2 .\" MAN PAGE COMMENTS to
5 .\" Information Network Services
6 .\" Case Western Reserve University
9 .\" Last Change: Wed Apr 1 12:16:09 EST 1998
11 .\" bash_builtins, strip all but Built-Ins section
13 .TH BASH 1 "1998 Apr 1" GNU
15 .\" There's some problem with having a `@'
16 .\" in a tagged paragraph with the BSD man macros.
17 .\" It has to do with `@' appearing in the }1 macro.
18 .\" This is a problem on 4.3 BSD and Ultrix, but Sun
19 .\" appears to have fixed it.
20 .\" If you're seeing the characters
21 .\" `@u-3p' appearing before the lines reading
22 .\" `possible-hostname-completions
23 .\" and `complete-hostname' down in READLINE,
24 .\" then uncomment this redefinition.
29 .if !"\\$1"" .nr )I \\$1n
32 .in \\n()Ru+\\n(INu+\\n()Iu
34 .ie !\\n()Iu+\\n()Ru-\w
\a\\*(]X
\au-3p \{\\*(]X
36 .el \\*(]X\h
\a|\\n()Iu+\\n()Ru
\a\c
40 .\" File Name macro. This used to be `.PN', for Path Name,
41 .\" but Sun doesn't seem to like that very much.
47 bash \- GNU Bourne-Again SHell
53 .if n Bash is Copyright (C) 1989, 1991, 1993, 1995, 1996 by the Free Software Foundation, Inc.
54 .if t Bash is Copyright \(co 1989, 1991, 1993, 1995, 1996 by the Free Software Foundation, Inc.
57 is an \fBsh\fR-compatible command language interpreter that
58 executes commands read from the standard input or from a file.
60 also incorporates useful features from the \fIKorn\fP and \fIC\fP
61 shells (\fBksh\fP and \fBcsh\fP).
64 is intended to be a conformant implementation of the IEEE
65 POSIX Shell and Tools specification (IEEE Working Group 1003\.2).
67 In addition to the single-character shell options documented in the
68 description of the \fBset\fR builtin command, \fBbash\fR
69 interprets the following options when it is invoked:
76 option is present, then commands are read from
78 If there are arguments after the
80 they are assigned to the positional parameters, starting with
86 option is present, the shell becomes
96 option is present, the shell is
102 option is present, or if no arguments remain after option
103 processing, then commands are read from the standard input.
104 This option allows the positional parameters to be set
105 when invoking an interactive shell.
108 A list of all double-quoted strings preceded by \fB$\fP
109 is printed on the standard ouput.
110 These are the strings that
111 are subject to language translation when the current locale
113 This implies the \fB\-n\fP option; no commands will be executed.
118 signals the end of options and disables further option processing.
119 Any arguments after the
121 are treated as filenames and arguments. An argument of
123 is equivalent to \fB\-\-\fP.
127 also interprets a number of multi-character options.
128 These options must appear on the command line before the
129 single-character options in order for them to be recognized.
133 .B \-\-dump\-po\-strings
134 Equivalent to \fB\-D\fP, but the output is in the GNU \fIgettext\fP
135 \fBpo\fP (portable object) file format.
138 Equivalent to \fB\-D\fP.
141 Display a usage message on standard output and exit successfully.
146 act as if it had been invoked as a login shell (see
154 library to read command lines if interactive.
157 Do not read either the system-wide startup file
159 or any of the personal initialization files
160 .IR ~/.bash_profile ,
166 reads these files when it is invoked as a login shell (see
172 Do not read and execute the personal initialization file
174 if the shell is interactive.
175 This option is on by default if the shell is invoked as
179 Change the behavior of \fBbash\fP where the default operation differs
180 from the POSIX 1003.2 standard to match the standard.
182 \fB\-\-rcfile\fP \fIfile\fP
183 Execute commands from
185 instead of the standard personal initialization file
187 if the shell is interactive (see
193 The shell becomes restricted (see
195 .B "RESTRICTED SHELL"
199 Equivalent to \fB\-v\fP.
202 Show version information for this instance of
204 on the standard output and exit successfully.
207 If arguments remain after option processing, and neither the
211 option has been supplied, the first argument is assumed to
212 be the name of a file containing shell commands.
215 is invoked in this fashion,
217 is set to the name of the file, and the positional parameters
218 are set to the remaining arguments.
220 reads and executes commands from this file, then exits.
221 \fBBash\fP's exit status is the exit status of the last command
222 executed in the script.
223 If no commands are executed, the exit status is 0.
225 A \fIlogin shell\fP is one whose first character of argument zero is a
227 or one started with the
231 An \fIinteractive\fP shell is one whose standard input and output are
232 both connected to terminals (as determined by
234 or one started with the
246 allowing a shell script or a startup file to test this state.
248 The following paragraphs describe how
250 executes its startup files.
251 If any of the files exist but cannot be read,
254 Tildes are expanded in file names as described below under
263 is invoked as an interactive login shell, it first reads and
264 executes commands from the file \fI/etc/profile\fP, if that
266 After reading that file, it looks for \fI~/.bash_profile\fP,
267 \fI~/.bash_login\fP, and \fI~/.profile\fP, in that order, and reads
268 and executes commands from the first one that exists and is readable.
271 option may be used when the shell is started to inhibit this behavior.
273 When a login shell exits,
275 reads and executes commands from the file \fI~/.bash_logout\fP, if it
278 When an interactive shell that is not a login shell is started,
280 reads and executes commands from \fI~/.bashrc\fP, if that file exists.
281 This may be inhibited by using the
284 The \fB\-\-rcfile\fP \fIfile\fP option will force
286 to read and execute commands from \fIfile\fP instead of \fI~/.bashrc\fP.
290 is started non-interactively, to run a shell script, for example, it
291 looks for the variable
294 in the environment, expands its value if it appears there, and uses the
295 expanded value as the name of a file to read and execute.
297 behaves as if the following command were executed:
300 \f(CWif [ \-n "$BASH_ENV" ]; then . "$BASH_ENV"; fi\fP
306 variable is not used to search for the file name.
310 is invoked with the name
312 it tries to mimic the startup behavior of historical versions of
314 as closely as possible,
315 while conforming to the POSIX standard as well.
316 When invoked as an interactive login shell, it first attempts to
317 read and execute commands from
324 option may be used to inhibit this behavior.
325 When invoked as an interactive shell with the name
328 looks for the variable
331 expands its value if it is defined, and uses the
332 expanded value as the name of a file to read and execute.
333 Since a shell invoked as
335 does not attempt to read and execute commands from any other startup
338 option has no effect.
339 A non-interactive shell invoked with the name
341 does not attempt to read any startup files.
347 mode after the startup files are read.
355 command line option, it follows the POSIX standard for startup files.
356 In this mode, interactive shells expand the
359 variable and commands are read and executed from the file
360 whose name is the expanded value.
361 No other startup files are read.
364 attempts to determine when it is being run by the remote shell
365 daemon, usually \fIrshd\fP.
368 determines it is being run by \fIrshd\fP, it reads and executes
369 commands from \fI~/.bashrc\fP, if that file exists and is readable.
370 It will not do this if invoked as \fBsh\fP.
373 option may be used to inhibit this behavior, and the
375 option may be used to force another file to be read, but
376 \fIrshd\fP does not generally invoke the shell with those options
377 or allow them to be specified.
380 The following definitions are used throughout the rest of this
388 A sequence of characters considered as a single unit by the shell.
395 consisting only of alphanumeric characters and underscores, and
396 beginning with an alphabetic character or an underscore. Also
401 A character that, when unquoted, separates words. One of the following:
405 .if t \fB| & ; ( ) < > space tab\fP
406 .if n \fB| & ; ( ) < > space tab\fP
411 A \fItoken\fP that performs a control function. It is one of the following
415 .if t \fB\(bv\(bv & && ; ;; ( ) | <newline>\fP
416 .if n \fB|| & && ; ;; ( ) | <newline>\fP
420 \fIReserved words\fP are words that have a special meaning to the shell.
421 The following words are recognized as reserved when unquoted and either
422 the first word of a simple command (see
425 below) or the third word of a
433 .if n ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
434 .if t ! case do done elif else esac fi for function if in select then until while { } time [[ ]]
440 A \fIsimple command\fP is a sequence of optional variable assignments
441 followed by \fBblank\fP-separated words and redirections, and
442 terminated by a \fIcontrol operator\fP. The first word
443 specifies the command to be executed. The remaining words are
444 passed as arguments to the invoked command.
446 The return value of a \fIsimple command\fP is its exit status, or
447 128+\fIn\^\fP if the command is terminated by signal
451 A \fIpipeline\fP is a sequence of one or more commands separated by
454 The format for a pipeline is:
457 [\fBtime\fP [\fB\-p\fP]] [ ! ] \fIcommand\fP [ \fB|\fP \fIcommand2\fP ... ]
460 The standard output of
462 is connected to the standard input of
464 This connection is performed before any redirections specified by the
472 precedes a pipeline, the exit status of that
473 pipeline is the logical NOT of the exit status of the last command.
474 Otherwise, the status of the pipeline is the exit status of the last
476 The shell waits for all commands in the pipeline to
477 terminate before returning a value.
481 reserved word precedes a pipeline, the elapsed as well as user and
482 system time consumed by its execution are reported when the pipeline
484 The \fB\-p\fP option changes the output format to that specified by POSIX.
488 variable may be set to a format string that specifies how the timing
489 information should be displayed; see the description of
496 Each command in a pipeline is executed as a separate process (i.e., in a
500 A \fIlist\fP is a sequence of one or more pipelines separated by one
507 and optionally terminated by one of
513 Of these list operators,
517 have equal precedence, followed by
521 which have equal precedence.
523 If a command is terminated by the control operator
525 the shell executes the command in the \fIbackground\fP
526 in a subshell. The shell does not wait for the command to
527 finish, and the return status is 0. Commands separated by a
529 are executed sequentially; the shell waits for each
530 command to terminate in turn. The return status is the
531 exit status of the last command executed.
533 The control operators
537 denote AND lists and OR lists, respectively.
538 An AND list has the form
541 \fIcommand\fP \fB&&\fP \fIcommand2\fP
545 is executed if, and only if,
547 returns an exit status of zero.
549 An OR list has the form
552 \fIcommand\fP \fB\(bv\(bv\fP \fIcommand2\fP
557 is executed if and only if
559 returns a non-zero exit status. The return status of
560 AND and OR lists is the exit status of the last command
561 executed in the list.
562 .SS Compound Commands
564 A \fIcompound command\fP is one of the following:
567 \fIlist\fP is executed in a subshell. Variable assignments and builtin
568 commands that affect the shell's environment do not remain in effect
569 after the command completes. The return status is the exit status of
573 \fIlist\fP is simply executed in the current shell environment.
574 \fIlist\fP must be terminated with a newline or semicolon.
575 This is known as a \fIgroup command\fP.
576 The return status is the exit status of
580 The \fIexpression\fP is evaluated according to the rules described
583 .BR "ARITHMETIC EVALUATION" .
584 If the value of the expression is non-zero, the return status is 0;
585 otherwise the return status is 1. This is exactly equivalent to
586 \fBlet "\fIexpression\fP"\fR.
588 \fB[[\fP \fIexpression\fP \fB]]\fP
589 Return a status of 0 or 1 depending on the evaluation of
590 the conditional expression \fIexpression\fP.
591 Expressions are composed of the primaries described below under
593 .BR "CONDITIONAL EXPRESSIONS" .
594 Word splitting and pathname expansion are not performed on the words
595 between the \fB[[\fP and \fB]]\fP; tilde expansion, parameter and
596 variable expansion, arithmetic expansion, command substitution, process
597 substitution, and quote removal are performed.
600 When the \fB==\fP and \fB!=\fP operators are used, the string to the
601 right of the operator is considered a pattern and matched according
602 to the rules described below under \fBPattern Matching\fP.
603 The return value is 0 if the string matches or does not match
604 the pattern, respectively, and 1 otherwise.
605 Any part of the pattern may be quoted to force it to be matched as a
609 Expressions may be combined using the following operators, listed
610 in decreasing order of precedence:
616 .B ( \fIexpression\fP )
617 Returns the value of \fIexpression\fP.
618 This may be used to override the normal precedence of operators.
620 .B ! \fIexpression\fP
625 \fIexpression1\fP \fB&&\fP \fIexpression2\fP
632 .if t \fIexpression1\fP \fB\(bv\(bv\fP \fIexpression2\fP
633 .if n \fIexpression1\fP \fB||\fP \fIexpression2\fP
645 operators do not execute \fIexpression2\fP if the value of
646 \fIexpression1\fP is sufficient to determine the return value of
647 the entire conditional expression.
649 \fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP; ] \fBdo\fP \fIlist\fP ; \fBdone\fP
650 The list of words following \fBin\fP is expanded, generating a list
651 of items. The variable \fIname\fP is set to each element of this list
652 in turn, and \fIlist\fP is executed each time. If the \fBin\fP
653 \fIword\fP is omitted, the \fBfor\fP command executes \fIlist\fP
654 once for each positional parameter that is set (see
658 The return status is the exit status of the last command that executes.
659 If the expansion of the items following \fBin\fP results in an empty
660 list, no commands are executed, and the return status is 0.
662 \fBselect\fP \fIname\fP [ \fBin\fP \fIword\fP; ] \fBdo\fP \fIlist\fP ; \fBdone\fP
663 The list of words following \fBin\fP is expanded, generating a list
664 of items. The set of expanded words is printed on the standard
665 error, each preceded by a number. If the \fBin\fP
666 \fIword\fP is omitted, the positional parameters are printed (see
671 prompt is then displayed and a line read from the standard input.
672 If the line consists of a number corresponding to one of
673 the displayed words, then the value of
675 is set to that word. If the line is empty, the words and prompt
676 are displayed again. If EOF is read, the command completes. Any
677 other value read causes
679 to be set to null. The line read is saved in the variable
683 is executed after each selection until a
690 is the exit status of the last command executed in
692 or zero if no commands were executed.
694 \fBcase\fP \fIword\fP \fBin\fP [ ( \fIpattern\fP [ \fB|\fP \fIpattern\fP ] \
695 ... ) \fIlist\fP ;; ] ... \fBesac\fP
696 A \fBcase\fP command first expands \fIword\fP, and tries to match
697 it against each \fIpattern\fP in turn, using the same matching rules
698 as for pathname expansion (see
699 .B Pathname Expansion
700 below). When a match is found, the
701 corresponding \fIlist\fP is executed. After the first match, no
702 subsequent matches are attempted. The exit status is zero if no
703 pattern matches. Otherwise, it is the exit status of the
704 last command executed in \fIlist\fP.
706 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist;\fP \
707 [ \fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; ] ... \
708 [ \fBelse\fP \fIlist\fP; ] \fBfi\fP
712 is executed. If its exit status is zero, the
713 \fBthen\fP \fIlist\fP is executed. Otherwise, each \fBelif\fP
714 \fIlist\fP is executed in turn, and if its exit status is zero,
715 the corresponding \fBthen\fP \fIlist\fP is executed and the
716 command completes. Otherwise, the \fBelse\fP \fIlist\fP is
717 executed, if present. The exit status is the exit status of the
718 last command executed, or zero if no condition tested true.
721 \fBwhile\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
723 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
725 The \fBwhile\fP command continuously executes the \fBdo\fP
726 \fIlist\fP as long as the last command in \fIlist\fP returns
727 an exit status of zero. The \fBuntil\fP command is identical
728 to the \fBwhile\fP command, except that the test is negated;
732 is executed as long as the last command in
734 returns a non-zero exit status.
735 The exit status of the \fBwhile\fP and \fBuntil\fP commands
737 of the last \fBdo\fP \fIlist\fP command executed, or zero if
740 [ \fBfunction\fP ] \fIname\fP () { \fIlist\fP; }
741 This defines a function named \fIname\fP. The \fIbody\fP of the
744 of commands between { and }. This list
745 is executed whenever \fIname\fP is specified as the
746 name of a simple command. The exit status of a function is
747 the exit status of the last command executed in the body. (See
752 In a non-interactive shell, or an interactive shell in which the
753 .B interactive_comments
756 builtin is enabled (see
758 .B "SHELL BUILTIN COMMANDS"
759 below), a word beginning with
761 causes that word and all remaining characters on that line to
762 be ignored. An interactive shell without the
763 .B interactive_comments
764 option enabled does not allow comments. The
765 .B interactive_comments
766 option is on by default in interactive shells.
768 \fIQuoting\fP is used to remove the special meaning of certain
769 characters or words to the shell. Quoting can be used to
770 disable special treatment for special characters, to prevent
771 reserved words from being recognized as such, and to prevent
774 Each of the \fImetacharacters\fP listed above under
777 has special meaning to the shell and must be quoted if they are to
778 represent themselves. There are three quoting mechanisms: the
779 .IR "escape character" ,
780 single quotes, and double quotes.
782 A non-quoted backslash (\fB\e\fP) is the
783 .IR "escape character" .
784 It preserves the literal value of the next character that follows,
785 with the exception of <newline>. If a \fB\e\fP<newline> pair
786 appears, and the backslash is not itself quoted, the \fB\e\fP<newline>
787 is treated as a line continuation (that is, it is removed from the
788 input stream and effectively ignored).
790 Enclosing characters in single quotes preserves the literal value
791 of each character within the quotes. A single quote may not occur
792 between single quotes, even when preceded by a backslash.
794 Enclosing characters in double quotes preserves the literal value
795 of all characters within the quotes, with the exception of
804 retain their special meaning within double quotes. The backslash
805 retains its special meaning only when followed by one of the following
813 A double quote may be quoted within double quotes by preceding it with
816 The special parameters
820 have special meaning when in double
826 Words of the form \fB$\fP'\fIstring\fP' are treated specially. The
827 word expands to \fIstring\fP, with backslash-escaped characters replaced
828 as specifed by the ANSI C standard. Backslash escape sequences, if
829 present, are decoded as follows:
861 the character whose ASCII code is the octal value \fInnn\fP
862 (one to three digits)
865 the character whose ASCII code is the hexadecimal value \fInnn\fP
866 (one to three digits)
870 The translated result is single-quoted, as if the dollar sign had
873 A double-quoted string preceded by a dollar sign (\fB$\fP) will cause
874 the string to be translated according to the current locale.
875 If the current locale is \fBC\fP or \fBPOSIX\fP, the dollar sign
877 If the string is translated and replaced, the replacement is
882 is an entity that stores values.
885 a number, or one of the special characters listed below under
886 .BR "Special Parameters" .
887 For the shell's purposes, a
889 is a parameter denoted by a
892 A parameter is set if it has been assigned a value. The null string is
893 a valid value. Once a variable is set, it may be unset only by using
898 .B SHELL BUILTIN COMMANDS
903 may be assigned to by a statement of the form
906 \fIname\fP=[\fIvalue\fP]
911 is not given, the variable is assigned the null string. All
913 undergo tilde expansion, parameter and variable expansion, string
914 expansion, command substitution, arithmetic expansion, and quote
918 below). If the variable has its
924 .BR "SHELL BUILTIN COMMANDS" )
927 is subject to arithmetic expansion even if the $((...)) expansion is
929 .B "Arithmetic Expansion"
931 Word splitting is not performed, with the exception
932 of \fB"$@"\fP as explained below under
933 .BR "Special Parameters" .
934 Pathname expansion is not performed.
935 .SS Positional Parameters
938 .I positional parameter
939 is a parameter denoted by one or more
940 digits, other than the single digit 0. Positional parameters are
941 assigned from the shell's arguments when it is invoked,
942 and may be reassigned using the
944 builtin command. Positional parameters may not be assigned to
945 with assignment statements. The positional parameters are
946 temporarily replaced when a shell function is executed (see
951 When a positional parameter consisting of more than a single
952 digit is expanded, it must be enclosed in braces (see
956 .SS Special Parameters
958 The shell treats several parameters specially. These parameters may
959 only be referenced; assignment to them is not allowed.
