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BASH_BUILTINS(1) General Commands Manual BASH_BUILTINS(1)
NNAAMMEE
bash, :, ., [, alias, bg, bind, break, builtin, caller, cd, command,
compgen, complete, compopt, continue, declare, dirs, disown, echo, en-
able, eval, exec, exit, export, false, fc, fg, getopts, hash, help,
history, jobs, kill, let, local, logout, mapfile, popd, printf, pushd,
pwd, read, readonly, return, set, shift, shopt, source, suspend, test,
times, trap, true, type, typeset, ulimit, umask, unalias, unset, wait -
bash built-in commands, see bbaasshh(1)
BBAASSHH BBUUIILLTTIINN CCOOMMMMAANNDDSS
Unless otherwise noted, each builtin command documented in this section
as accepting options preceded by -- accepts ---- to signify the end of the
options. The ::, ttrruuee, ffaallssee, and tteesstt/[[ builtins do not accept options
and do not treat ---- specially. The eexxiitt, llooggoouutt, rreettuurrnn, bbrreeaakk, ccoonn--
ttiinnuuee, lleett, and sshhiifftt builtins accept and process arguments beginning
with -- without requiring ----. Other builtins that accept arguments but
are not specified as accepting options interpret arguments beginning
with -- as invalid options and require ---- to prevent this interpreta-
tion.
:: [_a_r_g_u_m_e_n_t_s]
No effect; the command does nothing beyond expanding _a_r_g_u_m_e_n_t_s
and performing any specified redirections. The return status is
zero.
.. _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
ssoouurrccee _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
Read and execute commands from _f_i_l_e_n_a_m_e in the current shell en-
vironment and return the exit status of the last command exe-
cuted from _f_i_l_e_n_a_m_e. If _f_i_l_e_n_a_m_e does not contain a slash,
filenames in PPAATTHH are used to find the directory containing
_f_i_l_e_n_a_m_e. The file searched for in PPAATTHH need not be executable.
When bbaasshh is not in _p_o_s_i_x _m_o_d_e, the current directory is
searched if no file is found in PPAATTHH. If the ssoouurrcceeppaatthh option
to the sshhoopptt builtin command is turned off, the PPAATTHH is not
searched. If any _a_r_g_u_m_e_n_t_s are supplied, they become the posi-
tional parameters when _f_i_l_e_n_a_m_e is executed. Otherwise the po-
sitional parameters are unchanged. If the --TT option is enabled,
ssoouurrccee inherits any trap on DDEEBBUUGG; if it is not, any DDEEBBUUGG trap
string is saved and restored around the call to ssoouurrccee, and
ssoouurrccee unsets the DDEEBBUUGG trap while it executes. If --TT is not
set, and the sourced file changes the DDEEBBUUGG trap, the new value
is retained when ssoouurrccee completes. The return status is the
status of the last command exited within the script (0 if no
commands are executed), and false if _f_i_l_e_n_a_m_e is not found or
cannot be read.
aalliiaass [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
AAlliiaass with no arguments or with the --pp option prints the list of
aliases in the form aalliiaass _n_a_m_e=_v_a_l_u_e on standard output. When
arguments are supplied, an alias is defined for each _n_a_m_e whose
_v_a_l_u_e is given. A trailing space in _v_a_l_u_e causes the next word
to be checked for alias substitution when the alias is expanded.
For each _n_a_m_e in the argument list for which no _v_a_l_u_e is sup-
plied, the name and value of the alias is printed. AAlliiaass re-
turns true unless a _n_a_m_e is given for which no alias has been
defined.
bbgg [_j_o_b_s_p_e_c ...]
Resume each suspended job _j_o_b_s_p_e_c in the background, as if it
had been started with &&. If _j_o_b_s_p_e_c is not present, the shell's
notion of the _c_u_r_r_e_n_t _j_o_b is used. bbgg _j_o_b_s_p_e_c returns 0 unless
run when job control is disabled or, when run with job control
enabled, any specified _j_o_b_s_p_e_c was not found or was started
without job control.
bbiinndd [--mm _k_e_y_m_a_p] [--llppssvvPPSSVVXX]
bbiinndd [--mm _k_e_y_m_a_p] [--qq _f_u_n_c_t_i_o_n] [--uu _f_u_n_c_t_i_o_n] [--rr _k_e_y_s_e_q]
bbiinndd [--mm _k_e_y_m_a_p] --ff _f_i_l_e_n_a_m_e
bbiinndd [--mm _k_e_y_m_a_p] --xx _k_e_y_s_e_q:_s_h_e_l_l_-_c_o_m_m_a_n_d
bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_f_u_n_c_t_i_o_n_-_n_a_m_e
bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d
Display current rreeaaddlliinnee key and function bindings, bind a key
sequence to a rreeaaddlliinnee function or macro, or set a rreeaaddlliinnee
variable. Each non-option argument is a command as it would ap-
pear in _._i_n_p_u_t_r_c, but each binding or command must be passed as
a separate argument; e.g., '"\C-x\C-r": re-read-init-file'. Op-
tions, if supplied, have the following meanings:
--mm _k_e_y_m_a_p
Use _k_e_y_m_a_p as the keymap to be affected by the subsequent
bindings. Acceptable _k_e_y_m_a_p names are _e_m_a_c_s_, _e_m_a_c_s_-_s_t_a_n_-
_d_a_r_d_, _e_m_a_c_s_-_m_e_t_a_, _e_m_a_c_s_-_c_t_l_x_, _v_i_, _v_i_-_m_o_v_e_, _v_i_-_c_o_m_m_a_n_d,
and _v_i_-_i_n_s_e_r_t. _v_i is equivalent to _v_i_-_c_o_m_m_a_n_d (_v_i_-_m_o_v_e
is also a synonym); _e_m_a_c_s is equivalent to _e_m_a_c_s_-_s_t_a_n_-
_d_a_r_d.
--ll List the names of all rreeaaddlliinnee functions.
--pp Display rreeaaddlliinnee function names and bindings in such a
way that they can be re-read.
--PP List current rreeaaddlliinnee function names and bindings.
--ss Display rreeaaddlliinnee key sequences bound to macros and the
strings they output in such a way that they can be re-
read.
--SS Display rreeaaddlliinnee key sequences bound to macros and the
strings they output.
--vv Display rreeaaddlliinnee variable names and values in such a way
that they can be re-read.
--VV List current rreeaaddlliinnee variable names and values.
--ff _f_i_l_e_n_a_m_e
Read key bindings from _f_i_l_e_n_a_m_e.
--qq _f_u_n_c_t_i_o_n
Query about which keys invoke the named _f_u_n_c_t_i_o_n.
--uu _f_u_n_c_t_i_o_n
Unbind all keys bound to the named _f_u_n_c_t_i_o_n.
--rr _k_e_y_s_e_q
Remove any current binding for _k_e_y_s_e_q.
--xx _k_e_y_s_e_q::_s_h_e_l_l_-_c_o_m_m_a_n_d
Cause _s_h_e_l_l_-_c_o_m_m_a_n_d to be executed whenever _k_e_y_s_e_q is en-
tered. When _s_h_e_l_l_-_c_o_m_m_a_n_d is executed, the shell sets
the RREEAADDLLIINNEE__LLIINNEE variable to the contents of the rreeaadd--
lliinnee line buffer and the RREEAADDLLIINNEE__PPOOIINNTT and RREEAADDLLIINNEE__MMAARRKK
variables to the current location of the insertion point
and the saved insertion point (the mark), respectively.
If the executed command changes the value of any of RREEAADD--
LLIINNEE__LLIINNEE, RREEAADDLLIINNEE__PPOOIINNTT, or RREEAADDLLIINNEE__MMAARRKK, those new
values will be reflected in the editing state.
--XX List all key sequences bound to shell commands and the
associated commands in a format that can be reused as in-
put.
The return value is 0 unless an unrecognized option is given or
an error occurred.
bbrreeaakk [_n]
Exit from within a ffoorr, wwhhiillee, uunnttiill, or sseelleecctt loop. If _n is
specified, break _n levels. _n must be >= 1. If _n is greater
than the number of enclosing loops, all enclosing loops are ex-
ited. The return value is 0 unless _n is not greater than or
equal to 1.
bbuuiillttiinn _s_h_e_l_l_-_b_u_i_l_t_i_n [_a_r_g_u_m_e_n_t_s]
Execute the specified shell builtin, passing it _a_r_g_u_m_e_n_t_s, and
return its exit status. This is useful when defining a function
whose name is the same as a shell builtin, retaining the func-
tionality of the builtin within the function. The ccdd builtin is
commonly redefined this way. The return status is false if
_s_h_e_l_l_-_b_u_i_l_t_i_n is not a shell builtin command.
ccaalllleerr [_e_x_p_r]
Returns the context of any active subroutine call (a shell func-
tion or a script executed with the .. or ssoouurrccee builtins). With-
out _e_x_p_r, ccaalllleerr displays the line number and source filename of
the current subroutine call. If a non-negative integer is sup-
plied as _e_x_p_r, ccaalllleerr displays the line number, subroutine name,
and source file corresponding to that position in the current
execution call stack. This extra information may be used, for
example, to print a stack trace. The current frame is frame 0.
The return value is 0 unless the shell is not executing a sub-
routine call or _e_x_p_r does not correspond to a valid position in
the call stack.
ccdd [--LL|[--PP [--ee]] [-@]] [_d_i_r]
Change the current directory to _d_i_r. if _d_i_r is not supplied,
the value of the HHOOMMEE shell variable is the default. Any addi-
tional arguments following _d_i_r are ignored. The variable CCDDPPAATTHH
defines the search path for the directory containing _d_i_r: each
directory name in CCDDPPAATTHH is searched for _d_i_r. Alternative di-
rectory names in CCDDPPAATTHH are separated by a colon (:). A null
directory name in CCDDPPAATTHH is the same as the current directory,
i.e., ``..''. If _d_i_r begins with a slash (/), then CCDDPPAATTHH is not
used. The --PP option causes ccdd to use the physical directory
structure by resolving symbolic links while traversing _d_i_r and
before processing instances of _._. in _d_i_r (see also the --PP option
to the sseett builtin command); the --LL option forces symbolic links
to be followed by resolving the link after processing instances
of _._. in _d_i_r. If _._. appears in _d_i_r, it is processed by removing
the immediately previous pathname component from _d_i_r, back to a
slash or the beginning of _d_i_r. If the --ee option is supplied
with --PP, and the current working directory cannot be success-
fully determined after a successful directory change, ccdd will
return an unsuccessful status. On systems that support it, the
--@@ option presents the extended attributes associated with a
file as a directory. An argument of -- is converted to $$OOLLDDPPWWDD
before the directory change is attempted. If a non-empty direc-
tory name from CCDDPPAATTHH is used, or if -- is the first argument,
and the directory change is successful, the absolute pathname of
the new working directory is written to the standard output.
The return value is true if the directory was successfully
changed; false otherwise.
ccoommmmaanndd [--ppVVvv] _c_o_m_m_a_n_d [_a_r_g ...]
Run _c_o_m_m_a_n_d with _a_r_g_s suppressing the normal shell function
lookup. Only builtin commands or commands found in the PPAATTHH are
executed. If the --pp option is given, the search for _c_o_m_m_a_n_d is
performed using a default value for PPAATTHH that is guaranteed to
find all of the standard utilities. If either the --VV or --vv op-
tion is supplied, a description of _c_o_m_m_a_n_d is printed. The --vv
option causes a single word indicating the command or filename
used to invoke _c_o_m_m_a_n_d to be displayed; the --VV option produces a
more verbose description. If the --VV or --vv option is supplied,
the exit status is 0 if _c_o_m_m_a_n_d was found, and 1 if not. If
neither option is supplied and an error occurred or _c_o_m_m_a_n_d can-
not be found, the exit status is 127. Otherwise, the exit sta-
tus of the ccoommmmaanndd builtin is the exit status of _c_o_m_m_a_n_d.
ccoommppggeenn [_o_p_t_i_o_n] [_w_o_r_d]
Generate possible completion matches for _w_o_r_d according to the
_o_p_t_i_o_ns, which may be any option accepted by the ccoommpplleettee
builtin with the exception of --pp and --rr, and write the matches
to the standard output. When using the --FF or --CC options, the
various shell variables set by the programmable completion fa-
cilities, while available, will not have useful values.
