2 .\" MAN PAGE COMMENTS to
5 .\" Information Network Services
6 .\" Case Western Reserve University
9 .\" Last Change: Mon Mar 5 10:19:14 EST 2001
11 .\" bash_builtins, strip all but Built-Ins section
14 .TH BASH 1 "2001 Mar 5" "GNU Bash-2.05"
16 .\" There's some problem with having a `@'
17 .\" in a tagged paragraph with the BSD man macros.
18 .\" It has to do with `@' appearing in the }1 macro.
19 .\" This is a problem on 4.3 BSD and Ultrix, but Sun
20 .\" appears to have fixed it.
21 .\" If you're seeing the characters
22 .\" `@u-3p' appearing before the lines reading
23 .\" `possible-hostname-completions
24 .\" and `complete-hostname' down in READLINE,
25 .\" then uncomment this redefinition.
30 .if !"\\$1"" .nr )I \\$1n
33 .in \\n()Ru+\\n(INu+\\n()Iu
35 .ie !\\n()Iu+\\n()Ru-\w
\a\\*(]X
\au-3p \{\\*(]X
37 .el \\*(]X\h
\a|\\n()Iu+\\n()Ru
\a\c
41 .\" File Name macro. This used to be `.PN', for Path Name,
42 .\" but Sun doesn't seem to like that very much.
48 bash \- GNU Bourne-Again SHell
54 .if n Bash is Copyright (C) 1989-2001 by the Free Software Foundation, Inc.
55 .if t Bash is Copyright \(co 1989-2001 by the Free Software Foundation, Inc.
58 is an \fBsh\fR-compatible command language interpreter that
59 executes commands read from the standard input or from a file.
61 also incorporates useful features from the \fIKorn\fP and \fIC\fP
62 shells (\fBksh\fP and \fBcsh\fP).
65 is intended to be a conformant implementation of the IEEE
66 POSIX Shell and Tools specification (IEEE Working Group 1003\.2).
68 In addition to the single-character shell options documented in the
69 description of the \fBset\fR builtin command, \fBbash\fR
70 interprets the following options when it is invoked:
77 option is present, then commands are read from
79 If there are arguments after the
81 they are assigned to the positional parameters, starting with
87 option is present, the shell becomes
97 option is present, the shell is
103 option is present, or if no arguments remain after option
104 processing, then commands are read from the standard input.
105 This option allows the positional parameters to be set
106 when invoking an interactive shell.
109 A list of all double-quoted strings preceded by \fB$\fP
110 is printed on the standard ouput.
111 These are the strings that
112 are subject to language translation when the current locale
113 is not \fBC\fP or \fBPOSIX\fP.
114 This implies the \fB\-n\fP option; no commands will be executed.
119 signals the end of options and disables further option processing.
120 Any arguments after the
122 are treated as filenames and arguments. An argument of
124 is equivalent to \fB\-\-\fP.
128 also interprets a number of multi-character options.
129 These options must appear on the command line before the
130 single-character options in order for them to be recognized.
134 .B \-\-dump\-po\-strings
135 Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
136 \fBpo\fP (portable object) file format.
139 Equivalent to \fB\-D\fP.
142 Display a usage message on standard output and exit successfully.
145 \fB\-\-init\-file\fP \fIfile\fP
147 \fB\-\-rcfile\fP \fIfile\fP
149 Execute commands from
151 instead of the standard personal initialization file
153 if the shell is interactive (see
161 act as if it had been invoked as a login shell (see
169 library to read command lines when the shell is interactive.
172 Do not read either the system-wide startup file
174 or any of the personal initialization files
175 .IR ~/.bash_profile ,
181 reads these files when it is invoked as a login shell (see
187 Do not read and execute the personal initialization file
189 if the shell is interactive.
190 This option is on by default if the shell is invoked as
194 Change the behavior of \fBbash\fP where the default operation differs
195 from the POSIX 1003.2 standard to match the standard (\fIposix mode\fP).
198 The shell becomes restricted (see
200 .B "RESTRICTED SHELL"
204 Equivalent to \fB\-v\fP.
207 Show version information for this instance of
209 on the standard output and exit successfully.
212 If arguments remain after option processing, and neither the
216 option has been supplied, the first argument is assumed to
217 be the name of a file containing shell commands.
220 is invoked in this fashion,
222 is set to the name of the file, and the positional parameters
223 are set to the remaining arguments.
225 reads and executes commands from this file, then exits.
226 \fBBash\fP's exit status is the exit status of the last command
227 executed in the script.
228 If no commands are executed, the exit status is 0.
230 A \fIlogin shell\fP is one whose first character of argument zero is a
232 or one started with the
236 An \fIinteractive\fP shell is one started without non-option arguments
240 whose standard input and output are
241 both connected to terminals (as determined by
243 or one started with the
255 allowing a shell script or a startup file to test this state.
257 The following paragraphs describe how
259 executes its startup files.
260 If any of the files exist but cannot be read,
263 Tildes are expanded in file names as described below under
272 is invoked as an interactive login shell, or as a non-interactive shell
273 with the \fB\-\-login\fP option, it first reads and
274 executes commands from the file \fI/etc/profile\fP, if that
276 After reading that file, it looks for \fI~/.bash_profile\fP,
277 \fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
278 and executes commands from the first one that exists and is readable.
281 option may be used when the shell is started to inhibit this behavior.
283 When a login shell exits,
285 reads and executes commands from the file \fI~/.bash_logout\fP, if it
288 When an interactive shell that is not a login shell is started,
290 reads and executes commands from \fI~/.bashrc\fP, if that file exists.
291 This may be inhibited by using the
294 The \fB\-\-rcfile\fP \fIfile\fP option will force
296 to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
300 is started non-interactively, to run a shell script, for example, it
301 looks for the variable
304 in the environment, expands its value if it appears there, and uses the
305 expanded value as the name of a file to read and execute.
307 behaves as if the following command were executed:
310 .if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
311 .if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
317 variable is not used to search for the file name.
321 is invoked with the name
323 it tries to mimic the startup behavior of historical versions of
325 as closely as possible,
326 while conforming to the POSIX standard as well.
327 When invoked as an interactive login shell, or a non-interactive
328 shell with the \fB\-\-login\fP option, it first attempts to
329 read and execute commands from
336 option may be used to inhibit this behavior.
337 When invoked as an interactive shell with the name
340 looks for the variable
343 expands its value if it is defined, and uses the
344 expanded value as the name of a file to read and execute.
345 Since a shell invoked as
347 does not attempt to read and execute commands from any other startup
350 option has no effect.
351 A non-interactive shell invoked with the name
353 does not attempt to read any other startup files.
359 mode after the startup files are read.
367 command line option, it follows the POSIX standard for startup files.
368 In this mode, interactive shells expand the
371 variable and commands are read and executed from the file
372 whose name is the expanded value.
373 No other startup files are read.
376 attempts to determine when it is being run by the remote shell
377 daemon, usually \fIrshd\fP.
380 determines it is being run by \fIrshd\fP, it reads and executes
381 commands from \fI~/.bashrc\fP, if that file exists and is readable.
382 It will not do this if invoked as \fBsh\fP.
385 option may be used to inhibit this behavior, and the
387 option may be used to force another file to be read, but
388 \fIrshd\fP does not generally invoke the shell with those options
389 or allow them to be specified.
391 If the shell is started with the effective user (group) id not equal to the
392 real user (group) id, and the \fB\-p\fP option is not supplied, no startup
393 files are read, shell functions are not inherited from the environment,
394 the \fBSHELLOPTS\fP variable, if it appears in the environment, is ignored,
395 and the effective user id is set to the real user id.
396 If the \fB\-p\fP option is supplied at invocation, the startup behavior is
397 the same, but the effective user id is not reset.
400 The following definitions are used throughout the rest of this
408 A sequence of characters considered as a single unit by the shell.
415 consisting only of alphanumeric characters and underscores, and
416 beginning with an alphabetic character or an underscore. Also
421 A character that, when unquoted, separates words. One of the following:
425 .if t \fB| & ; ( ) < > space tab\fP
426 .if n \fB| & ; ( ) < > space tab\fP
431 A \fItoken\fP that performs a control function. It is one of the following
435 .if t \fB\(bv\(bv & && ; ;; ( ) | <newline>\fP
436 .if n \fB|| & && ; ;; ( ) | <newline>\fP
440 \fIReserved words\fP are words that have a special meaning to the shell.
441 The following words are recognized as reserved when unquoted and either
442 the first word of a simple command (see
445 below) or the third word of a
453 .if n ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
454 .if t ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
460 A \fIsimple command\fP is a sequence of optional variable assignments
461 followed by \fBblank\fP-separated words and redirections, and
462 terminated by a \fIcontrol operator\fP. The first word
463 specifies the command to be executed. The remaining words are
464 passed as arguments to the invoked command.
466 The return value of a \fIsimple command\fP is its exit status, or
467 128+\fIn\^\fP if the command is terminated by signal
471 A \fIpipeline\fP is a sequence of one or more commands separated by
474 The format for a pipeline is:
477 [\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ \fB|\fP \fIcommand2\fP ... ]
480 The standard output of
482 is connected to the standard input of
484 This connection is performed before any redirections specified by the
492 precedes a pipeline, the exit status of that
493 pipeline is the logical NOT of the exit status of the last command.
494 Otherwise, the status of the pipeline is the exit status of the last
496 The shell waits for all commands in the pipeline to
497 terminate before returning a value.
501 reserved word precedes a pipeline, the elapsed as well as user and
502 system time consumed by its execution are reported when the pipeline
504 The \fB\-p\fP option changes the output format to that specified by POSIX.
508 variable may be set to a format string that specifies how the timing
509 information should be displayed; see the description of
516 Each command in a pipeline is executed as a separate process (i.e., in a
520 A \fIlist\fP is a sequence of one or more pipelines separated by one
527 and optionally terminated by one of
533 Of these list operators,
537 have equal precedence, followed by
541 which have equal precedence.
543 If a command is terminated by the control operator
545 the shell executes the command in the \fIbackground\fP
546 in a subshell. The shell does not wait for the command to
547 finish, and the return status is 0. Commands separated by a
549 are executed sequentially; the shell waits for each
550 command to terminate in turn. The return status is the
551 exit status of the last command executed.
553 The control operators
557 denote AND lists and OR lists, respectively.
558 An AND list has the form
561 \fIcommand1\fP \fB&&\fP \fIcommand2\fP
565 is executed if, and only if,
567 returns an exit status of zero.
569 An OR list has the form
572 \fIcommand1\fP \fB\(bv\(bv\fP \fIcommand2\fP
577 is executed if and only if
579 returns a non-zero exit status. The return status of
580 AND and OR lists is the exit status of the last command
581 executed in the list.
582 .SS Compound Commands
584 A \fIcompound command\fP is one of the following:
587 \fIlist\fP is executed in a subshell. Variable assignments and builtin
588 commands that affect the shell's environment do not remain in effect
589 after the command completes. The return status is the exit status of
593 \fIlist\fP is simply executed in the current shell environment.
594 \fIlist\fP must be terminated with a newline or semicolon.
595 This is known as a \fIgroup command\fP.
596 The return status is the exit status of
600 The \fIexpression\fP is evaluated according to the rules described
603 .BR "ARITHMETIC EVALUATION" .
604 If the value of the expression is non-zero, the return status is 0;
605 otherwise the return status is 1. This is exactly equivalent to
606 \fBlet "\fIexpression\fP"\fR.
608 \fB[[\fP \fIexpression\fP \fB]]\fP
609 Return a status of 0 or 1 depending on the evaluation of
610 the conditional expression \fIexpression\fP.
611 Expressions are composed of the primaries described below under
613 .BR "CONDITIONAL EXPRESSIONS" .
614 Word splitting and pathname expansion are not performed on the words
615 between the \fB[[\fP and \fB]]\fP; tilde expansion, parameter and
616 variable expansion, arithmetic expansion, command substitution, process
617 substitution, and quote removal are performed.
620 When the \fB==\fP and \fB!=\fP operators are used, the string to the
621 right of the operator is considered a pattern and matched according
622 to the rules described below under \fBPattern Matching\fP.
623 The return value is 0 if the string matches or does not match
624 the pattern, respectively, and 1 otherwise.
625 Any part of the pattern may be quoted to force it to be matched as a
629 Expressions may be combined using the following operators, listed
630 in decreasing order of precedence:
636 .B ( \fIexpression\fP )
637 Returns the value of \fIexpression\fP.
638 This may be used to override the normal precedence of operators.
640 .B ! \fIexpression\fP
645 \fIexpression1\fP \fB&&\fP \fIexpression2\fP
652 .if t \fIexpression1\fP \fB\(bv\(bv\fP \fIexpression2\fP
653 .if n \fIexpression1\fP \fB||\fP \fIexpression2\fP
665 operators do not execute \fIexpression2\fP if the value of
666 \fIexpression1\fP is sufficient to determine the return value of
667 the entire conditional expression.
669 \fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
670 The list of words following \fBin\fP is expanded, generating a list
672 The variable \fIname\fP is set to each element of this list
673 in turn, and \fIlist\fP is executed each time.
674 If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
675 \fIlist\fP once for each positional parameter that is set (see
679 The return status is the exit status of the last command that executes.
680 If the expansion of the items following \fBin\fP results in an empty
681 list, no commands are executed, and the return status is 0.
683 \fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
684 First, the arithmetic expression \fIexpr1\fP is evaluated according
685 to the rules described below under
687 .BR "ARITHMETIC EVALUATION" .
688 The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
689 until it evaluates to zero.
690 Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
691 executed and the arithmetic expression \fIexpr3\fP is evaluated.
692 If any expression is omitted, it behaves as if it evaluates to 1.
693 The return value is the exit status of the last command in \fIlist\fP
694 that is executed, or false if any of the expressions is invalid.
696 \fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
697 The list of words following \fBin\fP is expanded, generating a list
698 of items. The set of expanded words is printed on the standard
699 error, each preceded by a number. If the \fBin\fP
700 \fIword\fP is omitted, the positional parameters are printed (see
705 prompt is then displayed and a line read from the standard input.
706 If the line consists of a number corresponding to one of
707 the displayed words, then the value of
709 is set to that word. If the line is empty, the words and prompt
710 are displayed again. If EOF is read, the command completes. Any
711 other value read causes
713 to be set to null. The line read is saved in the variable
717 is executed after each selection until a
724 is the exit status of the last command executed in
726 or zero if no commands were executed.
728 \fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
729 ... ) \fIlist\fP ;; ] ... \fBesac\fP
730 A \fBcase\fP command first expands \fIword\fP, and tries to match
731 it against each \fIpattern\fP in turn, using the same matching rules
732 as for pathname expansion (see
733 .B Pathname Expansion
734 below). When a match is found, the
735 corresponding \fIlist\fP is executed. After the first match, no
736 subsequent matches are attempted. The exit status is zero if no
737 pattern matches. Otherwise, it is the exit status of the
738 last command executed in \fIlist\fP.
740 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist;\fP \
741 [ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
742 [ \fBelse\fP \fIlist\fP; ] \fBfi\fP
746 is executed. If its exit status is zero, the
747 \fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
748 \fIlist\fP is executed in turn, and if its exit status is zero,
749 the corresponding \fBthen\fP \fIlist\fP is executed and the
750 command completes. Otherwise, the \fBelse\fP \fIlist\fP is
751 executed, if present. The exit status is the exit status of the
752 last command executed, or zero if no condition tested true.
755 \fBwhile\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
757 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
759 The \fBwhile\fP command continuously executes the \fBdo\fP
760 \fIlist\fP as long as the last command in \fIlist\fP returns
761 an exit status of zero. The \fBuntil\fP command is identical
762 to the \fBwhile\fP command, except that the test is negated;
766 is executed as long as the last command in
768 returns a non-zero exit status.
769 The exit status of the \fBwhile\fP and \fBuntil\fP commands
771 of the last \fBdo\fP \fIlist\fP command executed, or zero if
774 [ \fBfunction\fP ] \fIname\fP () { \fIlist\fP; }
775 This defines a function named \fIname\fP. The \fIbody\fP of the
778 of commands between { and }. This list
779 is executed whenever \fIname\fP is specified as the
780 name of a simple command. The exit status of a function is
781 the exit status of the last command executed in the body. (See
786 In a non-interactive shell, or an interactive shell in which the
787 .B interactive_comments
790 builtin is enabled (see
792 .B "SHELL BUILTIN COMMANDS"
793 below), a word beginning with
795 causes that word and all remaining characters on that line to
796 be ignored. An interactive shell without the
797 .B interactive_comments
798 option enabled does not allow comments. The
799 .B interactive_comments
800 option is on by default in interactive shells.
802 \fIQuoting\fP is used to remove the special meaning of certain
803 characters or words to the shell. Quoting can be used to
804 disable special treatment for special characters, to prevent
805 reserved words from being recognized as such, and to prevent
808 Each of the \fImetacharacters\fP listed above under
811 has special meaning to the shell and must be quoted if it is to
814 When the command history expansion facilities are being used, the
815 \fIhistory expansion\fP character, usually \fB!\fP, must be quoted
816 to prevent history expansion.
818 There are three quoting mechanisms: the
819 .IR "escape character" ,
820 single quotes, and double quotes.
822 A non-quoted backslash (\fB\e\fP) is the
823 .IR "escape character" .
824 It preserves the literal value of the next character that follows,
825 with the exception of <newline>. If a \fB\e\fP<newline> pair
826 appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
827 is treated as a line continuation (that is, it is removed from the
828 input stream and effectively ignored).
830 Enclosing characters in single quotes preserves the literal value
831 of each character within the quotes. A single quote may not occur
832 between single quotes, even when preceded by a backslash.
834 Enclosing characters in double quotes preserves the literal value
835 of all characters within the quotes, with the exception of
844 retain their special meaning within double quotes. The backslash
845 retains its special meaning only when followed by one of the following
853 A double quote may be quoted within double quotes by preceding it with
856 The special parameters
860 have special meaning when in double
866 Words of the form \fB$\fP'\fIstring\fP' are treated specially. The
867 word expands to \fIstring\fP, with backslash-escaped characters replaced
868 as specifed by the ANSI C standard. Backslash escape sequences, if
869 present, are decoded as follows:
904 the character whose ASCII code is the octal value \fInnn\fP
905 (one to three digits)
908 the character whose ASCII code is the hexadecimal value \fInnn\fP
909 (one to three digits)
913 The expanded result is single-quoted, as if the dollar sign had
916 A double-quoted string preceded by a dollar sign (\fB$\fP) will cause
917 the string to be translated according to the current locale.
918 If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
920 If the string is translated and replaced, the replacement is
925 is an entity that stores values.
928 a number, or one of the special characters listed below under
929 .BR "Special Parameters" .
930 For the shell's purposes, a
932 is a parameter denoted by a
935 A parameter is set if it has been assigned a value. The null string is
936 a valid value. Once a variable is set, it may be unset only by using
941 .B SHELL BUILTIN COMMANDS
946 may be assigned to by a statement of the form
949 \fIname\fP=[\fIvalue\fP]
954 is not given, the variable is assigned the null string. All
956 undergo tilde expansion, parameter and variable expansion,
957 command substitution, arithmetic expansion, and quote
961 below). If the variable has its
967 .BR "SHELL BUILTIN COMMANDS" )
970 is subject to arithmetic expansion even if the $((...)) expansion is
972 .B "Arithmetic Expansion"
974 Word splitting is not performed, with the exception
975 of \fB"$@"\fP as explained below under
976 .BR "Special Parameters" .
977 Pathname expansion is not performed.
978 .SS Positional Parameters
981 .I positional parameter
982 is a parameter denoted by one or more
983 digits, other than the single digit 0. Positional parameters are
984 assigned from the shell's arguments when it is invoked,
985 and may be reassigned using the
987 builtin command. Positional parameters may not be assigned to
988 with assignment statements. The positional parameters are
989 temporarily replaced when a shell function is executed (see
994 When a positional parameter consisting of more than a single
995 digit is expanded, it must be enclosed in braces (see
999 .SS Special Parameters
1001 The shell treats several parameters specially. These parameters may
1002 only be referenced; assignment to them is not allowed.
1006 Expands to the positional parameters, starting from one. When the
1007 expansion occurs within double quotes, it expands to a single word
1008 with the value of each parameter separated by the first character
1012 special variable. That is, "\fB$*\fP" is equivalent
1013 to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
1015 is the first character of the value of the
1021 is unset, the parameters are separated by spaces.
1025 is null, the parameters are joined without intervening separators.
1028 Expands to the positional parameters, starting from one. When the
1029 expansion occurs within double quotes, each parameter expands to a
1030 separate word. That is, "\fB$@\fP" is equivalent to
1031 "\fB$1\fP" "\fB$2\fP" ...
1032 When there are no positional parameters, "\fB$@\fP" and
1034 expand to nothing (i.e., they are removed).
1037 Expands to the number of positional parameters in decimal.
1040 Expands to the status of the most recently executed foreground
1044 Expands to the current option flags as specified upon invocation,
1047 builtin command, or those set by the shell itself
1053 Expands to the process ID of the shell. In a () subshell, it
1054 expands to the process ID of the current shell, not the
1058 Expands to the process ID of the most recently executed background
1059 (asynchronous) command.
