1BASH_BUILTINS(1) General Commands Manual BASH_BUILTINS(1)
2
6 bash, :, ., [, alias, bg, bind, break, builtin, cd, command, compgen,
7 complete, continue, declare, dirs, disown, echo, enable, eval, exec,
8 exit, export, fc, fg, getopts, hash, help, history, jobs, kill, let,
9 local, logout, popd, printf, pushd, pwd, read, readonly, return, set,
10 shift, shopt, source, suspend, test, times, trap, type, typeset,
11 ulimit, umask, unalias, unset, wait - bash built-in commands, see
12 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. For example, the :, true, false, and test builtins do not
18 accept options.
19 : [arguments]
20 No effect; the command does nothing beyond expanding arguments
21 and performing any specified redirections. A zero exit code is
22 returned.
23 . filename [arguments]
25 source filename [arguments]
26 Read and execute commands from filename in the current shell
27 environment and return the exit status of the last command exe‐
28 cuted from filename. If filename does not contain a slash, file
29 names in PATH are used to find the directory containing file‐
30 name. The file searched for in PATH need not be executable.
31 When bash is not in posix mode, the current directory is
32 searched if no file is found in PATH. If the sourcepath option
33 to the shopt builtin command is turned off, the PATH is not
34 searched. If any arguments are supplied, they become the posi‐
35 tional parameters when filename is executed. Otherwise the
36 positional parameters are unchanged. The return status is the
37 status of the last command exited within the script (0 if no
38 commands are executed), and false if filename is not found or
39 cannot be read.
40 alias [-p] [name[=value] ...]
42 Alias with no arguments or with the -p option prints the list of
43 aliases in the form alias name=value on standard output. When
44 arguments are supplied, an alias is defined for each name whose
45 value is given. A trailing space in value causes the next word
46 to be checked for alias substitution when the alias is expanded.
47 For each name in the argument list for which no value is sup‐
48 plied, the name and value of the alias is printed. Alias
49 returns true unless a name is given for which no alias has been
50 defined.
51 bg [jobspec ...]
53 Resume each suspended job jobspec in the background, as if it
54 had been started with &. If jobspec is not present, the shell's
55 notion of the current job is used. bg jobspec returns 0 unless
56 run when job control is disabled or, when run with job control
57 enabled, any specified jobspec was not found or was started
58 without job control.
59 bind [-m keymap] [-lpsvPSV]
61 bind [-m keymap] [-q function] [-u function] [-r keyseq]
62 bind [-m keymap] -f filename
63 bind [-m keymap] -x keyseq:shell-command
64 bind [-m keymap] keyseq:function-name
65 bind readline-command
66 Display current readline key and function bindings, bind a key
67 sequence to a readline function or macro, or set a readline
68 variable. Each non-option argument is a command as it would
69 appear in .inputrc, but each binding or command must be passed
70 as a separate argument; e.g., '"\C-x\C-r": re-read-init-file'.
71 Options, if supplied, have the following meanings:
72 -m keymap
73 Use keymap as the keymap to be affected by the subsequent
74 bindings. Acceptable keymap names are emacs, emacs-stan‐
75 dard, emacs-meta, emacs-ctlx, vi, vi-move, vi-command,
76 and vi-insert. vi is equivalent to vi-command; emacs is
77 equivalent to emacs-standard.
78 -l List the names of all readline functions.
79 -p Display readline function names and bindings in such a
80 way that they can be re-read.
81 -P List current readline function names and bindings.
82 -v Display readline variable names and values in such a way
83 that they can be re-read.
84 -V List current readline variable names and values.
85 -s Display readline key sequences bound to macros and the
86 strings they output in such a way that they can be re-
87 read.
88 -S Display readline key sequences bound to macros and the
89 strings they output.
90 -f filename
91 Read key bindings from filename.
92 -q function
93 Query about which keys invoke the named function.
94 -u function
95 Unbind all keys bound to the named function.
96 -r keyseq
97 Remove any current binding for keyseq.
98 -x keyseq:shell-command
99 Cause shell-command to be executed whenever keyseq is
100 entered.
101 The return value is 0 unless an unrecognized option is given or
103 an error occurred.
104 break [n]
106 Exit from within a for, while, until, or select loop. If n is
107 specified, break n levels. n must be ≥ 1. If n is greater than
108 the number of enclosing loops, all enclosing loops are exited.
109 The return value is 0 unless the shell is not executing a loop
110 when break is executed.
111 builtin shell-builtin [arguments]
113 Execute the specified shell builtin, passing it arguments, and
114 return its exit status. This is useful when defining a function
115 whose name is the same as a shell builtin, retaining the func‐
116 tionality of the builtin within the function. The cd builtin is
117 commonly redefined this way. The return status is false if
118 shell-builtin is not a shell builtin command.
119 cd [-L|-P] [dir]
121 Change the current directory to dir. The variable HOME is the
122 default dir. The variable CDPATH defines the search path for
123 the directory containing dir. Alternative directory names in
124 CDPATH are separated by a colon (:). A null directory name in
125 CDPATH is the same as the current directory, i.e., ``.''. If
126 dir begins with a slash (/), then CDPATH is not used. The -P
127 option says to use the physical directory structure instead of
128 following symbolic links (see also the -P option to the set
129 builtin command); the -L option forces symbolic links to be fol‐
130 lowed. An argument of - is equivalent to $OLDPWD. If a non-
131 empty directory name from CDPATH is used, or if - is the first
132 argument, and the directory change is successful, the absolute
133 pathname of the new working directory is written to the standard
134 output. The return value is true if the directory was success‐
135 fully changed; false otherwise.
136 caller [expr]
138 Returns the context of any active subroutine call (a shell func‐
139 tion or a script executed with the . or source builtins. With‐
140 out expr, caller displays the line number and source filename of
141 the current subroutine call. If a non-negative integer is sup‐
142 plied as expr, caller displays the line number, subroutine name,
143 and source file corresponding to that position in the current
144 execution call stack. This extra information may be used, for
145 example, to print a stack trace. The current frame is frame 0.
146 The return value is 0 unless the shell is not executing a sub‐
147 routine call or expr does not correspond to a valid position in
148 the call stack.
149 command [-pVv] command [arg ...]
151 Run command with args suppressing the normal shell function
152 lookup. Only builtin commands or commands found in the PATH are
153 executed. If the -p option is given, the search for command is
154 performed using a default value for PATH that is guaranteed to
155 find all of the standard utilities. If either the -V or -v
156 option is supplied, a description of command is printed. The -v
157 option causes a single word indicating the command or file name
158 used to invoke command to be displayed; the -V option produces a
159 more verbose description. If the -V or -v option is supplied,
160 the exit status is 0 if command was found, and 1 if not. If
161 neither option is supplied and an error occurred or command can‐
162 not be found, the exit status is 127. Otherwise, the exit sta‐
163 tus of the command builtin is the exit status of command.
164 compgen [option] [word]
166 Generate possible completion matches for word according to the
167 options, which may be any option accepted by the complete
168 builtin with the exception of -p and -r, and write the matches
169 to the standard output. When using the -F or -C options, the
170 various shell variables set by the programmable completion
171 facilities, while available, will not have useful values.
172 The matches will be generated in the same way as if the program‐
174 mable completion code had generated them directly from a comple‐
175 tion specification with the same flags. If word is specified,
176 only those completions matching word will be displayed.
