performed, this expands each
- positional parameter to a separate word; if not within double
- quotes, these words are subject to word splitting. In contexts
+ positional parameter to a separate word; if not within double
+ quotes, these words are subject to word splitting. In contexts
where word splitting is not performed, such as the value portion
- of an assignment statement, this expands to a single word with
+ of an assignment statement, this expands to a single word with
each positional parameter separated by a space. When the expan-
- sion occurs within double quotes, and word splitting is per-
- formed, each parameter expands to a separate word. That is,
+ sion occurs within double quotes, and word splitting is per-
+ formed, each parameter expands to a separate word. That is,
"\b"$\b$@\b@"\b" is equivalent to "\b"$\b$1\b1"\b" "\b"$\b$2\b2"\b" .\b..\b..\b. If the double-quoted expan-
- sion occurs within a word, the expansion of the first parameter
+ sion occurs within a word, the expansion of the first parameter
is joined with the expansion of the beginning part of the origi-
nal word, and the expansion of the last parameter is joined with
the expansion of the last part of the original word. When there
- are no positional parameters, "\b"$\b$@\b@"\b" and $\b$@\b@ expand to nothing
+ 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
+ ?\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
+ 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$$\b$) Expands to the process ID of the shell. In a subshell, it
+ $\b$ ($\b$$\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$!\b!)Expands to the process ID of the job most recently placed
+ !\b! ($\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$0\b0 is set to the name of that file. If b\bba\bas\bsh\bh is
+ 0\b0 ($\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$0\b0 is set to the first argument
- after the string to be executed, if one is present. Otherwise,
+ after the string to be executed, if one is present. Otherwise,
it is set to the filename used to invoke b\bba\bas\bsh\bh, as given by argu-
ment zero.
S\bSh\bhe\bel\bll\bl V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs
The shell sets following variables:
- _\b_ ($\b$_\b_, an underscore) This has a number of meanings depending on
+ _\b_ ($\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-
+ 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 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
+ 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
+ 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
+ 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$$\b$ under certain circumstances, such as subshells
- that do not require b\bba\bas\bsh\bh to be re-initialized. Assignments to
- B\bBA\bAS\bSH\bHP\bPI\bID\bD have no effect. If B\bBA\bAS\bSH\bHP\bPI\bID\bD is unset, it loses its spe-
+ Expands to the process ID of the current b\bba\bas\bsh\bh process. This
+ differs from $\b$$\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
+ 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
+ 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
+ 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
+ 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-
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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.
+ 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-
+ $\b${\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-
+ 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-
+ 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-
+ 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
+ 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-
+ 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-
+ 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
+ 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
+ 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[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
+ 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
+ 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
+ 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-
+ 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-
+ 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
+ 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-
+ 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-
+ 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-
+ 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
+ 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
+ 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
+ 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-
+ 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-
+ 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
+ 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
+ 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-
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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-
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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(
+ 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-
+ 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
+ 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-
+ 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
(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
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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:~". Since
- tilde expansion takes place after ":" in assignment statements,
- make sure to quote assignments appropriately to avoid it as ap-
+ 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:~". Since
+ tilde expansion takes place after ":" in assignment statements,
+ make sure to quote assignments appropriately to avoid it as ap-
propriate.
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
+ 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.
+ 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-
+ 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-
+ 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,
+ 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
+ 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
+ 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"
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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-
+ 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
+ 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
+ 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
+ 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 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
+ 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 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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_
+ 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-
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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?"$_ has mail!"'
- B\bBa\bas\bsh\bh can be configured to supply a default value for this vari-
- able (there is no value by default), but the location of the
+ B\bBa\bas\bsh\bh can be configured to supply a default value for this vari-
+ able (there is no value by default), but the location of the
user mail files that it uses is system dependent (e.g.,
/var/mail/$\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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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).
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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]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
+ 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
+ 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 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-
+ 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
+ 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
+ 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-
+ 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
+ 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,
+ 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
+ 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-
+ 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-
+ 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
+ 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
+ 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).
