2 .\" MAN PAGE COMMENTS to
5 .\" Information Network Services
6 .\" Case Western Reserve University
9 .\" Last Change: Mon Jul 15 15:20:56 EDT 2002
11 .\" bash_builtins, strip all but Built-Ins section
14 .TH BASH 1 "2002 July 15" "GNU Bash-2.05b"
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) 1989-2002 by the Free Software Foundation, Inc.
55 .if t Bash is Copyright \(co 1989-2002 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 is
93 act as if it had been invoked as a login shell (see
101 option is present, the shell becomes
105 .B "RESTRICTED SHELL"
111 option is present, or if no arguments remain after option
112 processing, then commands are read from the standard input.
113 This option allows the positional parameters to be set
114 when invoking an interactive shell.
117 A list of all double-quoted strings preceded by \fB$\fP
118 is printed on the standard ouput.
119 These are the strings that
120 are subject to language translation when the current locale
121 is not \fBC\fP or \fBPOSIX\fP.
122 This implies the \fB\-n\fP option; no commands will be executed.
124 .B [\-+]O [\fIshopt_option\fP]
125 \fIshopt_option\fP is one of the shell options accepted by the
126 \fBshopt\fP builtin (see
128 .B SHELL BUILTIN COMMANDS
130 If \fIshopt_option\fP is present, \fB\-O\fP sets the value of that option;
132 If \fIshopt_option\fP is not supplied, the names and values of the shell
133 options accepted by \fBshopt\fP are printed on the standard output.
134 If the invocation option is \fB+O\fP, the output is displayed in a format
135 that may be reused as input.
140 signals the end of options and disables further option processing.
141 Any arguments after the
143 are treated as filenames and arguments. An argument of
145 is equivalent to \fB\-\-\fP.
149 also interprets a number of multi-character options.
150 These options must appear on the command line before the
151 single-character options to be recognized.
155 .B \-\-dump\-po\-strings
156 Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
157 \fBpo\fP (portable object) file format.
160 Equivalent to \fB\-D\fP.
163 Display a usage message on standard output and exit successfully.
165 \fB\-\-init\-file\fP \fIfile\fP
168 \fB\-\-rcfile\fP \fIfile\fP
170 Execute commands from
172 instead of the standard personal initialization file
174 if the shell is interactive (see
180 Equivalent to \fB\-l\fP.
185 library to read command lines when the shell is interactive.
188 Do not read either the system-wide startup file
190 or any of the personal initialization files
191 .IR ~/.bash_profile ,
197 reads these files when it is invoked as a login shell (see
203 Do not read and execute the personal initialization file
205 if the shell is interactive.
206 This option is on by default if the shell is invoked as
210 Change the behavior of \fBbash\fP where the default operation differs
211 from the POSIX 1003.2 standard to match the standard (\fIposix mode\fP).
214 The shell becomes restricted (see
216 .B "RESTRICTED SHELL"
220 Equivalent to \fB\-v\fP.
223 Show version information for this instance of
225 on the standard output and exit successfully.
228 If arguments remain after option processing, and neither the
232 option has been supplied, the first argument is assumed to
233 be the name of a file containing shell commands.
236 is invoked in this fashion,
238 is set to the name of the file, and the positional parameters
239 are set to the remaining arguments.
241 reads and executes commands from this file, then exits.
242 \fBBash\fP's exit status is the exit status of the last command
243 executed in the script.
244 If no commands are executed, the exit status is 0.
245 An attempt is first made to open the file in the current directory, and,
246 if no file is found, then the shell searches the directories in
251 A \fIlogin shell\fP is one whose first character of argument zero is a
253 or one started with the
257 An \fIinteractive\fP shell is one started without non-option arguments
261 whose standard input and output are
262 both connected to terminals (as determined by
264 or one started with the
276 allowing a shell script or a startup file to test this state.
278 The following paragraphs describe how
280 executes its startup files.
281 If any of the files exist but cannot be read,
284 Tildes are expanded in file names as described below under
293 is invoked as an interactive login shell, or as a non-interactive shell
294 with the \fB\-\-login\fP option, it first reads and
295 executes commands from the file \fI/etc/profile\fP, if that
297 After reading that file, it looks for \fI~/.bash_profile\fP,
298 \fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
299 and executes commands from the first one that exists and is readable.
302 option may be used when the shell is started to inhibit this behavior.
304 When a login shell exits,
306 reads and executes commands from the file \fI~/.bash_logout\fP, if it
309 When an interactive shell that is not a login shell is started,
311 reads and executes commands from \fI~/.bashrc\fP, if that file exists.
312 This may be inhibited by using the
315 The \fB\-\-rcfile\fP \fIfile\fP option will force
317 to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
321 is started non-interactively, to run a shell script, for example, it
322 looks for the variable
325 in the environment, expands its value if it appears there, and uses the
326 expanded value as the name of a file to read and execute.
328 behaves as if the following command were executed:
331 .if t \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
332 .if n if [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
338 variable is not used to search for the file name.
342 is invoked with the name
344 it tries to mimic the startup behavior of historical versions of
346 as closely as possible,
347 while conforming to the POSIX standard as well.
348 When invoked as an interactive login shell, or a non-interactive
349 shell with the \fB\-\-login\fP option, it first attempts to
350 read and execute commands from
357 option may be used to inhibit this behavior.
358 When invoked as an interactive shell with the name
361 looks for the variable
364 expands its value if it is defined, and uses the
365 expanded value as the name of a file to read and execute.
366 Since a shell invoked as
368 does not attempt to read and execute commands from any other startup
371 option has no effect.
372 A non-interactive shell invoked with the name
374 does not attempt to read any other startup files.
380 mode after the startup files are read.
388 command line option, it follows the POSIX standard for startup files.
389 In this mode, interactive shells expand the
392 variable and commands are read and executed from the file
393 whose name is the expanded value.
394 No other startup files are read.
397 attempts to determine when it is being run by the remote shell
398 daemon, usually \fIrshd\fP.
401 determines it is being run by \fIrshd\fP, it reads and executes
402 commands from \fI~/.bashrc\fP, if that file exists and is readable.
403 It will not do this if invoked as \fBsh\fP.
406 option may be used to inhibit this behavior, and the
408 option may be used to force another file to be read, but
409 \fIrshd\fP does not generally invoke the shell with those options
410 or allow them to be specified.
412 If the shell is started with the effective user (group) id not equal to the
413 real user (group) id, and the \fB\-p\fP option is not supplied, no startup
414 files are read, shell functions are not inherited from the environment, the
417 variable, if it appears in the environment, is ignored,
418 and the effective user id is set to the real user id.
419 If the \fB\-p\fP option is supplied at invocation, the startup behavior is
420 the same, but the effective user id is not reset.
423 The following definitions are used throughout the rest of this
431 A sequence of characters considered as a single unit by the shell.
438 consisting only of alphanumeric characters and underscores, and
439 beginning with an alphabetic character or an underscore. Also
444 A character that, when unquoted, separates words. One of the following:
448 .if t \fB| & ; ( ) < > space tab\fP
449 .if n \fB| & ; ( ) < > space tab\fP
454 A \fItoken\fP that performs a control function. It is one of the following
458 .if t \fB\(bv\(bv & && ; ;; ( ) | <newline>\fP
459 .if n \fB|| & && ; ;; ( ) | <newline>\fP
463 \fIReserved words\fP are words that have a special meaning to the shell.
464 The following words are recognized as reserved when unquoted and either
465 the first word of a simple command (see
468 below) or the third word of a
476 .if n ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
477 .if t ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
483 A \fIsimple command\fP is a sequence of optional variable assignments
484 followed by \fBblank\fP-separated words and redirections, and
485 terminated by a \fIcontrol operator\fP. The first word
486 specifies the command to be executed, and is passed as argument zero.
487 The remaining words are passed as arguments to the invoked command.
489 The return value of a \fIsimple command\fP is its exit status, or
490 128+\fIn\^\fP if the command is terminated by signal
494 A \fIpipeline\fP is a sequence of one or more commands separated by
497 The format for a pipeline is:
500 [\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ \fB|\fP \fIcommand2\fP ... ]
503 The standard output of
505 is connected via a pipe to the standard input of
507 This connection is performed before any redirections specified by the
515 precedes a pipeline, the exit status of that
516 pipeline is the logical NOT of the exit status of the last command.
517 Otherwise, the status of the pipeline is the exit status of the last
519 The shell waits for all commands in the pipeline to
520 terminate before returning a value.
524 reserved word precedes a pipeline, the elapsed as well as user and
525 system time consumed by its execution are reported when the pipeline
527 The \fB\-p\fP option changes the output format to that specified by POSIX.
531 variable may be set to a format string that specifies how the timing
532 information should be displayed; see the description of
539 Each command in a pipeline is executed as a separate process (i.e., in a
543 A \fIlist\fP is a sequence of one or more pipelines separated by one
550 and optionally terminated by one of
556 Of these list operators,
560 have equal precedence, followed by
564 which have equal precedence.
566 A sequence of one or more newlines may appear in a \fIlist\fP instead
567 of a semicolon to delimit commands.
569 If a command is terminated by the control operator
571 the shell executes the command in the \fIbackground\fP
572 in a subshell. The shell does not wait for the command to
573 finish, and the return status is 0. Commands separated by a
575 are executed sequentially; the shell waits for each
576 command to terminate in turn. The return status is the
577 exit status of the last command executed.
579 The control operators
583 denote AND lists and OR lists, respectively.
584 An AND list has the form
587 \fIcommand1\fP \fB&&\fP \fIcommand2\fP
591 is executed if, and only if,
593 returns an exit status of zero.
595 An OR list has the form
598 \fIcommand1\fP \fB\(bv\(bv\fP \fIcommand2\fP
603 is executed if and only if
605 returns a non-zero exit status. The return status of
606 AND and OR lists is the exit status of the last command
607 executed in the list.
608 .SS Compound Commands
610 A \fIcompound command\fP is one of the following:
613 \fIlist\fP is executed in a subshell. Variable assignments and builtin
614 commands that affect the shell's environment do not remain in effect
615 after the command completes. The return status is the exit status of
619 \fIlist\fP is simply executed in the current shell environment.
620 \fIlist\fP must be terminated with a newline or semicolon.
621 This is known as a \fIgroup command\fP.
622 The return status is the exit status of
624 Note that unlike the metacharacters \fB(\fP and \fB\)\fP, \fB{\fP and
625 \fB}\fP are \fIreserved words\fP and must occur where a reserved
626 word is permitted to be recognized. Since they do not cause a word
627 break, they must be separated from \fIlist\fP by whitespace.
630 The \fIexpression\fP is evaluated according to the rules described
633 .BR "ARITHMETIC EVALUATION" .
634 If the value of the expression is non-zero, the return status is 0;
635 otherwise the return status is 1. This is exactly equivalent to
636 \fBlet "\fIexpression\fP"\fR.
638 \fB[[\fP \fIexpression\fP \fB]]\fP
639 Return a status of 0 or 1 depending on the evaluation of
640 the conditional expression \fIexpression\fP.
641 Expressions are composed of the primaries described below under
643 .BR "CONDITIONAL EXPRESSIONS" .
644 Word splitting and pathname expansion are not performed on the words
645 between the \fB[[\fP and \fB]]\fP; tilde expansion, parameter and
646 variable expansion, arithmetic expansion, command substitution, process
647 substitution, and quote removal are performed.
650 When the \fB==\fP and \fB!=\fP operators are used, the string to the
651 right of the operator is considered a pattern and matched according
652 to the rules described below under \fBPattern Matching\fP.
653 The return value is 0 if the string matches or does not match
654 the pattern, respectively, and 1 otherwise.
655 Any part of the pattern may be quoted to force it to be matched as a
659 Expressions may be combined using the following operators, listed
660 in decreasing order of precedence:
666 .B ( \fIexpression\fP )
667 Returns the value of \fIexpression\fP.
668 This may be used to override the normal precedence of operators.
670 .B ! \fIexpression\fP
675 \fIexpression1\fP \fB&&\fP \fIexpression2\fP
682 .if t \fIexpression1\fP \fB\(bv\(bv\fP \fIexpression2\fP
683 .if n \fIexpression1\fP \fB||\fP \fIexpression2\fP
694 operators do not evaluate \fIexpression2\fP if the value of
695 \fIexpression1\fP is sufficient to determine the return value of
696 the entire conditional expression.
699 \fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
700 The list of words following \fBin\fP is expanded, generating a list
702 The variable \fIname\fP is set to each element of this list
703 in turn, and \fIlist\fP is executed each time.
704 If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
705 \fIlist\fP once for each positional parameter that is set (see
709 The return status is the exit status of the last command that executes.
710 If the expansion of the items following \fBin\fP results in an empty
711 list, no commands are executed, and the return status is 0.
713 \fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
714 First, the arithmetic expression \fIexpr1\fP is evaluated according
715 to the rules described below under
717 .BR "ARITHMETIC EVALUATION" .
718 The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
719 until it evaluates to zero.
720 Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
721 executed and the arithmetic expression \fIexpr3\fP is evaluated.
722 If any expression is omitted, it behaves as if it evaluates to 1.
723 The return value is the exit status of the last command in \fIlist\fP
724 that is executed, or false if any of the expressions is invalid.
726 \fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
727 The list of words following \fBin\fP is expanded, generating a list
728 of items. The set of expanded words is printed on the standard
729 error, each preceded by a number. If the \fBin\fP
730 \fIword\fP is omitted, the positional parameters are printed (see
735 prompt is then displayed and a line read from the standard input.
736 If the line consists of a number corresponding to one of
737 the displayed words, then the value of
739 is set to that word. If the line is empty, the words and prompt
740 are displayed again. If EOF is read, the command completes. Any
741 other value read causes
743 to be set to null. The line read is saved in the variable
747 is executed after each selection until a
752 is the exit status of the last command executed in
754 or zero if no commands were executed.
756 \fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
757 ... ) \fIlist\fP ;; ] ... \fBesac\fP
758 A \fBcase\fP command first expands \fIword\fP, and tries to match
759 it against each \fIpattern\fP in turn, using the same matching rules
760 as for pathname expansion (see
761 .B Pathname Expansion
762 below). When a match is found, the
763 corresponding \fIlist\fP is executed. After the first match, no
764 subsequent matches are attempted. The exit status is zero if no
765 pattern matches. Otherwise, it is the exit status of the
766 last command executed in \fIlist\fP.
768 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist;\fP \
769 [ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
770 [ \fBelse\fP \fIlist\fP; ] \fBfi\fP
774 is executed. If its exit status is zero, the
775 \fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
776 \fIlist\fP is executed in turn, and if its exit status is zero,
777 the corresponding \fBthen\fP \fIlist\fP is executed and the
778 command completes. Otherwise, the \fBelse\fP \fIlist\fP is
779 executed, if present. The exit status is the exit status of the
780 last command executed, or zero if no condition tested true.
782 \fBwhile\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
785 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
787 The \fBwhile\fP command continuously executes the \fBdo\fP
788 \fIlist\fP as long as the last command in \fIlist\fP returns
789 an exit status of zero. The \fBuntil\fP command is identical
790 to the \fBwhile\fP command, except that the test is negated;
794 is executed as long as the last command in
796 returns a non-zero exit status.
797 The exit status of the \fBwhile\fP and \fBuntil\fP commands
799 of the last \fBdo\fP \fIlist\fP command executed, or zero if
802 [ \fBfunction\fP ] \fIname\fP () { \fIlist\fP; }
803 This defines a function named \fIname\fP. The \fIbody\fP of the
806 of commands between { and }. This list
807 is executed whenever \fIname\fP is specified as the
808 name of a simple command. The exit status of a function is
809 the exit status of the last command executed in the body. (See
814 In a non-interactive shell, or an interactive shell in which the
815 .B interactive_comments
818 builtin is enabled (see
820 .B "SHELL BUILTIN COMMANDS"
821 below), a word beginning with
823 causes that word and all remaining characters on that line to
824 be ignored. An interactive shell without the
825 .B interactive_comments
826 option enabled does not allow comments. The
827 .B interactive_comments
828 option is on by default in interactive shells.
830 \fIQuoting\fP is used to remove the special meaning of certain
831 characters or words to the shell. Quoting can be used to
832 disable special treatment for special characters, to prevent
833 reserved words from being recognized as such, and to prevent
836 Each of the \fImetacharacters\fP listed above under
839 has special meaning to the shell and must be quoted if it is to
842 When the command history expansion facilities are being used, the
843 \fIhistory expansion\fP character, usually \fB!\fP, must be quoted
844 to prevent history expansion.
846 There are three quoting mechanisms: the
847 .IR "escape character" ,
848 single quotes, and double quotes.
850 A non-quoted backslash (\fB\e\fP) is the
851 .IR "escape character" .
852 It preserves the literal value of the next character that follows,
853 with the exception of <newline>. If a \fB\e\fP<newline> pair
854 appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
855 is treated as a line continuation (that is, it is removed from the
856 input stream and effectively ignored).
858 Enclosing characters in single quotes preserves the literal value
859 of each character within the quotes. A single quote may not occur
860 between single quotes, even when preceded by a backslash.
862 Enclosing characters in double quotes preserves the literal value
863 of all characters within the quotes, with the exception of
872 retain their special meaning within double quotes. The backslash
873 retains its special meaning only when followed by one of the following
881 A double quote may be quoted within double quotes by preceding it with
884 The special parameters
888 have special meaning when in double
894 Words of the form \fB$\fP'\fIstring\fP' are treated specially. The
895 word expands to \fIstring\fP, with backslash-escaped characters replaced
896 as specifed by the ANSI C standard. Backslash escape sequences, if
897 present, are decoded as follows:
932 the eight-bit character whose value is the octal value \fInnn\fP
933 (one to three digits)
936 the eight-bit character whose value is the hexadecimal value \fIHH\fP
937 (one or two hex digits)
940 a control-\fIx\fP character
944 The expanded result is single-quoted, as if the dollar sign had
947 A double-quoted string preceded by a dollar sign (\fB$\fP) will cause
948 the string to be translated according to the current locale.
949 If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
951 If the string is translated and replaced, the replacement is
956 is an entity that stores values.
959 a number, or one of the special characters listed below under
960 .BR "Special Parameters" .
961 For the shell's purposes, a
963 is a parameter denoted by a
965 A variable has a \fIvalue\fP and zero or more \fIattributes\fP.
966 Attributes are assigned using the
972 .BR "SHELL BUILTIN COMMANDS" ).
974 A parameter is set if it has been assigned a value. The null string is
975 a valid value. Once a variable is set, it may be unset only by using
980 .B SHELL BUILTIN COMMANDS
985 may be assigned to by a statement of the form
988 \fIname\fP=[\fIvalue\fP]
993 is not given, the variable is assigned the null string. All
995 undergo tilde expansion, parameter and variable expansion,
996 command substitution, arithmetic expansion, and quote
1000 below). If the variable has its
1004 is subject to arithmetic expansion even if the $((...)) expansion is
1006 .B "Arithmetic Expansion"
1008 Word splitting is not performed, with the exception
1009 of \fB"$@"\fP as explained below under
1010 .BR "Special Parameters" .
1011 Pathname expansion is not performed.
1012 Assignment statements may also appear as arguments to the
1020 .SS Positional Parameters
1023 .I positional parameter
1024 is a parameter denoted by one or more
1025 digits, other than the single digit 0. Positional parameters are
1026 assigned from the shell's arguments when it is invoked,
1027 and may be reassigned using the
1029 builtin command. Positional parameters may not be assigned to
1030 with assignment statements. The positional parameters are
1031 temporarily replaced when a shell function is executed (see
1036 When a positional parameter consisting of more than a single
1037 digit is expanded, it must be enclosed in braces (see
1041 .SS Special Parameters
1043 The shell treats several parameters specially. These parameters may
1044 only be referenced; assignment to them is not allowed.
1048 Expands to the positional parameters, starting from one. When the
1049 expansion occurs within double quotes, it expands to a single word
1050 with the value of each parameter separated by the first character
1054 special variable. That is, "\fB$*\fP" is equivalent
1055 to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
1057 is the first character of the value of the
1063 is unset, the parameters are separated by spaces.
1067 is null, the parameters are joined without intervening separators.
1070 Expands to the positional parameters, starting from one. When the
1071 expansion occurs within double quotes, each parameter expands to a
1072 separate word. That is, "\fB$@\fP" is equivalent to
1073 "\fB$1\fP" "\fB$2\fP" ...
1074 When there are no positional parameters, "\fB$@\fP" and
1076 expand to nothing (i.e., they are removed).
1079 Expands to the number of positional parameters in decimal.
1082 Expands to the status of the most recently executed foreground
1086 Expands to the current option flags as specified upon invocation,
1089 builtin command, or those set by the shell itself
1095 Expands to the process ID of the shell. In a () subshell, it
1096 expands to the process ID of the current shell, not the
1100 Expands to the process ID of the most recently executed background
1101 (asynchronous) command.
1104 Expands to the name of the shell or shell script. This is set at
1105 shell initialization. If
1107 is invoked with a file of commands,
1109 is set to the name of that file. If
1115 is set to the first argument after the string to be
1116 executed, if one is present. Otherwise, it is set
1117 to the file name used to invoke
1119 as given by argument zero.
1122 At shell startup, set to the absolute file name of the shell or shell
1123 script being executed as passed in the argument list.
1124 Subsequently, expands to the last argument to the previous command,
1126 Also set to the full file name of each command executed and placed in
1127 the environment exported to that command.
1128 When checking mail, this parameter holds the name of the mail file
1129 currently being checked.