The matches will be generated in the same way as if the program-
mable completion code had generated them directly from a comple-
tion specification with the same flags. If _w_o_r_d is specified,
only those completions matching _w_o_r_d will be displayed.
The return value is true unless an invalid option is supplied,
or no matches were generated.
ccoommpplleettee [--aabbccddeeffggjjkkssuuvv] [--oo _c_o_m_p_-_o_p_t_i_o_n] [--DDEEII] [--AA _a_c_t_i_o_n] [--GG _g_l_o_b_-
_p_a_t] [--WW _w_o_r_d_l_i_s_t]
[--FF _f_u_n_c_t_i_o_n] [--CC _c_o_m_m_a_n_d] [--XX _f_i_l_t_e_r_p_a_t] [--PP _p_r_e_f_i_x] [--SS _s_u_f_-
_f_i_x] _n_a_m_e [_n_a_m_e _._._.]
ccoommpplleettee --pprr [--DDEEII] [_n_a_m_e ...]
Specify how arguments to each _n_a_m_e should be completed. If the
--pp option is supplied, or if no options are supplied, existing
completion specifications are printed in a way that allows them
to be reused as input. The --rr option removes a completion spec-
ification for each _n_a_m_e, or, if no _n_a_m_es are supplied, all com-
pletion specifications. The --DD option indicates that other sup-
plied options and actions should apply to the ``default'' com-
mand completion; that is, completion attempted on a command for
which no completion has previously been defined. The --EE option
indicates that other supplied options and actions should apply
to ``empty'' command completion; that is, completion attempted
on a blank line. The --II option indicates that other supplied
options and actions should apply to completion on the initial
non-assignment word on the line, or after a command delimiter
such as ;; or ||, which is usually command name completion. If
multiple options are supplied, the --DD option takes precedence
over --EE, and both take precedence over --II. If any of --DD, --EE, or
--II are supplied, any other _n_a_m_e arguments are ignored; these
completions only apply to the case specified by the option.
The process of applying these completion specifications when
word completion is attempted is described above under PPrrooggrraamm--
mmaabbllee CCoommpplleettiioonn.
Other options, if specified, have the following meanings. The
arguments to the --GG, --WW, and --XX options (and, if necessary, the
--PP and --SS options) should be quoted to protect them from expan-
sion before the ccoommpplleettee builtin is invoked.
--oo _c_o_m_p_-_o_p_t_i_o_n
The _c_o_m_p_-_o_p_t_i_o_n controls several aspects of the comp-
spec's behavior beyond the simple generation of comple-
tions. _c_o_m_p_-_o_p_t_i_o_n may be one of:
bbaasshhddeeffaauulltt
Perform the rest of the default bbaasshh completions
if the compspec generates no matches.
ddeeffaauulltt Use readline's default filename completion if
the compspec generates no matches.
ddiirrnnaammeess
Perform directory name completion if the comp-
spec generates no matches.
ffiilleennaammeess
Tell readline that the compspec generates file-
names, so it can perform any filename-specific
processing (like adding a slash to directory
names, quoting special characters, or suppress-
ing trailing spaces). Intended to be used with
shell functions.
nnooqquuoottee Tell readline not to quote the completed words
if they are filenames (quoting filenames is the
default).
nnoossoorrtt Tell readline not to sort the list of possible
completions alphabetically.
nnoossppaaccee Tell readline not to append a space (the de-
fault) to words completed at the end of the
line.
pplluussddiirrss
After any matches defined by the compspec are
generated, directory name completion is at-
tempted and any matches are added to the results
of the other actions.
--AA _a_c_t_i_o_n
The _a_c_t_i_o_n may be one of the following to generate a
list of possible completions:
aalliiaass Alias names. May also be specified as --aa.
aarrrraayyvvaarr
Array variable names.
bbiinnddiinngg RReeaaddlliinnee key binding names.
bbuuiillttiinn Names of shell builtin commands. May also be
specified as --bb.
ccoommmmaanndd Command names. May also be specified as --cc.
ddiirreeccttoorryy
Directory names. May also be specified as --dd.
ddiissaabblleedd
Names of disabled shell builtins.
eennaabblleedd Names of enabled shell builtins.
eexxppoorrtt Names of exported shell variables. May also be
specified as --ee.
ffiillee File names. May also be specified as --ff.
ffuunnccttiioonn
Names of shell functions.
ggrroouupp Group names. May also be specified as --gg.
hheellppttooppiicc
Help topics as accepted by the hheellpp builtin.
hhoossttnnaammee
Hostnames, as taken from the file specified by
the HHOOSSTTFFIILLEE shell variable.
jjoobb Job names, if job control is active. May also
be specified as --jj.
kkeeyywwoorrdd Shell reserved words. May also be specified as
--kk.
rruunnnniinngg Names of running jobs, if job control is active.
sseerrvviiccee Service names. May also be specified as --ss.
sseettoopptt Valid arguments for the --oo option to the sseett
builtin.
sshhoopptt Shell option names as accepted by the sshhoopptt
builtin.
ssiiggnnaall Signal names.
ssttooppppeedd Names of stopped jobs, if job control is active.
uusseerr User names. May also be specified as --uu.
vvaarriiaabbllee
Names of all shell variables. May also be spec-
ified as --vv.
--CC _c_o_m_m_a_n_d
_c_o_m_m_a_n_d is executed in a subshell environment, and its
output is used as the possible completions.
--FF _f_u_n_c_t_i_o_n
The shell function _f_u_n_c_t_i_o_n is executed in the current
shell environment. When the function is executed, the
first argument ($$11) is the name of the command whose ar-
guments are being completed, the second argument ($$22) is
the word being completed, and the third argument ($$33) is
the word preceding the word being completed on the cur-
rent command line. When it finishes, the possible com-
pletions are retrieved from the value of the CCOOMMPPRREEPPLLYY
array variable.
--GG _g_l_o_b_p_a_t
The pathname expansion pattern _g_l_o_b_p_a_t is expanded to
generate the possible completions.
--PP _p_r_e_f_i_x
_p_r_e_f_i_x is added at the beginning of each possible com-
pletion after all other options have been applied.
--SS _s_u_f_f_i_x
_s_u_f_f_i_x is appended to each possible completion after all
other options have been applied.
--WW _w_o_r_d_l_i_s_t
The _w_o_r_d_l_i_s_t is split using the characters in the IIFFSS
special variable as delimiters, and each resultant word
is expanded. Shell quoting is honored within _w_o_r_d_l_i_s_t,
in order to provide a mechanism for the words to contain
shell metacharacters or characters in the value of IIFFSS.
The possible completions are the members of the resul-
tant list which match the word being completed.
--XX _f_i_l_t_e_r_p_a_t
_f_i_l_t_e_r_p_a_t is a pattern as used for pathname expansion.
It is applied to the list of possible completions gener-
ated by the preceding options and arguments, and each
completion matching _f_i_l_t_e_r_p_a_t is removed from the list.
A leading !! in _f_i_l_t_e_r_p_a_t negates the pattern; in this
case, any completion not matching _f_i_l_t_e_r_p_a_t is removed.
The return value is true unless an invalid option is supplied,
an option other than --pp or --rr is supplied without a _n_a_m_e argu-
ment, an attempt is made to remove a completion specification
for a _n_a_m_e for which no specification exists, or an error occurs
adding a completion specification.
ccoommppoopptt [--oo _o_p_t_i_o_n] [--DDEEII] [++oo _o_p_t_i_o_n] [_n_a_m_e]
Modify completion options for each _n_a_m_e according to the _o_p_-
_t_i_o_ns, or for the currently-executing completion if no _n_a_m_es are
supplied. If no _o_p_t_i_o_ns are given, display the completion op-
tions for each _n_a_m_e or the current completion. The possible
values of _o_p_t_i_o_n are those valid for the ccoommpplleettee builtin de-
scribed above. The --DD option indicates that other supplied op-
tions should apply to the ``default'' command completion; that
is, completion attempted on a command for which no completion
has previously been defined. The --EE option indicates that other
supplied options should apply to ``empty'' command completion;
that is, completion attempted on a blank line. The --II option
indicates that other supplied options should apply to completion
on the initial non-assignment word on the line, or after a com-
mand delimiter such as ;; or ||, which is usually command name
completion.
The return value is true unless an invalid option is supplied,
an attempt is made to modify the options for a _n_a_m_e for which no
completion specification exists, or an output error occurs.
ccoonnttiinnuuee [_n]
Resume the next iteration of the enclosing ffoorr, wwhhiillee, uunnttiill, or
sseelleecctt loop. If _n is specified, resume at the _nth enclosing
loop. _n must be >= 1. If _n is greater than the number of en-
closing loops, the last enclosing loop (the ``top-level'' loop)
is resumed. The return value is 0 unless _n is not greater than
or equal to 1.
ddeeccllaarree [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
ttyyppeesseett [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
Declare variables and/or give them attributes. If no _n_a_m_es are
given then display the values of variables. The --pp option will
display the attributes and values of each _n_a_m_e. When --pp is used
with _n_a_m_e arguments, additional options, other than --ff and --FF,
are ignored. When --pp is supplied without _n_a_m_e arguments, it
will display the attributes and values of all variables having
the attributes specified by the additional options. If no other
options are supplied with --pp, ddeeccllaarree will display the at-
tributes and values of all shell variables. The --ff option will
restrict the display to shell functions. The --FF option inhibits
the display of function definitions; only the function name and
attributes are printed. If the eexxttddeebbuugg shell option is enabled
using sshhoopptt, the source file name and line number where each
_n_a_m_e is defined are displayed as well. The --FF option implies
--ff. The --gg option forces variables to be created or modified at
the global scope, even when ddeeccllaarree is executed in a shell func-
tion. It is ignored in all other cases. The --II option causes
local variables to inherit the attributes (except the _n_a_m_e_r_e_f
attribute) and value of any existing variable with the same _n_a_m_e
at a surrounding scope. If there is no existing variable, the
local variable is initially unset. The following options can be
used to restrict output to variables with the specified attri-
bute or to give variables attributes:
--aa Each _n_a_m_e is an indexed array variable (see AArrrraayyss
above).
--AA Each _n_a_m_e is an associative array variable (see AArrrraayyss
above).
--ff Use function names only.
--ii The variable is treated as an integer; arithmetic evalua-
tion (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN above) is performed when
the variable is assigned a value.
--ll When the variable is assigned a value, all upper-case
characters are converted to lower-case. The upper-case
attribute is disabled.
--nn Give each _n_a_m_e the _n_a_m_e_r_e_f attribute, making it a name
reference to another variable. That other variable is
defined by the value of _n_a_m_e. All references, assign-
ments, and attribute modifications to _n_a_m_e, except those
using or changing the --nn attribute itself, are performed
on the variable referenced by _n_a_m_e's value. The nameref
attribute cannot be applied to array variables.
--rr Make _n_a_m_es readonly. These names cannot then be assigned
values by subsequent assignment statements or unset.
--tt Give each _n_a_m_e the _t_r_a_c_e attribute. Traced functions in-
herit the DDEEBBUUGG and RREETTUURRNN traps from the calling shell.
The trace attribute has no special meaning for variables.
--uu When the variable is assigned a value, all lower-case
characters are converted to upper-case. The lower-case
attribute is disabled.
--xx Mark _n_a_m_es for export to subsequent commands via the en-
vironment.
