2 .\" MAN PAGE COMMENTS to
5 .\" Case Western Reserve University
8 .\" Last Change: Mon Dec 29 16:49:01 EST 2008
10 .\" bash_builtins, strip all but Built-Ins section
13 .TH BASH 1 "2008 December 29" "GNU Bash-4.0"
15 .\" There's some problem with having a `@'
16 .\" in a tagged paragraph with the BSD man macros.
17 .\" It has to do with `@' appearing in the }1 macro.
18 .\" This is a problem on 4.3 BSD and Ultrix, but Sun
19 .\" appears to have fixed it.
20 .\" If you're seeing the characters
21 .\" `@u-3p' appearing before the lines reading
22 .\" `possible-hostname-completions
23 .\" and `complete-hostname' down in READLINE,
24 .\" then uncomment this redefinition.
29 .if !"\\$1"" .nr )I \\$1n
32 .in \\n()Ru+\\n(INu+\\n()Iu
34 .ie !\\n()Iu+\\n()Ru-\w
\a\\*(]X
\au-3p \{\\*(]X
36 .el \\*(]X\h
\a|\\n()Iu+\\n()Ru
\a\c
40 .\" File Name macro. This used to be `.PN', for Path Name,
41 .\" but Sun doesn't seem to like that very much.
47 bash \- GNU Bourne-Again SHell
53 .if n Bash is Copyright (C) 1989-2009 by the Free Software Foundation, Inc.
54 .if t Bash is Copyright \(co 1989-2009 by the Free Software Foundation, Inc.
57 is an \fBsh\fR-compatible command language interpreter that
58 executes commands read from the standard input or from a file.
60 also incorporates useful features from the \fIKorn\fP and \fIC\fP
61 shells (\fBksh\fP and \fBcsh\fP).
64 is intended to be a conformant implementation of the
65 Shell and Utilities portion of the IEEE POSIX specification
66 (IEEE Standard 1003.1).
68 can be configured to be POSIX-conformant by default.
70 In addition to the single-character shell options documented in the
71 description of the \fBset\fR builtin command, \fBbash\fR
72 interprets the following options when it is invoked:
79 option is present, then commands are read from
81 If there are arguments after the
83 they are assigned to the positional parameters, starting with
89 option is present, the shell is
95 act as if it had been invoked as a login shell (see
103 option is present, the shell becomes
107 .B "RESTRICTED SHELL"
113 option is present, or if no arguments remain after option
114 processing, then commands are read from the standard input.
115 This option allows the positional parameters to be set
116 when invoking an interactive shell.
119 A list of all double-quoted strings preceded by \fB$\fP
120 is printed on the standard output.
121 These are the strings that
122 are subject to language translation when the current locale
123 is not \fBC\fP or \fBPOSIX\fP.
124 This implies the \fB\-n\fP option; no commands will be executed.
126 .B [\-+]O [\fIshopt_option\fP]
127 \fIshopt_option\fP is one of the shell options accepted by the
128 \fBshopt\fP builtin (see
130 .B SHELL BUILTIN COMMANDS
132 If \fIshopt_option\fP is present, \fB\-O\fP sets the value of that option;
134 If \fIshopt_option\fP is not supplied, the names and values of the shell
135 options accepted by \fBshopt\fP are printed on the standard output.
136 If the invocation option is \fB+O\fP, the output is displayed in a format
137 that may be reused as input.
142 signals the end of options and disables further option processing.
143 Any arguments after the
145 are treated as filenames and arguments. An argument of
147 is equivalent to \fB\-\-\fP.
151 also interprets a number of multi-character options.
152 These options must appear on the command line before the
153 single-character options to be recognized.
158 Arrange for the debugger profile to be executed before the shell
160 Turns on extended debugging mode (see the description of the
165 and shell function tracing (see the description of the
166 \fB\-o functrace\fP option to the
170 .B \-\-dump\-po\-strings
171 Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
172 \fBpo\fP (portable object) file format.
175 Equivalent to \fB\-D\fP.
178 Display a usage message on standard output and exit successfully.
180 \fB\-\-init\-file\fP \fIfile\fP
183 \fB\-\-rcfile\fP \fIfile\fP
185 Execute commands from
187 instead of the standard personal initialization file
189 if the shell is interactive (see
195 Equivalent to \fB\-l\fP.
200 library to read command lines when the shell is interactive.
203 Do not read either the system-wide startup file
205 or any of the personal initialization files
206 .IR ~/.bash_profile ,
212 reads these files when it is invoked as a login shell (see
218 Do not read and execute the personal initialization file
220 if the shell is interactive.
221 This option is on by default if the shell is invoked as
225 Change the behavior of \fBbash\fP where the default operation differs
226 from the POSIX standard to match the standard (\fIposix mode\fP).
229 The shell becomes restricted (see
231 .B "RESTRICTED SHELL"
235 Equivalent to \fB\-v\fP.
238 Show version information for this instance of
240 on the standard output and exit successfully.
243 If arguments remain after option processing, and neither the
247 option has been supplied, the first argument is assumed to
248 be the name of a file containing shell commands.
251 is invoked in this fashion,
253 is set to the name of the file, and the positional parameters
254 are set to the remaining arguments.
256 reads and executes commands from this file, then exits.
257 \fBBash\fP's exit status is the exit status of the last command
258 executed in the script.
259 If no commands are executed, the exit status is 0.
260 An attempt is first made to open the file in the current directory, and,
261 if no file is found, then the shell searches the directories in
266 A \fIlogin shell\fP is one whose first character of argument zero is a
268 or one started with the
272 An \fIinteractive\fP shell is one started without non-option arguments
276 whose standard input and error are
277 both connected to terminals (as determined by
279 or one started with the
291 allowing a shell script or a startup file to test this state.
293 The following paragraphs describe how
295 executes its startup files.
296 If any of the files exist but cannot be read,
299 Tildes are expanded in file names as described below under
308 is invoked as an interactive login shell, or as a non-interactive shell
309 with the \fB\-\-login\fP option, it first reads and
310 executes commands from the file \fI/etc/profile\fP, if that
312 After reading that file, it looks for \fI~/.bash_profile\fP,
313 \fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
314 and executes commands from the first one that exists and is readable.
317 option may be used when the shell is started to inhibit this behavior.
319 When a login shell exits,
321 reads and executes commands from the file \fI~/.bash_logout\fP, if it
324 When an interactive shell that is not a login shell is started,
326 reads and executes commands from \fI~/.bashrc\fP, if that file exists.
327 This may be inhibited by using the
330 The \fB\-\-rcfile\fP \fIfile\fP option will force
332 to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
336 is started non-interactively, to run a shell script, for example, it
337 looks for the variable
340 in the environment, expands its value if it appears there, and uses the
341 expanded value as the name of a file to read and execute.
343 behaves as if the following command were executed:
346 .if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
347 .if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
353 variable is not used to search for the file name.
357 is invoked with the name
359 it tries to mimic the startup behavior of historical versions of
361 as closely as possible,
362 while conforming to the POSIX standard as well.
363 When invoked as an interactive login shell, or a non-interactive
364 shell with the \fB\-\-login\fP option, it first attempts to
365 read and execute commands from
372 option may be used to inhibit this behavior.
373 When invoked as an interactive shell with the name
376 looks for the variable
379 expands its value if it is defined, and uses the
380 expanded value as the name of a file to read and execute.
381 Since a shell invoked as
383 does not attempt to read and execute commands from any other startup
386 option has no effect.
387 A non-interactive shell invoked with the name
389 does not attempt to read any other startup files.
395 mode after the startup files are read.
403 command line option, it follows the POSIX standard for startup files.
404 In this mode, interactive shells expand the
407 variable and commands are read and executed from the file
408 whose name is the expanded value.
409 No other startup files are read.
412 attempts to determine when it is being run with its standard input
413 connected to a a network connection, as if by the remote shell
414 daemon, usually \fIrshd\fP, or the secure shell daemon \fIsshd\fP.
417 determines it is being run in this fashion, it reads and executes
418 commands from \fI~/.bashrc\fP, if that file exists and is readable.
419 It will not do this if invoked as \fBsh\fP.
422 option may be used to inhibit this behavior, and the
424 option may be used to force another file to be read, but
425 \fIrshd\fP does not generally invoke the shell with those options
426 or allow them to be specified.
428 If the shell is started with the effective user (group) id not equal to the
429 real user (group) id, and the \fB\-p\fP option is not supplied, no startup
430 files are read, shell functions are not inherited from the environment, the
433 variable, if it appears in the environment, is ignored,
434 and the effective user id is set to the real user id.
435 If the \fB\-p\fP option is supplied at invocation, the startup behavior is
436 the same, but the effective user id is not reset.
439 The following definitions are used throughout the rest of this
447 A sequence of characters considered as a single unit by the shell.
454 consisting only of alphanumeric characters and underscores, and
455 beginning with an alphabetic character or an underscore. Also
460 A character that, when unquoted, separates words. One of the following:
464 .if t \fB| & ; ( ) < > space tab\fP
465 .if n \fB| & ; ( ) < > space tab\fP
470 A \fItoken\fP that performs a control function. It is one of the following
474 .if t \fB\(bv\(bv & && ; ;; ( ) | |& <newline>\fP
475 .if n \fB|| & && ; ;; ( ) | |& <newline>\fP
479 \fIReserved words\fP are words that have a special meaning to the shell.
480 The following words are recognized as reserved when unquoted and either
481 the first word of a simple command (see
484 below) or the third word of a
492 .if n ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
493 .if t ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
498 A \fIsimple command\fP is a sequence of optional variable assignments
499 followed by \fBblank\fP-separated words and redirections, and
500 terminated by a \fIcontrol operator\fP. The first word
501 specifies the command to be executed, and is passed as argument zero.
502 The remaining words are passed as arguments to the invoked command.
504 The return value of a \fIsimple command\fP is its exit status, or
505 128+\fIn\^\fP if the command is terminated by signal
509 A \fIpipeline\fP is a sequence of one or more commands separated by
510 one of the control operators
513 The format for a pipeline is:
516 [\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ [\fB|\fP\(bv\fB|&\fP] \fIcommand2\fP ... ]
519 The standard output of
521 is connected via a pipe to the standard input of
523 This connection is performed before any redirections specified by the
528 If \fB|&\fP is used, the standard error of \fIcommand\fP is connected to
529 \fIcommand2\fP's standard input through the pipe; it is shorthand for
531 This implicit redirection of the standard error is performed after any
532 redirections specified by the command.
534 The return status of a pipeline is the exit status of the last
535 command, unless the \fBpipefail\fP option is enabled.
536 If \fBpipefail\fP is enabled, the pipeline's return status is the
537 value of the last (rightmost) command to exit with a non-zero status,
538 or zero if all commands exit successfully.
541 precedes a pipeline, the exit status of that pipeline is the logical
542 negation of the exit status as described above.
543 The shell waits for all commands in the pipeline to
544 terminate before returning a value.
548 reserved word precedes a pipeline, the elapsed as well as user and
549 system time consumed by its execution are reported when the pipeline
551 The \fB\-p\fP option changes the output format to that specified by POSIX.
555 variable may be set to a format string that specifies how the timing
556 information should be displayed; see the description of
563 Each command in a pipeline is executed as a separate process (i.e., in a
567 A \fIlist\fP is a sequence of one or more pipelines separated by one
574 and optionally terminated by one of
580 Of these list operators,
584 have equal precedence, followed by
588 which have equal precedence.
590 A sequence of one or more newlines may appear in a \fIlist\fP instead
591 of a semicolon to delimit commands.
593 If a command is terminated by the control operator
595 the shell executes the command in the \fIbackground\fP
596 in a subshell. The shell does not wait for the command to
597 finish, and the return status is 0. Commands separated by a
599 are executed sequentially; the shell waits for each
600 command to terminate in turn. The return status is the
601 exit status of the last command executed.
603 AND and OR lists are sequences of one of more pipelines separated by the
604 \fB&&\fP and \fB\(bv\(bv\fP control operators, respectively.
605 AND and OR lists are executed with left associativity.
606 An AND list has the form
609 \fIcommand1\fP \fB&&\fP \fIcommand2\fP
613 is executed if, and only if,
615 returns an exit status of zero.
617 An OR list has the form
620 \fIcommand1\fP \fB\(bv\(bv\fP \fIcommand2\fP
625 is executed if and only if
627 returns a non-zero exit status.
629 AND and OR lists is the exit status of the last command
630 executed in the list.
631 .SS Compound Commands
633 A \fIcompound command\fP is one of the following:
636 \fIlist\fP is executed in a subshell environment (see
638 \fBCOMMAND EXECUTION ENVIRONMENT\fP
640 Variable assignments and builtin
641 commands that affect the shell's environment do not remain in effect
642 after the command completes. The return status is the exit status of
646 \fIlist\fP is simply executed in the current shell environment.
647 \fIlist\fP must be terminated with a newline or semicolon.
648 This is known as a \fIgroup command\fP.
649 The return status is the exit status of
651 Note that unlike the metacharacters \fB(\fP and \fB)\fP, \fB{\fP and
652 \fB}\fP are \fIreserved words\fP and must occur where a reserved
653 word is permitted to be recognized. Since they do not cause a word
654 break, they must be separated from \fIlist\fP by whitespace or another
658 The \fIexpression\fP is evaluated according to the rules described
661 .BR "ARITHMETIC EVALUATION" .
662 If the value of the expression is non-zero, the return status is 0;
663 otherwise the return status is 1. This is exactly equivalent to
664 \fBlet "\fIexpression\fP"\fR.
666 \fB[[\fP \fIexpression\fP \fB]]\fP
667 Return a status of 0 or 1 depending on the evaluation of
668 the conditional expression \fIexpression\fP.
669 Expressions are composed of the primaries described below under
671 .BR "CONDITIONAL EXPRESSIONS" .
672 Word splitting and pathname expansion are not performed on the words
673 between the \fB[[\fP and \fB]]\fP; tilde expansion, parameter and
674 variable expansion, arithmetic expansion, command substitution, process
675 substitution, and quote removal are performed.
676 Conditional operators such as \fB\-f\fP must be unquoted to be recognized
680 When the \fB==\fP and \fB!=\fP operators are used, the string to the
681 right of the operator is considered a pattern and matched according
682 to the rules described below under \fBPattern Matching\fP.
685 is enabled, the match is performed without regard to the case
686 of alphabetic characters.
687 The return value is 0 if the string matches (\fB==\fP) or does not match
688 (\fB!=\fP) the pattern, and 1 otherwise.
689 Any part of the pattern may be quoted to force it to be matched as a
693 An additional binary operator, \fB=~\fP, is available, with the same
694 precedence as \fB==\fP and \fB!=\fP.
695 When it is used, the string to the right of the operator is considered
696 an extended regular expression and matched accordingly (as in \fIregex\fP(3)).
697 The return value is 0 if the string matches
698 the pattern, and 1 otherwise.
699 If the regular expression is syntactically incorrect, the conditional
700 expression's return value is 2.
703 is enabled, the match is performed without regard to the case
704 of alphabetic characters.
705 Any part of the pattern may be quoted to force it to be matched as a
707 Substrings matched by parenthesized subexpressions within the regular
708 expression are saved in the array variable \fBBASH_REMATCH\fP.
709 The element of \fBBASH_REMATCH\fP with index 0 is the portion of the string
710 matching the entire regular expression.
711 The element of \fBBASH_REMATCH\fP with index \fIn\fP is the portion of the
712 string matching the \fIn\fPth parenthesized subexpression.
715 Expressions may be combined using the following operators, listed
716 in decreasing order of precedence:
722 .B ( \fIexpression\fP )
723 Returns the value of \fIexpression\fP.
724 This may be used to override the normal precedence of operators.
726 .B ! \fIexpression\fP
731 \fIexpression1\fP \fB&&\fP \fIexpression2\fP
738 .if t \fIexpression1\fP \fB\(bv\(bv\fP \fIexpression2\fP
739 .if n \fIexpression1\fP \fB||\fP \fIexpression2\fP
750 operators do not evaluate \fIexpression2\fP if the value of
751 \fIexpression1\fP is sufficient to determine the return value of
752 the entire conditional expression.
755 \fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
756 The list of words following \fBin\fP is expanded, generating a list
758 The variable \fIname\fP is set to each element of this list
759 in turn, and \fIlist\fP is executed each time.
760 If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
761 \fIlist\fP once for each positional parameter that is set (see
765 The return status is the exit status of the last command that executes.
766 If the expansion of the items following \fBin\fP results in an empty
767 list, no commands are executed, and the return status is 0.
769 \fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
770 First, the arithmetic expression \fIexpr1\fP is evaluated according
771 to the rules described below under
773 .BR "ARITHMETIC EVALUATION" .
774 The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
775 until it evaluates to zero.
776 Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
777 executed and the arithmetic expression \fIexpr3\fP is evaluated.
778 If any expression is omitted, it behaves as if it evaluates to 1.
779 The return value is the exit status of the last command in \fIlist\fP
780 that is executed, or false if any of the expressions is invalid.
782 \fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
783 The list of words following \fBin\fP is expanded, generating a list
784 of items. The set of expanded words is printed on the standard
785 error, each preceded by a number. If the \fBin\fP
786 \fIword\fP is omitted, the positional parameters are printed (see
791 prompt is then displayed and a line read from the standard input.
792 If the line consists of a number corresponding to one of
793 the displayed words, then the value of
795 is set to that word. If the line is empty, the words and prompt
796 are displayed again. If EOF is read, the command completes. Any
797 other value read causes
799 to be set to null. The line read is saved in the variable
803 is executed after each selection until a
808 is the exit status of the last command executed in
810 or zero if no commands were executed.
812 \fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
813 ... ) \fIlist\fP ;; ] ... \fBesac\fP
814 A \fBcase\fP command first expands \fIword\fP, and tries to match
815 it against each \fIpattern\fP in turn, using the same matching rules
816 as for pathname expansion (see
817 .B Pathname Expansion
819 The \fIword\fP is expanded using tilde
820 expansion, parameter and variable expansion, arithmetic substitution,
821 command substitution, process substitution and quote removal.
822 Each \fIpattern\fP examined is expanded using tilde
823 expansion, parameter and variable expansion, arithmetic substitution,
824 command substitution, and process substitution.
827 is enabled, the match is performed without regard to the case
828 of alphabetic characters.
829 When a match is found, the corresponding \fIlist\fP is executed.
830 If the \fB;;\fP operator is used, no subsequent matches are attempted after
831 the first pattern match.
832 Using \fB;&\fP in place of \fB;;\fP causes execution to continue with
833 the \fIlist\fP associated with the next set of patterns.
834 Using \fB;;&\fP in place of \fB;;\fP causes the shell to test the next
835 pattern list in the statement, if any, and execute any associated \fIlist\fP
836 on a successful match.
837 The exit status is zero if no
838 pattern matches. Otherwise, it is the exit status of the
839 last command executed in \fIlist\fP.
841 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist;\fP \
842 [ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
843 [ \fBelse\fP \fIlist\fP; ] \fBfi\fP
847 is executed. If its exit status is zero, the
848 \fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
849 \fIlist\fP is executed in turn, and if its exit status is zero,
850 the corresponding \fBthen\fP \fIlist\fP is executed and the
851 command completes. Otherwise, the \fBelse\fP \fIlist\fP is
852 executed, if present. The exit status is the exit status of the
853 last command executed, or zero if no condition tested true.
855 \fBwhile\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
858 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
860 The \fBwhile\fP command continuously executes the \fBdo\fP
861 \fIlist\fP as long as the last command in \fIlist\fP returns
862 an exit status of zero. The \fBuntil\fP command is identical
863 to the \fBwhile\fP command, except that the test is negated;
867 is executed as long as the last command in
869 returns a non-zero exit status.
870 The exit status of the \fBwhile\fP and \fBuntil\fP commands
872 of the last \fBdo\fP \fIlist\fP command executed, or zero if
876 A \fIcoprocess\fP is a shell command preceded by the \fBcoproc\fP reserved
878 A coprocess is executed asynchronously in a subshell, as if the command
879 had been terminated with the \fB&\fP control operator, with a two-way pipe
880 established between the executing shell and the coprocess.
882 The format for a coprocess is:
885 \fBcoproc\fP [\fINAME\fP] \fIcommand\fP [\fIredirections\fP]
888 This creates a coprocess named \fINAME\fP.
889 If \fINAME\fP is not supplied, the default name is \fICOPROC\fP.
890 When the coproc is executed, the shell creates an array variable (see
892 below) named \fINAME\fP in the context of the executing shell.
893 The standard output of
895 is connected via a pipe to a file descriptor in the executing shell,
896 and that file descriptor is assigned to \fINAME\fP[0].
897 The standard input of
899 is connected via a pipe to a file descriptor in the executing shell,
900 and that file descriptor is assigned to \fINAME\fP[1].
901 This pipe is established before any redirections specified by the
906 The file descriptors can be utilized as arguments to shell commands
907 and redirections using standard word expansions.
908 The process id of the shell spawned to execute the coprocess is
909 available as the value of the variable \fINAME\fP_PID.
911 builtin command may be used to wait for the coprocess to terminate.
913 The return status of a coprocess is the exit status of \fIcommand\fP.
914 .SS Shell Function Definitions
916 A shell function is an object that is called like a simple command and
917 executes a compound command with a new set of positional parameters.
918 Shell functions are declared as follows:
920 [ \fBfunction\fP ] \fIname\fP () \fIcompound\-command\fP [\fIredirection\fP]
921 This defines a function named \fIname\fP.
922 The reserved word \fBfunction\fP is optional.
923 If the \fBfunction\fP reserved word is supplied, the parentheses are optional.
924 The \fIbody\fP of the function is the compound command
926 (see \fBCompound Commands\fP above).
927 That command is usually a \fIlist\fP of commands between { and }, but
928 may be any command listed under \fBCompound Commands\fP above.
929 \fIcompound\-command\fP is executed whenever \fIname\fP is specified as the
930 name of a simple command.
931 Any redirections (see
934 below) specified when a function is defined are performed
935 when the function is executed.
936 The exit status of a function definition is zero unless a syntax error
937 occurs or a readonly function with the same name already exists.
938 When executed, the exit status of a function is the exit status of the
939 last command executed in the body. (See
944 In a non-interactive shell, or an interactive shell in which the
945 .B interactive_comments
948 builtin is enabled (see
950 .B "SHELL BUILTIN COMMANDS"
951 below), a word beginning with
953 causes that word and all remaining characters on that line to
954 be ignored. An interactive shell without the
955 .B interactive_comments
956 option enabled does not allow comments. The
957 .B interactive_comments
958 option is on by default in interactive shells.
960 \fIQuoting\fP is used to remove the special meaning of certain
961 characters or words to the shell. Quoting can be used to
962 disable special treatment for special characters, to prevent
963 reserved words from being recognized as such, and to prevent
966 Each of the \fImetacharacters\fP listed above under
969 has special meaning to the shell and must be quoted if it is to
972 When the command history expansion facilities are being used
977 \fIhistory expansion\fP character, usually \fB!\fP, must be quoted
978 to prevent history expansion.
980 There are three quoting mechanisms: the
981 .IR "escape character" ,
982 single quotes, and double quotes.
984 A non-quoted backslash (\fB\e\fP) is the
985 .IR "escape character" .
986 It preserves the literal value of the next character that follows,
987 with the exception of <newline>. If a \fB\e\fP<newline> pair
988 appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
989 is treated as a line continuation (that is, it is removed from the
990 input stream and effectively ignored).
992 Enclosing characters in single quotes preserves the literal value
993 of each character within the quotes. A single quote may not occur
994 between single quotes, even when preceded by a backslash.
996 Enclosing characters in double quotes preserves the literal value
997 of all characters within the quotes, with the exception of
1001 and, when history expansion is enabled,
1007 retain their special meaning within double quotes. The backslash
1008 retains its special meaning only when followed by one of the following
1016 A double quote may be quoted within double quotes by preceding it with
1018 If enabled, history expansion will be performed unless an
1020 appearing in double quotes is escaped using a backslash.
1021 The backslash preceding the
1025 The special parameters
1029 have special meaning when in double
1035 Words of the form \fB$\fP\(aq\fIstring\fP\(aq are treated specially. The
1036 word expands to \fIstring\fP, with backslash-escaped characters replaced
1037 as specified by the ANSI C standard. Backslash escape sequences, if
1038 present, are decoded as follows:
1073 the eight-bit character whose value is the octal value \fInnn\fP
1074 (one to three digits)
1077 the eight-bit character whose value is the hexadecimal value \fIHH\fP
1078 (one or two hex digits)
1081 a control-\fIx\fP character
1085 The expanded result is single-quoted, as if the dollar sign had
1088 A double-quoted string preceded by a dollar sign (\fB$\fP) will cause
1089 the string to be translated according to the current locale.
1090 If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
1092 If the string is translated and replaced, the replacement is
1097 is an entity that stores values.
1100 a number, or one of the special characters listed below under
1101 .BR "Special Parameters" .
1104 is a parameter denoted by a
1106 A variable has a \fIvalue\fP and zero or more \fIattributes\fP.
1107 Attributes are assigned using the
1109 builtin command (see
1113 .BR "SHELL BUILTIN COMMANDS" ).
1115 A parameter is set if it has been assigned a value. The null string is
1116 a valid value. Once a variable is set, it may be unset only by using
1119 builtin command (see
1121 .B SHELL BUILTIN COMMANDS
1126 may be assigned to by a statement of the form
1129 \fIname\fP=[\fIvalue\fP]
1134 is not given, the variable is assigned the null string. All
1136 undergo tilde expansion, parameter and variable expansion,
1137 command substitution, arithmetic expansion, and quote
1141 below). If the variable has its
1145 is evaluated as an arithmetic expression even if the $((...)) expansion is
1147 .B "Arithmetic Expansion"
1149 Word splitting is not performed, with the exception
1150 of \fB"$@"\fP as explained below under
1151 .BR "Special Parameters" .
1152 Pathname expansion is not performed.
1153 Assignment statements may also appear as arguments to the
1163 In the context where an assignment statement is assigning a value
1164 to a shell variable or array index, the += operator can be used to
1165 append to or add to the variable's previous value.
1166 When += is applied to a variable for which the integer attribute has been
1167 set, \fIvalue\fP is evaluated as an arithmetic expression and added to the
1168 variable's current value, which is also evaluated.
1169 When += is applied to an array variable using compound assignment (see
1172 variable's value is not unset (as it is when using =), and new values are
1173 appended to the array beginning at one greater than the array's maximum index
1174 (for indexed arrays) or added as additional key\-value pairs in an
1176 When applied to a string-valued variable, \fIvalue\fP is expanded and
1177 appended to the variable's value.
