1BASH_BUILTINS(1) General Commands Manual BASH_BUILTINS(1)
2
6 bash, :, ., [, alias, bg, bind, break, builtin, caller, cd, command,
7 compgen, complete, compopt, continue, declare, dirs, disown, echo,
8 enable, eval, exec, exit, export, false, fc, fg, getopts, hash, help,
9 history, jobs, kill, let, local, logout, mapfile, popd, printf, pushd,
10 pwd, read, readonly, return, set, shift, shopt, source, suspend, test,
11 times, trap, true, type, typeset, ulimit, umask, unalias, unset, wait -
12 bash built-in commands, see bash(1)
13
15 Unless otherwise noted, each builtin command documented in this section
16 as accepting options preceded by - accepts -- to signify the end of the
17 options. The :, true, false, and test/[ builtins do not accept options
18 and do not treat -- specially. The exit, logout, return, break, con‐
19 tinue, let, and shift builtins accept and process arguments beginning
20 with - without requiring --. Other builtins that accept arguments but
21 are not specified as accepting options interpret arguments beginning
22 with - as invalid options and require -- to prevent this interpreta‐
23 tion.
24 : [arguments]
25 No effect; the command does nothing beyond expanding arguments
26 and performing any specified redirections. The return status is
27 zero.
28 . filename [arguments]
30 source filename [arguments]
31 Read and execute commands from filename in the current shell
32 environment and return the exit status of the last command exe‐
33 cuted from filename. If filename does not contain a slash,
34 filenames in PATH are used to find the directory containing
35 filename. The file searched for in PATH need not be executable.
36 When bash is not in posix mode, the current directory is
37 searched if no file is found in PATH. If the sourcepath option
38 to the shopt builtin command is turned off, the PATH is not
39 searched. If any arguments are supplied, they become the posi‐
40 tional parameters when filename is executed. Otherwise the
41 positional parameters are unchanged. If the -T option is
42 enabled, source inherits any trap on DEBUG; if it is not, any
43 DEBUG trap string is saved and restored around the call to
44 source, and source unsets the DEBUG trap while it executes. If
45 -T is not set, and the sourced file changes the DEBUG trap, the
46 new value is retained when source completes. The return status
47 is the status of the last command exited within the script (0 if
48 no commands are executed), and false if filename is not found or
49 cannot be read.
50 alias [-p] [name[=value] ...]
52 Alias with no arguments or with the -p option prints the list of
53 aliases in the form alias name=value on standard output. When
54 arguments are supplied, an alias is defined for each name whose
55 value is given. A trailing space in value causes the next word
56 to be checked for alias substitution when the alias is expanded.
57 For each name in the argument list for which no value is sup‐
58 plied, the name and value of the alias is printed. Alias
59 returns true unless a name is given for which no alias has been
60 defined.
61 bg [jobspec ...]
63 Resume each suspended job jobspec in the background, as if it
64 had been started with &. If jobspec is not present, the shell's
65 notion of the current job is used. bg jobspec returns 0 unless
66 run when job control is disabled or, when run with job control
67 enabled, any specified jobspec was not found or was started
68 without job control.
69 bind [-m keymap] [-lpsvPSVX]
71 bind [-m keymap] [-q function] [-u function] [-r keyseq]
72 bind [-m keymap] -f filename
73 bind [-m keymap] -x keyseq:shell-command
74 bind [-m keymap] keyseq:function-name
75 bind [-m keymap] keyseq:readline-command
76 Display current readline key and function bindings, bind a key
77 sequence to a readline function or macro, or set a readline
78 variable. Each non-option argument is a command as it would
79 appear in .inputrc, but each binding or command must be passed
80 as a separate argument; e.g., '"\C-x\C-r": re-read-init-file'.
81 Options, if supplied, have the following meanings:
82 -m keymap
83 Use keymap as the keymap to be affected by the subsequent
84 bindings. Acceptable keymap names are emacs, emacs-stan‐
85 dard, emacs-meta, emacs-ctlx, vi, vi-move, vi-command,
86 and vi-insert. vi is equivalent to vi-command (vi-move
87 is also a synonym); emacs is equivalent to emacs-stan‐
88 dard.
89 -l List the names of all readline functions.
90 -p Display readline function names and bindings in such a
91 way that they can be re-read.
92 -P List current readline function names and bindings.
93 -s Display readline key sequences bound to macros and the
94 strings they output in such a way that they can be re-
95 read.
96 -S Display readline key sequences bound to macros and the
97 strings they output.
98 -v Display readline variable names and values in such a way
99 that they can be re-read.
100 -V List current readline variable names and values.
101 -f filename
102 Read key bindings from filename.
103 -q function
104 Query about which keys invoke the named function.
105 -u function
106 Unbind all keys bound to the named function.
107 -r keyseq
108 Remove any current binding for keyseq.
109 -x keyseq:shell-command
110 Cause shell-command to be executed whenever keyseq is
111 entered. When shell-command is executed, the shell sets
112 the READLINE_LINE variable to the contents of the read‐
113 line line buffer and the READLINE_POINT variable to the
114 current location of the insertion point. If the executed
115 command changes the value of READLINE_LINE or READ‐
116 LINE_POINT, those new values will be reflected in the
117 editing state.
118 -X List all key sequences bound to shell commands and the
119 associated commands in a format that can be reused as
120 input.
121 The return value is 0 unless an unrecognized option is given or
123 an error occurred.
124 break [n]
126 Exit from within a for, while, until, or select loop. If n is
127 specified, break n levels. n must be ≥ 1. If n is greater than
128 the number of enclosing loops, all enclosing loops are exited.
129 The return value is 0 unless n is not greater than or equal to
130 1.
131 builtin shell-builtin [arguments]
133 Execute the specified shell builtin, passing it arguments, and
134 return its exit status. This is useful when defining a function
135 whose name is the same as a shell builtin, retaining the func‐
136 tionality of the builtin within the function. The cd builtin is
137 commonly redefined this way. The return status is false if
138 shell-builtin is not a shell builtin command.
139 caller [expr]
141 Returns the context of any active subroutine call (a shell func‐
142 tion or a script executed with the . or source builtins). With‐
143 out expr, caller displays the line number and source filename of
144 the current subroutine call. If a non-negative integer is sup‐
145 plied as expr, caller displays the line number, subroutine name,
146 and source file corresponding to that position in the current
147 execution call stack. This extra information may be used, for
148 example, to print a stack trace. The current frame is frame 0.
149 The return value is 0 unless the shell is not executing a sub‐
150 routine call or expr does not correspond to a valid position in
151 the call stack.
152 cd [-L|[-P [-e]] [-@]] [dir]
154 Change the current directory to dir. if dir is not supplied,
155 the value of the HOME shell variable is the default. Any addi‐
156 tional arguments following dir are ignored. The variable CDPATH
157 defines the search path for the directory containing dir: each
158 directory name in CDPATH is searched for dir. Alternative
159 directory names in CDPATH are separated by a colon (:). A null
160 directory name in CDPATH is the same as the current directory,
161 i.e., ``.''. If dir begins with a slash (/), then CDPATH is not
162 used. The -P option causes cd to use the physical directory
163 structure by resolving symbolic links while traversing dir and
164 before processing instances of .. in dir (see also the -P option
165 to the set builtin command); the -L option forces symbolic links
166 to be followed by resolving the link after processing instances
167 of .. in dir. If .. appears in dir, it is processed by removing
168 the immediately previous pathname component from dir, back to a
169 slash or the beginning of dir. If the -e option is supplied
170 with -P, and the current working directory cannot be success‐
171 fully determined after a successful directory change, cd will
172 return an unsuccessful status. On systems that support it, the
173 -@ option presents the extended attributes associated with a
174 file as a directory. An argument of - is converted to $OLDPWD
175 before the directory change is attempted. If a non-empty direc‐
176 tory name from CDPATH is used, or if - is the first argument,
177 and the directory change is successful, the absolute pathname of
178 the new working directory is written to the standard output.
179 The return value is true if the directory was successfully
180 changed; false otherwise.
181 command [-pVv] command [arg ...]
183 Run command with args suppressing the normal shell function
184 lookup. Only builtin commands or commands found in the PATH are
185 executed. If the -p option is given, the search for command is
186 performed using a default value for PATH that is guaranteed to
187 find all of the standard utilities. If either the -V or -v
188 option is supplied, a description of command is printed. The -v
189 option causes a single word indicating the command or filename
190 used to invoke command to be displayed; the -V option produces a
191 more verbose description. If the -V or -v option is supplied,
192 the exit status is 0 if command was found, and 1 if not. If
193 neither option is supplied and an error occurred or command can‐
194 not be found, the exit status is 127. Otherwise, the exit sta‐
195 tus of the command builtin is the exit status of command.
196 compgen [option] [word]
198 Generate possible completion matches for word according to the
199 options, which may be any option accepted by the complete
200 builtin with the exception of -p and -r, and write the matches
201 to the standard output. When using the -F or -C options, the
202 various shell variables set by the programmable completion
203 facilities, while available, will not have useful values.
204 The matches will be generated in the same way as if the program‐
206 mable completion code had generated them directly from a comple‐
207 tion specification with the same flags. If word is specified,
208 only those completions matching word will be displayed.
209 The return value is true unless an invalid option is supplied,
211 or no matches were generated.
212 complete [-abcdefgjksuv] [-o comp-option] [-DEI] [-A action] [-G glob‐
214 pat] [-W wordlist] [-F function] [-C command]
215 [-X filterpat] [-P prefix] [-S suffix] name [name ...]
216 complete -pr [-DEI] [name ...]