Using `+' instead of `-' turns off the attribute instead, with
the exceptions that ++aa and ++AA may not be used to destroy array
variables and ++rr will not remove the readonly attribute. When
used in a function, ddeeccllaarree and ttyyppeesseett make each _n_a_m_e local, as
with the llooccaall command, unless the --gg option is supplied. If a
variable name is followed by =_v_a_l_u_e, the value of the variable
is set to _v_a_l_u_e. When using --aa or --AA and the compound assign-
ment syntax to create array variables, additional attributes do
not take effect until subsequent assignments. The return value
is 0 unless an invalid option is encountered, an attempt is made
to define a function using ``-f foo=bar'', an attempt is made to
assign a value to a readonly variable, an attempt is made to as-
sign a value to an array variable without using the compound as-
signment syntax (see AArrrraayyss above), one of the _n_a_m_e_s is not a
valid shell variable name, an attempt is made to turn off read-
only status for a readonly variable, an attempt is made to turn
off array status for an array variable, or an attempt is made to
display a non-existent function with --ff.
ddiirrss [[--ccllppvv]] [[++_n]] [[--_n]]
Without options, displays the list of currently remembered di-
rectories. The default display is on a single line with direc-
tory names separated by spaces. Directories are added to the
list with the ppuusshhdd command; the ppooppdd command removes entries
from the list. The current directory is always the first direc-
tory in the stack.
--cc Clears the directory stack by deleting all of the en-
tries.
--ll Produces a listing using full pathnames; the default
listing format uses a tilde to denote the home directory.
--pp Print the directory stack with one entry per line.
--vv Print the directory stack with one entry per line, pre-
fixing each entry with its index in the stack.
++_n Displays the _nth entry counting from the left of the list
shown by ddiirrss when invoked without options, starting with
zero.
--_n Displays the _nth entry counting from the right of the
list shown by ddiirrss when invoked without options, starting
with zero.
The return value is 0 unless an invalid option is supplied or _n
indexes beyond the end of the directory stack.
ddiissoowwnn [--aarr] [--hh] [_j_o_b_s_p_e_c ... | _p_i_d ... ]
Without options, remove each _j_o_b_s_p_e_c from the table of active
jobs. If _j_o_b_s_p_e_c is not present, and neither the --aa nor the --rr
option is supplied, the _c_u_r_r_e_n_t _j_o_b is used. If the --hh option
is given, each _j_o_b_s_p_e_c is not removed from the table, but is
marked so that SSIIGGHHUUPP is not sent to the job if the shell re-
ceives a SSIIGGHHUUPP. If no _j_o_b_s_p_e_c is supplied, the --aa option means
to remove or mark all jobs; the --rr option without a _j_o_b_s_p_e_c ar-
gument restricts operation to running jobs. The return value is
0 unless a _j_o_b_s_p_e_c does not specify a valid job.
eecchhoo [--nneeEE] [_a_r_g ...]
Output the _a_r_gs, separated by spaces, followed by a newline.
The return status is 0 unless a write error occurs. If --nn is
specified, the trailing newline is suppressed. If the --ee option
is given, interpretation of the following backslash-escaped
characters is enabled. The --EE option disables the interpreta-
tion of these escape characters, even on systems where they are
interpreted by default. The xxppgg__eecchhoo shell option may be used
to dynamically determine whether or not eecchhoo expands these es-
cape characters by default. eecchhoo does not interpret ---- to mean
the end of options. eecchhoo interprets the following escape se-
quences:
\\aa alert (bell)
\\bb backspace
\\cc suppress further output
\\ee
\\EE an escape character
\\ff form feed
\\nn new line
\\rr carriage return
\\tt horizontal tab
\\vv vertical tab
\\\\ backslash
\\00_n_n_n the eight-bit character whose value is the octal value
_n_n_n (zero to three octal digits)
\\xx_H_H the eight-bit character whose value is the hexadecimal
value _H_H (one or two hex digits)
\\uu_H_H_H_H the Unicode (ISO/IEC 10646) character whose value is the
hexadecimal value _H_H_H_H (one to four hex digits)
\\UU_H_H_H_H_H_H_H_H
the Unicode (ISO/IEC 10646) character whose value is the
hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits)
eennaabbllee [--aa] [--ddnnppss] [--ff _f_i_l_e_n_a_m_e] [_n_a_m_e ...]
Enable and disable builtin shell commands. Disabling a builtin
allows a disk command which has the same name as a shell builtin
to be executed without specifying a full pathname, even though
the shell normally searches for builtins before disk commands.
If --nn is used, each _n_a_m_e is disabled; otherwise, _n_a_m_e_s are en-
abled. For example, to use the tteesstt binary found via the PPAATTHH
instead of the shell builtin version, run ``enable -n test''.
The --ff option means to load the new builtin command _n_a_m_e from
shared object _f_i_l_e_n_a_m_e, on systems that support dynamic loading.
The --dd option will delete a builtin previously loaded with --ff.
If no _n_a_m_e arguments are given, or if the --pp option is supplied,
a list of shell builtins is printed. With no other option argu-
ments, the list consists of all enabled shell builtins. If --nn
is supplied, only disabled builtins are printed. If --aa is sup-
plied, the list printed includes all builtins, with an indica-
tion of whether or not each is enabled. If --ss is supplied, the
output is restricted to the POSIX _s_p_e_c_i_a_l builtins. The return
value is 0 unless a _n_a_m_e is not a shell builtin or there is an
error loading a new builtin from a shared object.
eevvaall [_a_r_g ...]
The _a_r_gs are read and concatenated together into a single com-
mand. This command is then read and executed by the shell, and
its exit status is returned as the value of eevvaall. If there are
no _a_r_g_s, or only null arguments, eevvaall returns 0.
eexxeecc [--ccll] [--aa _n_a_m_e] [_c_o_m_m_a_n_d [_a_r_g_u_m_e_n_t_s]]
If _c_o_m_m_a_n_d is specified, it replaces the shell. No new process
is created. The _a_r_g_u_m_e_n_t_s become the arguments to _c_o_m_m_a_n_d. If
the --ll option is supplied, the shell places a dash at the begin-
ning of the zeroth argument passed to _c_o_m_m_a_n_d. This is what _l_o_-
_g_i_n(1) does. The --cc option causes _c_o_m_m_a_n_d to be executed with
an empty environment. If --aa is supplied, the shell passes _n_a_m_e
as the zeroth argument to the executed command. If _c_o_m_m_a_n_d can-
not be executed for some reason, a non-interactive shell exits,
unless the eexxeeccffaaiill shell option is enabled. In that case, it
returns failure. An interactive shell returns failure if the
file cannot be executed. A subshell exits unconditionally if
eexxeecc fails. If _c_o_m_m_a_n_d is not specified, any redirections take
effect in the current shell, and the return status is 0. If
there is a redirection error, the return status is 1.
eexxiitt [_n]
Cause the shell to exit with a status of _n. If _n is omitted,
the exit status is that of the last command executed. A trap on
EEXXIITT is executed before the shell terminates.
eexxppoorrtt [--ffnn] [_n_a_m_e[=_w_o_r_d]] ...
eexxppoorrtt --pp
The supplied _n_a_m_e_s are marked for automatic export to the envi-
ronment of subsequently executed commands. If the --ff option is
given, the _n_a_m_e_s refer to functions. If no _n_a_m_e_s are given, or
if the --pp option is supplied, a list of names of all exported
variables is printed. The --nn option causes the export property
to be removed from each _n_a_m_e. If a variable name is followed by
=_w_o_r_d, the value of the variable is set to _w_o_r_d. eexxppoorrtt returns
an exit status of 0 unless an invalid option is encountered, one
of the _n_a_m_e_s is not a valid shell variable name, or --ff is sup-
plied with a _n_a_m_e that is not a function.
ffcc [--ee _e_n_a_m_e] [--llnnrr] [_f_i_r_s_t] [_l_a_s_t]
ffcc --ss [_p_a_t=_r_e_p] [_c_m_d]
The first form selects a range of commands from _f_i_r_s_t to _l_a_s_t
from the history list and displays or edits and re-executes
them. _F_i_r_s_t and _l_a_s_t may be specified as a string (to locate
the last command beginning with that string) or as a number (an
index into the history list, where a negative number is used as
an offset from the current command number). When listing, a
_f_i_r_s_t or _l_a_s_t of 0 is equivalent to -1 and -0 is equivalent to
the current command (usually the ffcc command); otherwise 0 is
equivalent to -1 and -0 is invalid. If _l_a_s_t is not specified,
it is set to the current command for listing (so that ``fc -l
-10'' prints the last 10 commands) and to _f_i_r_s_t otherwise. If
_f_i_r_s_t is not specified, it is set to the previous command for
editing and -16 for listing.
The --nn option suppresses the command numbers when listing. The
--rr option reverses the order of the commands. If the --ll option
is given, the commands are listed on standard output. Other-
wise, the editor given by _e_n_a_m_e is invoked on a file containing
those commands. If _e_n_a_m_e is not given, the value of the FFCCEEDDIITT
variable is used, and the value of EEDDIITTOORR if FFCCEEDDIITT is not set.
If neither variable is set, _v_i is used. When editing is com-
plete, the edited commands are echoed and executed.
In the second form, _c_o_m_m_a_n_d is re-executed after each instance
of _p_a_t is replaced by _r_e_p. _C_o_m_m_a_n_d is interpreted the same as
_f_i_r_s_t above. A useful alias to use with this is ``r="fc -s"'',
so that typing ``r cc'' runs the last command beginning with
``cc'' and typing ``r'' re-executes the last command.
If the first form is used, the return value is 0 unless an in-
valid option is encountered or _f_i_r_s_t or _l_a_s_t specify history
lines out of range. If the --ee option is supplied, the return
value is the value of the last command executed or failure if an
error occurs with the temporary file of commands. If the second
form is used, the return status is that of the command re-exe-
cuted, unless _c_m_d does not specify a valid history line, in
which case ffcc returns failure.
ffgg [_j_o_b_s_p_e_c]
Resume _j_o_b_s_p_e_c in the foreground, and make it the current job.
If _j_o_b_s_p_e_c is not present, the shell's notion of the _c_u_r_r_e_n_t _j_o_b
is used. The return value is that of the command placed into
the foreground, or failure if run when job control is disabled
or, when run with job control enabled, if _j_o_b_s_p_e_c does not spec-
ify a valid job or _j_o_b_s_p_e_c specifies a job that was started
without job control.
ggeettooppttss _o_p_t_s_t_r_i_n_g _n_a_m_e [_a_r_g _._._.]
ggeettooppttss is used by shell procedures to parse positional parame-
ters. _o_p_t_s_t_r_i_n_g contains the option characters to be recog-
nized; if a character is followed by a colon, the option is ex-
pected to have an argument, which should be separated from it by
white space. The colon and question mark characters may not be
used as option characters. Each time it is invoked, ggeettooppttss
places the next option in the shell variable _n_a_m_e, initializing
_n_a_m_e if it does not exist, and the index of the next argument to
be processed into the variable OOPPTTIINNDD. OOPPTTIINNDD is initialized to
1 each time the shell or a shell script is invoked. When an op-
tion requires an argument, ggeettooppttss places that argument into the
variable OOPPTTAARRGG. The shell does not reset OOPPTTIINNDD automatically;
it must be manually reset between multiple calls to ggeettooppttss
within the same shell invocation if a new set of parameters is
to be used.
When the end of options is encountered, ggeettooppttss exits with a re-
turn value greater than zero. OOPPTTIINNDD is set to the index of the
first non-option argument, and _n_a_m_e is set to ?.
ggeettooppttss normally parses the positional parameters, but if more
arguments are supplied as _a_r_g values, ggeettooppttss parses those in-
stead.
ggeettooppttss can report errors in two ways. If the first character
of _o_p_t_s_t_r_i_n_g is a colon, _s_i_l_e_n_t error reporting is used. In
normal operation, diagnostic messages are printed when invalid
options or missing option arguments are encountered. If the
variable OOPPTTEERRRR is set to 0, no error messages will be dis-
played, even if the first character of _o_p_t_s_t_r_i_n_g is not a colon.
If an invalid option is seen, ggeettooppttss places ? into _n_a_m_e and, if
not silent, prints an error message and unsets OOPPTTAARRGG. If
ggeettooppttss is silent, the option character found is placed in OOPP--
TTAARRGG and no diagnostic message is printed.
