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BASH(1) General Commands Manual BASH(1)
NNAAMMEE
bash - GNU Bourne-Again SHell
SSYYNNOOPPSSIISS
bbaasshh [options] [command_string | file]
CCOOPPYYRRIIGGHHTT
Bash is Copyright (C) 1989-2020 by the Free Software Foundation, Inc.
DDEESSCCRRIIPPTTIIOONN
BBaasshh is an sshh-compatible command language interpreter that executes
commands read from the standard input or from a file. BBaasshh also incor-
porates useful features from the _K_o_r_n and _C shells (kksshh and ccsshh).
BBaasshh is intended to be a conformant implementation of the Shell and
Utilities portion of the IEEE POSIX specification (IEEE Standard
1003.1). BBaasshh can be configured to be POSIX-conformant by default.
OOPPTTIIOONNSS
All of the single-character shell options documented in the description
of the sseett builtin command, including --oo, can be used as options when
the shell is invoked. In addition, bbaasshh interprets the following op-
tions when it is invoked:
--cc If the --cc option is present, then commands are read from the
first non-option argument _c_o_m_m_a_n_d___s_t_r_i_n_g. If there are argu-
ments after the _c_o_m_m_a_n_d___s_t_r_i_n_g, the first argument is as-
signed to $$00 and any remaining arguments are assigned to the
positional parameters. The assignment to $$00 sets the name of
the shell, which is used in warning and error messages.
--ii If the --ii option is present, the shell is _i_n_t_e_r_a_c_t_i_v_e.
--ll Make bbaasshh act as if it had been invoked as a login shell (see
IINNVVOOCCAATTIIOONN below).
--rr If the --rr option is present, the shell becomes _r_e_s_t_r_i_c_t_e_d
(see RREESSTTRRIICCTTEEDD SSHHEELLLL below).
--ss If the --ss option is present, or if no arguments remain after
option processing, then commands are read from the standard
input. This option allows the positional parameters to be
set when invoking an interactive shell or when reading input
through a pipe.
--DD A list of all double-quoted strings preceded by $$ is printed
on the standard output. These are the strings that are sub-
ject to language translation when the current locale is not CC
or PPOOSSIIXX. This implies the --nn option; no commands will be
executed.
[[--++]]OO [[_s_h_o_p_t___o_p_t_i_o_n]]
_s_h_o_p_t___o_p_t_i_o_n is one of the shell options accepted by the
sshhoopptt builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). If
_s_h_o_p_t___o_p_t_i_o_n is present, --OO sets the value of that option; ++OO
unsets it. If _s_h_o_p_t___o_p_t_i_o_n is not supplied, the names and
values of the shell options accepted by sshhoopptt are printed on
the standard output. If the invocation option is ++OO, the
output is displayed in a format that may be reused as input.
---- A ---- signals the end of options and disables further option
processing. Any arguments after the ---- are treated as file-
names and arguments. An argument of -- is equivalent to ----.
BBaasshh also interprets a number of multi-character options. These op-
tions must appear on the command line before the single-character op-
tions to be recognized.
----ddeebbuuggggeerr
Arrange for the debugger profile to be executed before the shell
starts. Turns on extended debugging mode (see the description
of the eexxttddeebbuugg option to the sshhoopptt builtin below).
----dduummpp--ppoo--ssttrriinnggss
Equivalent to --DD, but the output is in the GNU _g_e_t_t_e_x_t ppoo (por-
table object) file format.
----dduummpp--ssttrriinnggss
Equivalent to --DD.
----hheellpp Display a usage message on standard output and exit success-
fully.
----iinniitt--ffiillee _f_i_l_e
----rrccffiillee _f_i_l_e
Execute commands from _f_i_l_e instead of the standard personal ini-
tialization file _~_/_._b_a_s_h_r_c if the shell is interactive (see IINN--
VVOOCCAATTIIOONN below).
----llooggiinn
Equivalent to --ll.
----nnooeeddiittiinngg
Do not use the GNU rreeaaddlliinnee library to read command lines when
the shell is interactive.
----nnoopprrooffiillee
Do not read either the system-wide startup file _/_e_t_c_/_p_r_o_f_i_l_e or
any of the personal initialization files _~_/_._b_a_s_h___p_r_o_f_i_l_e,
_~_/_._b_a_s_h___l_o_g_i_n, or _~_/_._p_r_o_f_i_l_e. By default, bbaasshh reads these
files when it is invoked as a login shell (see IINNVVOOCCAATTIIOONN be-
low).
----nnoorrcc Do not read and execute the personal initialization file
_~_/_._b_a_s_h_r_c if the shell is interactive. This option is on by de-
fault if the shell is invoked as sshh.
----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.
----rreessttrriicctteedd
The shell becomes restricted (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).
----vveerrbboossee
Equivalent to --vv.
----vveerrssiioonn
Show version information for this instance of bbaasshh on the stan-
dard output and exit successfully.
AARRGGUUMMEENNTTSS
If arguments remain after option processing, and neither the --cc nor the
--ss option has been supplied, the first argument is assumed to be the
name of a file containing shell commands. If bbaasshh is invoked in this
fashion, $$00 is set to the name of the file, and the positional parame-
ters are set to the remaining arguments. BBaasshh reads and executes com-
mands from this file, then exits. BBaasshh's exit status is the exit sta-
tus of the last command executed in the script. If no commands are ex-
ecuted, the exit status is 0. An attempt is first made to open the
file in the current directory, and, if no file is found, then the shell
searches the directories in PPAATTHH for the script.
IINNVVOOCCAATTIIOONN
A _l_o_g_i_n _s_h_e_l_l is one whose first character of argument zero is a --, or
one started with the ----llooggiinn option.
An _i_n_t_e_r_a_c_t_i_v_e shell is one started without non-option arguments (un-
less --ss is specified) and without the --cc option whose standard input
and error are both connected to terminals (as determined by _i_s_a_t_t_y(3)),
or one started with the --ii option. PPSS11 is set and $$-- includes ii if
bbaasshh is interactive, allowing a shell script or a startup file to test
this state.
The following paragraphs describe how bbaasshh executes its startup files.
If any of the files exist but cannot be read, bbaasshh reports an error.
Tildes are expanded in filenames as described below under TTiillddee EExxppaann--
ssiioonn in the EEXXPPAANNSSIIOONN section.
When bbaasshh is invoked as an interactive login shell, or as a non-inter-
active shell with the ----llooggiinn option, it first reads and executes com-
mands from the file _/_e_t_c_/_p_r_o_f_i_l_e, if that file exists. After reading
that file, it looks for _~_/_._b_a_s_h___p_r_o_f_i_l_e, _~_/_._b_a_s_h___l_o_g_i_n, and _~_/_._p_r_o_f_i_l_e,
in that order, and reads and executes commands from the first one that
exists and is readable. The ----nnoopprrooffiillee option may be used when the
shell is started to inhibit this behavior.
When an interactive login shell exits, or a non-interactive login shell
executes the eexxiitt builtin command, bbaasshh reads and executes commands
from the file _~_/_._b_a_s_h___l_o_g_o_u_t, if it exists.
When an interactive shell that is not a login shell is started, bbaasshh
reads and executes commands from _~_/_._b_a_s_h_r_c, if that file exists. This
may be inhibited by using the ----nnoorrcc option. The ----rrccffiillee _f_i_l_e option
will force bbaasshh to read and execute commands from _f_i_l_e instead of
_~_/_._b_a_s_h_r_c.
When bbaasshh is started non-interactively, to run a shell script, for ex-
ample, it looks for the variable BBAASSHH__EENNVV in the environment, expands
its value if it appears there, and uses the expanded value as the name
of a file to read and execute. BBaasshh behaves as if the following com-
mand were executed:
if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
but the value of the PPAATTHH variable is not used to search for the file-
name.
If bbaasshh is invoked with the name sshh, it tries to mimic the startup be-
havior of historical versions of sshh as closely as possible, while con-
forming to the POSIX standard as well. When invoked as an interactive
login shell, or a non-interactive shell with the ----llooggiinn option, it
first attempts to read and execute commands from _/_e_t_c_/_p_r_o_f_i_l_e and
_~_/_._p_r_o_f_i_l_e, in that order. The ----nnoopprrooffiillee option may be used to in-
hibit this behavior. When invoked as an interactive shell with the
name sshh, bbaasshh looks for the variable EENNVV, expands its value if it is
defined, and uses the expanded value as the name of a file to read and
execute. Since a shell invoked as sshh does not attempt to read and exe-
cute commands from any other startup files, the ----rrccffiillee option has no
effect. A non-interactive shell invoked with the name sshh does not at-
tempt to read any other startup files. When invoked as sshh, bbaasshh enters
_p_o_s_i_x mode after the startup files are read.
When bbaasshh is started in _p_o_s_i_x mode, as with the ----ppoossiixx command line
option, it follows the POSIX standard for startup files. In this mode,
interactive shells expand the EENNVV variable and commands are read and
executed from the file whose name is the expanded value. No other
startup files are read.
BBaasshh attempts to determine when it is being run with its standard input
connected to a network connection, as when executed by the remote shell
daemon, usually _r_s_h_d, or the secure shell daemon _s_s_h_d. If bbaasshh deter-
mines it is being run in this fashion, it reads and executes commands
from _~_/_._b_a_s_h_r_c, if that file exists and is readable. It will not do
this if invoked as sshh. The ----nnoorrcc option may be used to inhibit this
behavior, and the ----rrccffiillee option may be used to force another file to
be read, but neither _r_s_h_d nor _s_s_h_d generally invoke the shell with
those options or allow them to be specified.
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 supplied, no startup
files are read, shell functions are not inherited from the environment,
the SSHHEELLLLOOPPTTSS, BBAASSHHOOPPTTSS, CCDDPPAATTHH, and GGLLOOBBIIGGNNOORREE variables, if they ap-
pear in the environment, are ignored, and the effective user id is set
to the real user id. If the --pp option is supplied at invocation, the
startup behavior is the same, but the effective user id is not reset.
DDEEFFIINNIITTIIOONNSS
The following definitions are used throughout the rest of this docu-
ment.
bbllaannkk A space or tab.
wwoorrdd A sequence of characters considered as a single unit by the
shell. Also known as a ttookkeenn.
nnaammee A _w_o_r_d consisting only of alphanumeric characters and under-
scores, and beginning with an alphabetic character or an under-
score. Also referred to as an iiddeennttiiffiieerr.
mmeettaacchhaarraacctteerr
A character that, when unquoted, separates words. One of the
following:
|| && ;; (( )) << >> ssppaaccee ttaabb nneewwlliinnee
ccoonnttrrooll ooppeerraattoorr
A _t_o_k_e_n that performs a control function. It is one of the fol-
lowing symbols:
|||| && &&&& ;; ;;;; ;;&& ;;;;&& (( )) || ||&& <<nneewwlliinnee>>
RREESSEERRVVEEDD WWOORRDDSS
_R_e_s_e_r_v_e_d _w_o_r_d_s are words that have a special meaning to the shell. The
following words are recognized as reserved when unquoted and either the
first word of a command (see SSHHEELLLL GGRRAAMMMMAARR below), the third word of a
ccaassee or sseelleecctt command (only iinn is valid), or the third word of a ffoorr
command (only iinn and ddoo are valid):
!! ccaassee ccoopprroocc ddoo ddoonnee eelliiff eellssee eessaacc ffii ffoorr ffuunnccttiioonn iiff iinn sseelleecctt
tthheenn uunnttiill wwhhiillee {{ }} ttiimmee [[[[ ]]]]
SSHHEELLLL GGRRAAMMMMAARR
SSiimmppllee CCoommmmaannddss
A _s_i_m_p_l_e _c_o_m_m_a_n_d is a sequence of optional variable assignments fol-
lowed by bbllaannkk-separated words and redirections, and terminated by a
_c_o_n_t_r_o_l _o_p_e_r_a_t_o_r. The first word specifies the command to be executed,
and is passed as argument zero. The remaining words are passed as ar-
guments to the invoked command.
The return value of a _s_i_m_p_l_e _c_o_m_m_a_n_d is its exit status, or 128+_n if
the command is terminated by signal _n.
PPiippeelliinneess
A _p_i_p_e_l_i_n_e is a sequence of one or more commands separated by one of
the control operators || or ||&&. The format for a pipeline is:
[ttiimmee [--pp]] [ ! ] _c_o_m_m_a_n_d [ [|||||&&] _c_o_m_m_a_n_d_2 ... ]
The standard output of _c_o_m_m_a_n_d is connected via a pipe to the standard
input of _c_o_m_m_a_n_d_2. This connection is performed before any redirec-
tions specified by the command (see RREEDDIIRREECCTTIIOONN below). If ||&& is used,
_c_o_m_m_a_n_d's standard error, in addition to its standard output, is con-
nected to _c_o_m_m_a_n_d_2's standard input through the pipe; it is shorthand
for 22>>&&11 ||. This implicit redirection of the standard error to the
standard output is performed after any redirections specified by the
command.
The return status of a pipeline is the exit status of the last command,
unless the ppiippeeffaaiill option is enabled. If ppiippeeffaaiill is enabled, the
pipeline's return status is the value of the last (rightmost) command
to exit with a non-zero status, or zero if all commands exit success-
fully. If the reserved word !! precedes a pipeline, the exit status of
that pipeline is the logical negation of the exit status as described
above. The shell waits for all commands in the pipeline to terminate
before returning a value.
If the ttiimmee reserved word precedes a pipeline, the elapsed as well as
user and system time consumed by its execution are reported when the
pipeline terminates. The --pp option changes the output format to that
specified by POSIX. When the shell is in _p_o_s_i_x _m_o_d_e, it does not rec-
ognize ttiimmee as a reserved word if the next token begins with a `-'.
The TTIIMMEEFFOORRMMAATT variable may be set to a format string that specifies
how the timing information should be displayed; see the description of
TTIIMMEEFFOORRMMAATT under SShheellll VVaarriiaabblleess below.
When the shell is in _p_o_s_i_x _m_o_d_e, ttiimmee may be followed by a newline. In
this case, the shell displays the total user and system time consumed
by the shell and its children. The TTIIMMEEFFOORRMMAATT variable may be used to
specify the format of the time information.
Each command in a pipeline is executed as a separate process (i.e., in
a subshell). See CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT for a description of a
subshell environment. If the llaassttppiippee option is enabled using the
sshhoopptt builtin (see the description of sshhoopptt below), the last element of
a pipeline may be run by the shell process.
LLiissttss
A _l_i_s_t is a sequence of one or more pipelines separated by one of the
operators ;;, &&, &&&&, or ||||, and optionally terminated by one of ;;, &&, or
<<nneewwlliinnee>>.
Of these list operators, &&&& and |||| have equal precedence, followed by ;;
and &&, which have equal precedence.
A sequence of one or more newlines may appear in a _l_i_s_t instead of a
semicolon to delimit commands.
If a command is terminated by the control operator &&, the shell exe-
cutes the command in the _b_a_c_k_g_r_o_u_n_d in a subshell. The shell does not
wait for the command to finish, and the return status is 0. These are
referred to as _a_s_y_n_c_h_r_o_n_o_u_s commands. Commands separated by a ;; are
executed sequentially; the shell waits for each command to terminate in
turn. The return status is the exit status of the last command exe-
cuted.
AND and OR lists are sequences of one or more pipelines separated by
the &&&& and |||| control operators, respectively. AND and OR lists are
executed with left associativity. An AND list has the form
_c_o_m_m_a_n_d_1 &&&& _c_o_m_m_a_n_d_2
_c_o_m_m_a_n_d_2 is executed if, and only if, _c_o_m_m_a_n_d_1 returns an exit status
of zero (success).
An OR list has the form
_c_o_m_m_a_n_d_1 |||| _c_o_m_m_a_n_d_2
_c_o_m_m_a_n_d_2 is executed if, and only if, _c_o_m_m_a_n_d_1 returns a non-zero exit
status. The return status of AND and OR lists is the exit status of
the last command executed in the list.
CCoommppoouunndd CCoommmmaannddss
A _c_o_m_p_o_u_n_d _c_o_m_m_a_n_d is one of the following. In most cases a _l_i_s_t in a
command's description may be separated from the rest of the command by
one or more newlines, and may be followed by a newline in place of a
semicolon.
(_l_i_s_t) _l_i_s_t is executed in a subshell environment (see CCOOMMMMAANNDD EEXXEECCUU--
TTIIOONN EENNVVIIRROONNMMEENNTT below). Variable assignments and builtin com-
mands that affect the shell's environment do not remain in ef-
fect after the command completes. The return status is the exit
status of _l_i_s_t.
{ _l_i_s_t; }
_l_i_s_t is simply executed in the current shell environment. _l_i_s_t
must be terminated with a newline or semicolon. This is known
as a _g_r_o_u_p _c_o_m_m_a_n_d. The return status is the exit status of
_l_i_s_t. Note that unlike the metacharacters (( and )), {{ and }} are
_r_e_s_e_r_v_e_d _w_o_r_d_s and must occur where a reserved word is permitted
to be recognized. Since they do not cause a word break, they
must be separated from _l_i_s_t by whitespace or another shell
metacharacter.
((_e_x_p_r_e_s_s_i_o_n))
The _e_x_p_r_e_s_s_i_o_n is evaluated according to the rules described be-
low under AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN. If the value of the expression
is non-zero, the return status is 0; otherwise the return status
is 1. This is exactly equivalent to lleett ""_e_x_p_r_e_s_s_i_o_n"".
[[[[ _e_x_p_r_e_s_s_i_o_n ]]]]
Return a status of 0 or 1 depending on the evaluation of the
conditional expression _e_x_p_r_e_s_s_i_o_n. Expressions are composed of
the primaries described below under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS.
Word splitting and pathname expansion are not performed on the
words between the [[[[ and ]]]]; tilde expansion, parameter and
variable expansion, arithmetic expansion, command substitution,
process substitution, and quote removal are performed. Condi-
tional operators such as --ff must be unquoted to be recognized as
primaries.
When used with [[[[, the << and >> operators sort lexicographically
using the current locale.
When the ==== and !!== operators are used, the string to the right
of the operator is considered a pattern and matched according to
the rules described below under PPaatttteerrnn MMaattcchhiinngg, as if the eexxtt--
gglloobb shell option were enabled. The == operator is equivalent to
====. If the nnooccaasseemmaattcchh shell option is enabled, the match is
performed without regard to the case of alphabetic characters.
The return value is 0 if the string matches (====) or does not
match (!!==) the pattern, and 1 otherwise. Any part of the pat-
tern may be quoted to force the quoted portion to be matched as
a string.