217 Specify how arguments to each name should be completed. If the
218 -p option is supplied, or if no options are supplied, existing
219 completion specifications are printed in a way that allows them
220 to be reused as input. The -r option removes a completion spec‐
221 ification for each name, or, if no names are supplied, all com‐
222 pletion specifications. The -D option indicates that other sup‐
223 plied options and actions should apply to the ``default'' com‐
224 mand completion; that is, completion attempted on a command for
225 which no completion has previously been defined. The -E option
226 indicates that other supplied options and actions should apply
227 to ``empty'' command completion; that is, completion attempted
228 on a blank line. The -I option indicates that other supplied
229 options and actions should apply to completion on the inital
230 non-assignment word on the line, or after a command delimiter
231 such as ; or |, which is usually command name completion. If
232 multiple options are supplied, the -D option takes precedence
233 over -E, and both take precedence over -I. If any of -D, -E, or
234 -I are supplied, any other name arguments are ignored; these
235 completions only apply to the case specified by the option.
236 The process of applying these completion specifications when
238 word completion is attempted is described above under Program‐
239 mable Completion.
240 Other options, if specified, have the following meanings. The
242 arguments to the -G, -W, and -X options (and, if necessary, the
243 -P and -S options) should be quoted to protect them from expan‐
244 sion before the complete builtin is invoked.
245 -o comp-option
246 The comp-option controls several aspects of the comp‐
247 spec's behavior beyond the simple generation of comple‐
248 tions. comp-option may be one of:
249 bashdefault
250 Perform the rest of the default bash completions
251 if the compspec generates no matches.
252 default Use readline's default filename completion if
253 the compspec generates no matches.
254 dirnames
255 Perform directory name completion if the comp‐
256 spec generates no matches.
257 filenames
258 Tell readline that the compspec generates file‐
259 names, so it can perform any filename-specific
260 processing (like adding a slash to directory
261 names, quoting special characters, or suppress‐
262 ing trailing spaces). Intended to be used with
263 shell functions.
264 noquote Tell readline not to quote the completed words
265 if they are filenames (quoting filenames is the
266 default).
267 nosort Tell readline not to sort the list of possible
268 completions alphabetically.
269 nospace Tell readline not to append a space (the
270 default) to words completed at the end of the
271 line.
272 plusdirs
273 After any matches defined by the compspec are
274 generated, directory name completion is
275 attempted and any matches are added to the
276 results of the other actions.
277 -A action
278 The action may be one of the following to generate a
279 list of possible completions:
280 alias Alias names. May also be specified as -a.
281 arrayvar
282 Array variable names.
283 binding Readline key binding names.
284 builtin Names of shell builtin commands. May also be
285 specified as -b.
286 command Command names. May also be specified as -c.
287 directory
288 Directory names. May also be specified as -d.
289 disabled
290 Names of disabled shell builtins.
291 enabled Names of enabled shell builtins.
292 export Names of exported shell variables. May also be
293 specified as -e.
294 file File names. May also be specified as -f.
295 function
296 Names of shell functions.
297 group Group names. May also be specified as -g.
298 helptopic
299 Help topics as accepted by the help builtin.
300 hostname
301 Hostnames, as taken from the file specified by
302 the HOSTFILE shell variable.
303 job Job names, if job control is active. May also
304 be specified as -j.
305 keyword Shell reserved words. May also be specified as
306 -k.
307 running Names of running jobs, if job control is active.
308 service Service names. May also be specified as -s.
309 setopt Valid arguments for the -o option to the set
310 builtin.
311 shopt Shell option names as accepted by the shopt
312 builtin.
313 signal Signal names.
314 stopped Names of stopped jobs, if job control is active.
315 user User names. May also be specified as -u.
316 variable
317 Names of all shell variables. May also be spec‐
318 ified as -v.
319 -C command
320 command is executed in a subshell environment, and its
321 output is used as the possible completions.
322 -F function
323 The shell function function is executed in the current
324 shell environment. When the function is executed, the
325 first argument ($1) is the name of the command whose
326 arguments are being completed, the second argument ($2)
327 is the word being completed, and the third argument ($3)
328 is the word preceding the word being completed on the
329 current command line. When it finishes, the possible
330 completions are retrieved from the value of the COMPRE‐
331 PLY array variable.
332 -G globpat
333 The pathname expansion pattern globpat is expanded to
334 generate the possible completions.
335 -P prefix
336 prefix is added at the beginning of each possible com‐
337 pletion after all other options have been applied.
338 -S suffix
339 suffix is appended to each possible completion after all
340 other options have been applied.
341 -W wordlist
342 The wordlist is split using the characters in the IFS
343 special variable as delimiters, and each resultant word
344 is expanded. Shell quoting is honored within wordlist,
345 in order to provide a mechanism for the words to contain
346 shell metacharacters or characters in the value of IFS.
347 The possible completions are the members of the resul‐
348 tant list which match the word being completed.
349 -X filterpat
350 filterpat is a pattern as used for pathname expansion.
351 It is applied to the list of possible completions gener‐
352 ated by the preceding options and arguments, and each
353 completion matching filterpat is removed from the list.
354 A leading ! in filterpat negates the pattern; in this
355 case, any completion not matching filterpat is removed.
356 The return value is true unless an invalid option is supplied,
358 an option other than -p or -r is supplied without a name argu‐
359 ment, an attempt is made to remove a completion specification
360 for a name for which no specification exists, or an error occurs
361 adding a completion specification.
362 compopt [-o option] [-DEI] [+o option] [name]
364 Modify completion options for each name according to the
365 options, or for the currently-executing completion if no names
366 are supplied. If no options are given, display the completion
367 options for each name or the current completion. The possible
368 values of option are those valid for the complete builtin
369 described above. The -D option indicates that other supplied
370 options should apply to the ``default'' command completion; that
371 is, completion attempted on a command for which no completion
372 has previously been defined. The -E option indicates that other
373 supplied options should apply to ``empty'' command completion;
374 that is, completion attempted on a blank line. The -I option
375 indicates that other supplied options should apply to completion
376 on the inital non-assignment word on the line, or after a com‐
377 mand delimiter such as ; or |, which is usually command name
378 completion.
379 The return value is true unless an invalid option is supplied,
381 an attempt is made to modify the options for a name for which no
382 completion specification exists, or an output error occurs.
383 continue [n]
385 Resume the next iteration of the enclosing for, while, until, or
386 select loop. If n is specified, resume at the nth enclosing
387 loop. n must be ≥ 1. If n is greater than the number of
388 enclosing loops, the last enclosing loop (the ``top-level''
389 loop) is resumed. The return value is 0 unless n is not greater
390 than or equal to 1.
391 declare [-aAfFgilnrtux] [-p] [name[=value] ...]
393 typeset [-aAfFgilnrtux] [-p] [name[=value] ...]
394 Declare variables and/or give them attributes. If no names are
395 given then display the values of variables. The -p option will
396 display the attributes and values of each name. When -p is used
397 with name arguments, additional options, other than -f and -F,
398 are ignored. When -p is supplied without name arguments, it
399 will display the attributes and values of all variables having
400 the attributes specified by the additional options. If no other
401 options are supplied with -p, declare will display the
402 attributes and values of all shell variables. The -f option
403 will restrict the display to shell functions. The -F option
404 inhibits the display of function definitions; only the function
405 name and attributes are printed. If the extdebug shell option
406 is enabled using shopt, the source file name and line number
407 where each name is defined are displayed as well. The -F option
408 implies -f. The -g option forces variables to be created or
409 modified at the global scope, even when declare is executed in a
410 shell function. It is ignored in all other cases. The follow‐
411 ing options can be used to restrict output to variables with the
412 specified attribute or to give variables attributes:
413 -a Each name is an indexed array variable (see Arrays
414 above).
415 -A Each name is an associative array variable (see Arrays
416 above).
417 -f Use function names only.
418 -i The variable is treated as an integer; arithmetic evalua‐
419 tion (see ARITHMETIC EVALUATION above) is performed when
420 the variable is assigned a value.
421 -l When the variable is assigned a value, all upper-case
422 characters are converted to lower-case. The upper-case
423 attribute is disabled.
424 -n Give each name the nameref attribute, making it a name
425 reference to another variable. That other variable is
426 defined by the value of name. All references, assign‐
427 ments, and attribute modifications to name, except those
428 using or changing the -n attribute itself, are performed
429 on the variable referenced by name's value. The nameref
430 attribute cannot be applied to array variables.
431 -r Make names readonly. These names cannot then be assigned
432 values by subsequent assignment statements or unset.
433 -t Give each name the trace attribute. Traced functions
434 inherit the DEBUG and RETURN traps from the calling
435 shell. The trace attribute has no special meaning for
436 variables.
437 -u When the variable is assigned a value, all lower-case
438 characters are converted to upper-case. The lower-case
439 attribute is disabled.
440 -x Mark names for export to subsequent commands via the
441 environment.
442 Using `+' instead of `-' turns off the attribute instead, with
444 the exceptions that +a and +A may not be used to destroy array
445 variables and +r will not remove the readonly attribute. When
446 used in a function, declare and typeset make each name local, as
447 with the local command, unless the -g option is supplied. If a
448 variable name is followed by =value, the value of the variable
449 is set to value. When using -a or -A and the compound assign‐
450 ment syntax to create array variables, additional attributes do
451 not take effect until subsequent assignments. The return value
452 is 0 unless an invalid option is encountered, an attempt is made
453 to define a function using ``-f foo=bar'', an attempt is made to
454 assign a value to a readonly variable, an attempt is made to
455 assign a value to an array variable without using the compound
456 assignment syntax (see Arrays above), one of the names is not a
457 valid shell variable name, an attempt is made to turn off read‐
458 only status for a readonly variable, an attempt is made to turn
459 off array status for an array variable, or an attempt is made to
460 display a non-existent function with -f.
461 dirs [-clpv] [+n] [-n]
463 Without options, displays the list of currently remembered
464 directories. The default display is on a single line with
465 directory names separated by spaces. Directories are added to
466 the list with the pushd command; the popd command removes
467 entries from the list. The current directory is always the
468 first directory in the stack.
469 -c Clears the directory stack by deleting all of the
470 entries.
471 -l Produces a listing using full pathnames; the default
472 listing format uses a tilde to denote the home directory.
