--- /dev/null
+This is the Bash FAQ, version 3.24, for Bash version 2.05b.
+
+This document contains a set of frequently-asked questions concerning
+Bash, the GNU Bourne-Again Shell. Bash is a freely-available command
+interpreter with advanced features for both interactive use and shell
+programming.
+
+Another good source of basic information about shells is the collection
+of FAQ articles periodically posted to comp.unix.shell.
+
+Questions and comments concerning this document should be sent to
+chet@po.cwru.edu.
+
+This document is available for anonymous FTP with the URL
+
+ftp://ftp.cwru.edu/pub/bash/FAQ
+
+The Bash home page is http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html
+
+----------
+Contents:
+
+Section A: The Basics
+
+A1) What is it?
+A2) What's the latest version?
+A3) Where can I get it?
+A4) On what machines will bash run?
+A5) Will bash run on operating systems other than Unix?
+A6) How can I build bash with gcc?
+A7) How can I make bash my login shell?
+A8) I just changed my login shell to bash, and now I can't FTP into my
+ machine. Why not?
+A9) What's the `POSIX 1003.2 standard'?
+A10) What is the bash `posix mode'?
+
+Section B: The latest version
+
+B1) What's new in version 2.05b?
+B2) Are there any user-visible incompatibilities between bash-2.05b and
+ bash-1.14.7?
+
+Section C: Differences from other Unix shells
+
+C1) How does bash differ from sh, the Bourne shell?
+C2) How does bash differ from the Korn shell, version ksh88?
+C3) Which new features in ksh-93 are not in bash, and which are?
+
+Section D: Why does bash do some things differently than other Unix shells?
+
+D1) Why does bash run a different version of `command' than
+ `which command' says it will?
+D2) Why doesn't bash treat brace expansions exactly like csh?
+D3) Why doesn't bash have csh variable modifiers?
+D4) How can I make my csh aliases work when I convert to bash?
+D5) How can I pipe standard output and standard error from one command to
+ another, like csh does with `|&'?
+D6) Now that I've converted from ksh to bash, are there equivalents to
+ ksh features like autoloaded functions and the `whence' command?
+
+Section E: Why does bash do certain things the way it does?
+
+E1) Why is the bash builtin `test' slightly different from /bin/test?
+E2) Why does bash sometimes say `Broken pipe'?
+E3) When I have terminal escape sequences in my prompt, why does bash
+ wrap lines at the wrong column?
+E4) If I pipe the output of a command into `read variable', why doesn't
+ the output show up in $variable when the read command finishes?
+E5) I have a bunch of shell scripts that use backslash-escaped characters
+ in arguments to `echo'. Bash doesn't interpret these characters. Why
+ not, and how can I make it understand them?
+E6) Why doesn't a while or for loop get suspended when I type ^Z?
+E7) What about empty for loops in Makefiles?
+E8) Why does the arithmetic evaluation code complain about `08'?
+E9) Why does the pattern matching expression [A-Z]* match files beginning
+ with every letter except `z'?
+E10) Why does `cd //' leave $PWD as `//'?
+E11) If I resize my xterm while another program is running, why doesn't bash
+ notice the change?
+
+Section F: Things to watch out for on certain Unix versions
+
+F1) Why can't I use command line editing in my `cmdtool'?
+F2) I built bash on Solaris 2. Why do globbing expansions and filename
+ completion chop off the first few characters of each filename?
+F3) Why does bash dump core after I interrupt username completion or
+ `~user' tilde expansion on a machine running NIS?
+F4) I'm running SVR4.2. Why is the line erased every time I type `@'?
+F5) Why does bash report syntax errors when my C News scripts use a
+ redirection before a subshell command?
+F6) Why can't I use vi-mode editing on Red Hat Linux 6.1?
+F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on
+ HP/UX 11.x?
+
+Section G: How can I get bash to do certain common things?
+
+G1) How can I get bash to read and display eight-bit characters?
+G2) How do I write a function `x' to replace builtin command `x', but
+ still invoke the command from within the function?
+G3) How can I find the value of a shell variable whose name is the value
+ of another shell variable?
+G4) How can I make the bash `time' reserved word print timing output that
+ looks like the output from my system's /usr/bin/time?
+G5) How do I get the current directory into my prompt?
+G6) How can I rename "*.foo" to "*.bar"?
+G7) How can I translate a filename from uppercase to lowercase?
+G8) How can I write a filename expansion (globbing) pattern that will match
+ all files in the current directory except "." and ".."?
+
+Section H: Where do I go from here?
+
+H1) How do I report bugs in bash, and where should I look for fixes and
+ advice?
+H2) What kind of bash documentation is there?
+H3) What's coming in future versions?
+H4) What's on the bash `wish list'?
+H5) When will the next release appear?
+
+----------
+Section A: The Basics
+
+A1) What is it?
+
+Bash is a Unix command interpreter (shell). It is an implementation of
+the Posix 1003.2 shell standard, and resembles the Korn and System V
+shells.
+
+Bash contains a number of enhancements over those shells, both
+for interactive use and shell programming. Features geared
+toward interactive use include command line editing, command
+history, job control, aliases, and prompt expansion. Programming
+features include additional variable expansions, shell
+arithmetic, and a number of variables and options to control
+shell behavior.
+
+Bash was originally written by Brian Fox of the Free Software
+Foundation. The current developer and maintainer is Chet Ramey
+of Case Western Reserve University.
+
+A2) What's the latest version?
+
+The latest version is 2.05b, first made available on Wednesday, 17
+July, 2002.
+
+A3) Where can I get it?
+
+Bash is the GNU project's shell, and so is available from the
+master GNU archive site, ftp.gnu.org, and its mirrors. The
+latest version is also available for FTP from ftp.cwru.edu.
+The following URLs tell how to get version 2.05b:
+
+ftp://ftp.gnu.org/pub/gnu/bash/bash-2.05b.tar.gz
+ftp://ftp.cwru.edu/pub/bash/bash-2.05b.tar.gz
+
+Formatted versions of the documentation are available with the URLs:
+
+ftp://ftp.gnu.org/pub/gnu/bash/bash-doc-2.05b.tar.gz
+ftp://ftp.cwru.edu/pub/bash/bash-doc-2.05b.tar.gz
+
+A4) On what machines will bash run?
+
+Bash has been ported to nearly every version of UNIX. All you
+should have to do to build it on a machine for which a port
+exists is to type `configure' and then `make'. The build process
+will attempt to discover the version of UNIX you have and tailor
+itself accordingly, using a script created by GNU autoconf.
+
+More information appears in the file `INSTALL' in the distribution.
+
+The Bash web page (http://cnswww.cns.cwru.edu/~chet/bash/bashtop.html)
+explains how to obtain binary versions of bash for most of the major
+commercial Unix systems.
+
+A5) Will bash run on operating systems other than Unix?
+
+Configuration specifics for Unix-like systems such as QNX and
+LynxOS are included in the distribution. Bash-2.05 and later
+versions should compile and run on Minix 2.0 (patches were
+contributed), but I don't believe anyone has built bash-2.x on
+earlier Minix versions yet.
+
+Bash has been ported to versions of Windows implementing the Win32
+programming interface. This includes Windows 95 and Windows NT.
+The port was done by Cygnus Solutions as part of their CYGWIN
+project. For more information about the project, look at the URLs
+
+http://www.cygwin.com/
+http://sourceware.cygnus.com/cygwin
+
+Cygnus originally ported bash-1.14.7, and that port was part of their
+early GNU-Win32 (the original name) releases. Cygnus has also done a
+port of bash-2.05 to the CYGWIN environment, and it is available as
+part of their current release.
+
+Bash-2.05b should require no local Cygnus changes to build and run under
+CYGWIN.
+
+The Cygnus port works only on Intel machines. There is a port of bash
+(I don't know which version) to the alpha/NT environment available from
+
+ftp://ftp.gnustep.org//pub/win32/bash-alpha-nt-1.01.tar.gz
+
+DJ Delorie has a port of bash-2.x which runs under MS-DOS, as part
+of the DJGPP project. For more information on the project, see
+
+http://www.delorie.com/djgpp/
+
+I have been told that the original DJGPP port was done by Daisuke Aoyama.
+
+Mark Elbrecht <snowball3@bigfoot.com> has sent me notice that bash-2.04
+is available for DJGPP V2. The files are available as:
+
+ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204b.zip binary
+ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204d.zip documentation
+ftp://ftp.simtel.net/pub/simtelnet/gnu/djgpp/v2gnu/bsh204s.zip source
+
+Mark has begun to work with bash-2.05, but I don't know the status.
+
+Ports of bash-1.12 and bash-2.0 are available for OS/2 from
+
+ftp://hobbes.nmsu.edu/pub/os2/util/shell/bash_112.zip
+ftp://hobbes.nmsu.edu/pub/os2/util/shell/bash-2.0(253).zip
+
+I haven't looked at either, but the second appears to be a binary-only
+distribution. Beware.
+
+I have received word that Bash (I'm not sure which version, but I
+believe that it's at least bash-2.02.1) is the standard shell on
+BeOS.
+
+A6) How can I build bash with gcc?
+
+Bash configures to use gcc by default if it is available. Read the
+file INSTALL in the distribution for more information.
+
+A7) How can I make bash my login shell?
+
+Some machines let you use `chsh' to change your login shell. Other
+systems use `passwd -s' or `passwd -e'. If one of these works for
+you, that's all you need. Note that many systems require the full
+pathname to a shell to appear in /etc/shells before you can make it
+your login shell. For this, you may need the assistance of your
+friendly local system administrator.
+
+If you cannot do this, you can still use bash as your login shell, but
+you need to perform some tricks. The basic idea is to add a command
+to your login shell's startup file to replace your login shell with
+bash.
+
+For example, if your login shell is csh or tcsh, and you have installed
+bash in /usr/gnu/bin/bash, add the following line to ~/.login:
+
+ if ( -f /usr/gnu/bin/bash ) exec /usr/gnu/bin/bash --login
+
+(the `--login' tells bash that it is a login shell).
+
+It's not a good idea to put this command into ~/.cshrc, because every
+csh you run without the `-f' option, even ones started to run csh scripts,
+reads that file. If you must put the command in ~/.cshrc, use something
+like
+
+ if ( $?prompt ) exec /usr/gnu/bin/bash --login
+
+to ensure that bash is exec'd only when the csh is interactive.
+
+If your login shell is sh or ksh, you have to do two things.
+
+First, create an empty file in your home directory named `.bash_profile'.
+The existence of this file will prevent the exec'd bash from trying to
+read ~/.profile, and re-execing itself over and over again. ~/.bash_profile
+is the first file bash tries to read initialization commands from when
+it is invoked as a login shell.
+
+Next, add a line similar to the above to ~/.profile:
+
+ [ -f /usr/gnu/bin/bash ] && [ -x /usr/gnu/bin/bash ] && \
+ exec /usr/gnu/bin/bash --login
+
+This will cause login shells to replace themselves with bash running as
+a login shell. Once you have this working, you can copy your initialization
+code from ~/.profile to ~/.bash_profile.
+
+I have received word that the recipe supplied above is insufficient for
+machines running CDE. CDE has a maze of twisty little startup files, all
+slightly different.
+
+If you cannot change your login shell in the password file to bash, you
+will have to (apparently) live with CDE using the shell in the password
+file to run its startup scripts. If you have changed your shell to bash,
+there is code in the CDE startup files (on Solaris, at least) that attempts
+to do the right thing. It is, however, often broken, and may require that
+you use the $BASH_ENV trick described below.
+
+`dtterm' claims to use $SHELL as the default program to start, so if you
+can change $SHELL in the CDE startup files, you should be able to use bash
+in your terminal windows.
+
+Setting DTSOURCEPROFILE in ~/.dtprofile will cause the `Xsession' program
+to read your login shell's startup files. You may be able to use bash for
+the rest of the CDE programs by setting SHELL to bash in ~/.dtprofile as
+well, but I have not tried this.
+
+You can use the above `exec' recipe to start bash when not logging in with
+CDE by testing the value of the DT variable:
+
+ if [ -n "$DT" ]; then
+ [ -f /usr/gnu/bin/bash ] && exec /usr/gnu/bin/bash --login
+ fi
+
+If CDE starts its shells non-interactively during login, the login shell
+startup files (~/.profile, ~/.bash_profile) will not be sourced at login.
+To get around this problem, append a line similar to the following to your
+~/.dtprofile:
+
+ BASH_ENV=${HOME}/.bash_profile ; export BASH_ENV
+
+and add the following line to the beginning of ~/.bash_profile:
+
+ unset BASH_ENV
+
+A8) I just changed my login shell to bash, and now I can't FTP into my
+ machine. Why not?
+
+You must add the full pathname to bash to the file /etc/shells. As
+noted in the answer to the previous question, many systems require
+this before you can make bash your login shell.
+
+Most versions of ftpd use this file to prohibit `special' users
+such as `uucp' and `news' from using FTP.
+
+A9) What's the `POSIX 1003.2 standard'?
+
+POSIX is a name originally coined by Richard Stallman for a
+family of open system standards based on UNIX. There are a
+number of aspects of UNIX under consideration for
+standardization, from the basic system services at the system
+call and C library level to applications and tools to system
+administration and management. Each area of standardization is
+assigned to a working group in the 1003 series.
+
+The POSIX Shell and Utilities standard has been developed by IEEE
+Working Group 1003.2 (POSIX.2). It concentrates on the command
+interpreter interface and utility programs commonly executed from
+the command line or by other programs. An initial version of the
+standard has been approved and published by the IEEE, and work is
+currently underway to update it.
+
+Bash is concerned with the aspects of the shell's behavior
+defined by POSIX.2. The shell command language has of course
+been standardized, including the basic flow control and program
+execution constructs, I/O redirection and pipelining, argument
+handling, variable expansion, and quoting.
+
+The `special' builtins, which must be implemented as part of the
+shell to provide the desired functionality, are specified as
+being part of the shell; examples of these are `eval' and
+`export'. Other utilities appear in the sections of POSIX.2 not
+devoted to the shell which are commonly (and in some cases must
+be) implemented as builtin commands, such as `read' and `test'.
+POSIX.2 also specifies aspects of the shell's interactive
+behavior as part of the UPE, including job control and command
+line editing. Only vi-style line editing commands have been
+standardized; emacs editing commands were left out due to
+objections.
+
+The Open Group has made an older version of its Single Unix
+Specification (version 2), which is very similar to POSIX.2,
+available on the web at
+
+http://www.opengroup.org/onlinepubs/007908799/
+
+The Single Unix Specification, version 3, is available on the web at
+
+http://www.opengroup.org/onlinepubs/007904975/
+
+A10) What is the bash `posix mode'?
+
+Although bash is an implementation of the POSIX.2 shell
+specification, there are areas where the bash default behavior
+differs from that spec. The bash `posix mode' changes the bash
+behavior in these areas so that it obeys the spec more closely.
+
+Posix mode is entered by starting bash with the --posix or
+'-o posix' option or executing `set -o posix' after bash is running.
+
+The specific aspects of bash which change when posix mode is
+active are listed in the file POSIX in the bash distribution.
+They are also listed in a section in the Bash Reference Manual
+(from which that file is generated).
+
+Section B: The latest version
+
+B1) What's new in version 2.05b?
+
+The raison d'etre for bash-2.05b is to make a second intermediate
+release containing the first of the new features to be available
+in bash-3.0 and get feedback on those features before proceeding.
+The major new feature is multibyte character support in both Bash
+and Readline.
+
+Bash-2.05b contains the following new features (see the manual page for
+complete descriptions and the CHANGES and NEWS files in the bash-2.05b
+distribution):
+
+o support for multibyte characters has been added to both bash and readline
+
+o the DEBUG trap is now run *before* simple commands, ((...)) commands,
+ [[...]] conditional commands, and for ((...)) loops
+
+o the shell now performs arithmetic in the largest integer size the machine
+ supports (intmax_t)
+
+o there is a new \D{...} prompt expansion; passes the `...' to strftime(3)
+ and inserts the result into the expanded prompt
+
+o there is a new `here-string' redirection operator: <<< word
+
+o when displaying variables, function attributes and definitions are shown
+ separately, allowing them to be re-used as input (attempting to re-use
+ the old output would result in syntax errors).
+
+o `read' has a new `-u fd' option to read from a specified file descriptor
+
+o the bash debugger in examples/bashdb has been modified to work with the
+ new DEBUG trap semantics, the command set has been made more gdb-like,
+ and the changes to $LINENO make debugging functions work better
+
+o the expansion of $LINENO inside a shell function is only relative to the
+ function start if the shell is interactive -- if the shell is running a
+ script, $LINENO expands to the line number in the script. This is as
+ POSIX-2001 requires
+
+
+A short feature history dating from Bash-2.0:
+
+Bash-2.05a introduced the following new features:
+
+o The `printf' builtin has undergone major work
+
+o There is a new read-only `shopt' option: login_shell, which is set by
+ login shells and unset otherwise
+
+o New `\A' prompt string escape sequence; expanding to time in 24-hour
+ HH:MM format
+
+o New `-A group/-g' option to complete and compgen; goes group name
+ completion
+
+o New [+-]O invocation option to set and unset `shopt' options at startup
+
+o ksh-like `ERR' trap
+
+o `for' loops now allow empty word lists after the `in' reserved word
+
+o new `hard' and `soft' arguments for the `ulimit' builtin
+
+o Readline can be configured to place the user at the same point on the line
+ when retrieving commands from the history list
+
+o Readline can be configured to skip `hidden' files (filenames with a leading
+ `.' on Unix) when performing completion
+
+Bash-2.05 introduced the following new features:
+
+o This version has once again reverted to using locales and strcoll(3) when
+ processing pattern matching bracket expressions, as POSIX requires.
+o Added a new `--init-file' invocation argument as a synonym for `--rcfile',
+ per the new GNU coding standards.
+o The /dev/tcp and /dev/udp redirections now accept service names as well as
+ port numbers.
+o `complete' and `compgen' now take a `-o value' option, which controls some
+ of the aspects of that compspec. Valid values are:
+
+ default - perform bash default completion if programmable
+ completion produces no matches
+ dirnames - perform directory name completion if programmable
+ completion produces no matches
+ filenames - tell readline that the compspec produces filenames,
+ so it can do things like append slashes to
+ directory names and suppress trailing spaces
+o A new loadable builtin, realpath, which canonicalizes and expands symlinks
+ in pathname arguments.