1062 Expands to the name of the shell or shell script. This is set at
1063 shell initialization. If
1065 is invoked with a file of commands,
1067 is set to the name of that file. If
1073 is set to the first argument after the string to be
1074 executed, if one is present. Otherwise, it is set
1075 to the file name used to invoke
1077 as given by argument zero.
1080 At shell startup, set to the absolute file name of the shell or shell
1081 script being executed as passed in the argument list.
1082 Subsequently, expands to the last argument to the previous command,
1084 Also set to the full file name of each command executed and placed in
1085 the environment exported to that command.
1086 When checking mail, this parameter holds the name of the mail file
1087 currently being checked.
1091 The following variables are set by the shell:
1096 The process ID of the shell's parent. This variable is readonly.
1099 The current working directory as set by the
1104 The previous working directory as set by the
1109 Set to the line of input read by the
1111 builtin command when no arguments are supplied.
1114 Expands to the user ID of the current user, initialized at shell startup.
1115 This variable is readonly.
1118 Expands to the effective user ID of the current user, initialized at
1119 shell startup. This variable is readonly.
1122 An array variable containing the list of groups of which the current
1127 have no effect and return an error status.
1131 is unset, it loses its special properties, even if it is
1135 Expands to the full file name used to invoke this instance of
1139 Expands to a string describing the version of this instance of
1143 A readonly array variable whose members hold version information for
1146 The values assigned to the array members are as follows:
1151 .B BASH_VERSINFO[\fR0\fP]
1152 The major version number (the \fIrelease\fP).
1154 .B BASH_VERSINFO[\fR1\fP]
1155 The minor version number (the \fIversion\fP).
1157 .B BASH_VERSINFO[\fR2\fP]
1160 .B BASH_VERSINFO[\fR3\fP]
1163 .B BASH_VERSINFO[\fR4\fP]
1164 The release status (e.g., \fIbeta1\fP).
1166 .B BASH_VERSINFO[\fR5\fP]
1167 The value of \fBMACHTYPE\fP.
1172 Incremented by one each time an instance of
1177 Each time this parameter is referenced, a random integer between
1179 generated. The sequence of random numbers may be initialized by assigning
1186 is unset, it loses its special properties, even if it is
1190 Each time this parameter is
1191 referenced, the number of seconds since shell invocation is returned. If a
1192 value is assigned to
1195 the value returned upon subsequent
1197 the number of seconds since the assignment plus the value assigned.
1201 is unset, it loses its special properties, even if it is
1205 Each time this parameter is referenced, the shell substitutes
1206 a decimal number representing the current sequential line number
1207 (starting with 1) within a script or function. When not in a
1208 script or function, the value substituted is not guaranteed to
1213 is unset, it loses its special properties, even if it is
1217 The history number, or index in the history list, of the current
1222 is unset, it loses its special properties, even if it is
1226 The name of any currently-executing shell function.
1227 This variable exists only when a shell function is executing.
1231 have no effect and return an error status.
1235 is unset, it loses its special properties, even if it is
1239 An array variable (see
1241 below) containing the current contents of the directory stack.
1242 Directories appear in the stack in the order they are displayed by the
1245 Assigning to members of this array variable may be used to modify
1246 directories already in the stack, but the
1250 builtins must be used to add and remove directories.
1251 Assignment to this variable will not change the current directory.
1255 is unset, it loses its special properties, even if it is
1259 An array variable (see
1261 below) containing a list of exit status values from the processes
1262 in the most-recently-executed foreground pipeline (which may
1263 contain only a single command).
1266 The value of the last option argument processed by the
1268 builtin command (see
1270 .B SHELL BUILTIN COMMANDS
1274 The index of the next argument to be processed by the
1276 builtin command (see
1278 .B SHELL BUILTIN COMMANDS
1282 Automatically set to the name of the current host.
1285 Automatically set to a string that uniquely
1286 describes the type of machine on which
1289 The default is system-dependent.
1292 Automatically set to a string that
1293 describes the operating system on which
1296 The default is system-dependent.
1299 Automatically set to a string that fully describes the system
1302 is executing, in the standard GNU \fIcpu-company-system\fP format.
1303 The default is system-dependent.
1306 A colon-separated list of enabled shell options. Each word in
1307 the list is a valid argument for the
1311 builtin command (see
1313 .B "SHELL BUILTIN COMMANDS"
1314 below). The options appearing in
1317 are those reported as
1320 If this variable is in the environment when
1322 starts up, each shell option in the list will be enabled before
1323 reading any startup files.
1324 This variable is read-only.
1327 An array variable (see \fBArrays\fP below) consisting of the individual
1328 words in the current command line.
1329 This variable is available only in shell functions invoked by the
1330 programmable completion facilities (see \fBProgrammable Completion\fP
1334 An index into \fB${COMP_WORDS}\fP of the word containing the current
1336 This variable is available only in shell functions invoked by the
1337 programmable completion facilities (see \fBProgrammable Completion\fP
1341 The current command line.
1342 This variable is available only in shell functions and external
1343 commands invoked by the
1344 programmable completion facilities (see \fBProgrammable Completion\fP
1348 The index of the current cursor position relative to the beginning of
1349 the current command.
1350 If the current cursor position is at the end of the current command,
1351 the value of this variable is equal to \fB${#COMP_LINE}\fP.
1352 This variable is available only in shell functions and external
1353 commands invoked by the
1354 programmable completion facilities (see \fBProgrammable Completion\fP
1358 The following variables are used by the shell. In some cases,
1360 assigns a default value to a variable; these cases are noted
1367 .I Internal Field Separator
1369 for word splitting after expansion and to
1370 split lines into words with the
1372 builtin command. The default value is
1373 ``<space><tab><newline>''.
1376 The search path for commands. It
1377 is a colon-separated list of directories in which
1378 the shell looks for commands (see
1380 .B COMMAND EXECUTION
1381 below). The default path is system-dependent,
1382 and is set by the administrator who installs
1385 .if t \f(CW/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.\fP.
1386 .if n ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.''.
1389 The home directory of the current user; the default argument for the
1390 \fBcd\fP builtin command.
1391 The value of this variable is also used when performing tilde expansion.
1394 The search path for the
1397 This is a colon-separated list of directories in which the shell looks
1398 for destination directories specified by the
1401 A sample value is ``.:~:/usr''.
1404 If this parameter is set when \fBbash\fP is executing a shell script,
1405 its value is interpreted as a filename containing commands to
1406 initialize the shell, as in
1411 is subjected to parameter expansion, command substitution, and arithmetic
1412 expansion before being interpreted as a file name.
1415 is not used to search for the resultant file name.
1418 If this parameter is set to a file name and the
1421 variable is not set,
1423 informs the user of the arrival of mail in the specified file.
1429 checks for mail. The default is 60 seconds. When it is time to check
1430 for mail, the shell does so before displaying the primary prompt.
1431 If this variable is unset, or set to a value that is not a number
1432 greater than or equal to zero, the shell disables mail checking.
1435 A colon-separated list of file names to be checked for mail.
1436 The message to be printed when mail arrives in a particular file
1437 may be specified by separating the file name from the message with a `?'.
1438 When used in the text of the message, \fB$_\fP expands to the name of
1439 the current mailfile.
1443 \fBMAILPATH\fP='/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"'
1446 supplies a default value for this variable, but the location of the user
1447 mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
1451 The value of this parameter is expanded (see
1454 below) and used as the primary prompt string. The default value is
1455 ``\fB\es\-\ev\e$ \fP''.
1458 The value of this parameter is expanded as with
1460 and used as the secondary prompt string. The default is
1464 The value of this parameter is used as the prompt for the
1472 The value of this parameter is expanded as with
1474 and the value is printed before each command
1476 displays during an execution trace. The first character of
1479 is replicated multiple times, as necessary, to indicate multiple
1480 levels of indirection. The default is ``\fB+ \fP''.
1483 The value of this parameter is used as a format string specifying
1484 how the timing information for pipelines prefixed with the
1486 reserved word should be displayed.
1487 The \fB%\fP character introduces an escape sequence that is
1488 expanded to a time value or other information.
1489 The escape sequences and their meanings are as follows; the
1490 braces denote optional portions.
1499 The elapsed time in seconds.
1502 The number of CPU seconds spent in user mode.
1505 The number of CPU seconds spent in system mode.
1508 The CPU percentage, computed as (%U + %S) / %R.
1512 The optional \fIp\fP is a digit specifying the \fIprecision\fP,
1513 the number of fractional digits after a decimal point.
1514 A value of 0 causes no decimal point or fraction to be output.
1515 At most three places after the decimal point may be specified;
1516 values of \fIp\fP greater than 3 are changed to 3.
1517 If \fIp\fP is not specified, the value 3 is used.
1519 The optional \fBl\fP specifies a longer format, including
1520 minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
1521 The value of \fIp\fP determines whether or not the fraction is
1524 If this variable is not set, \fBbash\fP acts as if it had the
1525 value \fB$'\enreal\et%3lR\enuser\et%3lU\ensys\t%3lS'\fP.
1526 If the value is null, no timing information is displayed.
1527 A trailing newline is added when the format string is displayed.
1530 The number of commands to remember in the command history (see
1533 below). The default value is 500.
1536 The name of the file in which command history is saved (see
1539 below). The default value is \fI~/.bash_history\fP. If unset, the
1540 command history is not saved when an interactive shell exits.
1543 The maximum number of lines contained in the history file. When this
1544 variable is assigned a value, the history file is truncated, if
1545 necessary, to contain no more than that number of lines. The default
1546 value is 500. The history file is also truncated to this size after
1547 writing it when an interactive shell exits.
1550 If set to the value 1,
1552 displays error messages generated by the
1554 builtin command (see
1556 .B SHELL BUILTIN COMMANDS
1560 is initialized to 1 each time the shell is invoked or a shell
1564 Used to determine the locale category for any category not specifically
1565 selected with a variable starting with \fBLC_\fP.
1568 This variable overrides the value of \fBLANG\fP and any other
1569 \fBLC_\fP variable specifying a locale category.
1572 This variable determines the collation order used when sorting the
1573 results of pathname expansion, and determines the behavior of range
1574 expressions, equivalence classes, and collating sequences within
1575 pathname expansion and pattern matching.
1578 This variable determines the interpretation of characters and the
1579 behavior of character classes within pathname expansion and pattern
1583 This variable determines the locale used to translate double-quoted
1584 strings preceded by a \fB$\fP.
1587 This variable determines the locale category used for number formatting.
1590 Used by the \fBselect\fP builtin command to determine the column length
1591 for printing selection lists. Automatically set upon receipt of a SIGWINCH.
1594 Used by the \fBselect\fP builtin command to determine the terminal width
1595 when printing selection lists. Automatically set upon receipt of a SIGWINCH.
1598 If set, the value is executed as a command prior to issuing each primary
1603 action of an interactive shell on receipt of an
1606 character as the sole input. If set, the value is the number of
1610 characters which must be
1611 typed as the first characters on an input line before
1613 exits. If the variable exists but does not have a numeric value, or
1614 has no value, the default value is 10. If it does not exist,
1617 signifies the end of input to the shell.
1620 If set to a value greater than zero, the value is interpreted as the
1621 number of seconds to wait for input after issuing the primary prompt.
1623 terminates after waiting for that number of seconds if input does
1627 The default editor for the
1632 A colon-separated list of suffixes to ignore when performing
1633 filename completion (see
1637 A filename whose suffix matches one of the entries in
1640 is excluded from the list of matched filenames.
1641 A sample value is ``.o:~''.
1644 A colon-separated list of patterns defining the set of filenames to
1645 be ignored by pathname expansion.
1646 If a filename matched by a pathname expansion pattern also matches one
1650 it is removed from the list of matches.
1653 The filename for the
1655 startup file, overriding the default of
1663 If set to a value of
1665 lines which begin with a
1667 character are not entered on the history list.
1668 If set to a value of
1670 lines matching the last history line are not entered.
1673 combines the two options.
1674 If unset, or if set to any other value than those above,
1676 by the parser are saved on the history list, subject to the value
1679 This variable's function is superseded by
1681 The second and subsequent lines of a multi-line compound command are
1682 not tested, and are added to the history regardless of the value of
1686 A colon-separated list of patterns used to decide which command lines
1687 should be saved on the history list. Each pattern is anchored at the
1688 beginning of the line and must match the complete line (no implicit
1689 `\fB*\fP' is appended). Each pattern is tested against the line
1690 after the checks specified by
1693 In addition to the normal shell pattern matching characters, `\fB&\fP'
1694 matches the previous history line. `\fB&\fP' may be escaped using a
1695 backslash; the backslash is removed before attempting a match.
1696 The second and subsequent lines of a multi-line compound command are
1697 not tested, and are added to the history regardless of the value of
1701 The two or three characters which control history expansion
1702 and tokenization (see
1704 .B HISTORY EXPANSION
1705 below). The first character is the \fIhistory expansion\fP character,
1706 the character which signals the start of a history
1707 expansion, normally `\fB!\fP'.
1708 The second character is the \fIquick substitution\fP
1709 character, which is used as shorthand for re-running the previous
1710 command entered, substituting one string for another in the command.
1711 The default is `\fB^\fP'.
1712 The optional third character is the character
1713 which indicates that the remainder of the line is a comment when found
1714 as the first character of a word, normally `\fB#\fP'. The history
1715 comment character causes history substitution to be skipped for the
1716 remaining words on the line. It does not necessarily cause the shell
1717 parser to treat the rest of the line as a comment.
1720 Contains the name of a file in the same format as
1722 that should be read when the shell needs to complete a
1724 The list of possible hostname completions may be changed while the
1726 the next time hostname completion is attempted after the
1729 adds the contents of the new file to the existing list.
1733 is set, but has no value, \fBbash\fP attempts to read
1735 to obtain the list of possible hostname completions.
1739 is unset, the hostname list is cleared.
1742 This variable controls how the shell interacts with the user and
1743 job control. If this variable is set, single word simple
1744 commands without redirections are treated as candidates for resumption
1745 of an existing stopped job. There is no ambiguity allowed; if there is
1746 more than one job beginning with the string typed, the job most recently
1747 accessed is selected. The
1749 of a stopped job, in this context, is the command line used to
1753 the string supplied must match the name of a stopped job exactly;
1756 the string supplied needs to match a substring of the name of a
1759 value provides functionality analogous to the
1764 below). If set to any other value, the supplied string must
1765 be a prefix of a stopped job's name; this provides functionality
1771 An array variable from which \fBbash\fP reads the possible completions
1772 generated by a shell function invoked by the programmable completion
1773 facility (see \fBProgrammable Completion\fP below).
1777 provides one-dimensional array variables. Any variable may be used as
1780 builtin will explicitly declare an array. There is no maximum
1781 limit on the size of an array, nor any requirement that members
1782 be indexed or assigned contiguously. Arrays are indexed using
1783 integers and are zero-based.
1785 An array is created automatically if any variable is assigned to using
1786 the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
1788 is treated as an arithmetic expression that must evaluate to a number
1789 greater than or equal to zero. To explicitly declare an array, use
1790 .B declare \-a \fIname\fP
1793 .B SHELL BUILTIN COMMANDS
1795 .B declare \-a \fIname\fP[\fIsubscript\fP]
1796 is also accepted; the \fIsubscript\fP is ignored. Attributes may be
1797 specified for an array variable using the
1801 builtins. Each attribute applies to all members of an array.
1803 Arrays are assigned to using compound assignments of the form
1804 \fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
1805 \fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP. Only
1806 \fIstring\fP is required. If
1807 the optional brackets and subscript are supplied, that index is assigned to;
1808 otherwise the index of the element assigned is the last index assigned
1809 to by the statement plus one. Indexing starts at zero.
1810 This syntax is also accepted by the
1812 builtin. Individual array elements may be assigned to using the
1813 \fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
1815 Any element of an array may be referenced using
1816 ${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
1817 conflicts with pathname expansion. If
1818 \fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
1819 all members of \fIname\fP. These subscripts differ only when the
1820 word appears within double quotes. If the word is double-quoted,
1821 ${\fIname\fP[*]} expands to a single
1822 word with the value of each array member separated by the first
1826 special variable, and ${\fIname\fP[@]} expands each element of
1827 \fIname\fP to a separate word. When there are no array members,
1828 ${\fIname\fP[@]} expands to nothing. This is analogous to the expansion
1829 of the special parameters \fB*\fP and \fB@\fP (see
1830 .B Special Parameters
1831 above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
1832 ${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
1833 \fB@\fP, the expansion is the number of elements in the array.
1834 Referencing an array variable without a subscript is equivalent to
1835 referencing element zero.
1839 builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
1840 destroys the array element at index \fIsubscript\fP.
1841 \fBunset\fP \fIname\fP, where \fIname\fP is an array, or
1842 \fBunset\fP \fIname\fP[\fIsubscript\fP], where
1843 \fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
1850 builtins each accept a
1852 option to specify an array. The
1856 option to assign a list of words read from the standard input
1861 builtins display array values in a way that allows them to be
1862 reused as assignments.
1864 Expansion is performed on the command line after it has been split into
1865 words. There are seven kinds of expansion performed:
1866 .IR "brace expansion" ,
1867 .IR "tilde expansion" ,
1868 .IR "parameter and variable expansion" ,
1869 .IR "command substitution" ,
1870 .IR "arithmetic expansion" ,
1871 .IR "word splitting" ,
1873 .IR "pathname expansion" .
1875 The order of expansions is: brace expansion, tilde expansion,
1876 parameter, variable and arithmetic expansion and
1877 command substitution
1878 (done in a left-to-right fashion), word splitting, and pathname
1881 On systems that can support it, there is an additional expansion
1882 available: \fIprocess substitution\fP.
1884 Only brace expansion, word splitting, and pathname expansion
1885 can change the number of words of the expansion; other expansions
1886 expand a single word to a single word.
1887 The only exceptions to this are the expansions of
1888 "\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
1889 as explained above (see
1894 .I "Brace expansion"
1895 is a mechanism by which arbitrary strings
1896 may be generated. This mechanism is similar to
1897 \fIpathname expansion\fP, but the filenames generated
1898 need not exist. Patterns to be brace expanded take
1899 the form of an optional
1901 followed by a series of comma-separated strings
1902 between a pair of braces, followed by an optional
1904 The preamble is prefixed to each string contained
1905 within the braces, and the postscript is then appended
1906 to each resulting string, expanding left to right.
1908 Brace expansions may be nested. The results of each expanded
1909 string are not sorted; left to right order is preserved.
1910 For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
1912 Brace expansion is performed before any other expansions,
1913 and any characters special to other expansions are preserved
1914 in the result. It is strictly textual.
1916 does not apply any syntactic interpretation to the context of the
1917 expansion or the text between the braces.
1919 A correctly-formed brace expansion must contain unquoted opening
1920 and closing braces, and at least one unquoted comma.
1921 Any incorrectly formed brace expansion is left unchanged.
1922 A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
1923 being considered part of a brace expression.
1924 To avoid conflicts with parameter expansion, the string \fB${\fP
1925 is not considered eligible for brace expansion.
1927 This construct is typically used as shorthand when the common
1928 prefix of the strings to be generated is longer than in the
1932 mkdir /usr/local/src/bash/{old,new,dist,bugs}
1936 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
1939 Brace expansion introduces a slight incompatibility with
1940 historical versions of
1943 does not treat opening or closing braces specially when they
1944 appear as part of a word, and preserves them in the output.
1946 removes braces from words as a consequence of brace
1947 expansion. For example, a word entered to
1950 appears identically in the output. The same word is
1955 If strict compatibility with
1961 option or disable brace expansion with the
1967 .B SHELL BUILTIN COMMANDS
1971 If a word begins with an unquoted tilde character (`\fB~\fP'), all of
1972 the characters preceding the first unquoted slash (or all characters,
1973 if there is no unquoted slash) are considered a \fItilde-prefix\fP.
1974 If none of the characters in the tilde-prefix are quoted, the
1975 characters in the tilde-prefix following the tilde are treated as a
1976 possible \fIlogin name\fP.
1977 If this login name is the null string, the tilde is replaced with the
1978 value of the shell parameter
1984 is unset, the home directory of the user executing the shell is
1985 substituted instead.
1986 Otherwise, the tilde-prefix is replaced with the home directory
1987 associated with the specified login name.
1989 If the tilde-prefix is a `~+', the value of the shell variable
1992 replaces the tilde-prefix.
1993 If the tilde-prefix is a `~\-', the value of the shell variable
1996 if it is set, is substituted.
1997 If the characters following the tilde in the tilde-prefix consist
1998 of a number \fIN\fP, optionally prefixed
1999 by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
2000 element from the directory stack, as it would be displayed by the
2002 builtin invoked with the tilde-prefix as an argument.
2003 If the characters following the tilde in the tilde-prefix consist of a
2004 number without a leading `+' or `\-', `+' is assumed.
2006 If the login name is invalid, or the tilde expansion fails, the word
2009 Each variable assignment is checked for unquoted tilde-prefixes immediately
2014 In these cases, tilde expansion is also performed.
2015 Consequently, one may use file names with tildes in assignments to
2023 and the shell assigns the expanded value.
2024 .SS Parameter Expansion
2026 The `\fB$\fP' character introduces parameter expansion,
2027 command substitution, or arithmetic expansion. The parameter name
2028 or symbol to be expanded may be enclosed in braces, which
2029 are optional but serve to protect the variable to be expanded from
2030 characters immediately following it which could be
2031 interpreted as part of the name.