1178 .SS Positional Parameters
1181 .I positional parameter
1182 is a parameter denoted by one or more
1183 digits, other than the single digit 0. Positional parameters are
1184 assigned from the shell's arguments when it is invoked,
1185 and may be reassigned using the
1187 builtin command. Positional parameters may not be assigned to
1188 with assignment statements. The positional parameters are
1189 temporarily replaced when a shell function is executed (see
1194 When a positional parameter consisting of more than a single
1195 digit is expanded, it must be enclosed in braces (see
1199 .SS Special Parameters
1201 The shell treats several parameters specially. These parameters may
1202 only be referenced; assignment to them is not allowed.
1206 Expands to the positional parameters, starting from one. When the
1207 expansion occurs within double quotes, it expands to a single word
1208 with the value of each parameter separated by the first character
1212 special variable. That is, "\fB$*\fP" is equivalent
1213 to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
1215 is the first character of the value of the
1221 is unset, the parameters are separated by spaces.
1225 is null, the parameters are joined without intervening separators.
1228 Expands to the positional parameters, starting from one. When the
1229 expansion occurs within double quotes, each parameter expands to a
1230 separate word. That is, "\fB$@\fP" is equivalent to
1231 "\fB$1\fP" "\fB$2\fP" ...
1232 If the double-quoted expansion occurs within a word, the expansion of
1233 the first parameter is joined with the beginning part of the original
1234 word, and the expansion of the last parameter is joined with the last
1235 part of the original word.
1236 When there are no positional parameters, "\fB$@\fP" and
1238 expand to nothing (i.e., they are removed).
1241 Expands to the number of positional parameters in decimal.
1244 Expands to the exit status of the most recently executed foreground
1248 Expands to the current option flags as specified upon invocation,
1251 builtin command, or those set by the shell itself
1257 Expands to the process ID of the shell. In a () subshell, it
1258 expands to the process ID of the current shell, not the
1262 Expands to the process ID of the most recently executed background
1263 (asynchronous) command.
1266 Expands to the name of the shell or shell script. This is set at
1267 shell initialization. If
1269 is invoked with a file of commands,
1271 is set to the name of that file. If
1277 is set to the first argument after the string to be
1278 executed, if one is present. Otherwise, it is set
1279 to the file name used to invoke
1281 as given by argument zero.
1284 At shell startup, set to the absolute pathname used to invoke the
1285 shell or shell script being executed as passed in the environment
1287 Subsequently, expands to the last argument to the previous command,
1289 Also set to the full pathname used to invoke each command executed
1290 and placed in the environment exported to that command.
1291 When checking mail, this parameter holds the name of the mail file
1292 currently being checked.
1296 The following variables are set by the shell:
1301 Expands to the full file name used to invoke this instance of
1305 Expands to the process id of the current \fBbash\fP process.
1306 This differs from \fB$$\fP under certain circumstances, such as subshells
1307 that do not require \fBbash\fP to be re-initialized.
1310 An associative array variable whose members correspond to the internal
1311 list of aliases as maintained by the \fBalias\fP builtin
1312 Elements added to this array appear in the alias list; unsetting array
1313 elements cause aliases to be removed from the alias list.
1316 An array variable whose values are the number of parameters in each
1317 frame of the current \fBbash\fP execution call stack.
1319 parameters to the current subroutine (shell function or script executed
1320 with \fB.\fP or \fBsource\fP) is at the top of the stack.
1321 When a subroutine is executed, the number of parameters passed is pushed onto
1323 The shell sets \fBBASH_ARGC\fP only when in extended debugging mode
1324 (see the description of the
1331 An array variable containing all of the parameters in the current \fBbash\fP
1332 execution call stack. The final parameter of the last subroutine call
1333 is at the top of the stack; the first parameter of the initial call is
1334 at the bottom. When a subroutine is executed, the parameters supplied
1335 are pushed onto \fBBASH_ARGV\fP.
1336 The shell sets \fBBASH_ARGV\fP only when in extended debugging mode
1337 (see the description of the
1344 An associative array variable whose members correspond to the internal
1345 hash table of commands as maintained by the \fBhash\fP builtin.
1346 Elements added to this array appear in the hash table; unsetting array
1347 elements cause commands to be removed from the hash table.
1350 The command currently being executed or about to be executed, unless the
1351 shell is executing a command as the result of a trap,
1352 in which case it is the command executing at the time of the trap.
1354 .B BASH_EXECUTION_STRING
1355 The command argument to the \fB\-c\fP invocation option.
1358 An array variable whose members are the line numbers in source files
1359 corresponding to each member of \fBFUNCNAME\fP.
1360 \fB${BASH_LINENO[\fP\fI$i\fP\fB]}\fP is the line number in the source
1361 file where \fB${FUNCNAME[\fP\fI$i\fP\fB]}\fP was called
1362 (or \fB${BASH_LINENO[\fP\fI$i-1\fP\fB]}\fP if referenced within another
1364 The corresponding source file name is \fB${BASH_SOURCE[\fP\fI$i\fP\fB]}\fB.
1365 Use \fBLINENO\fP to obtain the current line number.
1368 An array variable whose members are assigned by the \fB=~\fP binary
1369 operator to the \fB[[\fP conditional command.
1370 The element with index 0 is the portion of the string
1371 matching the entire regular expression.
1372 The element with index \fIn\fP is the portion of the
1373 string matching the \fIn\fPth parenthesized subexpression.
1374 This variable is read-only.
1377 An array variable whose members are the source filenames corresponding
1378 to the elements in the \fBFUNCNAME\fP array variable.
1381 Incremented by one each time a subshell or subshell environment is spawned.
1382 The initial value is 0.
1385 A readonly array variable whose members hold version information for
1388 The values assigned to the array members are as follows:
1393 .B BASH_VERSINFO[\fR0\fP]
1394 The major version number (the \fIrelease\fP).
1396 .B BASH_VERSINFO[\fR1\fP]
1397 The minor version number (the \fIversion\fP).
1399 .B BASH_VERSINFO[\fR2\fP]
1402 .B BASH_VERSINFO[\fR3\fP]
1405 .B BASH_VERSINFO[\fR4\fP]
1406 The release status (e.g., \fIbeta1\fP).
1408 .B BASH_VERSINFO[\fR5\fP]
1409 The value of \fBMACHTYPE\fP.
1414 Expands to a string describing the version of this instance of
1418 An index into \fB${COMP_WORDS}\fP of the word containing the current
1420 This variable is available only in shell functions invoked by the
1421 programmable completion facilities (see \fBProgrammable Completion\fP
1425 The key (or final key of a key sequence) used to invoke the current
1426 completion function.
1429 The current command line.
1430 This variable is available only in shell functions and external
1431 commands invoked by the
1432 programmable completion facilities (see \fBProgrammable Completion\fP
1436 The index of the current cursor position relative to the beginning of
1437 the current command.
1438 If the current cursor position is at the end of the current command,
1439 the value of this variable is equal to \fB${#COMP_LINE}\fP.
1440 This variable is available only in shell functions and external
1441 commands invoked by the
1442 programmable completion facilities (see \fBProgrammable Completion\fP
1446 Set to an integer value corresponding to the type of completion attempted
1447 that caused a completion function to be called:
1448 \fITAB\fP, for normal completion,
1449 \fI?\fP, for listing completions after successive tabs,
1450 \fI!\fP, for listing alternatives on partial word completion,
1451 \fI@\fP, to list completions if the word is not unmodified,
1453 \fI%\fP, for menu completion.
1454 This variable is available only in shell functions and external
1455 commands invoked by the
1456 programmable completion facilities (see \fBProgrammable Completion\fP
1460 The set of characters that the Readline library treats as word
1461 separators when performing word completion.
1465 is unset, it loses its special properties, even if it is
1469 An array variable (see \fBArrays\fP below) consisting of the individual
1470 words in the current command line.
1471 The words are split on shell metacharacters as the shell parser would
1473 This variable is available only in shell functions invoked by the
1474 programmable completion facilities (see \fBProgrammable Completion\fP
1478 An array variable (see
1480 below) containing the current contents of the directory stack.
1481 Directories appear in the stack in the order they are displayed by the
1484 Assigning to members of this array variable may be used to modify
1485 directories already in the stack, but the
1489 builtins must be used to add and remove directories.
1490 Assignment to this variable will not change the current directory.
1494 is unset, it loses its special properties, even if it is
1498 Expands to the effective user ID of the current user, initialized at
1499 shell startup. This variable is readonly.
1502 An array variable containing the names of all shell functions
1503 currently in the execution call stack.
1504 The element with index 0 is the name of any currently-executing
1506 The bottom-most element is
1507 .if t \f(CW"main"\fP.
1509 This variable exists only when a shell function is executing.
1513 have no effect and return an error status.
1517 is unset, it loses its special properties, even if it is
1521 An array variable containing the list of groups of which the current
1526 have no effect and return an error status.
1530 is unset, it loses its special properties, even if it is
1534 The history number, or index in the history list, of the current
1539 is unset, it loses its special properties, even if it is
1543 Automatically set to the name of the current host.
1546 Automatically set to a string that uniquely
1547 describes the type of machine on which
1550 The default is system-dependent.
1553 Each time this parameter is referenced, the shell substitutes
1554 a decimal number representing the current sequential line number
1555 (starting with 1) within a script or function. When not in a
1556 script or function, the value substituted is not guaranteed to
1561 is unset, it loses its special properties, even if it is
1565 Automatically set to a string that fully describes the system
1568 is executing, in the standard GNU \fIcpu-company-system\fP format.
1569 The default is system-dependent.
1572 The previous working directory as set by the
1577 The value of the last option argument processed by the
1579 builtin command (see
1581 .B SHELL BUILTIN COMMANDS
1585 The index of the next argument to be processed by the
1587 builtin command (see
1589 .B SHELL BUILTIN COMMANDS
1593 Automatically set to a string that
1594 describes the operating system on which
1597 The default is system-dependent.
1600 An array variable (see
1602 below) containing a list of exit status values from the processes
1603 in the most-recently-executed foreground pipeline (which may
1604 contain only a single command).
1607 The process ID of the shell's parent. This variable is readonly.
1610 The current working directory as set by the
1615 Each time this parameter is referenced, a random integer between
1617 generated. The sequence of random numbers may be initialized by assigning
1624 is unset, it loses its special properties, even if it is
1628 Set to the line of input read by the
1630 builtin command when no arguments are supplied.
1633 Each time this parameter is
1634 referenced, the number of seconds since shell invocation is returned. If a
1635 value is assigned to
1638 the value returned upon subsequent
1640 the number of seconds since the assignment plus the value assigned.
1644 is unset, it loses its special properties, even if it is
1648 A colon-separated list of enabled shell options. Each word in
1649 the list is a valid argument for the
1653 builtin command (see
1655 .B "SHELL BUILTIN COMMANDS"
1656 below). The options appearing in
1659 are those reported as
1662 If this variable is in the environment when
1664 starts up, each shell option in the list will be enabled before
1665 reading any startup files.
1666 This variable is read-only.
1669 Incremented by one each time an instance of
1674 Expands to the user ID of the current user, initialized at shell startup.
1675 This variable is readonly.
1678 The following variables are used by the shell. In some cases,
1680 assigns a default value to a variable; these cases are noted
1686 If this parameter is set when \fBbash\fP is executing a shell script,
1687 its value is interpreted as a filename containing commands to
1688 initialize the shell, as in
1693 is subjected to parameter expansion, command substitution, and arithmetic
1694 expansion before being interpreted as a file name.
1697 is not used to search for the resultant file name.
1700 The search path for the
1703 This is a colon-separated list of directories in which the shell looks
1704 for destination directories specified by the
1708 .if t \f(CW".:~:/usr"\fP.
1712 Used by the \fBselect\fP builtin command to determine the terminal width
1713 when printing selection lists. Automatically set upon receipt of a SIGWINCH.
1716 An array variable from which \fBbash\fP reads the possible completions
1717 generated by a shell function invoked by the programmable completion
1718 facility (see \fBProgrammable Completion\fP below).
1721 If \fBbash\fP finds this variable in the environment when the shell starts
1725 it assumes that the shell is running in an emacs shell buffer and disables
1729 The default editor for the
1734 A colon-separated list of suffixes to ignore when performing
1735 filename completion (see
1739 A filename whose suffix matches one of the entries in
1742 is excluded from the list of matched filenames.
1744 .if t \f(CW".o:~"\fP.
1748 A colon-separated list of patterns defining the set of filenames to
1749 be ignored by pathname expansion.
1750 If a filename matched by a pathname expansion pattern also matches one
1754 it is removed from the list of matches.
1757 A colon-separated list of values controlling how commands are saved on
1759 If the list of values includes
1761 lines which begin with a
1763 character are not saved in the history list.
1766 causes lines matching the previous history entry to not be saved.
1769 is shorthand for \fIignorespace\fP and \fIignoredups\fP.
1772 causes all previous lines matching the current line to be removed from
1773 the history list before that line is saved.
1774 Any value not in the above list is ignored.
1775 If \fBHISTCONTROL\fP is unset, or does not include a valid value,
1776 all lines read by the shell parser are saved on the history list,
1777 subject to the value of
1779 The second and subsequent lines of a multi-line compound command are
1780 not tested, and are added to the history regardless of the value of
1784 The name of the file in which command history is saved (see
1787 below). The default value is \fI~/.bash_history\fP. If unset, the
1788 command history is not saved when an interactive shell exits.
1791 The maximum number of lines contained in the history file. When this
1792 variable is assigned a value, the history file is truncated, if
1793 necessary, by removing the oldest entries,
1794 to contain no more than that number of lines. The default
1795 value is 500. The history file is also truncated to this size after
1796 writing it when an interactive shell exits.
1799 A colon-separated list of patterns used to decide which command lines
1800 should be saved on the history list. Each pattern is anchored at the
1801 beginning of the line and must match the complete line (no implicit
1802 `\fB*\fP' is appended). Each pattern is tested against the line
1803 after the checks specified by
1806 In addition to the normal shell pattern matching characters, `\fB&\fP'
1807 matches the previous history line. `\fB&\fP' may be escaped using a
1808 backslash; the backslash is removed before attempting a match.
1809 The second and subsequent lines of a multi-line compound command are
1810 not tested, and are added to the history regardless of the value of
1814 The number of commands to remember in the command history (see
1817 below). The default value is 500.
1820 If this variable is set and not null, its value is used as a format string
1821 for \fIstrftime\fP(3) to print the time stamp associated with each history
1822 entry displayed by the \fBhistory\fP builtin.
1823 If this variable is set, time stamps are written to the history file so
1824 they may be preserved across shell sessions.
1825 This uses the history comment character to distinguish timestamps from
1826 other history lines.
1829 The home directory of the current user; the default argument for the
1830 \fBcd\fP builtin command.
1831 The value of this variable is also used when performing tilde expansion.
1834 Contains the name of a file in the same format as
1836 that should be read when the shell needs to complete a
1838 The list of possible hostname completions may be changed while the
1840 the next time hostname completion is attempted after the
1843 adds the contents of the new file to the existing list.
1847 is set, but has no value, \fBbash\fP attempts to read
1849 to obtain the list of possible hostname completions.
1853 is unset, the hostname list is cleared.
1857 .I Internal Field Separator
1859 for word splitting after expansion and to
1860 split lines into words with the
1862 builtin command. The default value is
1863 ``<space><tab><newline>''.
1867 action of an interactive shell on receipt of an
1870 character as the sole input. If set, the value is the number of
1874 characters which must be
1875 typed as the first characters on an input line before
1877 exits. If the variable exists but does not have a numeric value, or
1878 has no value, the default value is 10. If it does not exist,
1881 signifies the end of input to the shell.
1884 The filename for the
1886 startup file, overriding the default of
1894 Used to determine the locale category for any category not specifically
1895 selected with a variable starting with \fBLC_\fP.
1898 This variable overrides the value of \fBLANG\fP and any other
1899 \fBLC_\fP variable specifying a locale category.
1902 This variable determines the collation order used when sorting the
1903 results of pathname expansion, and determines the behavior of range
1904 expressions, equivalence classes, and collating sequences within
1905 pathname expansion and pattern matching.
1908 This variable determines the interpretation of characters and the
1909 behavior of character classes within pathname expansion and pattern
1913 This variable determines the locale used to translate double-quoted
1914 strings preceded by a \fB$\fP.
1917 This variable determines the locale category used for number formatting.
1920 Used by the \fBselect\fP builtin command to determine the column length
1921 for printing selection lists. Automatically set upon receipt of a SIGWINCH.
1924 If this parameter is set to a file name and the
1927 variable is not set,
1929 informs the user of the arrival of mail in the specified file.
1935 checks for mail. The default is 60 seconds. When it is time to check
1936 for mail, the shell does so before displaying the primary prompt.
1937 If this variable is unset, or set to a value that is not a number
1938 greater than or equal to zero, the shell disables mail checking.
1941 A colon-separated list of file names to be checked for mail.
1942 The message to be printed when mail arrives in a particular file
1943 may be specified by separating the file name from the message with a `?'.
1944 When used in the text of the message, \fB$_\fP expands to the name of
1945 the current mailfile.
1949 \fBMAILPATH\fP=\(aq/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"\(aq
1952 supplies a default value for this variable, but the location of the user
1953 mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
1957 If set to the value 1,
1959 displays error messages generated by the
1961 builtin command (see
1963 .B SHELL BUILTIN COMMANDS
1967 is initialized to 1 each time the shell is invoked or a shell
1971 The search path for commands. It
1972 is a colon-separated list of directories in which
1973 the shell looks for commands (see
1975 .B COMMAND EXECUTION
1977 A zero-length (null) directory name in the value of \fBPATH\fP indicates the
1979 A null directory name may appear as two adjacent colons, or as an initial
1981 The default path is system-dependent,
1982 and is set by the administrator who installs
1985 .if t \f(CW/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin\fP.
1986 .if n ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.
1989 If this variable is in the environment when \fBbash\fP starts, the shell
1990 enters \fIposix mode\fP before reading the startup files, as if the
1992 invocation option had been supplied. If it is set while the shell is
1993 running, \fBbash\fP enables \fIposix mode\fP, as if the command
1994 .if t \f(CWset -o posix\fP
1995 .if n \fIset -o posix\fP
1999 If set, the value is executed as a command prior to issuing each primary
2003 If set to a number greater than zero, the value is used as the number of
2004 trailing directory components to retain when expanding the \fB\ew\fB and
2005 \fB\eW\fP prompt string escapes (see
2008 below). Characters removed are replaced with an ellipsis.
2011 The value of this parameter is expanded (see
2014 below) and used as the primary prompt string. The default value is
2015 ``\fB\es\-\ev\e$ \fP''.
2018 The value of this parameter is expanded as with
2020 and used as the secondary prompt string. The default is
2024 The value of this parameter is used as the prompt for the
2032 The value of this parameter is expanded as with
2034 and the value is printed before each command
2036 displays during an execution trace. The first character of
2039 is replicated multiple times, as necessary, to indicate multiple
2040 levels of indirection. The default is ``\fB+ \fP''.
2043 The full pathname to the shell is kept in this environment variable.
2044 If it is not set when the shell starts,
2046 assigns to it the full pathname of the current user's login shell.
2049 The value of this parameter is used as a format string specifying
2050 how the timing information for pipelines prefixed with the
2052 reserved word should be displayed.
2053 The \fB%\fP character introduces an escape sequence that is
2054 expanded to a time value or other information.
2055 The escape sequences and their meanings are as follows; the
2056 braces denote optional portions.
2065 The elapsed time in seconds.
2068 The number of CPU seconds spent in user mode.
2071 The number of CPU seconds spent in system mode.
2074 The CPU percentage, computed as (%U + %S) / %R.
2078 The optional \fIp\fP is a digit specifying the \fIprecision\fP,
2079 the number of fractional digits after a decimal point.
2080 A value of 0 causes no decimal point or fraction to be output.
2081 At most three places after the decimal point may be specified;
2082 values of \fIp\fP greater than 3 are changed to 3.
2083 If \fIp\fP is not specified, the value 3 is used.
2085 The optional \fBl\fP specifies a longer format, including
2086 minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
2087 The value of \fIp\fP determines whether or not the fraction is
2090 If this variable is not set, \fBbash\fP acts as if it had the
2091 value \fB$\(aq\enreal\et%3lR\enuser\et%3lU\ensys\t%3lS\(aq\fP.
2092 If the value is null, no timing information is displayed.
2093 A trailing newline is added when the format string is displayed.
2096 If set to a value greater than zero, \fBTMOUT\fP is treated as the
2097 default timeout for the \fBread\fP builtin.
2098 The \fBselect\fP command terminates if input does not arrive
2099 after \fBTMOUT\fP seconds when input is coming from a terminal.
2100 In an interactive shell, the value is interpreted as the
2101 number of seconds to wait for input after issuing the primary prompt.
2103 terminates after waiting for that number of seconds if input does
2107 If set, \fBBash\fP uses its value as the name of a directory in which
2108 \fBBash\fP creates temporary files for the shell's use.
2111 This variable controls how the shell interacts with the user and
2112 job control. If this variable is set, single word simple
2113 commands without redirections are treated as candidates for resumption
2114 of an existing stopped job. There is no ambiguity allowed; if there is
2115 more than one job beginning with the string typed, the job most recently
2116 accessed is selected. The
2118 of a stopped job, in this context, is the command line used to
2122 the string supplied must match the name of a stopped job exactly;
2125 the string supplied needs to match a substring of the name of a
2128 value provides functionality analogous to the
2133 below). If set to any other value, the supplied string must
2134 be a prefix of a stopped job's name; this provides functionality
2135 analogous to the \fB%\fP\fIstring\fP job identifier.
2138 The two or three characters which control history expansion
2139 and tokenization (see
2141 .B HISTORY EXPANSION
2142 below). The first character is the \fIhistory expansion\fP character,
2143 the character which signals the start of a history
2144 expansion, normally `\fB!\fP'.
2145 The second character is the \fIquick substitution\fP
2146 character, which is used as shorthand for re-running the previous
2147 command entered, substituting one string for another in the command.
2148 The default is `\fB^\fP'.
2149 The optional third character is the character
2150 which indicates that the remainder of the line is a comment when found
2151 as the first character of a word, normally `\fB#\fP'. The history
2152 comment character causes history substitution to be skipped for the
2153 remaining words on the line. It does not necessarily cause the shell
2154 parser to treat the rest of the line as a comment.
2158 provides one-dimensional indexed and associative array variables.
2159 Any variable may be used as an indexed array; the
2161 builtin will explicitly declare an array.
2163 limit on the size of an array, nor any requirement that members
2164 be indexed or assigned contiguously.
2165 Indexed arrays are referenced using integers (including arithmetic
2166 expressions) and are zero-based; associative arrays are referenced
2167 using arbitrary strings.
2169 An indexed array is created automatically if any variable is assigned to
2170 using the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
2172 is treated as an arithmetic expression that must evaluate to a number
2173 greater than or equal to zero. To explicitly declare an indexed array,
2175 .B declare \-a \fIname\fP
2178 .B SHELL BUILTIN COMMANDS
2180 .B declare \-a \fIname\fP[\fIsubscript\fP]
2181 is also accepted; the \fIsubscript\fP is ignored.
2183 Associative arrays are created using
2184 .BR "declare \-A \fIname\fP" .
2187 specified for an array variable using the
2191 builtins. Each attribute applies to all members of an array.
2193 Arrays are assigned to using compound assignments of the form
2194 \fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
2195 \fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP.
2196 Indexed array assignments do not require the bracket and subscript.
2197 When assigning to indexed arrays, if the optional brackets and subscript
2198 are supplied, that index is assigned to;
2199 otherwise the index of the element assigned is the last index assigned
2200 to by the statement plus one. Indexing starts at zero.
2202 When assigning to an associative array, the subscript is required.
2204 This syntax is also accepted by the
2206 builtin. Individual array elements may be assigned to using the
2207 \fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
2209 Any element of an array may be referenced using
2210 ${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
2211 conflicts with pathname expansion. If
2212 \fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
2213 all members of \fIname\fP. These subscripts differ only when the
2214 word appears within double quotes. If the word is double-quoted,
2215 ${\fIname\fP[*]} expands to a single
2216 word with the value of each array member separated by the first
2220 special variable, and ${\fIname\fP[@]} expands each element of
2221 \fIname\fP to a separate word. When there are no array members,
2222 ${\fIname\fP[@]} expands to nothing.
2223 If the double-quoted expansion occurs within a word, the expansion of
2224 the first parameter is joined with the beginning part of the original
2225 word, and the expansion of the last parameter is joined with the last
2226 part of the original word.
2227 This is analogous to the expansion
2228 of the special parameters \fB*\fP and \fB@\fP (see
2229 .B Special Parameters
2230 above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
2231 ${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
2232 \fB@\fP, the expansion is the number of elements in the array.
2233 Referencing an array variable without a subscript is equivalent to
2234 referencing the array with a subscript of 0.
2238 builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
2239 destroys the array element at index \fIsubscript\fP.
2240 Care must be taken to avoid unwanted side effects caused by filename
2242 \fBunset\fP \fIname\fP, where \fIname\fP is an array, or
2243 \fBunset\fP \fIname\fP[\fIsubscript\fP], where
2244 \fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
2251 builtins each accept a
2253 option to specify an indexed array and a
2255 option to specify an associative array.
2260 option to assign a list of words read from the standard input
2265 builtins display array values in a way that allows them to be
2266 reused as assignments.
2268 Expansion is performed on the command line after it has been split into
2269 words. There are seven kinds of expansion performed:
2270 .IR "brace expansion" ,
2271 .IR "tilde expansion" ,
2272 .IR "parameter and variable expansion" ,
2273 .IR "command substitution" ,
2274 .IR "arithmetic expansion" ,
2275 .IR "word splitting" ,
2277 .IR "pathname expansion" .
2279 The order of expansions is: brace expansion, tilde expansion,
2280 parameter, variable and arithmetic expansion and
2281 command substitution
2282 (done in a left-to-right fashion), word splitting, and pathname
2285 On systems that can support it, there is an additional expansion
2286 available: \fIprocess substitution\fP.
2288 Only brace expansion, word splitting, and pathname expansion
2289 can change the number of words of the expansion; other expansions
2290 expand a single word to a single word.
2291 The only exceptions to this are the expansions of
2292 "\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
2293 as explained above (see
2298 .I "Brace expansion"
2299 is a mechanism by which arbitrary strings
2300 may be generated. This mechanism is similar to
2301 \fIpathname expansion\fP, but the filenames generated
2302 need not exist. Patterns to be brace expanded take
2303 the form of an optional
2305 followed by either a series of comma-separated strings or
2306 a sequence expression between a pair of braces, followed by
2309 The preamble is prefixed to each string contained
2310 within the braces, and the postscript is then appended
2311 to each resulting string, expanding left to right.
2313 Brace expansions may be nested. The results of each expanded
2314 string are not sorted; left to right order is preserved.