+o When `set' is called without options, it prints function defintions in a
+ way that allows them to be reused as input. This affects `declare' and
+ `declare -p' as well. This only happens when the shell is not in POSIX
+ mode, since POSIX.2 forbids this behavior.
+
+Bash-2.04 introduced the following new features:
+
+o Programmable word completion with the new `complete' and `compgen' builtins;
+ examples are provided in examples/complete/complete-examples
+o `history' has a new `-d' option to delete a history entry
+o `bind' has a new `-x' option to bind key sequences to shell commands
+o The prompt expansion code has new `\j' and `\l' escape sequences
+o The `no_empty_cmd_completion' shell option, if enabled, inhibits
+ command completion when TAB is typed on an empty line
+o `help' has a new `-s' option to print a usage synopsis
+o New arithmetic operators: var++, var--, ++var, --var, expr1,expr2 (comma)
+o New ksh93-style arithmetic for command:
+ for ((expr1 ; expr2; expr3 )); do list; done
+o `read' has new options: `-t', `-n', `-d', `-s'
+o The redirection code handles several filenames specially: /dev/fd/N,
+ /dev/stdin, /dev/stdout, /dev/stderr
+o The redirection code now recognizes /dev/tcp/HOST/PORT and
+ /dev/udp/HOST/PORT and tries to open a TCP or UDP socket, respectively,
+ to the specified port on the specified host
+o The ${!prefix*} expansion has been implemented
+o A new FUNCNAME variable, which expands to the name of a currently-executing
+ function
+o The GROUPS variable is no longer readonly
+o A new shopt `xpg_echo' variable, to control the behavior of echo with
+ respect to backslash-escape sequences at runtime
+o The NON_INTERACTIVE_LOGIN_SHELLS #define has returned
+
+The version of Readline released with Bash-2.04, Readline-4.1, had several
+new features as well:
+
+o Parentheses matching is always compiled into readline, and controllable
+ with the new `blink-matching-paren' variable
+o The history-search-forward and history-search-backward functions now leave
+ point at the end of the line when the search string is empty, like
+ reverse-search-history, and forward-search-history
+o A new function for applications: rl_on_new_line_with_prompt()
+o New variables for applications: rl_already_prompted, and rl_gnu_readline_p
+
+
+Bash-2.03 had very few new features, in keeping with the convention
+that odd-numbered releases provide mainly bug fixes. A number of new
+features were added to Readline, mostly at the request of the Cygnus
+folks.
+
+A new shopt option, `restricted_shell', so that startup files can test
+ whether or not the shell was started in restricted mode
+Filename generation is now performed on the words between ( and ) in
+ compound array assignments (this is really a bug fix)
+OLDPWD is now auto-exported, as POSIX.2 requires
+ENV and BASH_ENV are read-only variables in a restricted shell
+Bash may now be linked against an already-installed Readline library,
+ as long as the Readline library is version 4 or newer
+All shells begun with the `--login' option will source the login shell
+ startup files, even if the shell is not interactive
+
+There were lots of changes to the version of the Readline library released
+along with Bash-2.03. For a complete list of the changes, read the file
+CHANGES in the Bash-2.03 distribution.
+
+Bash-2.02 contained the following new features:
+
+a new version of malloc (based on the old GNU malloc code in previous
+ bash versions) that is more page-oriented, more conservative
+ with memory usage, does not `orphan' large blocks when they
+ are freed, is usable on 64-bit machines, and has allocation
+ checking turned on unconditionally
+POSIX.2-style globbing character classes ([:alpha:], [:alnum:], etc.)
+POSIX.2-style globbing equivalence classes
+POSIX.2-style globbing collating symbols
+the ksh [[...]] extended conditional command
+the ksh egrep-style extended pattern matching operators
+a new `printf' builtin
+the ksh-like $(<filename) command substitution, which is equivalent to
+ $(cat filename)
+new tilde prefixes that expand to directories from the directory stack
+new `**' arithmetic operator to do exponentiation
+case-insensitive globbing (filename expansion)
+menu completion a la tcsh
+`magic-space' history expansion function like tcsh
+the readline inputrc `language' has a new file inclusion directive ($include)
+
+Bash-2.01 contained only a few new features:
+
+new `GROUPS' builtin array variable containing the user's group list
+new bindable readline commands: history-and-alias-expand-line and
+ alias-expand-line
+
+Bash-2.0 contained extensive changes and new features from bash-1.14.7.
+Here's a short list:
+
+new `time' reserved word to time pipelines, shell builtins, and
+ shell functions
+one-dimensional arrays with a new compound assignment statement,
+ appropriate expansion constructs and modifications to some
+ of the builtins (read, declare, etc.) to use them
+new quoting syntaxes for ANSI-C string expansion and locale-specific
+ string translation
+new expansions to do substring extraction, pattern replacement, and
+ indirect variable expansion
+new builtins: `disown' and `shopt'
+new variables: HISTIGNORE, SHELLOPTS, PIPESTATUS, DIRSTACK, GLOBIGNORE,
+ MACHTYPE, BASH_VERSINFO
+special handling of many unused or redundant variables removed
+ (e.g., $notify, $glob_dot_filenames, $no_exit_on_failed_exec)
+dynamic loading of new builtin commands; many loadable examples provided
+new prompt expansions: \a, \e, \n, \H, \T, \@, \v, \V
+history and aliases available in shell scripts
+new readline variables: enable-keypad, mark-directories, input-meta,
+ visible-stats, disable-completion, comment-begin
+new readline commands to manipulate the mark and operate on the region
+new readline emacs mode commands and bindings for ksh-88 compatibility
+updated and extended builtins
+new DEBUG trap
+expanded (and now documented) restricted shell mode
+
+implementation stuff:
+autoconf-based configuration
+nearly all of the bugs reported since version 1.14 have been fixed
+most builtins converted to use builtin `getopt' for consistency
+most builtins use -p option to display output in a reusable form
+ (for consistency)
+grammar tighter and smaller (66 reduce-reduce conflicts gone)
+lots of code now smaller and faster
+test suite greatly expanded
+
+B2) Are there any user-visible incompatibilities between bash-2.05b and
+ bash-1.14.7?
+
+There are a few incompatibilities between version 1.14.7 and version 2.05b.
+They are detailed in the file COMPAT in the bash distribution. That file
+is not meant to be all-encompassing; send mail to bash-maintainers@gnu.org
+if if you find something that's not mentioned there.
+
+Section C: Differences from other Unix shells
+
+C1) How does bash differ from sh, the Bourne shell?
+
+This is a non-comprehensive list of features that differentiate bash
+from the SVR4.2 shell. The bash manual page explains these more
+completely.
+
+Things bash has that sh does not:
+ long invocation options
+ [+-]O invocation option
+ -l invocation option
+ `!' reserved word to invert pipeline return value
+ `time' reserved word to time pipelines and shell builtins
+ the `function' reserved word
+ the `select' compound command and reserved word
+ arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
+ new $'...' and $"..." quoting
+ the $(...) form of command substitution
+ the $(<filename) form of command substitution, equivalent to
+ $(cat filename)
+ the ${#param} parameter value length operator
+ the ${!param} indirect parameter expansion operator
+ the ${!param*} prefix expansion operator
+ the ${param:offset[:length]} parameter substring operator
+ the ${param/pat[/string]} parameter pattern substitution operator
+ expansions to perform substring removal (${p%[%]w}, ${p#[#]w})
+ expansion of positional parameters beyond $9 with ${num}
+ variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, REPLY,
+ TIMEFORMAT, PPID, PWD, OLDPWD, SHLVL, RANDOM, SECONDS,
+ LINENO, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE, HOSTNAME,
+ ENV, PS3, PS4, DIRSTACK, PIPESTATUS, HISTSIZE, HISTFILE,
+ HISTFILESIZE, HISTCONTROL, HISTIGNORE, GLOBIGNORE, GROUPS,
+ PROMPT_COMMAND, FCEDIT, FIGNORE, IGNOREEOF, INPUTRC,
+ SHELLOPTS, OPTERR, HOSTFILE, TMOUT, FUNCNAME, histchars,
+ auto_resume
+ DEBUG trap
+ ERR trap
+ variable arrays with new compound assignment syntax
+ redirections: <>, &>, >|, <<<, [n]<&word-, [n]>&word-
+ prompt string special char translation and variable expansion
+ auto-export of variables in initial environment
+ command search finds functions before builtins
+ bash return builtin will exit a file sourced with `.'
+ builtins: cd -/-L/-P, exec -l/-c/-a, echo -e/-E, hash -d/-l/-p/-t.
+ export -n/-f/-p/name=value, pwd -L/-P,
+ read -e/-p/-a/-t/-n/-d/-s/-u,
+ readonly -a/-f/name=value, trap -l, set +o,
+ set -b/-m/-o option/-h/-p/-B/-C/-H/-P,
+ unset -f/-v, ulimit -m/-p/-u,
+ type -a/-p/-t/-f/-P, suspend -f, kill -n,
+ test -o optname/s1 == s2/s1 < s2/s1 > s2/-nt/-ot/-ef/-O/-G/-S
+ bash reads ~/.bashrc for interactive shells, $ENV for non-interactive
+ bash restricted shell mode is more extensive
+ bash allows functions and variables with the same name
+ brace expansion
+ tilde expansion
+ arithmetic expansion with $((...)) and `let' builtin
+ the `[[...]]' extended conditional command
+ process substitution
+ aliases and alias/unalias builtins
+ local variables in functions and `local' builtin
+ readline and command-line editing with programmable completion
+ command history and history/fc builtins
+ csh-like history expansion
+ other new bash builtins: bind, command, compgen, complete, builtin,
+ declare/typeset, dirs, enable, fc, help,
+ history, logout, popd, pushd, disown, shopt,
+ printf
+ exported functions
+ filename generation when using output redirection (command >a*)
+ POSIX.2-style globbing character classes
+ POSIX.2-style globbing equivalence classes
+ POSIX.2-style globbing collating symbols
+ egrep-like extended pattern matching operators
+ case-insensitive pattern matching and globbing
+ variable assignments preceding commands affect only that command,
+ even for builtins and functions
+ posix mode
+ redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr,
+ /dev/tcp/host/port, /dev/udp/host/port
+
+Things sh has that bash does not:
+ uses variable SHACCT to do shell accounting
+ includes `stop' builtin (bash can use alias stop='kill -s STOP')
+ `newgrp' builtin
+ turns on job control if called as `jsh'
+ $TIMEOUT (like bash $TMOUT)
+ `^' is a synonym for `|'
+ new SVR4.2 sh builtins: mldmode, priv
+
+Implementation differences:
+ redirection to/from compound commands causes sh to create a subshell
+ bash does not allow unbalanced quotes; sh silently inserts them at EOF
+ bash does not mess with signal 11
+ sh sets (euid, egid) to (uid, gid) if -p not supplied and uid < 100
+ bash splits only the results of expansions on IFS, using POSIX.2
+ field splitting rules; sh splits all words on IFS
+ sh does not allow MAILCHECK to be unset (?)
+ sh does not allow traps on SIGALRM or SIGCHLD
+ bash allows multiple option arguments when invoked (e.g. -x -v);
+ sh allows only a single option argument (`sh -x -v' attempts
+ to open a file named `-v', and, on SunOS 4.1.4, dumps core.
+ On Solaris 2.4 and earlier versions, sh goes into an infinite
+ loop.)
+ sh exits a script if any builtin fails; bash exits only if one of
+ the POSIX.2 `special' builtins fails
+
+C2) How does bash differ from the Korn shell, version ksh88?
+
+Things bash has or uses that ksh88 does not:
+ long invocation options
+ [-+]O invocation option
+ -l invocation option
+ `!' reserved word
+ arithmetic for command: for ((expr1 ; expr2; expr3 )); do list; done
+ arithmetic in largest machine-supported size (intmax_t)
+ posix mode and posix conformance
+ command hashing
+ tilde expansion for assignment statements that look like $PATH
+ process substitution with named pipes if /dev/fd is not available
+ the ${!param} indirect parameter expansion operator
+ the ${!param*} prefix expansion operator
+ the ${param:offset[:length]} parameter substring operator
+ the ${param/pat[/string]} parameter pattern substitution operator
+ variables: BASH, BASH_VERSION, BASH_VERSINFO, UID, EUID, SHLVL,
+ TIMEFORMAT, HISTCMD, HOSTTYPE, OSTYPE, MACHTYPE,
+ HISTFILESIZE, HISTIGNORE, HISTCONTROL, PROMPT_COMMAND,
+ IGNOREEOF, FIGNORE, INPUTRC, HOSTFILE, DIRSTACK,
+ PIPESTATUS, HOSTNAME, OPTERR, SHELLOPTS, GLOBIGNORE,
+ GROUPS, FUNCNAME, histchars, auto_resume
+ prompt expansion with backslash escapes and command substitution
+ redirection: &> (stdout and stderr), <<<, [n]<&word-, [n]>&word-
+ more extensive and extensible editing and programmable completion
+ builtins: bind, builtin, command, declare, dirs, echo -e/-E, enable,
+ exec -l/-c/-a, fc -s, export -n/-f/-p, hash, help, history,
+ jobs -x/-r/-s, kill -s/-n/-l, local, logout, popd, pushd,
+ read -e/-p/-a/-t/-n/-d/-s, readonly -a/-n/-f/-p,
+ set -o braceexpand/-o histexpand/-o interactive-comments/
+ -o notify/-o physical/-o posix/-o hashall/-o onecmd/
+ -h/-B/-C/-b/-H/-P, set +o, suspend, trap -l, type,
+ typeset -a/-F/-p, ulimit -u, umask -S, alias -p, shopt,
+ disown, printf, complete, compgen
+ `!' csh-style history expansion
+ POSIX.2-style globbing character classes
+ POSIX.2-style globbing equivalence classes
+ POSIX.2-style globbing collating symbols
+ egrep-like extended pattern matching operators
+ case-insensitive pattern matching and globbing
+ `**' arithmetic operator to do exponentiation
+ redirection to /dev/fd/N, /dev/stdin, /dev/stdout, /dev/stderr
+ arrays of unlimited size
+ TMOUT is default timeout for `read' and `select'
+
+Things ksh88 has or uses that bash does not:
+ tracked aliases (alias -t)
+ variables: ERRNO, FPATH, EDITOR, VISUAL
+ co-processes (|&, >&p, <&p)
+ weirdly-scoped functions
+ typeset +f to list all function names without definitions
+ text of command history kept in a file, not memory
+ builtins: alias -x, cd old new, fc -e -, newgrp, print,
+ read -p/-s/var?prompt, set -A/-o gmacs/
+ -o bgnice/-o markdirs/-o nolog/-o trackall/-o viraw/-s,
+ typeset -H/-L/-R/-Z/-A/-ft/-fu/-fx/-l/-u/-t, whence
+ using environment to pass attributes of exported variables
+ arithmetic evaluation done on arguments to some builtins
+ reads .profile from $PWD when invoked as login shell
+
+Implementation differences:
+ ksh runs last command of a pipeline in parent shell context
+ bash has brace expansion by default (ksh88 compile-time option)
+ bash has fixed startup file for all interactive shells; ksh reads $ENV
+ bash has exported functions
+ bash command search finds functions before builtins
+ bash waits for all commands in pipeline to exit before returning status
+ emacs-mode editing has some slightly different key bindings
+
+C3) Which new features in ksh-93 are not in bash, and which are?
+
+New things in ksh-93 not in bash-2.05b:
+ associative arrays
+ floating point arithmetic and variables
+ math library functions
+ ${!name[sub]} name of subscript for associative array
+ `.' is allowed in variable names to create a hierarchical namespace
+ more extensive compound assignment syntax
+ discipline functions
+ `sleep' and `getconf' builtins (bash has loadable versions)
+ typeset -n and `nameref' variables
+ KEYBD trap
+ variables: .sh.edchar, .sh.edmode, .sh.edcol, .sh.edtext, .sh.version,
+ .sh.name, .sh.subscript, .sh.value, .sh.match, HISTEDIT
+ backreferences in pattern matching (\N)
+ `&' operator in pattern lists for matching
+ print -f (bash uses printf)
+ `fc' has been renamed to `hist'
+ `.' can execute shell functions
+ exit statuses between 0 and 255
+ set -o pipefail
+ `+=' variable assignment operator
+ FPATH and PATH mixing
+ getopts -a
+ -I invocation option
+ DEBUG trap now executed before each simple command, instead of after
+ printf %H, %P, %T, %Z modifiers, output base for %d
+ lexical scoping for local variables in `ksh' functions
+ no scoping for local variables in `POSIX' functions
+
+New things in ksh-93 present in bash-2.05b:
+ [n]<&word- and [n]>&word- redirections (combination dup and close)
+ for (( expr1; expr2; expr3 )) ; do list; done - arithmetic for command
+ ?:, ++, --, `expr1 , expr2' arithmetic operators
+ expansions: ${!param}, ${param:offset[:len]}, ${param/pat[/str]},
+ ${!param*}
+ compound array assignment
+ the `!' reserved word
+ loadable builtins -- but ksh uses `builtin' while bash uses `enable'
+ `command', `builtin', `disown' builtins
+ new $'...' and $"..." quoting
+ FIGNORE (but bash uses GLOBIGNORE), HISTCMD
+ set -o notify/-C
+ changes to kill builtin
+ read -A (bash uses read -a)
+ read -t/-d
+ trap -p
+ exec -c/-a
+ `.' restores the positional parameters when it completes
+ POSIX.2 `test'
+ umask -S
+ unalias -a
+ command and arithmetic substitution performed on PS1, PS4, and ENV
+ command name completion
+ ENV processed only for interactive shells
+
+Section D: Why does bash do some things differently than other Unix shells?
+
+D1) Why does bash run a different version of `command' than
+ `which command' says it will?
+
+On many systems, `which' is actually a csh script that assumes
+you're running csh. In tcsh, `which' and its cousin `where'
+are builtins. On other Unix systems, `which' is a perl script
+that uses the PATH environment variable.