2033 When braces are used, the matching ending brace is the first `\fB}\fP'
2034 not escaped by a backslash or within a quoted string, and not within an
2035 embedded arithmetic expansion, command substitution, or paramter
2041 The value of \fIparameter\fP is substituted. The braces are required
2044 is a positional parameter with more than one digit,
2047 is followed by a character which is not to be
2048 interpreted as part of its name.
2051 If the first character of \fIparameter\fP is an exclamation point,
2052 a level of variable indirection is introduced.
2053 \fBBash\fP uses the value of the variable formed from the rest of
2054 \fIparameter\fP as the name of the variable; this variable is then
2055 expanded and that value is used in the rest of the substitution, rather
2056 than the value of \fIparameter\fP itself.
2057 This is known as \fIindirect expansion\fP.
2058 The exception to this is the expansion of ${!\fIprefix\fP*}
2061 In each of the cases below, \fIword\fP is subject to tilde expansion,
2062 parameter expansion, command substitution, and arithmetic expansion.
2063 When not performing substring expansion, \fBbash\fP tests for a parameter
2064 that is unset or null; omitting the colon results in a test only for a
2065 parameter that is unset.
2069 ${\fIparameter\fP\fB:\-\fP\fIword\fP}
2070 \fBUse Default Values\fP. If
2072 is unset or null, the expansion of
2074 is substituted. Otherwise, the value of
2078 ${\fIparameter\fP\fB:=\fP\fIword\fP}
2079 \fBAssign Default Values\fP.
2082 is unset or null, the expansion of
2088 is then substituted. Positional parameters and special parameters may
2089 not be assigned to in this way.
2091 ${\fIparameter\fP\fB:?\fP\fIword\fP}
2092 \fBDisplay Error if Null or Unset\fP.
2095 is null or unset, the expansion of \fIword\fP (or a message to that effect
2098 is not present) is written to the standard error and the shell, if it
2099 is not interactive, exits. Otherwise, the value of \fIparameter\fP is
2102 ${\fIparameter\fP\fB:+\fP\fIword\fP}
2103 \fBUse Alternate Value\fP.
2106 is null or unset, nothing is substituted, otherwise the expansion of
2111 ${\fIparameter\fP\fB:\fP\fIoffset\fP}
2113 ${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
2115 \fBSubstring Expansion.\fP
2116 Expands to up to \fIlength\fP characters of \fIparameter\fP
2117 starting at the character specified by \fIoffset\fP.
2118 If \fIlength\fP is omitted, expands to the substring of
2119 \fIparameter\fP starting at the character specified by \fIoffset\fP.
2120 \fIlength\fP and \fIoffset\fP are arithmetic expressions (see
2123 ARITHMETIC EVALUATION
2125 \fIlength\fP must evaluate to a number greater than or equal to zero.
2126 If \fIoffset\fP evaluates to a number less than zero, the value
2127 is used as an offset from the end of the value of \fIparameter\fP.
2128 If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
2129 parameters beginning at \fIoffset\fP.
2130 If \fIparameter\fP is an array name indexed by @ or *,
2131 the result is the \fIlength\fP
2132 members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2133 Substring indexing is zero-based unless the positional parameters
2134 are used, in which case the indexing starts at 1.
2136 ${\fB!\fP\fIprefix\fP\fB*\fP}
2137 Expands to the names of variables whose names begin with \fIprefix\fP,
2138 separated by the first character of the
2143 ${\fB#\fP\fIparameter\fP}
2144 The length in characters of the value of \fIparameter\fP is substituted.
2151 the value substituted is the number of positional parameters.
2154 is an array name subscripted by
2158 the value substituted is the number of elements in the array.
2161 ${\fIparameter\fP\fB#\fP\fIword\fP}
2163 ${\fIparameter\fP\fB##\fP\fIword\fP}
2167 is expanded to produce a pattern just as in pathname
2168 expansion. If the pattern matches the beginning of
2171 then the result of the expansion is the expanded value of
2173 with the shortest matching pattern (the ``\fB#\fP'' case) or the
2174 longest matching pattern (the ``\fB##\fP'' case) deleted.
2181 the pattern removal operation is applied to each positional
2182 parameter in turn, and the expansion is the resultant list.
2185 is an array variable subscripted with
2189 the pattern removal operation is applied to each member of the
2190 array in turn, and the expansion is the resultant list.
2193 ${\fIparameter\fP\fB%\fP\fIword\fP}
2195 ${\fIparameter\fP\fB%%\fP\fIword\fP}
2197 The \fIword\fP is expanded to produce a pattern just as in
2199 If the pattern matches a trailing portion of the expanded value of
2201 then the result of the expansion is the expanded value of
2203 with the shortest matching pattern (the ``\fB%\fP'' case) or the
2204 longest matching pattern (the ``\fB%%\fP'' case) deleted.
2211 the pattern removal operation is applied to each positional
2212 parameter in turn, and the expansion is the resultant list.
2215 is an array variable subscripted with
2219 the pattern removal operation is applied to each member of the
2220 array in turn, and the expansion is the resultant list.
2223 ${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2225 ${\fIparameter\fP\fB//\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2227 The \fIpattern\fP is expanded to produce a pattern just as in
2229 \fIParameter\fP is expanded and the longest match of \fIpattern\fP
2230 against its value is replaced with \fIstring\fP.
2231 In the first form, only the first match is replaced.
2232 The second form causes all matches of \fIpattern\fP to be
2233 replaced with \fIstring\fP.
2234 If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
2235 of the expanded value of \fIparameter\fP.
2236 If \fIpattern\fP begins with \fB%\fP, it must match at the end
2237 of the expanded value of \fIparameter\fP.
2238 If \fIstring\fP is null, matches of \fIpattern\fP are deleted
2239 and the \fB/\fP following \fIpattern\fP may be omitted.
2246 the substitution operation is applied to each positional
2247 parameter in turn, and the expansion is the resultant list.
2250 is an array variable subscripted with
2254 the substitution operation is applied to each member of the
2255 array in turn, and the expansion is the resultant list.
2256 .SS Command Substitution
2258 \fICommand substitution\fP allows the output of a command to replace
2259 the command name. There are two forms:
2263 \fB$(\fP\fIcommand\fP\|\fB)\fP
2267 \fB`\fP\fIcommand\fP\fB`\fP
2271 performs the expansion by executing \fIcommand\fP and
2272 replacing the command substitution with the standard output of the
2273 command, with any trailing newlines deleted.
2274 Embedded newlines are not deleted, but they may be removed during
2276 The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
2277 the equivalent but faster \fB$(< \fIfile\fP)\fR.
2279 When the old-style backquote form of substitution is used,
2280 backslash retains its literal meaning except when followed by
2285 The first backquote not preceded by a backslash terminates the
2286 command substitution.
2287 When using the $(\^\fIcommand\fP\|) form, all characters between the
2288 parentheses make up the command; none are treated specially.
2290 Command substitutions may be nested. To nest when using the backquoted form,
2291 escape the inner backquotes with backslashes.
2293 If the substitution appears within double quotes, word splitting and
2294 pathname expansion are not performed on the results.
2295 .SS Arithmetic Expansion
2297 Arithmetic expansion allows the evaluation of an arithmetic expression
2298 and the substitution of the result. The format for arithmetic expansion is:
2301 \fB$((\fP\fIexpression\fP\fB))\fP
2306 is treated as if it were within double quotes, but a double quote
2307 inside the parentheses is not treated specially.
2308 All tokens in the expression undergo parameter expansion, string
2309 expansion, command substitution, and quote removal.
2310 Arithmetic substitutions may be nested.
2312 The evaluation is performed according to the rules listed below under
2314 .BR "ARITHMETIC EVALUATION" .
2319 prints a message indicating failure and no substitution occurs.
2320 .SS Process Substitution
2322 \fIProcess substitution\fP is supported on systems that support named
2323 pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
2324 It takes the form of
2325 \fB<(\fP\fIlist\^\fP\fB)\fP
2327 \fB>(\fP\fIlist\^\fP\fB)\fP.
2328 The process \fIlist\fP is run with its input or output connected to a
2329 \fIFIFO\fP or some file in \fB/dev/fd\fP. The name of this file is
2330 passed as an argument to the current command as the result of the
2331 expansion. If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
2332 the file will provide input for \fIlist\fP. If the
2333 \fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
2334 argument should be read to obtain the output of \fIlist\fP.
2336 When available, process substitution is performed
2337 simultaneously with parameter and variable expansion,
2338 command substitution,
2339 and arithmetic expansion.
2342 The shell scans the results of
2343 parameter expansion,
2344 command substitution,
2346 arithmetic expansion
2347 that did not occur within double quotes for
2348 .IR "word splitting" .
2350 The shell treats each character of
2353 as a delimiter, and splits the results of the other
2354 expansions into words on these characters. If
2359 .BR <space><tab><newline> ,
2364 characters serves to delimit words. If
2367 has a value other than the default, then sequences of
2368 the whitespace characters
2372 are ignored at the beginning and end of the
2373 word, as long as the whitespace character is in the
2380 whitespace character).
2387 whitespace, along with any adjacent
2390 whitespace characters, delimits a field.
2394 whitespace characters is also treated as a delimiter.
2398 is null, no word splitting occurs.
2400 Explicit null arguments (\^\f3"\^"\fP or \^\f3'\^'\fP\^) are retained.
2401 Unquoted implicit null arguments, resulting from the expansion of
2402 parameters that have no values, are removed.
2403 If a parameter with no value is expanded within double quotes, a
2404 null argument results and is retained.
2406 Note that if no expansion occurs, no splitting
2408 .SS Pathname Expansion
2410 After word splitting,
2413 option has been set,
2415 scans each word for the characters
2420 If one of these characters appears, then the word is
2423 and replaced with an alphabetically sorted list of
2424 file names matching the pattern.
2425 If no matching file names are found,
2426 and the shell option
2428 is disabled, the word is left unchanged.
2431 option is set, and no matches are found,
2432 the word is removed.
2435 is enabled, the match is performed without regard to the case
2436 of alphabetic characters.
2437 When a pattern is used for pathname expansion,
2440 at the start of a name or immediately following a slash
2441 must be matched explicitly, unless the shell option
2444 When matching a pathname, the slash character must always be
2448 character is not treated specially.
2449 See the description of
2453 .B SHELL BUILTIN COMMANDS
2454 for a description of the
2464 shell variable may be used to restrict the set of file names matching a
2469 is set, each matching file name that also matches one of the patterns in
2472 is removed from the list of matches.
2477 are always ignored, even when
2480 is set. However, setting
2483 has the effect of enabling the
2485 shell option, so all other file names beginning with a
2488 To get the old behavior of ignoring file names beginning with a
2492 one of the patterns in
2497 option is disabled when
2502 \fBPattern Matching\fP
2504 Any character that appears in a pattern, other than the special pattern
2505 characters described below, matches itself. The NUL character may not
2506 occur in a pattern. The special pattern characters must be quoted if
2507 they are to be matched literally.
2509 The special pattern characters have the following meanings:
2514 Matches any string, including the null string.
2517 Matches any single character.
2520 Matches any one of the enclosed characters. A pair of characters
2521 separated by a hyphen denotes a
2522 \fIrange expression\fP;
2523 any character that sorts between those two characters, inclusive,
2524 using the current locale's collating sequence and character set,
2525 is matched. If the first character following the
2531 then any character not enclosed is matched.
2532 The sorting order of characters in range expressions is determined by
2533 the current locale and the value of the \fBLC_COLLATE\fP shell variable,
2537 may be matched by including it as the first or last character
2541 may be matched by including it as the first character
2550 \fIcharacter classes\fP can be specified using the syntax
2551 \fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
2552 following classes defined in the POSIX.2 standard:
2556 .if n alnum alpha ascii blank cntrl digit graph lower print punct space upper xdigit
2557 .if t alnum alpha ascii blank cntrl digit graph lower print punct space upper xdigit
2559 A character class matches any character belonging to that class.
2567 an \fIequivalence class\fP can be specified using the syntax
2568 \fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
2569 same collation weight (as defined by the current locale) as
2570 the character \fIc\fP.
2578 the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
2583 If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
2584 builtin, several extended pattern matching operators are recognized.
2585 In the following description, a \fIpattern-list\fP is a list of one
2586 or more patterns separated by a \fB|\fP.
2587 Composite patterns may be formed using one or more of the following
2593 \fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
2594 Matches zero or one occurrence of the given patterns
2596 \fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
2597 Matches zero or more occurrences of the given patterns
2599 \fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
2600 Matches one or more occurrences of the given patterns
2602 \fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
2603 Matches exactly one of the given patterns
2605 \fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
2606 Matches anything except one of the given patterns
2611 After the preceding expansions, all unquoted occurrences of the
2615 and \^\f3"\fP\^ that did not result from one of the above
2616 expansions are removed.
2618 Before a command is executed, its input and output
2621 using a special notation interpreted by the shell.
2622 Redirection may also be used to open and close files for the
2623 current shell execution environment. The following redirection
2624 operators may precede or appear anywhere within a
2628 Redirections are processed in the order they appear, from
2631 In the following descriptions, if the file descriptor number is
2632 omitted, and the first character of the redirection operator is
2634 the redirection refers to the standard input (file descriptor
2635 0). If the first character of the redirection operator is
2637 the redirection refers to the standard output (file descriptor
2640 The word following the redirection operator in the following
2641 descriptions, unless otherwise noted, is subjected to brace expansion,
2642 tilde expansion, parameter expansion, command substitution, arithmetic
2643 expansion, quote removal, pathname expansion, and word splitting.
2644 If it expands to more than one word,
2648 Note that the order of redirections is significant. For example,
2652 ls \fB>\fP dirlist 2\fB>&\fP1
2655 directs both standard output and standard error to the file
2660 ls 2\fB>&\fP1 \fB>\fP dirlist
2663 directs only the standard output to file
2665 because the standard error was duplicated as standard output
2666 before the standard output was redirected to
2669 \fBBash\fP handles several filenames specially when they are used in
2670 redirections, as described in the following table:
2676 If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
2679 File descriptor 0 is duplicated.
2682 File descriptor 1 is duplicated.
2685 File descriptor 2 is duplicated.
2687 .B /dev/tcp/\fIhost\fP/\fIport\fP
2688 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
2689 is an integer port number, \fBbash\fP attempts to open a TCP connection
2690 to the corresponding socket.
2692 .B /dev/udp/\fIhost\fP/\fIport\fP
2693 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
2694 is an integer port number, \fBbash\fP attempts to open a UDP connection
2695 to the corresponding socket.
2699 A failure to open or create a file causes the redirection to fail.
2700 .SS Redirecting Input
2702 Redirection of input causes the file whose name results from
2705 to be opened for reading on file descriptor
2707 or the standard input (file descriptor 0) if
2711 The general format for redirecting input is:
2714 [\fIn\fP]\fB<\fP\fIword\fP
2716 .SS Redirecting Output
2718 Redirection of output causes the file whose name results from
2721 to be opened for writing on file descriptor
2723 or the standard output (file descriptor 1) if
2725 is not specified. If the file does not exist it is created;
2726 if it does exist it is truncated to zero size.
2728 The general format for redirecting output is:
2731 [\fIn\fP]\fB>\fP\fIword\fP
2734 If the redirection operator is
2740 builtin has been enabled, the redirection will fail if the file
2741 whose name results from the expansion of \fIword\fP exists and is
2743 If the redirection operator is
2745 or the redirection operator is
2751 builtin command is not enabled, the redirection is attempted even
2752 if the file named by \fIword\fP exists.
2753 .SS Appending Redirected Output
2755 Redirection of output in this fashion
2756 causes the file whose name results from
2759 to be opened for appending on file descriptor
2761 or the standard output (file descriptor 1) if
2763 is not specified. If the file does not exist it is created.
2765 The general format for appending output is:
2768 [\fIn\fP]\fB>>\fP\fIword\fP
2771 .SS Redirecting Standard Output and Standard Error
2775 standard output (file descriptor 1) and
2776 the standard error output (file descriptor 2)
2777 to be redirected to the file whose name is the
2780 with this construct.
2782 There are two formats for redirecting standard output and
2793 Of the two forms, the first is preferred.
2794 This is semantically equivalent to
2797 \fB>\fP\fIword\fP 2\fB>&\fP1
2801 This type of redirection instructs the shell to read input from the
2802 current source until a line containing only
2804 (with no trailing blanks)
2806 the lines read up to that point are then used as the standard
2807 input for a command.
2809 The format of here-documents is as follows:
2813 \fB<<\fP[\fB\-\fP]\fIword\fP
2814 \fIhere\-document\fP
2819 No parameter expansion, command substitution, arithmetic expansion,
2820 or pathname expansion is performed on
2822 If any characters in
2826 is the result of quote removal on
2828 and the lines in the here-document are not expanded.
2829 If \fIword\fP is unquoted,
2830 all lines of the here-document are subjected to parameter expansion,
2831 command substitution, and arithmetic expansion. In the latter
2832 case, the character sequence
2836 must be used to quote the characters
2842 If the redirection operator is
2844 then all leading tab characters are stripped from input lines and the
2848 here-documents within shell scripts to be indented in a
2850 .SS "Duplicating File Descriptors"
2852 The redirection operator
2855 [\fIn\fP]\fB<&\fP\fIword\fP
2858 is used to duplicate input file descriptors.
2861 expands to one or more digits, the file descriptor denoted by
2863 is made to be a copy of that file descriptor.
2866 do not specify a file descriptor open for input, a redirection error occurs.
2875 is not specified, the standard input (file descriptor 0) is used.
2880 [\fIn\fP]\fB>&\fP\fIword\fP
2883 is used similarly to duplicate output file descriptors. If
2885 is not specified, the standard output (file descriptor 1) is used.
2888 do not specify a file descriptor open for output, a redirection error occurs.
2889 As a special case, if \fIn\fP is omitted, and \fIword\fP does not
2890 expand to one or more digits, the standard output and standard
2891 error are redirected as described previously.
2892 .SS "Opening File Descriptors for Reading and Writing"
2894 The redirection operator
2897 [\fIn\fP]\fB<>\fP\fIword\fP
2900 causes the file whose name is the expansion of
2902 to be opened for both reading and writing on file descriptor
2904 or on file descriptor 0 if
2906 is not specified. If the file does not exist, it is created.
2908 \fIAliases\fP allow a string to be substituted for a word when it is used
2909 as the first word of a simple command.
2910 The shell maintains a list of aliases that may be set and unset with the
2914 builtin commands (see
2916 .B SHELL BUILTIN COMMANDS
2918 The first word of each command, if unquoted,
2919 is checked to see if it has an
2920 alias. If so, that word is replaced by the text of the alias.
2921 The alias name and the replacement text may contain any valid
2922 shell input, including the
2924 listed above, with the exception that the alias name may not
2925 contain \fI=\fP. The first word of the replacement text is tested
2926 for aliases, but a word that is identical to an alias being expanded
2927 is not expanded a second time. This means that one may alias
2933 does not try to recursively expand the replacement text.
2934 If the last character of the alias value is a
2936 then the next command
2937 word following the alias is also checked for alias expansion.
2939 Aliases are created and listed with the
2941 command, and removed with the
2945 There is no mechanism for using arguments in the replacement text.
2946 If arguments are needed, a shell function should be used (see
2951 Aliases are not expanded when the shell is not interactive, unless
2954 shell option is set using
2956 (see the description of
2960 \fBSHELL BUILTIN COMMANDS\fP
2963 The rules concerning the definition and use of aliases are
2966 always reads at least one complete line
2967 of input before executing any
2968 of the commands on that line. Aliases are expanded when a
2969 command is read, not when it is executed. Therefore, an
2970 alias definition appearing on the same line as another
2971 command does not take effect until the next line of input is read.
2972 The commands following the alias definition
2973 on that line are not affected by the new alias.
2974 This behavior is also an issue when functions are executed.
2975 Aliases are expanded when a function definition is read,
2976 not when the function is executed, because a function definition
2977 is itself a compound command. As a consequence, aliases
2978 defined in a function are not available until after that
2979 function is executed. To be safe, always put
2980 alias definitions on a separate line, and do not use
2982 in compound commands.
2984 For almost every purpose, aliases are superseded by
2987 A shell function, defined as described above under
2989 .BR "SHELL GRAMMAR" ,
2990 stores a series of commands for later execution.
2991 When the name of a shell function is used as a simple command name,
2992 the list of commands associated with that function name is executed.
2993 Functions are executed in the context of the
2994 current shell; no new process is created to interpret
2995 them (contrast this with the execution of a shell script).
2996 When a function is executed, the arguments to the
2997 function become the positional parameters
2998 during its execution.
2999 The special parameter
3001 is updated to reflect the change. Positional parameter 0
3006 variable is set to the name of the function while the function
3008 All other aspects of the shell execution
3009 environment are identical between a function and its caller
3010 with the exception that the
3013 trap (see the description of the
3017 .B SHELL BUILTIN COMMANDS
3018 below) is not inherited.
3020 Variables local to the function may be declared with the
3022 builtin command. Ordinarily, variables and their values
3023 are shared between the function and its caller.