If a required argument is not found, and ggeettooppttss is not silent,
a question mark (??) is placed in _n_a_m_e, OOPPTTAARRGG is unset, and a
diagnostic message is printed. If ggeettooppttss is silent, then a
colon (::) is placed in _n_a_m_e and OOPPTTAARRGG is set to the option
character found.
ggeettooppttss returns true if an option, specified or unspecified, is
found. It returns false if the end of options is encountered or
an error occurs.
hhaasshh [--llrr] [--pp _f_i_l_e_n_a_m_e] [--ddtt] [_n_a_m_e]
Each time hhaasshh is invoked, the full pathname of the command _n_a_m_e
is determined by searching the directories in $$PPAATTHH and remem-
bered. Any previously-remembered pathname is discarded. If the
--pp option is supplied, no path search is performed, and _f_i_l_e_n_a_m_e
is used as the full filename of the command. The --rr option
causes the shell to forget all remembered locations. The --dd op-
tion causes the shell to forget the remembered location of each
_n_a_m_e. If the --tt option is supplied, the full pathname to which
each _n_a_m_e corresponds is printed. If multiple _n_a_m_e arguments
are supplied with --tt, the _n_a_m_e is printed before the hashed full
pathname. The --ll option causes output to be displayed in a for-
mat that may be reused as input. If no arguments are given, or
if only --ll is supplied, information about remembered commands is
printed. The return status is true unless a _n_a_m_e is not found
or an invalid option is supplied.
hheellpp [--ddmmss] [_p_a_t_t_e_r_n]
Display helpful information about builtin commands. If _p_a_t_t_e_r_n
is specified, hheellpp gives detailed help on all commands matching
_p_a_t_t_e_r_n; otherwise help for all the builtins and shell control
structures is printed.
--dd Display a short description of each _p_a_t_t_e_r_n
--mm Display the description of each _p_a_t_t_e_r_n in a manpage-like
format
--ss Display only a short usage synopsis for each _p_a_t_t_e_r_n
The return status is 0 unless no command matches _p_a_t_t_e_r_n.
hhiissttoorryy [[_n]]
hhiissttoorryy --cc
hhiissttoorryy --dd _o_f_f_s_e_t
hhiissttoorryy --dd _s_t_a_r_t-_e_n_d
hhiissttoorryy --aannrrww [_f_i_l_e_n_a_m_e]
hhiissttoorryy --pp _a_r_g [_a_r_g _._._.]
hhiissttoorryy --ss _a_r_g [_a_r_g _._._.]
With no options, display the command history list with line num-
bers. Lines listed with a ** have been modified. An argument of
_n lists only the last _n lines. If the shell variable HHIISSTTTTIIMMEE--
FFOORRMMAATT is set and not null, it is used as a format string for
_s_t_r_f_t_i_m_e(3) to display the time stamp associated with each dis-
played history entry. No intervening blank is printed between
the formatted time stamp and the history line. If _f_i_l_e_n_a_m_e is
supplied, it is used as the name of the history file; if not,
the value of HHIISSTTFFIILLEE is used. Options, if supplied, have the
following meanings:
--cc Clear the history list by deleting all the entries.
--dd _o_f_f_s_e_t
Delete the history entry at position _o_f_f_s_e_t. If _o_f_f_s_e_t
is negative, it is interpreted as relative to one greater
than the last history position, so negative indices count
back from the end of the history, and an index of -1
refers to the current hhiissttoorryy --dd command.
--dd _s_t_a_r_t-_e_n_d
Delete the history entries between positions _s_t_a_r_t and
_e_n_d, inclusive. Positive and negative values for _s_t_a_r_t
and _e_n_d are interpreted as described above.
--aa Append the ``new'' history lines to the history file.
These are history lines entered since the beginning of
the current bbaasshh session, but not already appended to the
history file.
--nn Read the history lines not already read from the history
file into the current history list. These are lines ap-
pended to the history file since the beginning of the
current bbaasshh session.
--rr Read the contents of the history file and append them to
the current history list.
--ww Write the current history list to the history file, over-
writing the history file's contents.
--pp Perform history substitution on the following _a_r_g_s and
display the result on the standard output. Does not
store the results in the history list. Each _a_r_g must be
quoted to disable normal history expansion.
--ss Store the _a_r_g_s in the history list as a single entry.
The last command in the history list is removed before
the _a_r_g_s are added.
If the HHIISSTTTTIIMMEEFFOORRMMAATT variable is set, the time stamp informa-
tion associated with each history entry is written to the his-
tory file, marked with the history comment character. When the
history file is read, lines beginning with the history comment
character followed immediately by a digit are interpreted as
timestamps for the following history entry. The return value is
0 unless an invalid option is encountered, an error occurs while
reading or writing the history file, an invalid _o_f_f_s_e_t is sup-
plied as an argument to --dd, or the history expansion supplied as
an argument to --pp fails.
jjoobbss [--llnnpprrss] [ _j_o_b_s_p_e_c ... ]
jjoobbss --xx _c_o_m_m_a_n_d [ _a_r_g_s ... ]
The first form lists the active jobs. The options have the fol-
lowing meanings:
--ll List process IDs in addition to the normal information.
--nn Display information only about jobs that have changed
status since the user was last notified of their status.
--pp List only the process ID of the job's process group
leader.
--rr Display only running jobs.
--ss Display only stopped jobs.
If _j_o_b_s_p_e_c is given, output is restricted to information about
that job. The return status is 0 unless an invalid option is
encountered or an invalid _j_o_b_s_p_e_c is supplied.
If the --xx option is supplied, jjoobbss replaces any _j_o_b_s_p_e_c found in
_c_o_m_m_a_n_d or _a_r_g_s with the corresponding process group ID, and ex-
ecutes _c_o_m_m_a_n_d passing it _a_r_g_s, returning its exit status.
kkiillll [--ss _s_i_g_s_p_e_c | --nn _s_i_g_n_u_m | --_s_i_g_s_p_e_c] [_p_i_d | _j_o_b_s_p_e_c] ...
kkiillll --ll|--LL [_s_i_g_s_p_e_c | _e_x_i_t___s_t_a_t_u_s]
Send the signal named by _s_i_g_s_p_e_c or _s_i_g_n_u_m to the processes
named by _p_i_d or _j_o_b_s_p_e_c. _s_i_g_s_p_e_c is either a case-insensitive
signal name such as SSIIGGKKIILLLL (with or without the SSIIGG prefix) or
a signal number; _s_i_g_n_u_m is a signal number. If _s_i_g_s_p_e_c is not
present, then SSIIGGTTEERRMM is assumed. An argument of --ll lists the
signal names. If any arguments are supplied when --ll is given,
the names of the signals corresponding to the arguments are
listed, and the return status is 0. The _e_x_i_t___s_t_a_t_u_s argument to
--ll is a number specifying either a signal number or the exit
status of a process terminated by a signal. The --LL option is
equivalent to --ll. kkiillll returns true if at least one signal was
successfully sent, or false if an error occurs or an invalid op-
tion is encountered.
lleett _a_r_g [_a_r_g ...]
Each _a_r_g is an arithmetic expression to be evaluated (see AARRIITTHH--
MMEETTIICC EEVVAALLUUAATTIIOONN above). If the last _a_r_g evaluates to 0, lleett
returns 1; 0 is returned otherwise.
llooccaall [_o_p_t_i_o_n] [_n_a_m_e[=_v_a_l_u_e] ... | - ]
For each argument, a local variable named _n_a_m_e is created, and
assigned _v_a_l_u_e. The _o_p_t_i_o_n can be any of the options accepted
by ddeeccllaarree. When llooccaall is used within a function, it causes the
variable _n_a_m_e to have a visible scope restricted to that func-
tion and its children. If _n_a_m_e is -, the set of shell options
is made local to the function in which llooccaall is invoked: shell
options changed using the sseett builtin inside the function are
restored to their original values when the function returns.
The restore is effected as if a series of sseett commands were exe-
cuted to restore the values that were in place before the func-
tion. With no operands, llooccaall writes a list of local variables
to the standard output. It is an error to use llooccaall when not
within a function. The return status is 0 unless llooccaall is used
outside a function, an invalid _n_a_m_e is supplied, or _n_a_m_e is a
readonly variable.
llooggoouutt Exit a login shell.
mmaappffiillee [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC
_c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y]
rreeaaddaarrrraayy [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC
_c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y]
Read lines from the standard input into the indexed array vari-
able _a_r_r_a_y, or from file descriptor _f_d if the --uu option is sup-
plied. The variable MMAAPPFFIILLEE is the default _a_r_r_a_y. Options, if
supplied, have the following meanings:
--dd The first character of _d_e_l_i_m is used to terminate each
input line, rather than newline. If _d_e_l_i_m is the empty
string, mmaappffiillee will terminate a line when it reads a NUL
character.
--nn Copy at most _c_o_u_n_t lines. If _c_o_u_n_t is 0, all lines are
copied.
--OO Begin assigning to _a_r_r_a_y at index _o_r_i_g_i_n. The default
index is 0.
--ss Discard the first _c_o_u_n_t lines read.
--tt Remove a trailing _d_e_l_i_m (default newline) from each line
read.
--uu Read lines from file descriptor _f_d instead of the stan-
dard input.
--CC Evaluate _c_a_l_l_b_a_c_k each time _q_u_a_n_t_u_m lines are read. The
--cc option specifies _q_u_a_n_t_u_m.
--cc Specify the number of lines read between each call to
_c_a_l_l_b_a_c_k.
If --CC is specified without --cc, the default quantum is 5000.
When _c_a_l_l_b_a_c_k is evaluated, it is supplied the index of the next
array element to be assigned and the line to be assigned to that
element as additional arguments. _c_a_l_l_b_a_c_k is evaluated after
the line is read but before the array element is assigned.
If not supplied with an explicit origin, mmaappffiillee will clear _a_r_-
_r_a_y before assigning to it.
mmaappffiillee returns successfully unless an invalid option or option
argument is supplied, _a_r_r_a_y is invalid or unassignable, or if
_a_r_r_a_y is not an indexed array.
ppooppdd [-nn] [+_n] [-_n]
Removes entries from the directory stack. With no arguments,
removes the top directory from the stack, and performs a ccdd to
the new top directory. Arguments, if supplied, have the follow-
ing meanings:
--nn Suppresses the normal change of directory when removing
directories from the stack, so that only the stack is ma-
nipulated.
++_n Removes the _nth entry counting from the left of the list
shown by ddiirrss, starting with zero. For example: ``popd
+0'' removes the first directory, ``popd +1'' the second.
--_n Removes the _nth entry counting from the right of the list
shown by ddiirrss, starting with zero. For example: ``popd
-0'' removes the last directory, ``popd -1'' the next to
last.
If the ppooppdd command is successful, a ddiirrss is performed as well,
and the return status is 0. ppooppdd returns false if an invalid
option is encountered, the directory stack is empty, a non-exis-
tent directory stack entry is specified, or the directory change
fails.
pprriinnttff [--vv _v_a_r] _f_o_r_m_a_t [_a_r_g_u_m_e_n_t_s]
Write the formatted _a_r_g_u_m_e_n_t_s to the standard output under the
control of the _f_o_r_m_a_t. The --vv option causes the output to be
assigned to the variable _v_a_r rather than being printed to the
standard output.
The _f_o_r_m_a_t is a character string which contains three types of
objects: plain characters, which are simply copied to standard
output, character escape sequences, which are converted and
copied to the standard output, and format specifications, each
of which causes printing of the next successive _a_r_g_u_m_e_n_t. In
addition to the standard _p_r_i_n_t_f(1) format specifications, pprriinnttff
interprets the following extensions:
%%bb causes pprriinnttff to expand backslash escape sequences in the
corresponding _a_r_g_u_m_e_n_t in the same way as eecchhoo --ee.
%%qq causes pprriinnttff to output the corresponding _a_r_g_u_m_e_n_t in a
format that can be reused as shell input.
%%((_d_a_t_e_f_m_t))TT
causes pprriinnttff to output the date-time string resulting
from using _d_a_t_e_f_m_t as a format string for _s_t_r_f_t_i_m_e(3).
The corresponding _a_r_g_u_m_e_n_t is an integer representing the
number of seconds since the epoch. Two special argument
values may be used: -1 represents the current time, and
-2 represents the time the shell was invoked. If no ar-
gument is specified, conversion behaves as if -1 had been
given. This is an exception to the usual pprriinnttff behav-
ior.