1133 The following variables are set by the shell:
1138 Expands to the full file name used to invoke this instance of
1142 A readonly array variable whose members hold version information for
1145 The values assigned to the array members are as follows:
1150 .B BASH_VERSINFO[\fR0\fP]
1151 The major version number (the \fIrelease\fP).
1153 .B BASH_VERSINFO[\fR1\fP]
1154 The minor version number (the \fIversion\fP).
1156 .B BASH_VERSINFO[\fR2\fP]
1159 .B BASH_VERSINFO[\fR3\fP]
1162 .B BASH_VERSINFO[\fR4\fP]
1163 The release status (e.g., \fIbeta1\fP).
1165 .B BASH_VERSINFO[\fR5\fP]
1166 The value of \fBMACHTYPE\fP.
1171 Expands to a string describing the version of this instance of
1175 An index into \fB${COMP_WORDS}\fP of the word containing the current
1177 This variable is available only in shell functions invoked by the
1178 programmable completion facilities (see \fBProgrammable Completion\fP
1182 The current command line.
1183 This variable is available only in shell functions and external
1184 commands invoked by the
1185 programmable completion facilities (see \fBProgrammable Completion\fP
1189 The index of the current cursor position relative to the beginning of
1190 the current command.
1191 If the current cursor position is at the end of the current command,
1192 the value of this variable is equal to \fB${#COMP_LINE}\fP.
1193 This variable is available only in shell functions and external
1194 commands invoked by the
1195 programmable completion facilities (see \fBProgrammable Completion\fP
1199 An array variable (see \fBArrays\fP below) consisting of the individual
1200 words in the current command line.
1201 This variable is available only in shell functions invoked by the
1202 programmable completion facilities (see \fBProgrammable Completion\fP
1206 An array variable (see
1208 below) containing the current contents of the directory stack.
1209 Directories appear in the stack in the order they are displayed by the
1212 Assigning to members of this array variable may be used to modify
1213 directories already in the stack, but the
1217 builtins must be used to add and remove directories.
1218 Assignment to this variable will not change the current directory.
1222 is unset, it loses its special properties, even if it is
1226 Expands to the effective user ID of the current user, initialized at
1227 shell startup. This variable is readonly.
1230 The name of any currently-executing shell function.
1231 This variable exists only when a shell function is executing.
1235 have no effect and return an error status.
1239 is unset, it loses its special properties, even if it is
1243 An array variable containing the list of groups of which the current
1248 have no effect and return an error status.
1252 is unset, it loses its special properties, even if it is
1256 The history number, or index in the history list, of the current
1261 is unset, it loses its special properties, even if it is
1265 Automatically set to the name of the current host.
1268 Automatically set to a string that uniquely
1269 describes the type of machine on which
1272 The default is system-dependent.
1275 Each time this parameter is referenced, the shell substitutes
1276 a decimal number representing the current sequential line number
1277 (starting with 1) within a script or function. When not in a
1278 script or function, the value substituted is not guaranteed to
1283 is unset, it loses its special properties, even if it is
1287 Automatically set to a string that fully describes the system
1290 is executing, in the standard GNU \fIcpu-company-system\fP format.
1291 The default is system-dependent.
1294 The previous working directory as set by the
1299 The value of the last option argument processed by the
1301 builtin command (see
1303 .B SHELL BUILTIN COMMANDS
1307 The index of the next argument to be processed by the
1309 builtin command (see
1311 .B SHELL BUILTIN COMMANDS
1315 Automatically set to a string that
1316 describes the operating system on which
1319 The default is system-dependent.
1322 An array variable (see
1324 below) containing a list of exit status values from the processes
1325 in the most-recently-executed foreground pipeline (which may
1326 contain only a single command).
1329 The process ID of the shell's parent. This variable is readonly.
1332 The current working directory as set by the
1337 Each time this parameter is referenced, a random integer between
1339 generated. The sequence of random numbers may be initialized by assigning
1346 is unset, it loses its special properties, even if it is
1350 Set to the line of input read by the
1352 builtin command when no arguments are supplied.
1355 Each time this parameter is
1356 referenced, the number of seconds since shell invocation is returned. If a
1357 value is assigned to
1360 the value returned upon subsequent
1362 the number of seconds since the assignment plus the value assigned.
1366 is unset, it loses its special properties, even if it is
1370 A colon-separated list of enabled shell options. Each word in
1371 the list is a valid argument for the
1375 builtin command (see
1377 .B "SHELL BUILTIN COMMANDS"
1378 below). The options appearing in
1381 are those reported as
1384 If this variable is in the environment when
1386 starts up, each shell option in the list will be enabled before
1387 reading any startup files.
1388 This variable is read-only.
1391 Incremented by one each time an instance of
1396 Expands to the user ID of the current user, initialized at shell startup.
1397 This variable is readonly.
1400 The following variables are used by the shell. In some cases,
1402 assigns a default value to a variable; these cases are noted
1408 If this parameter is set when \fBbash\fP is executing a shell script,
1409 its value is interpreted as a filename containing commands to
1410 initialize the shell, as in
1415 is subjected to parameter expansion, command substitution, and arithmetic
1416 expansion before being interpreted as a file name.
1419 is not used to search for the resultant file name.
1422 The search path for the
1425 This is a colon-separated list of directories in which the shell looks
1426 for destination directories specified by the
1430 .if t \f(CW".:~:/usr"\fP.
1434 Used by the \fBselect\fP builtin command to determine the terminal width
1435 when printing selection lists. Automatically set upon receipt of a SIGWINCH.
1438 An array variable from which \fBbash\fP reads the possible completions
1439 generated by a shell function invoked by the programmable completion
1440 facility (see \fBProgrammable Completion\fP below).
1443 The default editor for the
1448 A colon-separated list of suffixes to ignore when performing
1449 filename completion (see
1453 A filename whose suffix matches one of the entries in
1456 is excluded from the list of matched filenames.
1458 .if t \f(CW".o:~"\fP.
1462 A colon-separated list of patterns defining the set of filenames to
1463 be ignored by pathname expansion.
1464 If a filename matched by a pathname expansion pattern also matches one
1468 it is removed from the list of matches.
1471 If set to a value of
1473 lines which begin with a
1475 character are not entered on the history list.
1476 If set to a value of
1478 lines matching the last history line are not entered.
1481 combines the two options.
1482 If unset, or if set to any other value than those above,
1484 by the parser are saved on the history list, subject to the value
1487 This variable's function is superseded by
1489 The second and subsequent lines of a multi-line compound command are
1490 not tested, and are added to the history regardless of the value of
1494 The name of the file in which command history is saved (see
1497 below). The default value is \fI~/.bash_history\fP. If unset, the
1498 command history is not saved when an interactive shell exits.
1501 The maximum number of lines contained in the history file. When this
1502 variable is assigned a value, the history file is truncated, if
1503 necessary, to contain no more than that number of lines. The default
1504 value is 500. The history file is also truncated to this size after
1505 writing it when an interactive shell exits.
1508 A colon-separated list of patterns used to decide which command lines
1509 should be saved on the history list. Each pattern is anchored at the
1510 beginning of the line and must match the complete line (no implicit
1511 `\fB*\fP' is appended). Each pattern is tested against the line
1512 after the checks specified by
1515 In addition to the normal shell pattern matching characters, `\fB&\fP'
1516 matches the previous history line. `\fB&\fP' may be escaped using a
1517 backslash; the backslash is removed before attempting a match.
1518 The second and subsequent lines of a multi-line compound command are
1519 not tested, and are added to the history regardless of the value of
1523 The number of commands to remember in the command history (see
1526 below). The default value is 500.
1529 The home directory of the current user; the default argument for the
1530 \fBcd\fP builtin command.
1531 The value of this variable is also used when performing tilde expansion.
1534 Contains the name of a file in the same format as
1536 that should be read when the shell needs to complete a
1538 The list of possible hostname completions may be changed while the
1540 the next time hostname completion is attempted after the
1543 adds the contents of the new file to the existing list.
1547 is set, but has no value, \fBbash\fP attempts to read
1549 to obtain the list of possible hostname completions.
1553 is unset, the hostname list is cleared.
1557 .I Internal Field Separator
1559 for word splitting after expansion and to
1560 split lines into words with the
1562 builtin command. The default value is
1563 ``<space><tab><newline>''.
1567 action of an interactive shell on receipt of an
1570 character as the sole input. If set, the value is the number of
1574 characters which must be
1575 typed as the first characters on an input line before
1577 exits. If the variable exists but does not have a numeric value, or
1578 has no value, the default value is 10. If it does not exist,
1581 signifies the end of input to the shell.
1584 The filename for the
1586 startup file, overriding the default of
1594 Used to determine the locale category for any category not specifically
1595 selected with a variable starting with \fBLC_\fP.
1598 This variable overrides the value of \fBLANG\fP and any other
1599 \fBLC_\fP variable specifying a locale category.
1602 This variable determines the collation order used when sorting the
1603 results of pathname expansion, and determines the behavior of range
1604 expressions, equivalence classes, and collating sequences within
1605 pathname expansion and pattern matching.
1608 This variable determines the interpretation of characters and the
1609 behavior of character classes within pathname expansion and pattern
1613 This variable determines the locale used to translate double-quoted
1614 strings preceded by a \fB$\fP.
1617 This variable determines the locale category used for number formatting.
1620 Used by the \fBselect\fP builtin command to determine the column length
1621 for printing selection lists. Automatically set upon receipt of a SIGWINCH.
1624 If this parameter is set to a file name and the
1627 variable is not set,
1629 informs the user of the arrival of mail in the specified file.
1635 checks for mail. The default is 60 seconds. When it is time to check
1636 for mail, the shell does so before displaying the primary prompt.
1637 If this variable is unset, or set to a value that is not a number
1638 greater than or equal to zero, the shell disables mail checking.
1641 A colon-separated list of file names to be checked for mail.
1642 The message to be printed when mail arrives in a particular file
1643 may be specified by separating the file name from the message with a `?'.
1644 When used in the text of the message, \fB$_\fP expands to the name of
1645 the current mailfile.
1649 \fBMAILPATH\fP='/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"'
1652 supplies a default value for this variable, but the location of the user
1653 mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
1657 If set to the value 1,
1659 displays error messages generated by the
1661 builtin command (see
1663 .B SHELL BUILTIN COMMANDS
1667 is initialized to 1 each time the shell is invoked or a shell
1671 The search path for commands. It
1672 is a colon-separated list of directories in which
1673 the shell looks for commands (see
1675 .B COMMAND EXECUTION
1676 below). The default path is system-dependent,
1677 and is set by the administrator who installs
1680 .if t \f(CW/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.\fP.
1681 .if n ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.''.
1684 If this variable is in the environment when \fBbash\fP starts, the shell
1685 enters \fIposix mode\fP before reading the startup files, as if the
1687 invocation option had been supplied. If it is set while the shell is
1688 running, \fBbash\fP enables \fIposix mode\fP, as if the command
1689 .if t \f(CWset -o posix\fP
1690 .if n \fIset -o posix\fP
1694 If set, the value is executed as a command prior to issuing each primary
1698 The value of this parameter is expanded (see
1701 below) and used as the primary prompt string. The default value is
1702 ``\fB\es\-\ev\e$ \fP''.
1705 The value of this parameter is expanded as with
1707 and used as the secondary prompt string. The default is
1711 The value of this parameter is used as the prompt for the
1719 The value of this parameter is expanded as with
1721 and the value is printed before each command
1723 displays during an execution trace. The first character of
1726 is replicated multiple times, as necessary, to indicate multiple
1727 levels of indirection. The default is ``\fB+ \fP''.
1730 The value of this parameter is used as a format string specifying
1731 how the timing information for pipelines prefixed with the
1733 reserved word should be displayed.
1734 The \fB%\fP character introduces an escape sequence that is
1735 expanded to a time value or other information.
1736 The escape sequences and their meanings are as follows; the
1737 braces denote optional portions.
1746 The elapsed time in seconds.
1749 The number of CPU seconds spent in user mode.
1752 The number of CPU seconds spent in system mode.
1755 The CPU percentage, computed as (%U + %S) / %R.
1759 The optional \fIp\fP is a digit specifying the \fIprecision\fP,
1760 the number of fractional digits after a decimal point.
1761 A value of 0 causes no decimal point or fraction to be output.
1762 At most three places after the decimal point may be specified;
1763 values of \fIp\fP greater than 3 are changed to 3.
1764 If \fIp\fP is not specified, the value 3 is used.
1766 The optional \fBl\fP specifies a longer format, including
1767 minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
1768 The value of \fIp\fP determines whether or not the fraction is
1771 If this variable is not set, \fBbash\fP acts as if it had the
1772 value \fB$'\enreal\et%3lR\enuser\et%3lU\ensys\t%3lS'\fP.
1773 If the value is null, no timing information is displayed.
1774 A trailing newline is added when the format string is displayed.
1777 If set to a value greater than zero, \fBTMOUT\fP is treated as the
1778 default timeout for the \fBread\fP builtin.
1779 The \fBselect\fP command terminates if input does not arrive
1780 after \fBTMOUT\fP seconds when input is coming from a terminal.
1781 In an interactive shell, the value is interpreted as the
1782 number of seconds to wait for input after issuing the primary prompt.
1784 terminates after waiting for that number of seconds if input does
1788 This variable controls how the shell interacts with the user and
1789 job control. If this variable is set, single word simple
1790 commands without redirections are treated as candidates for resumption
1791 of an existing stopped job. There is no ambiguity allowed; if there is
1792 more than one job beginning with the string typed, the job most recently
1793 accessed is selected. The
1795 of a stopped job, in this context, is the command line used to
1799 the string supplied must match the name of a stopped job exactly;
1802 the string supplied needs to match a substring of the name of a
1805 value provides functionality analogous to the
1810 below). If set to any other value, the supplied string must
1811 be a prefix of a stopped job's name; this provides functionality
1817 The two or three characters which control history expansion
1818 and tokenization (see
1820 .B HISTORY EXPANSION
1821 below). The first character is the \fIhistory expansion\fP character,
1822 the character which signals the start of a history
1823 expansion, normally `\fB!\fP'.
1824 The second character is the \fIquick substitution\fP
1825 character, which is used as shorthand for re-running the previous
1826 command entered, substituting one string for another in the command.
1827 The default is `\fB^\fP'.
1828 The optional third character is the character
1829 which indicates that the remainder of the line is a comment when found
1830 as the first character of a word, normally `\fB#\fP'. The history
1831 comment character causes history substitution to be skipped for the
1832 remaining words on the line. It does not necessarily cause the shell
1833 parser to treat the rest of the line as a comment.
1837 provides one-dimensional array variables. Any variable may be used as
1840 builtin will explicitly declare an array. There is no maximum
1841 limit on the size of an array, nor any requirement that members
1842 be indexed or assigned contiguously. Arrays are indexed using
1843 integers and are zero-based.
1845 An array is created automatically if any variable is assigned to using
1846 the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
1848 is treated as an arithmetic expression that must evaluate to a number
1849 greater than or equal to zero. To explicitly declare an array, use
1850 .B declare \-a \fIname\fP
1853 .B SHELL BUILTIN COMMANDS
1855 .B declare \-a \fIname\fP[\fIsubscript\fP]
1856 is also accepted; the \fIsubscript\fP is ignored. Attributes may be
1857 specified for an array variable using the
1861 builtins. Each attribute applies to all members of an array.
1863 Arrays are assigned to using compound assignments of the form
1864 \fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
1865 \fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP. Only
1866 \fIstring\fP is required. If
1867 the optional brackets and subscript are supplied, that index is assigned to;
1868 otherwise the index of the element assigned is the last index assigned
1869 to by the statement plus one. Indexing starts at zero.
1870 This syntax is also accepted by the
1872 builtin. Individual array elements may be assigned to using the
1873 \fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
1875 Any element of an array may be referenced using
1876 ${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
1877 conflicts with pathname expansion. If
1878 \fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
1879 all members of \fIname\fP. These subscripts differ only when the
1880 word appears within double quotes. If the word is double-quoted,
1881 ${\fIname\fP[*]} expands to a single
1882 word with the value of each array member separated by the first
1886 special variable, and ${\fIname\fP[@]} expands each element of
1887 \fIname\fP to a separate word. When there are no array members,
1888 ${\fIname\fP[@]} expands to nothing. This is analogous to the expansion
1889 of the special parameters \fB*\fP and \fB@\fP (see
1890 .B Special Parameters
1891 above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
1892 ${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
1893 \fB@\fP, the expansion is the number of elements in the array.
1894 Referencing an array variable without a subscript is equivalent to
1895 referencing element zero.
1899 builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
1900 destroys the array element at index \fIsubscript\fP.
1901 \fBunset\fP \fIname\fP, where \fIname\fP is an array, or
1902 \fBunset\fP \fIname\fP[\fIsubscript\fP], where
1903 \fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
1910 builtins each accept a
1912 option to specify an array. The
1916 option to assign a list of words read from the standard input
1921 builtins display array values in a way that allows them to be
1922 reused as assignments.
1924 Expansion is performed on the command line after it has been split into
1925 words. There are seven kinds of expansion performed:
1926 .IR "brace expansion" ,
1927 .IR "tilde expansion" ,
1928 .IR "parameter and variable expansion" ,
1929 .IR "command substitution" ,
1930 .IR "arithmetic expansion" ,
1931 .IR "word splitting" ,
1933 .IR "pathname expansion" .
1935 The order of expansions is: brace expansion, tilde expansion,
1936 parameter, variable and arithmetic expansion and
1937 command substitution
1938 (done in a left-to-right fashion), word splitting, and pathname
1941 On systems that can support it, there is an additional expansion
1942 available: \fIprocess substitution\fP.
1944 Only brace expansion, word splitting, and pathname expansion
1945 can change the number of words of the expansion; other expansions
1946 expand a single word to a single word.
1947 The only exceptions to this are the expansions of
1948 "\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
1949 as explained above (see
1954 .I "Brace expansion"
1955 is a mechanism by which arbitrary strings
1956 may be generated. This mechanism is similar to
1957 \fIpathname expansion\fP, but the filenames generated
1958 need not exist. Patterns to be brace expanded take
1959 the form of an optional
1961 followed by a series of comma-separated strings
1962 between a pair of braces, followed by an optional
1964 The preamble is prefixed to each string contained
1965 within the braces, and the postscript is then appended
1966 to each resulting string, expanding left to right.
1968 Brace expansions may be nested. The results of each expanded
1969 string are not sorted; left to right order is preserved.
1970 For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
1972 Brace expansion is performed before any other expansions,
1973 and any characters special to other expansions are preserved
1974 in the result. It is strictly textual.
1976 does not apply any syntactic interpretation to the context of the
1977 expansion or the text between the braces.
1979 A correctly-formed brace expansion must contain unquoted opening
1980 and closing braces, and at least one unquoted comma.
1981 Any incorrectly formed brace expansion is left unchanged.
1982 A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
1983 being considered part of a brace expression.
1984 To avoid conflicts with parameter expansion, the string \fB${\fP
1985 is not considered eligible for brace expansion.
1987 This construct is typically used as shorthand when the common
1988 prefix of the strings to be generated is longer than in the
1992 mkdir /usr/local/src/bash/{old,new,dist,bugs}
1996 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
1999 Brace expansion introduces a slight incompatibility with
2000 historical versions of
2003 does not treat opening or closing braces specially when they
2004 appear as part of a word, and preserves them in the output.
2006 removes braces from words as a consequence of brace
2007 expansion. For example, a word entered to
2010 appears identically in the output. The same word is
2015 If strict compatibility with
2021 option or disable brace expansion with the
2027 .B SHELL BUILTIN COMMANDS
2031 If a word begins with an unquoted tilde character (`\fB~\fP'), all of
2032 the characters preceding the first unquoted slash (or all characters,
2033 if there is no unquoted slash) are considered a \fItilde-prefix\fP.
2034 If none of the characters in the tilde-prefix are quoted, the
2035 characters in the tilde-prefix following the tilde are treated as a
2036 possible \fIlogin name\fP.
2037 If this login name is the null string, the tilde is replaced with the
2038 value of the shell parameter
2044 is unset, the home directory of the user executing the shell is
2045 substituted instead.
2046 Otherwise, the tilde-prefix is replaced with the home directory
2047 associated with the specified login name.
2049 If the tilde-prefix is a `~+', the value of the shell variable
2052 replaces the tilde-prefix.
2053 If the tilde-prefix is a `~\-', the value of the shell variable
2056 if it is set, is substituted.
2057 If the characters following the tilde in the tilde-prefix consist
2058 of a number \fIN\fP, optionally prefixed
2059 by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
2060 element from the directory stack, as it would be displayed by the
2062 builtin invoked with the tilde-prefix as an argument.
2063 If the characters following the tilde in the tilde-prefix consist of a
2064 number without a leading `+' or `\-', `+' is assumed.
2066 If the login name is invalid, or the tilde expansion fails, the word
2069 Each variable assignment is checked for unquoted tilde-prefixes immediately
2074 In these cases, tilde expansion is also performed.
2075 Consequently, one may use file names with tildes in assignments to
2083 and the shell assigns the expanded value.
2084 .SS Parameter Expansion
2086 The `\fB$\fP' character introduces parameter expansion,
2087 command substitution, or arithmetic expansion. The parameter name
2088 or symbol to be expanded may be enclosed in braces, which
2089 are optional but serve to protect the variable to be expanded from
2090 characters immediately following it which could be
2091 interpreted as part of the name.
2093 When braces are used, the matching ending brace is the first `\fB}\fP'
2094 not escaped by a backslash or within a quoted string, and not within an
2095 embedded arithmetic expansion, command substitution, or paramter
2101 The value of \fIparameter\fP is substituted. The braces are required
2104 is a positional parameter with more than one digit,
2107 is followed by a character which is not to be
2108 interpreted as part of its name.
2111 If the first character of \fIparameter\fP is an exclamation point,
2112 a level of variable indirection is introduced.
2113 \fBBash\fP uses the value of the variable formed from the rest of
2114 \fIparameter\fP as the name of the variable; this variable is then
2115 expanded and that value is used in the rest of the substitution, rather
2116 than the value of \fIparameter\fP itself.
2117 This is known as \fIindirect expansion\fP.
2118 The exception to this is the expansion of ${!\fIprefix\fP*}
2121 In each of the cases below, \fIword\fP is subject to tilde expansion,
2122 parameter expansion, command substitution, and arithmetic expansion.
2123 When not performing substring expansion, \fBbash\fP tests for a parameter
2124 that is unset or null; omitting the colon results in a test only for a
2125 parameter that is unset.