3025 If the builtin command
3027 is executed in a function, the function completes and
3028 execution resumes with the next command after the function
3029 call. When a function completes, the values of the
3030 positional parameters and the special parameter
3032 are restored to the values they had prior to the function's
3035 Function names and definitions may be listed with the
3041 builtin commands. The
3047 will list the function names only.
3048 Functions may be exported so that subshells
3049 automatically have them defined with the
3055 Functions may be recursive. No limit is imposed on the number
3057 .SH "ARITHMETIC EVALUATION"
3058 The shell allows arithmetic expressions to be evaluated, under
3059 certain circumstances (see the \fBlet\fP builtin command and
3060 \fBArithmetic Expansion\fP).
3061 Evaluation is done in long integers with no check for overflow,
3062 though division by 0 is trapped and flagged as an error.
3063 The operators and their precedence and associativity are the same
3064 as in the C language.
3065 The following list of operators is grouped into levels of
3066 equal-precedence operators.
3067 The levels are listed in order of decreasing precedence.
3071 .B \fIid\fP++ \fIid\fP\-\-
3072 variable post-increment and post-decrement
3074 .B ++\fIid\fP \-\-\fIid\fP
3075 variable pre-increment and pre-decrement
3078 unary minus and plus
3081 logical and bitwise negation
3087 multiplication, division, remainder
3090 addition, subtraction
3093 left and right bitwise shifts
3099 equality and inequality
3105 bitwise exclusive OR
3116 .B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
3117 conditional evaluation
3119 .B = *= /= %= += \-= <<= >>= &= ^= |=
3122 .B \fIexpr1\fP , \fIexpr2\fP
3126 Shell variables are allowed as operands; parameter expansion is
3127 performed before the expression is evaluated.
3128 Within an expression, shell variables may also be referenced by name
3129 without using the parameter expansion syntax.
3130 The value of a variable is evaluated as an arithmetic expression
3131 when it is referenced.
3132 A shell variable need not have its integer attribute
3133 turned on to be used in an expression.
3135 Constants with a leading 0 are interpreted as octal numbers.
3136 A leading 0x or 0X denotes hexadecimal.
3137 Otherwise, numbers take the form [\fIbase#\fP]n, where \fIbase\fP
3138 is a decimal number between 2 and 64 representing the arithmetic
3139 base, and \fIn\fP is a number in that base.
3140 If \fIbase#\fP is omitted, then base 10 is used.
3141 The digits greater than 9 are represented by the lowercase letters,
3142 the uppercase letters, _, and @, in that order.
3143 If \fIbase\fP is less than or equal to 36, lowercase and uppercase
3144 letters may be used interchangably to represent numbers between 10
3147 Operators are evaluated in order of precedence. Sub-expressions in
3148 parentheses are evaluated first and may override the precedence
3150 .SH "CONDITIONAL EXPRESSIONS"
3151 Conditional expressions are used by the \fB[[\fP compound command and
3152 the \fBtest\fP and \fB[\fP builtin commands to test file attributes
3153 and perform string and arithmetic comparisons.
3154 Expressions are formed from the following unary or binary primaries.
3155 If any \fIfile\fP argument to one of the primaries is of the form
3156 \fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
3157 If the \fIfile\fP argument to one of the primaries is one of
3158 \fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
3159 descriptor 0, 1, or 2, respectively, is checked.
3164 True if \fIfile\fP exists.
3167 True if \fIfile\fP exists and is a block special file.
3170 True if \fIfile\fP exists and is a character special file.
3173 True if \fIfile\fP exists and is a directory.
3176 True if \fIfile\fP exists.
3179 True if \fIfile\fP exists and is a regular file.
3182 True if \fIfile\fP exists and is set-group-id.
3185 True if \fIfile\fP exists and is a symbolic link.
3188 True if \fIfile\fP exists and its ``sticky'' bit is set.
3191 True if \fIfile\fP exists and is a named pipe (FIFO).
3194 True if \fIfile\fP exists and is readable.
3197 True if \fIfile\fP exists and has a size greater than zero.
3200 True if file descriptor
3202 is open and refers to a terminal.
3205 True if \fIfile\fP exists and its set-user-id bit is set.
3208 True if \fIfile\fP exists and is writable.
3211 True if \fIfile\fP exists and is executable.
3214 True if \fIfile\fP exists and is owned by the effective user id.
3217 True if \fIfile\fP exists and is owned by the effective group id.
3220 True if \fIfile\fP exists and is a symbolic link.
3223 True if \fIfile\fP exists and is a socket.
3226 True if \fIfile\fP exists and has been modified since it was last read.
3228 \fIfile1\fP \-\fBnt\fP \fIfile2\fP
3229 True if \fIfile1\fP is newer (according to
3230 modification date) than \fIfile2\fP.
3232 \fIfile1\fP \-\fBot\fP \fIfile2\fP
3233 True if \fIfile1\fP is older than \fIfile2\fP.
3235 \fIfile1\fP \fB\-ef\fP \fIfile2\fP
3236 True if \fIfile1\fP and \fIfile2\fP have the same device and
3239 .B \-o \fIoptname\fP
3240 True if shell option
3243 See the list of options under the description of the
3250 True if the length of \fIstring\fP is zero.
3255 True if the length of
3259 \fIstring1\fP \fB==\fP \fIstring2\fP
3260 True if the strings are equal. \fB=\fP may be used in place of
3263 \fIstring1\fP \fB!=\fP \fIstring2\fP
3264 True if the strings are not equal.
3266 \fIstring1\fP \fB<\fP \fIstring2\fP
3267 True if \fIstring1\fP sorts before \fIstring2\fP lexicographically
3268 in the current locale.
3270 \fIstring1\fP \fB>\fP \fIstring2\fP
3271 True if \fIstring1\fP sorts after \fIstring2\fP lexicographically
3272 in the current locale.
3274 .I \fIarg1\fP \fBOP\fP \fIarg2\fP
3285 These arithmetic binary operators return true if \fIarg1\fP
3286 is equal to, not equal to, less than, less than or equal to,
3287 greater than, or greater than or equal to \fIarg2\fP, respectively.
3291 may be positive or negative integers.
3293 .SH "SIMPLE COMMAND EXPANSION"
3294 When a simple command is executed, the shell performs the following
3295 expansions, assignments, and redirections, from left to right.
3297 The words that the parser has marked as variable assignments (those
3298 preceding the command name) and redirections are saved for later
3301 The words that are not variable assignments or redirections are
3302 expanded. If any words remain after expansion, the first word
3303 is taken to be the name of the command and the remaining words are
3306 Redirections are performed as described above under
3310 The text after the \fB=\fP in each variable assignment undergoes tilde
3311 expansion, parameter expansion, command substitution, arithmetic expansion,
3312 and quote removal before being assigned to the variable.
3314 If no command name results, the variable assignments affect the current
3315 shell environment. Otherwise, the variables are added to the environment
3316 of the executed command and do not affect the current shell environment.
3317 If any of the assignments attempts to assign a value to a readonly variable,
3318 an error occurs, and the command exits with a non-zero status.
3320 If no command name results, redirections are performed, but do not
3321 affect the current shell environment. A redirection error causes the
3322 command to exit with a non-zero status.
3324 If there is a command name left after expansion, execution proceeds as
3325 described below. Otherwise, the command exits. If one of the expansions
3326 contained a command substitution, the exit status of the command is
3327 the exit status of the last command substitution performed. If there
3328 were no command substitutions, the command exits with a status of zero.
3329 .SH "COMMAND EXECUTION"
3330 After a command has been split into words, if it results in a
3331 simple command and an optional list of arguments, the following
3334 If the command name contains no slashes, the shell attempts to
3335 locate it. If there exists a shell function by that name, that
3336 function is invoked as described above in
3339 If the name does not match a function, the shell searches for
3340 it in the list of shell builtins. If a match is found, that
3343 If the name is neither a shell function nor a builtin,
3344 and contains no slashes,
3346 searches each element of the
3349 for a directory containing an executable file by that name.
3351 uses a hash table to remember the full pathnames of executable
3356 .B "SHELL BUILTIN COMMANDS"
3358 A full search of the directories in
3361 is performed only if the command is not found in the hash table.
3362 If the search is unsuccessful, the shell prints an error
3363 message and returns an exit status of 127.
3365 If the search is successful, or if the command name contains
3366 one or more slashes, the shell executes the named program in a
3367 separate execution environment.
3368 Argument 0 is set to the name given, and the remaining arguments
3369 to the command are set to the arguments given, if any.
3371 If this execution fails because the file is not in executable
3372 format, and the file is not a directory, it is assumed to be
3373 a \fIshell script\fP, a file
3374 containing shell commands. A subshell is spawned to execute
3375 it. This subshell reinitializes itself, so
3376 that the effect is as if a new shell had been invoked
3377 to handle the script, with the exception that the locations of
3378 commands remembered by the parent (see
3382 \fBSHELL BUILTIN COMMANDS\fP)
3383 are retained by the child.
3385 If the program is a file beginning with
3387 the remainder of the first line specifies an interpreter
3388 for the program. The shell executes the
3389 specified interpreter on operating systems that do not
3390 handle this executable format themselves. The arguments to the
3391 interpreter consist of a single optional argument following the
3392 interpreter name on the first line of the program, followed
3393 by the name of the program, followed by the command
3395 .SH COMMAND EXECUTION ENVIRONMENT
3396 The shell has an \fIexecution environment\fP, which consists of the
3400 open files inherited by the shell at invocation, as modified by
3401 redirections supplied to the \fBexec\fP builtin
3403 the current working directory as set by \fBcd\fP, \fBpushd\fP, or
3404 \fBpopd\fP, or inherited by the shell at invocation
3406 the file creation mode mask as set by \fBumask\fP or inherited from
3409 current traps set by \fBtrap\fP
3411 shell parameters that are set by variable assignment or with \fBset\fP
3412 or inherited from the shell's parent in the environment
3414 shell functions defined during execution or inherited from the shell's
3415 parent in the environment
3417 options enabled at invocation (either by default or with command-line
3418 arguments) or by \fBset\fP
3420 options enabled by \fBshopt\fP
3422 shell aliases defined with \fBalias\fP
3424 various process IDs, including those of background jobs, the value
3425 of \fB$$\fP, and the value of \fB$PPID\fP
3427 When a simple command other than a builtin or shell function
3428 is to be executed, it
3429 is invoked in a separate execution environment that consists of
3430 the following. Unless otherwise noted, the values are inherited
3434 the shell's open files, plus any modifications and additions specified
3435 by redirections to the command
3437 the current working directory
3439 the file creation mode mask
3441 shell variables marked for export, along with variables exported for
3442 the command, passed in the environment
3444 traps caught by the shell are reset to the values the inherited
3445 from the shell's parent, and traps ignored by the shell are ignored
3447 A command invoked in this separate environment cannot affect the
3448 shell's execution environment.
3450 Command substitution and asynchronous commands are invoked in a
3451 subshell environment that is a duplicate of the shell environment,
3452 except that traps caught by the shell are reset to the values
3453 that the shell inherited from its parent at invocation. Builtin
3454 commands that are invoked as part of a pipeline are also executed in a
3455 subshell environment. Changes made to the subshell environment
3456 cannot affect the shell's execution environment.
3458 When a program is invoked it is given an array of strings
3462 \fIname\fP\-\fIvalue\fP pairs, of the form
3463 .IR "name\fR=\fPvalue" .
3465 The shell provides several ways to manipulate the environment.
3466 On invocation, the shell scans its own environment and
3467 creates a parameter for each name found, automatically marking
3470 to child processes. Executed commands inherit the environment.
3475 commands allow parameters and functions to be added to and
3476 deleted from the environment. If the value of a parameter
3477 in the environment is modified, the new value becomes part
3478 of the environment, replacing the old. The environment
3479 inherited by any executed command consists of the shell's
3480 initial environment, whose values may be modified in the shell,
3481 less any pairs removed by the
3483 command, plus any additions via the
3489 The environment for any
3491 or function may be augmented temporarily by prefixing it with
3492 parameter assignments, as described above in
3495 These assignment statements affect only the environment seen
3500 option is set (see the
3502 builtin command below), then
3504 parameter assignments are placed in the environment for a command,
3505 not just those that precede the command name.
3509 invokes an external command, the variable
3511 is set to the full file name of the command and passed to that
3512 command in its environment.
3514 For the shell's purposes, a command which exits with a
3515 zero exit status has succeeded. An exit status of zero
3516 indicates success. A non-zero exit status indicates failure.
3517 When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
3518 the value of 128+\fIN\fP as the exit status.
3520 If a command is not found, the child process created to
3521 execute it returns a status of 127. If a command is found
3522 but is not executable, the return status is 126.
3524 If a command fails because of an error during expansion or redirection,
3525 the exit status is greater than zero.
3527 Shell builtin commands return a status of 0 (\fItrue\fP) if
3528 successful, and non-zero (\fIfalse\fP) if an error occurs
3530 All builtins return an exit status of 2 to indicate incorrect usage.
3532 \fBBash\fP itself returns the exit status of the last command
3533 executed, unless a syntax error occurs, in which case it exits
3534 with a non-zero value. See also the \fBexit\fP builtin
3537 When \fBbash\fP is interactive, in the absence of any traps, it ignores
3540 (so that \fBkill 0\fP does not kill an interactive shell),
3544 is caught and handled (so that the \fBwait\fP builtin is interruptible).
3545 In all cases, \fBbash\fP ignores
3548 If job control is in effect,
3559 Synchronous jobs started by \fBbash\fP have signal handlers
3560 set to the values inherited by the shell from its parent.
3561 When job control is not in effect, asynchronous commands
3569 Commands run as a result of command substitution ignore the
3570 keyboard-generated job control signals
3579 The shell exits by default upon receipt of a
3582 Before exiting, it resends the
3585 to all jobs, running or stopped.
3586 Stopped jobs are sent
3589 to ensure that they receive the
3592 To prevent the shell from
3593 sending the signal to a particular job, it should be removed from the
3598 .B "SHELL BUILTIN COMMANDS"
3608 shell option has been set with
3614 to all jobs when an interactive login shell exits.
3616 When \fBbash\fP receives a signal for which a trap has been set while
3617 waiting for a command to complete, the trap will not be executed until
3618 the command completes.
3619 When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
3620 builtin, the reception of a signal for which a trap has been set will
3621 cause the \fBwait\fP builtin to return immediately with an exit status
3622 greater than 128, immediately after which the trap is executed.
3625 refers to the ability to selectively stop (\fIsuspend\fP)
3626 the execution of processes and continue (\fIresume\fP)
3627 their execution at a later point. A user typically employs
3628 this facility via an interactive interface supplied jointly
3629 by the system's terminal driver and
3632 The shell associates a
3634 with each pipeline. It keeps a table of currently executing
3635 jobs, which may be listed with the
3639 starts a job asynchronously (in the
3641 it prints a line that looks like:
3647 indicating that this job is job number 1 and that the process ID
3648 of the last process in the pipeline associated with this job is 25647.
3649 All of the processes in a single pipeline are members of the same job.
3653 abstraction as the basis for job control.
3655 To facilitate the implementation of the user interface to job
3656 control, the operating system maintains the notion of a \fIcurrent terminal
3657 process group ID\fP. Members of this process group (processes whose
3658 process group ID is equal to the current terminal process group ID)
3659 receive keyboard-generated signals such as
3662 These processes are said to be in the
3665 processes are those whose process group ID differs from the terminal's;
3666 such processes are immune to keyboard-generated signals.
3667 Only foreground processes are allowed to read from or write to the
3668 terminal. Background processes which attempt to read from (write to) the
3671 .B SIGTTIN (SIGTTOU)
3672 signal by the terminal driver,
3673 which, unless caught, suspends the process.
3675 If the operating system on which
3680 contains facilities to use it.
3683 character (typically
3685 Control-Z) while a process is running
3686 causes that process to be stopped and returns control to
3689 .I "delayed suspend"
3690 character (typically
3692 Control-Y) causes the process to be stopped when it
3693 attempts to read input from the terminal, and control to
3696 The user may then manipulate the state of this job, using the
3698 command to continue it in the background, the
3700 command to continue it in the foreground, or
3703 command to kill it. A \fB^Z\fP takes effect immediately,
3704 and has the additional side effect of causing pending output
3705 and typeahead to be discarded.
3707 There are a number of ways to refer to a job in the shell.
3710 introduces a job name. Job number
3712 may be referred to as
3714 A job may also be referred to using a prefix of the name used to
3715 start it, or using a substring that appears in its command line.
3720 job. If a prefix matches more than one job,
3722 reports an error. Using
3724 on the other hand, refers to any job containing the string
3726 in its command line. If the substring matches more than one job,
3728 reports an error. The symbols
3732 refer to the shell's notion of the
3734 which is the last job stopped while it was in
3735 the foreground or started in the background.
3738 may be referenced using
3740 In output pertaining to jobs (e.g., the output of the
3742 command), the current job is always flagged with a
3744 and the previous job with a
3747 Simply naming a job can be used to bring it into the
3752 bringing job 1 from the background into the foreground.
3755 resumes job 1 in the background, equivalent to
3758 The shell learns immediately whenever a job changes state.
3761 waits until it is about to print a prompt before reporting
3762 changes in a job's status so as to not interrupt
3763 any other output. If the
3770 reports such changes immediately.
3772 If an attempt to exit
3774 is made while jobs are stopped, the shell prints a warning message. The
3776 command may then be used to inspect their status.
3777 If a second attempt to exit is made without an intervening command,
3778 the shell does not print another warning, and the stopped
3779 jobs are terminated.
3781 When executing interactively,
3783 displays the primary prompt
3786 when it is ready to read a command, and the secondary prompt
3789 when it needs more input to complete a command.
3791 allows these prompt strings to be customized by inserting a number of
3792 backslash-escaped special characters that are decoded as follows:
3797 an ASCII bell character (07)
3800 the date in "Weekday Month Date" format (e.g., "Tue May 26")
3803 an ASCII escape character (033)
3806 the hostname up to the first `.'
3812 the number of jobs currently managed by the shell
3815 the basename of the shell's terminal device name
3824 the name of the shell, the basename of
3826 (the portion following the final slash)
3829 the current time in 24-hour HH:MM:SS format
3832 the current time in 12-hour HH:MM:SS format
3835 the current time in 12-hour am/pm format
3838 the username of the current user
3841 the version of \fBbash\fP (e.g., 2.00)
3844 the release of \fBbash\fP, version + patchlevel (e.g., 2.00.0)
3847 the current working directory
3850 the basename of the current working directory
3853 the history number of this command
3856 the command number of this command
3859 if the effective UID is 0, a
3865 the character corresponding to the octal number \fInnn\fP
3871 begin a sequence of non-printing characters, which could be used to
3872 embed a terminal control sequence into the prompt
3875 end a sequence of non-printing characters
3879 The command number and the history number are usually different:
3880 the history number of a command is its position in the history
3881 list, which may include commands restored from the history file
3885 below), while the command number is the position in the sequence
3886 of commands executed during the current shell session.
3887 After the string is decoded, it is expanded via
3888 parameter expansion, command substitution, arithmetic
3889 expansion, and quote removal, subject to the value of the
3891 shell option (see the description of the
3895 .B "SHELL BUILTIN COMMANDS"
3898 This is the library that handles reading input when using an interactive
3901 option is given at shell invocation.
3902 By default, the line editing commands are similar to those of emacs.
3903 A vi-style line editing interface is also available.
3904 To turn off line editing after the shell is running, use the
3912 .B SHELL BUILTIN COMMANDS
3914 .SS "Readline Notation"
3916 In this section, the emacs-style notation is used to denote
3917 keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
3918 means Control\-N. Similarly,
3920 keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
3923 key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
3926 key. This makes ESC the \fImeta prefix\fP.
3927 The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
3928 or press the Escape key
3929 then hold the Control key while pressing the
3933 Readline commands may be given numeric
3935 which normally act as a repeat count.
3936 Sometimes, however, it is the sign of the argument that is significant.
3937 Passing a negative argument to a command that acts in the forward
3938 direction (e.g., \fBkill\-line\fP) causes that command to act in a
3940 Commands whose behavior with arguments deviates from this are noted
3943 When a command is described as \fIkilling\fP text, the text
3944 deleted is saved for possible future retrieval
3945 (\fIyanking\fP). The killed text is saved in a
3946 \fIkill ring\fP. Consecutive kills cause the text to be
3947 accumulated into one unit, which can be yanked all at once.
3948 Commands which do not kill text separate the chunks of text
3950 .SS "Readline Initialization"
3952 Readline is customized by putting commands in an initialization
3953 file (the \fIinputrc\fP file).
3954 The name of this file is taken from the value of the
3957 variable. If that variable is unset, the default is
3959 When a program which uses the readline library starts up, the
3960 initialization file is read, and the key bindings and variables
3962 There are only a few basic constructs allowed in the
3963 readline initialization file.
3964 Blank lines are ignored.
3965 Lines beginning with a \fB#\fP are comments.
3966 Lines beginning with a \fB$\fP indicate conditional constructs.
3967 Other lines denote key bindings and variable settings.
3969 The default key-bindings may be changed with an
3972 Other programs that use this library may add their own commands
3975 For example, placing
3978 M\-Control\-u: universal\-argument
3982 C\-Meta\-u: universal\-argument
3986 would make M\-C\-u execute the readline command
3987 .IR universal\-argument .