The %b, %q, and %T directives all use the field width and preci-
sion arguments from the format specification and write that many
bytes from (or use that wide a field for) the expanded argument,
which usually contains more characters than the original.
Arguments to non-string format specifiers are treated as C con-
stants, except that a leading plus or minus sign is allowed, and
if the leading character is a single or double quote, the value
is the ASCII value of the following character.
The _f_o_r_m_a_t is reused as necessary to consume all of the _a_r_g_u_-
_m_e_n_t_s. If the _f_o_r_m_a_t requires more _a_r_g_u_m_e_n_t_s than are supplied,
the extra format specifications behave as if a zero value or
null string, as appropriate, had been supplied. The return
value is zero on success, non-zero on failure.
ppuusshhdd [--nn] [+_n] [-_n]
ppuusshhdd [--nn] [_d_i_r]
Adds a directory to the top of the directory stack, or rotates
the stack, making the new top of the stack the current working
directory. With no arguments, ppuusshhdd exchanges the top two di-
rectories and returns 0, unless the directory stack is empty.
Arguments, if supplied, have the following meanings:
--nn Suppresses the normal change of directory when rotating
or adding directories to the stack, so that only the
stack is manipulated.
++_n Rotates the stack so that the _nth directory (counting
from the left of the list shown by ddiirrss, starting with
zero) is at the top.
--_n Rotates the stack so that the _nth directory (counting
from the right of the list shown by ddiirrss, starting with
zero) is at the top.
_d_i_r Adds _d_i_r to the directory stack at the top, making it the
new current working directory as if it had been supplied
as the argument to the ccdd builtin.
If the ppuusshhdd command is successful, a ddiirrss is performed as well.
If the first form is used, ppuusshhdd returns 0 unless the cd to _d_i_r
fails. With the second form, ppuusshhdd returns 0 unless the direc-
tory stack is empty, a non-existent directory stack element is
specified, or the directory change to the specified new current
directory fails.
ppwwdd [--LLPP]
Print the absolute pathname of the current working directory.
The pathname printed contains no symbolic links if the --PP option
is supplied or the --oo pphhyyssiiccaall option to the sseett builtin command
is enabled. If the --LL option is used, the pathname printed may
contain symbolic links. The return status is 0 unless an error
occurs while reading the name of the current directory or an in-
valid option is supplied.
rreeaadd [--eerrss] [--aa _a_n_a_m_e] [--dd _d_e_l_i_m] [--ii _t_e_x_t] [--nn _n_c_h_a_r_s] [--NN _n_c_h_a_r_s] [--pp
_p_r_o_m_p_t] [--tt _t_i_m_e_o_u_t] [--uu _f_d] [_n_a_m_e ...]
One line is read from the standard input, or from the file de-
scriptor _f_d supplied as an argument to the --uu option, split into
words as described above under WWoorrdd SSpplliittttiinngg, and the first
word is assigned to the first _n_a_m_e, the second word to the sec-
ond _n_a_m_e, and so on. If there are more words than names, the
remaining words and their intervening delimiters are assigned to
the last _n_a_m_e. If there are fewer words read from the input
stream than names, the remaining names are assigned empty val-
ues. The characters in IIFFSS are used to split the line into
words using the same rules the shell uses for expansion (de-
scribed above under WWoorrdd SSpplliittttiinngg). The backslash character
(\\) may be used to remove any special meaning for the next char-
acter read and for line continuation. Options, if supplied,
have the following meanings:
--aa _a_n_a_m_e
The words are assigned to sequential indices of the array
variable _a_n_a_m_e, starting at 0. _a_n_a_m_e is unset before any
new values are assigned. Other _n_a_m_e arguments are ig-
nored.
--dd _d_e_l_i_m
The first character of _d_e_l_i_m is used to terminate the in-
put line, rather than newline. If _d_e_l_i_m is the empty
string, rreeaadd will terminate a line when it reads a NUL
character.
--ee If the standard input is coming from a terminal, rreeaaddlliinnee
(see RREEAADDLLIINNEE above) is used to obtain the line. Read-
line uses the current (or default, if line editing was
not previously active) editing settings, but uses Read-
line's default filename completion.
--ii _t_e_x_t
If rreeaaddlliinnee is being used to read the line, _t_e_x_t is
placed into the editing buffer before editing begins.
--nn _n_c_h_a_r_s
rreeaadd returns after reading _n_c_h_a_r_s characters rather than
waiting for a complete line of input, but honors a delim-
iter if fewer than _n_c_h_a_r_s characters are read before the
delimiter.
--NN _n_c_h_a_r_s
rreeaadd returns after reading exactly _n_c_h_a_r_s characters
rather than waiting for a complete line of input, unless
EOF is encountered or rreeaadd times out. Delimiter charac-
ters encountered in the input are not treated specially
and do not cause rreeaadd to return until _n_c_h_a_r_s characters
are read. The result is not split on the characters in
IIFFSS; the intent is that the variable is assigned exactly
the characters read (with the exception of backslash; see
the --rr option below).
--pp _p_r_o_m_p_t
Display _p_r_o_m_p_t on standard error, without a trailing new-
line, before attempting to read any input. The prompt is
displayed only if input is coming from a terminal.
--rr Backslash does not act as an escape character. The back-
slash is considered to be part of the line. In particu-
lar, a backslash-newline pair may not then be used as a
line continuation.
--ss Silent mode. If input is coming from a terminal, charac-
ters are not echoed.
--tt _t_i_m_e_o_u_t
Cause rreeaadd to time out and return failure if a complete
line of input (or a specified number of characters) is
not read within _t_i_m_e_o_u_t seconds. _t_i_m_e_o_u_t may be a deci-
mal number with a fractional portion following the deci-
mal point. This option is only effective if rreeaadd is
reading input from a terminal, pipe, or other special
file; it has no effect when reading from regular files.
If rreeaadd times out, rreeaadd saves any partial input read into
the specified variable _n_a_m_e. If _t_i_m_e_o_u_t is 0, rreeaadd re-
turns immediately, without trying to read any data. The
exit status is 0 if input is available on the specified
file descriptor, non-zero otherwise. The exit status is
greater than 128 if the timeout is exceeded.
--uu _f_d Read input from file descriptor _f_d.
If no _n_a_m_e_s are supplied, the line read, without the ending de-
limiter but otherwise unmodified, is assigned to the variable
RREEPPLLYY. The exit status is zero, unless end-of-file is encoun-
tered, rreeaadd times out (in which case the status is greater than
128), a variable assignment error (such as assigning to a read-
only variable) occurs, or an invalid file descriptor is supplied
as the argument to --uu.
rreeaaddoonnllyy [--aaAAff] [--pp] [_n_a_m_e[=_w_o_r_d] ...]
The given _n_a_m_e_s are marked readonly; the values of these _n_a_m_e_s
may not be changed by subsequent assignment. If the --ff option
is supplied, the functions corresponding to the _n_a_m_e_s are so
marked. The --aa option restricts the variables to indexed ar-
rays; the --AA option restricts the variables to associative ar-
rays. If both options are supplied, --AA takes precedence. If no
_n_a_m_e arguments are given, or if the --pp option is supplied, a
list of all readonly names is printed. The other options may be
used to restrict the output to a subset of the set of readonly
names. The --pp option causes output to be displayed in a format
that may be reused as input. If a variable name is followed by
=_w_o_r_d, the value of the variable is set to _w_o_r_d. The return
status is 0 unless an invalid option is encountered, one of the
_n_a_m_e_s is not a valid shell variable name, or --ff is supplied with
a _n_a_m_e that is not a function.
rreettuurrnn [_n]
Causes a function to stop executing and return the value speci-
fied by _n to its caller. If _n is omitted, the return status is
that of the last command executed in the function body. If rree--
ttuurrnn is executed by a trap handler, the last command used to de-
termine the status is the last command executed before the trap
handler. If rreettuurrnn is executed during a DDEEBBUUGG trap, the last
command used to determine the status is the last command exe-
cuted by the trap handler before rreettuurrnn was invoked. If rreettuurrnn
is used outside a function, but during execution of a script by
the .. (ssoouurrccee) command, it causes the shell to stop executing
that script and return either _n or the exit status of the last
command executed within the script as the exit status of the
script. If _n is supplied, the return value is its least signif-
icant 8 bits. The return status is non-zero if rreettuurrnn is sup-
plied a non-numeric argument, or is used outside a function and
not during execution of a script by .. or ssoouurrccee. Any command
associated with the RREETTUURRNN trap is executed before execution re-
sumes after the function or script.
sseett [----aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [--oo _o_p_t_i_o_n_-_n_a_m_e] [_a_r_g ...]
sseett [++aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [++oo _o_p_t_i_o_n_-_n_a_m_e] [_a_r_g ...]
Without options, the name and value of each shell variable are
displayed in a format that can be reused as input for setting or
resetting the currently-set variables. Read-only variables can-
not be reset. In _p_o_s_i_x _m_o_d_e, only shell variables are listed.
The output is sorted according to the current locale. When op-
tions are specified, they set or unset shell attributes. Any
arguments remaining after option processing are treated as val-
ues for the positional parameters and are assigned, in order, to
$$11, $$22, ...... $$_n. Options, if specified, have the following
meanings:
--aa Each variable or function that is created or modified is
given the export attribute and marked for export to the
environment of subsequent commands.
--bb Report the status of terminated background jobs immedi-
ately, rather than before the next primary prompt. This
is effective only when job control is enabled.
--ee Exit immediately if a _p_i_p_e_l_i_n_e (which may consist of a
single _s_i_m_p_l_e _c_o_m_m_a_n_d), a _l_i_s_t, or a _c_o_m_p_o_u_n_d _c_o_m_m_a_n_d
(see SSHHEELLLL GGRRAAMMMMAARR above), exits with a non-zero status.
The shell does not exit if the command that fails is
part of the command list immediately following a wwhhiillee
or uunnttiill keyword, part of the test following the iiff or
eelliiff reserved words, part of any command executed in a
&&&& or |||| list except the command following the final &&&&
or ||||, any command in a pipeline but the last, or if the
command's return value is being inverted with !!. If a
compound command other than a subshell returns a non-
zero status because a command failed while --ee was being
ignored, the shell does not exit. A trap on EERRRR, if
set, is executed before the shell exits. This option
applies to the shell environment and each subshell envi-
ronment separately (see CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT
above), and may cause subshells to exit before executing
all the commands in the subshell.
If a compound command or shell function executes in a
context where --ee is being ignored, none of the commands
executed within the compound command or function body
will be affected by the --ee setting, even if --ee is set
and a command returns a failure status. If a compound
command or shell function sets --ee while executing in a
context where --ee is ignored, that setting will not have
any effect until the compound command or the command
containing the function call completes.
--ff Disable pathname expansion.
--hh Remember the location of commands as they are looked up
for execution. This is enabled by default.
--kk All arguments in the form of assignment statements are
placed in the environment for a command, not just those
that precede the command name.
--mm Monitor mode. Job control is enabled. This option is
on by default for interactive shells on systems that
support it (see JJOOBB CCOONNTTRROOLL above). All processes run
in a separate process group. When a background job com-
pletes, the shell prints a line containing its exit sta-
tus.
--nn Read commands but do not execute them. This may be used
to check a shell script for syntax errors. This is ig-
nored by interactive shells.
