2 .\" MAN PAGE COMMENTS to
5 .\" Information Network Services
6 .\" Case Western Reserve University
9 .\" Last Change: Tue Mar 14 11:36:43 EST 2000
11 .\" bash_builtins, strip all but Built-Ins section
14 .TH BASH 1 "2000 Mar 14" "GNU Bash-2.04"
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) 1989-1999 by the Free Software Foundation, Inc.
55 .if t Bash is Copyright \(co 1989-1999 by the Free Software Foundation, Inc.
58 is an \fBsh\fR-compatible command language interpreter that
59 executes commands read from the standard input or from a file.
61 also incorporates useful features from the \fIKorn\fP and \fIC\fP
62 shells (\fBksh\fP and \fBcsh\fP).
65 is intended to be a conformant implementation of the IEEE
66 POSIX Shell and Tools specification (IEEE Working Group 1003\.2).
68 In addition to the single-character shell options documented in the
69 description of the \fBset\fR builtin command, \fBbash\fR
70 interprets the following options when it is invoked:
77 option is present, then commands are read from
79 If there are arguments after the
81 they are assigned to the positional parameters, starting with
87 option is present, the shell becomes
97 option is present, the shell is
103 option is present, or if no arguments remain after option
104 processing, then commands are read from the standard input.
105 This option allows the positional parameters to be set
106 when invoking an interactive shell.
109 A list of all double-quoted strings preceded by \fB$\fP
110 is printed on the standard ouput.
111 These are the strings that
112 are subject to language translation when the current locale
114 This implies the \fB\-n\fP option; no commands will be executed.
119 signals the end of options and disables further option processing.
120 Any arguments after the
122 are treated as filenames and arguments. An argument of
124 is equivalent to \fB\-\-\fP.
128 also interprets a number of multi-character options.
129 These options must appear on the command line before the
130 single-character options in order for them to be recognized.
134 .B \-\-dump\-po\-strings
135 Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
136 \fBpo\fP (portable object) file format.
139 Equivalent to \fB\-D\fP.
142 Display a usage message on standard output and exit successfully.
147 act as if it had been invoked as a login shell (see
155 library to read command lines when the shell is interactive.
158 Do not read either the system-wide startup file
160 or any of the personal initialization files
161 .IR ~/.bash_profile ,
167 reads these files when it is invoked as a login shell (see
173 Do not read and execute the personal initialization file
175 if the shell is interactive.
176 This option is on by default if the shell is invoked as
180 Change the behavior of \fBbash\fP where the default operation differs
181 from the POSIX 1003.2 standard to match the standard.
183 \fB\-\-rcfile\fP \fIfile\fP
184 Execute commands from
186 instead of the standard personal initialization file
188 if the shell is interactive (see
194 The shell becomes restricted (see
196 .B "RESTRICTED SHELL"
200 Equivalent to \fB\-v\fP.
203 Show version information for this instance of
205 on the standard output and exit successfully.
208 If arguments remain after option processing, and neither the
212 option has been supplied, the first argument is assumed to
213 be the name of a file containing shell commands.
216 is invoked in this fashion,
218 is set to the name of the file, and the positional parameters
219 are set to the remaining arguments.
221 reads and executes commands from this file, then exits.
222 \fBBash\fP's exit status is the exit status of the last command
223 executed in the script.
224 If no commands are executed, the exit status is 0.
226 A \fIlogin shell\fP is one whose first character of argument zero is a
228 or one started with the
232 An \fIinteractive\fP shell is one started without non-option arguments
236 whose standard input and output are
237 both connected to terminals (as determined by
239 or one started with the
251 allowing a shell script or a startup file to test this state.
253 The following paragraphs describe how
255 executes its startup files.
256 If any of the files exist but cannot be read,
259 Tildes are expanded in file names as described below under
268 is invoked as an interactive login shell, or as a non-interactive shell
269 with the \fB\-\-login\fP option, it first reads and
270 executes commands from the file \fI/etc/profile\fP, if that
272 After reading that file, it looks for \fI~/.bash_profile\fP,
273 \fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
274 and executes commands from the first one that exists and is readable.
277 option may be used when the shell is started to inhibit this behavior.
279 When a login shell exits,
281 reads and executes commands from the file \fI~/.bash_logout\fP, if it
284 When an interactive shell that is not a login shell is started,
286 reads and executes commands from \fI~/.bashrc\fP, if that file exists.
287 This may be inhibited by using the
290 The \fB\-\-rcfile\fP \fIfile\fP option will force
292 to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
296 is started non-interactively, to run a shell script, for example, it
297 looks for the variable
300 in the environment, expands its value if it appears there, and uses the
301 expanded value as the name of a file to read and execute.
303 behaves as if the following command were executed:
306 \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
312 variable is not used to search for the file name.
316 is invoked with the name
318 it tries to mimic the startup behavior of historical versions of
320 as closely as possible,
321 while conforming to the POSIX standard as well.
322 When invoked as an interactive login shell, or a non-interactive
323 shell with the \fB\-\-login\fP option, it first attempts to
324 read and execute commands from
331 option may be used to inhibit this behavior.
332 When invoked as an interactive shell with the name
335 looks for the variable
338 expands its value if it is defined, and uses the
339 expanded value as the name of a file to read and execute.
340 Since a shell invoked as
342 does not attempt to read and execute commands from any other startup
345 option has no effect.
346 A non-interactive shell invoked with the name
348 does not attempt to read any other startup files.
354 mode after the startup files are read.
362 command line option, it follows the POSIX standard for startup files.
363 In this mode, interactive shells expand the
366 variable and commands are read and executed from the file
367 whose name is the expanded value.
368 No other startup files are read.
371 attempts to determine when it is being run by the remote shell
372 daemon, usually \fIrshd\fP.
375 determines it is being run by \fIrshd\fP, it reads and executes
376 commands from \fI~/.bashrc\fP, if that file exists and is readable.
377 It will not do this if invoked as \fBsh\fP.
380 option may be used to inhibit this behavior, and the
382 option may be used to force another file to be read, but
383 \fIrshd\fP does not generally invoke the shell with those options
384 or allow them to be specified.
386 If the shell is started with the effective user (group) id not equal to the
387 real user (group) id, and the \fB\-p\fP option is not supplied, no startup
388 files are read, shell functions are not inherited from the environment,
389 the \fBSHELLOPTS\fP variable, if it appears in the environment, is ignored,
390 and the effective user id is set to the real user id.
391 If the \fB\-p\fP option is supplied at invocation, the startup behavior is
392 the same, but the effective user id is not reset.
395 The following definitions are used throughout the rest of this
403 A sequence of characters considered as a single unit by the shell.
410 consisting only of alphanumeric characters and underscores, and
411 beginning with an alphabetic character or an underscore. Also
416 A character that, when unquoted, separates words. One of the following:
420 .if t \fB| & ; ( ) < > space tab\fP
421 .if n \fB| & ; ( ) < > space tab\fP
426 A \fItoken\fP that performs a control function. It is one of the following
430 .if t \fB\(bv\(bv & && ; ;; ( ) | <newline>\fP
431 .if n \fB|| & && ; ;; ( ) | <newline>\fP
435 \fIReserved words\fP are words that have a special meaning to the shell.
436 The following words are recognized as reserved when unquoted and either
437 the first word of a simple command (see
440 below) or the third word of a
448 .if n ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
449 .if t ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
455 A \fIsimple command\fP is a sequence of optional variable assignments
456 followed by \fBblank\fP-separated words and redirections, and
457 terminated by a \fIcontrol operator\fP. The first word
458 specifies the command to be executed. The remaining words are
459 passed as arguments to the invoked command.
461 The return value of a \fIsimple command\fP is its exit status, or
462 128+\fIn\^\fP if the command is terminated by signal
466 A \fIpipeline\fP is a sequence of one or more commands separated by
469 The format for a pipeline is:
472 [\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ \fB|\fP \fIcommand2\fP ... ]
475 The standard output of
477 is connected to the standard input of
479 This connection is performed before any redirections specified by the
487 precedes a pipeline, the exit status of that
488 pipeline is the logical NOT of the exit status of the last command.
489 Otherwise, the status of the pipeline is the exit status of the last
491 The shell waits for all commands in the pipeline to
492 terminate before returning a value.
496 reserved word precedes a pipeline, the elapsed as well as user and
497 system time consumed by its execution are reported when the pipeline
499 The \fB\-p\fP option changes the output format to that specified by POSIX.
503 variable may be set to a format string that specifies how the timing
504 information should be displayed; see the description of
511 Each command in a pipeline is executed as a separate process (i.e., in a
515 A \fIlist\fP is a sequence of one or more pipelines separated by one
522 and optionally terminated by one of
528 Of these list operators,
532 have equal precedence, followed by
536 which have equal precedence.
538 If a command is terminated by the control operator
540 the shell executes the command in the \fIbackground\fP
541 in a subshell. The shell does not wait for the command to
542 finish, and the return status is 0. Commands separated by a
544 are executed sequentially; the shell waits for each
545 command to terminate in turn. The return status is the
546 exit status of the last command executed.
548 The control operators
552 denote AND lists and OR lists, respectively.
553 An AND list has the form
556 \fIcommand1\fP \fB&&\fP \fIcommand2\fP
560 is executed if, and only if,
562 returns an exit status of zero.
564 An OR list has the form
567 \fIcommand1\fP \fB\(bv\(bv\fP \fIcommand2\fP
572 is executed if and only if
574 returns a non-zero exit status. The return status of
575 AND and OR lists is the exit status of the last command
576 executed in the list.
577 .SS Compound Commands
579 A \fIcompound command\fP is one of the following:
582 \fIlist\fP is executed in a subshell. Variable assignments and builtin
583 commands that affect the shell's environment do not remain in effect
584 after the command completes. The return status is the exit status of
588 \fIlist\fP is simply executed in the current shell environment.
589 \fIlist\fP must be terminated with a newline or semicolon.
590 This is known as a \fIgroup command\fP.
591 The return status is the exit status of
595 The \fIexpression\fP is evaluated according to the rules described
598 .BR "ARITHMETIC EVALUATION" .
599 If the value of the expression is non-zero, the return status is 0;
600 otherwise the return status is 1. This is exactly equivalent to
601 \fBlet "\fIexpression\fP"\fR.
603 \fB[[\fP \fIexpression\fP \fB]]\fP
604 Return a status of 0 or 1 depending on the evaluation of
605 the conditional expression \fIexpression\fP.
606 Expressions are composed of the primaries described below under
608 .BR "CONDITIONAL EXPRESSIONS" .
609 Word splitting and pathname expansion are not performed on the words
610 between the \fB[[\fP and \fB]]\fP; tilde expansion, parameter and
611 variable expansion, arithmetic expansion, command substitution, process
612 substitution, and quote removal are performed.
615 When the \fB==\fP and \fB!=\fP operators are used, the string to the
616 right of the operator is considered a pattern and matched according
617 to the rules described below under \fBPattern Matching\fP.
618 The return value is 0 if the string matches or does not match
619 the pattern, respectively, and 1 otherwise.
620 Any part of the pattern may be quoted to force it to be matched as a
624 Expressions may be combined using the following operators, listed
625 in decreasing order of precedence:
631 .B ( \fIexpression\fP )
632 Returns the value of \fIexpression\fP.
633 This may be used to override the normal precedence of operators.
635 .B ! \fIexpression\fP
640 \fIexpression1\fP \fB&&\fP \fIexpression2\fP
647 .if t \fIexpression1\fP \fB\(bv\(bv\fP \fIexpression2\fP
648 .if n \fIexpression1\fP \fB||\fP \fIexpression2\fP
660 operators do not execute \fIexpression2\fP if the value of
661 \fIexpression1\fP is sufficient to determine the return value of
662 the entire conditional expression.
664 \fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
665 The list of words following \fBin\fP is expanded, generating a list
667 The variable \fIname\fP is set to each element of this list
668 in turn, and \fIlist\fP is executed each time.
669 If the \fBin\fP \fIword\fP is omitted, the \fBfor\fP command executes
670 \fIlist\fP once for each positional parameter that is set (see
674 The return status is the exit status of the last command that executes.
675 If the expansion of the items following \fBin\fP results in an empty
676 list, no commands are executed, and the return status is 0.
678 \fBfor\fP (( \fIexpr1\fP ; \fIexpr2\fP ; \fIexpr3\fP )) ; \fBdo\fP \fIlist\fP ; \fBdone\fP
679 First, the arithmetic expression \fIexpr1\fP is evaluated according
680 to the rules described below under
682 .BR "ARITHMETIC EVALUATION" .
683 The arithmetic expression \fIexpr2\fP is then evaluated repeatedly
684 until it evaluates to zero.
685 Each time \fIexpr2\fP evaluates to a non-zero value, \fIlist\fP is
686 executed and the arithmetic expression \fIexpr3\fP is evaluated.
687 If any expression is omitted, it behaves as if it evaluates to 1.
688 The return value is the exit status of the last command in \fIlist\fP
689 that is executed, or false if any of the expressions is invalid.
691 \fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP ] ; \fBdo\fP \fIlist\fP ; \fBdone\fP
692 The list of words following \fBin\fP is expanded, generating a list
693 of items. The set of expanded words is printed on the standard
694 error, each preceded by a number. If the \fBin\fP
695 \fIword\fP is omitted, the positional parameters are printed (see
700 prompt is then displayed and a line read from the standard input.
701 If the line consists of a number corresponding to one of
702 the displayed words, then the value of
704 is set to that word. If the line is empty, the words and prompt
705 are displayed again. If EOF is read, the command completes. Any
706 other value read causes
708 to be set to null. The line read is saved in the variable
712 is executed after each selection until a
719 is the exit status of the last command executed in
721 or zero if no commands were executed.
723 \fBcase\fP \fIword\fP \fBin\fP [ [(] \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
724 ... ) \fIlist\fP ;; ] ... \fBesac\fP
725 A \fBcase\fP command first expands \fIword\fP, and tries to match
726 it against each \fIpattern\fP in turn, using the same matching rules
727 as for pathname expansion (see
728 .B Pathname Expansion
729 below). When a match is found, the
730 corresponding \fIlist\fP is executed. After the first match, no
731 subsequent matches are attempted. The exit status is zero if no
732 pattern matches. Otherwise, it is the exit status of the
733 last command executed in \fIlist\fP.
735 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist;\fP \
736 [ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
737 [ \fBelse\fP \fIlist\fP; ] \fBfi\fP
741 is executed. If its exit status is zero, the
742 \fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
743 \fIlist\fP is executed in turn, and if its exit status is zero,
744 the corresponding \fBthen\fP \fIlist\fP is executed and the
745 command completes. Otherwise, the \fBelse\fP \fIlist\fP is
746 executed, if present. The exit status is the exit status of the
747 last command executed, or zero if no condition tested true.
750 \fBwhile\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
752 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
754 The \fBwhile\fP command continuously executes the \fBdo\fP
755 \fIlist\fP as long as the last command in \fIlist\fP returns
756 an exit status of zero. The \fBuntil\fP command is identical
757 to the \fBwhile\fP command, except that the test is negated;
761 is executed as long as the last command in
763 returns a non-zero exit status.
764 The exit status of the \fBwhile\fP and \fBuntil\fP commands
766 of the last \fBdo\fP \fIlist\fP command executed, or zero if
769 [ \fBfunction\fP ] \fIname\fP () { \fIlist\fP; }
770 This defines a function named \fIname\fP. The \fIbody\fP of the
773 of commands between { and }. This list
774 is executed whenever \fIname\fP is specified as the
775 name of a simple command. The exit status of a function is
776 the exit status of the last command executed in the body. (See
781 In a non-interactive shell, or an interactive shell in which the
782 .B interactive_comments
785 builtin is enabled (see
787 .B "SHELL BUILTIN COMMANDS"
788 below), a word beginning with
790 causes that word and all remaining characters on that line to
791 be ignored. An interactive shell without the
792 .B interactive_comments
793 option enabled does not allow comments. The
794 .B interactive_comments
795 option is on by default in interactive shells.
797 \fIQuoting\fP is used to remove the special meaning of certain
798 characters or words to the shell. Quoting can be used to
799 disable special treatment for special characters, to prevent
800 reserved words from being recognized as such, and to prevent
803 Each of the \fImetacharacters\fP listed above under
806 has special meaning to the shell and must be quoted if it is to
809 When the command history expansion facilities are being used, the
810 \fIhistory expansion\fP character, usually \fB!\fP, must be quoted
811 to prevent history expansion.
813 There are three quoting mechanisms: the
814 .IR "escape character" ,
815 single quotes, and double quotes.
817 A non-quoted backslash (\fB\e\fP) is the
818 .IR "escape character" .
819 It preserves the literal value of the next character that follows,
820 with the exception of <newline>. If a \fB\e\fP<newline> pair
821 appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
822 is treated as a line continuation (that is, it is removed from the
823 input stream and effectively ignored).
825 Enclosing characters in single quotes preserves the literal value
826 of each character within the quotes. A single quote may not occur
827 between single quotes, even when preceded by a backslash.
829 Enclosing characters in double quotes preserves the literal value
830 of all characters within the quotes, with the exception of
839 retain their special meaning within double quotes. The backslash
840 retains its special meaning only when followed by one of the following
848 A double quote may be quoted within double quotes by preceding it with
851 The special parameters
855 have special meaning when in double
861 Words of the form \fB$\fP'\fIstring\fP' are treated specially. The
862 word expands to \fIstring\fP, with backslash-escaped characters replaced
863 as specifed by the ANSI C standard. Backslash escape sequences, if
864 present, are decoded as follows:
899 the character whose ASCII code is the octal value \fInnn\fP
900 (one to three digits)
903 the character whose ASCII code is the hexadecimal value \fInnn\fP
904 (one to three digits)
908 The expanded result is single-quoted, as if the dollar sign had
911 A double-quoted string preceded by a dollar sign (\fB$\fP) will cause
912 the string to be translated according to the current locale.
913 If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
915 If the string is translated and replaced, the replacement is
920 is an entity that stores values.
923 a number, or one of the special characters listed below under
924 .BR "Special Parameters" .
925 For the shell's purposes, a
927 is a parameter denoted by a
930 A parameter is set if it has been assigned a value. The null string is
931 a valid value. Once a variable is set, it may be unset only by using
936 .B SHELL BUILTIN COMMANDS
941 may be assigned to by a statement of the form
944 \fIname\fP=[\fIvalue\fP]
949 is not given, the variable is assigned the null string. All
951 undergo tilde expansion, parameter and variable expansion,
952 command substitution, arithmetic expansion, and quote
956 below). If the variable has its
962 .BR "SHELL BUILTIN COMMANDS" )
965 is subject to arithmetic expansion even if the $((...)) expansion is
967 .B "Arithmetic Expansion"
969 Word splitting is not performed, with the exception
970 of \fB"$@"\fP as explained below under
971 .BR "Special Parameters" .
972 Pathname expansion is not performed.
973 .SS Positional Parameters
976 .I positional parameter
977 is a parameter denoted by one or more
978 digits, other than the single digit 0. Positional parameters are
979 assigned from the shell's arguments when it is invoked,
980 and may be reassigned using the
982 builtin command. Positional parameters may not be assigned to
983 with assignment statements. The positional parameters are
984 temporarily replaced when a shell function is executed (see
989 When a positional parameter consisting of more than a single
990 digit is expanded, it must be enclosed in braces (see
994 .SS Special Parameters
996 The shell treats several parameters specially. These parameters may
997 only be referenced; assignment to them is not allowed.
1001 Expands to the positional parameters, starting from one. When the
1002 expansion occurs within double quotes, it expands to a single word
1003 with the value of each parameter separated by the first character
1007 special variable. That is, "\fB$*\fP" is equivalent
1008 to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
1010 is the first character of the value of the
1016 is unset, the parameters are separated by spaces.
1020 is null, the parameters are joined without intervening separators.
1023 Expands to the positional parameters, starting from one. When the
1024 expansion occurs within double quotes, each parameter expands to a
1025 separate word. That is, "\fB$@\fP" is equivalent to
1026 "\fB$1\fP" "\fB$2\fP" ...
1027 When there are no positional parameters, "\fB$@\fP" and
1029 expand to nothing (i.e., they are removed).
1032 Expands to the number of positional parameters in decimal.
1035 Expands to the status of the most recently executed foreground
1039 Expands to the current option flags as specified upon invocation,
1042 builtin command, or those set by the shell itself
1048 Expands to the process ID of the shell. In a () subshell, it
1049 expands to the process ID of the current shell, not the
1053 Expands to the process ID of the most recently executed background
1054 (asynchronous) command.
1057 Expands to the name of the shell or shell script. This is set at
1058 shell initialization. If
1060 is invoked with a file of commands,
1062 is set to the name of that file. If
1068 is set to the first argument after the string to be
1069 executed, if one is present. Otherwise, it is set
1070 to the file name used to invoke
1072 as given by argument zero.
1075 At shell startup, set to the absolute file name of the shell or shell
1076 script being executed as passed in the argument list.
1077 Subsequently, expands to the last argument to the previous command,
1079 Also set to the full file name of each command executed and placed in
1080 the environment exported to that command.
1081 When checking mail, this parameter holds the name of the mail file
1082 currently being checked.