3989 The following symbolic character names are recognized:
4002 In addition to command names, readline allows keys to be bound
4003 to a string that is inserted when the key is pressed (a \fImacro\fP).
4004 .SS "Readline Key Bindings"
4006 The syntax for controlling key bindings in the
4008 file is simple. All that is required is the name of the
4009 command or the text of a macro and a key sequence to which
4010 it should be bound. The name may be specified in one of two ways:
4011 as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
4012 prefixes, or as a key sequence.
4014 When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4016 is the name of a key spelled out in English. For example:
4019 Control-u: universal\-argument
4021 Meta-Rubout: backward-kill-word
4023 Control-o: "> output"
4026 In the above example,
4028 is bound to the function
4029 .BR universal\-argument ,
4031 is bound to the function
4032 .BR backward\-kill\-word ,
4035 is bound to run the macro
4036 expressed on the right hand side (that is, to insert the text
4037 .if t \f(CW> output\fP
4041 In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4045 above in that strings denoting
4046 an entire key sequence may be specified by placing the sequence
4047 within double quotes. Some GNU Emacs style key escapes can be
4048 used, as in the following example, but the symbolic character names
4052 "\eC\-u": universal\-argument
4054 "\eC\-x\eC\-r": re\-read\-init\-file
4056 "\ee[11~": "Function Key 1"
4061 is again bound to the function
4062 .BR universal\-argument .
4064 is bound to the function
4065 .BR re\-read\-init\-file ,
4068 is bound to insert the text
4069 .if t \f(CWFunction Key 1\fP.
4070 .if n ``Function Key 1''.
4072 The full set of GNU Emacs style escape sequences is
4096 In addition to the GNU Emacs style escape sequences, a second
4097 set of backslash escapes is available:
4126 the character whose ASCII code is the octal value \fInnn\fP
4127 (one to three digits)
4130 the character whose ASCII code is the hexadecimal value \fInnn\fP
4131 (one to three digits)
4135 When entering the text of a macro, single or double quotes must
4136 be used to indicate a macro definition.
4137 Unquoted text is assumed to be a function name.
4138 In the macro body, the backslash escapes described above are expanded.
4139 Backslash will quote any other character in the macro text,
4143 allows the current readline key bindings to be displayed or modified
4146 builtin command. The editing mode may be switched during interactive
4151 builtin command (see
4153 .B SHELL BUILTIN COMMANDS
4155 .SS "Readline Variables"
4157 Readline has variables that can be used to further customize its
4158 behavior. A variable may be set in the
4160 file with a statement of the form
4163 \fBset\fP \fIvariable\-name\fP \fIvalue\fP
4166 Except where noted, readline variables can take the values
4170 The variables and their default values are:
4174 .B bell\-style (audible)
4175 Controls what happens when readline wants to ring the terminal bell.
4176 If set to \fBnone\fP, readline never rings the bell. If set to
4177 \fBvisible\fP, readline uses a visible bell if one is available.
4178 If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
4180 .B comment\-begin (``#'')
4181 The string that is inserted when the readline
4183 command is executed.
4184 This command is bound to
4186 in emacs mode and to
4190 .B completion\-ignore\-case (Off)
4191 If set to \fBOn\fP, readline performs filename matching and completion
4192 in a case\-insensitive fashion.
4194 .B completion\-query\-items (100)
4195 This determines when the user is queried about viewing
4196 the number of possible completions
4197 generated by the \fBpossible\-completions\fP command.
4198 It may be set to any integer value greater than or equal to
4199 zero. If the number of possible completions is greater than
4200 or equal to the value of this variable, the user is asked whether
4201 or not he wishes to view them; otherwise they are simply listed
4204 .B convert\-meta (On)
4205 If set to \fBOn\fP, readline will convert characters with the
4206 eighth bit set to an ASCII key sequence
4207 by stripping the eighth bit and prefixing an
4208 escape character (in effect, using escape as the \fImeta prefix\fP).
4210 .B disable\-completion (Off)
4211 If set to \fBOn\fP, readline will inhibit word completion. Completion
4212 characters will be inserted into the line as if they had been
4213 mapped to \fBself-insert\fP.
4215 .B editing\-mode (emacs)
4216 Controls whether readline begins with a set of key bindings similar
4217 to \fIemacs\fP or \fIvi\fP.
4219 can be set to either
4224 .B enable\-keypad (Off)
4225 When set to \fBOn\fP, readline will try to enable the application
4226 keypad when it is called. Some systems need this to enable the
4229 .B expand\-tilde (Off)
4230 If set to \fBon\fP, tilde expansion is performed when readline
4231 attempts word completion.
4233 .B horizontal\-scroll\-mode (Off)
4234 When set to \fBOn\fP, makes readline use a single line for display,
4235 scrolling the input horizontally on a single screen line when it
4236 becomes longer than the screen width rather than wrapping to a new line.
4238 .B input\-meta (Off)
4239 If set to \fBOn\fP, readline will enable eight-bit input (that is,
4240 it will not strip the high bit from the characters it reads),
4241 regardless of what the terminal claims it can support. The name
4243 is a synonym for this variable.
4245 .B isearch\-terminators (``C\-[C\-J'')
4246 The string of characters that should terminate an incremental
4247 search without subsequently executing the character as a command.
4248 If this variable has not been given a value, the characters
4249 \fIESC\fP and \fIC\-J\fP will terminate an incremental search.
4252 Set the current readline keymap. The set of valid keymap names is
4253 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
4256 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
4257 equivalent to \fIemacs\-standard\fP. The default value is
4261 also affects the default keymap.
4263 .B mark\-directories (On)
4264 If set to \fBOn\fP, completed directory names have a slash
4267 .B mark\-modified\-lines (Off)
4268 If set to \fBOn\fP, history lines that have been modified are displayed
4269 with a preceding asterisk (\fB*\fP).
4271 .B output\-meta (Off)
4272 If set to \fBOn\fP, readline will display characters with the
4273 eighth bit set directly rather than as a meta-prefixed escape
4276 .B print\-completions\-horizontally (Off)
4277 If set to \fBOn\fP, readline will display completions with matches
4278 sorted horizontally in alphabetical order, rather than down the screen.
4280 .B show\-all\-if\-ambiguous (Off)
4281 This alters the default behavior of the completion functions. If
4284 words which have more than one possible completion cause the
4285 matches to be listed immediately instead of ringing the bell.
4287 .B visible\-stats (Off)
4288 If set to \fBOn\fP, a character denoting a file's type as reported
4289 by \fIstat\fP(2) is appended to the filename when listing possible
4292 .SS "Readline Conditional Constructs"
4294 Readline implements a facility similar in spirit to the conditional
4295 compilation features of the C preprocessor which allows key
4296 bindings and variable settings to be performed as the result
4297 of tests. There are four parser directives used.
4301 construct allows bindings to be made based on the
4302 editing mode, the terminal being used, or the application using
4303 readline. The text of the test extends to the end of the line;
4304 no characters are required to isolate it.
4307 The \fBmode=\fP form of the \fB$if\fP directive is used to test
4308 whether readline is in emacs or vi mode.
4309 This may be used in conjunction
4310 with the \fBset keymap\fP command, for instance, to set bindings in
4311 the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
4312 readline is starting out in emacs mode.
4314 The \fBterm=\fP form may be used to include terminal-specific
4315 key bindings, perhaps to bind the key sequences output by the
4316 terminal's function keys. The word on the right side of the
4318 is tested against the both full name of the terminal and the portion
4319 of the terminal name before the first \fB\-\fP. This allows
4326 .IP \fBapplication\fP
4327 The \fBapplication\fP construct is used to include
4328 application-specific settings. Each program using the readline
4329 library sets the \fIapplication name\fP, and an initialization
4330 file can test for a particular value.
4331 This could be used to bind key sequences to functions useful for
4332 a specific program. For instance, the following command adds a
4333 key sequence that quotes the current or previous word in Bash:
4338 # Quote the current or previous word
4339 "\eC\-xq": "\eeb\e"\eef\e""
4345 This command, as seen in the previous example, terminates an
4348 Commands in this branch of the \fB$if\fP directive are executed if
4351 This directive takes a single filename as an argument and reads commands
4352 and bindings from that file. For example, the following directive
4353 would read \fI/etc/inputrc\fP:
4357 \fB$include\fP \^ \fI/etc/inputrc\fP
4362 Readline provides commands for searching through the command history
4366 below) for lines containing a specified string.
4367 There are two search modes:
4370 .IR non-incremental .
4372 Incremental searches begin before the user has finished typing the
4374 As each character of the search string is typed, readline displays
4375 the next entry from the history matching the string typed so far.
4376 An incremental search requires only as many characters as needed to
4377 find the desired history entry.
4378 The characters present in the value of the \fBisearch-terminators\fP
4379 variable are used to terminate an incremental search.
4380 If that variable has not been assigned a value the Escape and
4381 Control-J characters will terminate an incremental search.
4382 Control-G will abort an incremental search and restore the original
4384 When the search is terminated, the history entry containing the
4385 search string becomes the current line.
4387 To find other matching entries in the history list, type Control-S or
4388 Control-R as appropriate.
4389 This will search backward or forward in the history for the next
4390 entry matching the search string typed so far.
4391 Any other key sequence bound to a readline command will terminate
4392 the search and execute that command.
4393 For instance, a \fInewline\fP will terminate the search and accept
4394 the line, thereby executing the command from the history list.
4396 Non-incremental searches read the entire search string before starting
4397 to search for matching history lines. The search string may be
4398 typed by the user or be part of the contents of the current line.
4399 .SS "Readline Command Names"
4401 The following is a list of the names of the commands and the default
4402 key sequences to which they are bound.
4403 Command names without an accompanying key sequence are unbound by default.
4404 In the following descriptions, \fIpoint\fP refers to the current cursor
4405 position, and \fImark\fP refers to a cursor position saved by the
4406 \fBset\-mark\fP command.
4407 The text between the point and mark is referred to as the \fIregion\fP.
4408 .SS Commands for Moving
4412 .B beginning\-of\-line (C\-a)
4413 Move to the start of the current line.
4415 .B end\-of\-line (C\-e)
4416 Move to the end of the line.
4418 .B forward\-char (C\-f)
4419 Move forward a character.
4421 .B backward\-char (C\-b)
4422 Move back a character.
4424 .B forward\-word (M\-f)
4425 Move forward to the end of the next word. Words are composed of
4426 alphanumeric characters (letters and digits).
4428 .B backward\-word (M\-b)
4429 Move back to the start of the current or previous word. Words are
4430 composed of alphanumeric characters (letters and digits).
4432 .B clear\-screen (C\-l)
4433 Clear the screen leaving the current line at the top of the screen.
4434 With an argument, refresh the current line without clearing the
4437 .B redraw\-current\-line
4438 Refresh the current line.
4440 .SS Commands for Manipulating the History
4444 .B accept\-line (Newline, Return)
4445 Accept the line regardless of where the cursor is. If this line is
4446 non-empty, add it to the history list according to the state of the
4449 variable. If the line is a modified history
4450 line, then restore the history line to its original state.
4452 .B previous\-history (C\-p)
4453 Fetch the previous command from the history list, moving back in
4456 .B next\-history (C\-n)
4457 Fetch the next command from the history list, moving forward in the
4460 .B beginning\-of\-history (M\-<)
4461 Move to the first line in the history.
4463 .B end\-of\-history (M\->)
4464 Move to the end of the input history, i.e., the line currently being
4467 .B reverse\-search\-history (C\-r)
4468 Search backward starting at the current line and moving `up' through
4469 the history as necessary. This is an incremental search.
4471 .B forward\-search\-history (C\-s)
4472 Search forward starting at the current line and moving `down' through
4473 the history as necessary. This is an incremental search.
4475 .B non\-incremental\-reverse\-search\-history (M\-p)
4476 Search backward through the history starting at the current line
4477 using a non-incremental search for a string supplied by the user.
4479 .B non\-incremental\-forward\-search\-history (M\-n)
4480 Search forward through the history using a non-incremental search for
4481 a string supplied by the user.
4483 .B history\-search\-forward
4484 Search forward through the history for the string of characters
4485 between the start of the current line and the point.
4486 This is a non-incremental search.
4488 .B history\-search\-backward
4489 Search backward through the history for the string of characters
4490 between the start of the current line and the point.
4491 This is a non-incremental search.
4493 .B yank\-nth\-arg (M\-C\-y)
4494 Insert the first argument to the previous command (usually
4495 the second word on the previous line) at point.
4498 insert the \fIn\fPth word from the previous command (the words
4499 in the previous command begin with word 0). A negative argument
4500 inserts the \fIn\fPth word from the end of the previous command.
4503 yank\-last\-arg (M\-.\^, M\-_\^)
4504 Insert the last argument to the previous command (the last word of
4505 the previous history entry). With an argument,
4506 behave exactly like \fByank\-nth\-arg\fP.
4507 Successive calls to \fByank\-last\-arg\fP move back through the history
4508 list, inserting the last argument of each line in turn.
4510 .B shell\-expand\-line (M\-C\-e)
4511 Expand the line as the shell does. This
4512 performs alias and history expansion as well as all of the shell
4513 word expansions. See
4515 .B HISTORY EXPANSION
4516 below for a description of history expansion.
4518 .B history\-expand\-line (M\-^)
4519 Perform history expansion on the current line.
4522 .B HISTORY EXPANSION
4523 below for a description of history expansion.
4526 Perform history expansion on the current line and insert a space.
4529 .B HISTORY EXPANSION
4530 below for a description of history expansion.
4532 .B alias\-expand\-line
4533 Perform alias expansion on the current line.
4537 above for a description of alias expansion.
4539 .B history\-and\-alias\-expand\-line
4540 Perform history and alias expansion on the current line.
4542 .B insert\-last\-argument (M\-.\^, M\-_\^)
4543 A synonym for \fByank\-last\-arg\fP.
4545 .B operate\-and\-get\-next (C\-o)
4546 Accept the current line for execution and fetch the next line
4547 relative to the current line from the history for editing. Any
4548 argument is ignored.
4550 .SS Commands for Changing Text
4554 .B delete\-char (C\-d)
4555 Delete the character at point. If point is at the
4556 beginning of the line, there are no characters in the line, and
4557 the last character typed was not bound to \fBdelete\-char\fP,
4562 .B backward\-delete\-char (Rubout)
4563 Delete the character behind the cursor. When given a numeric argument,
4564 save the deleted text on the kill ring.
4566 .B forward\-backward\-delete\-char
4567 Delete the character under the cursor, unless the cursor is at the
4568 end of the line, in which case the character behind the cursor is
4569 deleted. By default, this is not bound to a key.
4571 .B quoted\-insert (C\-q, C\-v)
4572 Add the next character typed to the line verbatim. This is
4573 how to insert characters like \fBC\-q\fP, for example.
4575 .B tab\-insert (C\-v TAB)
4576 Insert a tab character.
4578 .B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
4579 Insert the character typed.
4581 .B transpose\-chars (C\-t)
4582 Drag the character before point forward over the character at point,
4583 moving point forward as well.
4584 If point is at the end of the line, then this transposes
4585 the two characters before point.
4586 Negative arguments have no effect.
4588 .B transpose\-words (M\-t)
4589 Drag the word before point past the word after point,
4590 moving point over that word as well.
4592 .B upcase\-word (M\-u)
4593 Uppercase the current (or following) word. With a negative argument,
4594 uppercase the previous word, but do not move point.
4596 .B downcase\-word (M\-l)
4597 Lowercase the current (or following) word. With a negative argument,
4598 lowercase the previous word, but do not move point.
4600 .B capitalize\-word (M\-c)
4601 Capitalize the current (or following) word. With a negative argument,
4602 capitalize the previous word, but do not move point.
4604 .SS Killing and Yanking
4608 .B kill\-line (C\-k)
4609 Kill the text from point to the end of the line.
4611 .B backward\-kill\-line (C\-x Rubout)
4612 Kill backward to the beginning of the line.
4614 .B unix\-line\-discard (C\-u)
4615 Kill backward from point to the beginning of the line.
4616 The killed text is saved on the kill-ring.
4617 .\" There is no real difference between this and backward-kill-line
4619 .B kill\-whole\-line
4620 Kill all characters on the current line, no matter where point is.
4622 .B kill\-word (M\-d)
4623 Kill from point to the end of the current word, or if between
4624 words, to the end of the next word.
4625 Word boundaries are the same as those used by \fBforward\-word\fP.
4627 .B backward\-kill\-word (M\-Rubout)
4628 Kill the word behind point.
4629 Word boundaries are the same as those used by \fBbackward\-word\fP.
4631 .B unix\-word\-rubout (C\-w)
4632 Kill the word behind point, using white space as a word boundary.
4633 The killed text is saved on the kill-ring.
4635 .B delete\-horizontal\-space (M\-\e)
4636 Delete all spaces and tabs around point.
4639 Kill the text in the current region.
4641 .B copy\-region\-as\-kill
4642 Copy the text in the region to the kill buffer.
4644 .B copy\-backward\-word
4645 Copy the word before point to the kill buffer.
4646 The word boundaries are the same as \fBbackward\-word\fP.
4648 .B copy\-forward\-word
4649 Copy the word following point to the kill buffer.
4650 The word boundaries are the same as \fBforward\-word\fP.
4653 Yank the top of the kill ring into the buffer at point.
4656 Rotate the kill ring, and yank the new top. Only works following
4661 .SS Numeric Arguments
4665 .B digit\-argument (M\-0, M\-1, ..., M\-\-)
4666 Add this digit to the argument already accumulating, or start a new
4667 argument. M\-\- starts a negative argument.
4669 .B universal\-argument
4670 This is another way to specify an argument.
4671 If this command is followed by one or more digits, optionally with a
4672 leading minus sign, those digits define the argument.
4673 If the command is followed by digits, executing
4674 .B universal\-argument
4675 again ends the numeric argument, but is otherwise ignored.
4676 As a special case, if this command is immediately followed by a
4677 character that is neither a digit or minus sign, the argument count
4678 for the next command is multiplied by four.
4679 The argument count is initially one, so executing this function the
4680 first time makes the argument count four, a second time makes the
4681 argument count sixteen, and so on.
4688 Attempt to perform completion on the text before point.
4690 attempts completion treating the text as a variable (if the
4691 text begins with \fB$\fP), username (if the text begins with
4692 \fB~\fP), hostname (if the text begins with \fB@\fP), or
4693 command (including aliases and functions) in turn. If none
4694 of these produces a match, filename completion is attempted.
4696 .B possible\-completions (M\-?)
4697 List the possible completions of the text before point.
4699 .B insert\-completions (M\-*)
4700 Insert all completions of the text before point
4701 that would have been generated by
4702 \fBpossible\-completions\fP.
4705 Similar to \fBcomplete\fP, but replaces the word to be completed
4706 with a single match from the list of possible completions.
4707 Repeated execution of \fBmenu\-complete\fP steps through the list
4708 of possible completions, inserting each match in turn.
4709 At the end of the list of completions, the bell is rung
4710 (subject to the setting of \Bbell\-style\fP)
4711 and the original text is restored.
4712 An argument of \fIn\fP moves \fIn\fP positions forward in the list
4713 of matches; a negative argument may be used to move backward
4715 This command is intended to be bound to \fBTAB\fP, but is unbound
4718 .B delete\-char\-or\-list
4719 Deletes the character under the cursor if not at the beginning or
4720 end of the line (like \fBdelete\-char\fP).
4721 If at the end of the line, behaves identically to
4722 \fBpossible\-completions\fP.
4723 This command is unbound by default.
4725 .B complete\-filename (M\-/)
4726 Attempt filename completion on the text before point.
4728 .B possible\-filename\-completions (C\-x /)
4729 List the possible completions of the text before point,
4730 treating it as a filename.
4732 .B complete\-username (M\-~)
4733 Attempt completion on the text before point, treating
4736 .B possible\-username\-completions (C\-x ~)
4737 List the possible completions of the text before point,
4738 treating it as a username.
4740 .B complete\-variable (M\-$)
4741 Attempt completion on the text before point, treating
4742 it as a shell variable.
4744 .B possible\-variable\-completions (C\-x $)
4745 List the possible completions of the text before point,
4746 treating it as a shell variable.
4748 .B complete\-hostname (M\-@)
4749 Attempt completion on the text before point, treating
4752 .B possible\-hostname\-completions (C\-x @)
4753 List the possible completions of the text before point,
4754 treating it as a hostname.
4756 .B complete\-command (M\-!)
4757 Attempt completion on the text before point, treating
4758 it as a command name. Command completion attempts to
4759 match the text against aliases, reserved words, shell
4760 functions, shell builtins, and finally executable filenames,
4763 .B possible\-command\-completions (C\-x !)
4764 List the possible completions of the text before point,
4765 treating it as a command name.
4767 .B dynamic\-complete\-history (M\-TAB)
4768 Attempt completion on the text before point, comparing
4769 the text against lines from the history list for possible
4772 .B complete\-into\-braces (M\-{)
4773 Perform filename completion and insert the list of possible completions
4774 enclosed within braces so the list is available to the shell (see
4782 .B start\-kbd\-macro (C\-x (\^)
4783 Begin saving the characters typed into the current keyboard macro.
4785 .B end\-kbd\-macro (C\-x )\^)
4786 Stop saving the characters typed into the current keyboard macro
4787 and store the definition.