+
+The csh script version reads the csh startup files from your
+home directory and uses those to determine which `command' will
+be invoked. Since bash doesn't use any of those startup files,
+there's a good chance that your bash environment differs from
+your csh environment. The bash `type' builtin does everything
+`which' does, and will report correct results for the running
+shell. If you're really wedded to the name `which', try adding
+the following function definition to your .bashrc:
+
+ which()
+ {
+ builtin type "$@"
+ }
+
+If you're moving from tcsh and would like to bring `where' along
+as well, use this function:
+
+ where()
+ {
+ builtin type -a "$@"
+ }
+
+D2) Why doesn't bash treat brace expansions exactly like csh?
+
+The only difference between bash and csh brace expansion is that
+bash requires a brace expression to contain at least one unquoted
+comma if it is to be expanded. Any brace-surrounded word not
+containing an unquoted comma is left unchanged by the brace
+expansion code. This affords the greatest degree of sh
+compatibility.
+
+Bash, ksh, zsh, and pd-ksh all implement brace expansion this way.
+
+D3) Why doesn't bash have csh variable modifiers?
+
+Posix has specified a more powerful, albeit somewhat more cryptic,
+mechanism cribbed from ksh, and bash implements it.
+
+${parameter%word}
+ Remove smallest suffix pattern. The WORD is expanded to produce
+ a pattern. It then expands to the value of PARAMETER, with the
+ smallest portion of the suffix matched by the pattern deleted.
+
+ x=file.c
+ echo ${x%.c}.o
+ -->file.o
+
+${parameter%%word}
+
+ Remove largest suffix pattern. The WORD is expanded to produce
+ a pattern. It then expands to the value of PARAMETER, with the
+ largest portion of the suffix matched by the pattern deleted.
+
+ x=posix/src/std
+ echo ${x%%/*}
+ -->posix
+
+${parameter#word}
+ Remove smallest prefix pattern. The WORD is expanded to produce
+ a pattern. It then expands to the value of PARAMETER, with the
+ smallest portion of the prefix matched by the pattern deleted.
+
+ x=$HOME/src/cmd
+ echo ${x#$HOME}
+ -->/src/cmd
+
+${parameter##word}
+ Remove largest prefix pattern. The WORD is expanded to produce
+ a pattern. It then expands to the value of PARAMETER, with the
+ largest portion of the prefix matched by the pattern deleted.
+
+ x=/one/two/three
+ echo ${x##*/}
+ -->three
+
+
+Given
+ a=/a/b/c/d
+ b=b.xxx
+
+ csh bash result
+ --- ---- ------
+ $a:h ${a%/*} /a/b/c
+ $a:t ${a##*/} d
+ $b:r ${b%.*} b
+ $b:e ${b##*.} xxx
+
+
+D4) How can I make my csh aliases work when I convert to bash?
+
+Bash uses a different syntax to support aliases than csh does.
+The details can be found in the documentation. We have provided
+a shell script which does most of the work of conversion for you;
+this script can be found in ./examples/misc/aliasconv.sh. Here is
+how you use it:
+
+Start csh in the normal way for you. (e.g., `csh')
+
+Pipe the output of `alias' through `aliasconv.sh', saving the
+results into `bash_aliases':
+
+ alias | bash aliasconv.sh >bash_aliases
+
+Edit `bash_aliases', carefully reading through any created
+functions. You will need to change the names of some csh specific
+variables to the bash equivalents. The script converts $cwd to
+$PWD, $term to $TERM, $home to $HOME, $user to $USER, and $prompt
+to $PS1. You may also have to add quotes to avoid unwanted
+expansion.
+
+For example, the csh alias:
+
+ alias cd 'cd \!*; echo $cwd'
+
+is converted to the bash function:
+
+ cd () { command cd "$@"; echo $PWD ; }
+
+The only thing that needs to be done is to quote $PWD:
+
+ cd () { command cd "$@"; echo "$PWD" ; }
+
+Merge the edited file into your ~/.bashrc.
+
+There is an additional, more ambitious, script in
+examples/misc/cshtobash that attempts to convert your entire csh
+environment to its bash equivalent. This script can be run as
+simply `cshtobash' to convert your normal interactive
+environment, or as `cshtobash ~/.login' to convert your login
+environment.
+
+D5) How can I pipe standard output and standard error from one command to
+ another, like csh does with `|&'?
+
+Use
+ command 2>&1 | command2
+
+The key is to remember that piping is performed before redirection, so
+file descriptor 1 points to the pipe when it is duplicated onto file
+descriptor 2.
+
+D6) Now that I've converted from ksh to bash, are there equivalents to
+ ksh features like autoloaded functions and the `whence' command?
+
+There are features in ksh-88 and ksh-93 that do not have direct bash
+equivalents. Most, however, can be emulated with very little trouble.
+
+ksh-88 feature Bash equivalent
+-------------- ---------------
+compiled-in aliases set up aliases in .bashrc; some ksh aliases are
+ bash builtins (hash, history, type)
+coprocesses named pipe pairs (one for read, one for write)
+typeset +f declare -F
+cd, print, whence function substitutes in examples/functions/kshenv
+autoloaded functions examples/functions/autoload is the same as typeset -fu
+read var?prompt read -p prompt var
+
+ksh-93 feature Bash equivalent
+-------------- ---------------
+sleep, getconf Bash has loadable versions in examples/loadables
+${.sh.version} $BASH_VERSION
+print -f printf
+hist alias hist=fc
+$HISTEDIT $FCEDIT
+
+Section E: How can I get bash to do certain things, and why does bash do
+ things the way it does?
+
+E1) Why is the bash builtin `test' slightly different from /bin/test?
+
+The specific example used here is [ ! x -o x ], which is false.
+
+Bash's builtin `test' implements the Posix.2 spec, which can be
+summarized as follows (the wording is due to David Korn):
+
+Here is the set of rules for processing test arguments.
+
+ 0 Args: False
+ 1 Arg: True iff argument is not null.
+ 2 Args: If first arg is !, True iff second argument is null.
+ If first argument is unary, then true if unary test is true
+ Otherwise error.
+ 3 Args: If second argument is a binary operator, do binary test of $1 $3
+ If first argument is !, negate two argument test of $2 $3
+ If first argument is `(' and third argument is `)', do the
+ one-argument test of the second argument.
+ Otherwise error.
+ 4 Args: If first argument is !, negate three argument test of $2 $3 $4.
+ Otherwise unspecified
+ 5 or more Args: unspecified. (Historical shells would use their
+ current algorithm).
+
+The operators -a and -o are considered binary operators for the purpose
+of the 3 Arg case.
+
+As you can see, the test becomes (not (x or x)), which is false.
+
+E2) Why does bash sometimes say `Broken pipe'?
+
+If a sequence of commands appears in a pipeline, and one of the
+reading commands finishes before the writer has finished, the
+writer receives a SIGPIPE signal. Many other shells special-case
+SIGPIPE as an exit status in the pipeline and do not report it.
+For example, in:
+
+ ps -aux | head
+
+`head' can finish before `ps' writes all of its output, and ps
+will try to write on a pipe without a reader. In that case, bash
+will print `Broken pipe' to stderr when ps is killed by a
+SIGPIPE.
+
+You can build a version of bash that will not report SIGPIPE errors
+by uncommenting the definition of DONT_REPORT_SIGPIPE in the file
+config-top.h.
+
+E3) When I have terminal escape sequences in my prompt, why does bash
+ wrap lines at the wrong column?
+
+Readline, the line editing library that bash uses, does not know
+that the terminal escape sequences do not take up space on the
+screen. The redisplay code assumes, unless told otherwise, that
+each character in the prompt is a `printable' character that
+takes up one character position on the screen.
+
+You can use the bash prompt expansion facility (see the PROMPTING
+section in the manual page) to tell readline that sequences of
+characters in the prompt strings take up no screen space.
+
+Use the \[ escape to begin a sequence of non-printing characters,
+and the \] escape to signal the end of such a sequence.
+
+E4) If I pipe the output of a command into `read variable', why doesn't
+ the output show up in $variable when the read command finishes?
+
+This has to do with the parent-child relationship between Unix
+processes. It affects all commands run in pipelines, not just
+simple calls to `read'. For example, piping a command's output
+into a `while' loop that repeatedly calls `read' will result in
+the same behavior.
+
+Each element of a pipeline runs in a separate process, a child of
+the shell running the pipeline. A subprocess cannot affect its
+parent's environment. When the `read' command sets the variable
+to the input, that variable is set only in the subshell, not the
+parent shell. When the subshell exits, the value of the variable
+is lost.
+
+Many pipelines that end with `read variable' can be converted
+into command substitutions, which will capture the output of
+a specified command. The output can then be assigned to a
+variable:
+
+ grep ^gnu /usr/lib/news/active | wc -l | read ngroup
+
+can be converted into
+
+ ngroup=$(grep ^gnu /usr/lib/news/active | wc -l)
+
+This does not, unfortunately, work to split the text among
+multiple variables, as read does when given multiple variable
+arguments. If you need to do this, you can either use the
+command substitution above to read the output into a variable
+and chop up the variable using the bash pattern removal
+expansion operators or use some variant of the following
+approach.
+
+Say /usr/local/bin/ipaddr is the following shell script:
+
+#! /bin/sh
+host `hostname` | awk '/address/ {print $NF}'
+
+Instead of using
+
+ /usr/local/bin/ipaddr | read A B C D
+
+to break the local machine's IP address into separate octets, use
+
+ OIFS="$IFS"
+ IFS=.
+ set -- $(/usr/local/bin/ipaddr)
+ IFS="$OIFS"
+ A="$1" B="$2" C="$3" D="$4"
+
+Beware, however, that this will change the shell's positional
+parameters. If you need them, you should save them before doing
+this.
+
+This is the general approach -- in most cases you will not need to
+set $IFS to a different value.
+
+Some other user-supplied alternatives include:
+
+read A B C D << HERE
+ $(IFS=.; echo $(/usr/local/bin/ipaddr))
+HERE
+
+and, where process substitution is available,
+
+read A B C D < <(IFS=.; echo $(/usr/local/bin/ipaddr))
+
+E5) I have a bunch of shell scripts that use backslash-escaped characters
+ in arguments to `echo'. Bash doesn't interpret these characters. Why
+ not, and how can I make it understand them?
+
+This is the behavior of echo on most Unix System V machines.
+
+The bash builtin `echo' is modeled after the 9th Edition
+Research Unix version of `echo'. It does not interpret
+backslash-escaped characters in its argument strings by default;
+it requires the use of the -e option to enable the
+interpretation. The System V echo provides no way to disable the
+special characters; the bash echo has a -E option to disable
+them.
+
+There is a configuration option that will make bash behave like
+the System V echo and interpret things like `\t' by default. Run
+configure with the --enable-xpg-echo-default option to turn this
+on. Be aware that this will cause some of the tests run when you
+type `make tests' to fail.
+
+There is a shell option, `xpg_echo', settable with `shopt', that will
+change the behavior of echo at runtime. Enabling this option turns
+on expansion of backslash-escape sequences.
+
+E6) Why doesn't a while or for loop get suspended when I type ^Z?
+
+This is a consequence of how job control works on Unix. The only
+thing that can be suspended is the process group. This is a single
+command or pipeline of commands that the shell forks and executes.
+
+When you run a while or for loop, the only thing that the shell forks
+and executes are any commands in the while loop test and commands in
+the loop bodies. These, therefore, are the only things that can be
+suspended when you type ^Z.
+
+If you want to be able to stop the entire loop, you need to put it
+within parentheses, which will force the loop into a subshell that
+may be stopped (and subsequently restarted) as a single unit.
+
+E7) What about empty for loops in Makefiles?
+
+It's fairly common to see constructs like this in automatically-generated
+Makefiles:
+
+SUBDIRS = @SUBDIRS@
+
+ ...
+
+subdirs-clean:
+ for d in ${SUBDIRS}; do \
+ ( cd $$d && ${MAKE} ${MFLAGS} clean ) \
+ done
+
+When SUBDIRS is empty, this results in a command like this being passed to
+bash:
+
+ for d in ; do
+ ( cd $d && ${MAKE} ${MFLAGS} clean )
+ done
+
+In versions of bash before bash-2.05a, this was a syntax error. If the
+reserved word `in' was present, a word must follow it before the semicolon
+or newline. The language in the manual page referring to the list of words
+being empty referred to the list after it is expanded. These versions of
+bash required that there be at least one word following the `in' when the
+construct was parsed.
+
+The idiomatic Makefile solution is something like:
+
+SUBDIRS = @SUBDIRS@
+
+subdirs-clean:
+ subdirs=$SUBDIRS ; for d in $$subdirs; do \
+ ( cd $$d && ${MAKE} ${MFLAGS} clean ) \
+ done
+
+The latest drafts of the updated POSIX standard have changed this: the
+word list is no longer required. Bash versions 2.05a and later accept
+the new syntax.
+
+E8) Why does the arithmetic evaluation code complain about `08'?
+
+The bash arithmetic evaluation code (used for `let', $(()), (()), and in
+other places), interprets a leading `0' in numeric constants as denoting
+an octal number, and a leading `0x' as denoting hexadecimal. This is
+in accordance with the POSIX.2 spec, section 2.9.2.1, which states that
+arithmetic constants should be handled as signed long integers as defined
+by the ANSI/ISO C standard.
+
+The POSIX.2 interpretation committee has confirmed this:
+
+http://www.pasc.org/interps/unofficial/db/p1003.2/pasc-1003.2-173.html
+
+E9) Why does the pattern matching expression [A-Z]* match files beginning
+ with every letter except `z'?
+
+Bash-2.03, Bash-2.05 and later versions honor the current locale setting
+when processing ranges within pattern matching bracket expressions ([A-Z]).
+This is what POSIX.2 and SUSv3/XPG6 specify.
+
+The behavior of the matcher in bash-2.05 and later versions depends on the
+current LC_COLLATE setting. Setting this variable to `C' or `POSIX' will
+result in the traditional behavior ([A-Z] matches all uppercase ASCII
+characters). Many other locales, including the en_US locale (the default
+on many US versions of Linux) collate the upper and lower case letters like
+this:
+
+ AaBb...Zz
+
+which means that [A-Z] matches every letter except `z'. Others collate like
+
+ aAbBcC...zZ
+
+which means that [A-Z] matches every letter except `a'.
+
+The portable way to specify upper case letters is [:upper:] instead of
+A-Z; lower case may be specified as [:lower:] instead of a-z.
+
+Look at the manual pages for setlocale(3), strcoll(3), and, if it is
+present, locale(1). If you have locale(1), you can use it to find
+your current locale information even if you do not have any of the
+LC_ variables set.
+
+My advice is to put
+
+ export LC_COLLATE=C
+
+into /etc/profile and inspect any shell scripts run from cron for
+constructs like [A-Z]. This will prevent things like
+
+ rm [A-Z]*
+
+from removing every file in the current directory except those beginning
+with `z' and still allow individual users to change the collation order.
+Users may put the above command into their own profiles as well, of course.
+
+E10) Why does `cd //' leave $PWD as `//'?
+
+POSIX.2, in its description of `cd', says that *three* or more leading
+slashes may be replaced with a single slash when canonicalizing the
+current working directory.
+
+This is, I presume, for historical compatibility. Certain versions of
+Unix, and early network file systems, used paths of the form
+//hostname/path to access `path' on server `hostname'.
+
+E11) If I resize my xterm while another program is running, why doesn't bash
+ notice the change?
+
+This is another issue that deals with job control.
+
+The kernel maintains a notion of a current terminal process group. Members
+of this process group (processes whose process group ID is equal to the
+current terminal process group ID) receive terminal-generated signals like
+SIGWINCH. (For more details, see the JOB CONTROL section of the bash
+man page.)
+
+If a terminal is resized, the kernel sends SIGWINCH to each member of
+the terminal's current process group (the `foreground' process group).
+
+When bash is running with job control enabled, each pipeline (which may be
+a single command) is run in its own process group, different from bash's
+process group. This foreground process group receives the SIGWINCH; bash
+does not. Bash has no way of knowing that the terminal has been resized.
+
+There is a `checkwinsize' option, settable with the `shopt' builtin, that
+will cause bash to check the window size and adjust its idea of the
+terminal's dimensions each time a process stops or exits and returns control
+of the terminal to bash. Enable it with `shopt -s checkwinsize'.
+
+Section F: Things to watch out for on certain Unix versions
+
+F1) Why can't I use command line editing in my `cmdtool'?
+
+The problem is `cmdtool' and bash fighting over the input. When
+scrolling is enabled in a cmdtool window, cmdtool puts the tty in
+`raw mode' to permit command-line editing using the mouse for
+applications that cannot do it themselves. As a result, bash and
+cmdtool each try to read keyboard input immediately, with neither
+getting enough of it to be useful.
+
+This mode also causes cmdtool to not implement many of the
+terminal functions and control sequences appearing in the
+`sun-cmd' termcap entry. For a more complete explanation, see
+that file examples/suncmd.termcap in the bash distribution.
+
+`xterm' is a better choice, and gets along with bash much more
+smoothly.
+
+If you must use cmdtool, you can use the termcap description in
+examples/suncmd.termcap. Set the TERMCAP variable to the terminal
+description contained in that file, i.e.
+
+TERMCAP='Mu|sun-cmd:am:bs:km:pt:li#34:co#80:cl=^L:ce=\E[K:cd=\E[J:rs=\E[s:'
+
+Then export TERMCAP and start a new cmdtool window from that shell.
+The bash command-line editing should behave better in the new
+cmdtool. If this works, you can put the assignment to TERMCAP
+in your bashrc file.
+
+F2) I built bash on Solaris 2. Why do globbing expansions and filename
+ completion chop off the first few characters of each filename?
+
+This is the consequence of building bash on SunOS 5 and linking
+with the libraries in /usr/ucblib, but using the definitions
+and structures from files in /usr/include.
+
+The actual conflict is between the dirent structure in
+/usr/include/dirent.h and the struct returned by the version of
+`readdir' in libucb.a (a 4.3-BSD style `struct direct').
+
+Make sure you've got /usr/ccs/bin ahead of /usr/ucb in your $PATH
+when configuring and building bash. This will ensure that you
+use /usr/ccs/bin/cc or acc instead of /usr/ucb/cc and that you
+link with libc before libucb.
+
+If you have installed the Sun C compiler, you may also need to
+put /usr/ccs/bin and /opt/SUNWspro/bin into your $PATH before
+/usr/ucb.
+
+F3) Why does bash dump core after I interrupt username completion or
+ `~user' tilde expansion on a machine running NIS?
+
+This is a famous and long-standing bug in the SunOS YP (sorry, NIS)
+client library, which is part of libc.