473 -p Print the directory stack with one entry per line.
474 -v Print the directory stack with one entry per line, pre‐
475 fixing each entry with its index in the stack.
476 +n Displays the nth entry counting from the left of the list
477 shown by dirs when invoked without options, starting with
478 zero.
479 -n Displays the nth entry counting from the right of the
480 list shown by dirs when invoked without options, starting
481 with zero.
482 The return value is 0 unless an invalid option is supplied or n
484 indexes beyond the end of the directory stack.
485 disown [-ar] [-h] [jobspec ... | pid ... ]
487 Without options, remove each jobspec from the table of active
488 jobs. If jobspec is not present, and neither the -a nor the -r
489 option is supplied, the current job is used. If the -h option
490 is given, each jobspec is not removed from the table, but is
491 marked so that SIGHUP is not sent to the job if the shell
492 receives a SIGHUP. If no jobspec is supplied, the -a option
493 means to remove or mark all jobs; the -r option without a job‐
494 spec argument restricts operation to running jobs. The return
495 value is 0 unless a jobspec does not specify a valid job.
496 echo [-neE] [arg ...]
498 Output the args, separated by spaces, followed by a newline.
499 The return status is 0 unless a write error occurs. If -n is
500 specified, the trailing newline is suppressed. If the -e option
501 is given, interpretation of the following backslash-escaped
502 characters is enabled. The -E option disables the interpreta‐
503 tion of these escape characters, even on systems where they are
504 interpreted by default. The xpg_echo shell option may be used
505 to dynamically determine whether or not echo expands these
506 escape characters by default. echo does not interpret -- to
507 mean the end of options. echo interprets the following escape
508 sequences:
509 \a alert (bell)
510 \b backspace
511 \c suppress further output
512 \e
513 \E an escape character
514 \f form feed
515 \n new line
516 \r carriage return
517 \t horizontal tab
518 \v vertical tab
519 \\ backslash
520 \0nnn the eight-bit character whose value is the octal value
521 nnn (zero to three octal digits)
522 \xHH the eight-bit character whose value is the hexadecimal
523 value HH (one or two hex digits)
524 \uHHHH the Unicode (ISO/IEC 10646) character whose value is the
525 hexadecimal value HHHH (one to four hex digits)
526 \UHHHHHHHH
527 the Unicode (ISO/IEC 10646) character whose value is the
528 hexadecimal value HHHHHHHH (one to eight hex digits)
529 enable [-a] [-dnps] [-f filename] [name ...]
531 Enable and disable builtin shell commands. Disabling a builtin
532 allows a disk command which has the same name as a shell builtin
533 to be executed without specifying a full pathname, even though
534 the shell normally searches for builtins before disk commands.
535 If -n is used, each name is disabled; otherwise, names are
536 enabled. For example, to use the test binary found via the PATH
537 instead of the shell builtin version, run ``enable -n test''.
538 The -f option means to load the new builtin command name from
539 shared object filename, on systems that support dynamic loading.
540 The -d option will delete a builtin previously loaded with -f.
541 If no name arguments are given, or if the -p option is supplied,
542 a list of shell builtins is printed. With no other option argu‐
543 ments, the list consists of all enabled shell builtins. If -n
544 is supplied, only disabled builtins are printed. If -a is sup‐
545 plied, the list printed includes all builtins, with an indica‐
546 tion of whether or not each is enabled. If -s is supplied, the
547 output is restricted to the POSIX special builtins. The return
548 value is 0 unless a name is not a shell builtin or there is an
549 error loading a new builtin from a shared object.
550 eval [arg ...]
552 The args are read and concatenated together into a single com‐
553 mand. This command is then read and executed by the shell, and
554 its exit status is returned as the value of eval. If there are
555 no args, or only null arguments, eval returns 0.
556 exec [-cl] [-a name] [command [arguments]]
558 If command is specified, it replaces the shell. No new process
559 is created. The arguments become the arguments to command. If
560 the -l option is supplied, the shell places a dash at the begin‐
561 ning of the zeroth argument passed to command. This is what
562 login(1) does. The -c option causes command to be executed with
563 an empty environment. If -a is supplied, the shell passes name
564 as the zeroth argument to the executed command. If command can‐
565 not be executed for some reason, a non-interactive shell exits,
566 unless the execfail shell option is enabled. In that case, it
567 returns failure. An interactive shell returns failure if the
568 file cannot be executed. A subshell exits unconditionally if
569 exec fails. If command is not specified, any redirections take
570 effect in the current shell, and the return status is 0. If
571 there is a redirection error, the return status is 1.
572 exit [n]
574 Cause the shell to exit with a status of n. If n is omitted,
575 the exit status is that of the last command executed. A trap on
576 EXIT is executed before the shell terminates.
577 export [-fn] [name[=word]] ...
579 export -p
580 The supplied names are marked for automatic export to the envi‐
581 ronment of subsequently executed commands. If the -f option is
582 given, the names refer to functions. If no names are given, or
583 if the -p option is supplied, a list of names of all exported
584 variables is printed. The -n option causes the export property
585 to be removed from each name. If a variable name is followed by
586 =word, the value of the variable is set to word. export returns
587 an exit status of 0 unless an invalid option is encountered, one
588 of the names is not a valid shell variable name, or -f is sup‐
589 plied with a name that is not a function.
590 fc [-e ename] [-lnr] [first] [last]
592 fc -s [pat=rep] [cmd]
593 The first form selects a range of commands from first to last
594 from the history list and displays or edits and re-executes
595 them. First and last may be specified as a string (to locate
596 the last command beginning with that string) or as a number (an
597 index into the history list, where a negative number is used as
598 an offset from the current command number). If last is not
599 specified, it is set to the current command for listing (so that
600 ``fc -l -10'' prints the last 10 commands) and to first other‐
601 wise. If first is not specified, it is set to the previous com‐
602 mand for editing and -16 for listing.
603 The -n option suppresses the command numbers when listing. The
605 -r option reverses the order of the commands. If the -l option
606 is given, the commands are listed on standard output. Other‐
607 wise, the editor given by ename is invoked on a file containing
608 those commands. If ename is not given, the value of the FCEDIT
609 variable is used, and the value of EDITOR if FCEDIT is not set.
610 If neither variable is set, vi is used. When editing is com‐
611 plete, the edited commands are echoed and executed.
612 In the second form, command is re-executed after each instance
614 of pat is replaced by rep. Command is interpreted the same as
615 first above. A useful alias to use with this is ``r="fc -s"'',
616 so that typing ``r cc'' runs the last command beginning with
617 ``cc'' and typing ``r'' re-executes the last command.
618 If the first form is used, the return value is 0 unless an
620 invalid option is encountered or first or last specify history
621 lines out of range. If the -e option is supplied, the return
622 value is the value of the last command executed or failure if an
623 error occurs with the temporary file of commands. If the second
624 form is used, the return status is that of the command re-exe‐
625 cuted, unless cmd does not specify a valid history line, in
626 which case fc returns failure.
627 fg [jobspec]
629 Resume jobspec in the foreground, and make it the current job.
630 If jobspec is not present, the shell's notion of the current job
631 is used. The return value is that of the command placed into
632 the foreground, or failure if run when job control is disabled
633 or, when run with job control enabled, if jobspec does not spec‐
634 ify a valid job or jobspec specifies a job that was started
635 without job control.
636 getopts optstring name [args]
638 getopts is used by shell procedures to parse positional parame‐
639 ters. optstring contains the option characters to be recog‐
640 nized; if a character is followed by a colon, the option is
641 expected to have an argument, which should be separated from it
642 by white space. The colon and question mark characters may not
643 be used as option characters. Each time it is invoked, getopts
644 places the next option in the shell variable name, initializing
645 name if it does not exist, and the index of the next argument to
646 be processed into the variable OPTIND. OPTIND is initialized to
647 1 each time the shell or a shell script is invoked. When an
648 option requires an argument, getopts places that argument into
649 the variable OPTARG. The shell does not reset OPTIND automati‐
650 cally; it must be manually reset between multiple calls to
651 getopts within the same shell invocation if a new set of parame‐
652 ters is to be used.
653 When the end of options is encountered, getopts exits with a
655 return value greater than zero. OPTIND is set to the index of
656 the first non-option argument, and name is set to ?.
657 getopts normally parses the positional parameters, but if more
659 arguments are given in args, getopts parses those instead.
660 getopts can report errors in two ways. If the first character
662 of optstring is a colon, silent error reporting is used. In
663 normal operation, diagnostic messages are printed when invalid
664 options or missing option arguments are encountered. If the
665 variable OPTERR is set to 0, no error messages will be dis‐
666 played, even if the first character of optstring is not a colon.
667 If an invalid option is seen, getopts places ? into name and, if
669 not silent, prints an error message and unsets OPTARG. If
670 getopts is silent, the option character found is placed in
671 OPTARG and no diagnostic message is printed.
672 If a required argument is not found, and getopts is not silent,
674 a question mark (?) is placed in name, OPTARG is unset, and a
675 diagnostic message is printed. If getopts is silent, then a
676 colon (:) is placed in name and OPTARG is set to the option
677 character found.
678 getopts returns true if an option, specified or unspecified, is
680 found. It returns false if the end of options is encountered or
681 an error occurs.
682 hash [-lr] [-p filename] [-dt] [name]
684 Each time hash is invoked, the full pathname of the command name
685 is determined by searching the directories in $PATH and remem‐
686 bered. Any previously-remembered pathname is discarded. If the
687 -p option is supplied, no path search is performed, and filename
688 is used as the full filename of the command. The -r option
689 causes the shell to forget all remembered locations. The -d
690 option causes the shell to forget the remembered location of
691 each name. If the -t option is supplied, the full pathname to
692 which each name corresponds is printed. If multiple name argu‐
693 ments are supplied with -t, the name is printed before the
694 hashed full pathname. The -l option causes output to be dis‐
695 played in a format that may be reused as input. If no arguments
696 are given, or if only -l is supplied, information about remem‐
697 bered commands is printed. The return status is true unless a
698 name is not found or an invalid option is supplied.