An additional binary operator, ==~~, is available, with the same
precedence as ==== and !!==. When it is used, the string to the
right of the operator is considered a POSIX extended regular ex-
pression and matched accordingly (using the POSIX _r_e_g_c_o_m_p and
_r_e_g_e_x_e_c interfaces usually described in _r_e_g_e_x(3)). The return
value is 0 if the string matches the pattern, and 1 otherwise.
If the regular expression is syntactically incorrect, the condi-
tional expression's return value is 2. If the nnooccaasseemmaattcchh shell
option is enabled, the match is performed without regard to the
case of alphabetic characters. Any part of the pattern may be
quoted to force the quoted portion to be matched as a string.
Bracket expressions in regular expressions must be treated care-
fully, since normal quoting characters lose their meanings be-
tween brackets. If the pattern is stored in a shell variable,
quoting the variable expansion forces the entire pattern to be
matched as a string.
The pattern will match if it matches any part of the string.
Anchor the pattern using the ^^ and $$ regular expression opera-
tors to force it to match the entire string. The array variable
BBAASSHH__RREEMMAATTCCHH records which parts of the string matched the pat-
tern. The element of BBAASSHH__RREEMMAATTCCHH with index 0 contains the
portion of the string matching the entire regular expression.
Substrings matched by parenthesized subexpressions within the
regular expression are saved in the remaining BBAASSHH__RREEMMAATTCCHH in-
dices. The element of BBAASSHH__RREEMMAATTCCHH with index _n is the portion
of the string matching the _nth parenthesized subexpression.
Expressions may be combined using the following operators,
listed in decreasing order of precedence:
(( _e_x_p_r_e_s_s_i_o_n ))
Returns the value of _e_x_p_r_e_s_s_i_o_n. This may be used to
override the normal precedence of operators.
!! _e_x_p_r_e_s_s_i_o_n
True if _e_x_p_r_e_s_s_i_o_n is false.
_e_x_p_r_e_s_s_i_o_n_1 &&&& _e_x_p_r_e_s_s_i_o_n_2
True if both _e_x_p_r_e_s_s_i_o_n_1 and _e_x_p_r_e_s_s_i_o_n_2 are true.
_e_x_p_r_e_s_s_i_o_n_1 |||| _e_x_p_r_e_s_s_i_o_n_2
True if either _e_x_p_r_e_s_s_i_o_n_1 or _e_x_p_r_e_s_s_i_o_n_2 is true.
The &&&& and |||| operators do not evaluate _e_x_p_r_e_s_s_i_o_n_2 if the value
of _e_x_p_r_e_s_s_i_o_n_1 is sufficient to determine the return value of
the entire conditional expression.
ffoorr _n_a_m_e [ [ iinn [ _w_o_r_d _._._. ] ] ; ] ddoo _l_i_s_t ; ddoonnee
The list of words following iinn is expanded, generating a list of
items. The variable _n_a_m_e is set to each element of this list in
turn, and _l_i_s_t is executed each time. If the iinn _w_o_r_d is omit-
ted, the ffoorr command executes _l_i_s_t once for each positional pa-
rameter that is set (see PPAARRAAMMEETTEERRSS below). The return status
is the exit status of the last command that executes. If the
expansion of the items following iinn results in an empty list, no
commands are executed, and the return status is 0.
ffoorr (( _e_x_p_r_1 ; _e_x_p_r_2 ; _e_x_p_r_3 )) ; ddoo _l_i_s_t ; ddoonnee
First, the arithmetic expression _e_x_p_r_1 is evaluated according to
the rules described below under AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN. The
arithmetic expression _e_x_p_r_2 is then evaluated repeatedly until
it evaluates to zero. Each time _e_x_p_r_2 evaluates to a non-zero
value, _l_i_s_t is executed and the arithmetic expression _e_x_p_r_3 is
evaluated. If any expression is omitted, it behaves as if it
evaluates to 1. The return value is the exit status of the last
command in _l_i_s_t that is executed, or false if any of the expres-
sions is invalid.
sseelleecctt _n_a_m_e [ iinn _w_o_r_d ] ; ddoo _l_i_s_t ; ddoonnee
The list of words following iinn is expanded, generating a list of
items. The set of expanded words is printed on the standard er-
ror, each preceded by a number. If the iinn _w_o_r_d is omitted, the
positional parameters are printed (see PPAARRAAMMEETTEERRSS below). The
PPSS33 prompt is then displayed and a line read from the standard
input. If the line consists of a number corresponding to one of
the displayed words, then the value of _n_a_m_e is set to that word.
If the line is empty, the words and prompt are displayed again.
If EOF is read, the command completes. Any other value read
causes _n_a_m_e to be set to null. The line read is saved in the
variable RREEPPLLYY. The _l_i_s_t is executed after each selection until
a bbrreeaakk command is executed. The exit status of sseelleecctt is the
exit status of the last command executed in _l_i_s_t, or zero if no
commands were executed.
ccaassee _w_o_r_d iinn [ [(] _p_a_t_t_e_r_n [ || _p_a_t_t_e_r_n ] ... ) _l_i_s_t ;; ] ... eessaacc
A ccaassee command first expands _w_o_r_d, and tries to match it against
each _p_a_t_t_e_r_n in turn, using the matching rules described under
PPaatttteerrnn MMaattcchhiinngg below. The _w_o_r_d is expanded using tilde expan-
sion, parameter and variable expansion, arithmetic expansion,
command substitution, process substitution and quote removal.
Each _p_a_t_t_e_r_n examined is expanded using tilde expansion, parame-
ter and variable expansion, arithmetic expansion, command sub-
stitution, and process substitution. If the nnooccaasseemmaattcchh shell
option is enabled, the match is performed without regard to the
case of alphabetic characters. When a match is found, the cor-
responding _l_i_s_t is executed. If the ;;;; operator is used, no
subsequent matches are attempted after the first pattern match.
Using ;;&& in place of ;;;; causes execution to continue with the
_l_i_s_t associated with the next set of patterns. Using ;;;;&& in
place of ;;;; causes the shell to test the next pattern list in
the statement, if any, and execute any associated _l_i_s_t on a suc-
cessful match, continuing the case statement execution as if the
pattern list had not matched. The exit status is zero if no
pattern matches. Otherwise, it is the exit status of the last
command executed in _l_i_s_t.
iiff _l_i_s_t; tthheenn _l_i_s_t; [ eelliiff _l_i_s_t; tthheenn _l_i_s_t; ] ... [ eellssee _l_i_s_t; ] ffii
The iiff _l_i_s_t is executed. If its exit status is zero, the tthheenn
_l_i_s_t is executed. Otherwise, each eelliiff _l_i_s_t is executed in
turn, and if its exit status is zero, the corresponding tthheenn
_l_i_s_t is executed and the command completes. Otherwise, the eellssee
_l_i_s_t is executed, if present. The exit status is the exit sta-
tus of the last command executed, or zero if no condition tested
true.
wwhhiillee _l_i_s_t_-_1; ddoo _l_i_s_t_-_2; ddoonnee
uunnttiill _l_i_s_t_-_1; ddoo _l_i_s_t_-_2; ddoonnee
The wwhhiillee command continuously executes the list _l_i_s_t_-_2 as long
as the last command in the list _l_i_s_t_-_1 returns an exit status of
zero. The uunnttiill command is identical to the wwhhiillee command, ex-
cept that the test is negated: _l_i_s_t_-_2 is executed as long as the
last command in _l_i_s_t_-_1 returns a non-zero exit status. The exit
status of the wwhhiillee and uunnttiill commands is the exit status of the
last command executed in _l_i_s_t_-_2, or zero if none was executed.
CCoopprroocceesssseess
A _c_o_p_r_o_c_e_s_s is a shell command preceded by the ccoopprroocc reserved word. A
coprocess is executed asynchronously in a subshell, as if the command
had been terminated with the && control operator, with a two-way pipe
established between the executing shell and the coprocess.
The format for a coprocess is:
ccoopprroocc [_N_A_M_E] _c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n_s]
This creates a coprocess named _N_A_M_E. If _N_A_M_E is not supplied, the de-
fault name is CCOOPPRROOCC. _N_A_M_E must not be supplied if _c_o_m_m_a_n_d is a _s_i_m_p_l_e
_c_o_m_m_a_n_d (see above); otherwise, it is interpreted as the first word of
the simple command. When the coprocess is executed, the shell creates
an array variable (see AArrrraayyss below) named _N_A_M_E in the context of the
executing shell. The standard output of _c_o_m_m_a_n_d is connected via a
pipe to a file descriptor in the executing shell, and that file de-
scriptor is assigned to _N_A_M_E[0]. The standard input of _c_o_m_m_a_n_d is con-
nected via a pipe to a file descriptor in the executing shell, and that
file descriptor is assigned to _N_A_M_E[1]. This pipe is established be-
fore any redirections specified by the command (see RREEDDIIRREECCTTIIOONN below).
The file descriptors can be utilized as arguments to shell commands and
redirections using standard word expansions. Other than those created
to execute command and process substitutions, the file descriptors are
not available in subshells. The process ID of the shell spawned to ex-
ecute the coprocess is available as the value of the variable _N_A_M_E_PID.
The wwaaiitt builtin command may be used to wait for the coprocess to ter-
minate.
Since the coprocess is created as an asynchronous command, the ccoopprroocc
command always returns success. The return status of a coprocess is
the exit status of _c_o_m_m_a_n_d.
SShheellll FFuunnccttiioonn DDeeffiinniittiioonnss
A shell function is an object that is called like a simple command and
executes a compound command with a new set of positional parameters.
Shell functions are declared as follows:
_f_n_a_m_e () _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n]
ffuunnccttiioonn _f_n_a_m_e [()] _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n]
This defines a function named _f_n_a_m_e. The reserved word ffuunnccttiioonn
is optional. If the ffuunnccttiioonn reserved word is supplied, the
parentheses are optional. The _b_o_d_y of the function is the com-
pound command _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d (see CCoommppoouunndd CCoommmmaannddss above).
That command is usually a _l_i_s_t of commands between { and }, but
may be any command listed under CCoommppoouunndd CCoommmmaannddss above, with
one exception: If the ffuunnccttiioonn reserved word is used, but the
parentheses are not supplied, the braces are required. _c_o_m_-
_p_o_u_n_d_-_c_o_m_m_a_n_d is executed whenever _f_n_a_m_e is specified as the
name of a simple command. When in _p_o_s_i_x _m_o_d_e, _f_n_a_m_e must be a
valid shell _n_a_m_e and may not be the name of one of the POSIX
_s_p_e_c_i_a_l _b_u_i_l_t_i_n_s. In default mode, a function name can be any
unquoted shell word that does not contain $$. Any redirections
(see RREEDDIIRREECCTTIIOONN below) specified when a function is defined are
performed when the function is executed. The exit status of a
function definition is zero unless a syntax error occurs or a
readonly function with the same name already exists. When exe-
cuted, the exit status of a function is the exit status of the
last command executed in the body. (See FFUUNNCCTTIIOONNSS below.)
CCOOMMMMEENNTTSS
In a non-interactive shell, or an interactive shell in which the iinntteerr--
aaccttiivvee__ccoommmmeennttss option to the sshhoopptt builtin is enabled (see SSHHEELLLL
BBUUIILLTTIINN CCOOMMMMAANNDDSS below), a word beginning with ## causes that word and
all remaining characters on that line to be ignored. An interactive
shell without the iinntteerraaccttiivvee__ccoommmmeennttss option enabled does not allow
comments. The iinntteerraaccttiivvee__ccoommmmeennttss option is on by default in interac-
tive shells.
QQUUOOTTIINNGG
_Q_u_o_t_i_n_g is used to remove the special meaning of certain characters or
words to the shell. Quoting can be used to disable special treatment
for special characters, to prevent reserved words from being recognized
as such, and to prevent parameter expansion.
Each of the _m_e_t_a_c_h_a_r_a_c_t_e_r_s listed above under DDEEFFIINNIITTIIOONNSS has special
meaning to the shell and must be quoted if it is to represent itself.
When the command history expansion facilities are being used (see HHIISS--
TTOORRYY EEXXPPAANNSSIIOONN below), the _h_i_s_t_o_r_y _e_x_p_a_n_s_i_o_n character, usually !!, must
be quoted to prevent history expansion.
There are three quoting mechanisms: the _e_s_c_a_p_e _c_h_a_r_a_c_t_e_r, single
quotes, and double quotes.
A non-quoted backslash (\\) is the _e_s_c_a_p_e _c_h_a_r_a_c_t_e_r. It preserves the
literal value of the next character that follows, with the exception of
<newline>. If a \\<newline> pair appears, and the backslash is not it-
self quoted, the \\<newline> is treated as a line continuation (that is,
it is removed from the input stream and effectively ignored).
Enclosing characters in single quotes preserves the literal value of
each character within the quotes. A single quote may not occur between
single quotes, even when preceded by a backslash.
Enclosing characters in double quotes preserves the literal value of
all characters within the quotes, with the exception of $$, ``, \\, and,
when history expansion is enabled, !!. When the shell is in _p_o_s_i_x _m_o_d_e,
the !! has no special meaning within double quotes, even when history
expansion is enabled. The characters $$ and `` retain their special
meaning within double quotes. The backslash retains its special mean-
ing only when followed by one of the following characters: $$, ``, "", \\,
or <<nneewwlliinnee>>. A double quote may be quoted within double quotes by
preceding it with a backslash. If enabled, history expansion will be
performed unless an !! appearing in double quotes is escaped using a
backslash. The backslash preceding the !! is not removed.
The special parameters ** and @@ have special meaning when in double
quotes (see PPAARRAAMMEETTEERRSS below).
Words of the form $$'_s_t_r_i_n_g' are treated specially. The word expands to
_s_t_r_i_n_g, with backslash-escaped characters replaced as specified by the
ANSI C standard. Backslash escape sequences, if present, are decoded
as follows:
\\aa alert (bell)
\\bb backspace
\\ee
\\EE an escape character
\\ff form feed
\\nn new line
\\rr carriage return
\\tt horizontal tab
\\vv vertical tab
\\\\ backslash
\\'' single quote
\\"" double quote
\\?? question mark
\\_n_n_n the eight-bit character whose value is the octal value
_n_n_n (one to three octal digits)
\\xx_H_H the eight-bit character whose value is the hexadecimal
value _H_H (one or two hex digits)
\\uu_H_H_H_H the Unicode (ISO/IEC 10646) character whose value is the
hexadecimal value _H_H_H_H (one to four hex digits)
\\UU_H_H_H_H_H_H_H_H
the Unicode (ISO/IEC 10646) character whose value is the
hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits)
\\cc_x a control-_x character
The expanded result is single-quoted, as if the dollar sign had not
been present.
A double-quoted string preceded by a dollar sign ($$"_s_t_r_i_n_g") will cause
the string to be translated according to the current locale. The _g_e_t_-
_t_e_x_t infrastructure performs the message catalog lookup and transla-
tion, using the LLCC__MMEESSSSAAGGEESS and TTEEXXTTDDOOMMAAIINN shell variables. If the
current locale is CC or PPOOSSIIXX, or if there are no translations avail-
able, the dollar sign is ignored. If the string is translated and re-
placed, the replacement is double-quoted.
PPAARRAAMMEETTEERRSS
A _p_a_r_a_m_e_t_e_r is an entity that stores values. It can be a _n_a_m_e, a num-
ber, or one of the special characters listed below under SSppeecciiaall PPaarraamm--
eetteerrss. A _v_a_r_i_a_b_l_e is a parameter denoted by a _n_a_m_e. A variable has a
_v_a_l_u_e and zero or more _a_t_t_r_i_b_u_t_e_s. Attributes are assigned using the
ddeeccllaarree builtin command (see ddeeccllaarree below in SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS).
A parameter is set if it has been assigned a value. The null string is
a valid value. Once a variable is set, it may be unset only by using
the uunnsseett builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
A _v_a_r_i_a_b_l_e may be assigned to by a statement of the form
_n_a_m_e=[_v_a_l_u_e]
If _v_a_l_u_e is not given, the variable is assigned the null string. All
_v_a_l_u_e_s undergo tilde expansion, parameter and variable expansion, com-
mand substitution, arithmetic expansion, and quote removal (see EEXXPPAANN--
SSIIOONN below). If the variable has its iinntteeggeerr attribute set, then _v_a_l_u_e
is evaluated as an arithmetic expression even if the $((...)) expansion
is not used (see AArriitthhmmeettiicc EExxppaannssiioonn below). Word splitting is not
performed, with the exception of ""$$@@"" as explained below under SSppeecciiaall
PPaarraammeetteerrss. Pathname expansion is not performed. Assignment state-
ments may also appear as arguments to the aalliiaass, ddeeccllaarree, ttyyppeesseett, eexx--
ppoorrtt, rreeaaddoonnllyy, and llooccaall builtin commands (_d_e_c_l_a_r_a_t_i_o_n commands).
When in _p_o_s_i_x _m_o_d_e, these builtins may appear in a command after one or
more instances of the ccoommmmaanndd builtin and retain these assignment
statement properties.
In the context where an assignment statement is assigning a value to a
shell variable or array index, the += operator can be used to append to
or add to the variable's previous value. This includes arguments to
builtin commands such as ddeeccllaarree that accept assignment statements
(_d_e_c_l_a_r_a_t_i_o_n commands). When += is applied to a variable for which the
_i_n_t_e_g_e_r attribute has been set, _v_a_l_u_e is evaluated as an arithmetic ex-
pression and added to the variable's current value, which is also eval-
uated. When += is applied to an array variable using compound assign-
ment (see AArrrraayyss below), the variable's value is not unset (as it is
when using =), and new values are appended to the array beginning at
one greater than the array's maximum index (for indexed arrays) or
added as additional key-value pairs in an associative array. When ap-
plied to a string-valued variable, _v_a_l_u_e is expanded and appended to
the variable's value.
A variable can be assigned the _n_a_m_e_r_e_f attribute using the --nn option to
the ddeeccllaarree or llooccaall builtin commands (see the descriptions of ddeeccllaarree
and llooccaall below) to create a _n_a_m_e_r_e_f, or a reference to another vari-
able. This allows variables to be manipulated indirectly. Whenever
the nameref variable is referenced, assigned to, unset, or has its at-
tributes modified (other than using or changing the _n_a_m_e_r_e_f attribute
itself), the operation is actually performed on the variable specified
by the nameref variable's value. A nameref is commonly used within
shell functions to refer to a variable whose name is passed as an argu-
ment to the function. For instance, if a variable name is passed to a
shell function as its first argument, running
declare -n ref=$1
inside the function creates a nameref variable rreeff whose value is the
variable name passed as the first argument. References and assignments
to rreeff, and changes to its attributes, are treated as references, as-
signments, and attribute modifications to the variable whose name was
passed as $$11. If the control variable in a ffoorr loop has the nameref
attribute, the list of words can be a list of shell variables, and a
name reference will be established for each word in the list, in turn,
when the loop is executed. Array variables cannot be given the nnaammeerreeff
attribute. However, nameref variables can reference array variables
and subscripted array variables. Namerefs can be unset using the --nn
option to the uunnsseett builtin. Otherwise, if uunnsseett is executed with the
name of a nameref variable as an argument, the variable referenced by
the nameref variable will be unset.