963 Expands to the positional parameters, starting from one. When the
964 expansion occurs within double quotes, it expands to a single word
965 with the value of each parameter separated by the first character
969 special variable. That is, "\fB$*\fP" is equivalent
970 to "\fB$1\fP\fIc\fP\fB$2\fP\fIc\fP\fB...\fP", where
972 is the first character of the value of the
978 is unset, the parameters are separated by spaces.
982 is null, the parameters are joined without intervening separators.
985 Expands to the positional parameters, starting from one. When the
986 expansion occurs within double quotes, each parameter expands to a
987 separate word. That is, "\fB$@\fP" is equivalent to
988 "\fB$1\fP" "\fB$2\fP" ...
989 When there are no positional parameters, "\fB$@\fP" and
991 expand to nothing (i.e., they are removed).
994 Expands to the number of positional parameters in decimal.
997 Expands to the status of the most recently executed foreground
1001 Expands to the current option flags as specified upon invocation,
1004 builtin command, or those set by the shell itself
1010 Expands to the process ID of the shell. In a () subshell, it
1011 expands to the process ID of the current shell, not the
1015 Expands to the process ID of the most recently executed background
1016 (asynchronous) command.
1019 Expands to the name of the shell or shell script. This is set at
1020 shell initialization. If
1022 is invoked with a file of commands,
1024 is set to the name of that file. If
1030 is set to the first argument after the string to be
1031 executed, if one is present. Otherwise, it is set
1032 to the file name used to invoke
1034 as given by argument zero.
1037 At shell startup, set to the absolute file name of the shell or shell
1038 script being executed as passed in the argument list.
1039 Subsequently, expands to the last argument to the previous command,
1041 Also set to the full file name of each command executed and placed in
1042 the environment exported to that command.
1043 When checking mail, this parameter holds the name of the mail file
1044 currently being checked.
1048 The following variables are set by the shell:
1053 The process ID of the shell's parent. This variable is readonly.
1056 The current working directory as set by the
1061 The previous working directory as set by the
1066 Set to the line of input read by the
1068 builtin command when no arguments are supplied.
1071 Expands to the user ID of the current user, initialized at shell startup.
1072 This variable is readonly.
1075 Expands to the effective user ID of the current user, initialized at
1076 shell startup. This variable is readonly.
1079 An array variable containing the list of groups of which the current
1080 user is a member. This variable is readonly.
1083 Expands to the full file name used to invoke this instance of
1087 Expands to a string describing the version of this instance of
1091 A readonly array variable whose members hold version information for
1094 The values assigned to the array members are as follows:
1099 .B BASH_VERSINFO[\fR0\fP]
1100 The major version number (the \fIrelease\fP).
1102 .B BASH_VERSINFO[\fR1\fP]
1103 The minor version number (the \fIversion\fP).
1105 .B BASH_VERSINFO[\fR2\fP]
1108 .B BASH_VERSINFO[\fR3\fP]
1111 .B BASH_VERSINFO[\fR4\fP]
1112 The release status (e.g., \fIbeta1\fP).
1114 .B BASH_VERSINFO[\fR5\fP]
1115 The value of \fBMACHTYPE\fP.
1120 Incremented by one each time an instance of
1125 Each time this parameter is referenced, a random integer between
1127 generated. The sequence of random numbers may be initialized by assigning
1134 is unset, it loses its special properties, even if it is
1138 Each time this parameter is
1139 referenced, the number of seconds since shell invocation is returned. If a
1140 value is assigned to
1143 the value returned upon subsequent
1145 the number of seconds since the assignment plus the value assigned.
1149 is unset, it loses its special properties, even if it is
1153 Each time this parameter is referenced, the shell substitutes
1154 a decimal number representing the current sequential line number
1155 (starting with 1) within a script or function. When not in a
1156 script or function, the value substituted is not guaranteed to
1161 is unset, it loses its special properties, even if it is
1165 The history number, or index in the history list, of the current
1170 is unset, it loses its special properties, even if it is
1174 An array variable (see
1176 below) containing the current contents of the directory stack.
1177 Directories appear in the stack in the order they are displayed by the
1180 Assigning to members of this array variable may be used to modify
1181 directories already in the stack, but the
1185 builtins must be used to add and remove directories.
1186 Assignment to this variable will not change the current directory.
1190 is unset, it loses its special properties, even if it is
1194 An array variable (see
1196 below) containing a list of exit status values from the processes
1197 in the most-recently-executed foreground pipeline (which may
1198 contain only a single command).
1201 The value of the last option argument processed by the
1203 builtin command (see
1205 .B SHELL BUILTIN COMMANDS
1209 The index of the next argument to be processed by the
1211 builtin command (see
1213 .B SHELL BUILTIN COMMANDS
1217 Automatically set to the name of the current host.
1220 Automatically set to a string that uniquely
1221 describes the type of machine on which
1224 The default is system-dependent.
1227 Automatically set to a string that
1228 describes the operating system on which
1231 The default is system-dependent.
1234 Automatically set to a string that fully describes the system
1237 is executing, in the standard GNU \fIcpu-company-system\fP format.
1238 The default is system-dependent.
1241 A colon-separated list of enabled shell options. Each word in
1242 the list is a valid argument for the
1246 builtin command (see
1248 .B "SHELL BUILTIN COMMANDS"
1249 below). The options appearing in
1252 are those reported as
1255 If this variable is in the environment when
1257 starts up, each shell option in the list will be enabled before
1258 reading any startup files.
1259 This variable is read-only.
1262 The following variables are used by the shell. In some cases,
1264 assigns a default value to a variable; these cases are noted
1271 .I Internal Field Separator
1273 for word splitting after expansion and to
1274 split lines into words with the
1276 builtin command. The default value is
1277 ``<space><tab><newline>''.
1280 The search path for commands. It
1281 is a colon-separated list of directories in which
1282 the shell looks for commands (see
1284 .B COMMAND EXECUTION
1285 below). The default path is system-dependent,
1286 and is set by the administrator who installs
1288 A common value is ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.''.
1291 The home directory of the current user; the default argument for the
1292 \fBcd\fP builtin command.
1293 The value of this variable is also used when performing tilde expansion.
1296 The search path for the
1299 This is a colon-separated list of directories in which the shell looks
1300 for destination directories specified by the
1303 A sample value is ``.:~:/usr''.
1306 If this parameter is set when \fBbash\fP is executing a shell script,
1307 its value is interpreted as a filename containing commands to
1308 initialize the shell, as in
1313 is subjected to parameter expansion, command substitution, and arithmetic
1314 expansion before being interpreted as a file name.
1317 is not used to search for the resultant file name.
1320 If this parameter is set to a file name and the
1323 variable is not set,
1325 informs the user of the arrival of mail in the specified file.
1331 checks for mail. The default is 60 seconds. When it is time to check
1332 for mail, the shell does so before displaying the primary prompt.
1333 If this variable is unset, the shell disables mail checking.
1336 A colon-separated list of file names to be checked for mail.
1337 The message to be printed when mail arrives in a particular file
1338 may be specified by separating the file name from the message with a `?'.
1339 When used in the text of the message, \fB$_\fP expands to the name of
1340 the current mailfile.
1344 \fBMAILPATH\fP='/usr/spool/mail/bfox?"You have mail":~/shell\-mail?"$_ has mail!"'
1347 supplies a default value for this variable, but the location of the user
1348 mail files that it uses is system dependent (e.g., /usr/spool/mail/\fB$USER\fP).
1352 The value of this parameter is expanded (see
1355 below) and used as the primary prompt string. The default value is
1356 ``\fB\es\-\ev\e$ \fP''.
1359 The value of this parameter is expanded as with
1361 and used as the secondary prompt string. The default is
1365 The value of this parameter is used as the prompt for the
1373 The value of this parameter is expanded as with
1375 and the value is printed before each command
1377 displays during an execution trace. The first character of
1380 is replicated multiple times, as necessary, to indicate multiple
1381 levels of indirection. The default is ``\fB+ \fP''.
1384 The value of this parameter is used as a format string specifying
1385 how the timing information for pipelines prefixed with the
1387 reserved word should be displayed.
1388 The \fB%\fP character introduces an escape sequence that is
1389 expanded to a time value or other information.
1390 The escape sequences and their meanings are as follows; the
1391 braces denote optional portions.
1400 The elapsed time in seconds.
1403 The number of CPU seconds spent in user mode.
1406 The number of CPU seconds spent in system mode.
1409 The CPU percentage, computed as (%U + %S) / %R.
1413 The optional \fIp\fP is a digit specifying the \fIprecision\fP,
1414 the number of fractional digits after a decimal point.
1415 A value of 0 causes no decimal point or fraction to be output.
1416 At most three places after the decimal point may be specified;
1417 values of \fIp\fP greater than 3 are changed to 3.
1418 If \fIp\fP is not specified, the value 3 is used.
1420 The optional \fBl\fP specifies a longer format, including
1421 minutes, of the form \fIMM\fPm\fISS\fP.\fIFF\fPs.
1422 The value of \fIp\fP determines whether or not the fraction is
1425 If this variable is not set, \fBbash\fP acts as if it had the
1426 value \fB$'\enreal\et%3lR\enuser\et%3lU\ensys\t%3lS'\fP.
1427 If the value is null, no timing information is displayed.
1428 A trailing newline is added when the format string is displayed.
1431 The number of commands to remember in the command history (see
1434 below). The default value is 500.
1437 The name of the file in which command history is saved (see
1440 below). The default value is \fI~/.bash_history\fP. If unset, the
1441 command history is not saved when an interactive shell exits.
1444 The maximum number of lines contained in the history file. When this
1445 variable is assigned a value, the history file is truncated, if
1446 necessary, to contain no more than that number of lines. The default
1447 value is 500. The history file is also truncated to this size after
1448 writing it when an interactive shell exits.
1451 If set to the value 1,
1453 displays error messages generated by the
1455 builtin command (see
1457 .B SHELL BUILTIN COMMANDS
1461 is initialized to 1 each time the shell is invoked or a shell
1465 Used to determine the locale category for any category not specifically
1466 selected with a variable starting with \fBLC_\fP.
1469 This variable overrides the value of \fBLANG\fP and any other
1470 \fBLC_\fP variable specifying a locale category.
1473 This variable determines the collation order used when sorting the
1474 results of pathname expansion, and determines the behavior of range
1475 expressions, equivalence classes, and collating sequences within
1476 pathname expansion and pattern matching.
1479 This variable determines the interpretation of characters and the
1480 behavior of character classes within pathname expansion and pattern
1484 This variable determines the locale used to translate double-quoted
1485 strings preceded by a \fB$\fP.
1488 If set, the value is executed as a command prior to issuing each primary
1493 action of an interactive shell on receipt of an
1496 character as the sole input. If set, the value is the number of
1500 characters which must be
1501 typed as the first characters on an input line before
1503 exits. If the variable exists but does not have a numeric value, or
1504 has no value, the default value is 10. If it does not exist,
1507 signifies the end of input to the shell.
1510 If set to a value greater than zero, the value is interpreted as the
1511 number of seconds to wait for input after issuing the primary prompt.
1513 terminates after waiting for that number of seconds if input does
1517 The default editor for the
1522 A colon-separated list of suffixes to ignore when performing
1523 filename completion (see
1527 A filename whose suffix matches one of the entries in
1530 is excluded from the list of matched filenames.
1531 A sample value is ``.o:~''.
1534 A colon-separated list of patterns defining the set of filenames to
1535 be ignored by pathname expansion.
1536 If a filename matched by a pathname expansion pattern also matches one
1540 it is removed from the list of matches.
1543 The filename for the
1545 startup file, overriding the default of
1553 If set to a value of
1555 lines which begin with a
1557 character are not entered on the history list. If set to
1560 lines matching the last history line are not entered.
1563 combines the two options.
1564 If unset, or if set to any other value than those above,
1566 by the parser are saved on the history list, subject to the value
1569 This variable's function is superseded by
1571 The second and subsequent lines of a multi-line compound command are
1572 not tested, and are added to the history regardless of the value of
1576 A colon-separated list of patterns used to decide which command lines
1577 should be saved on the history list. Each pattern is anchored at the
1578 beginning of the line and must fully specify the line (no implicit
1579 `\fB*\fP' is appended). Each pattern is tested against the line
1580 after the checks specified by
1583 In addition to the normal shell pattern matching characters, `\fB&\fP'
1584 matches the previous history line. `\fB&\fP' may be escaped using a
1585 backslash. The backslash is removed before attempting a match.
1586 The second and subsequent lines of a multi-line compound command are
1587 not tested, and are added to the history regardless of the value of
1591 The two or three characters which control history expansion
1592 and tokenization (see
1594 .B HISTORY EXPANSION
1595 below). The first character is the
1596 .IR "history expansion character" ,
1597 the character which signals the start of a history
1598 expansion, normally `\fB!\fP'.
1599 The second character is the
1600 .IR "quick substitution"
1601 character, which is used as shorthand for re-running the previous
1602 command entered, substituting one string for another in the command.
1603 The default is `\fB^\fP'.
1604 The optional third character is the character
1605 which indicates that the remainder of the line is a comment when found
1606 as the first character of a word, normally `\fB#\fP'. The history
1607 comment character causes history substitution to be skipped for the
1608 remaining words on the line. It does not necessarily cause the shell
1609 parser to treat the rest of the line as a comment.
1612 Contains the name of a file in the same format as
1614 that should be read when the shell needs to complete a
1615 hostname. The file may be changed interactively; the next
1616 time hostname completion is attempted
1618 adds the contents of the new file to the already existing database.
1621 This variable controls how the shell interacts with the user and
1622 job control. If this variable is set, single word simple
1623 commands without redirections are treated as candidates for resumption
1624 of an existing stopped job. There is no ambiguity allowed; if there is
1625 more than one job beginning with the string typed, the job most recently
1626 accessed is selected. The
1628 of a stopped job, in this context, is the command line used to
1632 the string supplied must match the name of a stopped job exactly;
1635 the string supplied needs to match a substring of the name of a
1638 value provides functionality analogous to the
1643 below). If set to any other value, the supplied string must
1644 be a prefix of a stopped job's name; this provides functionality
1651 provides one-dimensional array variables. Any variable may be used as
1654 builtin will explicitly declare an array. There is no maximum
1655 limit on the size of an array, nor any requirement that members
1656 be indexed or assigned contiguously. Arrays are indexed using
1657 integers and are zero-based.
1659 An array is created automatically if any variable is assigned to using
1660 the syntax \fIname\fP[\fIsubscript\fP]=\fIvalue\fP. The
1662 is treated as an arithmetic expression that must evaluate to a number
1663 greater than or equal to zero. To explicitly declare an array, use
1664 .B declare \-a \fIname\fP
1667 .B SHELL BUILTIN COMMANDS
1669 .B declare \-a \fIname\fP[\fIsubscript\fP]
1670 is also accepted; the \fIsubscript\fP is ignored. Attributes may be
1671 specified for an array variable using the
1675 builtins. Each attribute applies to all members of an array.
1677 Arrays are assigned to using compound assignments of the form
1678 \fIname\fP=\fB(\fPvalue\fI1\fP ... value\fIn\fP\fB)\fP, where each
1679 \fIvalue\fP is of the form [\fIsubscript\fP]=\fIstring\fP. Only
1680 \fIstring\fP is required. If
1681 the optional brackets and subscript are supplied, that index is assigned to;
1682 otherwise the index of the element assigned is the last index assigned
1683 to by the statement plus one. Indexing starts at zero.
1684 This syntax is also accepted by the
1686 builtin. Individual array elements may be assigned to using the
1687 \fIname\fP[\fIsubscript\fP]=\fIvalue\fP syntax introduced above.
1689 Any element of an array may be referenced using
1690 ${\fIname\fP[\fIsubscript\fP]}. The braces are required to avoid
1691 conflicts with pathname expansion. If
1692 \fIsubscript\fP is \fB@\fP or \fB*\fP, the word expands to
1693 all members of \fIname\fP. These subscripts differ only when the
1694 word appears within double quotes. If the word is double-quoted,
1695 ${\fIname\fP[*]} expands to a single
1696 word with the value of each array member separated by the first
1700 special variable, and ${\fIname\fP[@]} expands each element of
1701 \fIname\fP to a separate word. When there are no array members,
1702 ${\fIname\fP[@]} expands to nothing. This is analogous to the expansion
1703 of the special parameters \fB*\fP and \fB@\fP (see
1704 .B Special Parameters
1705 above). ${#\fIname\fP[\fIsubscript\fP]} expands to the length of
1706 ${\fIname\fP[\fIsubscript\fP]}. If \fIsubscript\fP is \fB*\fP or
1707 \fB@\fP, the expansion is the number of elements in the array.
1708 Referencing an array variable without a subscript is equivalent to
1709 referencing element zero.
1713 builtin is used to destroy arrays. \fBunset\fP \fBname\fP[\fIsubscript\fP]
1714 destroys the array element at index \fIsubscript\fP.
1715 \fBunset\fP \fIname\fP, where \fIname\fP is an array, or
1716 \fBunset\fP \fIname\fP[\fIsubscript\fP], where
1717 \fIsubscript\fP is \fB*\fP or \fB@\fP, removes the entire array.
1724 builtins each accept a
1726 option to specify an array. The
1730 option to assign a list of words read from the standard input
1735 builtins display array values in a way that allows them to be
1736 reused as assignments.
1738 Expansion is performed on the command line after it has been split into
1739 words. There are seven kinds of expansion performed:
1740 .IR "brace expansion" ,
1741 .IR "tilde expansion" ,
1742 .IR "parameter and variable expansion" ,
1743 .IR "command substitution" ,
1744 .IR "arithmetic expansion" ,
1745 .IR "word splitting" ,
1747 .IR "pathname expansion" .
1749 The order of expansions is: brace expansion, tilde expansion,
1750 parameter, variable and arithmetic expansion and
1751 command substitution
1752 (done in a left-to-right fashion), word splitting, and pathname
1755 On systems that can support it, there is an additional expansion
1756 available: \fIprocess substitution\fP.
1758 Only brace expansion, word splitting, and pathname expansion
1759 can change the number of words of the expansion; other expansions
1760 expand a single word to a single word.
1761 The only exceptions to this are the expansions of
1762 "\fB$@\fP" and "\fB${\fP\fIname\fP\fB[@]}\fP"
1763 as explained above (see
1768 .I "Brace expansion"
1769 is a mechanism by which arbitrary strings
1770 may be generated. This mechanism is similar to
1771 \fIpathname expansion\fP, but the filenames generated
1772 need not exist. Patterns to be brace expanded take
1773 the form of an optional
1775 followed by a series of comma-separated strings
1776 between a pair of braces, followed by an optional
1778 The preamble is prefixed to each string contained
1779 within the braces, and the postscript is then appended
1780 to each resulting string, expanding left to right.
1782 Brace expansions may be nested. The results of each expanded
1783 string are not sorted; left to right order is preserved.
1784 For example, a\fB{\fPd,c,b\fB}\fPe expands into `ade ace abe'.
1786 Brace expansion is performed before any other expansions,
1787 and any characters special to other expansions are preserved
1788 in the result. It is strictly textual.
1790 does not apply any syntactic interpretation to the context of the
1791 expansion or the text between the braces.
1793 A correctly-formed brace expansion must contain unquoted opening
1794 and closing braces, and at least one unquoted comma.
1795 Any incorrectly formed brace expansion is left unchanged.
1796 A \fB{\fP or \fB,\fP may be quoted with a backslash to prevent its
1797 being considered part of a brace expression.
1799 This construct is typically used as shorthand when the common
1800 prefix of the strings to be generated is longer than in the
1804 mkdir /usr/local/src/bash/{old,new,dist,bugs}
1808 chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
1811 Brace expansion introduces a slight incompatibility with
1812 historical versions of
1815 does not treat opening or closing braces specially when they
1816 appear as part of a word, and preserves them in the output.
1818 removes braces from words as a consequence of brace
1819 expansion. For example, a word entered to
1822 appears identically in the output. The same word is
1827 If strict compatibility with
1833 option or disable brace expansion with the
1839 .B SHELL BUILTIN COMMANDS
1843 If a word begins with an unquoted tilde character (`\fB~\fP'), all of
1844 the characters preceding the first unquoted slash (or all characters,
1845 if there is no unquoted slash) are considered a \fItilde-prefix\fP.