--oo _o_p_t_i_o_n_-_n_a_m_e
The _o_p_t_i_o_n_-_n_a_m_e can be one of the following:
aalllleexxppoorrtt
Same as --aa.
bbrraacceeeexxppaanndd
Same as --BB.
eemmaaccss Use an emacs-style command line editing inter-
face. This is enabled by default when the shell
is interactive, unless the shell is started with
the ----nnooeeddiittiinngg option. This also affects the
editing interface used for rreeaadd --ee.
eerrrreexxiitt Same as --ee.
eerrrrttrraaccee
Same as --EE.
ffuunnccttrraaccee
Same as --TT.
hhaasshhaallll Same as --hh.
hhiisstteexxppaanndd
Same as --HH.
hhiissttoorryy Enable command history, as described above under
HHIISSTTOORRYY. This option is on by default in inter-
active shells.
iiggnnoorreeeeooff
The effect is as if the shell command ``IG-
NOREEOF=10'' had been executed (see SShheellll VVaarrii--
aabblleess above).
kkeeyywwoorrdd Same as --kk.
mmoonniittoorr Same as --mm.
nnoocclloobbbbeerr
Same as --CC.
nnooeexxeecc Same as --nn.
nnoogglloobb Same as --ff.
nnoolloogg Currently ignored.
nnoottiiffyy Same as --bb.
nnoouunnsseett Same as --uu.
oonneeccmmdd Same as --tt.
pphhyyssiiccaall
Same as --PP.
ppiippeeffaaiill
If set, the return value of a pipeline is the
value of the last (rightmost) command to exit
with a non-zero status, or zero if all commands
in the pipeline exit successfully. This option
is disabled by default.
ppoossiixx Change the behavior of bbaasshh where the default
operation differs from the POSIX standard to
match the standard (_p_o_s_i_x _m_o_d_e). See SSEEEE AALLSSOO
below for a reference to a document that details
how posix mode affects bash's behavior.
pprriivviilleeggeedd
Same as --pp.
vveerrbboossee Same as --vv.
vvii Use a vi-style command line editing interface.
This also affects the editing interface used for
rreeaadd --ee.
xxttrraaccee Same as --xx.
If --oo is supplied with no _o_p_t_i_o_n_-_n_a_m_e, the values of the
current options are printed. If ++oo is supplied with no
_o_p_t_i_o_n_-_n_a_m_e, a series of sseett commands to recreate the
current option settings is displayed on the standard
output.
--pp Turn on _p_r_i_v_i_l_e_g_e_d mode. In this mode, the $$EENNVV and
$$BBAASSHH__EENNVV files are not processed, shell functions are
not inherited from the environment, and the SSHHEELLLLOOPPTTSS,
BBAASSHHOOPPTTSS, CCDDPPAATTHH, and GGLLOOBBIIGGNNOORREE variables, if they ap-
pear in the environment, are ignored. If the shell is
started with the effective user (group) id not equal to
the real user (group) id, and the --pp option is not sup-
plied, these actions are taken and the effective user id
is set to the real user id. If the --pp option is sup-
plied at startup, the effective user id is not reset.
Turning this option off causes the effective user and
group ids to be set to the real user and group ids.
--tt Exit after reading and executing one command.
--uu Treat unset variables and parameters other than the spe-
cial parameters "@" and "*" as an error when performing
parameter expansion. If expansion is attempted on an
unset variable or parameter, the shell prints an error
message, and, if not interactive, exits with a non-zero
status.
--vv Print shell input lines as they are read.
--xx After expanding each _s_i_m_p_l_e _c_o_m_m_a_n_d, ffoorr command, ccaassee
command, sseelleecctt command, or arithmetic ffoorr command, dis-
play the expanded value of PPSS44, followed by the command
and its expanded arguments or associated word list.
--BB The shell performs brace expansion (see BBrraaccee EExxppaannssiioonn
above). This is on by default.
--CC If set, bbaasshh does not overwrite an existing file with
the >>, >>&&, and <<>> redirection operators. This may be
overridden when creating output files by using the redi-
rection operator >>|| instead of >>.
--EE If set, any trap on EERRRR is inherited by shell functions,
command substitutions, and commands executed in a sub-
shell environment. The EERRRR trap is normally not inher-
ited in such cases.
--HH Enable !! style history substitution. This option is on
by default when the shell is interactive.
--PP If set, the shell does not resolve symbolic links when
executing commands such as ccdd that change the current
working directory. It uses the physical directory
structure instead. By default, bbaasshh follows the logical
chain of directories when performing commands which
change the current directory.
--TT If set, any traps on DDEEBBUUGG and RREETTUURRNN are inherited by
shell functions, command substitutions, and commands ex-
ecuted in a subshell environment. The DDEEBBUUGG and RREETTUURRNN
traps are normally not inherited in such cases.
---- If no arguments follow this option, then the positional
parameters are unset. Otherwise, the positional parame-
ters are set to the _a_r_gs, even if some of them begin
with a --.
-- Signal the end of options, cause all remaining _a_r_gs to
be assigned to the positional parameters. The --xx and --vv
options are turned off. If there are no _a_r_gs, the posi-
tional parameters remain unchanged.
The options are off by default unless otherwise noted. Using +
rather than - causes these options to be turned off. The op-
tions can also be specified as arguments to an invocation of the
shell. The current set of options may be found in $$--. The re-
turn status is always true unless an invalid option is encoun-
tered.
sshhiifftt [_n]
The positional parameters from _n+1 ... are renamed to $$11 ........
Parameters represented by the numbers $$## down to $$##-_n+1 are un-
set. _n must be a non-negative number less than or equal to $$##.
If _n is 0, no parameters are changed. If _n is not given, it is
assumed to be 1. If _n is greater than $$##, the positional param-
eters are not changed. The return status is greater than zero
if _n is greater than $$## or less than zero; otherwise 0.
sshhoopptt [--ppqqssuu] [--oo] [_o_p_t_n_a_m_e ...]
Toggle the values of settings controlling optional shell behav-
ior. The settings can be either those listed below, or, if the
--oo option is used, those available with the --oo option to the sseett
builtin command. With no options, or with the --pp option, a list
of all settable options is displayed, with an indication of
whether or not each is set; if _o_p_t_n_a_m_e_s are supplied, the output
is restricted to those options. The --pp option causes output to
be displayed in a form that may be reused as input. Other op-
tions have the following meanings:
--ss Enable (set) each _o_p_t_n_a_m_e.
--uu Disable (unset) each _o_p_t_n_a_m_e.
--qq Suppresses normal output (quiet mode); the return status
indicates whether the _o_p_t_n_a_m_e is set or unset. If multi-
ple _o_p_t_n_a_m_e arguments are given with --qq, the return sta-
tus is zero if all _o_p_t_n_a_m_e_s are enabled; non-zero other-
wise.
--oo Restricts the values of _o_p_t_n_a_m_e to be those defined for
the --oo option to the sseett builtin.
If either --ss or --uu is used with no _o_p_t_n_a_m_e arguments, sshhoopptt
shows only those options which are set or unset, respectively.
Unless otherwise noted, the sshhoopptt options are disabled (unset)
by default.
The return status when listing options is zero if all _o_p_t_n_a_m_e_s
are enabled, non-zero otherwise. When setting or unsetting op-
tions, the return status is zero unless an _o_p_t_n_a_m_e is not a
valid shell option.
The list of sshhoopptt options is:
aassssoocc__eexxppaanndd__oonnccee
If set, the shell suppresses multiple evaluation of as-
sociative array subscripts during arithmetic expression
evaluation, while executing builtins that can perform
variable assignments, and while executing builtins that
perform array dereferencing.
aauuttooccdd If set, a command name that is the name of a directory
is executed as if it were the argument to the ccdd com-
mand. This option is only used by interactive shells.
ccddaabbllee__vvaarrss
If set, an argument to the ccdd builtin command that is
not a directory is assumed to be the name of a variable
whose value is the directory to change to.
ccddssppeellll If set, minor errors in the spelling of a directory com-
ponent in a ccdd command will be corrected. The errors
checked for are transposed characters, a missing charac-
ter, and one character too many. If a correction is
found, the corrected filename is printed, and the com-
mand proceeds. This option is only used by interactive
shells.
cchheecckkhhaasshh
If set, bbaasshh checks that a command found in the hash ta-
ble exists before trying to execute it. If a hashed
command no longer exists, a normal path search is per-
formed.
cchheecckkjjoobbss
If set, bbaasshh lists the status of any stopped and running
jobs before exiting an interactive shell. If any jobs
are running, this causes the exit to be deferred until a
second exit is attempted without an intervening command
(see JJOOBB CCOONNTTRROOLL above). The shell always postpones ex-
iting if any jobs are stopped.
cchheecckkwwiinnssiizzee
If set, bbaasshh checks the window size after each external
(non-builtin) command and, if necessary, updates the
values of LLIINNEESS and CCOOLLUUMMNNSS. This option is enabled by
default.
ccmmddhhiisstt If set, bbaasshh attempts to save all lines of a multiple-
line command in the same history entry. This allows
easy re-editing of multi-line commands. This option is
enabled by default, but only has an effect if command
history is enabled, as described above under HHIISSTTOORRYY.
ccoommppaatt3311
ccoommppaatt3322
ccoommppaatt4400
ccoommppaatt4411
ccoommppaatt4422
ccoommppaatt4433
ccoommppaatt4444
These control aspects of the shell's compatibility mode
(see SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE below).
ccoommpplleettee__ffuullllqquuoottee
If set, bbaasshh quotes all shell metacharacters in file-
names and directory names when performing completion.
If not set, bbaasshh removes metacharacters such as the dol-
lar sign from the set of characters that will be quoted
in completed filenames when these metacharacters appear
in shell variable references in words to be completed.
This means that dollar signs in variable names that ex-
pand to directories will not be quoted; however, any
dollar signs appearing in filenames will not be quoted,
either. This is active only when bash is using back-
slashes to quote completed filenames. This variable is
set by default, which is the default bash behavior in
versions through 4.2.
ddiirreexxppaanndd
If set, bbaasshh replaces directory names with the results
of word expansion when performing filename completion.
This changes the contents of the readline editing buf-
fer. If not set, bbaasshh attempts to preserve what the
user typed.
ddiirrssppeellll
If set, bbaasshh attempts spelling correction on directory
names during word completion if the directory name ini-
tially supplied does not exist.
ddoottgglloobb If set, bbaasshh includes filenames beginning with a `.' in
the results of pathname expansion. The filenames ````..''''
and ````....'''' must always be matched explicitly, even if
ddoottgglloobb is set.
eexxeeccffaaiill
If set, a non-interactive shell will not exit if it can-
not execute the file specified as an argument to the
eexxeecc builtin command. An interactive shell does not
exit if eexxeecc fails.
eexxppaanndd__aalliiaasseess
If set, aliases are expanded as described above under
AALLIIAASSEESS. This option is enabled by default for interac-
tive shells.
eexxttddeebbuugg
If set at shell invocation, or in a shell startup file,
arrange to execute the debugger profile before the shell
starts, identical to the ----ddeebbuuggggeerr option. If set af-
ter invocation, behavior intended for use by debuggers
is enabled:
11.. The --FF option to the ddeeccllaarree builtin displays the
source file name and line number corresponding to
each function name supplied as an argument.
22.. If the command run by the DDEEBBUUGG trap returns a
non-zero value, the next command is skipped and
not executed.
33.. If the command run by the DDEEBBUUGG trap returns a
value of 2, and the shell is executing in a sub-
routine (a shell function or a shell script exe-
cuted by the .. or ssoouurrccee builtins), the shell
simulates a call to rreettuurrnn.
44.. BBAASSHH__AARRGGCC and BBAASSHH__AARRGGVV are updated as described
in their descriptions above.
55.. Function tracing is enabled: command substitu-
tion, shell functions, and subshells invoked with
(( _c_o_m_m_a_n_d )) inherit the DDEEBBUUGG and RREETTUURRNN traps.