699 help [-dms] [pattern]
701 Display helpful information about builtin commands. If pattern
702 is specified, help gives detailed help on all commands matching
703 pattern; otherwise help for all the builtins and shell control
704 structures is printed.
705 -d Display a short description of each pattern
706 -m Display the description of each pattern in a manpage-like
707 format
708 -s Display only a short usage synopsis for each pattern
709 The return status is 0 unless no command matches pattern.
711 history [n]
713 history -c
714 history -d offset
715 history -d start-end
716 history -anrw [filename]
717 history -p arg [arg ...]
718 history -s arg [arg ...]
719 With no options, display the command history list with line num‐
720 bers. Lines listed with a * have been modified. An argument of
721 n lists only the last n lines. If the shell variable HISTTIME‐
722 FORMAT is set and not null, it is used as a format string for
723 strftime(3) to display the time stamp associated with each dis‐
724 played history entry. No intervening blank is printed between
725 the formatted time stamp and the history line. If filename is
726 supplied, it is used as the name of the history file; if not,
727 the value of HISTFILE is used. Options, if supplied, have the
728 following meanings:
729 -c Clear the history list by deleting all the entries.
730 -d offset
731 Delete the history entry at position offset. If offset
732 is negative, it is interpreted as relative to one greater
733 than the last history position, so negative indices count
734 back from the end of the history, and an index of -1
735 refers to the current history -d command.
736 -d start-end
737 Delete the history entries between positions start and
738 end, inclusive. Positive and negative values for start
739 and end are interpreted as described above.
740 -a Append the ``new'' history lines to the history file.
741 These are history lines entered since the beginning of
742 the current bash session, but not already appended to the
743 history file.
744 -n Read the history lines not already read from the history
745 file into the current history list. These are lines
746 appended to the history file since the beginning of the
747 current bash session.
748 -r Read the contents of the history file and append them to
749 the current history list.
750 -w Write the current history list to the history file, over‐
751 writing the history file's contents.
752 -p Perform history substitution on the following args and
753 display the result on the standard output. Does not
754 store the results in the history list. Each arg must be
755 quoted to disable normal history expansion.
756 -s Store the args in the history list as a single entry.
757 The last command in the history list is removed before
758 the args are added.
759 If the HISTTIMEFORMAT variable is set, the time stamp informa‐
761 tion associated with each history entry is written to the his‐
762 tory file, marked with the history comment character. When the
763 history file is read, lines beginning with the history comment
764 character followed immediately by a digit are interpreted as
765 timestamps for the following history entry. The return value is
766 0 unless an invalid option is encountered, an error occurs while
767 reading or writing the history file, an invalid offset is sup‐
768 plied as an argument to -d, or the history expansion supplied as
769 an argument to -p fails.
770 jobs [-lnprs] [ jobspec ... ]
772 jobs -x command [ args ... ]
773 The first form lists the active jobs. The options have the fol‐
774 lowing meanings:
775 -l List process IDs in addition to the normal information.
776 -n Display information only about jobs that have changed
777 status since the user was last notified of their status.
778 -p List only the process ID of the job's process group
779 leader.
780 -r Display only running jobs.
781 -s Display only stopped jobs.
782 If jobspec is given, output is restricted to information about
784 that job. The return status is 0 unless an invalid option is
785 encountered or an invalid jobspec is supplied.
786 If the -x option is supplied, jobs replaces any jobspec found in
788 command or args with the corresponding process group ID, and
789 executes command passing it args, returning its exit status.
790 kill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...
792 kill -l|-L [sigspec | exit_status]
793 Send the signal named by sigspec or signum to the processes
794 named by pid or jobspec. sigspec is either a case-insensitive
795 signal name such as SIGKILL (with or without the SIG prefix) or
796 a signal number; signum is a signal number. If sigspec is not
797 present, then SIGTERM is assumed. An argument of -l lists the
798 signal names. If any arguments are supplied when -l is given,
799 the names of the signals corresponding to the arguments are
800 listed, and the return status is 0. The exit_status argument to
801 -l is a number specifying either a signal number or the exit
802 status of a process terminated by a signal. The -L option is
803 equivalent to -l. kill returns true if at least one signal was
804 successfully sent, or false if an error occurs or an invalid
805 option is encountered.
806 let arg [arg ...]
808 Each arg is an arithmetic expression to be evaluated (see ARITH‐
809 METIC EVALUATION above). If the last arg evaluates to 0, let
810 returns 1; 0 is returned otherwise.
811 local [option] [name[=value] ... | - ]
813 For each argument, a local variable named name is created, and
814 assigned value. The option can be any of the options accepted
815 by declare. When local is used within a function, it causes the
816 variable name to have a visible scope restricted to that func‐
817 tion and its children. If name is -, the set of shell options
818 is made local to the function in which local is invoked: shell
819 options changed using the set builtin inside the function are
820 restored to their original values when the function returns.
821 With no operands, local writes a list of local variables to the
822 standard output. It is an error to use local when not within a
823 function. The return status is 0 unless local is used outside a
824 function, an invalid name is supplied, or name is a readonly
825 variable.
826 logout Exit a login shell.
828 mapfile [-d delim] [-n count] [-O origin] [-s count] [-t] [-u fd] [-C
830 callback] [-c quantum] [array]
831 readarray [-d delim] [-n count] [-O origin] [-s count] [-t] [-u fd] [-C
832 callback] [-c quantum] [array]
833 Read lines from the standard input into the indexed array vari‐
834 able array, or from file descriptor fd if the -u option is sup‐
835 plied. The variable MAPFILE is the default array. Options, if
836 supplied, have the following meanings:
837 -d The first character of delim is used to terminate each
838 input line, rather than newline. If delim is the empty
839 string, mapfile will terminate a line when it reads a NUL
840 character.
841 -n Copy at most count lines. If count is 0, all lines are
842 copied.
843 -O Begin assigning to array at index origin. The default
844 index is 0.
845 -s Discard the first count lines read.
846 -t Remove a trailing delim (default newline) from each line
847 read.
848 -u Read lines from file descriptor fd instead of the stan‐
849 dard input.
850 -C Evaluate callback each time quantum lines are read. The
851 -c option specifies quantum.
852 -c Specify the number of lines read between each call to
853 callback.
854 If -C is specified without -c, the default quantum is 5000.
856 When callback is evaluated, it is supplied the index of the next
857 array element to be assigned and the line to be assigned to that
858 element as additional arguments. callback is evaluated after
859 the line is read but before the array element is assigned.
860 If not supplied with an explicit origin, mapfile will clear
862 array before assigning to it.
863 mapfile returns successfully unless an invalid option or option
865 argument is supplied, array is invalid or unassignable, or if
866 array is not an indexed array.
867 popd [-n] [+n] [-n]
869 Removes entries from the directory stack. With no arguments,
870 removes the top directory from the stack, and performs a cd to
871 the new top directory. Arguments, if supplied, have the follow‐
872 ing meanings:
873 -n Suppresses the normal change of directory when removing
874 directories from the stack, so that only the stack is
875 manipulated.
876 +n Removes the nth entry counting from the left of the list
877 shown by dirs, starting with zero. For example: ``popd
878 +0'' removes the first directory, ``popd +1'' the second.
879 -n Removes the nth entry counting from the right of the list
880 shown by dirs, starting with zero. For example: ``popd
881 -0'' removes the last directory, ``popd -1'' the next to
882 last.
883 If the popd command is successful, a dirs is performed as well,
885 and the return status is 0. popd returns false if an invalid
886 option is encountered, the directory stack is empty, a non-exis‐
887 tent directory stack entry is specified, or the directory change
888 fails.
889 printf [-v var] format [arguments]
891 Write the formatted arguments to the standard output under the
892 control of the format. The -v option causes the output to be
893 assigned to the variable var rather than being printed to the
894 standard output.
895 The format is a character string which contains three types of
897 objects: plain characters, which are simply copied to standard
898 output, character escape sequences, which are converted and
899 copied to the standard output, and format specifications, each
900 of which causes printing of the next successive argument. In
901 addition to the standard printf(1) format specifications, printf
902 interprets the following extensions:
903 %b causes printf to expand backslash escape sequences in the
904 corresponding argument in the same way as echo -e.
905 %q causes printf to output the corresponding argument in a
906 format that can be reused as shell input.
907 %(datefmt)T
908 causes printf to output the date-time string resulting
909 from using datefmt as a format string for strftime(3).
910 The corresponding argument is an integer representing the
911 number of seconds since the epoch. Two special argument
912 values may be used: -1 represents the current time, and
913 -2 represents the time the shell was invoked. If no
914 argument is specified, conversion behaves as if -1 had
915 been given. This is an exception to the usual printf
916 behavior.
917 Arguments to non-string format specifiers are treated as C con‐
919 stants, except that a leading plus or minus sign is allowed, and
920 if the leading character is a single or double quote, the value
921 is the ASCII value of the following character.
922 The format is reused as necessary to consume all of the argu‐
924 ments. If the format requires more arguments than are supplied,
925 the extra format specifications behave as if a zero value or
926 null string, as appropriate, had been supplied. The return
927 value is zero on success, non-zero on failure.
928 pushd [-n] [+n] [-n]
930 pushd [-n] [dir]
931 Adds a directory to the top of the directory stack, or rotates
932 the stack, making the new top of the stack the current working
933 directory. With no arguments, pushd exchanges the top two
934 directories and returns 0, unless the directory stack is empty.
935 Arguments, if supplied, have the following meanings:
936 -n Suppresses the normal change of directory when rotating
937 or adding directories to the stack, so that only the
938 stack is manipulated.
939 +n Rotates the stack so that the nth directory (counting
940 from the left of the list shown by dirs, starting with
941 zero) is at the top.