1846 If none of the characters in the tilde-prefix are quoted, the
1847 characters in the tilde-prefix following the tilde are treated as a
1848 possible \fIlogin name\fP.
1849 If this login name is the null string, the tilde is replaced with the
1850 value of the shell parameter
1856 is unset, the home directory of the user executing the shell is
1857 substituted instead.
1858 Otherwise, the tilde-prefix is replaced with the home directory
1859 associated with the specified login name.
1861 If the tilde-prefix is a `~+', the value of the shell variable
1864 replaces the tilde-prefix.
1865 If the tilde-prefix is a `~\-', the value of the shell variable
1868 if it is set, is substituted.
1869 If the characters following the tilde in the tilde-prefix consist
1870 of a number \fIN\fP, optionally prefixed
1871 by a `+' or a `\-', the tilde-prefix is replaced with the corresponding
1872 element from the directory stack, as it would be displayed by the
1874 builtin invoked with the tilde-prefix as an argument.
1875 If the characters following the tilde in the tilde-prefix consist of a
1876 number without a leading `+' or `\-', `+' is assumed.
1878 If the login name is invalid, or the tilde expansion fails, the word
1881 Each variable assignment is checked for unquoted tilde-prefixes immediately
1886 In these cases, tilde expansion is also performed.
1887 Consequently, one may use file names with tildes in assignments to
1895 and the shell assigns the expanded value.
1896 .SS Parameter Expansion
1898 The `\fB$\fP' character introduces parameter expansion,
1899 command substitution, or arithmetic expansion. The parameter name
1900 or symbol to be expanded may be enclosed in braces, which
1901 are optional but serve to protect the variable to be expanded from
1902 characters immediately following it which could be
1903 interpreted as part of the name.
1905 When braces are used, the matching ending brace is the first `\fB}\fP'
1906 not escaped by a backslash or within a quoted string, and not within an
1907 embedded arithmetic expansion, command substitution, or paramter
1913 The value of \fIparameter\fP is substituted. The braces are required
1916 is a positional parameter with more than one digit,
1919 is followed by a character which is not to be
1920 interpreted as part of its name.
1923 If the first character of \fIparameter\fP is an exclamation point,
1924 a level of variable indirection is introduced.
1925 \fBBash\fP uses the value of the variable formed from the rest of
1926 \fIparameter\fP as the name of the variable; this variable is then
1927 expanded and that value used in the rest of the substitution, rather
1928 than the value of \fIparameter\fP itself.
1929 This is known as \fIindirect expansion\fP.
1931 In each of the cases below, \fIword\fP is subject to tilde expansion,
1932 parameter expansion, command substitution, and arithmetic expansion.
1933 When not performing substring expansion, \fBbash\fP tests for a parameter
1934 that is unset or null; omitting the colon results in a test only for a
1935 parameter that is unset.
1939 ${\fIparameter\fP\fB:\-\fP\fIword\fP}
1940 \fBUse Default Values\fP. If
1942 is unset or null, the expansion of
1944 is substituted. Otherwise, the value of
1948 ${\fIparameter\fP\fB:=\fP\fIword\fP}
1949 \fBAssign Default Values\fP.
1952 is unset or null, the expansion of
1958 is then substituted. Positional parameters and special parameters may
1959 not be assigned to in this way.
1961 ${\fIparameter\fP\fB:?\fP\fIword\fP}
1962 \fBDisplay Error if Null or Unset\fP.
1965 is null or unset, the expansion of \fIword\fP (or a message to that effect
1968 is not present) is written to the standard error and the shell, if it
1969 is not interactive, exits. Otherwise, the value of \fIparameter\fP is
1972 ${\fIparameter\fP\fB:+\fP\fIword\fP}
1973 \fBUse Alternate Value\fP.
1976 is null or unset, nothing is substituted, otherwise the expansion of
1981 ${\fIparameter\fP\fB:\fP\fIoffset\fP}
1983 ${\fIparameter\fP\fB:\fP\fIoffset\fP\fB:\fP\fIlength\fP}
1985 \fBSubstring Expansion.\fP
1986 Expands to up to \fIlength\fP characters of \fIparameter\fP,
1987 starting at the characters specified by \fIoffset\fP.
1988 If \fIlength\fP is omitted, expands to the substring of
1989 \fIparameter\fP, starting at the character specified by \fIoffset\fP.
1990 \fIlength\fP and \fIoffset\fP are arithmetic expressions (see
1993 ARITHMETIC EVALUATION
1995 \fIlength\fP must evaluate to a number greater than or equal to zero.
1996 If \fIoffset\fP evaluates to a number less than zero, the value
1997 is used as an offset from the end of the value of \fIparameter\fP.
1998 If \fIparameter\fP is \fB@\fP, the result is \fIlength\fP positional
1999 parameters beginning at \fIoffset\fP.
2000 If \fIparameter\fP is an array name indexed by @ or *,
2001 the result is the \fIlength\fP
2002 members of the array beginning with ${\fIparameter\fP[\fIoffset\fP]}.
2003 Substring indexing is zero-based unless the positional parameters
2004 are used, in which case the indexing starts at 1.
2006 ${\fB#\fP\fIparameter\fP}
2007 The length in characters of the value of \fIparameter\fP is substituted.
2014 the value substituted is the number of positional parameters.
2017 is an array name subscripted by
2021 the value substituted is the number of elements in the array.
2024 ${\fIparameter\fP\fB#\fP\fIword\fP}
2026 ${\fIparameter\fP\fB##\fP\fIword\fP}
2030 is expanded to produce a pattern just as in pathname
2031 expansion. If the pattern matches the beginning of
2034 then the result of the expansion is the expanded value of
2036 with the shortest matching pattern (the ``\fB#\fP'' case) or the
2037 longest matching pattern (the ``\fB##\fP'' case) deleted.
2044 the pattern removal operation is applied to each positional
2045 parameter in turn, and the expansion is the resultant list.
2048 is an array variable subscripted with
2052 the pattern removal operation is applied to each member of the
2053 array in turn, and the expansion is the resultant list.
2056 ${\fIparameter\fP\fB%\fP\fIword\fP}
2058 ${\fIparameter\fP\fB%%\fP\fIword\fP}
2060 The \fIword\fP is expanded to produce a pattern just as in
2062 If the pattern matches a trailing portion of the expanded value of
2064 then the result of the expansion is the expanded value of
2066 with the shortest matching pattern (the ``\fB%\fP'' case) or the
2067 longest matching pattern (the ``\fB%%\fP'' case) deleted.
2074 the pattern removal operation is applied to each positional
2075 parameter in turn, and the expansion is the resultant list.
2078 is an array variable subscripted with
2082 the pattern removal operation is applied to each member of the
2083 array in turn, and the expansion is the resultant list.
2086 ${\fIparameter\fP\fB/\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2088 ${\fIparameter\fP\fB//\fP\fIpattern\fP\fB/\fP\fIstring\fP}
2090 The \fIpattern\fP is expanded to produce a pattern just as in
2092 \fIParameter\fP is expanded and the longest match of \fIpattern\fP
2093 against its value is replaced with \fIstring\fP.
2094 In the first form, only the first match is replaced.
2095 The second form causes all matches of \fIpattern\fP to be
2096 replaced with \fIstring\fP.
2097 If \fIpattern\fP begins with \fB#\fP, it must match at the beginning
2099 If \fIpattern\fP begins with \fB%\fP, it must match at the end
2101 If \fIstring\fP is null, matches of \fIpattern\fP are deleted
2102 and the \fB/\fP following \fIpattern\fP may be omitted.
2109 the substitution operation is applied to each positional
2110 parameter in turn, and the expansion is the resultant list.
2113 is an array variable subscripted with
2117 the substitution operation is applied to each member of the
2118 array in turn, and the expansion is the resultant list.
2119 .SS Command Substitution
2121 \fICommand substitution\fP allows the output of a command to replace
2122 the command name. There are two forms:
2126 \fB$(\fP\fIcommand\fP\|\fB)\fP
2130 \fB`\fP\fIcommand\fP\fB`\fP
2134 performs the expansion by executing \fIcommand\fP and
2135 replacing the command substitution with the standard output of the
2136 command, with any trailing newlines deleted.
2137 Embedded newlines are not deleted, but they may be removed during
2139 The command substitution \fB$(cat \fIfile\fP)\fR can be replaced by
2140 the equivalent but faster \fB$(< \fIfile\fP)\fR.
2142 When the old-style backquote form of substitution is used,
2143 backslash retains its literal meaning except when followed by
2148 The first backquote not preceded by a backslash terminates the
2149 command substitution.
2150 When using the $(\^\fIcommand\fP\|) form, all characters between the
2151 parentheses make up the command; none are treated specially.
2153 Command substitutions may be nested. To nest when using the backquoted form,
2154 escape the inner backquotes with backslashes.
2156 If the substitution appears within double quotes, word splitting and
2157 pathname expansion are not performed on the results.
2158 .SS Arithmetic Expansion
2160 Arithmetic expansion allows the evaluation of an arithmetic expression
2161 and the substitution of the result. The format for arithmetic expansion is:
2164 \fB$((\fP\fIexpression\fP\fB))\fP
2169 is treated as if it were within double quotes, but a double quote
2170 inside the parentheses is not treated specially.
2171 All tokens in the expression undergo parameter expansion, string
2172 expansion, command substitution, and quote removal.
2173 Arithmetic substitutions may be nested.
2175 The evaluation is performed according to the rules listed below under
2177 .BR "ARITHMETIC EVALUATION" .
2182 prints a message indicating failure and no substitution occurs.
2183 .SS Process Substitution
2185 \fIProcess substitution\fP is supported on systems that support named
2186 pipes (\fIFIFOs\fP) or the \fB/dev/fd\fP method of naming open files.
2187 It takes the form of
2188 \fB<(\fP\fIlist\^\fP\fB)\fP
2190 \fB>(\fP\fIlist\^\fP\fB)\fP.
2191 The process \fIlist\fP is run with its input or output connected to a
2192 \fIFIFO\fP or some file in \fB/dev/fd\fP. The name of this file is
2193 passed as an argument to the current command as the result of the
2194 expansion. If the \fB>(\fP\fIlist\^\fP\fB)\fP form is used, writing to
2195 the file will provide input for \fIlist\fP. If the
2196 \fB<(\fP\fIlist\^\fP\fB)\fP form is used, the file passed as an
2197 argument should be read to obtain the output of \fIlist\fP.
2199 When available, \fIprocess substitution\fP is performed
2200 simultaneously with parameter and variable expansion,
2201 command substitution,
2202 and arithmetic expansion.
2205 The shell scans the results of
2206 parameter expansion,
2207 command substitution,
2209 arithmetic expansion
2210 that did not occur within double quotes for
2211 .IR "word splitting" .
2213 The shell treats each character of
2216 as a delimiter, and splits the results of the other
2217 expansions into words on these characters. If
2222 .BR <space><tab><newline> ,
2227 characters serves to delimit words. If
2230 has a value other than the default, then sequences of
2231 the whitespace characters
2235 are ignored at the beginning and end of the
2236 word, as long as the whitespace character is in the
2243 whitespace character).
2250 whitespace, along with any adjacent
2253 whitespace characters, delimits a field.
2257 whitespace characters is also treated as a delimiter.
2261 is null, no word splitting occurs.
2263 Explicit null arguments (\^\f3"\^"\fP or \^\f3'\^'\fP\^) are retained.
2264 Unquoted implicit null arguments, resulting from the expansion of
2266 that have no values, are removed.
2267 If a parameter with no value is expanded within double quotes, a
2268 null argument results and is retained.
2270 Note that if no expansion occurs, no splitting
2272 .SS Pathname Expansion
2274 After word splitting,
2277 option has been set,
2279 scans each word for the characters
2285 If one of these characters appears, then the word is
2288 and replaced with an alphabetically sorted list of
2289 file names matching the pattern.
2290 If no matching file names are found,
2291 and the shell option
2293 is disabled, the word is left unchanged.
2296 option is set, and no matches are found,
2297 the word is removed.
2300 is enabled, the match is performed without regard to the case
2301 of alphabetic characters.
2302 When a pattern is used for pathname expansion,
2305 at the start of a name or immediately following a slash
2306 must be matched explicitly, unless the shell option
2309 When matching a pathname, the slash character must always be
2313 character is not treated specially.
2314 See the description of
2318 .B SHELL BUILTIN COMMANDS
2319 for a description of the
2329 shell variable may be used to restrict the set of file names matching a
2334 is set, each matching file name that also matches one of the patterns in
2337 is removed from the list of matches.
2342 are always ignored, even when
2345 is set. However, setting
2348 has the effect of enabling the
2350 shell option, so all other file names beginning with a
2353 To get the old behavior of ignoring file names beginning with a
2357 one of the patterns in
2362 option is disabled when
2367 \fBPattern Matching\fP
2369 Any character that appears in a pattern, other than the special pattern
2370 characters described below, matches itself. The NUL character may not
2371 occur in a pattern. The special pattern characters must be quoted if
2372 they are to be matched literally.
2374 The special pattern characters have the following meanings:
2379 Matches any string, including the null string.
2382 Matches any single character.
2385 Matches any one of the enclosed characters. A pair of characters
2386 separated by a minus sign denotes a
2388 any character lexically between those two characters, inclusive,
2389 is matched. If the first character following the
2395 then any character not enclosed is matched.
2398 may be matched by including it as the first or last character
2402 may be matched by including it as the first character
2411 \fIcharacter classes\fP can be specified using the syntax
2412 \fB[:\fP\fIclass\fP\fB:]\fP, where \fIclass\fP is one of the
2413 following classes defined in the POSIX.2 standard:
2417 .if n alnum alpha ascii blank cntrl digit graph lower print punct space upper xdigit
2418 .if t alnum alpha ascii blank cntrl digit graph lower print punct space upper xdigit
2420 A character class matches any character belonging to that class.
2428 an \fIequivalence class\fP can be specified using the syntax
2429 \fB[=\fP\fIc\fP\fB=]\fP, which matches all characters with the
2430 same collation weight (as defined by the current locale) as
2431 the character \fIc\fP.
2439 the syntax \fB[.\fP\fIsymbol\fP\fB.]\fP matches the collating symbol
2444 If the \fBextglob\fP shell option is enabled using the \fBshopt\fP
2445 builtin, several extended pattern matching operators are recognized.
2446 In the following description, a \fIpattern\-list\fP is a list of one
2447 or more patterns separated by a \fB|\fP.
2448 Composite patterns may be formed using one or more of the following
2454 \fB?(\fP\^\fIpattern-list\^\fP\fB)\fP
2455 Matches zero or one occurrence of the given patterns
2457 \fB*(\fP\^\fIpattern-list\^\fP\fB)\fP
2458 Matches zero or more occurrences of the given patterns
2460 \fB+(\fP\^\fIpattern-list\^\fP\fB)\fP
2461 Matches one or more occurrences of the given patterns
2463 \fB@(\fP\^\fIpattern-list\^\fP\fB)\fP
2464 Matches exactly one of the given patterns
2466 \fB!(\fP\^\fIpattern-list\^\fP\fB)\fP
2467 Matches anything except one of the given patterns
2472 After the preceding expansions, all unquoted occurrences of the
2476 and \^\f3"\fP\^ that did not result from one of the above
2477 expansions are removed.
2479 Before a command is executed, its input and output
2482 using a special notation interpreted by the shell.
2483 Redirection may also be used to open and close files for the
2484 current shell execution environment. The following redirection
2485 operators may precede or appear anywhere within a
2489 Redirections are processed in the order they appear, from
2492 In the following descriptions, if the file descriptor number is
2493 omitted, and the first character of the redirection operator is
2495 the redirection refers to the standard input (file descriptor
2496 0). If the first character of the redirection operator is
2498 the redirection refers to the standard output (file descriptor
2501 The word following the redirection operator in the following
2502 descriptions, unless otherwise noted, is subjected to brace expansion,
2503 tilde expansion, parameter expansion, command substitution, arithmetic
2504 expansion, quote removal, and pathname expansion.
2505 If it expands to more than one word,
2509 Note that the order of redirections is significant. For example,
2513 ls \fB>\fP dirlist 2\fB>&\fP1
2516 directs both standard output and standard error to the file
2521 ls 2\fB>&\fP1 \fB>\fP dirlist
2524 directs only the standard output to file
2526 because the standard error was duplicated as standard output
2527 before the standard output was redirected to
2530 A failure to open or create a file causes the redirection to fail.
2531 .SS Redirecting Input
2533 Redirection of input causes the file whose name results from
2536 to be opened for reading on file descriptor
2538 or the standard input (file descriptor 0) if
2542 The general format for redirecting input is:
2545 [\fIn\fP]\fB<\fP\fIword\fP
2547 .SS Redirecting Output
2549 Redirection of output causes the file whose name results from
2552 to be opened for writing on file descriptor
2554 or the standard output (file descriptor 1) if
2556 is not specified. If the file does not exist it is created;
2557 if it does exist it is truncated to zero size.
2559 The general format for redirecting output is:
2562 [\fIn\fP]\fB>\fP\fIword\fP
2565 If the redirection operator is
2571 builtin has been enabled, the redirection will fail if the filename
2572 whose name results from the expansion of \fIword\fP exists and is
2574 If the redirection operator is
2576 or the redirection operator is
2582 builtin command is not enabled, the redirection is attempted even
2583 if the file named by \fIword\fP exists.
2584 .SS Appending Redirected Output
2586 Redirection of output in this fashion
2587 causes the file whose name results from
2590 to be opened for appending on file descriptor
2592 or the standard output (file descriptor 1) if
2594 is not specified. If the file does not exist it is created.
2596 The general format for appending output is:
2599 [\fIn\fP]\fB>>\fP\fIword\fP
2602 .SS Redirecting Standard Output and Standard Error
2606 standard output (file descriptor 1) and
2607 the standard error output (file descriptor 2)
2608 to be redirected to the file whose name is the
2611 with this construct.
2613 There are two formats for redirecting standard output and
2624 Of the two forms, the first is preferred.
2625 This is semantically equivalent to
2628 \fB>\fP\fIword\fP 2\fB>&\fP1
2632 This type of redirection instructs the shell to read input from the
2633 current source until a line containing only
2635 (with no trailing blanks)
2637 the lines read up to that point are then used as the standard
2638 input for a command.
2640 The format of here-documents is as follows:
2644 \fB<<\fP[\fB\-\fP]\fIword\fP
2645 \fIhere\-document\fP
2650 No parameter expansion, command substitution, pathname
2651 expansion, or arithmetic expansion is performed on
2653 If any characters in
2657 is the result of quote removal on
2659 and the lines in the here-document are not expanded.
2660 If \fIword\fP is unquoted,
2661 all lines of the here-document are subjected to parameter expansion,
2662 command substitution, and arithmetic expansion. In the latter
2667 must be used to quote the characters
2673 If the redirection operator is
2675 then all leading tab characters are stripped from input lines and the
2679 here-documents within shell scripts to be indented in a
2681 .SS "Duplicating File Descriptors"
2683 The redirection operator
2686 [\fIn\fP]\fB<&\fP\fIword\fP
2689 is used to duplicate input file descriptors.
2692 expands to one or more digits, the file descriptor denoted by
2694 is made to be a copy of that file descriptor.
2697 do not specify a file descriptor open for input, a redirection error occurs.
2706 is not specified, the standard input (file descriptor 0) is used.
2711 [\fIn\fP]\fB>&\fP\fIword\fP
2714 is used similarly to duplicate output file descriptors. If
2716 is not specified, the standard output (file descriptor 1) is used.
2719 do not specify a file descriptor open for output, a redirection error occurs.
2720 As a special case, if \fIn\fP is omitted, and \fIword\fP does not
2721 expand to one or more digits, the standard output and standard
2722 error are redirected as described previously.