177 The return value is true unless an invalid option is supplied,
179 or no matches were generated.
180 complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W
182 wordlist] [-P prefix] [-S suffix]
183 [-X filterpat] [-F function] [-C command] name [name ...]
184 complete -pr [name ...]
185 Specify how arguments to each name should be completed. If the
186 -p option is supplied, or if no options are supplied, existing
187 completion specifications are printed in a way that allows them
188 to be reused as input. The -r option removes a completion spec‐
189 ification for each name, or, if no names are supplied, all com‐
190 pletion specifications.
191 The process of applying these completion specifications when
193 word completion is attempted is described above under Program‐
194 mable Completion.
195 Other options, if specified, have the following meanings. The
197 arguments to the -G, -W, and -X options (and, if necessary, the
198 -P and -S options) should be quoted to protect them from expan‐
199 sion before the complete builtin is invoked.
200 -o comp-option
201 The comp-option controls several aspects of the comp‐
202 spec's behavior beyond the simple generation of comple‐
203 tions. comp-option may be one of:
204 bashdefault
205 Perform the rest of the default bash completions
206 if the compspec generates no matches.
207 default Use readline's default filename completion if
208 the compspec generates no matches.
209 dirnames
210 Perform directory name completion if the comp‐
211 spec generates no matches.
212 filenames
213 Tell readline that the compspec generates file‐
214 names, so it can perform any filename-specific
215 processing (like adding a slash to directory
216 names or suppressing trailing spaces). Intended
217 to be used with shell functions.
218 nospace Tell readline not to append a space (the
219 default) to words completed at the end of the
220 line.
221 plusdirs
222 After any matches defined by the compspec are
223 generated, directory name completion is
224 attempted and any matches are added to the
225 results of the other actions.
226 -A action
227 The action may be one of the following to generate a
228 list of possible completions:
229 alias Alias names. May also be specified as -a.
230 arrayvar
231 Array variable names.
232 binding Readline key binding names.
233 builtin Names of shell builtin commands. May also be
234 specified as -b.
235 command Command names. May also be specified as -c.
236 directory
237 Directory names. May also be specified as -d.
238 disabled
239 Names of disabled shell builtins.
240 enabled Names of enabled shell builtins.
241 export Names of exported shell variables. May also be
242 specified as -e.
243 file File names. May also be specified as -f.
244 function
245 Names of shell functions.
246 group Group names. May also be specified as -g.
247 helptopic
248 Help topics as accepted by the help builtin.
249 hostname
250 Hostnames, as taken from the file specified by
251 the HOSTFILE shell variable.
252 job Job names, if job control is active. May also
253 be specified as -j.
254 keyword Shell reserved words. May also be specified as
255 -k.
256 running Names of running jobs, if job control is active.
257 service Service names. May also be specified as -s.
258 setopt Valid arguments for the -o option to the set
259 builtin.
260 shopt Shell option names as accepted by the shopt
261 builtin.
262 signal Signal names.
263 stopped Names of stopped jobs, if job control is active.
264 user User names. May also be specified as -u.
265 variable
266 Names of all shell variables. May also be spec‐
267 ified as -v.
268 -G globpat
269 The filename expansion pattern globpat is expanded to
270 generate the possible completions.
271 -W wordlist
272 The wordlist is split using the characters in the IFS
273 special variable as delimiters, and each resultant word
274 is expanded. The possible completions are the members
275 of the resultant list which match the word being com‐
276 pleted.
277 -C command
278 command is executed in a subshell environment, and its
279 output is used as the possible completions.
280 -F function
281 The shell function function is executed in the current
282 shell environment. When it finishes, the possible com‐
283 pletions are retrieved from the value of the COMPREPLY
284 array variable.
285 -X filterpat
286 filterpat is a pattern as used for filename expansion.
287 It is applied to the list of possible completions gener‐
288 ated by the preceding options and arguments, and each
289 completion matching filterpat is removed from the list.
290 A leading ! in filterpat negates the pattern; in this
291 case, any completion not matching filterpat is removed.
292 -P prefix
293 prefix is added at the beginning of each possible com‐
294 pletion after all other options have been applied.
295 -S suffix
296 suffix is appended to each possible completion after all
297 other options have been applied.
298 The return value is true unless an invalid option is supplied,
300 an option other than -p or -r is supplied without a name argu‐
301 ment, an attempt is made to remove a completion specification
302 for a name for which no specification exists, or an error occurs
303 adding a completion specification.
304 continue [n]
306 Resume the next iteration of the enclosing for, while, until, or
307 select loop. If n is specified, resume at the nth enclosing
308 loop. n must be ≥ 1. If n is greater than the number of
309 enclosing loops, the last enclosing loop (the ``top-level''
310 loop) is resumed. The return value is 0 unless the shell is not
311 executing a loop when continue is executed.
312 declare [-afFirtx] [-p] [name[=value] ...]
314 typeset [-afFirtx] [-p] [name[=value] ...]
315 Declare variables and/or give them attributes. If no names are
316 given then display the values of variables. The -p option will
317 display the attributes and values of each name. When -p is
318 used, additional options are ignored. The -F option inhibits
319 the display of function definitions; only the function name and
320 attributes are printed. If the extdebug shell option is enabled
321 using shopt, the source file name and line number where the
322 function is defined are displayed as well. The -F option
323 implies -f. The following options can be used to restrict out‐
324 put to variables with the specified attribute or to give vari‐
325 ables attributes:
326 -a Each name is an array variable (see Arrays above).
327 -f Use function names only.
328 -i The variable is treated as an integer; arithmetic evalua‐
329 tion (see ARITHMETIC EVALUATION ) is performed when the
330 variable is assigned a value.
331 -r Make names readonly. These names cannot then be assigned
332 values by subsequent assignment statements or unset.
333 -t Give each name the trace attribute. Traced functions
334 inherit the DEBUG and RETURN traps from the calling
335 shell. The trace attribute has no special meaning for
336 variables.
337 -x Mark names for export to subsequent commands via the
338 environment.
339 Using `+' instead of `-' turns off the attribute instead, with
341 the exception that +a may not be used to destroy an array vari‐
342 able. When used in a function, makes each name local, as with
343 the local command. If a variable name is followed by =value,
344 the value of the variable is set to value. The return value is
345 0 unless an invalid option is encountered, an attempt is made to
346 define a function using ``-f foo=bar'', an attempt is made to
347 assign a value to a readonly variable, an attempt is made to
348 assign a value to an array variable without using the compound
349 assignment syntax (see Arrays above), one of the names is not a
350 valid shell variable name, an attempt is made to turn off read‐
351 only status for a readonly variable, an attempt is made to turn
352 off array status for an array variable, or an attempt is made to
353 display a non-existent function with -f.
354 dirs [-clpv] [+n] [-n]
356 Without options, displays the list of currently remembered
357 directories. The default display is on a single line with
358 directory names separated by spaces. Directories are added to
359 the list with the pushd command; the popd command removes
360 entries from the list.
361 +n Displays the nth entry counting from the left of the list
362 shown by dirs when invoked without options, starting with
363 zero.
364 -n Displays the nth entry counting from the right of the
365 list shown by dirs when invoked without options, starting
366 with zero.
367 -c Clears the directory stack by deleting all of the
368 entries.
369 -l Produces a longer listing; the default listing format
370 uses a tilde to denote the home directory.