1086 The following variables are set by the shell:
1091 The process ID of the shell's parent. This variable is readonly.
1094 The current working directory as set by the
1099 The previous working directory as set by the
1104 Set to the line of input read by the
1106 builtin command when no arguments are supplied.
1109 Expands to the user ID of the current user, initialized at shell startup.
1110 This variable is readonly.
1113 Expands to the effective user ID of the current user, initialized at
1114 shell startup. This variable is readonly.
1117 An array variable containing the list of groups of which the current
1122 have no effect and are silently discarded.
1126 is unset, it loses its special properties, even if it is
1130 Expands to the full file name used to invoke this instance of
1134 Expands to a string describing the version of this instance of
1138 A readonly array variable whose members hold version information for
1141 The values assigned to the array members are as follows:
1146 .B BASH_VERSINFO[\fR0\fP]
1147 The major version number (the \fIrelease\fP).
1149 .B BASH_VERSINFO[\fR1\fP]
1150 The minor version number (the \fIversion\fP).
1152 .B BASH_VERSINFO[\fR2\fP]
1155 .B BASH_VERSINFO[\fR3\fP]
1158 .B BASH_VERSINFO[\fR4\fP]
1159 The release status (e.g., \fIbeta1\fP).
1161 .B BASH_VERSINFO[\fR5\fP]
1162 The value of \fBMACHTYPE\fP.
1167 Incremented by one each time an instance of
1172 Each time this parameter is referenced, a random integer between
1174 generated. The sequence of random numbers may be initialized by assigning
1181 is unset, it loses its special properties, even if it is
1185 Each time this parameter is
1186 referenced, the number of seconds since shell invocation is returned. If a
1187 value is assigned to
1190 the value returned upon subsequent
1192 the number of seconds since the assignment plus the value assigned.
1196 is unset, it loses its special properties, even if it is
1200 Each time this parameter is referenced, the shell substitutes
1201 a decimal number representing the current sequential line number
1202 (starting with 1) within a script or function. When not in a
1203 script or function, the value substituted is not guaranteed to
1208 is unset, it loses its special properties, even if it is
1212 The history number, or index in the history list, of the current
1217 is unset, it loses its special properties, even if it is
1221 The name of any currently-executing shell function.
1222 This variable exists only when a shell function is executing.
1226 have no effect and are silently discarded.
1230 is unset, it loses its special properties, even if it is
1234 An array variable (see
1236 below) containing the current contents of the directory stack.
1237 Directories appear in the stack in the order they are displayed by the
1240 Assigning to members of this array variable may be used to modify
1241 directories already in the stack, but the
1245 builtins must be used to add and remove directories.
1246 Assignment to this variable will not change the current directory.
1250 is unset, it loses its special properties, even if it is
1254 An array variable (see
1256 below) containing a list of exit status values from the processes
1257 in the most-recently-executed foreground pipeline (which may
1258 contain only a single command).
1261 The value of the last option argument processed by the
1263 builtin command (see
1265 .B SHELL BUILTIN COMMANDS
1269 The index of the next argument to be processed by the
1271 builtin command (see
1273 .B SHELL BUILTIN COMMANDS
1277 Automatically set to the name of the current host.
1280 Automatically set to a string that uniquely
1281 describes the type of machine on which
1284 The default is system-dependent.
1287 Automatically set to a string that
1288 describes the operating system on which
1291 The default is system-dependent.
1294 Automatically set to a string that fully describes the system
1297 is executing, in the standard GNU \fIcpu-company-system\fP format.
1298 The default is system-dependent.
1301 A colon-separated list of enabled shell options. Each word in
1302 the list is a valid argument for the
1306 builtin command (see
1308 .B "SHELL BUILTIN COMMANDS"
1309 below). The options appearing in
1312 are those reported as
1315 If this variable is in the environment when
1317 starts up, each shell option in the list will be enabled before
1318 reading any startup files.
1319 This variable is read-only.
1322 An array variable (see \fBArrays\fP below) consisting of the individual
1323 words in the current command line.
1324 This variable is available only in shell functions invoked by the
1325 programmable completion facilities (see \fBProgrammable Completion\fP
1329 An index into \fB${COMP_WORDS}\fP of the word containing the current
1331 This variable is available only in shell functions invoked by the
1332 programmable completion facilities (see \fBProgrammable Completion\fP
1336 The current command line.
1337 This variable is available only in shell functions and external
1338 commands invoked by the
1339 programmable completion facilities (see \fBProgrammable Completion\fP
1343 The index of the current cursor position relative to the beginning of
1344 the current command.
1345 If the current cursor position is at the end of the current command,
1346 the value of this variable is equal to \fB${#COMP_LINE}\fP.
1347 This variable is available only in shell functions and external
1348 commands invoked by the
1349 programmable completion facilities (see \fBProgrammable Completion\fP
1353 The following variables are used by the shell. In some cases,
1355 assigns a default value to a variable; these cases are noted
1362 .I Internal Field Separator
1364 for word splitting after expansion and to
1365 split lines into words with the
1367 builtin command. The default value is
1368 ``<space><tab><newline>''.
1371 The search path for commands. It
1372 is a colon-separated list of directories in which
1373 the shell looks for commands (see
1375 .B COMMAND EXECUTION
1376 below). The default path is system-dependent,
1377 and is set by the administrator who installs
1379 A common value is ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.''.
1382 The home directory of the current user; the default argument for the
1383 \fBcd\fP builtin command.
1384 The value of this variable is also used when performing tilde expansion.
1387 The search path for the
1390 This is a colon-separated list of directories in which the shell looks
1391 for destination directories specified by the
1394 A sample value is ``.:~:/usr''.
1397 If this parameter is set when \fBbash\fP is executing a shell script,
1398 its value is interpreted as a filename containing commands to
1399 initialize the shell, as in
1404 is subjected to parameter expansion, command substitution, and arithmetic
1405 expansion before being interpreted as a file name.
1408 is not used to search for the resultant file name.
1411 If this parameter is set to a file name and the
1414 variable is not set,
1416 informs the user of the arrival of mail in the specified file.
1422 checks for mail. The default is 60 seconds. When it is time to check
1423 for mail, the shell does so before displaying the primary prompt.
1424 If this variable is unset, the shell disables mail checking.
1427 A colon-separated list of file names to be checked for mail.
1428 The message to be printed when mail arrives in a particular file
1429 may be specified by separating the file name from the message with a `?'.
1430 When used in the text of the message, \fB$_\fP expands to the name of
1431 the current mailfile.
1435 \fBMAILPATH\fP='/var/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"'
1438 supplies a default value for this variable, but the location of the user
1439 mail files that it uses is system dependent (e.g., /var/mail/\fB$USER\fP).
1443 The value of this parameter is expanded (see
1446 below) and used as the primary prompt string. The default value is
1447 ``\fB\es\-\ev\e$ \fP''.
1450 The value of this parameter is expanded as with
1452 and used as the secondary prompt string. The default is
1456 The value of this parameter is used as the prompt for the
1464 The value of this parameter is expanded as with
1466 and the value is printed before each command
1468 displays during an execution trace. The first character of
1471 is replicated multiple times, as necessary, to indicate multiple
1472 levels of indirection. The default is ``\fB+ \fP''.
1475 The value of this parameter is used as a format string specifying
1476 how the timing information for pipelines prefixed with the
1478 reserved word should be displayed.
1479 The \fB%\fP character introduces an escape sequence that is
1480 expanded to a time value or other information.
1481 The escape sequences and their meanings are as follows; the
1482 braces denote optional portions.
1491 The elapsed time in seconds.
1494 The number of CPU seconds spent in user mode.
1497 The number of CPU seconds spent in system mode.
1500 The CPU percentage, computed as (%U + %S) / %R.
1504 The optional \fIp\fP is a digit specifying the \fIprecision\fP,
1505 the number of fractional digits after a decimal point.
1506 A value of 0 causes no decimal point or fraction to be output.
1507 At most three places after the decimal point may be specified;
1508 values of \fIp\fP greater than 3 are changed to 3.
1509 If \fIp\fP is not specified, the value 3 is used.
1511 The optional \fBl\fP specifies a longer format, including
1512 minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
1513 The value of \fIp\fP determines whether or not the fraction is
1516 If this variable is not set, \fBbash\fP acts as if it had the
1517 value \fB$'\enreal\et%3lR\enuser\et%3lU\ensys\t%3lS'\fP.
1518 If the value is null, no timing information is displayed.
1519 A trailing newline is added when the format string is displayed.
1522 The number of commands to remember in the command history (see
1525 below). The default value is 500.
1528 The name of the file in which command history is saved (see
1531 below). The default value is \fI~/.bash_history\fP. If unset, the
1532 command history is not saved when an interactive shell exits.
1535 The maximum number of lines contained in the history file. When this
1536 variable is assigned a value, the history file is truncated, if
1537 necessary, to contain no more than that number of lines. The default
1538 value is 500. The history file is also truncated to this size after
1539 writing it when an interactive shell exits.
1542 If set to the value 1,
1544 displays error messages generated by the
1546 builtin command (see
1548 .B SHELL BUILTIN COMMANDS
1552 is initialized to 1 each time the shell is invoked or a shell
1556 Used to determine the locale category for any category not specifically
1557 selected with a variable starting with \fBLC_\fP.
1560 This variable overrides the value of \fBLANG\fP and any other
1561 \fBLC_\fP variable specifying a locale category.
1564 This variable determines the collation order used when sorting the
1565 results of pathname expansion, and determines the behavior of range
1566 expressions, equivalence classes, and collating sequences within
1567 pathname expansion and pattern matching.
1570 This variable determines the interpretation of characters and the
1571 behavior of character classes within pathname expansion and pattern
1575 This variable determines the locale used to translate double-quoted
1576 strings preceded by a \fB$\fP.
1579 This variable determines the locale category used for number formatting.
1582 If set, the value is executed as a command prior to issuing each primary
1587 action of an interactive shell on receipt of an
1590 character as the sole input. If set, the value is the number of
1594 characters which must be
1595 typed as the first characters on an input line before
1597 exits. If the variable exists but does not have a numeric value, or
1598 has no value, the default value is 10. If it does not exist,
1601 signifies the end of input to the shell.
1604 If set to a value greater than zero, the value is interpreted as the
1605 number of seconds to wait for input after issuing the primary prompt.
1607 terminates after waiting for that number of seconds if input does
1611 The default editor for the
1616 A colon-separated list of suffixes to ignore when performing
1617 filename completion (see
1621 A filename whose suffix matches one of the entries in
1624 is excluded from the list of matched filenames.
1625 A sample value is ``.o:~''.
1628 A colon-separated list of patterns defining the set of filenames to
1629 be ignored by pathname expansion.
1630 If a filename matched by a pathname expansion pattern also matches one
1634 it is removed from the list of matches.
1637 The filename for the
1639 startup file, overriding the default of
1647 If set to a value of
1649 lines which begin with a
1651 character are not entered on the history list.
1652 If set to a value of
1654 lines matching the last history line are not entered.
1657 combines the two options.
1658 If unset, or if set to any other value than those above,
1660 by the parser are saved on the history list, subject to the value
1663 This variable's function is superseded by
1665 The second and subsequent lines of a multi-line compound command are
1666 not tested, and are added to the history regardless of the value of
1670 A colon-separated list of patterns used to decide which command lines
1671 should be saved on the history list. Each pattern is anchored at the
1672 beginning of the line and must match the complete line (no implicit
1673 `\fB*\fP' is appended). Each pattern is tested against the line
1674 after the checks specified by
1677 In addition to the normal shell pattern matching characters, `\fB&\fP'
1678 matches the previous history line. `\fB&\fP' may be escaped using a
1679 backslash; the backslash is removed before attempting a match.
1680 The second and subsequent lines of a multi-line compound command are
1681 not tested, and are added to the history regardless of the value of
1685 The two or three characters which control history expansion
1686 and tokenization (see
1688 .B HISTORY EXPANSION
1689 below). The first character is the \fIhistory expansion\fP character,
1690 the character which signals the start of a history
1691 expansion, normally `\fB!\fP'.
1692 The second character is the \fIquick substitution\fP
1693 character, which is used as shorthand for re-running the previous
1694 command entered, substituting one string for another in the command.
1695 The default is `\fB^\fP'.
1696 The optional third character is the character
1697 which indicates that the remainder of the line is a comment when found
1698 as the first character of a word, normally `\fB#\fP'. The history
1699 comment character causes history substitution to be skipped for the
1700 remaining words on the line. It does not necessarily cause the shell
1701 parser to treat the rest of the line as a comment.
1704 Contains the name of a file in the same format as
1706 that should be read when the shell needs to complete a
1708 The list of possible hostname completions may be changed while the
1710 the next time hostname completion is attempted after the
1713 adds the contents of the new file to the existing list.
1717 is set, but has no value, \fBbash\fP attempts to read
1719 to obtain the list of possible hostname completions.
1723 is unset, the hostname list is cleared.
1726 This variable controls how the shell interacts with the user and
1727 job control. If this variable is set, single word simple
1728 commands without redirections are treated as candidates for resumption
1729 of an existing stopped job. There is no ambiguity allowed; if there is
1730 more than one job beginning with the string typed, the job most recently
1731 accessed is selected. The
1733 of a stopped job, in this context, is the command line used to
1737 the string supplied must match the name of a stopped job exactly;
1740 the string supplied needs to match a substring of the name of a
1743 value provides functionality analogous to the
1748 below). If set to any other value, the supplied string must
1749 be a prefix of a stopped job's name; this provides functionality
1755 An array variable from which \fBbash\fP reads the possible completions
1756 generated by a shell function invoked by the programmable completion
1757 facility (see \fBProgrammable Completion\fP below).
1761 provides one-dimensional array variables. Any variable may be used as
1764 builtin will explicitly declare an array. There is no maximum
1765 limit on the size of an array, nor any requirement that members
1766 be indexed or assigned contiguously. Arrays are indexed using
1767 integers and are zero-based.
1769 An array is created automatically if any variable is assigned to using
1770 the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
1772 is treated as an arithmetic expression that must evaluate to a number
1773 greater than or equal to zero. To explicitly declare an array, use
1774 .B declare \-a \fIname\fP
1777 .B SHELL BUILTIN COMMANDS
1779 .B declare \-a \fIname\fP[\fIsubscript\fP]
1780 is also accepted; the \fIsubscript\fP is ignored. Attributes may be
1781 specified for an array variable using the
1785 builtins. Each attribute applies to all members of an array.
1787 Arrays are assigned to using compound assignments of the form
1788 \fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
1789 \fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP. Only
1790 \fIstring\fP is required. If
1791 the optional brackets and subscript are supplied, that index is assigned to;
1792 otherwise the index of the element assigned is the last index assigned
1793 to by the statement plus one. Indexing starts at zero.
1794 This syntax is also accepted by the
1796 builtin. Individual array elements may be assigned to using the
1797 \fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
1799 Any element of an array may be referenced using
1800 ${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
1801 conflicts with pathname expansion. If
1802 \fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
1803 all members of \fIname\fP. These subscripts differ only when the
1804 word appears within double quotes. If the word is double-quoted,
1805 ${\fIname\fP[*]} expands to a single
1806 word with the value of each array member separated by the first
1810 special variable, and ${\fIname\fP[@]} expands each element of
1811 \fIname\fP to a separate word. When there are no array members,
1812 ${\fIname\fP[@]} expands to nothing. This is analogous to the expansion
1813 of the special parameters \fB*\fP and \fB@\fP (see
1814 .B Special Parameters
1815 above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
1816 ${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
1817 \fB@\fP, the expansion is the number of elements in the array.
1818 Referencing an array variable without a subscript is equivalent to
1819 referencing element zero.
1823 builtin is used to destroy arrays. \fBunset\fP \fIname\fP[\fIsubscript\fP]
1824 destroys the array element at index \fIsubscript\fP.
1825 \fBunset\fP \fIname\fP, where \fIname\fP is an array, or
1826 \fBunset\fP \fIname\fP[\fIsubscript\fP], where
1827 \fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
1834 builtins each accept a
1836 option to specify an array. The
1840 option to assign a list of words read from the standard input
1845 builtins display array values in a way that allows them to be
1846 reused as assignments.
1848 Expansion is performed on the command line after it has been split into
1849 words. There are seven kinds of expansion performed:
1850 .IR "brace expansion" ,
1851 .IR "tilde expansion" ,
1852 .IR "parameter and variable expansion" ,
1853 .IR "command substitution" ,
1854 .IR "arithmetic expansion" ,
1855 .IR "word splitting" ,
1857 .IR "pathname expansion" .
1859 The order of expansions is: brace expansion, tilde expansion,
1860 parameter, variable and arithmetic expansion and
1861 command substitution
1862 (done in a left-to-right fashion), word splitting, and pathname
1865 On systems that can support it, there is an additional expansion
1866 available: \fIprocess substitution\fP.
1868 Only brace expansion, word splitting, and pathname expansion
1869 can change the number of words of the expansion; other expansions
1870 expand a single word to a single word.
1871 The only exceptions to this are the expansions of
1872 "\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
1873 as explained above (see
1878 .I "Brace expansion"
1879 is a mechanism by which arbitrary strings
1880 may be generated. This mechanism is similar to
1881 \fIpathname expansion\fP, but the filenames generated
1882 need not exist. Patterns to be brace expanded take
1883 the form of an optional
1885 followed by a series of comma-separated strings
1886 between a pair of braces, followed by an optional
1888 The preamble is prefixed to each string contained
1889 within the braces, and the postscript is then appended
1890 to each resulting string, expanding left to right.
1892 Brace expansions may be nested. The results of each expanded
1893 string are not sorted; left to right order is preserved.
1894 For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
1896 Brace expansion is performed before any other expansions,
1897 and any characters special to other expansions are preserved
1898 in the result. It is strictly textual.
1900 does not apply any syntactic interpretation to the context of the
1901 expansion or the text between the braces.
1903 A correctly-formed brace expansion must contain unquoted opening
1904 and closing braces, and at least one unquoted comma.
1905 Any incorrectly formed brace expansion is left unchanged.
1906 A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
1907 being considered part of a brace expression.
1908 To avoid conflicts with parameter expansion, the string \fB${\fP
1909 is not considered eligible for brace expansion.
1911 This construct is typically used as shorthand when the common
1912 prefix of the strings to be generated is longer than in the
1916 mkdir /usr/local/src/bash/{old,new,dist,bugs}
1920 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
1923 Brace expansion introduces a slight incompatibility with
1924 historical versions of
1927 does not treat opening or closing braces specially when they
1928 appear as part of a word, and preserves them in the output.
1930 removes braces from words as a consequence of brace
1931 expansion. For example, a word entered to
1934 appears identically in the output. The same word is
1939 If strict compatibility with
1945 option or disable brace expansion with the
1951 .B SHELL BUILTIN COMMANDS
1955 If a word begins with an unquoted tilde character (`\fB~\fP'), all of
1956 the characters preceding the first unquoted slash (or all characters,
1957 if there is no unquoted slash) are considered a \fItilde-prefix\fP.
1958 If none of the characters in the tilde-prefix are quoted, the
1959 characters in the tilde-prefix following the tilde are treated as a
1960 possible \fIlogin name\fP.
1961 If this login name is the null string, the tilde is replaced with the
1962 value of the shell parameter
1968 is unset, the home directory of the user executing the shell is
1969 substituted instead.
1970 Otherwise, the tilde-prefix is replaced with the home directory
1971 associated with the specified login name.
1973 If the tilde-prefix is a `~+', the value of the shell variable
1976 replaces the tilde-prefix.
1977 If the tilde-prefix is a `~\-', the value of the shell variable
1980 if it is set, is substituted.
1981 If the characters following the tilde in the tilde-prefix consist
1982 of a number \fIN\fP, optionally prefixed
1983 by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
1984 element from the directory stack, as it would be displayed by the
1986 builtin invoked with the tilde-prefix as an argument.
1987 If the characters following the tilde in the tilde-prefix consist of a
1988 number without a leading `+' or `\-', `+' is assumed.
1990 If the login name is invalid, or the tilde expansion fails, the word
1993 Each variable assignment is checked for unquoted tilde-prefixes immediately
1998 In these cases, tilde expansion is also performed.
1999 Consequently, one may use file names with tildes in assignments to
2007 and the shell assigns the expanded value.
2008 .SS Parameter Expansion
2010 The `\fB$\fP' character introduces parameter expansion,
2011 command substitution, or arithmetic expansion. The parameter name
2012 or symbol to be expanded may be enclosed in braces, which
2013 are optional but serve to protect the variable to be expanded from
2014 characters immediately following it which could be
2015 interpreted as part of the name.
2017 When braces are used, the matching ending brace is the first `\fB}\fP'
2018 not escaped by a backslash or within a quoted string, and not within an
2019 embedded arithmetic expansion, command substitution, or paramter
2025 The value of \fIparameter\fP is substituted. The braces are required
2028 is a positional parameter with more than one digit,
2031 is followed by a character which is not to be
2032 interpreted as part of its name.
2035 If the first character of \fIparameter\fP is an exclamation point,
2036 a level of variable indirection is introduced.