2723 .SS "Opening File Descriptors for Reading and Writing"
2725 The redirection operator
2728 [\fIn\fP]\fB<>\fP\fIword\fP
2731 causes the file whose name is the expansion of
2733 to be opened for both reading and writing on file descriptor
2735 or on file descriptor 0 if
2737 is not specified. If the file does not exist, it is created.
2739 Aliases allow a string to be substituted for a word when it is used
2740 as the first word of a simple command.
2741 The shell maintains a list of
2743 that may be set and unset with the
2747 builtin commands (see
2749 .B SHELL BUILTIN COMMANDS
2751 The first word of each command, if unquoted,
2752 is checked to see if it has an
2753 alias. If so, that word is replaced by the text of the alias.
2754 The alias name and the replacement text may contain any valid
2755 shell input, including the
2757 listed above, with the exception that the alias name may not
2758 contain \fI=\fP. The first word of the replacement text is tested
2759 for aliases, but a word that is identical to an alias being expanded
2760 is not expanded a second time. This means that one may alias
2766 does not try to recursively expand the replacement text.
2767 If the last character of the alias value is a
2769 then the next command
2770 word following the alias is also checked for alias expansion.
2772 Aliases are created and listed with the
2774 command, and removed with the
2778 There is no mechanism for using arguments in the replacement text.
2779 If arguments are needed, a shell function should be used.
2781 Aliases are not expanded when the shell is not interactive, unless
2784 shell option is set using
2786 (see the description of
2790 \fBSHELL BUILTIN COMMANDS\fP
2793 The rules concerning the definition and use of aliases are
2796 always reads at least one complete line
2797 of input before executing any
2798 of the commands on that line. Aliases are expanded when a
2799 command is read, not when it is executed. Therefore, an
2800 alias definition appearing on the same line as another
2801 command does not take effect until the next line of input is read.
2802 The commands following the alias definition
2803 on that line are not affected by the new alias.
2804 This behavior is also an issue when functions are executed.
2805 Aliases are expanded when a function definition is read,
2806 not when the function is executed, because a function definition
2807 is itself a compound command. As a consequence, aliases
2808 defined in a function are not available until after that
2809 function is executed. To be safe, always put
2810 alias definitions on a separate line, and do not use
2812 in compound commands.
2814 For almost every purpose, aliases are superseded by
2817 A shell function, defined as described above under
2819 .BR "SHELL GRAMMAR" ,
2820 stores a series of commands for later execution.
2821 Functions are executed in the context of the
2822 current shell; no new process is created to interpret
2823 them (contrast this with the execution of a shell script).
2824 When a function is executed, the arguments to the
2825 function become the positional parameters
2826 during its execution. The special parameter
2828 is updated to reflect the change. Positional parameter 0
2829 is unchanged. All other aspects of the shell execution
2830 environment are identical between a function and its caller
2831 with the exception that the
2834 trap (see the description of the
2838 .B SHELL BUILTIN COMMANDS
2839 below) is not inherited.
2841 Variables local to the function may be declared with the
2843 builtin command. Ordinarily, variables and their values
2844 are shared between the function and its caller.
2846 If the builtin command
2848 is executed in a function, the function completes and
2849 execution resumes with the next command after the function
2850 call. When a function completes, the values of the
2851 positional parameters and the special parameter
2853 are restored to the values they had prior to the function's
2856 Function names and definitions may be listed with the
2862 builtin commands. The
2868 will list the function names only.
2869 Functions may be exported so that subshells
2870 automatically have them defined with the
2876 Functions may be recursive. No limit is imposed on the number
2878 .SH "ARITHMETIC EVALUATION"
2879 The shell allows arithmetic expressions to be evaluated, under
2880 certain circumstances (see the \fBlet\fP builtin command and
2881 \fBArithmetic Expansion\fP).
2882 Evaluation is done in long integers with no check for overflow,
2883 though division by 0 is trapped and flagged as an error.
2884 The following list of operators is grouped into levels of
2885 equal-precedence operators.
2886 The levels are listed in order of decreasing precedence.
2891 unary minus and plus
2894 logical and bitwise negation
2900 multiplication, division, remainder
2903 addition, subtraction
2906 left and right bitwise shifts
2912 equality and inequality
2918 bitwise exclusive OR
2929 .B \fIexpr\fP?\fIexpr\fP:\fIexpr\fP
2930 conditional evaluation
2932 .B = *= /= %= += \-= <<= >>= &= ^= |=
2936 Shell variables are allowed as operands; parameter expansion is
2937 performed before the expression is evaluated.
2938 The value of a parameter is coerced to a long integer within
2939 an expression. A shell variable need not have its integer attribute
2940 turned on to be used in an expression.
2942 Constants with a leading 0 are interpreted as octal numbers.
2943 A leading 0x or 0X denotes hexadecimal.
2944 Otherwise, numbers take the form [\fIbase#\fP]n, where \fIbase\fP
2945 is a decimal number between 2 and 64 representing the arithmetic
2946 base, and \fIn\fP is a number in that base.
2947 If \fIbase\fP is omitted, then base 10 is used.
2948 The digits greater than 9 are represented by the lowercase letters,
2949 the uppercase letters, _, and @, in that order.
2950 If \fIbase\fP is less than or equal to 36, lowercase and uppercase
2951 letters may be used interchangably to represent numbers between 10
2954 Operators are evaluated in order of precedence. Sub-expressions in
2955 parentheses are evaluated first and may override the precedence
2957 .SH "CONDITIONAL EXPRESSIONS"
2958 Conditional expressions are used by the \fB[[\fP compound command and
2959 the \fBtest\fP and \fB[\fP builtin commands to test file attributes
2960 and perform string and arithmetic comparisons.
2961 Expressions are formed from the following unary or binary primaries.
2962 If any \fIfile\fP argument to one of the primaries is of the form
2963 /dev/fd/\fIn\fP, then file descriptor \fIn\fP is checked.
2968 True if \fIfile\fP exists.
2971 True if \fIfile\fP exists and is a block special file.
2974 True if \fIfile\fP exists and is a character special file.
2977 True if \fIfile\fP exists and is a directory.
2980 True if \fIfile\fP exists.
2983 True if \fIfile\fP exists and is a regular file.
2986 True if \fIfile\fP exists and is set-group-id.
2989 True if \fIfile\fP exists and its ``sticky'' bit is set.
2992 True if \fIfile\fP exists and is a named pipe (FIFO).
2995 True if \fIfile\fP exists and is readable.
2998 True if \fIfile\fP exists and has a size greater than zero.
3001 True if file descriptor
3003 is open and refers to a terminal.
3006 True if \fIfile\fP exists and its set-user-id bit is set.
3009 True if \fIfile\fP exists and is writable.
3012 True if \fIfile\fP exists and is executable.
3015 True if \fIfile\fP exists and is owned by the effective user id.
3018 True if \fIfile\fP exists and is owned by the effective group id.
3021 True if \fIfile\fP exists and is a symbolic link.
3024 True if \fIfile\fP exists and is a socket.
3027 True if \fIfile\fP exists and has been modified since it was last read.
3029 \fIfile1\fP \-\fBnt\fP \fIfile2\fP
3030 True if \fIfile1\fP is newer (according to
3031 modification date) than \fIfile2\fP.
3033 \fIfile1\fP \-\fBot\fP \fIfile2\fP
3034 True if \fIfile1\fP is older than \fIfile2\fP.
3036 \fIfile1\fP \fB\-ef\fP \fIfile2\fP
3037 True if \fIfile1\fP and \fIfile2\fP have the same device and
3040 .B \-o \fIoptname\fP
3041 True if shell option
3044 See the list of options under the description of the
3051 True if the length of \fIstring\fP is zero.
3056 True if the length of
3060 \fIstring1\fP \fB==\fP \fIstring2\fP
3061 True if the strings are equal. \fB=\fP may be used in place of
3064 \fIstring1\fP \fB!=\fP \fIstring2\fP
3065 True if the strings are not equal.
3067 \fIstring1\fP \fB<\fP \fIstring2\fP
3068 True if \fIstring1\fP sorts before \fIstring2\fP lexicographically
3069 in the current locale.
3071 \fIstring1\fP \fB>\fP \fIstring2\fP
3072 True if \fIstring1\fP sorts after \fIstring2\fP lexicographically
3073 in the current locale.
3075 .I \fIarg1\fP \fBOP\fP \fIarg2\fP
3086 These arithmetic binary operators return true if \fIarg1\fP
3087 is equal to, not equal to, less than, less than or equal to,
3088 greater than, or greater than or equal to \fIarg2\fP, respectively.
3092 may be positive or negative integers.
3094 .SH "SIMPLE COMMAND EXPANSION"
3095 When a simple command is executed, the shell performs the following
3096 expansions, assignments, and redirections, from left to right.
3098 The words that the parser has marked as variable assignments (those
3099 preceding the command name) and redirections are saved for later
3102 The words that are not variable assignments or redirections are
3103 expanded. If any words remain after expansion, the first word
3104 is taken to be the name of the command and the remaining words are
3107 Redirections are performed as described above under
3111 The text after the \fB=\fP in each variable assignment undergoes tilde
3112 expansion, parameter expansion, command substitution, arithmetic expansion,
3113 and quote removal before being assigned to the variable.
3115 If no command name results, the variable assignments affect the current
3116 shell environment. Otherwise, the variables are added to the environment
3117 of the executed command and do not affect the current shell environment.
3118 If any of the assignments attempts to assign a value to a readonly variable,
3119 an error occurs, and the command exits with a non-zero status.
3121 If no command name results, redirections are performed, but do not
3122 affect the current shell environment. A redirection error causes the
3123 command to exit with a non-zero status.
3125 If there is a command name left after expansion, execution proceeds as
3126 described below. Otherwise, the command exits. If one of the expansions
3127 contained a command substitution, the exit status of the command is
3128 the exit status of the last command substitution performed. If there
3129 were no command substitutions, the command exits with a status of zero.
3130 .SH "COMMAND EXECUTION"
3131 After a command has been split into words, if it results in a
3132 simple command and an optional list of arguments, the following
3135 If the command name contains no slashes, the shell attempts to
3136 locate it. If there exists a shell function by that name, that
3137 function is invoked as described above in
3140 If the name does not match a function, the shell searches for
3141 it in the list of shell builtins. If a match is found, that
3144 If the name is neither a shell function nor a builtin,
3145 and contains no slashes,
3147 searches each element of the
3150 for a directory containing an executable file by that name.
3152 uses a hash table to remember the full file names of executable
3157 .B "SHELL BUILTIN COMMANDS"
3159 A full search of the directories in
3162 is performed only if the command is not found in the hash table.
3163 If the search is unsuccessful, the shell prints an error
3164 message and returns an exit status of 127.
3166 If the search is successful, or if the command name contains
3167 one or more slashes, the shell executes the named program in a
3168 separate execution environment.
3169 Argument 0 is set to the name given, and the remaining arguments
3170 to the command are set to the arguments given, if any.
3172 If this execution fails because the file is not in executable
3173 format, and the file is not a directory, it is assumed to be
3174 a \fIshell script\fP, a file
3175 containing shell commands. A subshell is spawned to execute
3176 it. This subshell reinitializes itself, so
3177 that the effect is as if a new shell had been invoked
3178 to handle the script, with the exception that the locations of
3179 commands remembered by the parent (see
3183 \fBSHELL BUILTIN COMMANDS\fP)
3184 are retained by the child.
3186 If the program is a file beginning with
3188 the remainder of the first line specifies an interpreter
3189 for the program. The shell executes the
3190 specified interpreter on operating systems that do not
3191 handle this executable format themselves. The arguments to the
3192 interpreter consist of a single optional argument following the
3193 interpreter name on the first line of the program, followed
3194 by the name of the program, followed by the command
3196 .SH COMMAND EXECUTION ENVIRONMENT
3197 The shell has an \fIexecution environment\fP, which consists of the
3201 open files inherited by the shell at invocation, as modified by
3202 redirections supplied to the \fBexec\fP builtin
3204 the current working directory as set by \fBcd\fP, \fBpushd\fP, or
3205 \fBpopd\fP, or inherited by the shell at invocation
3207 the file creation mode mask as set by \fBumask\fP or inherited from
3210 current traps set by \fBtrap\fP
3212 shell parameters that are set by variable assignment or with \fBset\fP
3213 or inherited from the shell's parent in the environment
3215 shell functions defined during execution or inherited from the shell's
3216 parent in the environment
3218 options enabled at invocation (either by default or with command-line
3219 arguments) or by \fBset\fP
3221 options enabled by \fBshopt\fP
3223 shell aliases defined with \fBalias\fP
3225 various process IDs, including those of background jobs, the value
3226 of \fB$$\fP, and the value of \fB$PPID\fP
3228 When a simple command other than a builtin or shell function
3229 is to be executed, it
3230 is invoked in a separate execution environment that consists of
3231 the following. Unless otherwise noted, the values are inherited
3235 the shell's open files, plus any modifications and additions specified
3236 by redirections to the command
3238 the current working directory
3240 the file creation mode mask
3242 shell variables marked for export, along with variables exported for
3243 the command, passed in the environment
3245 traps caught by the shell are reset to the values the inherited
3246 from the shell's parent, and traps ignored by the shell are ignored
3248 A command invoked in this separate environment cannot affect the
3249 shell's execution environment.
3251 Command substitution and asynchronous commands are invoked in a
3252 subshell environment that is a duplicate of the shell environment,
3253 except that traps caught by the shell are reset to the values
3254 that the shell inherited from its parent at invocation. Builtin
3255 commands that are invoked as part of a pipeline are also executed in a
3256 subshell environment. Changes made to the subshell environment
3257 cannot affect the shell's execution environment.
3259 When a program is invoked it is given an array of strings
3263 \fIname\fP\-\fIvalue\fP pairs, of the form
3264 .IR "name\fR=\fPvalue" .
3266 The shell allows you to manipulate the environment in several
3267 ways. On invocation, the shell scans its own environment and
3268 creates a parameter for each name found, automatically marking
3271 to child processes. Executed commands inherit the environment.
3276 commands allow parameters and functions to be added to and
3277 deleted from the environment. If the value of a parameter
3278 in the environment is modified, the new value becomes part
3279 of the environment, replacing the old. The environment
3280 inherited by any executed command consists of the shell's
3281 initial environment, whose values may be modified in the shell,
3282 less any pairs removed by the
3284 command, plus any additions via the
3290 The environment for any
3292 or function may be augmented temporarily by prefixing it with
3293 parameter assignments, as described above in
3296 These assignment statements affect only the environment seen
3301 option is set (see the
3303 builtin command below), then
3305 parameter assignments are placed in the environment for a command,
3306 not just those that precede the command name.
3310 invokes an external command, the variable
3312 is set to the full file name of the command and passed to that
3313 command in its environment.
3315 For the shell's purposes, a command which exits with a
3316 zero exit status has succeeded. An exit status of zero
3317 indicates success. A non-zero exit status indicates failure.
3318 When a command terminates on a fatal signal, \fBbash\fP uses
3319 the value of 128+\fBsignal\fP as the exit status.
3321 If a command is not found, the child process created to
3322 execute it returns a status of 127. If a command is found
3323 but is not executable, the return status is 126.
3325 If a command fails because of an error during expansion or redirection,
3326 the exit status is greater than zero.
3328 Shell builtin commands return a status of 0 (\fItrue\fP) if
3329 successful, and non-zero (\fIfalse\fP) if an error occurs
3331 All builtins return an exit status of 2 to indicate incorrect usage.
3333 \fBBash\fP itself returns the exit status of the last command
3334 executed, unless a syntax error occurs, in which case it exits
3335 with a non-zero value. See also the \fBexit\fP builtin
3338 When \fBbash\fP is interactive, in the absence of any traps, it ignores
3341 (so that \fBkill 0\fP does not kill an interactive shell),
3345 is caught and handled (so that the \fBwait\fP builtin is interruptible).
3346 In all cases, \fBbash\fP ignores
3349 If job control is in effect,
3360 Synchronous jobs started by \fBbash\fP have signal handlers
3361 set to the values inherited by the shell from its parent.
3362 When job control is not in effect, asynchronous commands
3370 Commands run as a result of command substitution ignore the
3371 keyboard-generated job control signals
3380 The shell exits by default upon receipt of a
3383 Before exiting, it resends the
3386 to all jobs, running or stopped.
3387 Stopped jobs are sent
3390 to ensure that they receive the
3393 To prevent the shell from
3394 sending the signal to a particular job, it should be removed from the
3399 .B "SHELL BUILTIN COMMANDS"
3409 shell option has been set with
3415 to all jobs when an interactive login shell exits.
3417 When \fBbash\fP receives a signal for which a trap has been set while
3418 waiting for a command to complete, the trap will not be executed until
3419 the command completes.
3420 When \fBbash\fP is waiting for an asynchronous command via the \fBwait\fP
3421 builtin, the reception of a signal for which a trap has been set will
3422 cause the \fBwait\fP builtin to return immediately with an exit status
3423 greater than 128, immediately after which the trap is executed.
3426 refers to the ability to selectively stop (\fIsuspend\fP)
3427 the execution of processes and continue (\fIresume\fP)
3428 their execution at a later point. A user typically employs
3429 this facility via an interactive interface supplied jointly
3430 by the system's terminal driver and
3433 The shell associates a
3435 with each pipeline. It keeps a table of currently executing
3436 jobs, which may be listed with the
3440 starts a job asynchronously (in the
3442 it prints a line that looks like:
3448 indicating that this job is job number 1 and that the process ID
3449 of the last process in the pipeline associated with this job is 25647.
3450 All of the processes in a single pipeline are members of the same job.
3454 abstraction as the basis for job control.
3456 To facilitate the implementation of the user interface to job
3457 control, the system maintains the notion of a \fIcurrent terminal
3458 process group ID\fP. Members of this process group (processes whose
3459 process group ID is equal to the current terminal process group ID)
3460 receive keyboard-generated signals such as
3463 These processes are said to be in the
3466 processes are those whose process group ID differs from the terminal's;
3467 such processes are immune to keyboard-generated signals.
3468 Only foreground processes are allowed to read from or write to the
3469 terminal. Background processes which attempt to read from (write to) the
3472 .B SIGTTIN (SIGTTOU)
3473 signal by the terminal driver,
3474 which, unless caught, suspends the process.
3476 If the operating system on which
3481 allows you to use it.
3484 character (typically
3486 Control-Z) while a process is running
3487 causes that process to be stopped and returns you to
3490 .I "delayed suspend"
3491 character (typically
3493 Control-Y) causes the process to be stopped when it
3494 attempts to read input from the terminal, and control to
3497 The user may then manipulate the state of this job, using the
3499 command to continue it in the background, the
3501 command to continue it in the foreground, or
3504 command to kill it. A \fB^Z\fP takes effect immediately,
3505 and has the additional side effect of causing pending output
3506 and typeahead to be discarded.
3508 There are a number of ways to refer to a job in the shell.
3511 introduces a job name. Job number
3513 may be referred to as
3515 A job may also be referred to using a prefix of the name used to
3516 start it, or using a substring that appears in its command line.
3521 job. If a prefix matches more than one job,
3523 reports an error. Using
3525 on the other hand, refers to any job containing the string
3527 in its command line. If the substring matches more than one job,
3529 reports an error. The symbols
3533 refer to the shell's notion of the
3535 which is the last job stopped while it was in
3536 the foreground or started in the background.
3539 may be referenced using
3541 In output pertaining to jobs (e.g., the output of the
3543 command), the current job is always flagged with a
3545 and the previous job with a
3548 Simply naming a job can be used to bring it into the
3553 bringing job 1 from the background into the foreground.
3556 resumes job 1 in the background, equivalent to
3559 The shell learns immediately whenever a job changes state.
3562 waits until it is about to print a prompt before reporting
3563 changes in a job's status so as to not interrupt
3564 any other output. If the
3571 reports such changes immediately.
3573 If an attempt to exit
3575 is made while jobs are stopped, the shell prints a warning message. The
3577 command may then be used to inspect their status.
3578 If a second attempt to exit is made without an intervening command,
3579 the shell does not print another warning, and the stopped
3580 jobs are terminated.