2129 ${\fIparameter\fP\fB:\-\fP\fIword\fP}
2130 \fBUse Default Values\fP. If
2132 is unset or null, the expansion of
2134 is substituted. Otherwise, the value of
2138 ${\fIparameter\fP\fB:=\fP\fIword\fP}
2139 \fBAssign Default Values\fP.
2142 is unset or null, the expansion of
2148 is then substituted. Positional parameters and special parameters may
2149 not be assigned to in this way.
2151 ${\fIparameter\fP\fB:?\fP\fIword\fP}
2152 \fBDisplay Error if Null or Unset\fP.
2155 is null or unset, the expansion of \fIword\fP (or a message to that effect
2158 is not present) is written to the standard error and the shell, if it
2159 is not interactive, exits. Otherwise, the value of \fIparameter\fP is
2162 ${\fIparameter\fP\fB:+\fP\fIword\fP}
2163 \fBUse Alternate Value\fP.
2166 is null or unset, nothing is substituted, otherwise the expansion of
2170 ${\fIparameter\fP\fB:\fP\fIoffset\fP}
2173 ${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
2175 \fBSubstring Expansion.\fP
2176 Expands to up to \fIlength\fP characters of \fIparameter\fP
2177 starting at the character specified by \fIoffset\fP.
2178 If \fIlength\fP is omitted, expands to the substring of
2179 \fIparameter\fP starting at the character specified by \fIoffset\fP.
2180 \fIlength\fP and \fIoffset\fP are arithmetic expressions (see
2183 ARITHMETIC EVALUATION
2185 \fIlength\fP must evaluate to a number greater than or equal to zero.
2186 If \fIoffset\fP evaluates to a number less than zero, the value
2187 is used as an offset from the end of the value of \fIparameter\fP.
2188 If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
2189 parameters beginning at \fIoffset\fP.
2190 If \fIparameter\fP is an array name indexed by @ or *,
2191 the result is the \fIlength\fP
2192 members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2193 Substring indexing is zero-based unless the positional parameters
2194 are used, in which case the indexing starts at 1.
2196 ${\fB!\fP\fIprefix\fP\fB*\fP}
2197 Expands to the names of variables whose names begin with \fIprefix\fP,
2198 separated by the first character of the
2203 ${\fB#\fP\fIparameter\fP}
2204 The length in characters of the value of \fIparameter\fP is substituted.
2211 the value substituted is the number of positional parameters.
2214 is an array name subscripted by
2218 the value substituted is the number of elements in the array.
2220 ${\fIparameter\fP\fB#\fP\fIword\fP}
2223 ${\fIparameter\fP\fB##\fP\fIword\fP}
2227 is expanded to produce a pattern just as in pathname
2228 expansion. If the pattern matches the beginning of
2231 then the result of the expansion is the expanded value of
2233 with the shortest matching pattern (the ``\fB#\fP'' case) or the
2234 longest matching pattern (the ``\fB##\fP'' case) deleted.
2241 the pattern removal operation is applied to each positional
2242 parameter in turn, and the expansion is the resultant list.
2245 is an array variable subscripted with
2249 the pattern removal operation is applied to each member of the
2250 array in turn, and the expansion is the resultant list.
2252 ${\fIparameter\fP\fB%\fP\fIword\fP}
2255 ${\fIparameter\fP\fB%%\fP\fIword\fP}
2257 The \fIword\fP is expanded to produce a pattern just as in
2259 If the pattern matches a trailing portion of the expanded value of
2261 then the result of the expansion is the expanded value of
2263 with the shortest matching pattern (the ``\fB%\fP'' case) or the
2264 longest matching pattern (the ``\fB%%\fP'' case) deleted.
2271 the pattern removal operation is applied to each positional
2272 parameter in turn, and the expansion is the resultant list.
2275 is an array variable subscripted with
2279 the pattern removal operation is applied to each member of the
2280 array in turn, and the expansion is the resultant list.
2282 ${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2285 ${\fIparameter\fP\fB//\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2287 The \fIpattern\fP is expanded to produce a pattern just as in
2289 \fIParameter\fP is expanded and the longest match of \fIpattern\fP
2290 against its value is replaced with \fIstring\fP.
2291 In the first form, only the first match is replaced.
2292 The second form causes all matches of \fIpattern\fP to be
2293 replaced with \fIstring\fP.
2294 If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
2295 of the expanded value of \fIparameter\fP.
2296 If \fIpattern\fP begins with \fB%\fP, it must match at the end
2297 of the expanded value of \fIparameter\fP.
2298 If \fIstring\fP is null, matches of \fIpattern\fP are deleted
2299 and the \fB/\fP following \fIpattern\fP may be omitted.
2306 the substitution operation is applied to each positional
2307 parameter in turn, and the expansion is the resultant list.
2310 is an array variable subscripted with
2314 the substitution operation is applied to each member of the
2315 array in turn, and the expansion is the resultant list.
2316 .SS Command Substitution
2318 \fICommand substitution\fP allows the output of a command to replace
2319 the command name. There are two forms:
2323 \fB$(\fP\fIcommand\fP\|\fB)\fP
2327 \fB`\fP\fIcommand\fP\fB`\fP
2331 performs the expansion by executing \fIcommand\fP and
2332 replacing the command substitution with the standard output of the
2333 command, with any trailing newlines deleted.
2334 Embedded newlines are not deleted, but they may be removed during
2336 The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
2337 the equivalent but faster \fB$(< \fIfile\fP)\fR.
2339 When the old-style backquote form of substitution is used,
2340 backslash retains its literal meaning except when followed by
2345 The first backquote not preceded by a backslash terminates the
2346 command substitution.
2347 When using the $(\^\fIcommand\fP\|) form, all characters between the
2348 parentheses make up the command; none are treated specially.
2350 Command substitutions may be nested. To nest when using the backquoted form,
2351 escape the inner backquotes with backslashes.
2353 If the substitution appears within double quotes, word splitting and
2354 pathname expansion are not performed on the results.
2355 .SS Arithmetic Expansion
2357 Arithmetic expansion allows the evaluation of an arithmetic expression
2358 and the substitution of the result. The format for arithmetic expansion is:
2361 \fB$((\fP\fIexpression\fP\fB))\fP
2366 is treated as if it were within double quotes, but a double quote
2367 inside the parentheses is not treated specially.
2368 All tokens in the expression undergo parameter expansion, string
2369 expansion, command substitution, and quote removal.
2370 Arithmetic substitutions may be nested.
2372 The evaluation is performed according to the rules listed below under
2374 .BR "ARITHMETIC EVALUATION" .
2379 prints a message indicating failure and no substitution occurs.
2380 .SS Process Substitution
2382 \fIProcess substitution\fP is supported on systems that support named
2383 pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
2384 It takes the form of
2385 \fB<(\fP\fIlist\^\fP\fB)\fP
2387 \fB>(\fP\fIlist\^\fP\fB)\fP.
2388 The process \fIlist\fP is run with its input or output connected to a
2389 \fIFIFO\fP or some file in \fB/dev/fd\fP. The name of this file is
2390 passed as an argument to the current command as the result of the
2391 expansion. If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
2392 the file will provide input for \fIlist\fP. If the
2393 \fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
2394 argument should be read to obtain the output of \fIlist\fP.
2396 When available, process substitution is performed
2397 simultaneously with parameter and variable expansion,
2398 command substitution,
2399 and arithmetic expansion.
2402 The shell scans the results of
2403 parameter expansion,
2404 command substitution,
2406 arithmetic expansion
2407 that did not occur within double quotes for
2408 .IR "word splitting" .
2410 The shell treats each character of
2413 as a delimiter, and splits the results of the other
2414 expansions into words on these characters. If
2419 .BR <space><tab><newline> ,
2424 characters serves to delimit words. If
2427 has a value other than the default, then sequences of
2428 the whitespace characters
2432 are ignored at the beginning and end of the
2433 word, as long as the whitespace character is in the
2440 whitespace character).
2447 whitespace, along with any adjacent
2450 whitespace characters, delimits a field.
2454 whitespace characters is also treated as a delimiter.
2458 is null, no word splitting occurs.
2460 Explicit null arguments (\^\f3"\^"\fP or \^\f3'\^'\fP\^) are retained.
2461 Unquoted implicit null arguments, resulting from the expansion of
2462 parameters that have no values, are removed.
2463 If a parameter with no value is expanded within double quotes, a
2464 null argument results and is retained.
2466 Note that if no expansion occurs, no splitting
2468 .SS Pathname Expansion
2470 After word splitting,
2473 option has been set,
2475 scans each word for the characters
2480 If one of these characters appears, then the word is
2483 and replaced with an alphabetically sorted list of
2484 file names matching the pattern.
2485 If no matching file names are found,
2486 and the shell option
2488 is disabled, the word is left unchanged.
2491 option is set, and no matches are found,
2492 the word is removed.
2495 is enabled, the match is performed without regard to the case
2496 of alphabetic characters.
2497 When a pattern is used for pathname expansion,
2500 at the start of a name or immediately following a slash
2501 must be matched explicitly, unless the shell option
2504 When matching a pathname, the slash character must always be
2508 character is not treated specially.
2509 See the description of
2513 .B SHELL BUILTIN COMMANDS
2514 for a description of the
2524 shell variable may be used to restrict the set of file names matching a
2529 is set, each matching file name that also matches one of the patterns in
2532 is removed from the list of matches.
2537 are always ignored, even when
2540 is set. However, setting
2543 has the effect of enabling the
2545 shell option, so all other file names beginning with a
2548 To get the old behavior of ignoring file names beginning with a
2552 one of the patterns in
2557 option is disabled when
2562 \fBPattern Matching\fP
2564 Any character that appears in a pattern, other than the special pattern
2565 characters described below, matches itself. The NUL character may not
2566 occur in a pattern. The special pattern characters must be quoted if
2567 they are to be matched literally.
2569 The special pattern characters have the following meanings:
2574 Matches any string, including the null string.
2577 Matches any single character.
2580 Matches any one of the enclosed characters. A pair of characters
2581 separated by a hyphen denotes a
2582 \fIrange expression\fP;
2583 any character that sorts between those two characters, inclusive,
2584 using the current locale's collating sequence and character set,
2585 is matched. If the first character following the
2591 then any character not enclosed is matched.
2592 The sorting order of characters in range expressions is determined by
2593 the current locale and the value of the \fBLC_COLLATE\fP shell variable,
2597 may be matched by including it as the first or last character
2601 may be matched by including it as the first character
2610 \fIcharacter classes\fP can be specified using the syntax
2611 \fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
2612 following classes defined in the POSIX.2 standard:
2616 .if n alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
2617 .if t alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit
2619 A character class matches any character belonging to that class.
2620 The \fBword\fP character class matches letters, digits, and the character _.
2628 an \fIequivalence class\fP can be specified using the syntax
2629 \fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
2630 same collation weight (as defined by the current locale) as
2631 the character \fIc\fP.
2639 the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
2644 If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
2645 builtin, several extended pattern matching operators are recognized.
2646 In the following description, a \fIpattern-list\fP is a list of one
2647 or more patterns separated by a \fB|\fP.
2648 Composite patterns may be formed using one or more of the following
2654 \fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
2655 Matches zero or one occurrence of the given patterns
2657 \fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
2658 Matches zero or more occurrences of the given patterns
2660 \fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
2661 Matches one or more occurrences of the given patterns
2663 \fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
2664 Matches exactly one of the given patterns
2666 \fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
2667 Matches anything except one of the given patterns
2672 After the preceding expansions, all unquoted occurrences of the
2676 and \^\f3"\fP\^ that did not result from one of the above
2677 expansions are removed.
2679 Before a command is executed, its input and output
2682 using a special notation interpreted by the shell.
2683 Redirection may also be used to open and close files for the
2684 current shell execution environment. The following redirection
2685 operators may precede or appear anywhere within a
2689 Redirections are processed in the order they appear, from
2692 In the following descriptions, if the file descriptor number is
2693 omitted, and the first character of the redirection operator is
2695 the redirection refers to the standard input (file descriptor
2696 0). If the first character of the redirection operator is
2698 the redirection refers to the standard output (file descriptor
2701 The word following the redirection operator in the following
2702 descriptions, unless otherwise noted, is subjected to brace expansion,
2703 tilde expansion, parameter expansion, command substitution, arithmetic
2704 expansion, quote removal, pathname expansion, and word splitting.
2705 If it expands to more than one word,
2709 Note that the order of redirections is significant. For example,
2713 ls \fB>\fP dirlist 2\fB>&\fP1
2716 directs both standard output and standard error to the file
2721 ls 2\fB>&\fP1 \fB>\fP dirlist
2724 directs only the standard output to file
2726 because the standard error was duplicated as standard output
2727 before the standard output was redirected to
2730 \fBBash\fP handles several filenames specially when they are used in
2731 redirections, as described in the following table:
2737 If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
2740 File descriptor 0 is duplicated.
2743 File descriptor 1 is duplicated.
2746 File descriptor 2 is duplicated.
2748 .B /dev/tcp/\fIhost\fP/\fIport\fP
2749 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
2750 is an integer port number or service name, \fBbash\fP attempts to open
2751 a TCP connection to the corresponding socket.
2753 .B /dev/udp/\fIhost\fP/\fIport\fP
2754 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
2755 is an integer port number or service name, \fBbash\fP attempts to open
2756 a UDP connection to the corresponding socket.
2760 A failure to open or create a file causes the redirection to fail.
2761 .SS Redirecting Input
2763 Redirection of input causes the file whose name results from
2766 to be opened for reading on file descriptor
2768 or the standard input (file descriptor 0) if
2772 The general format for redirecting input is:
2775 [\fIn\fP]\fB<\fP\fIword\fP
2777 .SS Redirecting Output
2779 Redirection of output causes the file whose name results from
2782 to be opened for writing on file descriptor
2784 or the standard output (file descriptor 1) if
2786 is not specified. If the file does not exist it is created;
2787 if it does exist it is truncated to zero size.
2789 The general format for redirecting output is:
2792 [\fIn\fP]\fB>\fP\fIword\fP
2795 If the redirection operator is
2801 builtin has been enabled, the redirection will fail if the file
2802 whose name results from the expansion of \fIword\fP exists and is
2804 If the redirection operator is
2806 or the redirection operator is
2812 builtin command is not enabled, the redirection is attempted even
2813 if the file named by \fIword\fP exists.
2814 .SS Appending Redirected Output
2816 Redirection of output in this fashion
2817 causes the file whose name results from
2820 to be opened for appending on file descriptor
2822 or the standard output (file descriptor 1) if
2824 is not specified. If the file does not exist it is created.
2826 The general format for appending output is:
2829 [\fIn\fP]\fB>>\fP\fIword\fP
2832 .SS Redirecting Standard Output and Standard Error
2836 standard output (file descriptor 1) and
2837 the standard error output (file descriptor 2)
2838 to be redirected to the file whose name is the
2841 with this construct.
2843 There are two formats for redirecting standard output and
2854 Of the two forms, the first is preferred.
2855 This is semantically equivalent to
2858 \fB>\fP\fIword\fP 2\fB>&\fP1
2862 This type of redirection instructs the shell to read input from the
2863 current source until a line containing only
2865 (with no trailing blanks)
2867 the lines read up to that point are then used as the standard
2868 input for a command.
2870 The format of here-documents is:
2874 \fB<<\fP[\fB\-\fP]\fIword\fP
2880 No parameter expansion, command substitution, arithmetic expansion,
2881 or pathname expansion is performed on
2883 If any characters in
2887 is the result of quote removal on
2889 and the lines in the here-document are not expanded.
2890 If \fIword\fP is unquoted,
2891 all lines of the here-document are subjected to parameter expansion,
2892 command substitution, and arithmetic expansion. In the latter
2893 case, the character sequence
2897 must be used to quote the characters
2903 If the redirection operator is
2905 then all leading tab characters are stripped from input lines and the
2909 here-documents within shell scripts to be indented in a
2912 A variant of here documents, the format is:
2920 The \fIword\fP is expanded and supplied to the command on its standard
2922 .SS "Duplicating File Descriptors"
2924 The redirection operator
2927 [\fIn\fP]\fB<&\fP\fIword\fP
2930 is used to duplicate input file descriptors.
2933 expands to one or more digits, the file descriptor denoted by
2935 is made to be a copy of that file descriptor.
2938 do not specify a file descriptor open for input, a redirection error occurs.
2947 is not specified, the standard input (file descriptor 0) is used.
2952 [\fIn\fP]\fB>&\fP\fIword\fP
2955 is used similarly to duplicate output file descriptors. If
2957 is not specified, the standard output (file descriptor 1) is used.
2960 do not specify a file descriptor open for output, a redirection error occurs.
2961 As a special case, if \fIn\fP is omitted, and \fIword\fP does not
2962 expand to one or more digits, the standard output and standard
2963 error are redirected as described previously.
2964 .SS "Moving File Descriptors"
2966 The redirection operator
2969 [\fIn\fP]\fB<&\fP\fIdigit\fP\fB\-\fP
2972 moves the file descriptor \fIdigit\fP to file descriptor
2974 or the standard input (file descriptor 0) if \fIn\fP is not specified.
2975 \fIdigit\fP is closed after being duplicated to \fIn\fP.
2977 Similarly, the redirection operator
2980 [\fIn\fP]\fB>&\fP\fIdigit\fP\fB\-\fP
2983 moves the file descriptor \fIdigit\fP to file descriptor
2985 or the standard output (file descriptor 1) if \fIn\fP is not specified.
2986 .SS "Opening File Descriptors for Reading and Writing"
2988 The redirection operator
2991 [\fIn\fP]\fB<>\fP\fIword\fP
2994 causes the file whose name is the expansion of
2996 to be opened for both reading and writing on file descriptor
2998 or on file descriptor 0 if
3000 is not specified. If the file does not exist, it is created.
3002 \fIAliases\fP allow a string to be substituted for a word when it is used
3003 as the first word of a simple command.
3004 The shell maintains a list of aliases that may be set and unset with the
3008 builtin commands (see
3010 .B SHELL BUILTIN COMMANDS
3012 The first word of each command, if unquoted,
3013 is checked to see if it has an
3014 alias. If so, that word is replaced by the text of the alias.
3015 The alias name and the replacement text may contain any valid
3016 shell input, including the
3018 listed above, with the exception that the alias name may not
3019 contain \fI=\fP. The first word of the replacement text is tested
3020 for aliases, but a word that is identical to an alias being expanded
3021 is not expanded a second time. This means that one may alias
3027 does not try to recursively expand the replacement text.
3028 If the last character of the alias value is a
3030 then the next command
3031 word following the alias is also checked for alias expansion.
3033 Aliases are created and listed with the
3035 command, and removed with the
3039 There is no mechanism for using arguments in the replacement text.
3040 If arguments are needed, a shell function should be used (see
3045 Aliases are not expanded when the shell is not interactive, unless
3048 shell option is set using
3050 (see the description of
3054 \fBSHELL BUILTIN COMMANDS\fP
3057 The rules concerning the definition and use of aliases are
3060 always reads at least one complete line
3061 of input before executing any
3062 of the commands on that line. Aliases are expanded when a
3063 command is read, not when it is executed. Therefore, an
3064 alias definition appearing on the same line as another
3065 command does not take effect until the next line of input is read.
3066 The commands following the alias definition
3067 on that line are not affected by the new alias.
3068 This behavior is also an issue when functions are executed.
3069 Aliases are expanded when a function definition is read,
3070 not when the function is executed, because a function definition
3071 is itself a compound command. As a consequence, aliases
3072 defined in a function are not available until after that
3073 function is executed. To be safe, always put
3074 alias definitions on a separate line, and do not use
3076 in compound commands.
3078 For almost every purpose, aliases are superseded by
3081 A shell function, defined as described above under
3083 .BR "SHELL GRAMMAR" ,
3084 stores a series of commands for later execution.
3085 When the name of a shell function is used as a simple command name,
3086 the list of commands associated with that function name is executed.
3087 Functions are executed in the context of the
3088 current shell; no new process is created to interpret
3089 them (contrast this with the execution of a shell script).
3090 When a function is executed, the arguments to the
3091 function become the positional parameters
3092 during its execution.
3093 The special parameter
3095 is updated to reflect the change. Positional parameter 0
3100 variable is set to the name of the function while the function
3102 All other aspects of the shell execution
3103 environment are identical between a function and its caller
3104 with the exception that the
3107 trap (see the description of the
3111 .B SHELL BUILTIN COMMANDS
3112 below) is not inherited unless the function has been given the
3113 \fBtrace\fP attribute (see the description of the
3118 Variables local to the function may be declared with the
3120 builtin command. Ordinarily, variables and their values
3121 are shared between the function and its caller.
3123 If the builtin command
3125 is executed in a function, the function completes and
3126 execution resumes with the next command after the function
3127 call. When a function completes, the values of the
3128 positional parameters and the special parameter
3130 are restored to the values they had prior to the function's
3133 Function names and definitions may be listed with the
3139 builtin commands. The
3145 will list the function names only.
3146 Functions may be exported so that subshells
3147 automatically have them defined with the
3153 Functions may be recursive. No limit is imposed on the number
3155 .SH "ARITHMETIC EVALUATION"
3156 The shell allows arithmetic expressions to be evaluated, under
3157 certain circumstances (see the \fBlet\fP builtin command and
3158 \fBArithmetic Expansion\fP).
3159 Evaluation is done in fixed-width integers with no check for overflow,
3160 though division by 0 is trapped and flagged as an error.
3161 The operators and their precedence and associativity are the same
3162 as in the C language.
3163 The following list of operators is grouped into levels of
3164 equal-precedence operators.
3165 The levels are listed in order of decreasing precedence.
3169 .B \fIid\fP++ \fIid\fP\-\-
3170 variable post-increment and post-decrement
3172 .B ++\fIid\fP \-\-\fIid\fP
3173 variable pre-increment and pre-decrement
3176 unary minus and plus
3179 logical and bitwise negation
3185 multiplication, division, remainder
3188 addition, subtraction
3191 left and right bitwise shifts
3197 equality and inequality
3203 bitwise exclusive OR
3214 .B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
3215 conditional evaluation
3217 .B = *= /= %= += \-= <<= >>= &= ^= |=
3220 .B \fIexpr1\fP , \fIexpr2\fP
3224 Shell variables are allowed as operands; parameter expansion is
3225 performed before the expression is evaluated.