+
+The YP library code keeps static state -- a pointer into the data
+returned from the server. When YP initializes itself (setpwent),
+it looks at this pointer and calls free on it if it's non-null.
+So far, so good.
+
+If one of the YP functions is interrupted during getpwent (the
+exact function is interpretwithsave()), and returns NULL, the
+pointer is freed without being reset to NULL, and the function
+returns. The next time getpwent is called, it sees that this
+pointer is non-null, calls free, and the bash free() blows up
+because it's being asked to free freed memory.
+
+The traditional Unix mallocs allow memory to be freed multiple
+times; that's probably why this has never been fixed. You can
+run configure with the `--without-gnu-malloc' option to use
+the C library malloc and avoid the problem.
+
+F4) I'm running SVR4.2. Why is the line erased every time I type `@'?
+
+The `@' character is the default `line kill' character in most
+versions of System V, including SVR4.2. You can change this
+character to whatever you want using `stty'. For example, to
+change the line kill character to control-u, type
+
+ stty kill ^U
+
+where the `^' and `U' can be two separate characters.
+
+F5) Why does bash report syntax errors when my C News scripts use a
+ redirection before a subshell command?
+
+The actual command in question is something like
+
+ < file ( command )
+
+According to the grammar given in the POSIX.2 standard, this construct
+is, in fact, a syntax error. Redirections may only precede `simple
+commands'. A subshell construct such as the above is one of the shell's
+`compound commands'. A redirection may only follow a compound command.
+
+This affects the mechanical transformation of commands that use `cat'
+to pipe a file into a command (a favorite Useless-Use-Of-Cat topic on
+comp.unix.shell). While most commands of the form
+
+ cat file | command
+
+can be converted to `< file command', shell control structures such as
+loops and subshells require `command < file'.
+
+The file CWRU/sh-redir-hack in the bash-2.05a distribution is an
+(unofficial) patch to parse.y that will modify the grammar to
+support this construct. It will not apply with `patch'; you must
+modify parse.y by hand. Note that if you apply this, you must
+recompile with -DREDIRECTION_HACK. This introduces a large
+number of reduce/reduce conflicts into the shell grammar.
+
+F6) Why can't I use vi-mode editing on Red Hat Linux 6.1?
+
+The short answer is that Red Hat screwed up.
+
+The long answer is that they shipped an /etc/inputrc that only works
+for emacs mode editing, and then screwed all the vi users by setting
+INPUTRC to /etc/inputrc in /etc/profile.
+
+The short fix is to do one of the following: remove or rename
+/etc/inputrc, set INPUTRC=~/.inputrc in ~/.bashrc (or .bash_profile,
+but make sure you export it if you do), remove the assignment to
+INPUTRC from /etc/profile, add
+
+ set keymap emacs
+
+to the beginning of /etc/inputrc, or bracket the key bindings in
+/etc/inputrc with these lines
+
+ $if mode=emacs
+ [...]
+ $endif
+
+F7) Why do bash-2.05a and bash-2.05b fail to compile `printf.def' on
+ HP/UX 11.x?
+
+HP/UX's support for long double is imperfect at best.
+
+GCC will support it without problems, but the HP C library functions
+like strtold(3) and printf(3) don't actually work with long doubles.
+HP implemented a `long_double' type as a 4-element array of 32-bit
+ints, and that is what the library functions use. The ANSI C
+`long double' type is a 128-bit floating point scalar.
+
+The easiest fix, until HP fixes things up, is to edit the generated
+config.h and #undef the HAVE_LONG_DOUBLE line. After doing that,
+the compilation should complete successfully.
+
+Section G: How can I get bash to do certain common things?
+
+G1) How can I get bash to read and display eight-bit characters?
+
+This is a process requiring several steps.
+
+First, you must ensure that the `physical' data path is a full eight
+bits. For xterms, for example, the `vt100' resources `eightBitInput'
+and `eightBitOutput' should be set to `true'.
+
+Once you have set up an eight-bit path, you must tell the kernel and
+tty driver to leave the eighth bit of characters alone when processing
+keyboard input. Use `stty' to do this:
+
+ stty cs8 -istrip -parenb
+
+For old BSD-style systems, you can use
+
+ stty pass8
+
+You may also need
+
+ stty even odd
+
+Finally, you need to tell readline that you will be inputting and
+displaying eight-bit characters. You use readline variables to do
+this. These variables can be set in your .inputrc or using the bash
+`bind' builtin. Here's an example using `bind':
+
+ bash$ bind 'set convert-meta off'
+ bash$ bind 'set meta-flag on'
+ bash$ bind 'set output-meta on'
+
+The `set' commands between the single quotes may also be placed
+in ~/.inputrc.
+
+G2) How do I write a function `x' to replace builtin command `x', but
+ still invoke the command from within the function?
+
+This is why the `command' and `builtin' builtins exist. The
+`command' builtin executes the command supplied as its first
+argument, skipping over any function defined with that name. The
+`builtin' builtin executes the builtin command given as its first
+argument directly.
+
+For example, to write a function to replace `cd' that writes the
+hostname and current directory to an xterm title bar, use
+something like the following:
+
+ cd()
+ {
+ builtin cd "$@" && xtitle "$HOST: $PWD"
+ }
+
+This could also be written using `command' instead of `builtin';
+the version above is marginally more efficient.
+
+G3) How can I find the value of a shell variable whose name is the value
+ of another shell variable?
+
+Versions of Bash newer than Bash-2.0 support this directly. You can use
+
+ ${!var}
+
+For example, the following sequence of commands will echo `z':
+
+ var1=var2
+ var2=z
+ echo ${!var1}
+
+For sh compatibility, use the `eval' builtin. The important
+thing to remember is that `eval' expands the arguments you give
+it again, so you need to quote the parts of the arguments that
+you want `eval' to act on.
+
+For example, this expression prints the value of the last positional
+parameter:
+
+ eval echo \"\$\{$#\}\"
+
+The expansion of the quoted portions of this expression will be
+deferred until `eval' runs, while the `$#' will be expanded
+before `eval' is executed. In versions of bash later than bash-2.0,
+
+ echo ${!#}
+
+does the same thing.
+
+This is not the same thing as ksh93 `nameref' variables, though the syntax
+is similar. I may add namerefs in a future bash version.
+
+G4) How can I make the bash `time' reserved word print timing output that
+ looks like the output from my system's /usr/bin/time?
+
+The bash command timing code looks for a variable `TIMEFORMAT' and
+uses its value as a format string to decide how to display the
+timing statistics.
+
+The value of TIMEFORMAT is a string with `%' escapes expanded in a
+fashion similar in spirit to printf(3). The manual page explains
+the meanings of the escape sequences in the format string.
+
+If TIMEFORMAT is not set, bash acts as if the following assignment had
+been performed:
+
+ TIMEFORMAT=$'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS'
+
+The POSIX.2 default time format (used by `time -p command') is
+
+ TIMEFORMAT=$'real %2R\nuser %2U\nsys %2S'
+
+The BSD /usr/bin/time format can be emulated with:
+
+ TIMEFORMAT=$'\t%1R real\t%1U user\t%1S sys'
+
+The System V /usr/bin/time format can be emulated with:
+
+ TIMEFORMAT=$'\nreal\t%1R\nuser\t%1U\nsys\t%1S'
+
+The ksh format can be emulated with:
+
+ TIMEFORMAT=$'\nreal\t%2lR\nuser\t%2lU\nsys\t%2lS'
+
+G5) How do I get the current directory into my prompt?
+
+Bash provides a number of backslash-escape sequences which are expanded
+when the prompt string (PS1 or PS2) is displayed. The full list is in
+the manual page.
+
+The \w expansion gives the full pathname of the current directory, with
+a tilde (`~') substituted for the current value of $HOME. The \W
+expansion gives the basename of the current directory. To put the full
+pathname of the current directory into the path without any tilde
+subsitution, use $PWD. Here are some examples:
+
+ PS1='\w$ ' # current directory with tilde
+ PS1='\W$ ' # basename of current directory
+ PS1='$PWD$ ' # full pathname of current directory
+
+The single quotes are important in the final example to prevent $PWD from
+being expanded when the assignment to PS1 is performed.
+
+G6) How can I rename "*.foo" to "*.bar"?
+
+Use the pattern removal functionality described in D3. The following `for'
+loop will do the trick:
+
+ for f in *.foo; do
+ mv $f ${f%foo}bar
+ done
+
+G7) How can I translate a filename from uppercase to lowercase?
+
+The script examples/functions/lowercase, originally written by John DuBois,
+will do the trick. The converse is left as an exercise.
+
+G8) How can I write a filename expansion (globbing) pattern that will match
+ all files in the current directory except "." and ".."?
+
+You must have set the `extglob' shell option using `shopt -s extglob' to use
+this:
+
+ echo .!(.|) *
+
+A solution that works without extended globbing is given in the Unix Shell
+FAQ, posted periodically to comp.unix.shell.
+
+Section H: Where do I go from here?
+
+H1) How do I report bugs in bash, and where should I look for fixes and
+ advice?
+
+Use the `bashbug' script to report bugs. It is built and
+installed at the same time as bash. It provides a standard
+template for reporting a problem and automatically includes
+information about your configuration and build environment.
+
+`bashbug' sends its reports to bug-bash@gnu.org, which
+is a large mailing list gatewayed to the usenet newsgroup gnu.bash.bug.
+
+Bug fixes, answers to questions, and announcements of new releases
+are all posted to gnu.bash.bug. Discussions concerning bash features
+and problems also take place there.
+
+To reach the bash maintainers directly, send mail to
+bash-maintainers@gnu.org.
+
+H2) What kind of bash documentation is there?
+
+First, look in the doc directory in the bash distribution. It should
+contain at least the following files:
+
+bash.1 an extensive, thorough Unix-style manual page
+builtins.1 a manual page covering just bash builtin commands
+bashref.texi a reference manual in GNU tex`info format
+bashref.info an info version of the reference manual
+FAQ this file
+article.ms text of an article written for The Linux Journal
+readline.3 a man page describing readline
+
+Postscript, HTML, and ASCII files created from the above source are
+available in the documentation distribution.
+
+There is additional documentation available for anonymous FTP from host
+ftp.cwru.edu in the `pub/bash' directory.
+
+Cameron Newham and Bill Rosenblatt have written a book on bash, published
+by O'Reilly and Associates. The book is based on Bill Rosenblatt's Korn
+Shell book. The title is ``Learning the Bash Shell'', and the ISBN number
+is 1-56592-147-X. Look for it in fine bookstores near you. This book
+covers bash-1.14, but has an appendix describing some of the new features
+in bash-2.0.
+
+A second edition of this book is available, published in January, 1998.
+The ISBN number is 1-56592-347-2. Look for it in the same fine bookstores
+or on the web.
+
+The GNU Bash Reference Manual has been published as a printed book by
+Network Theory Ltd (Paperback, ISBN: 0-9541617-7-7, Feb 2003). It covers
+bash-2.0 and is available from most online bookstores (see
+http://www.network-theory.co.uk/bash/manual/ for details). The publisher
+will donate $1 to the Free Software Foundation for each copy sold.
+
+H3) What's coming in future versions?
+
+These are features I hope to include in a future version of bash.
+
+a better bash debugger (a minimally-tested version is included with bash-2.05b)
+associative arrays
+co-processes, but with a new-style syntax that looks like function declaration
+
+H4) What's on the bash `wish list' for future versions?
+
+These are features that may or may not appear in a future version of bash.
+
+breaking some of the shell functionality into embeddable libraries
+a module system like zsh's, using dynamic loading like builtins
+better internationalization using GNU `gettext'
+date-stamped command history
+a bash programmer's guide with a chapter on creating loadable builtins
+a better loadable interface to perl with access to the shell builtins and
+ variables (contributions gratefully accepted)
+ksh93-like `nameref' variables
+ksh93-like `+=' variable assignment operator
+ksh93-like `xx.yy' variables (including some of the .sh.* variables) and
+ associated disipline functions
+Some of the new ksh93 pattern matching operators, like backreferencing
+
+H5) When will the next release appear?
+
+The next version will appear sometime in 2002. Never make predictions.
+
+
+This document is Copyright 1995-2003 by Chester Ramey.
+
+Permission is hereby granted, without written agreement and
+without license or royalty fees, to use, copy, and distribute
+this document for any purpose, provided that the above copyright
+notice appears in all copies of this document and that the
+contents of this document remain unaltered.
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
- the description of the s\bsh\bho\bop\bpt\bt b\bbu\bui\bil\blt\bti\bin\bn b\bbe\bel\blo\bow\bw u\bun\bnd\bde\ber\br S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN
- C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS f\bfo\bor\br a\ba d\bde\bes\bsc\bcr\bri\bip\bpt\bti\bio\bon\bn o\bof\bf t\bth\bhe\be v\bva\bar\bri\bio\bou\bus\bs c\bco\bom\bmp\bpa\bat\bti\bib\bbi\bil\bli\bit\bty\by l\ble\bev\bve\bel\bls\bs
- a\ban\bnd\bd t\bth\bhe\bei\bir\br e\bef\bff\bfe\bec\bct\bts\bs.\b. T\bTh\bhe\be v\bva\bal\blu\bue\be m\bma\bay\by b\bbe\be a\ba d\bde\bec\bci\bim\bma\bal\bl n\bnu\bum\bmb\bbe\ber\br (\b(e\be.\b.g\bg.\b.,\b,
- 4\b4.\b.2\b2)\b) o\bor\br a\ban\bn i\bin\bnt\bte\beg\bge\ber\br (\b(e\be.\b.g\bg.\b.,\b, 4\b42\b2)\b) c\bco\bor\brr\bre\bes\bsp\bpo\bon\bnd\bdi\bin\bng\bg t\bto\bo t\bth\bhe\be d\bde\bes\bsi\bir\bre\bed\bd c\bco\bom\bm-\b-
- p\bpa\bat\bti\bib\bbi\bil\bli\bit\bty\by l\ble\bev\bve\bel\bl.\b. I\bIf\bf B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT i\bis\bs u\bun\bns\bse\bet\bt o\bor\br s\bse\bet\bt t\bto\bo t\bth\bhe\be e\bem\bmp\bpt\bty\by
- s\bst\btr\bri\bin\bng\bg,\b, t\bth\bhe\be c\bco\bom\bmp\bpa\bat\bti\bib\bbi\bil\bli\bit\bty\by l\ble\bev\bve\bel\bl i\bis\bs s\bse\bet\bt t\bto\bo t\bth\bhe\be d\bde\bef\bfa\bau\bul\blt\bt f\bfo\bor\br t\bth\bhe\be
- c\bcu\bur\brr\bre\ben\bnt\bt v\bve\ber\brs\bsi\bio\bon\bn.\b. I\bIf\bf B\bBA\bAS\bSH\bH_\b_C\bCO\bOM\bMP\bPA\bAT\bT i\bis\bs s\bse\bet\bt t\bto\bo a\ba v\bva\bal\blu\bue\be t\bth\bha\bat\bt i\bis\bs n\bno\bot\bt
- o\bon\bne\be o\bof\bf t\bth\bhe\be v\bva\bal\bli\bid\bd c\bco\bom\bmp\bpa\bat\bti\bib\bbi\bil\bli\bit\bty\by l\ble\bev\bve\bel\bls\bs,\b, t\bth\bhe\be s\bsh\bhe\bel\bll\bl p\bpr\bri\bin\bnt\bts\bs a\ban\bn e\ber\brr\bro\bor\br
- m\bme\bes\bss\bsa\bag\bge\be a\ban\bnd\bd s\bse\bet\bts\bs t\bth\bhe\be c\bco\bom\bmp\bpa\bat\bti\bib\bbi\bil\bli\bit\bty\by l\ble\bev\bve\bel\bl t\bto\bo t\bth\bhe\be d\bde\bef\bfa\bau\bul\blt\bt f\bfo\bor\br t\bth\bhe\be
- c\bcu\bur\brr\bre\ben\bnt\bt v\bve\ber\brs\bsi\bio\bon\bn.\b. T\bTh\bhe\be v\bva\bal\bli\bid\bd c\bco\bom\bmp\bpa\bat\bti\bib\bbi\bil\bli\bit\bty\by l\ble\bev\bve\bel\bls\bs c\bco\bor\brr\bre\bes\bsp\bpo\bon\bnd\bd t\bto\bo
- t\bth\bhe\be c\bco\bom\bmp\bpa\bat\bti\bib\bbi\bil\bli\bit\bty\by o\bop\bpt\bti\bio\bon\bns\bs a\bac\bcc\bce\bep\bpt\bte\bed\bd b\bby\by t\bth\bhe\be s\bsh\bho\bop\bpt\bt b\bbu\bui\bil\blt\bti\bin\bn
- d\bde\bes\bsc\bcr\bri\bib\bbe\bed\bd b\bbe\bel\blo\bow\bw (\b(f\bfo\bor\br e\bex\bxa\bam\bmp\bpl\ble\be,\b, c\bco\bom\bmp\bpa\bat\bt4\b42\b2 m\bme\bea\ban\bns\bs t\bth\bha\bat\bt 4\b4.\b.2\b2 a\ban\bnd\bd 4\b42\b2 a\bar\bre\be
- v\bva\bal\bli\bid\bd v\bva\bal\blu\bue\bes\bs)\b).\b. T\bTh\bhe\be c\bcu\bur\brr\bre\ben\bnt\bt v\bve\ber\brs\bsi\bio\bon\bn i\bis\bs a\bal\bls\bso\bo a\ba v\bva\bal\bli\bid\bd v\bva\bal\blu\bue\be.\b.
+ the description of the s\bsh\bho\bop\bpt\bt builtin below under S\bSH\bHE\bEL\bLL\bL B\bBU\bUI\bIL\bLT\bTI\bIN\bN
+ C\bCO\bOM\bMM\bMA\bAN\bND\bDS\bS for a description of the various compatibility levels
+ and their effects. The value may be a decimal number (e.g.,
+ 4.2) or an integer (e.g., 42) corresponding to the desired com-
+ patibility 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. The valid compatibility levels correspond to
+ the compatibility options accepted by the s\bsh\bho\bop\bpt\bt builtin
+ described below (for example, c\bco\bom\bmp\bpa\bat\bt4\b42\b2 means that 4.2 and 42 are
+ valid values). 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 value is interpreted as a filename containing commands to
An array variable is considered set if a subscript has been assigned a
value. The null string is a valid value.