3582 When executing interactively,
3584 displays the primary prompt
3587 when it is ready to read a command, and the secondary prompt
3590 when it needs more input to complete a command.
3592 allows these prompt strings to be customized by inserting a number of
3593 backslash-escaped special characters that are decoded as follows:
3598 an ASCII bell character (07)
3601 the date in "Weekday Month Date" format (e.g., "Tue May 26")
3604 an ASCII escape character (033)
3607 the hostname up to the first `.'
3619 the name of the shell, the basename of
3621 (the portion following the final slash)
3624 the current time in 24-hour HH:MM:SS format
3627 the current time in 12-hour HH:MM:SS format
3630 the current time in 12-hour am/pm format
3633 the username of the current user
3636 the version of \fBbash\fP (e.g., 2.00)
3639 the release of \fBbash\fP, version + patchlevel (e.g., 2.00.0)
3642 the current working directory
3645 the basename of the current working directory
3648 the history number of this command
3651 the command number of this command
3654 if the effective UID is 0, a
3660 the character corresponding to the octal number \fInnn\fP
3666 begin a sequence of non-printing characters, which could be used to
3667 embed a terminal control sequence into the prompt
3670 end a sequence of non-printing characters
3674 The command number and the history number are usually different:
3675 the history number of a command is its position in the history
3676 list, which may include commands restored from the history file
3680 below), while the command number is the position in the sequence
3681 of commands executed during the current shell session.
3682 After the string is decoded, it is expanded via
3683 parameter expansion, command substitution, arithmetic expansion,
3684 string expansion, and quote removal, subject to the value of the
3686 shell option (see the description of the
3690 .B "SHELL BUILTIN COMMANDS"
3693 This is the library that handles reading input when using an interactive
3696 option is given at shell invocation.
3697 By default, the line editing commands are similar to those of emacs.
3698 A vi-style line editing interface is also available.
3699 To turn off line editing after the shell is running, use the
3707 .B SHELL BUILTIN COMMANDS
3709 .SS "Readline Notation"
3711 In this section, the emacs-style notation is used to denote
3712 keystrokes. Control keys are denoted by C\-\fIkey\fR, e.g., C\-n
3713 means Control\-N. Similarly,
3715 keys are denoted by M\-\fIkey\fR, so M\-x means Meta\-X. (On keyboards
3718 key, M\-\fIx\fP means ESC \fIx\fP, i.e., press the Escape key
3721 key. This makes ESC the \fImeta prefix\fP.
3722 The combination M\-C\-\fIx\fP means ESC\-Control\-\fIx\fP,
3723 or press the Escape key
3724 then hold the Control key while pressing the
3728 Readline commands may be given numeric
3730 which normally act as a repeat count.
3731 Sometimes, however, it is the sign of the argument that is significant.
3732 Passing a negative argument to a command that acts in the forward
3733 direction (e.g., \fBkill\-line\fP) causes that command to act in a
3735 Commands whose behavior with arguments deviates from this are noted
3738 When a command is described as \fIkilling\fP text, the text
3739 deleted is saved for possible future retrieval
3740 (\fIyanking\fP). The killed text is saved in a
3741 \fIkill ring\fP. Consecutive kills cause the text to be
3742 accumulated into one unit, which can be yanked all at once.
3743 Commands which do not kill text separate the chunks of text
3745 .SS "Readline Initialization"
3747 Readline is customized by putting commands in an initialization
3748 file (the \fIinputrc\fP file).
3749 The name of this file is taken from the value of the
3752 variable. If that variable is unset, the default is
3754 When a program which uses the readline library starts up, the
3755 initialization file is read, and the key bindings and variables
3757 There are only a few basic constructs allowed in the
3758 readline initialization file.
3759 Blank lines are ignored.
3760 Lines beginning with a \fB#\fP are comments.
3761 Lines beginning with a \fB$\fP indicate conditional constructs.
3762 Other lines denote key bindings and variable settings.
3764 The default key-bindings may be changed with an
3767 Other programs that use this library may add their own commands
3770 For example, placing
3773 M\-Control\-u: universal\-argument
3777 C\-Meta\-u: universal\-argument
3781 would make M\-C\-u execute the readline command
3782 .IR universal\-argument .
3784 The following symbolic character names are recognized:
3796 In addition to command names, readline allows keys to be bound
3797 to a string that is inserted when the key is pressed (a \fImacro\fP).
3798 .SS "Readline Key Bindings"
3800 The syntax for controlling key bindings in the
3802 file is simple. All that is required is the name of the
3803 command or the text of a macro and a key sequence to which
3804 it should be bound. The name may be specified in one of two ways:
3805 as a symbolic key name, possibly with \fIMeta\-\fP or \fIControl\-\fP
3806 prefixes, or as a key sequence.
3807 When using the form \fBkeyname\fP:\^\fIfunction\-name\fP or \fImacro\fP,
3809 is the name of a key spelled out in English. For example:
3812 Control-u: universal\-argument
3814 Meta-Rubout: backward-kill-word
3816 Control-o: "> output"
3819 In the above example,
3821 is bound to the function
3822 .BR universal\-argument ,
3824 is bound to the function
3825 .BR backward\-kill\-word ,
3828 is bound to run the macro
3829 expressed on the right hand side (that is, to insert the text
3833 In the second form, \fB"keyseq"\fP:\^\fIfunction\-name\fP or \fImacro\fP,
3837 above in that strings denoting
3838 an entire key sequence may be specified by placing the sequence
3839 within double quotes. Some GNU Emacs style key escapes can be
3840 used, as in the following example.
3843 "\eC\-u": universal\-argument
3845 "\eC\-x\eC\-r": re\-read\-init\-file
3847 "\ee[11~": "Function Key 1"
3852 is again bound to the function
3853 .BR universal\-argument .
3855 is bound to the function
3856 .BR re\-read\-init\-file ,
3859 is bound to insert the text
3860 .BR "Function Key 1" .
3861 The full set of GNU Emacs style escape sequences is
3885 In addition to the GNU Emacs style escape sequences, a second
3886 set of backslash escapes is available:
3915 the character whose ASCII code is the octal value \fInnn\fP
3916 (one to three digits)
3919 the character whose ASCII code is the hexadecimal value \fInnn\fP
3920 (one to three digits)
3924 When entering the text of a macro, single or double quotes must
3925 be used to indicate a macro definition.
3926 Unquoted text is assumed to be a function name.
3927 In the macro body, the backslash escapes described above are expanded.
3928 Backslash will quote any other character in the macro text,
3932 allows the current readline key bindings to be displayed or modified
3935 builtin command. The editing mode may be switched during interactive
3940 builtin command (see
3942 .B SHELL BUILTIN COMMANDS
3944 .SS "Readline Variables"
3946 Readline has variables that can be used to further customize its
3947 behavior. A variable may be set in the
3949 file with a statement of the form
3952 \fBset\fP \fIvariable\-name\fP \fIvalue\fP
3955 Except where noted, readline variables can take the values
3959 The variables and their default values are:
3963 .B bell\-style (audible)
3964 Controls what happens when readline wants to ring the terminal bell.
3965 If set to \fBnone\fP, readline never rings the bell. If set to
3966 \fBvisible\fP, readline uses a visible bell if one is available.
3967 If set to \fBaudible\fP, readline attempts to ring the terminal's bell.
3969 .B comment\-begin (``#'')
3970 The string that is inserted when the
3973 command is executed.
3974 This command is bound to
3976 in emacs mode and to
3980 .B completion\-ignore\-case (Off)
3981 If set to \fBOn\fP, readline performs filename matching and completion
3982 in a case\-insensitive fashion.
3984 .B completion\-query\-items (100)
3985 This determines when the user is queried about viewing
3986 the number of possible completions
3987 generated by the \fBpossible\-completions\fP command.
3988 It may be set to any integer value greater than or equal to
3989 zero. If the number of possible completions is greater than
3990 or equal to the value of this variable, the user is asked whether
3991 or not he wishes to view them; otherwise they are simply listed
3994 .B convert\-meta (On)
3995 If set to \fBOn\fP, readline will convert characters with the
3996 eighth bit set to an ASCII key sequence
3997 by stripping the eighth bit and prepending an
3998 escape character (in effect, using escape as the \fImeta prefix\fP).
4000 .B disable\-completion (Off)
4001 If set to \fBOn\fP, readline will inhibit word completion. Completion
4002 characters will be inserted into the line as if they had been
4003 mapped to \fBself-insert\fP.
4005 .B editing\-mode (emacs)
4006 Controls whether readline begins with a set of key bindings similar
4007 to \fIemacs\fP or \fIvi\fP.
4009 can be set to either
4014 .B enable\-keypad (Off)
4015 When set to \fBOn\fP, readline will try to enable the application
4016 keypad when it is called. Some systems need this to enable the
4019 .B expand\-tilde (Off)
4020 If set to \fBon\fP, tilde expansion is performed when readline
4021 attempts word completion.
4023 .B horizontal\-scroll\-mode (Off)
4024 When set to \fBOn\fP, makes readline use a single line for display,
4025 scrolling the input horizontally on a single screen line when it
4026 becomes longer than the screen width rather than wrapping to a new line.
4028 .B input\-meta (Off)
4029 If set to \fBOn\fP, readline will enable eight-bit input (that is,
4030 it will not strip the high bit from the characters it reads),
4031 regardless of what the terminal claims it can support. The name
4033 is a synonym for this variable.
4036 Set the current readline keymap. The set of valid keymap names is
4037 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
4040 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
4041 equivalent to \fIemacs\-standard\fP. The default value is
4045 also affects the default keymap.
4047 .B mark\-directories (On)
4048 If set to \fBOn\fP, completed directory names have a slash
4051 .B mark\-modified\-lines (Off)
4052 If set to \fBOn\fP, history lines that have been modified are displayed
4053 with a preceding asterisk (\fB*\fP).
4055 .B output\-meta (Off)
4056 If set to \fBOn\fP, readline will display characters with the
4057 eighth bit set directly rather than as a meta-prefixed escape
4060 .B print\-completions\-horizontally (Off)
4061 If set to \fBOn\fP, readline will display completions with matches
4062 sorted horizontally in alphabetical order, rather than down the screen.
4064 .B show\-all\-if\-ambiguous (Off)
4065 This alters the default behavior of the completion functions. If
4068 words which have more than one possible completion cause the
4069 matches to be listed immediately instead of ringing the bell.
4071 .B visible\-stats (Off)
4072 If set to \fBOn\fP, a character denoting a file's type as reported
4073 by \fIstat\fP(2) is appended to the filename when listing possible
4076 .SS "Readline Conditional Constructs"
4078 Readline implements a facility similar in spirit to the conditional
4079 compilation features of the C preprocessor which allows key
4080 bindings and variable settings to be performed as the result
4081 of tests. There are four parser directives used.
4085 construct allows bindings to be made based on the
4086 editing mode, the terminal being used, or the application using
4087 readline. The text of the test extends to the end of the line;
4088 no characters are required to isolate it.
4091 The \fBmode=\fP form of the \fB$if\fP directive is used to test
4092 whether readline is in emacs or vi mode.
4093 This may be used in conjunction
4094 with the \fBset keymap\fP command, for instance, to set bindings in
4095 the \fIemacs\-standard\fP and \fIemacs\-ctlx\fP keymaps only if
4096 readline is starting out in emacs mode.
4098 The \fBterm=\fP form may be used to include terminal-specific
4099 key bindings, perhaps to bind the key sequences output by the
4100 terminal's function keys. The word on the right side of the
4102 is tested against the both full name of the terminal and the portion
4103 of the terminal name before the first \fB\-\fP. This allows
4110 .IP \fBapplication\fP
4111 The \fBapplication\fP construct is used to include
4112 application-specific settings. Each program using the readline
4113 library sets the \fIapplication name\fP, and an initialization
4114 file can test for a particular value.
4115 This could be used to bind key sequences to functions useful for
4116 a specific program. For instance, the following command adds a
4117 key sequence that quotes the current or previous word in Bash:
4122 # Quote the current or previous word
4123 "\eC\-xq": "\eeb\e"\eef\e""
4129 This command, as seen in the previous example, terminates an
4132 Commands in this branch of the \fB$if\fP directive are executed if
4135 This directive takes a single filename as an argument and reads commands
4136 and bindings from that file. For example, the following directive
4137 would read \fI/etc/inputrc\fP:
4141 \fB$include\fP \^ \fI/etc/inputrc\fP
4146 Readline provides commands for searching through the command history
4150 below) for lines containing a specified string.
4151 There are two search modes:
4154 .IR non-incremental .
4156 Incremental searches begin before the user has finished typing the
4158 As each character of the search string is typed, readline displays
4159 the next entry from the history matching the string typed so far.
4160 An incremental search requires only as many characters as needed to
4161 find the desired history entry.
4162 The Escape character is used to terminate an incremental search.
4163 Control-J will also terminate the search.
4164 Control-G will abort an incremental search and restore the original
4166 When the search is terminated, the history entry containing the
4167 search string becomes the current line.
4168 To find other matching entries in the history list, type Control-S or
4169 Control-R as appropriate.
4170 This will search backward or forward in the history for the next
4171 entry matching the search string typed so far.
4172 Any other key sequence bound to a readline command will terminate
4173 the search and execute that command.
4174 For instance, a \fInewline\fP will terminate the search and accept
4175 the line, thereby executing the command from the history list.
4177 Non-incremental searches read the entire search string before starting
4178 to search for matching history lines. The search string may be
4179 typed by the user or be part of the contents of the current line.
4180 .SS "Readline Command Names"
4182 The following is a list of the names of the commands and the default
4183 key sequences to which they are bound.
4184 Command names without an accompanying key sequence are unbound by default.
4185 .SS Commands for Moving
4189 .B beginning\-of\-line (C\-a)
4190 Move to the start of the current line.
4192 .B end\-of\-line (C\-e)
4193 Move to the end of the line.
4195 .B forward\-char (C\-f)
4196 Move forward a character.
4198 .B backward\-char (C\-b)
4199 Move back a character.
4201 .B forward\-word (M\-f)
4202 Move forward to the end of the next word. Words are composed of
4203 alphanumeric characters (letters and digits).
4205 .B backward\-word (M\-b)
4206 Move back to the start of this, or the previous, word. Words are
4207 composed of alphanumeric characters (letters and digits).
4209 .B clear\-screen (C\-l)
4210 Clear the screen leaving the current line at the top of the screen.
4211 With an argument, refresh the current line without clearing the
4214 .B redraw\-current\-line
4215 Refresh the current line.
4217 .SS Commands for Manipulating the History
4221 .B accept\-line (Newline, Return)
4222 Accept the line regardless of where the cursor is. If this line is
4223 non-empty, add it to the history list according to the state of the
4226 variable. If the line is a modified history
4227 line, then restore the history line to its original state.
4229 .B previous\-history (C\-p)
4230 Fetch the previous command from the history list, moving back in
4233 .B next\-history (C\-n)
4234 Fetch the next command from the history list, moving forward in the
4237 .B beginning\-of\-history (M\-<)
4238 Move to the first line in the history.
4240 .B end\-of\-history (M\->)
4241 Move to the end of the input history, i.e., the line currently being
4244 .B reverse\-search\-history (C\-r)
4245 Search backward starting at the current line and moving `up' through
4246 the history as necessary. This is an incremental search.
4248 .B forward\-search\-history (C\-s)
4249 Search forward starting at the current line and moving `down' through
4250 the history as necessary. This is an incremental search.
4252 .B non\-incremental\-reverse\-search\-history (M\-p)
4253 Search backward through the history starting at the current line
4254 using a non-incremental search for a string supplied by the user.
4256 .B non\-incremental\-forward\-search\-history (M\-n)
4257 Search forward through the history using a non-incremental search for
4258 a string supplied by the user.
4260 .B history\-search\-forward
4261 Search forward through the history for the string of characters
4262 between the start of the current line and the current cursor
4263 position (the \fIpoint\fP).
4264 This is a non-incremental search.
4266 .B history\-search\-backward
4267 Search backward through the history for the string of characters
4268 between the start of the current line and the point.
4269 This is a non-incremental search.
4271 .B yank\-nth\-arg (M\-C\-y)
4272 Insert the first argument to the previous command (usually
4273 the second word on the previous line) at point (the current
4274 cursor position). With an argument
4276 insert the \fIn\fPth word from the previous command (the words
4277 in the previous command begin with word 0). A negative argument
4278 inserts the \fIn\fPth word from the end of the previous command.
4281 yank\-last\-arg (M\-.\^, M\-_\^)
4282 Insert the last argument to the previous command (the last word of
4283 the previous history entry). With an argument,
4284 behave exactly like \fByank\-nth\-arg\fP.
4285 Successive calls to \fByank\-last\-arg\fP move back through the history
4286 list, inserting the last argument of each line in turn.
4288 .B shell\-expand\-line (M\-C\-e)
4289 Expand the line as the shell does. This
4290 performs alias and history expansion as well as all of the shell
4291 word expansions. See
4293 .B HISTORY EXPANSION
4294 below for a description of history expansion.
4296 .B history\-expand\-line (M\-^)
4297 Perform history expansion on the current line.
4300 .B HISTORY EXPANSION
4301 below for a description of history expansion.
4304 Perform history expansion on the current line and insert a space.
4307 .B HISTORY EXPANSION
4308 below for a description of history expansion.
4310 .B alias\-expand\-line
4311 Perform alias expansion on the current line.
4315 above for a description of alias expansion.
4317 .B history\-and\-alias\-expand\-line
4318 Perform history and alias expansion on the current line.
4320 .B insert\-last\-argument (M\-.\^, M\-_\^)
4321 A synonym for \fByank\-last\-arg\fP.
4323 .B operate\-and\-get\-next (C\-o)
4324 Accept the current line for execution and fetch the next line
4325 relative to the current line from the history for editing. Any
4326 argument is ignored.
4328 .SS Commands for Changing Text
4332 .B delete\-char (C\-d)
4333 Delete the character under the cursor. If point is at the
4334 beginning of the line, there are no characters in the line, and
4335 the last character typed was not bound to \fBdelete\-char\fP,
4340 .B backward\-delete\-char (Rubout)
4341 Delete the character behind the cursor. When given a numeric argument,
4342 save the deleted text on the kill ring.
4344 .B quoted\-insert (C\-q, C\-v)
4345 Add the next character typed to the line verbatim. This is
4346 how to insert characters like \fBC\-q\fP, for example.
4348 .B tab\-insert (C\-v TAB)
4349 Insert a tab character.
4351 .B self\-insert (a,\ b,\ A,\ 1,\ !,\ ...)
4352 Insert the character typed.
4354 .B transpose\-chars (C\-t)
4355 Drag the character before point forward over the character at point.
4356 Point moves forward as well. If point is at the end of the line, then
4357 transpose the two characters before point. Negative arguments don't work.
4359 .B transpose\-words (M\-t)
4360 Drag the word behind the cursor past the word in front of the cursor
4361 moving the cursor over that word as well.
4363 .B upcase\-word (M\-u)
4364 Uppercase the current (or following) word. With a negative argument,
4365 uppercase the previous word, but do not move point.
4367 .B downcase\-word (M\-l)
4368 Lowercase the current (or following) word. With a negative argument,
4369 lowercase the previous word, but do not move point.
4371 .B capitalize\-word (M\-c)
4372 Capitalize the current (or following) word. With a negative argument,
4373 capitalize the previous word, but do not move point.
4375 .SS Killing and Yanking
4379 .B kill\-line (C\-k)
4380 Kill the text from the current cursor position to the end of the line.
4382 .B backward\-kill\-line (C\-x Rubout)
4383 Kill backward to the beginning of the line.
4385 .B unix\-line\-discard (C\-u)
4386 Kill backward from point to the beginning of the line.
4387 The killed text is saved on the kill-ring.
4388 \" There is no real difference between this and backward-kill-line
4390 .B kill\-whole\-line
4391 Kill all characters on the current line, no matter where the
4394 .B kill\-word (M\-d)
4395 Kill from the cursor to the end of the current word, or if between
4396 words, to the end of the next word. Word boundaries are the same as
4397 those used by \fBforward\-word\fP.