371 -p Print the directory stack with one entry per line.
372 -v Print the directory stack with one entry per line, pre‐
373 fixing each entry with its index in the stack.
374 The return value is 0 unless an invalid option is supplied or n
376 indexes beyond the end of the directory stack.
377 disown [-ar] [-h] [jobspec ...]
379 Without options, each jobspec is removed from the table of
380 active jobs. If the -h option is given, each jobspec is not
381 removed from the table, but is marked so that SIGHUP is not sent
382 to the job if the shell receives a SIGHUP. If no jobspec is
383 present, and neither the -a nor the -r option is supplied, the
384 current job is used. If no jobspec is supplied, the -a option
385 means to remove or mark all jobs; the -r option without a job‐
386 spec argument restricts operation to running jobs. The return
387 value is 0 unless a jobspec does not specify a valid job.
388 echo [-neE] [arg ...]
390 Output the args, separated by spaces, followed by a newline.
391 The return status is always 0. If -n is specified, the trailing
392 newline is suppressed. If the -e option is given, interpreta‐
393 tion of the following backslash-escaped characters is enabled.
394 The -E option disables the interpretation of these escape char‐
395 acters, even on systems where they are interpreted by default.
396 The xpg_echo shell option may be used to dynamically determine
397 whether or not echo expands these escape characters by default.
398 echo does not interpret -- to mean the end of options. echo
399 interprets the following escape sequences:
400 \a alert (bell)
401 \b backspace
402 \c suppress trailing newline
403 \e an escape character
404 \f form feed
405 \n new line
406 \r carriage return
407 \t horizontal tab
408 \v vertical tab
409 \\ backslash
410 \0nnn the eight-bit character whose value is the octal value
411 nnn (zero to three octal digits)
412 \xHH the eight-bit character whose value is the hexadecimal
413 value HH (one or two hex digits)
414 enable [-adnps] [-f filename] [name ...]
416 Enable and disable builtin shell commands. Disabling a builtin
417 allows a disk command which has the same name as a shell builtin
418 to be executed without specifying a full pathname, even though
419 the shell normally searches for builtins before disk commands.
420 If -n is used, each name is disabled; otherwise, names are
421 enabled. For example, to use the test binary found via the PATH
422 instead of the shell builtin version, run ``enable -n test''.
423 The -f option means to load the new builtin command name from
424 shared object filename, on systems that support dynamic loading.
425 The -d option will delete a builtin previously loaded with -f.
426 If no name arguments are given, or if the -p option is supplied,
427 a list of shell builtins is printed. With no other option argu‐
428 ments, the list consists of all enabled shell builtins. If -n
429 is supplied, only disabled builtins are printed. If -a is sup‐
430 plied, the list printed includes all builtins, with an indica‐
431 tion of whether or not each is enabled. If -s is supplied, the
432 output is restricted to the POSIX special builtins. The return
433 value is 0 unless a name is not a shell builtin or there is an
434 error loading a new builtin from a shared object.
435 eval [arg ...]
437 The args are read and concatenated together into a single com‐
438 mand. This command is then read and executed by the shell, and
439 its exit status is returned as the value of eval. If there are
440 no args, or only null arguments, eval returns 0.
441 exec [-cl] [-a name] [command [arguments]]
443 If command is specified, it replaces the shell. No new process
444 is created. The arguments become the arguments to command. If
445 the -l option is supplied, the shell places a dash at the begin‐
446 ning of the zeroth arg passed to command. This is what login(1)
447 does. The -c option causes command to be executed with an empty
448 environment. If -a is supplied, the shell passes name as the
449 zeroth argument to the executed command. If command cannot be
450 executed for some reason, a non-interactive shell exits, unless
451 the shell option execfail is enabled, in which case it returns
452 failure. An interactive shell returns failure if the file can‐
453 not be executed. If command is not specified, any redirections
454 take effect in the current shell, and the return status is 0.
455 If there is a redirection error, the return status is 1.
456 exit [n]
458 Cause the shell to exit with a status of n. If n is omitted,
459 the exit status is that of the last command executed. A trap on
460 EXIT is executed before the shell terminates.
461 export [-fn] [name[=word]] ...
463 export -p
464 The supplied names are marked for automatic export to the envi‐
465 ronment of subsequently executed commands. If the -f option is
466 given, the names refer to functions. If no names are given, or
467 if the -p option is supplied, a list of all names that are
468 exported in this shell is printed. The -n option causes the
469 export property to be removed from each name. If a variable
470 name is followed by =word, the value of the variable is set to
471 word. export returns an exit status of 0 unless an invalid
472 option is encountered, one of the names is not a valid shell
473 variable name, or -f is supplied with a name that is not a func‐
474 tion.
475 fc [-e ename] [-nlr] [first] [last]
477 fc -s [pat=rep] [cmd]
478 Fix Command. In the first form, a range of commands from first
479 to last is selected from the history list. First and last may
480 be specified as a string (to locate the last command beginning
481 with that string) or as a number (an index into the history
482 list, where a negative number is used as an offset from the cur‐
483 rent command number). If last is not specified it is set to the
484 current command for listing (so that ``fc -l -10'' prints the
485 last 10 commands) and to first otherwise. If first is not spec‐
486 ified it is set to the previous command for editing and -16 for
487 listing.
488 The -n option suppresses the command numbers when listing. The
490 -r option reverses the order of the commands. If the -l option
491 is given, the commands are listed on standard output. Other‐
492 wise, the editor given by ename is invoked on a file containing
493 those commands. If ename is not given, the value of the FCEDIT
494 variable is used, and the value of EDITOR if FCEDIT is not set.
495 If neither variable is set, is used. When editing is complete,
496 the edited commands are echoed and executed.
497 In the second form, command is re-executed after each instance
499 of pat is replaced by rep. A useful alias to use with this is
500 ``r="fc -s"'', so that typing ``r cc'' runs the last command
501 beginning with ``cc'' and typing ``r'' re-executes the last com‐
502 mand.
503 If the first form is used, the return value is 0 unless an
505 invalid option is encountered or first or last specify history
506 lines out of range. If the -e option is supplied, the return
507 value is the value of the last command executed or failure if an
508 error occurs with the temporary file of commands. If the second
509 form is used, the return status is that of the command re-exe‐
510 cuted, unless cmd does not specify a valid history line, in
511 which case fc returns failure.
512 fg [jobspec]
514 Resume jobspec in the foreground, and make it the current job.
515 If jobspec is not present, the shell's notion of the current job
516 is used. The return value is that of the command placed into
517 the foreground, or failure if run when job control is disabled
518 or, when run with job control enabled, if jobspec does not spec‐
519 ify a valid job or jobspec specifies a job that was started
520 without job control.
521 getopts optstring name [args]
523 getopts is used by shell procedures to parse positional parame‐
524 ters. optstring contains the option characters to be recog‐
525 nized; if a character is followed by a colon, the option is
526 expected to have an argument, which should be separated from it
527 by white space. The colon and question mark characters may not
528 be used as option characters. Each time it is invoked, getopts
529 places the next option in the shell variable name, initializing
530 name if it does not exist, and the index of the next argument to
531 be processed into the variable OPTIND. OPTIND is initialized to
532 1 each time the shell or a shell script is invoked. When an
533 option requires an argument, getopts places that argument into
534 the variable OPTARG. The shell does not reset OPTIND automati‐
535 cally; it must be manually reset between multiple calls to
536 getopts within the same shell invocation if a new set of parame‐
537 ters is to be used.