PPoossiittiioonnaall PPaarraammeetteerrss
A _p_o_s_i_t_i_o_n_a_l _p_a_r_a_m_e_t_e_r is a parameter denoted by one or more digits,
other than the single digit 0. Positional parameters are assigned from
the shell's arguments when it is invoked, and may be reassigned using
the sseett builtin command. Positional parameters may not be assigned to
with assignment statements. The positional parameters are temporarily
replaced when a shell function is executed (see FFUUNNCCTTIIOONNSS below).
When a positional parameter consisting of more than a single digit is
expanded, it must be enclosed in braces (see EEXXPPAANNSSIIOONN below).
SSppeecciiaall PPaarraammeetteerrss
The shell treats several parameters specially. These parameters may
only be referenced; assignment to them is not allowed.
** Expands to the positional parameters, starting from one. When
the expansion is not within double quotes, each positional pa-
rameter expands to a separate word. In contexts where it is
performed, those words are subject to further word splitting and
pathname expansion. When the expansion occurs within double
quotes, it expands to a single word with the value of each pa-
rameter separated by the first character of the IIFFSS special
variable. That is, "$$**" is equivalent to "$$11_c$$22_c......", where _c
is the first character of the value of the IIFFSS variable. If IIFFSS
is unset, the parameters are separated by spaces. If IIFFSS is
null, the parameters are joined without intervening separators.
@@ Expands to the positional parameters, starting from one. In
contexts where word splitting is performed, this expands each
positional parameter to a separate word; if not within double
quotes, these words are subject to word splitting. In contexts
where word splitting is not performed, this expands to a single
word with each positional parameter separated by a space. When
the expansion occurs within double quotes, each parameter ex-
pands to a separate word. That is, "$$@@" is equivalent to "$$11"
"$$22" ... If the double-quoted expansion occurs within a word,
the expansion of the first parameter is joined with the begin-
ning part of the original word, and the expansion of the last
parameter is joined with the last part of the original word.
When there are no positional parameters, "$$@@" and $$@@ expand to
nothing (i.e., they are removed).
## Expands to the number of positional parameters in decimal.
?? Expands to the exit status of the most recently executed fore-
ground pipeline.
-- Expands to the current option flags as specified upon invoca-
tion, by the sseett builtin command, or those set by the shell it-
self (such as the --ii option).
$$ Expands to the process ID of the shell. In a () subshell, it
expands to the process ID of the current shell, not the sub-
shell.
!! Expands to the process ID of the job most recently placed into
the background, whether executed as an asynchronous command or
using the bbgg builtin (see JJOOBB CCOONNTTRROOLL below).
00 Expands to the name of the shell or shell script. This is set
at shell initialization. If bbaasshh is invoked with a file of com-
mands, $$00 is set to the name of that file. If bbaasshh is started
with the --cc option, then $$00 is set to the first argument after
the string to be executed, if one is present. Otherwise, it is
set to the filename used to invoke bbaasshh, as given by argument
zero.
SShheellll VVaarriiaabblleess
The following variables are set by the shell:
__ At shell startup, set to the pathname used to invoke the shell
or shell script being executed as passed in the environment or
argument list. Subsequently, expands to the last argument to
the previous simple command executed in the foreground, after
expansion. Also set to the full pathname used to invoke each
command executed and placed in the environment exported to that
command. When checking mail, this parameter holds the name of
the mail file currently being checked.
BBAASSHH Expands to the full filename used to invoke this instance of
bbaasshh.
BBAASSHHOOPPTTSS
A colon-separated list of enabled shell options. Each word in
the list is a valid argument for the --ss option to the sshhoopptt
builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). The options
appearing in BBAASSHHOOPPTTSS are those reported as _o_n by sshhoopptt. If
this variable is in the environment when bbaasshh starts up, each
shell option in the list will be enabled before reading any
startup files. This variable is read-only.
BBAASSHHPPIIDD
Expands to the process ID of the current bbaasshh process. This
differs from $$$$ under certain circumstances, such as subshells
that do not require bbaasshh to be re-initialized. Assignments to
BBAASSHHPPIIDD have no effect. If BBAASSHHPPIIDD is unset, it loses its spe-
cial properties, even if it is subsequently reset.
BBAASSHH__AALLIIAASSEESS
An associative array variable whose members correspond to the
internal list of aliases as maintained by the aalliiaass builtin.
Elements added to this array appear in the alias list; however,
unsetting array elements currently does not cause aliases to be
removed from the alias list. If BBAASSHH__AALLIIAASSEESS is unset, it loses
its special properties, even if it is subsequently reset.
BBAASSHH__AARRGGCC
An array variable whose values are the number of parameters in
each frame of the current bbaasshh execution call stack. The number
of parameters to the current subroutine (shell function or
script executed with .. or ssoouurrccee) is at the top of the stack.
When a subroutine is executed, the number of parameters passed
is pushed onto BBAASSHH__AARRGGCC. The shell sets BBAASSHH__AARRGGCC only when in
extended debugging mode (see the description of the eexxttddeebbuugg op-
tion to the sshhoopptt builtin below). Setting eexxttddeebbuugg after the
shell has started to execute a script, or referencing this vari-
able when eexxttddeebbuugg is not set, may result in inconsistent val-
ues.
BBAASSHH__AARRGGVV
An array variable containing all of the parameters in the cur-
rent bbaasshh execution call stack. The final parameter of the last
subroutine call is at the top of the stack; the first parameter
of the initial call is at the bottom. When a subroutine is exe-
cuted, the parameters supplied are pushed onto BBAASSHH__AARRGGVV. The
shell sets BBAASSHH__AARRGGVV only when in extended debugging mode (see
the description of the eexxttddeebbuugg option to the sshhoopptt builtin be-
low). Setting eexxttddeebbuugg after the shell has started to execute a
script, or referencing this variable when eexxttddeebbuugg is not set,
may result in inconsistent values.
BBAASSHH__AARRGGVV00
When referenced, this variable expands to the name of the shell
or shell script (identical to $$00; see the description of special
parameter 0 above). Assignment to BBAASSHH__AARRGGVV00 causes the value
assigned to also be assigned to $$00. If BBAASSHH__AARRGGVV00 is unset, it
loses its special properties, even if it is subsequently reset.
BBAASSHH__CCMMDDSS
An associative array variable whose members correspond to the
internal hash table of commands as maintained by the hhaasshh
builtin. Elements added to this array appear in the hash table;
however, unsetting array elements currently does not cause com-
mand names to be removed from the hash table. If BBAASSHH__CCMMDDSS is
unset, it loses its special properties, even if it is subse-
quently reset.
BBAASSHH__CCOOMMMMAANNDD
The command currently being executed or about to be executed,
unless the shell is executing a command as the result of a trap,
in which case it is the command executing at the time of the
trap. If BBAASSHH__CCOOMMMMAANNDD is unset, it loses its special proper-
ties, even if it is subsequently reset.
BBAASSHH__EEXXEECCUUTTIIOONN__SSTTRRIINNGG
The command argument to the --cc invocation option.
BBAASSHH__LLIINNEENNOO
An array variable whose members are the line numbers in source
files where each corresponding member of FFUUNNCCNNAAMMEE was invoked.
$${{BBAASSHH__LLIINNEENNOO[[_$_i]]}} is the line number in the source file
($${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}}) where $${{FFUUNNCCNNAAMMEE[[_$_i]]}} was called (or
$${{BBAASSHH__LLIINNEENNOO[[_$_i_-_1]]}} if referenced within another shell func-
tion). Use LLIINNEENNOO to obtain the current line number.
BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH
A colon-separated list of directories in which the shell looks
for dynamically loadable builtins specified by the eennaabbllee com-
mand.
BBAASSHH__RREEMMAATTCCHH
An array variable whose members are assigned by the ==~~ binary
operator to the [[[[ conditional command. The element with index
0 is the portion of the string matching the entire regular ex-
pression. The element with index _n is the portion of the string
matching the _nth parenthesized subexpression.
BBAASSHH__SSOOUURRCCEE
An array variable whose members are the source filenames where
the corresponding shell function names in the FFUUNNCCNNAAMMEE array
variable are defined. The shell function $${{FFUUNNCCNNAAMMEE[[_$_i]]}} is de-
fined in the file $${{BBAASSHH__SSOOUURRCCEE[[_$_i]]}} and called from
$${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}}.
BBAASSHH__SSUUBBSSHHEELLLL
Incremented by one within each subshell or subshell environment
when the shell begins executing in that environment. The ini-
tial value is 0. If BBAASSHH__SSUUBBSSHHEELLLL is unset, it loses its spe-
cial properties, even if it is subsequently reset.
BBAASSHH__VVEERRSSIINNFFOO
A readonly array variable whose members hold version information
for this instance of bbaasshh. The values assigned to the array
members are as follows:
BBAASSHH__VVEERRSSIINNFFOO[[0]] The major version number (the _r_e_l_e_a_s_e).
BBAASSHH__VVEERRSSIINNFFOO[[1]] The minor version number (the _v_e_r_s_i_o_n).
BBAASSHH__VVEERRSSIINNFFOO[[2]] The patch level.
BBAASSHH__VVEERRSSIINNFFOO[[3]] The build version.
BBAASSHH__VVEERRSSIINNFFOO[[4]] The release status (e.g., _b_e_t_a_1).
BBAASSHH__VVEERRSSIINNFFOO[[5]] The value of MMAACCHHTTYYPPEE.
BBAASSHH__VVEERRSSIIOONN
Expands to a string describing the version of this instance of
bbaasshh.
CCOOMMPP__CCWWOORRDD
An index into $${{CCOOMMPP__WWOORRDDSS}} of the word containing the current
cursor position. This variable is available only in shell func-
tions invoked by the programmable completion facilities (see
PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
CCOOMMPP__KKEEYY
The key (or final key of a key sequence) used to invoke the cur-
rent completion function.
CCOOMMPP__LLIINNEE
The current command line. This variable is available only in
shell functions and external commands invoked by the program-
mable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
CCOOMMPP__PPOOIINNTT
The index of the current cursor position relative to the begin-
ning of the current command. If the current cursor position is
at the end of the current command, the value of this variable is
equal to $${{##CCOOMMPP__LLIINNEE}}. This variable is available only in
shell functions and external commands invoked by the program-
mable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
CCOOMMPP__TTYYPPEE
Set to an integer value corresponding to the type of completion
attempted that caused a completion function to be called: _T_A_B,
for normal completion, _?, for listing completions after succes-
sive tabs, _!, for listing alternatives on partial word comple-
tion, _@, to list completions if the word is not unmodified, or
_%, for menu completion. This variable is available only in
shell functions and external commands invoked by the program-
mable completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
CCOOMMPP__WWOORRDDBBRREEAAKKSS
The set of characters that the rreeaaddlliinnee library treats as word
separators when performing word completion. If CCOOMMPP__WWOORRDDBBRREEAAKKSS
is unset, it loses its special properties, even if it is subse-
quently reset.
CCOOMMPP__WWOORRDDSS
An array variable (see AArrrraayyss below) consisting of the individ-
ual words in the current command line. The line is split into
words as rreeaaddlliinnee would split it, using CCOOMMPP__WWOORRDDBBRREEAAKKSS as de-
scribed above. This variable is available only in shell func-
tions invoked by the programmable completion facilities (see
PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
CCOOPPRROOCC An array variable (see AArrrraayyss below) created to hold the file
descriptors for output from and input to an unnamed coprocess
(see CCoopprroocceesssseess above).
DDIIRRSSTTAACCKK
An array variable (see AArrrraayyss below) containing the current con-
tents of the directory stack. Directories appear in the stack
in the order they are displayed by the ddiirrss builtin. Assigning
to members of this array variable may be used to modify directo-
ries already in the stack, but the ppuusshhdd and ppooppdd builtins must
be used to add and remove directories. Assignment to this vari-
able will not change the current directory. If DDIIRRSSTTAACCKK is un-
set, it loses its special properties, even if it is subsequently
reset.
EEPPOOCCHHRREEAALLTTIIMMEE
Each time this parameter is referenced, it expands to the number
of seconds since the Unix Epoch (see _t_i_m_e(3)) as a floating
point value with micro-second granularity. Assignments to
EEPPOOCCHHRREEAALLTTIIMMEE are ignored. If EEPPOOCCHHRREEAALLTTIIMMEE is unset, it loses
its special properties, even if it is subsequently reset.
EEPPOOCCHHSSEECCOONNDDSS
Each time this parameter is referenced, it expands to the number
of seconds since the Unix Epoch (see _t_i_m_e(3)). Assignments to
EEPPOOCCHHSSEECCOONNDDSS are ignored. If EEPPOOCCHHSSEECCOONNDDSS is unset, it loses
its special properties, even if it is subsequently reset.
EEUUIIDD Expands to the effective user ID of the current user, initial-
ized at shell startup. This variable is readonly.
FFUUNNCCNNAAMMEE
An array variable containing the names of all shell functions
currently in the execution call stack. The element with index 0
is the name of any currently-executing shell function. The bot-
tom-most element (the one with the highest index) is "main".
This variable exists only when a shell function is executing.
Assignments to FFUUNNCCNNAAMMEE have no effect. If FFUUNNCCNNAAMMEE is unset,
it loses its special properties, even if it is subsequently re-
set.
This variable can be used with BBAASSHH__LLIINNEENNOO and BBAASSHH__SSOOUURRCCEE.
Each element of FFUUNNCCNNAAMMEE has corresponding elements in
BBAASSHH__LLIINNEENNOO and BBAASSHH__SSOOUURRCCEE to describe the call stack. For in-
stance, $${{FFUUNNCCNNAAMMEE[[_$_i]]}} was called from the file
$${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}} at line number $${{BBAASSHH__LLIINNEENNOO[[_$_i]]}}. The
ccaalllleerr builtin displays the current call stack using this infor-
mation.
GGRROOUUPPSS An array variable containing the list of groups of which the
current user is a member. Assignments to GGRROOUUPPSS have no effect.
If GGRROOUUPPSS is unset, it loses its special properties, even if it
is subsequently reset.
HHIISSTTCCMMDD
The history number, or index in the history list, of the current
command. Assignments to HHIISSTTCCMMDD are ignored. If HHIISSTTCCMMDD is un-
set, it loses its special properties, even if it is subsequently
reset.
HHOOSSTTNNAAMMEE
Automatically set to the name of the current host.
HHOOSSTTTTYYPPEE
Automatically set to a string that uniquely describes the type
of machine on which bbaasshh is executing. The default is system-
dependent.
LLIINNEENNOO Each time this parameter is referenced, the shell substitutes a
decimal number representing the current sequential line number
(starting with 1) within a script or function. When not in a
script or function, the value substituted is not guaranteed to
be meaningful. If LLIINNEENNOO is unset, it loses its special proper-
ties, even if it is subsequently reset.
MMAACCHHTTYYPPEE
Automatically set to a string that fully describes the system
type on which bbaasshh is executing, in the standard GNU _c_p_u_-_c_o_m_-
_p_a_n_y_-_s_y_s_t_e_m format. The default is system-dependent.
MMAAPPFFIILLEE
An array variable (see AArrrraayyss below) created to hold the text
read by the mmaappffiillee builtin when no variable name is supplied.
OOLLDDPPWWDD The previous working directory as set by the ccdd command.
OOPPTTAARRGG The value of the last option argument processed by the ggeettooppttss
builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
OOPPTTIINNDD The index of the next argument to be processed by the ggeettooppttss
builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
OOSSTTYYPPEE Automatically set to a string that describes the operating sys-
tem on which bbaasshh is executing. The default is system-depen-
dent.
PPIIPPEESSTTAATTUUSS
An array variable (see AArrrraayyss below) containing a list of exit
status values from the processes in the most-recently-executed
foreground pipeline (which may contain only a single command).
PPPPIIDD The process ID of the shell's parent. This variable is read-
only.
PPWWDD The current working directory as set by the ccdd command.
RRAANNDDOOMM Each time this parameter is referenced, it expands to a random
integer between 0 and 32767. Assigning a value to RRAANNDDOOMM ini-
tializes (seeds) the sequence of random numbers. If RRAANNDDOOMM is
unset, it loses its special properties, even if it is subse-
quently reset.
RREEAADDLLIINNEE__LLIINNEE
The contents of the rreeaaddlliinnee line buffer, for use with "bind -x"
(see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
RREEAADDLLIINNEE__MMAARRKK
The position of the mark (saved insertion point) in the rreeaaddlliinnee
line buffer, for use with "bind -x" (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS
below). The characters between the insertion point and the mark
are often called the _r_e_g_i_o_n.
RREEAADDLLIINNEE__PPOOIINNTT
The position of the insertion point in the rreeaaddlliinnee line buffer,
for use with "bind -x" (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
RREEPPLLYY Set to the line of input read by the rreeaadd builtin command when
no arguments are supplied.
SSEECCOONNDDSS
Each time this parameter is referenced, the number of seconds
since shell invocation is returned. If a value is assigned to
SSEECCOONNDDSS, the value returned upon subsequent references is the
number of seconds since the assignment plus the value assigned.
The number of seconds at shell invocation and the current time
is always determined by querying the system clock. If SSEECCOONNDDSS
is unset, it loses its special properties, even if it is subse-
quently reset.
SSHHEELLLLOOPPTTSS
A colon-separated list of enabled shell options. Each word in
the list is a valid argument for the --oo option to the sseett
builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). The options
appearing in SSHHEELLLLOOPPTTSS are those reported as _o_n by sseett --oo. If
this variable is in the environment when bbaasshh starts up, each
shell option in the list will be enabled before reading any
startup files. This variable is read-only.
SSHHLLVVLL Incremented by one each time an instance of bbaasshh is started.
SSRRAANNDDOOMM
This variable expands to a 32-bit pseudo-random number each time
it is referenced. The random number generator is not linear on
systems that support /dev/urandom or _a_r_c_4_r_a_n_d_o_m, so each re-
turned number has no relationship to the numbers preceding it.