2315 For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
2317 A sequence expression takes the form
2318 \fB{\fP\fIx\fP\fB..\fP\fIy\fP\fB[..\fP\fIincr\fP\fB]}\fP,
2319 where \fIx\fP and \fIy\fP are either integers or single characters,
2320 and \fIincr\fP, an optional increment, is an integer.
2321 When integers are supplied, the expression expands to each number between
2322 \fIx\fP and \fIy\fP, inclusive.
2323 Supplied integers may be prefixed with \fI0\fP to force each term to have the
2324 same width. When either \fIx\fP or \fPy\fP begins with a zero, the shell
2325 attempts to force all generated terms to contain the same number of digits,
2326 zero-padding where necessary.
2327 When characters are supplied, the expression expands to each character
2328 lexicographically between \fIx\fP and \fIy\fP, inclusive. Note that
2329 both \fIx\fP and \fIy\fP must be of the same type.
2330 When the increment is supplied, it is used as the difference between
2331 each term. The default increment is 1 or -1 as appropriate.
2333 Brace expansion is performed before any other expansions,
2334 and any characters special to other expansions are preserved
2335 in the result. It is strictly textual.
2337 does not apply any syntactic interpretation to the context of the
2338 expansion or the text between the braces.
2340 A correctly-formed brace expansion must contain unquoted opening
2341 and closing braces, and at least one unquoted comma or a valid
2342 sequence expression.
2343 Any incorrectly formed brace expansion is left unchanged.
2344 A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
2345 being considered part of a brace expression.
2346 To avoid conflicts with parameter expansion, the string \fB${\fP
2347 is not considered eligible for brace expansion.
2349 This construct is typically used as shorthand when the common
2350 prefix of the strings to be generated is longer than in the
2354 mkdir /usr/local/src/bash/{old,new,dist,bugs}
2358 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
2361 Brace expansion introduces a slight incompatibility with
2362 historical versions of
2365 does not treat opening or closing braces specially when they
2366 appear as part of a word, and preserves them in the output.
2368 removes braces from words as a consequence of brace
2369 expansion. For example, a word entered to
2372 appears identically in the output. The same word is
2377 If strict compatibility with
2383 option or disable brace expansion with the
2389 .B SHELL BUILTIN COMMANDS
2393 If a word begins with an unquoted tilde character (`\fB~\fP'), all of
2394 the characters preceding the first unquoted slash (or all characters,
2395 if there is no unquoted slash) are considered a \fItilde-prefix\fP.
2396 If none of the characters in the tilde-prefix are quoted, the
2397 characters in the tilde-prefix following the tilde are treated as a
2398 possible \fIlogin name\fP.
2399 If this login name is the null string, the tilde is replaced with the
2400 value of the shell parameter
2406 is unset, the home directory of the user executing the shell is
2407 substituted instead.
2408 Otherwise, the tilde-prefix is replaced with the home directory
2409 associated with the specified login name.
2411 If the tilde-prefix is a `~+', the value of the shell variable
2414 replaces the tilde-prefix.
2415 If the tilde-prefix is a `~\-', the value of the shell variable
2418 if it is set, is substituted.
2419 If the characters following the tilde in the tilde-prefix consist
2420 of a number \fIN\fP, optionally prefixed
2421 by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
2422 element from the directory stack, as it would be displayed by the
2424 builtin invoked with the tilde-prefix as an argument.
2425 If the characters following the tilde in the tilde-prefix consist of a
2426 number without a leading `+' or `\-', `+' is assumed.
2428 If the login name is invalid, or the tilde expansion fails, the word
2431 Each variable assignment is checked for unquoted tilde-prefixes immediately
2436 In these cases, tilde expansion is also performed.
2437 Consequently, one may use file names with tildes in assignments to
2445 and the shell assigns the expanded value.
2446 .SS Parameter Expansion
2448 The `\fB$\fP' character introduces parameter expansion,
2449 command substitution, or arithmetic expansion. The parameter name
2450 or symbol to be expanded may be enclosed in braces, which
2451 are optional but serve to protect the variable to be expanded from
2452 characters immediately following it which could be
2453 interpreted as part of the name.
2455 When braces are used, the matching ending brace is the first `\fB}\fP'
2456 not escaped by a backslash or within a quoted string, and not within an
2457 embedded arithmetic expansion, command substitution, or parameter
2463 The value of \fIparameter\fP is substituted. The braces are required
2466 is a positional parameter with more than one digit,
2469 is followed by a character which is not to be
2470 interpreted as part of its name.
2473 If the first character of \fIparameter\fP is an exclamation point,
2474 a level of variable indirection is introduced.
2475 \fBBash\fP uses the value of the variable formed from the rest of
2476 \fIparameter\fP as the name of the variable; this variable is then
2477 expanded and that value is used in the rest of the substitution, rather
2478 than the value of \fIparameter\fP itself.
2479 This is known as \fIindirect expansion\fP.
2480 The exceptions to this are the expansions of ${!\fIprefix\fP*} and
2481 ${\fB!\fP\fIname\fP[\fI@\fP]} described below.
2482 The exclamation point must immediately follow the left brace in order to
2483 introduce indirection.
2485 In each of the cases below, \fIword\fP is subject to tilde expansion,
2486 parameter expansion, command substitution, and arithmetic expansion.
2487 When not performing substring expansion, \fBbash\fP tests for a parameter
2488 that is unset or null; omitting the colon results in a test only for a
2489 parameter that is unset.
2493 ${\fIparameter\fP\fB:\-\fP\fIword\fP}
2494 \fBUse Default Values\fP. If
2496 is unset or null, the expansion of
2498 is substituted. Otherwise, the value of
2502 ${\fIparameter\fP\fB:=\fP\fIword\fP}
2503 \fBAssign Default Values\fP.
2506 is unset or null, the expansion of
2512 is then substituted. Positional parameters and special parameters may
2513 not be assigned to in this way.
2515 ${\fIparameter\fP\fB:?\fP\fIword\fP}
2516 \fBDisplay Error if Null or Unset\fP.
2519 is null or unset, the expansion of \fIword\fP (or a message to that effect
2522 is not present) is written to the standard error and the shell, if it
2523 is not interactive, exits. Otherwise, the value of \fIparameter\fP is
2526 ${\fIparameter\fP\fB:+\fP\fIword\fP}
2527 \fBUse Alternate Value\fP.
2530 is null or unset, nothing is substituted, otherwise the expansion of
2534 ${\fIparameter\fP\fB:\fP\fIoffset\fP}
2537 ${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
2539 \fBSubstring Expansion.\fP
2540 Expands to up to \fIlength\fP characters of \fIparameter\fP
2541 starting at the character specified by \fIoffset\fP.
2542 If \fIlength\fP is omitted, expands to the substring of
2543 \fIparameter\fP starting at the character specified by \fIoffset\fP.
2544 \fIlength\fP and \fIoffset\fP are arithmetic expressions (see
2547 ARITHMETIC EVALUATION
2549 \fIlength\fP must evaluate to a number greater than or equal to zero.
2550 If \fIoffset\fP evaluates to a number less than zero, the value
2551 is used as an offset from the end of the value of \fIparameter\fP.
2552 If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
2553 parameters beginning at \fIoffset\fP.
2554 If \fIparameter\fP is an indexed array name subscripted by @ or *,
2555 the result is the \fIlength\fP
2556 members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2557 A negative \fIoffset\fP is taken relative to one greater than the maximum
2558 index of the specified array.
2559 Substring expansion applied to an associative array produces undefined
2561 Note that a negative offset must be separated from the colon by at least
2562 one space to avoid being confused with the :- expansion.
2563 Substring indexing is zero-based unless the positional parameters
2564 are used, in which case the indexing starts at 1 by default.
2565 If \fIoffset\fP is 0, and the positional parameters are used, \fB$0\fP is
2566 prefixed to the list.
2568 ${\fB!\fP\fIprefix\fP\fB*\fP}
2571 ${\fB!\fP\fIprefix\fP\fB@\fP}
2573 \fBNames matching prefix.\fP
2574 Expands to the names of variables whose names begin with \fIprefix\fP,
2575 separated by the first character of the
2579 When \fI@\fP is used and the expansion appears within double quotes, each
2580 variable name expands to a separate word.
2582 ${\fB!\fP\fIname\fP[\fI@\fP]}
2585 ${\fB!\fP\fIname\fP[\fI*\fP]}
2587 \fBList of array keys.\fP
2588 If \fIname\fP is an array variable, expands to the list of array indices
2589 (keys) assigned in \fIname\fP.
2590 If \fIname\fP is not an array, expands to 0 if \fIname\fP is set and null
2592 When \fI@\fP is used and the expansion appears within double quotes, each
2593 key expands to a separate word.
2595 ${\fB#\fP\fIparameter\fP}
2596 \fBParameter length.\fP
2597 The length in characters of the value of \fIparameter\fP is substituted.
2604 the value substituted is the number of positional parameters.
2607 is an array name subscripted by
2611 the value substituted is the number of elements in the array.
2613 ${\fIparameter\fP\fB#\fP\fIword\fP}
2616 ${\fIparameter\fP\fB##\fP\fIword\fP}
2618 \fBRemove matching prefix pattern.\fP
2621 is expanded to produce a pattern just as in pathname
2622 expansion. If the pattern matches the beginning of
2625 then the result of the expansion is the expanded value of
2627 with the shortest matching pattern (the ``\fB#\fP'' case) or the
2628 longest matching pattern (the ``\fB##\fP'' case) deleted.
2635 the pattern removal operation is applied to each positional
2636 parameter in turn, and the expansion is the resultant list.
2639 is an array variable subscripted with
2643 the pattern removal operation is applied to each member of the
2644 array in turn, and the expansion is the resultant list.
2646 ${\fIparameter\fP\fB%\fP\fIword\fP}
2649 ${\fIparameter\fP\fB%%\fP\fIword\fP}
2651 \fBRemove matching suffix pattern.\fP
2652 The \fIword\fP is expanded to produce a pattern just as in
2654 If the pattern matches a trailing portion of the expanded value of
2656 then the result of the expansion is the expanded value of
2658 with the shortest matching pattern (the ``\fB%\fP'' case) or the
2659 longest matching pattern (the ``\fB%%\fP'' case) deleted.
2666 the pattern removal operation is applied to each positional
2667 parameter in turn, and the expansion is the resultant list.
2670 is an array variable subscripted with
2674 the pattern removal operation is applied to each member of the
2675 array in turn, and the expansion is the resultant list.
2677 ${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2678 \fBPattern substitution.\fP
2679 The \fIpattern\fP is expanded to produce a pattern just as in
2681 \fIParameter\fP is expanded and the longest match of \fIpattern\fP
2682 against its value is replaced with \fIstring\fP.
2683 If \fIpattern\fP begins with \fB/\fP, all matches of \fIpattern\fP are
2684 replaced with \fIstring\fP. Normally only the first match is replaced.
2685 If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
2686 of the expanded value of \fIparameter\fP.
2687 If \fIpattern\fP begins with \fB%\fP, it must match at the end
2688 of the expanded value of \fIparameter\fP.
2689 If \fIstring\fP is null, matches of \fIpattern\fP are deleted
2690 and the \fB/\fP following \fIpattern\fP may be omitted.
2697 the substitution operation is applied to each positional
2698 parameter in turn, and the expansion is the resultant list.
2701 is an array variable subscripted with
2705 the substitution operation is applied to each member of the
2706 array in turn, and the expansion is the resultant list.
2708 ${\fIparameter\fP\fB^\fP\fIpattern\fP}
2711 ${\fIparameter\fP\fB^^\fP\fIpattern\fP}
2713 ${\fIparameter\fP\fB,\fP\fIpattern\fP}
2715 ${\fIparameter\fP\fB,,\fP\fIpattern\fP}
2717 \fBCase modification.\fP
2718 This expansion modifies the case of alphabetic characters in \fIparameter\fP.
2719 The \fIpattern\fP is expanded to produce a pattern just as in
2721 The \fB^\fP operator converts lowercase letters matching \fIpattern\fP
2722 to uppercase; the \fB,\fP operator converts matching uppercase letters
2724 The \fB^^\fP and \fB,,\fP expansions convert each matched character in the
2725 expanded value; the \fB^\fP and \fB,\fP expansions match and convert only
2726 the first character.
2727 If \fIpattern\fP is omitted, it is treated like a \fB?\fP, which matches
2735 the case modification operation is applied to each positional
2736 parameter in turn, and the expansion is the resultant list.
2739 is an array variable subscripted with
2743 the case modification operation is applied to each member of the
2744 array in turn, and the expansion is the resultant list.
2745 .SS Command Substitution
2747 \fICommand substitution\fP allows the output of a command to replace
2748 the command name. There are two forms:
2752 \fB$(\fP\fIcommand\fP\|\fB)\fP
2756 \fB\`\fP\fIcommand\fP\fB\`\fP
2760 performs the expansion by executing \fIcommand\fP and
2761 replacing the command substitution with the standard output of the
2762 command, with any trailing newlines deleted.
2763 Embedded newlines are not deleted, but they may be removed during
2765 The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
2766 the equivalent but faster \fB$(< \fIfile\fP)\fR.
2768 When the old-style backquote form of substitution is used,
2769 backslash retains its literal meaning except when followed by
2774 The first backquote not preceded by a backslash terminates the
2775 command substitution.
2776 When using the $(\^\fIcommand\fP\|) form, all characters between the
2777 parentheses make up the command; none are treated specially.
2779 Command substitutions may be nested. To nest when using the backquoted form,
2780 escape the inner backquotes with backslashes.
2782 If the substitution appears within double quotes, word splitting and
2783 pathname expansion are not performed on the results.
2784 .SS Arithmetic Expansion
2786 Arithmetic expansion allows the evaluation of an arithmetic expression
2787 and the substitution of the result. The format for arithmetic expansion is:
2790 \fB$((\fP\fIexpression\fP\fB))\fP
2795 is treated as if it were within double quotes, but a double quote
2796 inside the parentheses is not treated specially.
2797 All tokens in the expression undergo parameter expansion, string
2798 expansion, command substitution, and quote removal.
2799 Arithmetic expansions may be nested.
2801 The evaluation is performed according to the rules listed below under
2803 .BR "ARITHMETIC EVALUATION" .
2808 prints a message indicating failure and no substitution occurs.
2809 .SS Process Substitution
2811 \fIProcess substitution\fP is supported on systems that support named
2812 pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
2813 It takes the form of
2814 \fB<(\fP\fIlist\^\fP\fB)\fP
2816 \fB>(\fP\fIlist\^\fP\fB)\fP.
2817 The process \fIlist\fP is run with its input or output connected to a
2818 \fIFIFO\fP or some file in \fB/dev/fd\fP. The name of this file is
2819 passed as an argument to the current command as the result of the
2820 expansion. If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
2821 the file will provide input for \fIlist\fP. If the
2822 \fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
2823 argument should be read to obtain the output of \fIlist\fP.
2825 When available, process substitution is performed
2826 simultaneously with parameter and variable expansion,
2827 command substitution,
2828 and arithmetic expansion.
2831 The shell scans the results of
2832 parameter expansion,
2833 command substitution,
2835 arithmetic expansion
2836 that did not occur within double quotes for
2837 .IR "word splitting" .
2839 The shell treats each character of
2842 as a delimiter, and splits the results of the other
2843 expansions into words on these characters. If
2848 .BR <space><tab><newline> ,
2855 at the beginning and end of the results of the previous
2856 expansions are ignored, and
2860 characters not at the beginning or end serves to delimit words.
2864 has a value other than the default, then sequences of
2865 the whitespace characters
2869 are ignored at the beginning and end of the
2870 word, as long as the whitespace character is in the
2877 whitespace character).
2884 whitespace, along with any adjacent
2887 whitespace characters, delimits a field.
2891 whitespace characters is also treated as a delimiter.
2895 is null, no word splitting occurs.
2897 Explicit null arguments (\^\f3"\^"\fP or \^\f3\(aq\^\(aq\fP\^) are retained.
2898 Unquoted implicit null arguments, resulting from the expansion of
2899 parameters that have no values, are removed.
2900 If a parameter with no value is expanded within double quotes, a
2901 null argument results and is retained.
2903 Note that if no expansion occurs, no splitting
2905 .SS Pathname Expansion
2907 After word splitting,
2910 option has been set,
2912 scans each word for the characters
2917 If one of these characters appears, then the word is
2920 and replaced with an alphabetically sorted list of
2921 file names matching the pattern.
2922 If no matching file names are found,
2923 and the shell option
2925 is not enabled, the word is left unchanged.
2928 option is set, and no matches are found,
2929 the word is removed.
2932 shell option is set, and no matches are found, an error message
2933 is printed and the command is not executed.
2936 is enabled, the match is performed without regard to the case
2937 of alphabetic characters.
2938 When a pattern is used for pathname expansion,
2941 at the start of a name or immediately following a slash
2942 must be matched explicitly, unless the shell option
2945 When matching a pathname, the slash character must always be
2949 character is not treated specially.
2950 See the description of
2954 .B SHELL BUILTIN COMMANDS
2955 for a description of the
2966 shell variable may be used to restrict the set of file names matching a
2971 is set, each matching file name that also matches one of the patterns in
2974 is removed from the list of matches.
2979 are always ignored when
2982 is set and not null. However, setting
2985 to a non-null value has the effect of enabling the
2987 shell option, so all other file names beginning with a
2990 To get the old behavior of ignoring file names beginning with a
2994 one of the patterns in
2999 option is disabled when
3004 \fBPattern Matching\fP
3006 Any character that appears in a pattern, other than the special pattern
3007 characters described below, matches itself. The NUL character may not
3008 occur in a pattern. A backslash escapes the following character; the
3009 escaping backslash is discarded when matching.
3010 The special pattern characters must be quoted if
3011 they are to be matched literally.
3013 The special pattern characters have the following meanings:
3018 Matches any string, including the null string.
3019 When the \fBglobstar\fP shell option is enabled, and \fB*\fP is used in
3020 a filename expansion context, two adjacent \fB*\fPs used as a single
3021 pattern will match all files and zero or more directories and
3023 If followed by a \fB/\fP, two adjacent \fB*\fPs will match only directories
3027 Matches any single character.
3030 Matches any one of the enclosed characters. A pair of characters
3031 separated by a hyphen denotes a
3032 \fIrange expression\fP;
3033 any character that sorts between those two characters, inclusive,
3034 using the current locale's collating sequence and character set,
3035 is matched. If the first character following the
3041 then any character not enclosed is matched.
3042 The sorting order of characters in range expressions is determined by
3043 the current locale and the value of the \fBLC_COLLATE\fP shell variable,
3047 may be matched by including it as the first or last character
3051 may be matched by including it as the first character
3060 \fIcharacter classes\fP can be specified using the syntax
3061 \fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
3062 following classes defined in the POSIX standard:
3066 .if n alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
3067 .if t alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
3069 A character class matches any character belonging to that class.
3070 The \fBword\fP character class matches letters, digits, and the character _.
3078 an \fIequivalence class\fP can be specified using the syntax
3079 \fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
3080 same collation weight (as defined by the current locale) as
3081 the character \fIc\fP.
3089 the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
3094 If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
3095 builtin, several extended pattern matching operators are recognized.
3096 In the following description, a \fIpattern-list\fP is a list of one
3097 or more patterns separated by a \fB|\fP.
3098 Composite patterns may be formed using one or more of the following
3104 \fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
3105 Matches zero or one occurrence of the given patterns
3107 \fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
3108 Matches zero or more occurrences of the given patterns
3110 \fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
3111 Matches one or more occurrences of the given patterns
3113 \fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
3114 Matches one of the given patterns
3116 \fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
3117 Matches anything except one of the given patterns
3122 After the preceding expansions, all unquoted occurrences of the
3126 and \^\f3"\fP\^ that did not result from one of the above
3127 expansions are removed.
3129 Before a command is executed, its input and output
3132 using a special notation interpreted by the shell.
3133 Redirection may also be used to open and close files for the
3134 current shell execution environment. The following redirection
3135 operators may precede or appear anywhere within a
3139 Redirections are processed in the order they appear, from
3142 In the following descriptions, if the file descriptor number is
3143 omitted, and the first character of the redirection operator is
3145 the redirection refers to the standard input (file descriptor
3146 0). If the first character of the redirection operator is
3148 the redirection refers to the standard output (file descriptor
3151 The word following the redirection operator in the following
3152 descriptions, unless otherwise noted, is subjected to brace expansion,
3153 tilde expansion, parameter expansion, command substitution, arithmetic
3154 expansion, quote removal, pathname expansion, and word splitting.
3155 If it expands to more than one word,
3159 Note that the order of redirections is significant. For example,
3163 ls \fB>\fP dirlist 2\fB>&\fP1
3166 directs both standard output and standard error to the file
3171 ls 2\fB>&\fP1 \fB>\fP dirlist
3174 directs only the standard output to file
3176 because the standard error was duplicated as standard output
3177 before the standard output was redirected to
3180 \fBBash\fP handles several filenames specially when they are used in
3181 redirections, as described in the following table:
3187 If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
3190 File descriptor 0 is duplicated.
3193 File descriptor 1 is duplicated.
3196 File descriptor 2 is duplicated.
3198 .B /dev/tcp/\fIhost\fP/\fIport\fP
3199 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3200 is an integer port number or service name, \fBbash\fP attempts to open
3201 a TCP connection to the corresponding socket.
3203 .B /dev/udp/\fIhost\fP/\fIport\fP
3204 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
3205 is an integer port number or service name, \fBbash\fP attempts to open
3206 a UDP connection to the corresponding socket.
3210 A failure to open or create a file causes the redirection to fail.
3212 Redirections using file descriptors greater than 9 should be used with
3213 care, as they may conflict with file descriptors the shell uses
3215 .SS Redirecting Input
3217 Redirection of input causes the file whose name results from
3220 to be opened for reading on file descriptor
3222 or the standard input (file descriptor 0) if
3226 The general format for redirecting input is:
3229 [\fIn\fP]\fB<\fP\fIword\fP
3231 .SS Redirecting Output
3233 Redirection of output causes the file whose name results from
3236 to be opened for writing on file descriptor
3238 or the standard output (file descriptor 1) if
3240 is not specified. If the file does not exist it is created;
3241 if it does exist it is truncated to zero size.
3243 The general format for redirecting output is:
3246 [\fIn\fP]\fB>\fP\fIword\fP
3249 If the redirection operator is
3255 builtin has been enabled, the redirection will fail if the file
3256 whose name results from the expansion of \fIword\fP exists and is
3258 If the redirection operator is
3260 or the redirection operator is
3266 builtin command is not enabled, the redirection is attempted even
3267 if the file named by \fIword\fP exists.
3268 .SS Appending Redirected Output
3270 Redirection of output in this fashion
3271 causes the file whose name results from
3274 to be opened for appending on file descriptor
3276 or the standard output (file descriptor 1) if
3278 is not specified. If the file does not exist it is created.
3280 The general format for appending output is:
3283 [\fIn\fP]\fB>>\fP\fIword\fP
3286 .SS Redirecting Standard Output and Standard Error
3288 This construct allows both the
3289 standard output (file descriptor 1) and
3290 the standard error output (file descriptor 2)
3291 to be redirected to the file whose name is the
3295 There are two formats for redirecting standard output and
3306 Of the two forms, the first is preferred.
3307 This is semantically equivalent to
3310 \fB>\fP\fIword\fP 2\fB>&\fP1
3313 .SS Appending Standard Output and Standard Error
3315 This construct allows both the
3316 standard output (file descriptor 1) and
3317 the standard error output (file descriptor 2)
3318 to be appended to the file whose name is the
3322 The format for appending standard output and standard error is:
3328 This is semantically equivalent to
3331 \fB>>\fP\fIword\fP 2\fB>&\fP1
3335 This type of redirection instructs the shell to read input from the
3336 current source until a line containing only
3338 (with no trailing blanks)
3340 the lines read up to that point are then used as the standard
3341 input for a command.
3343 The format of here-documents is:
3347 \fB<<\fP[\fB\-\fP]\fIword\fP
3353 No parameter expansion, command substitution, arithmetic expansion,
3354 or pathname expansion is performed on
3356 If any characters in
3360 is the result of quote removal on
3362 and the lines in the here-document are not expanded.
3363 If \fIword\fP is unquoted,
3364 all lines of the here-document are subjected to parameter expansion,
3365 command substitution, and arithmetic expansion. In the latter
3366 case, the character sequence
3370 must be used to quote the characters
3376 If the redirection operator is
3378 then all leading tab characters are stripped from input lines and the
3382 here-documents within shell scripts to be indented in a
3385 A variant of here documents, the format is:
3393 The \fIword\fP is expanded and supplied to the command on its standard
3395 .SS "Duplicating File Descriptors"
3397 The redirection operator
3400 [\fIn\fP]\fB<&\fP\fIword\fP
3403 is used to duplicate input file descriptors.
3406 expands to one or more digits, the file descriptor denoted by
3408 is made to be a copy of that file descriptor.
3411 do not specify a file descriptor open for input, a redirection error occurs.
3420 is not specified, the standard input (file descriptor 0) is used.
3425 [\fIn\fP]\fB>&\fP\fIword\fP
3428 is used similarly to duplicate output file descriptors. If
3430 is not specified, the standard output (file descriptor 1) is used.
3433 do not specify a file descriptor open for output, a redirection error occurs.
3434 As a special case, if \fIn\fP is omitted, and \fIword\fP does not
3435 expand to one or more digits, the standard output and standard
3436 error are redirected as described previously.
3437 .SS "Moving File Descriptors"
3439 The redirection operator
3442 [\fIn\fP]\fB<&\fP\fIdigit\fP\fB\-\fP
3445 moves the file descriptor \fIdigit\fP to file descriptor
3447 or the standard input (file descriptor 0) if \fIn\fP is not specified.
3448 \fIdigit\fP is closed after being duplicated to \fIn\fP.
3450 Similarly, the redirection operator
3453 [\fIn\fP]\fB>&\fP\fIdigit\fP\fB\-\fP
3456 moves the file descriptor \fIdigit\fP to file descriptor
3458 or the standard output (file descriptor 1) if \fIn\fP is not specified.
3459 .SS "Opening File Descriptors for Reading and Writing"
3461 The redirection operator
3464 [\fIn\fP]\fB<>\fP\fIword\fP
3467 causes the file whose name is the expansion of
3469 to be opened for both reading and writing on file descriptor
3471 or on file descriptor 0 if
3473 is not specified. If the file does not exist, it is created.
3475 \fIAliases\fP allow a string to be substituted for a word when it is used
3476 as the first word of a simple command.
3477 The shell maintains a list of aliases that may be set and unset with the
3481 builtin commands (see
3483 .B SHELL BUILTIN COMMANDS
3485 The first word of each simple command, if unquoted,
3486 is checked to see if it has an
3487 alias. If so, that word is replaced by the text of the alias.