538 When the end of options is encountered, getopts exits with a
540 return value greater than zero. OPTIND is set to the index of
541 the first non-option argument, and name is set to ?.
542 getopts normally parses the positional parameters, but if more
544 arguments are given in args, getopts parses those instead.
545 getopts can report errors in two ways. If the first character
547 of optstring is a colon, silent error reporting is used. In
548 normal operation diagnostic messages are printed when invalid
549 options or missing option arguments are encountered. If the
550 variable OPTERR is set to 0, no error messages will be dis‐
551 played, even if the first character of optstring is not a colon.
552 If an invalid option is seen, getopts places ? into name and, if
554 not silent, prints an error message and unsets OPTARG. If
555 getopts is silent, the option character found is placed in
556 OPTARG and no diagnostic message is printed.
557 If a required argument is not found, and getopts is not silent,
559 a question mark (?) is placed in name, OPTARG is unset, and a
560 diagnostic message is printed. If getopts is silent, then a
561 colon (:) is placed in name and OPTARG is set to the option
562 character found.
563 getopts returns true if an option, specified or unspecified, is
565 found. It returns false if the end of options is encountered or
566 an error occurs.
567 hash [-lr] [-p filename] [-dt] [name]
569 For each name, the full file name of the command is determined
570 by searching the directories in $PATH and remembered. If the -p
571 option is supplied, no path search is performed, and filename is
572 used as the full file name of the command. The -r option causes
573 the shell to forget all remembered locations. The -d option
574 causes the shell to forget the remembered location of each name.
575 If the -t option is supplied, the full pathname to which each
576 name corresponds is printed. If multiple name arguments are
577 supplied with -t, the name is printed before the hashed full
578 pathname. The -l option causes output to be displayed in a for‐
579 mat that may be reused as input. If no arguments are given, or
580 if only -l is supplied, information about remembered commands is
581 printed. The return status is true unless a name is not found
582 or an invalid option is supplied.
583 help [-s] [pattern]
585 Display helpful information about builtin commands. If pattern
586 is specified, help gives detailed help on all commands matching
587 pattern; otherwise help for all the builtins and shell control
588 structures is printed. The -s option restricts the information
589 displayed to a short usage synopsis. The return status is 0
590 unless no command matches pattern.
591 history [n]
593 history -c
594 history -d offset
595 history -anrw [filename]
596 history -p arg [arg ...]
597 history -s arg [arg ...]
598 With no options, display the command history list with line num‐
599 bers. Lines listed with a * have been modified. An argument of
600 n lists only the last n lines. If the shell variable HISTTIME‐
601 FORMAT is set and not null, it is used as a format string for
602 strftime(3) to display the time stamp associated with each dis‐
603 played history entry. No intervening blank is printed between
604 the formatted time stamp and the history line. If filename is
605 supplied, it is used as the name of the history file; if not,
606 the value of HISTFILE is used. Options, if supplied, have the
607 following meanings:
608 -c Clear the history list by deleting all the entries.
609 -d offset
610 Delete the history entry at position offset.
611 -a Append the ``new'' history lines (history lines entered
612 since the beginning of the current bash session) to the
613 history file.
614 -n Read the history lines not already read from the history
615 file into the current history list. These are lines
616 appended to the history file since the beginning of the
617 current bash session.
618 -r Read the contents of the history file and use them as the
619 current history.
620 -w Write the current history to the history file, overwrit‐
621 ing the history file's contents.
622 -p Perform history substitution on the following args and
623 display the result on the standard output. Does not
624 store the results in the history list. Each arg must be
625 quoted to disable normal history expansion.
626 -s Store the args in the history list as a single entry.
627 The last command in the history list is removed before
628 the args are added.
629 If the HISTTIMEFORMAT is set, the time stamp information associ‐
631 ated with each history entry is written to the history file.
632 The return value is 0 unless an invalid option is encountered,
633 an error occurs while reading or writing the history file, an
634 invalid offset is supplied as an argument to -d, or the history
635 expansion supplied as an argument to -p fails.
636 jobs [-lnprs] [ jobspec ... ]
638 jobs -x command [ args ... ]
639 The first form lists the active jobs. The options have the fol‐
640 lowing meanings:
641 -l List process IDs in addition to the normal information.
642 -p List only the process ID of the job's process group
643 leader.
644 -n Display information only about jobs that have changed
645 status since the user was last notified of their status.
646 -r Restrict output to running jobs.
647 -s Restrict output to stopped jobs.
648 If jobspec is given, output is restricted to information about
650 that job. The return status is 0 unless an invalid option is
651 encountered or an invalid jobspec is supplied.
652 If the -x option is supplied, jobs replaces any jobspec found in
654 command or args with the corresponding process group ID, and
655 executes command passing it args, returning its exit status.
656 kill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...
658 kill -l [sigspec | exit_status]
659 Send the signal named by sigspec or signum to the processes
660 named by pid or jobspec. sigspec is either a case-insensitive
661 signal name such as SIGKILL (with or without the SIG prefix) or
662 a signal number; signum is a signal number. If sigspec is not
663 present, then SIGTERM is assumed. An argument of -l lists the
664 signal names. If any arguments are supplied when -l is given,
665 the names of the signals corresponding to the arguments are
666 listed, and the return status is 0. The exit_status argument to
667 -l is a number specifying either a signal number or the exit
668 status of a process terminated by a signal. kill returns true
669 if at least one signal was successfully sent, or false if an
670 error occurs or an invalid option is encountered.
671 let arg [arg ...]
673 Each arg is an arithmetic expression to be evaluated (see ARITH‐
674 METIC EVALUATION). If the last arg evaluates to 0, let returns
675 1; 0 is returned otherwise.
676 local [option] [name[=value] ...]
678 For each argument, a local variable named name is created, and
679 assigned value. The option can be any of the options accepted
680 by declare. When local is used within a function, it causes the
681 variable name to have a visible scope restricted to that func‐
682 tion and its children. With no operands, local writes a list of
683 local variables to the standard output. It is an error to use
684 local when not within a function. The return status is 0 unless
685 local is used outside a function, an invalid name is supplied,
686 or name is a readonly variable.
687 logout Exit a login shell.
689 popd [-n] [+n] [-n]
691 Removes entries from the directory stack. With no arguments,
692 removes the top directory from the stack, and performs a cd to
693 the new top directory. Arguments, if supplied, have the follow‐
694 ing meanings:
695 +n Removes the nth entry counting from the left of the list
696 shown by dirs, starting with zero. For example: ``popd
697 +0'' removes the first directory, ``popd +1'' the second.
698 -n Removes the nth entry counting from the right of the list
699 shown by dirs, starting with zero. For example: ``popd
700 -0'' removes the last directory, ``popd -1'' the next to
701 last.
702 -n Suppresses the normal change of directory when removing
703 directories from the stack, so that only the stack is
704 manipulated.
705 If the popd command is successful, a dirs is performed as well,
707 and the return status is 0. popd returns false if an invalid
708 option is encountered, the directory stack is empty, a non-exis‐
709 tent directory stack entry is specified, or the directory change
710 fails.