3226 Within an expression, shell variables may also be referenced by name
3227 without using the parameter expansion syntax.
3228 The value of a variable is evaluated as an arithmetic expression
3229 when it is referenced.
3230 A shell variable need not have its integer attribute
3231 turned on to be used in an expression.
3233 Constants with a leading 0 are interpreted as octal numbers.
3234 A leading 0x or 0X denotes hexadecimal.
3235 Otherwise, numbers take the form [\fIbase#\fP]n, where \fIbase\fP
3236 is a decimal number between 2 and 64 representing the arithmetic
3237 base, and \fIn\fP is a number in that base.
3238 If \fIbase#\fP is omitted, then base 10 is used.
3239 The digits greater than 9 are represented by the lowercase letters,
3240 the uppercase letters, @, and _, in that order.
3241 If \fIbase\fP is less than or equal to 36, lowercase and uppercase
3242 letters may be used interchangably to represent numbers between 10
3245 Operators are evaluated in order of precedence. Sub-expressions in
3246 parentheses are evaluated first and may override the precedence
3248 .SH "CONDITIONAL EXPRESSIONS"
3249 Conditional expressions are used by the \fB[[\fP compound command and
3250 the \fBtest\fP and \fB[\fP builtin commands to test file attributes
3251 and perform string and arithmetic comparisons.
3252 Expressions are formed from the following unary or binary primaries.
3253 If any \fIfile\fP argument to one of the primaries is of the form
3254 \fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
3255 If the \fIfile\fP argument to one of the primaries is one of
3256 \fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
3257 descriptor 0, 1, or 2, respectively, is checked.
3262 True if \fIfile\fP exists.
3265 True if \fIfile\fP exists and is a block special file.
3268 True if \fIfile\fP exists and is a character special file.
3271 True if \fIfile\fP exists and is a directory.
3274 True if \fIfile\fP exists.
3277 True if \fIfile\fP exists and is a regular file.
3280 True if \fIfile\fP exists and is set-group-id.
3283 True if \fIfile\fP exists and is a symbolic link.
3286 True if \fIfile\fP exists and its ``sticky'' bit is set.
3289 True if \fIfile\fP exists and is a named pipe (FIFO).
3292 True if \fIfile\fP exists and is readable.
3295 True if \fIfile\fP exists and has a size greater than zero.
3298 True if file descriptor
3300 is open and refers to a terminal.
3303 True if \fIfile\fP exists and its set-user-id bit is set.
3306 True if \fIfile\fP exists and is writable.
3309 True if \fIfile\fP exists and is executable.
3312 True if \fIfile\fP exists and is owned by the effective user id.
3315 True if \fIfile\fP exists and is owned by the effective group id.
3318 True if \fIfile\fP exists and is a symbolic link.
3321 True if \fIfile\fP exists and is a socket.
3324 True if \fIfile\fP exists and has been modified since it was last read.
3326 \fIfile1\fP \-\fBnt\fP \fIfile2\fP
3327 True if \fIfile1\fP is newer (according to modification date) than \fIfile2\fP,
3328 or if \fIfile1\fP exists and \fPfile2\fP does not.
3330 \fIfile1\fP \-\fBot\fP \fIfile2\fP
3331 True if \fIfile1\fP is older than \fIfile2\fP, or if \fIfile2\fP exists
3332 and \fIfile1\fP does not.
3334 \fIfile1\fP \fB\-ef\fP \fIfile2\fP
3335 True if \fIfile1\fP and \fIfile2\fP refer to the same device and
3338 .B \-o \fIoptname\fP
3339 True if shell option
3342 See the list of options under the description of the
3349 True if the length of \fIstring\fP is zero.
3354 True if the length of
3358 \fIstring1\fP \fB==\fP \fIstring2\fP
3359 True if the strings are equal. \fB=\fP may be used in place of
3360 \fB==\fP for strict POSIX compliance.
3362 \fIstring1\fP \fB!=\fP \fIstring2\fP
3363 True if the strings are not equal.
3365 \fIstring1\fP \fB<\fP \fIstring2\fP
3366 True if \fIstring1\fP sorts before \fIstring2\fP lexicographically
3367 in the current locale.
3369 \fIstring1\fP \fB>\fP \fIstring2\fP
3370 True if \fIstring1\fP sorts after \fIstring2\fP lexicographically
3371 in the current locale.
3373 .I \fIarg1\fP \fBOP\fP \fIarg2\fP
3384 These arithmetic binary operators return true if \fIarg1\fP
3385 is equal to, not equal to, less than, less than or equal to,
3386 greater than, or greater than or equal to \fIarg2\fP, respectively.
3390 may be positive or negative integers.
3392 .SH "SIMPLE COMMAND EXPANSION"
3393 When a simple command is executed, the shell performs the following
3394 expansions, assignments, and redirections, from left to right.
3396 The words that the parser has marked as variable assignments (those
3397 preceding the command name) and redirections are saved for later
3400 The words that are not variable assignments or redirections are
3401 expanded. If any words remain after expansion, the first word
3402 is taken to be the name of the command and the remaining words are
3405 Redirections are performed as described above under
3409 The text after the \fB=\fP in each variable assignment undergoes tilde
3410 expansion, parameter expansion, command substitution, arithmetic expansion,
3411 and quote removal before being assigned to the variable.
3413 If no command name results, the variable assignments affect the current
3414 shell environment. Otherwise, the variables are added to the environment
3415 of the executed command and do not affect the current shell environment.
3416 If any of the assignments attempts to assign a value to a readonly variable,
3417 an error occurs, and the command exits with a non-zero status.
3419 If no command name results, redirections are performed, but do not
3420 affect the current shell environment. A redirection error causes the
3421 command to exit with a non-zero status.
3423 If there is a command name left after expansion, execution proceeds as
3424 described below. Otherwise, the command exits. If one of the expansions
3425 contained a command substitution, the exit status of the command is
3426 the exit status of the last command substitution performed. If there
3427 were no command substitutions, the command exits with a status of zero.
3428 .SH "COMMAND EXECUTION"
3429 After a command has been split into words, if it results in a
3430 simple command and an optional list of arguments, the following
3433 If the command name contains no slashes, the shell attempts to
3434 locate it. If there exists a shell function by that name, that
3435 function is invoked as described above in
3438 If the name does not match a function, the shell searches for
3439 it in the list of shell builtins. If a match is found, that
3442 If the name is neither a shell function nor a builtin,
3443 and contains no slashes,
3445 searches each element of the
3448 for a directory containing an executable file by that name.
3450 uses a hash table to remember the full pathnames of executable
3455 .B "SHELL BUILTIN COMMANDS"
3457 A full search of the directories in
3460 is performed only if the command is not found in the hash table.
3461 If the search is unsuccessful, the shell prints an error
3462 message and returns an exit status of 127.
3464 If the search is successful, or if the command name contains
3465 one or more slashes, the shell executes the named program in a
3466 separate execution environment.
3467 Argument 0 is set to the name given, and the remaining arguments
3468 to the command are set to the arguments given, if any.
3470 If this execution fails because the file is not in executable
3471 format, and the file is not a directory, it is assumed to be
3472 a \fIshell script\fP, a file
3473 containing shell commands. A subshell is spawned to execute
3474 it. This subshell reinitializes itself, so
3475 that the effect is as if a new shell had been invoked
3476 to handle the script, with the exception that the locations of
3477 commands remembered by the parent (see
3481 \fBSHELL BUILTIN COMMANDS\fP)
3482 are retained by the child.
3484 If the program is a file beginning with
3486 the remainder of the first line specifies an interpreter
3487 for the program. The shell executes the
3488 specified interpreter on operating systems that do not
3489 handle this executable format themselves. The arguments to the
3490 interpreter consist of a single optional argument following the
3491 interpreter name on the first line of the program, followed
3492 by the name of the program, followed by the command
3494 .SH COMMAND EXECUTION ENVIRONMENT
3495 The shell has an \fIexecution environment\fP, which consists of the
3499 open files inherited by the shell at invocation, as modified by
3500 redirections supplied to the \fBexec\fP builtin
3502 the current working directory as set by \fBcd\fP, \fBpushd\fP, or
3503 \fBpopd\fP, or inherited by the shell at invocation
3505 the file creation mode mask as set by \fBumask\fP or inherited from
3508 current traps set by \fBtrap\fP
3510 shell parameters that are set by variable assignment or with \fBset\fP
3511 or inherited from the shell's parent in the environment
3513 shell functions defined during execution or inherited from the shell's
3514 parent in the environment
3516 options enabled at invocation (either by default or with command-line
3517 arguments) or by \fBset\fP
3519 options enabled by \fBshopt\fP
3521 shell aliases defined with \fBalias\fP
3523 various process IDs, including those of background jobs, the value
3524 of \fB$$\fP, and the value of \fB$PPID\fP
3526 When a simple command other than a builtin or shell function
3527 is to be executed, it
3528 is invoked in a separate execution environment that consists of
3529 the following. Unless otherwise noted, the values are inherited
3533 the shell's open files, plus any modifications and additions specified
3534 by redirections to the command
3536 the current working directory
3538 the file creation mode mask
3540 shell variables marked for export, along with variables exported for
3541 the command, passed in the environment
3543 traps caught by the shell are reset to the values the inherited
3544 from the shell's parent, and traps ignored by the shell are ignored
3546 A command invoked in this separate environment cannot affect the
3547 shell's execution environment.
3549 Command substitution and asynchronous commands are invoked in a
3550 subshell environment that is a duplicate of the shell environment,
3551 except that traps caught by the shell are reset to the values
3552 that the shell inherited from its parent at invocation. Builtin
3553 commands that are invoked as part of a pipeline are also executed in a
3554 subshell environment. Changes made to the subshell environment
3555 cannot affect the shell's execution environment.
3557 If a command is followed by a \fB&\fP and job control is not active, the
3558 default standard input for the command is the empty file \fI/dev/null\fP.
3559 Otherwise, the invoked command inherits the file descriptors of the calling
3560 shell as modified by redirections.
3562 When a program is invoked it is given an array of strings
3566 \fIname\fP\-\fIvalue\fP pairs, of the form
3567 .IR "name\fR=\fPvalue" .
3569 The shell provides several ways to manipulate the environment.
3570 On invocation, the shell scans its own environment and
3571 creates a parameter for each name found, automatically marking
3574 to child processes. Executed commands inherit the environment.
3579 commands allow parameters and functions to be added to and
3580 deleted from the environment. If the value of a parameter
3581 in the environment is modified, the new value becomes part
3582 of the environment, replacing the old. The environment
3583 inherited by any executed command consists of the shell's
3584 initial environment, whose values may be modified in the shell,
3585 less any pairs removed by the
3587 command, plus any additions via the
3593 The environment for any
3595 or function may be augmented temporarily by prefixing it with
3596 parameter assignments, as described above in
3599 These assignment statements affect only the environment seen
3604 option is set (see the
3606 builtin command below), then
3608 parameter assignments are placed in the environment for a command,
3609 not just those that precede the command name.
3613 invokes an external command, the variable
3615 is set to the full file name of the command and passed to that
3616 command in its environment.
3618 For the shell's purposes, a command which exits with a
3619 zero exit status has succeeded. An exit status of zero
3620 indicates success. A non-zero exit status indicates failure.
3621 When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
3622 the value of 128+\fIN\fP as the exit status.
3624 If a command is not found, the child process created to
3625 execute it returns a status of 127. If a command is found
3626 but is not executable, the return status is 126.
3628 If a command fails because of an error during expansion or redirection,
3629 the exit status is greater than zero.
3631 Shell builtin commands return a status of 0 (\fItrue\fP) if
3632 successful, and non-zero (\fIfalse\fP) if an error occurs
3634 All builtins return an exit status of 2 to indicate incorrect usage.
3636 \fBBash\fP itself returns the exit status of the last command
3637 executed, unless a syntax error occurs, in which case it exits
3638 with a non-zero value. See also the \fBexit\fP builtin
3641 When \fBbash\fP is interactive, in the absence of any traps, it ignores
3644 (so that \fBkill 0\fP does not kill an interactive shell),
3648 is caught and handled (so that the \fBwait\fP builtin is interruptible).
3649 In all cases, \fBbash\fP ignores
3652 If job control is in effect,
3663 Synchronous jobs started by \fBbash\fP have signal handlers
3664 set to the values inherited by the shell from its parent.
3665 When job control is not in effect, asynchronous commands
3673 Commands run as a result of command substitution ignore the
3674 keyboard-generated job control signals
3683 The shell exits by default upon receipt of a
3686 Before exiting, an interactive shell resends the
3689 to all jobs, running or stopped.
3690 Stopped jobs are sent
3693 to ensure that they receive the
3696 To prevent the shell from
3697 sending the signal to a particular job, it should be removed from the
3702 .B "SHELL BUILTIN COMMANDS"
3712 shell option has been set with
3718 to all jobs when an interactive login shell exits.
3720 When \fBbash\fP receives a signal for which a trap has been set while
3721 waiting for a command to complete, the trap will not be executed until
3722 the command completes.
3723 When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
3724 builtin, the reception of a signal for which a trap has been set will
3725 cause the \fBwait\fP builtin to return immediately with an exit status
3726 greater than 128, immediately after which the trap is executed.
3729 refers to the ability to selectively stop (\fIsuspend\fP)
3730 the execution of processes and continue (\fIresume\fP)
3731 their execution at a later point. A user typically employs
3732 this facility via an interactive interface supplied jointly
3733 by the system's terminal driver and
3736 The shell associates a
3738 with each pipeline. It keeps a table of currently executing
3739 jobs, which may be listed with the
3743 starts a job asynchronously (in the
3745 it prints a line that looks like:
3751 indicating that this job is job number 1 and that the process ID
3752 of the last process in the pipeline associated with this job is 25647.
3753 All of the processes in a single pipeline are members of the same job.
3757 abstraction as the basis for job control.
3759 To facilitate the implementation of the user interface to job
3760 control, the operating system maintains the notion of a \fIcurrent terminal
3761 process group ID\fP. Members of this process group (processes whose
3762 process group ID is equal to the current terminal process group ID)
3763 receive keyboard-generated signals such as
3766 These processes are said to be in the
3769 processes are those whose process group ID differs from the terminal's;
3770 such processes are immune to keyboard-generated signals.
3771 Only foreground processes are allowed to read from or write to the
3772 terminal. Background processes which attempt to read from (write to) the
3775 .B SIGTTIN (SIGTTOU)
3776 signal by the terminal driver,
3777 which, unless caught, suspends the process.
3779 If the operating system on which
3784 contains facilities to use it.
3787 character (typically
3789 Control-Z) while a process is running
3790 causes that process to be stopped and returns control to
3793 .I "delayed suspend"
3794 character (typically
3796 Control-Y) causes the process to be stopped when it
3797 attempts to read input from the terminal, and control to
3800 The user may then manipulate the state of this job, using the
3802 command to continue it in the background, the
3804 command to continue it in the foreground, or
3807 command to kill it. A \fB^Z\fP takes effect immediately,
3808 and has the additional side effect of causing pending output
3809 and typeahead to be discarded.
3811 There are a number of ways to refer to a job in the shell.
3814 introduces a job name. Job number
3816 may be referred to as
3818 A job may also be referred to using a prefix of the name used to
3819 start it, or using a substring that appears in its command line.
3824 job. If a prefix matches more than one job,
3826 reports an error. Using
3828 on the other hand, refers to any job containing the string
3830 in its command line. If the substring matches more than one job,
3832 reports an error. The symbols
3836 refer to the shell's notion of the
3838 which is the last job stopped while it was in
3839 the foreground or started in the background.
3842 may be referenced using
3844 In output pertaining to jobs (e.g., the output of the
3846 command), the current job is always flagged with a
3848 and the previous job with a
3851 Simply naming a job can be used to bring it into the
3856 bringing job 1 from the background into the foreground.
3859 resumes job 1 in the background, equivalent to
3862 The shell learns immediately whenever a job changes state.
3865 waits until it is about to print a prompt before reporting
3866 changes in a job's status so as to not interrupt
3867 any other output. If the
3874 reports such changes immediately.
3878 is executed for each child that exits.
3880 If an attempt to exit
3882 is made while jobs are stopped, the shell prints a warning message. The
3884 command may then be used to inspect their status.
3885 If a second attempt to exit is made without an intervening command,
3886 the shell does not print another warning, and the stopped
3887 jobs are terminated.
3889 When executing interactively,
3891 displays the primary prompt
3894 when it is ready to read a command, and the secondary prompt
3897 when it needs more input to complete a command.
3899 allows these prompt strings to be customized by inserting a number of
3900 backslash-escaped special characters that are decoded as follows:
3905 an ASCII bell character (07)
3908 the date in "Weekday Month Date" format (e.g., "Tue May 26")
3910 .B \eD{\fIformat\fP}
3911 the \fIformat\fP is passed to \fIstrftime\fP(3) and the result is inserted
3912 into the prompt string; an empty \fIformat\fP results in a locale-specific
3913 time representation. The braces are required
3916 an ASCII escape character (033)
3919 the hostname up to the first `.'
3925 the number of jobs currently managed by the shell
3928 the basename of the shell's terminal device name
3937 the name of the shell, the basename of
3939 (the portion following the final slash)
3942 the current time in 24-hour HH:MM:SS format
3945 the current time in 12-hour HH:MM:SS format
3948 the current time in 12-hour am/pm format
3951 the current time in 24-hour HH:MM format
3954 the username of the current user
3957 the version of \fBbash\fP (e.g., 2.00)
3960 the release of \fBbash\fP, version + patchelvel (e.g., 2.00.0)
3963 the current working directory
3966 the basename of the current working directory
3969 the history number of this command
3972 the command number of this command
3975 if the effective UID is 0, a
3981 the character corresponding to the octal number \fInnn\fP
3987 begin a sequence of non-printing characters, which could be used to
3988 embed a terminal control sequence into the prompt
3991 end a sequence of non-printing characters
3995 The command number and the history number are usually different:
3996 the history number of a command is its position in the history
3997 list, which may include commands restored from the history file
4001 below), while the command number is the position in the sequence
4002 of commands executed during the current shell session.
4003 After the string is decoded, it is expanded via
4004 parameter expansion, command substitution, arithmetic
4005 expansion, and quote removal, subject to the value of the
4007 shell option (see the description of the
4011 .B "SHELL BUILTIN COMMANDS"
4014 This is the library that handles reading input when using an interactive
4017 option is given at shell invocation.
4018 By default, the line editing commands are similar to those of emacs.
4019 A vi-style line editing interface is also available.
4020 To turn off line editing after the shell is running, use the
4028 .B SHELL BUILTIN COMMANDS
4030 .SS "Readline Notation"
4032 In this section, the emacs-style notation is used to denote
4033 keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
4034 means Control\-N. Similarly,
4036 keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
4039 key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
4042 key. This makes ESC the \fImeta prefix\fP.
4043 The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
4044 or press the Escape key
4045 then hold the Control key while pressing the
4049 Readline commands may be given numeric
4051 which normally act as a repeat count.
4052 Sometimes, however, it is the sign of the argument that is significant.
4053 Passing a negative argument to a command that acts in the forward
4054 direction (e.g., \fBkill\-line\fP) causes that command to act in a
4056 Commands whose behavior with arguments deviates from this are noted
4059 When a command is described as \fIkilling\fP text, the text
4060 deleted is saved for possible future retrieval
4061 (\fIyanking\fP). The killed text is saved in a
4062 \fIkill ring\fP. Consecutive kills cause the text to be
4063 accumulated into one unit, which can be yanked all at once.
4064 Commands which do not kill text separate the chunks of text
4066 .SS "Readline Initialization"
4068 Readline is customized by putting commands in an initialization
4069 file (the \fIinputrc\fP file).
4070 The name of this file is taken from the value of the
4073 variable. If that variable is unset, the default is
4075 When a program which uses the readline library starts up, the
4076 initialization file is read, and the key bindings and variables
4078 There are only a few basic constructs allowed in the
4079 readline initialization file.
4080 Blank lines are ignored.
4081 Lines beginning with a \fB#\fP are comments.
4082 Lines beginning with a \fB$\fP indicate conditional constructs.
4083 Other lines denote key bindings and variable settings.
4085 The default key-bindings may be changed with an
4088 Other programs that use this library may add their own commands
4091 For example, placing
4094 M\-Control\-u: universal\-argument
4098 C\-Meta\-u: universal\-argument
4102 would make M\-C\-u execute the readline command
4103 .IR universal\-argument .
4105 The following symbolic character names are recognized:
4118 In addition to command names, readline allows keys to be bound
4119 to a string that is inserted when the key is pressed (a \fImacro\fP).
4120 .SS "Readline Key Bindings"
4122 The syntax for controlling key bindings in the
4124 file is simple. All that is required is the name of the
4125 command or the text of a macro and a key sequence to which
4126 it should be bound. The name may be specified in one of two ways:
4127 as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
4128 prefixes, or as a key sequence.
4130 When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4132 is the name of a key spelled out in English. For example:
4135 Control-u: universal\-argument
4137 Meta-Rubout: backward-kill-word
4139 Control-o: "> output"
4142 In the above example,
4144 is bound to the function
4145 .BR universal\-argument ,
4147 is bound to the function
4148 .BR backward\-kill\-word ,
4151 is bound to run the macro
4152 expressed on the right hand side (that is, to insert the text
4153 .if t \f(CW> output\fP
4157 In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4161 above in that strings denoting
4162 an entire key sequence may be specified by placing the sequence
4163 within double quotes. Some GNU Emacs style key escapes can be
4164 used, as in the following example, but the symbolic character names
4168 "\eC\-u": universal\-argument
4170 "\eC\-x\eC\-r": re\-read\-init\-file
4172 "\ee[11~": "Function Key 1"
4177 is again bound to the function
4178 .BR universal\-argument .