The random number generator cannot be seeded, so assignments to
this variable have no effect. If SSRRAANNDDOOMM is unset, it loses its
special properties, even if it is subsequently reset.
UUIIDD Expands to the user ID of the current user, initialized at shell
startup. This variable is readonly.
The following variables are used by the shell. In some cases, bbaasshh as-
signs a default value to a variable; these cases are noted below.
BBAASSHH__CCOOMMPPAATT
The value is used to set the shell's compatibility level. See
SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE below for a description of the various
compatibility levels and their effects. The value may be a dec-
imal number (e.g., 4.2) or an integer (e.g., 42) corresponding
to the desired compatibility level. If BBAASSHH__CCOOMMPPAATT is unset or
set to the empty string, the compatibility level is set to the
default for the current version. If BBAASSHH__CCOOMMPPAATT is set to a
value that is not one of the valid compatibility levels, the
shell prints an error message and sets the compatibility level
to the default for the current version. The valid values corre-
spond to the compatibility levels described below under BBSSHHEELLLL--
COMPATIBILITYMMOODDEE. For example, 4.2 and 42 are valid values
that correspond to the ccoommppaatt4422 sshhoopptt option and set the compat-
ibility level to 42. The current version is also a valid value.
BBAASSHH__EENNVV
If this parameter is set when bbaasshh is executing a shell script,
its value is interpreted as a filename containing commands to
initialize the shell, as in _~_/_._b_a_s_h_r_c. The value of BBAASSHH__EENNVV is
subjected to parameter expansion, command substitution, and
arithmetic expansion before being interpreted as a filename.
PPAATTHH is not used to search for the resultant filename.
BBAASSHH__XXTTRRAACCEEFFDD
If set to an integer corresponding to a valid file descriptor,
bbaasshh will write the trace output generated when _s_e_t _-_x is en-
abled to that file descriptor. The file descriptor is closed
when BBAASSHH__XXTTRRAACCEEFFDD is unset or assigned a new value. Unsetting
BBAASSHH__XXTTRRAACCEEFFDD or assigning it the empty string causes the trace
output to be sent to the standard error. Note that setting
BBAASSHH__XXTTRRAACCEEFFDD to 2 (the standard error file descriptor) and then
unsetting it will result in the standard error being closed.
CCDDPPAATTHH The search path for the ccdd command. This is a colon-separated
list of directories in which the shell looks for destination di-
rectories specified by the ccdd command. A sample value is
".:~:/usr".
CCHHIILLDD__MMAAXX
Set the number of exited child status values for the shell to
remember. Bash will not allow this value to be decreased below
a POSIX-mandated minimum, and there is a maximum value (cur-
rently 8192) that this may not exceed. The minimum value is
system-dependent.
CCOOLLUUMMNNSS
Used by the sseelleecctt compound command to determine the terminal
width when printing selection lists. Automatically set if the
cchheecckkwwiinnssiizzee option is enabled or in an interactive shell upon
receipt of a SSIIGGWWIINNCCHH.
CCOOMMPPRREEPPLLYY
An array variable from which bbaasshh reads the possible completions
generated by a shell function invoked by the programmable com-
pletion facility (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below). Each ar-
ray element contains one possible completion.
EEMMAACCSS If bbaasshh finds this variable in the environment when the shell
starts with value "t", it assumes that the shell is running in
an Emacs shell buffer and disables line editing.
EENNVV Expanded and executed similarly to BBAASSHH__EENNVV (see IINNVVOOCCAATTIIOONN
above) when an interactive shell is invoked in _p_o_s_i_x _m_o_d_e.
EEXXEECCIIGGNNOORREE
A colon-separated list of shell patterns (see PPaatttteerrnn MMaattcchhiinngg)
defining the list of filenames to be ignored by command search
using PPAATTHH. Files whose full pathnames match one of these pat-
terns are not considered executable files for the purposes of
completion and command execution via PPAATTHH lookup. This does not
affect the behavior of the [[, tteesstt, and [[[[ commands. Full path-
names in the command hash table are not subject to EEXXEECCIIGGNNOORREE.
Use this variable to ignore shared library files that have the
executable bit set, but are not executable files. The pattern
matching honors the setting of the eexxttgglloobb shell option.
FFCCEEDDIITT The default editor for the ffcc builtin command.
FFIIGGNNOORREE
A colon-separated list of suffixes to ignore when performing
filename completion (see RREEAADDLLIINNEE below). A filename whose suf-
fix matches one of the entries in FFIIGGNNOORREE is excluded from the
list of matched filenames. A sample value is ".o:~".
FFUUNNCCNNEESSTT
If set to a numeric value greater than 0, defines a maximum
function nesting level. Function invocations that exceed this
nesting level will cause the current command to abort.
GGLLOOBBIIGGNNOORREE
A colon-separated list of patterns defining the set of file
names to be ignored by pathname expansion. If a file name
matched by a pathname expansion pattern also matches one of the
patterns in GGLLOOBBIIGGNNOORREE, it is removed from the list of matches.
HHIISSTTCCOONNTTRROOLL
A colon-separated list of values controlling how commands are
saved on the history list. If the list of values includes _i_g_-
_n_o_r_e_s_p_a_c_e, lines which begin with a ssppaaccee character are not
saved in the history list. A value of _i_g_n_o_r_e_d_u_p_s causes lines
matching the previous history entry to not be saved. A value of
_i_g_n_o_r_e_b_o_t_h is shorthand for _i_g_n_o_r_e_s_p_a_c_e and _i_g_n_o_r_e_d_u_p_s. A value
of _e_r_a_s_e_d_u_p_s causes all previous lines matching the current line
to be removed from the history list before that line is saved.
Any value not in the above list is ignored. If HHIISSTTCCOONNTTRROOLL is
unset, or does not include a valid value, all lines read by the
shell parser are saved on the history list, subject to the value
of HHIISSTTIIGGNNOORREE. The second and subsequent lines of a multi-line
compound command are not tested, and are added to the history
regardless of the value of HHIISSTTCCOONNTTRROOLL.
HHIISSTTFFIILLEE
The name of the file in which command history is saved (see HHIISS--
TTOORRYY below). The default value is _~_/_._b_a_s_h___h_i_s_t_o_r_y. If unset,
the command history is not saved when a shell exits.
HHIISSTTFFIILLEESSIIZZEE
The maximum number of lines contained in the history file. When
this variable is assigned a value, the history file is trun-
cated, if necessary, to contain no more than that number of
lines by removing the oldest entries. The history file is also
truncated to this size after writing it when a shell exits. If
the value is 0, the history file is truncated to zero size.
Non-numeric values and numeric values less than zero inhibit
truncation. The shell sets the default value to the value of
HHIISSTTSSIIZZEE after reading any startup files.
HHIISSTTIIGGNNOORREE
A colon-separated list of patterns used to decide which command
lines should be saved on the history list. Each pattern is an-
chored at the beginning of the line and must match the complete
line (no implicit `**' is appended). Each pattern is tested
against the line after the checks specified by HHIISSTTCCOONNTTRROOLL are
applied. In addition to the normal shell pattern matching char-
acters, `&&' matches the previous history line. `&&' may be es-
caped using a backslash; the backslash is removed before at-
tempting a match. The second and subsequent lines of a multi-
line compound command are not tested, and are added to the his-
tory regardless of the value of HHIISSTTIIGGNNOORREE. The pattern match-
ing honors the setting of the eexxttgglloobb shell option.
HHIISSTTSSIIZZEE
The number of commands to remember in the command history (see
HHIISSTTOORRYY below). If the value is 0, commands are not saved in
the history list. Numeric values less than zero result in every
command being saved on the history list (there is no limit).
The shell sets the default value to 500 after reading any
startup files.
HHIISSTTTTIIMMEEFFOORRMMAATT
If this variable is set and not null, its value is used as a
format string for _s_t_r_f_t_i_m_e(3) to print the time stamp associated
with each history entry displayed by the hhiissttoorryy builtin. If
this variable is set, time stamps are written to the history
file so they may be preserved across shell sessions. This uses
the history comment character to distinguish timestamps from
other history lines.
HHOOMMEE The home directory of the current user; the default argument for
the ccdd builtin command. The value of this variable is also used
when performing tilde expansion.
HHOOSSTTFFIILLEE
Contains the name of a file in the same format as _/_e_t_c_/_h_o_s_t_s
that should be read when the shell needs to complete a hostname.
The list of possible hostname completions may be changed while
the shell is running; the next time hostname completion is at-
tempted after the value is changed, bbaasshh adds the contents of
the new file to the existing list. If HHOOSSTTFFIILLEE is set, but has
no value, or does not name a readable file, bbaasshh attempts to
read _/_e_t_c_/_h_o_s_t_s to obtain the list of possible hostname comple-
tions. When HHOOSSTTFFIILLEE is unset, the hostname list is cleared.
IIFFSS The _I_n_t_e_r_n_a_l _F_i_e_l_d _S_e_p_a_r_a_t_o_r that is used for word splitting af-
ter expansion and to split lines into words with the rreeaadd
builtin command. The default value is ``<space><tab><new-
line>''.
IIGGNNOORREEEEOOFF
Controls the action of an interactive shell on receipt of an EEOOFF
character as the sole input. If set, the value is the number of
consecutive EEOOFF characters which must be typed as the first
characters on an input line before bbaasshh exits. If the variable
exists but does not have a numeric value, or has no value, the
default value is 10. If it does not exist, EEOOFF signifies the
end of input to the shell.
IINNPPUUTTRRCC
The filename for the rreeaaddlliinnee startup file, overriding the de-
fault of _~_/_._i_n_p_u_t_r_c (see RREEAADDLLIINNEE below).
IINNSSIIDDEE__EEMMAACCSS
If this variable appears in the environment when the shell
starts, bbaasshh assumes that it is running inside an Emacs shell
buffer and may disable line editing, depending on the value of
TTEERRMM.
LLAANNGG Used to determine the locale category for any category not
specifically selected with a variable starting with LLCC__.
LLCC__AALLLL This variable overrides the value of LLAANNGG and any other LLCC__
variable specifying a locale category.
LLCC__CCOOLLLLAATTEE
This variable determines the collation order used when sorting
the results of pathname expansion, and determines the behavior
of range expressions, equivalence classes, and collating se-
quences within pathname expansion and pattern matching.
LLCC__CCTTYYPPEE
This variable determines the interpretation of characters and
the behavior of character classes within pathname expansion and
pattern matching.
LLCC__MMEESSSSAAGGEESS
This variable determines the locale used to translate double-
quoted strings preceded by a $$.
LLCC__NNUUMMEERRIICC
This variable determines the locale category used for number
formatting.
LLCC__TTIIMMEE
This variable determines the locale category used for data and
time formatting.
LLIINNEESS Used by the sseelleecctt compound command to determine the column
length for printing selection lists. Automatically set if the
cchheecckkwwiinnssiizzee option is enabled or in an interactive shell upon
receipt of a SSIIGGWWIINNCCHH.
MMAAIILL If this parameter is set to a file or directory name and the
MMAAIILLPPAATTHH variable is not set, bbaasshh informs the user of the ar-
rival of mail in the specified file or Maildir-format directory.
MMAAIILLCCHHEECCKK
Specifies how often (in seconds) bbaasshh checks for mail. The de-
fault is 60 seconds. When it is time to check for mail, the
shell does so before displaying the primary prompt. If this
variable is unset, or set to a value that is not a number
greater than or equal to zero, the shell disables mail checking.
MMAAIILLPPAATTHH
A colon-separated list of filenames to be checked for mail. The
message to be printed when mail arrives in a particular file may
be specified by separating the filename from the message with a
`?'. When used in the text of the message, $$__ expands to the
name of the current mailfile. Example:
MMAAIILLPPAATTHH='/var/mail/bfox?"You have mail":~/shell-mail?"$_ has
mail!"'
BBaasshh can be configured to supply a default value for this vari-
able (there is no value by default), but the location of the
user mail files that it uses is system dependent (e.g.,
/var/mail/$$UUSSEERR).
OOPPTTEERRRR If set to the value 1, bbaasshh displays error messages generated by
the ggeettooppttss builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
OOPPTTEERRRR is initialized to 1 each time the shell is invoked or a
shell script is executed.
PPAATTHH The search path for commands. It is a colon-separated list of
directories in which the shell looks for commands (see CCOOMMMMAANNDD
EEXXEECCUUTTIIOONN below). A zero-length (null) directory name in the
value of PPAATTHH indicates the current directory. A null directory
name may appear as two adjacent colons, or as an initial or
trailing colon. The default path is system-dependent, and is
set by the administrator who installs bbaasshh. A common value is
``/usr/local/bin:/usr/lo-
cal/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
PPOOSSIIXXLLYY__CCOORRRREECCTT
If this variable is in the environment when bbaasshh starts, the
shell enters _p_o_s_i_x _m_o_d_e before reading the startup files, as if
the ----ppoossiixx invocation option had been supplied. If it is set
while the shell is running, bbaasshh enables _p_o_s_i_x _m_o_d_e, as if the
command _s_e_t _-_o _p_o_s_i_x had been executed. When the shell enters
_p_o_s_i_x _m_o_d_e, it sets this variable if it was not already set.
PPRROOMMPPTT__CCOOMMMMAANNDD
If this variable is set, and is an array, the value of each set
element is executed as a command prior to issuing each primary
prompt. If this is set but not an array variable, its value is
used as a command to execute instead.
PPRROOMMPPTT__DDIIRRTTRRIIMM
If set to a number greater than zero, the value is used as the
number of trailing directory components to retain when expanding
the \\ww and \\WW prompt string escapes (see PPRROOMMPPTTIINNGG below).
Characters removed are replaced with an ellipsis.
PPSS00 The value of this parameter is expanded (see PPRROOMMPPTTIINNGG below)
and displayed by interactive shells after reading a command and
before the command is executed.
PPSS11 The value of this parameter is expanded (see PPRROOMMPPTTIINNGG below)
and used as the primary prompt string. The default value is
``\\ss--\\vv\\$$ ''.
PPSS22 The value of this parameter is expanded as with PPSS11 and used as
the secondary prompt string. The default is ``>> ''.
PPSS33 The value of this parameter is used as the prompt for the sseelleecctt
command (see SSHHEELLLL GGRRAAMMMMAARR above).
PPSS44 The value of this parameter is expanded as with PPSS11 and the
value is printed before each command bbaasshh displays during an ex-
ecution trace. The first character of the expanded value of PPSS44
is replicated multiple times, as necessary, to indicate multiple
levels of indirection. The default is ``++ ''.
SSHHEELLLL This variable expands to the full pathname to the shell. If it
is not set when the shell starts, bbaasshh assigns to it the full
pathname of the current user's login shell.
TTIIMMEEFFOORRMMAATT
The value of this parameter is used as a format string specify-
ing how the timing information for pipelines prefixed with the
ttiimmee reserved word should be displayed. The %% character intro-
duces an escape sequence that is expanded to a time value or
other information. The escape sequences and their meanings are
as follows; the braces denote optional portions.
%%%% A literal %%.
%%[[_p]][[ll]]RR The elapsed time in seconds.
%%[[_p]][[ll]]UU The number of CPU seconds spent in user mode.
%%[[_p]][[ll]]SS The number of CPU seconds spent in system mode.
%%PP The CPU percentage, computed as (%U + %S) / %R.
The optional _p is a digit specifying the _p_r_e_c_i_s_i_o_n, the number
of fractional digits after a decimal point. A value of 0 causes
no decimal point or fraction to be output. At most three places
after the decimal point may be specified; values of _p greater
than 3 are changed to 3. If _p is not specified, the value 3 is
used.
The optional ll specifies a longer format, including minutes, of
the form _M_Mm_S_S._F_Fs. The value of _p determines whether or not
the fraction is included.
If this variable is not set, bbaasshh acts as if it had the value
$$''\\nnrreeaall\\tt%%33llRR\\nnuusseerr\\tt%%33llUU\\nnssyyss\\tt%%33llSS''. If the value is null,
no timing information is displayed. A trailing newline is added
when the format string is displayed.
TTMMOOUUTT If set to a value greater than zero, TTMMOOUUTT is treated as the de-
fault timeout for the rreeaadd builtin. The sseelleecctt command termi-
nates if input does not arrive after TTMMOOUUTT seconds when input is
coming from a terminal. In an interactive shell, the value is
interpreted as the number of seconds to wait for a line of input
after issuing the primary prompt. BBaasshh terminates after waiting
for that number of seconds if a complete line of input does not
arrive.
TTMMPPDDIIRR If set, bbaasshh uses its value as the name of a directory in which
bbaasshh creates temporary files for the shell's use.
aauuttoo__rreessuummee
This variable controls how the shell interacts with the user and
job control. If this variable is set, single word simple com-
mands without redirections are treated as candidates for resump-
tion of an existing stopped job. There is no ambiguity allowed;
if there is more than one job beginning with the string typed,
the job most recently accessed is selected. The _n_a_m_e of a
stopped job, in this context, is the command line used to start
it. If set to the value _e_x_a_c_t, the string supplied must match
the name of a stopped job exactly; if set to _s_u_b_s_t_r_i_n_g, the
string supplied needs to match a substring of the name of a
stopped job. The _s_u_b_s_t_r_i_n_g value provides functionality analo-
gous to the %%?? job identifier (see JJOOBB CCOONNTTRROOLL below). If set
to any other value, the supplied string must be a prefix of a
stopped job's name; this provides functionality analogous to the
%%_s_t_r_i_n_g job identifier.
hhiissttcchhaarrss
The two or three characters which control history expansion and
tokenization (see HHIISSTTOORRYY EEXXPPAANNSSIIOONN below). The first character
is the _h_i_s_t_o_r_y _e_x_p_a_n_s_i_o_n character, the character which signals
the start of a history expansion, normally `!!'. The second
character is the _q_u_i_c_k _s_u_b_s_t_i_t_u_t_i_o_n character, which is used as
shorthand for re-running the previous command entered, substi-
tuting one string for another in the command. The default is
`^^'. The optional third character is the character which indi-
cates that the remainder of the line is a comment when found as
the first character of a word, normally `##'. The history com-
ment character causes history substitution to be skipped for the
remaining words on the line. It does not necessarily cause the
shell parser to treat the rest of the line as a comment.
AArrrraayyss
BBaasshh provides one-dimensional indexed and associative array variables.
Any variable may be used as an indexed array; the ddeeccllaarree builtin will
explicitly declare an array. There is no maximum limit on the size of
an array, nor any requirement that members be indexed or assigned con-
tiguously. Indexed arrays are referenced using integers (including
arithmetic expressions) and are zero-based; associative arrays are ref-
erenced using arbitrary strings. Unless otherwise noted, indexed array
indices must be non-negative integers.