4399 .B backward\-kill\-word (M\-Rubout)
4400 Kill the word behind the cursor. Word boundaries are the same as
4401 those used by \fBbackward\-word\fP.
4403 .B unix\-word\-rubout (C\-w)
4404 Kill the word behind the cursor, using white space as a word boundary.
4405 The word boundaries are different from \fBbackward\-kill\-word\fP.
4407 .B delete\-horizontal\-space (M\-\e)
4408 Delete all spaces and tabs around point.
4411 Kill the text between the point and \fImark\fP (saved cursor position).
4412 This text is referred to as the \fIregion\fP.
4414 .B copy\-region\-as\-kill
4415 Copy the text in the region to the kill buffer.
4417 .B copy\-backward\-word
4418 Copy the word before point to the kill buffer.
4419 The word boundaries are the same as \fBbackward\-word\fP.
4421 .B copy\-forward\-word
4422 Copy the word following point to the kill buffer.
4423 The word boundaries are the same as \fBforward\-word\fP.
4426 Yank the top of the kill ring into the buffer at the cursor.
4429 Rotate the kill ring, and yank the new top. Only works following
4434 .SS Numeric Arguments
4438 .B digit\-argument (M\-0, M\-1, ..., M\-\-)
4439 Add this digit to the argument already accumulating, or start a new
4440 argument. M\-\- starts a negative argument.
4442 .B universal\-argument
4443 This is another way to specify an argument.
4444 If this command is followed by one or more digits, optionally with a
4445 leading minus sign, those digits define the argument.
4446 If the command is followed by digits, executing
4447 .B universal\-argument
4448 again ends the numeric argument, but is otherwise ignored.
4449 As a special case, if this command is immediately followed by a
4450 character that is neither a digit or minus sign, the argument count
4451 for the next command is multiplied by four.
4452 The argument count is initially one, so executing this function the
4453 first time makes the argument count four, a second time makes the
4454 argument count sixteen, and so on.
4461 Attempt to perform completion on the text before point.
4463 attempts completion treating the text as a variable (if the
4464 text begins with \fB$\fP), username (if the text begins with
4465 \fB~\fP), hostname (if the text begins with \fB@\fP), or
4466 command (including aliases and functions) in turn. If none
4467 of these produces a match, filename completion is attempted.
4469 .B possible\-completions (M\-?)
4470 List the possible completions of the text before point.
4472 .B insert\-completions (M\-*)
4473 Insert all completions of the text before point
4474 that would have been generated by
4475 \fBpossible\-completions\fP.
4478 Similar to \fBcomplete\fP, but replaces the word to be completed
4479 with a single match from the list of possible completions.
4480 Repeated execution of \fBmenu\-complete\fP steps through the list
4481 of possible completions, inserting each match in turn.
4482 At the end of the list of completions, the bell is rung and the
4483 original text is restored.
4484 An argument of \fIn\fP moves \fIn\fP positions forward in the list
4485 of matches; a negative argument may be used to move backward
4487 This command is intended to be bound to \fBTAB\fP, but is unbound
4490 .B complete\-filename (M\-/)
4491 Attempt filename completion on the text before point.
4493 .B possible\-filename\-completions (C\-x /)
4494 List the possible completions of the text before point,
4495 treating it as a filename.
4497 .B complete\-username (M\-~)
4498 Attempt completion on the text before point, treating
4501 .B possible\-username\-completions (C\-x ~)
4502 List the possible completions of the text before point,
4503 treating it as a username.
4505 .B complete\-variable (M\-$)
4506 Attempt completion on the text before point, treating
4507 it as a shell variable.
4509 .B possible\-variable\-completions (C\-x $)
4510 List the possible completions of the text before point,
4511 treating it as a shell variable.
4513 .B complete\-hostname (M\-@)
4514 Attempt completion on the text before point, treating
4517 .B possible\-hostname\-completions (C\-x @)
4518 List the possible completions of the text before point,
4519 treating it as a hostname.
4521 .B complete\-command (M\-!)
4522 Attempt completion on the text before point, treating
4523 it as a command name. Command completion attempts to
4524 match the text against aliases, reserved words, shell
4525 functions, shell builtins, and finally executable filenames,
4528 .B possible\-command\-completions (C\-x !)
4529 List the possible completions of the text before point,
4530 treating it as a command name.
4532 .B dynamic\-complete\-history (M\-TAB)
4533 Attempt completion on the text before point, comparing
4534 the text against lines from the history list for possible
4537 .B complete\-into\-braces (M\-{)
4538 Perform filename completion and return the list of possible completions
4539 enclosed within braces so the list is available to the shell (see
4547 .B start\-kbd\-macro (C\-x (\^)
4548 Begin saving the characters typed into the current keyboard macro.
4550 .B end\-kbd\-macro (C\-x )\^)
4551 Stop saving the characters typed into the current keyboard macro
4552 and store the definition.
4554 .B call\-last\-kbd\-macro (C\-x e)
4555 Re-execute the last keyboard macro defined, by making the characters
4556 in the macro appear as if typed at the keyboard.
4562 .B re\-read\-init\-file (C\-x C\-r)
4563 Read in the contents of the \fIinputrc\fP file, and incorporate
4564 any bindings or variable assignments found there.
4567 Abort the current editing command and
4568 ring the terminal's bell (subject to the setting of
4571 .B do\-uppercase\-version (M\-a, M\-b, M\-\fIx\fP, ...)
4572 If the metafied character \fIx\fP is lowercase, run the command
4573 that is bound to the corresponding uppercase character.
4575 .B prefix\-meta (ESC)
4576 Metafy the next character typed.
4583 .B undo (C\-_, C\-x C\-u)
4584 Incremental undo, separately remembered for each line.
4586 .B revert\-line (M\-r)
4587 Undo all changes made to this line. This is like executing the
4589 command enough times to return the line to its initial state.
4591 .B tilde\-expand (M\-~)
4592 Perform tilde expansion on the current word.
4594 .B set\-mark (C\-@, M\-<space>)
4595 Set the mark to the current point. If a
4596 numeric argument is supplied, the mark is set to that position.
4598 .B exchange\-point\-and\-mark (C\-x C\-x)
4599 Swap the point with the mark. The current cursor position is set to
4600 the saved position, and the old cursor position is saved as the mark.
4602 .B character\-search (C\-])
4603 A character is read and point is moved to the next occurrence of that
4604 character. A negative count searches for previous occurrences.
4606 .B character\-search\-backward (M\-C\-])
4607 A character is read and point is moved to the previous occurrence of that
4608 character. A negative count searches for subsequent occurrences.
4610 .B insert\-comment (M\-#)
4614 variable is inserted at the beginning of the current line, and the line
4615 is accepted as if a newline had been typed. This makes the current line
4618 .B glob\-expand\-word (C\-x *)
4619 The word before point is treated as a pattern for pathname expansion,
4620 and the list of matching file names is inserted, replacing the word.
4622 .B glob\-list\-expansions (C\-x g)
4623 The list of expansions that would have been generated by
4624 .B glob\-expand\-word
4625 is displayed, and the line is redrawn.
4628 Print all of the functions and their key bindings to the
4629 readline output stream. If a numeric argument is supplied,
4630 the output is formatted in such a way that it can be made part
4631 of an \fIinputrc\fP file.
4634 Print all of the settable readline variables and their values to the
4635 readline output stream. If a numeric argument is supplied,
4636 the output is formatted in such a way that it can be made part
4637 of an \fIinputrc\fP file.
4640 Print all of the readline key sequences bound to macros and the
4641 strings they ouput. If a numeric argument is supplied,
4642 the output is formatted in such a way that it can be made part
4643 of an \fIinputrc\fP file.
4645 .B display\-shell\-version (C\-x C\-v)
4646 Display version information about the current instance of
4654 builtin is enabled, the shell provides access to the
4655 \fIcommand history\fP,
4656 the list of commands previously typed. The text of the last
4659 commands (default 500) is saved in a history list. The shell
4660 stores each command in the history list prior to parameter and
4661 variable expansion (see
4664 above) but after history expansion is performed, subject to the
4665 values of the shell variables
4671 On startup, the history is initialized from the file named by
4675 (default \fI~/.bash_history\fP).
4678 is truncated, if necessary, to contain no more than
4682 When an interactive shell exits, the last
4685 lines are copied from the history list to
4690 shell option is enabled
4691 (see the description of
4695 .B "SHELL BUILTIN COMMANDS"
4696 below), the lines are appended to the history file,
4697 otherwise the history file is overwritten.
4701 is unset, or if the history file is unwritable, the history is
4702 not saved. After saving the history, the history file is truncated
4703 to contain no more than
4709 is not set, no truncation is performed.
4715 .B SHELL BUILTIN COMMANDS
4716 below) may be used to list or edit and re-execute a portion of
4720 builtin can be used to display or modify the history list and
4721 manipulate the history file.
4722 When using the command-line editing, search commands
4723 are available in each editing mode that provide access to the
4726 The shell allows control over which commands are saved on the history
4733 variables may be set to cause the shell to save only a subset of the
4737 shell option, if enabled, causes the shell to attempt to save each
4738 line of a multi-line command in the same history entry, adding
4739 semicolons where necessary to preserve syntactic correctness.
4742 shell option causes the shell to save the command with embedded newlines
4743 instead of semicolons. See the description of the
4747 .B "SHELL BUILTIN COMMANDS"
4748 for information on setting and unsetting shell options.
4749 .SH "HISTORY EXPANSION"
4751 The shell supports a history expansion feature that
4752 is similar to the history expansion in
4754 This section describes what syntax features are available. This
4755 feature is enabled by default for interactive shells, and can be
4760 builtin command (see
4762 .B SHELL BUILTIN COMMANDS
4763 below). Non-interactive shells do not perform history expansion
4766 History expansions introduce words from the history list into
4767 the input stream, making it easy to repeat commands, insert the
4768 arguments to a previous command into the current input line, or
4769 fix errors in previous commands quickly.
4771 History expansion is performed immediately after a complete line
4772 is read, before the shell breaks it into words.
4773 It takes place in two parts.
4774 The first is to determine which line from the history list
4775 to use during substitution.
4776 The second is to select portions of that line for inclusion into
4778 The line selected from the history is the \fIevent\fP,
4779 and the portions of that line that are acted upon are \fIwords\fP.
4780 Various \fImodifiers\fP are available to manipulate the selected words.
4781 The line is broken into words in the same fashion as when reading input,
4782 so that several \fImetacharacter\fP-separated words surrounded by
4783 quotes are considered one word.
4784 History expansions are introduced by the appearance of the
4785 history expansion character, which is \^\fB!\fP\^ by default.
4786 Only backslash (\^\fB\e\fP\^) and single quotes can quote
4787 the history expansion character.
4789 Several shell options settable with the
4791 builtin may be used to tailor the behavior of history expansion.
4794 shell option is enabled (see the description of the
4798 is being used, history substitutions are not immediately passed to
4800 Instead, the expanded line is reloaded into the
4802 editing buffer for further modification.
4805 is being used, and the
4807 shell option is enabled, a failed history substitution will be reloaded
4810 editing buffer for correction.
4815 builtin command may be used to see what a history expansion will
4821 builtin may be used to add commands to the end of the history list
4822 without actually executing them, so that they are available for
4825 The shell allows control of the various characters used by the
4826 history expansion mechanism (see the description of
4829 .BR "Shell Variables" ).
4830 .SS Event Designators
4832 An event designator is a reference to a command line entry in the
4838 Start a history substitution, except when followed by a
4843 Refer to command line
4847 Refer to the current command line minus
4851 Refer to the previous command. This is a synonym for `!\-1'.
4854 Refer to the most recent command starting with
4857 .B !?\fIstring\fR\fB[?]\fR
4858 Refer to the most recent command containing
4860 The trailing \fB?\fP may be omitted if
4862 is followed immediately by a newline.
4864 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
4865 Quick substitution. Repeat the last command, replacing
4870 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
4871 (see \fBModifiers\fP below).
4874 The entire command line typed so far.
4876 .SS Word Designators
4878 Word designators are used to select desired words from the event.
4881 separates the event specification from the word designator.
4882 It may be omitted if the word designator begins with a
4889 Words are numbered from the beginning of the line,
4890 with the first word being denoted by 0 (zero).
4891 Words are inserted into the current line separated by single spaces.
4896 The zeroth word. For the shell, this is the command
4903 The first argument. That is, word 1.
4909 The word matched by the most recent `?\fIstring\fR?' search.
4912 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
4915 All of the words but the zeroth. This is a synonym
4916 for `\fI1\-$\fP'. It is not an error to use
4918 if there is just one
4919 word in the event; the empty string is returned in that case.
4922 Abbreviates \fIx\-$\fP.
4925 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
4928 If a word designator is supplied without an event specification, the
4929 previous command is used as the event.
4932 After the optional word designator, there may appear a sequence of
4933 one or more of the following modifiers, each preceded by a `:'.
4939 Remove a trailing file name component, leaving only the head.
4942 Remove all leading file name components, leaving the tail.
4945 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
4949 Remove all but the trailing suffix.
4952 Print the new command but do not execute it.
4955 Quote the substituted words, escaping further substitutions.
4958 Quote the substituted words as with
4960 but break into words at
4964 .B s/\fIold\fP/\fInew\fP/
4967 for the first occurrence of
4969 in the event line. Any delimiter can be used in place of /. The
4970 final delimiter is optional if it is the last character of the
4971 event line. The delimiter may be quoted in
4975 with a single backslash. If & appears in
4979 A single backslash will quote the &. If
4981 is null, it is set to the last
4983 substituted, or, if no previous history substitutions took place,
4987 .B !?\fIstring\fR\fB[?]\fR
4991 Repeat the previous substitution.
4994 Cause changes to be applied over the entire event line. This is
4995 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
4996 or `\fB:&\fP'. If used with
4997 `\fB:s\fP', any delimiter can be used
4998 in place of /, and the final delimiter is optional
4999 if it is the last character of the event line.
5001 .SH "SHELL BUILTIN COMMANDS"
5002 .\" start of bash_builtins
5005 Unless otherwise noted, each builtin command documented in this
5006 section as accepting options preceded by
5010 to signify the end of the options.
5014 \fB:\fP [\fIarguments\fP]
5016 No effect; the command does nothing beyond expanding
5018 and performing any specified
5019 redirections. A zero exit code is returned.
5022 \fB .\| \fP \fIfilename\fP [\fIarguments\fP]
5024 \fBsource\fP \fIfilename\fP [\fIarguments\fP]
5026 Read and execute commands from
5029 shell environment and return the exit status of the last command
5034 does not contain a slash, file names in
5037 are used to find the directory containing
5039 The file searched for in
5042 need not be executable. The current directory is
5043 searched if no file is found in
5050 builtin command is turned off, the
5054 If any \fIarguments\fP are supplied, they become the positional
5055 parameters when \fIfilename\fP is executed. Otherwise the positional
5056 parameters are unchanged.
5057 The return status is the status of the last command exited within
5058 the script (0 if no commands are executed), and false if
5060 is not found or cannot be read.
5062 \fBalias\fP [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP] ...]
5063 \fBAlias\fP with no arguments or with the
5065 option prints the list of aliases in the form
5066 \fBalias\fP \fIname\fP=\fIvalue\fP on standard output.
5067 When arguments are supplied, an alias is defined for
5068 each \fIname\fP whose \fIvalue\fP is given.
5069 A trailing space in \fIvalue\fP causes the next word to be
5070 checked for alias substitution when the alias is expanded.
5071 For each \fIname\fP in the argument list for which no \fIvalue\fP
5072 is supplied, the name and value of the alias is printed.
5073 \fBAlias\fP returns true unless a \fIname\fP is given for which
5074 no alias has been defined.
5076 \fBbg\fP [\fIjobspec\fP]
5077 Resume the suspended job \fIjobspec\fP in the background, as if it
5078 had been started with
5080 If \fIjobspec\fP is not present, the shell's notion of the
5081 \fIcurrent job\fP is used.
5084 returns 0 unless run when job control is disabled or, when run with
5085 job control enabled, if \fIjobspec\fP was not found or started without
5089 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-lpsvPSV\fP]
5091 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] [\fB\-q\fP \fIfunction\fP] [\fB\-u\fP \fIfunction\fP] [\fB\-r\fP \fIkeyseq\fP]
5093 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fB\-f\fP \fIfilename\fP
5095 \fBbind\fP [\fB\-m\fP \fIkeymap\fP] \fIkeyseq\fP:\fIfunction\-name\fP
5099 key and function bindings, or bind a key sequence to a
5101 function or macro. The binding syntax accepted is identical to that of
5103 but each binding must be passed as a separate argument;
5104 e.g., '"\eC\-x\eC\-r": re\-read\-init\-file'. Options, if supplied, have the
5112 as the keymap to be affected by the subsequent bindings.
5116 \fIemacs, emacs\-standard, emacs\-meta, emacs\-ctlx, vi,
5119 \fIvi\fP is equivalent to \fIvi\-command\fP; \fIemacs\fP is
5120 equivalent to \fIemacs\-standard\fP.
5123 List the names of all \fBreadline\fP functions.
5126 Display \fBreadline\fP function names and bindings in such a way
5127 that they can be re-read.
5130 List current \fBreadline\fP function names and bindings.
5133 Display \fBreadline\fP variable names and values in such a way that they
5137 List current \fBreadline\fP variable names and values.
5140 Display \fBreadline\fP key sequences bound to macros and the strings
5141 they output in such a way that they can be re-read.
5144 Display \fBreadline\fP key sequences bound to macros and the strings
5147 .B \-f \fIfilename\fP
5148 Read key bindings from \fIfilename\fP.
5150 .B \-q \fIfunction\fP
5151 Query about which keys invoke the named \fIfunction\fP.
5153 .B \-u \fIfunction\fP
5154 Unbind all keys bound to the named \fIfunction\fP.
5157 Remove any current binding for \fIkeyseq\fP.
5160 The return value is 0 unless an unrecognized option is given or an
5164 \fBbreak\fP [\fIn\fP]
5171 loop. If \fIn\fP is specified, break \fIn\fP levels.
5175 is greater than the number of enclosing loops, all enclosing loops
5176 are exited. The return value is 0 unless the shell is not executing
5181 \fBbuiltin\fP \fIshell\-builtin\fP [\fIarguments\fP]
5182 Execute the specified shell builtin, passing it
5184 and return its exit status.
5185 This is useful when defining a
5186 function whose name is the same as a shell builtin,
5187 retaining the functionality of the builtin within the function.
5188 The \fBcd\fP builtin is commonly redefined this way.
5189 The return status is false if
5191 is not a shell builtin command.
5193 \fBcd\fP [\fB\-LP\fP] [\fIdir\fP]
5194 Change the current directory to \fIdir\fP. The variable
5203 defines the search path for the directory containing
5205 Alternative directory names in
5208 are separated by a colon (:). A null directory name in
5211 is the same as the current directory, i.e., ``\fB.\fP''. If
5213 begins with a slash (/),
5219 option says to use the physical directory structure instead of
5220 following symbolic links (see also the
5224 builtin command); the
5226 option forces symbolic links to be followed. An argument of
5231 The return value is true if the directory was successfully changed;
5234 \fBcommand\fP [\fB\-pVv\fP] \fIcommand\fP [\fIarg\fP ...]
5239 suppressing the normal shell function lookup. Only builtin
5240 commands or commands found in the
5243 are executed. If the
5245 option is given, the search for
5247 is performed using a default value for
5249 that is guaranteed to find all of the standard utilities.
5254 option is supplied, a description of
5258 option causes a single word indicating the command or file name
5261 to be displayed; the
5263 option produces a more verbose description.
5268 option is supplied, the exit status is 0 if
5270 was found, and 1 if not. If neither option is supplied and
5271 an error occurred or
5273 cannot be found, the exit status is 127. Otherwise, the exit status of the
5275 builtin is the exit status of
5278 \fBcontinue\fP [\fIn\fP]
5279 Resume the next iteration of the enclosing
5288 is specified, resume at the \fIn\fPth enclosing loop.