942 -n Rotates the stack so that the nth directory (counting
943 from the right of the list shown by dirs, starting with
944 zero) is at the top.
945 dir Adds dir to the directory stack at the top, making it the
946 new current working directory as if it had been supplied
947 as the argument to the cd builtin.
948 If the pushd command is successful, a dirs is performed as well.
950 If the first form is used, pushd returns 0 unless the cd to dir
951 fails. With the second form, pushd returns 0 unless the direc‐
952 tory stack is empty, a non-existent directory stack element is
953 specified, or the directory change to the specified new current
954 directory fails.
955 pwd [-LP]
957 Print the absolute pathname of the current working directory.
958 The pathname printed contains no symbolic links if the -P option
959 is supplied or the -o physical option to the set builtin command
960 is enabled. If the -L option is used, the pathname printed may
961 contain symbolic links. The return status is 0 unless an error
962 occurs while reading the name of the current directory or an
963 invalid option is supplied.
964 read [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p
966 prompt] [-t timeout] [-u fd] [name ...]
967 One line is read from the standard input, or from the file
968 descriptor fd supplied as an argument to the -u option, split
969 into words as described above under Word Splitting, and the
970 first word is assigned to the first name, the second word to the
971 second name, and so on. If there are more words than names, the
972 remaining words and their intervening delimiters are assigned to
973 the last name. If there are fewer words read from the input
974 stream than names, the remaining names are assigned empty val‐
975 ues. The characters in IFS are used to split the line into
976 words using the same rules the shell uses for expansion
977 (described above under Word Splitting). The backslash character
978 (\) may be used to remove any special meaning for the next char‐
979 acter read and for line continuation. Options, if supplied,
980 have the following meanings:
981 -a aname
982 The words are assigned to sequential indices of the array
983 variable aname, starting at 0. aname is unset before any
984 new values are assigned. Other name arguments are
985 ignored.
986 -d delim
987 The first character of delim is used to terminate the
988 input line, rather than newline. If delim is the empty
989 string, read will terminate a line when it reads a NUL
990 character.
991 -e If the standard input is coming from a terminal, readline
992 (see READLINE above) is used to obtain the line. Read‐
993 line uses the current (or default, if line editing was
994 not previously active) editing settings, but uses Read‐
995 line's default filename completion.
996 -i text
997 If readline is being used to read the line, text is
998 placed into the editing buffer before editing begins.
999 -n nchars
1000 read returns after reading nchars characters rather than
1001 waiting for a complete line of input, but honors a delim‐
1002 iter if fewer than nchars characters are read before the
1003 delimiter.
1004 -N nchars
1005 read returns after reading exactly nchars characters
1006 rather than waiting for a complete line of input, unless
1007 EOF is encountered or read times out. Delimiter charac‐
1008 ters encountered in the input are not treated specially
1009 and do not cause read to return until nchars characters
1010 are read. The result is not split on the characters in
1011 IFS; the intent is that the variable is assigned exactly
1012 the characters read (with the exception of backslash; see
1013 the -r option below).
1014 -p prompt
1015 Display prompt on standard error, without a trailing new‐
1016 line, before attempting to read any input. The prompt is
1017 displayed only if input is coming from a terminal.
1018 -r Backslash does not act as an escape character. The back‐
1019 slash is considered to be part of the line. In particu‐
1020 lar, a backslash-newline pair may not then be used as a
1021 line continuation.
1022 -s Silent mode. If input is coming from a terminal, charac‐
1023 ters are not echoed.
1024 -t timeout
1025 Cause read to time out and return failure if a complete
1026 line of input (or a specified number of characters) is
1027 not read within timeout seconds. timeout may be a deci‐
1028 mal number with a fractional portion following the deci‐
1029 mal point. This option is only effective if read is
1030 reading input from a terminal, pipe, or other special
1031 file; it has no effect when reading from regular files.
1032 If read times out, read saves any partial input read into
1033 the specified variable name. If timeout is 0, read
1034 returns immediately, without trying to read any data.
1035 The exit status is 0 if input is available on the speci‐
1036 fied file descriptor, non-zero otherwise. The exit sta‐
1037 tus is greater than 128 if the timeout is exceeded.
1038 -u fd Read input from file descriptor fd.
1039 If no names are supplied, the line read is assigned to the vari‐
1041 able REPLY. The exit status is zero, unless end-of-file is
1042 encountered, read times out (in which case the status is greater
1043 than 128), a variable assignment error (such as assigning to a
1044 readonly variable) occurs, or an invalid file descriptor is sup‐
1045 plied as the argument to -u.
1046 readonly [-aAf] [-p] [name[=word] ...]
1048 The given names are marked readonly; the values of these names
1049 may not be changed by subsequent assignment. If the -f option
1050 is supplied, the functions corresponding to the names are so
1051 marked. The -a option restricts the variables to indexed
1052 arrays; the -A option restricts the variables to associative
1053 arrays. If both options are supplied, -A takes precedence. If
1054 no name arguments are given, or if the -p option is supplied, a
1055 list of all readonly names is printed. The other options may be
1056 used to restrict the output to a subset of the set of readonly
1057 names. The -p option causes output to be displayed in a format
1058 that may be reused as input. If a variable name is followed by
1059 =word, the value of the variable is set to word. The return
1060 status is 0 unless an invalid option is encountered, one of the
1061 names is not a valid shell variable name, or -f is supplied with
1062 a name that is not a function.
1063 return [n]
1065 Causes a function to stop executing and return the value speci‐
1066 fied by n to its caller. If n is omitted, the return status is
1067 that of the last command executed in the function body. If
1068 return is executed by a trap handler, the last command used to
1069 determine the status is the last command executed before the
1070 trap handler. If return is executed during a DEBUG trap, the
1071 last command used to determine the status is the last command
1072 executed by the trap handler before return was invoked. If
1073 return is used outside a function, but during execution of a
1074 script by the . (source) command, it causes the shell to stop
1075 executing that script and return either n or the exit status of
1076 the last command executed within the script as the exit status
1077 of the script. If n is supplied, the return value is its least
1078 significant 8 bits. The return status is non-zero if return is
1079 supplied a non-numeric argument, or is used outside a function
1080 and not during execution of a script by . or source. Any com‐
1081 mand associated with the RETURN trap is executed before execu‐
1082 tion resumes after the function or script.
1083 set [--abefhkmnptuvxBCEHPT] [-o option-name] [arg ...]
1085 set [+abefhkmnptuvxBCEHPT] [+o option-name] [arg ...]
1086 Without options, the name and value of each shell variable are
1087 displayed in a format that can be reused as input for setting or
1088 resetting the currently-set variables. Read-only variables can‐
1089 not be reset. In posix mode, only shell variables are listed.
1090 The output is sorted according to the current locale. When
1091 options are specified, they set or unset shell attributes. Any
1092 arguments remaining after option processing are treated as val‐
1093 ues for the positional parameters and are assigned, in order, to
1094 $1, $2, ... $n. Options, if specified, have the following
1095 meanings:
1096 -a Each variable or function that is created or modified is
1097 given the export attribute and marked for export to the
1098 environment of subsequent commands.
1099 -b Report the status of terminated background jobs immedi‐
1100 ately, rather than before the next primary prompt. This
1101 is effective only when job control is enabled.
1102 -e Exit immediately if a pipeline (which may consist of a
1103 single simple command), a list, or a compound command
1104 (see SHELL GRAMMAR above), exits with a non-zero status.
1105 The shell does not exit if the command that fails is
1106 part of the command list immediately following a while
1107 or until keyword, part of the test following the if or
1108 elif reserved words, part of any command executed in a
1109 && or || list except the command following the final &&
1110 or ||, any command in a pipeline but the last, or if the
1111 command's return value is being inverted with !. If a
1112 compound command other than a subshell returns a non-
1113 zero status because a command failed while -e was being
1114 ignored, the shell does not exit. A trap on ERR, if
1115 set, is executed before the shell exits. This option
1116 applies to the shell environment and each subshell envi‐
1117 ronment separately (see COMMAND EXECUTION ENVIRONMENT
1118 above), and may cause subshells to exit before executing
1119 all the commands in the subshell.
1120 If a compound command or shell function executes in a
1122 context where -e is being ignored, none of the commands
1123 executed within the compound command or function body
1124 will be affected by the -e setting, even if -e is set
1125 and a command returns a failure status. If a compound
1126 command or shell function sets -e while executing in a
1127 context where -e is ignored, that setting will not have
1128 any effect until the compound command or the command
1129 containing the function call completes.
1130 -f Disable pathname expansion.
1131 -h Remember the location of commands as they are looked up
1132 for execution. This is enabled by default.
1133 -k All arguments in the form of assignment statements are
1134 placed in the environment for a command, not just those
1135 that precede the command name.
1136 -m Monitor mode. Job control is enabled. This option is
1137 on by default for interactive shells on systems that
1138 support it (see JOB CONTROL above). All processes run
1139 in a separate process group. When a background job com‐
1140 pletes, the shell prints a line containing its exit sta‐
1141 tus.
1142 -n Read commands but do not execute them. This may be used
1143 to check a shell script for syntax errors. This is
1144 ignored by interactive shells.
1145 -o option-name
1146 The option-name can be one of the following:
1147 allexport
1148 Same as -a.
1149 braceexpand
1150 Same as -B.
1151 emacs Use an emacs-style command line editing inter‐
1152 face. This is enabled by default when the shell
1153 is interactive, unless the shell is started with
1154 the --noediting option. This also affects the
1155 editing interface used for read -e.
1156 errexit Same as -e.
1157 errtrace
1158 Same as -E.
1159 functrace
1160 Same as -T.
1161 hashall Same as -h.
1162 histexpand
1163 Same as -H.
1164 history Enable command history, as described above under
1165 HISTORY. This option is on by default in inter‐
1166 active shells.
1167 ignoreeof
1168 The effect is as if the shell command
1169 ``IGNOREEOF=10'' had been executed (see Shell
1170 Variables above).
1171 keyword Same as -k.