An indexed array is created automatically if any variable is assigned
to using the syntax _n_a_m_e[_s_u_b_s_c_r_i_p_t]=_v_a_l_u_e. The _s_u_b_s_c_r_i_p_t is treated as
an arithmetic expression that must evaluate to a number. To explicitly
declare an indexed array, use ddeeccllaarree --aa _n_a_m_e (see SSHHEELLLL BBUUIILLTTIINN CCOOMM--
MMAANNDDSS below). ddeeccllaarree --aa _n_a_m_e[[_s_u_b_s_c_r_i_p_t]] is also accepted; the _s_u_b_-
_s_c_r_i_p_t is ignored.
Associative arrays are created using ddeeccllaarree --AA _n_a_m_e.
Attributes may be specified for an array variable using the ddeeccllaarree and
rreeaaddoonnllyy builtins. Each attribute applies to all members of an array.
Arrays are assigned to using compound assignments of the form
_n_a_m_e=((value_1 ... value_n)), where each _v_a_l_u_e may be of the form [_s_u_b_-
_s_c_r_i_p_t]=_s_t_r_i_n_g. Indexed array assignments do not require anything but
_s_t_r_i_n_g. Each _v_a_l_u_e in the list is expanded using all the shell expan-
sions described below under EEXXPPAANNSSIIOONN. When assigning to indexed ar-
rays, if the optional brackets and subscript are supplied, that index
is assigned to; otherwise the index of the element assigned is the last
index assigned to by the statement plus one. Indexing starts at zero.
When assigning to an associative array, the words in a compound assign-
ment may be either assignment statements, for which the subscript is
required, or a list of words that is interpreted as a sequence of al-
ternating keys and values: _n_a_m_e=(( _k_e_y_1 _v_a_l_u_e_1 _k_e_y_2 _v_a_l_u_e_2 ...)). These
are treated identically to _n_a_m_e=(( [_k_e_y_1]=_v_a_l_u_e_1 [_k_e_y_2]=_v_a_l_u_e_2 ...)).
The first word in the list determines how the remaining words are in-
terpreted; all assignments in a list must be of the same type. When
using key/value pairs, the keys may not be missing or empty; a final
missing value is treated like the empty string.
This syntax is also accepted by the ddeeccllaarree builtin. Individual array
elements may be assigned to using the _n_a_m_e[_s_u_b_s_c_r_i_p_t]=_v_a_l_u_e syntax in-
troduced above. When assigning to an indexed array, if _n_a_m_e is sub-
scripted by a negative number, that number is interpreted as relative
to one greater than the maximum index of _n_a_m_e, so negative indices
count back from the end of the array, and an index of -1 references the
last element.
Any element of an array may be referenced using ${_n_a_m_e[_s_u_b_s_c_r_i_p_t]}.
The braces are required to avoid conflicts with pathname expansion. If
_s_u_b_s_c_r_i_p_t is @@ or **, the word expands to all members of _n_a_m_e. These
subscripts differ only when the word appears within double quotes. If
the word is double-quoted, ${_n_a_m_e[*]} expands to a single word with the
value of each array member separated by the first character of the IIFFSS
special variable, and ${_n_a_m_e[@]} expands each element of _n_a_m_e to a sep-
arate word. When there are no array members, ${_n_a_m_e[@]} expands to
nothing. If the double-quoted expansion occurs within a word, the ex-
pansion of the first parameter is joined with the beginning part of the
original word, and the expansion of the last parameter is joined with
the last part of the original word. This is analogous to the expansion
of the special parameters ** and @@ (see SSppeecciiaall PPaarraammeetteerrss above).
${#_n_a_m_e[_s_u_b_s_c_r_i_p_t]} expands to the length of ${_n_a_m_e[_s_u_b_s_c_r_i_p_t]}. If
_s_u_b_s_c_r_i_p_t is ** or @@, the expansion is the number of elements in the ar-
ray. If the _s_u_b_s_c_r_i_p_t used to reference an element of an indexed array
evaluates to a number less than zero, it is interpreted as relative to
one greater than the maximum index of the array, so negative indices
count back from the end of the array, and an index of -1 references the
last element.
Referencing an array variable without a subscript is equivalent to ref-
erencing the array with a subscript of 0. Any reference to a variable
using a valid subscript is legal, and bbaasshh will create an array if nec-
essary.
An array variable is considered set if a subscript has been assigned a
value. The null string is a valid value.
It is possible to obtain the keys (indices) of an array as well as the
values. ${!!_n_a_m_e[_@]} and ${!!_n_a_m_e[_*]} expand to the indices assigned in
array variable _n_a_m_e. The treatment when in double quotes is similar to
the expansion of the special parameters _@ and _* within double quotes.
The uunnsseett builtin is used to destroy arrays. uunnsseett _n_a_m_e[_s_u_b_s_c_r_i_p_t] de-
stroys the array element at index _s_u_b_s_c_r_i_p_t, for both indexed and asso-
ciative arrays. Negative subscripts to indexed arrays are interpreted
as described above. Unsetting the last element of an array variable
does not unset the variable. uunnsseett _n_a_m_e, where _n_a_m_e is an array, or
uunnsseett _n_a_m_e[_s_u_b_s_c_r_i_p_t], where _s_u_b_s_c_r_i_p_t is ** or @@, removes the entire
array.
When using a variable name with a subscript as an argument to a com-
mand, such as with uunnsseett, without using the word expansion syntax de-
scribed above, the argument is subject to pathname expansion. If path-
name expansion is not desired, the argument should be quoted.
The ddeeccllaarree, llooccaall, and rreeaaddoonnllyy builtins each accept a --aa option to
specify an indexed array and a --AA option to specify an associative ar-
ray. If both options are supplied, --AA takes precedence. The rreeaadd
builtin accepts a --aa option to assign a list of words read from the
standard input to an array. The sseett and ddeeccllaarree builtins display array
values in a way that allows them to be reused as assignments.
EEXXPPAANNSSIIOONN
Expansion is performed on the command line after it has been split into
words. There are seven kinds of expansion performed: _b_r_a_c_e _e_x_p_a_n_s_i_o_n,
_t_i_l_d_e _e_x_p_a_n_s_i_o_n, _p_a_r_a_m_e_t_e_r _a_n_d _v_a_r_i_a_b_l_e _e_x_p_a_n_s_i_o_n, _c_o_m_m_a_n_d _s_u_b_s_t_i_t_u_-
_t_i_o_n, _a_r_i_t_h_m_e_t_i_c _e_x_p_a_n_s_i_o_n, _w_o_r_d _s_p_l_i_t_t_i_n_g, and _p_a_t_h_n_a_m_e _e_x_p_a_n_s_i_o_n.
The order of expansions is: brace expansion; tilde expansion, parameter
and variable expansion, arithmetic expansion, and command substitution
(done in a left-to-right fashion); word splitting; and pathname expan-
sion.
On systems that can support it, there is an additional expansion avail-
able: _p_r_o_c_e_s_s _s_u_b_s_t_i_t_u_t_i_o_n. This is performed at the same time as
tilde, parameter, variable, and arithmetic expansion and command sub-
stitution.
After these expansions are performed, quote characters present in the
original word are removed unless they have been quoted themselves
(_q_u_o_t_e _r_e_m_o_v_a_l).
Only brace expansion, word splitting, and pathname expansion can in-
crease the number of words of the expansion; other expansions expand a
single word to a single word. The only exceptions to this are the ex-
pansions of "$$@@" and "$${{_n_a_m_e[[@@]]}}", and, in most cases, $$** and
$${{_n_a_m_e[[**]]}} as explained above (see PPAARRAAMMEETTEERRSS).
BBrraaccee EExxppaannssiioonn
_B_r_a_c_e _e_x_p_a_n_s_i_o_n is a mechanism by which arbitrary strings may be gener-
ated. This mechanism is similar to _p_a_t_h_n_a_m_e _e_x_p_a_n_s_i_o_n, but the file-
names generated need not exist. Patterns to be brace expanded take the
form of an optional _p_r_e_a_m_b_l_e, followed by either a series of comma-sep-
arated strings or a sequence expression between a pair of braces, fol-
lowed by an optional _p_o_s_t_s_c_r_i_p_t. The preamble is prefixed to each
string contained within the braces, and the postscript is then appended
to each resulting string, expanding left to right.
Brace expansions may be nested. The results of each expanded string
are not sorted; left to right order is preserved. For example,
a{{d,c,b}}e expands into `ade ace abe'.
A sequence expression takes the form {{_x...._y[[...._i_n_c_r]]}}, where _x and _y are
either integers or single characters, and _i_n_c_r, an optional increment,
is an integer. When integers are supplied, the expression expands to
each number between _x and _y, inclusive. Supplied integers may be pre-
fixed with _0 to force each term to have the same width. When either _x
or _y begins with a zero, the shell attempts to force all generated
terms to contain the same number of digits, zero-padding where neces-
sary. When characters are supplied, the expression expands to each
character lexicographically between _x and _y, inclusive, using the de-
fault C locale. Note that both _x and _y must be of the same type. When
the increment is supplied, it is used as the difference between each
term. The default increment is 1 or -1 as appropriate.
Brace expansion is performed before any other expansions, and any char-
acters special to other expansions are preserved in the result. It is
strictly textual. BBaasshh does not apply any syntactic interpretation to
the context of the expansion or the text between the braces.
A correctly-formed brace expansion must contain unquoted opening and
closing braces, and at least one unquoted comma or a valid sequence ex-
pression. Any incorrectly formed brace expansion is left unchanged. A
{{ or ,, may be quoted with a backslash to prevent its being considered
part of a brace expression. To avoid conflicts with parameter expan-
sion, the string $${{ is not considered eligible for brace expansion, and
inhibits brace expansion until the closing }}.
This construct is typically used as shorthand when the common prefix of
the strings to be generated is longer than in the above example:
mkdir /usr/local/src/bash/{old,new,dist,bugs}
or
chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
Brace expansion introduces a slight incompatibility with historical
versions of sshh. sshh does not treat opening or closing braces specially
when they appear as part of a word, and preserves them in the output.
BBaasshh removes braces from words as a consequence of brace expansion.
For example, a word entered to sshh as _f_i_l_e_{_1_,_2_} appears identically in
the output. The same word is output as _f_i_l_e_1 _f_i_l_e_2 after expansion by
bbaasshh. If strict compatibility with sshh is desired, start bbaasshh with the
++BB option or disable brace expansion with the ++BB option to the sseett com-
mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
TTiillddee EExxppaannssiioonn
If a word begins with an unquoted tilde character (`~~'), all of the
characters preceding the first unquoted slash (or all characters, if
there is no unquoted slash) are considered a _t_i_l_d_e_-_p_r_e_f_i_x. If none of
the characters in the tilde-prefix are quoted, the characters in the
tilde-prefix following the tilde are treated as a possible _l_o_g_i_n _n_a_m_e.
If this login name is the null string, the tilde is replaced with the
value of the shell parameter HHOOMMEE. If HHOOMMEE is unset, the home direc-
tory of the user executing the shell is substituted instead. Other-
wise, the tilde-prefix is replaced with the home directory associated
with the specified login name.
If the tilde-prefix is a `~+', the value of the shell variable PPWWDD re-
places the tilde-prefix. If the tilde-prefix is a `~-', the value of
the shell variable OOLLDDPPWWDD, if it is set, is substituted. If the char-
acters following the tilde in the tilde-prefix consist of a number _N,
optionally prefixed by a `+' or a `-', the tilde-prefix is replaced
with the corresponding element from the directory stack, as it would be
displayed by the ddiirrss builtin invoked with the tilde-prefix as an argu-
ment. If the characters following the tilde in the tilde-prefix con-
sist of a number without a leading `+' or `-', `+' is assumed.
If the login name is invalid, or the tilde expansion fails, the word is
unchanged.
Each variable assignment is checked for unquoted tilde-prefixes immedi-
ately following a :: or the first ==. In these cases, tilde expansion is
also performed. Consequently, one may use filenames with tildes in as-
signments to PPAATTHH, MMAAIILLPPAATTHH, and CCDDPPAATTHH, and the shell assigns the ex-
panded value.
Bash also performs tilde expansion on words satisfying the conditions
of variable assignments (as described above under PPAARRAAMMEETTEERRSS) when they
appear as arguments to simple commands. Bash does not do this, except
for the _d_e_c_l_a_r_a_t_i_o_n commands listed above, when in _p_o_s_i_x _m_o_d_e.
PPaarraammeetteerr EExxppaannssiioonn
The `$$' character introduces parameter expansion, command substitution,
or arithmetic expansion. The parameter name or symbol to be expanded
may be enclosed in braces, which are optional but serve to protect the
variable to be expanded from characters immediately following it which
could be interpreted as part of the name.
When braces are used, the matching ending brace is the first `}}' not
escaped by a backslash or within a quoted string, and not within an em-
bedded arithmetic expansion, command substitution, or parameter expan-
sion.
${_p_a_r_a_m_e_t_e_r}
The value of _p_a_r_a_m_e_t_e_r is substituted. The braces are required
when _p_a_r_a_m_e_t_e_r is a positional parameter with more than one
digit, or when _p_a_r_a_m_e_t_e_r is followed by a character which is not
to be interpreted as part of its name. The _p_a_r_a_m_e_t_e_r is a shell
parameter as described above PPAARRAAMMEETTEERRSS) or an array reference
(AArrrraayyss).
If the first character of _p_a_r_a_m_e_t_e_r is an exclamation point (!!), and
_p_a_r_a_m_e_t_e_r is not a _n_a_m_e_r_e_f, it introduces a level of indirection. BBaasshh
uses the value formed by expanding the rest of _p_a_r_a_m_e_t_e_r as the new _p_a_-
_r_a_m_e_t_e_r; this is then expanded and that value is used in the rest of
the expansion, rather than the expansion of the original _p_a_r_a_m_e_t_e_r.
This is known as _i_n_d_i_r_e_c_t _e_x_p_a_n_s_i_o_n. The value is subject to tilde ex-
pansion, parameter expansion, command substitution, and arithmetic ex-
pansion. If _p_a_r_a_m_e_t_e_r is a nameref, this expands to the name of the
parameter referenced by _p_a_r_a_m_e_t_e_r instead of performing the complete
indirect expansion. The exceptions to this are the expansions of
${!!_p_r_e_f_i_x**} and ${!!_n_a_m_e[_@]} described below. The exclamation point
must immediately follow the left brace in order to introduce indirec-
tion.
In each of the cases below, _w_o_r_d is subject to tilde expansion, parame-
ter expansion, command substitution, and arithmetic expansion.
When not performing substring expansion, using the forms documented be-
low (e.g., ::--), bbaasshh tests for a parameter that is unset or null.
Omitting the colon results in a test only for a parameter that is un-
set.
${_p_a_r_a_m_e_t_e_r::--_w_o_r_d}
UUssee DDeeffaauulltt VVaalluueess. If _p_a_r_a_m_e_t_e_r is unset or null, the expan-
sion of _w_o_r_d is substituted. Otherwise, the value of _p_a_r_a_m_e_t_e_r
is substituted.
${_p_a_r_a_m_e_t_e_r::==_w_o_r_d}
AAssssiiggnn DDeeffaauulltt VVaalluueess. If _p_a_r_a_m_e_t_e_r is unset or null, the ex-
pansion of _w_o_r_d is assigned to _p_a_r_a_m_e_t_e_r. The value of _p_a_r_a_m_e_-
_t_e_r is then substituted. Positional parameters and special pa-
rameters may not be assigned to in this way.
${_p_a_r_a_m_e_t_e_r::??_w_o_r_d}
DDiissppllaayy EErrrroorr iiff NNuullll oorr UUnnsseett. If _p_a_r_a_m_e_t_e_r is null or unset,
the expansion of _w_o_r_d (or a message to that effect if _w_o_r_d is
not present) is written to the standard error and the shell, if
it is not interactive, exits. Otherwise, the value of _p_a_r_a_m_e_t_e_r
is substituted.
${_p_a_r_a_m_e_t_e_r::++_w_o_r_d}
UUssee AAlltteerrnnaattee VVaalluuee. If _p_a_r_a_m_e_t_e_r is null or unset, nothing is
substituted, otherwise the expansion of _w_o_r_d is substituted.
${_p_a_r_a_m_e_t_e_r::_o_f_f_s_e_t}
${_p_a_r_a_m_e_t_e_r::_o_f_f_s_e_t::_l_e_n_g_t_h}
SSuubbssttrriinngg EExxppaannssiioonn. Expands to up to _l_e_n_g_t_h characters of the
value of _p_a_r_a_m_e_t_e_r starting at the character specified by _o_f_f_-
_s_e_t. If _p_a_r_a_m_e_t_e_r is @@, an indexed array subscripted by @@ or **,
or an associative array name, the results differ as described
below. If _l_e_n_g_t_h is omitted, expands to the substring of the
value of _p_a_r_a_m_e_t_e_r starting at the character specified by _o_f_f_s_e_t
and extending to the end of the value. _l_e_n_g_t_h and _o_f_f_s_e_t are
arithmetic expressions (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN below).
If _o_f_f_s_e_t evaluates to a number less than zero, the value is
used as an offset in characters from the end of the value of _p_a_-
_r_a_m_e_t_e_r. If _l_e_n_g_t_h evaluates to a number less than zero, it is
interpreted as an offset in characters from the end of the value
of _p_a_r_a_m_e_t_e_r rather than a number of characters, and the expan-
sion is the characters between _o_f_f_s_e_t and that result. Note
that a negative offset must be separated from the colon by at
least one space to avoid being confused with the ::-- expansion.
If _p_a_r_a_m_e_t_e_r is @@, the result is _l_e_n_g_t_h positional parameters
beginning at _o_f_f_s_e_t. A negative _o_f_f_s_e_t is taken relative to one
greater than the greatest positional parameter, so an offset of
-1 evaluates to the last positional parameter. It is an expan-
sion error if _l_e_n_g_t_h evaluates to a number less than zero.
If _p_a_r_a_m_e_t_e_r is an indexed array name subscripted by @ or *, the
result is the _l_e_n_g_t_h members of the array beginning with ${_p_a_-
_r_a_m_e_t_e_r[_o_f_f_s_e_t]}. A negative _o_f_f_s_e_t is taken relative to one
greater than the maximum index of the specified array. It is an
expansion error if _l_e_n_g_t_h evaluates to a number less than zero.
Substring expansion applied to an associative array produces un-
defined results.
Substring indexing is zero-based unless the positional parame-
ters are used, in which case the indexing starts at 1 by de-
fault. If _o_f_f_s_e_t is 0, and the positional parameters are used,
$$00 is prefixed to the list.