4789 .B call\-last\-kbd\-macro (C\-x e)
4790 Re-execute the last keyboard macro defined, by making the characters
4791 in the macro appear as if typed at the keyboard.
4797 .B re\-read\-init\-file (C\-x C\-r)
4798 Read in the contents of the \fIinputrc\fP file, and incorporate
4799 any bindings or variable assignments found there.
4802 Abort the current editing command and
4803 ring the terminal's bell (subject to the setting of
4806 .B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
4807 If the metafied character \fIx\fP is lowercase, run the command
4808 that is bound to the corresponding uppercase character.
4810 .B prefix\-meta (ESC)
4811 Metafy the next character typed.
4818 .B undo (C\-_, C\-x C\-u)
4819 Incremental undo, separately remembered for each line.
4821 .B revert\-line (M\-r)
4822 Undo all changes made to this line. This is like executing the
4824 command enough times to return the line to its initial state.
4826 .B tilde\-expand (M\-&)
4827 Perform tilde expansion on the current word.
4829 .B set\-mark (C\-@, M\-<space>)
4830 Set the mark to the point. If a
4831 numeric argument is supplied, the mark is set to that position.
4833 .B exchange\-point\-and\-mark (C\-x C\-x)
4834 Swap the point with the mark. The current cursor position is set to
4835 the saved position, and the old cursor position is saved as the mark.
4837 .B character\-search (C\-])
4838 A character is read and point is moved to the next occurrence of that
4839 character. A negative count searches for previous occurrences.
4841 .B character\-search\-backward (M\-C\-])
4842 A character is read and point is moved to the previous occurrence of that
4843 character. A negative count searches for subsequent occurrences.
4845 .B insert\-comment (M\-#)
4846 The value of the readline
4848 variable is inserted at the beginning of the current line, and the line
4849 is accepted as if a newline had been typed. The default value of
4850 \fBcomment\-begin\fP causes this command to make the current line
4853 .B glob\-expand\-word (C\-x *)
4854 The word before point is treated as a pattern for pathname expansion,
4855 and the list of matching file names is inserted, replacing the word.
4857 .B glob\-list\-expansions (C\-x g)
4858 The list of expansions that would have been generated by
4859 .B glob\-expand\-word
4860 is displayed, and the line is redrawn.
4863 Print all of the functions and their key bindings to the
4864 readline output stream. If a numeric argument is supplied,
4865 the output is formatted in such a way that it can be made part
4866 of an \fIinputrc\fP file.
4869 Print all of the settable readline variables and their values to the
4870 readline output stream. If a numeric argument is supplied,
4871 the output is formatted in such a way that it can be made part
4872 of an \fIinputrc\fP file.
4875 Print all of the readline key sequences bound to macros and the
4876 strings they ouput. If a numeric argument is supplied,
4877 the output is formatted in such a way that it can be made part
4878 of an \fIinputrc\fP file.
4880 .B display\-shell\-version (C\-x C\-v)
4881 Display version information about the current instance of
4884 .SS Programmable Completion
4886 When word completion is attempted for an argument to a command for
4887 which a completion specification (a \fIcompspec\fP) has been defined
4888 using the \fBcomplete\fP builtin (see
4890 .B "SHELL BUILTIN COMMANDS"
4891 below), the programmable completion facilities are invoked.
4893 First, the command name is identified.
4894 If a compspec has been defined for that command, the
4895 compspec is used to generate the list of possible completions for the word.
4896 If the command word is a full pathname, a compspec for the full
4897 pathname is searched for first.
4898 If no compspec is found for the full pathname, an attempt is made to
4899 find a compspec for the portion following the final slash.
4901 Once a compspec has been found, it is used to generate the list of
4903 If a compspec is not found, the default \fBbash\fP completion as
4904 described above under \fBCompleting\fP is performed.
4906 First, the actions specified by the compspec are used.
4907 Only matches which are prefixed by the word being completed are
4913 option is used for filename or directory name completion, the shell
4917 is used to filter the matches.
4919 Any completions specified by a filename expansion pattern to the
4920 \fB\-G\fP option are generated next.
4921 The words generated by the pattern need not match the word
4926 shell variable is not used to filter the matches, but the
4931 Next, the string specified as the argument to the \fB\-W\fP option
4933 The string is first split using the characters in the
4936 special variable as delimiters.
4937 Shell quoting is honored.
4938 Each word is then expanded using
4939 brace expansion, tilde expansion, parameter and variable expansion,
4940 command substitution, arithmetic expansion, and pathname expansion,
4941 as described above under
4944 The results are split using the rules described above under
4945 \fBWord Splitting\fP.
4946 The results of the expansion are prefix-matched against the word being
4947 completed, and the matching words become the possible completions.
4949 After these matches have been generated, any shell function or command
4950 specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
4951 When the command or function is invoked, the
4957 variables are assigned values as described above under
4958 \fBShell Variables\fP.
4959 If a shell function is being invoked, the
4965 variables are also set.
4966 When the function or command is invoked, the first argument is the
4967 name of the command whose arguments are being completed, the
4968 second argument is the word being completed, and the third argument
4969 is the word preceding the word being completed on the current command line.
4970 No filtering of the generated completions against the word being completed
4971 is performed; the function or command has complete freedom in generating
4974 Any function specified with \fB\-F\fP is invoked first.
4975 The function may use any of the shell facilities, including the
4976 \fBcompgen\fP builtin described below, to generate the matches.
4977 It must put the possible completions in the
4982 Next, any command specified with the \fB\-C\fP option is invoked
4983 in an environment equivalent to command substitution.
4984 It should print a list of completions, one per line, to the
4986 Backslash may be used to escape a newline, if necessary.
4988 After all of the possible completions are generated, any filter
4989 specified with the \fB\-X\fP option is applied to the list.
4990 The filter is a pattern as used for pathname expansion; a \fB&\fP
4991 in the pattern is replaced with the text of the word being completed.
4992 A literal \fB&\fP may be escaped with a backslash; the backslash
4993 is removed before attempting a match.
4994 Any completion that matches the pattern will be removed from the list.
4995 A leading \fB!\fP negates the pattern; in this case any completion
4996 not matching the pattern will be removed.
4998 Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
4999 options are added to each member of the completion list, and the result is
5000 returned to the readline completion code as the list of possible
5003 If the previously-applied actions do not generate any matches, and the
5004 \fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
5005 compspec was defined, directory name completion is attempted.
5007 By default, if a compspec is found, whatever it generates is returned
5008 to the completion code as the full set of possible completions.
5009 The default \fBbash\fP completions are not attempted, and the readline
5010 default of filename completion is disabled.
5011 If the \fB-o default\fP option was supplied to \fBcomplete\fP when the
5012 compspec was defined, readline's default completion will be performed
5013 if the compspec generates no matches.
5019 builtin is enabled, the shell provides access to the
5020 \fIcommand history\fP,
5021 the list of commands previously typed.
5022 The value of the \fBHISTSIZE\fP variable is used as the
5023 number of commands to save in a history list.
5024 The text of the last
5027 commands (default 500) is saved. The shell
5028 stores each command in the history list prior to parameter and
5029 variable expansion (see
5032 above) but after history expansion is performed, subject to the
5033 values of the shell variables
5040 On startup, the history is initialized from the file named by
5044 (default \fI~/.bash_history\fP).
5045 The file named by the value of
5048 is truncated, if necessary, to contain no more than
5049 the number of lines specified by the value of
5052 When an interactive shell exits, the last
5055 lines are copied from the history list to
5060 shell option is enabled
5061 (see the description of
5065 .B "SHELL BUILTIN COMMANDS"
5066 below), the lines are appended to the history file,
5067 otherwise the history file is overwritten.
5071 is unset, or if the history file is unwritable, the history is
5072 not saved. After saving the history, the history file is truncated
5073 to contain no more than
5079 is not set, no truncation is performed.
5085 .B SHELL BUILTIN COMMANDS
5086 below) may be used to list or edit and re-execute a portion of
5090 builtin may be used to display or modify the history list and
5091 manipulate the history file.
5092 When using command-line editing, search commands
5093 are available in each editing mode that provide access to the
5096 The shell allows control over which commands are saved on the history
5103 variables may be set to cause the shell to save only a subset of the
5107 shell option, if enabled, causes the shell to attempt to save each
5108 line of a multi-line command in the same history entry, adding
5109 semicolons where necessary to preserve syntactic correctness.
5112 shell option causes the shell to save the command with embedded newlines
5113 instead of semicolons. See the description of the
5117 .B "SHELL BUILTIN COMMANDS"
5118 for information on setting and unsetting shell options.
5119 .SH "HISTORY EXPANSION"
5121 The shell supports a history expansion feature that
5122 is similar to the history expansion in
5124 This section describes what syntax features are available. This
5125 feature is enabled by default for interactive shells, and can be
5130 builtin command (see
5132 .B SHELL BUILTIN COMMANDS
5133 below). Non-interactive shells do not perform history expansion
5136 History expansions introduce words from the history list into
5137 the input stream, making it easy to repeat commands, insert the
5138 arguments to a previous command into the current input line, or
5139 fix errors in previous commands quickly.
5141 History expansion is performed immediately after a complete line
5142 is read, before the shell breaks it into words.
5143 It takes place in two parts.
5144 The first is to determine which line from the history list
5145 to use during substitution.
5146 The second is to select portions of that line for inclusion into
5148 The line selected from the history is the \fIevent\fP,
5149 and the portions of that line that are acted upon are \fIwords\fP.
5150 Various \fImodifiers\fP are available to manipulate the selected words.
5151 The line is broken into words in the same fashion as when reading input,
5152 so that several \fImetacharacter\fP-separated words surrounded by
5153 quotes are considered one word.
5154 History expansions are introduced by the appearance of the
5155 history expansion character, which is \^\fB!\fP\^ by default.
5156 Only backslash (\^\fB\e\fP\^) and single quotes can quote
5157 the history expansion character.
5159 Several shell options settable with the
5161 builtin may be used to tailor the behavior of history expansion.
5164 shell option is enabled (see the description of the
5168 is being used, history substitutions are not immediately passed to
5170 Instead, the expanded line is reloaded into the
5172 editing buffer for further modification.
5175 is being used, and the
5177 shell option is enabled, a failed history substitution will be reloaded
5180 editing buffer for correction.
5185 builtin command may be used to see what a history expansion will
5191 builtin may be used to add commands to the end of the history list
5192 without actually executing them, so that they are available for
5195 The shell allows control of the various characters used by the
5196 history expansion mechanism (see the description of
5199 .BR "Shell Variables" ).
5200 .SS Event Designators
5202 An event designator is a reference to a command line entry in the
5208 Start a history substitution, except when followed by a
5213 Refer to command line
5217 Refer to the current command line minus
5221 Refer to the previous command. This is a synonym for `!\-1'.
5224 Refer to the most recent command starting with
5227 .B !?\fIstring\fR\fB[?]\fR
5228 Refer to the most recent command containing
5230 The trailing \fB?\fP may be omitted if
5232 is followed immediately by a newline.
5234 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
5235 Quick substitution. Repeat the last command, replacing
5240 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
5241 (see \fBModifiers\fP below).
5244 The entire command line typed so far.
5246 .SS Word Designators
5248 Word designators are used to select desired words from the event.
5251 separates the event specification from the word designator.
5252 It may be omitted if the word designator begins with a
5259 Words are numbered from the beginning of the line,
5260 with the first word being denoted by 0 (zero).
5261 Words are inserted into the current line separated by single spaces.
5266 The zeroth word. For the shell, this is the command
5273 The first argument. That is, word 1.
5279 The word matched by the most recent `?\fIstring\fR?' search.
5282 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
5285 All of the words but the zeroth. This is a synonym
5286 for `\fI1\-$\fP'. It is not an error to use
5288 if there is just one
5289 word in the event; the empty string is returned in that case.
5292 Abbreviates \fIx\-$\fP.
5295 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
5298 If a word designator is supplied without an event specification, the
5299 previous command is used as the event.
5302 After the optional word designator, there may appear a sequence of
5303 one or more of the following modifiers, each preceded by a `:'.
5309 Remove a trailing file name component, leaving only the head.
5312 Remove all leading file name components, leaving the tail.
5315 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
5319 Remove all but the trailing suffix.
5322 Print the new command but do not execute it.
5325 Quote the substituted words, escaping further substitutions.
5328 Quote the substituted words as with
5330 but break into words at
5334 .B s/\fIold\fP/\fInew\fP/
5337 for the first occurrence of
5339 in the event line. Any delimiter can be used in place of /. The
5340 final delimiter is optional if it is the last character of the
5341 event line. The delimiter may be quoted in
5345 with a single backslash. If & appears in
5349 A single backslash will quote the &. If
5351 is null, it is set to the last
5353 substituted, or, if no previous history substitutions took place,
5357 .B !?\fIstring\fR\fB[?]\fR
5361 Repeat the previous substitution.
5364 Cause changes to be applied over the entire event line. This is
5365 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
5366 or `\fB:&\fP'. If used with
5367 `\fB:s\fP', any delimiter can be used
5368 in place of /, and the final delimiter is optional
5369 if it is the last character of the event line.
5371 .SH "SHELL BUILTIN COMMANDS"
5372 .\" start of bash_builtins
5375 Unless otherwise noted, each builtin command documented in this
5376 section as accepting options preceded by
5380 to signify the end of the options.
5384 \fB:\fP [\fIarguments\fP]
5386 No effect; the command does nothing beyond expanding
5388 and performing any specified
5389 redirections. A zero exit code is returned.
5392 \fB .\| \fP \fIfilename\fP [\fIarguments\fP]
5394 \fBsource\fP \fIfilename\fP [\fIarguments\fP]
5396 Read and execute commands from
5399 shell environment and return the exit status of the last command
5404 does not contain a slash, file names in
5407 are used to find the directory containing
5409 The file searched for in
5412 need not be executable.
5413 When \fBbash\fP is not in \fIposix mode\fP, the current directory is
5414 searched if no file is found in
5421 builtin command is turned off, the
5425 If any \fIarguments\fP are supplied, they become the positional
5426 parameters when \fIfilename\fP is executed. Otherwise the positional
5427 parameters are unchanged.
5428 The return status is the status of the last command exited within
5429 the script (0 if no commands are executed), and false if
5431 is not found or cannot be read.
5433 \fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
5434 \fBAlias\fP with no arguments or with the
5436 option prints the list of aliases in the form
5437 \fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
5438 When arguments are supplied, an alias is defined for
5439 each \fIname\fP whose \fIvalue\fP is given.
5440 A trailing space in \fIvalue\fP causes the next word to be
5441 checked for alias substitution when the alias is expanded.
5442 For each \fIname\fP in the argument list for which no \fIvalue\fP
5443 is supplied, the name and value of the alias is printed.
5444 \fBAlias\fP returns true unless a \fIname\fP is given for which
5445 no alias has been defined.
5447 \fBbg\fP [\fIjobspec\fP]
5448 Resume the suspended job \fIjobspec\fP in the background, as if it
5449 had been started with
5451 If \fIjobspec\fP is not present, the shell's notion of the
5452 \fIcurrent job\fP is used.
5455 returns 0 unless run when job control is disabled or, when run with
5456 job control enabled, if \fIjobspec\fP was not found or started without
5460 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSV\fP]
5462 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
5464 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
5466 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
5468 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
5472 key and function bindings, or bind a key sequence to a
5474 function or macro. The binding syntax accepted is identical to that of
5476 but each binding must be passed as a separate argument;
5477 e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'. Options, if supplied, have the
5485 as the keymap to be affected by the subsequent bindings.
5489 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
5490 vi\-move, vi\-command\fP, and
5492 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
5493 equivalent to \fIemacs\-standard\fP.
5496 List the names of all \fBreadline\fP functions.
5499 Display \fBreadline\fP function names and bindings in such a way
5500 that they can be re-read.
5503 List current \fBreadline\fP function names and bindings.
5506 Display \fBreadline\fP variable names and values in such a way that they
5510 List current \fBreadline\fP variable names and values.
5513 Display \fBreadline\fP key sequences bound to macros and the strings
5514 they output in such a way that they can be re-read.
5517 Display \fBreadline\fP key sequences bound to macros and the strings
5520 .B \-f \fIfilename\fP
5521 Read key bindings from \fIfilename\fP.
5523 .B \-q \fIfunction\fP
5524 Query about which keys invoke the named \fIfunction\fP.
5526 .B \-u \fIfunction\fP
5527 Unbind all keys bound to the named \fIfunction\fP.
5530 Remove any current binding for \fIkeyseq\fP.
5532 .B \-x \fIkeyseq\fP:\fIshell\-command\fP
5533 Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
5537 The return value is 0 unless an unrecognized option is given or an
5541 \fBbreak\fP [\fIn\fP]
5548 loop. If \fIn\fP is specified, break \fIn\fP levels.
5552 is greater than the number of enclosing loops, all enclosing loops
5553 are exited. The return value is 0 unless the shell is not executing
5558 \fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
5559 Execute the specified shell builtin, passing it
5561 and return its exit status.
5562 This is useful when defining a
5563 function whose name is the same as a shell builtin,
5564 retaining the functionality of the builtin within the function.
5565 The \fBcd\fP builtin is commonly redefined this way.
5566 The return status is false if
5568 is not a shell builtin command.
5570 \fBcd\fP [\fB\-LP\fP] [\fIdir\fP]
5571 Change the current directory to \fIdir\fP. The variable
5580 defines the search path for the directory containing
5582 Alternative directory names in
5585 are separated by a colon (:). A null directory name in
5588 is the same as the current directory, i.e., ``\fB.\fP''. If
5590 begins with a slash (/),
5596 option says to use the physical directory structure instead of
5597 following symbolic links (see also the
5601 builtin command); the
5603 option forces symbolic links to be followed. An argument of
5608 The return value is true if the directory was successfully changed;
5611 \fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
5616 suppressing the normal shell function lookup. Only builtin
5617 commands or commands found in the
5620 are executed. If the
5622 option is given, the search for
5624 is performed using a default value for
5626 that is guaranteed to find all of the standard utilities.
5631 option is supplied, a description of
5635 option causes a single word indicating the command or file name
5638 to be displayed; the
5640 option produces a more verbose description.
5645 option is supplied, the exit status is 0 if
5647 was found, and 1 if not. If neither option is supplied and
5648 an error occurred or
5650 cannot be found, the exit status is 127. Otherwise, the exit status of the
5652 builtin is the exit status of
5655 \fBcompgen\fP [\fIoption\fP] [\fIword\fP]
5656 Generate possible completion matches for \fIword\fP according to
5657 the \fIoption\fPs, which may be any option accepted by the
5659 builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
5660 the matches to the standard output.
5661 When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
5662 set by the programmable completion facilities, while available, will not
5665 The matches will be generated in the same way as if the programmable
5666 completion code had generated them directly from a completion specification
5667 with the same flags.
5668 If \fIword\fP is specified, only those completions matching \fIword\fP
5671 The return value is true unless an invalid option is supplied, or no
5672 matches were generated.
5675 \fBcomplete\fP [\fB\-abcdefjkvu\fP] [\fB\-o\fP \fIcomp-option\fP] [\fB\-A\fP \fIaction\fP] [\fB\-G\fP \fIglobpat\fP] [\fB\-W\fP \fIwordlist\fP] [\fB\-P\fP \fIprefix\fP] [\fB\-S\fP \fIsuffix\fP]
5677 [\fB\-X\fP \fIfilterpat\fP] [\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP] \fIname\fP [\fIname ...\fP]
5679 \fBcomplete\fP \fB\-pr\fP [\fIname\fP ...]
5681 Specify how arguments to each \fIname\fP should be completed.
5682 If the \fB\-p\fP option is supplied, or if no options are supplied,
5683 existing completion specifications are printed in a way that allows
5684 them to be reused as input.
5685 The \fB\-r\fP option removes a completion specification for
5686 each \fIname\fP, or, if no \fIname\fPs are supplied, all
5687 completion specifications.
5689 The process of applying these completion specifications when word completion
5690 is attempted is described above under \fBProgrammable Completion\fP.
5692 Other options, if specified, have the following meanings.
5693 The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
5694 (and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
5695 should be quoted to protect them from expansion before the
5701 \fB\-o\fP \fIcomp-option\fP
5702 The \fIcomp-option\fP controls several aspects of the compspec's behavior
5703 beyond the simple generation of completions.
5704 \fIcomp-option\fP may be one of:
5708 Use readline's default completion if the compspec generates no matches.
5711 Perform directory name completion if the compspec generates no matches.
5714 Tell readline that the compspec generates filenames, so it can perform any
5715 filename\-specific processing (like adding a slash to directory names or
5716 suppressing trailing spaces). Intended to be used with shell functions.
5719 \fB\-A\fP \fIaction\fP
5720 The \fIaction\fP may be one of the following to generate a list of possible
5725 Alias names. May also be specified as \fB\-a\fP.
5728 Array variable names.
5731 \fBReadline\fP key binding names.