5292 is greater than the number of enclosing loops, the last enclosing loop
5293 (the ``top-level'' loop) is resumed. The return value is 0 unless the
5294 shell is not executing a loop when
5299 \fBdeclare\fP [\fB\-afFirx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP]]
5301 \fBtypeset\fP [\fB\-afFirx\fP] [\fB\-p\fP] [\fIname\fP[=\fIvalue\fP]]
5303 Declare variables and/or give them attributes.
5304 If no \fIname\fPs are given then display the values of variables.
5307 option will display the attributes and values of each
5311 is used, additional options are ignored.
5314 option inhibits the display of function definitions; only the
5315 function name and attributes are printed.
5320 The following options can
5321 be used to restrict output to variables with the specified attribute or
5322 to give variables attributes:
5327 Each \fIname\fP is an array variable (see
5332 Use function names only.
5335 The variable is treated as an integer; arithmetic evaluation (see
5337 .B "ARITHMETIC EVALUATION" ") "
5338 is performed when the variable is assigned a value.
5341 Make \fIname\fPs readonly. These names cannot then be assigned values
5342 by subsequent assignment statements or unset.
5345 Mark \fIname\fPs for export to subsequent commands via the environment.
5348 Using `+' instead of `\-'
5349 turns off the attribute instead, with the exception that \fB+a\fP
5350 may not be used to destroy an array variable. When used in a function,
5352 \fIname\fP local, as with the
5354 command. The return value is 0 unless an invalid option is encountered,
5355 an attempt is made to define a function using "\-f foo=bar",
5356 an attempt is made to assign a value to a readonly variable,
5357 an attempt is made to assign a value to an array variable without
5358 using the compound assignment syntax (see
5360 above), one of the \fInames\fP is not a valid shell variable name,
5361 an attempt is made to turn off readonly status for a readonly variable,
5362 an attempt is made to turn off array status for an array variable,
5363 or an attempt is made to display a non-existent function with \-f.
5366 .B dirs [\fB\-clpv\fP] [+\fIn\fP] [\-\fIn\fP]
5367 Without options, displays the list of currently remembered directories.
5368 The default display is on a single line with directory names separated
5370 Directories are added to the list with the
5374 command removes entries from the list.
5379 Displays the \fIn\fPth entry counting from the left of the list
5382 when invoked without options, starting with zero.
5385 Displays the \fIn\fPth entry counting from the right of the list
5388 when invoked without options, starting with zero.
5391 Clears the directory stack by deleting all of the entries.
5394 Produces a longer listing; the default listing format uses a
5395 tilde to denote the home directory.
5398 Print the directory stack with one entry per line.
5401 Print the directory stack with one entry per line,
5402 prefixing each entry with its index in the stack.
5405 The return value is 0 unless an
5406 invalid option is supplied or \fIn\fP indexes beyond the end
5407 of the directory stack.
5410 \fBdisown\fP [\fB\-ar\fP] [\fB\-h\fP] [\fIjobspec\fP ...]
5411 Without options, each
5413 is removed from the table of active jobs.
5414 If the \fB\-h\fP option is given, each
5416 is not removed from the table, but is marked so that
5419 is not sent to the job if the shell receives a
5424 is present, and neither the
5428 option is supplied, the \fIcurrent job\fP is used.
5433 option means to remove or mark all jobs; the
5437 argument restricts operation to running jobs.
5438 The return value is 0 unless a
5440 does not specify a valid job.
5442 \fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]
5443 Output the \fIarg\fPs, separated by spaces, followed by a newline.
5444 The return status is always 0.
5445 If \fB\-n\fP is specified, the trailing newline is
5446 suppressed. If the \fB\-e\fP option is given, interpretation of
5447 the following backslash-escaped characters is enabled. The
5449 option disables the interpretation of these escape characters,
5450 even on systems where they are interpreted by default.
5454 to mean the end of options.
5456 interprets the following escape sequences:
5467 suppress trailing newline
5491 the character whose ASCII code is the octal value \fInnn\fP
5492 (one to three digits)
5495 the character whose ASCII code is the hexadecimal value \fInnn\fP
5496 (one to three digits)
5500 \fBenable\fP [\fB\-adnps\fP] [\fB\-f\fP \fIfilename\fP] [\fIname\fP ...]
5501 Enable and disable builtin shell commands.
5502 Disabling a builtin allows a disk command which has the same name
5503 as a shell builtin to be executed with specifying a full pathname,
5504 even though the shell normally searches for builtins before disk commands.
5505 If \fB\-n\fP is used, each \fIname\fP
5506 is disabled; otherwise,
5507 \fInames\fP are enabled. For example, to use the
5509 binary found via the
5512 instead of the shell builtin version, run
5513 \f(CWenable -n test\fP.
5516 option means to load the new builtin command
5520 on systems that support dynamic loading. The
5522 option will delete a builtin previously loaded with
5524 If no \fIname\fP arguments are given, or if the
5526 option is supplied, a list of shell builtins is printed.
5527 With no other option arguments, the list consists of all enabled
5529 If \fB\-n\fP is supplied, only disabled builtins are printed.
5530 If \fB\-a\fP is supplied, the list printed includes all builtins, with an
5531 indication of whether or not each is enabled.
5532 If \fB\-s\fP is supplied, the output is restricted to the POSIX
5533 \fIspecial\fP builtins.
5534 The return value is 0 unless a
5536 is not a shell builtin or there is a problem loading a new builtin
5537 from a shared object.
5539 \fBeval\fP [\fIarg\fP ...]
5540 The \fIarg\fPs are read and concatenated together into a single
5541 command. This command is then read and executed by the shell, and
5542 its exit status is returned as the value of
5546 or only null arguments,
5550 \fBexec\fP [\fB\-cl\fP] [\fB\-a\fP \fIname\fP] [\fIcommand\fP [\fIarguments\fP]]
5553 is specified, it replaces the shell.
5554 No new process is created. The
5556 become the arguments to \fIcommand\fP.
5560 the shell places a dash in the zeroth arg passed to
5568 to be executed with an empty environment. If
5570 is supplied, the shell passes
5572 as the zeroth argument to the executed command. If
5574 cannot be executed for some reason, a non-interactive shell exits,
5575 unless the shell option
5577 is enabled, in which case it returns failure.
5578 An interactive shell returns failure if the file cannot be executed.
5581 is not specified, any redirections take effect in the current shell,
5582 and the return status is 0. If there is a redirection error, the
5585 \fBexit\fP [\fIn\fP]
5586 Cause the shell to exit
5587 with a status of \fIn\fP. If
5589 is omitted, the exit status
5590 is that of the last command executed.
5594 is executed before the shell terminates.
5597 \fBexport\fP [\fB\-fn\fP\^] [\fIname\fP[=\fIword\fP]] ...
5603 are marked for automatic export to the environment of
5604 subsequently executed commands. If the
5612 are given, or if the
5614 option is supplied, a list
5615 of all names that are exported in this shell is printed.
5618 option causes the export property to be removed from the
5621 returns an exit status of 0 unless an invalid option is
5623 one of the \fInames\fP is not a valid shell variable name, or
5627 that is not a function.
5630 \fBfc\fP [\fB\-e\fP \fIename\fP] [\fB\-nlr\fP] [\fIfirst\fP] [\fIlast\fP]
5632 \fBfc\fP \fB\-s\fP [\fIpat\fP=\fIrep\fP] [\fIcmd\fP]
5634 Fix Command. In the first form, a range of commands from
5638 is selected from the history list.
5642 may be specified as a string (to locate the last command beginning
5643 with that string) or as a number (an index into the history list,
5644 where a negative number is used as an offset from the current
5647 is not specified it is set to
5648 the current command for listing (so that
5650 prints the last 10 commands) and to
5655 is not specified it is set to the previous
5656 command for editing and \-16 for listing.
5661 the command numbers when listing. The
5663 option reverses the order of
5664 the commands. If the
5667 the commands are listed on
5668 standard output. Otherwise, the editor given by
5671 on a file containing those commands. If
5677 variable is used, and
5684 is not set. If neither variable is set,
5686 is used. When editing is complete, the edited commands are
5687 echoed and executed.
5689 In the second form, \fIcommand\fP is re-executed after each instance
5690 of \fIpat\fP is replaced by \fIrep\fP.
5691 A useful alias to use with this is
5693 .if t \f(CWr='fc \-s'\fP,
5697 runs the last command beginning with
5703 re-executes the last command.
5705 If the first form is used, the return value is 0 unless an invalid
5706 option is encountered or
5710 specify history lines out of range.
5713 option is supplied, the return value is the value of the last
5714 command executed or failure if an error occurs with the temporary
5715 file of commands. If the second form is used, the return status
5716 is that of the command re-executed, unless
5718 does not specify a valid history line, in which case
5722 \fBfg\fP [\fIjobspec\fP]
5725 in the foreground, and make it the current job.
5728 is not present, the shell's notion of the \fIcurrent job\fP is used.
5729 The return value is that of the command placed into the foreground,
5730 or failure if run when job control is disabled or, when run with
5731 job control enabled, if
5733 does not specify a valid job or
5735 specifies a job that was started without job control.
5737 \fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIargs\fP]
5739 is used by shell procedures to parse positional parameters.
5741 contains the option letters to be recognized; if a letter
5742 is followed by a colon, the option is expected to have an
5743 argument, which should be separated from it by white space.
5744 Each time it is invoked,
5746 places the next option in the shell variable
5750 if it does not exist,
5751 and the index of the next argument to be processed into the
5757 is initialized to 1 each time the shell or a shell script
5758 is invoked. When an option requires an argument,
5760 places that argument into the variable
5763 The shell does not reset
5766 automatically; it must be manually reset between multiple
5769 within the same shell invocation if a new set of parameters
5772 When the end of options is encountered, \fBgetopts\fP exits with a
5773 return value greater than zero.
5774 \fBOPTIND\fP is set to the index of the first non-option argument,
5775 and \fBname\fP is set to ?.
5778 normally parses the positional parameters, but if more arguments are
5782 parses those instead.
5785 can report errors in two ways. If the first character of
5789 error reporting is used. In normal operation diagnostic messages
5790 are printed when invalid options or missing option arguments are
5795 is set to 0, no error messages will be displayed, even if the first
5800 If an invalid option is seen,
5805 prints an error message and unsets
5811 the option character found is placed in
5814 and no diagnostic message is printed.
5816 If a required argument is not found, and
5819 a question mark (\^\fB?\fP\^) is placed in
5822 is unset, and a diagnostic message is printed.
5825 is silent, then a colon (\^\fB:\fP\^) is placed in
5830 is set to the option character found.
5833 returns true if an option, specified or unspecified, is found.
5834 It returns false if the end of options is encountered or an
5837 \fBhash\fP [\fB\-r\fP] [\fB\-p\fP \fIfilename\fP] [\fIname\fP]
5840 the full file name of the command is determined by searching
5846 option is supplied, no path search is performed, and
5848 is used as the full file name of the command.
5851 option causes the shell to forget all
5852 remembered locations. If no arguments are given, information
5853 about remembered commands is printed.
5854 The return status is true unless a
5856 is not found or an invalid option is supplied.
5858 \fBhelp\fP [\fIpattern\fP]
5859 Display helpful information about builtin commands. If
5863 gives detailed help on all commands matching
5865 otherwise help for all the builtins and shell control structures
5866 is printed. The return status is 0 unless no command matches
5870 \fBhistory\fP [\fB\-c\fP] [\fIn\fP]
5872 \fBhistory\fP \fB\-anrw\fP [\fIfilename\fP]
5874 \fBhistory\fP \fB\-p\fP \fIarg\fP [\fIarg ...\fP]
5876 \fBhistory\fP \fB\-s\fP \fIarg\fP [\fIarg ...\fP]
5878 With no options, display the command
5879 history list with line numbers. Lines listed
5882 have been modified. An argument of
5886 lines. If \fIfilename\fP is supplied, it is used as the
5887 name of the history file; if not, the value of
5890 is used. Options, if supplied, have the following meanings:
5895 Append the ``new'' history lines (history lines entered since the
5896 beginning of the current \fBbash\fP session) to the history file.
5899 Read the history lines not already read from the history
5900 file into the current history list. These are lines
5901 appended to the history file since the beginning of the
5902 current \fBbash\fP session.
5905 Read the contents of the history file
5906 and use them as the current history.
5909 Write the current history to the history file, overwriting the
5910 history file's contents.
5913 Clear the history list by deleting all the entries.
5916 Perform history substitution on the following \fIargs\fP and display
5917 the result on the standard output.
5918 Does not store the results in the history list.
5919 Each \fIarg\fP must be quoted to disable normal history expansion.
5924 in the history list as a single entry. The last command in the
5925 history list is removed before the
5930 The return value is 0 unless an invalid option is encountered or an
5931 error occurs while reading or writing the history file.
5935 \fBjobs\fP [\fB\-lnprs\fP] [ \fIjobspec\fP ... ]
5937 \fBjobs\fP \fB\-x\fP \fIcommand\fP [ \fIargs\fP ... ]
5939 The first form lists the active jobs. The options have the following
5946 in addition to the normal information.
5949 List only the process ID of the job's process group
5953 Display information only about jobs that have changed status since
5954 the user was last notified of their status.
5957 Restrict output to running jobs.
5960 Restrict output to stopped jobs.
5965 is given, output is restricted to information about that job.
5966 The return status is 0 unless an invalid option is encountered
5981 with the corresponding process group ID, and executes
5985 returning its exit status.
5989 \fBkill\fP [\fB\-s\fP \fIsigspec\fP | \fB\-n\fP \fIsignum\fP | \fB\-\fP\fIsigspec\fP] [\fIpid\fP | \fIjobspec\fP] ...
5991 \fBkill\fP \fB\-l\fP [\fIsigspec\fP | \fIexit_status\fP]
5993 Send the signal named by
5997 to the processes named by
6002 is either a signal name such as
6007 is a signal number. If
6009 is a signal name, the name may be
6010 given with or without the
6016 is not present, then
6022 lists the signal names.
6023 If any arguments are supplied when
6025 is given, the names of the signals corresponding to the arguments are
6026 listed, and the return status is 0.
6027 The \fIexit_status\fP argument to
6029 is a number specifying either a signal number or the exit status of
6030 a process terminated by a signal.
6032 returns true if at least one signal was successfully sent, or false
6033 if an error occurs or an invalid option is encountered.
6035 \fBlet\fP \fIarg\fP [\fIarg\fP ...]
6038 is an arithmetic expression to be evaluated (see
6040 .BR "ARITHMETIC EVALUATION" ).
6045 returns 1; 0 is returned otherwise.
6047 \fBlocal\fP [\fIname\fP[=\fIvalue\fP] ...]
6048 For each argument, a local variable named
6050 is created, and assigned
6054 is used within a function, it causes the variable
6056 to have a visible scope restricted to that function and its children.
6059 writes a list of local variables to the standard output. It is
6062 when not within a function. The return status is 0 unless
6064 is used outside a function, or an invalid
6071 \fBpopd\fP [\-\fBn\fP] [+\fIn\fP] [\-\fIn\fP]
6072 Removes entries from the directory stack. With no arguments,
6073 removes the top directory from the stack, and performs a
6075 to the new top directory.
6076 Arguments, if supplied, have the following meanings:
6081 Removes the \fIn\fPth entry counting from the left of the list
6084 starting with zero. For example: ``popd +0''
6085 removes the first directory, ``popd +1'' the second.
6088 Removes the \fIn\fPth entry counting from the right of the list
6091 starting with zero. For example: ``popd -0''
6092 removes the last directory, ``popd -1'' the next to last.
6095 Suppresses the normal change of directory when removing directories
6096 from the stack, so that only the stack is manipulated.
6101 command is successful, a
6103 is performed as well, and the return status is 0.
6105 returns false if an invalid option is encountered, the directory stack
6106 is empty, a non-existent directory stack entry is specified, or the
6107 directory change fails.
6110 \fBprintf\fP \fIformat\fP [\fIarguments\fP]
6111 Write the formatted \fIarguments\fP to the standard output under the
6112 control of the \fIformat\fP.
6113 The \fIformat\fP is a character string which contains three types of objects:
6114 plain characters, which are simply copied to standard output, character
6115 escape sequences, which are converted and copied to the standard output, and
6116 format specifications, each of which causes printing of the next successive
6118 In addition to the standard \fIprintf\fP(1) formats, %b causes
6119 \fBprintf\fP to expand backslash escape sequences in the corresponding
6120 \fIargument\fP, and %q causes \fBprintf\fP to output the corresponding
6121 \fIargument\fP in a format that can be reused as shell input.
6123 The \fIformat\fP is reused as necessary to consume all of the \fIarguments\fP.
6124 If the \fIformat\fP requires more \fIarguments\fP than are supplied, the
6125 extra format specifications behave as if a zero value or null string, as
6126 appropriate, had been supplied.
6129 \fBpushd\fP [\fB\-n\fP] [\fIdir\fP]
6131 \fBpushd\fP [\fB\-n\fP] [+\fIn\fP] [\-\fIn\fP]
6133 Adds a directory to the top of the directory stack, or rotates
6134 the stack, making the new top of the stack the current working
6135 directory. With no arguments, exchanges the top two directories
6136 and returns 0, unless the directory stack is empty.
6137 Arguments, if supplied, have the following meanings:
6142 Rotates the stack so that the \fIn\fPth directory
6143 (counting from the left of the list shown by
6149 Rotates the stack so that the \fIn\fPth directory
6150 (counting from the right of the list shown by
6152 starting with zero) is at the top.
6155 Suppresses the normal change of directory when adding directories
6156 to the stack, so that only the stack is manipulated.
6161 to the directory stack at the top, making it the
6162 new current working directory.
6167 command is successful, a
6169 is performed as well.
6170 If the first form is used,
6172 returns 0 unless the cd to
6174 fails. With the second form,
6176 returns 0 unless the directory stack is empty,
6177 a non-existent directory stack element is specified,
6178 or the directory change to the specified new current directory
6182 \fBpwd\fP [\fB\-LP\fP]
6183 Print the absolute file name of the current working directory.
6184 The file name printed contains no symbolic links if the
6186 option is supplied or the
6190 builtin command is enabled.
6193 option is used, symbolic links are followed.
6194 The return status is 0 unless an error occurs while
6195 reading the name of the current directory or an
6196 invalid option is supplied.
6198 \fBread\fP [\fB\-er\fP] [\fB\-a\fP \fIaname\fP] [\fB\-p\fP \fIprompt\fP] [\fIname\fP ...]
6199 One line is read from the standard input, and the first word
6200 is assigned to the first
6202 the second word to the second
6204 and so on, with leftover words and their intervening separators assigned
6207 If there are fewer words read from the standard input than names,
6208 the remaining names are assigned empty values.
6212 are used to split the line into words.
6213 Options, if supplied, have the following meanings:
6218 A backslash-newline pair is not ignored, and
6219 the backslash is considered to be part of the line.
6222 Display \fIprompt\fP, without a
6223 trailing newline, before attempting to read any input. The prompt
6224 is displayed only if input is coming from a terminal.
6227 The words are assigned to sequential indices
6228 of the array variable
6232 is unset before any new values are assigned.
6233 Other \fIname\fP arguments are ignored.
6236 If the standard input
6237 is coming from a terminal,
6242 above) is used to obtain the line.
6247 are supplied, the line read is assigned to the variable
6250 The return code is zero, unless end-of-file is encountered.
6253 \fBreadonly\fP [\fB\-apf\fP] [\fIname\fP ...]
6256 \fInames\fP are marked readonly; the values of these
6258 may not be changed by subsequent assignment.
6261 option is supplied, the functions corresponding to the
6266 option restricts the variables to arrays.
6269 arguments are given, or if the
6271 option is supplied, a list of all readonly names is printed.
6274 option causes output to be displayed in a format thatmay be reused as input.
6275 The return status is 0 unless an invalid option is encountered,
6278 is not a valid shell variable name, or
6282 that is not a function.