2037 \fBBash\fP uses the value of the variable formed from the rest of
2038 \fIparameter\fP as the name of the variable; this variable is then
2039 expanded and that value is used in the rest of the substitution, rather
2040 than the value of \fIparameter\fP itself.
2041 This is known as \fIindirect expansion\fP.
2042 The exception to this is the expansion of ${!\fIprefix\fP*}
2045 In each of the cases below, \fIword\fP is subject to tilde expansion,
2046 parameter expansion, command substitution, and arithmetic expansion.
2047 When not performing substring expansion, \fBbash\fP tests for a parameter
2048 that is unset or null; omitting the colon results in a test only for a
2049 parameter that is unset.
2053 ${\fIparameter\fP\fB:\-\fP\fIword\fP}
2054 \fBUse Default Values\fP. If
2056 is unset or null, the expansion of
2058 is substituted. Otherwise, the value of
2062 ${\fIparameter\fP\fB:=\fP\fIword\fP}
2063 \fBAssign Default Values\fP.
2066 is unset or null, the expansion of
2072 is then substituted. Positional parameters and special parameters may
2073 not be assigned to in this way.
2075 ${\fIparameter\fP\fB:?\fP\fIword\fP}
2076 \fBDisplay Error if Null or Unset\fP.
2079 is null or unset, the expansion of \fIword\fP (or a message to that effect
2082 is not present) is written to the standard error and the shell, if it
2083 is not interactive, exits. Otherwise, the value of \fIparameter\fP is
2086 ${\fIparameter\fP\fB:+\fP\fIword\fP}
2087 \fBUse Alternate Value\fP.
2090 is null or unset, nothing is substituted, otherwise the expansion of
2095 ${\fIparameter\fP\fB:\fP\fIoffset\fP}
2097 ${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
2099 \fBSubstring Expansion.\fP
2100 Expands to up to \fIlength\fP characters of \fIparameter\fP
2101 starting at the character specified by \fIoffset\fP.
2102 If \fIlength\fP is omitted, expands to the substring of
2103 \fIparameter\fP starting at the character specified by \fIoffset\fP.
2104 \fIlength\fP and \fIoffset\fP are arithmetic expressions (see
2107 ARITHMETIC EVALUATION
2109 \fIlength\fP must evaluate to a number greater than or equal to zero.
2110 If \fIoffset\fP evaluates to a number less than zero, the value
2111 is used as an offset from the end of the value of \fIparameter\fP.
2112 If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
2113 parameters beginning at \fIoffset\fP.
2114 If \fIparameter\fP is an array name indexed by @ or *,
2115 the result is the \fIlength\fP
2116 members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2117 Substring indexing is zero-based unless the positional parameters
2118 are used, in which case the indexing starts at 1.
2120 ${\fB!\fP\fIprefix\fP\fB*\fP}
2121 Expands to the names of variables whose names begin with \fIprefix\fP,
2122 separated by the first character of the
2127 ${\fB#\fP\fIparameter\fP}
2128 The length in characters of the value of \fIparameter\fP is substituted.
2135 the value substituted is the number of positional parameters.
2138 is an array name subscripted by
2142 the value substituted is the number of elements in the array.
2145 ${\fIparameter\fP\fB#\fP\fIword\fP}
2147 ${\fIparameter\fP\fB##\fP\fIword\fP}
2151 is expanded to produce a pattern just as in pathname
2152 expansion. If the pattern matches the beginning of
2155 then the result of the expansion is the expanded value of
2157 with the shortest matching pattern (the ``\fB#\fP'' case) or the
2158 longest matching pattern (the ``\fB##\fP'' case) deleted.
2165 the pattern removal operation is applied to each positional
2166 parameter in turn, and the expansion is the resultant list.
2169 is an array variable subscripted with
2173 the pattern removal operation is applied to each member of the
2174 array in turn, and the expansion is the resultant list.
2177 ${\fIparameter\fP\fB%\fP\fIword\fP}
2179 ${\fIparameter\fP\fB%%\fP\fIword\fP}
2181 The \fIword\fP is expanded to produce a pattern just as in
2183 If the pattern matches a trailing portion of the expanded value of
2185 then the result of the expansion is the expanded value of
2187 with the shortest matching pattern (the ``\fB%\fP'' case) or the
2188 longest matching pattern (the ``\fB%%\fP'' case) deleted.
2195 the pattern removal operation is applied to each positional
2196 parameter in turn, and the expansion is the resultant list.
2199 is an array variable subscripted with
2203 the pattern removal operation is applied to each member of the
2204 array in turn, and the expansion is the resultant list.
2207 ${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2209 ${\fIparameter\fP\fB//\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2211 The \fIpattern\fP is expanded to produce a pattern just as in
2213 \fIParameter\fP is expanded and the longest match of \fIpattern\fP
2214 against its value is replaced with \fIstring\fP.
2215 In the first form, only the first match is replaced.
2216 The second form causes all matches of \fIpattern\fP to be
2217 replaced with \fIstring\fP.
2218 If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
2219 of the expanded value of \fIparameter\fP.
2220 If \fIpattern\fP begins with \fB%\fP, it must match at the end
2221 of the expanded value of \fIparameter\fP.
2222 If \fIstring\fP is null, matches of \fIpattern\fP are deleted
2223 and the \fB/\fP following \fIpattern\fP may be omitted.
2230 the substitution operation is applied to each positional
2231 parameter in turn, and the expansion is the resultant list.
2234 is an array variable subscripted with
2238 the substitution operation is applied to each member of the
2239 array in turn, and the expansion is the resultant list.
2240 .SS Command Substitution
2242 \fICommand substitution\fP allows the output of a command to replace
2243 the command name. There are two forms:
2247 \fB$(\fP\fIcommand\fP\|\fB)\fP
2251 \fB`\fP\fIcommand\fP\fB`\fP
2255 performs the expansion by executing \fIcommand\fP and
2256 replacing the command substitution with the standard output of the
2257 command, with any trailing newlines deleted.
2258 Embedded newlines are not deleted, but they may be removed during
2260 The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
2261 the equivalent but faster \fB$(< \fIfile\fP)\fR.
2263 When the old-style backquote form of substitution is used,
2264 backslash retains its literal meaning except when followed by
2269 The first backquote not preceded by a backslash terminates the
2270 command substitution.
2271 When using the $(\^\fIcommand\fP\|) form, all characters between the
2272 parentheses make up the command; none are treated specially.
2274 Command substitutions may be nested. To nest when using the backquoted form,
2275 escape the inner backquotes with backslashes.
2277 If the substitution appears within double quotes, word splitting and
2278 pathname expansion are not performed on the results.
2279 .SS Arithmetic Expansion
2281 Arithmetic expansion allows the evaluation of an arithmetic expression
2282 and the substitution of the result. The format for arithmetic expansion is:
2285 \fB$((\fP\fIexpression\fP\fB))\fP
2290 is treated as if it were within double quotes, but a double quote
2291 inside the parentheses is not treated specially.
2292 All tokens in the expression undergo parameter expansion, string
2293 expansion, command substitution, and quote removal.
2294 Arithmetic substitutions may be nested.
2296 The evaluation is performed according to the rules listed below under
2298 .BR "ARITHMETIC EVALUATION" .
2303 prints a message indicating failure and no substitution occurs.
2304 .SS Process Substitution
2306 \fIProcess substitution\fP is supported on systems that support named
2307 pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
2308 It takes the form of
2309 \fB<(\fP\fIlist\^\fP\fB)\fP
2311 \fB>(\fP\fIlist\^\fP\fB)\fP.
2312 The process \fIlist\fP is run with its input or output connected to a
2313 \fIFIFO\fP or some file in \fB/dev/fd\fP. The name of this file is
2314 passed as an argument to the current command as the result of the
2315 expansion. If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
2316 the file will provide input for \fIlist\fP. If the
2317 \fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
2318 argument should be read to obtain the output of \fIlist\fP.
2320 When available, process substitution is performed
2321 simultaneously with parameter and variable expansion,
2322 command substitution,
2323 and arithmetic expansion.
2326 The shell scans the results of
2327 parameter expansion,
2328 command substitution,
2330 arithmetic expansion
2331 that did not occur within double quotes for
2332 .IR "word splitting" .
2334 The shell treats each character of
2337 as a delimiter, and splits the results of the other
2338 expansions into words on these characters. If
2343 .BR <space><tab><newline> ,
2348 characters serves to delimit words. If
2351 has a value other than the default, then sequences of
2352 the whitespace characters
2356 are ignored at the beginning and end of the
2357 word, as long as the whitespace character is in the
2364 whitespace character).
2371 whitespace, along with any adjacent
2374 whitespace characters, delimits a field.
2378 whitespace characters is also treated as a delimiter.
2382 is null, no word splitting occurs.
2384 Explicit null arguments (\^\f3"\^"\fP or \^\f3'\^'\fP\^) are retained.
2385 Unquoted implicit null arguments, resulting from the expansion of
2386 parameters that have no values, are removed.
2387 If a parameter with no value is expanded within double quotes, a
2388 null argument results and is retained.
2390 Note that if no expansion occurs, no splitting
2392 .SS Pathname Expansion
2394 After word splitting,
2397 option has been set,
2399 scans each word for the characters
2404 If one of these characters appears, then the word is
2407 and replaced with an alphabetically sorted list of
2408 file names matching the pattern.
2409 If no matching file names are found,
2410 and the shell option
2412 is disabled, the word is left unchanged.
2415 option is set, and no matches are found,
2416 the word is removed.
2419 is enabled, the match is performed without regard to the case
2420 of alphabetic characters.
2421 When a pattern is used for pathname expansion,
2424 at the start of a name or immediately following a slash
2425 must be matched explicitly, unless the shell option
2428 When matching a pathname, the slash character must always be
2432 character is not treated specially.
2433 See the description of
2437 .B SHELL BUILTIN COMMANDS
2438 for a description of the
2448 shell variable may be used to restrict the set of file names matching a
2453 is set, each matching file name that also matches one of the patterns in
2456 is removed from the list of matches.
2461 are always ignored, even when
2464 is set. However, setting
2467 has the effect of enabling the
2469 shell option, so all other file names beginning with a
2472 To get the old behavior of ignoring file names beginning with a
2476 one of the patterns in
2481 option is disabled when
2486 \fBPattern Matching\fP
2488 Any character that appears in a pattern, other than the special pattern
2489 characters described below, matches itself. The NUL character may not
2490 occur in a pattern. The special pattern characters must be quoted if
2491 they are to be matched literally.
2493 The special pattern characters have the following meanings:
2498 Matches any string, including the null string.
2501 Matches any single character.
2504 Matches any one of the enclosed characters. A pair of characters
2505 separated by a minus sign denotes a
2507 any character lexically between those two characters, inclusive,
2508 is matched. If the first character following the
2514 then any character not enclosed is matched.
2517 may be matched by including it as the first or last character
2521 may be matched by including it as the first character
2530 \fIcharacter classes\fP can be specified using the syntax
2531 \fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
2532 following classes defined in the POSIX.2 standard:
2536 .if n alnum alpha ascii blank cntrl digit graph lower print punct space upper xdigit
2537 .if t alnum alpha ascii blank cntrl digit graph lower print punct space upper xdigit
2539 A character class matches any character belonging to that class.
2547 an \fIequivalence class\fP can be specified using the syntax
2548 \fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
2549 same collation weight (as defined by the current locale) as
2550 the character \fIc\fP.
2558 the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
2563 If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
2564 builtin, several extended pattern matching operators are recognized.
2565 In the following description, a \fIpattern-list\fP is a list of one
2566 or more patterns separated by a \fB|\fP.
2567 Composite patterns may be formed using one or more of the following
2573 \fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
2574 Matches zero or one occurrence of the given patterns
2576 \fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
2577 Matches zero or more occurrences of the given patterns
2579 \fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
2580 Matches one or more occurrences of the given patterns
2582 \fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
2583 Matches exactly one of the given patterns
2585 \fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
2586 Matches anything except one of the given patterns
2591 After the preceding expansions, all unquoted occurrences of the
2595 and \^\f3"\fP\^ that did not result from one of the above
2596 expansions are removed.
2598 Before a command is executed, its input and output
2601 using a special notation interpreted by the shell.
2602 Redirection may also be used to open and close files for the
2603 current shell execution environment. The following redirection
2604 operators may precede or appear anywhere within a
2608 Redirections are processed in the order they appear, from
2611 In the following descriptions, if the file descriptor number is
2612 omitted, and the first character of the redirection operator is
2614 the redirection refers to the standard input (file descriptor
2615 0). If the first character of the redirection operator is
2617 the redirection refers to the standard output (file descriptor
2620 The word following the redirection operator in the following
2621 descriptions, unless otherwise noted, is subjected to brace expansion,
2622 tilde expansion, parameter expansion, command substitution, arithmetic
2623 expansion, quote removal, pathname expansion, and word splitting.
2624 If it expands to more than one word,
2628 Note that the order of redirections is significant. For example,
2632 ls \fB>\fP dirlist 2\fB>&\fP1
2635 directs both standard output and standard error to the file
2640 ls 2\fB>&\fP1 \fB>\fP dirlist
2643 directs only the standard output to file
2645 because the standard error was duplicated as standard output
2646 before the standard output was redirected to
2649 \fBBash\fP handles several filenames specially when they are used in
2650 redirections, as described in the following table:
2656 If \fIfd\fP is a valid integer, file descriptor \fIfd\fP is duplicated.
2659 File descriptor 0 is duplicated.
2662 File descriptor 1 is duplicated.
2665 File descriptor 2 is duplicated.
2667 .B /dev/tcp/\fIhost\fP/\fIport\fP
2668 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
2669 is an integer port number, \fBbash\fP attempts to open a TCP connection
2670 to the corresponding socket.
2672 .B /dev/udp/\fIhost\fP/\fIport\fP
2673 If \fIhost\fP is a valid hostname or Internet address, and \fIport\fP
2674 is an integer port number, \fBbash\fP attempts to open a UDP connection
2675 to the corresponding socket.
2679 A failure to open or create a file causes the redirection to fail.
2680 .SS Redirecting Input
2682 Redirection of input causes the file whose name results from
2685 to be opened for reading on file descriptor
2687 or the standard input (file descriptor 0) if
2691 The general format for redirecting input is:
2694 [\fIn\fP]\fB<\fP\fIword\fP
2696 .SS Redirecting Output
2698 Redirection of output causes the file whose name results from
2701 to be opened for writing on file descriptor
2703 or the standard output (file descriptor 1) if
2705 is not specified. If the file does not exist it is created;
2706 if it does exist it is truncated to zero size.
2708 The general format for redirecting output is:
2711 [\fIn\fP]\fB>\fP\fIword\fP
2714 If the redirection operator is
2720 builtin has been enabled, the redirection will fail if the file
2721 whose name results from the expansion of \fIword\fP exists and is
2723 If the redirection operator is
2725 or the redirection operator is
2731 builtin command is not enabled, the redirection is attempted even
2732 if the file named by \fIword\fP exists.
2733 .SS Appending Redirected Output
2735 Redirection of output in this fashion
2736 causes the file whose name results from
2739 to be opened for appending on file descriptor
2741 or the standard output (file descriptor 1) if
2743 is not specified. If the file does not exist it is created.
2745 The general format for appending output is:
2748 [\fIn\fP]\fB>>\fP\fIword\fP
2751 .SS Redirecting Standard Output and Standard Error
2755 standard output (file descriptor 1) and
2756 the standard error output (file descriptor 2)
2757 to be redirected to the file whose name is the
2760 with this construct.
2762 There are two formats for redirecting standard output and
2773 Of the two forms, the first is preferred.
2774 This is semantically equivalent to
2777 \fB>\fP\fIword\fP 2\fB>&\fP1
2781 This type of redirection instructs the shell to read input from the
2782 current source until a line containing only
2784 (with no trailing blanks)
2786 the lines read up to that point are then used as the standard
2787 input for a command.
2789 The format of here-documents is as follows:
2793 \fB<<\fP[\fB\-\fP]\fIword\fP
2794 \fIhere\-document\fP
2799 No parameter expansion, command substitution, arithmetic expansion,
2800 or pathname expansion is performed on
2802 If any characters in
2806 is the result of quote removal on
2808 and the lines in the here-document are not expanded.
2809 If \fIword\fP is unquoted,
2810 all lines of the here-document are subjected to parameter expansion,
2811 command substitution, and arithmetic expansion. In the latter
2812 case, the character sequence
2816 must be used to quote the characters
2822 If the redirection operator is
2824 then all leading tab characters are stripped from input lines and the
2828 here-documents within shell scripts to be indented in a
2830 .SS "Duplicating File Descriptors"
2832 The redirection operator
2835 [\fIn\fP]\fB<&\fP\fIword\fP
2838 is used to duplicate input file descriptors.
2841 expands to one or more digits, the file descriptor denoted by
2843 is made to be a copy of that file descriptor.
2846 do not specify a file descriptor open for input, a redirection error occurs.
2855 is not specified, the standard input (file descriptor 0) is used.
2860 [\fIn\fP]\fB>&\fP\fIword\fP
2863 is used similarly to duplicate output file descriptors. If
2865 is not specified, the standard output (file descriptor 1) is used.
2868 do not specify a file descriptor open for output, a redirection error occurs.
2869 As a special case, if \fIn\fP is omitted, and \fIword\fP does not
2870 expand to one or more digits, the standard output and standard
2871 error are redirected as described previously.
2872 .SS "Opening File Descriptors for Reading and Writing"
2874 The redirection operator
2877 [\fIn\fP]\fB<>\fP\fIword\fP
2880 causes the file whose name is the expansion of
2882 to be opened for both reading and writing on file descriptor
2884 or on file descriptor 0 if
2886 is not specified. If the file does not exist, it is created.
2888 \fIAliases\fP allow a string to be substituted for a word when it is used
2889 as the first word of a simple command.
2890 The shell maintains a list of aliases that may be set and unset with the
2894 builtin commands (see
2896 .B SHELL BUILTIN COMMANDS
2898 The first word of each command, if unquoted,
2899 is checked to see if it has an
2900 alias. If so, that word is replaced by the text of the alias.
2901 The alias name and the replacement text may contain any valid
2902 shell input, including the
2904 listed above, with the exception that the alias name may not
2905 contain \fI=\fP. The first word of the replacement text is tested
2906 for aliases, but a word that is identical to an alias being expanded
2907 is not expanded a second time. This means that one may alias
2913 does not try to recursively expand the replacement text.
2914 If the last character of the alias value is a
2916 then the next command
2917 word following the alias is also checked for alias expansion.
2919 Aliases are created and listed with the
2921 command, and removed with the
2925 There is no mechanism for using arguments in the replacement text.
2926 If arguments are needed, a shell function should be used (see
2931 Aliases are not expanded when the shell is not interactive, unless
2934 shell option is set using
2936 (see the description of
2940 \fBSHELL BUILTIN COMMANDS\fP
2943 The rules concerning the definition and use of aliases are
2946 always reads at least one complete line
2947 of input before executing any
2948 of the commands on that line. Aliases are expanded when a
2949 command is read, not when it is executed. Therefore, an
2950 alias definition appearing on the same line as another
2951 command does not take effect until the next line of input is read.
2952 The commands following the alias definition
2953 on that line are not affected by the new alias.
2954 This behavior is also an issue when functions are executed.
2955 Aliases are expanded when a function definition is read,
2956 not when the function is executed, because a function definition
2957 is itself a compound command. As a consequence, aliases
2958 defined in a function are not available until after that
2959 function is executed. To be safe, always put
2960 alias definitions on a separate line, and do not use
2962 in compound commands.
2964 For almost every purpose, aliases are superseded by
2967 A shell function, defined as described above under
2969 .BR "SHELL GRAMMAR" ,
2970 stores a series of commands for later execution.
2971 When the name of a shell function is used as a simple command name,
2972 the list of commands associated with that function name is executed.
2973 Functions are executed in the context of the
2974 current shell; no new process is created to interpret
2975 them (contrast this with the execution of a shell script).
2976 When a function is executed, the arguments to the
2977 function become the positional parameters
2978 during its execution.
2979 The special parameter
2981 is updated to reflect the change. Positional parameter 0
2986 variable is set to the name of the function while the function
2988 All other aspects of the shell execution
2989 environment are identical between a function and its caller
2990 with the exception that the
2993 trap (see the description of the
2997 .B SHELL BUILTIN COMMANDS
2998 below) is not inherited.
3000 Variables local to the function may be declared with the
3002 builtin command. Ordinarily, variables and their values
3003 are shared between the function and its caller.
3005 If the builtin command
3007 is executed in a function, the function completes and
3008 execution resumes with the next command after the function
3009 call. When a function completes, the values of the
3010 positional parameters and the special parameter
3012 are restored to the values they had prior to the function's
3015 Function names and definitions may be listed with the
3021 builtin commands. The
3027 will list the function names only.
3028 Functions may be exported so that subshells
3029 automatically have them defined with the
3035 Functions may be recursive. No limit is imposed on the number
3037 .SH "ARITHMETIC EVALUATION"
3038 The shell allows arithmetic expressions to be evaluated, under
3039 certain circumstances (see the \fBlet\fP builtin command and
3040 \fBArithmetic Expansion\fP).