- 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]
- destroys the array element at index _\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt. Negative subscripts to
- indexed arrays are interpreted as described above. Care must be taken
- to avoid unwanted side effects caused by pathname expansion. u\bun\bns\bse\bet\bt
+ 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]
+ destroys the array element at index _\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt. Negative subscripts to
+ indexed arrays are interpreted as described above. Care must be taken
+ to avoid unwanted side effects caused by pathname expansion. u\bun\bns\bse\bet\bt
_\bn_\ba_\bm_\be, where _\bn_\ba_\bm_\be is an array, or u\bun\bns\bse\bet\bt _\bn_\ba_\bm_\be[_\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt], where _\bs_\bu_\bb_\bs_\bc_\br_\bi_\bp_\bt
is *\b* or @\b@, removes the entire array.
- 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
- array. 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
+ array. 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.
E\bEX\bXP\bPA\bAN\bNS\bSI\bIO\bON\bN
Expansion is performed on the command line after it has been split into
- words. There are seven kinds of expansion performed: _\bb_\br_\ba_\bc_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn,
- _\bt_\bi_\bl_\bd_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br _\ba_\bn_\bd _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, _\bc_\bo_\bm_\bm_\ba_\bn_\bd _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\b-
+ words. There are seven kinds of expansion performed: _\bb_\br_\ba_\bc_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn,
+ _\bt_\bi_\bl_\bd_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br _\ba_\bn_\bd _\bv_\ba_\br_\bi_\ba_\bb_\bl_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, _\bc_\bo_\bm_\bm_\ba_\bn_\bd _\bs_\bu_\bb_\bs_\bt_\bi_\bt_\bu_\b-
_\bt_\bi_\bo_\bn, _\ba_\br_\bi_\bt_\bh_\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, and _\bp_\ba_\bt_\bh_\bn_\ba_\bm_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn.
- The order of expansions is: brace expansion, tilde expansion, parame-
- ter, variable and arithmetic expansion and command substitution (done
+ The order of expansions is: brace expansion, tilde expansion, parame-
+ ter, variable and arithmetic expansion and command substitution (done
in a left-to-right fashion), word splitting, and pathname expansion.
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.
Only brace expansion, word splitting, and pathname expansion can change
- the number of words of the expansion; other expansions expand a single
- word to a single word. The only exceptions to this are the expansions
+ the number of words of the expansion; other expansions expand a single
+ word to a single word. The only exceptions to this are the expansions
of "$\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 by which arbitrary strings may be gener-
- ated. This mechanism is similar to _\bp_\ba_\bt_\bh_\bn_\ba_\bm_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, but the file-
+ ated. This mechanism is similar to _\bp_\ba_\bt_\bh_\bn_\ba_\bm_\be _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn, but the file-
names generated need not exist. Patterns to be brace expanded take the
form of an optional _\bp_\br_\be_\ba_\bm_\bb_\bl_\be, followed by either a series of comma-sep-
- arated strings or a sequence expression between a pair of braces, fol-
- lowed by an optional _\bp_\bo_\bs_\bt_\bs_\bc_\br_\bi_\bp_\bt. The preamble is prefixed to each
+ arated strings or a sequence expression between a pair of braces, fol-
+ lowed by an optional _\bp_\bo_\bs_\bt_\bs_\bc_\br_\bi_\bp_\bt. The preamble is prefixed to each
string contained within the braces, and the postscript is then appended
to each resulting string, expanding left to right.
- Brace expansions may be nested. The results of each expanded string
- are not sorted; left to right order is preserved. For example,
+ Brace expansions may be nested. The results of each expanded string
+ are not sorted; left to right order is preserved. For example,
a{\b{d,c,b}\b}e expands into `ade ace abe'.
- A sequence expression takes the form {\b{_\bx.\b..\b._\by[\b[.\b..\b._\bi_\bn_\bc_\br]\b]}\b}, where _\bx and _\by are
- either integers or single characters, 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. Supplied integers may be pre-
- fixed with _\b0 to force each term to have the same width. When either _\bx
- or _\by begins with a zero, the shell attempts to force all generated
- terms to contain the same number of digits, zero-padding where neces-
- sary. When characters are supplied, the expression expands to each
- character lexicographically between _\bx and _\by, inclusive, using the
- default C locale. Note that both _\bx and _\by must be of the same type.
- When the increment is supplied, it is used as the difference between
+ A sequence expression takes the form {\b{_\bx.\b..\b._\by[\b[.\b..\b._\bi_\bn_\bc_\br]\b]}\b}, where _\bx and _\by are
+ either integers or single characters, 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. Supplied integers may be pre-
+ fixed with _\b0 to force each term to have the same width. When either _\bx
+ or _\by begins with a zero, the shell attempts to force all generated
+ terms to contain the same number of digits, zero-padding where neces-
+ sary. When characters are supplied, the expression expands to each
+ character lexicographically between _\bx and _\by, inclusive, using the
+ default C locale. Note that both _\bx and _\by must be of the same type.
+ When the increment is supplied, it is used as the difference between
each term. The default increment is 1 or -1 as appropriate.
Brace expansion is performed before any other expansions, and any 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
- closing braces, and at least one unquoted comma or a valid sequence
- expression. Any incorrectly formed brace expansion is left unchanged.
+ A correctly-formed brace expansion must contain unquoted opening and
+ closing braces, and at least one unquoted comma or a valid sequence
+ expression. Any incorrectly formed brace expansion is left unchanged.
A {\b{ or ,\b, may be quoted with a backslash to prevent its being considered
- part of a brace expression. To avoid conflicts with parameter expan-
+ part of a brace expression. To avoid conflicts with parameter expan-
sion, the string $\b${\b{ is not considered eligible for brace expansion.
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.
- For example, a word entered to s\bsh\bh as _\bf_\bi_\bl_\be_\b{_\b1_\b,_\b2_\b} appears identically in
- the output. The same word is output as _\bf_\bi_\bl_\be_\b1 _\bf_\bi_\bl_\be_\b2 after expansion by
- b\bba\bas\bsh\bh. If strict compatibility with s\bsh\bh is desired, start b\bba\bas\bsh\bh with the
+ 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 _\bf_\bi_\bl_\be_\b{_\b1_\b,_\b2_\b} appears identically in
+ the output. The same word is output as _\bf_\bi_\bl_\be_\b1 _\bf_\bi_\bl_\be_\b2 after expansion by
+ b\bba\bas\bsh\bh. If strict compatibility with s\bsh\bh is desired, 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 com-
mand (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).
T\bTi\bil\bld\bde\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
- If a word begins with an unquoted tilde character (`~\b~'), all of the
- characters preceding the first unquoted slash (or all characters, if
- there is no unquoted slash) are considered a _\bt_\bi_\bl_\bd_\be_\b-_\bp_\br_\be_\bf_\bi_\bx. If none of
- the characters in the tilde-prefix are quoted, the characters in the
- tilde-prefix following the tilde are treated as a possible _\bl_\bo_\bg_\bi_\bn _\bn_\ba_\bm_\be.
- If this login name is the null string, the tilde is replaced with the
- value of the shell parameter H\bHO\bOM\bME\bE. If H\bHO\bOM\bME\bE is unset, the home direc-
- tory of the user executing the shell is substituted instead. Other-
- wise, the tilde-prefix is replaced with the home directory associated
+ 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 home direc-
+ tory of the user executing the shell is substituted 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
+ If the tilde-prefix is a `~+', the value of the shell variable P\bPW\bWD\bD
replaces the tilde-prefix. If the tilde-prefix is a `~-', the value of
- the shell variable O\bOL\bLD\bDP\bPW\bWD\bD, if it is set, is substituted. If the char-
- acters following the tilde in the tilde-prefix consist of a number _\bN,
- optionally prefixed by a `+' or a `-', the tilde-prefix is replaced
+ the shell variable O\bOL\bLD\bDP\bPW\bWD\bD, if it is set, is substituted. If the char-
+ acters 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 tilde-prefix as an argu-
- ment. If the characters following the tilde in the tilde-prefix con-
+ ment. If the characters following the tilde in the tilde-prefix con-
sist of a number without a leading `+' or `-', `+' is assumed.
If the login name is invalid, or the tilde expansion fails, the word is
Each variable assignment is checked for unquoted tilde-prefixes immedi-
ately following a :\b: or the first =\b=. In these cases, tilde expansion is
- also performed. Consequently, one may use filenames with tildes in
- assignments 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
+ also performed. Consequently, one may use filenames with tildes in
+ assignments 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
expanded value.
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
- escaped by a backslash or within a quoted string, and not within an
+ 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
embedded arithmetic expansion, command substitution, or parameter
expansion.
${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br}
- The value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is substituted. The braces are required
- when _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is a positional parameter with more than one
+ The value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is substituted. The braces are required
+ when _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is a positional parameter with more than one
digit, or when _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is followed by a character which is not
to be interpreted as part of its name. The _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is a shell
- parameter as described above P\bPA\bAR\bRA\bAM\bME\bET\bTE\bER\bRS\bS) or an array reference
+ 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!), it
+ If the first character of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is an exclamation point (!\b!), it
introduces a level of variable indirection. B\bBa\bas\bsh\bh uses the value of the
variable formed from the rest of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br as the name of the variable;
- this variable is then expanded and that value is used in the rest of
- the substitution, rather than the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br itself. This is
+ this variable is then expanded and that value is used in the rest of
+ the substitution, rather than the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br itself. This is
known as _\bi_\bn_\bd_\bi_\br_\be_\bc_\bt _\be_\bx_\bp_\ba_\bn_\bs_\bi_\bo_\bn. The exceptions to this are the expansions
- of ${!\b!_\bp_\br_\be_\bf_\bi_\bx*\b*} and ${!\b!_\bn_\ba_\bm_\be[_\b@]} described below. The exclamation point
- must immediately follow the left brace in order to introduce indirec-
+ of ${!\b!_\bp_\br_\be_\bf_\bi_\bx*\b*} and ${!\b!_\bn_\ba_\bm_\be[_\b@]} described below. The exclamation point
+ must immediately follow the left brace in order to introduce indirec-
tion.
In each of the cases below, _\bw_\bo_\br_\bd is subject to tilde expansion, parame-
ter expansion, command substitution, and arithmetic expansion.
- When not performing substring expansion, using the forms documented
- below (e.g., :\b:-\b-), b\bba\bas\bsh\bh tests for a parameter that is unset or null.
- Omitting the colon results in a test only for a parameter that is
+ When not performing substring expansion, using the forms documented
+ below (e.g., :\b:-\b-), b\bba\bas\bsh\bh tests for a parameter that is unset or null.
+ Omitting the colon results in a test only for a parameter that is
unset.
${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br:\b:-\b-_\bw_\bo_\br_\bd}
- U\bUs\bse\be D\bDe\bef\bfa\bau\bul\blt\bt V\bVa\bal\blu\bue\bes\bs. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is unset or null, the expan-
- sion of _\bw_\bo_\br_\bd is substituted. Otherwise, the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
+ U\bUs\bse\be D\bDe\bef\bfa\bau\bul\blt\bt V\bVa\bal\blu\bue\bes\bs. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is unset or null, the expan-
+ sion of _\bw_\bo_\br_\bd is substituted. Otherwise, the value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
is substituted.
${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br:\b:=\b=_\bw_\bo_\br_\bd}
- A\bAs\bss\bsi\big\bgn\bn D\bDe\bef\bfa\bau\bul\blt\bt V\bVa\bal\blu\bue\bes\bs. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is unset or null, the
+ A\bAs\bss\bsi\big\bgn\bn D\bDe\bef\bfa\bau\bul\blt\bt V\bVa\bal\blu\bue\bes\bs. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is unset or null, the
expansion of _\bw_\bo_\br_\bd is assigned to _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br. The value of _\bp_\ba_\br_\ba_\bm_\b-
- _\be_\bt_\be_\br is then substituted. Positional parameters and special
+ _\be_\bt_\be_\br is then substituted. Positional parameters and special
parameters may not be assigned to in this way.
${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br:\b:?\b?_\bw_\bo_\br_\bd}
- D\bDi\bis\bsp\bpl\bla\bay\by E\bEr\brr\bro\bor\br i\bif\bf N\bNu\bul\bll\bl o\bor\br U\bUn\bns\bse\bet\bt. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is null or unset,
- the expansion of _\bw_\bo_\br_\bd (or a message to that effect if _\bw_\bo_\br_\bd is
- not present) is written to the standard error and the shell, if
+ D\bDi\bis\bsp\bpl\bla\bay\by E\bEr\brr\bro\bor\br i\bif\bf N\bNu\bul\bll\bl o\bor\br U\bUn\bns\bse\bet\bt. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is null or unset,
+ the expansion of _\bw_\bo_\br_\bd (or a message to that effect if _\bw_\bo_\br_\bd is
+ not present) is written to the standard error and the shell, if
it is not interactive, exits. 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 null or unset, nothing is
+ U\bUs\bse\be A\bAl\blt\bte\ber\brn\bna\bat\bte\be V\bVa\bal\blu\bue\be. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is null or unset, nothing is
substituted, otherwise the expansion of _\bw_\bo_\br_\bd is substituted.
${_\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-
+ 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@, an indexed array subscripted by @\b@ or *\b*,
- or an associative array name, the results differ as described
- below. If _\bl_\be_\bn_\bg_\bt_\bh is omitted, expands to the substring of the
+ or an associative array name, the results differ as described
+ below. If _\bl_\be_\bn_\bg_\bt_\bh is omitted, 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. _\bl_\be_\bn_\bg_\bt_\bh and _\bo_\bf_\bf_\bs_\be_\bt are
+ and extending to the end of the value. _\bl_\be_\bn_\bg_\bt_\bh and _\bo_\bf_\bf_\bs_\be_\bt are
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 below).
- If _\bo_\bf_\bf_\bs_\be_\bt evaluates to a number less than zero, the value is
- used as an offset in characters from the end of the value of
- _\bp_\ba_\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
- expansion 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- expan-
+ 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_\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
+ expansion 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- expan-
sion.
- If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@, the result is _\bl_\be_\bn_\bg_\bt_\bh positional parameters
+ If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@, the result is _\bl_\be_\bn_\bg_\bt_\bh positional parameters
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. It is an expan-
+ greater than the greatest positional parameter, so an offset of
+ -1 evaluates to the last positional parameter. It is an expan-
sion 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_\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
+ result is the _\bl_\be_\bn_\bg_\bt_\bh members of the array beginning with
+ ${_\bp_\ba_\br_\ba_\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
+ Substring expansion applied to an associative array produces
undefined results.
- Substring indexing is zero-based unless the positional parame-
- ters are used, in which case the indexing starts at 1 by
- default. If _\bo_\bf_\bf_\bs_\be_\bt is 0, and the positional parameters are
+ Substring indexing is zero-based unless the positional parame-
+ ters are used, in which case the indexing starts at 1 by
+ default. 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. The length in characters of the value of
- _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is substituted. 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. The length in characters of the value of
+ _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is substituted. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is *\b* or @\b@, the value
+ substituted is the number of positional parameters. If _\bp_\ba_\br_\ba_\bm_\be_\b-
+ _\bt_\be_\br is an array name subscripted by *\b* or @\b@, the value substi-
+ tuted is the number of elements in the array. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is
+ an indexed array name subscripted by a negative number, that
+ number is interpreted as relative to one greater than the maxi-
+ mum index of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br, so negative indices count back from the
+ end of the array, and an index of -1 references the last ele-
ment.
${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br#\b#_\bw_\bo_\br_\bd}
${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br#\b##\b#_\bw_\bo_\br_\bd}
R\bRe\bem\bmo\bov\bve\be m\bma\bat\btc\bch\bhi\bin\bng\bg p\bpr\bre\bef\bfi\bix\bx p\bpa\bat\btt\bte\ber\brn\bn. The _\bw_\bo_\br_\bd is expanded to produce
a pattern just as in pathname expansion. 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 ``#\b#'' case) or the longest matching pat-
- tern (the ``#\b##\b#'' 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 parame-
+ 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 ``#\b#'' case) or the longest matching pat-
+ tern (the ``#\b##\b#'' 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 parame-
ter in turn, and the expansion is the resultant list. If _\bp_\ba_\br_\ba_\bm_\b-
- _\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
+ _\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%_\bw_\bo_\br_\bd}
${_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br%\b%%\b%_\bw_\bo_\br_\bd}
R\bRe\bem\bmo\bov\bve\be m\bma\bat\btc\bch\bhi\bin\bng\bg s\bsu\buf\bff\bfi\bix\bx p\bpa\bat\btt\bte\ber\brn\bn. The _\bw_\bo_\br_\bd is expanded to produce
a pattern just as in pathname expansion. 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 expansion is the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br with
- the shortest matching pattern (the ``%\b%'' case) or the longest
- matching pattern (the ``%\b%%\b%'' case) deleted. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@
- or *\b*, the pattern removal 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 pattern removal operation is applied to each member of
+ a trailing portion of the expanded 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 ``%\b%'' case) or the longest
+ matching pattern (the ``%\b%%\b%'' case) deleted. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@
+ or *\b*, the pattern removal 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 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}
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 just as in pathname expansion. _\bP_\ba_\br_\ba_\bm_\be_\bt_\be_\br is expanded and
- the longest match of _\bp_\ba_\bt_\bt_\be_\br_\bn against its value is replaced with
- _\bs_\bt_\br_\bi_\bn_\bg. If _\bp_\ba_\bt_\bt_\be_\br_\bn begins with /\b/, all matches of _\bp_\ba_\bt_\bt_\be_\br_\bn are
- replaced with _\bs_\bt_\br_\bi_\bn_\bg. Normally only the first match is
+ tern just as in pathname expansion. _\bP_\ba_\br_\ba_\bm_\be_\bt_\be_\br is expanded and
+ the longest match of _\bp_\ba_\bt_\bt_\be_\br_\bn against its value is replaced with
+ _\bs_\bt_\br_\bi_\bn_\bg. If _\bp_\ba_\bt_\bt_\be_\br_\bn begins with /\b/, all matches of _\bp_\ba_\bt_\bt_\be_\br_\bn are
+ replaced with _\bs_\bt_\br_\bi_\bn_\bg. Normally only the first match is
replaced. If _\bp_\ba_\bt_\bt_\be_\br_\bn begins with #\b#, it must match at the begin-
ning of the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br. If _\bp_\ba_\bt_\bt_\be_\br_\bn begins with
- %\b%, it must match at the end of the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br.