711 printf [-v var] format [arguments]
713 Write the formatted arguments to the standard output under the
714 control of the format. The format is a character string which
715 contains three types of objects: plain characters, which are
716 simply copied to standard output, character escape sequences,
717 which are converted and copied to the standard output, and for‐
718 mat specifications, each of which causes printing of the next
719 successive argument. In addition to the standard printf(1) for‐
720 mats, %b causes printf to expand backslash escape sequences in
721 the corresponding argument (except that \c terminates output,
722 backslashes in \', \", and \? are not removed, and octal escapes
723 beginning with \0 may contain up to four digits), and %q causes
724 printf to output the corresponding argument in a format that can
725 be reused as shell input.
726 The -v option causes the output to be assigned to the variable
728 var rather than being printed to the standard output.
729 The format is reused as necessary to consume all of the argu‐
731 ments. If the format requires more arguments than are supplied,
732 the extra format specifications behave as if a zero value or
733 null string, as appropriate, had been supplied. The return
734 value is zero on success, non-zero on failure.
735 pushd [-n] [dir]
737 pushd [-n] [+n] [-n]
738 Adds a directory to the top of the directory stack, or rotates
739 the stack, making the new top of the stack the current working
740 directory. With no arguments, exchanges the top two directories
741 and returns 0, unless the directory stack is empty. Arguments,
742 if supplied, have the following meanings:
743 +n Rotates the stack so that the nth directory (counting
744 from the left of the list shown by dirs, starting with
745 zero) is at the top.
746 -n Rotates the stack so that the nth directory (counting
747 from the right of the list shown by dirs, starting with
748 zero) is at the top.
749 -n Suppresses the normal change of directory when adding
750 directories to the stack, so that only the stack is
751 manipulated.
752 dir Adds dir to the directory stack at the top, making it the
753 new current working directory.
754 If the pushd command is successful, a dirs is performed as well.
756 If the first form is used, pushd returns 0 unless the cd to dir
757 fails. With the second form, pushd returns 0 unless the direc‐
758 tory stack is empty, a non-existent directory stack element is
759 specified, or the directory change to the specified new current
760 directory fails.
761 pwd [-LP]
763 Print the absolute pathname of the current working directory.
764 The pathname printed contains no symbolic links if the -P option
765 is supplied or the -o physical option to the set builtin command
766 is enabled. If the -L option is used, the pathname printed may
767 contain symbolic links. The return status is 0 unless an error
768 occurs while reading the name of the current directory or an
769 invalid option is supplied.
770 read [-ers] [-u fd] [-t timeout] [-a aname] [-p prompt] [-n nchars] [-d
772 delim] [name ...]
773 One line is read from the standard input, or from the file
774 descriptor fd supplied as an argument to the -u option, and the
775 first word is assigned to the first name, the second word to the
776 second name, and so on, with leftover words and their interven‐
777 ing separators assigned to the last name. If there are fewer
778 words read from the input stream than names, the remaining names
779 are assigned empty values. The characters in IFS are used to
780 split the line into words. The backslash character (\) may be
781 used to remove any special meaning for the next character read
782 and for line continuation. Options, if supplied, have the fol‐
783 lowing meanings:
784 -a aname
785 The words are assigned to sequential indices of the array
786 variable aname, starting at 0. aname is unset before any
787 new values are assigned. Other name arguments are
788 ignored.
789 -d delim
790 The first character of delim is used to terminate the
791 input line, rather than newline.
792 -e If the standard input is coming from a terminal, readline
793 (see READLINE above) is used to obtain the line.
794 -n nchars
795 read returns after reading nchars characters rather than
796 waiting for a complete line of input.
797 -p prompt
798 Display prompt on standard error, without a trailing new‐
799 line, before attempting to read any input. The prompt is
800 displayed only if input is coming from a terminal.
801 -r Backslash does not act as an escape character. The back‐
802 slash is considered to be part of the line. In particu‐
803 lar, a backslash-newline pair may not be used as a line
804 continuation.
805 -s Silent mode. If input is coming from a terminal, charac‐
806 ters are not echoed.
807 -t timeout
808 Cause read to time out and return failure if a complete
809 line of input is not read within timeout seconds. This
810 option has no effect if read is not reading input from
811 the terminal or a pipe.
812 -u fd Read input from file descriptor fd.
813 If no names are supplied, the line read is assigned to the vari‐
815 able REPLY. The return code is zero, unless end-of-file is
816 encountered, read times out, or an invalid file descriptor is
817 supplied as the argument to -u.
818 readonly [-apf] [name[=word] ...]
820 The given names are marked readonly; the values of these names
821 may not be changed by subsequent assignment. If the -f option
822 is supplied, the functions corresponding to the names are so
823 marked. The -a option restricts the variables to arrays. If no
824 name arguments are given, or if the -p option is supplied, a
825 list of all readonly names is printed. The -p option causes
826 output to be displayed in a format that may be reused as input.
827 If a variable name is followed by =word, the value of the vari‐
828 able is set to word. The return status is 0 unless an invalid
829 option is encountered, one of the names is not a valid shell
830 variable name, or -f is supplied with a name that is not a func‐
831 tion.
832 return [n]
834 Causes a function to exit with the return value specified by n.
835 If n is omitted, the return status is that of the last command
836 executed in the function body. If used outside a function, but
837 during execution of a script by the . (source) command, it
838 causes the shell to stop executing that script and return either
839 n or the exit status of the last command executed within the
840 script as the exit status of the script. If used outside a
841 function and not during execution of a script by ., the return
842 status is false. Any command associated with the RETURN trap is
843 executed before execution resumes after the function or script.
844 set [--abefhkmnptuvxBCHP] [-o option] [arg ...]
846 Without options, the name and value of each shell variable are
847 displayed in a format that can be reused as input for setting or
848 resetting the currently-set variables. Read-only variables can‐
849 not be reset. In posix mode, only shell variables are listed.
850 The output is sorted according to the current locale. When
851 options are specified, they set or unset shell attributes. Any
852 arguments remaining after the options are processed are treated
853 as values for the positional parameters and are assigned, in
854 order, to $1, $2, ... $n. Options, if specified, have the fol‐
855 lowing meanings:
856 -a Automatically mark variables and functions which are
857 modified or created for export to the environment of
858 subsequent commands.
859 -b Report the status of terminated background jobs immedi‐
860 ately, rather than before the next primary prompt. This
861 is effective only when job control is enabled.
862 -e Exit immediately if a simple command (see SHELL GRAMMAR
863 above) exits with a non-zero status. The shell does not
864 exit if the command that fails is part of the command
865 list immediately following a while or until keyword,
866 part of the test in an if statement, part of a && or ⎪⎪
867 list, or if the command's return value is being inverted
868 via !. A trap on ERR, if set, is executed before the
869 shell exits.
870 -f Disable pathname expansion.
871 -h Remember the location of commands as they are looked up
872 for execution. This is enabled by default.
873 -k All arguments in the form of assignment statements are
874 placed in the environment for a command, not just those
875 that precede the command name.
876 -m Monitor mode. Job control is enabled. This option is
877 on by default for interactive shells on systems that
878 support it (see JOB CONTROL above). Background pro‐
879 cesses run in a separate process group and a line con‐
880 taining their exit status is printed upon their comple‐
881 tion.
882 -n Read commands but do not execute them. This may be used
883 to check a shell script for syntax errors. This is
884 ignored by interactive shells.
885 -o option-name
886 The option-name can be one of the following:
887 allexport
888 Same as -a.
889 braceexpand
890 Same as -B.
891 emacs Use an emacs-style command line editing inter‐
892 face. This is enabled by default when the shell
893 is interactive, unless the shell is started with
894 the --noediting option.