66.. Error tracing is enabled: command substitution,
shell functions, and subshells invoked with ((
_c_o_m_m_a_n_d )) inherit the EERRRR trap.
eexxttgglloobb If set, the extended pattern matching features described
above under PPaatthhnnaammee EExxppaannssiioonn are enabled.
eexxttqquuoottee
If set, $$'_s_t_r_i_n_g' and $$"_s_t_r_i_n_g" quoting is performed
within $${{_p_a_r_a_m_e_t_e_r}} expansions enclosed in double
quotes. This option is enabled by default.
ffaaiillgglloobb
If set, patterns which fail to match filenames during
pathname expansion result in an expansion error.
ffoorrccee__ffiiggnnoorree
If set, the suffixes specified by the FFIIGGNNOORREE shell
variable cause words to be ignored when performing word
completion even if the ignored words are the only possi-
ble completions. See SSHHEELLLL VVAARRIIAABBLLEESS above for a de-
scription of FFIIGGNNOORREE. This option is enabled by de-
fault.
gglloobbaasscciiiirraannggeess
If set, range expressions used in pattern matching
bracket expressions (see PPaatttteerrnn MMaattcchhiinngg above) behave
as if in the traditional C locale when performing com-
parisons. That is, the current locale's collating se-
quence is not taken into account, so bb will not collate
between AA and BB, and upper-case and lower-case ASCII
characters will collate together.
gglloobbssttaarr
If set, the pattern **** used in a pathname expansion con-
text will match all files and zero or more directories
and subdirectories. If the pattern is followed by a //,
only directories and subdirectories match.
ggnnuu__eerrrrffmmtt
If set, shell error messages are written in the standard
GNU error message format.
hhiissttaappppeenndd
If set, the history list is appended to the file named
by the value of the HHIISSTTFFIILLEE variable when the shell ex-
its, rather than overwriting the file.
hhiissttrreeeeddiitt
If set, and rreeaaddlliinnee is being used, a user is given the
opportunity to re-edit a failed history substitution.
hhiissttvveerriiffyy
If set, and rreeaaddlliinnee is being used, the results of his-
tory substitution are not immediately passed to the
shell parser. Instead, the resulting line is loaded
into the rreeaaddlliinnee editing buffer, allowing further modi-
fication.
hhoossttccoommpplleettee
If set, and rreeaaddlliinnee is being used, bbaasshh will attempt to
perform hostname completion when a word containing a @@
is being completed (see CCoommpplleettiinngg under RREEAADDLLIINNEE
above). This is enabled by default.
hhuuppoonneexxiitt
If set, bbaasshh will send SSIIGGHHUUPP to all jobs when an inter-
active login shell exits.
iinnhheerriitt__eerrrreexxiitt
If set, command substitution inherits the value of the
eerrrreexxiitt option, instead of unsetting it in the subshell
environment. This option is enabled when _p_o_s_i_x _m_o_d_e is
enabled.
iinntteerraaccttiivvee__ccoommmmeennttss
If set, allow a word beginning with ## to cause that word
and all remaining characters on that line to be ignored
in an interactive shell (see CCOOMMMMEENNTTSS above). This op-
tion is enabled by default.
llaassttppiippee
If set, and job control is not active, the shell runs
the last command of a pipeline not executed in the back-
ground in the current shell environment.
lliitthhiisstt If set, and the ccmmddhhiisstt option is enabled, multi-line
commands are saved to the history with embedded newlines
rather than using semicolon separators where possible.
llooccaallvvaarr__iinnhheerriitt
If set, local variables inherit the value and attributes
of a variable of the same name that exists at a previous
scope before any new value is assigned. The nameref at-
tribute is not inherited.
llooccaallvvaarr__uunnsseett
If set, calling uunnsseett on local variables in previous
function scopes marks them so subsequent lookups find
them unset until that function returns. This is identi-
cal to the behavior of unsetting local variables at the
current function scope.
llooggiinn__sshheellll
The shell sets this option if it is started as a login
shell (see IINNVVOOCCAATTIIOONN above). The value may not be
changed.
mmaaiillwwaarrnn
If set, and a file that bbaasshh is checking for mail has
been accessed since the last time it was checked, the
message ``The mail in _m_a_i_l_f_i_l_e has been read'' is dis-
played.
nnoo__eemmppttyy__ccmmdd__ccoommpplleettiioonn
If set, and rreeaaddlliinnee is being used, bbaasshh will not at-
tempt to search the PPAATTHH for possible completions when
completion is attempted on an empty line.
nnooccaasseegglloobb
If set, bbaasshh matches filenames in a case-insensitive
fashion when performing pathname expansion (see PPaatthhnnaammee
EExxppaannssiioonn above).
nnooccaasseemmaattcchh
If set, bbaasshh matches patterns in a case-insensitive
fashion when performing matching while executing ccaassee or
[[[[ conditional commands, when performing pattern substi-
tution word expansions, or when filtering possible com-
pletions as part of programmable completion.
nnuullllgglloobb
If set, bbaasshh allows patterns which match no files (see
PPaatthhnnaammee EExxppaannssiioonn above) to expand to a null string,
rather than themselves.
pprrooggccoommpp
If set, the programmable completion facilities (see PPrroo--
ggrraammmmaabbllee CCoommpplleettiioonn above) are enabled. This option is
enabled by default.
pprrooggccoommpp__aalliiaass
If set, and programmable completion is enabled, bbaasshh
treats a command name that doesn't have any completions
as a possible alias and attempts alias expansion. If it
has an alias, bbaasshh attempts programmable completion us-
ing the command word resulting from the expanded alias.
pprroommppttvvaarrss
If set, prompt strings undergo parameter expansion, com-
mand substitution, arithmetic expansion, and quote re-
moval after being expanded as described in PPRROOMMPPTTIINNGG
above. This option is enabled by default.
rreessttrriicctteedd__sshheellll
The shell sets this option if it is started in re-
stricted mode (see RREESSTTRRIICCTTEEDD SSHHEELLLL below). The value
may not be changed. This is not reset when the startup
files are executed, allowing the startup files to dis-
cover whether or not a shell is restricted.
sshhiifftt__vveerrbboossee
If set, the sshhiifftt builtin prints an error message when
the shift count exceeds the number of positional parame-
ters.
ssoouurrcceeppaatthh
If set, the ssoouurrccee (..) builtin uses the value of PPAATTHH to
find the directory containing the file supplied as an
argument. This option is enabled by default.
xxppgg__eecchhoo
If set, the eecchhoo builtin expands backslash-escape se-
quences by default.
ssuussppeenndd [--ff]
Suspend the execution of this shell until it receives a SSIIGGCCOONNTT
signal. A login shell cannot be suspended; the --ff option can be
used to override this and force the suspension. The return sta-
tus is 0 unless the shell is a login shell and --ff is not sup-
plied, or if job control is not enabled.
tteesstt _e_x_p_r
[[ _e_x_p_r ]]
Return a status of 0 (true) or 1 (false) depending on the evalu-
ation of the conditional expression _e_x_p_r. Each operator and op-
erand must be a separate argument. Expressions are composed of
the primaries described in the bbaasshh manual page under CCOONNDDII--
TTIIOONNAALL EEXXPPRREESSSSIIOONNSS. tteesstt does not accept any options, nor does
it accept and ignore an argument of ---- as signifying the end of
options.
Expressions may be combined using the following operators,
listed in decreasing order of precedence. The evaluation de-
pends on the number of arguments; see below. Operator prece-
dence is used when there are five or more arguments.
!! _e_x_p_r True if _e_x_p_r is false.
(( _e_x_p_r ))
Returns the value of _e_x_p_r. This may be used to override
the normal precedence of operators.
_e_x_p_r_1 -aa _e_x_p_r_2
True if both _e_x_p_r_1 and _e_x_p_r_2 are true.
_e_x_p_r_1 -oo _e_x_p_r_2
True if either _e_x_p_r_1 or _e_x_p_r_2 is true.
tteesstt and [[ evaluate conditional expressions using a set of rules
based on the number of arguments.
0 arguments
The expression is false.
1 argument
The expression is true if and only if the argument is not
null.
2 arguments
If the first argument is !!, the expression is true if and
only if the second argument is null. If the first argu-
ment is one of the unary conditional operators listed
above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, the expression is
true if the unary test is true. If the first argument is
not a valid unary conditional operator, the expression is
false.
3 arguments
The following conditions are applied in the order listed.
If the second argument is one of the binary conditional
operators listed above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, the
result of the expression is the result of the binary test
using the first and third arguments as operands. The --aa
and --oo operators are considered binary operators when
there are three arguments. If the first argument is !!,
the value is the negation of the two-argument test using
the second and third arguments. If the first argument is
exactly (( and the third argument is exactly )), the result
is the one-argument test of the second argument. Other-
wise, the expression is false.
4 arguments
If the first argument is !!, the result is the negation of
the three-argument expression composed of the remaining
arguments. Otherwise, the expression is parsed and eval-
uated according to precedence using the rules listed
above.
5 or more arguments
The expression is parsed and evaluated according to
precedence using the rules listed above.
When used with tteesstt or [[, the << and >> operators sort lexico-
graphically using ASCII ordering.
ttiimmeess Print the accumulated user and system times for the shell and
for processes run from the shell. The return status is 0.
ttrraapp [--llpp] [[_a_r_g] _s_i_g_s_p_e_c ...]
The command _a_r_g is to be read and executed when the shell re-
ceives signal(s) _s_i_g_s_p_e_c. If _a_r_g is absent (and there is a sin-
gle _s_i_g_s_p_e_c) or --, each specified signal is reset to its origi-
nal disposition (the value it had upon entrance to the shell).
If _a_r_g is the null string the signal specified by each _s_i_g_s_p_e_c
is ignored by the shell and by the commands it invokes. If _a_r_g
is not present and --pp has been supplied, then the trap commands
associated with each _s_i_g_s_p_e_c are displayed. If no arguments are
supplied or if only --pp is given, ttrraapp prints the list of com-
mands associated with each signal. The --ll option causes the
shell to print a list of signal names and their corresponding
numbers. Each _s_i_g_s_p_e_c is either a signal name defined in <_s_i_g_-
_n_a_l_._h>, or a signal number. Signal names are case insensitive
and the SSIIGG prefix is optional.
If a _s_i_g_s_p_e_c is EEXXIITT (0) the command _a_r_g is executed on exit
from the shell. If a _s_i_g_s_p_e_c is DDEEBBUUGG, the command _a_r_g is exe-
cuted before every _s_i_m_p_l_e _c_o_m_m_a_n_d, _f_o_r command, _c_a_s_e command,
_s_e_l_e_c_t command, every arithmetic _f_o_r command, and before the
first command executes in a shell function (see SSHHEELLLL GGRRAAMMMMAARR
above). Refer to the description of the eexxttddeebbuugg option to the
sshhoopptt builtin for details of its effect on the DDEEBBUUGG trap. If a
_s_i_g_s_p_e_c is RREETTUURRNN, the command _a_r_g is executed each time a shell
function or a script executed with the .. or ssoouurrccee builtins fin-
ishes executing.
If a _s_i_g_s_p_e_c is EERRRR, the command _a_r_g is executed whenever a
pipeline (which may consist of a single simple command), a list,
or a compound command returns a non-zero exit status, subject to
the following conditions. The EERRRR trap is not executed if the
failed command is part of the command list immediately following
a wwhhiillee or uunnttiill keyword, part of the test in an _i_f statement,
part of a command executed in a &&&& or |||| list except the command
following the final &&&& or ||||, any command in a pipeline but the
last, or if the command's return value is being inverted using
!!. These are the same conditions obeyed by the eerrrreexxiitt (--ee) op-
tion.
Signals ignored upon entry to the shell cannot be trapped or re-
set. Trapped signals that are not being ignored are reset to
their original values in a subshell or subshell environment when
one is created. The return status is false if any _s_i_g_s_p_e_c is
invalid; otherwise ttrraapp returns true.
ttyyppee [--aaffttppPP] _n_a_m_e [_n_a_m_e ...]
With no options, indicate how each _n_a_m_e would be interpreted if
used as a command name. If the --tt option is used, ttyyppee prints a
string which is one of _a_l_i_a_s, _k_e_y_w_o_r_d, _f_u_n_c_t_i_o_n, _b_u_i_l_t_i_n, or
_f_i_l_e if _n_a_m_e is an alias, shell reserved word, function,
builtin, or disk file, respectively. If the _n_a_m_e is not found,
then nothing is printed, and an exit status of false is re-
turned. If the --pp option is used, ttyyppee either returns the name
of the disk file that would be executed if _n_a_m_e were specified
as a command name, or nothing if ``type -t name'' would not re-
turn _f_i_l_e. The --PP option forces a PPAATTHH search for each _n_a_m_e,
even if ``type -t name'' would not return _f_i_l_e. If a command is
hashed, --pp and --PP print the hashed value, which is not necessar-
ily the file that appears first in PPAATTHH. If the --aa option is
used, ttyyppee prints all of the places that contain an executable
named _n_a_m_e. This includes aliases and functions, if and only if
the --pp option is not also used. The table of hashed commands is
not consulted when using --aa. The --ff option suppresses shell
function lookup, as with the ccoommmmaanndd builtin. ttyyppee returns true
if all of the arguments are found, false if any are not found.
uulliimmiitt [--HHSS] --aa
uulliimmiitt [--HHSS] [--bbccddeeffiikkllmmnnppqqrrssttuuvvxxPPRRTT [_l_i_m_i_t]]
Provides control over the resources available to the shell and
to processes started by it, on systems that allow such control.