+ %\b%, it must match at the end of the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br.
If _\bs_\bt_\br_\bi_\bn_\bg is null, matches of _\bp_\ba_\bt_\bt_\be_\br_\bn are deleted and the /\b/ fol-
lowing _\bp_\ba_\bt_\bt_\be_\br_\bn may be omitted. If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is @\b@ or *\b*, the sub-
- stitution 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 substitution
- operation is applied to each member of the array in turn, and
+ stitution 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 substitution
+ 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}
${_\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. The _\bp_\ba_\bt_\bt_\be_\br_\bn is expanded to pro-
+ 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. The _\bp_\ba_\bt_\bt_\be_\br_\bn is expanded to pro-
duce a pattern just as in pathname expansion. Each character in
- the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is tested against _\bp_\ba_\bt_\bt_\be_\br_\bn, and,
- if it matches the pattern, its case is converted. The pattern
- should not attempt to match more than one character. The ^\b^
- operator converts lowercase letters matching _\bp_\ba_\bt_\bt_\be_\br_\bn to upper-
+ the expanded value of _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is tested against _\bp_\ba_\bt_\bt_\be_\br_\bn, and,
+ if it matches the pattern, its case is converted. The pattern
+ should not attempt to match more than one character. The ^\b^
+ operator converts lowercase letters matching _\bp_\ba_\bt_\bt_\be_\br_\bn to upper-
case; the ,\b, operator converts matching uppercase letters to low-
ercase. The ^\b^^\b^ and ,\b,,\b, expansions convert each matched character
- in the expanded value; the ^\b^ and ,\b, expansions match and convert
- only the first character in the expanded value. 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
- 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 sub-
+ in the expanded value; the ^\b^ and ,\b, expansions match and convert
+ only the first character in the expanded value. 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
+ 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 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.
C\bCo\bom\bmm\bma\ban\bnd\bd S\bSu\bub\bbs\bst\bti\bit\btu\but\bti\bio\bon\bn
`\b`_\bc_\bo_\bm_\bm_\ba_\bn_\bd`\b`
B\bBa\bas\bsh\bh performs the expansion by executing _\bc_\bo_\bm_\bm_\ba_\bn_\bd and replacing the com-
- mand substitution with the standard output of the command, with any
+ mand substitution with the standard output of the command, with any
trailing newlines deleted. Embedded newlines are not deleted, but they
- may be removed during word splitting. The command substitution $\b$(\b(c\bca\bat\bt
+ may be removed during word splitting. The command 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).
- When the old-style backquote form of substitution is used, backslash
- retains its literal meaning except when followed by $\b$, `\b`, or \\b\. The
+ When the old-style backquote form of substitution is used, backslash
+ retains its literal meaning except when followed by $\b$, `\b`, or \\b\. The
first backquote not preceded by a backslash terminates the command sub-
- stitution. When using the $(_\bc_\bo_\bm_\bm_\ba_\bn_\bd) form, all characters between the
+ stitution. When using the $(_\bc_\bo_\bm_\bm_\ba_\bn_\bd) form, all characters between the
parentheses make up the command; none are treated specially.
Command substitutions may be nested. To nest when using the backquoted
form, escape the inner backquotes with backslashes.
- If the substitution appears within double quotes, word splitting and
+ If the substitution appears within double quotes, word splitting and
pathname expansion are not performed on the results.
A\bAr\bri\bit\bth\bhm\bme\bet\bti\bic\bc E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn
- Arithmetic expansion allows the evaluation of an arithmetic expression
- and the substitution of the result. The format for arithmetic expan-
+ Arithmetic expansion allows the evaluation of an arithmetic expression
+ and the substitution of the result. The format for arithmetic expan-
sion is:
$\b$(\b((\b(_\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn)\b))\b)
- The _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn is treated as if it were within double quotes, but a
- double quote inside the parentheses is not treated specially. All
- tokens in the expression undergo parameter expansion, string expansion,
- command substitution, and quote removal. Arithmetic expansions may be
+ The _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn is treated as if it were within double quotes, but a
+ double quote inside the parentheses is not treated specially. All
+ tokens in the expression undergo parameter and variable expansion, com-
+ mand substitution, and quote removal. The result is treated as the
+ arithmetic expression to be evaluated. Arithmetic expansions may be
nested.
The evaluation is performed according to the rules listed below under
ing separators assigned to the last _\bn_\ba_\bm_\be. If there are fewer
words read from the input stream than names, the remaining names
are assigned empty values. The characters in I\bIF\bFS\bS are used to
- split the line into words. The backslash character (\\b\) may be
- used to remove any special meaning for the next character read
- and for line continuation. Options, if supplied, have the fol-
- lowing meanings:
+ split the line into words using the same rules the shell uses
+ for expansion (described above under W\bWo\bor\brd\bd S\bSp\bpl\bli\bit\btt\bti\bin\bng\bg). The back-
+ slash character (\\b\) may be used to remove any special meaning
+ for the next character read and for line continuation. Options,
+ if supplied, have the following meanings:
-\b-a\ba _\ba_\bn_\ba_\bm_\be
The words are assigned to sequential indices of the array
variable _\ba_\bn_\ba_\bm_\be, starting at 0. _\ba_\bn_\ba_\bm_\be is unset before any
new values are assigned. Other _\bn_\ba_\bm_\be arguments are
ignored.
-\b-d\bd _\bd_\be_\bl_\bi_\bm
- The first character of _\bd_\be_\bl_\bi_\bm is used to terminate the
+ The first character of _\bd_\be_\bl_\bi_\bm is used to terminate the
input line, rather than newline.
-\b-e\be If the standard input is coming from a terminal, r\bre\bea\bad\bdl\bli\bin\bne\be
- (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE above) is used to obtain the line. Read-
- line uses the current (or default, if line editing was
+ (see R\bRE\bEA\bAD\bDL\bLI\bIN\bNE\bE above) is used to obtain the line. Read-
+ line uses the current (or default, if line editing was
not previously active) editing settings.
-\b-i\bi _\bt_\be_\bx_\bt
- If r\bre\bea\bad\bdl\bli\bin\bne\be is being used to read the line, _\bt_\be_\bx_\bt is
+ If r\bre\bea\bad\bdl\bli\bin\bne\be is being used to read the line, _\bt_\be_\bx_\bt is
placed into the editing buffer before editing begins.
-\b-n\bn _\bn_\bc_\bh_\ba_\br_\bs
- r\bre\bea\bad\bd returns after reading _\bn_\bc_\bh_\ba_\br_\bs characters rather than
- waiting for a complete line of input, but honor a delim-
- iter if fewer than _\bn_\bc_\bh_\ba_\br_\bs characters are read before the
+ r\bre\bea\bad\bd returns after reading _\bn_\bc_\bh_\ba_\br_\bs characters rather than
+ waiting for a complete line of input, but honor a delim-
+ iter if fewer than _\bn_\bc_\bh_\ba_\br_\bs characters are read before the
delimiter.
-\b-N\bN _\bn_\bc_\bh_\ba_\br_\bs
- r\bre\bea\bad\bd returns after reading exactly _\bn_\bc_\bh_\ba_\br_\bs characters
- rather than waiting for a complete line of input, unless
- EOF is encountered or r\bre\bea\bad\bd times out. Delimiter charac-
- ters encountered in the input are not treated specially
- and do not cause r\bre\bea\bad\bd to return until _\bn_\bc_\bh_\ba_\br_\bs characters
+ r\bre\bea\bad\bd returns after reading exactly _\bn_\bc_\bh_\ba_\br_\bs characters
+ rather than waiting for a complete line of input, unless
+ EOF is encountered or r\bre\bea\bad\bd times out. Delimiter charac-
+ ters encountered in the input are not treated specially
+ and do not cause r\bre\bea\bad\bd to return until _\bn_\bc_\bh_\ba_\br_\bs characters
are read.
-\b-p\bp _\bp_\br_\bo_\bm_\bp_\bt
Display _\bp_\br_\bo_\bm_\bp_\bt on standard error, without a trailing new-
line, before attempting to read any input. The prompt is
displayed only if input is coming from a terminal.
-\b-r\br Backslash does not act as an escape character. The back-
- slash is considered to be part of the line. In particu-
- lar, a backslash-newline pair may not be used as a line
+ slash is considered to be part of the line. In particu-
+ lar, a backslash-newline pair may not be used as a line
continuation.
-\b-s\bs Silent mode. If input is coming from a terminal, charac-
ters are not echoed.
-\b-t\bt _\bt_\bi_\bm_\be_\bo_\bu_\bt
- Cause r\bre\bea\bad\bd to time out and return failure if a complete
- line of input (or a specified number of characters) is
- not read within _\bt_\bi_\bm_\be_\bo_\bu_\bt seconds. _\bt_\bi_\bm_\be_\bo_\bu_\bt may be a deci-
- mal number with a fractional portion following the deci-
- mal point. This option is only effective if r\bre\bea\bad\bd is
- reading input from a terminal, pipe, or other special
- file; it has no effect when reading from regular files.
+ Cause r\bre\bea\bad\bd to time out and return failure if a complete
+ line of input (or a specified number of characters) is
+ not read within _\bt_\bi_\bm_\be_\bo_\bu_\bt seconds. _\bt_\bi_\bm_\be_\bo_\bu_\bt may be a deci-
+ mal number with a fractional portion following the deci-
+ mal point. This option is only effective if r\bre\bea\bad\bd is
+ reading input from a terminal, pipe, or other special
+ file; it has no effect when reading from regular files.
If r\bre\bea\bad\bd times out, r\bre\bea\bad\bd saves any partial input read into
- the specified variable _\bn_\ba_\bm_\be. If _\bt_\bi_\bm_\be_\bo_\bu_\bt is 0, r\bre\bea\bad\bd
- returns immediately, without trying to read any data.
- The exit status is 0 if input is available on the speci-
- fied file descriptor, non-zero otherwise. The exit sta-
+ the specified variable _\bn_\ba_\bm_\be. If _\bt_\bi_\bm_\be_\bo_\bu_\bt is 0, r\bre\bea\bad\bd
+ returns immediately, without trying to read any data.
+ The exit status is 0 if input is available on the speci-
+ fied file descriptor, non-zero otherwise. The exit sta-
tus is greater than 128 if the timeout is exceeded.
-\b-u\bu _\bf_\bd Read input from file descriptor _\bf_\bd.
If no _\bn_\ba_\bm_\be_\bs are supplied, the line read is assigned to the vari-
- able R\bRE\bEP\bPL\bLY\bY. The return code is zero, unless end-of-file is
- encountered, r\bre\bea\bad\bd times out (in which case the return code is
- greater than 128), a variable assignment error (such as assign-
- ing to a readonly variable) occurs, or an invalid file descrip-
+ able R\bRE\bEP\bPL\bLY\bY. The return code is zero, unless end-of-file is
+ encountered, r\bre\bea\bad\bd times out (in which case the return code is
+ greater than 128), a variable assignment error (such as assign-
+ ing to a readonly variable) occurs, or an invalid file descrip-
tor is supplied as the argument to -\b-u\bu.
r\bre\bea\bad\bdo\bon\bnl\bly\by [-\b-a\baA\bAf\bf] [-\b-p\bp] [_\bn_\ba_\bm_\be[=_\bw_\bo_\br_\bd] ...]
- The given _\bn_\ba_\bm_\be_\bs are marked readonly; the values of these _\bn_\ba_\bm_\be_\bs
- may not be changed by subsequent assignment. If the -\b-f\bf option
- is supplied, the functions corresponding to the _\bn_\ba_\bm_\be_\bs are so
- marked. The -\b-a\ba option restricts the variables to indexed
- arrays; the -\b-A\bA option restricts the variables to associative
- arrays. If both options are supplied, -\b-A\bA takes precedence. If
- no _\bn_\ba_\bm_\be arguments are given, or if the -\b-p\bp option is supplied, a
+ The given _\bn_\ba_\bm_\be_\bs are marked readonly; the values of these _\bn_\ba_\bm_\be_\bs
+ may not be changed by subsequent assignment. If the -\b-f\bf option
+ is supplied, the functions corresponding to the _\bn_\ba_\bm_\be_\bs are so
+ marked. The -\b-a\ba option restricts the variables to indexed
+ arrays; the -\b-A\bA option restricts the variables to associative
+ arrays. If both options are supplied, -\b-A\bA takes precedence. If
+ no _\bn_\ba_\bm_\be arguments are given, or if the -\b-p\bp option is supplied, a
list of all readonly names is printed. The other options may be
- used to restrict the output to a subset of the set of readonly
- names. The -\b-p\bp option causes output to be displayed in a format
- that may be reused as input. If a variable name is followed by
- =_\bw_\bo_\br_\bd, the value of the variable is set to _\bw_\bo_\br_\bd. The return
- status is 0 unless an invalid option is encountered, one of the
+ used to restrict the output to a subset of the set of readonly
+ names. The -\b-p\bp option causes output to be displayed in a format
+ that may be reused as input. If a variable name is followed by
+ =_\bw_\bo_\br_\bd, the value of the variable is set to _\bw_\bo_\br_\bd. The return
+ status is 0 unless an invalid option is encountered, one of the
_\bn_\ba_\bm_\be_\bs is not a valid shell variable name, or -\b-f\bf is supplied with
a _\bn_\ba_\bm_\be that is not a function.
r\bre\bet\btu\bur\brn\bn [_\bn]
- Causes a function to stop executing and return the value speci-
- fied by _\bn to its caller. If _\bn is omitted, the return status is
- that of the last command executed in the function body. If
- r\bre\bet\btu\bur\brn\bn is used outside a function, but during execution of a
- script by the .\b. (s\bso\bou\bur\brc\bce\be) command, it causes the shell to stop
- executing that script and return either _\bn or the exit status of
- the last command executed within the script as the exit status
- of the script. If _\bn is supplied, the return value is its least
- significant 8 bits. The return status is non-zero if r\bre\bet\btu\bur\brn\bn is
- supplied a non-numeric argument, or is used outside a function
- and not during execution of a script by .\b. or s\bso\bou\bur\brc\bce\be. Any com-
- mand associated with the R\bRE\bET\bTU\bUR\bRN\bN trap is executed before execu-
+ Causes a function to stop executing and return the value speci-
+ fied by _\bn to its caller. If _\bn is omitted, the return status is
+ that of the last command executed in the function body. If
+ r\bre\bet\btu\bur\brn\bn is used outside a function, but during execution of a
+ script by the .\b. (s\bso\bou\bur\brc\bce\be) command, it causes the shell to stop
+ executing that script and return either _\bn or the exit status of
+ the last command executed within the script as the exit status
+ of the script. If _\bn is supplied, the return value is its least
+ significant 8 bits. The return status is non-zero if r\bre\bet\btu\bur\brn\bn is
+ supplied a non-numeric argument, or is used outside a function
+ and not during execution of a script by .\b. or s\bso\bou\bur\brc\bce\be. Any com-
+ mand associated with the R\bRE\bET\bTU\bUR\bRN\bN trap is executed before execu-
tion resumes after the function or script.
s\bse\bet\bt [-\b--\b-a\bab\bbe\bef\bfh\bhk\bkm\bmn\bnp\bpt\btu\buv\bvx\bxB\bBC\bCE\bEH\bHP\bPT\bT] [-\b-o\bo _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be] [_\ba_\br_\bg ...]
s\bse\bet\bt [+\b+a\bab\bbe\bef\bfh\bhk\bkm\bmn\bnp\bpt\btu\buv\bvx\bxB\bBC\bCE\bEH\bHP\bPT\bT] [+\b+o\bo _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be] [_\ba_\br_\bg ...]
- Without options, the name and value of each shell variable are
+ Without options, the name and value of each shell variable are
displayed in a format that can be reused as input for setting or
resetting the currently-set variables. Read-only variables can-
- not be reset. In _\bp_\bo_\bs_\bi_\bx mode, only shell variables are listed.
- The output is sorted according to the current locale. When
- options are specified, they set or unset shell attributes. Any
- arguments remaining after option processing are treated as val-
+ not be reset. In _\bp_\bo_\bs_\bi_\bx mode, only shell variables are listed.
+ The output is sorted according to the current locale. When
+ options are specified, they set or unset shell attributes. Any
+ arguments remaining after option processing are treated as val-
ues for the positional parameters and are assigned, in order, to
- $\b$1\b1, $\b$2\b2, .\b..\b..\b. $\b$_\bn. Options, if specified, have the following
+ $\b$1\b1, $\b$2\b2, .\b..\b..\b. $\b$_\bn. Options, if specified, have the following
meanings:
- -\b-a\ba Automatically mark variables and functions which are
- modified or created for export to the environment of
+ -\b-a\ba Automatically mark variables and functions which are
+ modified or created for export to the environment of
subsequent commands.
- -\b-b\bb Report the status of terminated background jobs immedi-
+ -\b-b\bb Report the status of terminated background jobs immedi-
ately, rather than before the next primary prompt. This
is effective only when job control is enabled.