3488 The characters \fB/\fP, \fB$\fP, \fB\`\fP, and \fB=\fP and
3489 any of the shell \fImetacharacters\fP or quoting characters
3490 listed above may not appear in an alias name.
3491 The replacement text may contain any valid shell input,
3492 including shell metacharacters.
3493 The first word of the replacement text is tested
3494 for aliases, but a word that is identical to an alias being expanded
3495 is not expanded a second time.
3496 This means that one may alias
3502 does not try to recursively expand the replacement text.
3503 If the last character of the alias value is a
3505 then the next command
3506 word following the alias is also checked for alias expansion.
3508 Aliases are created and listed with the
3510 command, and removed with the
3514 There is no mechanism for using arguments in the replacement text.
3515 If arguments are needed, a shell function should be used (see
3520 Aliases are not expanded when the shell is not interactive, unless
3523 shell option is set using
3525 (see the description of
3529 \fBSHELL BUILTIN COMMANDS\fP
3532 The rules concerning the definition and use of aliases are
3535 always reads at least one complete line
3536 of input before executing any
3537 of the commands on that line. Aliases are expanded when a
3538 command is read, not when it is executed. Therefore, an
3539 alias definition appearing on the same line as another
3540 command does not take effect until the next line of input is read.
3541 The commands following the alias definition
3542 on that line are not affected by the new alias.
3543 This behavior is also an issue when functions are executed.
3544 Aliases are expanded when a function definition is read,
3545 not when the function is executed, because a function definition
3546 is itself a compound command. As a consequence, aliases
3547 defined in a function are not available until after that
3548 function is executed. To be safe, always put
3549 alias definitions on a separate line, and do not use
3551 in compound commands.
3553 For almost every purpose, aliases are superseded by
3556 A shell function, defined as described above under
3558 .BR "SHELL GRAMMAR" ,
3559 stores a series of commands for later execution.
3560 When the name of a shell function is used as a simple command name,
3561 the list of commands associated with that function name is executed.
3562 Functions are executed in the context of the
3563 current shell; no new process is created to interpret
3564 them (contrast this with the execution of a shell script).
3565 When a function is executed, the arguments to the
3566 function become the positional parameters
3567 during its execution.
3568 The special parameter
3570 is updated to reflect the change. Special parameter 0
3572 The first element of the
3575 variable is set to the name of the function while the function
3577 All other aspects of the shell execution
3578 environment are identical between a function and its caller
3579 with the exception that the
3584 traps (see the description of the
3588 .B SHELL BUILTIN COMMANDS
3589 below) are not inherited unless the function has been given the
3590 \fBtrace\fP attribute (see the description of the
3593 builtin below) or the
3594 \fB\-o functrace\fP shell option has been enabled with
3595 the \fBset\fP builtin
3596 (in which case all functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps).
3598 Variables local to the function may be declared with the
3600 builtin command. Ordinarily, variables and their values
3601 are shared between the function and its caller.
3603 If the builtin command
3605 is executed in a function, the function completes and
3606 execution resumes with the next command after the function
3608 Any command associated with the \fBRETURN\fP trap is executed
3609 before execution resumes.
3610 When a function completes, the values of the
3611 positional parameters and the special parameter
3613 are restored to the values they had prior to the function's
3616 Function names and definitions may be listed with the
3622 builtin commands. The
3628 will list the function names only
3629 (and optionally the source file and line number, if the \fBextdebug\fP
3630 shell option is enabled).
3631 Functions may be exported so that subshells
3632 automatically have them defined with the
3637 A function definition may be deleted using the \fB\-f\fP option to
3641 Note that shell functions and variables with the same name may result
3642 in multiple identically-named entries in the environment passed to the
3644 Care should be taken in cases where this may cause a problem.
3646 Functions may be recursive. No limit is imposed on the number
3648 .SH "ARITHMETIC EVALUATION"
3649 The shell allows arithmetic expressions to be evaluated, under
3650 certain circumstances (see the \fBlet\fP and \fBdeclare\fP builtin
3651 commands and \fBArithmetic Expansion\fP).
3652 Evaluation is done in fixed-width integers with no check for overflow,
3653 though division by 0 is trapped and flagged as an error.
3654 The operators and their precedence, associativity, and values
3655 are the same as in the C language.
3656 The following list of operators is grouped into levels of
3657 equal-precedence operators.
3658 The levels are listed in order of decreasing precedence.
3662 .B \fIid\fP++ \fIid\fP\-\-
3663 variable post-increment and post-decrement
3665 .B ++\fIid\fP \-\-\fIid\fP
3666 variable pre-increment and pre-decrement
3669 unary minus and plus
3672 logical and bitwise negation
3678 multiplication, division, remainder
3681 addition, subtraction
3684 left and right bitwise shifts
3690 equality and inequality
3696 bitwise exclusive OR
3707 .B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
3708 conditional operator
3710 .B = *= /= %= += \-= <<= >>= &= ^= |=
3713 .B \fIexpr1\fP , \fIexpr2\fP
3717 Shell variables are allowed as operands; parameter expansion is
3718 performed before the expression is evaluated.
3719 Within an expression, shell variables may also be referenced by name
3720 without using the parameter expansion syntax.
3721 A shell variable that is null or unset evaluates to 0 when referenced
3722 by name without using the parameter expansion syntax.
3723 The value of a variable is evaluated as an arithmetic expression
3724 when it is referenced, or when a variable which has been given the
3725 \fIinteger\fP attribute using \fBdeclare -i\fP is assigned a value.
3726 A null value evaluates to 0.
3727 A shell variable need not have its integer attribute
3728 turned on to be used in an expression.
3730 Constants with a leading 0 are interpreted as octal numbers.
3731 A leading 0x or 0X denotes hexadecimal.
3732 Otherwise, numbers take the form [\fIbase#\fP]n, where \fIbase\fP
3733 is a decimal number between 2 and 64 representing the arithmetic
3734 base, and \fIn\fP is a number in that base.
3735 If \fIbase#\fP is omitted, then base 10 is used.
3736 The digits greater than 9 are represented by the lowercase letters,
3737 the uppercase letters, @, and _, in that order.
3738 If \fIbase\fP is less than or equal to 36, lowercase and uppercase
3739 letters may be used interchangeably to represent numbers between 10
3742 Operators are evaluated in order of precedence. Sub-expressions in
3743 parentheses are evaluated first and may override the precedence
3745 .SH "CONDITIONAL EXPRESSIONS"
3746 Conditional expressions are used by the \fB[[\fP compound command and
3747 the \fBtest\fP and \fB[\fP builtin commands to test file attributes
3748 and perform string and arithmetic comparisons.
3749 Expressions are formed from the following unary or binary primaries.
3750 If any \fIfile\fP argument to one of the primaries is of the form
3751 \fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
3752 If the \fIfile\fP argument to one of the primaries is one of
3753 \fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
3754 descriptor 0, 1, or 2, respectively, is checked.
3756 Unless otherwise specified, primaries that operate on files follow symbolic
3757 links and operate on the target of the link, rather than the link itself.
3762 True if \fIfile\fP exists.
3765 True if \fIfile\fP exists and is a block special file.
3768 True if \fIfile\fP exists and is a character special file.
3771 True if \fIfile\fP exists and is a directory.
3774 True if \fIfile\fP exists.
3777 True if \fIfile\fP exists and is a regular file.
3780 True if \fIfile\fP exists and is set-group-id.
3783 True if \fIfile\fP exists and is a symbolic link.
3786 True if \fIfile\fP exists and its ``sticky'' bit is set.
3789 True if \fIfile\fP exists and is a named pipe (FIFO).
3792 True if \fIfile\fP exists and is readable.
3795 True if \fIfile\fP exists and has a size greater than zero.
3798 True if file descriptor
3800 is open and refers to a terminal.
3803 True if \fIfile\fP exists and its set-user-id bit is set.
3806 True if \fIfile\fP exists and is writable.
3809 True if \fIfile\fP exists and is executable.
3812 True if \fIfile\fP exists and is owned by the effective user id.
3815 True if \fIfile\fP exists and is owned by the effective group id.
3818 True if \fIfile\fP exists and is a symbolic link.
3821 True if \fIfile\fP exists and is a socket.
3824 True if \fIfile\fP exists and has been modified since it was last read.
3826 \fIfile1\fP \-\fBnt\fP \fIfile2\fP
3827 True if \fIfile1\fP is newer (according to modification date) than \fIfile2\fP,
3828 or if \fIfile1\fP exists and \fPfile2\fP does not.
3830 \fIfile1\fP \-\fBot\fP \fIfile2\fP
3831 True if \fIfile1\fP is older than \fIfile2\fP, or if \fIfile2\fP exists
3832 and \fIfile1\fP does not.
3834 \fIfile1\fP \fB\-ef\fP \fIfile2\fP
3835 True if \fIfile1\fP and \fIfile2\fP refer to the same device and
3838 .B \-o \fIoptname\fP
3839 True if shell option
3842 See the list of options under the description of the
3849 True if the length of \fIstring\fP is zero.
3856 True if the length of
3860 \fIstring1\fP \fB==\fP \fIstring2\fP
3861 True if the strings are equal. \fB=\fP may be used in place of
3862 \fB==\fP for strict POSIX compliance.
3864 \fIstring1\fP \fB!=\fP \fIstring2\fP
3865 True if the strings are not equal.
3867 \fIstring1\fP \fB<\fP \fIstring2\fP
3868 True if \fIstring1\fP sorts before \fIstring2\fP lexicographically
3869 in the current locale.
3871 \fIstring1\fP \fB>\fP \fIstring2\fP
3872 True if \fIstring1\fP sorts after \fIstring2\fP lexicographically
3873 in the current locale.
3875 .I \fIarg1\fP \fBOP\fP \fIarg2\fP
3886 These arithmetic binary operators return true if \fIarg1\fP
3887 is equal to, not equal to, less than, less than or equal to,
3888 greater than, or greater than or equal to \fIarg2\fP, respectively.
3892 may be positive or negative integers.
3894 .SH "SIMPLE COMMAND EXPANSION"
3895 When a simple command is executed, the shell performs the following
3896 expansions, assignments, and redirections, from left to right.
3898 The words that the parser has marked as variable assignments (those
3899 preceding the command name) and redirections are saved for later
3902 The words that are not variable assignments or redirections are
3903 expanded. If any words remain after expansion, the first word
3904 is taken to be the name of the command and the remaining words are
3907 Redirections are performed as described above under
3911 The text after the \fB=\fP in each variable assignment undergoes tilde
3912 expansion, parameter expansion, command substitution, arithmetic expansion,
3913 and quote removal before being assigned to the variable.
3915 If no command name results, the variable assignments affect the current
3916 shell environment. Otherwise, the variables are added to the environment
3917 of the executed command and do not affect the current shell environment.
3918 If any of the assignments attempts to assign a value to a readonly variable,
3919 an error occurs, and the command exits with a non-zero status.
3921 If no command name results, redirections are performed, but do not
3922 affect the current shell environment. A redirection error causes the
3923 command to exit with a non-zero status.
3925 If there is a command name left after expansion, execution proceeds as
3926 described below. Otherwise, the command exits. If one of the expansions
3927 contained a command substitution, the exit status of the command is
3928 the exit status of the last command substitution performed. If there
3929 were no command substitutions, the command exits with a status of zero.
3930 .SH "COMMAND EXECUTION"
3931 After a command has been split into words, if it results in a
3932 simple command and an optional list of arguments, the following
3935 If the command name contains no slashes, the shell attempts to
3936 locate it. If there exists a shell function by that name, that
3937 function is invoked as described above in
3940 If the name does not match a function, the shell searches for
3941 it in the list of shell builtins. If a match is found, that
3944 If the name is neither a shell function nor a builtin,
3945 and contains no slashes,
3947 searches each element of the
3950 for a directory containing an executable file by that name.
3952 uses a hash table to remember the full pathnames of executable
3957 .B "SHELL BUILTIN COMMANDS"
3959 A full search of the directories in
3962 is performed only if the command is not found in the hash table.
3963 If the search is unsuccessful, the shell searches for a defined shell
3964 function named \fBcommand_not_found_handle\fP.
3965 If that function exists, it is invoked with the original command and
3966 the original command's arguments as its arguments, and the function's
3967 exit status becomes the exit status of the shell.
3968 If that function is not defined, the shell prints an error
3969 message and returns an exit status of 127.
3971 If the search is successful, or if the command name contains
3972 one or more slashes, the shell executes the named program in a
3973 separate execution environment.
3974 Argument 0 is set to the name given, and the remaining arguments
3975 to the command are set to the arguments given, if any.
3977 If this execution fails because the file is not in executable
3978 format, and the file is not a directory, it is assumed to be
3979 a \fIshell script\fP, a file
3980 containing shell commands. A subshell is spawned to execute
3981 it. This subshell reinitializes itself, so
3982 that the effect is as if a new shell had been invoked
3983 to handle the script, with the exception that the locations of
3984 commands remembered by the parent (see
3988 \fBSHELL BUILTIN COMMANDS\fP)
3989 are retained by the child.
3991 If the program is a file beginning with
3993 the remainder of the first line specifies an interpreter
3994 for the program. The shell executes the
3995 specified interpreter on operating systems that do not
3996 handle this executable format themselves. The arguments to the
3997 interpreter consist of a single optional argument following the
3998 interpreter name on the first line of the program, followed
3999 by the name of the program, followed by the command
4001 .SH COMMAND EXECUTION ENVIRONMENT
4002 The shell has an \fIexecution environment\fP, which consists of the
4006 open files inherited by the shell at invocation, as modified by
4007 redirections supplied to the \fBexec\fP builtin
4009 the current working directory as set by \fBcd\fP, \fBpushd\fP, or
4010 \fBpopd\fP, or inherited by the shell at invocation
4012 the file creation mode mask as set by \fBumask\fP or inherited from
4015 current traps set by \fBtrap\fP
4017 shell parameters that are set by variable assignment or with \fBset\fP
4018 or inherited from the shell's parent in the environment
4020 shell functions defined during execution or inherited from the shell's
4021 parent in the environment
4023 options enabled at invocation (either by default or with command-line
4024 arguments) or by \fBset\fP
4026 options enabled by \fBshopt\fP
4028 shell aliases defined with \fBalias\fP
4030 various process IDs, including those of background jobs, the value
4031 of \fB$$\fP, and the value of \fB$PPID\fP
4033 When a simple command other than a builtin or shell function
4034 is to be executed, it
4035 is invoked in a separate execution environment that consists of
4036 the following. Unless otherwise noted, the values are inherited
4040 the shell's open files, plus any modifications and additions specified
4041 by redirections to the command
4043 the current working directory
4045 the file creation mode mask
4047 shell variables and functions marked for export, along with variables
4048 exported for the command, passed in the environment
4050 traps caught by the shell are reset to the values inherited from the
4051 shell's parent, and traps ignored by the shell are ignored
4053 A command invoked in this separate environment cannot affect the
4054 shell's execution environment.
4056 Command substitution, commands grouped with parentheses,
4057 and asynchronous commands are invoked in a
4058 subshell environment that is a duplicate of the shell environment,
4059 except that traps caught by the shell are reset to the values
4060 that the shell inherited from its parent at invocation. Builtin
4061 commands that are invoked as part of a pipeline are also executed in a
4062 subshell environment. Changes made to the subshell environment
4063 cannot affect the shell's execution environment.
4065 Subshells spawned to execute command substitutions inherit the value of
4066 the \fB\-e\fP option from the parent shell. When not in posix mode,
4067 Bash clears the \fB\-e\fP option in such subshells.
4069 If a command is followed by a \fB&\fP and job control is not active, the
4070 default standard input for the command is the empty file \fI/dev/null\fP.
4071 Otherwise, the invoked command inherits the file descriptors of the calling
4072 shell as modified by redirections.
4074 When a program is invoked it is given an array of strings
4078 \fIname\fP\-\fIvalue\fP pairs, of the form
4079 .IR "name\fR=\fPvalue" .
4081 The shell provides several ways to manipulate the environment.
4082 On invocation, the shell scans its own environment and
4083 creates a parameter for each name found, automatically marking
4086 to child processes. Executed commands inherit the environment.
4091 commands allow parameters and functions to be added to and
4092 deleted from the environment. If the value of a parameter
4093 in the environment is modified, the new value becomes part
4094 of the environment, replacing the old. The environment
4095 inherited by any executed command consists of the shell's
4096 initial environment, whose values may be modified in the shell,
4097 less any pairs removed by the
4099 command, plus any additions via the
4105 The environment for any
4107 or function may be augmented temporarily by prefixing it with
4108 parameter assignments, as described above in
4111 These assignment statements affect only the environment seen
4116 option is set (see the
4118 builtin command below), then
4120 parameter assignments are placed in the environment for a command,
4121 not just those that precede the command name.
4125 invokes an external command, the variable
4127 is set to the full file name of the command and passed to that
4128 command in its environment.
4131 The exit status of an executed command is the value returned by the
4132 \fIwaitpid\fP system call or equivalent function. Exit statuses
4133 fall between 0 and 255, though, as explained below, the shell may
4134 use values above 125 specially. Exit statuses from shell builtins and
4135 compound commands are also limited to this range. Under certain
4136 circumstances, the shell will use special values to indicate specific
4139 For the shell's purposes, a command which exits with a
4140 zero exit status has succeeded. An exit status of zero
4141 indicates success. A non-zero exit status indicates failure.
4142 When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
4143 the value of 128+\fIN\fP as the exit status.
4145 If a command is not found, the child process created to
4146 execute it returns a status of 127. If a command is found
4147 but is not executable, the return status is 126.
4149 If a command fails because of an error during expansion or redirection,
4150 the exit status is greater than zero.
4152 Shell builtin commands return a status of 0 (\fItrue\fP) if
4153 successful, and non-zero (\fIfalse\fP) if an error occurs
4155 All builtins return an exit status of 2 to indicate incorrect usage.
4157 \fBBash\fP itself returns the exit status of the last command
4158 executed, unless a syntax error occurs, in which case it exits
4159 with a non-zero value. See also the \fBexit\fP builtin
4162 When \fBbash\fP is interactive, in the absence of any traps, it ignores
4165 (so that \fBkill 0\fP does not kill an interactive shell),
4169 is caught and handled (so that the \fBwait\fP builtin is interruptible).
4170 In all cases, \fBbash\fP ignores
4173 If job control is in effect,
4184 Non-builtin commands run by \fBbash\fP have signal handlers
4185 set to the values inherited by the shell from its parent.
4186 When job control is not in effect, asynchronous commands
4193 in addition to these inherited handlers.
4194 Commands run as a result of command substitution ignore the
4195 keyboard-generated job control signals
4204 The shell exits by default upon receipt of a
4207 Before exiting, an interactive shell resends the
4210 to all jobs, running or stopped.
4211 Stopped jobs are sent
4214 to ensure that they receive the
4217 To prevent the shell from
4218 sending the signal to a particular job, it should be removed from the
4223 .B "SHELL BUILTIN COMMANDS"
4233 shell option has been set with
4239 to all jobs when an interactive login shell exits.
4241 If \fBbash\fP is waiting for a command to complete and receives a signal
4242 for which a trap has been set, the trap will not be executed until
4243 the command completes.
4244 When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
4245 builtin, the reception of a signal for which a trap has been set will
4246 cause the \fBwait\fP builtin to return immediately with an exit status
4247 greater than 128, immediately after which the trap is executed.
4250 refers to the ability to selectively stop (\fIsuspend\fP)
4251 the execution of processes and continue (\fIresume\fP)
4252 their execution at a later point. A user typically employs
4253 this facility via an interactive interface supplied jointly
4254 by the system's terminal driver and
4257 The shell associates a
4259 with each pipeline. It keeps a table of currently executing
4260 jobs, which may be listed with the
4264 starts a job asynchronously (in the
4266 it prints a line that looks like:
4272 indicating that this job is job number 1 and that the process ID
4273 of the last process in the pipeline associated with this job is 25647.
4274 All of the processes in a single pipeline are members of the same job.
4278 abstraction as the basis for job control.
4280 To facilitate the implementation of the user interface to job
4281 control, the operating system maintains the notion of a \fIcurrent terminal
4282 process group ID\fP. Members of this process group (processes whose
4283 process group ID is equal to the current terminal process group ID)
4284 receive keyboard-generated signals such as
4287 These processes are said to be in the
4290 processes are those whose process group ID differs from the terminal's;
4291 such processes are immune to keyboard-generated signals.
4292 Only foreground processes are allowed to read from or write to the
4293 terminal. Background processes which attempt to read from (write to) the
4296 .B SIGTTIN (SIGTTOU)
4297 signal by the terminal driver,
4298 which, unless caught, suspends the process.
4300 If the operating system on which
4305 contains facilities to use it.
4308 character (typically
4310 Control-Z) while a process is running
4311 causes that process to be stopped and returns control to
4314 .I "delayed suspend"
4315 character (typically
4317 Control-Y) causes the process to be stopped when it
4318 attempts to read input from the terminal, and control to
4321 The user may then manipulate the state of this job, using the
4323 command to continue it in the background, the
4325 command to continue it in the foreground, or
4328 command to kill it. A \fB^Z\fP takes effect immediately,
4329 and has the additional side effect of causing pending output
4330 and typeahead to be discarded.
4332 There are a number of ways to refer to a job in the shell.
4335 introduces a job specification (\fIjobspec\fP). Job number
4337 may be referred to as
4339 A job may also be referred to using a prefix of the name used to
4340 start it, or using a substring that appears in its command line.
4345 job. If a prefix matches more than one job,
4347 reports an error. Using
4349 on the other hand, refers to any job containing the string
4351 in its command line. If the substring matches more than one job,
4353 reports an error. The symbols
4357 refer to the shell's notion of the
4359 which is the last job stopped while it was in
4360 the foreground or started in the background.
4363 may be referenced using
4365 If there is only a single job, \fB%+\fP and \fB%\-\fP can both be used
4366 to refer to that job.
4367 In output pertaining to jobs (e.g., the output of the
4369 command), the current job is always flagged with a
4371 and the previous job with a
4373 A single % (with no accompanying job specification) also refers to the
4376 Simply naming a job can be used to bring it into the
4381 bringing job 1 from the background into the foreground.
4384 resumes job 1 in the background, equivalent to
4387 The shell learns immediately whenever a job changes state.
4390 waits until it is about to print a prompt before reporting
4391 changes in a job's status so as to not interrupt
4392 any other output. If the
4399 reports such changes immediately.
4403 is executed for each child that exits.
4405 If an attempt to exit
4407 is made while jobs are stopped (or, if the \fBcheckjobs\fP shell option has
4408 been enabled using the \fBshopt\fP builtin, running), the shell prints a
4409 warning message, and, if the \fBcheckjobs\fP option is enabled, lists the
4410 jobs and their statuses.
4413 command may then be used to inspect their status.
4414 If a second attempt to exit is made without an intervening command,
4415 the shell does not print another warning, and any stopped
4416 jobs are terminated.
4418 When executing interactively,
4420 displays the primary prompt
4423 when it is ready to read a command, and the secondary prompt
4426 when it needs more input to complete a command.
4428 allows these prompt strings to be customized by inserting a number of
4429 backslash-escaped special characters that are decoded as follows:
4434 an ASCII bell character (07)
4437 the date in "Weekday Month Date" format (e.g., "Tue May 26")
4439 .B \eD{\fIformat\fP}
4440 the \fIformat\fP is passed to \fIstrftime\fP(3) and the result is inserted
4441 into the prompt string; an empty \fIformat\fP results in a locale-specific
4442 time representation. The braces are required
4445 an ASCII escape character (033)
4448 the hostname up to the first `.'
4454 the number of jobs currently managed by the shell
4457 the basename of the shell's terminal device name
4466 the name of the shell, the basename of
4468 (the portion following the final slash)
4471 the current time in 24-hour HH:MM:SS format
4474 the current time in 12-hour HH:MM:SS format
4477 the current time in 12-hour am/pm format
4480 the current time in 24-hour HH:MM format
4483 the username of the current user
4486 the version of \fBbash\fP (e.g., 2.00)
4489 the release of \fBbash\fP, version + patch level (e.g., 2.00.0)
4492 the current working directory, with \fB$HOME\fP abbreviated with a tilde
4493 (uses the \fB$PROMPT_DIRTRIM\fP variable)
4496 the basename of the current working directory, with \fB$HOME\fP
4497 abbreviated with a tilde
4500 the history number of this command
4503 the command number of this command
4506 if the effective UID is 0, a
4512 the character corresponding to the octal number \fInnn\fP
4518 begin a sequence of non-printing characters, which could be used to
4519 embed a terminal control sequence into the prompt
4522 end a sequence of non-printing characters
4526 The command number and the history number are usually different:
4527 the history number of a command is its position in the history
4528 list, which may include commands restored from the history file
4532 below), while the command number is the position in the sequence
4533 of commands executed during the current shell session.
4534 After the string is decoded, it is expanded via
4535 parameter expansion, command substitution, arithmetic
4536 expansion, and quote removal, subject to the value of the
4538 shell option (see the description of the
4542 .B "SHELL BUILTIN COMMANDS"
4545 This is the library that handles reading input when using an interactive
4548 option is given at shell invocation.
4549 Line editing is also used when using the \fB\-e\fP option to the
4551 By default, the line editing commands are similar to those of emacs.
4552 A vi-style line editing interface is also available.
4553 Line editing can be enabled at any time using the
4561 .B SHELL BUILTIN COMMANDS
4563 To turn off line editing after the shell is running, use the
4570 .SS "Readline Notation"
4572 In this section, the emacs-style notation is used to denote
4573 keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
4574 means Control\-N. Similarly,
4576 keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
4579 key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
4582 key. This makes ESC the \fImeta prefix\fP.
4583 The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
4584 or press the Escape key
4585 then hold the Control key while pressing the
4589 Readline commands may be given numeric
4591 which normally act as a repeat count.
4592 Sometimes, however, it is the sign of the argument that is significant.
4593 Passing a negative argument to a command that acts in the forward
4594 direction (e.g., \fBkill\-line\fP) causes that command to act in a
4596 Commands whose behavior with arguments deviates from this are noted
4599 When a command is described as \fIkilling\fP text, the text
4600 deleted is saved for possible future retrieval
4601 (\fIyanking\fP). The killed text is saved in a
4602 \fIkill ring\fP. Consecutive kills cause the text to be
4603 accumulated into one unit, which can be yanked all at once.
4604 Commands which do not kill text separate the chunks of text
4606 .SS "Readline Initialization"
4608 Readline is customized by putting commands in an initialization
4609 file (the \fIinputrc\fP file).