4180 is bound to the function
4181 .BR re\-read\-init\-file ,
4184 is bound to insert the text
4185 .if t \f(CWFunction Key 1\fP.
4186 .if n ``Function Key 1''.
4188 The full set of GNU Emacs style escape sequences is
4212 In addition to the GNU Emacs style escape sequences, a second
4213 set of backslash escapes is available:
4242 the eight-bit character whose value is the octal value \fInnn\fP
4243 (one to three digits)
4246 the eight-bit character whose value is the hexadecimal value \fIHH\fP
4247 (one or two hex digits)
4251 When entering the text of a macro, single or double quotes must
4252 be used to indicate a macro definition.
4253 Unquoted text is assumed to be a function name.
4254 In the macro body, the backslash escapes described above are expanded.
4255 Backslash will quote any other character in the macro text,
4259 allows the current readline key bindings to be displayed or modified
4262 builtin command. The editing mode may be switched during interactive
4267 builtin command (see
4269 .B SHELL BUILTIN COMMANDS
4271 .SS "Readline Variables"
4273 Readline has variables that can be used to further customize its
4274 behavior. A variable may be set in the
4276 file with a statement of the form
4279 \fBset\fP \fIvariable\-name\fP \fIvalue\fP
4282 Except where noted, readline variables can take the values
4286 The variables and their default values are:
4290 .B bell\-style (audible)
4291 Controls what happens when readline wants to ring the terminal bell.
4292 If set to \fBnone\fP, readline never rings the bell. If set to
4293 \fBvisible\fP, readline uses a visible bell if one is available.
4294 If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
4296 .B comment\-begin (``#'')
4297 The string that is inserted when the readline
4299 command is executed.
4300 This command is bound to
4302 in emacs mode and to
4306 .B completion\-ignore\-case (Off)
4307 If set to \fBOn\fP, readline performs filename matching and completion
4308 in a case\-insensitive fashion.
4310 .B completion\-query\-items (100)
4311 This determines when the user is queried about viewing
4312 the number of possible completions
4313 generated by the \fBpossible\-completions\fP command.
4314 It may be set to any integer value greater than or equal to
4315 zero. If the number of possible completions is greater than
4316 or equal to the value of this variable, the user is asked whether
4317 or not he wishes to view them; otherwise they are simply listed
4320 .B convert\-meta (On)
4321 If set to \fBOn\fP, readline will convert characters with the
4322 eighth bit set to an ASCII key sequence
4323 by stripping the eighth bit and prefixing an
4324 escape character (in effect, using escape as the \fImeta prefix\fP).
4326 .B disable\-completion (Off)
4327 If set to \fBOn\fP, readline will inhibit word completion. Completion
4328 characters will be inserted into the line as if they had been
4329 mapped to \fBself-insert\fP.
4331 .B editing\-mode (emacs)
4332 Controls whether readline begins with a set of key bindings similar
4333 to \fIemacs\fP or \fIvi\fP.
4335 can be set to either
4340 .B enable\-keypad (Off)
4341 When set to \fBOn\fP, readline will try to enable the application
4342 keypad when it is called. Some systems need this to enable the
4345 .B expand\-tilde (Off)
4346 If set to \fBon\fP, tilde expansion is performed when readline
4347 attempts word completion.
4349 .B history-preserve-point
4350 If set to \fBon\fP, the history code attempts to place point at the
4351 same location on each history line retrived with \fBprevious-history\fP
4352 or \fBnext-history\fP.
4354 .B horizontal\-scroll\-mode (Off)
4355 When set to \fBOn\fP, makes readline use a single line for display,
4356 scrolling the input horizontally on a single screen line when it
4357 becomes longer than the screen width rather than wrapping to a new line.
4359 .B input\-meta (Off)
4360 If set to \fBOn\fP, readline will enable eight-bit input (that is,
4361 it will not strip the high bit from the characters it reads),
4362 regardless of what the terminal claims it can support. The name
4364 is a synonym for this variable.
4366 .B isearch\-terminators (``C\-[C\-J'')
4367 The string of characters that should terminate an incremental
4368 search without subsequently executing the character as a command.
4369 If this variable has not been given a value, the characters
4370 \fIESC\fP and \fIC\-J\fP will terminate an incremental search.
4373 Set the current readline keymap. The set of valid keymap names is
4374 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
4377 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
4378 equivalent to \fIemacs\-standard\fP. The default value is
4382 also affects the default keymap.
4384 .B mark\-directories (On)
4385 If set to \fBOn\fP, completed directory names have a slash
4388 .B mark\-modified\-lines (Off)
4389 If set to \fBOn\fP, history lines that have been modified are displayed
4390 with a preceding asterisk (\fB*\fP).
4392 .B mark\-symlinked\-directories (Off)
4393 If set to \fBOn\fP, completed names which are symbolic links to directories
4394 have a slash appended (subject to the value of
4395 \fBmark\-directories\fP).
4397 .B match\-hidden\-files (On)
4398 This variable, when set to \fBOn\fP, causes readline to match files whose
4399 names begin with a `.' (hidden files) when performing filename
4400 completion, unless the leading `.' is
4401 supplied by the user in the filename to be completed.
4403 .B output\-meta (Off)
4404 If set to \fBOn\fP, readline will display characters with the
4405 eighth bit set directly rather than as a meta-prefixed escape
4408 .B page\-completions (On)
4409 If set to \fBOn\fP, readline uses an internal \fImore\fP-like pager
4410 to display a screenful of possible completions at a time.
4412 .B print\-completions\-horizontally (Off)
4413 If set to \fBOn\fP, readline will display completions with matches
4414 sorted horizontally in alphabetical order, rather than down the screen.
4416 .B show\-all\-if\-ambiguous (Off)
4417 This alters the default behavior of the completion functions. If
4420 words which have more than one possible completion cause the
4421 matches to be listed immediately instead of ringing the bell.
4423 .B visible\-stats (Off)
4424 If set to \fBOn\fP, a character denoting a file's type as reported
4425 by \fIstat\fP(2) is appended to the filename when listing possible
4428 .SS "Readline Conditional Constructs"
4430 Readline implements a facility similar in spirit to the conditional
4431 compilation features of the C preprocessor which allows key
4432 bindings and variable settings to be performed as the result
4433 of tests. There are four parser directives used.
4437 construct allows bindings to be made based on the
4438 editing mode, the terminal being used, or the application using
4439 readline. The text of the test extends to the end of the line;
4440 no characters are required to isolate it.
4443 The \fBmode=\fP form of the \fB$if\fP directive is used to test
4444 whether readline is in emacs or vi mode.
4445 This may be used in conjunction
4446 with the \fBset keymap\fP command, for instance, to set bindings in
4447 the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
4448 readline is starting out in emacs mode.
4450 The \fBterm=\fP form may be used to include terminal-specific
4451 key bindings, perhaps to bind the key sequences output by the
4452 terminal's function keys. The word on the right side of the
4454 is tested against the both full name of the terminal and the portion
4455 of the terminal name before the first \fB\-\fP. This allows
4462 .IP \fBapplication\fP
4463 The \fBapplication\fP construct is used to include
4464 application-specific settings. Each program using the readline
4465 library sets the \fIapplication name\fP, and an initialization
4466 file can test for a particular value.
4467 This could be used to bind key sequences to functions useful for
4468 a specific program. For instance, the following command adds a
4469 key sequence that quotes the current or previous word in Bash:
4474 # Quote the current or previous word
4475 "\eC\-xq": "\eeb\e"\eef\e""
4481 This command, as seen in the previous example, terminates an
4484 Commands in this branch of the \fB$if\fP directive are executed if
4487 This directive takes a single filename as an argument and reads commands
4488 and bindings from that file. For example, the following directive
4489 would read \fI/etc/inputrc\fP:
4493 \fB$include\fP \^ \fI/etc/inputrc\fP
4498 Readline provides commands for searching through the command history
4502 below) for lines containing a specified string.
4503 There are two search modes:
4506 .IR non-incremental .
4508 Incremental searches begin before the user has finished typing the
4510 As each character of the search string is typed, readline displays
4511 the next entry from the history matching the string typed so far.
4512 An incremental search requires only as many characters as needed to
4513 find the desired history entry.
4514 The characters present in the value of the \fBisearch-terminators\fP
4515 variable are used to terminate an incremental search.
4516 If that variable has not been assigned a value the Escape and
4517 Control-J characters will terminate an incremental search.
4518 Control-G will abort an incremental search and restore the original
4520 When the search is terminated, the history entry containing the
4521 search string becomes the current line.
4523 To find other matching entries in the history list, type Control-S or
4524 Control-R as appropriate.
4525 This will search backward or forward in the history for the next
4526 entry matching the search string typed so far.
4527 Any other key sequence bound to a readline command will terminate
4528 the search and execute that command.
4529 For instance, a \fInewline\fP will terminate the search and accept
4530 the line, thereby executing the command from the history list.
4532 Readline remembers the last incremental search string. If two
4533 Control-Rs are typed without any intervening characters defining a
4534 new search string, any remembered search string is used.
4536 Non-incremental searches read the entire search string before starting
4537 to search for matching history lines. The search string may be
4538 typed by the user or be part of the contents of the current line.
4539 .SS "Readline Command Names"
4541 The following is a list of the names of the commands and the default
4542 key sequences to which they are bound.
4543 Command names without an accompanying key sequence are unbound by default.
4544 In the following descriptions, \fIpoint\fP refers to the current cursor
4545 position, and \fImark\fP refers to a cursor position saved by the
4546 \fBset\-mark\fP command.
4547 The text between the point and mark is referred to as the \fIregion\fP.
4548 .SS Commands for Moving
4552 .B beginning\-of\-line (C\-a)
4553 Move to the start of the current line.
4555 .B end\-of\-line (C\-e)
4556 Move to the end of the line.
4558 .B forward\-char (C\-f)
4559 Move forward a character.
4561 .B backward\-char (C\-b)
4562 Move back a character.
4564 .B forward\-word (M\-f)
4565 Move forward to the end of the next word. Words are composed of
4566 alphanumeric characters (letters and digits).
4568 .B backward\-word (M\-b)
4569 Move back to the start of the current or previous word. Words are
4570 composed of alphanumeric characters (letters and digits).
4572 .B clear\-screen (C\-l)
4573 Clear the screen leaving the current line at the top of the screen.
4574 With an argument, refresh the current line without clearing the
4577 .B redraw\-current\-line
4578 Refresh the current line.
4580 .SS Commands for Manipulating the History
4584 .B accept\-line (Newline, Return)
4585 Accept the line regardless of where the cursor is. If this line is
4586 non-empty, add it to the history list according to the state of the
4589 variable. If the line is a modified history
4590 line, then restore the history line to its original state.
4592 .B previous\-history (C\-p)
4593 Fetch the previous command from the history list, moving back in
4596 .B next\-history (C\-n)
4597 Fetch the next command from the history list, moving forward in the
4600 .B beginning\-of\-history (M\-<)
4601 Move to the first line in the history.
4603 .B end\-of\-history (M\->)
4604 Move to the end of the input history, i.e., the line currently being
4607 .B reverse\-search\-history (C\-r)
4608 Search backward starting at the current line and moving `up' through
4609 the history as necessary. This is an incremental search.
4611 .B forward\-search\-history (C\-s)
4612 Search forward starting at the current line and moving `down' through
4613 the history as necessary. This is an incremental search.
4615 .B non\-incremental\-reverse\-search\-history (M\-p)
4616 Search backward through the history starting at the current line
4617 using a non-incremental search for a string supplied by the user.
4619 .B non\-incremental\-forward\-search\-history (M\-n)
4620 Search forward through the history using a non-incremental search for
4621 a string supplied by the user.
4623 .B history\-search\-forward
4624 Search forward through the history for the string of characters
4625 between the start of the current line and the point.
4626 This is a non-incremental search.
4628 .B history\-search\-backward
4629 Search backward through the history for the string of characters
4630 between the start of the current line and the point.
4631 This is a non-incremental search.
4633 .B yank\-nth\-arg (M\-C\-y)
4634 Insert the first argument to the previous command (usually
4635 the second word on the previous line) at point.
4638 insert the \fIn\fPth word from the previous command (the words
4639 in the previous command begin with word 0). A negative argument
4640 inserts the \fIn\fPth word from the end of the previous command.
4643 yank\-last\-arg (M\-.\^, M\-_\^)
4644 Insert the last argument to the previous command (the last word of
4645 the previous history entry). With an argument,
4646 behave exactly like \fByank\-nth\-arg\fP.
4647 Successive calls to \fByank\-last\-arg\fP move back through the history
4648 list, inserting the last argument of each line in turn.
4650 .B shell\-expand\-line (M\-C\-e)
4651 Expand the line as the shell does. This
4652 performs alias and history expansion as well as all of the shell
4653 word expansions. See
4655 .B HISTORY EXPANSION
4656 below for a description of history expansion.
4658 .B history\-expand\-line (M\-^)
4659 Perform history expansion on the current line.
4662 .B HISTORY EXPANSION
4663 below for a description of history expansion.
4666 Perform history expansion on the current line and insert a space.
4669 .B HISTORY EXPANSION
4670 below for a description of history expansion.
4672 .B alias\-expand\-line
4673 Perform alias expansion on the current line.
4677 above for a description of alias expansion.
4679 .B history\-and\-alias\-expand\-line
4680 Perform history and alias expansion on the current line.
4682 .B insert\-last\-argument (M\-.\^, M\-_\^)
4683 A synonym for \fByank\-last\-arg\fP.
4685 .B operate\-and\-get\-next (C\-o)
4686 Accept the current line for execution and fetch the next line
4687 relative to the current line from the history for editing. Any
4688 argument is ignored.
4690 .B edit\-and\-execute\-command (C\-xC\-e)
4691 Invoke an editor on the current command line, and execute the result as shell
4693 \fBBash\fP attempts to invoke
4698 and \fIemacs\fP as the editor, in that order.
4700 .SS Commands for Changing Text
4704 .B delete\-char (C\-d)
4705 Delete the character at point. If point is at the
4706 beginning of the line, there are no characters in the line, and
4707 the last character typed was not bound to \fBdelete\-char\fP,
4712 .B backward\-delete\-char (Rubout)
4713 Delete the character behind the cursor. When given a numeric argument,
4714 save the deleted text on the kill ring.
4716 .B forward\-backward\-delete\-char
4717 Delete the character under the cursor, unless the cursor is at the
4718 end of the line, in which case the character behind the cursor is
4721 .B quoted\-insert (C\-q, C\-v)
4722 Add the next character typed to the line verbatim. This is
4723 how to insert characters like \fBC\-q\fP, for example.
4725 .B tab\-insert (C\-v TAB)
4726 Insert a tab character.
4728 .B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
4729 Insert the character typed.
4731 .B transpose\-chars (C\-t)
4732 Drag the character before point forward over the character at point,
4733 moving point forward as well.
4734 If point is at the end of the line, then this transposes
4735 the two characters before point.
4736 Negative arguments have no effect.
4738 .B transpose\-words (M\-t)
4739 Drag the word before point past the word after point,
4740 moving point over that word as well.
4741 If point is at the end of the line, this transposes
4742 the last two words on the line.
4744 .B upcase\-word (M\-u)
4745 Uppercase the current (or following) word. With a negative argument,
4746 uppercase the previous word, but do not move point.
4748 .B downcase\-word (M\-l)
4749 Lowercase the current (or following) word. With a negative argument,
4750 lowercase the previous word, but do not move point.
4752 .B capitalize\-word (M\-c)
4753 Capitalize the current (or following) word. With a negative argument,
4754 capitalize the previous word, but do not move point.
4757 Toggle overwrite mode. With an explicit positive numeric argument,
4758 switches to overwrite mode. With an explicit non-positive numeric
4759 argument, switches to insert mode. This command affects only
4760 \fBemacs\fP mode; \fBvi\fP mode does overwrite differently.
4761 Each call to \fIreadline()\fP starts in insert mode.
4762 In overwrite mode, characters bound to \fBself\-insert\fP replace
4763 the text at point rather than pushing the text to the right.
4764 Characters bound to \fBbackward\-delete\-char\fP replace the character
4765 before point with a space. By default, this command is unbound.
4767 .SS Killing and Yanking
4771 .B kill\-line (C\-k)
4772 Kill the text from point to the end of the line.
4774 .B backward\-kill\-line (C\-x Rubout)
4775 Kill backward to the beginning of the line.
4777 .B unix\-line\-discard (C\-u)
4778 Kill backward from point to the beginning of the line.
4779 The killed text is saved on the kill-ring.
4780 .\" There is no real difference between this and backward-kill-line
4782 .B kill\-whole\-line
4783 Kill all characters on the current line, no matter where point is.
4785 .B kill\-word (M\-d)
4786 Kill from point to the end of the current word, or if between
4787 words, to the end of the next word.
4788 Word boundaries are the same as those used by \fBforward\-word\fP.
4790 .B backward\-kill\-word (M\-Rubout)
4791 Kill the word behind point.
4792 Word boundaries are the same as those used by \fBbackward\-word\fP.
4794 .B unix\-word\-rubout (C\-w)
4795 Kill the word behind point, using white space as a word boundary.
4796 The killed text is saved on the kill-ring.
4798 .B delete\-horizontal\-space (M\-\e)
4799 Delete all spaces and tabs around point.
4802 Kill the text in the current region.
4804 .B copy\-region\-as\-kill
4805 Copy the text in the region to the kill buffer.
4807 .B copy\-backward\-word
4808 Copy the word before point to the kill buffer.
4809 The word boundaries are the same as \fBbackward\-word\fP.
4811 .B copy\-forward\-word
4812 Copy the word following point to the kill buffer.
4813 The word boundaries are the same as \fBforward\-word\fP.
4816 Yank the top of the kill ring into the buffer at point.
4819 Rotate the kill ring, and yank the new top. Only works following
4824 .SS Numeric Arguments
4828 .B digit\-argument (M\-0, M\-1, ..., M\-\-)
4829 Add this digit to the argument already accumulating, or start a new
4830 argument. M\-\- starts a negative argument.
4832 .B universal\-argument
4833 This is another way to specify an argument.
4834 If this command is followed by one or more digits, optionally with a
4835 leading minus sign, those digits define the argument.
4836 If the command is followed by digits, executing
4837 .B universal\-argument
4838 again ends the numeric argument, but is otherwise ignored.
4839 As a special case, if this command is immediately followed by a
4840 character that is neither a digit or minus sign, the argument count
4841 for the next command is multiplied by four.
4842 The argument count is initially one, so executing this function the
4843 first time makes the argument count four, a second time makes the
4844 argument count sixteen, and so on.
4851 Attempt to perform completion on the text before point.
4853 attempts completion treating the text as a variable (if the
4854 text begins with \fB$\fP), username (if the text begins with
4855 \fB~\fP), hostname (if the text begins with \fB@\fP), or
4856 command (including aliases and functions) in turn. If none
4857 of these produces a match, filename completion is attempted.
4859 .B possible\-completions (M\-?)
4860 List the possible completions of the text before point.
4862 .B insert\-completions (M\-*)
4863 Insert all completions of the text before point
4864 that would have been generated by
4865 \fBpossible\-completions\fP.
4868 Similar to \fBcomplete\fP, but replaces the word to be completed
4869 with a single match from the list of possible completions.
4870 Repeated execution of \fBmenu\-complete\fP steps through the list
4871 of possible completions, inserting each match in turn.
4872 At the end of the list of completions, the bell is rung
4873 (subject to the setting of \fBbell\-style\fP)
4874 and the original text is restored.
4875 An argument of \fIn\fP moves \fIn\fP positions forward in the list
4876 of matches; a negative argument may be used to move backward
4878 This command is intended to be bound to \fBTAB\fP, but is unbound
4881 .B delete\-char\-or\-list
4882 Deletes the character under the cursor if not at the beginning or
4883 end of the line (like \fBdelete\-char\fP).
4884 If at the end of the line, behaves identically to
4885 \fBpossible\-completions\fP.
4886 This command is unbound by default.
4888 .B complete\-filename (M\-/)
4889 Attempt filename completion on the text before point.
4891 .B possible\-filename\-completions (C\-x /)
4892 List the possible completions of the text before point,
4893 treating it as a filename.
4895 .B complete\-username (M\-~)
4896 Attempt completion on the text before point, treating
4899 .B possible\-username\-completions (C\-x ~)
4900 List the possible completions of the text before point,
4901 treating it as a username.
4903 .B complete\-variable (M\-$)
4904 Attempt completion on the text before point, treating
4905 it as a shell variable.
4907 .B possible\-variable\-completions (C\-x $)
4908 List the possible completions of the text before point,
4909 treating it as a shell variable.
4911 .B complete\-hostname (M\-@)
4912 Attempt completion on the text before point, treating
4915 .B possible\-hostname\-completions (C\-x @)
4916 List the possible completions of the text before point,
4917 treating it as a hostname.
4919 .B complete\-command (M\-!)
4920 Attempt completion on the text before point, treating
4921 it as a command name. Command completion attempts to
4922 match the text against aliases, reserved words, shell
4923 functions, shell builtins, and finally executable filenames,
4926 .B possible\-command\-completions (C\-x !)
4927 List the possible completions of the text before point,
4928 treating it as a command name.
4930 .B dynamic\-complete\-history (M\-TAB)
4931 Attempt completion on the text before point, comparing
4932 the text against lines from the history list for possible
4935 .B complete\-into\-braces (M\-{)
4936 Perform filename completion and insert the list of possible completions
4937 enclosed within braces so the list is available to the shell (see
4945 .B start\-kbd\-macro (C\-x (\^)
4946 Begin saving the characters typed into the current keyboard macro.
4948 .B end\-kbd\-macro (C\-x )\^)
4949 Stop saving the characters typed into the current keyboard macro
4950 and store the definition.
4952 .B call\-last\-kbd\-macro (C\-x e)
4953 Re-execute the last keyboard macro defined, by making the characters
4954 in the macro appear as if typed at the keyboard.