895 errtrace
896 Same as -E.
897 functrace
898 Same as -T.
899 errexit Same as -e.
900 hashall Same as -h.
901 histexpand
902 Same as -H.
903 history Enable command history, as described above under
904 HISTORY. This option is on by default in inter‐
905 active shells.
906 ignoreeof
907 The effect is as if the shell command
908 ``IGNOREEOF=10'' had been executed (see Shell
909 Variables above).
910 keyword Same as -k.
911 monitor Same as -m.
912 noclobber
913 Same as -C.
914 noexec Same as -n.
915 noglob Same as -f. nolog Currently ignored.
916 notify Same as -b.
917 nounset Same as -u.
918 onecmd Same as -t.
919 physical
920 Same as -P.
921 pipefail
922 If set, the return value of a pipeline is the
923 value of the last (rightmost) command to exit
924 with a non-zero status, or zero if all commands
925 in the pipeline exit successfully. This option
926 is disabled by default.
927 posix Change the behavior of bash where the default
928 operation differs from the POSIX standard to
929 match the standard (posix mode).
930 privileged
931 Same as -p.
932 verbose Same as -v.
933 vi Use a vi-style command line editing interface.
934 xtrace Same as -x.
935 If -o is supplied with no option-name, the values of the
936 current options are printed. If +o is supplied with no
937 option-name, a series of set commands to recreate the
938 current option settings is displayed on the standard
939 output.
940 -p Turn on privileged mode. In this mode, the $ENV and
941 $BASH_ENV files are not processed, shell functions are
942 not inherited from the environment, and the SHELLOPTS
943 variable, if it appears in the environment, is ignored.
944 If the shell is started with the effective user (group)
945 id not equal to the real user (group) id, and the -p
946 option is not supplied, these actions are taken and the
947 effective user id is set to the real user id. If the -p
948 option is supplied at startup, the effective user id is
949 not reset. Turning this option off causes the effective
950 user and group ids to be set to the real user and group
951 ids.
952 -t Exit after reading and executing one command.
953 -u Treat unset variables as an error when performing param‐
954 eter expansion. If expansion is attempted on an unset
955 variable, the shell prints an error message, and, if not
956 interactive, exits with a non-zero status.
957 -v Print shell input lines as they are read.
958 -x After expanding each simple command, for command, case
959 command, select command, or arithmetic for command, dis‐
960 play the expanded value of PS4, followed by the command
961 and its expanded arguments or associated word list.
962 -B The shell performs brace expansion (see Brace Expansion
963 above). This is on by default.
964 -C If set, bash does not overwrite an existing file with
965 the >, >&, and <> redirection operators. This may be
966 overridden when creating output files by using the redi‐
967 rection operator >| instead of >.
968 -E If set, any trap on ERR is inherited by shell functions,
969 command substitutions, and commands executed in a sub‐
970 shell environment. The ERR trap is normally not inher‐
971 ited in such cases.
972 -H Enable ! style history substitution. This option is on
973 by default when the shell is interactive.
974 -P If set, the shell does not follow symbolic links when
975 executing commands such as cd that change the current
976 working directory. It uses the physical directory
977 structure instead. By default, bash follows the logical
978 chain of directories when performing commands which
979 change the current directory.
980 -T If set, any traps on DEBUG and RETURN are inherited by
981 shell functions, command substitutions, and commands
982 executed in a subshell environment. The DEBUG and
983 RETURN traps are normally not inherited in such cases.
984 -- If no arguments follow this option, then the positional
985 parameters are unset. Otherwise, the positional parame‐
986 ters are set to the args, even if some of them begin
987 with a -.
988 - Signal the end of options, cause all remaining args to
989 be assigned to the positional parameters. The -x and -v
990 options are turned off. If there are no args, the posi‐
991 tional parameters remain unchanged.
992 The options are off by default unless otherwise noted. Using +
994 rather than - causes these options to be turned off. The
995 options can also be specified as arguments to an invocation of
996 the shell. The current set of options may be found in $-. The
997 return status is always true unless an invalid option is encoun‐
998 tered.
999 shift [n]
1001 The positional parameters from n+1 ... are renamed to $1 ....
1002 Parameters represented by the numbers $# down to $#-n+1 are
1003 unset. n must be a non-negative number less than or equal to
1004 $#. If n is 0, no parameters are changed. If n is not given,
1005 it is assumed to be 1. If n is greater than $#, the positional
1006 parameters are not changed. The return status is greater than
1007 zero if n is greater than $# or less than zero; otherwise 0.
1008 shopt [-pqsu] [-o] [optname ...]
1010 Toggle the values of variables controlling optional shell behav‐
1011 ior. With no options, or with the -p option, a list of all set‐
1012 table options is displayed, with an indication of whether or not
1013 each is set. The -p option causes output to be displayed in a
1014 form that may be reused as input. Other options have the fol‐
1015 lowing meanings:
1016 -s Enable (set) each optname.
1017 -u Disable (unset) each optname.
1018 -q Suppresses normal output (quiet mode); the return status
1019 indicates whether the optname is set or unset. If multi‐
1020 ple optname arguments are given with -q, the return sta‐
1021 tus is zero if all optnames are enabled; non-zero other‐
1022 wise.
1023 -o Restricts the values of optname to be those defined for
1024 the -o option to the set builtin.
1025 If either -s or -u is used with no optname arguments, the dis‐
1027 play is limited to those options which are set or unset, respec‐
1028 tively. Unless otherwise noted, the shopt options are disabled
1029 (unset) by default.
1030 The return status when listing options is zero if all optnames
1032 are enabled, non-zero otherwise. When setting or unsetting
1033 options, the return status is zero unless an optname is not a
1034 valid shell option.
1035 The list of shopt options is:
1037 cdable_vars
1039 If set, an argument to the cd builtin command that is
1040 not a directory is assumed to be the name of a variable
1041 whose value is the directory to change to.
1042 cdspell If set, minor errors in the spelling of a directory com‐
1043 ponent in a cd command will be corrected. The errors
1044 checked for are transposed characters, a missing charac‐
1045 ter, and one character too many. If a correction is
1046 found, the corrected file name is printed, and the com‐
1047 mand proceeds. This option is only used by interactive
1048 shells.
1049 checkhash
1050 If set, bash checks that a command found in the hash ta‐
1051 ble exists before trying to execute it. If a hashed
1052 command no longer exists, a normal path search is per‐
1053 formed.
1054 checkwinsize
1055 If set, bash checks the window size after each command
1056 and, if necessary, updates the values of LINES and COL‐
1057 UMNS.
1058 cmdhist If set, bash attempts to save all lines of a multiple-
1059 line command in the same history entry. This allows
1060 easy re-editing of multi-line commands.
1061 dotglob If set, bash includes filenames beginning with a `.' in
1062 the results of pathname expansion.
1063 execfail
1064 If set, a non-interactive shell will not exit if it can‐
1065 not execute the file specified as an argument to the
1066 exec builtin command. An interactive shell does not
1067 exit if exec fails.
1068 expand_aliases
1069 If set, aliases are expanded as described above under
1070 ALIASES. This option is enabled by default for interac‐
1071 tive shells.