${!!_p_r_e_f_i_x**}
${!!_p_r_e_f_i_x@@}
NNaammeess mmaattcchhiinngg pprreeffiixx. Expands to the names of variables whose
names begin with _p_r_e_f_i_x, separated by the first character of the
IIFFSS special variable. When _@ is used and the expansion appears
within double quotes, each variable name expands to a separate
word.
${!!_n_a_m_e[_@]}
${!!_n_a_m_e[_*]}
LLiisstt ooff aarrrraayy kkeeyyss. If _n_a_m_e is an array variable, expands to
the list of array indices (keys) assigned in _n_a_m_e. If _n_a_m_e is
not an array, expands to 0 if _n_a_m_e is set and null otherwise.
When _@ is used and the expansion appears within double quotes,
each key expands to a separate word.
${##_p_a_r_a_m_e_t_e_r}
PPaarraammeetteerr lleennggtthh. The length in characters of the value of _p_a_-
_r_a_m_e_t_e_r is substituted. If _p_a_r_a_m_e_t_e_r is ** or @@, the value sub-
stituted is the number of positional parameters. If _p_a_r_a_m_e_t_e_r
is an array name subscripted by ** or @@, the value substituted is
the number of elements in the array. If _p_a_r_a_m_e_t_e_r is an indexed
array name subscripted by a negative number, that number is in-
terpreted as relative to one greater than the maximum index of
_p_a_r_a_m_e_t_e_r, so negative indices count back from the end of the
array, and an index of -1 references the last element.
${_p_a_r_a_m_e_t_e_r##_w_o_r_d}
${_p_a_r_a_m_e_t_e_r####_w_o_r_d}
RReemmoovvee mmaattcchhiinngg pprreeffiixx ppaatttteerrnn. The _w_o_r_d is expanded to produce
a pattern just as in pathname expansion, and matched against the
expanded value of _p_a_r_a_m_e_t_e_r using the rules described under PPaatt--
tteerrnn MMaattcchhiinngg below. If the pattern matches the beginning of
the value of _p_a_r_a_m_e_t_e_r, then the result of the expansion is the
expanded value of _p_a_r_a_m_e_t_e_r with the shortest matching pattern
(the ``##'' case) or the longest matching pattern (the ``####''
case) deleted. If _p_a_r_a_m_e_t_e_r is @@ or **, the pattern removal op-
eration is applied to each positional parameter in turn, and the
expansion is the resultant list. If _p_a_r_a_m_e_t_e_r is an array vari-
able subscripted with @@ or **, the pattern removal operation is
applied to each member of the array in turn, and the expansion
is the resultant list.
${_p_a_r_a_m_e_t_e_r%%_w_o_r_d}
${_p_a_r_a_m_e_t_e_r%%%%_w_o_r_d}
RReemmoovvee mmaattcchhiinngg ssuuffffiixx ppaatttteerrnn. The _w_o_r_d is expanded to produce
a pattern just as in pathname expansion, and matched against the
expanded value of _p_a_r_a_m_e_t_e_r using the rules described under PPaatt--
tteerrnn MMaattcchhiinngg below. If the pattern matches a trailing portion
of the expanded value of _p_a_r_a_m_e_t_e_r, then the result of the ex-
pansion is the expanded value of _p_a_r_a_m_e_t_e_r with the shortest
matching pattern (the ``%%'' case) or the longest matching pat-
tern (the ``%%%%'' case) deleted. If _p_a_r_a_m_e_t_e_r is @@ or **, the
pattern removal operation is applied to each positional parame-
ter in turn, and the expansion is the resultant list. If _p_a_r_a_m_-
_e_t_e_r is an array variable subscripted with @@ or **, the pattern
removal operation is applied to each member of the array in
turn, and the expansion is the resultant list.
${_p_a_r_a_m_e_t_e_r//_p_a_t_t_e_r_n//_s_t_r_i_n_g}
PPaatttteerrnn ssuubbssttiittuuttiioonn. The _p_a_t_t_e_r_n is expanded to produce a pat-
tern just as in pathname expansion, _P_a_r_a_m_e_t_e_r is expanded and
the longest match of _p_a_t_t_e_r_n against its value is replaced with
_s_t_r_i_n_g. The match is performed using the rules described under
PPaatttteerrnn MMaattcchhiinngg below. If _p_a_t_t_e_r_n begins with //, all matches
of _p_a_t_t_e_r_n are replaced with _s_t_r_i_n_g. Normally only the first
match is replaced. If _p_a_t_t_e_r_n begins with ##, it must match at
the beginning of the expanded value of _p_a_r_a_m_e_t_e_r. If _p_a_t_t_e_r_n
begins with %%, it must match at the end of the expanded value of
_p_a_r_a_m_e_t_e_r. If _s_t_r_i_n_g is null, matches of _p_a_t_t_e_r_n are deleted
and the // following _p_a_t_t_e_r_n may be omitted. If the nnooccaasseemmaattcchh
shell option is enabled, the match is performed without regard
to the case of alphabetic characters. If _p_a_r_a_m_e_t_e_r is @@ or **,
the substitution operation is applied to each positional parame-
ter in turn, and the expansion is the resultant list. If _p_a_r_a_m_-
_e_t_e_r is an array variable subscripted with @@ or **, the substitu-
tion operation is applied to each member of the array in turn,
and the expansion is the resultant list.
${_p_a_r_a_m_e_t_e_r^^_p_a_t_t_e_r_n}
${_p_a_r_a_m_e_t_e_r^^^^_p_a_t_t_e_r_n}
${_p_a_r_a_m_e_t_e_r,,_p_a_t_t_e_r_n}
${_p_a_r_a_m_e_t_e_r,,,,_p_a_t_t_e_r_n}
CCaassee mmooddiiffiiccaattiioonn. This expansion modifies the case of alpha-
betic characters in _p_a_r_a_m_e_t_e_r. The _p_a_t_t_e_r_n is expanded to pro-
duce a pattern just as in pathname expansion. Each character in
the expanded value of _p_a_r_a_m_e_t_e_r is tested against _p_a_t_t_e_r_n, and,
if it matches the pattern, its case is converted. The pattern
should not attempt to match more than one character. The ^^ op-
erator converts lowercase letters matching _p_a_t_t_e_r_n to uppercase;
the ,, operator converts matching uppercase letters to lowercase.
The ^^^^ and ,,,, expansions convert each matched character in the
expanded value; the ^^ and ,, expansions match and convert only
the first character in the expanded value. If _p_a_t_t_e_r_n is omit-
ted, it is treated like a ??, which matches every character. If
_p_a_r_a_m_e_t_e_r is @@ or **, the case modification operation is applied
to each positional parameter in turn, and the expansion is the
resultant list. If _p_a_r_a_m_e_t_e_r is an array variable subscripted
with @@ or **, the case modification operation is applied to each
member of the array in turn, and the expansion is the resultant
list.
${_p_a_r_a_m_e_t_e_r@@_o_p_e_r_a_t_o_r}
PPaarraammeetteerr ttrraannssffoorrmmaattiioonn. The expansion is either a transforma-
tion of the value of _p_a_r_a_m_e_t_e_r or information about _p_a_r_a_m_e_t_e_r
itself, depending on the value of _o_p_e_r_a_t_o_r. Each _o_p_e_r_a_t_o_r is a
single letter:
UU The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r
with lowercase alphabetic characters converted to upper-
case.
uu The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r
with the first character converted to uppercase, if it is
alphabetic.
LL The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r
with uppercase alphabetic characters converted to lower-
case.
QQ The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r
quoted in a format that can be reused as input.
EE The expansion is a string that is the value of _p_a_r_a_m_e_t_e_r
with backslash escape sequences expanded as with the
$$''......'' quoting mechanism.
PP The expansion is a string that is the result of expanding
the value of _p_a_r_a_m_e_t_e_r as if it were a prompt string (see
PPRROOMMPPTTIINNGG below).
AA The expansion is a string in the form of an assignment
statement or ddeeccllaarree command that, if evaluated, will
recreate _p_a_r_a_m_e_t_e_r with its attributes and value.
KK Produces a possibly-quoted version of the value of _p_a_r_a_m_-
_e_t_e_r, except that it prints the values of indexed and as-
sociative arrays as a sequence of quoted key-value pairs
(see AArrrraayyss above).
aa The expansion is a string consisting of flag values rep-
resenting _p_a_r_a_m_e_t_e_r's attributes.
If _p_a_r_a_m_e_t_e_r is @@ or **, the operation is applied to each posi-
tional parameter in turn, and the expansion is the resultant
list. If _p_a_r_a_m_e_t_e_r is an array variable subscripted with @@ or
**, the operation is applied to each member of the array in turn,
and the expansion is the resultant list.
The result of the expansion is subject to word splitting and
pathname expansion as described below.
CCoommmmaanndd SSuubbssttiittuuttiioonn
_C_o_m_m_a_n_d _s_u_b_s_t_i_t_u_t_i_o_n allows the output of a command to replace the com-
mand name. There are two forms:
$$((_c_o_m_m_a_n_d))
or
``_c_o_m_m_a_n_d``
BBaasshh performs the expansion by executing _c_o_m_m_a_n_d in a subshell environ-
ment and replacing the command substitution with the standard output of
the command, with any trailing newlines deleted. Embedded newlines are
not deleted, but they may be removed during word splitting. The com-
mand substitution $$((ccaatt _f_i_l_e)) can be replaced by the equivalent but
faster $$((<< _f_i_l_e)).
When the old-style backquote form of substitution is used, backslash
retains its literal meaning except when followed by $$, ``, or \\. The
first backquote not preceded by a backslash terminates the command sub-
stitution. When using the $(_c_o_m_m_a_n_d) form, all characters between the
parentheses make up the command; none are treated specially.
Command substitutions may be nested. To nest when using the backquoted
form, escape the inner backquotes with backslashes.
If the substitution appears within double quotes, word splitting and
pathname expansion are not performed on the results.
AArriitthhmmeettiicc EExxppaannssiioonn
Arithmetic expansion allows the evaluation of an arithmetic expression
and the substitution of the result. The format for arithmetic expan-
sion is:
$$((((_e_x_p_r_e_s_s_i_o_n))))
The _e_x_p_r_e_s_s_i_o_n is treated as if it were within double quotes, but a
double quote inside the parentheses is not treated specially. All to-
kens in the expression undergo parameter and variable expansion, com-
mand substitution, and quote removal. The result is treated as the
arithmetic expression to be evaluated. Arithmetic expansions may be
nested.
The evaluation is performed according to the rules listed below under
AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN. If _e_x_p_r_e_s_s_i_o_n is invalid, bbaasshh prints a message
indicating failure and no substitution occurs.
PPrroocceessss SSuubbssttiittuuttiioonn
_P_r_o_c_e_s_s _s_u_b_s_t_i_t_u_t_i_o_n allows a process's input or output to be referred
to using a filename. It takes the form of <<((_l_i_s_t)) or >>((_l_i_s_t)). The
process _l_i_s_t is run asynchronously, and its input or output appears as
a filename. This filename is passed as an argument to the current com-
mand as the result of the expansion. If the >>((_l_i_s_t)) form is used,
writing to the file will provide input for _l_i_s_t. If the <<((_l_i_s_t)) form
is used, the file passed as an argument should be read to obtain the
output of _l_i_s_t. Process substitution is supported on systems that sup-
port named pipes (_F_I_F_O_s) or the //ddeevv//ffdd method of naming open files.
When available, process substitution is performed simultaneously with
parameter and variable expansion, command substitution, and arithmetic
expansion.
WWoorrdd SSpplliittttiinngg
The shell scans the results of parameter expansion, command substitu-
tion, and arithmetic expansion that did not occur within double quotes
for _w_o_r_d _s_p_l_i_t_t_i_n_g.
The shell treats each character of IIFFSS as a delimiter, and splits the
results of the other expansions into words using these characters as
field terminators. If IIFFSS is unset, or its value is exactly
<<ssppaaccee>><<ttaabb>><<nneewwlliinnee>>, the default, then sequences of <<ssppaaccee>>, <<ttaabb>>,
and <<nneewwlliinnee>> at the beginning and end of the results of the previous
expansions are ignored, and any sequence of IIFFSS characters not at the
beginning or end serves to delimit words. If IIFFSS has a value other
than the default, then sequences of the whitespace characters ssppaaccee,
ttaabb, and nneewwlliinnee are ignored at the beginning and end of the word, as
long as the whitespace character is in the value of IIFFSS (an IIFFSS white-
space character). Any character in IIFFSS that is not IIFFSS whitespace,
along with any adjacent IIFFSS whitespace characters, delimits a field. A
sequence of IIFFSS whitespace characters is also treated as a delimiter.
If the value of IIFFSS is null, no word splitting occurs.
Explicit null arguments ("""" or '''') are retained and passed to commands
as empty strings. Unquoted implicit null arguments, resulting from the
expansion of parameters that have no values, are removed. If a parame-
ter with no value is expanded within double quotes, a null argument re-
sults and is retained and passed to a command as an empty string. When
a quoted null argument appears as part of a word whose expansion is
non-null, the null argument is removed. That is, the word -d'' becomes
-d after word splitting and null argument removal.
Note that if no expansion occurs, no splitting is performed.
PPaatthhnnaammee EExxppaannssiioonn
After word splitting, unless the --ff option has been set, bbaasshh scans
each word for the characters **, ??, and [[. If one of these characters
appears, and is not quoted, then the word is regarded as a _p_a_t_t_e_r_n, and
replaced with an alphabetically sorted list of filenames matching the
pattern (see PPaatttteerrnn MMaattcchhiinngg below). If no matching filenames are
found, and the shell option nnuullllgglloobb is not enabled, the word is left
unchanged. If the nnuullllgglloobb option is set, and no matches are found,
the word is removed. If the ffaaiillgglloobb shell option is set, and no
matches are found, an error message is printed and the command is not
executed. If the shell option nnooccaasseegglloobb is enabled, the match is per-
formed without regard to the case of alphabetic characters. When a
pattern is used for pathname expansion, the character ````..'''' at the
start of a name or immediately following a slash must be matched ex-
plicitly, unless the shell option ddoottgglloobb is set. The filenames ````..''''
and ````....'''' must always be matched explicitly, even if ddoottgglloobb is set.
In other cases, the ````..'''' character is not treated specially. When
matching a pathname, the slash character must always be matched explic-
itly by a slash in the pattern, but in other matching contexts it can
be matched by a special pattern character as described below under PPaatt--
tteerrnn MMaattcchhiinngg. See the description of sshhoopptt below under SSHHEELLLL BBUUIILLTTIINN
CCOOMMMMAANNDDSS for a description of the nnooccaasseegglloobb, nnuullllgglloobb, ffaaiillgglloobb, and
ddoottgglloobb shell options.
The GGLLOOBBIIGGNNOORREE shell variable may be used to restrict the set of file
names matching a _p_a_t_t_e_r_n. If GGLLOOBBIIGGNNOORREE is set, each matching file
name that also matches one of the patterns in GGLLOOBBIIGGNNOORREE is removed
from the list of matches. If the nnooccaasseegglloobb option is set, the match-
ing against the patterns in GGLLOOBBIIGGNNOORREE is performed without regard to
case. The filenames ````..'''' and ````....'''' are always ignored when GGLLOOBBIIGG--
NNOORREE is set and not null. However, setting GGLLOOBBIIGGNNOORREE to a non-null
value has the effect of enabling the ddoottgglloobb shell option, so all other
filenames beginning with a ````..'''' will match. To get the old behavior
of ignoring filenames beginning with a ````..'''', make ````..**'''' one of the
patterns in GGLLOOBBIIGGNNOORREE. The ddoottgglloobb option is disabled when GGLLOOBBIIGGNNOORREE
is unset. The pattern matching honors the setting of the eexxttgglloobb shell
option.
PPaatttteerrnn MMaattcchhiinngg
Any character that appears in a pattern, other than the special pattern
characters described below, matches itself. The NUL character may not
occur in a pattern. A backslash escapes the following character; the
escaping backslash is discarded when matching. The special pattern
characters must be quoted if they are to be matched literally.
The special pattern characters have the following meanings:
** Matches any string, including the null string. When the
gglloobbssttaarr shell option is enabled, and ** is used in a
pathname expansion context, two adjacent **s used as a
single pattern will match all files and zero or more di-
rectories and subdirectories. If followed by a //, two
adjacent **s will match only directories and subdirecto-
ries.
?? Matches any single character.
[[......]] Matches any one of the enclosed characters. A pair of
characters separated by a hyphen denotes a _r_a_n_g_e _e_x_p_r_e_s_-
_s_i_o_n; any character that falls between those two charac-
ters, inclusive, using the current locale's collating se-
quence and character set, is matched. If the first char-
acter following the [[ is a !! or a ^^ then any character
not enclosed is matched. The sorting order of characters
in range expressions is determined by the current locale
and the values of the LLCC__CCOOLLLLAATTEE or LLCC__AALLLL shell vari-
ables, if set. To obtain the traditional interpretation
of range expressions, where [[aa--dd]] is equivalent to
[[aabbccdd]], set value of the LLCC__AALLLL shell variable to CC, or
enable the gglloobbaasscciiiirraannggeess shell option. A -- may be
matched by including it as the first or last character in
the set. A ]] may be matched by including it as the first
character in the set.
Within [[ and ]], _c_h_a_r_a_c_t_e_r _c_l_a_s_s_e_s can be specified using
the syntax [[::_c_l_a_s_s::]], where _c_l_a_s_s is one of the following
classes defined in the POSIX standard:
aallnnuumm aallpphhaa aasscciiii bbllaannkk ccnnttrrll ddiiggiitt ggrraapphh lloowweerr pprriinntt
ppuunncctt ssppaaccee uuppppeerr wwoorrdd xxddiiggiitt
A character class matches any character belonging to that
class. The wwoorrdd character class matches letters, digits,
and the character _.
Within [[ and ]], an _e_q_u_i_v_a_l_e_n_c_e _c_l_a_s_s can be specified us-
ing the syntax [[==_c==]], which matches all characters with
the same collation weight (as defined by the current lo-
cale) as the character _c.
Within [[ and ]], the syntax [[.._s_y_m_b_o_l..]] matches the collat-
ing symbol _s_y_m_b_o_l.