4960 .B re\-read\-init\-file (C\-x C\-r)
4961 Read in the contents of the \fIinputrc\fP file, and incorporate
4962 any bindings or variable assignments found there.
4965 Abort the current editing command and
4966 ring the terminal's bell (subject to the setting of
4969 .B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
4970 If the metafied character \fIx\fP is lowercase, run the command
4971 that is bound to the corresponding uppercase character.
4973 .B prefix\-meta (ESC)
4974 Metafy the next character typed.
4981 .B undo (C\-_, C\-x C\-u)
4982 Incremental undo, separately remembered for each line.
4984 .B revert\-line (M\-r)
4985 Undo all changes made to this line. This is like executing the
4987 command enough times to return the line to its initial state.
4989 .B tilde\-expand (M\-&)
4990 Perform tilde expansion on the current word.
4992 .B set\-mark (C\-@, M\-<space>)
4993 Set the mark to the point. If a
4994 numeric argument is supplied, the mark is set to that position.
4996 .B exchange\-point\-and\-mark (C\-x C\-x)
4997 Swap the point with the mark. The current cursor position is set to
4998 the saved position, and the old cursor position is saved as the mark.
5000 .B character\-search (C\-])
5001 A character is read and point is moved to the next occurrence of that
5002 character. A negative count searches for previous occurrences.
5004 .B character\-search\-backward (M\-C\-])
5005 A character is read and point is moved to the previous occurrence of that
5006 character. A negative count searches for subsequent occurrences.
5008 .B insert\-comment (M\-#)
5009 Without a numeric argument, the value of the readline
5011 variable is inserted at the beginning of the current line.
5012 If a numeric argument is supplied, this command acts as a toggle: if
5013 the characters at the beginning of the line do not match the value
5014 of \fBcomment\-begin\fP, the value is inserted, otherwise
5015 the characters in \fBcomment-begin\fP are deleted from the beginning of
5017 In either case, the line is accepted as if a newline had been typed.
5018 The default value of
5019 \fBcomment\-begin\fP causes this command to make the current line
5021 If a numeric argument causes the comment character to be removed, the line
5022 will be executed by the shell.
5024 .B glob\-complete\-word (M\-g)
5025 The word before point is treated as a pattern for pathname expansion,
5026 with an asterisk implicitly appended. This pattern is used to
5027 generate a list of matching file names for possible completions.
5029 .B glob\-expand\-word (C\-x *)
5030 The word before point is treated as a pattern for pathname expansion,
5031 and the list of matching file names is inserted, replacing the word.
5032 If a numeric argument is supplied, an asterisk is appended before
5035 .B glob\-list\-expansions (C\-x g)
5036 The list of expansions that would have been generated by
5037 .B glob\-expand\-word
5038 is displayed, and the line is redrawn.
5039 If a numeric argument is supplied, an asterisk is appended before
5043 Print all of the functions and their key bindings to the
5044 readline output stream. If a numeric argument is supplied,
5045 the output is formatted in such a way that it can be made part
5046 of an \fIinputrc\fP file.
5049 Print all of the settable readline variables and their values to the
5050 readline output stream. If a numeric argument is supplied,
5051 the output is formatted in such a way that it can be made part
5052 of an \fIinputrc\fP file.
5055 Print all of the readline key sequences bound to macros and the
5056 strings they ouput. If a numeric argument is supplied,
5057 the output is formatted in such a way that it can be made part
5058 of an \fIinputrc\fP file.
5060 .B display\-shell\-version (C\-x C\-v)
5061 Display version information about the current instance of
5064 .SS Programmable Completion
5066 When word completion is attempted for an argument to a command for
5067 which a completion specification (a \fIcompspec\fP) has been defined
5068 using the \fBcomplete\fP builtin (see
5070 .B "SHELL BUILTIN COMMANDS"
5071 below), the programmable completion facilities are invoked.
5073 First, the command name is identified.
5074 If a compspec has been defined for that command, the
5075 compspec is used to generate the list of possible completions for the word.
5076 If the command word is a full pathname, a compspec for the full
5077 pathname is searched for first.
5078 If no compspec is found for the full pathname, an attempt is made to
5079 find a compspec for the portion following the final slash.
5081 Once a compspec has been found, it is used to generate the list of
5083 If a compspec is not found, the default \fBbash\fP completion as
5084 described above under \fBCompleting\fP is performed.
5086 First, the actions specified by the compspec are used.
5087 Only matches which are prefixed by the word being completed are
5093 option is used for filename or directory name completion, the shell
5097 is used to filter the matches.
5099 Any completions specified by a filename expansion pattern to the
5100 \fB\-G\fP option are generated next.
5101 The words generated by the pattern need not match the word
5106 shell variable is not used to filter the matches, but the
5111 Next, the string specified as the argument to the \fB\-W\fP option
5113 The string is first split using the characters in the
5116 special variable as delimiters.
5117 Shell quoting is honored.
5118 Each word is then expanded using
5119 brace expansion, tilde expansion, parameter and variable expansion,
5120 command substitution, arithmetic expansion, and pathname expansion,
5121 as described above under
5124 The results are split using the rules described above under
5125 \fBWord Splitting\fP.
5126 The results of the expansion are prefix-matched against the word being
5127 completed, and the matching words become the possible completions.
5129 After these matches have been generated, any shell function or command
5130 specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
5131 When the command or function is invoked, the
5137 variables are assigned values as described above under
5138 \fBShell Variables\fP.
5139 If a shell function is being invoked, the
5145 variables are also set.
5146 When the function or command is invoked, the first argument is the
5147 name of the command whose arguments are being completed, the
5148 second argument is the word being completed, and the third argument
5149 is the word preceding the word being completed on the current command line.
5150 No filtering of the generated completions against the word being completed
5151 is performed; the function or command has complete freedom in generating
5154 Any function specified with \fB\-F\fP is invoked first.
5155 The function may use any of the shell facilities, including the
5156 \fBcompgen\fP builtin described below, to generate the matches.
5157 It must put the possible completions in the
5162 Next, any command specified with the \fB\-C\fP option is invoked
5163 in an environment equivalent to command substitution.
5164 It should print a list of completions, one per line, to the
5166 Backslash may be used to escape a newline, if necessary.
5168 After all of the possible completions are generated, any filter
5169 specified with the \fB\-X\fP option is applied to the list.
5170 The filter is a pattern as used for pathname expansion; a \fB&\fP
5171 in the pattern is replaced with the text of the word being completed.
5172 A literal \fB&\fP may be escaped with a backslash; the backslash
5173 is removed before attempting a match.
5174 Any completion that matches the pattern will be removed from the list.
5175 A leading \fB!\fP negates the pattern; in this case any completion
5176 not matching the pattern will be removed.
5178 Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
5179 options are added to each member of the completion list, and the result is
5180 returned to the readline completion code as the list of possible
5183 If the previously-applied actions do not generate any matches, and the
5184 \fB\-o dirnames\fP option was supplied to \fBcomplete\fP when the
5185 compspec was defined, directory name completion is attempted.
5187 By default, if a compspec is found, whatever it generates is returned
5188 to the completion code as the full set of possible completions.
5189 The default \fBbash\fP completions are not attempted, and the readline
5190 default of filename completion is disabled.
5191 If the \fB-o default\fP option was supplied to \fBcomplete\fP when the
5192 compspec was defined, readline's default completion will be performed
5193 if the compspec generates no matches.
5195 When a compspec indicates that directory name completion is desired,
5196 the programmable completion functions force readline to append a slash
5197 to completed names which are symbolic links to directories, subject to
5198 the value of the \fBmark\-directories\fP readline variable, regardless
5199 of the setting of the \fBmark-symlinked\-directories\fP readline variable.
5205 builtin is enabled, the shell provides access to the
5206 \fIcommand history\fP,
5207 the list of commands previously typed.
5208 The value of the \fBHISTSIZE\fP variable is used as the
5209 number of commands to save in a history list.
5210 The text of the last
5213 commands (default 500) is saved. The shell
5214 stores each command in the history list prior to parameter and
5215 variable expansion (see
5218 above) but after history expansion is performed, subject to the
5219 values of the shell variables
5226 On startup, the history is initialized from the file named by
5230 (default \fI~/.bash_history\fP).
5231 The file named by the value of
5234 is truncated, if necessary, to contain no more than
5235 the number of lines specified by the value of
5238 When an interactive shell exits, the last
5241 lines are copied from the history list to
5246 shell option is enabled
5247 (see the description of
5251 .B "SHELL BUILTIN COMMANDS"
5252 below), the lines are appended to the history file,
5253 otherwise the history file is overwritten.
5257 is unset, or if the history file is unwritable, the history is
5258 not saved. After saving the history, the history file is truncated
5259 to contain no more than
5265 is not set, no truncation is performed.
5271 .B SHELL BUILTIN COMMANDS
5272 below) may be used to list or edit and re-execute a portion of
5276 builtin may be used to display or modify the history list and
5277 manipulate the history file.
5278 When using command-line editing, search commands
5279 are available in each editing mode that provide access to the
5282 The shell allows control over which commands are saved on the history
5289 variables may be set to cause the shell to save only a subset of the
5293 shell option, if enabled, causes the shell to attempt to save each
5294 line of a multi-line command in the same history entry, adding
5295 semicolons where necessary to preserve syntactic correctness.
5298 shell option causes the shell to save the command with embedded newlines
5299 instead of semicolons. See the description of the
5303 .B "SHELL BUILTIN COMMANDS"
5304 for information on setting and unsetting shell options.
5305 .SH "HISTORY EXPANSION"
5307 The shell supports a history expansion feature that
5308 is similar to the history expansion in
5310 This section describes what syntax features are available. This
5311 feature is enabled by default for interactive shells, and can be
5316 builtin command (see
5318 .B SHELL BUILTIN COMMANDS
5319 below). Non-interactive shells do not perform history expansion
5322 History expansions introduce words from the history list into
5323 the input stream, making it easy to repeat commands, insert the
5324 arguments to a previous command into the current input line, or
5325 fix errors in previous commands quickly.
5327 History expansion is performed immediately after a complete line
5328 is read, before the shell breaks it into words.
5329 It takes place in two parts.
5330 The first is to determine which line from the history list
5331 to use during substitution.
5332 The second is to select portions of that line for inclusion into
5334 The line selected from the history is the \fIevent\fP,
5335 and the portions of that line that are acted upon are \fIwords\fP.
5336 Various \fImodifiers\fP are available to manipulate the selected words.
5337 The line is broken into words in the same fashion as when reading input,
5338 so that several \fImetacharacter\fP-separated words surrounded by
5339 quotes are considered one word.
5340 History expansions are introduced by the appearance of the
5341 history expansion character, which is \^\fB!\fP\^ by default.
5342 Only backslash (\^\fB\e\fP\^) and single quotes can quote
5343 the history expansion character.
5345 Several shell options settable with the
5347 builtin may be used to tailor the behavior of history expansion.
5350 shell option is enabled (see the description of the
5354 is being used, history substitutions are not immediately passed to
5356 Instead, the expanded line is reloaded into the
5358 editing buffer for further modification.
5361 is being used, and the
5363 shell option is enabled, a failed history substitution will be reloaded
5366 editing buffer for correction.
5371 builtin command may be used to see what a history expansion will
5377 builtin may be used to add commands to the end of the history list
5378 without actually executing them, so that they are available for
5381 The shell allows control of the various characters used by the
5382 history expansion mechanism (see the description of
5385 .BR "Shell Variables" ).
5386 .SS Event Designators
5388 An event designator is a reference to a command line entry in the
5394 Start a history substitution, except when followed by a
5399 Refer to command line
5403 Refer to the current command line minus
5407 Refer to the previous command. This is a synonym for `!\-1'.
5410 Refer to the most recent command starting with
5413 .B !?\fIstring\fR\fB[?]\fR
5414 Refer to the most recent command containing
5416 The trailing \fB?\fP may be omitted if
5418 is followed immediately by a newline.
5420 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
5421 Quick substitution. Repeat the last command, replacing
5426 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
5427 (see \fBModifiers\fP below).
5430 The entire command line typed so far.
5432 .SS Word Designators
5434 Word designators are used to select desired words from the event.
5437 separates the event specification from the word designator.
5438 It may be omitted if the word designator begins with a
5445 Words are numbered from the beginning of the line,
5446 with the first word being denoted by 0 (zero).
5447 Words are inserted into the current line separated by single spaces.
5452 The zeroth word. For the shell, this is the command
5459 The first argument. That is, word 1.
5465 The word matched by the most recent `?\fIstring\fR?' search.
5468 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
5471 All of the words but the zeroth. This is a synonym
5472 for `\fI1\-$\fP'. It is not an error to use
5474 if there is just one
5475 word in the event; the empty string is returned in that case.
5478 Abbreviates \fIx\-$\fP.
5481 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
5484 If a word designator is supplied without an event specification, the
5485 previous command is used as the event.
5488 After the optional word designator, there may appear a sequence of
5489 one or more of the following modifiers, each preceded by a `:'.
5495 Remove a trailing file name component, leaving only the head.
5498 Remove all leading file name components, leaving the tail.
5501 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
5505 Remove all but the trailing suffix.
5508 Print the new command but do not execute it.
5511 Quote the substituted words, escaping further substitutions.
5514 Quote the substituted words as with
5516 but break into words at
5520 .B s/\fIold\fP/\fInew\fP/
5523 for the first occurrence of
5525 in the event line. Any delimiter can be used in place of /. The
5526 final delimiter is optional if it is the last character of the
5527 event line. The delimiter may be quoted in
5531 with a single backslash. If & appears in
5535 A single backslash will quote the &. If
5537 is null, it is set to the last
5539 substituted, or, if no previous history substitutions took place,
5543 .B !?\fIstring\fR\fB[?]\fR
5547 Repeat the previous substitution.
5550 Cause changes to be applied over the entire event line. This is
5551 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
5552 or `\fB:&\fP'. If used with
5553 `\fB:s\fP', any delimiter can be used
5554 in place of /, and the final delimiter is optional
5555 if it is the last character of the event line.
5557 .SH "SHELL BUILTIN COMMANDS"
5558 .\" start of bash_builtins
5561 Unless otherwise noted, each builtin command documented in this
5562 section as accepting options preceded by
5566 to signify the end of the options.
5570 \fB:\fP [\fIarguments\fP]
5572 No effect; the command does nothing beyond expanding
5574 and performing any specified
5575 redirections. A zero exit code is returned.
5577 \fB .\| \fP \fIfilename\fP [\fIarguments\fP]
5580 \fBsource\fP \fIfilename\fP [\fIarguments\fP]
5582 Read and execute commands from
5585 shell environment and return the exit status of the last command
5590 does not contain a slash, file names in
5593 are used to find the directory containing
5595 The file searched for in
5598 need not be executable.
5599 When \fBbash\fP is not in \fIposix mode\fP, the current directory is
5600 searched if no file is found in
5607 builtin command is turned off, the
5611 If any \fIarguments\fP are supplied, they become the positional
5612 parameters when \fIfilename\fP is executed. Otherwise the positional
5613 parameters are unchanged.
5614 The return status is the status of the last command exited within
5615 the script (0 if no commands are executed), and false if
5617 is not found or cannot be read.
5619 \fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
5620 \fBAlias\fP with no arguments or with the
5622 option prints the list of aliases in the form
5623 \fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
5624 When arguments are supplied, an alias is defined for
5625 each \fIname\fP whose \fIvalue\fP is given.
5626 A trailing space in \fIvalue\fP causes the next word to be
5627 checked for alias substitution when the alias is expanded.
5628 For each \fIname\fP in the argument list for which no \fIvalue\fP
5629 is supplied, the name and value of the alias is printed.
5630 \fBAlias\fP returns true unless a \fIname\fP is given for which
5631 no alias has been defined.
5633 \fBbg\fP [\fIjobspec\fP]
5634 Resume the suspended job \fIjobspec\fP in the background, as if it
5635 had been started with
5637 If \fIjobspec\fP is not present, the shell's notion of the
5638 \fIcurrent job\fP is used.
5641 returns 0 unless run when job control is disabled or, when run with
5642 job control enabled, if \fIjobspec\fP was not found or started without
5645 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSV\fP]
5648 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
5650 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
5652 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
5654 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
5656 \fBbind\fP \fIreadline\-command\fP
5660 key and function bindings, bind a key sequence to a
5662 function or macro, or set a
5665 Each non-option argument is a command as it would appear in
5667 but each binding or command must be passed as a separate argument;
5668 e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'.
5669 Options, if supplied, have the following meanings:
5676 as the keymap to be affected by the subsequent bindings.
5680 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
5681 vi\-move, vi\-command\fP, and
5683 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
5684 equivalent to \fIemacs\-standard\fP.
5687 List the names of all \fBreadline\fP functions.
5690 Display \fBreadline\fP function names and bindings in such a way
5691 that they can be re-read.
5694 List current \fBreadline\fP function names and bindings.
5697 Display \fBreadline\fP variable names and values in such a way that they
5701 List current \fBreadline\fP variable names and values.
5704 Display \fBreadline\fP key sequences bound to macros and the strings
5705 they output in such a way that they can be re-read.
5708 Display \fBreadline\fP key sequences bound to macros and the strings
5711 .B \-f \fIfilename\fP
5712 Read key bindings from \fIfilename\fP.
5714 .B \-q \fIfunction\fP
5715 Query about which keys invoke the named \fIfunction\fP.
5717 .B \-u \fIfunction\fP
5718 Unbind all keys bound to the named \fIfunction\fP.
5721 Remove any current binding for \fIkeyseq\fP.
5723 .B \-x \fIkeyseq\fP:\fIshell\-command\fP
5724 Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
5728 The return value is 0 unless an unrecognized option is given or an
5732 \fBbreak\fP [\fIn\fP]
5739 loop. If \fIn\fP is specified, break \fIn\fP levels.
5743 is greater than the number of enclosing loops, all enclosing loops
5744 are exited. The return value is 0 unless the shell is not executing
5749 \fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
5750 Execute the specified shell builtin, passing it
5752 and return its exit status.
5753 This is useful when defining a
5754 function whose name is the same as a shell builtin,
5755 retaining the functionality of the builtin within the function.
5756 The \fBcd\fP builtin is commonly redefined this way.
5757 The return status is false if
5759 is not a shell builtin command.
5761 \fBcd\fP [\fB\-L|-P\fP] [\fIdir\fP]
5762 Change the current directory to \fIdir\fP. The variable
5771 defines the search path for the directory containing
5773 Alternative directory names in
5776 are separated by a colon (:). A null directory name in
5779 is the same as the current directory, i.e., ``\fB.\fP''. If
5781 begins with a slash (/),
5787 option says to use the physical directory structure instead of
5788 following symbolic links (see also the
5792 builtin command); the
5794 option forces symbolic links to be followed. An argument of
5799 The return value is true if the directory was successfully changed;
5802 \fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
5807 suppressing the normal shell function lookup. Only builtin
5808 commands or commands found in the
5811 are executed. If the
5813 option is given, the search for
5815 is performed using a default value for
5817 that is guaranteed to find all of the standard utilities.
5822 option is supplied, a description of
5826 option causes a single word indicating the command or file name
5829 to be displayed; the
5831 option produces a more verbose description.
5836 option is supplied, the exit status is 0 if
5838 was found, and 1 if not. If neither option is supplied and
5839 an error occurred or
5841 cannot be found, the exit status is 127. Otherwise, the exit status of the
5843 builtin is the exit status of
5846 \fBcompgen\fP [\fIoption\fP] [\fIword\fP]
5847 Generate possible completion matches for \fIword\fP according to
5848 the \fIoption\fPs, which may be any option accepted by the
5850 builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
5851 the matches to the standard output.
5852 When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
5853 set by the programmable completion facilities, while available, will not
5856 The matches will be generated in the same way as if the programmable
5857 completion code had generated them directly from a completion specification
5858 with the same flags.
5859 If \fIword\fP is specified, only those completions matching \fIword\fP
5862 The return value is true unless an invalid option is supplied, or no
5863 matches were generated.
5865 \fBcomplete\fP [\fB\-abcdefgjksuv\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]
5867 [\fB\-X\fP \fIfilterpat\fP] [\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP] \fIname\fP [\fIname ...\fP]
5870 \fBcomplete\fP \fB\-pr\fP [\fIname\fP ...]
5872 Specify how arguments to each \fIname\fP should be completed.
5873 If the \fB\-p\fP option is supplied, or if no options are supplied,
5874 existing completion specifications are printed in a way that allows
5875 them to be reused as input.
5876 The \fB\-r\fP option removes a completion specification for
5877 each \fIname\fP, or, if no \fIname\fPs are supplied, all
5878 completion specifications.
5880 The process of applying these completion specifications when word completion
5881 is attempted is described above under \fBProgrammable Completion\fP.
5883 Other options, if specified, have the following meanings.
5884 The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
5885 (and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
5886 should be quoted to protect them from expansion before the
5892 \fB\-o\fP \fIcomp-option\fP
5893 The \fIcomp-option\fP controls several aspects of the compspec's behavior
5894 beyond the simple generation of completions.
5895 \fIcomp-option\fP may be one of:
5899 Use readline's default filename completion if the compspec generates
5903 Perform directory name completion if the compspec generates no matches.
5906 Tell readline that the compspec generates filenames, so it can perform any
5907 filename\-specific processing (like adding a slash to directory names or
5908 suppressing trailing spaces). Intended to be used with shell functions.
5911 Tell readline not to append a space (the default) to words completed at
5912 the end of the line.
5915 \fB\-A\fP \fIaction\fP
5916 The \fIaction\fP may be one of the following to generate a list of possible
5921 Alias names. May also be specified as \fB\-a\fP.
5924 Array variable names.
5927 \fBReadline\fP key binding names.