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-
+ ... 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
+ 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
+ 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
+ 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-
+ 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-
+ 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
+ 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
If one of the word expansions in a compound array assignment unsets the
variable, the results are unspecified.
- 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
+ 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.
+ 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-
+ 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
+ ${#_\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
+ 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
+ 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
+ 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
+ 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-
+ 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-
+ 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
+ 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
+ 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-
+ 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
_\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 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-
+ 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
+ _\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-
+ 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
+ _\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
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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 "${" is not considered eligible for brace expan-
+ A "{" or Q , may be quoted with a backslash to prevent its being con-
+ sidered part of a brace expression. To avoid conflicts with parameter
+ expansion, the string "${" 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
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.
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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-
+ 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-
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ _\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
+ 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
+ _\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
+ 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 performing the first four expansions documented below (:\b:-\b-, :\b:=\b=, :\b:?\b?,
- and :\b:+\b+), including the colon, b\bba\bas\bsh\bh tests for a parameter that is unset
+ and :\b:+\b+), including the colon, 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, or unset if
- the colon is not present, the expansion of _\bw_\bo_\br_\bd is substituted.
+ 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, or unset if
+ the colon is not present, the expansion 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, or unset
- if the colon is not present, the expansion of _\bw_\bo_\br_\bd is assigned
+ 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, or unset
+ if the colon is not present, the expansion 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 unset or null,
- or unset if the colon is not present, the shell writes the ex-
- pansion of _\bw_\bo_\br_\bd (or a message to that effect 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 ex-
+ 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 unset or null,
+ or unset if the colon is not present, the shell writes the ex-
+ pansion of _\bw_\bo_\br_\bd (or a message to that effect 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 ex-
pansion. 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}
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 unset or null, or unset if
- the colon is not present, nothing is substituted, otherwise the
+ the colon is not present, 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),
+ 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-
+ 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
+ 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
+ _\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
+ 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
+ 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
+ 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
+ _\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,
+ 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
+ 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
+ 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,
+ 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-
+ 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}
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
+ 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}
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
+ 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}
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-
+ 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-
+ _\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
+ arithmetic expansion, command and process substitution, and
quote removal.
- In the first form above, only the first match is replaced. If
+ 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
+ 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
+ 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
+ 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\
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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.
+ 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
+ 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-
+ 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
+ ^\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-
+ 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-
+ 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
+ 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
+ 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-
+ 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
+ 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-
+ 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
+ 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
+ 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-
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
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
+ 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
+ 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-
+ 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 ";"; and the close brace must be in a position where a reserved
- word may appear (i.e., preceded by a command terminator such as semi-
- colon). 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
+ word may appear (i.e., preceded by a command terminator such as semi-
+ colon). 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
+ 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
+ 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 ";", the construct
- behaves like the form above but preserves any trailing newlines in the
- output of _\bc_\bo_\bm_\bm_\ba_\bn_\bd instead of removing them. This form is useful when
- the trailing newlines are significant and should not be stripped from
+ behaves like the form above but preserves any trailing newlines in the
+ output of _\bc_\bo_\bm_\bm_\ba_\bn_\bd instead of removing them. This form is useful when
+ the trailing newlines are significant and should not be stripped from
the command's output.
If the first character following the open brace is a "|", 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-
+ 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
+ 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
$\b$(\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-
+ 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-
+ 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-
+ 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
+ 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 continue to execute the command in which the error
+ to standard error indicating failure, does not perform the substitu-
+ tion, and does not continue to execute the command in which the error
occurs.
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
+ _\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, as long as it is not a null command without redirections,
- 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
+ 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 >\b>(\b(_\bl_\bi_\bs_\bt)\b) form is used, writing to the file provides input for
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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,
+ 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
+ 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
+ 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-
+ 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
+ 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,
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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 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-
+ *\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-
+ [\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,
+ 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
+ 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 characters included in the range, are determined by
the collating sequence of the current locale and the val-
ues 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.