1072 extdebug
1073 If set, behavior intended for use by debuggers is
1074 enabled:
1075 1. The -F option to the declare builtin displays the
1076 source file name and line number corresponding to
1077 each function name supplied as an argument.
1078 2. If the command run by the DEBUG trap returns a
1079 non-zero value, the next command is skipped and
1080 not executed.
1081 3. If the command run by the DEBUG trap returns a
1082 value of 2, and the shell is executing in a sub‐
1083 routine (a shell function or a shell script exe‐
1084 cuted by the . or source builtins), a call to
1085 return is simulated.
1086 4. BASH_ARGC and BASH_ARGV are updated as described
1087 in their descriptions above.
1088 5. Function tracing is enabled: command substitu‐
1089 tion, shell functions, and subshells invoked with
1090 ( command ) inherit the DEBUG and RETURN traps.
1091 6. Error tracing is enabled: command substitution,
1092 shell functions, and subshells invoked with (
1093 command ) inherit the ERROR trap.
1094 extglob If set, the extended pattern matching features described
1095 above under Pathname Expansion are enabled.
1096 extquote
1097 If set, $'string' and $"string" quoting is performed
1098 within ${parameter} expansions enclosed in double
1099 quotes. This option is enabled by default.
1100 failglob
1101 If set, patterns which fail to match filenames during
1102 pathname expansion result in an expansion error.
1103 force_fignore
1104 If set, the suffixes specified by the FIGNORE shell
1105 variable cause words to be ignored when performing word
1106 completion even if the ignored words are the only possi‐
1107 ble completions. See SHELL VARIABLES above for a
1108 description of FIGNORE. This option is enabled by
1109 default.
1110 gnu_errfmt
1111 If set, shell error messages are written in the standard
1112 GNU error message format.
1113 histappend
1114 If set, the history list is appended to the file named
1115 by the value of the HISTFILE variable when the shell
1116 exits, rather than overwriting the file.
1117 histreedit
1118 If set, and readline is being used, a user is given the
1119 opportunity to re-edit a failed history substitution.
1120 histverify
1121 If set, and readline is being used, the results of his‐
1122 tory substitution are not immediately passed to the
1123 shell parser. Instead, the resulting line is loaded
1124 into the readline editing buffer, allowing further modi‐
1125 fication.
1126 hostcomplete
1127 If set, and readline is being used, bash will attempt to
1128 perform hostname completion when a word containing a @
1129 is being completed (see Completing under READLINE
1130 above). This is enabled by default.
1131 huponexit
1132 If set, bash will send SIGHUP to all jobs when an inter‐
1133 active login shell exits.
1134 interactive_comments
1135 If set, allow a word beginning with # to cause that word
1136 and all remaining characters on that line to be ignored
1137 in an interactive shell (see COMMENTS above). This
1138 option is enabled by default.
1139 lithist If set, and the cmdhist option is enabled, multi-line
1140 commands are saved to the history with embedded newlines
1141 rather than using semicolon separators where possible.
1142 login_shell
1143 The shell sets this option if it is started as a login
1144 shell (see INVOCATION above). The value may not be
1145 changed.
1146 mailwarn
1147 If set, and a file that bash is checking for mail has
1148 been accessed since the last time it was checked, the
1149 message ``The mail in mailfile has been read'' is dis‐
1150 played.
1151 no_empty_cmd_completion
1152 If set, and readline is being used, bash will not
1153 attempt to search the PATH for possible completions when
1154 completion is attempted on an empty line.
1155 nocaseglob
1156 If set, bash matches filenames in a case-insensitive
1157 fashion when performing pathname expansion (see Pathname
1158 Expansion above).
1159 nocasematch
1160 If set, bash matches patterns in a case-insensitive
1161 fashion when performing matching while executing case or
1162 [[ conditional commands.
1163 nullglob
1164 If set, bash allows patterns which match no files (see
1165 Pathname Expansion above) to expand to a null string,
1166 rather than themselves.
1167 progcomp
1168 If set, the programmable completion facilities (see Pro‐
1169 grammable Completion above) are enabled. This option is
1170 enabled by default.
1171 promptvars
1172 If set, prompt strings undergo parameter expansion, com‐
1173 mand substitution, arithmetic expansion, and quote
1174 removal after being expanded as described in PROMPTING
1175 above. This option is enabled by default.
1176 restricted_shell
1177 The shell sets this option if it is started in
1178 restricted mode (see RESTRICTED SHELL below). The value
1179 may not be changed. This is not reset when the startup
1180 files are executed, allowing the startup files to dis‐
1181 cover whether or not a shell is restricted.
1182 shift_verbose
1183 If set, the shift builtin prints an error message when
1184 the shift count exceeds the number of positional parame‐
1185 ters.
1186 sourcepath
1187 If set, the source (.) builtin uses the value of PATH to
1188 find the directory containing the file supplied as an
1189 argument. This option is enabled by default.
1190 xpg_echo
1191 If set, the echo builtin expands backslash-escape
1192 sequences by default.
1193 suspend [-f]
1194 Suspend the execution of this shell until it receives a SIGCONT
1195 signal. The -f option says not to complain if this is a login
1196 shell; just suspend anyway. The return status is 0 unless the
1197 shell is a login shell and -f is not supplied, or if job control
1198 is not enabled.
1199 test expr
1200 [ expr ]
1201 Return a status of 0 or 1 depending on the evaluation of the
1202 conditional expression expr. Each operator and operand must be
1203 a separate argument. Expressions are composed of the primaries
1204 described above under CONDITIONAL EXPRESSIONS. test does not
1205 accept any options, nor does it accept and ignore an argument of
1206 -- as signifying the end of options.
1207 Expressions may be combined using the following operators,
1209 listed in decreasing order of precedence.
1210 ! expr True if expr is false.
1211 ( expr )
1212 Returns the value of expr. This may be used to override
1213 the normal precedence of operators.
1214 expr1 -a expr2
1215 True if both expr1 and expr2 are true.
1216 expr1 -o expr2
1217 True if either expr1 or expr2 is true.
1218 test and [ evaluate conditional expressions using a set of rules
1220 based on the number of arguments.
1221 0 arguments
1223 The expression is false.
1224 1 argument
1225 The expression is true if and only if the argument is not
1226 null.
1227 2 arguments
1228 If the first argument is !, the expression is true if and
1229 only if the second argument is null. If the first argu‐
1230 ment is one of the unary conditional operators listed
1231 above under CONDITIONAL EXPRESSIONS, the expression is
1232 true if the unary test is true. If the first argument is
1233 not a valid unary conditional operator, the expression is
1234 false.
1235 3 arguments
1236 If the second argument is one of the binary conditional
1237 operators listed above under CONDITIONAL EXPRESSIONS, the
1238 result of the expression is the result of the binary test
1239 using the first and third arguments as operands. If the
1240 first argument is !, the value is the negation of the
1241 two-argument test using the second and third arguments.
1242 If the first argument is exactly ( and the third argument
1243 is exactly ), the result is the one-argument test of the
1244 second argument. Otherwise, the expression is false.
1245 The -a and -o operators are considered binary operators
1246 in this case.
1247 4 arguments
1248 If the first argument is !, the result is the negation of
1249 the three-argument expression composed of the remaining
1250 arguments. Otherwise, the expression is parsed and eval‐
1251 uated according to precedence using the rules listed
1252 above.
1253 5 or more arguments
1254 The expression is parsed and evaluated according to
1255 precedence using the rules listed above.