5930 Names of shell builtin commands. May also be specified as \fB\-b\fP.
5933 Command names. May also be specified as \fB\-c\fP.
5936 Directory names. May also be specified as \fB\-d\fP.
5939 Names of disabled shell builtins.
5942 Names of enabled shell builtins.
5945 Names of exported shell variables. May also be specified as \fB\-e\fP.
5948 File names. May also be specified as \fB\-f\fP.
5951 Names of shell functions.
5954 Group names. May also be specified as \fB\-g\fP.
5957 Help topics as accepted by the \fBhelp\fP builtin.
5960 Hostnames, as taken from the file specified by the
5966 Job names, if job control is active. May also be specified as \fB\-j\fP.
5969 Shell reserved words. May also be specified as \fB\-k\fP.
5972 Names of running jobs, if job control is active.
5975 Service names. May also be specified as \fB\-s\fP.
5978 Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
5981 Shell option names as accepted by the \fBshopt\fP builtin.
5987 Names of stopped jobs, if job control is active.
5990 User names. May also be specified as \fB\-u\fP.
5993 Names of all shell variables. May also be specified as \fB\-v\fP.
5996 \fB\-G\fP \fIglobpat\fP
5997 The filename expansion pattern \fIglobpat\fP is expanded to generate
5998 the possible completions.
6000 \fB\-W\fP \fIwordlist\fP
6001 The \fIwordlist\fP is split using the characters in the
6004 special variable as delimiters, and each resultant word is expanded.
6005 The possible completions are the members of the resultant list which
6006 match the word being completed.
6008 \fB\-C\fP \fIcommand\fP
6009 \fIcommand\fP is executed in a subshell environment, and its output is
6010 used as the possible completions.
6012 \fB\-F\fP \fIfunction\fP
6013 The shell function \fIfunction\fP is executed in the current shell
6015 When it finishes, the possible completions are retrieved from the value
6021 \fB\-X\fP \fIfilterpat\fP
6022 \fIfilterpat\fP is a pattern as used for filename expansion.
6023 It is applied to the list of possible completions generated by the
6024 preceding options and arguments, and each completion matching
6025 \fIfilterpat\fP is removed from the list.
6026 A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
6027 case, any completion not matching \fIfilterpat\fP is removed.
6029 \fB\-P\fP \fIprefix\fP
6030 \fIprefix\fP is added at the beginning of each possible completion
6031 after all other options have been applied.
6033 \fB\-S\fP \fIsuffix\fP
6034 \fIsuffix\fP is appended to each possible completion
6035 after all other options have been applied.
6038 The return value is true unless an invalid option is supplied, an option
6039 other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
6040 argument, an attempt is made to remove a completion specification for
6041 a \fIname\fP for which no specification exists, or
6042 an error occurs adding a completion specification.
6045 \fBcontinue\fP [\fIn\fP]
6046 Resume the next iteration of the enclosing
6055 is specified, resume at the \fIn\fPth enclosing loop.
6059 is greater than the number of enclosing loops, the last enclosing loop
6060 (the ``top-level'' loop) is resumed. The return value is 0 unless the
6061 shell is not executing a loop when
6065 \fBdeclare\fP [\fB\-afFirtx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP]]
6068 \fBtypeset\fP [\fB\-afFirtx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP]]
6070 Declare variables and/or give them attributes.
6071 If no \fIname\fPs are given then display the values of variables.
6074 option will display the attributes and values of each
6078 is used, additional options are ignored.
6081 option inhibits the display of function definitions; only the
6082 function name and attributes are printed.
6087 The following options can
6088 be used to restrict output to variables with the specified attribute or
6089 to give variables attributes:
6094 Each \fIname\fP is an array variable (see
6099 Use function names only.
6102 The variable is treated as an integer; arithmetic evaluation (see
6104 .B "ARITHMETIC EVALUATION" ") "
6105 is performed when the variable is assigned a value.
6108 Make \fIname\fPs readonly. These names cannot then be assigned values
6109 by subsequent assignment statements or unset.
6112 Give each \fIname\fP the \fItrace\fP attribute.
6113 Traced functions inherit the \fBDEBUG\fP trap from the calling shell.
6114 The trace attribute has no special meaning for variables.
6117 Mark \fIname\fPs for export to subsequent commands via the environment.
6120 Using `+' instead of `\-'
6121 turns off the attribute instead, with the exception that \fB+a\fP
6122 may not be used to destroy an array variable. When used in a function,
6124 \fIname\fP local, as with the
6126 command. The return value is 0 unless an invalid option is encountered,
6127 an attempt is made to define a function using
6128 .if n ``\-f foo=bar'',
6129 .if t \f(CW\-f foo=bar\fP,
6130 an attempt is made to assign a value to a readonly variable,
6131 an attempt is made to assign a value to an array variable without
6132 using the compound assignment syntax (see
6134 above), one of the \fInames\fP is not a valid shell variable name,
6135 an attempt is made to turn off readonly status for a readonly variable,
6136 an attempt is made to turn off array status for an array variable,
6137 or an attempt is made to display a non-existent function with \fB\-f\fP.
6140 .B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
6141 Without options, displays the list of currently remembered directories.
6142 The default display is on a single line with directory names separated
6144 Directories are added to the list with the
6148 command removes entries from the list.
6153 Displays the \fIn\fPth entry counting from the left of the list
6156 when invoked without options, starting with zero.
6159 Displays the \fIn\fPth entry counting from the right of the list
6162 when invoked without options, starting with zero.
6165 Clears the directory stack by deleting all of the entries.
6168 Produces a longer listing; the default listing format uses a
6169 tilde to denote the home directory.
6172 Print the directory stack with one entry per line.
6175 Print the directory stack with one entry per line,
6176 prefixing each entry with its index in the stack.
6179 The return value is 0 unless an
6180 invalid option is supplied or \fIn\fP indexes beyond the end
6181 of the directory stack.
6184 \fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ...]
6185 Without options, each
6187 is removed from the table of active jobs.
6188 If the \fB\-h\fP option is given, each
6190 is not removed from the table, but is marked so that
6193 is not sent to the job if the shell receives a
6198 is present, and neither the
6202 option is supplied, the \fIcurrent job\fP is used.
6207 option means to remove or mark all jobs; the
6211 argument restricts operation to running jobs.
6212 The return value is 0 unless a
6214 does not specify a valid job.
6216 \fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
6217 Output the \fIarg\fPs, separated by spaces, followed by a newline.
6218 The return status is always 0.
6219 If \fB\-n\fP is specified, the trailing newline is
6220 suppressed. If the \fB\-e\fP option is given, interpretation of
6221 the following backslash-escaped characters is enabled. The
6223 option disables the interpretation of these escape characters,
6224 even on systems where they are interpreted by default.
6225 The \fBxpg_echo\fP shell option may be used to
6226 dynamically determine whether or not \fBecho\fP expands these
6227 escape characters by default.
6231 to mean the end of options.
6233 interprets the following escape sequences:
6244 suppress trailing newline
6268 the eight-bit character whose value is the octal value \fInnn\fP
6269 (zero to three octal digits)
6272 the eight-bit character whose value is the octal value \fInnn\fP
6273 (one to three octal digits)
6276 the eight-bit character whose value is the hexadecimal value \fIHH\fP
6277 (one or two hex digits)
6281 \fBenable\fP [\fB\-adnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
6282 Enable and disable builtin shell commands.
6283 Disabling a builtin allows a disk command which has the same name
6284 as a shell builtin to be executed without specifying a full pathname,
6285 even though the shell normally searches for builtins before disk commands.
6286 If \fB\-n\fP is used, each \fIname\fP
6287 is disabled; otherwise,
6288 \fInames\fP are enabled. For example, to use the
6290 binary found via the
6293 instead of the shell builtin version, run
6294 .if t \f(CWenable -n test\fP.
6295 .if n ``enable -n test''.
6298 option means to load the new builtin command
6302 on systems that support dynamic loading. The
6304 option will delete a builtin previously loaded with
6306 If no \fIname\fP arguments are given, or if the
6308 option is supplied, a list of shell builtins is printed.
6309 With no other option arguments, the list consists of all enabled
6311 If \fB\-n\fP is supplied, only disabled builtins are printed.
6312 If \fB\-a\fP is supplied, the list printed includes all builtins, with an
6313 indication of whether or not each is enabled.
6314 If \fB\-s\fP is supplied, the output is restricted to the POSIX
6315 \fIspecial\fP builtins.
6316 The return value is 0 unless a
6318 is not a shell builtin or there is an error loading a new builtin
6319 from a shared object.
6321 \fBeval\fP [\fIarg\fP ...]
6322 The \fIarg\fPs are read and concatenated together into a single
6323 command. This command is then read and executed by the shell, and
6324 its exit status is returned as the value of
6328 or only null arguments,
6332 \fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
6335 is specified, it replaces the shell.
6336 No new process is created. The
6338 become the arguments to \fIcommand\fP.
6342 the shell places a dash at the beginning of the zeroth arg passed to
6350 to be executed with an empty environment. If
6352 is supplied, the shell passes
6354 as the zeroth argument to the executed command. If
6356 cannot be executed for some reason, a non-interactive shell exits,
6357 unless the shell option
6359 is enabled, in which case it returns failure.
6360 An interactive shell returns failure if the file cannot be executed.
6363 is not specified, any redirections take effect in the current shell,
6364 and the return status is 0. If there is a redirection error, the
6367 \fBexit\fP [\fIn\fP]
6368 Cause the shell to exit
6369 with a status of \fIn\fP. If
6371 is omitted, the exit status
6372 is that of the last command executed.
6376 is executed before the shell terminates.
6378 \fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
6385 are marked for automatic export to the environment of
6386 subsequently executed commands. If the
6394 are given, or if the
6396 option is supplied, a list
6397 of all names that are exported in this shell is printed.
6400 option causes the export property to be removed from the
6403 returns an exit status of 0 unless an invalid option is
6405 one of the \fInames\fP is not a valid shell variable name, or
6409 that is not a function.
6411 \fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-nlr\fP] [\fIfirst\fP] [\fIlast\fP]
6414 \fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
6416 Fix Command. In the first form, a range of commands from
6420 is selected from the history list.
6424 may be specified as a string (to locate the last command beginning
6425 with that string) or as a number (an index into the history list,
6426 where a negative number is used as an offset from the current
6429 is not specified it is set to
6430 the current command for listing (so that
6431 .if n ``fc \-l \-10''
6432 .if t \f(CWfc \-l \-10\fP
6433 prints the last 10 commands) and to
6438 is not specified it is set to the previous
6439 command for editing and \-16 for listing.
6444 the command numbers when listing. The
6446 option reverses the order of
6447 the commands. If the
6450 the commands are listed on
6451 standard output. Otherwise, the editor given by
6454 on a file containing those commands. If
6460 variable is used, and
6467 is not set. If neither variable is set,
6469 is used. When editing is complete, the edited commands are
6470 echoed and executed.
6472 In the second form, \fIcommand\fP is re-executed after each instance
6473 of \fIpat\fP is replaced by \fIrep\fP.
6474 A useful alias to use with this is
6476 .if t \f(CWr='fc \-s'\fP,
6480 runs the last command beginning with
6486 re-executes the last command.
6488 If the first form is used, the return value is 0 unless an invalid
6489 option is encountered or
6493 specify history lines out of range.
6496 option is supplied, the return value is the value of the last
6497 command executed or failure if an error occurs with the temporary
6498 file of commands. If the second form is used, the return status
6499 is that of the command re-executed, unless
6501 does not specify a valid history line, in which case
6505 \fBfg\fP [\fIjobspec\fP]
6508 in the foreground, and make it the current job.
6511 is not present, the shell's notion of the \fIcurrent job\fP is used.
6512 The return value is that of the command placed into the foreground,
6513 or failure if run when job control is disabled or, when run with
6514 job control enabled, if
6516 does not specify a valid job or
6518 specifies a job that was started without job control.
6520 \fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
6522 is used by shell procedures to parse positional parameters.
6524 contains the option characters to be recognized; if a character
6525 is followed by a colon, the option is expected to have an
6526 argument, which should be separated from it by white space.
6527 The colon and question mark characters may not be used as
6529 Each time it is invoked,
6531 places the next option in the shell variable
6535 if it does not exist,
6536 and the index of the next argument to be processed into the
6542 is initialized to 1 each time the shell or a shell script
6543 is invoked. When an option requires an argument,
6545 places that argument into the variable
6548 The shell does not reset
6551 automatically; it must be manually reset between multiple
6554 within the same shell invocation if a new set of parameters
6557 When the end of options is encountered, \fBgetopts\fP exits with a
6558 return value greater than zero.
6559 \fBOPTIND\fP is set to the index of the first non-option argument,
6560 and \fBname\fP is set to ?.
6563 normally parses the positional parameters, but if more arguments are
6567 parses those instead.
6570 can report errors in two ways. If the first character of
6574 error reporting is used. In normal operation diagnostic messages
6575 are printed when invalid options or missing option arguments are
6580 is set to 0, no error messages will be displayed, even if the first
6585 If an invalid option is seen,
6590 prints an error message and unsets
6596 the option character found is placed in
6599 and no diagnostic message is printed.
6601 If a required argument is not found, and
6604 a question mark (\^\fB?\fP\^) is placed in
6608 is unset, and a diagnostic message is printed.
6611 is silent, then a colon (\^\fB:\fP\^) is placed in
6616 is set to the option character found.
6619 returns true if an option, specified or unspecified, is found.
6620 It returns false if the end of options is encountered or an
6623 \fBhash\fP [\fB\-lr\fP] [\fB\-p\fP \fIfilename\fP] [\fB\-dt\fP] [\fIname\fP]
6626 the full file name of the command is determined by searching
6632 option is supplied, no path search is performed, and
6634 is used as the full file name of the command.
6637 option causes the shell to forget all
6638 remembered locations.
6641 option causes the shell to forget the remembered location of each \fIname\fP.
6644 option is supplied, the full pathname to which each \fIname\fP corresponds
6645 is printed. If multiple \fIname\fP arguments are supplied with \fB\-t\fP,
6646 the \fIname\fP is printed before the hashed full pathname.
6649 option causes output to be displayed in a format that may be reused as input.
6650 If no arguments are given, or if only \fB\-l\fP is supplied,
6651 information about remembered commands is printed.
6652 The return status is true unless a
6654 is not found or an invalid option is supplied.
6656 \fBhelp\fP [\fB\-s\fP] [\fIpattern\fP]
6657 Display helpful information about builtin commands. If
6661 gives detailed help on all commands matching
6663 otherwise help for all the builtins and shell control structures
6665 The \fB\-s\fP option restricts the information displayed to a short
6667 The return status is 0 unless no command matches
6670 \fBhistory [\fIn\fP]
6673 \fBhistory\fP \fB\-c\fP
6675 \fBhistory \-d\fP \fIoffset\fP
6677 \fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
6679 \fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
6681 \fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
6683 With no options, display the command
6684 history list with line numbers. Lines listed
6687 have been modified. An argument of
6691 lines. If \fIfilename\fP is supplied, it is used as the
6692 name of the history file; if not, the value of
6695 is used. Options, if supplied, have the following meanings:
6700 Clear the history list by deleting all the entries.
6702 \fB\-d\fP \fIoffset\fP
6703 Delete the history entry at position \fIoffset\fP.
6706 Append the ``new'' history lines (history lines entered since the
6707 beginning of the current \fBbash\fP session) to the history file.
6710 Read the history lines not already read from the history
6711 file into the current history list. These are lines
6712 appended to the history file since the beginning of the
6713 current \fBbash\fP session.
6716 Read the contents of the history file
6717 and use them as the current history.
6720 Write the current history to the history file, overwriting the
6721 history file's contents.
6724 Perform history substitution on the following \fIargs\fP and display
6725 the result on the standard output.
6726 Does not store the results in the history list.
6727 Each \fIarg\fP must be quoted to disable normal history expansion.
6732 in the history list as a single entry. The last command in the
6733 history list is removed before the
6738 The return value is 0 unless an invalid option is encountered, an
6739 error occurs while reading or writing the history file, an invalid
6740 \fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
6741 history expansion supplied as an argument to \fB\-p\fP fails.
6744 \fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
6747 \fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
6749 The first form lists the active jobs. The options have the following
6756 in addition to the normal information.
6759 List only the process ID of the job's process group
6763 Display information only about jobs that have changed status since
6764 the user was last notified of their status.
6767 Restrict output to running jobs.
6770 Restrict output to stopped jobs.
6775 is given, output is restricted to information about that job.
6776 The return status is 0 unless an invalid option is encountered
6791 with the corresponding process group ID, and executes
6795 returning its exit status.
6798 \fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
6801 \fBkill\fP \fB\-l\fP [\fIsigspec\fP | \fIexit_status\fP]
6803 Send the signal named by
6807 to the processes named by
6812 is either a signal name such as
6817 is a signal number. If
6819 is a signal name, the name may be
6820 given with or without the
6826 is not present, then
6832 lists the signal names.
6833 If any arguments are supplied when
6835 is given, the names of the signals corresponding to the arguments are
6836 listed, and the return status is 0.
6837 The \fIexit_status\fP argument to
6839 is a number specifying either a signal number or the exit status of
6840 a process terminated by a signal.
6842 returns true if at least one signal was successfully sent, or false
6843 if an error occurs or an invalid option is encountered.
6845 \fBlet\fP \fIarg\fP [\fIarg\fP ...]
6848 is an arithmetic expression to be evaluated (see
6850 .BR "ARITHMETIC EVALUATION" ).
6855 returns 1; 0 is returned otherwise.
6857 \fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ...]
6858 For each argument, a local variable named
6860 is created, and assigned
6862 The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
6865 is used within a function, it causes the variable
6867 to have a visible scope restricted to that function and its children.
6870 writes a list of local variables to the standard output. It is
6873 when not within a function. The return status is 0 unless
6875 is used outside a function, an invalid
6878 \fIname\fP is a readonly variable.
6883 \fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
6884 Removes entries from the directory stack. With no arguments,
6885 removes the top directory from the stack, and performs a
6887 to the new top directory.
6888 Arguments, if supplied, have the following meanings:
6893 Removes the \fIn\fPth entry counting from the left of the list
6896 starting with zero. For example:
6898 .if t \f(CWpopd +0\fP
6899 removes the first directory,
6901 .if t \f(CWpopd +1\fP
6905 Removes the \fIn\fPth entry counting from the right of the list
6908 starting with zero. For example:
6910 .if t \f(CWpopd -0\fP
6911 removes the last directory,
6913 .if t \f(CWpopd -1\fP
6917 Suppresses the normal change of directory when removing directories
6918 from the stack, so that only the stack is manipulated.
6923 command is successful, a
6925 is performed as well, and the return status is 0.
6927 returns false if an invalid option is encountered, the directory stack
6928 is empty, a non-existent directory stack entry is specified, or the
6929 directory change fails.
6932 \fBprintf\fP \fIformat\fP [\fIarguments\fP]
6933 Write the formatted \fIarguments\fP to the standard output under the
6934 control of the \fIformat\fP.
6935 The \fIformat\fP is a character string which contains three types of objects:
6936 plain characters, which are simply copied to standard output, character
6937 escape sequences, which are converted and copied to the standard output, and
6938 format specifications, each of which causes printing of the next successive
6940 In addition to the standard \fIprintf\fP(1) formats, \fB%b\fP causes
6941 \fBprintf\fP to expand backslash escape sequences in the corresponding
6942 \fIargument\fP, and \fB%q\fP causes \fBprintf\fP to output the corresponding
6943 \fIargument\fP in a format that can be reused as shell input.
6945 The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
6946 If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
6947 extra format specifications behave as if a zero value or null string, as
6948 appropriate, had been supplied. The return value is zero on success,
6949 non-zero on failure.
6951 \fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
6954 \fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
6956 Adds a directory to the top of the directory stack, or rotates
6957 the stack, making the new top of the stack the current working
6958 directory. With no arguments, exchanges the top two directories
6959 and returns 0, unless the directory stack is empty.
6960 Arguments, if supplied, have the following meanings:
6965 Rotates the stack so that the \fIn\fPth directory
6966 (counting from the left of the list shown by
6972 Rotates the stack so that the \fIn\fPth directory
6973 (counting from the right of the list shown by
6975 starting with zero) is at the top.
6978 Suppresses the normal change of directory when adding directories
6979 to the stack, so that only the stack is manipulated.
6984 to the directory stack at the top, making it the
6985 new current working directory.
6990 command is successful, a
6992 is performed as well.
6993 If the first form is used,
6995 returns 0 unless the cd to
6997 fails. With the second form,
6999 returns 0 unless the directory stack is empty,
7000 a non-existent directory stack element is specified,
7001 or the directory change to the specified new current directory
7005 \fBpwd\fP [\fB\-LP\fP]
7006 Print the absolute pathname of the current working directory.
7007 The pathname printed contains no symbolic links if the
7009 option is supplied or the
7013 builtin command is enabled.
7016 option is used, the pathname printed may contain symbolic links.
7017 The return status is 0 unless an error occurs while
7018 reading the name of the current directory or an
7019 invalid option is supplied.
7021 \fBread\fP [\fB\-ers\fP] [\fB\-u\fP \fIfd\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 ...]
7022 One line is read from the standard input, or from the file descriptor
7023 \fIfd\fP supplied as an argument to the \fB\-u\fP option, and the first word
7024 is assigned to the first
7026 the second word to the second
7028 and so on, with leftover words and their intervening separators assigned
7031 If there are fewer words read from the input stream than names,
7032 the remaining names are assigned empty values.
7036 are used to split the line into words.
7037 The backslash character (\fB\e\fP) may be used to remove any special
7038 meaning for the next character read and for line continuation.
7039 Options, if supplied, have the following meanings:
7044 The words are assigned to sequential indices
7045 of the array variable
7049 is unset before any new values are assigned.
7050 Other \fIname\fP arguments are ignored.
7053 The first character of \fIdelim\fP is used to terminate the input line,
7054 rather than newline.
7057 If the standard input
7058 is coming from a terminal,
7063 above) is used to obtain the line.
7066 \fBread\fP returns after reading \fInchars\fP characters rather than
7067 waiting for a complete line of input.
7070 Display \fIprompt\fP on standard error, without a
7071 trailing newline, before attempting to read any input. The prompt
7072 is displayed only if input is coming from a terminal.