3041 Evaluation is done in long integers with no check for overflow,
3042 though division by 0 is trapped and flagged as an error.
3043 The operators and their precedence and associativity are the same
3044 as in the C language.
3045 The following list of operators is grouped into levels of
3046 equal-precedence operators.
3047 The levels are listed in order of decreasing precedence.
3051 .B \fIid\fP++ \fIid\fP\-\-
3052 variable post-increment and post-decrement
3054 .B ++\fIid\fP \-\-\fIid\fP
3055 variable pre-increment and pre-decrement
3058 unary minus and plus
3061 logical and bitwise negation
3067 multiplication, division, remainder
3070 addition, subtraction
3073 left and right bitwise shifts
3079 equality and inequality
3085 bitwise exclusive OR
3096 .B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
3097 conditional evaluation
3099 .B = *= /= %= += \-= <<= >>= &= ^= |=
3102 .B \fIexpr1\fP , \fIexpr2\fP
3106 Shell variables are allowed as operands; parameter expansion is
3107 performed before the expression is evaluated.
3108 Within an expression, shell variables may also be referenced by name
3109 without using the parameter expansion syntax.
3110 The value of a variable is evaluated as an arithmetic expression
3111 when it is referenced.
3112 A shell variable need not have its integer attribute
3113 turned on to be used in an expression.
3115 Constants with a leading 0 are interpreted as octal numbers.
3116 A leading 0x or 0X denotes hexadecimal.
3117 Otherwise, numbers take the form [\fIbase#\fP]n, where \fIbase\fP
3118 is a decimal number between 2 and 64 representing the arithmetic
3119 base, and \fIn\fP is a number in that base.
3120 If \fIbase#\fP is omitted, then base 10 is used.
3121 The digits greater than 9 are represented by the lowercase letters,
3122 the uppercase letters, _, and @, in that order.
3123 If \fIbase\fP is less than or equal to 36, lowercase and uppercase
3124 letters may be used interchangably to represent numbers between 10
3127 Operators are evaluated in order of precedence. Sub-expressions in
3128 parentheses are evaluated first and may override the precedence
3130 .SH "CONDITIONAL EXPRESSIONS"
3131 Conditional expressions are used by the \fB[[\fP compound command and
3132 the \fBtest\fP and \fB[\fP builtin commands to test file attributes
3133 and perform string and arithmetic comparisons.
3134 Expressions are formed from the following unary or binary primaries.
3135 If any \fIfile\fP argument to one of the primaries is of the form
3136 \fI/dev/fd/n\fP, then file descriptor \fIn\fP is checked.
3137 If the \fIfile\fP argument to one of the primaries is one of
3138 \fI/dev/stdin\fP, \fI/dev/stdout\fP, or \fI/dev/stderr\fP, file
3139 descriptor 0, 1, or 2, respectively, is checked.
3144 True if \fIfile\fP exists.
3147 True if \fIfile\fP exists and is a block special file.
3150 True if \fIfile\fP exists and is a character special file.
3153 True if \fIfile\fP exists and is a directory.
3156 True if \fIfile\fP exists.
3159 True if \fIfile\fP exists and is a regular file.
3162 True if \fIfile\fP exists and is set-group-id.
3165 True if \fIfile\fP exists and is a symbolic link.
3168 True if \fIfile\fP exists and its ``sticky'' bit is set.
3171 True if \fIfile\fP exists and is a named pipe (FIFO).
3174 True if \fIfile\fP exists and is readable.
3177 True if \fIfile\fP exists and has a size greater than zero.
3180 True if file descriptor
3182 is open and refers to a terminal.
3185 True if \fIfile\fP exists and its set-user-id bit is set.
3188 True if \fIfile\fP exists and is writable.
3191 True if \fIfile\fP exists and is executable.
3194 True if \fIfile\fP exists and is owned by the effective user id.
3197 True if \fIfile\fP exists and is owned by the effective group id.
3200 True if \fIfile\fP exists and is a symbolic link.
3203 True if \fIfile\fP exists and is a socket.
3206 True if \fIfile\fP exists and has been modified since it was last read.
3208 \fIfile1\fP \-\fBnt\fP \fIfile2\fP
3209 True if \fIfile1\fP is newer (according to
3210 modification date) than \fIfile2\fP.
3212 \fIfile1\fP \-\fBot\fP \fIfile2\fP
3213 True if \fIfile1\fP is older than \fIfile2\fP.
3215 \fIfile1\fP \fB\-ef\fP \fIfile2\fP
3216 True if \fIfile1\fP and \fIfile2\fP have the same device and
3219 .B \-o \fIoptname\fP
3220 True if shell option
3223 See the list of options under the description of the
3230 True if the length of \fIstring\fP is zero.
3235 True if the length of
3239 \fIstring1\fP \fB==\fP \fIstring2\fP
3240 True if the strings are equal. \fB=\fP may be used in place of
3243 \fIstring1\fP \fB!=\fP \fIstring2\fP
3244 True if the strings are not equal.
3246 \fIstring1\fP \fB<\fP \fIstring2\fP
3247 True if \fIstring1\fP sorts before \fIstring2\fP lexicographically
3248 in the current locale.
3250 \fIstring1\fP \fB>\fP \fIstring2\fP
3251 True if \fIstring1\fP sorts after \fIstring2\fP lexicographically
3252 in the current locale.
3254 .I \fIarg1\fP \fBOP\fP \fIarg2\fP
3265 These arithmetic binary operators return true if \fIarg1\fP
3266 is equal to, not equal to, less than, less than or equal to,
3267 greater than, or greater than or equal to \fIarg2\fP, respectively.
3271 may be positive or negative integers.
3273 .SH "SIMPLE COMMAND EXPANSION"
3274 When a simple command is executed, the shell performs the following
3275 expansions, assignments, and redirections, from left to right.
3277 The words that the parser has marked as variable assignments (those
3278 preceding the command name) and redirections are saved for later
3281 The words that are not variable assignments or redirections are
3282 expanded. If any words remain after expansion, the first word
3283 is taken to be the name of the command and the remaining words are
3286 Redirections are performed as described above under
3290 The text after the \fB=\fP in each variable assignment undergoes tilde
3291 expansion, parameter expansion, command substitution, arithmetic expansion,
3292 and quote removal before being assigned to the variable.
3294 If no command name results, the variable assignments affect the current
3295 shell environment. Otherwise, the variables are added to the environment
3296 of the executed command and do not affect the current shell environment.
3297 If any of the assignments attempts to assign a value to a readonly variable,
3298 an error occurs, and the command exits with a non-zero status.
3300 If no command name results, redirections are performed, but do not
3301 affect the current shell environment. A redirection error causes the
3302 command to exit with a non-zero status.
3304 If there is a command name left after expansion, execution proceeds as
3305 described below. Otherwise, the command exits. If one of the expansions
3306 contained a command substitution, the exit status of the command is
3307 the exit status of the last command substitution performed. If there
3308 were no command substitutions, the command exits with a status of zero.
3309 .SH "COMMAND EXECUTION"
3310 After a command has been split into words, if it results in a
3311 simple command and an optional list of arguments, the following
3314 If the command name contains no slashes, the shell attempts to
3315 locate it. If there exists a shell function by that name, that
3316 function is invoked as described above in
3319 If the name does not match a function, the shell searches for
3320 it in the list of shell builtins. If a match is found, that
3323 If the name is neither a shell function nor a builtin,
3324 and contains no slashes,
3326 searches each element of the
3329 for a directory containing an executable file by that name.
3331 uses a hash table to remember the full pathnames of executable
3336 .B "SHELL BUILTIN COMMANDS"
3338 A full search of the directories in
3341 is performed only if the command is not found in the hash table.
3342 If the search is unsuccessful, the shell prints an error
3343 message and returns an exit status of 127.
3345 If the search is successful, or if the command name contains
3346 one or more slashes, the shell executes the named program in a
3347 separate execution environment.
3348 Argument 0 is set to the name given, and the remaining arguments
3349 to the command are set to the arguments given, if any.
3351 If this execution fails because the file is not in executable
3352 format, and the file is not a directory, it is assumed to be
3353 a \fIshell script\fP, a file
3354 containing shell commands. A subshell is spawned to execute
3355 it. This subshell reinitializes itself, so
3356 that the effect is as if a new shell had been invoked
3357 to handle the script, with the exception that the locations of
3358 commands remembered by the parent (see
3362 \fBSHELL BUILTIN COMMANDS\fP)
3363 are retained by the child.
3365 If the program is a file beginning with
3367 the remainder of the first line specifies an interpreter
3368 for the program. The shell executes the
3369 specified interpreter on operating systems that do not
3370 handle this executable format themselves. The arguments to the
3371 interpreter consist of a single optional argument following the
3372 interpreter name on the first line of the program, followed
3373 by the name of the program, followed by the command
3375 .SH COMMAND EXECUTION ENVIRONMENT
3376 The shell has an \fIexecution environment\fP, which consists of the
3380 open files inherited by the shell at invocation, as modified by
3381 redirections supplied to the \fBexec\fP builtin
3383 the current working directory as set by \fBcd\fP, \fBpushd\fP, or
3384 \fBpopd\fP, or inherited by the shell at invocation
3386 the file creation mode mask as set by \fBumask\fP or inherited from
3389 current traps set by \fBtrap\fP
3391 shell parameters that are set by variable assignment or with \fBset\fP
3392 or inherited from the shell's parent in the environment
3394 shell functions defined during execution or inherited from the shell's
3395 parent in the environment
3397 options enabled at invocation (either by default or with command-line
3398 arguments) or by \fBset\fP
3400 options enabled by \fBshopt\fP
3402 shell aliases defined with \fBalias\fP
3404 various process IDs, including those of background jobs, the value
3405 of \fB$$\fP, and the value of \fB$PPID\fP
3407 When a simple command other than a builtin or shell function
3408 is to be executed, it
3409 is invoked in a separate execution environment that consists of
3410 the following. Unless otherwise noted, the values are inherited
3414 the shell's open files, plus any modifications and additions specified
3415 by redirections to the command
3417 the current working directory
3419 the file creation mode mask
3421 shell variables marked for export, along with variables exported for
3422 the command, passed in the environment
3424 traps caught by the shell are reset to the values the inherited
3425 from the shell's parent, and traps ignored by the shell are ignored
3427 A command invoked in this separate environment cannot affect the
3428 shell's execution environment.
3430 Command substitution and asynchronous commands are invoked in a
3431 subshell environment that is a duplicate of the shell environment,
3432 except that traps caught by the shell are reset to the values
3433 that the shell inherited from its parent at invocation. Builtin
3434 commands that are invoked as part of a pipeline are also executed in a
3435 subshell environment. Changes made to the subshell environment
3436 cannot affect the shell's execution environment.
3438 When a program is invoked it is given an array of strings
3442 \fIname\fP\-\fIvalue\fP pairs, of the form
3443 .IR "name\fR=\fPvalue" .
3445 The shell provides several ways to manipulate the environment.
3446 On invocation, the shell scans its own environment and
3447 creates a parameter for each name found, automatically marking
3450 to child processes. Executed commands inherit the environment.
3455 commands allow parameters and functions to be added to and
3456 deleted from the environment. If the value of a parameter
3457 in the environment is modified, the new value becomes part
3458 of the environment, replacing the old. The environment
3459 inherited by any executed command consists of the shell's
3460 initial environment, whose values may be modified in the shell,
3461 less any pairs removed by the
3463 command, plus any additions via the
3469 The environment for any
3471 or function may be augmented temporarily by prefixing it with
3472 parameter assignments, as described above in
3475 These assignment statements affect only the environment seen
3480 option is set (see the
3482 builtin command below), then
3484 parameter assignments are placed in the environment for a command,
3485 not just those that precede the command name.
3489 invokes an external command, the variable
3491 is set to the full file name of the command and passed to that
3492 command in its environment.
3494 For the shell's purposes, a command which exits with a
3495 zero exit status has succeeded. An exit status of zero
3496 indicates success. A non-zero exit status indicates failure.
3497 When a command terminates on a fatal signal \fIN\fP, \fBbash\fP uses
3498 the value of 128+\fIN\fP as the exit status.
3500 If a command is not found, the child process created to
3501 execute it returns a status of 127. If a command is found
3502 but is not executable, the return status is 126.
3504 If a command fails because of an error during expansion or redirection,
3505 the exit status is greater than zero.
3507 Shell builtin commands return a status of 0 (\fItrue\fP) if
3508 successful, and non-zero (\fIfalse\fP) if an error occurs
3510 All builtins return an exit status of 2 to indicate incorrect usage.
3512 \fBBash\fP itself returns the exit status of the last command
3513 executed, unless a syntax error occurs, in which case it exits
3514 with a non-zero value. See also the \fBexit\fP builtin
3517 When \fBbash\fP is interactive, in the absence of any traps, it ignores
3520 (so that \fBkill 0\fP does not kill an interactive shell),
3524 is caught and handled (so that the \fBwait\fP builtin is interruptible).
3525 In all cases, \fBbash\fP ignores
3528 If job control is in effect,
3539 Synchronous jobs started by \fBbash\fP have signal handlers
3540 set to the values inherited by the shell from its parent.
3541 When job control is not in effect, asynchronous commands
3549 Commands run as a result of command substitution ignore the
3550 keyboard-generated job control signals
3559 The shell exits by default upon receipt of a
3562 Before exiting, it resends the
3565 to all jobs, running or stopped.
3566 Stopped jobs are sent
3569 to ensure that they receive the
3572 To prevent the shell from
3573 sending the signal to a particular job, it should be removed from the
3578 .B "SHELL BUILTIN COMMANDS"
3588 shell option has been set with
3594 to all jobs when an interactive login shell exits.
3596 When \fBbash\fP receives a signal for which a trap has been set while
3597 waiting for a command to complete, the trap will not be executed until
3598 the command completes.
3599 When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
3600 builtin, the reception of a signal for which a trap has been set will
3601 cause the \fBwait\fP builtin to return immediately with an exit status
3602 greater than 128, immediately after which the trap is executed.
3605 refers to the ability to selectively stop (\fIsuspend\fP)
3606 the execution of processes and continue (\fIresume\fP)
3607 their execution at a later point. A user typically employs
3608 this facility via an interactive interface supplied jointly
3609 by the system's terminal driver and
3612 The shell associates a
3614 with each pipeline. It keeps a table of currently executing
3615 jobs, which may be listed with the
3619 starts a job asynchronously (in the
3621 it prints a line that looks like:
3627 indicating that this job is job number 1 and that the process ID
3628 of the last process in the pipeline associated with this job is 25647.
3629 All of the processes in a single pipeline are members of the same job.
3633 abstraction as the basis for job control.
3635 To facilitate the implementation of the user interface to job
3636 control, the operating system maintains the notion of a \fIcurrent terminal
3637 process group ID\fP. Members of this process group (processes whose
3638 process group ID is equal to the current terminal process group ID)
3639 receive keyboard-generated signals such as
3642 These processes are said to be in the
3645 processes are those whose process group ID differs from the terminal's;
3646 such processes are immune to keyboard-generated signals.
3647 Only foreground processes are allowed to read from or write to the
3648 terminal. Background processes which attempt to read from (write to) the
3651 .B SIGTTIN (SIGTTOU)
3652 signal by the terminal driver,
3653 which, unless caught, suspends the process.
3655 If the operating system on which
3660 contains facilities to use it.
3663 character (typically
3665 Control-Z) while a process is running
3666 causes that process to be stopped and returns control to
3669 .I "delayed suspend"
3670 character (typically
3672 Control-Y) causes the process to be stopped when it
3673 attempts to read input from the terminal, and control to
3676 The user may then manipulate the state of this job, using the
3678 command to continue it in the background, the
3680 command to continue it in the foreground, or
3683 command to kill it. A \fB^Z\fP takes effect immediately,
3684 and has the additional side effect of causing pending output
3685 and typeahead to be discarded.
3687 There are a number of ways to refer to a job in the shell.
3690 introduces a job name. Job number
3692 may be referred to as
3694 A job may also be referred to using a prefix of the name used to
3695 start it, or using a substring that appears in its command line.
3700 job. If a prefix matches more than one job,
3702 reports an error. Using
3704 on the other hand, refers to any job containing the string
3706 in its command line. If the substring matches more than one job,
3708 reports an error. The symbols
3712 refer to the shell's notion of the
3714 which is the last job stopped while it was in
3715 the foreground or started in the background.
3718 may be referenced using
3720 In output pertaining to jobs (e.g., the output of the
3722 command), the current job is always flagged with a
3724 and the previous job with a
3727 Simply naming a job can be used to bring it into the
3732 bringing job 1 from the background into the foreground.
3735 resumes job 1 in the background, equivalent to
3738 The shell learns immediately whenever a job changes state.
3741 waits until it is about to print a prompt before reporting
3742 changes in a job's status so as to not interrupt
3743 any other output. If the
3750 reports such changes immediately.
3752 If an attempt to exit
3754 is made while jobs are stopped, the shell prints a warning message. The
3756 command may then be used to inspect their status.
3757 If a second attempt to exit is made without an intervening command,
3758 the shell does not print another warning, and the stopped
3759 jobs are terminated.
3761 When executing interactively,
3763 displays the primary prompt
3766 when it is ready to read a command, and the secondary prompt
3769 when it needs more input to complete a command.
3771 allows these prompt strings to be customized by inserting a number of
3772 backslash-escaped special characters that are decoded as follows:
3777 an ASCII bell character (07)
3780 the date in "Weekday Month Date" format (e.g., "Tue May 26")
3783 an ASCII escape character (033)
3786 the hostname up to the first `.'
3792 the number of jobs currently managed by the shell
3795 the basename of the shell's terminal device name
3804 the name of the shell, the basename of
3806 (the portion following the final slash)
3809 the current time in 24-hour HH:MM:SS format
3812 the current time in 12-hour HH:MM:SS format
3815 the current time in 12-hour am/pm format
3818 the username of the current user
3821 the version of \fBbash\fP (e.g., 2.00)
3824 the release of \fBbash\fP, version + patchlevel (e.g., 2.00.0)
3827 the current working directory
3830 the basename of the current working directory
3833 the history number of this command
3836 the command number of this command
3839 if the effective UID is 0, a
3845 the character corresponding to the octal number \fInnn\fP
3851 begin a sequence of non-printing characters, which could be used to
3852 embed a terminal control sequence into the prompt
3855 end a sequence of non-printing characters
3859 The command number and the history number are usually different:
3860 the history number of a command is its position in the history
3861 list, which may include commands restored from the history file
3865 below), while the command number is the position in the sequence
3866 of commands executed during the current shell session.
3867 After the string is decoded, it is expanded via
3868 parameter expansion, command substitution, arithmetic
3869 expansion, and quote removal, subject to the value of the
3871 shell option (see the description of the
3875 .B "SHELL BUILTIN COMMANDS"
3878 This is the library that handles reading input when using an interactive
3881 option is given at shell invocation.
3882 By default, the line editing commands are similar to those of emacs.
3883 A vi-style line editing interface is also available.
3884 To turn off line editing after the shell is running, use the
3892 .B SHELL BUILTIN COMMANDS
3894 .SS "Readline Notation"
3896 In this section, the emacs-style notation is used to denote
3897 keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
3898 means Control\-N. Similarly,
3900 keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
3903 key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
3906 key. This makes ESC the \fImeta prefix\fP.
3907 The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
3908 or press the Escape key
3909 then hold the Control key while pressing the
3913 Readline commands may be given numeric
3915 which normally act as a repeat count.
3916 Sometimes, however, it is the sign of the argument that is significant.
3917 Passing a negative argument to a command that acts in the forward
3918 direction (e.g., \fBkill\-line\fP) causes that command to act in a
3920 Commands whose behavior with arguments deviates from this are noted
3923 When a command is described as \fIkilling\fP text, the text
3924 deleted is saved for possible future retrieval
3925 (\fIyanking\fP). The killed text is saved in a
3926 \fIkill ring\fP. Consecutive kills cause the text to be
3927 accumulated into one unit, which can be yanked all at once.
3928 Commands which do not kill text separate the chunks of text
3930 .SS "Readline Initialization"
3932 Readline is customized by putting commands in an initialization
3933 file (the \fIinputrc\fP file).
3934 The name of this file is taken from the value of the
3937 variable. If that variable is unset, the default is
3939 When a program which uses the readline library starts up, the
3940 initialization file is read, and the key bindings and variables
3942 There are only a few basic constructs allowed in the
3943 readline initialization file.
3944 Blank lines are ignored.
3945 Lines beginning with a \fB#\fP are comments.
3946 Lines beginning with a \fB$\fP indicate conditional constructs.
3947 Other lines denote key bindings and variable settings.
3949 The default key-bindings may be changed with an
3952 Other programs that use this library may add their own commands
3955 For example, placing
3958 M\-Control\-u: universal\-argument
3962 C\-Meta\-u: universal\-argument
3966 would make M\-C\-u execute the readline command
3967 .IR universal\-argument .
3969 The following symbolic character names are recognized:
3982 In addition to command names, readline allows keys to be bound
3983 to a string that is inserted when the key is pressed (a \fImacro\fP).