- -\b-e\be Exit immediately if a _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be (which may consist of a
- single _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd), a _\bl_\bi_\bs_\bt, or a _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd _\bc_\bo_\bm_\bm_\ba_\bn_\bd
- (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR above), exits with a non-zero sta-
- tus. The shell does not exit if the command that fails
- is part of the command list immediately following a
- w\bwh\bhi\bil\ble\be or u\bun\bnt\bti\bil\bl keyword, part of the test following the
- i\bif\bf or e\bel\bli\bif\bf reserved words, part of any command executed
- in a &\b&&\b& or |\b||\b| list except the command following the
- final &\b&&\b& or |\b||\b|, any command in a pipeline but the last,
- or if the command's return value is being inverted with
- !\b!. If a compound command other than a subshell returns
- a non-zero status because a command failed while -\b-e\be was
- being ignored, the shell does not exit. A trap on E\bER\bRR\bR,
+ -\b-e\be Exit immediately if a _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be (which may consist of a
+ single _\bs_\bi_\bm_\bp_\bl_\be _\bc_\bo_\bm_\bm_\ba_\bn_\bd), a _\bl_\bi_\bs_\bt, or a _\bc_\bo_\bm_\bp_\bo_\bu_\bn_\bd _\bc_\bo_\bm_\bm_\ba_\bn_\bd
+ (see S\bSH\bHE\bEL\bLL\bL G\bGR\bRA\bAM\bMM\bMA\bAR\bR above), exits with a non-zero sta-
+ tus. The shell does not exit if the command that fails
+ is part of the command list immediately following a
+ w\bwh\bhi\bil\ble\be or u\bun\bnt\bti\bil\bl keyword, part of the test following the
+ i\bif\bf or e\bel\bli\bif\bf reserved words, part of any command executed
+ in a &\b&&\b& or |\b||\b| list except the command following the
+ final &\b&&\b& or |\b||\b|, any command in a pipeline but the last,
+ or if the command's return value is being inverted with
+ !\b!. If a compound command other than a subshell returns
+ a non-zero status because a command failed while -\b-e\be was
+ being ignored, the shell does not exit. A trap on E\bER\bRR\bR,
if set, is executed before the shell exits. This option
applies to the shell environment and each subshell envi-
- ronment separately (see C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN E\bEN\bNV\bVI\bIR\bRO\bON\bNM\bME\bEN\bNT\bT
+ ronment separately (see C\bCO\bOM\bMM\bMA\bAN\bND\bD E\bEX\bXE\bEC\bCU\bUT\bTI\bIO\bON\bN E\bEN\bNV\bVI\bIR\bRO\bON\bNM\bME\bEN\bNT\bT
above), and may cause subshells to exit before executing
all the commands in the subshell.
- If a compound command or shell function executes in a
- context where -\b-e\be is being ignored, none of the commands
- executed within the compound command or function body
- will be affected by the -\b-e\be setting, even if -\b-e\be is set
- and a command returns a failure status. If a compound
- command or shell function sets -\b-e\be while executing in a
- context where -\b-e\be is ignored, that setting will not have
- any effect until the compound command or the command
+ If a compound command or shell function executes in a
+ context where -\b-e\be is being ignored, none of the commands
+ executed within the compound command or function body
+ will be affected by the -\b-e\be setting, even if -\b-e\be is set
+ and a command returns a failure status. If a compound
+ command or shell function sets -\b-e\be while executing in a
+ context where -\b-e\be is ignored, that setting will not have
+ any effect until the compound command or the command
containing the function call completes.
-\b-f\bf Disable pathname expansion.
- -\b-h\bh Remember the location of commands as they are looked up
+ -\b-h\bh Remember the location of commands as they are looked up
for execution. This is enabled by default.
- -\b-k\bk All arguments in the form of assignment statements are
- placed in the environment for a command, not just those
+ -\b-k\bk All arguments in the form of assignment statements are
+ placed in the environment for a command, not just those
that precede the command name.
- -\b-m\bm Monitor mode. Job control is enabled. This option is
- on by default for interactive shells on systems that
- support it (see J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL above). All processes run
+ -\b-m\bm Monitor mode. Job control is enabled. This option is
+ on by default for interactive shells on systems that
+ support it (see J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL above). All processes run
in a separate process group. When a background job com-
pletes, the shell prints a line containing its exit sta-
tus.
-\b-n\bn Read commands but do not execute them. This may be used
- to check a shell script for syntax errors. This is
+ to check a shell script for syntax errors. This is
ignored by interactive shells.
-\b-o\bo _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be
The _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be can be one of the following:
Same as -\b-a\ba.
b\bbr\bra\bac\bce\bee\bex\bxp\bpa\ban\bnd\bd
Same as -\b-B\bB.
- e\bem\bma\bac\bcs\bs Use an emacs-style command line editing inter-
+ e\bem\bma\bac\bcs\bs Use an emacs-style command line editing inter-
face. This is enabled by default when the shell
is interactive, unless the shell is started with
- the -\b--\b-n\bno\boe\bed\bdi\bit\bti\bin\bng\bg option. This also affects the
+ the -\b--\b-n\bno\boe\bed\bdi\bit\bti\bin\bng\bg option. This also affects the
editing interface used for r\bre\bea\bad\bd -\b-e\be.
e\ber\brr\bre\bex\bxi\bit\bt Same as -\b-e\be.
e\ber\brr\brt\btr\bra\bac\bce\be
H\bHI\bIS\bST\bTO\bOR\bRY\bY. This option is on by default in inter-
active shells.
i\big\bgn\bno\bor\bre\bee\beo\bof\bf
- The effect is as if the shell command
- ``IGNOREEOF=10'' had been executed (see S\bSh\bhe\bel\bll\bl
+ The effect is as if the shell command
+ ``IGNOREEOF=10'' had been executed (see S\bSh\bhe\bel\bll\bl
V\bVa\bar\bri\bia\bab\bbl\ble\bes\bs above).
k\bke\bey\byw\bwo\bor\brd\bd Same as -\b-k\bk.
m\bmo\bon\bni\bit\bto\bor\br Same as -\b-m\bm.
p\bph\bhy\bys\bsi\bic\bca\bal\bl
Same as -\b-P\bP.
p\bpi\bip\bpe\bef\bfa\bai\bil\bl
- If set, the return value of a pipeline is the
- value of the last (rightmost) command to exit
- with a non-zero status, or zero if all commands
- in the pipeline exit successfully. This option
+ If set, the return value of a pipeline is the
+ value of the last (rightmost) command to exit
+ with a non-zero status, or zero if all commands
+ in the pipeline exit successfully. This option
is disabled by default.
- p\bpo\bos\bsi\bix\bx Change the behavior of b\bba\bas\bsh\bh where the default
- operation differs from the POSIX standard to
- match the standard (_\bp_\bo_\bs_\bi_\bx _\bm_\bo_\bd_\be). See S\bSE\bEE\bE A\bAL\bLS\bSO\bO
+ p\bpo\bos\bsi\bix\bx Change the behavior of b\bba\bas\bsh\bh where the default
+ operation differs from the POSIX standard to
+ match the standard (_\bp_\bo_\bs_\bi_\bx _\bm_\bo_\bd_\be). See S\bSE\bEE\bE A\bAL\bLS\bSO\bO
below for a reference to a document that details
how posix mode affects bash's behavior.
p\bpr\bri\biv\bvi\bil\ble\beg\bge\bed\bd
Same as -\b-p\bp.
v\bve\ber\brb\bbo\bos\bse\be Same as -\b-v\bv.
- v\bvi\bi Use a vi-style command line editing interface.
+ v\bvi\bi Use a vi-style command line editing interface.
This also affects the editing interface used for
r\bre\bea\bad\bd -\b-e\be.
x\bxt\btr\bra\bac\bce\be Same as -\b-x\bx.
If -\b-o\bo is supplied with no _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be, the values of the
- current options are printed. If +\b+o\bo is supplied with no
- _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be, a series of s\bse\bet\bt commands to recreate the
- current option settings is displayed on the standard
+ current options are printed. If +\b+o\bo is supplied with no
+ _\bo_\bp_\bt_\bi_\bo_\bn_\b-_\bn_\ba_\bm_\be, a series of s\bse\bet\bt commands to recreate the
+ current option settings is displayed on the standard
output.
- -\b-p\bp Turn on _\bp_\br_\bi_\bv_\bi_\bl_\be_\bg_\be_\bd mode. In this mode, the $\b$E\bEN\bNV\bV and
- $\b$B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV files are not processed, shell functions are
- not inherited from the environment, and 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
+ -\b-p\bp Turn on _\bp_\br_\bi_\bv_\bi_\bl_\be_\bg_\be_\bd mode. In this mode, the $\b$E\bEN\bNV\bV and
+ $\b$B\bBA\bAS\bSH\bH_\b_E\bEN\bNV\bV files are not processed, shell functions are
+ not inherited from the environment, and 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, 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 sup-
+ 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. If the -\b-p\bp option is sup-
- plied at startup, the effective user id is not reset.
- Turning this option off causes the effective user and
+ is set to the real user id. If the -\b-p\bp option is sup-
+ plied 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-t\bt Exit after reading and executing one command.
-\b-u\bu Treat unset variables and parameters other than the spe-
- cial parameters "@" and "*" 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 "*" 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
+ play the expanded value of P\bPS\bS4\b4, followed by the command
and its expanded arguments or associated word list.
- -\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. This may be
+ -\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. This may be
overridden when creating output files by using the redi-
rection operator >\b>|\b| instead of >\b>.
-\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
- shell functions, command substitutions, and commands
- executed in a subshell environment. The D\bDE\bEB\bBU\bUG\bG and
+ -\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
+ executed 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, then the positional
+ -\b--\b- If no arguments follow this option, then the positional
parameters are unset. Otherwise, the positional parame-
- ters are set to the _\ba_\br_\bgs, even if some of them begin
+ ters are set to the _\ba_\br_\bgs, even if some of them begin
with a -\b-.
- -\b- Signal the end of options, cause all remaining _\ba_\br_\bgs to
+ -\b- Signal the end of options, cause all remaining _\ba_\br_\bgs to
be assigned to the positional parameters. The -\b-x\bx and -\b-v\bv
options are turned off. If there are no _\ba_\br_\bgs, the posi-
tional parameters remain unchanged.
- The options are off by default unless otherwise noted. Using +
- rather than - causes these options to be turned off. The
- options can also be specified as arguments to an invocation of
- the shell. The current set of options may be found in $\b$-\b-. The
+ The options are off by default unless otherwise noted. Using +
+ rather than - causes these options to be turned off. The
+ options can also be specified as arguments to an invocation of
+ the shell. The current set of options may be found in $\b$-\b-. The
return status is always true unless an invalid option is encoun-
tered.
s\bsh\bhi\bif\bft\bt [_\bn]
- The positional parameters from _\bn+1 ... are renamed 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
+ The positional parameters from _\bn+1 ... are renamed to $\b$1\b1 .\b..\b..\b..\b.
+ Parameters represented by the numbers $\b$#\b# down to $\b$#\b#-_\bn+1 are
+ unset. _\bn must be a non-negative number less than or equal to
+ $\b$#\b#. If _\bn is 0, no parameters are changed. If _\bn is not given,
+ it is assumed to be 1. If _\bn is greater than $\b$#\b#, the positional
+ parameters are not changed. The return status is greater than
zero if _\bn is greater than $\b$#\b# or less than zero; otherwise 0.
s\bsh\bho\bop\bpt\bt [-\b-p\bpq\bqs\bsu\bu] [-\b-o\bo] [_\bo_\bp_\bt_\bn_\ba_\bm_\be ...]
Toggle the values of variables controlling optional shell behav-
ior. With no options, or with the -\b-p\bp option, a list of all set-
table options is displayed, with an indication of whether or not
- each is set. The -\b-p\bp option causes output to be displayed in a
- form that may be reused as input. Other options have the fol-
+ each is set. The -\b-p\bp option causes output to be displayed in a
+ form that may be reused as input. Other options have the fol-
lowing 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 given with -\b-q\bq, the return sta-
- tus is zero if all _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs are enabled; non-zero other-
+ ple _\bo_\bp_\bt_\bn_\ba_\bm_\be arguments are given with -\b-q\bq, the return sta-
+ tus is zero if all _\bo_\bp_\bt_\bn_\ba_\bm_\be_\bs are enabled; non-zero other-
wise.
- -\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
- options, 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
+ options, 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\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.
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, minor errors in the spelling of a directory com-
- ponent in a c\bcd\bd command will be corrected. The errors
+ ponent in a c\bcd\bd command will be corrected. The errors
checked for are transposed characters, a missing charac-
- ter, and one character too many. If a correction is
- found, the corrected filename is printed, and the com-
- mand proceeds. This option is only used by interactive
+ ter, and one character too many. If a correction is
+ found, the corrected filename is printed, and the com-
+ mand proceeds. 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, a normal path search is per-
+ ble exists before trying to execute it. If a hashed
+ command no longer exists, a normal path search is per-
formed.
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, this causes the exit to be deferred until a
- second exit is attempted without an intervening command
- (see J\bJO\bOB\bB C\bCO\bON\bNT\bTR\bRO\bOL\bL above). The shell always postpones
+ second exit is attempted without an intervening command
+ (see J\bJO\bOB\bB C\bCO\bON\bNT\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 command
- and, if necessary, updates the values of L\bLI\bIN\bNE\bES\bS and C\bCO\bOL\bL-\b-
+ If set, b\bba\bas\bsh\bh checks the window size after each command
+ and, if necessary, updates the values of L\bLI\bIN\bNE\bES\bS and C\bCO\bOL\bL-\b-
U\bUM\bMN\bNS\bS.
- 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
+ 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.
c\bco\bom\bmp\bpa\bat\bt3\b31\b1
If set, b\bba\bas\bsh\bh changes its behavior to that of version 3.1
- with respect to quoted arguments to the [\b[[\b[ conditional
+ with respect to quoted arguments to the [\b[[\b[ conditional
command's =\b=~\b~ operator and locale-specific string compar-
- ison when using the [\b[[\b[ conditional command's <\b< and >\b>
- operators. Bash versions prior to bash-4.1 use ASCII
+ ison when using the [\b[[\b[ conditional command's <\b< and >\b>
+ operators. Bash versions prior to bash-4.1 use ASCII
collation and _\bs_\bt_\br_\bc_\bm_\bp(3); bash-4.1 and later use the cur-
rent locale's collation sequence and _\bs_\bt_\br_\bc_\bo_\bl_\bl(3).
c\bco\bom\bmp\bpa\bat\bt3\b32\b2
If set, b\bba\bas\bsh\bh changes its behavior to that of version 3.2
- with respect to locale-specific string comparison when
- using the [\b[[\b[ conditional command's <\b< and >\b> operators
+ with respect to locale-specific string comparison when
+ using the [\b[[\b[ conditional command's <\b< and >\b> operators
(see previous item).
c\bco\bom\bmp\bpa\bat\bt4\b40\b0
If set, b\bba\bas\bsh\bh changes its behavior to that of version 4.0
- with respect to locale-specific string comparison when
- using the [\b[[\b[ conditional command's <\b< and >\b> operators
- (see description of c\bco\bom\bmp\bpa\bat\bt3\b31\b1) and the effect of inter-
- rupting a command list. Bash versions 4.0 and later
- interrupt the list as if the shell received the inter-
- rupt; previous versions continue with the next command
+ with respect to locale-specific string comparison when
+ using the [\b[[\b[ conditional command's <\b< and >\b> operators
+ (see description of c\bco\bom\bmp\bpa\bat\bt3\b31\b1) and the effect of inter-
+ rupting a command list. Bash versions 4.0 and later
+ interrupt the list as if the shell received the inter-
+ rupt; previous versions continue with the next command
in the list.
c\bco\bom\bmp\bpa\bat\bt4\b41\b1
- If set, b\bba\bas\bsh\bh, when in _\bp_\bo_\bs_\bi_\bx mode, treats a single quote
- in a double-quoted parameter expansion as a special
- character. The single quotes must match (an even num-
- ber) and the characters between the single quotes are
- considered quoted. This is the behavior of posix mode
- through version 4.1. The default bash behavior remains
+ If set, b\bba\bas\bsh\bh, when in _\bp_\bo_\bs_\bi_\bx mode, treats a single quote
+ in a double-quoted parameter expansion as a special
+ character. The single quotes must match (an even num-
+ ber) and the characters between the single quotes are
+ considered quoted. This is the behavior of posix mode
+ through version 4.1. The default bash behavior remains
as in previous versions.
c\bco\bom\bmp\bpa\bat\bt4\b42\b2
- If set, b\bba\bas\bsh\bh does not process the replacement string in
- the pattern substitution word expansion using quote
+ If set, b\bba\bas\bsh\bh does not process the replacement string in
+ the pattern substitution word expansion using quote
removal.
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
- expand to directories will not be quoted; however, any
- dollar signs appearing in filenames will not be quoted,
- either. This is active only when bash is using 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
+ expand to directories will not be quoted; however, any
+ dollar signs appearing in filenames will not be quoted,
+ either. This is active only when bash is using 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 readline 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
+ 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.
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 command. An interactive shell does not
+ not execute the file specified as an argument to the
+ e\bex\bxe\bec\bc builtin command. 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, behavior intended for use by debuggers is
+ If set, 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), a call to
+ 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), a call to
r\bre\bet\btu\bur\brn\bn is simulated.
- 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, 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 are enabled.
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
- description of F\bFI\bIG\bGN\bNO\bOR\bRE\bE. This option is enabled by
+ description of F\bFI\bIG\bGN\bNO\bOR\bRE\bE. This option is enabled by
default.
g\bgl\blo\bob\bba\bas\bsc\bci\bii\bir\bra\ban\bng\bge\bes\bs
- If set, range expressions used in pattern matching (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
+ If set, range expressions used in pattern matching (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 comparisons. That is, the cur-
- rent locale's collating sequence is not taken into
- account, so b\bb will not collate between A\bA and B\bB, and
- upper-case and lower-case ASCII characters will collate
+ rent locale's collating sequence is not taken 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\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
- by the value of the H\bHI\bIS\bST\bTF\bFI\bIL\bLE\bE variable when the shell
+ 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
exits, 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, a user is given the
+ If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, a user is given the
opportunity to re-edit a failed history substitution.
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\bnt\bte\ber\bra\bac\bct\bti\biv\bve\be_\b_c\bco\bom\bmm\bme\ben\bnt\bts\bs
If set, allow a word beginning with #\b# to cause that word
- and all remaining characters on that line to be ignored
- in an interactive shell (see C\bCO\bOM\bMM\bME\bEN\bNT\bTS\bS above). This
+ and all remaining characters on that line to be ignored
+ in an 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\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, the
- message ``The mail in _\bm_\ba_\bi_\bl_\bf_\bi_\bl_\be has been read'' is dis-
+ 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, the
+ message ``The mail in _\bm_\ba_\bi_\bl_\bf_\bi_\bl_\be has been read'' is dis-
played.
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 will not
+ If set, and r\bre\bea\bad\bdl\bli\bin\bne\be is being used, b\bba\bas\bsh\bh will not
attempt to search the P\bPA\bAT\bTH\bH for possible completions when
completion is attempted 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.
n\bnu\bul\bll\blg\bgl\blo\bob\bb
- If set, b\bba\bas\bsh\bh allows patterns which match no files (see
- P\bPa\bat\bth\bhn\bna\bam\bme\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn above) to expand to a null string,
+ If set, b\bba\bas\bsh\bh allows patterns which match no files (see
+ P\bPa\bat\bth\bhn\bna\bam\bme\be E\bEx\bxp\bpa\ban\bns\bsi\bio\bon\bn above) to expand to a null string,
rather than themselves.
p\bpr\bro\bog\bgc\bco\bom\bmp\bp
If set, the programmable completion facilities (see P\bPr\bro\bo-\b-
enabled by default.