1172 monitor Same as -m.
1173 noclobber
1174 Same as -C.
1175 noexec Same as -n.
1176 noglob Same as -f.
1177 nolog Currently ignored.
1178 notify Same as -b.
1179 nounset Same as -u.
1180 onecmd Same as -t.
1181 physical
1182 Same as -P.
1183 pipefail
1184 If set, the return value of a pipeline is the
1185 value of the last (rightmost) command to exit
1186 with a non-zero status, or zero if all commands
1187 in the pipeline exit successfully. This option
1188 is disabled by default.
1189 posix Change the behavior of bash where the default
1190 operation differs from the POSIX standard to
1191 match the standard (posix mode). See SEE ALSO
1192 below for a reference to a document that details
1193 how posix mode affects bash's behavior.
1194 privileged
1195 Same as -p.
1196 verbose Same as -v.
1197 vi Use a vi-style command line editing interface.
1198 This also affects the editing interface used for
1199 read -e.
1200 xtrace Same as -x.
1201 If -o is supplied with no option-name, the values of the
1202 current options are printed. If +o is supplied with no
1203 option-name, a series of set commands to recreate the
1204 current option settings is displayed on the standard
1205 output.
1206 -p Turn on privileged mode. In this mode, the $ENV and
1207 $BASH_ENV files are not processed, shell functions are
1208 not inherited from the environment, and the SHELLOPTS,
1209 BASHOPTS, CDPATH, and GLOBIGNORE variables, if they
1210 appear in the environment, are ignored. If the shell is
1211 started with the effective user (group) id not equal to
1212 the real user (group) id, and the -p option is not sup‐
1213 plied, these actions are taken and the effective user id
1214 is set to the real user id. If the -p option is sup‐
1215 plied at startup, the effective user id is not reset.
1216 Turning this option off causes the effective user and
1217 group ids to be set to the real user and group ids.
1218 -t Exit after reading and executing one command.
1219 -u Treat unset variables and parameters other than the spe‐
1220 cial parameters "@" and "*" as an error when performing
1221 parameter expansion. If expansion is attempted on an
1222 unset variable or parameter, the shell prints an error
1223 message, and, if not interactive, exits with a non-zero
1224 status.
1225 -v Print shell input lines as they are read.
1226 -x After expanding each simple command, for command, case
1227 command, select command, or arithmetic for command, dis‐
1228 play the expanded value of PS4, followed by the command
1229 and its expanded arguments or associated word list.
1230 -B The shell performs brace expansion (see Brace Expansion
1231 above). This is on by default.
1232 -C If set, bash does not overwrite an existing file with
1233 the >, >&, and <> redirection operators. This may be
1234 overridden when creating output files by using the redi‐
1235 rection operator >| instead of >.
1236 -E If set, any trap on ERR is inherited by shell functions,
1237 command substitutions, and commands executed in a sub‐
1238 shell environment. The ERR trap is normally not inher‐
1239 ited in such cases.
1240 -H Enable ! style history substitution. This option is on
1241 by default when the shell is interactive.
1242 -P If set, the shell does not resolve symbolic links when
1243 executing commands such as cd that change the current
1244 working directory. It uses the physical directory
1245 structure instead. By default, bash follows the logical
1246 chain of directories when performing commands which
1247 change the current directory.
1248 -T If set, any traps on DEBUG and RETURN are inherited by
1249 shell functions, command substitutions, and commands
1250 executed in a subshell environment. The DEBUG and
1251 RETURN traps are normally not inherited in such cases.
1252 -- If no arguments follow this option, then the positional
1253 parameters are unset. Otherwise, the positional parame‐
1254 ters are set to the args, even if some of them begin
1255 with a -.
1256 - Signal the end of options, cause all remaining args to
1257 be assigned to the positional parameters. The -x and -v
1258 options are turned off. If there are no args, the posi‐
1259 tional parameters remain unchanged.
1260 The options are off by default unless otherwise noted. Using +
1262 rather than - causes these options to be turned off. The
1263 options can also be specified as arguments to an invocation of
1264 the shell. The current set of options may be found in $-. The
1265 return status is always true unless an invalid option is encoun‐
1266 tered.
1267 shift [n]
1269 The positional parameters from n+1 ... are renamed to $1 ....
1270 Parameters represented by the numbers $# down to $#-n+1 are
1271 unset. n must be a non-negative number less than or equal to
1272 $#. If n is 0, no parameters are changed. If n is not given,
1273 it is assumed to be 1. If n is greater than $#, the positional
1274 parameters are not changed. The return status is greater than
1275 zero if n is greater than $# or less than zero; otherwise 0.
1276 shopt [-pqsu] [-o] [optname ...]
1278 Toggle the values of settings controlling optional shell behav‐
1279 ior. The settings can be either those listed below, or, if the
1280 -o option is used, those available with the -o option to the set
1281 builtin command. With no options, or with the -p option, a list
1282 of all settable options is displayed, with an indication of
1283 whether or not each is set; if optnames are supplied, the output
1284 is restricted to those options. The -p option causes output to
1285 be displayed in a form that may be reused as input. Other
1286 options have the following meanings:
1287 -s Enable (set) each optname.
1288 -u Disable (unset) each optname.
1289 -q Suppresses normal output (quiet mode); the return status
1290 indicates whether the optname is set or unset. If multi‐
1291 ple optname arguments are given with -q, the return sta‐
1292 tus is zero if all optnames are enabled; non-zero other‐
1293 wise.
1294 -o Restricts the values of optname to be those defined for
1295 the -o option to the set builtin.
1296 If either -s or -u is used with no optname arguments, shopt
1298 shows only those options which are set or unset, respectively.
1299 Unless otherwise noted, the shopt options are disabled (unset)
1300 by default.
1301 The return status when listing options is zero if all optnames
1303 are enabled, non-zero otherwise. When setting or unsetting
1304 options, the return status is zero unless an optname is not a
1305 valid shell option.
1306 The list of shopt options is:
1308 assoc_expand_once
1310 If set, the shell suppresses multiple evaluation of
1311 associative array subscripts during arithmetic expres‐
1312 sion evaluation, while executing builtins that can per‐
1313 form variable assignments, and while executing builtins
1314 that perform array dereferencing.
1315 autocd If set, a command name that is the name of a directory
1316 is executed as if it were the argument to the cd com‐
1317 mand. This option is only used by interactive shells.
1318 cdable_vars
1319 If set, an argument to the cd builtin command that is
1320 not a directory is assumed to be the name of a variable
1321 whose value is the directory to change to.
1322 cdspell If set, minor errors in the spelling of a directory com‐
1323 ponent in a cd command will be corrected. The errors
1324 checked for are transposed characters, a missing charac‐
1325 ter, and one character too many. If a correction is
1326 found, the corrected filename is printed, and the com‐
1327 mand proceeds. This option is only used by interactive
1328 shells.
1329 checkhash
1330 If set, bash checks that a command found in the hash ta‐
1331 ble exists before trying to execute it. If a hashed
1332 command no longer exists, a normal path search is per‐
1333 formed.
1334 checkjobs
1335 If set, bash lists the status of any stopped and running
1336 jobs before exiting an interactive shell. If any jobs
1337 are running, this causes the exit to be deferred until a
1338 second exit is attempted without an intervening command
1339 (see JOB CONTROL above). The shell always postpones
1340 exiting if any jobs are stopped.
1341 checkwinsize
1342 If set, bash checks the window size after each external
1343 (non-builtin) command and, if necessary, updates the
1344 values of LINES and COLUMNS. This option is enabled by
1345 default.
1346 cmdhist If set, bash attempts to save all lines of a multiple-
1347 line command in the same history entry. This allows
1348 easy re-editing of multi-line commands. This option is
1349 enabled by default, but only has an effect if command
1350 history is enabled, as described above under HISTORY.
1351 compat31
1352 If set, bash changes its behavior to that of version 3.1
1353 with respect to quoted arguments to the [[ conditional
1354 command's =~ operator and locale-specific string compar‐
1355 ison when using the [[ conditional command's < and >
1356 operators. Bash versions prior to bash-4.1 use ASCII
1357 collation and strcmp(3); bash-4.1 and later use the cur‐
1358 rent locale's collation sequence and strcoll(3).
1359 compat32
1360 If set, bash changes its behavior to that of version 3.2
1361 with respect to locale-specific string comparison when
1362 using the [[ conditional command's < and > operators
1363 (see previous item) and the effect of interrupting a
1364 command list. Bash versions 3.2 and earlier continue
1365 with the next command in the list after one terminates
1366 due to an interrupt.
1367 compat40
1368 If set, bash changes its behavior to that of version 4.0
1369 with respect to locale-specific string comparison when
1370 using the [[ conditional command's < and > operators
1371 (see description of compat31) and the effect of inter‐
1372 rupting a command list. Bash versions 4.0 and later
1373 interrupt the list as if the shell received the inter‐
1374 rupt; previous versions continue with the next command
1375 in the list.
1376 compat41
1377 If set, bash, when in posix mode, treats a single quote
1378 in a double-quoted parameter expansion as a special
1379 character. The single quotes must match (an even num‐
1380 ber) and the characters between the single quotes are
1381 considered quoted. This is the behavior of posix mode
1382 through version 4.1. The default bash behavior remains
1383 as in previous versions.
1384 compat42
1385 If set, bash does not process the replacement string in
1386 the pattern substitution word expansion using quote
1387 removal.
1388 compat43
1389 If set, bash does not print a warning message if an
1390 attempt is made to use a quoted compound array assign‐
1391 ment as an argument to declare, makes word expansion
1392 errors non-fatal errors that cause the current command
1393 to fail (the default behavior is to make them fatal
1394 errors that cause the shell to exit), and does not reset
1395 the loop state when a shell function is executed (this
1396 allows break or continue in a shell function to affect
1397 loops in the caller's context).