3984 .SS "Readline Key Bindings"
3986 The syntax for controlling key bindings in the
3988 file is simple. All that is required is the name of the
3989 command or the text of a macro and a key sequence to which
3990 it should be bound. The name may be specified in one of two ways:
3991 as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
3992 prefixes, or as a key sequence.
3993 When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
3995 is the name of a key spelled out in English. For example:
3998 Control-u: universal\-argument
4000 Meta-Rubout: backward-kill-word
4002 Control-o: "> output"
4005 In the above example,
4007 is bound to the function
4008 .BR universal\-argument ,
4010 is bound to the function
4011 .BR backward\-kill\-word ,
4014 is bound to run the macro
4015 expressed on the right hand side (that is, to insert the text
4019 In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
4023 above in that strings denoting
4024 an entire key sequence may be specified by placing the sequence
4025 within double quotes. Some GNU Emacs style key escapes can be
4026 used, as in the following example.
4029 "\eC\-u": universal\-argument
4031 "\eC\-x\eC\-r": re\-read\-init\-file
4033 "\ee[11~": "Function Key 1"
4038 is again bound to the function
4039 .BR universal\-argument .
4041 is bound to the function
4042 .BR re\-read\-init\-file ,
4045 is bound to insert the text
4046 .BR "Function Key 1" .
4047 The full set of GNU Emacs style escape sequences is
4071 In addition to the GNU Emacs style escape sequences, a second
4072 set of backslash escapes is available:
4101 the character whose ASCII code is the octal value \fInnn\fP
4102 (one to three digits)
4105 the character whose ASCII code is the hexadecimal value \fInnn\fP
4106 (one to three digits)
4110 When entering the text of a macro, single or double quotes must
4111 be used to indicate a macro definition.
4112 Unquoted text is assumed to be a function name.
4113 In the macro body, the backslash escapes described above are expanded.
4114 Backslash will quote any other character in the macro text,
4118 allows the current readline key bindings to be displayed or modified
4121 builtin command. The editing mode may be switched during interactive
4126 builtin command (see
4128 .B SHELL BUILTIN COMMANDS
4130 .SS "Readline Variables"
4132 Readline has variables that can be used to further customize its
4133 behavior. A variable may be set in the
4135 file with a statement of the form
4138 \fBset\fP \fIvariable\-name\fP \fIvalue\fP
4141 Except where noted, readline variables can take the values
4145 The variables and their default values are:
4149 .B bell\-style (audible)
4150 Controls what happens when readline wants to ring the terminal bell.
4151 If set to \fBnone\fP, readline never rings the bell. If set to
4152 \fBvisible\fP, readline uses a visible bell if one is available.
4153 If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
4155 .B comment\-begin (``#'')
4156 The string that is inserted when the readline
4158 command is executed.
4159 This command is bound to
4161 in emacs mode and to
4165 .B completion\-ignore\-case (Off)
4166 If set to \fBOn\fP, readline performs filename matching and completion
4167 in a case\-insensitive fashion.
4169 .B completion\-query\-items (100)
4170 This determines when the user is queried about viewing
4171 the number of possible completions
4172 generated by the \fBpossible\-completions\fP command.
4173 It may be set to any integer value greater than or equal to
4174 zero. If the number of possible completions is greater than
4175 or equal to the value of this variable, the user is asked whether
4176 or not he wishes to view them; otherwise they are simply listed
4179 .B convert\-meta (On)
4180 If set to \fBOn\fP, readline will convert characters with the
4181 eighth bit set to an ASCII key sequence
4182 by stripping the eighth bit and prefixing an
4183 escape character (in effect, using escape as the \fImeta prefix\fP).
4185 .B disable\-completion (Off)
4186 If set to \fBOn\fP, readline will inhibit word completion. Completion
4187 characters will be inserted into the line as if they had been
4188 mapped to \fBself-insert\fP.
4190 .B editing\-mode (emacs)
4191 Controls whether readline begins with a set of key bindings similar
4192 to \fIemacs\fP or \fIvi\fP.
4194 can be set to either
4199 .B enable\-keypad (Off)
4200 When set to \fBOn\fP, readline will try to enable the application
4201 keypad when it is called. Some systems need this to enable the
4204 .B expand\-tilde (Off)
4205 If set to \fBon\fP, tilde expansion is performed when readline
4206 attempts word completion.
4208 .B horizontal\-scroll\-mode (Off)
4209 When set to \fBOn\fP, makes readline use a single line for display,
4210 scrolling the input horizontally on a single screen line when it
4211 becomes longer than the screen width rather than wrapping to a new line.
4213 .B input\-meta (Off)
4214 If set to \fBOn\fP, readline will enable eight-bit input (that is,
4215 it will not strip the high bit from the characters it reads),
4216 regardless of what the terminal claims it can support. The name
4218 is a synonym for this variable.
4220 .B isearch\-terminators (``C\-[C\-J'')
4221 The string of characters that should terminate an incremental
4222 search without subsequently executing the character as a command.
4223 If this variable has not been given a value, the characters
4224 \fIESC\fP and \fIC\-J\fP will terminate an incremental search.
4227 Set the current readline keymap. The set of valid keymap names is
4228 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
4231 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
4232 equivalent to \fIemacs\-standard\fP. The default value is
4236 also affects the default keymap.
4238 .B mark\-directories (On)
4239 If set to \fBOn\fP, completed directory names have a slash
4242 .B mark\-modified\-lines (Off)
4243 If set to \fBOn\fP, history lines that have been modified are displayed
4244 with a preceding asterisk (\fB*\fP).
4246 .B output\-meta (Off)
4247 If set to \fBOn\fP, readline will display characters with the
4248 eighth bit set directly rather than as a meta-prefixed escape
4251 .B print\-completions\-horizontally (Off)
4252 If set to \fBOn\fP, readline will display completions with matches
4253 sorted horizontally in alphabetical order, rather than down the screen.
4255 .B show\-all\-if\-ambiguous (Off)
4256 This alters the default behavior of the completion functions. If
4259 words which have more than one possible completion cause the
4260 matches to be listed immediately instead of ringing the bell.
4262 .B visible\-stats (Off)
4263 If set to \fBOn\fP, a character denoting a file's type as reported
4264 by \fIstat\fP(2) is appended to the filename when listing possible
4267 .SS "Readline Conditional Constructs"
4269 Readline implements a facility similar in spirit to the conditional
4270 compilation features of the C preprocessor which allows key
4271 bindings and variable settings to be performed as the result
4272 of tests. There are four parser directives used.
4276 construct allows bindings to be made based on the
4277 editing mode, the terminal being used, or the application using
4278 readline. The text of the test extends to the end of the line;
4279 no characters are required to isolate it.
4282 The \fBmode=\fP form of the \fB$if\fP directive is used to test
4283 whether readline is in emacs or vi mode.
4284 This may be used in conjunction
4285 with the \fBset keymap\fP command, for instance, to set bindings in
4286 the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
4287 readline is starting out in emacs mode.
4289 The \fBterm=\fP form may be used to include terminal-specific
4290 key bindings, perhaps to bind the key sequences output by the
4291 terminal's function keys. The word on the right side of the
4293 is tested against the both full name of the terminal and the portion
4294 of the terminal name before the first \fB\-\fP. This allows
4301 .IP \fBapplication\fP
4302 The \fBapplication\fP construct is used to include
4303 application-specific settings. Each program using the readline
4304 library sets the \fIapplication name\fP, and an initialization
4305 file can test for a particular value.
4306 This could be used to bind key sequences to functions useful for
4307 a specific program. For instance, the following command adds a
4308 key sequence that quotes the current or previous word in Bash:
4313 # Quote the current or previous word
4314 "\eC\-xq": "\eeb\e"\eef\e""
4320 This command, as seen in the previous example, terminates an
4323 Commands in this branch of the \fB$if\fP directive are executed if
4326 This directive takes a single filename as an argument and reads commands
4327 and bindings from that file. For example, the following directive
4328 would read \fI/etc/inputrc\fP:
4332 \fB$include\fP \^ \fI/etc/inputrc\fP
4337 Readline provides commands for searching through the command history
4341 below) for lines containing a specified string.
4342 There are two search modes:
4345 .IR non-incremental .
4347 Incremental searches begin before the user has finished typing the
4349 As each character of the search string is typed, readline displays
4350 the next entry from the history matching the string typed so far.
4351 An incremental search requires only as many characters as needed to
4352 find the desired history entry.
4353 The characters present in the value of the \fBisearch-terminators\fP
4354 variable are used to terminate an incremental search.
4355 If that variable has not been assigned a value the Escape and
4356 Control-J characters will terminate an incremental search.
4357 Control-G will abort an incremental search and restore the original
4359 When the search is terminated, the history entry containing the
4360 search string becomes the current line.
4362 To find other matching entries in the history list, type Control-S or
4363 Control-R as appropriate.
4364 This will search backward or forward in the history for the next
4365 entry matching the search string typed so far.
4366 Any other key sequence bound to a readline command will terminate
4367 the search and execute that command.
4368 For instance, a \fInewline\fP will terminate the search and accept
4369 the line, thereby executing the command from the history list.
4371 Non-incremental searches read the entire search string before starting
4372 to search for matching history lines. The search string may be
4373 typed by the user or be part of the contents of the current line.
4374 .SS "Readline Command Names"
4376 The following is a list of the names of the commands and the default
4377 key sequences to which they are bound.
4378 Command names without an accompanying key sequence are unbound by default.
4379 In the following descriptions, \fIpoint\fP refers to the current cursor
4380 position, and \fImark\fP refers to a cursor position saved by the
4381 \fBset\-mark\fP command.
4382 The text between the point and mark is referred to as the \fIregion\fP.
4383 .SS Commands for Moving
4387 .B beginning\-of\-line (C\-a)
4388 Move to the start of the current line.
4390 .B end\-of\-line (C\-e)
4391 Move to the end of the line.
4393 .B forward\-char (C\-f)
4394 Move forward a character.
4396 .B backward\-char (C\-b)
4397 Move back a character.
4399 .B forward\-word (M\-f)
4400 Move forward to the end of the next word. Words are composed of
4401 alphanumeric characters (letters and digits).
4403 .B backward\-word (M\-b)
4404 Move back to the start of the current or previous word. Words are
4405 composed of alphanumeric characters (letters and digits).
4407 .B clear\-screen (C\-l)
4408 Clear the screen leaving the current line at the top of the screen.
4409 With an argument, refresh the current line without clearing the
4412 .B redraw\-current\-line
4413 Refresh the current line.
4415 .SS Commands for Manipulating the History
4419 .B accept\-line (Newline, Return)
4420 Accept the line regardless of where the cursor is. If this line is
4421 non-empty, add it to the history list according to the state of the
4424 variable. If the line is a modified history
4425 line, then restore the history line to its original state.
4427 .B previous\-history (C\-p)
4428 Fetch the previous command from the history list, moving back in
4431 .B next\-history (C\-n)
4432 Fetch the next command from the history list, moving forward in the
4435 .B beginning\-of\-history (M\-<)
4436 Move to the first line in the history.
4438 .B end\-of\-history (M\->)
4439 Move to the end of the input history, i.e., the line currently being
4442 .B reverse\-search\-history (C\-r)
4443 Search backward starting at the current line and moving `up' through
4444 the history as necessary. This is an incremental search.
4446 .B forward\-search\-history (C\-s)
4447 Search forward starting at the current line and moving `down' through
4448 the history as necessary. This is an incremental search.
4450 .B non\-incremental\-reverse\-search\-history (M\-p)
4451 Search backward through the history starting at the current line
4452 using a non-incremental search for a string supplied by the user.
4454 .B non\-incremental\-forward\-search\-history (M\-n)
4455 Search forward through the history using a non-incremental search for
4456 a string supplied by the user.
4458 .B history\-search\-forward
4459 Search forward through the history for the string of characters
4460 between the start of the current line and the point.
4461 This is a non-incremental search.
4463 .B history\-search\-backward
4464 Search backward through the history for the string of characters
4465 between the start of the current line and the point.
4466 This is a non-incremental search.
4468 .B yank\-nth\-arg (M\-C\-y)
4469 Insert the first argument to the previous command (usually
4470 the second word on the previous line) at point (the current
4471 cursor position). With an argument
4473 insert the \fIn\fPth word from the previous command (the words
4474 in the previous command begin with word 0). A negative argument
4475 inserts the \fIn\fPth word from the end of the previous command.
4478 yank\-last\-arg (M\-.\^, M\-_\^)
4479 Insert the last argument to the previous command (the last word of
4480 the previous history entry). With an argument,
4481 behave exactly like \fByank\-nth\-arg\fP.
4482 Successive calls to \fByank\-last\-arg\fP move back through the history
4483 list, inserting the last argument of each line in turn.
4485 .B shell\-expand\-line (M\-C\-e)
4486 Expand the line as the shell does. This
4487 performs alias and history expansion as well as all of the shell
4488 word expansions. See
4490 .B HISTORY EXPANSION
4491 below for a description of history expansion.
4493 .B history\-expand\-line (M\-^)
4494 Perform history expansion on the current line.
4497 .B HISTORY EXPANSION
4498 below for a description of history expansion.
4501 Perform history expansion on the current line and insert a space.
4504 .B HISTORY EXPANSION
4505 below for a description of history expansion.
4507 .B alias\-expand\-line
4508 Perform alias expansion on the current line.
4512 above for a description of alias expansion.
4514 .B history\-and\-alias\-expand\-line
4515 Perform history and alias expansion on the current line.
4517 .B insert\-last\-argument (M\-.\^, M\-_\^)
4518 A synonym for \fByank\-last\-arg\fP.
4520 .B operate\-and\-get\-next (C\-o)
4521 Accept the current line for execution and fetch the next line
4522 relative to the current line from the history for editing. Any
4523 argument is ignored.
4525 .SS Commands for Changing Text
4529 .B delete\-char (C\-d)
4530 Delete the character under the cursor. If point is at the
4531 beginning of the line, there are no characters in the line, and
4532 the last character typed was not bound to \fBdelete\-char\fP,
4537 .B backward\-delete\-char (Rubout)
4538 Delete the character behind the cursor. When given a numeric argument,
4539 save the deleted text on the kill ring.
4541 .B forward\-backward\-delete\-char
4542 Delete the character under the cursor, unless the cursor is at the
4543 end of the line, in which case the character behind the cursor is
4544 deleted. By default, this is not bound to a key.
4546 .B quoted\-insert (C\-q, C\-v)
4547 Add the next character typed to the line verbatim. This is
4548 how to insert characters like \fBC\-q\fP, for example.
4550 .B tab\-insert (C\-v TAB)
4551 Insert a tab character.
4553 .B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
4554 Insert the character typed.
4556 .B transpose\-chars (C\-t)
4557 Drag the character before point forward over the character at point.
4558 Point moves forward as well.
4559 If point is at the end of the line, then transpose the two characters
4561 Negative arguments have no effect.
4563 .B transpose\-words (M\-t)
4564 Drag the word before point past the word after point,
4565 moving the point over that word as well.
4567 .B upcase\-word (M\-u)
4568 Uppercase the current (or following) word. With a negative argument,
4569 uppercase the previous word, but do not move point.
4571 .B downcase\-word (M\-l)
4572 Lowercase the current (or following) word. With a negative argument,
4573 lowercase the previous word, but do not move point.
4575 .B capitalize\-word (M\-c)
4576 Capitalize the current (or following) word. With a negative argument,
4577 capitalize the previous word, but do not move point.
4579 .SS Killing and Yanking
4583 .B kill\-line (C\-k)
4584 Kill the text from point to the end of the line.
4586 .B backward\-kill\-line (C\-x Rubout)
4587 Kill backward to the beginning of the line.
4589 .B unix\-line\-discard (C\-u)
4590 Kill backward from point to the beginning of the line.
4591 The killed text is saved on the kill-ring.
4592 .\" There is no real difference between this and backward-kill-line
4594 .B kill\-whole\-line
4595 Kill all characters on the current line, no matter where point is.
4597 .B kill\-word (M\-d)
4598 Kill from point to the end of the current word, or if between
4599 words, to the end of the next word.
4600 Word boundaries are the same as those used by \fBforward\-word\fP.
4602 .B backward\-kill\-word (M\-Rubout)
4603 Kill the word behind point.
4604 Word boundaries are the same as those used by \fBbackward\-word\fP.
4606 .B unix\-word\-rubout (C\-w)
4607 Kill the word behind point, using white space as a word boundary.
4608 The word boundaries are different from \fBbackward\-kill\-word\fP.
4609 The killed text is saved on the kill-ring.
4611 .B delete\-horizontal\-space (M\-\e)
4612 Delete all spaces and tabs around point.
4615 Kill the text in the current region.
4617 .B copy\-region\-as\-kill
4618 Copy the text in the region to the kill buffer.
4620 .B copy\-backward\-word
4621 Copy the word before point to the kill buffer.
4622 The word boundaries are the same as \fBbackward\-word\fP.
4624 .B copy\-forward\-word
4625 Copy the word following point to the kill buffer.
4626 The word boundaries are the same as \fBforward\-word\fP.
4629 Yank the top of the kill ring into the buffer at the cursor.
4632 Rotate the kill ring, and yank the new top. Only works following
4637 .SS Numeric Arguments
4641 .B digit\-argument (M\-0, M\-1, ..., M\-\-)
4642 Add this digit to the argument already accumulating, or start a new
4643 argument. M\-\- starts a negative argument.
4645 .B universal\-argument
4646 This is another way to specify an argument.
4647 If this command is followed by one or more digits, optionally with a
4648 leading minus sign, those digits define the argument.
4649 If the command is followed by digits, executing
4650 .B universal\-argument
4651 again ends the numeric argument, but is otherwise ignored.
4652 As a special case, if this command is immediately followed by a
4653 character that is neither a digit or minus sign, the argument count
4654 for the next command is multiplied by four.
4655 The argument count is initially one, so executing this function the
4656 first time makes the argument count four, a second time makes the
4657 argument count sixteen, and so on.
4664 Attempt to perform completion on the text before point.
4666 attempts completion treating the text as a variable (if the
4667 text begins with \fB$\fP), username (if the text begins with
4668 \fB~\fP), hostname (if the text begins with \fB@\fP), or
4669 command (including aliases and functions) in turn. If none
4670 of these produces a match, filename completion is attempted.
4672 .B possible\-completions (M\-?)
4673 List the possible completions of the text before point.
4675 .B insert\-completions (M\-*)
4676 Insert all completions of the text before point
4677 that would have been generated by
4678 \fBpossible\-completions\fP.
4681 Similar to \fBcomplete\fP, but replaces the word to be completed
4682 with a single match from the list of possible completions.
4683 Repeated execution of \fBmenu\-complete\fP steps through the list
4684 of possible completions, inserting each match in turn.
4685 At the end of the list of completions, the bell is rung and the
4686 original text is restored.
4687 An argument of \fIn\fP moves \fIn\fP positions forward in the list
4688 of matches; a negative argument may be used to move backward
4690 This command is intended to be bound to \fBTAB\fP, but is unbound
4693 .B delete\-char\-or\-list
4694 Deletes the character under the cursor if not at the beginning or
4695 end of the line (like \fBdelete\-char\fP).
4696 If at the end of the line, behaves identically to
4697 \fBpossible\-completions\fP.
4698 This command is unbound by default.
4700 .B complete\-filename (M\-/)
4701 Attempt filename completion on the text before point.
4703 .B possible\-filename\-completions (C\-x /)
4704 List the possible completions of the text before point,
4705 treating it as a filename.
4707 .B complete\-username (M\-~)
4708 Attempt completion on the text before point, treating
4711 .B possible\-username\-completions (C\-x ~)
4712 List the possible completions of the text before point,
4713 treating it as a username.
4715 .B complete\-variable (M\-$)
4716 Attempt completion on the text before point, treating
4717 it as a shell variable.
4719 .B possible\-variable\-completions (C\-x $)
4720 List the possible completions of the text before point,
4721 treating it as a shell variable.
4723 .B complete\-hostname (M\-@)
4724 Attempt completion on the text before point, treating
4727 .B possible\-hostname\-completions (C\-x @)
4728 List the possible completions of the text before point,
4729 treating it as a hostname.
4731 .B complete\-command (M\-!)
4732 Attempt completion on the text before point, treating
4733 it as a command name. Command completion attempts to
4734 match the text against aliases, reserved words, shell
4735 functions, shell builtins, and finally executable filenames,
4738 .B possible\-command\-completions (C\-x !)
4739 List the possible completions of the text before point,
4740 treating it as a command name.
4742 .B dynamic\-complete\-history (M\-TAB)
4743 Attempt completion on the text before point, comparing
4744 the text against lines from the history list for possible
4747 .B complete\-into\-braces (M\-{)
4748 Perform filename completion and insert the list of possible completions
4749 enclosed within braces so the list is available to the shell (see
4757 .B start\-kbd\-macro (C\-x (\^)
4758 Begin saving the characters typed into the current keyboard macro.
4760 .B end\-kbd\-macro (C\-x )\^)
4761 Stop saving the characters typed into the current keyboard macro
4762 and store the definition.
4764 .B call\-last\-kbd\-macro (C\-x e)
4765 Re-execute the last keyboard macro defined, by making the characters
4766 in the macro appear as if typed at the keyboard.