5734 Names of shell builtin commands. May also be specified as \fB\-b\fP.
5737 Command names. May also be specified as \fB\-c\fP.
5740 Directory names. May also be specified as \fB\-d\fP.
5743 Names of disabled shell builtins.
5746 Names of enabled shell builtins.
5749 Names of exported shell variables. May also be specified as \fB\-e\fP.
5752 File names. May also be specified as \fB\-f\fP.
5755 Names of shell functions.
5758 Help topics as accepted by the \fBhelp\fP builtin.
5761 Hostnames, as taken from the file specified by the
5767 Job names, if job control is active. May also be specified as \fB\-j\fP.
5770 Shell reserved words. May also be specified as \fB\-k\fP.
5773 Names of running jobs, if job control is active.
5776 Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
5779 Shell option names as accepted by the \fBshopt\fP builtin.
5785 Names of stopped jobs, if job control is active.
5788 User names. May also be specified as \fB\-u\fP.
5791 Names of all shell variables. May also be specified as \fB\-v\fP.
5794 \fB\-G\fP \fIglobpat\fP
5795 The filename expansion pattern \fIglobpat\fP is expanded to generate
5796 the possible completions.
5798 \fB\-W\fP \fIwordlist\fP
5799 The \fIwordlist\fP is split using the characters in the
5802 special variable as delimiters, and each resultant word is expanded.
5803 The possible completions are the members of the resultant list which
5804 match the word being completed.
5806 \fB\-C\fP \fIcommand\fP
5807 \fIcommand\fP is executed in a subshell environment, and its output is
5808 used as the possible completions.
5810 \fB\-F\fP \fIfunction\fP
5811 The shell function \fIfunction\fP is executed in the current shell
5813 When it finishes, the possible completions are retrieved from the value
5819 \fB\-X\fP \fIfilterpat\fP
5820 \fIfilterpat\fP is a pattern as used for filename expansion.
5821 It is applied to the list of possible completions generated by the
5822 preceding options and arguments, and each completion matching
5823 \fIfilterpat\fP is removed from the list.
5824 A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
5825 case, any completion not matching \fIfilterpat\fP is removed.
5827 \fB\-P\fP \fIprefix\fP
5828 \fIprefix\fP is added at the beginning of each possible completion
5829 after all other options have been applied.
5831 \fB\-S\fP \fIsuffix\fP
5832 \fIsuffix\fP is appended to each possible completion
5833 after all other options have been applied.
5836 The return value is true unless an invalid option is supplied, an option
5837 other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
5838 argument, an attempt is made to remove a completion specification for
5839 a \fIname\fP for which no specification exists, or
5840 an error occurs adding a completion specification.
5843 \fBcontinue\fP [\fIn\fP]
5844 Resume the next iteration of the enclosing
5853 is specified, resume at the \fIn\fPth enclosing loop.
5857 is greater than the number of enclosing loops, the last enclosing loop
5858 (the ``top-level'' loop) is resumed. The return value is 0 unless the
5859 shell is not executing a loop when
5864 \fBdeclare\fP [\fB\-afFirx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP]]
5866 \fBtypeset\fP [\fB\-afFirx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP]]
5868 Declare variables and/or give them attributes.
5869 If no \fIname\fPs are given then display the values of variables.
5872 option will display the attributes and values of each
5876 is used, additional options are ignored.
5879 option inhibits the display of function definitions; only the
5880 function name and attributes are printed.
5885 The following options can
5886 be used to restrict output to variables with the specified attribute or
5887 to give variables attributes:
5892 Each \fIname\fP is an array variable (see
5897 Use function names only.
5900 The variable is treated as an integer; arithmetic evaluation (see
5902 .B "ARITHMETIC EVALUATION" ") "
5903 is performed when the variable is assigned a value.
5906 Make \fIname\fPs readonly. These names cannot then be assigned values
5907 by subsequent assignment statements or unset.
5910 Mark \fIname\fPs for export to subsequent commands via the environment.
5913 Using `+' instead of `\-'
5914 turns off the attribute instead, with the exception that \fB+a\fP
5915 may not be used to destroy an array variable. When used in a function,
5917 \fIname\fP local, as with the
5919 command. The return value is 0 unless an invalid option is encountered,
5920 an attempt is made to define a function using
5921 .if n ``\-f foo=bar'',
5922 .if t \f(CW\-f foo=bar\fP,
5923 an attempt is made to assign a value to a readonly variable,
5924 an attempt is made to assign a value to an array variable without
5925 using the compound assignment syntax (see
5927 above), one of the \fInames\fP is not a valid shell variable name,
5928 an attempt is made to turn off readonly status for a readonly variable,
5929 an attempt is made to turn off array status for an array variable,
5930 or an attempt is made to display a non-existent function with \fB\-f\fP.
5933 .B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
5934 Without options, displays the list of currently remembered directories.
5935 The default display is on a single line with directory names separated
5937 Directories are added to the list with the
5941 command removes entries from the list.
5946 Displays the \fIn\fPth entry counting from the left of the list
5949 when invoked without options, starting with zero.
5952 Displays the \fIn\fPth entry counting from the right of the list
5955 when invoked without options, starting with zero.
5958 Clears the directory stack by deleting all of the entries.
5961 Produces a longer listing; the default listing format uses a
5962 tilde to denote the home directory.
5965 Print the directory stack with one entry per line.
5968 Print the directory stack with one entry per line,
5969 prefixing each entry with its index in the stack.
5972 The return value is 0 unless an
5973 invalid option is supplied or \fIn\fP indexes beyond the end
5974 of the directory stack.
5977 \fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ...]
5978 Without options, each
5980 is removed from the table of active jobs.
5981 If the \fB\-h\fP option is given, each
5983 is not removed from the table, but is marked so that
5986 is not sent to the job if the shell receives a
5991 is present, and neither the
5995 option is supplied, the \fIcurrent job\fP is used.
6000 option means to remove or mark all jobs; the
6004 argument restricts operation to running jobs.
6005 The return value is 0 unless a
6007 does not specify a valid job.
6009 \fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
6010 Output the \fIarg\fPs, separated by spaces, followed by a newline.
6011 The return status is always 0.
6012 If \fB\-n\fP is specified, the trailing newline is
6013 suppressed. If the \fB\-e\fP option is given, interpretation of
6014 the following backslash-escaped characters is enabled. The
6016 option disables the interpretation of these escape characters,
6017 even on systems where they are interpreted by default.
6018 The \fBxpg_echo\fP shell option may be used to
6019 dynamically determine whether or not \fBecho\fP expands these
6020 escape characters by default.
6024 to mean the end of options.
6026 interprets the following escape sequences:
6037 suppress trailing newline
6061 the character whose ASCII code is the octal value \fInnn\fP
6062 (one to three digits)
6065 the character whose ASCII code is the hexadecimal value \fInnn\fP
6066 (one to three digits)
6070 \fBenable\fP [\fB\-adnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
6071 Enable and disable builtin shell commands.
6072 Disabling a builtin allows a disk command which has the same name
6073 as a shell builtin to be executed without specifying a full pathname,
6074 even though the shell normally searches for builtins before disk commands.
6075 If \fB\-n\fP is used, each \fIname\fP
6076 is disabled; otherwise,
6077 \fInames\fP are enabled. For example, to use the
6079 binary found via the
6082 instead of the shell builtin version, run
6083 .if t \f(CWenable -n test\fP.
6084 .if n ``enable -n test''.
6087 option means to load the new builtin command
6091 on systems that support dynamic loading. The
6093 option will delete a builtin previously loaded with
6095 If no \fIname\fP arguments are given, or if the
6097 option is supplied, a list of shell builtins is printed.
6098 With no other option arguments, the list consists of all enabled
6100 If \fB\-n\fP is supplied, only disabled builtins are printed.
6101 If \fB\-a\fP is supplied, the list printed includes all builtins, with an
6102 indication of whether or not each is enabled.
6103 If \fB\-s\fP is supplied, the output is restricted to the POSIX
6104 \fIspecial\fP builtins.
6105 The return value is 0 unless a
6107 is not a shell builtin or there is an error loading a new builtin
6108 from a shared object.
6110 \fBeval\fP [\fIarg\fP ...]
6111 The \fIarg\fPs are read and concatenated together into a single
6112 command. This command is then read and executed by the shell, and
6113 its exit status is returned as the value of
6117 or only null arguments,
6121 \fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
6124 is specified, it replaces the shell.
6125 No new process is created. The
6127 become the arguments to \fIcommand\fP.
6131 the shell places a dash at the beginning of the zeroth arg passed to
6139 to be executed with an empty environment. If
6141 is supplied, the shell passes
6143 as the zeroth argument to the executed command. If
6145 cannot be executed for some reason, a non-interactive shell exits,
6146 unless the shell option
6148 is enabled, in which case it returns failure.
6149 An interactive shell returns failure if the file cannot be executed.
6152 is not specified, any redirections take effect in the current shell,
6153 and the return status is 0. If there is a redirection error, the
6156 \fBexit\fP [\fIn\fP]
6157 Cause the shell to exit
6158 with a status of \fIn\fP. If
6160 is omitted, the exit status
6161 is that of the last command executed.
6165 is executed before the shell terminates.
6168 \fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
6174 are marked for automatic export to the environment of
6175 subsequently executed commands. If the
6183 are given, or if the
6185 option is supplied, a list
6186 of all names that are exported in this shell is printed.
6189 option causes the export property to be removed from the
6192 returns an exit status of 0 unless an invalid option is
6194 one of the \fInames\fP is not a valid shell variable name, or
6198 that is not a function.
6201 \fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-nlr\fP] [\fIfirst\fP] [\fIlast\fP]
6203 \fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
6205 Fix Command. In the first form, a range of commands from
6209 is selected from the history list.
6213 may be specified as a string (to locate the last command beginning
6214 with that string) or as a number (an index into the history list,
6215 where a negative number is used as an offset from the current
6218 is not specified it is set to
6219 the current command for listing (so that
6220 .if n ``fc \-l \-10''
6221 .if t \f(CWfc \-l \-10\fP
6222 prints the last 10 commands) and to
6227 is not specified it is set to the previous
6228 command for editing and \-16 for listing.
6233 the command numbers when listing. The
6235 option reverses the order of
6236 the commands. If the
6239 the commands are listed on
6240 standard output. Otherwise, the editor given by
6243 on a file containing those commands. If
6249 variable is used, and
6256 is not set. If neither variable is set,
6258 is used. When editing is complete, the edited commands are
6259 echoed and executed.
6261 In the second form, \fIcommand\fP is re-executed after each instance
6262 of \fIpat\fP is replaced by \fIrep\fP.
6263 A useful alias to use with this is
6265 .if t \f(CWr='fc \-s'\fP,
6269 runs the last command beginning with
6275 re-executes the last command.
6277 If the first form is used, the return value is 0 unless an invalid
6278 option is encountered or
6282 specify history lines out of range.
6285 option is supplied, the return value is the value of the last
6286 command executed or failure if an error occurs with the temporary
6287 file of commands. If the second form is used, the return status
6288 is that of the command re-executed, unless
6290 does not specify a valid history line, in which case
6294 \fBfg\fP [\fIjobspec\fP]
6297 in the foreground, and make it the current job.
6300 is not present, the shell's notion of the \fIcurrent job\fP is used.
6301 The return value is that of the command placed into the foreground,
6302 or failure if run when job control is disabled or, when run with
6303 job control enabled, if
6305 does not specify a valid job or
6307 specifies a job that was started without job control.
6309 \fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
6311 is used by shell procedures to parse positional parameters.
6313 contains the option characters to be recognized; if a character
6314 is followed by a colon, the option is expected to have an
6315 argument, which should be separated from it by white space.
6316 The colon and question mark characters may not be used as
6318 Each time it is invoked,
6320 places the next option in the shell variable
6324 if it does not exist,
6325 and the index of the next argument to be processed into the
6331 is initialized to 1 each time the shell or a shell script
6332 is invoked. When an option requires an argument,
6334 places that argument into the variable
6337 The shell does not reset
6340 automatically; it must be manually reset between multiple
6343 within the same shell invocation if a new set of parameters
6346 When the end of options is encountered, \fBgetopts\fP exits with a
6347 return value greater than zero.
6348 \fBOPTIND\fP is set to the index of the first non-option argument,
6349 and \fBname\fP is set to ?.
6352 normally parses the positional parameters, but if more arguments are
6356 parses those instead.
6359 can report errors in two ways. If the first character of
6363 error reporting is used. In normal operation diagnostic messages
6364 are printed when invalid options or missing option arguments are
6369 is set to 0, no error messages will be displayed, even if the first
6374 If an invalid option is seen,
6379 prints an error message and unsets
6385 the option character found is placed in
6388 and no diagnostic message is printed.
6390 If a required argument is not found, and
6393 a question mark (\^\fB?\fP\^) is placed in
6396 is unset, and a diagnostic message is printed.
6399 is silent, then a colon (\^\fB:\fP\^) is placed in
6404 is set to the option character found.
6407 returns true if an option, specified or unspecified, is found.
6408 It returns false if the end of options is encountered or an
6411 \fBhash\fP [\fB\-r\fP] [\fB\-p\fP \fIfilename\fP] [\fIname\fP]
6414 the full file name of the command is determined by searching
6420 option is supplied, no path search is performed, and
6422 is used as the full file name of the command.
6425 option causes the shell to forget all
6426 remembered locations. If no arguments are given, information
6427 about remembered commands is printed.
6428 The return status is true unless a
6430 is not found or an invalid option is supplied.
6432 \fBhelp\fP [\fB\-s\fP] [\fIpattern\fP]
6433 Display helpful information about builtin commands. If
6437 gives detailed help on all commands matching
6439 otherwise help for all the builtins and shell control structures
6441 The \fB\-s\fP option restricts the information displayed to a short
6443 The return status is 0 unless no command matches
6447 \fBhistory [\fIn\fP]
6449 \fBhistory\fP \fB\-c\fP
6451 \fBhistory \-d\fP \fIoffset\fP
6453 \fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
6455 \fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
6457 \fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
6459 With no options, display the command
6460 history list with line numbers. Lines listed
6463 have been modified. An argument of
6467 lines. If \fIfilename\fP is supplied, it is used as the
6468 name of the history file; if not, the value of
6471 is used. Options, if supplied, have the following meanings:
6476 Clear the history list by deleting all the entries.
6478 \fB\-d\fP \fIoffset\fP
6479 Delete the history entry at position \fIoffset\fP.
6482 Append the ``new'' history lines (history lines entered since the
6483 beginning of the current \fBbash\fP session) to the history file.
6486 Read the history lines not already read from the history
6487 file into the current history list. These are lines
6488 appended to the history file since the beginning of the
6489 current \fBbash\fP session.
6492 Read the contents of the history file
6493 and use them as the current history.
6496 Write the current history to the history file, overwriting the
6497 history file's contents.
6500 Perform history substitution on the following \fIargs\fP and display
6501 the result on the standard output.
6502 Does not store the results in the history list.
6503 Each \fIarg\fP must be quoted to disable normal history expansion.
6508 in the history list as a single entry. The last command in the
6509 history list is removed before the
6514 The return value is 0 unless an invalid option is encountered, an
6515 error occurs while reading or writing the history file, an invalid
6516 \fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
6517 history expansion supplied as an argument to \fB\-p\fP fails.
6521 \fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
6523 \fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
6525 The first form lists the active jobs. The options have the following
6532 in addition to the normal information.
6535 List only the process ID of the job's process group
6539 Display information only about jobs that have changed status since
6540 the user was last notified of their status.
6543 Restrict output to running jobs.
6546 Restrict output to stopped jobs.
6551 is given, output is restricted to information about that job.
6552 The return status is 0 unless an invalid option is encountered
6567 with the corresponding process group ID, and executes
6571 returning its exit status.
6575 \fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
6577 \fBkill\fP \fB\-l\fP [\fIsigspec\fP | \fIexit_status\fP]
6579 Send the signal named by
6583 to the processes named by
6588 is either a signal name such as
6593 is a signal number. If
6595 is a signal name, the name may be
6596 given with or without the
6602 is not present, then
6608 lists the signal names.
6609 If any arguments are supplied when
6611 is given, the names of the signals corresponding to the arguments are
6612 listed, and the return status is 0.
6613 The \fIexit_status\fP argument to
6615 is a number specifying either a signal number or the exit status of
6616 a process terminated by a signal.
6618 returns true if at least one signal was successfully sent, or false
6619 if an error occurs or an invalid option is encountered.
6621 \fBlet\fP \fIarg\fP [\fIarg\fP ...]
6624 is an arithmetic expression to be evaluated (see
6626 .BR "ARITHMETIC EVALUATION" ).
6631 returns 1; 0 is returned otherwise.
6633 \fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ...]
6634 For each argument, a local variable named
6636 is created, and assigned
6638 The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
6641 is used within a function, it causes the variable
6643 to have a visible scope restricted to that function and its children.
6646 writes a list of local variables to the standard output. It is
6649 when not within a function. The return status is 0 unless
6651 is used outside a function, an invalid
6654 \fIname\fP is a readonly variable.
6659 \fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
6660 Removes entries from the directory stack. With no arguments,
6661 removes the top directory from the stack, and performs a
6663 to the new top directory.
6664 Arguments, if supplied, have the following meanings:
6669 Removes the \fIn\fPth entry counting from the left of the list
6672 starting with zero. For example:
6674 .if t \f(CWpopd +0\fP
6675 removes the first directory,
6677 .if t \f(CWpopd +1\fP
6681 Removes the \fIn\fPth entry counting from the right of the list
6684 starting with zero. For example:
6686 .if t \f(CWpopd -0\fP
6687 removes the last directory,
6689 .if t \f(CWpopd -1\fP
6693 Suppresses the normal change of directory when removing directories
6694 from the stack, so that only the stack is manipulated.
6699 command is successful, a
6701 is performed as well, and the return status is 0.
6703 returns false if an invalid option is encountered, the directory stack
6704 is empty, a non-existent directory stack entry is specified, or the
6705 directory change fails.
6708 \fBprintf\fP \fIformat\fP [\fIarguments\fP]
6709 Write the formatted \fIarguments\fP to the standard output under the
6710 control of the \fIformat\fP.
6711 The \fIformat\fP is a character string which contains three types of objects:
6712 plain characters, which are simply copied to standard output, character
6713 escape sequences, which are converted and copied to the standard output, and
6714 format specifications, each of which causes printing of the next successive
6716 In addition to the standard \fIprintf\fP(1) formats, %b causes
6717 \fBprintf\fP to expand backslash escape sequences in the corresponding
6718 \fIargument\fP, and %q causes \fBprintf\fP to output the corresponding
6719 \fIargument\fP in a format that can be reused as shell input.
6721 The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
6722 If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
6723 extra format specifications behave as if a zero value or null string, as
6724 appropriate, had been supplied. The return value is zero on success,
6725 non-zero on failure.
6728 \fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
6730 \fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
6732 Adds a directory to the top of the directory stack, or rotates
6733 the stack, making the new top of the stack the current working
6734 directory. With no arguments, exchanges the top two directories
6735 and returns 0, unless the directory stack is empty.
6736 Arguments, if supplied, have the following meanings:
6741 Rotates the stack so that the \fIn\fPth directory
6742 (counting from the left of the list shown by
6748 Rotates the stack so that the \fIn\fPth directory
6749 (counting from the right of the list shown by
6751 starting with zero) is at the top.
6754 Suppresses the normal change of directory when adding directories
6755 to the stack, so that only the stack is manipulated.
6760 to the directory stack at the top, making it the
6761 new current working directory.
6766 command is successful, a
6768 is performed as well.
6769 If the first form is used,
6771 returns 0 unless the cd to
6773 fails. With the second form,
6775 returns 0 unless the directory stack is empty,
6776 a non-existent directory stack element is specified,
6777 or the directory change to the specified new current directory
6781 \fBpwd\fP [\fB\-LP\fP]
6782 Print the absolute pathname of the current working directory.
6783 The pathname printed contains no symbolic links if the
6785 option is supplied or the
6789 builtin command is enabled.
6792 option is used, the pathname printed may contain symbolic links.
6793 The return status is 0 unless an error occurs while
6794 reading the name of the current directory or an
6795 invalid option is supplied.
6797 \fBread\fP [\fB\-ers\fP] [\fB\-t\fP \fItimeout\fP] [\fB\-a\fP \fIaname\fP] [\fB\-p\fP \fIprompt\fP] [\fB\-n\fP \fInchars\fP] [\fB\-d\fP \fIdelim\fP] [\fIname\fP ...]
6798 One line is read from the standard input, and the first word
6799 is assigned to the first
6801 the second word to the second
6803 and so on, with leftover words and their intervening separators assigned
6806 If there are fewer words read from the standard input than names,
6807 the remaining names are assigned empty values.
6811 are used to split the line into words.
6812 The backslash character (\fB\e\fP) may be used to remove any special
6813 meaning for the next character read and for line continuation.
6814 Options, if supplied, have the following meanings:
6819 The words are assigned to sequential indices
6820 of the array variable
6824 is unset before any new values are assigned.
6825 Other \fIname\fP arguments are ignored.
6828 The first character of \fIdelim\fP is used to terminate the input line,
6829 rather than newline.
6832 If the standard input
6833 is coming from a terminal,
6838 above) is used to obtain the line.
6841 \fBread\fP returns after reading \fInchars\fP characters rather than
6842 waiting for a complete line of input.
6845 Display \fIprompt\fP, without a
6846 trailing newline, before attempting to read any input. The prompt
6847 is displayed only if input is coming from a terminal.