4610 The name of this file is taken from the value of the
4613 variable. If that variable is unset, the default is
4615 When a program which uses the readline library starts up, the
4616 initialization file is read, and the key bindings and variables
4618 There are only a few basic constructs allowed in the
4619 readline initialization file.
4620 Blank lines are ignored.
4621 Lines beginning with a \fB#\fP are comments.
4622 Lines beginning with a \fB$\fP indicate conditional constructs.
4623 Other lines denote key bindings and variable settings.
4625 The default key-bindings may be changed with an
4628 Other programs that use this library may add their own commands
4631 For example, placing
4634 M\-Control\-u: universal\-argument
4638 C\-Meta\-u: universal\-argument
4642 would make M\-C\-u execute the readline command
4643 .IR universal\-argument .
4645 The following symbolic character names are recognized:
4658 In addition to command names, readline allows keys to be bound
4659 to a string that is inserted when the key is pressed (a \fImacro\fP).
4660 .SS "Readline Key Bindings"
4662 The syntax for controlling key bindings in the
4664 file is simple. All that is required is the name of the
4665 command or the text of a macro and a key sequence to which
4666 it should be bound. The name may be specified in one of two ways:
4667 as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
4668 prefixes, or as a key sequence.
4670 When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4672 is the name of a key spelled out in English. For example:
4675 Control-u: universal\-argument
4677 Meta-Rubout: backward-kill-word
4679 Control-o: "> output"
4682 In the above example,
4684 is bound to the function
4685 .BR universal\-argument ,
4687 is bound to the function
4688 .BR backward\-kill\-word ,
4691 is bound to run the macro
4692 expressed on the right hand side (that is, to insert the text
4693 .if t \f(CW> output\fP
4697 In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4701 above in that strings denoting
4702 an entire key sequence may be specified by placing the sequence
4703 within double quotes. Some GNU Emacs style key escapes can be
4704 used, as in the following example, but the symbolic character names
4708 "\eC\-u": universal\-argument
4710 "\eC\-x\eC\-r": re\-read\-init\-file
4712 "\ee[11~": "Function Key 1"
4717 is again bound to the function
4718 .BR universal\-argument .
4720 is bound to the function
4721 .BR re\-read\-init\-file ,
4724 is bound to insert the text
4725 .if t \f(CWFunction Key 1\fP.
4726 .if n ``Function Key 1''.
4728 The full set of GNU Emacs style escape sequences is
4752 In addition to the GNU Emacs style escape sequences, a second
4753 set of backslash escapes is available:
4782 the eight-bit character whose value is the octal value \fInnn\fP
4783 (one to three digits)
4786 the eight-bit character whose value is the hexadecimal value \fIHH\fP
4787 (one or two hex digits)
4791 When entering the text of a macro, single or double quotes must
4792 be used to indicate a macro definition.
4793 Unquoted text is assumed to be a function name.
4794 In the macro body, the backslash escapes described above are expanded.
4795 Backslash will quote any other character in the macro text,
4796 including " and \(aq.
4799 allows the current readline key bindings to be displayed or modified
4802 builtin command. The editing mode may be switched during interactive
4807 builtin command (see
4809 .B SHELL BUILTIN COMMANDS
4811 .SS "Readline Variables"
4813 Readline has variables that can be used to further customize its
4814 behavior. A variable may be set in the
4816 file with a statement of the form
4819 \fBset\fP \fIvariable\-name\fP \fIvalue\fP
4822 Except where noted, readline variables can take the values
4826 (without regard to case).
4827 Unrecognized variable names are ignored.
4828 When a variable value is read, empty or null values, "on" (case-insensitive),
4829 and "1" are equivalent to \fBOn\fP. All other values are equivalent to
4831 The variables and their default values are:
4835 .B bell\-style (audible)
4836 Controls what happens when readline wants to ring the terminal bell.
4837 If set to \fBnone\fP, readline never rings the bell. If set to
4838 \fBvisible\fP, readline uses a visible bell if one is available.
4839 If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
4841 .B bind\-tty\-special\-chars (On)
4842 If set to \fBOn\fP, readline attempts to bind the control characters
4843 treated specially by the kernel's terminal driver to their readline
4846 .B comment\-begin (``#'')
4847 The string that is inserted when the readline
4849 command is executed.
4850 This command is bound to
4852 in emacs mode and to
4856 .B completion\-ignore\-case (Off)
4857 If set to \fBOn\fP, readline performs filename matching and completion
4858 in a case\-insensitive fashion.
4860 .B completion\-prefix\-display\-length (0)
4861 The length in characters of the common prefix of a list of possible
4862 completions that is displayed without modification. When set to a
4863 value greater than zero, common prefixes longer than this value are
4864 replaced with an ellipsis when displaying possible completions.
4866 .B completion\-query\-items (100)
4867 This determines when the user is queried about viewing
4868 the number of possible completions
4869 generated by the \fBpossible\-completions\fP command.
4870 It may be set to any integer value greater than or equal to
4871 zero. If the number of possible completions is greater than
4872 or equal to the value of this variable, the user is asked whether
4873 or not he wishes to view them; otherwise they are simply listed
4876 .B convert\-meta (On)
4877 If set to \fBOn\fP, readline will convert characters with the
4878 eighth bit set to an ASCII key sequence
4879 by stripping the eighth bit and prefixing an
4880 escape character (in effect, using escape as the \fImeta prefix\fP).
4882 .B disable\-completion (Off)
4883 If set to \fBOn\fP, readline will inhibit word completion. Completion
4884 characters will be inserted into the line as if they had been
4885 mapped to \fBself-insert\fP.
4887 .B editing\-mode (emacs)
4888 Controls whether readline begins with a set of key bindings similar
4889 to \fIemacs\fP or \fIvi\fP.
4891 can be set to either
4896 .B enable\-keypad (Off)
4897 When set to \fBOn\fP, readline will try to enable the application
4898 keypad when it is called. Some systems need this to enable the
4901 .B expand\-tilde (Off)
4902 If set to \fBon\fP, tilde expansion is performed when readline
4903 attempts word completion.
4905 .B history\-preserve\-point (Off)
4906 If set to \fBon\fP, the history code attempts to place point at the
4907 same location on each history line retrieved with \fBprevious-history\fP
4908 or \fBnext-history\fP.
4910 .B history\-size (0)
4911 Set the maximum number of history entries saved in the history list. If
4912 set to zero, the number of entries in the history list is not limited.
4914 .B horizontal\-scroll\-mode (Off)
4915 When set to \fBOn\fP, makes readline use a single line for display,
4916 scrolling the input horizontally on a single screen line when it
4917 becomes longer than the screen width rather than wrapping to a new line.
4919 .B input\-meta (Off)
4920 If set to \fBOn\fP, readline will enable eight-bit input (that is,
4921 it will not strip the high bit from the characters it reads),
4922 regardless of what the terminal claims it can support. The name
4924 is a synonym for this variable.
4926 .B isearch\-terminators (``C\-[C\-J'')
4927 The string of characters that should terminate an incremental
4928 search without subsequently executing the character as a command.
4929 If this variable has not been given a value, the characters
4930 \fIESC\fP and \fIC\-J\fP will terminate an incremental search.
4933 Set the current readline keymap. The set of valid keymap names is
4934 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
4937 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
4938 equivalent to \fIemacs\-standard\fP. The default value is
4942 also affects the default keymap.
4944 .B mark\-directories (On)
4945 If set to \fBOn\fP, completed directory names have a slash
4948 .B mark\-modified\-lines (Off)
4949 If set to \fBOn\fP, history lines that have been modified are displayed
4950 with a preceding asterisk (\fB*\fP).
4952 .B mark\-symlinked\-directories (Off)
4953 If set to \fBOn\fP, completed names which are symbolic links to directories
4954 have a slash appended (subject to the value of
4955 \fBmark\-directories\fP).
4957 .B match\-hidden\-files (On)
4958 This variable, when set to \fBOn\fP, causes readline to match files whose
4959 names begin with a `.' (hidden files) when performing filename
4960 completion, unless the leading `.' is
4961 supplied by the user in the filename to be completed.
4963 .B output\-meta (Off)
4964 If set to \fBOn\fP, readline will display characters with the
4965 eighth bit set directly rather than as a meta-prefixed escape
4968 .B page\-completions (On)
4969 If set to \fBOn\fP, readline uses an internal \fImore\fP-like pager
4970 to display a screenful of possible completions at a time.
4972 .B print\-completions\-horizontally (Off)
4973 If set to \fBOn\fP, readline will display completions with matches
4974 sorted horizontally in alphabetical order, rather than down the screen.
4976 .B revert\-all\-at\-newline (Off)
4977 If set to \fBon\fP, readline will undo all changes to history lines
4978 before returning when \fBaccept\-line\fP is executed. By default,
4979 history lines may be modified and retain individual undo lists across
4980 calls to \fBreadline\fP.
4982 .B show\-all\-if\-ambiguous (Off)
4983 This alters the default behavior of the completion functions. If
4986 words which have more than one possible completion cause the
4987 matches to be listed immediately instead of ringing the bell.
4989 .B show\-all\-if\-unmodified (Off)
4990 This alters the default behavior of the completion functions in
4991 a fashion similar to \fBshow\-all\-if\-ambiguous\fP.
4994 words which have more than one possible completion without any
4995 possible partial completion (the possible completions don't share
4996 a common prefix) cause the matches to be listed immediately instead
4997 of ringing the bell.
4999 .B visible\-stats (Off)
5000 If set to \fBOn\fP, a character denoting a file's type as reported
5001 by \fIstat\fP(2) is appended to the filename when listing possible
5004 .SS "Readline Conditional Constructs"
5006 Readline implements a facility similar in spirit to the conditional
5007 compilation features of the C preprocessor which allows key
5008 bindings and variable settings to be performed as the result
5009 of tests. There are four parser directives used.
5013 construct allows bindings to be made based on the
5014 editing mode, the terminal being used, or the application using
5015 readline. The text of the test extends to the end of the line;
5016 no characters are required to isolate it.
5019 The \fBmode=\fP form of the \fB$if\fP directive is used to test
5020 whether readline is in emacs or vi mode.
5021 This may be used in conjunction
5022 with the \fBset keymap\fP command, for instance, to set bindings in
5023 the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
5024 readline is starting out in emacs mode.
5026 The \fBterm=\fP form may be used to include terminal-specific
5027 key bindings, perhaps to bind the key sequences output by the
5028 terminal's function keys. The word on the right side of the
5030 is tested against the both full name of the terminal and the portion
5031 of the terminal name before the first \fB\-\fP. This allows
5038 .IP \fBapplication\fP
5039 The \fBapplication\fP construct is used to include
5040 application-specific settings. Each program using the readline
5041 library sets the \fIapplication name\fP, and an initialization
5042 file can test for a particular value.
5043 This could be used to bind key sequences to functions useful for
5044 a specific program. For instance, the following command adds a
5045 key sequence that quotes the current or previous word in Bash:
5050 # Quote the current or previous word
5051 "\eC\-xq": "\eeb\e"\eef\e""
5057 This command, as seen in the previous example, terminates an
5060 Commands in this branch of the \fB$if\fP directive are executed if
5063 This directive takes a single filename as an argument and reads commands
5064 and bindings from that file. For example, the following directive
5065 would read \fI/etc/inputrc\fP:
5069 \fB$include\fP \^ \fI/etc/inputrc\fP
5074 Readline provides commands for searching through the command history
5078 below) for lines containing a specified string.
5079 There are two search modes:
5082 .IR non-incremental .
5084 Incremental searches begin before the user has finished typing the
5086 As each character of the search string is typed, readline displays
5087 the next entry from the history matching the string typed so far.
5088 An incremental search requires only as many characters as needed to
5089 find the desired history entry.
5090 The characters present in the value of the \fBisearch-terminators\fP
5091 variable are used to terminate an incremental search.
5092 If that variable has not been assigned a value the Escape and
5093 Control-J characters will terminate an incremental search.
5094 Control-G will abort an incremental search and restore the original
5096 When the search is terminated, the history entry containing the
5097 search string becomes the current line.
5099 To find other matching entries in the history list, type Control-S or
5100 Control-R as appropriate.
5101 This will search backward or forward in the history for the next
5102 entry matching the search string typed so far.
5103 Any other key sequence bound to a readline command will terminate
5104 the search and execute that command.
5105 For instance, a \fInewline\fP will terminate the search and accept
5106 the line, thereby executing the command from the history list.
5108 Readline remembers the last incremental search string. If two
5109 Control-Rs are typed without any intervening characters defining a
5110 new search string, any remembered search string is used.
5112 Non-incremental searches read the entire search string before starting
5113 to search for matching history lines. The search string may be
5114 typed by the user or be part of the contents of the current line.
5115 .SS "Readline Command Names"
5117 The following is a list of the names of the commands and the default
5118 key sequences to which they are bound.
5119 Command names without an accompanying key sequence are unbound by default.
5120 In the following descriptions, \fIpoint\fP refers to the current cursor
5121 position, and \fImark\fP refers to a cursor position saved by the
5122 \fBset\-mark\fP command.
5123 The text between the point and mark is referred to as the \fIregion\fP.
5124 .SS Commands for Moving
5128 .B beginning\-of\-line (C\-a)
5129 Move to the start of the current line.
5131 .B end\-of\-line (C\-e)
5132 Move to the end of the line.
5134 .B forward\-char (C\-f)
5135 Move forward a character.
5137 .B backward\-char (C\-b)
5138 Move back a character.
5140 .B forward\-word (M\-f)
5141 Move forward to the end of the next word. Words are composed of
5142 alphanumeric characters (letters and digits).
5144 .B backward\-word (M\-b)
5145 Move back to the start of the current or previous word.
5146 Words are composed of alphanumeric characters (letters and digits).
5148 .B shell\-forward\-word
5149 Move forward to the end of the next word.
5150 Words are delimited by non-quoted shell metacharacters.
5152 .B shell\-backward\-word
5153 Move back to the start of the current or previous word.
5154 Words are delimited by non-quoted shell metacharacters.
5156 .B clear\-screen (C\-l)
5157 Clear the screen leaving the current line at the top of the screen.
5158 With an argument, refresh the current line without clearing the
5161 .B redraw\-current\-line
5162 Refresh the current line.
5164 .SS Commands for Manipulating the History
5168 .B accept\-line (Newline, Return)
5169 Accept the line regardless of where the cursor is. If this line is
5170 non-empty, add it to the history list according to the state of the
5173 variable. If the line is a modified history
5174 line, then restore the history line to its original state.
5176 .B previous\-history (C\-p)
5177 Fetch the previous command from the history list, moving back in
5180 .B next\-history (C\-n)
5181 Fetch the next command from the history list, moving forward in the
5184 .B beginning\-of\-history (M\-<)
5185 Move to the first line in the history.
5187 .B end\-of\-history (M\->)
5188 Move to the end of the input history, i.e., the line currently being
5191 .B reverse\-search\-history (C\-r)
5192 Search backward starting at the current line and moving `up' through
5193 the history as necessary. This is an incremental search.
5195 .B forward\-search\-history (C\-s)
5196 Search forward starting at the current line and moving `down' through
5197 the history as necessary. This is an incremental search.
5199 .B non\-incremental\-reverse\-search\-history (M\-p)
5200 Search backward through the history starting at the current line
5201 using a non-incremental search for a string supplied by the user.
5203 .B non\-incremental\-forward\-search\-history (M\-n)
5204 Search forward through the history using a non-incremental search for
5205 a string supplied by the user.
5207 .B history\-search\-forward
5208 Search forward through the history for the string of characters
5209 between the start of the current line and the point.
5210 This is a non-incremental search.
5212 .B history\-search\-backward
5213 Search backward through the history for the string of characters
5214 between the start of the current line and the point.
5215 This is a non-incremental search.
5217 .B yank\-nth\-arg (M\-C\-y)
5218 Insert the first argument to the previous command (usually
5219 the second word on the previous line) at point.
5222 insert the \fIn\fPth word from the previous command (the words
5223 in the previous command begin with word 0). A negative argument
5224 inserts the \fIn\fPth word from the end of the previous command.
5225 Once the argument \fIn\fP is computed, the argument is extracted
5226 as if the "!\fIn\fP" history expansion had been specified.
5229 yank\-last\-arg (M\-.\^, M\-_\^)
5230 Insert the last argument to the previous command (the last word of
5231 the previous history entry). With an argument,
5232 behave exactly like \fByank\-nth\-arg\fP.
5233 Successive calls to \fByank\-last\-arg\fP move back through the history
5234 list, inserting the last argument of each line in turn.
5235 The history expansion facilities are used to extract the last argument,
5236 as if the "!$" history expansion had been specified.
5238 .B shell\-expand\-line (M\-C\-e)
5239 Expand the line as the shell does. This
5240 performs alias and history expansion as well as all of the shell
5241 word expansions. See
5243 .B HISTORY EXPANSION
5244 below for a description of history expansion.
5246 .B history\-expand\-line (M\-^)
5247 Perform history expansion on the current line.
5250 .B HISTORY EXPANSION
5251 below for a description of history expansion.
5254 Perform history expansion on the current line and insert a space.
5257 .B HISTORY EXPANSION
5258 below for a description of history expansion.
5260 .B alias\-expand\-line
5261 Perform alias expansion on the current line.
5265 above for a description of alias expansion.
5267 .B history\-and\-alias\-expand\-line
5268 Perform history and alias expansion on the current line.
5270 .B insert\-last\-argument (M\-.\^, M\-_\^)
5271 A synonym for \fByank\-last\-arg\fP.
5273 .B operate\-and\-get\-next (C\-o)
5274 Accept the current line for execution and fetch the next line
5275 relative to the current line from the history for editing. Any
5276 argument is ignored.
5278 .B edit\-and\-execute\-command (C\-xC\-e)
5279 Invoke an editor on the current command line, and execute the result as shell
5281 \fBBash\fP attempts to invoke
5286 and \fIemacs\fP as the editor, in that order.
5288 .SS Commands for Changing Text
5292 .B delete\-char (C\-d)
5293 Delete the character at point. If point is at the
5294 beginning of the line, there are no characters in the line, and
5295 the last character typed was not bound to \fBdelete\-char\fP,
5300 .B backward\-delete\-char (Rubout)
5301 Delete the character behind the cursor. When given a numeric argument,
5302 save the deleted text on the kill ring.
5304 .B forward\-backward\-delete\-char
5305 Delete the character under the cursor, unless the cursor is at the
5306 end of the line, in which case the character behind the cursor is
5309 .B quoted\-insert (C\-q, C\-v)
5310 Add the next character typed to the line verbatim. This is
5311 how to insert characters like \fBC\-q\fP, for example.
5313 .B tab\-insert (C\-v TAB)
5314 Insert a tab character.
5316 .B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
5317 Insert the character typed.
5319 .B transpose\-chars (C\-t)
5320 Drag the character before point forward over the character at point,
5321 moving point forward as well.
5322 If point is at the end of the line, then this transposes
5323 the two characters before point.
5324 Negative arguments have no effect.
5326 .B transpose\-words (M\-t)
5327 Drag the word before point past the word after point,
5328 moving point over that word as well.
5329 If point is at the end of the line, this transposes
5330 the last two words on the line.
5332 .B upcase\-word (M\-u)
5333 Uppercase the current (or following) word. With a negative argument,
5334 uppercase the previous word, but do not move point.
5336 .B downcase\-word (M\-l)
5337 Lowercase the current (or following) word. With a negative argument,
5338 lowercase the previous word, but do not move point.
5340 .B capitalize\-word (M\-c)
5341 Capitalize the current (or following) word. With a negative argument,
5342 capitalize the previous word, but do not move point.
5345 Toggle overwrite mode. With an explicit positive numeric argument,
5346 switches to overwrite mode. With an explicit non-positive numeric
5347 argument, switches to insert mode. This command affects only
5348 \fBemacs\fP mode; \fBvi\fP mode does overwrite differently.
5349 Each call to \fIreadline()\fP starts in insert mode.
5350 In overwrite mode, characters bound to \fBself\-insert\fP replace
5351 the text at point rather than pushing the text to the right.
5352 Characters bound to \fBbackward\-delete\-char\fP replace the character
5353 before point with a space. By default, this command is unbound.
5355 .SS Killing and Yanking
5359 .B kill\-line (C\-k)
5360 Kill the text from point to the end of the line.
5362 .B backward\-kill\-line (C\-x Rubout)
5363 Kill backward to the beginning of the line.
5365 .B unix\-line\-discard (C\-u)
5366 Kill backward from point to the beginning of the line.
5367 The killed text is saved on the kill-ring.
5368 .\" There is no real difference between this and backward-kill-line
5370 .B kill\-whole\-line
5371 Kill all characters on the current line, no matter where point is.
5373 .B kill\-word (M\-d)
5374 Kill from point to the end of the current word, or if between
5375 words, to the end of the next word.
5376 Word boundaries are the same as those used by \fBforward\-word\fP.
5378 .B backward\-kill\-word (M\-Rubout)
5379 Kill the word behind point.
5380 Word boundaries are the same as those used by \fBbackward\-word\fP.
5382 .B shell\-kill\-word (M\-d)
5383 Kill from point to the end of the current word, or if between
5384 words, to the end of the next word.
5385 Word boundaries are the same as those used by \fBshell\-forward\-word\fP.
5387 .B shell\-backward\-kill\-word (M\-Rubout)
5388 Kill the word behind point.
5389 Word boundaries are the same as those used by \fBshell\-backward\-word\fP.
5391 .B unix\-word\-rubout (C\-w)
5392 Kill the word behind point, using white space as a word boundary.
5393 The killed text is saved on the kill-ring.
5395 .B unix\-filename\-rubout
5396 Kill the word behind point, using white space and the slash character
5397 as the word boundaries.
5398 The killed text is saved on the kill-ring.
5400 .B delete\-horizontal\-space (M\-\e)
5401 Delete all spaces and tabs around point.
5404 Kill the text in the current region.
5406 .B copy\-region\-as\-kill
5407 Copy the text in the region to the kill buffer.
5409 .B copy\-backward\-word
5410 Copy the word before point to the kill buffer.
5411 The word boundaries are the same as \fBbackward\-word\fP.
5413 .B copy\-forward\-word
5414 Copy the word following point to the kill buffer.
5415 The word boundaries are the same as \fBforward\-word\fP.
5418 Yank the top of the kill ring into the buffer at point.
5421 Rotate the kill ring, and yank the new top. Only works following
5426 .SS Numeric Arguments
5430 .B digit\-argument (M\-0, M\-1, ..., M\-\-)
5431 Add this digit to the argument already accumulating, or start a new
5432 argument. M\-\- starts a negative argument.
5434 .B universal\-argument
5435 This is another way to specify an argument.
5436 If this command is followed by one or more digits, optionally with a
5437 leading minus sign, those digits define the argument.
5438 If the command is followed by digits, executing
5439 .B universal\-argument
5440 again ends the numeric argument, but is otherwise ignored.
5441 As a special case, if this command is immediately followed by a
5442 character that is neither a digit or minus sign, the argument count
5443 for the next command is multiplied by four.
5444 The argument count is initially one, so executing this function the
5445 first time makes the argument count four, a second time makes the
5446 argument count sixteen, and so on.
5453 Attempt to perform completion on the text before point.
5455 attempts completion treating the text as a variable (if the
5456 text begins with \fB$\fP), username (if the text begins with
5457 \fB~\fP), hostname (if the text begins with \fB@\fP), or
5458 command (including aliases and functions) in turn. If none
5459 of these produces a match, filename completion is attempted.
5461 .B possible\-completions (M\-?)
5462 List the possible completions of the text before point.
5464 .B insert\-completions (M\-*)
5465 Insert all completions of the text before point
5466 that would have been generated by
5467 \fBpossible\-completions\fP.
5470 Similar to \fBcomplete\fP, but replaces the word to be completed
5471 with a single match from the list of possible completions.
5472 Repeated execution of \fBmenu\-complete\fP steps through the list
5473 of possible completions, inserting each match in turn.
5474 At the end of the list of completions, the bell is rung
5475 (subject to the setting of \fBbell\-style\fP)
5476 and the original text is restored.
5477 An argument of \fIn\fP moves \fIn\fP positions forward in the list
5478 of matches; a negative argument may be used to move backward
5480 This command is intended to be bound to \fBTAB\fP, but is unbound
5483 .B delete\-char\-or\-list
5484 Deletes the character under the cursor if not at the beginning or
5485 end of the line (like \fBdelete\-char\fP).
5486 If at the end of the line, behaves identically to
5487 \fBpossible\-completions\fP.
5488 This command is unbound by default.
5490 .B complete\-filename (M\-/)
5491 Attempt filename completion on the text before point.
5493 .B possible\-filename\-completions (C\-x /)
5494 List the possible completions of the text before point,
5495 treating it as a filename.
5497 .B complete\-username (M\-~)
5498 Attempt completion on the text before point, treating
5501 .B possible\-username\-completions (C\-x ~)
5502 List the possible completions of the text before point,
5503 treating it as a username.
5505 .B complete\-variable (M\-$)
5506 Attempt completion on the text before point, treating
5507 it as a shell variable.
5509 .B possible\-variable\-completions (C\-x $)
5510 List the possible completions of the text before point,
5511 treating it as a shell variable.
5513 .B complete\-hostname (M\-@)
5514 Attempt completion on the text before point, treating
5517 .B possible\-hostname\-completions (C\-x @)
5518 List the possible completions of the text before point,
5519 treating it as a hostname.
5521 .B complete\-command (M\-!)
5522 Attempt completion on the text before point, treating
5523 it as a command name. Command completion attempts to
5524 match the text against aliases, reserved words, shell
5525 functions, shell builtins, and finally executable filenames,
5528 .B possible\-command\-completions (C\-x !)
5529 List the possible completions of the text before point,
5530 treating it as a command name.
5532 .B dynamic\-complete\-history (M\-TAB)
5533 Attempt completion on the text before point, comparing
5534 the text against lines from the history list for possible
5538 Attempt menu completion on the text before point, comparing
5539 the text against lines from the history list for possible
5542 .B complete\-into\-braces (M\-{)
5543 Perform filename completion and insert the list of possible completions
5544 enclosed within braces so the list is available to the shell (see
5552 .B start\-kbd\-macro (C\-x (\^)
5553 Begin saving the characters typed into the current keyboard macro.
5555 .B end\-kbd\-macro (C\-x )\^)
5556 Stop saving the characters typed into the current keyboard macro
5557 and store the definition.
5559 .B call\-last\-kbd\-macro (C\-x e)
5560 Re-execute the last keyboard macro defined, by making the characters
5561 in the macro appear as if typed at the keyboard.
5567 .B re\-read\-init\-file (C\-x C\-r)
5568 Read in the contents of the \fIinputrc\fP file, and incorporate
5569 any bindings or variable assignments found there.