4772 .B re\-read\-init\-file (C\-x C\-r)
4773 Read in the contents of the \fIinputrc\fP file, and incorporate
4774 any bindings or variable assignments found there.
4777 Abort the current editing command and
4778 ring the terminal's bell (subject to the setting of
4781 .B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
4782 If the metafied character \fIx\fP is lowercase, run the command
4783 that is bound to the corresponding uppercase character.
4785 .B prefix\-meta (ESC)
4786 Metafy the next character typed.
4793 .B undo (C\-_, C\-x C\-u)
4794 Incremental undo, separately remembered for each line.
4796 .B revert\-line (M\-r)
4797 Undo all changes made to this line. This is like executing the
4799 command enough times to return the line to its initial state.
4801 .B tilde\-expand (M\-&)
4802 Perform tilde expansion on the current word.
4804 .B set\-mark (C\-@, M\-<space>)
4805 Set the mark to the current point. If a
4806 numeric argument is supplied, the mark is set to that position.
4808 .B exchange\-point\-and\-mark (C\-x C\-x)
4809 Swap the point with the mark. The current cursor position is set to
4810 the saved position, and the old cursor position is saved as the mark.
4812 .B character\-search (C\-])
4813 A character is read and point is moved to the next occurrence of that
4814 character. A negative count searches for previous occurrences.
4816 .B character\-search\-backward (M\-C\-])
4817 A character is read and point is moved to the previous occurrence of that
4818 character. A negative count searches for subsequent occurrences.
4820 .B insert\-comment (M\-#)
4821 The value of the readline
4823 variable is inserted at the beginning of the current line, and the line
4824 is accepted as if a newline had been typed. The default value of
4825 \fBcomment\-begin\fP causes this command to make the current line
4828 .B glob\-expand\-word (C\-x *)
4829 The word before point is treated as a pattern for pathname expansion,
4830 and the list of matching file names is inserted, replacing the word.
4832 .B glob\-list\-expansions (C\-x g)
4833 The list of expansions that would have been generated by
4834 .B glob\-expand\-word
4835 is displayed, and the line is redrawn.
4838 Print all of the functions and their key bindings to the
4839 readline output stream. If a numeric argument is supplied,
4840 the output is formatted in such a way that it can be made part
4841 of an \fIinputrc\fP file.
4844 Print all of the settable readline variables and their values to the
4845 readline output stream. If a numeric argument is supplied,
4846 the output is formatted in such a way that it can be made part
4847 of an \fIinputrc\fP file.
4850 Print all of the readline key sequences bound to macros and the
4851 strings they ouput. If a numeric argument is supplied,
4852 the output is formatted in such a way that it can be made part
4853 of an \fIinputrc\fP file.
4855 .B display\-shell\-version (C\-x C\-v)
4856 Display version information about the current instance of
4859 .SS Programmable Completion
4861 When word completion is attempted for an argument to a command for
4862 which a completion specification (a \fIcompspec\fP) has been defined
4863 using the \fBcomplete\fP builtin (see
4865 .B "SHELL BUILTIN COMMANDS"
4866 below), the programmable completion facilities are invoked.
4868 First, the command name is identified.
4869 If a compspec has been defined for that command, the
4870 compspec is used to generate the list of possible completions for the word.
4871 If the command word is a full pathname, a compspec for the full
4872 pathname is searched for first.
4873 If no compspec is found for the full pathname, an attempt is made to
4874 find a compspec for the portion following the final slash.
4876 Once a compspec has been found, it is used to generate the list of
4878 If a compspec is not found, the default \fBbash\fP completion as
4879 described above under \fBCompleting\fP is performed.
4881 First, the actions specified by the compspec are used.
4882 Only matches which are prefixed by the word being completed are
4888 option is used for filename or directory name completion, the shell
4892 is used to filter the matches.
4894 Any completions specified by a filename expansion pattern to the
4895 \fB\-G\fP option are generated next.
4896 The words generated by the pattern need not match the word
4901 shell variable is not used to filter the matches, but the
4906 Next, the string specified as the argument to the \fB\-W\fP option
4908 The string is first split using the characters in the
4911 special variable as delimiters.
4912 Shell quoting is honored.
4913 Each word is then expanded using
4914 brace expansion, tilde expansion, parameter and variable expansion,
4915 command substitution, arithmetic expansion, and pathname expansion,
4916 as described above under
4919 The results are split using the rules described above under
4920 \fBWord Splitting\fP.
4921 The results of the expansion are prefix-matched against the word being
4922 completed, and the matching words become the possible completions.
4924 After these matches have been generated, any shell function or command
4925 specified with the \fB\-F\fP and \fB\-C\fP options is invoked.
4926 When the command or function is invoked, the
4932 variables are assigned values as described above under
4933 \fBShell Variables\fP.
4934 If a shell function is being invoked, the
4940 variables are also set.
4941 When the function or command is invoked, the first argument is the
4942 name of the command whose arguments are being completed, the
4943 second argument is the word being completed, and the third argument
4944 is the word preceding the word being completed on the current command line.
4945 No filtering of the generated completions against the word being completed
4946 is performed; the function or command has complete freedom in generating
4949 Any function specified with \fB\-F\fP is invoked first.
4950 The function may use any of the shell facilities, including the
4951 \fBcompgen\fP builtin described below, to generate the matches.
4952 It must put the possible completions in the
4957 Next, any command specified with the \fB\-C\fP option is invoked
4958 in an environment equivalent to command substitution.
4959 It should print a list of completions, one per line, to the
4961 Backslash may be used to escape a newline, if necessary.
4963 After all of the possible completions are generated, any filter
4964 specified with the \fB\-X\fP option is applied to the list.
4965 The filter is a pattern as used for pathname expansion; a \fB&\fP
4966 in the pattern is replaced with the text of the word being completed.
4967 A literal \fB&\fP may be escaped with a backslash; the backslash
4968 is removed before attempting a match.
4969 Any completion that matches the pattern will be removed from the list.
4970 A leading \fB!\fP negates the pattern; in this case any completion
4971 not matching the pattern will be removed.
4973 Finally, any prefix and suffix specified with the \fB\-P\fP and \fB\-S\fP
4974 options are added to each member of the completion list, and the result is
4975 returned to the readline completion code as the list of possible
4978 If a compspec is found, whatever it generates is returned to the completion
4979 code as the full set of possible completions.
4980 The default \fBbash\fP completions are not attempted, and the readline
4981 default of filename completion is disabled.
4987 builtin is enabled, the shell provides access to the
4988 \fIcommand history\fP,
4989 the list of commands previously typed.
4990 The value of the \fBHISTSIZE\fP variable is used as the
4991 number of commands to save in a history list.
4992 The text of the last
4995 commands (default 500) is saved. The shell
4996 stores each command in the history list prior to parameter and
4997 variable expansion (see
5000 above) but after history expansion is performed, subject to the
5001 values of the shell variables
5008 On startup, the history is initialized from the file named by
5012 (default \fI~/.bash_history\fP).
5013 The file named by the value of
5016 is truncated, if necessary, to contain no more than
5017 the number of lines specified by the value of
5020 When an interactive shell exits, the last
5023 lines are copied from the history list to
5028 shell option is enabled
5029 (see the description of
5033 .B "SHELL BUILTIN COMMANDS"
5034 below), the lines are appended to the history file,
5035 otherwise the history file is overwritten.
5039 is unset, or if the history file is unwritable, the history is
5040 not saved. After saving the history, the history file is truncated
5041 to contain no more than
5047 is not set, no truncation is performed.
5053 .B SHELL BUILTIN COMMANDS
5054 below) may be used to list or edit and re-execute a portion of
5058 builtin may be used to display or modify the history list and
5059 manipulate the history file.
5060 When using command-line editing, search commands
5061 are available in each editing mode that provide access to the
5064 The shell allows control over which commands are saved on the history
5071 variables may be set to cause the shell to save only a subset of the
5075 shell option, if enabled, causes the shell to attempt to save each
5076 line of a multi-line command in the same history entry, adding
5077 semicolons where necessary to preserve syntactic correctness.
5080 shell option causes the shell to save the command with embedded newlines
5081 instead of semicolons. See the description of the
5085 .B "SHELL BUILTIN COMMANDS"
5086 for information on setting and unsetting shell options.
5087 .SH "HISTORY EXPANSION"
5089 The shell supports a history expansion feature that
5090 is similar to the history expansion in
5092 This section describes what syntax features are available. This
5093 feature is enabled by default for interactive shells, and can be
5098 builtin command (see
5100 .B SHELL BUILTIN COMMANDS
5101 below). Non-interactive shells do not perform history expansion
5104 History expansions introduce words from the history list into
5105 the input stream, making it easy to repeat commands, insert the
5106 arguments to a previous command into the current input line, or
5107 fix errors in previous commands quickly.
5109 History expansion is performed immediately after a complete line
5110 is read, before the shell breaks it into words.
5111 It takes place in two parts.
5112 The first is to determine which line from the history list
5113 to use during substitution.
5114 The second is to select portions of that line for inclusion into
5116 The line selected from the history is the \fIevent\fP,
5117 and the portions of that line that are acted upon are \fIwords\fP.
5118 Various \fImodifiers\fP are available to manipulate the selected words.
5119 The line is broken into words in the same fashion as when reading input,
5120 so that several \fImetacharacter\fP-separated words surrounded by
5121 quotes are considered one word.
5122 History expansions are introduced by the appearance of the
5123 history expansion character, which is \^\fB!\fP\^ by default.
5124 Only backslash (\^\fB\e\fP\^) and single quotes can quote
5125 the history expansion character.
5127 Several shell options settable with the
5129 builtin may be used to tailor the behavior of history expansion.
5132 shell option is enabled (see the description of the
5136 is being used, history substitutions are not immediately passed to
5138 Instead, the expanded line is reloaded into the
5140 editing buffer for further modification.
5143 is being used, and the
5145 shell option is enabled, a failed history substitution will be reloaded
5148 editing buffer for correction.
5153 builtin command may be used to see what a history expansion will
5159 builtin may be used to add commands to the end of the history list
5160 without actually executing them, so that they are available for
5163 The shell allows control of the various characters used by the
5164 history expansion mechanism (see the description of
5167 .BR "Shell Variables" ).
5168 .SS Event Designators
5170 An event designator is a reference to a command line entry in the
5176 Start a history substitution, except when followed by a
5181 Refer to command line
5185 Refer to the current command line minus
5189 Refer to the previous command. This is a synonym for `!\-1'.
5192 Refer to the most recent command starting with
5195 .B !?\fIstring\fR\fB[?]\fR
5196 Refer to the most recent command containing
5198 The trailing \fB?\fP may be omitted if
5200 is followed immediately by a newline.
5202 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
5203 Quick substitution. Repeat the last command, replacing
5208 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
5209 (see \fBModifiers\fP below).
5212 The entire command line typed so far.
5214 .SS Word Designators
5216 Word designators are used to select desired words from the event.
5219 separates the event specification from the word designator.
5220 It may be omitted if the word designator begins with a
5227 Words are numbered from the beginning of the line,
5228 with the first word being denoted by 0 (zero).
5229 Words are inserted into the current line separated by single spaces.
5234 The zeroth word. For the shell, this is the command
5241 The first argument. That is, word 1.
5247 The word matched by the most recent `?\fIstring\fR?' search.
5250 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
5253 All of the words but the zeroth. This is a synonym
5254 for `\fI1\-$\fP'. It is not an error to use
5256 if there is just one
5257 word in the event; the empty string is returned in that case.
5260 Abbreviates \fIx\-$\fP.
5263 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
5266 If a word designator is supplied without an event specification, the
5267 previous command is used as the event.
5270 After the optional word designator, there may appear a sequence of
5271 one or more of the following modifiers, each preceded by a `:'.
5277 Remove a trailing file name component, leaving only the head.
5280 Remove all leading file name components, leaving the tail.
5283 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
5287 Remove all but the trailing suffix.
5290 Print the new command but do not execute it.
5293 Quote the substituted words, escaping further substitutions.
5296 Quote the substituted words as with
5298 but break into words at
5302 .B s/\fIold\fP/\fInew\fP/
5305 for the first occurrence of
5307 in the event line. Any delimiter can be used in place of /. The
5308 final delimiter is optional if it is the last character of the
5309 event line. The delimiter may be quoted in
5313 with a single backslash. If & appears in
5317 A single backslash will quote the &. If
5319 is null, it is set to the last
5321 substituted, or, if no previous history substitutions took place,
5325 .B !?\fIstring\fR\fB[?]\fR
5329 Repeat the previous substitution.
5332 Cause changes to be applied over the entire event line. This is
5333 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
5334 or `\fB:&\fP'. If used with
5335 `\fB:s\fP', any delimiter can be used
5336 in place of /, and the final delimiter is optional
5337 if it is the last character of the event line.
5339 .SH "SHELL BUILTIN COMMANDS"
5340 .\" start of bash_builtins
5343 Unless otherwise noted, each builtin command documented in this
5344 section as accepting options preceded by
5348 to signify the end of the options.
5352 \fB:\fP [\fIarguments\fP]
5354 No effect; the command does nothing beyond expanding
5356 and performing any specified
5357 redirections. A zero exit code is returned.
5360 \fB .\| \fP \fIfilename\fP [\fIarguments\fP]
5362 \fBsource\fP \fIfilename\fP [\fIarguments\fP]
5364 Read and execute commands from
5367 shell environment and return the exit status of the last command
5372 does not contain a slash, file names in
5375 are used to find the directory containing
5377 The file searched for in
5380 need not be executable. The current directory is
5381 searched if no file is found in
5388 builtin command is turned off, the
5392 If any \fIarguments\fP are supplied, they become the positional
5393 parameters when \fIfilename\fP is executed. Otherwise the positional
5394 parameters are unchanged.
5395 The return status is the status of the last command exited within
5396 the script (0 if no commands are executed), and false if
5398 is not found or cannot be read.
5400 \fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
5401 \fBAlias\fP with no arguments or with the
5403 option prints the list of aliases in the form
5404 \fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
5405 When arguments are supplied, an alias is defined for
5406 each \fIname\fP whose \fIvalue\fP is given.
5407 A trailing space in \fIvalue\fP causes the next word to be
5408 checked for alias substitution when the alias is expanded.
5409 For each \fIname\fP in the argument list for which no \fIvalue\fP
5410 is supplied, the name and value of the alias is printed.
5411 \fBAlias\fP returns true unless a \fIname\fP is given for which
5412 no alias has been defined.
5414 \fBbg\fP [\fIjobspec\fP]
5415 Resume the suspended job \fIjobspec\fP in the background, as if it
5416 had been started with
5418 If \fIjobspec\fP is not present, the shell's notion of the
5419 \fIcurrent job\fP is used.
5422 returns 0 unless run when job control is disabled or, when run with
5423 job control enabled, if \fIjobspec\fP was not found or started without
5427 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSV\fP]
5429 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
5431 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
5433 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-x\fP \fIkeyseq\fP:\fIshell\-command\fP
5435 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
5439 key and function bindings, or bind a key sequence to a
5441 function or macro. The binding syntax accepted is identical to that of
5443 but each binding must be passed as a separate argument;
5444 e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'. Options, if supplied, have the
5452 as the keymap to be affected by the subsequent bindings.
5456 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
5459 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
5460 equivalent to \fIemacs\-standard\fP.
5463 List the names of all \fBreadline\fP functions.
5466 Display \fBreadline\fP function names and bindings in such a way
5467 that they can be re-read.
5470 List current \fBreadline\fP function names and bindings.
5473 Display \fBreadline\fP variable names and values in such a way that they
5477 List current \fBreadline\fP variable names and values.
5480 Display \fBreadline\fP key sequences bound to macros and the strings
5481 they output in such a way that they can be re-read.
5484 Display \fBreadline\fP key sequences bound to macros and the strings
5487 .B \-f \fIfilename\fP
5488 Read key bindings from \fIfilename\fP.
5490 .B \-q \fIfunction\fP
5491 Query about which keys invoke the named \fIfunction\fP.
5493 .B \-u \fIfunction\fP
5494 Unbind all keys bound to the named \fIfunction\fP.
5497 Remove any current binding for \fIkeyseq\fP.
5499 .B \-x \fIkeyseq\fP:\fIshell\-command\fP
5500 Cause \fIshell\-command\fP to be executed whenever \fIkeyseq\fP is
5504 The return value is 0 unless an unrecognized option is given or an
5508 \fBbreak\fP [\fIn\fP]
5515 loop. If \fIn\fP is specified, break \fIn\fP levels.
5519 is greater than the number of enclosing loops, all enclosing loops
5520 are exited. The return value is 0 unless the shell is not executing
5525 \fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
5526 Execute the specified shell builtin, passing it
5528 and return its exit status.
5529 This is useful when defining a
5530 function whose name is the same as a shell builtin,
5531 retaining the functionality of the builtin within the function.
5532 The \fBcd\fP builtin is commonly redefined this way.
5533 The return status is false if
5535 is not a shell builtin command.
5537 \fBcd\fP [\fB\-LP\fP] [\fIdir\fP]
5538 Change the current directory to \fIdir\fP. The variable
5547 defines the search path for the directory containing
5549 Alternative directory names in
5552 are separated by a colon (:). A null directory name in
5555 is the same as the current directory, i.e., ``\fB.\fP''. If
5557 begins with a slash (/),
5563 option says to use the physical directory structure instead of
5564 following symbolic links (see also the
5568 builtin command); the
5570 option forces symbolic links to be followed. An argument of
5575 The return value is true if the directory was successfully changed;
5578 \fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
5583 suppressing the normal shell function lookup. Only builtin
5584 commands or commands found in the
5587 are executed. If the
5589 option is given, the search for
5591 is performed using a default value for
5593 that is guaranteed to find all of the standard utilities.
5598 option is supplied, a description of
5602 option causes a single word indicating the command or file name
5605 to be displayed; the
5607 option produces a more verbose description.
5612 option is supplied, the exit status is 0 if
5614 was found, and 1 if not. If neither option is supplied and
5615 an error occurred or
5617 cannot be found, the exit status is 127. Otherwise, the exit status of the
5619 builtin is the exit status of
5622 \fBcompgen\fP [\fIoption\fP] [\fIword\fP]
5623 Generate possible completion matches for \fIword\fP according to
5624 the \fIoption\fPs, which may be any option accepted by the
5626 builtin with the exception of \fB\-p\fP and \fB\-r\fP, and write
5627 the matches to the standard output.
5628 When using the \fB\-F\fP or \fB\-C\fP options, the various shell variables
5629 set by the programmable completion facilities, while available, will not
5632 The matches will be generated in the same way as if the programmable
5633 completion code had generated them directly from a completion specification
5634 with the same flags.
5635 If \fIword\fP is specified, only those completions matching \fIword\fP
5638 The return value is true unless an invalid option is supplied, or no
5639 matches were generated.
5642 \fBcomplete\fP [\fB\-abcdefjkvu\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]
5644 [\fB\-X\fP \fIfilterpat\fP] [\fB\-F\fP \fIfunction\fP] [\fB\-C\fP \fIcommand\fP] \fIname\fP [\fIname ...\fP]
5646 \fBcomplete\fP \fB\-pr\fP [\fIname\fP ...]
5648 Specify how arguments to each \fIname\fP should be completed.
5649 If the \fB\-p\fP option is supplied, or if no options are supplied,
5650 existing completion specifications are printed in a way that allows
5651 them to be reused as input.
5652 The \fB\-r\fP option removes a completion specification for
5653 each \fIname\fP, or, if no \fIname\fPs are supplied, all
5654 completion specifications.
5656 The process of applying these completion specifications when word completion
5657 is attempted is described above under \fBProgrammable Completion\fP.
5659 Other options, if specified, have the following meanings.
5660 The arguments to the \fB\-G\fP, \fB\-W\fP, and \fB\-X\fP options
5661 (and, if necessary, the \fB\-P\fP and \fB\-S\fP options)
5662 should be quoted to protect them from expansion before the
5668 \fB\-A\fP \fIaction\fP
5669 The \fIaction\fP may be one of the following to generate a list of possible
5674 Alias names. May also be specified as \fB\-a\fP.
5677 Array variable names.
5680 \fBReadline\fP key binding names.
5683 Names of shell builtin commands. May also be specified as \fB\-b\fP.
5686 Command names. May also be specified as \fB\-c\fP.
5689 Directory names. May also be specified as \fB\-d\fP.
5692 Names of disabled shell builtins.
5695 Names of enabled shell builtins.
5698 Names of exported shell variables. May also be specified as \fB\-e\fP.
5701 File names. May also be specified as \fB\-f\fP.
5704 Names of shell functions.
5707 Help topics as accepted by the \fBhelp\fP builtin.
5710 Hostnames, as taken from the file specified by the
5716 Job names, if job control is active. May also be specified as \fB\-j\fP.
5719 Shell reserved words. May also be specified as \fB\-k\fP.
5722 Names of running jobs, if job control is active.
5725 Valid arguments for the \fB\-o\fP option to the \fBset\fP builtin.
5728 Shell option names as accepted by the \fBshopt\fP builtin.
5734 Names of stopped jobs, if job control is active.
5737 User names. May also be specified as \fB\-u\fP.
5740 Names of all shell variables. May also be specified as \fB\-v\fP.
5743 \fB\-G\fP \fIglobpat\fP
5744 The filename expansion pattern \fIglobpat\fP is expanded to generate
5745 the possible completions.