If the eexxttgglloobb shell option is enabled using the sshhoopptt builtin, several
extended pattern matching operators are recognized. In the following
description, a _p_a_t_t_e_r_n_-_l_i_s_t is a list of one or more patterns separated
by a ||. Composite patterns may be formed using one or more of the fol-
lowing sub-patterns:
??((_p_a_t_t_e_r_n_-_l_i_s_t))
Matches zero or one occurrence of the given patterns
**((_p_a_t_t_e_r_n_-_l_i_s_t))
Matches zero or more occurrences of the given patterns
++((_p_a_t_t_e_r_n_-_l_i_s_t))
Matches one or more occurrences of the given patterns
@@((_p_a_t_t_e_r_n_-_l_i_s_t))
Matches one of the given patterns
!!((_p_a_t_t_e_r_n_-_l_i_s_t))
Matches anything except one of the given patterns
Complicated extended pattern matching against long strings is slow, es-
pecially when the patterns contain alternations and the strings contain
multiple matches. Using separate matches against shorter strings, or
using arrays of strings instead of a single long string, may be faster.
QQuuoottee RReemmoovvaall
After the preceding expansions, all unquoted occurrences of the charac-
ters \\, '', and "" that did not result from one of the above expansions
are removed.
RREEDDIIRREECCTTIIOONN
Before a command is executed, its input and output may be _r_e_d_i_r_e_c_t_e_d
using a special notation interpreted by the shell. Redirection allows
commands' file handles to be duplicated, opened, closed, made to refer
to different files, and can change the files the command reads from and
writes to. Redirection may also be used to modify file handles in the
current shell execution environment. The following redirection opera-
tors may precede or appear anywhere within a _s_i_m_p_l_e _c_o_m_m_a_n_d or may fol-
low a _c_o_m_m_a_n_d. Redirections are processed in the order they appear,
from left to right.
Each redirection that may be preceded by a file descriptor number may
instead be preceded by a word of the form {_v_a_r_n_a_m_e}. In this case, for
each redirection operator except >&- and <&-, the shell will allocate a
file descriptor greater than or equal to 10 and assign it to _v_a_r_n_a_m_e.
If >&- or <&- is preceded by {_v_a_r_n_a_m_e}, the value of _v_a_r_n_a_m_e defines
the file descriptor to close. If {_v_a_r_n_a_m_e} is supplied, the redirect-
ion persists beyond the scope of the command, allowing the shell pro-
grammer to manage the file descriptor himself.
In the following descriptions, if the file descriptor number is omit-
ted, and the first character of the redirection operator is <<, the re-
direction refers to the standard input (file descriptor 0). If the
first character of the redirection operator is >>, the redirection
refers to the standard output (file descriptor 1).
The word following the redirection operator in the following descrip-
tions, unless otherwise noted, is subjected to brace expansion, tilde
expansion, parameter and variable expansion, command substitution,
arithmetic expansion, quote removal, pathname expansion, and word
splitting. If it expands to more than one word, bbaasshh reports an error.
Note that the order of redirections is significant. For example, the
command
ls >> dirlist 2>>&&1
directs both standard output and standard error to the file _d_i_r_l_i_s_t,
while the command
ls 2>>&&1 >> dirlist
directs only the standard output to file _d_i_r_l_i_s_t, because the standard
error was duplicated from the standard output before the standard out-
put was redirected to _d_i_r_l_i_s_t.
BBaasshh handles several filenames specially when they are used in redirec-
tions, as described in the following table. If the operating system on
which bbaasshh is running provides these special files, bash will use them;
otherwise it will emulate them internally with the behavior described
below.
//ddeevv//ffdd//_f_d
If _f_d is a valid integer, file descriptor _f_d is dupli-
cated.
//ddeevv//ssttddiinn
File descriptor 0 is duplicated.
//ddeevv//ssttddoouutt
File descriptor 1 is duplicated.
//ddeevv//ssttddeerrrr
File descriptor 2 is duplicated.
//ddeevv//ttccpp//_h_o_s_t//_p_o_r_t
If _h_o_s_t is a valid hostname or Internet address, and _p_o_r_t
is an integer port number or service name, bbaasshh attempts
to open the corresponding TCP socket.
//ddeevv//uuddpp//_h_o_s_t//_p_o_r_t
If _h_o_s_t is a valid hostname or Internet address, and _p_o_r_t
is an integer port number or service name, bbaasshh attempts
to open the corresponding UDP socket.
A failure to open or create a file causes the redirection to fail.
Redirections using file descriptors greater than 9 should be used with
care, as they may conflict with file descriptors the shell uses inter-
nally.
RReeddiirreeccttiinngg IInnppuutt
Redirection of input causes the file whose name results from the expan-
sion of _w_o_r_d to be opened for reading on file descriptor _n, or the
standard input (file descriptor 0) if _n is not specified.
The general format for redirecting input is:
[_n]<<_w_o_r_d
RReeddiirreeccttiinngg OOuuttppuutt
Redirection of output causes the file whose name results from the ex-
pansion of _w_o_r_d to be opened for writing on file descriptor _n, or the
standard output (file descriptor 1) if _n is not specified. If the file
does not exist it is created; if it does exist it is truncated to zero
size.
The general format for redirecting output is:
[_n]>>_w_o_r_d
If the redirection operator is >>, and the nnoocclloobbbbeerr option to the sseett
builtin has been enabled, the redirection will fail if the file whose
name results from the expansion of _w_o_r_d exists and is a regular file.
If the redirection operator is >>||, or the redirection operator is >> and
the nnoocclloobbbbeerr option to the sseett builtin command is not enabled, the re-
direction is attempted even if the file named by _w_o_r_d exists.
AAppppeennddiinngg RReeddiirreecctteedd OOuuttppuutt
Redirection of output in this fashion causes the file whose name re-
sults from the expansion of _w_o_r_d to be opened for appending on file de-
scriptor _n, or the standard output (file descriptor 1) if _n is not
specified. If the file does not exist it is created.
The general format for appending output is:
[_n]>>>>_w_o_r_d
RReeddiirreeccttiinngg SSttaannddaarrdd OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr
This construct allows both the standard output (file descriptor 1) and
the standard error output (file descriptor 2) to be redirected to the
file whose name is the expansion of _w_o_r_d.
There are two formats for redirecting standard output and standard er-
ror:
&&>>_w_o_r_d
and
>>&&_w_o_r_d
Of the two forms, the first is preferred. This is semantically equiva-
lent to
>>_w_o_r_d 2>>&&1
When using the second form, _w_o_r_d may not expand to a number or --. If
it does, other redirection operators apply (see DDuupplliiccaattiinngg FFiillee DDee--
ssccrriippttoorrss below) for compatibility reasons.
AAppppeennddiinngg SSttaannddaarrdd OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr
This construct allows both the standard output (file descriptor 1) and
the standard error output (file descriptor 2) to be appended to the
file whose name is the expansion of _w_o_r_d.
The format for appending standard output and standard error is:
&&>>>>_w_o_r_d
This is semantically equivalent to
>>>>_w_o_r_d 2>>&&1
(see DDuupplliiccaattiinngg FFiillee DDeessccrriippttoorrss below).
HHeerree DDooccuummeennttss
This type of redirection instructs the shell to read input from the
current source until a line containing only _d_e_l_i_m_i_t_e_r (with no trailing
blanks) is seen. All of the lines read up to that point are then used
as the standard input (or file descriptor _n if _n is specified) for a
command.
The format of here-documents is:
[_n]<<<<[--]_w_o_r_d
_h_e_r_e_-_d_o_c_u_m_e_n_t
_d_e_l_i_m_i_t_e_r
No parameter and variable expansion, command substitution, arithmetic
expansion, or pathname expansion is performed on _w_o_r_d. If any part of
_w_o_r_d is quoted, the _d_e_l_i_m_i_t_e_r is the result of quote removal on _w_o_r_d,
and the lines in the here-document are not expanded. If _w_o_r_d is un-
quoted, all lines of the here-document are subjected to parameter ex-
pansion, command substitution, and arithmetic expansion, the character
sequence \\<<nneewwlliinnee>> is ignored, and \\ must be used to quote the charac-
ters \\, $$, and ``.
If the redirection operator is <<<<--, then all leading tab characters are
stripped from input lines and the line containing _d_e_l_i_m_i_t_e_r. This al-
lows here-documents within shell scripts to be indented in a natural
fashion.
HHeerree SSttrriinnggss
A variant of here documents, the format is:
[_n]<<<<<<_w_o_r_d
The _w_o_r_d undergoes tilde expansion, parameter and variable expansion,
command substitution, arithmetic expansion, and quote removal. Path-
name expansion and word splitting are not performed. The result is
supplied as a single string, with a newline appended, to the command on
its standard input (or file descriptor _n if _n is specified).
DDuupplliiccaattiinngg FFiillee DDeessccrriippttoorrss
The redirection operator
[_n]<<&&_w_o_r_d
is used to duplicate input file descriptors. If _w_o_r_d expands to one or
more digits, the file descriptor denoted by _n is made to be a copy of
that file descriptor. If the digits in _w_o_r_d do not specify a file de-
scriptor open for input, a redirection error occurs. If _w_o_r_d evaluates
to --, file descriptor _n is closed. If _n is not specified, the standard
input (file descriptor 0) is used.
The operator
[_n]>>&&_w_o_r_d
is used similarly to duplicate output file descriptors. If _n is not
specified, the standard output (file descriptor 1) is used. If the
digits in _w_o_r_d do not specify a file descriptor open for output, a re-
direction error occurs. If _w_o_r_d evaluates to --, file descriptor _n is
closed. As a special case, if _n is omitted, and _w_o_r_d does not expand
to one or more digits or --, the standard output and standard error are
redirected as described previously.
MMoovviinngg FFiillee DDeessccrriippttoorrss
The redirection operator
[_n]<<&&_d_i_g_i_t--
moves the file descriptor _d_i_g_i_t to file descriptor _n, or the standard
input (file descriptor 0) if _n is not specified. _d_i_g_i_t is closed after
being duplicated to _n.
Similarly, the redirection operator
[_n]>>&&_d_i_g_i_t--
moves the file descriptor _d_i_g_i_t to file descriptor _n, or the standard
output (file descriptor 1) if _n is not specified.
OOppeenniinngg FFiillee DDeessccrriippttoorrss ffoorr RReeaaddiinngg aanndd WWrriittiinngg
The redirection operator
[_n]<<>>_w_o_r_d
causes the file whose name is the expansion of _w_o_r_d to be opened for
both reading and writing on file descriptor _n, or on file descriptor 0
if _n is not specified. If the file does not exist, it is created.
AALLIIAASSEESS
_A_l_i_a_s_e_s allow a string to be substituted for a word when it is used as
the first word of a simple command. The shell maintains a list of
aliases that may be set and unset with the aalliiaass and uunnaalliiaass builtin
commands (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). The first word of each
simple command, if unquoted, is checked to see if it has an alias. If
so, that word is replaced by the text of the alias. The characters //,
$$, ``, and == and any of the shell _m_e_t_a_c_h_a_r_a_c_t_e_r_s or quoting characters
listed above may not appear in an alias name. The replacement text may
contain any valid shell input, including shell metacharacters. The
first word of the replacement text is tested for aliases, but a word
that is identical to an alias being expanded is not expanded a second
time. This means that one may alias llss to llss --FF, for instance, and
bbaasshh does not try to recursively expand the replacement text. If the
last character of the alias value is a _b_l_a_n_k, then the next command
word following the alias is also checked for alias expansion.
Aliases are created and listed with the aalliiaass command, and removed with
the uunnaalliiaass command.
There is no mechanism for using arguments in the replacement text. If
arguments are needed, a shell function should be used (see FFUUNNCCTTIIOONNSS
below).
Aliases are not expanded when the shell is not interactive, unless the
eexxppaanndd__aalliiaasseess shell option is set using sshhoopptt (see the description of
sshhoopptt under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
The rules concerning the definition and use of aliases are somewhat
confusing. BBaasshh always reads at least one complete line of input, and
all lines that make up a compound command, before executing any of the
commands on that line or the compound command. Aliases are expanded
when a command is read, not when it is executed. Therefore, an alias
definition appearing on the same line as another command does not take
effect until the next line of input is read. The commands following
the alias definition on that line are not affected by the new alias.
This behavior is also an issue when functions are executed. Aliases
are expanded when a function definition is read, not when the function
is executed, because a function definition is itself a command. As a
consequence, aliases defined in a function are not available until af-
ter that function is executed. To be safe, always put alias defini-
tions on a separate line, and do not use aalliiaass in compound commands.
For almost every purpose, aliases are superseded by shell functions.
FFUUNNCCTTIIOONNSS
A shell function, defined as described above under SSHHEELLLL GGRRAAMMMMAARR,
stores a series of commands for later execution. When the name of a
shell function is used as a simple command name, the list of commands
associated with that function name is executed. Functions are executed
in the context of the current shell; no new process is created to in-
terpret them (contrast this with the execution of a shell script).
When a function is executed, the arguments to the function become the
positional parameters during its execution. The special parameter ## is
updated to reflect the change. Special parameter 00 is unchanged. The
first element of the FFUUNNCCNNAAMMEE variable is set to the name of the func-
tion while the function is executing.
All other aspects of the shell execution environment are identical be-
tween a function and its caller with these exceptions: the DDEEBBUUGG and
RREETTUURRNN traps (see the description of the ttrraapp builtin under SSHHEELLLL
BBUUIILLTTIINN CCOOMMMMAANNDDSS below) are not inherited unless the function has been
given the ttrraaccee attribute (see the description of the ddeeccllaarree builtin
below) or the --oo ffuunnccttrraaccee shell option has been enabled with the sseett
builtin (in which case all functions inherit the DDEEBBUUGG and RREETTUURRNN
traps), and the EERRRR trap is not inherited unless the --oo eerrrrttrraaccee shell
option has been enabled.
Variables local to the function may be declared with the llooccaall builtin
command. Ordinarily, variables and their values are shared between the
function and its caller. If a variable is declared llooccaall, the vari-
able's visible scope is restricted to that function and its children
(including the functions it calls). Local variables "shadow" variables
with the same name declared at previous scopes. For instance, a local
variable declared in a function hides a global variable of the same
name: references and assignments refer to the local variable, leaving
the global variable unmodified. When the function returns, the global
variable is once again visible.
The shell uses _d_y_n_a_m_i_c _s_c_o_p_i_n_g to control a variable's visibility
within functions. With dynamic scoping, visible variables and their
values are a result of the sequence of function calls that caused exe-
cution to reach the current function. The value of a variable that a
function sees depends on its value within its caller, if any, whether
that caller is the "global" scope or another shell function. This is
also the value that a local variable declaration "shadows", and the
value that is restored when the function returns.
For example, if a variable _v_a_r is declared as local in function _f_u_n_c_1,
and _f_u_n_c_1 calls another function _f_u_n_c_2, references to _v_a_r made from
within _f_u_n_c_2 will resolve to the local variable _v_a_r from _f_u_n_c_1, shadow-
ing any global variable named _v_a_r.
The uunnsseett builtin also acts using the same dynamic scope: if a variable
is local to the current scope, uunnsseett will unset it; otherwise the unset
will refer to the variable found in any calling scope as described
above. If a variable at the current local scope is unset, it will re-
main so until it is reset in that scope or until the function returns.
Once the function returns, any instance of the variable at a previous
scope will become visible. If the unset acts on a variable at a previ-
ous scope, any instance of a variable with that name that had been
shadowed will become visible.
The FFUUNNCCNNEESSTT variable, if set to a numeric value greater than 0, de-
fines a maximum function nesting level. Function invocations that ex-
ceed the limit cause the entire command to abort.
If the builtin command rreettuurrnn is executed in a function, the function
completes and execution resumes with the next command after the func-
tion call. Any command associated with the RREETTUURRNN trap is executed be-
fore execution resumes. When a function completes, the values of the
positional parameters and the special parameter ## are restored to the
values they had prior to the function's execution.
Function names and definitions may be listed with the --ff option to the
ddeeccllaarree or ttyyppeesseett builtin commands. The --FF option to ddeeccllaarree or ttyyppee--
sseett will list the function names only (and optionally the source file
and line number, if the eexxttddeebbuugg shell option is enabled). Functions
may be exported so that subshells automatically have them defined with
the --ff option to the eexxppoorrtt builtin. A function definition may be
deleted using the --ff option to the uunnsseett builtin.
Functions may be recursive. The FFUUNNCCNNEESSTT variable may be used to limit
the depth of the function call stack and restrict the number of func-
tion invocations. By default, no limit is imposed on the number of re-
cursive calls.
AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN
The shell allows arithmetic expressions to be evaluated, under certain
circumstances (see the lleett and ddeeccllaarree builtin commands, the (((( com-
pound command, and AArriitthhmmeettiicc EExxppaannssiioonn). Evaluation is done in fixed-
width integers with no check for overflow, though division by 0 is
trapped and flagged as an error. The operators and their precedence,
associativity, and values are the same as in the C language. The fol-
lowing list of operators is grouped into levels of equal-precedence op-
erators. The levels are listed in order of decreasing precedence.
_i_d++++ _i_d----
variable post-increment and post-decrement
-- ++ unary minus and plus
++++_i_d ----_i_d
variable pre-increment and pre-decrement
!! ~~ logical and bitwise negation
**** exponentiation
** // %% multiplication, division, remainder
++ -- addition, subtraction
<<<< >>>> left and right bitwise shifts
<<== >>== << >>
comparison
==== !!== equality and inequality
&& bitwise AND
^^ bitwise exclusive OR
|| bitwise OR
&&&& logical AND
|||| logical OR
_e_x_p_r??_e_x_p_r::_e_x_p_r
conditional operator
== **== //== %%== ++== --== <<<<== >>>>== &&== ^^== ||==
assignment
_e_x_p_r_1 ,, _e_x_p_r_2
comma
Shell variables are allowed as operands; parameter expansion is per-
formed before the expression is evaluated. Within an expression, shell
variables may also be referenced by name without using the parameter
expansion syntax. A shell variable that is null or unset evaluates to
0 when referenced by name without using the parameter expansion syntax.
The value of a variable is evaluated as an arithmetic expression when
it is referenced, or when a variable which has been given the _i_n_t_e_g_e_r
attribute using ddeeccllaarree --ii is assigned a value. A null value evaluates
to 0. A shell variable need not have its _i_n_t_e_g_e_r attribute turned on
to be used in an expression.
Integer constants follow the C language definition, without suffixes or
character constants. Constants with a leading 0 are interpreted as oc-
tal numbers. A leading 0x or 0X denotes hexadecimal. Otherwise, num-
bers take the form [_b_a_s_e_#]n, where the optional _b_a_s_e is a decimal num-
ber between 2 and 64 representing the arithmetic base, and _n is a num-
ber in that base. If _b_a_s_e_# is omitted, then base 10 is used. When
specifying _n, if a non-digit is required, the digits greater than 9 are
represented by the lowercase letters, the uppercase letters, @, and _,
in that order. If _b_a_s_e is less than or equal to 36, lowercase and up-
percase letters may be used interchangeably to represent numbers be-
tween 10 and 35.