5572 Abort the current editing command and
5573 ring the terminal's bell (subject to the setting of
5576 .B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
5577 If the metafied character \fIx\fP is lowercase, run the command
5578 that is bound to the corresponding uppercase character.
5580 .B prefix\-meta (ESC)
5581 Metafy the next character typed.
5588 .B undo (C\-_, C\-x C\-u)
5589 Incremental undo, separately remembered for each line.
5591 .B revert\-line (M\-r)
5592 Undo all changes made to this line. This is like executing the
5594 command enough times to return the line to its initial state.
5596 .B tilde\-expand (M\-&)
5597 Perform tilde expansion on the current word.
5599 .B set\-mark (C\-@, M\-<space>)
5600 Set the mark to the point. If a
5601 numeric argument is supplied, the mark is set to that position.
5603 .B exchange\-point\-and\-mark (C\-x C\-x)
5604 Swap the point with the mark. The current cursor position is set to
5605 the saved position, and the old cursor position is saved as the mark.
5607 .B character\-search (C\-])
5608 A character is read and point is moved to the next occurrence of that
5609 character. A negative count searches for previous occurrences.
5611 .B character\-search\-backward (M\-C\-])
5612 A character is read and point is moved to the previous occurrence of that
5613 character. A negative count searches for subsequent occurrences.
5615 .B insert\-comment (M\-#)
5616 Without a numeric argument, the value of the readline
5618 variable is inserted at the beginning of the current line.
5619 If a numeric argument is supplied, this command acts as a toggle: if
5620 the characters at the beginning of the line do not match the value
5621 of \fBcomment\-begin\fP, the value is inserted, otherwise
5622 the characters in \fBcomment-begin\fP are deleted from the beginning of
5624 In either case, the line is accepted as if a newline had been typed.
5625 The default value of
5626 \fBcomment\-begin\fP causes this command to make the current line
5628 If a numeric argument causes the comment character to be removed, the line
5629 will be executed by the shell.
5631 .B glob\-complete\-word (M\-g)
5632 The word before point is treated as a pattern for pathname expansion,
5633 with an asterisk implicitly appended. This pattern is used to
5634 generate a list of matching file names for possible completions.
5636 .B glob\-expand\-word (C\-x *)
5637 The word before point is treated as a pattern for pathname expansion,
5638 and the list of matching file names is inserted, replacing the word.
5639 If a numeric argument is supplied, an asterisk is appended before
5642 .B glob\-list\-expansions (C\-x g)
5643 The list of expansions that would have been generated by
5644 .B glob\-expand\-word
5645 is displayed, and the line is redrawn.
5646 If a numeric argument is supplied, an asterisk is appended before
5650 Print all of the functions and their key bindings to the
5651 readline output stream. If a numeric argument is supplied,
5652 the output is formatted in such a way that it can be made part
5653 of an \fIinputrc\fP file.
5656 Print all of the settable readline variables and their values to the
5657 readline output stream. If a numeric argument is supplied,
5658 the output is formatted in such a way that it can be made part
5659 of an \fIinputrc\fP file.
5662 Print all of the readline key sequences bound to macros and the
5663 strings they output. If a numeric argument is supplied,
5664 the output is formatted in such a way that it can be made part
5665 of an \fIinputrc\fP file.
5667 .B display\-shell\-version (C\-x C\-v)
5668 Display version information about the current instance of
5671 .SS Programmable Completion
5673 When word completion is attempted for an argument to a command for
5674 which a completion specification (a \fIcompspec\fP) has been defined
5675 using the \fBcomplete\fP builtin (see
5677 .B "SHELL BUILTIN COMMANDS"
5678 below), the programmable completion facilities are invoked.
5680 First, the command name is identified.
5681 If a compspec has been defined for that command, the
5682 compspec is used to generate the list of possible completions for the word.
5683 If the command word is a full pathname, a compspec for the full
5684 pathname is searched for first.
5685 If no compspec is found for the full pathname, an attempt is made to
5686 find a compspec for the portion following the final slash.
5688 Once a compspec has been found, it is used to generate the list of
5690 If a compspec is not found, the default \fBbash\fP completion as
5691 described above under \fBCompleting\fP is performed.
5693 First, the actions specified by the compspec are used.
5694 Only matches which are prefixed by the word being completed are
5700 option is used for filename or directory name completion, the shell
5704 is used to filter the matches.
5706 Any completions specified by a filename expansion pattern to the
5707 \fB\-G\fP option are generated next.
5708 The words generated by the pattern need not match the word
5713 shell variable is not used to filter the matches, but the
5718 Next, the string specified as the argument to the \fB\-W\fP option
5720 The string is first split using the characters in the
5723 special variable as delimiters.
5724 Shell quoting is honored.
5725 Each word is then expanded using
5726 brace expansion, tilde expansion, parameter and variable expansion,
5727 command substitution, and arithmetic expansion,
5728 as described above under
5731 The results are split using the rules described above under
5732 \fBWord Splitting\fP.
5733 The results of the expansion are prefix-matched against the word being
5734 completed, and the matching words become the possible completions.
5736 After these matches have been generated, any shell function or command
5737 specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
5738 When the command or function is invoked, the
5748 variables are assigned values as described above under
5749 \fBShell Variables\fP.
5750 If a shell function is being invoked, the
5756 variables are also set.
5757 When the function or command is invoked, the first argument is the
5758 name of the command whose arguments are being completed, the
5759 second argument is the word being completed, and the third argument
5760 is the word preceding the word being completed on the current command line.
5761 No filtering of the generated completions against the word being completed
5762 is performed; the function or command has complete freedom in generating
5765 Any function specified with \fB\-F\fP is invoked first.
5766 The function may use any of the shell facilities, including the
5767 \fBcompgen\fP builtin described below, to generate the matches.
5768 It must put the possible completions in the
5773 Next, any command specified with the \fB\-C\fP option is invoked
5774 in an environment equivalent to command substitution.
5775 It should print a list of completions, one per line, to the
5777 Backslash may be used to escape a newline, if necessary.
5779 After all of the possible completions are generated, any filter
5780 specified with the \fB\-X\fP option is applied to the list.
5781 The filter is a pattern as used for pathname expansion; a \fB&\fP
5782 in the pattern is replaced with the text of the word being completed.
5783 A literal \fB&\fP may be escaped with a backslash; the backslash
5784 is removed before attempting a match.
5785 Any completion that matches the pattern will be removed from the list.
5786 A leading \fB!\fP negates the pattern; in this case any completion
5787 not matching the pattern will be removed.
5789 Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
5790 options are added to each member of the completion list, and the result is
5791 returned to the readline completion code as the list of possible
5794 If the previously-applied actions do not generate any matches, and the
5795 \fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
5796 compspec was defined, directory name completion is attempted.
5798 If the \fB\-o plusdirs\fP option was supplied to \fBcomplete\fP when the
5799 compspec was defined, directory name completion is attempted and any
5800 matches are added to the results of the other actions.
5802 By default, if a compspec is found, whatever it generates is returned
5803 to the completion code as the full set of possible completions.
5804 The default \fBbash\fP completions are not attempted, and the readline
5805 default of filename completion is disabled.
5806 If the \fB\-o bashdefault\fP option was supplied to \fBcomplete\fP when
5807 the compspec was defined, the \fBbash\fP default completions are attempted
5808 if the compspec generates no matches.
5809 If the \fB\-o default\fP option was supplied to \fBcomplete\fP when the
5810 compspec was defined, readline's default completion will be performed
5811 if the compspec (and, if attempted, the default \fBbash\fP completions)
5812 generate no matches.
5814 When a compspec indicates that directory name completion is desired,
5815 the programmable completion functions force readline to append a slash
5816 to completed names which are symbolic links to directories, subject to
5817 the value of the \fBmark\-directories\fP readline variable, regardless
5818 of the setting of the \fBmark-symlinked\-directories\fP readline variable.
5824 builtin is enabled, the shell provides access to the
5825 \fIcommand history\fP,
5826 the list of commands previously typed.
5827 The value of the \fBHISTSIZE\fP variable is used as the
5828 number of commands to save in a history list.
5829 The text of the last
5832 commands (default 500) is saved. The shell
5833 stores each command in the history list prior to parameter and
5834 variable expansion (see
5837 above) but after history expansion is performed, subject to the
5838 values of the shell variables
5845 On startup, the history is initialized from the file named by
5849 (default \fI~/.bash_history\fP).
5850 The file named by the value of
5853 is truncated, if necessary, to contain no more than
5854 the number of lines specified by the value of
5857 When the history file is read,
5858 lines beginning with the history comment character followed immediately
5859 by a digit are interpreted as timestamps for the preceding history line.
5860 These timestamps are optionally displayed depending on the value of the
5864 When an interactive shell exits, the last
5867 lines are copied from the history list to
5872 shell option is enabled
5873 (see the description of
5877 .B "SHELL BUILTIN COMMANDS"
5878 below), the lines are appended to the history file,
5879 otherwise the history file is overwritten.
5883 is unset, or if the history file is unwritable, the history is
5888 variable is set, time stamps are written to the history file, marked
5889 with the history comment character, so
5890 they may be preserved across shell sessions.
5891 This uses the history comment character to distinguish timestamps from
5892 other history lines.
5893 After saving the history, the history file is truncated
5894 to contain no more than
5900 is not set, no truncation is performed.
5906 .B SHELL BUILTIN COMMANDS
5907 below) may be used to list or edit and re-execute a portion of
5911 builtin may be used to display or modify the history list and
5912 manipulate the history file.
5913 When using command-line editing, search commands
5914 are available in each editing mode that provide access to the
5917 The shell allows control over which commands are saved on the history
5924 variables may be set to cause the shell to save only a subset of the
5928 shell option, if enabled, causes the shell to attempt to save each
5929 line of a multi-line command in the same history entry, adding
5930 semicolons where necessary to preserve syntactic correctness.
5933 shell option causes the shell to save the command with embedded newlines
5934 instead of semicolons. See the description of the
5938 .B "SHELL BUILTIN COMMANDS"
5939 for information on setting and unsetting shell options.
5940 .SH "HISTORY EXPANSION"
5942 The shell supports a history expansion feature that
5943 is similar to the history expansion in
5945 This section describes what syntax features are available. This
5946 feature is enabled by default for interactive shells, and can be
5951 builtin command (see
5953 .B SHELL BUILTIN COMMANDS
5954 below). Non-interactive shells do not perform history expansion
5957 History expansions introduce words from the history list into
5958 the input stream, making it easy to repeat commands, insert the
5959 arguments to a previous command into the current input line, or
5960 fix errors in previous commands quickly.
5962 History expansion is performed immediately after a complete line
5963 is read, before the shell breaks it into words.
5964 It takes place in two parts.
5965 The first is to determine which line from the history list
5966 to use during substitution.
5967 The second is to select portions of that line for inclusion into
5969 The line selected from the history is the \fIevent\fP,
5970 and the portions of that line that are acted upon are \fIwords\fP.
5971 Various \fImodifiers\fP are available to manipulate the selected words.
5972 The line is broken into words in the same fashion as when reading input,
5973 so that several \fImetacharacter\fP-separated words surrounded by
5974 quotes are considered one word.
5975 History expansions are introduced by the appearance of the
5976 history expansion character, which is \^\fB!\fP\^ by default.
5977 Only backslash (\^\fB\e\fP\^) and single quotes can quote
5978 the history expansion character.
5980 Several characters inhibit history expansion if found immediately
5981 following the history expansion character, even if it is unquoted:
5982 space, tab, newline, carriage return, and \fB=\fP.
5983 If the \fBextglob\fP shell option is enabled, \fB(\fP will also
5986 Several shell options settable with the
5988 builtin may be used to tailor the behavior of history expansion.
5991 shell option is enabled (see the description of the
5995 is being used, history substitutions are not immediately passed to
5997 Instead, the expanded line is reloaded into the
5999 editing buffer for further modification.
6002 is being used, and the
6004 shell option is enabled, a failed history substitution will be reloaded
6007 editing buffer for correction.
6012 builtin command may be used to see what a history expansion will
6018 builtin may be used to add commands to the end of the history list
6019 without actually executing them, so that they are available for
6022 The shell allows control of the various characters used by the
6023 history expansion mechanism (see the description of
6026 .BR "Shell Variables" ).
6028 the history comment character to mark history timestamps when
6029 writing the history file.
6030 .SS Event Designators
6032 An event designator is a reference to a command line entry in the
6038 Start a history substitution, except when followed by a
6040 newline, carriage return, =
6041 or ( (when the \fBextglob\fP shell option is enabled using
6042 the \fBshopt\fP builtin).
6045 Refer to command line
6049 Refer to the current command line minus
6053 Refer to the previous command. This is a synonym for `!\-1'.
6056 Refer to the most recent command starting with
6059 .B !?\fIstring\fR\fB[?]\fR
6060 Refer to the most recent command containing
6062 The trailing \fB?\fP may be omitted if
6064 is followed immediately by a newline.
6066 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
6067 Quick substitution. Repeat the last command, replacing
6072 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
6073 (see \fBModifiers\fP below).
6076 The entire command line typed so far.
6078 .SS Word Designators
6080 Word designators are used to select desired words from the event.
6083 separates the event specification from the word designator.
6084 It may be omitted if the word designator begins with a
6091 Words are numbered from the beginning of the line,
6092 with the first word being denoted by 0 (zero).
6093 Words are inserted into the current line separated by single spaces.
6098 The zeroth word. For the shell, this is the command
6105 The first argument. That is, word 1.
6111 The word matched by the most recent `?\fIstring\fR?' search.
6114 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
6117 All of the words but the zeroth. This is a synonym
6118 for `\fI1\-$\fP'. It is not an error to use
6120 if there is just one
6121 word in the event; the empty string is returned in that case.
6124 Abbreviates \fIx\-$\fP.
6127 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
6130 If a word designator is supplied without an event specification, the
6131 previous command is used as the event.
6134 After the optional word designator, there may appear a sequence of
6135 one or more of the following modifiers, each preceded by a `:'.
6141 Remove a trailing file name component, leaving only the head.
6144 Remove all leading file name components, leaving the tail.
6147 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
6151 Remove all but the trailing suffix.
6154 Print the new command but do not execute it.
6157 Quote the substituted words, escaping further substitutions.
6160 Quote the substituted words as with
6162 but break into words at
6166 .B s/\fIold\fP/\fInew\fP/
6169 for the first occurrence of
6171 in the event line. Any delimiter can be used in place of /. The
6172 final delimiter is optional if it is the last character of the
6173 event line. The delimiter may be quoted in
6177 with a single backslash. If & appears in
6181 A single backslash will quote the &. If
6183 is null, it is set to the last
6185 substituted, or, if no previous history substitutions took place,
6189 .B !?\fIstring\fR\fB[?]\fR
6193 Repeat the previous substitution.
6196 Cause changes to be applied over the entire event line. This is
6197 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
6198 or `\fB:&\fP'. If used with
6199 `\fB:s\fP', any delimiter can be used
6200 in place of /, and the final delimiter is optional
6201 if it is the last character of the event line.
6202 An \fBa\fP may be used as a synonym for \fBg\fP.
6205 Apply the following `\fBs\fP' modifier once to each word in the event line.
6207 .SH "SHELL BUILTIN COMMANDS"
6208 .\" start of bash_builtins
6211 Unless otherwise noted, each builtin command documented in this
6212 section as accepting options preceded by
6216 to signify the end of the options.
6217 For example, the \fB:\fP, \fBtrue\fP, \fBfalse\fP, and \fBtest\fP builtins
6218 do not accept options.
6222 \fB:\fP [\fIarguments\fP]
6224 No effect; the command does nothing beyond expanding
6226 and performing any specified
6227 redirections. A zero exit code is returned.
6229 \fB .\| \fP \fIfilename\fP [\fIarguments\fP]
6232 \fBsource\fP \fIfilename\fP [\fIarguments\fP]
6234 Read and execute commands from
6237 shell environment and return the exit status of the last command
6242 does not contain a slash, file names in
6245 are used to find the directory containing
6247 The file searched for in
6250 need not be executable.
6251 When \fBbash\fP is not in \fIposix mode\fP, the current directory is
6252 searched if no file is found in
6259 builtin command is turned off, the
6263 If any \fIarguments\fP are supplied, they become the positional
6264 parameters when \fIfilename\fP is executed. Otherwise the positional
6265 parameters are unchanged.
6266 The return status is the status of the last command exited within
6267 the script (0 if no commands are executed), and false if
6269 is not found or cannot be read.
6271 \fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6272 \fBAlias\fP with no arguments or with the
6274 option prints the list of aliases in the form
6275 \fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
6276 When arguments are supplied, an alias is defined for
6277 each \fIname\fP whose \fIvalue\fP is given.
6278 A trailing space in \fIvalue\fP causes the next word to be
6279 checked for alias substitution when the alias is expanded.
6280 For each \fIname\fP in the argument list for which no \fIvalue\fP
6281 is supplied, the name and value of the alias is printed.
6282 \fBAlias\fP returns true unless a \fIname\fP is given for which
6283 no alias has been defined.
6285 \fBbg\fP [\fIjobspec\fP ...]
6286 Resume each suspended job \fIjobspec\fP in the background, as if it
6287 had been started with
6291 is not present, the shell's notion of the \fIcurrent job\fP is used.
6294 returns 0 unless run when job control is disabled or, when run with
6295 job control enabled, any specified \fIjobspec\fP was not found
6296 or was started without job control.
6298 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSV\fP]
6301 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
6303 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
6305 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
6307 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
6309 \fBbind\fP \fIreadline\-command\fP
6313 key and function bindings, bind a key sequence to a
6315 function or macro, or set a
6318 Each non-option argument is a command as it would appear in
6320 but each binding or command must be passed as a separate argument;
6321 e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'.
6322 Options, if supplied, have the following meanings:
6329 as the keymap to be affected by the subsequent bindings.
6333 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
6334 vi\-move, vi\-command\fP, and
6336 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
6337 equivalent to \fIemacs\-standard\fP.
6340 List the names of all \fBreadline\fP functions.
6343 Display \fBreadline\fP function names and bindings in such a way
6344 that they can be re-read.
6347 List current \fBreadline\fP function names and bindings.
6350 Display \fBreadline\fP key sequences bound to macros and the strings
6351 they output in such a way that they can be re-read.
6354 Display \fBreadline\fP key sequences bound to macros and the strings
6358 Display \fBreadline\fP variable names and values in such a way that they
6362 List current \fBreadline\fP variable names and values.
6364 .B \-f \fIfilename\fP
6365 Read key bindings from \fIfilename\fP.
6367 .B \-q \fIfunction\fP
6368 Query about which keys invoke the named \fIfunction\fP.
6370 .B \-u \fIfunction\fP
6371 Unbind all keys bound to the named \fIfunction\fP.
6374 Remove any current binding for \fIkeyseq\fP.
6376 .B \-x \fIkeyseq\fP:\fIshell\-command\fP
6377 Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
6379 When \fIshell\-command\fP is executed, the shell sets the
6381 variable to the contents of the \fBreadline\fP line buffer and the
6383 variable to the current location of the insertion point.
6384 If the executed command changes the value of
6387 .BR READLINE_POINT ,
6388 those new values will be reflected in the editing state.
6391 The return value is 0 unless an unrecognized option is given or an
6395 \fBbreak\fP [\fIn\fP]
6402 loop. If \fIn\fP is specified, break \fIn\fP levels.
6406 is greater than the number of enclosing loops, all enclosing loops
6408 The return value is 0 unless \fIn\fP is not greater than or equal to 1.
6410 \fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
6411 Execute the specified shell builtin, passing it
6413 and return its exit status.
6414 This is useful when defining a
6415 function whose name is the same as a shell builtin,
6416 retaining the functionality of the builtin within the function.
6417 The \fBcd\fP builtin is commonly redefined this way.
6418 The return status is false if
6420 is not a shell builtin command.
6422 \fBcaller\fP [\fIexpr\fP]
6423 Returns the context of any active subroutine call (a shell function or
6424 a script executed with the \fB.\fP or \fBsource\fP builtins.
6425 Without \fIexpr\fP, \fBcaller\fP displays the line number and source
6426 filename of the current subroutine call.
6427 If a non-negative integer is supplied as \fIexpr\fP, \fBcaller\fP
6428 displays the line number, subroutine name, and source file corresponding
6429 to that position in the current execution call stack. This extra
6430 information may be used, for example, to print a stack trace. The
6431 current frame is frame 0.
6432 The return value is 0 unless the shell is not executing a subroutine
6433 call or \fIexpr\fP does not correspond to a valid position in the
6436 \fBcd\fP [\fB\-L|-P\fP] [\fIdir\fP]
6437 Change the current directory to \fIdir\fP. The variable
6446 defines the search path for the directory containing
6448 Alternative directory names in
6451 are separated by a colon (:). A null directory name in
6454 is the same as the current directory, i.e., ``\fB.\fP''. If
6456 begins with a slash (/),
6462 option says to use the physical directory structure instead of
6463 following symbolic links (see also the
6467 builtin command); the
6469 option forces symbolic links to be followed. An argument of
6474 If a non-empty directory name from \fBCDPATH\fP is used, or if
6475 \fB\-\fP is the first argument, and the directory change is
6476 successful, the absolute pathname of the new working directory is
6477 written to the standard output.
6478 The return value is true if the directory was successfully changed;
6481 \fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
6486 suppressing the normal shell function lookup. Only builtin
6487 commands or commands found in the
6490 are executed. If the
6492 option is given, the search for
6494 is performed using a default value for
6496 that is guaranteed to find all of the standard utilities.
6501 option is supplied, a description of
6505 option causes a single word indicating the command or file name
6508 to be displayed; the
6510 option produces a more verbose description.
6515 option is supplied, the exit status is 0 if
6517 was found, and 1 if not. If neither option is supplied and
6518 an error occurred or
6520 cannot be found, the exit status is 127. Otherwise, the exit status of the
6522 builtin is the exit status of
6525 \fBcompgen\fP [\fIoption\fP] [\fIword\fP]
6526 Generate possible completion matches for \fIword\fP according to
6527 the \fIoption\fPs, which may be any option accepted by the
6529 builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
6530 the matches to the standard output.
6531 When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
6532 set by the programmable completion facilities, while available, will not
6535 The matches will be generated in the same way as if the programmable
6536 completion code had generated them directly from a completion specification
6537 with the same flags.
6538 If \fIword\fP is specified, only those completions matching \fIword\fP
6541 The return value is true unless an invalid option is supplied, or no
6542 matches were generated.
6544 \fBcomplete\fP [\fB\-abcdefgjksuv\fP] [\fB\-o\fP \fIcomp-option\fP] [\fB\-E\fP] [\fB\-A\fP \fIaction\fP] [\fB\-G\fP \fIglobpat\fP] [\fB\-W\fP \fIwordlist\fP] [\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP]
6546 [\fB\-X\fP \fIfilterpat\fP] [\fB\-P\fP \fIprefix\fP] [\fB\-S\fP \fIsuffix\fP] \fIname\fP [\fIname ...\fP]
6549 \fBcomplete\fP \fB\-pr\fP [\fB\-E\fP] [\fIname\fP ...]
6551 Specify how arguments to each \fIname\fP should be completed.
6552 If the \fB\-p\fP option is supplied, or if no options are supplied,
6553 existing completion specifications are printed in a way that allows
6554 them to be reused as input.
6555 The \fB\-r\fP option removes a completion specification for
6556 each \fIname\fP, or, if no \fIname\fPs are supplied, all
6557 completion specifications.
6558 The \fB\-E\fP option indicates that the remaining options and actions should
6559 apply to ``empty'' command completion; that is, completion attempted on a
6562 The process of applying these completion specifications when word completion
6563 is attempted is described above under \fBProgrammable Completion\fP.
6565 Other options, if specified, have the following meanings.
6566 The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
6567 (and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
6568 should be quoted to protect them from expansion before the
6574 \fB\-o\fP \fIcomp-option\fP
6575 The \fIcomp-option\fP controls several aspects of the compspec's behavior
6576 beyond the simple generation of completions.
6577 \fIcomp-option\fP may be one of:
6581 Perform the rest of the default \fBbash\fP completions if the compspec
6582 generates no matches.
6585 Use readline's default filename completion if the compspec generates
6589 Perform directory name completion if the compspec generates no matches.
6592 Tell readline that the compspec generates filenames, so it can perform any
6593 filename\-specific processing (like adding a slash to directory names,
6594 quoting special characters, or suppressing trailing spaces).
6595 Intended to be used with shell functions.
6598 Tell readline not to append a space (the default) to words completed at
6599 the end of the line.
6602 After any matches defined by the compspec are generated,
6603 directory name completion is attempted and any
6604 matches are added to the results of the other actions.
6607 \fB\-A\fP \fIaction\fP
6608 The \fIaction\fP may be one of the following to generate a list of possible
6613 Alias names. May also be specified as \fB\-a\fP.
6616 Array variable names.
6619 \fBReadline\fP key binding names.
6622 Names of shell builtin commands. May also be specified as \fB\-b\fP.
6625 Command names. May also be specified as \fB\-c\fP.
6628 Directory names. May also be specified as \fB\-d\fP.
6631 Names of disabled shell builtins.
6634 Names of enabled shell builtins.
6637 Names of exported shell variables. May also be specified as \fB\-e\fP.
6640 File names. May also be specified as \fB\-f\fP.
6643 Names of shell functions.
6646 Group names. May also be specified as \fB\-g\fP.
6649 Help topics as accepted by the \fBhelp\fP builtin.
6652 Hostnames, as taken from the file specified by the
6658 Job names, if job control is active. May also be specified as \fB\-j\fP.
6661 Shell reserved words. May also be specified as \fB\-k\fP.
6664 Names of running jobs, if job control is active.
6667 Service names. May also be specified as \fB\-s\fP.
6670 Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
6673 Shell option names as accepted by the \fBshopt\fP builtin.
6679 Names of stopped jobs, if job control is active.
6682 User names. May also be specified as \fB\-u\fP.
6685 Names of all shell variables. May also be specified as \fB\-v\fP.
6688 \fB\-G\fP \fIglobpat\fP
6689 The filename expansion pattern \fIglobpat\fP is expanded to generate
6690 the possible completions.
6692 \fB\-W\fP \fIwordlist\fP
6693 The \fIwordlist\fP is split using the characters in the
6696 special variable as delimiters, and each resultant word is expanded.
6697 The possible completions are the members of the resultant list which
6698 match the word being completed.
6700 \fB\-C\fP \fIcommand\fP
6701 \fIcommand\fP is executed in a subshell environment, and its output is
6702 used as the possible completions.
6704 \fB\-F\fP \fIfunction\fP
6705 The shell function \fIfunction\fP is executed in the current shell
6707 When it finishes, the possible completions are retrieved from the value
6713 \fB\-X\fP \fIfilterpat\fP
6714 \fIfilterpat\fP is a pattern as used for filename expansion.