1398 compat44
1399 If set, bash saves the positional parameters to
1400 BASH_ARGV and BASH_ARGC before they are used, regardless
1401 of whether or not extended debugging mode is enabled.
1402 complete_fullquote
1403 If set, bash quotes all shell metacharacters in file‐
1404 names and directory names when performing completion.
1405 If not set, bash removes metacharacters such as the dol‐
1406 lar sign from the set of characters that will be quoted
1407 in completed filenames when these metacharacters appear
1408 in shell variable references in words to be completed.
1409 This means that dollar signs in variable names that
1410 expand to directories will not be quoted; however, any
1411 dollar signs appearing in filenames will not be quoted,
1412 either. This is active only when bash is using back‐
1413 slashes to quote completed filenames. This variable is
1414 set by default, which is the default bash behavior in
1415 versions through 4.2.
1416 direxpand
1417 If set, bash replaces directory names with the results
1418 of word expansion when performing filename completion.
1419 This changes the contents of the readline editing buf‐
1420 fer. If not set, bash attempts to preserve what the
1421 user typed.
1422 dirspell
1423 If set, bash attempts spelling correction on directory
1424 names during word completion if the directory name ini‐
1425 tially supplied does not exist.
1426 dotglob If set, bash includes filenames beginning with a `.' in
1427 the results of pathname expansion. The filenames ``.''
1428 and ``..'' must always be matched explicitly, even if
1429 dotglob is set.
1430 execfail
1431 If set, a non-interactive shell will not exit if it can‐
1432 not execute the file specified as an argument to the
1433 exec builtin command. An interactive shell does not
1434 exit if exec fails.
1435 expand_aliases
1436 If set, aliases are expanded as described above under
1437 ALIASES. This option is enabled by default for interac‐
1438 tive shells.
1439 extdebug
1440 If set at shell invocation, arrange to execute the
1441 debugger profile before the shell starts, identical to
1442 the --debugger option. If set after invocation, behav‐
1443 ior intended for use by debuggers is enabled:
1444 1. The -F option to the declare builtin displays the
1445 source file name and line number corresponding to
1446 each function name supplied as an argument.
1447 2. If the command run by the DEBUG trap returns a
1448 non-zero value, the next command is skipped and
1449 not executed.
1450 3. If the command run by the DEBUG trap returns a
1451 value of 2, and the shell is executing in a sub‐
1452 routine (a shell function or a shell script exe‐
1453 cuted by the . or source builtins), the shell
1454 simulates a call to return.
1455 4. BASH_ARGC and BASH_ARGV are updated as described
1456 in their descriptions above.
1457 5. Function tracing is enabled: command substitu‐
1458 tion, shell functions, and subshells invoked with
1459 ( command ) inherit the DEBUG and RETURN traps.
1460 6. Error tracing is enabled: command substitution,
1461 shell functions, and subshells invoked with (
1462 command ) inherit the ERR trap.
1463 extglob If set, the extended pattern matching features described
1464 above under Pathname Expansion are enabled.
1465 extquote
1466 If set, $'string' and $"string" quoting is performed
1467 within ${parameter} expansions enclosed in double
1468 quotes. This option is enabled by default.
1469 failglob
1470 If set, patterns which fail to match filenames during
1471 pathname expansion result in an expansion error.
1472 force_fignore
1473 If set, the suffixes specified by the FIGNORE shell
1474 variable cause words to be ignored when performing word
1475 completion even if the ignored words are the only possi‐
1476 ble completions. See SHELL VARIABLES above for a
1477 description of FIGNORE. This option is enabled by
1478 default.
1479 globasciiranges
1480 If set, range expressions used in pattern matching
1481 bracket expressions (see Pattern Matching above) behave
1482 as if in the traditional C locale when performing com‐
1483 parisons. That is, the current locale's collating
1484 sequence is not taken into account, so b will not col‐
1485 late between A and B, and upper-case and lower-case
1486 ASCII characters will collate together.
1487 globstar
1488 If set, the pattern ** used in a pathname expansion con‐
1489 text will match all files and zero or more directories
1490 and subdirectories. If the pattern is followed by a /,
1491 only directories and subdirectories match.
1492 gnu_errfmt
1493 If set, shell error messages are written in the standard
1494 GNU error message format.
1495 histappend
1496 If set, the history list is appended to the file named
1497 by the value of the HISTFILE variable when the shell
1498 exits, rather than overwriting the file.
1499 histreedit
1500 If set, and readline is being used, a user is given the
1501 opportunity to re-edit a failed history substitution.
1502 histverify
1503 If set, and readline is being used, the results of his‐
1504 tory substitution are not immediately passed to the
1505 shell parser. Instead, the resulting line is loaded
1506 into the readline editing buffer, allowing further modi‐
1507 fication.
1508 hostcomplete
1509 If set, and readline is being used, bash will attempt to
1510 perform hostname completion when a word containing a @
1511 is being completed (see Completing under READLINE
1512 above). This is enabled by default.
1513 huponexit
1514 If set, bash will send SIGHUP to all jobs when an inter‐
1515 active login shell exits.
1516 inherit_errexit
1517 If set, command substitution inherits the value of the
1518 errexit option, instead of unsetting it in the subshell
1519 environment. This option is enabled when posix mode is
1520 enabled.
1521 interactive_comments
1522 If set, allow a word beginning with # to cause that word
1523 and all remaining characters on that line to be ignored
1524 in an interactive shell (see COMMENTS above). This
1525 option is enabled by default.
1526 lastpipe
1527 If set, and job control is not active, the shell runs
1528 the last command of a pipeline not executed in the back‐
1529 ground in the current shell environment.
1530 lithist If set, and the cmdhist option is enabled, multi-line
1531 commands are saved to the history with embedded newlines
1532 rather than using semicolon separators where possible.
1533 localvar_inherit
1534 If set, local variables inherit the value and attributes
1535 of a variable of the same name that exists at a previous
1536 scope before any new value is assigned. The nameref
1537 attribute is not inherited.
1538 localvar_unset
1539 If set, calling unset on local variables in previous
1540 function scopes marks them so subsequent lookups find
1541 them unset until that function returns. This is identi‐
1542 cal to the behavior of unsetting local variables at the
1543 current function scope.
1544 login_shell
1545 The shell sets this option if it is started as a login
1546 shell (see INVOCATION above). The value may not be
1547 changed.
1548 mailwarn
1549 If set, and a file that bash is checking for mail has
1550 been accessed since the last time it was checked, the
1551 message ``The mail in mailfile has been read'' is dis‐
1552 played.
1553 no_empty_cmd_completion
1554 If set, and readline is being used, bash will not
1555 attempt to search the PATH for possible completions when
1556 completion is attempted on an empty line.
1557 nocaseglob
1558 If set, bash matches filenames in a case-insensitive
1559 fashion when performing pathname expansion (see Pathname
1560 Expansion above).
1561 nocasematch
1562 If set, bash matches patterns in a case-insensitive
1563 fashion when performing matching while executing case or
1564 [[ conditional commands, when performing pattern substi‐
1565 tution word expansions, or when filtering possible com‐
1566 pletions as part of programmable completion.
1567 nullglob
1568 If set, bash allows patterns which match no files (see
1569 Pathname Expansion above) to expand to a null string,
1570 rather than themselves.
1571 progcomp
1572 If set, the programmable completion facilities (see Pro‐
1573 grammable Completion above) are enabled. This option is
1574 enabled by default.
1575 progcomp_alias
1576 If set, and programmable completion is enabled, bash
1577 treats a command name that doesn't have any completions
1578 as a possible alias and attempts alias expansion. If it
1579 has an alias, bash attempts programmable completion
1580 using the command word resulting from the expanded
1581 alias.
1582 promptvars
1583 If set, prompt strings undergo parameter expansion, com‐
1584 mand substitution, arithmetic expansion, and quote
1585 removal after being expanded as described in PROMPTING
1586 above. This option is enabled by default.
1587 restricted_shell
1588 The shell sets this option if it is started in
1589 restricted mode (see RESTRICTED SHELL below). The value
1590 may not be changed. This is not reset when the startup
1591 files are executed, allowing the startup files to dis‐
1592 cover whether or not a shell is restricted.
1593 shift_verbose
1594 If set, the shift builtin prints an error message when
1595 the shift count exceeds the number of positional parame‐
1596 ters.
1597 sourcepath
1598 If set, the source (.) builtin uses the value of PATH to
1599 find the directory containing the file supplied as an
1600 argument. This option is enabled by default.
1601 xpg_echo
1602 If set, the echo builtin expands backslash-escape
1603 sequences by default.
1604 suspend [-f]
1606 Suspend the execution of this shell until it receives a SIGCONT
1607 signal. A login shell cannot be suspended; the -f option can be
1608 used to override this and force the suspension. The return sta‐
1609 tus is 0 unless the shell is a login shell and -f is not sup‐
1610 plied, or if job control is not enabled.
1611 test expr
1613 [ expr ]
1614 Return a status of 0 (true) or 1 (false) depending on the evalu‐
1615 ation of the conditional expression expr. Each operator and op‐
1616 erand must be a separate argument. Expressions are composed of
1617 the primaries described above under CONDITIONAL EXPRESSIONS.
1618 test does not accept any options, nor does it accept and ignore
1619 an argument of -- as signifying the end of options.
1620 Expressions may be combined using the following operators,
1622 listed in decreasing order of precedence. The evaluation
1623 depends on the number of arguments; see below. Operator prece‐
1624 dence is used when there are five or more arguments.
1625 ! expr True if expr is false.
1626 ( expr )
1627 Returns the value of expr. This may be used to override
1628 the normal precedence of operators.
1629 expr1 -a expr2
1630 True if both expr1 and expr2 are true.
1631 expr1 -o expr2
1632 True if either expr1 or expr2 is true.
1633 test and [ evaluate conditional expressions using a set of rules
1635 based on the number of arguments.
1636 0 arguments
1638 The expression is false.
1639 1 argument
1640 The expression is true if and only if the argument is not
1641 null.