The --HH and --SS options specify that the hard or soft limit is set
for the given resource. A hard limit cannot be increased by a
non-root user once it is set; a soft limit may be increased up
to the value of the hard limit. If neither --HH nor --SS is speci-
fied, both the soft and hard limits are set. The value of _l_i_m_i_t
can be a number in the unit specified for the resource or one of
the special values hhaarrdd, ssoofftt, or uunnlliimmiitteedd, which stand for the
current hard limit, the current soft limit, and no limit, re-
spectively. If _l_i_m_i_t is omitted, the current value of the soft
limit of the resource is printed, unless the --HH option is given.
When more than one resource is specified, the limit name and
unit, if appropriate, are printed before the value. Other op-
tions are interpreted as follows:
--aa All current limits are reported; no limits are set
--bb The maximum socket buffer size
--cc The maximum size of core files created
--dd The maximum size of a process's data segment
--ee The maximum scheduling priority ("nice")
--ff The maximum size of files written by the shell and its
children
--ii The maximum number of pending signals
--kk The maximum number of kqueues that may be allocated
--ll The maximum size that may be locked into memory
--mm The maximum resident set size (many systems do not honor
this limit)
--nn The maximum number of open file descriptors (most systems
do not allow this value to be set)
--pp The pipe size in 512-byte blocks (this may not be set)
--qq The maximum number of bytes in POSIX message queues
--rr The maximum real-time scheduling priority
--ss The maximum stack size
--tt The maximum amount of cpu time in seconds
--uu The maximum number of processes available to a single
user
--vv The maximum amount of virtual memory available to the
shell and, on some systems, to its children
--xx The maximum number of file locks
--PP The maximum number of pseudoterminals
--RR The maximum time a real-time process can run before
blocking, in microseconds
--TT The maximum number of threads
If _l_i_m_i_t is given, and the --aa option is not used, _l_i_m_i_t is the
new value of the specified resource. If no option is given,
then --ff is assumed. Values are in 1024-byte increments, except
for --tt, which is in seconds; --RR, which is in microseconds; --pp,
which is in units of 512-byte blocks; --PP, --TT, --bb, --kk, --nn, and
--uu, which are unscaled values; and, when in posix mode, --cc and
--ff, which are in 512-byte increments. The return status is 0
unless an invalid option or argument is supplied, or an error
occurs while setting a new limit.
uummaasskk [--pp] [--SS] [_m_o_d_e]
The user file-creation mask is set to _m_o_d_e. If _m_o_d_e begins with
a digit, it is interpreted as an octal number; otherwise it is
interpreted as a symbolic mode mask similar to that accepted by
_c_h_m_o_d(1). If _m_o_d_e is omitted, the current value of the mask is
printed. The --SS option causes the mask to be printed in sym-
bolic form; the default output is an octal number. If the --pp
option is supplied, and _m_o_d_e is omitted, the output is in a form
that may be reused as input. The return status is 0 if the mode
was successfully changed or if no _m_o_d_e argument was supplied,
and false otherwise.
uunnaalliiaass [-aa] [_n_a_m_e ...]
Remove each _n_a_m_e from the list of defined aliases. If --aa is
supplied, all alias definitions are removed. The return value
is true unless a supplied _n_a_m_e is not a defined alias.
uunnsseett [-ffvv] [-nn] [_n_a_m_e ...]
For each _n_a_m_e, remove the corresponding variable or function.
If the --vv option is given, each _n_a_m_e refers to a shell variable,
and that variable is removed. Read-only variables may not be
unset. If --ff is specified, each _n_a_m_e refers to a shell func-
tion, and the function definition is removed. If the --nn option
is supplied, and _n_a_m_e is a variable with the _n_a_m_e_r_e_f attribute,
_n_a_m_e will be unset rather than the variable it references. --nn
has no effect if the --ff option is supplied. If no options are
supplied, each _n_a_m_e refers to a variable; if there is no vari-
able by that name, a function with that name, if any, is unset.
Each unset variable or function is removed from the environment
passed to subsequent commands. If any of BBAASSHH__AALLIIAASSEESS,
BBAASSHH__AARRGGVV00, BBAASSHH__CCMMDDSS, BBAASSHH__CCOOMMMMAANNDD, BBAASSHH__SSUUBBSSHHEELLLL, BBAASSHHPPIIDD,
CCOOMMPP__WWOORRDDBBRREEAAKKSS, DDIIRRSSTTAACCKK, EEPPOOCCHHRREEAALLTTIIMMEE, EEPPOOCCHHSSEECCOONNDDSS, FFUUNNCC--
NNAAMMEE, GGRROOUUPPSS, HHIISSTTCCMMDD, LLIINNEENNOO, RRAANNDDOOMM, SSEECCOONNDDSS, or SSRRAANNDDOOMM are
unset, they lose their special properties, even if they are sub-
sequently reset. The exit status is true unless a _n_a_m_e is read-
only.
wwaaiitt [--ffnn] [--pp _v_a_r_n_a_m_e] [_i_d _._._.]
Wait for each specified child process and return its termination
status. Each _i_d may be a process ID or a job specification; if
a job spec is given, all processes in that job's pipeline are
waited for. If _i_d is not given, wwaaiitt waits for all running
background jobs and the last-executed process substitution, if
its process id is the same as $$!!, and the return status is zero.
If the --nn option is supplied, wwaaiitt waits for a single job from
the list of _i_ds or, if no _i_ds are supplied, any job, to complete
and returns its exit status. If none of the supplied arguments
is a child of the shell, or if no arguments are supplied and the
shell has no unwaited-for children, the exit status is 127. If
the --pp option is supplied, the process or job identifier of the
job for which the exit status is returned is assigned to the
variable _v_a_r_n_a_m_e named by the option argument. The variable
will be unset initially, before any assignment. This is useful
only when the --nn option is supplied. Supplying the --ff option,
when job control is enabled, forces wwaaiitt to wait for _i_d to ter-
minate before returning its status, instead of returning when it
changes status. If _i_d specifies a non-existent process or job,
the return status is 127. Otherwise, the return status is the
exit status of the last process or job waited for.
SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE
Bash-4.0 introduced the concept of a `shell compatibility level', spec-
ified as a set of options to the shopt builtin ccoommppaatt3311, ccoommppaatt3322, ccoomm--
ppaatt4400, ccoommppaatt4411, and so on). There is only one current compatibility
level -- each option is mutually exclusive. The compatibility level is
intended to allow users to select behavior from previous versions that
is incompatible with newer versions while they migrate scripts to use
current features and behavior. It's intended to be a temporary solu-
tion.
This section does not mention behavior that is standard for a particu-
lar version (e.g., setting ccoommppaatt3322 means that quoting the rhs of the
regexp matching operator quotes special regexp characters in the word,
which is default behavior in bash-3.2 and above).
If a user enables, say, ccoommppaatt3322, it may affect the behavior of other
compatibility levels up to and including the current compatibility
level. The idea is that each compatibility level controls behavior
that changed in that version of bbaasshh, but that behavior may have been
present in earlier versions. For instance, the change to use locale-
based comparisons with the [[[[ command came in bash-4.1, and earlier
versions used ASCII-based comparisons, so enabling ccoommppaatt3322 will enable
ASCII-based comparisons as well. That granularity may not be suffi-
cient for all uses, and as a result users should employ compatibility
levels carefully. Read the documentation for a particular feature to
find out the current behavior.
Bash-4.3 introduced a new shell variable: BBAASSHH__CCOOMMPPAATT. The value as-
signed to this variable (a decimal version number like 4.2, or an inte-
ger corresponding to the ccoommppaatt_N_N option, like 42) determines the com-
patibility level.
Starting with bash-4.4, Bash has begun deprecating older compatibility
levels. Eventually, the options will be removed in favor of BBAASSHH__CCOOMM--
PPAATT.
Bash-5.0 is the final version for which there will be an individual
shopt option for the previous version. Users should use BBAASSHH__CCOOMMPPAATT on
bash-5.0 and later versions.
The following table describes the behavior changes controlled by each
compatibility level setting. The ccoommppaatt_N_N tag is used as shorthand for
setting the compatibility level to _N_N using one of the following mecha-
nisms. For versions prior to bash-5.0, the compatibility level may be
set using the corresponding ccoommppaatt_N_N shopt option. For bash-4.3 and
later versions, the BBAASSHH__CCOOMMPPAATT variable is preferred, and it is re-
quired for bash-5.1 and later versions.
ccoommppaatt3311
+o quoting the rhs of the [[[[ command's regexp matching oper-
ator (=~) has no special effect
ccoommppaatt3322
+o interrupting a command list such as "a ; b ; c" causes
the execution of the next command in the list (in
bash-4.0 and later versions, the shell acts as if it re-
ceived the interrupt, so interrupting one command in a
list aborts the execution of the entire list)
ccoommppaatt4400
+o the << and >> operators to the [[[[ command do not consider
the current locale when comparing strings; they use ASCII
ordering. Bash versions prior to bash-4.1 use ASCII col-
lation and _s_t_r_c_m_p(3); bash-4.1 and later use the current
locale's collation sequence and _s_t_r_c_o_l_l(3).
ccoommppaatt4411
+o in _p_o_s_i_x mode, ttiimmee may be followed by options and still
be recognized as a reserved word (this is POSIX interpre-
tation 267)
+o in _p_o_s_i_x mode, the parser requires that an even number of
single quotes occur in the _w_o_r_d portion of a double-
quoted parameter expansion and treats them specially, so
that characters within the single quotes are considered
quoted (this is POSIX interpretation 221)
ccoommppaatt4422
+o the replacement string in double-quoted pattern substitu-
tion does not undergo quote removal, as it does in ver-
sions after bash-4.2
+o in posix mode, single quotes are considered special when
expanding the _w_o_r_d portion of a double-quoted parameter
expansion and can be used to quote a closing brace or
other special character (this is part of POSIX interpre-
tation 221); in later versions, single quotes are not
special within double-quoted word expansions
ccoommppaatt4433
+o the shell does not print a warning message if an attempt
is made to use a quoted compound assignment as an argu-
ment to declare (declare -a foo='(1 2)'). Later versions
warn that this usage is deprecated
+o word expansion errors are considered non-fatal errors
that cause the current command to fail, even in posix
mode (the default behavior is to make them fatal errors
that cause the shell to exit)
+o when executing a shell function, the loop state
(while/until/etc.) is not reset, so bbrreeaakk or ccoonnttiinnuuee in
that function will break or continue loops in the calling
context. Bash-4.4 and later reset the loop state to pre-
vent this
ccoommppaatt4444
+o the shell sets up the values used by BBAASSHH__AARRGGVV and
BBAASSHH__AARRGGCC so they can expand to the shell's positional
parameters even if extended debugging mode is not enabled
+o a subshell inherits loops from its parent context, so
bbrreeaakk or ccoonnttiinnuuee will cause the subshell to exit.
Bash-5.0 and later reset the loop state to prevent the
exit
+o variable assignments preceding builtins like eexxppoorrtt and
rreeaaddoonnllyy that set attributes continue to affect variables
with the same name in the calling environment even if the
shell is not in posix mode
ccoommppaatt5500
+o Bash-5.1 changed the way $$RRAANNDDOOMM is generated to intro-
duce slightly more randomness. If the shell compatibility
level is set to 50 or lower, it reverts to the method
from bash-5.0 and previous versions, so seeding the ran-
dom number generator by assigning a value to RRAANNDDOOMM will
produce the same sequence as in bash-5.0
+o If the command hash table is empty, bash versions prior
to bash-5.1 printed an informational message to that ef-
fect, even when producing output that can be reused as
input. Bash-5.1 suppresses that message when the --ll op-
tion is supplied.
SSEEEE AALLSSOO
bash(1), sh(1)
GNU Bash 5.0 2004 Apr 20 BASH_BUILTINS(1)