- For example, in the C locale, [\b[a\ba-\b-d\bd]\b] is equivalent to
- [\b[a\bab\bbc\bcd\bd]\b]. Many locales sort characters in dictionary or-
- der, and in these locales [\b[a\ba-\b-d\bd]\b] is typically not equiva-
- lent to [\b[a\bab\bbc\bcd\bd]\b]; it might be equivalent to [\b[a\baB\bBb\bbC\bCc\bcD\bDd\bd]\b] or
- [\b[a\baA\bAb\bbB\bBc\bcC\bCd\bd]\b]. To obtain the traditional interpretation of
- range expressions, where [\b[a\ba-\b-d\bd]\b] is equivalent to [\b[a\bab\bbc\bcd\bd]\b],
+ For example, in the C locale, [\b[a\ba-\b-d\bd]\b] is equivalent to
+ [\b[a\bab\bbc\bcd\bd]\b]. Many locales sort characters in dictionary or-
+ der, and in these locales [\b[a\ba-\b-d\bd]\b] is typically not equiva-
+ lent to [\b[a\bab\bbc\bcd\bd]\b]; it might be equivalent to [\b[a\baB\bBb\bbC\bCc\bcD\bDd\bd]\b] or
+ [\b[a\baA\bAb\bbB\bBc\bcC\bCd\bd]\b]. To obtain the traditional 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\bii\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
+ 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
+ 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
+ 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
+ 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]
+ 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
+ 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
+ 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 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-
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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.
+ 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-
+ 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
+ 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
+ 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,
+ 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
+ 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-
+ 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
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
+ 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
+ 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-
+ 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
+ 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:
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
+ 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
+ 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
+ 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.
[_\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
+ 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-
+ There are two formats for redirecting standard output and standard er-
ror:
&\b&>\b>_\bw_\bo_\br_\bd
>\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-
+ 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
(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
+ 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-
+ 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:
_\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
+ 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
+ _\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 as a line continuation, and \\b\ must be used to quote the charac-
- ters \\b\, $\b$, and `\b`; however, double quote characters have no special
+ ters \\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
+ 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
+ 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
[_\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
+ 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).
[_\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-
+ 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
+ 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
+ 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
[_\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
+ 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.
[_\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
+ 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
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
+ _\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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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,
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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-
+ 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-
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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,
+ 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-
+ 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
+ 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-
_\be_\bx_\bp_\br_\b1 ,\b, _\be_\bx_\bp_\br_\b2
comma
- Shell variables are allowed as operands; parameter expansion is per-
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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-
+ 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,
+ 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-
+ 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
-\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-
+ 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
+ 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
+ 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
+ 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-
+ 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_\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,
+ 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 _\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-
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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-
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ +\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
+ +\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
+ +\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
+ +\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-
+ +\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
+ +\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-
+ 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
+ +\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
+ +\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
+ 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-
+ 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
+ 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
+ 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, un-
+ 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, un-
less the command has an explicit redirection involving the standard in-
- put. Otherwise, the invoked command inherits the file descriptors of
+ put. Otherwise, the invoked command inherits the file descriptors of
the calling 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
+ 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
+ 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, 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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,
+ 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-
+ 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
+ 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
+ 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 and
- command lists. In all cases, b\bba\bas\bsh\bh ignores S\bSI\bIG\bGQ\bQU\bUI\bIT\bT. If job control is
+ When b\bba\bas\bsh\bh receives S\bSI\bIG\bGI\bIN\bNT\bT, it breaks out of any executing loops and
+ command lists. 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 ignores 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-
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
+ 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-
+ 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
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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.
+ 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-
+ 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
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
+ 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
+ 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-
+ 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-
+ 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-
+ 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-
+ 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
+ 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,
+ 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
+ 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-
+ 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
+ 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,
+ 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
+ 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
+ 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
+ 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
+ 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-
+ 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
+ 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-
+ 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
+ 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-
+ 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
+ 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-
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ \\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
+ 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.,
+ \\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
+ \\b\s\bs The name of the shell: the basename of $\b$0\b0 (the portion
following the final slash).
\\b\t\bt The current time in 24-hour HH:MM:SS format.