7075 Backslash does not act as an escape character.
7076 The backslash is considered to be part of the line.
7077 In particular, a backslash-newline pair may not be used as a line
7081 Silent mode. If input is coming from a terminal, characters are
7084 .B \-t \fItimeout\fP
7085 Cause \fBread\fP to time out and return failure if a complete line of
7086 input is not read within \fItimeout\fP seconds.
7087 This option has no effect if \fBread\fP is not reading input from the
7091 Read input from file descriptor \fIfd\fP.
7096 are supplied, the line read is assigned to the variable
7099 The return code is zero, unless end-of-file is encountered, \fBread\fP
7100 times out, or an invalid file descriptor is supplied as the argument to
7104 \fBreadonly\fP [\fB\-apf\fP] [\fIname\fP ...]
7107 \fInames\fP are marked readonly; the values of these
7109 may not be changed by subsequent assignment.
7112 option is supplied, the functions corresponding to the
7117 option restricts the variables to arrays.
7120 arguments are given, or if the
7122 option is supplied, a list of all readonly names is printed.
7125 option causes output to be displayed in a format that
7126 may be reused as input.
7127 The return status is 0 unless an invalid option is encountered,
7130 is not a valid shell variable name, or
7134 that is not a function.
7136 \fBreturn\fP [\fIn\fP]
7137 Causes a function to exit with the return value specified by
7141 is omitted, the return status is that of the last command
7142 executed in the function body. If used outside a function,
7143 but during execution of a script by the
7145 (\fBsource\fP) command, it causes the shell to stop executing
7146 that script and return either
7148 or the exit status of the last command executed within the
7149 script as the exit status of the script. If used outside a
7150 function and not during execution of a script by \fB.\fP\^,
7151 the return status is false.
7153 \fBset\fP [\fB\-\-abefhkmnptuvxBCHP\fP] [\fB\-o\fP \fIoption\fP] [\fIarg\fP ...]
7154 Without options, the name and value of each shell variable are displayed
7155 in a format that can be reused as input.
7156 The output is sorted according to the current locale.
7157 When options are specified, they set or unset shell attributes.
7158 Any arguments remaining after the options are processed are treated
7159 as values for the positional parameters and are assigned, in order, to
7164 Options, if specified, have the following meanings:
7169 Automatically mark variables and functions which are modified or created
7170 for export to the environment of subsequent commands.
7173 Report the status of terminated background jobs
7174 immediately, rather than before the next primary prompt. This is
7175 effective only when job control is enabled.
7178 Exit immediately if a \fIsimple command\fP (see
7181 above) exits with a non-zero status. The shell does not exit if the
7182 command that fails is part of an
7189 statement, part of a
7193 list, or if the command's return value is
7196 A trap on \fBERR\fP, if set, is executed before the shell exits.
7199 Disable pathname expansion.
7202 Remember the location of commands as they are looked up for execution.
7203 This is enabled by default.
7206 All arguments in the form of assignment statements
7207 are placed in the environment for a command, not just
7208 those that precede the command name.
7211 Monitor mode. Job control is enabled. This option is on
7212 by default for interactive shells on systems that support
7216 above). Background processes run in a separate process
7217 group and a line containing their exit status is printed
7218 upon their completion.
7221 Read commands but do not execute them. This may be used to
7222 check a shell script for syntax errors. This is ignored by
7225 .B \-o \fIoption\-name\fP
7226 The \fIoption\-name\fP can be one of the following:
7238 Use an emacs-style command line editing interface. This is enabled
7239 by default when the shell is interactive, unless the shell is started
7257 Enable command history, as described above under
7260 This option is on by default in interactive shells.
7263 The effect is as if the shell command
7264 .if t \f(CWIGNOREEOF=10\fP
7265 .if n ``IGNOREEOF=10''
7310 Change the behavior of
7312 where the default operation differs
7313 from the POSIX 1003.2 standard to match the standard (\fIposix mode\fP).
7324 Use a vi-style command line editing interface.
7333 is supplied with no \fIoption\-name\fP, the values of the current options are
7337 is supplied with no \fIoption\-name\fP, a series of
7339 commands to recreate the current option settings is displayed on
7340 the standard output.
7346 mode. In this mode, the
7352 files are not processed, shell functions are not inherited from the
7353 environment, and the
7356 variable, if it appears in the environment, is ignored.
7357 If the shell is started with the effective user (group) id not equal to the
7358 real user (group) id, and the \fB\-p\fP option is not supplied, these actions
7359 are taken and the effective user id is set to the real user id.
7360 If the \fB\-p\fP option is supplied at startup, the effective user id is
7362 Turning this option off causes the effective user
7363 and group ids to be set to the real user and group ids.
7366 Exit after reading and executing one command.
7369 Treat unset variables as an error when performing
7370 parameter expansion. If expansion is attempted on an
7371 unset variable, the shell prints an error message, and,
7372 if not interactive, exits with a non-zero status.
7375 Print shell input lines as they are read.
7378 After expanding each \fIsimple command\fP,
7379 display the expanded value of
7382 followed by the command and its expanded arguments.
7385 The shell performs brace expansion (see
7387 above). This is on by default.
7392 does not overwrite an existing file with the
7397 redirection operators. This may be overridden when
7398 creating output files by using the redirection operator
7406 style history substitution. This option is on by
7407 default when the shell is interactive.
7410 If set, the shell does not follow symbolic links when executing
7413 that change the current working directory. It uses the
7414 physical directory structure instead. By default,
7416 follows the logical chain of directories when performing commands
7417 which change the current directory.
7420 If no arguments follow this option, then the positional parameters are
7421 unset. Otherwise, the positional parameters are set to the
7422 \fIarg\fPs, even if some of them begin with a
7426 Signal the end of options, cause all remaining \fIarg\fPs to be
7427 assigned to the positional parameters. The
7431 options are turned off.
7432 If there are no \fIarg\fPs,
7433 the positional parameters remain unchanged.
7436 The options are off by default unless otherwise noted.
7437 Using + rather than \- causes these options to be turned off.
7438 The options can also be specified as arguments to an invocation of
7440 The current set of options may be found in
7442 The return status is always true unless an invalid option is encountered.
7445 \fBshift\fP [\fIn\fP]
7446 The positional parameters from \fIn\fP+1 ... are renamed to
7449 Parameters represented by the numbers \fB$#\fP
7450 down to \fB$#\fP\-\fIn\fP+1 are unset.
7452 must be a non-negative number less than or equal to \fB$#\fP.
7455 is 0, no parameters are changed.
7458 is not given, it is assumed to be 1.
7461 is greater than \fB$#\fP, the positional parameters are not changed.
7462 The return status is greater than zero if
7466 or less than zero; otherwise 0.
7468 \fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
7469 Toggle the values of variables controlling optional shell behavior.
7470 With no options, or with the
7472 option, a list of all settable options is displayed, with
7473 an indication of whether or not each is set.
7474 The \fB\-p\fP option causes output to be displayed in a form that
7475 may be reused as input.
7476 Other options have the following meanings:
7481 Enable (set) each \fIoptname\fP.
7484 Disable (unset) each \fIoptname\fP.
7487 Suppresses normal output (quiet mode); the return status indicates
7488 whether the \fIoptname\fP is set or unset.
7489 If multiple \fIoptname\fP arguments are given with
7491 the return status is zero if all \fIoptnames\fP are enabled; non-zero
7495 Restricts the values of \fIoptname\fP to be those defined for the
7506 is used with no \fIoptname\fP arguments, the display is limited to
7507 those options which are set or unset, respectively.
7508 Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
7511 The return status when listing options is zero if all \fIoptnames\fP
7512 are enabled, non-zero otherwise. When setting or unsetting options,
7513 the return status is zero unless an \fIoptname\fP is not a valid shell
7516 The list of \fBshopt\fP options is:
7522 If set, an argument to the
7524 builtin command that
7525 is not a directory is assumed to be the name of a variable whose
7526 value is the directory to change to.
7529 If set, minor errors in the spelling of a directory component in a
7531 command will be corrected.
7532 The errors checked for are transposed characters,
7533 a missing character, and one character too many.
7534 If a correction is found, the corrected file name is printed,
7535 and the command proceeds.
7536 This option is only used by interactive shells.
7539 If set, \fBbash\fP checks that a command found in the hash
7540 table exists before trying to execute it. If a hashed command no
7541 longer exists, a normal path search is performed.
7544 If set, \fBbash\fP checks the window size after each command
7545 and, if necessary, updates the values of
7555 attempts to save all lines of a multiple-line
7556 command in the same history entry. This allows
7557 easy re-editing of multi-line commands.
7562 includes filenames beginning with a `.' in the results of pathname
7566 If set, a non-interactive shell will not exit if
7567 it cannot execute the file specified as an argument to the
7569 builtin command. An interactive shell does not exit if
7574 If set, aliases are expanded as described above under
7577 This option is enabled by default for interactive shells.
7580 If set, the extended pattern matching features described above under
7581 \fBPathname Expansion\fP are enabled.
7584 If set, the history list is appended to the file named by the value
7587 variable when the shell exits, rather than overwriting the file.
7592 is being used, a user is given the opportunity to re-edit a
7593 failed history substitution.
7598 is being used, the results of history substitution are not immediately
7599 passed to the shell parser. Instead, the resulting line is loaded into
7600 the \fBreadline\fP editing buffer, allowing further modification.
7605 is being used, \fBbash\fP will attempt to perform hostname completion when a
7606 word containing a \fB@\fP is being completed (see
7612 This is enabled by default.
7615 If set, \fBbash\fP will send
7618 to all jobs when an interactive login shell exits.
7620 .B interactive_comments
7621 If set, allow a word beginning with
7623 to cause that word and all remaining characters on that
7624 line to be ignored in an interactive shell (see
7627 above). This option is enabled by default.
7632 option is enabled, multi-line commands are saved to the history with
7633 embedded newlines rather than using semicolon separators where possible.
7636 The shell sets this option if it is started as a login shell (see
7640 The value may not be changed.
7643 If set, and a file that \fBbash\fP is checking for mail has been
7644 accessed since the last time it was checked, the message ``The mail in
7645 \fImailfile\fP has been read'' is displayed.
7647 .B no_empty_cmd_completion
7652 will not attempt to search the \fBPATH\fP for possible completions when
7653 completion is attempted on an empty line.
7658 matches filenames in a case\-insensitive fashion when performing pathname
7660 .B Pathname Expansion
7666 allows patterns which match no
7668 .B Pathname Expansion
7670 to expand to a null string, rather than themselves.
7673 If set, the programmable completion facilities (see
7674 \fBProgrammable Completion\fP above) are enabled.
7675 This option is enabled by default.
7678 If set, prompt strings undergo variable and parameter expansion after
7679 being expanded as described in
7682 above. This option is enabled by default.
7685 The shell sets this option if it is started in restricted mode (see
7687 .B "RESTRICTED SHELL"
7689 The value may not be changed.
7690 This is not reset when the startup files are executed, allowing
7691 the startup files to discover whether or not a shell is restricted.
7696 builtin prints an error message when the shift count exceeds the
7697 number of positional parameters.
7701 \fBsource\fP (\fB.\fP) builtin uses the value of
7704 to find the directory containing the file supplied as an argument.
7705 This option is enabled by default.
7708 If set, the \fBecho\fP builtin expands backslash-escape sequences
7712 \fBsuspend\fP [\fB\-f\fP]
7713 Suspend the execution of this shell until it receives a
7718 option says not to complain if this is
7719 a login shell; just suspend anyway. The return status is 0 unless
7720 the shell is a login shell and
7722 is not supplied, or if job control is not enabled.
7724 \fBtest\fP \fIexpr\fP
7727 \fB[\fP \fIexpr\fP \fB]\fP
7728 Return a status of 0 or 1 depending on
7729 the evaluation of the conditional expression
7731 Each operator and operand must be a separate argument.
7732 Expressions are composed of the primaries described above under
7734 .BR "CONDITIONAL EXPRESSIONS" .
7737 Expressions may be combined using the following operators, listed
7738 in decreasing order of precedence.
7748 Returns the value of \fIexpr\fP.
7749 This may be used to override the normal precedence of operators.
7751 \fIexpr1\fP \-\fBa\fP \fIexpr2\fP
7758 \fIexpr1\fP \-\fBo\fP \fIexpr2\fP
7766 \fBtest\fP and \fB[\fP evaluate conditional
7767 expressions using a set of rules based on the number of arguments.
7773 The expression is false.
7776 The expression is true if and only if the argument is not null.
7779 If the first argument is \fB!\fP, the expression is true if and
7780 only if the second argument is null.
7781 If the first argument is one of the unary conditional operators listed above
7784 .BR "CONDITIONAL EXPRESSIONS" ,
7785 the expression is true if the unary test is true.
7786 If the first argument is not a valid unary conditional operator, the expression
7790 If the second argument is one of the binary conditional operators listed above
7793 .BR "CONDITIONAL EXPRESSIONS" ,
7794 the result of the expression is the result of the binary test using
7795 the first and third arguments as operands.
7796 If the first argument is \fB!\fP, the value is the negation of
7797 the two-argument test using the second and third arguments.
7798 If the first argument is exactly \fB(\fP and the third argument is
7799 exactly \fB)\fP, the result is the one-argument test of the second
7801 Otherwise, the expression is false.
7802 The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
7806 If the first argument is \fB!\fP, the result is the negation of
7807 the three-argument expression composed of the remaining arguments.
7808 Otherwise, the expression is parsed and evaluated according to
7809 precedence using the rules listed above.
7812 The expression is parsed and evaluated according to precedence
7813 using the rules listed above.
7818 Print the accumulated user and system times for the shell and
7819 for processes run from the shell. The return status is 0.
7821 \fBtrap\fP [\fB\-lp\fP] [\fIarg\fP] [\fIsigspec\fP ...]
7824 is to be read and executed when the shell receives
7831 all specified signals are
7832 reset to their original values (the values they had
7833 upon entrance to the shell).
7836 is the null string the signal specified by each
7838 is ignored by the shell and by the commands it invokes.
7843 has been supplied, then the trap commands associated with each
7846 If no arguments are supplied or if only
7850 prints the list of commands associated with each signal number.
7854 a signal name defined in <\fIsignal.h\fP>, or a signal number.
7862 is executed on exit from the shell.
7870 is executed after every \fIsimple command\fP (see
7881 is executed whenever a simple command has a non\-zero exit status.
7885 trap is not executed if the failed command is part of an
7892 statement, part of a
7896 list, or if the command's return value is
7901 option causes the shell to print a list of signal names and
7902 their corresponding numbers.
7903 Signals ignored upon entry to the shell cannot be trapped or reset.
7904 Trapped signals are reset to their original values in a child
7905 process when it is created.
7906 The return status is false if any
7908 is invalid; otherwise
7912 \fBtype\fP [\fB\-aftpP\fP] \fIname\fP [\fIname\fP ...]
7916 would be interpreted if used as a command name.
7921 prints a string which is one of
7930 is an alias, shell reserved word, function, builtin, or disk file,
7934 is not found, then nothing is printed, and an exit status of false
7940 either returns the name of the disk file
7941 that would be executed if
7943 were specified as a command name,
7945 .if t \f(CWtype -t name\fP
7946 .if n ``type -t name''
7954 search for each \fIname\fP, even if
7955 .if t \f(CWtype -t name\fP
7956 .if n ``type -t name''
7959 If a command is hashed,
7963 print the hashed value, not necessarily the file that appears
7971 prints all of the places that contain
7974 This includes aliases and functions,
7977 option is not also used.
7978 The table of hashed commands is not consulted
7983 option suppresses shell function lookup, as with the \fBcommand\fP builtin.
7985 returns true if any of the arguments are found, false if
7988 \fBulimit\fP [\fB\-SHacdflmnpstuv\fP [\fIlimit\fP]]
7989 Provides control over the resources available to the shell and to
7990 processes started by it, on systems that allow such control.
7991 The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
7992 set for the given resource. A hard limit cannot be increased once it
7993 is set; a soft limit may be increased up to the value of the hard limit.
7994 If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
7998 can be a number in the unit specified for the resource
7999 or one of the special values
8004 which stand for the current hard limit, the current soft limit, and
8005 no limit, respectively.
8008 is omitted, the current value of the soft limit of the resource is
8009 printed, unless the \fB\-H\fP option is given. When more than one
8010 resource is specified, the limit name and unit are printed before the value.
8011 Other options are interpreted as follows:
8016 All current limits are reported
8019 The maximum size of core files created
8022 The maximum size of a process's data segment
8025 The maximum size of files created by the shell
8028 The maximum size that may be locked into memory
8031 The maximum resident set size
8034 The maximum number of open file descriptors (most systems do not
8035 allow this value to be set)
8038 The pipe size in 512-byte blocks (this may not be set)
8041 The maximum stack size
8044 The maximum amount of cpu time in seconds
8047 The maximum number of processes available to a single user
8050 The maximum amount of virtual memory available to the shell
8055 is given, it is the new value of the specified resource (the
8057 option is display only).
8058 If no option is given, then
8060 is assumed. Values are in 1024-byte increments, except for
8062 which is in seconds,
8064 which is in units of 512-byte blocks,
8069 which are unscaled values.
8070 The return status is 0 unless an invalid option or argument is supplied,
8071 or an error occurs while setting a new limit.
8074 \fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
8075 The user file-creation mask is set to
8079 begins with a digit, it
8080 is interpreted as an octal number; otherwise
8081 it is interpreted as a symbolic mode mask similar
8086 is omitted, the current value of the mask is printed.
8089 option causes the mask to be printed in symbolic form; the
8090 default output is an octal number.
8093 option is supplied, and
8095 is omitted, the output is in a form that may be reused as input.
8096 The return status is 0 if the mode was successfully changed or if
8097 no \fImode\fP argument was supplied, and false otherwise.
8099 \fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
8100 Remove each \fIname\fP from the list of defined aliases. If
8102 is supplied, all alias definitions are removed. The return
8103 value is true unless a supplied
8105 is not a defined alias.
8107 \fBunset\fP [\-\fBfv\fP] [\fIname\fP ...]
8110 remove the corresponding variable or function.
8111 If no options are supplied, or the
8113 option is given, each
8115 refers to a shell variable.
8116 Read-only variables may not be unset.
8122 refers to a shell function, and the function definition
8124 Each unset variable or function is removed from the environment
8125 passed to subsequent commands.
8142 are unset, they lose their special properties, even if they are
8143 subsequently reset. The exit status is true unless a
8145 does not exist or is readonly.
8147 \fBwait\fP [\fIn\fP]
8148 Wait for the specified process and return its termination
8152 ID or a job specification; if a job spec is given, all processes
8153 in that job's pipeline are waited for. If
8155 is not given, all currently active child processes
8156 are waited for, and the return status is zero. If
8158 specifies a non-existent process or job, the return status is
8159 127. Otherwise, the return status is the exit status of the last
8160 process or job waited for.
8163 .SH "RESTRICTED SHELL"
8169 is started with the name
8173 option is supplied at invocation,
8174 the shell becomes restricted.
8175 A restricted shell is used to
8176 set up an environment more controlled than the standard shell.
8177 It behaves identically to
8179 with the exception that the following are disallowed or not performed:
8181 changing directories with \fBcd\fP
8183 setting or unsetting the values of
8190 specifying command names containing
8193 specifying a file name containing a
8195 as an argument to the
8199 Specifying a filename containing a slash as an argument to the
8205 importing function definitions from the shell environment at startup
8207 parsing the value of \fBSHELLOPTS\fP from the shell environment at startup
8209 redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
8213 builtin command to replace the shell with another command
8215 adding or deleting builtin commands with the
8223 Using the \fBenable\fP builtin command to enable disabled shell builtins
8231 turning off restricted mode with
8232 \fBset +r\fP or \fBset +o restricted\fP.
8234 These restrictions are enforced after any startup files are read.
8236 When a command that is found to be a shell script is executed (see
8238 .B "COMMAND EXECUTION"
8241 turns off any restrictions in the shell spawned to execute the
8248 \fIBash Reference Manual\fP, Brian Fox and Chet Ramey
8250 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
8252 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
8254 \fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE
8256 \fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
8258 \fIemacs\fP(1), \fIvi\fP(1)
8266 The \fBbash\fP executable
8269 The systemwide initialization file, executed for login shells
8272 The personal initialization file, executed for login shells
8275 The individual per-interactive-shell startup file
8278 The individual login shell cleanup file, executed when a login shell exits
8281 Individual \fIreadline\fP initialization file
8284 Brian Fox, Free Software Foundation
8288 Chet Ramey, Case Western Reserve University
8292 If you find a bug in
8294 you should report it. But first, you should
8295 make sure that it really is a bug, and that it appears in the latest
8300 Once you have determined that a bug actually exists, use the
8302 command to submit a bug report.
8303 If you have a fix, you are encouraged to mail that as well!
8304 Suggestions and `philosophical' bug reports may be mailed
8305 to \fIbug-bash@gnu.org\fP or posted to the Usenet
8309 ALL bug reports should include:
8313 The version number of \fBbash\fR
8315 The hardware and operating system
8317 The compiler used to compile
8319 A description of the bug behaviour
8321 A short script or `recipe' which exercises the bug
8325 inserts the first three items automatically into the template
8326 it provides for filing a bug report.
8328 Comments and bug reports concerning
8329 this manual page should be directed to
8330 .IR chet@ins.CWRU.Edu .
8333 It's too big and too slow.
8335 There are some subtle differences between
8337 and traditional versions of
8339 mostly because of the
8344 Aliases are confusing in some uses.
8346 Shell builtin commands and functions are not stoppable/restartable.
8348 Compound commands and command sequences of the form `a ; b ; c'
8349 are not handled gracefully when process suspension is attempted.
8350 When a process is stopped, the shell immediately executes the next
8351 command in the sequence.
8352 It suffices to place the sequence of commands between
8353 parentheses to force it into a subshell, which may be stopped as
8356 Commands inside of \fB$(\fP...\fB)\fP command substitution are not
8357 parsed until substitution is attempted. This will delay error
8358 reporting until some time after the command is entered.
8360 Array variables may not (yet) be exported.
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