1642 2 arguments
1643 If the first argument is !, the expression is true if and
1644 only if the second argument is null. If the first argu‐
1645 ment is one of the unary conditional operators listed
1646 above under CONDITIONAL EXPRESSIONS, the expression is
1647 true if the unary test is true. If the first argument is
1648 not a valid unary conditional operator, the expression is
1649 false.
1650 3 arguments
1651 The following conditions are applied in the order listed.
1652 If the second argument is one of the binary conditional
1653 operators listed above under CONDITIONAL EXPRESSIONS, the
1654 result of the expression is the result of the binary test
1655 using the first and third arguments as operands. The -a
1656 and -o operators are considered binary operators when
1657 there are three arguments. If the first argument is !,
1658 the value is the negation of the two-argument test using
1659 the second and third arguments. If the first argument is
1660 exactly ( and the third argument is exactly ), the result
1661 is the one-argument test of the second argument. Other‐
1662 wise, the expression is false.
1663 4 arguments
1664 If the first argument is !, the result is the negation of
1665 the three-argument expression composed of the remaining
1666 arguments. Otherwise, the expression is parsed and eval‐
1667 uated according to precedence using the rules listed
1668 above.
1669 5 or more arguments
1670 The expression is parsed and evaluated according to
1671 precedence using the rules listed above.
1672 When used with test or [, the < and > operators sort lexico‐
1674 graphically using ASCII ordering.
1675 times Print the accumulated user and system times for the shell and
1677 for processes run from the shell. The return status is 0.
1678 trap [-lp] [[arg] sigspec ...]
1680 The command arg is to be read and executed when the shell
1681 receives signal(s) sigspec. If arg is absent (and there is a
1682 single sigspec) or -, each specified signal is reset to its
1683 original disposition (the value it had upon entrance to the
1684 shell). If arg is the null string the signal specified by each
1685 sigspec is ignored by the shell and by the commands it invokes.
1686 If arg is not present and -p has been supplied, then the trap
1687 commands associated with each sigspec are displayed. If no
1688 arguments are supplied or if only -p is given, trap prints the
1689 list of commands associated with each signal. The -l option
1690 causes the shell to print a list of signal names and their cor‐
1691 responding numbers. Each sigspec is either a signal name
1692 defined in <signal.h>, or a signal number. Signal names are
1693 case insensitive and the SIG prefix is optional.
1694 If a sigspec is EXIT (0) the command arg is executed on exit
1696 from the shell. If a sigspec is DEBUG, the command arg is exe‐
1697 cuted before every simple command, for command, case command,
1698 select command, every arithmetic for command, and before the
1699 first command executes in a shell function (see SHELL GRAMMAR
1700 above). Refer to the description of the extdebug option to the
1701 shopt builtin for details of its effect on the DEBUG trap. If a
1702 sigspec is RETURN, the command arg is executed each time a shell
1703 function or a script executed with the . or source builtins fin‐
1704 ishes executing.
1705 If a sigspec is ERR, the command arg is executed whenever a
1707 pipeline (which may consist of a single simple command), a list,
1708 or a compound command returns a non-zero exit status, subject to
1709 the following conditions. The ERR trap is not executed if the
1710 failed command is part of the command list immediately following
1711 a while or until keyword, part of the test in an if statement,
1712 part of a command executed in a && or || list except the command
1713 following the final && or ||, any command in a pipeline but the
1714 last, or if the command's return value is being inverted using
1715 !. These are the same conditions obeyed by the errexit (-e)
1716 option.
1717 Signals ignored upon entry to the shell cannot be trapped, reset
1719 or listed. Trapped signals that are not being ignored are reset
1720 to their original values in a subshell or subshell environment
1721 when one is created. The return status is false if any sigspec
1722 is invalid; otherwise trap returns true.
1723 type [-aftpP] name [name ...]
1725 With no options, indicate how each name would be interpreted if
1726 used as a command name. If the -t option is used, type prints a
1727 string which is one of alias, keyword, function, builtin, or
1728 file if name is an alias, shell reserved word, function,
1729 builtin, or disk file, respectively. If the name is not found,
1730 then nothing is printed, and an exit status of false is
1731 returned. If the -p option is used, type either returns the
1732 name of the disk file that would be executed if name were speci‐
1733 fied as a command name, or nothing if ``type -t name'' would not
1734 return file. The -P option forces a PATH search for each name,
1735 even if ``type -t name'' would not return file. If a command is
1736 hashed, -p and -P print the hashed value, which is not necessar‐
1737 ily the file that appears first in PATH. If the -a option is
1738 used, type prints all of the places that contain an executable
1739 named name. This includes aliases and functions, if and only if
1740 the -p option is not also used. The table of hashed commands is
1741 not consulted when using -a. The -f option suppresses shell
1742 function lookup, as with the command builtin. type returns true
1743 if all of the arguments are found, false if any are not found.
1744 ulimit [-HSabcdefiklmnpqrstuvxPT [limit]]
1746 Provides control over the resources available to the shell and
1747 to processes started by it, on systems that allow such control.
1748 The -H and -S options specify that the hard or soft limit is set
1749 for the given resource. A hard limit cannot be increased by a
1750 non-root user once it is set; a soft limit may be increased up
1751 to the value of the hard limit. If neither -H nor -S is speci‐
1752 fied, both the soft and hard limits are set. The value of limit
1753 can be a number in the unit specified for the resource or one of
1754 the special values hard, soft, or unlimited, which stand for the
1755 current hard limit, the current soft limit, and no limit,
1756 respectively. If limit is omitted, the current value of the
1757 soft limit of the resource is printed, unless the -H option is
1758 given. When more than one resource is specified, the limit name
1759 and unit are printed before the value. Other options are inter‐
1760 preted as follows:
1761 -a All current limits are reported
1762 -b The maximum socket buffer size
1763 -c The maximum size of core files created
1764 -d The maximum size of a process's data segment
1765 -e The maximum scheduling priority ("nice")
1766 -f The maximum size of files written by the shell and its
1767 children
1768 -i The maximum number of pending signals
1769 -k The maximum number of kqueues that may be allocated
1770 -l The maximum size that may be locked into memory
1771 -m The maximum resident set size (many systems do not honor
1772 this limit)
1773 -n The maximum number of open file descriptors (most systems
1774 do not allow this value to be set)
1775 -p The pipe size in 512-byte blocks (this may not be set)
1776 -q The maximum number of bytes in POSIX message queues
1777 -r The maximum real-time scheduling priority
1778 -s The maximum stack size
1779 -t The maximum amount of cpu time in seconds
1780 -u The maximum number of processes available to a single
1781 user
1782 -v The maximum amount of virtual memory available to the
1783 shell and, on some systems, to its children
1784 -x The maximum number of file locks
1785 -P The maximum number of pseudoterminals
1786 -T The maximum number of threads
1787 If limit is given, and the -a option is not used, limit is the
1789 new value of the specified resource. If no option is given,
1790 then -f is assumed. Values are in 1024-byte increments, except
1791 for -t, which is in seconds; -p, which is in units of 512-byte
1792 blocks; -P, -T, -b, -k, -n, and -u, which are unscaled values;
1793 and, when in posix mode, -c and -f, which are in 512-byte incre‐
1794 ments. The return status is 0 unless an invalid option or argu‐
1795 ment is supplied, or an error occurs while setting a new limit.
1796 In POSIX Mode 512-byte blocks are used for the `-c' and `-f'
1797 options.
1798 umask [-p] [-S] [mode]
1800 The user file-creation mask is set to mode. If mode begins with
1801 a digit, it is interpreted as an octal number; otherwise it is
1802 interpreted as a symbolic mode mask similar to that accepted by
1803 chmod(1). If mode is omitted, the current value of the mask is
1804 printed. The -S option causes the mask to be printed in sym‐
1805 bolic form; the default output is an octal number. If the -p
1806 option is supplied, and mode is omitted, the output is in a form
1807 that may be reused as input. The return status is 0 if the mode
1808 was successfully changed or if no mode argument was supplied,
1809 and false otherwise.
1810 unalias [-a] [name ...]
1812 Remove each name from the list of defined aliases. If -a is
1813 supplied, all alias definitions are removed. The return value
1814 is true unless a supplied name is not a defined alias.
1815 unset [-fv] [-n] [name ...]
1817 For each name, remove the corresponding variable or function.
1818 If the -v option is given, each name refers to a shell variable,
1819 and that variable is removed. Read-only variables may not be
1820 unset. If -f is specified, each name refers to a shell func‐
1821 tion, and the function definition is removed. If the -n option
1822 is supplied, and name is a variable with the nameref attribute,
1823 name will be unset rather than the variable it references. -n
1824 has no effect if the -f option is supplied. If no options are
1825 supplied, each name refers to a variable; if there is no vari‐
1826 able by that name, any function with that name is unset. Each
1827 unset variable or function is removed from the environment
1828 passed to subsequent commands. If any of COMP_WORDBREAKS, RAN‐
1829 DOM, SECONDS, LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are
1830 unset, they lose their special properties, even if they are sub‐
1831 sequently reset. The exit status is true unless a name is read‐
1832 only.
1833 wait [-fn] [id ...]
1835 Wait for each specified child process and return its termination
1836 status. Each id may be a process ID or a job specification; if
1837 a job spec is given, all processes in that job's pipeline are
1838 waited for. If id is not given, all currently active child pro‐
1839 cesses are waited for, and the return status is zero. If the -n
1840 option is supplied, wait waits for any job to terminate and
1841 returns its exit status. If the -f option is supplied, and job
1842 control is enabled, wait forces id to terminate before returning
1843 its status, instead of returning when it changes status. If id
1844 specifies a non-existent process or job, the return status is
1845 127. Otherwise, the return status is the exit status of the
1846 last process or job waited for.
1847
1849 bash(1), sh(1)
1850GNU Bash 5.0 2004 Apr 20 BASH_BUILTINS(1)