5747 \fB\-W\fP \fIwordlist\fP
5748 The \fIwordlist\fP is split using the characters in the
5751 special variable as delimiters, and each resultant word is expanded.
5752 The possible completions are the members of the resultant list which
5753 match the word being completed.
5755 \fB\-C\fP \fIcommand\fP
5756 \fIcommand\fP is executed in a subshell environment, and its output is
5757 used as the possible completions.
5759 \fB\-F\fP \fIfunction\fP
5760 The shell function \fIfunction\fP is executed in the current shell
5762 When it finishes, the possible completions are retrieved from the value
5768 \fB\-X\fP \fIfilterpat\fP
5769 \fIfilterpat\fP is a pattern as used for filename expansion.
5770 It is applied to the list of possible completions generated by the
5771 preceding options and arguments, and each completion matching
5772 \fIfilterpat\fP is removed from the list.
5773 A leading \fB!\fP in \fIfilterpat\fP negates the pattern; in this
5774 case, any completion not matching \fIfilterpat\fP is removed.
5776 \fB\-P\fP \fIprefix\fP
5777 \fIprefix\fP is added at the beginning of each possible completion
5778 after all other options have been applied.
5780 \fB\-S\fP \fIsuffix\fP
5781 \fIsuffix\fP is appended to each possible completion
5782 after all other options have been applied.
5785 The return value is true unless an invalid option is supplied, an option
5786 other than \fB\-p\fP or \fB\-r\fP is supplied without a \fIname\fP
5787 argument, an attempt is made to remove a completion specification for
5788 a \fIname\fP for which no specification exists, or
5789 an error occurs adding a completion specification.
5792 \fBcontinue\fP [\fIn\fP]
5793 Resume the next iteration of the enclosing
5802 is specified, resume at the \fIn\fPth enclosing loop.
5806 is greater than the number of enclosing loops, the last enclosing loop
5807 (the ``top-level'' loop) is resumed. The return value is 0 unless the
5808 shell is not executing a loop when
5813 \fBdeclare\fP [\fB\-afFirx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP]]
5815 \fBtypeset\fP [\fB\-afFirx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP]]
5817 Declare variables and/or give them attributes.
5818 If no \fIname\fPs are given then display the values of variables.
5821 option will display the attributes and values of each
5825 is used, additional options are ignored.
5828 option inhibits the display of function definitions; only the
5829 function name and attributes are printed.
5834 The following options can
5835 be used to restrict output to variables with the specified attribute or
5836 to give variables attributes:
5841 Each \fIname\fP is an array variable (see
5846 Use function names only.
5849 The variable is treated as an integer; arithmetic evaluation (see
5851 .B "ARITHMETIC EVALUATION" ") "
5852 is performed when the variable is assigned a value.
5855 Make \fIname\fPs readonly. These names cannot then be assigned values
5856 by subsequent assignment statements or unset.
5859 Mark \fIname\fPs for export to subsequent commands via the environment.
5862 Using `+' instead of `\-'
5863 turns off the attribute instead, with the exception that \fB+a\fP
5864 may not be used to destroy an array variable. When used in a function,
5866 \fIname\fP local, as with the
5868 command. The return value is 0 unless an invalid option is encountered,
5869 an attempt is made to define a function using
5870 .if n ``\-f foo=bar'',
5871 .if t \f(CW\-f foo=bar\fP,
5872 an attempt is made to assign a value to a readonly variable,
5873 an attempt is made to assign a value to an array variable without
5874 using the compound assignment syntax (see
5876 above), one of the \fInames\fP is not a valid shell variable name,
5877 an attempt is made to turn off readonly status for a readonly variable,
5878 an attempt is made to turn off array status for an array variable,
5879 or an attempt is made to display a non-existent function with \fB\-f\fP.
5882 .B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
5883 Without options, displays the list of currently remembered directories.
5884 The default display is on a single line with directory names separated
5886 Directories are added to the list with the
5890 command removes entries from the list.
5895 Displays the \fIn\fPth entry counting from the left of the list
5898 when invoked without options, starting with zero.
5901 Displays the \fIn\fPth entry counting from the right of the list
5904 when invoked without options, starting with zero.
5907 Clears the directory stack by deleting all of the entries.
5910 Produces a longer listing; the default listing format uses a
5911 tilde to denote the home directory.
5914 Print the directory stack with one entry per line.
5917 Print the directory stack with one entry per line,
5918 prefixing each entry with its index in the stack.
5921 The return value is 0 unless an
5922 invalid option is supplied or \fIn\fP indexes beyond the end
5923 of the directory stack.
5926 \fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ...]
5927 Without options, each
5929 is removed from the table of active jobs.
5930 If the \fB\-h\fP option is given, each
5932 is not removed from the table, but is marked so that
5935 is not sent to the job if the shell receives a
5940 is present, and neither the
5944 option is supplied, the \fIcurrent job\fP is used.
5949 option means to remove or mark all jobs; the
5953 argument restricts operation to running jobs.
5954 The return value is 0 unless a
5956 does not specify a valid job.
5958 \fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
5959 Output the \fIarg\fPs, separated by spaces, followed by a newline.
5960 The return status is always 0.
5961 If \fB\-n\fP is specified, the trailing newline is
5962 suppressed. If the \fB\-e\fP option is given, interpretation of
5963 the following backslash-escaped characters is enabled. The
5965 option disables the interpretation of these escape characters,
5966 even on systems where they are interpreted by default.
5967 The \fBxpg_echo\fP shell option to the may be used to
5968 dynamically determine whether or not \fBecho\fP expands these
5969 escape characters by default.
5973 to mean the end of options.
5975 interprets the following escape sequences:
5986 suppress trailing newline
6010 the character whose ASCII code is the octal value \fInnn\fP
6011 (one to three digits)
6014 the character whose ASCII code is the hexadecimal value \fInnn\fP
6015 (one to three digits)
6019 \fBenable\fP [\fB\-adnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
6020 Enable and disable builtin shell commands.
6021 Disabling a builtin allows a disk command which has the same name
6022 as a shell builtin to be executed without specifying a full pathname,
6023 even though the shell normally searches for builtins before disk commands.
6024 If \fB\-n\fP is used, each \fIname\fP
6025 is disabled; otherwise,
6026 \fInames\fP are enabled. For example, to use the
6028 binary found via the
6031 instead of the shell builtin version, run
6032 \f(CWenable -n test\fP.
6035 option means to load the new builtin command
6039 on systems that support dynamic loading. The
6041 option will delete a builtin previously loaded with
6043 If no \fIname\fP arguments are given, or if the
6045 option is supplied, a list of shell builtins is printed.
6046 With no other option arguments, the list consists of all enabled
6048 If \fB\-n\fP is supplied, only disabled builtins are printed.
6049 If \fB\-a\fP is supplied, the list printed includes all builtins, with an
6050 indication of whether or not each is enabled.
6051 If \fB\-s\fP is supplied, the output is restricted to the POSIX
6052 \fIspecial\fP builtins.
6053 The return value is 0 unless a
6055 is not a shell builtin or there is an error loading a new builtin
6056 from a shared object.
6058 \fBeval\fP [\fIarg\fP ...]
6059 The \fIarg\fPs are read and concatenated together into a single
6060 command. This command is then read and executed by the shell, and
6061 its exit status is returned as the value of
6065 or only null arguments,
6069 \fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
6072 is specified, it replaces the shell.
6073 No new process is created. The
6075 become the arguments to \fIcommand\fP.
6079 the shell places a dash at the beginning of the zeroth arg passed to
6087 to be executed with an empty environment. If
6089 is supplied, the shell passes
6091 as the zeroth argument to the executed command. If
6093 cannot be executed for some reason, a non-interactive shell exits,
6094 unless the shell option
6096 is enabled, in which case it returns failure.
6097 An interactive shell returns failure if the file cannot be executed.
6100 is not specified, any redirections take effect in the current shell,
6101 and the return status is 0. If there is a redirection error, the
6104 \fBexit\fP [\fIn\fP]
6105 Cause the shell to exit
6106 with a status of \fIn\fP. If
6108 is omitted, the exit status
6109 is that of the last command executed.
6113 is executed before the shell terminates.
6116 \fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
6122 are marked for automatic export to the environment of
6123 subsequently executed commands. If the
6131 are given, or if the
6133 option is supplied, a list
6134 of all names that are exported in this shell is printed.
6137 option causes the export property to be removed from the
6140 returns an exit status of 0 unless an invalid option is
6142 one of the \fInames\fP is not a valid shell variable name, or
6146 that is not a function.
6149 \fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-nlr\fP] [\fIfirst\fP] [\fIlast\fP]
6151 \fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
6153 Fix Command. In the first form, a range of commands from
6157 is selected from the history list.
6161 may be specified as a string (to locate the last command beginning
6162 with that string) or as a number (an index into the history list,
6163 where a negative number is used as an offset from the current
6166 is not specified it is set to
6167 the current command for listing (so that
6168 .if n ``fc \-l \-10''
6169 .if t \f(CWfc \-l \-10\fP
6170 prints the last 10 commands) and to
6175 is not specified it is set to the previous
6176 command for editing and \-16 for listing.
6181 the command numbers when listing. The
6183 option reverses the order of
6184 the commands. If the
6187 the commands are listed on
6188 standard output. Otherwise, the editor given by
6191 on a file containing those commands. If
6197 variable is used, and
6204 is not set. If neither variable is set,
6206 is used. When editing is complete, the edited commands are
6207 echoed and executed.
6209 In the second form, \fIcommand\fP is re-executed after each instance
6210 of \fIpat\fP is replaced by \fIrep\fP.
6211 A useful alias to use with this is
6213 .if t \f(CWr='fc \-s'\fP,
6217 runs the last command beginning with
6223 re-executes the last command.
6225 If the first form is used, the return value is 0 unless an invalid
6226 option is encountered or
6230 specify history lines out of range.
6233 option is supplied, the return value is the value of the last
6234 command executed or failure if an error occurs with the temporary
6235 file of commands. If the second form is used, the return status
6236 is that of the command re-executed, unless
6238 does not specify a valid history line, in which case
6242 \fBfg\fP [\fIjobspec\fP]
6245 in the foreground, and make it the current job.
6248 is not present, the shell's notion of the \fIcurrent job\fP is used.
6249 The return value is that of the command placed into the foreground,
6250 or failure if run when job control is disabled or, when run with
6251 job control enabled, if
6253 does not specify a valid job or
6255 specifies a job that was started without job control.
6257 \fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
6259 is used by shell procedures to parse positional parameters.
6261 contains the option characters to be recognized; if a character
6262 is followed by a colon, the option is expected to have an
6263 argument, which should be separated from it by white space.
6264 The colon and question mark characters may not be used as
6266 Each time it is invoked,
6268 places the next option in the shell variable
6272 if it does not exist,
6273 and the index of the next argument to be processed into the
6279 is initialized to 1 each time the shell or a shell script
6280 is invoked. When an option requires an argument,
6282 places that argument into the variable
6285 The shell does not reset
6288 automatically; it must be manually reset between multiple
6291 within the same shell invocation if a new set of parameters
6294 When the end of options is encountered, \fBgetopts\fP exits with a
6295 return value greater than zero.
6296 \fBOPTIND\fP is set to the index of the first non-option argument,
6297 and \fBname\fP is set to ?.
6300 normally parses the positional parameters, but if more arguments are
6304 parses those instead.
6307 can report errors in two ways. If the first character of
6311 error reporting is used. In normal operation diagnostic messages
6312 are printed when invalid options or missing option arguments are
6317 is set to 0, no error messages will be displayed, even if the first
6322 If an invalid option is seen,
6327 prints an error message and unsets
6333 the option character found is placed in
6336 and no diagnostic message is printed.
6338 If a required argument is not found, and
6341 a question mark (\^\fB?\fP\^) is placed in
6344 is unset, and a diagnostic message is printed.
6347 is silent, then a colon (\^\fB:\fP\^) is placed in
6352 is set to the option character found.
6355 returns true if an option, specified or unspecified, is found.
6356 It returns false if the end of options is encountered or an
6359 \fBhash\fP [\fB\-r\fP] [\fB\-p\fP \fIfilename\fP] [\fIname\fP]
6362 the full file name of the command is determined by searching
6368 option is supplied, no path search is performed, and
6370 is used as the full file name of the command.
6373 option causes the shell to forget all
6374 remembered locations. If no arguments are given, information
6375 about remembered commands is printed.
6376 The return status is true unless a
6378 is not found or an invalid option is supplied.
6380 \fBhelp\fP [\fB\-s\fP] [\fIpattern\fP]
6381 Display helpful information about builtin commands. If
6385 gives detailed help on all commands matching
6387 otherwise help for all the builtins and shell control structures
6389 The \fB\-s\fP option restricts the information displayed to a short
6391 The return status is 0 unless no command matches
6395 \fBhistory [\fIn\fP]
6397 \fBhistory\fP \fB\-c\fP
6399 \fBhistory \-d\fP \fIoffset\fP
6401 \fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
6403 \fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
6405 \fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
6407 With no options, display the command
6408 history list with line numbers. Lines listed
6411 have been modified. An argument of
6415 lines. If \fIfilename\fP is supplied, it is used as the
6416 name of the history file; if not, the value of
6419 is used. Options, if supplied, have the following meanings:
6424 Clear the history list by deleting all the entries.
6426 \fB\-d\fP \fIoffset\fP
6427 Delete the history entry at position \fIoffset\fP.
6430 Append the ``new'' history lines (history lines entered since the
6431 beginning of the current \fBbash\fP session) to the history file.
6434 Read the history lines not already read from the history
6435 file into the current history list. These are lines
6436 appended to the history file since the beginning of the
6437 current \fBbash\fP session.
6440 Read the contents of the history file
6441 and use them as the current history.
6444 Write the current history to the history file, overwriting the
6445 history file's contents.
6448 Perform history substitution on the following \fIargs\fP and display
6449 the result on the standard output.
6450 Does not store the results in the history list.
6451 Each \fIarg\fP must be quoted to disable normal history expansion.
6456 in the history list as a single entry. The last command in the
6457 history list is removed before the
6462 The return value is 0 unless an invalid option is encountered, an
6463 error occurs while reading or writing the history file, an invalid
6464 \fIoffset\fP is supplied as an argument to \fB\-d\fP, or the
6465 history expansion supplied as an argument to \fB\-p\fP fails.
6469 \fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
6471 \fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
6473 The first form lists the active jobs. The options have the following
6480 in addition to the normal information.
6483 List only the process ID of the job's process group
6487 Display information only about jobs that have changed status since
6488 the user was last notified of their status.
6491 Restrict output to running jobs.
6494 Restrict output to stopped jobs.
6499 is given, output is restricted to information about that job.
6500 The return status is 0 unless an invalid option is encountered
6515 with the corresponding process group ID, and executes
6519 returning its exit status.
6523 \fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
6525 \fBkill\fP \fB\-l\fP [\fIsigspec\fP | \fIexit_status\fP]
6527 Send the signal named by
6531 to the processes named by
6536 is either a signal name such as
6541 is a signal number. If
6543 is a signal name, the name may be
6544 given with or without the
6550 is not present, then
6556 lists the signal names.
6557 If any arguments are supplied when
6559 is given, the names of the signals corresponding to the arguments are
6560 listed, and the return status is 0.
6561 The \fIexit_status\fP argument to
6563 is a number specifying either a signal number or the exit status of
6564 a process terminated by a signal.
6566 returns true if at least one signal was successfully sent, or false
6567 if an error occurs or an invalid option is encountered.
6569 \fBlet\fP \fIarg\fP [\fIarg\fP ...]
6572 is an arithmetic expression to be evaluated (see
6574 .BR "ARITHMETIC EVALUATION" ).
6579 returns 1; 0 is returned otherwise.
6581 \fBlocal\fP [\fIoption\fP] [\fIname\fP[=\fIvalue\fP] ...]
6582 For each argument, a local variable named
6584 is created, and assigned
6586 The \fIoption\fP can be any of the options accepted by \fBdeclare\fP.
6589 is used within a function, it causes the variable
6591 to have a visible scope restricted to that function and its children.
6594 writes a list of local variables to the standard output. It is
6597 when not within a function. The return status is 0 unless
6599 is used outside a function, an invalid
6602 \fIname\fP is a readonly variable.
6607 \fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
6608 Removes entries from the directory stack. With no arguments,
6609 removes the top directory from the stack, and performs a
6611 to the new top directory.
6612 Arguments, if supplied, have the following meanings:
6617 Removes the \fIn\fPth entry counting from the left of the list
6620 starting with zero. For example:
6622 .if t \f(CWpopd +0\fP
6623 removes the first directory,
6625 .if t \f(CWpopd +1\fP
6629 Removes the \fIn\fPth entry counting from the right of the list
6632 starting with zero. For example:
6634 .if t \f(CWpopd -0\fP
6635 removes the last directory,
6637 .if t \f(CWpopd -1\fP
6641 Suppresses the normal change of directory when removing directories
6642 from the stack, so that only the stack is manipulated.
6647 command is successful, a
6649 is performed as well, and the return status is 0.
6651 returns false if an invalid option is encountered, the directory stack
6652 is empty, a non-existent directory stack entry is specified, or the
6653 directory change fails.
6656 \fBprintf\fP \fIformat\fP [\fIarguments\fP]
6657 Write the formatted \fIarguments\fP to the standard output under the
6658 control of the \fIformat\fP.
6659 The \fIformat\fP is a character string which contains three types of objects:
6660 plain characters, which are simply copied to standard output, character
6661 escape sequences, which are converted and copied to the standard output, and
6662 format specifications, each of which causes printing of the next successive
6664 In addition to the standard \fIprintf\fP(1) formats, %b causes
6665 \fBprintf\fP to expand backslash escape sequences in the corresponding
6666 \fIargument\fP, and %q causes \fBprintf\fP to output the corresponding
6667 \fIargument\fP in a format that can be reused as shell input.
6669 The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
6670 If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
6671 extra format specifications behave as if a zero value or null string, as
6672 appropriate, had been supplied. The return value is zero on success,
6673 non-zero on failure.
6676 \fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
6678 \fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
6680 Adds a directory to the top of the directory stack, or rotates
6681 the stack, making the new top of the stack the current working
6682 directory. With no arguments, exchanges the top two directories
6683 and returns 0, unless the directory stack is empty.
6684 Arguments, if supplied, have the following meanings:
6689 Rotates the stack so that the \fIn\fPth directory
6690 (counting from the left of the list shown by
6696 Rotates the stack so that the \fIn\fPth directory
6697 (counting from the right of the list shown by
6699 starting with zero) is at the top.
6702 Suppresses the normal change of directory when adding directories
6703 to the stack, so that only the stack is manipulated.
6708 to the directory stack at the top, making it the
6709 new current working directory.
6714 command is successful, a
6716 is performed as well.
6717 If the first form is used,
6719 returns 0 unless the cd to
6721 fails. With the second form,
6723 returns 0 unless the directory stack is empty,
6724 a non-existent directory stack element is specified,
6725 or the directory change to the specified new current directory
6729 \fBpwd\fP [\fB\-LP\fP]
6730 Print the absolute pathname of the current working directory.
6731 The pathname printed contains no symbolic links if the
6733 option is supplied or the
6737 builtin command is enabled.
6740 option is used, the pathname printed may contain symbolic links.
6741 The return status is 0 unless an error occurs while
6742 reading the name of the current directory or an
6743 invalid option is supplied.
6745 \fBread\fP [\fB\-ers\fP] [\fB\-t\fP \fItimeout\fP] [\fB\-a\fP \fIaname\fP] [\fB\-p\fP \fIprompt\fP] [\fB\-n\fP \fInchars\fP] [\fB\-d\fP \fIdelim\fP] [\fIname\fP ...]
6746 One line is read from the standard input, and the first word
6747 is assigned to the first
6749 the second word to the second
6751 and so on, with leftover words and their intervening separators assigned
6754 If there are fewer words read from the standard input than names,
6755 the remaining names are assigned empty values.
6759 are used to split the line into words.
6760 The backslash character (\fB\e\fP) may be used to remove any special
6761 meaning for the next character read and for line continuation.
6762 Options, if supplied, have the following meanings:
6767 The words are assigned to sequential indices
6768 of the array variable
6772 is unset before any new values are assigned.
6773 Other \fIname\fP arguments are ignored.
6776 The first character of \fIdelim\fP is used to terminate the input line,
6777 rather than newline.
6780 If the standard input
6781 is coming from a terminal,
6786 above) is used to obtain the line.
6789 \fBread\fP returns after reading \fInchars\fP characters rather than
6790 waiting for a complete line of input.
6793 Display \fIprompt\fP, without a
6794 trailing newline, before attempting to read any input. The prompt
6795 is displayed only if input is coming from a terminal.