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
- removal after being expanded as described in P\bPR\bRO\bOM\bMP\bPT\bTI\bIN\bNG\bG
+ mand substitution, arithmetic expansion, and quote
+ removal 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
+ The shell sets this option if it is started in
restricted 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-
+ 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 s\bso\bou\bur\brc\bce\be (.\b.) builtin uses the value of P\bPA\bAT\bTH\bH to
- find the directory containing the file supplied as an
+ find the directory containing the file supplied as an
argument. This option is enabled by default.
x\bxp\bpg\bg_\b_e\bec\bch\bho\bo
- If set, the e\bec\bch\bho\bo builtin expands backslash-escape
+ If set, the e\bec\bch\bho\bo builtin expands backslash-escape
sequences by default.
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
+ Suspend the execution of this shell until it receives a S\bSI\bIG\bGC\bCO\bON\bNT\bT
signal. A login shell cannot be suspended; the -\b-f\bf option can be
used to override this and force the suspension. The return sta-
- tus is 0 unless the shell is a login shell and -\b-f\bf is not sup-
+ tus is 0 unless the shell is a login shell and -\b-f\bf is not sup-
plied, or if job control is not enabled.
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 op-
- erand 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
+ erand 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,
+ Expressions may be combined using the following operators,
listed in decreasing order of precedence. The evaluation
- depends on the number of arguments; see below. Operator prece-
+ depends on the number of arguments; see below. Operator prece-
dence is used 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
the normal precedence of operators.
_\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
If the first argument is !\b!, the result is the negation of
- the three-argument expression composed of the remaining
+ the three-argument expression composed of the remaining
arguments. Otherwise, the expression is parsed and eval-
- uated according to precedence using the rules listed
+ uated 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 used with t\bte\bes\bst\bt or [\b[, the <\b< and >\b> operators sort lexico-
+ When used with t\bte\bes\bst\bt or [\b[, the <\b< and >\b> operators sort lexico-
graphically using ASCII ordering.
- 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\bp] [[_\ba_\br_\bg] _\bs_\bi_\bg_\bs_\bp_\be_\bc ...]
- The command _\ba_\br_\bg is to be read and executed when the shell
- receives signal(s) _\bs_\bi_\bg_\bs_\bp_\be_\bc. If _\ba_\br_\bg is absent (and there is a
- single _\bs_\bi_\bg_\bs_\bp_\be_\bc) or -\b-, each specified signal is reset to its
- original disposition (the value it had upon entrance to the
- shell). If _\ba_\br_\bg 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 _\ba_\br_\bg is not present and -\b-p\bp has been supplied, then the trap
- commands associated with each _\bs_\bi_\bg_\bs_\bp_\be_\bc are displayed. If no
- arguments are supplied or if only -\b-p\bp is given, t\btr\bra\bap\bp prints the
- list of commands associated with each signal. The -\b-l\bl option
- causes the shell to print a list of signal names and their cor-
- responding 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
+ The command _\ba_\br_\bg is to be read and executed when the shell
+ receives signal(s) _\bs_\bi_\bg_\bs_\bp_\be_\bc. If _\ba_\br_\bg is absent (and there is a
+ single _\bs_\bi_\bg_\bs_\bp_\be_\bc) or -\b-, each specified signal is reset to its
+ original disposition (the value it had upon entrance to the
+ shell). If _\ba_\br_\bg 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 _\ba_\br_\bg is not present and -\b-p\bp has been supplied, then the trap
+ commands associated with each _\bs_\bi_\bg_\bs_\bp_\be_\bc are displayed. If no
+ arguments are supplied or if only -\b-p\bp is given, t\btr\bra\bap\bp prints the
+ list of commands associated with each signal. The -\b-l\bl option
+ causes the shell to print a list of signal names and their cor-
+ responding 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 insensitive and the S\bSI\bIG\bG prefix is optional.
- If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bEX\bXI\bIT\bT (0) the command _\ba_\br_\bg is executed on exit
- from the shell. If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is D\bDE\bEB\bBU\bUG\bG, the command _\ba_\br_\bg is exe-
- cuted 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, every arithmetic _\bf_\bo_\br command, 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 option to the
+ If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bEX\bXI\bIT\bT (0) the command _\ba_\br_\bg is executed on exit
+ from the shell. If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is D\bDE\bEB\bBU\bUG\bG, the command _\ba_\br_\bg is exe-
+ cuted 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, every arithmetic _\bf_\bo_\br command, 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 option to the
s\bsh\bho\bop\bpt\bt builtin for details of its effect 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, the command _\ba_\br_\bg is executed each time a shell
function or a script executed with the .\b. or s\bso\bou\bur\brc\bce\be builtins fin-
ishes executing.
- If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bER\bRR\bR, the command _\ba_\br_\bg is executed whenever a a
+ If a _\bs_\bi_\bg_\bs_\bp_\be_\bc is E\bER\bRR\bR, the command _\ba_\br_\bg is executed whenever a 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
+ 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 keyword, part of the test in an _\bi_\bf statement,
+ a w\bwh\bhi\bil\ble\be or u\bun\bnt\bti\bil\bl keyword, part of the test in an _\bi_\bf statement,
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, 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)
+ following the final &\b&&\b& or |\b||\b|, any command in a pipeline but the
+ last, 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)
option.
- Signals ignored upon entry to the shell cannot be trapped or
- reset. Trapped signals that are not being ignored are reset to
+ Signals ignored upon entry to the shell cannot be trapped or
+ reset. Trapped signals that are not being ignored are reset to
their original values in a subshell or subshell environment when
- one is created. The return status is false if any _\bs_\bi_\bg_\bs_\bp_\be_\bc is
+ 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\bty\byp\bpe\be [-\b-a\baf\bft\btp\bpP\bP] _\bn_\ba_\bm_\be [_\bn_\ba_\bm_\be ...]
- With no options, indicate how each _\bn_\ba_\bm_\be would be interpreted if
+ With no options, 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 disk file, respectively. If the _\bn_\ba_\bm_\be is not found,
- then nothing is printed, and an exit status of false is
- returned. If the -\b-p\bp option is used, t\bty\byp\bpe\be either returns the
+ 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 disk file, respectively. If the _\bn_\ba_\bm_\be is not found,
+ then nothing is printed, and an exit status of false is
+ returned. If the -\b-p\bp option is used, t\bty\byp\bpe\be either returns the
name of the disk file that would be executed if _\bn_\ba_\bm_\be were speci-
fied as a command name, 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,
+ return _\bf_\bi_\bl_\be. The -\b-P\bP option forces a P\bPA\bAT\bTH\bH search for each _\bn_\ba_\bm_\be,
even if ``type -t name'' would not return _\bf_\bi_\bl_\be. If a command is
hashed, -\b-p\bp and -\b-P\bP print the hashed value, which is not necessar-
- ily 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 an executable
+ ily 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 an executable
named _\bn_\ba_\bm_\be. This includes aliases and functions, if and only if
the -\b-p\bp option is not also used. The table of hashed commands is
- not consulted when using -\b-a\ba. The -\b-f\bf option suppresses shell
+ not consulted when using -\b-a\ba. The -\b-f\bf option suppresses shell
function lookup, as with the c\bco\bom\bmm\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\bST\bTa\bab\bbc\bcd\bde\bef\bfi\bil\blm\bmn\bnp\bpq\bqr\brs\bst\btu\buv\bvx\bx [_\bl_\bi_\bm_\bi_\bt]]
- Provides control over the resources available to the shell and
- to processes started by it, on systems that allow such control.
+ Provides control over the resources available to the shell and
+ to processes started by it, on systems that allow such control.
The -\b-H\bH and -\b-S\bS options specify that 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-
+ for the given resource. A hard limit cannot be increased by a
+ non-root user once it is set; a soft limit may be increased up
+ to the value of the hard limit. If neither -\b-H\bH nor -\b-S\bS is speci-
fied, both the soft and hard limits are set. 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, the current value of the
- soft limit of the resource is printed, unless the -\b-H\bH option is
+ current hard limit, the current soft limit, and no limit,
+ respectively. If _\bl_\bi_\bm_\bi_\bt is omitted, the current value of the
+ soft limit of the resource is printed, unless the -\b-H\bH option is
given. When more than one resource is specified, the limit name
and unit are printed before the value. Other options are inter-
preted as follows:
-\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-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-T\bT The maximum number of threads
- If _\bl_\bi_\bm_\bi_\bt is given, 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 given,
- then -\b-f\bf is assumed. Values are in 1024-byte increments, except
- for -\b-t\bt, which is in seconds; -\b-p\bp, which is in units of 512-byte
- blocks; and -\b-T\bT, -\b-b\bb, -\b-n\bn, and -\b-u\bu, which are unscaled values. The
- return status is 0 unless an invalid option or argument is sup-
+ If _\bl_\bi_\bm_\bi_\bt is given, 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 given,
+ then -\b-f\bf is assumed. Values are in 1024-byte increments, except
+ for -\b-t\bt, which is in seconds; -\b-p\bp, which is in units of 512-byte
+ blocks; and -\b-T\bT, -\b-b\bb, -\b-n\bn, and -\b-u\bu, which are unscaled values. The
+ return status is 0 unless an invalid option or argument is sup-
plied, 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]
The user file-creation mask is set to _\bm_\bo_\bd_\be. If _\bm_\bo_\bd_\be begins with
- a digit, it is interpreted as an octal number; otherwise it is
- interpreted as a symbolic mode mask similar to that accepted by
- _\bc_\bh_\bm_\bo_\bd(1). If _\bm_\bo_\bd_\be is omitted, the current value of the mask is
- printed. The -\b-S\bS option causes the mask to be printed in sym-
- bolic form; the default output is an octal number. If the -\b-p\bp
+ a digit, it is interpreted as an octal number; otherwise it is
+ interpreted as a symbolic mode mask similar to that accepted by
+ _\bc_\bh_\bm_\bo_\bd(1). If _\bm_\bo_\bd_\be is omitted, the current value of the mask is
+ printed. The -\b-S\bS option causes the mask to be printed in sym-
+ bolic form; 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 0 if the mode
- was successfully changed or if no _\bm_\bo_\bd_\be argument was supplied,
+ was successfully changed or if no _\bm_\bo_\bd_\be argument was supplied,
and false 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, all alias definitions are removed. The return value
+ Remove each _\bn_\ba_\bm_\be from the list of defined aliases. If -\b-a\ba is
+ supplied, all alias definitions are removed. 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. Read-only variables may not be
- unset. If -\b-f\bf is specified, each _\bn_\ba_\bm_\be refers to a shell func-
- tion, and the function definition is removed. 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. If no options are
- supplied, each _\bn_\ba_\bm_\be refers to a variable; if there is no vari-
- able by that name, any function with that name is unset. Each
- unset variable or function is removed from the environment
- passed to subsequent commands. If any of C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS, R\bRA\bAN\bN-\b-
+ and that variable is removed. Read-only variables may not be
+ unset. If -\b-f\bf is specified, each _\bn_\ba_\bm_\be refers to a shell func-
+ tion, and the function definition is removed. 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. If no options are
+ supplied, each _\bn_\ba_\bm_\be refers to a variable; if there is no vari-
+ able by that name, any function with that name is unset. Each
+ unset variable or function is removed from the environment
+ passed to subsequent commands. If any of C\bCO\bOM\bMP\bP_\b_W\bWO\bOR\bRD\bDB\bBR\bRE\bEA\bAK\bKS\bS, R\bRA\bAN\bN-\b-
D\bDO\bOM\bM, S\bSE\bEC\bCO\bON\bND\bDS\bS, L\bLI\bIN\bNE\bEN\bNO\bO, H\bHI\bIS\bST\bTC\bCM\bMD\bD, F\bFU\bUN\bNC\bCN\bNA\bAM\bME\bE, G\bGR\bRO\bOU\bUP\bPS\bS, or D\bDI\bIR\bRS\bST\bTA\bAC\bCK\bK are
unset, they lose their special properties, even if they are sub-
sequently reset. The exit status is true unless a _\bn_\ba_\bm_\be is read-
only.
w\bwa\bai\bit\bt [-\b--\b-n\bn] [_\bn _\b._\b._\b.]
- Wait for each specified process and return its termination sta-
- tus. Each _\bn may be a process ID or a job specification; if a
- job spec is given, all processes in that job's pipeline are
- waited for. If _\bn is not given, all currently active child pro-
- cesses are waited for, and the return status is zero. If the
- -\b--\b-n\bn option is supplied, w\bwa\bai\bit\bt waits for any job to terminate and
- returns its exit status. If _\bn specifies a non-existent process
- or job, the return status is 127. Otherwise, the return status
+ Wait for each specified process and return its termination sta-
+ tus. Each _\bn may be a process ID or a job specification; if a
+ job spec is given, all processes in that job's pipeline are
+ waited for. If _\bn is not given, all currently active child pro-
+ cesses are waited for, and the return status is zero. If the
+ -\b--\b-n\bn option is supplied, w\bwa\bai\bit\bt waits for any job to terminate and
+ returns its exit status. If _\bn specifies a non-existent process
+ or job, the return status is 127. Otherwise, the return status
is the exit status of the last process or job waited for.
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 restricted. 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 restricted. 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 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 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 value of S\bSH\bHE\bEL\bLL\bLO\bOP\bPT\bTS\bS from the shell environment at
+ +\bo parsing the value of S\bSH\bHE\bEL\bLL\bLO\bOP\bPT\bTS\bS from the shell environment at
startup
+\bo redirecting output using the >, >|, <>, >&, &>, and >> redirect-
+\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
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
_\bB_\ba_\bs_\bh _\bR_\be_\bf_\be_\br_\be_\bn_\bc_\be _\bM_\ba_\bn_\bu_\ba_\bl, Brian Fox and Chet Ramey
_\bT_\bh_\be _\bG_\bn_\bu _\bR_\be_\ba_\bd_\bl_\bi_\bn_\be _\bL_\bi_\bb_\br_\ba_\br_\by, Brian Fox and Chet Ramey
_\bT_\bh_\be _\bG_\bn_\bu _\bH_\bi_\bs_\bt_\bo_\br_\by _\bL_\bi_\bb_\br_\ba_\br_\by, Brian Fox and Chet Ramey
- _\bP_\bo_\br_\bt_\ba_\bb_\bl_\be _\bO_\bp_\be_\br_\ba_\bt_\bi_\bn_\bg _\bS_\by_\bs_\bt_\be_\bm _\bI_\bn_\bt_\be_\br_\bf_\ba_\bc_\be _\b(_\bP_\bO_\bS_\bI_\bX_\b) _\bP_\ba_\br_\bt _\b2_\b: _\bS_\bh_\be_\bl_\bl _\ba_\bn_\bd _\bU_\bt_\bi_\bl_\bi_\b-
- _\bt_\bi_\be_\bs, IEEE
+ _\bP_\bo_\br_\bt_\ba_\bb_\bl_\be _\bO_\bp_\be_\br_\ba_\bt_\bi_\bn_\bg _\bS_\by_\bs_\bt_\be_\bm _\bI_\bn_\bt_\be_\br_\bf_\ba_\bc_\be _\b(_\bP_\bO_\bS_\bI_\bX_\b) _\bP_\ba_\br_\bt _\b2_\b: _\bS_\bh_\be_\bl_\bl _\ba_\bn_\bd _\bU_\bt_\bi_\bl_\bi_\b-
+ _\bt_\bi_\be_\bs, IEEE --
+ http://pubs.opengroup.org/onlinepubs/9699919799/
http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
_\bs_\bh(1), _\bk_\bs_\bh(1), _\bc_\bs_\bh(1)
_\be_\bm_\ba_\bc_\bs(1), _\bv_\bi(1)
_\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._\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,\b, you should report it. But first, you should
- make sure that it really is a bug, and that it appears in the latest
- version of b\bba\bas\bsh\bh. The latest version is always available from
+ make sure that it really is a bug, and that it appears in the latest
+ version of b\bba\bas\bsh\bh. The latest version is always available from
_\bf_\bt_\bp_\b:_\b/_\b/_\bf_\bt_\bp_\b._\bg_\bn_\bu_\b._\bo_\br_\bg_\b/_\bp_\bu_\bb_\b/_\bg_\bn_\bu_\b/_\bb_\ba_\bs_\bh_\b/.
- 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! Suggestions and `philosophical' bug reports may
- be mailed to _\bb_\bu_\bg_\b-_\bb_\ba_\bs_\bh_\b@_\bg_\bn_\bu_\b._\bo_\br_\bg or posted to the Usenet newsgroup
+ 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! Suggestions and `philosophical' bug reports may
+ be mailed to _\bb_\bu_\bg_\b-_\bb_\ba_\bs_\bh_\b@_\bg_\bn_\bu_\b._\bo_\br_\bg or posted to the Usenet newsgroup
g\bgn\bnu\bu.\b.b\bba\bas\bsh\bh.\b.b\bbu\bug\bg.
ALL bug reports should include:
A description of the bug behaviour
A short script or `recipe' which exercises the bug
- _\bb_\ba_\bs_\bh_\bb_\bu_\bg inserts the first three items automatically into the template
+ _\bb_\ba_\bs_\bh_\bb_\bu_\bg inserts the first three items automatically into the template
it provides for filing a bug report.
Comments and bug reports concerning this manual page should be directed
Shell builtin commands and functions are not stoppable/restartable.
Compound commands and command sequences of the form `a ; b ; c' are not
- handled gracefully when process suspension is attempted. When a
- process is stopped, the shell immediately executes the next command in
- the sequence. It suffices to place the sequence of commands between
- parentheses to force it into a subshell, which may be stopped as a
+ handled gracefully when process suspension is attempted. When a
+ process is stopped, the shell immediately executes the next command in
+ the sequence. It suffices to place the sequence of commands between
+ parentheses to force it into a subshell, which may be stopped as a
unit.
Array variables may not (yet) be exported.
-GNU Bash 4.2 2013 March 4 BASH(1)
+GNU Bash 4.3 2013 March 21 BASH(1)
projects / thirdparty / bash.git / commitdiff