6715 It is applied to the list of possible completions generated by the
6716 preceding options and arguments, and each completion matching
6717 \fIfilterpat\fP is removed from the list.
6718 A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
6719 case, any completion not matching \fIfilterpat\fP is removed.
6721 \fB\-P\fP \fIprefix\fP
6722 \fIprefix\fP is added at the beginning of each possible completion
6723 after all other options have been applied.
6725 \fB\-S\fP \fIsuffix\fP
6726 \fIsuffix\fP is appended to each possible completion
6727 after all other options have been applied.
6730 The return value is true unless an invalid option is supplied, an option
6731 other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
6732 argument, an attempt is made to remove a completion specification for
6733 a \fIname\fP for which no specification exists, or
6734 an error occurs adding a completion specification.
6737 \fBcompopt\fP [\fB\-o\fP \fIoption\fP] [\fB+o\fP \fIoption\fP] [\fIname\fP]
6738 Modify completion options for each \fIname\fP according to the
6739 \fIoption\fPs, or for the
6740 currently-execution completion if no \fIname\fPs are supplied.
6741 If no \fIoption\fPs are given, display the completion options for each
6742 \fIname\fP or the current completion.
6743 The possible values of \fIoption\fP are those valid for the \fBcomplete\fP
6744 builtin described above.
6746 The return value is true unless an invalid option is supplied, an attempt
6747 is made to modify the options for a \fIname\fP for which no completion
6748 specification exists, or an output error occurs.
6750 \fBcontinue\fP [\fIn\fP]
6751 Resume the next iteration of the enclosing
6760 is specified, resume at the \fIn\fPth enclosing loop.
6764 is greater than the number of enclosing loops, the last enclosing loop
6765 (the ``top-level'' loop) is resumed.
6766 The return value is 0 unless \fIn\fP is not greater than or equal to 1.
6768 \fBdeclare\fP [\fB\-aAfFilrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6771 \fBtypeset\fP [\fB\-aAfFilrtux\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
6773 Declare variables and/or give them attributes.
6774 If no \fIname\fPs are given then display the values of variables.
6777 option will display the attributes and values of each
6781 is used with \fIname\fP arguments, additional options are ignored.
6784 is supplied without \fIname\fP arguments, it will display the attributes
6785 and values of all variables having the attributes specified by the
6787 If no other options are supplied with \fB\-p\fP, \fBdeclare\fP will display
6788 the attributes and values of all shell variables. The \fB\-f\fP option
6789 will restrict the display to shell functions.
6792 option inhibits the display of function definitions; only the
6793 function name and attributes are printed.
6794 If the \fBextdebug\fP shell option is enabled using \fBshopt\fP,
6795 the source file name and line number where the function is defined
6796 are displayed as well. The
6800 The following options can
6801 be used to restrict output to variables with the specified attribute or
6802 to give variables attributes:
6807 Each \fIname\fP is an indexed array variable (see
6812 Each \fIname\fP is an associative array variable (see
6817 Use function names only.
6820 The variable is treated as an integer; arithmetic evaluation (see
6822 .B "ARITHMETIC EVALUATION" ") "
6823 is performed when the variable is assigned a value.
6826 When the variable is assigned a value, all upper-case characters are
6827 converted to lower-case.
6828 The upper-case attribute is disabled.
6831 Make \fIname\fPs readonly. These names cannot then be assigned values
6832 by subsequent assignment statements or unset.
6835 Give each \fIname\fP the \fItrace\fP attribute.
6836 Traced functions inherit the \fBDEBUG\fP and \fBRETURN\fP traps from
6838 The trace attribute has no special meaning for variables.
6841 When the variable is assigned a value, all lower-case characters are
6842 converted to upper-case.
6843 The lower-case attribute is disabled.
6846 Mark \fIname\fPs for export to subsequent commands via the environment.
6849 Using `+' instead of `\-'
6850 turns off the attribute instead,
6851 with the exceptions that \fB+a\fP
6852 may not be used to destroy an array variable and \fB+r\fB will not
6853 remove the readonly attribute.
6854 When used in a function,
6856 \fIname\fP local, as with the
6859 If a variable name is followed by =\fIvalue\fP, the value of
6860 the variable is set to \fIvalue\fP.
6861 The return value is 0 unless an invalid option is encountered,
6862 an attempt is made to define a function using
6863 .if n ``\-f foo=bar'',
6864 .if t \f(CW\-f foo=bar\fP,
6865 an attempt is made to assign a value to a readonly variable,
6866 an attempt is made to assign a value to an array variable without
6867 using the compound assignment syntax (see
6869 above), one of the \fInames\fP is not a valid shell variable name,
6870 an attempt is made to turn off readonly status for a readonly variable,
6871 an attempt is made to turn off array status for an array variable,
6872 or an attempt is made to display a non-existent function with \fB\-f\fP.
6875 .B dirs [+\fIn\fP] [\-\fIn\fP] [\fB\-cplv\fP]
6876 Without options, displays the list of currently remembered directories.
6877 The default display is on a single line with directory names separated
6879 Directories are added to the list with the
6883 command removes entries from the list.
6888 Displays the \fIn\fPth entry counting from the left of the list
6891 when invoked without options, starting with zero.
6894 Displays the \fIn\fPth entry counting from the right of the list
6897 when invoked without options, starting with zero.
6900 Clears the directory stack by deleting all of the entries.
6903 Produces a longer listing; the default listing format uses a
6904 tilde to denote the home directory.
6907 Print the directory stack with one entry per line.
6910 Print the directory stack with one entry per line,
6911 prefixing each entry with its index in the stack.
6914 The return value is 0 unless an
6915 invalid option is supplied or \fIn\fP indexes beyond the end
6916 of the directory stack.
6919 \fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ...]
6920 Without options, each
6922 is removed from the table of active jobs.
6925 is not present, and neither \fB\-a\fB nor \fB\-r\fP is supplied,
6926 the shell's notion of the \fIcurrent job\fP is used.
6927 If the \fB\-h\fP option is given, each
6929 is not removed from the table, but is marked so that
6932 is not sent to the job if the shell receives a
6937 is present, and neither the
6941 option is supplied, the \fIcurrent job\fP is used.
6946 option means to remove or mark all jobs; the
6950 argument restricts operation to running jobs.
6951 The return value is 0 unless a
6953 does not specify a valid job.
6955 \fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
6956 Output the \fIarg\fPs, separated by spaces, followed by a newline.
6957 The return status is always 0.
6958 If \fB\-n\fP is specified, the trailing newline is
6959 suppressed. If the \fB\-e\fP option is given, interpretation of
6960 the following backslash-escaped characters is enabled. The
6962 option disables the interpretation of these escape characters,
6963 even on systems where they are interpreted by default.
6964 The \fBxpg_echo\fP shell option may be used to
6965 dynamically determine whether or not \fBecho\fP expands these
6966 escape characters by default.
6968 does not interpret \fB\-\-\fP to mean the end of options.
6970 interprets the following escape sequences:
6981 suppress further output
7005 the eight-bit character whose value is the octal value \fInnn\fP
7006 (zero to three octal digits)
7009 the eight-bit character whose value is the hexadecimal value \fIHH\fP
7010 (one or two hex digits)
7014 \fBenable\fP [\fB\-a\fP] [\fB\-dnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
7015 Enable and disable builtin shell commands.
7016 Disabling a builtin allows a disk command which has the same name
7017 as a shell builtin to be executed without specifying a full pathname,
7018 even though the shell normally searches for builtins before disk commands.
7019 If \fB\-n\fP is used, each \fIname\fP
7020 is disabled; otherwise,
7021 \fInames\fP are enabled. For example, to use the
7023 binary found via the
7026 instead of the shell builtin version, run
7027 .if t \f(CWenable -n test\fP.
7028 .if n ``enable -n test''.
7031 option means to load the new builtin command
7035 on systems that support dynamic loading. The
7037 option will delete a builtin previously loaded with
7039 If no \fIname\fP arguments are given, or if the
7041 option is supplied, a list of shell builtins is printed.
7042 With no other option arguments, the list consists of all enabled
7044 If \fB\-n\fP is supplied, only disabled builtins are printed.
7045 If \fB\-a\fP is supplied, the list printed includes all builtins, with an
7046 indication of whether or not each is enabled.
7047 If \fB\-s\fP is supplied, the output is restricted to the POSIX
7048 \fIspecial\fP builtins.
7049 The return value is 0 unless a
7051 is not a shell builtin or there is an error loading a new builtin
7052 from a shared object.
7054 \fBeval\fP [\fIarg\fP ...]
7055 The \fIarg\fPs are read and concatenated together into a single
7056 command. This command is then read and executed by the shell, and
7057 its exit status is returned as the value of
7061 or only null arguments,
7065 \fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
7068 is specified, it replaces the shell.
7069 No new process is created. The
7071 become the arguments to \fIcommand\fP.
7075 the shell places a dash at the beginning of the zeroth argument passed to
7083 to be executed with an empty environment. If
7085 is supplied, the shell passes
7087 as the zeroth argument to the executed command. If
7089 cannot be executed for some reason, a non-interactive shell exits,
7090 unless the shell option
7092 is enabled, in which case it returns failure.
7093 An interactive shell returns failure if the file cannot be executed.
7096 is not specified, any redirections take effect in the current shell,
7097 and the return status is 0. If there is a redirection error, the
7100 \fBexit\fP [\fIn\fP]
7101 Cause the shell to exit
7102 with a status of \fIn\fP. If
7104 is omitted, the exit status
7105 is that of the last command executed.
7109 is executed before the shell terminates.
7111 \fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
7118 are marked for automatic export to the environment of
7119 subsequently executed commands. If the
7127 are given, or if the
7129 option is supplied, a list
7130 of all names that are exported in this shell is printed.
7133 option causes the export property to be removed from each
7135 If a variable name is followed by =\fIword\fP, the value of
7136 the variable is set to \fIword\fP.
7138 returns an exit status of 0 unless an invalid option is
7140 one of the \fInames\fP is not a valid shell variable name, or
7144 that is not a function.
7146 \fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-lnr\fP] [\fIfirst\fP] [\fIlast\fP]
7149 \fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
7151 Fix Command. In the first form, a range of commands from
7155 is selected from the history list.
7159 may be specified as a string (to locate the last command beginning
7160 with that string) or as a number (an index into the history list,
7161 where a negative number is used as an offset from the current
7164 is not specified it is set to
7165 the current command for listing (so that
7166 .if n ``fc \-l \-10''
7167 .if t \f(CWfc \-l \-10\fP
7168 prints the last 10 commands) and to
7173 is not specified it is set to the previous
7174 command for editing and \-16 for listing.
7179 the command numbers when listing. The
7181 option reverses the order of
7182 the commands. If the
7185 the commands are listed on
7186 standard output. Otherwise, the editor given by
7189 on a file containing those commands. If
7195 variable is used, and
7202 is not set. If neither variable is set,
7204 is used. When editing is complete, the edited commands are
7205 echoed and executed.
7207 In the second form, \fIcommand\fP is re-executed after each instance
7208 of \fIpat\fP is replaced by \fIrep\fP.
7209 A useful alias to use with this is
7210 .if n ``r="fc -s"'',
7211 .if t \f(CWr='fc \-s'\fP,
7215 runs the last command beginning with
7221 re-executes the last command.
7223 If the first form is used, the return value is 0 unless an invalid
7224 option is encountered or
7228 specify history lines out of range.
7231 option is supplied, the return value is the value of the last
7232 command executed or failure if an error occurs with the temporary
7233 file of commands. If the second form is used, the return status
7234 is that of the command re-executed, unless
7236 does not specify a valid history line, in which case
7240 \fBfg\fP [\fIjobspec\fP]
7243 in the foreground, and make it the current job.
7246 is not present, the shell's notion of the \fIcurrent job\fP is used.
7247 The return value is that of the command placed into the foreground,
7248 or failure if run when job control is disabled or, when run with
7249 job control enabled, if
7251 does not specify a valid job or
7253 specifies a job that was started without job control.
7255 \fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
7257 is used by shell procedures to parse positional parameters.
7259 contains the option characters to be recognized; if a character
7260 is followed by a colon, the option is expected to have an
7261 argument, which should be separated from it by white space.
7262 The colon and question mark characters may not be used as
7264 Each time it is invoked,
7266 places the next option in the shell variable
7270 if it does not exist,
7271 and the index of the next argument to be processed into the
7277 is initialized to 1 each time the shell or a shell script
7278 is invoked. When an option requires an argument,
7280 places that argument into the variable
7283 The shell does not reset
7286 automatically; it must be manually reset between multiple
7289 within the same shell invocation if a new set of parameters
7292 When the end of options is encountered, \fBgetopts\fP exits with a
7293 return value greater than zero.
7294 \fBOPTIND\fP is set to the index of the first non-option argument,
7295 and \fBname\fP is set to ?.
7298 normally parses the positional parameters, but if more arguments are
7302 parses those instead.
7305 can report errors in two ways. If the first character of
7309 error reporting is used. In normal operation diagnostic messages
7310 are printed when invalid options or missing option arguments are
7315 is set to 0, no error messages will be displayed, even if the first
7320 If an invalid option is seen,
7325 prints an error message and unsets
7331 the option character found is placed in
7334 and no diagnostic message is printed.
7336 If a required argument is not found, and
7339 a question mark (\^\fB?\fP\^) is placed in
7343 is unset, and a diagnostic message is printed.
7346 is silent, then a colon (\^\fB:\fP\^) is placed in
7351 is set to the option character found.
7354 returns true if an option, specified or unspecified, is found.
7355 It returns false if the end of options is encountered or an
7358 \fBhash\fP [\fB\-lr\fP] [\fB\-p\fP \fIfilename\fP] [\fB\-dt\fP] [\fIname\fP]
7361 the full file name of the command is determined by searching
7367 option is supplied, no path search is performed, and
7369 is used as the full file name of the command.
7372 option causes the shell to forget all
7373 remembered locations.
7376 option causes the shell to forget the remembered location of each \fIname\fP.
7379 option is supplied, the full pathname to which each \fIname\fP corresponds
7380 is printed. If multiple \fIname\fP arguments are supplied with \fB\-t\fP,
7381 the \fIname\fP is printed before the hashed full pathname.
7384 option causes output to be displayed in a format that may be reused as input.
7385 If no arguments are given, or if only \fB\-l\fP is supplied,
7386 information about remembered commands is printed.
7387 The return status is true unless a
7389 is not found or an invalid option is supplied.
7391 \fBhelp\fP [\fB\-dms\fP] [\fIpattern\fP]
7392 Display helpful information about builtin commands. If
7396 gives detailed help on all commands matching
7398 otherwise help for all the builtins and shell control structures
7404 Display a short description of each \fIpattern\fP
7407 Display the description of each \fIpattern\fP in a manpage-like format
7410 Display only a short usage synopsis for each \fIpattern\fP
7413 The return status is 0 unless no command matches
7416 \fBhistory [\fIn\fP]
7419 \fBhistory\fP \fB\-c\fP
7421 \fBhistory \-d\fP \fIoffset\fP
7423 \fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
7425 \fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
7427 \fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
7429 With no options, display the command
7430 history list with line numbers. Lines listed
7433 have been modified. An argument of
7438 If the shell variable \fBHISTTIMEFORMAT\fP is set and not null,
7439 it is used as a format string for \fIstrftime\fP(3) to display
7440 the time stamp associated with each displayed history entry.
7441 No intervening blank is printed between the formatted time stamp
7442 and the history line.
7443 If \fIfilename\fP is supplied, it is used as the
7444 name of the history file; if not, the value of
7447 is used. Options, if supplied, have the following meanings:
7452 Clear the history list by deleting all the entries.
7454 \fB\-d\fP \fIoffset\fP
7455 Delete the history entry at position \fIoffset\fP.
7458 Append the ``new'' history lines (history lines entered since the
7459 beginning of the current \fBbash\fP session) to the history file.
7462 Read the history lines not already read from the history
7463 file into the current history list. These are lines
7464 appended to the history file since the beginning of the
7465 current \fBbash\fP session.
7468 Read the contents of the history file
7469 and use them as the current history.
7472 Write the current history to the history file, overwriting the
7473 history file's contents.
7476 Perform history substitution on the following \fIargs\fP and display
7477 the result on the standard output.
7478 Does not store the results in the history list.
7479 Each \fIarg\fP must be quoted to disable normal history expansion.
7484 in the history list as a single entry. The last command in the
7485 history list is removed before the
7490 If the \fBHISTTIMEFORMAT\fP is set, the time stamp information
7491 associated with each history entry is written to the history file,
7492 marked with the history comment character.
7493 When the history file is read, lines beginning with the history
7494 comment character followed immediately by a digit are interpreted
7495 as timestamps for the previous history line.
7496 The return value is 0 unless an invalid option is encountered, an
7497 error occurs while reading or writing the history file, an invalid
7498 \fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
7499 history expansion supplied as an argument to \fB\-p\fP fails.
7502 \fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
7505 \fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
7507 The first form lists the active jobs. The options have the following
7514 in addition to the normal information.
7517 List only the process ID of the job's process group
7521 Display information only about jobs that have changed status since
7522 the user was last notified of their status.
7525 Restrict output to running jobs.
7528 Restrict output to stopped jobs.
7533 is given, output is restricted to information about that job.
7534 The return status is 0 unless an invalid option is encountered
7549 with the corresponding process group ID, and executes
7553 returning its exit status.
7556 \fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
7559 \fBkill\fP \fB\-l\fP [\fIsigspec\fP | \fIexit_status\fP]
7561 Send the signal named by
7565 to the processes named by
7570 is either a case-insensitive signal name such as
7573 (with or without the
7576 prefix) or a signal number;
7581 is not present, then
7587 lists the signal names.
7588 If any arguments are supplied when
7590 is given, the names of the signals corresponding to the arguments are
7591 listed, and the return status is 0.
7592 The \fIexit_status\fP argument to
7594 is a number specifying either a signal number or the exit status of
7595 a process terminated by a signal.
7597 returns true if at least one signal was successfully sent, or false
7598 if an error occurs or an invalid option is encountered.
7600 \fBlet\fP \fIarg\fP [\fIarg\fP ...]
7603 is an arithmetic expression to be evaluated (see
7605 .BR "ARITHMETIC EVALUATION" ).
7610 returns 1; 0 is returned otherwise.
7612 \fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ...]
7613 For each argument, a local variable named
7615 is created, and assigned
7617 The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
7620 is used within a function, it causes the variable
7622 to have a visible scope restricted to that function and its children.
7625 writes a list of local variables to the standard output. It is
7628 when not within a function. The return status is 0 unless
7630 is used outside a function, an invalid
7633 \fIname\fP is a readonly variable.
7638 \fBmapfile\fP [\fB\-n\fP \fIcount\fP] [\fB\-O\fP \fIorigin\fP] [\fB\-s\fP \fIcount\fP] [\fB\-t\fP] [\fB\-u\fP \fIfd\fP] [\fB\-C\fP \fIcallback\fP] [\fB\-c\fP \fIquantum\fP] [\fIarray\fP]
7639 Read lines from the standard input into array variable
7641 or from file descriptor
7646 The variable \fBMAPFILE\fP is the default \fIarray\fP.
7647 Options, if supplied, have the following meanings:
7654 lines. If \fIcount\fP is 0, all lines are copied.
7661 The default index is 0.
7664 Discard the first \fIcount\fP lines read.
7667 Remove a trailing line from each line read.
7670 Read lines from file descriptor \fIfd\fP instead of the standard input.
7675 each time \fIquantum\fP lines are read. The \fB\-c\fP option specifies
7679 Specify the number of lines read between each call to
7685 is specified without
7687 the default quantum is 5000.
7689 If not supplied with an explicit origin, \fBmapfile\fP will clear \fIarray\fP
7690 before assigning to it.
7692 \fBmapfile\fP returns successfully unless an invalid option or option
7693 argument is supplied, or \fIarray\fP is invalid or unassignable.
7696 \fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
7697 Removes entries from the directory stack. With no arguments,
7698 removes the top directory from the stack, and performs a
7700 to the new top directory.
7701 Arguments, if supplied, have the following meanings:
7706 Suppresses the normal change of directory when removing directories
7707 from the stack, so that only the stack is manipulated.
7710 Removes the \fIn\fPth entry counting from the left of the list
7713 starting with zero. For example:
7715 .if t \f(CWpopd +0\fP
7716 removes the first directory,
7718 .if t \f(CWpopd +1\fP
7722 Removes the \fIn\fPth entry counting from the right of the list
7725 starting with zero. For example:
7727 .if t \f(CWpopd -0\fP
7728 removes the last directory,
7730 .if t \f(CWpopd -1\fP
7736 command is successful, a
7738 is performed as well, and the return status is 0.
7740 returns false if an invalid option is encountered, the directory stack
7741 is empty, a non-existent directory stack entry is specified, or the
7742 directory change fails.
7745 \fBprintf\fP [\fB\-v\fP \fIvar\fP] \fIformat\fP [\fIarguments\fP]
7746 Write the formatted \fIarguments\fP to the standard output under the
7747 control of the \fIformat\fP.
7748 The \fIformat\fP is a character string which contains three types of objects:
7749 plain characters, which are simply copied to standard output, character
7750 escape sequences, which are converted and copied to the standard output, and
7751 format specifications, each of which causes printing of the next successive
7753 In addition to the standard \fIprintf\fP(1) formats, \fB%b\fP causes
7754 \fBprintf\fP to expand backslash escape sequences in the corresponding
7755 \fIargument\fP (except that \fB\ec\fP terminates output, backslashes in
7756 \fB\e\(aq\fP, \fB\e"\fP, and \fB\e?\fP are not removed, and octal escapes
7757 beginning with \fB\e0\fP may contain up to four digits),
7758 and \fB%q\fP causes \fBprintf\fP to output the corresponding
7759 \fIargument\fP in a format that can be reused as shell input.
7761 The \fB\-v\fP option causes the output to be assigned to the variable
7762 \fIvar\fP rather than being printed to the standard output.
7764 The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
7765 If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
7766 extra format specifications behave as if a zero value or null string, as
7767 appropriate, had been supplied. The return value is zero on success,
7768 non-zero on failure.
7770 \fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
7773 \fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
7775 Adds a directory to the top of the directory stack, or rotates
7776 the stack, making the new top of the stack the current working
7777 directory. With no arguments, exchanges the top two directories
7778 and returns 0, unless the directory stack is empty.
7779 Arguments, if supplied, have the following meanings:
7784 Suppresses the normal change of directory when adding directories
7785 to the stack, so that only the stack is manipulated.
7788 Rotates the stack so that the \fIn\fPth directory
7789 (counting from the left of the list shown by
7795 Rotates the stack so that the \fIn\fPth directory
7796 (counting from the right of the list shown by
7798 starting with zero) is at the top.
7803 to the directory stack at the top, making it the
7804 new current working directory.
7809 command is successful, a
7811 is performed as well.
7812 If the first form is used,
7814 returns 0 unless the cd to
7816 fails. With the second form,
7818 returns 0 unless the directory stack is empty,
7819 a non-existent directory stack element is specified,
7820 or the directory change to the specified new current directory
7824 \fBpwd\fP [\fB\-LP\fP]
7825 Print the absolute pathname of the current working directory.
7826 The pathname printed contains no symbolic links if the
7828 option is supplied or the
7832 builtin command is enabled.
7835 option is used, the pathname printed may contain symbolic links.
7836 The return status is 0 unless an error occurs while
7837 reading the name of the current directory or an
7838 invalid option is supplied.
7840 \fBread\fP [\fB\-ers\fP] [\fB\-a\fP \fIaname\fP] [\fB\-d\fP \fIdelim\fP] [\fB\-\fP \fItext\fP] [\fB\-n\fP \fInchars\fP] [\fB\-p\fP \fIprompt\fP] [\fB\-t\fP \fItimeout\fP] [\fB\-u\fP \fIfd\fP] [\fIname\fP ...]
7841 One line is read from the standard input, or from the file descriptor
7842 \fIfd\fP supplied as an argument to the \fB\-u\fP option, and the first word
7843 is assigned to the first
7845 the second word to the second
7847 and so on, with leftover words and their intervening separators assigned
7850 If there are fewer words read from the input stream than names,
7851 the remaining names are assigned empty values.
7855 are used to split the line into words.
7856 The backslash character (\fB\e\fP) may be used to remove any special
7857 meaning for the next character read and for line continuation.
7858 Options, if supplied, have the following meanings:
7863 The words are assigned to sequential indices
7864 of the array variable
7868 is unset before any new values are assigned.
7869 Other \fIname\fP arguments are ignored.
7872 The first character of \fIdelim\fP is used to terminate the input line,
7873 rather than newline.
7876 If the standard input
7877 is coming from a terminal,
7882 above) is used to obtain the line.
7883 Readline uses the current (or default, if line editing was not previously
7884 active) editing settings.
7889 is being used to read the line, \fItext\fP is placed into the editing
7890 buffer before editing begins.
7893 \fBread\fP returns after reading \fInchars\fP characters rather than
7894 waiting for a complete line of input.
7897 Display \fIprompt\fP on standard error, without a
7898 trailing newline, before attempting to read any input. The prompt
7899 is displayed only if input is coming from a terminal.
7902 Backslash does not act as an escape character.
7903 The backslash is considered to be part of the line.
7904 In particular, a backslash-newline pair may not be used as a line
7908 Silent mode. If input is coming from a terminal, characters are
7911 .B \-t \fItimeout\fP
7912 Cause \fBread\fP to time out and return failure if a complete line of
7913 input is not read within \fItimeout\fP seconds.
7914 \fItimeout\fP may be a decimal number with a fractional portion following
7916 This option is only effective if \fBread\fP is reading input from a
7917 terminal, pipe, or other special file; it has no effect when reading
7919 If \fItimeout\fP is 0, \fBread\fP returns success if input is available on
7920 the specified file descriptor, failure otherwise.
7921 The exit status is greater than 128 if the timeout is exceeded.
7924 Read input from file descriptor \fIfd\fP.
7929 are supplied, the line read is assigned to the variable
7932 The return code is zero, unless end-of-file is encountered, \fBread\fP
7933 times out (in which case the return code is greater than 128), or an
7934 invalid file descriptor is supplied as the argument to \fB\-u\fP.
7937 \fBreadonly\fP [\fB\-aApf\fP] [\fIname\fP[=\fIword\fP] ...]
7940 \fInames\fP are marked readonly; the values of these
7942 may not be changed by subsequent assignment.
7945 option is supplied, the functions corresponding to the
7950 option restricts the variables to indexed arrays; the
7952 option restricts the variables to associative arrays.
7955 arguments are given, or if the
7957 option is supplied, a list of all readonly names is printed.