6798 Backslash does not act as an escape character.
6799 The backslash is considered to be part of the line.
6800 In particular, a backslash-newline pair may not be used as a line
6804 Silent mode. If input is coming from a terminal, characters are
6807 .B \-t \fItimeout\fP
6808 Cause \fBread\fP to time out and return failure if a complete line of
6809 input is not read within \fItimeout\fP seconds.
6810 This option has no effect if \fBread\fP is not reading input from the
6816 are supplied, the line read is assigned to the variable
6819 The return code is zero, unless end-of-file is encountered or \fBread\fP
6823 \fBreadonly\fP [\fB\-apf\fP] [\fIname\fP ...]
6826 \fInames\fP are marked readonly; the values of these
6828 may not be changed by subsequent assignment.
6831 option is supplied, the functions corresponding to the
6836 option restricts the variables to arrays.
6839 arguments are given, or if the
6841 option is supplied, a list of all readonly names is printed.
6844 option causes output to be displayed in a format that
6845 may be reused as input.
6846 The return status is 0 unless an invalid option is encountered,
6849 is not a valid shell variable name, or
6853 that is not a function.
6855 \fBreturn\fP [\fIn\fP]
6856 Causes a function to exit with the return value specified by
6860 is omitted, the return status is that of the last command
6861 executed in the function body. If used outside a function,
6862 but during execution of a script by the
6864 (\fBsource\fP) command, it causes the shell to stop executing
6865 that script and return either
6867 or the exit status of the last command executed within the
6868 script as the exit status of the script. If used outside a
6869 function and not during execution of a script by \fB.\fP\^,
6870 the return status is false.
6872 \fBset\fP [\fB\-\-abefhkmnptuvxBCHP\fP] [\fB\-o\fP \fIoption\fP] [\fIarg\fP ...]
6873 Without options, the name and value of each shell variable are displayed
6874 in a format that can be reused as input.
6875 The output is sorted according to the current locale.
6876 When options are specified, they set or unset shell attributes.
6877 Any arguments remaining after the options are processed are treated
6878 as values for the positional parameters and are assigned, in order, to
6883 Options, if specified, have the following meanings:
6888 Automatically mark variables which are modified or created for export
6889 to the environment of subsequent commands.
6892 Report the status of terminated background jobs
6893 immediately, rather than before the next primary prompt. This is
6894 effective only when job control is enabled.
6897 Exit immediately if a \fIsimple command\fP (see
6900 above) exits with a non-zero status. The shell does not exit if the
6901 command that fails is part of an
6908 statement, part of a
6912 list, or if the command's return value is
6917 Disable pathname expansion.
6920 Remember the location of commands as they are looked up for execution.
6921 This is enabled by default.
6924 All arguments in the form of assignment statements
6925 are placed in the environment for a command, not just
6926 those that precede the command name.
6929 Monitor mode. Job control is enabled. This option is on
6930 by default for interactive shells on systems that support
6934 above). Background processes run in a separate process
6935 group and a line containing their exit status is printed
6936 upon their completion.
6939 Read commands but do not execute them. This may be used to
6940 check a shell script for syntax errors. This is ignored by
6943 .B \-o \fIoption\-name\fP
6944 The \fIoption\-name\fP can be one of the following:
6956 Use an emacs-style command line editing interface. This is enabled
6957 by default when the shell is interactive, unless the shell is started
6975 Enable command history, as described above under
6978 This option is on by default in interactive shells.
6981 The effect is as if the shell command \f(CWIGNOREEOF=10\fP had been executed
7023 Change the behavior of
7025 where the default operation differs
7026 from the POSIX 1003.2 standard to match the standard.
7037 Use a vi-style command line editing interface.
7046 is supplied with no \fIoption\-name\fP, the values of the current options are
7050 is supplied with no \fIoption\-name\fP, a series of
7052 commands to recreate the current option settings is displayed on
7053 the standard output.
7059 mode. In this mode, the
7065 files are not processed, shell functions are not inherited from the
7066 environment, and the
7069 variable, if it appears in the environment, is ignored.
7070 If the shell is started with the effective user (group) id not equal to the
7071 real user (group) id, and the \fB\-p\fP option is not supplied, these actions
7072 are taken and the effective user id is set to the real user id.
7073 If the \fB\-p\fP option is supplied at startup, the effective user id is
7075 Turning this option off causes the effective user
7076 and group ids to be set to the real user and group ids.
7079 Exit after reading and executing one command.
7082 Treat unset variables as an error when performing
7083 parameter expansion. If expansion is attempted on an
7084 unset variable, the shell prints an error message, and,
7085 if not interactive, exits with a non-zero status.
7088 Print shell input lines as they are read.
7091 After expanding each \fIsimple command\fP,
7092 display the expanded value of
7095 followed by the command and its expanded arguments.
7098 The shell performs brace expansion (see
7100 above). This is on by default.
7105 does not overwrite an existing file with the
7110 redirection operators. This may be overridden when
7111 creating output files by using the redirection operator
7119 style history substitution. This option is on by
7120 default when the shell is interactive.
7123 If set, the shell does not follow symbolic links when executing
7126 that change the current working directory. It uses the
7127 physical directory structure instead. By default,
7129 follows the logical chain of directories when performing commands
7130 which change the current directory.
7133 If no arguments follow this option, then the positional parameters are
7134 unset. Otherwise, the positional parameters are set to the
7135 \fIarg\fPs, even if some of them begin with a
7139 Signal the end of options, cause all remaining \fIarg\fPs to be
7140 assigned to the positional parameters. The
7144 options are turned off.
7145 If there are no \fIarg\fPs,
7146 the positional parameters remain unchanged.
7149 The options are off by default unless otherwise noted.
7150 Using + rather than \- causes these options to be turned off.
7151 The options can also be specified as arguments to an invocation of
7153 The current set of options may be found in
7155 The return status is always true unless an invalid option is encountered.
7158 \fBshift\fP [\fIn\fP]
7159 The positional parameters from \fIn\fP+1 ... are renamed to
7162 Parameters represented by the numbers \fB$#\fP
7163 down to \fB$#\fP\-\fIn\fP+1 are unset.
7165 must be a non-negative number less than or equal to \fB$#\fP.
7168 is 0, no parameters are changed.
7171 is not given, it is assumed to be 1.
7174 is greater than \fB$#\fP, the positional parameters are not changed.
7175 The return status is greater than zero if
7179 or less than zero; otherwise 0.
7181 \fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
7182 Toggle the values of variables controlling optional shell behavior.
7183 With no options, or with the
7185 option, a list of all settable options is displayed, with
7186 an indication of whether or not each is set.
7187 The \fB\-p\fP option causes output to be displayed in a form that
7188 may be reused as input.
7189 Other options have the following meanings:
7194 Enable (set) each \fIoptname\fP.
7197 Disable (unset) each \fIoptname\fP.
7200 Suppresses normal output (quiet mode); the return status indicates
7201 whether the \fIoptname\fP is set or unset.
7202 If multiple \fIoptname\fP arguments are given with
7204 the return status is zero if all \fIoptnames\fP are enabled; non-zero
7208 Restricts the values of \fIoptname\fP to be those defined for the
7219 is used with no \fIoptname\fP arguments, the display is limited to
7220 those options which are set or unset, respectively.
7221 Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
7224 The return status when listing options is zero if all \fIoptnames\fP
7225 are enabled, non-zero otherwise. When setting or unsetting options,
7226 the return status is zero unless an \fIoptname\fP is not a valid shell
7229 The list of \fBshopt\fP options is:
7235 If set, an argument to the
7237 builtin command that
7238 is not a directory is assumed to be the name of a variable whose
7239 value is the directory to change to.
7242 If set, minor errors in the spelling of a directory component in a
7244 command will be corrected.
7245 The errors checked for are transposed characters,
7246 a missing character, and one character too many.
7247 If a correction is found, the corrected file name is printed,
7248 and the command proceeds.
7249 This option is only used by interactive shells.
7252 If set, \fBbash\fP checks that a command found in the hash
7253 table exists before trying to execute it. If a hashed command no
7254 longer exists, a normal path search is performed.
7257 If set, \fBbash\fP checks the window size after each command
7258 and, if necessary, updates the values of
7268 attempts to save all lines of a multiple-line
7269 command in the same history entry. This allows
7270 easy re-editing of multi-line commands.
7275 includes filenames beginning with a `.' in the results of pathname
7279 If set, a non-interactive shell will not exit if
7280 it cannot execute the file specified as an argument to the
7282 builtin command. An interactive shell does not exit if
7287 If set, aliases are expanded as described above under
7290 This option is enabled by default for interactive shells.
7293 If set, the extended pattern matching features described above under
7294 \fBPathname Expansion\fP are enabled.
7297 If set, the history list is appended to the file named by the value
7300 variable when the shell exits, rather than overwriting the file.
7305 is being used, a user is given the opportunity to re-edit a
7306 failed history substitution.
7311 is being used, the results of history substitution are not immediately
7312 passed to the shell parser. Instead, the resulting line is loaded into
7313 the \fBreadline\fP editing buffer, allowing further modification.
7318 is being used, \fBbash\fP will attempt to perform hostname completion when a
7319 word containing a \fB@\fP is being completed (see
7325 This is enabled by default.
7328 If set, \fBbash\fP will send
7331 to all jobs when an interactive login shell exits.
7333 .B interactive_comments
7334 If set, allow a word beginning with
7336 to cause that word and all remaining characters on that
7337 line to be ignored in an interactive shell (see
7340 above). This option is enabled by default.
7345 option is enabled, multi-line commands are saved to the history with
7346 embedded newlines rather than using semicolon separators where possible.
7349 If set, and a file that \fBbash\fP is checking for mail has been
7350 accessed since the last time it was checked, the message ``The mail in
7351 \fImailfile\fP has been read'' is displayed.
7353 .B no_empty_cmd_completion
7358 will not attempt to search the \fBPATH\fP for possible completions when
7359 completion is attempted on an empty line.
7364 matches filenames in a case\-insensitive fashion when performing pathname
7366 .B Pathname Expansion
7372 allows patterns which match no
7374 .B Pathname Expansion
7376 to expand to a null string, rather than themselves.
7379 If set, the programmable completion facilities (see
7380 \fBProgrammable Completion\fP above) are enabled.
7381 This option is enabled by default.
7384 If set, prompt strings undergo variable and parameter expansion after
7385 being expanded as described in
7388 above. This option is enabled by default.
7391 The shell sets this option if it is started in restricted mode (see
7393 .B "RESTRICTED SHELL"
7395 The value may not be changed.
7396 This is not reset when the startup files are executed, allowing
7397 the startup files to discover whether or not a shell is restricted.
7402 builtin prints an error message when the shift count exceeds the
7403 number of positional parameters.
7407 \fBsource\fP (\fB.\fP) builtin uses the value of
7410 to find the directory containing the file supplied as an argument.
7411 This option is enabled by default.
7414 If set, the \fBecho\fP builtin expands backslash-escape sequences
7418 \fBsuspend\fP [\fB\-f\fP]
7419 Suspend the execution of this shell until it receives a
7424 option says not to complain if this is
7425 a login shell; just suspend anyway. The return status is 0 unless
7426 the shell is a login shell and
7428 is not supplied, or if job control is not enabled.
7431 \fBtest\fP \fIexpr\fP
7433 \fB[\fP \fIexpr\fP \fB]\fP
7434 Return a status of 0 or 1 depending on
7435 the evaluation of the conditional expression
7437 Each operator and operand must be a separate argument.
7438 Expressions are composed of the primaries described above under
7440 .BR "CONDITIONAL EXPRESSIONS" .
7443 Expressions may be combined using the following operators, listed
7444 in decreasing order of precedence.
7454 Returns the value of \fIexpr\fP.
7455 This may be used to override the normal precedence of operators.
7457 \fIexpr1\fP \-\fBa\fP \fIexpr2\fP
7464 \fIexpr1\fP \-\fBo\fP \fIexpr2\fP
7472 \fBtest\fP and \fB[\fP evaluate conditional
7473 expressions using a set of rules based on the number of arguments.
7479 The expression is false.
7482 The expression is true if and only if the argument is not null.
7485 If the first argument is \fB!\fP, the expression is true if and
7486 only if the second argument is null.
7487 If the first argument is one of the unary conditional operators listed above
7490 .BR "CONDITIONAL EXPRESSIONS" ,
7491 the expression is true if the unary test is true.
7492 If the first argument is not a valid unary conditional operator, the expression
7496 If the second argument is one of the binary conditional operators listed above
7499 .BR "CONDITIONAL EXPRESSIONS" ,
7500 the result of the expression is the result of the binary test using
7501 the first and third arguments as operands.
7502 If the first argument is \fB!\fP, the value is the negation of
7503 the two-argument test using the second and third arguments.
7504 If the first argument is exactly \fB(\fP and the third argument is
7505 exactly \fB)\fP, the result is the one-argument test of the second
7507 Otherwise, the expression is false.
7508 The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
7512 If the first argument is \fB!\fP, the result is the negation of
7513 the three-argument expression composed of the remaining arguments.
7514 Otherwise, the expression is parsed and evaluated according to
7515 precedence using the rules listed above.
7518 The expression is parsed and evaluated according to precedence
7519 using the rules listed above.
7524 Print the accumulated user and system times for the shell and
7525 for processes run from the shell. The return status is 0.
7527 \fBtrap\fP [\fB\-lp\fP] [\fIarg\fP] [\fIsigspec\fP ...]
7530 is to be read and executed when the shell receives
7537 all specified signals are
7538 reset to their original values (the values they had
7539 upon entrance to the shell).
7542 is the null string the signal specified by each
7544 is ignored by the shell and by the commands it invokes.
7549 has been supplied, then the trap commands associated with each
7552 If no arguments are supplied or if only
7556 prints the list of commands associated with each signal number.
7560 a signal name defined in <\fIsignal.h\fP>, or a signal number.
7568 is executed on exit from the shell. If a
7575 is executed after every \fIsimple command\fP (see
7581 option causes the shell to print a list of signal names and
7582 their corresponding numbers.
7583 Signals ignored upon entry to the shell cannot be trapped or reset.
7584 Trapped signals are reset to their original values in a child
7585 process when it is created.
7586 The return status is false if any
7588 is invalid; otherwise
7592 \fBtype\fP [\fB\-atp\fP] \fIname\fP [\fIname\fP ...]
7596 would be interpreted if used as a command name.
7601 prints a string which is one of
7610 is an alias, shell reserved word, function, builtin, or disk file,
7614 is not found, then nothing is printed, and an exit status of false
7620 either returns the name of the disk file
7621 that would be executed if
7623 were specified as a command name,
7624 or nothing if \f(CWtype -t name\fP
7627 If a command is hashed,
7629 prints the hashed value, not necessarily the file that appears
7637 prints all of the places that contain
7640 This includes aliases and functions,
7643 option is not also used.
7644 The table of hashed commands is not consulted
7648 returns true if any of the arguments are found, false if
7651 \fBulimit\fP [\fB\-SHacdflmnpstuv\fP [\fIlimit\fP]]
7652 Provides control over the resources available to the shell and to
7653 processes started by it, on systems that allow such control. The
7656 can be a number in the unit specified for the resource, or the
7659 The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
7660 set for the given resource. A hard limit cannot be increased once it
7661 is set; a soft limit may be increased up to the value of the hard limit.
7662 If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
7666 is omitted, the current value of the soft limit of the resource is
7667 printed, unless the \fB\-H\fP option is given. When more than one
7668 resource is specified, the limit name and unit are printed before the value.
7669 Other options are interpreted as follows:
7674 All current limits are reported
7677 The maximum size of core files created
7680 The maximum size of a process's data segment
7683 The maximum size of files created by the shell
7686 The maximum size that may be locked into memory
7689 The maximum resident set size
7692 The maximum number of open file descriptors (most systems do not
7693 allow this value to be set)
7696 The pipe size in 512-byte blocks (this may not be set)
7699 The maximum stack size
7702 The maximum amount of cpu time in seconds
7705 The maximum number of processes available to a single user
7708 The maximum amount of virtual memory available to the shell
7713 is given, it is the new value of the specified resource (the
7715 option is display only).
7716 If no option is given, then
7718 is assumed. Values are in 1024-byte increments, except for
7720 which is in seconds,
7722 which is in units of 512-byte blocks,
7727 which are unscaled values. The return status is 0
7728 unless an invalid option is encountered, a non-numeric argument
7729 other than \fBunlimited\fP is supplied as \fIlimit\fP, or an
7730 error occurs while setting a new limit.
7733 \fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
7734 The user file-creation mask is set to
7738 begins with a digit, it
7739 is interpreted as an octal number; otherwise
7740 it is interpreted as a symbolic mode mask similar
7745 is omitted, the current value of the mask is printed.
7748 option causes the mask to be printed in symbolic form; the
7749 default output is an octal number.
7752 option is supplied, and
7754 is omitted, the output is in a form that may be reused as input.
7755 The return status is 0 if the mode was successfully changed or if
7756 no \fImode\fP argument was supplied, and false otherwise.
7758 \fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
7759 Remove each \fIname\fP from the list of defined aliases. If
7761 is supplied, all alias definitions are removed. The return
7762 value is true unless a supplied
7764 is not a defined alias.
7766 \fBunset\fP [\-\fBfv\fP] [\fIname\fP ...]
7769 remove the corresponding variable or function.
7770 If no options are supplied, or the
7772 option is given, each
7774 refers to a shell variable.
7775 Read-only variables may not be unset.
7781 refers to a shell function, and the function definition
7783 Each unset variable or function is removed from the environment
7784 passed to subsequent commands.
7801 are unset, they lose their special properties, even if they are
7802 subsequently reset. The exit status is true unless a
7804 does not exist or is readonly.
7806 \fBwait\fP [\fIn\fP]
7807 Wait for the specified process and return its termination
7811 ID or a job specification; if a job spec is given, all processes
7812 in that job's pipeline are waited for. If
7814 is not given, all currently active child processes
7815 are waited for, and the return status is zero. If
7817 specifies a non-existent process or job, the return status is
7818 127. Otherwise, the return status is the exit status of the last
7819 process or job waited for.
7822 .SH "RESTRICTED SHELL"
7828 is started with the name
7832 option is supplied at invocation,
7833 the shell becomes restricted.
7834 A restricted shell is used to
7835 set up an environment more controlled than the standard shell.
7836 It behaves identically to
7838 with the exception that the following are disallowed or not performed:
7840 changing directories with \fBcd\fP
7842 setting or unsetting the values of
7849 specifying command names containing
7852 specifying a file name containing a
7854 as an argument to the
7858 Specifying a filename containing a slash as an argument to the
7864 importing function definitions from the shell environment at startup
7866 parsing the value of \fBSHELLOPTS\fP from the shell environment at startup
7868 redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
7872 builtin command to replace the shell with another command
7874 adding or deleting builtin commands with the
7888 turning off restricted mode with
7889 \fBset +r\fP or \fBset +o restricted\fP.
7891 These restrictions are enforced after any startup files are read.
7893 When a command that is found to be a shell script is executed (see
7895 .B "COMMAND EXECUTION"
7898 turns off any restrictions in the shell spawned to execute the
7905 \fIBash Reference Manual\fP, Brian Fox and Chet Ramey
7907 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
7909 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
7911 \fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE
7913 \fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
7915 \fIemacs\fP(1), \fIvi\fP(1)
7923 The \fBbash\fP executable
7926 The systemwide initialization file, executed for login shells
7929 The personal initialization file, executed for login shells
7932 The individual per-interactive-shell startup file
7935 The individual login shell cleanup file, executed when a login shell exits
7938 Individual \fIreadline\fP initialization file
7941 Brian Fox, Free Software Foundation
7945 Chet Ramey, Case Western Reserve University
7949 If you find a bug in
7951 you should report it. But first, you should
7952 make sure that it really is a bug, and that it appears in the latest
7957 Once you have determined that a bug actually exists, use the
7959 command to submit a bug report.
7960 If you have a fix, you are encouraged to mail that as well!
7961 Suggestions and `philosophical' bug reports may be mailed
7962 to \fIbug-bash@gnu.org\fP or posted to the Usenet
7966 ALL bug reports should include:
7970 The version number of \fBbash\fR
7972 The hardware and operating system
7974 The compiler used to compile
7976 A description of the bug behaviour
7978 A short script or `recipe' which exercises the bug
7982 inserts the first three items automatically into the template
7983 it provides for filing a bug report.
7985 Comments and bug reports concerning
7986 this manual page should be directed to
7987 .IR chet@ins.CWRU.Edu .
7990 It's too big and too slow.
7992 There are some subtle differences between
7994 and traditional versions of
7996 mostly because of the
8001 Aliases are confusing in some uses.
8003 Shell builtin commands and functions are not stoppable/restartable.
8005 Compound commands and command sequences of the form `a ; b ; c'
8006 are not handled gracefully when process suspension is attempted.
8007 When a process is stopped, the shell immediately executes the next
8008 command in the sequence.
8009 It suffices to place the sequence of commands between
8010 parentheses to force it into a subshell, which may be stopped as
8013 Commands inside of \fB$(\fP...\fB)\fP command substitution are not
8014 parsed until substitution is attempted. This will delay error
8015 reporting until some time after the command is entered.
8017 Array variables may not (yet) be exported.
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