1256 times Print the accumulated user and system times for the shell and
1258 for processes run from the shell. The return status is 0.
1259 trap [-lp] [[arg] sigspec ...]
1261 The command arg is to be read and executed when the shell
1262 receives signal(s) sigspec. If arg is absent (and there is a
1263 single sigspec) or -, each specified signal is reset to its
1264 original disposition (the value it had upon entrance to the
1265 shell). If arg is the null string the signal specified by each
1266 sigspec is ignored by the shell and by the commands it invokes.
1267 If arg is not present and -p has been supplied, then the trap
1268 commands associated with each sigspec are displayed. If no
1269 arguments are supplied or if only -p is given, trap prints the
1270 list of commands associated with each signal. The -l option
1271 causes the shell to print a list of signal names and their cor‐
1272 responding numbers. Each sigspec is either a signal name
1273 defined in <signal.h>, or a signal number. Signal names are
1274 case insensitive and the SIG prefix is optional. If a sigspec
1275 is EXIT (0) the command arg is executed on exit from the shell.
1276 If a sigspec is DEBUG, the command arg is executed before every
1277 simple command, for command, case command, select command, every
1278 arithmetic for command, and before the first command executes in
1279 a shell function (see SHELL GRAMMAR above). Refer to the
1280 description of the extdebug option to the shopt builtin for
1281 details of its effect on the DEBUG trap. If a sigspec is ERR,
1282 the command arg is executed whenever a simple command has a
1283 non-zero exit status, subject to the following conditions. The
1284 ERR trap is not executed if the failed command is part of the
1285 command list immediately following a while or until keyword,
1286 part of the test in an if statement, part of a && or ⎪⎪ list, or
1287 if the command's return value is being inverted via !. These
1288 are the same conditions obeyed by the errexit option. If a
1289 sigspec is RETURN, the command arg is executed each time a shell
1290 function or a script executed with the . or source builtins fin‐
1291 ishes executing. Signals ignored upon entry to the shell cannot
1292 be trapped or reset. Trapped signals that are not being ignored
1293 are reset to their original values in a child process when it is
1294 created. The return status is false if any sigspec is invalid;
1295 otherwise trap returns true.
1296 type [-aftpP] name [name ...]
1298 With no options, indicate how each name would be interpreted if
1299 used as a command name. If the -t option is used, type prints a
1300 string which is one of alias, keyword, function, builtin, or
1301 file if name is an alias, shell reserved word, function,
1302 builtin, or disk file, respectively. If the name is not found,
1303 then nothing is printed, and an exit status of false is
1304 returned. If the -p option is used, type either returns the
1305 name of the disk file that would be executed if name were speci‐
1306 fied as a command name, or nothing if ``type -t name'' would not
1307 return file. The -P option forces a PATH search for each name,
1308 even if ``type -t name'' would not return file. If a command is
1309 hashed, -p and -P print the hashed value, not necessarily the
1310 file that appears first in PATH. If the -a option is used, type
1311 prints all of the places that contain an executable named name.
1312 This includes aliases and functions, if and only if the -p
1313 option is not also used. The table of hashed commands is not
1314 consulted when using -a. The -f option suppresses shell func‐
1315 tion lookup, as with the command builtin. type returns true if
1316 any of the arguments are found, false if none are found.
1317 ulimit [-SHacdefilmnpqrstuvx [limit]]
1319 Provides control over the resources available to the shell and
1320 to processes started by it, on systems that allow such control.
1321 The -H and -S options specify that the hard or soft limit is set
1322 for the given resource. A hard limit cannot be increased once
1323 it is set; a soft limit may be increased up to the value of the
1324 hard limit. If neither -H nor -S is specified, both the soft
1325 and hard limits are set. The value of limit can be a number in
1326 the unit specified for the resource or one of the special values
1327 hard, soft, or unlimited, which stand for the current hard
1328 limit, the current soft limit, and no limit, respectively. If
1329 limit is omitted, the current value of the soft limit of the
1330 resource is printed, unless the -H option is given. When more
1331 than one resource is specified, the limit name and unit are
1332 printed before the value. Other options are interpreted as fol‐
1333 lows:
1334 -a All current limits are reported
1335 -c The maximum size of core files created
1336 -d The maximum size of a process's data segment
1337 -e The maximum scheduling priority ("nice")
1338 -f The maximum size of files written by the shell and its
1339 children
1340 -i The maximum number of pending signals
1341 -l The maximum size that may be locked into memory
1342 -m The maximum resident set size (has no effect on Linux)
1343 -n The maximum number of open file descriptors (most systems
1344 do not allow this value to be set)
1345 -p The pipe size in 512-byte blocks (this may not be set)
1346 -q The maximum number of bytes in POSIX message queues
1347 -r The maximum real-time scheduling priority
1348 -s The maximum stack size
1349 -t The maximum amount of cpu time in seconds
1350 -u The maximum number of processes available to a single
1351 user
1352 -v The maximum amount of virtual memory available to the
1353 shell
1354 -x The maximum number of file locks
1355 If limit is given, it is the new value of the specified resource
1357 (the -a option is display only). If no option is given, then -f
1358 is assumed. Values are in 1024-byte increments, except for -t,
1359 which is in seconds, -p, which is in units of 512-byte blocks,
1360 and -n and -u, which are unscaled values. The return status is
1361 0 unless an invalid option or argument is supplied, or an error
1362 occurs while setting a new limit.
1363 umask [-p] [-S] [mode]
1365 The user file-creation mask is set to mode. If mode begins with
1366 a digit, it is interpreted as an octal number; otherwise it is
1367 interpreted as a symbolic mode mask similar to that accepted by
1368 chmod(1). If mode is omitted, the current value of the mask is
1369 printed. The -S option causes the mask to be printed in sym‐
1370 bolic form; the default output is an octal number. If the -p
1371 option is supplied, and mode is omitted, the output is in a form
1372 that may be reused as input. The return status is 0 if the mode
1373 was successfully changed or if no mode argument was supplied,
1374 and false otherwise.
1375 unalias [-a] [name ...]
1377 Remove each name from the list of defined aliases. If -a is
1378 supplied, all alias definitions are removed. The return value
1379 is true unless a supplied name is not a defined alias.
1380 unset [-fv] [name ...]
1382 For each name, remove the corresponding variable or function.
1383 If no options are supplied, or the -v option is given, each name
1384 refers to a shell variable. Read-only variables may not be
1385 unset. If -f is specified, each name refers to a shell func‐
1386 tion, and the function definition is removed. Each unset vari‐
1387 able or function is removed from the environment passed to sub‐
1388 sequent commands. If any of RANDOM, SECONDS, LINENO, HISTCMD,
1389 FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their special
1390 properties, even if they are subsequently reset. The exit sta‐
1391 tus is true unless a name is readonly.
1392 wait [n ...]
1394 Wait for each specified process and return its termination sta‐
1395 tus. Each n may be a process ID or a job specification; if a
1396 job spec is given, all processes in that job's pipeline are
1397 waited for. If n is not given, all currently active child pro‐
1398 cesses are waited for, and the return status is zero. If n
1399 specifies a non-existent process or job, the return status is
1400 127. Otherwise, the return status is the exit status of the
1401 last process or job waited for.
1402
1404 bash(1), sh(1)
1405GNU Bash-3.0 2004 Apr 20 BASH_BUILTINS(1)