6284 \fBreturn\fP [\fIn\fP]
6285 Causes a function to exit with the return value specified by
6289 is omitted, the return status is that of the last command
6290 executed in the function body. If used outside a function,
6291 but during execution of a script by the
6293 (\fBsource\fP) command, it causes the shell to stop executing
6294 that script and return either
6296 or the exit status of the last command executed within the
6297 script as the exit status of the script. If used outside a
6298 function and not during execution of a script by \fB.\fP\^,
6299 the return status is false.
6301 \fBset\fP [\fB\-\-abefhkmnptuvxBCHP\fP] [\fB\-o\fP \fIoption\fP] [\fIarg\fP ...]
6302 Without options, the name and value of each shell variable are displayed
6303 in a format that can be reused as input.
6304 The output is sorted according to the current locale.
6305 When options are specified, they set or unset shell attributes.
6306 Any arguments remaining after the options are processed are treated
6307 as values for the positional parameters and are assigned, in order, to
6312 Options, if specified, have the following meanings:
6317 Automatically mark variables which are modified or created for export
6318 to the environment of subsequent commands.
6321 Report the status of terminated background jobs
6322 immediately, rather than before the next primary prompt. This is
6323 effective only when job control is enabled.
6326 Exit immediately if a \fIsimple command\fP (see
6329 above) exits with a non-zero status. The shell does not exit if the
6330 command that fails is part of an
6337 statement, part of a
6341 list, or if the command's return value is
6346 Disable pathname expansion.
6349 Remember the location of commands as they are looked up for execution.
6350 This is enabled by default.
6353 All arguments in the form of assignment statements
6354 are placed in the environment for a command, not just
6355 those that precede the command name.
6358 Monitor mode. Job control is enabled. This option is on
6359 by default for interactive shells on systems that support
6363 above). Background processes run in a separate process
6364 group and a line containing their exit status is printed
6365 upon their completion.
6368 Read commands but do not execute them. This may be used to
6369 check a shell script for syntax errors. This is ignored by
6372 .B \-o \fIoption\-name\fP
6373 The \fIoption\-name\fP can be one of the following:
6385 Use an emacs-style command line editing interface. This is enabled
6386 by default when the shell is interactive, unless the shell is started
6404 Enable command history, as described above under
6407 This option is on by default in interactive shells.
6410 The effect is as if the shell command \f(CWIGNOREEOF=10\fP had been executed
6452 Change the behavior of
6454 where the default operation differs
6455 from the POSIX 1003.2 standard to match the standard.
6466 Use a vi-style command line editing interface.
6475 is supplied with no \fIoption\-name\fP, the values of the current options are
6479 is supplied with no \fIoption\-name\fP, a series of
6481 commands to recreate the current option settings is displayed on
6482 the standard output.
6488 mode. In this mode, the
6490 file is not processed, shell functions are not inherited from the
6491 environment, and the variable
6492 The \fBSHELLOPTS\fP variable, if it appears in the environment, is ignored.
6493 This is enabled automatically on startup if the effective user (group)
6494 id is not equal to the real user (group) id.
6495 Turning this option off causes the effective user
6496 and group ids to be set to the real user and group ids.
6499 Exit after reading and executing one command.
6502 Treat unset variables as an error when performing
6503 parameter expansion. If expansion is attempted on an
6504 unset variable, the shell prints an error message, and,
6505 if not interactive, exits with a non-zero status.
6508 Print shell input lines as they are read.
6511 After expanding each \fIsimple command\fP,
6512 display the expanded value of
6515 followed by the command and its expanded arguments.
6518 The shell performs brace expansion (see
6520 above). This is on by default.
6525 does not overwrite an existing file with the
6530 redirection operators. This may be overridden when
6531 creating output files by using the redirection operator
6539 style history substitution. This option is on by
6540 default when the shell is interactive.
6543 If set, the shell does not follow symbolic links when executing
6546 that change the current working directory. It uses the
6547 physical directory structure instead. By default,
6549 follows the logical chain of directories when performing commands
6550 which change the current directory.
6553 If no arguments follow this option, then the positional parameters are
6554 unset. Otherwise, the positional parameters are set to the
6555 \fIarg\fPs, even if some of them begin with a
6559 Signal the end of options, cause all remaining \fIarg\fPs to be
6560 assigned to the positional parameters. The
6564 options are turned off.
6565 If there are no \fIarg\fPs,
6566 the positional parameters remain unchanged.
6569 The options are off by default unless otherwise noted.
6570 Using + rather than \- causes these options to be turned off.
6571 The options can also be specified as arguments to an invocation of
6573 The current set of options may be found in
6575 The return status is always true unless an invalid option is encountered.
6578 \fBshift\fP [\fIn\fP]
6579 The positional parameters from \fIn\fP+1 ... are renamed to
6582 Parameters represented by the numbers \fB$#\fP
6583 down to \fB$#\fP\-\fIn\fP+1 are unset.
6585 must be a non-negative number less than or equal to \fB$#\fP.
6588 is 0, no parameters are changed.
6591 is not given, it is assumed to be 1.
6594 is greater than \fB$#\fP, the positional parameters are not changed.
6595 The return status is greater than zero if
6599 or less than zero; otherwise 0.
6601 \fBshopt\fP [\fB\-pqsu\fP] [\fB\-o\fP] [\fIoptname\fP ...]
6602 Toggle the values of variables controlling optional shell behavior.
6603 With no options, or with the
6605 option, a list of all settable options is displayed, with
6606 an indication of whether or not each is set.
6607 The \fB\-p\fP option causes output to be displayed in a form that
6608 may be reused as input.
6609 Other options have the following meanings:
6614 Enable (set) each \fIoptname\fP.
6617 Disable (unset) each \fIoptname\fP.
6620 Suppresses normal output (quiet mode); the return status indicates
6621 whether the \fIoptname\fP is set or unset.
6622 If multiple \fIoptname\fP arguments are given with
6624 the return status is zero if all \fIoptnames\fP are enabled; non-zero
6628 Restricts the values of \fIoptname\fP to be those defined for the
6639 is used with no \fIoptname\fP arguments, the display is limited to
6640 those options which are set or unset, respectively.
6641 Unless otherwise noted, the \fBshopt\fP options are disabled (unset)
6644 The return status when listing options is zero if all \fIoptnames\fP
6645 are enabled, non-zero otherwise. When setting or unsetting options,
6646 the return status is zero unless an \fIoptname\fP is not a valid shell
6649 The list of \fBshopt\fP options is:
6655 If set, an argument to the
6657 builtin command that
6658 is not a directory is assumed to be the name of a variable whose
6659 value is the directory to change to.
6662 If set, minor errors in the spelling of a directory component in a
6664 command will be corrected.
6665 The errors checked for are transposed characters,
6666 a missing character, and one character too many.
6667 If a correction is found, the corrected file name is printed,
6668 and the command proceeds.
6669 This option is only used by interactive shells.
6672 If set, \fBbash\fP checks that a command found in the hash
6673 table exists before trying to execute it. If a hashed command no
6674 longer exists, a normal path search is performed.
6677 If set, \fBbash\fP checks the window size after each command
6678 and, if necessary, updates the values of
6688 attempts to save all lines of a multiple-line
6689 command in the same history entry. This allows
6690 easy re-editing of multi-line commands.
6695 includes filenames beginning with a `.' in the results of pathname
6699 If set, a non-interactive shell will not exit if
6700 it cannot execute the file specified as an argument to the
6702 builtin command. An interactive shell does not exit if
6707 If set, aliases are expanded as described above under
6710 This option is enabled by default for interactive shells.
6713 If set, the extended pattern matching features described above under
6714 \fBPathname Expansion\fP are enabled.
6717 If set, the history list is appended to the file named by the value
6720 variable when the shell exits, rather than overwriting the file.
6725 is being used, a user is given the opportunity to re-edit a
6726 failed history substitution.
6731 is being used, the results of history substitution are not immediately
6732 passed to the shell parser. Instead, the resulting line is loaded into
6733 the \fBreadline\fP editing buffer, allowing further modification.
6738 is being used, \fBbash\fP will attempt to perform hostname completion when a
6739 word containing a \fB@\fP is being completed (see
6745 This is enabled by default.
6748 If set, \fBbash\fP will send
6751 to all jobs when an interactive login shell exits.
6753 .B interactive_comments
6754 If set, allow a word beginning with
6756 to cause that word and all remaining characters on that
6757 line to be ignored in an interactive shell (see
6760 above). This option is enabled by default.
6765 option is enabled, multi-line commands are saved to the history with
6766 embedded newlines rather than using semicolon separators where possible.
6769 If set, and a file that \fBbash\fP is checking for mail has been
6770 accessed since the last time it was checked, the message ``The mail in
6771 \fImailfile\fP has been read'' is displayed.
6776 matches filenames in a case\-insensitive fashion when performing pathname
6778 .B Pathname Expansion
6784 allows patterns which match no
6786 .B Pathname Expansion
6788 to expand to a null string, rather than themselves.
6791 If set, prompt strings undergo variable and parameter expansion after
6792 being expanded as described in
6795 above. This option is enabled by default.
6800 builtin prints an error message when the shift count exceeds the
6801 number of positional parameters.
6805 \fBsource\fP (\fB.\fP) builtin uses the value of
6808 to find the directory containing the file supplied as an argument.
6809 This option is enabled by default.
6812 \fBsuspend\fP [\fB\-f\fP]
6813 Suspend the execution of this shell until it receives a
6818 option says not to complain if this is
6819 a login shell; just suspend anyway. The return status is 0 unless
6820 the shell is a login shell and
6822 is not supplied, or if job control is not enabled.
6825 \fBtest\fP \fIexpr\fP
6827 \fB[\fP \fIexpr\fP \fB]\fP
6828 Return a status of 0 or 1 depending on
6829 the evaluation of the conditional expression
6831 Each operator and operand must be a separate argument.
6832 Expressions are composed of the primaries described above under
6834 .BR "CONDITIONAL EXPRESSIONS" .
6837 Expressions may be combined using the following operators, listed
6838 in decreasing order of precedence.
6848 Returns the value of \fIexpr\fP.
6849 This may be used to override the normal precedence of operators.
6851 \fIexpr1\fP \-\fBa\fP \fIexpr2\fP
6858 \fIexpr1\fP \-\fBo\fP \fIexpr2\fP
6866 \fBtest\fP and \fB[\fP evaluate conditional
6867 expressions using a set of rules based on the number of arguments.
6873 The expression is false.
6876 The expression is true if and only if the argument is not null.
6879 If the first argument is \fB!\fP, the expression is true if and
6880 only if the second argument is null.
6881 If the first argument is one of the unary conditional operators listed above
6884 .BR "CONDITIONAL EXPRESSIONS" ,
6885 the expression is true if the unary test is true.
6886 If the first argument is not a valid unary conditional operator, the expression
6890 If the second argument is one of the binary conditional operators listed above
6893 .BR "CONDITIONAL EXPRESSIONS" ,
6894 the result of the expression is the result of the binary test using
6895 the first and third arguments as operands.
6896 If the first argument is \fB!\fP, the value is the negation of
6897 the two-argument test using the second and third arguments.
6898 If the first argument is exactly \fB(\fP and the third argument is
6899 exactly \fB)\fP, the result is the one-argument test of the second
6901 Otherwise, the expression is false.
6902 The \fB\-a\fP and \fB\-o\fP operators are considered binary operators
6906 If the first argument is \fB!\fP, the result is the negation of
6907 the three-argument expression composed of the remaining arguments.
6908 Otherwise, the expression is parsed and evaluated according to
6909 precedence using the rules listed above.
6912 The expression is parsed and evaluated according to precedence
6913 using the rules listed above.
6918 Print the accumulated user and system times for the shell and
6919 for processes run from the shell. The return status is 0.
6921 \fBtrap\fP [\fB\-lp\fP] [\fIarg\fP] [\fIsigspec\fP ...]
6924 is to be read and executed when the shell receives
6931 all specified signals are
6932 reset to their original values (the values they had
6933 upon entrance to the shell).
6936 is the null string the signal specified by each
6938 is ignored by the shell and by the commands it invokes.
6943 then the trap commands associated with
6946 are displayed. If no arguments are supplied or if
6951 prints the list of commands associated with each signal number.
6955 a signal name defined in <\fIsignal.h\fP>, or a signal number.
6963 is executed on exit from the shell. If a
6970 is executed after every \fIsimple command\fP (see
6976 option causes the shell to print a list of signal names and
6977 their corresponding numbers.
6978 Signals ignored upon entry to the shell cannot be trapped or reset.
6979 Trapped signals are reset to their original values in a child
6980 process when it is created.
6981 The return status is false if any
6983 is invalid; otherwise
6987 \fBtype\fP [\fB\-atp\fP] \fIname\fP [\fIname\fP ...]
6991 would be interpreted if used as a command name.
6996 prints a string which is one of
7005 is an alias, shell reserved word, function, builtin, or disk file,
7009 is not found, then nothing is printed, and an exit status of false
7015 either returns the name of the disk file
7016 that would be executed if
7018 were specified as a command name,
7019 or nothing if \f(CWtype -t name\fP
7022 If a command is hashed,
7024 prints the hashed value, not necessarily the file that appears
7032 prints all of the places that contain
7035 This includes aliases and functions,
7038 option is not also used.
7039 The table of hashed commands is not consulted
7043 returns true if any of the arguments are found, false if
7046 \fBulimit\fP [\fB\-SHacdflmnpstuv\fP [\fIlimit\fP]]
7047 Provides control over the resources available to the shell and to
7048 processes started by it, on systems that allow such control. The
7051 can be a number in the unit specified for the resource, or the
7054 The \fB\-H\fP and \fB\-S\fP options specify that the hard or soft limit is
7055 set for the given resource. A hard limit cannot be increased once it
7056 is set; a soft limit may be increased up to the value of the hard limit.
7057 If neither \fB\-H\fP nor \fB\-S\fP is specified, both the soft and hard
7061 is omitted, the current value of the soft limit of the resource is
7062 printed, unless the \fB\-H\fP option is given. When more than one
7063 resource is specified, the limit name and unit are printed before the value.
7064 Other options are interpreted as follows:
7069 All current limits are reported
7072 The maximum size of core files created
7075 The maximum size of a process's data segment
7078 The maximum size of files created by the shell
7081 The maximum size that may be locked into memory
7084 The maximum resident set size
7087 The maximum number of open file descriptors (most systems do not
7088 allow this value to be set)
7091 The pipe size in 512-byte blocks (this may not be set)
7094 The maximum stack size
7097 The maximum amount of cpu time in seconds
7100 The maximum number of processes available to a single user
7103 The maximum amount of virtual memory available to the shell
7108 is given, it is the new value of the specified resource (the
7110 option is display only).
7111 If no option is given, then
7113 is assumed. Values are in 1024-byte increments, except for
7115 which is in seconds,
7117 which is in units of 512-byte blocks,
7122 which are unscaled values. The return status is 0
7123 unless an invalid option is encountered, a non-numeric argument
7124 other than \fBunlimited\fP is supplied as \fIlimit\fP, or an
7125 error occurs while setting a new limit.
7128 \fBumask\fP [\fB\-p\fP] [\fB\-S\fP] [\fImode\fP]
7129 The user file-creation mask is set to
7133 begins with a digit, it
7134 is interpreted as an octal number; otherwise
7135 it is interpreted as a symbolic mode mask similar
7140 is omitted, or if the
7142 option is supplied, the
7143 current value of the mask is printed.
7146 option causes the mask to be printed in symbolic form; the
7147 default output is an octal number.
7150 option is supplied, and
7152 is omitted, the output is in a form that may be reused as input.
7153 The return status is 0 if the mode was successfully changed or if
7154 no \fImode\fP argument was supplied, and false otherwise.
7156 \fBunalias\fP [\-\fBa\fP] [\fIname\fP ...]
7157 Remove \fIname\fPs from the list of defined aliases. If
7159 is supplied, all alias definitions are removed. The return
7160 value is true unless a supplied
7162 is not a defined alias.
7164 \fBunset\fP [\-\fBfv\fP] [\fIname\fP ...]
7167 remove the corresponding variable or function.
7168 If no options are supplied, or the
7170 option is given, each
7172 refers to a shell variable.
7173 Read-only variables may not be unset.
7179 refers to a shell function, and the function definition
7181 Each unset variable or function is removed from the environment
7182 passed to subsequent commands.
7195 are unset, they lose their special properties, even if they are
7196 subsequently reset. The exit status is true unless a
7198 does not exist or is readonly.
7200 \fBwait\fP [\fIn\fP]
7201 Wait for the specified process and return its termination
7205 ID or a job specification; if a job spec is given, all processes
7206 in that job's pipeline are waited for. If
7208 is not given, all currently active child processes
7209 are waited for, and the return status is zero. If
7211 specifies a non-existent process or job, the return status is
7212 127. Otherwise, the return status is the exit status of the last
7213 process or job waited for.
7216 .SH "RESTRICTED SHELL"
7220 is started with the name
7224 option is supplied at invocation,
7225 the shell becomes restricted.
7226 A restricted shell is used to
7227 set up an environment more controlled than the standard shell.
7228 It behaves identically to
7230 with the exception that the following are disallowed or not performed:
7232 changing directories with \fBcd\fP
7234 setting or unsetting the values of
7239 specifying command names containing
7242 specifying a file name containing a
7244 as an argument to the
7248 importing function definitions from the shell environment at startup
7250 parsing the value of \fBSHELLOPTS\fP from the shell environment at startup
7252 redirecting output using the >, >|, <>, >&, &>, and >> redirection operators
7256 builtin command to replace the shell with another command
7258 adding or deleting builtin commands with the
7272 turning off restricted mode with
7273 \fBset +r\fP or \fBset +o restricted\fP.
7275 These restrictions are enforced after any startup files are read.
7277 When a command that is found to be a shell script is executed (see
7279 .B "COMMAND EXECUTION"
7282 turns off any restrictions in the shell spawned to execute the
7287 \fIBash Features\fP, Brian Fox and Chet Ramey
7289 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
7291 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
7293 \fIPortable Operating System Interface (POSIX) Part 2: Shell and Utilities\fP, IEEE
7295 \fIsh\fP(1), \fIksh\fP(1), \fIcsh\fP(1)
7297 \fIemacs\fP(1), \fIvi\fP(1)
7305 The \fBbash\fP executable
7308 The systemwide initialization file, executed for login shells
7311 The personal initialization file, executed for login shells
7314 The individual per-interactive-shell startup file
7317 Individual \fIreadline\fP initialization file
7320 Brian Fox, Free Software Foundation
7324 Chet Ramey, Case Western Reserve University
7328 If you find a bug in
7330 you should report it. But first, you should
7331 make sure that it really is a bug, and that it appears in the latest
7336 Once you have determined that a bug actually exists, use the
7338 command to submit a bug report.
7339 If you have a fix, you are encouraged to mail that as well!
7340 Suggestions and `philosophical' bug reports may be mailed
7341 to \fIbug-bash@gnu.org\fP or posted to the Usenet
7345 ALL bug reports should include:
7349 The version number of \fBbash\fR
7351 The hardware and operating system
7353 The compiler used to compile
7355 A description of the bug behaviour
7357 A short script or `recipe' which exercises the bug
7361 inserts the first three items automatically into the template
7362 it provides for filing a bug report.
7364 Comments and bug reports concerning
7365 this manual page should be directed to
7366 .IR chet@ins.CWRU.Edu .
7369 It's too big and too slow.
7371 There are some subtle differences between
7373 and traditional versions of
7375 mostly because of the
7380 Aliases are confusing in some uses.
7382 Shell builtin commands and functions are not stoppable/restartable.
7384 Compound commands and command sequences of the form `a ; b ; c'
7385 are not handled gracefully when process suspension is attempted.
7386 When a process is stopped, the shell immediately executes the next
7387 command in the sequence.
7388 It suffices to place the sequence of commands between
7389 parentheses to force it into a subshell, which may be stopped as
7392 Commands inside of \fB$(\fP...\fB)\fP command substitution are not
7393 parsed until substitution is attempted. This will delay error
7394 reporting until some time after the command is entered.
7396 Array variables may not (yet) be exported.
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