\\b\T\bT The current time in 12-hour HH:MM:SS format.
\\b\u\bu The username of the current user.
\\b\v\bv The b\bba\bas\bsh\bh version (e.g., 2.00).
\\b\V\bV The b\bba\bas\bsh\bh release, version + patch level (e.g., 2.00.0)
- \\b\w\bw The value of the P\bPW\bWD\bD shell variable ($\b$P\bPW\bWD\bD), with $\b$H\bHO\bOM\bME\bE
- abbreviated with a tilde (uses the value of the
+ \\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
+ \\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. This escape is only useful when the prompt will
- be supplied to r\bre\bea\bad\bdl\bli\bin\bne\be, so it shouldn't be used in P\bPS\bS0\b0
- or P\bPS\bS4\b4 or when line editing is not enabled.
+ \\b\[\b[ Begin a sequence of non-printing characters, which could
+ be used to embed a terminal control sequence into the
+ prompt. This escape is only useful when the prompt will
+ be supplied to r\bre\bea\bad\bdl\bli\bin\bne\be, and is ignored and removed oth-
+ erwise, so it shouldn't be used in P\bPS\bS0\b0 or P\bPS\bS4\b4 or when
+ line editing is not enabled.
\\b\]\b] End a sequence of non-printing characters begun with \\b\[\b[.
The command number and the history number are usually different: the
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.
+ not read the $\b$E\bEN\bNV\bV and $\b$B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV files, does not inherit
+ shell functions from the environment, and ignores 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 appear in the environment. 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 sup-
+ plied, these actions are taken and the effective user id
+ is set to the real user id (see I\bIN\bNV\bVO\bOC\bCA\bAT\bTI\bIO\bON\bN above for
+ more details). 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
+ 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-
- tus, instead of returning when it changes status. If there are
- no _\bi_\bd arguments, w\bwa\bai\bit\bt waits until all background processes have
+ 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 there are
+ no _\bi_\bd arguments, w\bwa\bai\bit\bt waits until all background processes have
terminated.
- 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
<ftp://ftp.gnu.org/pub/gnu/bash/> and <http://git.savannah.gnu.org/
cgit/bash.git/snapshot/bash-master.tar.gz>.
- 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, as well as comments and bug reports concerning this manual
+ reports, as well as comments and bug reports concerning this manual
page, to to <bug-bash@gnu.org>.
_\bA_\bl_\bl bug reports should include:
+\bo the version number of b\bba\bas\bsh\bh ("echo $BASH_VERSION"),
+\bo the host platform and operating system ("uname -a"),
+\bo either
- (a) if you or an administrator built and installed b\bba\bas\bsh\bh from
- source, the name and version of the compiler used to build it,
+ (a) if you or an administrator built and installed b\bba\bas\bsh\bh from
+ source, the name and version of the compiler used to build it,
as reported by b\bba\bas\bsh\bh's "configure" script; or
- (b) if your site uses a distributor's b\bba\bas\bsh\bh package, the version of
+ (b) if your site uses a distributor's b\bba\bas\bsh\bh package, the version of
that package (for example, "dpkg -i bash" or "rpm -qi bash"),
+\bo a description of the behavior b\bba\bas\bsh\bh exhibited,
+\bo a description of the behavior you expected from b\bba\bas\bsh\bh, and
+\bo a short shell script or "recipe" exercising the unexpected behavior.
- _\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.
B\bBU\bUG\bGS\bS
It's too big and too slow.
- There are some subtle differences between b\bba\bas\bsh\bh and historical versions
- of s\bsh\bh, due mostly to b\bba\bas\bsh\bh's independent implementation and the evolu-
+ There are some subtle differences between b\bba\bas\bsh\bh and historical versions
+ of s\bsh\bh, due mostly to b\bba\bas\bsh\bh's independent implementation and the evolu-
tion 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-
+ 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 2026 May 18 _\bB_\bA_\bS_\bH(1)
+GNU Bash 5.3 2026 July 1 _\bB_\bA_\bS_\bH(1)
projects / thirdparty / bash.git / commitdiff