7960 option causes output to be displayed in a format that
7961 may be reused as input.
7962 If a variable name is followed by =\fIword\fP, the value of
7963 the variable is set to \fIword\fP.
7964 The return status is 0 unless an invalid option is encountered,
7967 is not a valid shell variable name, or
7971 that is not a function.
7973 \fBreturn\fP [\fIn\fP]
7974 Causes a function to exit with the return value specified by
7978 is omitted, the return status is that of the last command
7979 executed in the function body. If used outside a function,
7980 but during execution of a script by the
7982 (\fBsource\fP) command, it causes the shell to stop executing
7983 that script and return either
7985 or the exit status of the last command executed within the
7986 script as the exit status of the script. If used outside a
7987 function and not during execution of a script by \fB.\fP\^,
7988 the return status is false.
7989 Any command associated with the \fBRETURN\fP trap is executed
7990 before execution resumes after the function or script.
7992 \fBset\fP [\fB\-\-abefhkmnptuvxBCEHPT\fP] [\fB\-o\fP \fIoption\fP] [\fIarg\fP ...]
7995 \fBset\fP [\fB+abefhkmnptuvxBCEHPT\fP] [\fB+o\fP \fIoption\fP] [\fIarg\fP ...]
7997 Without options, the name and value of each shell variable are displayed
7998 in a format that can be reused as input
7999 for setting or resetting the currently-set variables.
8000 Read-only variables cannot be reset.
8001 In \fIposix mode\fP, only shell variables are listed.
8002 The output is sorted according to the current locale.
8003 When options are specified, they set or unset shell attributes.
8004 Any arguments remaining after option processing are treated
8005 as values for the positional parameters and are assigned, in order, to
8010 Options, if specified, have the following meanings:
8015 Automatically mark variables and functions which are modified or
8016 created for export to the environment of subsequent commands.
8019 Report the status of terminated background jobs
8020 immediately, rather than before the next primary prompt. This is
8021 effective only when job control is enabled.
8024 Exit immediately if a \fIsimple command\fP (see
8027 above) exits with a non-zero status.
8028 The shell does not exit if the
8029 command that fails is part of the command list immediately following a
8034 part of the test in an
8036 statement, part of a command executed in a
8041 any command in a pipeline but the last,
8042 or if the command's return value is
8045 Failing simple commands that are part of shell functions or command lists
8046 enclosed in braces or parentheses satisfying the above conditions do not
8047 cause the shell to exit.
8048 A trap on \fBERR\fP, if set, is executed before the shell exits.
8051 Disable pathname expansion.
8054 Remember the location of commands as they are looked up for execution.
8055 This is enabled by default.
8058 All arguments in the form of assignment statements
8059 are placed in the environment for a command, not just
8060 those that precede the command name.
8063 Monitor mode. Job control is enabled. This option is on
8064 by default for interactive shells on systems that support
8068 above). Background processes run in a separate process
8069 group and a line containing their exit status is printed
8070 upon their completion.
8073 Read commands but do not execute them. This may be used to
8074 check a shell script for syntax errors. This is ignored by
8077 .B \-o \fIoption\-name\fP
8078 The \fIoption\-name\fP can be one of the following:
8090 Use an emacs-style command line editing interface. This is enabled
8091 by default when the shell is interactive, unless the shell is started
8095 This also affects the editing interface used for \fBread \-e\fP.
8118 Enable command history, as described above under
8121 This option is on by default in interactive shells.
8124 The effect is as if the shell command
8125 .if t \f(CWIGNOREEOF=10\fP
8126 .if n ``IGNOREEOF=10''
8172 If set, the return value of a pipeline is the value of the last
8173 (rightmost) command to exit with a non-zero status, or zero if all
8174 commands in the pipeline exit successfully.
8175 This option is disabled by default.
8178 Change the behavior of
8180 where the default operation differs
8181 from the POSIX standard to match the standard (\fIposix mode\fP).
8192 Use a vi-style command line editing interface.
8193 This also affects the editing interface used for \fBread \-e\fP.
8202 is supplied with no \fIoption\-name\fP, the values of the current options are
8206 is supplied with no \fIoption\-name\fP, a series of
8208 commands to recreate the current option settings is displayed on
8209 the standard output.
8215 mode. In this mode, the
8221 files are not processed, shell functions are not inherited from the
8222 environment, and the
8228 variables, if they appear in the environment, are ignored.
8229 If the shell is started with the effective user (group) id not equal to the
8230 real user (group) id, and the \fB\-p\fP option is not supplied, these actions
8231 are taken and the effective user id is set to the real user id.
8232 If the \fB\-p\fP option is supplied at startup, the effective user id is
8234 Turning this option off causes the effective user
8235 and group ids to be set to the real user and group ids.
8238 Exit after reading and executing one command.
8241 Treat unset variables as an error when performing
8242 parameter expansion. If expansion is attempted on an
8243 unset variable, the shell prints an error message, and,
8244 if not interactive, exits with a non-zero status.
8247 Print shell input lines as they are read.
8250 After expanding each \fIsimple command\fP,
8251 \fBfor\fP command, \fBcase\fP command, \fBselect\fP command, or
8252 arithmetic \fBfor\fP command, display the expanded value of
8255 followed by the command and its expanded arguments
8256 or associated word list.
8259 The shell performs brace expansion (see
8261 above). This is on by default.
8266 does not overwrite an existing file with the
8271 redirection operators. This may be overridden when
8272 creating output files by using the redirection operator
8278 If set, any trap on \fBERR\fP is inherited by shell functions, command
8279 substitutions, and commands executed in a subshell environment.
8280 The \fBERR\fP trap is normally not inherited in such cases.
8285 style history substitution. This option is on by
8286 default when the shell is interactive.
8289 If set, the shell does not follow symbolic links when executing
8292 that change the current working directory. It uses the
8293 physical directory structure instead. By default,
8295 follows the logical chain of directories when performing commands
8296 which change the current directory.
8299 If set, any traps on \fBDEBUG\fP and \fBRETURN\fP are inherited by shell
8300 functions, command substitutions, and commands executed in a
8301 subshell environment.
8302 The \fBDEBUG\fP and \fBRETURN\fP traps are normally not inherited
8306 If no arguments follow this option, then the positional parameters are
8307 unset. Otherwise, the positional parameters are set to the
8308 \fIarg\fPs, even if some of them begin with a
8312 Signal the end of options, cause all remaining \fIarg\fPs to be
8313 assigned to the positional parameters. The
8317 options are turned off.
8318 If there are no \fIarg\fPs,
8319 the positional parameters remain unchanged.
8322 The options are off by default unless otherwise noted.
8323 Using + rather than \- causes these options to be turned off.
8324 The options can also be specified as arguments to an invocation of
8326 The current set of options may be found in
8328 The return status is always true unless an invalid option is encountered.
8331 \fBshift\fP [\fIn\fP]
8332 The positional parameters from \fIn\fP+1 ... are renamed to
8335 Parameters represented by the numbers \fB$#\fP
8336 down to \fB$#\fP\-\fIn\fP+1 are unset.
8338 must be a non-negative number less than or equal to \fB$#\fP.
8341 is 0, no parameters are changed.
8344 is not given, it is assumed to be 1.
8347 is greater than \fB$#\fP, the positional parameters are not changed.
8348 The return status is greater than zero if
8352 or less than zero; otherwise 0.
8354 \fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
8355 Toggle the values of variables controlling optional shell behavior.
8356 With no options, or with the
8358 option, a list of all settable options is displayed, with
8359 an indication of whether or not each is set.
8360 The \fB\-p\fP option causes output to be displayed in a form that
8361 may be reused as input.
8362 Other options have the following meanings:
8367 Enable (set) each \fIoptname\fP.
8370 Disable (unset) each \fIoptname\fP.
8373 Suppresses normal output (quiet mode); the return status indicates
8374 whether the \fIoptname\fP is set or unset.
8375 If multiple \fIoptname\fP arguments are given with
8377 the return status is zero if all \fIoptnames\fP are enabled; non-zero
8381 Restricts the values of \fIoptname\fP to be those defined for the
8392 is used with no \fIoptname\fP arguments, the display is limited to
8393 those options which are set or unset, respectively.
8394 Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
8397 The return status when listing options is zero if all \fIoptnames\fP
8398 are enabled, non-zero otherwise. When setting or unsetting options,
8399 the return status is zero unless an \fIoptname\fP is not a valid shell
8402 The list of \fBshopt\fP options is:
8408 If set, a command name that is the name of a directory is executed as if
8409 it were the argument to the \fBcd\fP command.
8410 This option is only used by interactive shells.
8413 If set, an argument to the
8415 builtin command that
8416 is not a directory is assumed to be the name of a variable whose
8417 value is the directory to change to.
8420 If set, minor errors in the spelling of a directory component in a
8422 command will be corrected.
8423 The errors checked for are transposed characters,
8424 a missing character, and one character too many.
8425 If a correction is found, the corrected file name is printed,
8426 and the command proceeds.
8427 This option is only used by interactive shells.
8430 If set, \fBbash\fP checks that a command found in the hash
8431 table exists before trying to execute it. If a hashed command no
8432 longer exists, a normal path search is performed.
8435 If set, \fBbash\fP lists the status of any stopped and running jobs before
8436 exiting an interactive shell. If any jobs are running, this causes
8437 the exit to be deferred until a second exit is attempted without an
8438 intervening command (see \fBJOB CONTROL\fP above). The shell always
8439 postpones exiting if any jobs are stopped.
8442 If set, \fBbash\fP checks the window size after each command
8443 and, if necessary, updates the values of
8453 attempts to save all lines of a multiple-line
8454 command in the same history entry. This allows
8455 easy re-editing of multi-line commands.
8460 changes its behavior to that of version 3.1 with respect to quoted
8461 arguments to the conditional command's =~ operator.
8466 attempts spelling correction on directory names during word completion
8467 if the directory name initially supplied does not exist.
8472 includes filenames beginning with a `.' in the results of pathname
8476 If set, a non-interactive shell will not exit if
8477 it cannot execute the file specified as an argument to the
8479 builtin command. An interactive shell does not exit if
8484 If set, aliases are expanded as described above under
8487 This option is enabled by default for interactive shells.
8490 If set, behavior intended for use by debuggers is enabled:
8494 The \fB\-F\fP option to the \fBdeclare\fP builtin displays the source
8495 file name and line number corresponding to each function name supplied
8499 If the command run by the \fBDEBUG\fP trap returns a non-zero value, the
8500 next command is skipped and not executed.
8503 If the command run by the \fBDEBUG\fP trap returns a value of 2, and the
8504 shell is executing in a subroutine (a shell function or a shell script
8505 executed by the \fB.\fP or \fBsource\fP builtins), a call to
8506 \fBreturn\fP is simulated.
8509 \fBBASH_ARGC\fP and \fBBASH_ARGV\fP are updated as described in their
8513 Function tracing is enabled: command substitution, shell functions, and
8514 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
8515 \fBDEBUG\fP and \fBRETURN\fP traps.
8518 Error tracing is enabled: command substitution, shell functions, and
8519 subshells invoked with \fB(\fP \fIcommand\fP \fB)\fP inherit the
8524 If set, the extended pattern matching features described above under
8525 \fBPathname Expansion\fP are enabled.
8528 If set, \fB$\fP\(aq\fIstring\fP\(aq and \fB$\fP"\fIstring\fP" quoting is
8529 performed within \fB${\fP\fIparameter\fP\fB}\fP expansions
8530 enclosed in double quotes. This option is enabled by default.
8533 If set, patterns which fail to match filenames during pathname expansion
8534 result in an expansion error.
8537 If set, the suffixes specified by the \fBFIGNORE\fP shell variable
8538 cause words to be ignored when performing word completion even if
8539 the ignored words are the only possible completions.
8542 \fBSHELL VARIABLES\fP
8543 above for a description of \fBFIGNORE\fP.
8544 This option is enabled by default.
8547 If set, the pattern \fB**\fP used in a filename expansion context will
8548 match a files and zero or more directories and subdirectories.
8549 If the pattern is followed by a \fB/\fP, only directories and
8550 subdirectories match.
8553 If set, shell error messages are written in the standard GNU error
8557 If set, the history list is appended to the file named by the value
8560 variable when the shell exits, rather than overwriting the file.
8565 is being used, a user is given the opportunity to re-edit a
8566 failed history substitution.
8571 is being used, the results of history substitution are not immediately
8572 passed to the shell parser. Instead, the resulting line is loaded into
8573 the \fBreadline\fP editing buffer, allowing further modification.
8578 is being used, \fBbash\fP will attempt to perform hostname completion when a
8579 word containing a \fB@\fP is being completed (see
8585 This is enabled by default.
8588 If set, \fBbash\fP will send
8591 to all jobs when an interactive login shell exits.
8593 .B interactive_comments
8594 If set, allow a word beginning with
8596 to cause that word and all remaining characters on that
8597 line to be ignored in an interactive shell (see
8600 above). This option is enabled by default.
8605 option is enabled, multi-line commands are saved to the history with
8606 embedded newlines rather than using semicolon separators where possible.
8609 The shell sets this option if it is started as a login shell (see
8613 The value may not be changed.
8616 If set, and a file that \fBbash\fP is checking for mail has been
8617 accessed since the last time it was checked, the message ``The mail in
8618 \fImailfile\fP has been read'' is displayed.
8620 .B no_empty_cmd_completion
8625 will not attempt to search the \fBPATH\fP for possible completions when
8626 completion is attempted on an empty line.
8631 matches filenames in a case\-insensitive fashion when performing pathname
8633 .B Pathname Expansion
8639 matches patterns in a case\-insensitive fashion when performing matching
8640 while executing \fBcase\fP or \fB[[\fP conditional commands.
8645 allows patterns which match no
8647 .B Pathname Expansion
8649 to expand to a null string, rather than themselves.
8652 If set, the programmable completion facilities (see
8653 \fBProgrammable Completion\fP above) are enabled.
8654 This option is enabled by default.
8657 If set, prompt strings undergo
8658 parameter expansion, command substitution, arithmetic
8659 expansion, and quote removal after being expanded as described in
8662 above. This option is enabled by default.
8665 The shell sets this option if it is started in restricted mode (see
8667 .B "RESTRICTED SHELL"
8669 The value may not be changed.
8670 This is not reset when the startup files are executed, allowing
8671 the startup files to discover whether or not a shell is restricted.
8676 builtin prints an error message when the shift count exceeds the
8677 number of positional parameters.
8681 \fBsource\fP (\fB.\fP) builtin uses the value of
8684 to find the directory containing the file supplied as an argument.
8685 This option is enabled by default.
8688 If set, the \fBecho\fP builtin expands backslash-escape sequences
8692 \fBsuspend\fP [\fB\-f\fP]
8693 Suspend the execution of this shell until it receives a
8696 signal. A login shell cannot be suspended; the
8698 option can be used to override this and force the suspension.
8699 The return status is 0 unless the shell is a login shell and
8701 is not supplied, or if job control is not enabled.
8703 \fBtest\fP \fIexpr\fP
8706 \fB[\fP \fIexpr\fP \fB]\fP
8707 Return a status of 0 or 1 depending on
8708 the evaluation of the conditional expression
8710 Each operator and operand must be a separate argument.
8711 Expressions are composed of the primaries described above under
8713 .BR "CONDITIONAL EXPRESSIONS" .
8714 \fBtest\fP does not accept any options, nor does it accept and ignore
8715 an argument of \fB\-\-\fP as signifying the end of options.
8718 Expressions may be combined using the following operators, listed
8719 in decreasing order of precedence.
8720 The evaluation depends on the number of arguments; see below.
8730 Returns the value of \fIexpr\fP.
8731 This may be used to override the normal precedence of operators.
8733 \fIexpr1\fP \-\fBa\fP \fIexpr2\fP
8740 \fIexpr1\fP \-\fBo\fP \fIexpr2\fP
8748 \fBtest\fP and \fB[\fP evaluate conditional
8749 expressions using a set of rules based on the number of arguments.
8755 The expression is false.
8758 The expression is true if and only if the argument is not null.
8761 If the first argument is \fB!\fP, the expression is true if and
8762 only if the second argument is null.
8763 If the first argument is one of the unary conditional operators listed above
8766 .BR "CONDITIONAL EXPRESSIONS" ,
8767 the expression is true if the unary test is true.
8768 If the first argument is not a valid unary conditional operator, the expression
8772 If the second argument is one of the binary conditional operators listed above
8775 .BR "CONDITIONAL EXPRESSIONS" ,
8776 the result of the expression is the result of the binary test using
8777 the first and third arguments as operands.
8778 The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
8779 when there are three arguments.
8780 If the first argument is \fB!\fP, the value is the negation of
8781 the two-argument test using the second and third arguments.
8782 If the first argument is exactly \fB(\fP and the third argument is
8783 exactly \fB)\fP, the result is the one-argument test of the second
8785 Otherwise, the expression is false.
8788 If the first argument is \fB!\fP, the result is the negation of
8789 the three-argument expression composed of the remaining arguments.
8790 Otherwise, the expression is parsed and evaluated according to
8791 precedence using the rules listed above.
8794 The expression is parsed and evaluated according to precedence
8795 using the rules listed above.
8800 Print the accumulated user and system times for the shell and
8801 for processes run from the shell. The return status is 0.
8803 \fBtrap\fP [\fB\-lp\fP] [[\fIarg\fP] \fIsigspec\fP ...]
8806 is to be read and executed when the shell receives
8811 is absent (and there is a single \fIsigspec\fP) or
8813 each specified signal is
8814 reset to its original disposition (the value it had
8815 upon entrance to the shell).
8818 is the null string the signal specified by each
8820 is ignored by the shell and by the commands it invokes.
8825 has been supplied, then the trap commands associated with each
8828 If no arguments are supplied or if only
8832 prints the list of commands associated with each signal.
8835 option causes the shell to print a list of signal names and
8836 their corresponding numbers.
8840 a signal name defined in <\fIsignal.h\fP>, or a signal number.
8841 Signal names are case insensitive and the SIG prefix is optional.
8849 is executed on exit from the shell.
8857 is executed before every \fIsimple command\fP, \fIfor\fP command,
8858 \fIcase\fP command, \fIselect\fP command, every arithmetic \fIfor\fP
8859 command, and before the first command executes in a shell function (see
8863 Refer to the description of the \fBextdebug\fP option to the
8864 \fBshopt\fP builtin for details of its effect on the \fBDEBUG\fP trap.
8872 is executed whenever a simple command has a non\-zero exit status,
8873 subject to the following conditions.
8877 trap is not executed if the failed
8878 command is part of the command list immediately following a
8883 part of the test in an
8885 statement, part of a command executed in a
8889 list, or if the command's return value is
8892 These are the same conditions obeyed by the \fBerrexit\fP option.
8900 is executed each time a shell function or a script executed with the
8901 \fB.\fP or \fBsource\fP builtins finishes executing.
8902 Signals ignored upon entry to the shell cannot be trapped or reset.
8903 Trapped signals that are not being ignored are reset to their original
8904 values in a child process when it is created.
8905 The return status is false if any
8907 is invalid; otherwise
8911 \fBtype\fP [\fB\-aftpP\fP] \fIname\fP [\fIname\fP ...]
8915 would be interpreted if used as a command name.
8920 prints a string which is one of
8929 is an alias, shell reserved word, function, builtin, or disk file,
8933 is not found, then nothing is printed, and an exit status of false
8939 either returns the name of the disk file
8940 that would be executed if
8942 were specified as a command name,
8944 .if t \f(CWtype -t name\fP
8945 .if n ``type -t name''
8953 search for each \fIname\fP, even if
8954 .if t \f(CWtype -t name\fP
8955 .if n ``type -t name''
8958 If a command is hashed,
8962 print the hashed value, not necessarily the file that appears
8970 prints all of the places that contain
8973 This includes aliases and functions,
8976 option is not also used.
8977 The table of hashed commands is not consulted
8982 option suppresses shell function lookup, as with the \fBcommand\fP builtin.
8984 returns true if all of the arguments are found, false if
8987 \fBulimit\fP [\fB\-HSTabcdefilmnpqrstuvx\fP [\fIlimit\fP]]
8988 Provides control over the resources available to the shell and to
8989 processes started by it, on systems that allow such control.
8990 The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
8991 set for the given resource.
8992 A hard limit cannot be increased by a non-root user once it is set;
8993 a soft limit may be increased up to the value of the hard limit.
8994 If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
8998 can be a number in the unit specified for the resource
8999 or one of the special values
9004 which stand for the current hard limit, the current soft limit, and
9005 no limit, respectively.
9008 is omitted, the current value of the soft limit of the resource is
9009 printed, unless the \fB\-H\fP option is given. When more than one
9010 resource is specified, the limit name and unit are printed before the value.
9011 Other options are interpreted as follows:
9016 All current limits are reported
9019 The maximum socket buffer size
9022 The maximum size of core files created
9025 The maximum size of a process's data segment
9028 The maximum scheduling priority ("nice")
9031 The maximum size of files written by the shell and its children
9034 The maximum number of pending signals
9037 The maximum size that may be locked into memory
9040 The maximum resident set size
9043 The maximum number of open file descriptors (most systems do not
9044 allow this value to be set)
9047 The pipe size in 512-byte blocks (this may not be set)
9050 The maximum number of bytes in POSIX message queues
9053 The maximum real-time scheduling priority
9056 The maximum stack size
9059 The maximum amount of cpu time in seconds
9062 The maximum number of processes available to a single user
9065 The maximum amount of virtual memory available to the shell
9068 The maximum number of file locks
9071 The maximum number of threads
9076 is given, it is the new value of the specified resource (the
9078 option is display only).
9079 If no option is given, then
9081 is assumed. Values are in 1024-byte increments, except for
9083 which is in seconds,
9085 which is in units of 512-byte blocks,
9092 which are unscaled values.
9093 The return status is 0 unless an invalid option or argument is supplied,
9094 or an error occurs while setting a new limit.
9097 \fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
9098 The user file-creation mask is set to
9102 begins with a digit, it
9103 is interpreted as an octal number; otherwise
9104 it is interpreted as a symbolic mode mask similar
9109 is omitted, the current value of the mask is printed.
9112 option causes the mask to be printed in symbolic form; the
9113 default output is an octal number.
9116 option is supplied, and
9118 is omitted, the output is in a form that may be reused as input.
9119 The return status is 0 if the mode was successfully changed or if
9120 no \fImode\fP argument was supplied, and false otherwise.
9122 \fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
9123 Remove each \fIname\fP from the list of defined aliases. If
9125 is supplied, all alias definitions are removed. The return
9126 value is true unless a supplied
9128 is not a defined alias.
9130 \fBunset\fP [\-\fBfv\fP] [\fIname\fP ...]
9133 remove the corresponding variable or function.
9134 If no options are supplied, or the
9136 option is given, each
9138 refers to a shell variable.
9139 Read-only variables may not be unset.
9144 refers to a shell function, and the function definition
9146 Each unset variable or function is removed from the environment
9147 passed to subsequent commands.
9164 are unset, they lose their special properties, even if they are
9165 subsequently reset. The exit status is true unless a
9169 \fBwait\fP [\fIn ...\fP]
9170 Wait for each specified process and return its termination status.
9174 ID or a job specification; if a job spec is given, all processes
9175 in that job's pipeline are waited for. If
9177 is not given, all currently active child processes
9178 are waited for, and the return status is zero. If
9180 specifies a non-existent process or job, the return status is
9181 127. Otherwise, the return status is the exit status of the last
9182 process or job waited for.
9185 .SH "RESTRICTED SHELL"
9191 is started with the name
9195 option is supplied at invocation,
9196 the shell becomes restricted.
9197 A restricted shell is used to
9198 set up an environment more controlled than the standard shell.
9199 It behaves identically to
9201 with the exception that the following are disallowed or not performed:
9203 changing directories with \fBcd\fP
9205 setting or unsetting the values of
9212 specifying command names containing
9215 specifying a file name containing a
9217 as an argument to the
9221 Specifying a filename containing a slash as an argument to the
9227 importing function definitions from the shell environment at startup
9229 parsing the value of \fBSHELLOPTS\fP from the shell environment at startup
9231 redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
9235 builtin command to replace the shell with another command
9237 adding or deleting builtin commands with the
9245 Using the \fBenable\fP builtin command to enable disabled shell builtins
9253 turning off restricted mode with
9254 \fBset +r\fP or \fBset +o restricted\fP.
9256 These restrictions are enforced after any startup files are read.
9258 .ie \n(zY=1 When a command that is found to be a shell script is executed,
9259 .el \{ When a command that is found to be a shell script is executed
9262 .B "COMMAND EXECUTION"
9266 turns off any restrictions in the shell spawned to execute the
9273 \fIBash Reference Manual\fP, Brian Fox and Chet Ramey
9275 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
9277 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
9279 \fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE
9281 \fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
9283 \fIemacs\fP(1), \fIvi\fP(1)
9291 The \fBbash\fP executable
9294 The systemwide initialization file, executed for login shells
9297 The personal initialization file, executed for login shells
9300 The individual per-interactive-shell startup file
9303 The individual login shell cleanup file, executed when a login shell exits
9306 Individual \fIreadline\fP initialization file
9309 Brian Fox, Free Software Foundation
9313 Chet Ramey, Case Western Reserve University
9317 If you find a bug in
9319 you should report it. But first, you should
9320 make sure that it really is a bug, and that it appears in the latest
9323 The latest version is always available from
9324 \fIftp://ftp.gnu.org/pub/bash/\fP.
9326 Once you have determined that a bug actually exists, use the
9328 command to submit a bug report.
9329 If you have a fix, you are encouraged to mail that as well!
9330 Suggestions and `philosophical' bug reports may be mailed
9331 to \fIbug-bash@gnu.org\fP or posted to the Usenet
9335 ALL bug reports should include:
9339 The version number of \fBbash\fR
9341 The hardware and operating system
9343 The compiler used to compile
9345 A description of the bug behaviour
9347 A short script or `recipe' which exercises the bug
9351 inserts the first three items automatically into the template
9352 it provides for filing a bug report.
9354 Comments and bug reports concerning
9355 this manual page should be directed to
9356 .IR chet@po.cwru.edu .
9359 It's too big and too slow.
9361 There are some subtle differences between
9363 and traditional versions of
9365 mostly because of the
9370 Aliases are confusing in some uses.
9372 Shell builtin commands and functions are not stoppable/restartable.
9374 Compound commands and command sequences of the form `a ; b ; c'
9375 are not handled gracefully when process suspension is attempted.
9376 When a process is stopped, the shell immediately executes the next
9377 command in the sequence.
9378 It suffices to place the sequence of commands between
9379 parentheses to force it into a subshell, which may be stopped as
9382 Array variables may not (yet) be exported.
9384 There may be only one active coprocess at a time.
projects / thirdparty / bash.git / blob