6850 Backslash does not act as an escape character.
6851 The backslash is considered to be part of the line.
6852 In particular, a backslash-newline pair may not be used as a line
6856 Silent mode. If input is coming from a terminal, characters are
6859 .B \-t \fItimeout\fP
6860 Cause \fBread\fP to time out and return failure if a complete line of
6861 input is not read within \fItimeout\fP seconds.
6862 This option has no effect if \fBread\fP is not reading input from the
6868 are supplied, the line read is assigned to the variable
6871 The return code is zero, unless end-of-file is encountered or \fBread\fP
6875 \fBreadonly\fP [\fB\-apf\fP] [\fIname\fP ...]
6878 \fInames\fP are marked readonly; the values of these
6880 may not be changed by subsequent assignment.
6883 option is supplied, the functions corresponding to the
6888 option restricts the variables to arrays.
6891 arguments are given, or if the
6893 option is supplied, a list of all readonly names is printed.
6896 option causes output to be displayed in a format that
6897 may be reused as input.
6898 The return status is 0 unless an invalid option is encountered,
6901 is not a valid shell variable name, or
6905 that is not a function.
6907 \fBreturn\fP [\fIn\fP]
6908 Causes a function to exit with the return value specified by
6912 is omitted, the return status is that of the last command
6913 executed in the function body. If used outside a function,
6914 but during execution of a script by the
6916 (\fBsource\fP) command, it causes the shell to stop executing
6917 that script and return either
6919 or the exit status of the last command executed within the
6920 script as the exit status of the script. If used outside a
6921 function and not during execution of a script by \fB.\fP\^,
6922 the return status is false.
6924 \fBset\fP [\fB\-\-abefhkmnptuvxBCHP\fP] [\fB\-o\fP \fIoption\fP] [\fIarg\fP ...]
6925 Without options, the name and value of each shell variable are displayed
6926 in a format that can be reused as input.
6927 The output is sorted according to the current locale.
6928 When options are specified, they set or unset shell attributes.
6929 Any arguments remaining after the options are processed are treated
6930 as values for the positional parameters and are assigned, in order, to
6935 Options, if specified, have the following meanings:
6940 Automatically mark variables and functions which are modified or created
6941 for export to the environment of subsequent commands.
6944 Report the status of terminated background jobs
6945 immediately, rather than before the next primary prompt. This is
6946 effective only when job control is enabled.
6949 Exit immediately if a \fIsimple command\fP (see
6952 above) exits with a non-zero status. The shell does not exit if the
6953 command that fails is part of an
6960 statement, part of a
6964 list, or if the command's return value is
6969 Disable pathname expansion.
6972 Remember the location of commands as they are looked up for execution.
6973 This is enabled by default.
6976 All arguments in the form of assignment statements
6977 are placed in the environment for a command, not just
6978 those that precede the command name.
6981 Monitor mode. Job control is enabled. This option is on
6982 by default for interactive shells on systems that support
6986 above). Background processes run in a separate process
6987 group and a line containing their exit status is printed
6988 upon their completion.
6991 Read commands but do not execute them. This may be used to
6992 check a shell script for syntax errors. This is ignored by
6995 .B \-o \fIoption\-name\fP
6996 The \fIoption\-name\fP can be one of the following:
7008 Use an emacs-style command line editing interface. This is enabled
7009 by default when the shell is interactive, unless the shell is started
7027 Enable command history, as described above under
7030 This option is on by default in interactive shells.
7033 The effect is as if the shell command
7034 .if t \f(CWIGNOREEOF=10\fP
7035 .if n ``IGNOREEOF=10''
7078 Change the behavior of
7080 where the default operation differs
7081 from the POSIX 1003.2 standard to match the standard (\fIposix mode\fP).
7092 Use a vi-style command line editing interface.
7101 is supplied with no \fIoption\-name\fP, the values of the current options are
7105 is supplied with no \fIoption\-name\fP, a series of
7107 commands to recreate the current option settings is displayed on
7108 the standard output.
7114 mode. In this mode, the
7120 files are not processed, shell functions are not inherited from the
7121 environment, and the
7124 variable, if it appears in the environment, is ignored.
7125 If the shell is started with the effective user (group) id not equal to the
7126 real user (group) id, and the \fB\-p\fP option is not supplied, these actions
7127 are taken and the effective user id is set to the real user id.
7128 If the \fB\-p\fP option is supplied at startup, the effective user id is
7130 Turning this option off causes the effective user
7131 and group ids to be set to the real user and group ids.
7134 Exit after reading and executing one command.
7137 Treat unset variables as an error when performing
7138 parameter expansion. If expansion is attempted on an
7139 unset variable, the shell prints an error message, and,
7140 if not interactive, exits with a non-zero status.
7143 Print shell input lines as they are read.
7146 After expanding each \fIsimple command\fP,
7147 display the expanded value of
7150 followed by the command and its expanded arguments.
7153 The shell performs brace expansion (see
7155 above). This is on by default.
7160 does not overwrite an existing file with the
7165 redirection operators. This may be overridden when
7166 creating output files by using the redirection operator
7174 style history substitution. This option is on by
7175 default when the shell is interactive.
7178 If set, the shell does not follow symbolic links when executing
7181 that change the current working directory. It uses the
7182 physical directory structure instead. By default,
7184 follows the logical chain of directories when performing commands
7185 which change the current directory.
7188 If no arguments follow this option, then the positional parameters are
7189 unset. Otherwise, the positional parameters are set to the
7190 \fIarg\fPs, even if some of them begin with a
7194 Signal the end of options, cause all remaining \fIarg\fPs to be
7195 assigned to the positional parameters. The
7199 options are turned off.
7200 If there are no \fIarg\fPs,
7201 the positional parameters remain unchanged.
7204 The options are off by default unless otherwise noted.
7205 Using + rather than \- causes these options to be turned off.
7206 The options can also be specified as arguments to an invocation of
7208 The current set of options may be found in
7210 The return status is always true unless an invalid option is encountered.
7213 \fBshift\fP [\fIn\fP]
7214 The positional parameters from \fIn\fP+1 ... are renamed to
7217 Parameters represented by the numbers \fB$#\fP
7218 down to \fB$#\fP\-\fIn\fP+1 are unset.
7220 must be a non-negative number less than or equal to \fB$#\fP.
7223 is 0, no parameters are changed.
7226 is not given, it is assumed to be 1.
7229 is greater than \fB$#\fP, the positional parameters are not changed.
7230 The return status is greater than zero if
7234 or less than zero; otherwise 0.
7236 \fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
7237 Toggle the values of variables controlling optional shell behavior.
7238 With no options, or with the
7240 option, a list of all settable options is displayed, with
7241 an indication of whether or not each is set.
7242 The \fB\-p\fP option causes output to be displayed in a form that
7243 may be reused as input.
7244 Other options have the following meanings:
7249 Enable (set) each \fIoptname\fP.
7252 Disable (unset) each \fIoptname\fP.
7255 Suppresses normal output (quiet mode); the return status indicates
7256 whether the \fIoptname\fP is set or unset.
7257 If multiple \fIoptname\fP arguments are given with
7259 the return status is zero if all \fIoptnames\fP are enabled; non-zero
7263 Restricts the values of \fIoptname\fP to be those defined for the
7274 is used with no \fIoptname\fP arguments, the display is limited to
7275 those options which are set or unset, respectively.
7276 Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
7279 The return status when listing options is zero if all \fIoptnames\fP
7280 are enabled, non-zero otherwise. When setting or unsetting options,
7281 the return status is zero unless an \fIoptname\fP is not a valid shell
7284 The list of \fBshopt\fP options is:
7290 If set, an argument to the
7292 builtin command that
7293 is not a directory is assumed to be the name of a variable whose
7294 value is the directory to change to.
7297 If set, minor errors in the spelling of a directory component in a
7299 command will be corrected.
7300 The errors checked for are transposed characters,
7301 a missing character, and one character too many.
7302 If a correction is found, the corrected file name is printed,
7303 and the command proceeds.
7304 This option is only used by interactive shells.
7307 If set, \fBbash\fP checks that a command found in the hash
7308 table exists before trying to execute it. If a hashed command no
7309 longer exists, a normal path search is performed.
7312 If set, \fBbash\fP checks the window size after each command
7313 and, if necessary, updates the values of
7323 attempts to save all lines of a multiple-line
7324 command in the same history entry. This allows
7325 easy re-editing of multi-line commands.
7330 includes filenames beginning with a `.' in the results of pathname
7334 If set, a non-interactive shell will not exit if
7335 it cannot execute the file specified as an argument to the
7337 builtin command. An interactive shell does not exit if
7342 If set, aliases are expanded as described above under
7345 This option is enabled by default for interactive shells.
7348 If set, the extended pattern matching features described above under
7349 \fBPathname Expansion\fP are enabled.
7352 If set, the history list is appended to the file named by the value
7355 variable when the shell exits, rather than overwriting the file.
7360 is being used, a user is given the opportunity to re-edit a
7361 failed history substitution.
7366 is being used, the results of history substitution are not immediately
7367 passed to the shell parser. Instead, the resulting line is loaded into
7368 the \fBreadline\fP editing buffer, allowing further modification.
7373 is being used, \fBbash\fP will attempt to perform hostname completion when a
7374 word containing a \fB@\fP is being completed (see
7380 This is enabled by default.
7383 If set, \fBbash\fP will send
7386 to all jobs when an interactive login shell exits.
7388 .B interactive_comments
7389 If set, allow a word beginning with
7391 to cause that word and all remaining characters on that
7392 line to be ignored in an interactive shell (see
7395 above). This option is enabled by default.
7400 option is enabled, multi-line commands are saved to the history with
7401 embedded newlines rather than using semicolon separators where possible.
7404 If set, and a file that \fBbash\fP is checking for mail has been
7405 accessed since the last time it was checked, the message ``The mail in
7406 \fImailfile\fP has been read'' is displayed.
7408 .B no_empty_cmd_completion
7413 will not attempt to search the \fBPATH\fP for possible completions when
7414 completion is attempted on an empty line.
7419 matches filenames in a case\-insensitive fashion when performing pathname
7421 .B Pathname Expansion
7427 allows patterns which match no
7429 .B Pathname Expansion
7431 to expand to a null string, rather than themselves.
7434 If set, the programmable completion facilities (see
7435 \fBProgrammable Completion\fP above) are enabled.
7436 This option is enabled by default.
7439 If set, prompt strings undergo variable and parameter expansion after
7440 being expanded as described in
7443 above. This option is enabled by default.
7446 The shell sets this option if it is started in restricted mode (see
7448 .B "RESTRICTED SHELL"
7450 The value may not be changed.
7451 This is not reset when the startup files are executed, allowing
7452 the startup files to discover whether or not a shell is restricted.
7457 builtin prints an error message when the shift count exceeds the
7458 number of positional parameters.
7462 \fBsource\fP (\fB.\fP) builtin uses the value of
7465 to find the directory containing the file supplied as an argument.
7466 This option is enabled by default.
7469 If set, the \fBecho\fP builtin expands backslash-escape sequences
7473 \fBsuspend\fP [\fB\-f\fP]
7474 Suspend the execution of this shell until it receives a
7479 option says not to complain if this is
7480 a login shell; just suspend anyway. The return status is 0 unless
7481 the shell is a login shell and
7483 is not supplied, or if job control is not enabled.
7486 \fBtest\fP \fIexpr\fP
7488 \fB[\fP \fIexpr\fP \fB]\fP
7489 Return a status of 0 or 1 depending on
7490 the evaluation of the conditional expression
7492 Each operator and operand must be a separate argument.
7493 Expressions are composed of the primaries described above under
7495 .BR "CONDITIONAL EXPRESSIONS" .
7498 Expressions may be combined using the following operators, listed
7499 in decreasing order of precedence.
7509 Returns the value of \fIexpr\fP.
7510 This may be used to override the normal precedence of operators.
7512 \fIexpr1\fP \-\fBa\fP \fIexpr2\fP
7519 \fIexpr1\fP \-\fBo\fP \fIexpr2\fP
7527 \fBtest\fP and \fB[\fP evaluate conditional
7528 expressions using a set of rules based on the number of arguments.
7534 The expression is false.
7537 The expression is true if and only if the argument is not null.
7540 If the first argument is \fB!\fP, the expression is true if and
7541 only if the second argument is null.
7542 If the first argument is one of the unary conditional operators listed above
7545 .BR "CONDITIONAL EXPRESSIONS" ,
7546 the expression is true if the unary test is true.
7547 If the first argument is not a valid unary conditional operator, the expression
7551 If the second argument is one of the binary conditional operators listed above
7554 .BR "CONDITIONAL EXPRESSIONS" ,
7555 the result of the expression is the result of the binary test using
7556 the first and third arguments as operands.
7557 If the first argument is \fB!\fP, the value is the negation of
7558 the two-argument test using the second and third arguments.
7559 If the first argument is exactly \fB(\fP and the third argument is
7560 exactly \fB)\fP, the result is the one-argument test of the second
7562 Otherwise, the expression is false.
7563 The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
7567 If the first argument is \fB!\fP, the result is the negation of
7568 the three-argument expression composed of the remaining arguments.
7569 Otherwise, the expression is parsed and evaluated according to
7570 precedence using the rules listed above.
7573 The expression is parsed and evaluated according to precedence
7574 using the rules listed above.
7579 Print the accumulated user and system times for the shell and
7580 for processes run from the shell. The return status is 0.
7582 \fBtrap\fP [\fB\-lp\fP] [\fIarg\fP] [\fIsigspec\fP ...]
7585 is to be read and executed when the shell receives
7592 all specified signals are
7593 reset to their original values (the values they had
7594 upon entrance to the shell).
7597 is the null string the signal specified by each
7599 is ignored by the shell and by the commands it invokes.
7604 has been supplied, then the trap commands associated with each
7607 If no arguments are supplied or if only
7611 prints the list of commands associated with each signal number.
7615 a signal name defined in <\fIsignal.h\fP>, or a signal number.
7623 is executed on exit from the shell. If a
7630 is executed after every \fIsimple command\fP (see
7636 option causes the shell to print a list of signal names and
7637 their corresponding numbers.
7638 Signals ignored upon entry to the shell cannot be trapped or reset.
7639 Trapped signals are reset to their original values in a child
7640 process when it is created.
7641 The return status is false if any
7643 is invalid; otherwise
7647 \fBtype\fP [\fB\-atp\fP] \fIname\fP [\fIname\fP ...]
7651 would be interpreted if used as a command name.
7656 prints a string which is one of
7665 is an alias, shell reserved word, function, builtin, or disk file,
7669 is not found, then nothing is printed, and an exit status of false
7675 either returns the name of the disk file
7676 that would be executed if
7678 were specified as a command name,
7680 .if t \f(CWtype -t name\fP
7681 .if n ``type -t name''
7684 If a command is hashed,
7686 prints the hashed value, not necessarily the file that appears
7694 prints all of the places that contain
7697 This includes aliases and functions,
7700 option is not also used.
7701 The table of hashed commands is not consulted
7705 returns true if any of the arguments are found, false if
7708 \fBulimit\fP [\fB\-SHacdflmnpstuv\fP [\fIlimit\fP]]
7709 Provides control over the resources available to the shell and to
7710 processes started by it, on systems that allow such control. The
7713 can be a number in the unit specified for the resource, or the
7716 The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
7717 set for the given resource. A hard limit cannot be increased once it
7718 is set; a soft limit may be increased up to the value of the hard limit.
7719 If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
7723 is omitted, the current value of the soft limit of the resource is
7724 printed, unless the \fB\-H\fP option is given. When more than one
7725 resource is specified, the limit name and unit are printed before the value.
7726 Other options are interpreted as follows:
7731 All current limits are reported
7734 The maximum size of core files created
7737 The maximum size of a process's data segment
7740 The maximum size of files created by the shell
7743 The maximum size that may be locked into memory
7746 The maximum resident set size
7749 The maximum number of open file descriptors (most systems do not
7750 allow this value to be set)
7753 The pipe size in 512-byte blocks (this may not be set)
7756 The maximum stack size
7759 The maximum amount of cpu time in seconds
7762 The maximum number of processes available to a single user
7765 The maximum amount of virtual memory available to the shell
7770 is given, it is the new value of the specified resource (the
7772 option is display only).
7773 If no option is given, then
7775 is assumed. Values are in 1024-byte increments, except for
7777 which is in seconds,
7779 which is in units of 512-byte blocks,
7784 which are unscaled values. The return status is 0
7785 unless an invalid option is encountered, a non-numeric argument
7786 other than \fBunlimited\fP is supplied as \fIlimit\fP, or an
7787 error occurs while setting a new limit.
7790 \fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
7791 The user file-creation mask is set to
7795 begins with a digit, it
7796 is interpreted as an octal number; otherwise
7797 it is interpreted as a symbolic mode mask similar
7802 is omitted, the current value of the mask is printed.
7805 option causes the mask to be printed in symbolic form; the
7806 default output is an octal number.
7809 option is supplied, and
7811 is omitted, the output is in a form that may be reused as input.
7812 The return status is 0 if the mode was successfully changed or if
7813 no \fImode\fP argument was supplied, and false otherwise.
7815 \fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
7816 Remove each \fIname\fP from the list of defined aliases. If
7818 is supplied, all alias definitions are removed. The return
7819 value is true unless a supplied
7821 is not a defined alias.
7823 \fBunset\fP [\-\fBfv\fP] [\fIname\fP ...]
7826 remove the corresponding variable or function.
7827 If no options are supplied, or the
7829 option is given, each
7831 refers to a shell variable.
7832 Read-only variables may not be unset.
7838 refers to a shell function, and the function definition
7840 Each unset variable or function is removed from the environment
7841 passed to subsequent commands.
7858 are unset, they lose their special properties, even if they are
7859 subsequently reset. The exit status is true unless a
7861 does not exist or is readonly.
7863 \fBwait\fP [\fIn\fP]
7864 Wait for the specified process and return its termination
7868 ID or a job specification; if a job spec is given, all processes
7869 in that job's pipeline are waited for. If
7871 is not given, all currently active child processes
7872 are waited for, and the return status is zero. If
7874 specifies a non-existent process or job, the return status is
7875 127. Otherwise, the return status is the exit status of the last
7876 process or job waited for.
7879 .SH "RESTRICTED SHELL"
7885 is started with the name
7889 option is supplied at invocation,
7890 the shell becomes restricted.
7891 A restricted shell is used to
7892 set up an environment more controlled than the standard shell.
7893 It behaves identically to
7895 with the exception that the following are disallowed or not performed:
7897 changing directories with \fBcd\fP
7899 setting or unsetting the values of
7906 specifying command names containing
7909 specifying a file name containing a
7911 as an argument to the
7915 Specifying a filename containing a slash as an argument to the
7921 importing function definitions from the shell environment at startup
7923 parsing the value of \fBSHELLOPTS\fP from the shell environment at startup
7925 redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
7929 builtin command to replace the shell with another command
7931 adding or deleting builtin commands with the
7945 turning off restricted mode with
7946 \fBset +r\fP or \fBset +o restricted\fP.
7948 These restrictions are enforced after any startup files are read.
7950 When a command that is found to be a shell script is executed (see
7952 .B "COMMAND EXECUTION"
7955 turns off any restrictions in the shell spawned to execute the
7962 \fIBash Reference Manual\fP, Brian Fox and Chet Ramey
7964 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
7966 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
7968 \fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE
7970 \fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
7972 \fIemacs\fP(1), \fIvi\fP(1)
7980 The \fBbash\fP executable
7983 The systemwide initialization file, executed for login shells
7986 The personal initialization file, executed for login shells
7989 The individual per-interactive-shell startup file
7992 The individual login shell cleanup file, executed when a login shell exits
7995 Individual \fIreadline\fP initialization file
7998 Brian Fox, Free Software Foundation
8002 Chet Ramey, Case Western Reserve University
8006 If you find a bug in
8008 you should report it. But first, you should
8009 make sure that it really is a bug, and that it appears in the latest
8014 Once you have determined that a bug actually exists, use the
8016 command to submit a bug report.
8017 If you have a fix, you are encouraged to mail that as well!
8018 Suggestions and `philosophical' bug reports may be mailed
8019 to \fIbug-bash@gnu.org\fP or posted to the Usenet
8023 ALL bug reports should include:
8027 The version number of \fBbash\fR
8029 The hardware and operating system
8031 The compiler used to compile
8033 A description of the bug behaviour
8035 A short script or `recipe' which exercises the bug
8039 inserts the first three items automatically into the template
8040 it provides for filing a bug report.
8042 Comments and bug reports concerning
8043 this manual page should be directed to
8044 .IR chet@ins.CWRU.Edu .
8047 It's too big and too slow.
8049 There are some subtle differences between
8051 and traditional versions of
8053 mostly because of the
8058 Aliases are confusing in some uses.
8060 Shell builtin commands and functions are not stoppable/restartable.
8062 Compound commands and command sequences of the form `a ; b ; c'
8063 are not handled gracefully when process suspension is attempted.
8064 When a process is stopped, the shell immediately executes the next
8065 command in the sequence.
8066 It suffices to place the sequence of commands between
8067 parentheses to force it into a subshell, which may be stopped as
8070 Commands inside of \fB$(\fP...\fB)\fP command substitution are not
8071 parsed until substitution is attempted. This will delay error
8072 reporting until some time after the command is entered.
8074 Array variables may not (yet) be exported.
projects / thirdparty / bash.git / blob