Operators are evaluated in order of precedence. Sub-expressions in
parentheses are evaluated first and may override the precedence rules
above.
CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS
Conditional expressions are used by the [[[[ compound command and the
tteesstt and [[ builtin commands to test file attributes and perform string
and arithmetic comparisons. The tteesstt and [[ commands determine their
behavior based on the number of arguments; see the descriptions of
those commands for any other command-specific actions.
Expressions are formed from the following unary or binary primaries.
BBaasshh handles several filenames specially when they are used in expres-
sions. If the operating system on which bbaasshh is running provides these
special files, bash will use them; otherwise it will emulate them in-
ternally with this behavior: If any _f_i_l_e argument to one of the pri-
maries is of the form _/_d_e_v_/_f_d_/_n, then file descriptor _n is checked. If
the _f_i_l_e argument to one of the primaries is one of _/_d_e_v_/_s_t_d_i_n,
_/_d_e_v_/_s_t_d_o_u_t, or _/_d_e_v_/_s_t_d_e_r_r, file descriptor 0, 1, or 2, respectively,
is checked.
Unless otherwise specified, primaries that operate on files follow sym-
bolic links and operate on the target of the link, rather than the link
itself.
When used with [[[[, the << and >> operators sort lexicographically using
the current locale. The tteesstt command sorts using ASCII ordering.
--aa _f_i_l_e
True if _f_i_l_e exists.
--bb _f_i_l_e
True if _f_i_l_e exists and is a block special file.
--cc _f_i_l_e
True if _f_i_l_e exists and is a character special file.
--dd _f_i_l_e
True if _f_i_l_e exists and is a directory.
--ee _f_i_l_e
True if _f_i_l_e exists.
--ff _f_i_l_e
True if _f_i_l_e exists and is a regular file.
--gg _f_i_l_e
True if _f_i_l_e exists and is set-group-id.
--hh _f_i_l_e
True if _f_i_l_e exists and is a symbolic link.
--kk _f_i_l_e
True if _f_i_l_e exists and its ``sticky'' bit is set.
--pp _f_i_l_e
True if _f_i_l_e exists and is a named pipe (FIFO).
--rr _f_i_l_e
True if _f_i_l_e exists and is readable.
--ss _f_i_l_e
True if _f_i_l_e exists and has a size greater than zero.
--tt _f_d True if file descriptor _f_d is open and refers to a terminal.
--uu _f_i_l_e
True if _f_i_l_e exists and its set-user-id bit is set.
--ww _f_i_l_e
True if _f_i_l_e exists and is writable.
--xx _f_i_l_e
True if _f_i_l_e exists and is executable.
--GG _f_i_l_e
True if _f_i_l_e exists and is owned by the effective group id.
--LL _f_i_l_e
True if _f_i_l_e exists and is a symbolic link.
--NN _f_i_l_e
True if _f_i_l_e exists and has been modified since it was last
read.
--OO _f_i_l_e
True if _f_i_l_e exists and is owned by the effective user id.
--SS _f_i_l_e
True if _f_i_l_e exists and is a socket.
_f_i_l_e_1 --eeff _f_i_l_e_2
True if _f_i_l_e_1 and _f_i_l_e_2 refer to the same device and inode num-
bers.
_f_i_l_e_1 -nntt _f_i_l_e_2
True if _f_i_l_e_1 is newer (according to modification date) than
_f_i_l_e_2, or if _f_i_l_e_1 exists and _f_i_l_e_2 does not.
_f_i_l_e_1 -oott _f_i_l_e_2
True if _f_i_l_e_1 is older than _f_i_l_e_2, or if _f_i_l_e_2 exists and _f_i_l_e_1
does not.
--oo _o_p_t_n_a_m_e
True if the shell option _o_p_t_n_a_m_e is enabled. See the list of
options under the description of the --oo option to the sseett
builtin below.
--vv _v_a_r_n_a_m_e
True if the shell variable _v_a_r_n_a_m_e is set (has been assigned a
value).
--RR _v_a_r_n_a_m_e
True if the shell variable _v_a_r_n_a_m_e is set and is a name refer-
ence.
--zz _s_t_r_i_n_g
True if the length of _s_t_r_i_n_g is zero.
_s_t_r_i_n_g
--nn _s_t_r_i_n_g
True if the length of _s_t_r_i_n_g is non-zero.
_s_t_r_i_n_g_1 ==== _s_t_r_i_n_g_2
_s_t_r_i_n_g_1 == _s_t_r_i_n_g_2
True if the strings are equal. == should be used with the tteesstt
command for POSIX conformance. When used with the [[[[ command,
this performs pattern matching as described above (CCoommppoouunndd CCoomm--
mmaannddss).
_s_t_r_i_n_g_1 !!== _s_t_r_i_n_g_2
True if the strings are not equal.
_s_t_r_i_n_g_1 << _s_t_r_i_n_g_2
True if _s_t_r_i_n_g_1 sorts before _s_t_r_i_n_g_2 lexicographically.
_s_t_r_i_n_g_1 >> _s_t_r_i_n_g_2
True if _s_t_r_i_n_g_1 sorts after _s_t_r_i_n_g_2 lexicographically.
_a_r_g_1 OOPP _a_r_g_2
OOPP is one of --eeqq, --nnee, --lltt, --llee, --ggtt, or --ggee. These arithmetic
binary operators return true if _a_r_g_1 is equal to, not equal to,
less than, less than or equal to, greater than, or greater than
or equal to _a_r_g_2, respectively. _A_r_g_1 and _a_r_g_2 may be positive
or negative integers. When used with the [[[[ command, _A_r_g_1 and
_A_r_g_2 are evaluated as arithmetic expressions (see AARRIITTHHMMEETTIICC
EEVVAALLUUAATTIIOONN above).
SSIIMMPPLLEE CCOOMMMMAANNDD EEXXPPAANNSSIIOONN
When a simple command is executed, the shell performs the following ex-
pansions, assignments, and redirections, from left to right, in the
following order.
1. The words that the parser has marked as variable assignments
(those preceding the command name) and redirections are saved
for later processing.
2. The words that are not variable assignments or redirections are
expanded. If any words remain after expansion, the first word
is taken to be the name of the command and the remaining words
are the arguments.
3. Redirections are performed as described above under RREEDDIIRREECCTTIIOONN.
4. The text after the == in each variable assignment undergoes tilde
expansion, parameter expansion, command substitution, arithmetic
expansion, and quote removal before being assigned to the vari-
able.
If no command name results, the variable assignments affect the current
shell environment. Otherwise, the variables are added to the environ-
ment of the executed command and do not affect the current shell envi-
ronment. If any of the assignments attempts to assign a value to a
readonly variable, an error occurs, and the command exits with a non-
zero status.
If no command name results, redirections are performed, but do not af-
fect the current shell environment. A redirection error causes the
command to exit with a non-zero status.
If there is a command name left after expansion, execution proceeds as
described below. Otherwise, the command exits. If one of the expan-
sions contained a command substitution, the exit status of the command
is the exit status of the last command substitution performed. If
there were no command substitutions, the command exits with a status of
zero.
CCOOMMMMAANNDD EEXXEECCUUTTIIOONN
After a command has been split into words, if it results in a simple
command and an optional list of arguments, the following actions are
taken.
If the command name contains no slashes, the shell attempts to locate
it. If there exists a shell function by that name, that function is
invoked as described above in FFUUNNCCTTIIOONNSS. If the name does not match a
function, the shell searches for it in the list of shell builtins. If
a match is found, that builtin is invoked.
If the name is neither a shell function nor a builtin, and contains no
slashes, bbaasshh searches each element of the PPAATTHH for a directory con-
taining an executable file by that name. BBaasshh uses a hash table to re-
member the full pathnames of executable files (see hhaasshh under SSHHEELLLL
BBUUIILLTTIINN CCOOMMMMAANNDDSS below). A full search of the directories in PPAATTHH is
performed only if the command is not found in the hash table. If the
search is unsuccessful, the shell searches for a defined shell function
named ccoommmmaanndd__nnoott__ffoouunndd__hhaannddllee. If that function exists, it is invoked
in a separate execution environment with the original command and the
original command's arguments as its arguments, and the function's exit
status becomes the exit status of that subshell. If that function is
not defined, the shell prints an error message and returns an exit sta-
tus of 127.
If the search is successful, or if the command name contains one or
more slashes, the shell executes the named program in a separate execu-
tion environment. Argument 0 is set to the name given, and the remain-
ing arguments to the command are set to the arguments given, if any.
If this execution fails because the file is not in executable format,
and the file is not a directory, it is assumed to be a _s_h_e_l_l _s_c_r_i_p_t, a
file containing shell commands. A subshell is spawned to execute it.
This subshell reinitializes itself, so that the effect is as if a new
shell had been invoked to handle the script, with the exception that
the locations of commands remembered by the parent (see hhaasshh below un-
der SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS) are retained by the child.
If the program is a file beginning with ##!!, the remainder of the first
line specifies an interpreter for the program. The shell executes the
specified interpreter on operating systems that do not handle this exe-
cutable format themselves. The arguments to the interpreter consist of
a single optional argument following the interpreter name on the first
line of the program, followed by the name of the program, followed by
the command arguments, if any.
CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT
The shell has an _e_x_e_c_u_t_i_o_n _e_n_v_i_r_o_n_m_e_n_t, which consists of the follow-
ing:
+o open files inherited by the shell at invocation, as modified by
redirections supplied to the eexxeecc builtin
+o the current working directory as set by ccdd, ppuusshhdd, or ppooppdd, or
inherited by the shell at invocation
+o the file creation mode mask as set by uummaasskk or inherited from
the shell's parent
+o current traps set by ttrraapp
+o shell parameters that are set by variable assignment or with sseett
or inherited from the shell's parent in the environment
+o shell functions defined during execution or inherited from the
shell's parent in the environment
+o options enabled at invocation (either by default or with com-
mand-line arguments) or by sseett
+o options enabled by sshhoopptt
+o shell aliases defined with aalliiaass
+o various process IDs, including those of background jobs, the
value of $$$$, and the value of PPPPIIDD
When a simple command other than a builtin or shell function is to be
executed, it is invoked in a separate execution environment that con-
sists of the following. Unless otherwise noted, the values are inher-
ited from the shell.
+o the shell's open files, plus any modifications and additions
specified by redirections to the command
+o the current working directory
+o the file creation mode mask
+o shell variables and functions marked for export, along with
variables exported for the command, passed in the environment
+o traps caught by the shell are reset to the values inherited from
the shell's parent, and traps ignored by the shell are ignored
A command invoked in this separate environment cannot affect the
shell's execution environment.
Command substitution, commands grouped with parentheses, and asynchro-
nous commands are invoked in a subshell environment that is a duplicate
of the shell environment, except that traps caught by the shell are re-
set to the values that the shell inherited from its parent at invoca-
tion. Builtin commands that are invoked as part of a pipeline are also
executed in a subshell environment. Changes made to the subshell envi-
ronment cannot affect the shell's execution environment.
Subshells spawned to execute command substitutions inherit the value of
the --ee option from the parent shell. When not in _p_o_s_i_x _m_o_d_e, bbaasshh
clears the --ee option in such subshells.
If a command is followed by a && and job control is not active, the de-
fault standard input for the command is the empty file _/_d_e_v_/_n_u_l_l. Oth-
erwise, the invoked command inherits the file descriptors of the call-
ing shell as modified by redirections.
EENNVVIIRROONNMMEENNTT
When a program is invoked it is given an array of strings called the
_e_n_v_i_r_o_n_m_e_n_t. This is a list of _n_a_m_e-_v_a_l_u_e pairs, of the form
_n_a_m_e=_v_a_l_u_e.
The shell provides several ways to manipulate the environment. On in-
vocation, the shell scans its own environment and creates a parameter
for each name found, automatically marking it for _e_x_p_o_r_t to child pro-
cesses. Executed commands inherit the environment. The eexxppoorrtt and ddee--
ccllaarree --xx commands allow parameters and functions to be added to and
deleted from the environment. If the value of a parameter in the envi-
ronment is modified, the new value becomes part of the environment, re-
placing the old. The environment inherited by any executed command
consists of the shell's initial environment, whose values may be modi-
fied in the shell, less any pairs removed by the uunnsseett command, plus
any additions via the eexxppoorrtt and ddeeccllaarree --xx commands.
The environment for any _s_i_m_p_l_e _c_o_m_m_a_n_d or function may be augmented
temporarily by prefixing it with parameter assignments, as described
above in PPAARRAAMMEETTEERRSS. These assignment statements affect only the envi-
ronment seen by that command.
If the --kk option is set (see the sseett builtin command below), then _a_l_l
parameter assignments are placed in the environment for a command, not
just those that precede the command name.
When bbaasshh invokes an external command, the variable __ is set to the
full filename of the command and passed to that command in its environ-
ment.
EEXXIITT SSTTAATTUUSS
The exit status of an executed command is the value returned by the
_w_a_i_t_p_i_d system call or equivalent function. Exit statuses fall between
0 and 255, though, as explained below, the shell may use values above
125 specially. Exit statuses from shell builtins and compound commands
are also limited to this range. Under certain circumstances, the shell
will use special values to indicate specific failure modes.
For the shell's purposes, a command which exits with a zero exit status
has succeeded. An exit status of zero indicates success. A non-zero
exit status indicates failure. When a command terminates on a fatal
signal _N, bbaasshh uses the value of 128+_N as the exit status.
If a command is not found, the child process created to execute it re-
turns a status of 127. If a command is found but is not executable,
the return status is 126.
If a command fails because of an error during expansion or redirection,
the exit status is greater than zero.
Shell builtin commands return a status of 0 (_t_r_u_e) if successful, and
non-zero (_f_a_l_s_e) if an error occurs while they execute. All builtins
return an exit status of 2 to indicate incorrect usage, generally in-
valid options or missing arguments.
BBaasshh itself returns the exit status of the last command executed, un-
less a syntax error occurs, in which case it exits with a non-zero
value. See also the eexxiitt builtin command below.
SSIIGGNNAALLSS
When bbaasshh is interactive, in the absence of any traps, it ignores
SSIIGGTTEERRMM (so that kkiillll 00 does not kill an interactive shell), and SSIIGGIINNTT
is caught and handled (so that the wwaaiitt builtin is interruptible). In
all cases, bbaasshh ignores SSIIGGQQUUIITT. If job control is in effect, bbaasshh ig-
nores SSIIGGTTTTIINN, SSIIGGTTTTOOUU, and SSIIGGTTSSTTPP.
Non-builtin commands run by bbaasshh have signal handlers set to the values
inherited by the shell from its parent. When job control is not in ef-
fect, asynchronous commands ignore SSIIGGIINNTT and SSIIGGQQUUIITT in addition to
these inherited handlers. Commands run as a result of command substi-
tution ignore the keyboard-generated job control signals SSIIGGTTTTIINN, SSIIGGTT--
TTOOUU, and SSIIGGTTSSTTPP.
The shell exits by default upon receipt of a SSIIGGHHUUPP. Before exiting,
an interactive shell resends the SSIIGGHHUUPP to all jobs, running or
stopped. Stopped jobs are sent SSIIGGCCOONNTT to ensure that they receive the
SSIIGGHHUUPP. To prevent the shell from sending the signal to a particular
job, it should be removed from the jobs table with the ddiissoowwnn builtin
(see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) or marked to not receive SSIIGGHHUUPP us-
ing ddiissoowwnn --hh.
If the hhuuppoonneexxiitt shell option has been set with sshhoopptt, bbaasshh sends a
SSIIGGHHUUPP to all jobs when an interactive login shell exits.
If bbaasshh is waiting for a command to complete and receives a signal for
which a trap has been set, the trap will not be executed until the com-
mand completes. When bbaasshh is waiting for an asynchronous command via
the wwaaiitt builtin, the reception of a signal for which a trap has been
set will cause the wwaaiitt builtin to return immediately with an exit sta-
tus greater than 128, immediately after which the trap is executed.
JJOOBB CCOONNTTRROOLL
_J_o_b _c_o_n_t_r_o_l refers to the ability to selectively stop (_s_u_s_p_e_n_d) the ex-
ecution of processes and continue (_r_e_s_u_m_e) their execution at a later
point. A user typically employs this facility via an interactive in-
terface supplied jointly by the operating system kernel's terminal
driver and bbaasshh.
The shell associates a _j_o_b with each pipeline. It keeps a table of
currently executing jobs, which may be listed with the jjoobbss command.
When bbaasshh starts a job asynchronously (in the _b_a_c_k_g_r_o_u_n_d), it prints a
line that looks like:
[1] 25647
indicating that this job is job number 1 and that the process ID of the
last process in the pipeline associated with this job is 25647. All of
the processes in a single pipeline are members of the same job. BBaasshh
uses the _j_o_b abstraction as the basis for job control.
To facilitate the implementation of the user interface to job control,
the operating system maintains the notion of a _c_u_r_r_e_n_t _t_e_r_m_i_n_a_l _p_r_o_c_e_s_s
_g_r_o_u_p _I_D. Members of this process group (processes whose process group
ID is equal to the current terminal process group ID) receive keyboard-
generated signals such as SSIIGGIINNTT. These processes are said to be in
the _f_o_r_e_g_r_o_u_n_d. _B_a_c_k_g_r_o_u_n_d processes are those whose process group ID
differs from the terminal's; such processes are immune to keyboard-gen-
erated signals. Only foreground processes are allowed to read from or,
if the user so specifies with stty tostop, write to the terminal.
Background processes which attempt to read from (write to when stty
tostop is in effect) the terminal are sent a SSIIGGTTTTIINN ((SSIIGGTTTTOOUU)) signal
by the kernel's terminal driver, which, unless caught, suspends the
process.
If the operating system on which bbaasshh is running supports job control,
bbaasshh contains facilities to use it. Typing the _s_u_s_p_e_n_d character (typ-
ically ^^ZZ, Control-Z) while a process is running causes that process to
be stopped and returns control to bbaasshh. Typing the _d_e_l_a_y_e_d _s_u_s_p_e_n_d
character (typically ^^YY, Control-Y) causes the process to be stopped
when it attempts to read input from the terminal, and control to be re-
turned to bbaasshh. The user may then manipulate the state of this job,
using the bbgg command to continue it in the background, the ffgg command
to continue it in the foreground, or the kkiillll command to kill it. A ^^ZZ
takes effect immediately, and has the additional side effect of causing
pending output and typeahead to be discarded.
There are a number of ways to refer to a job in the shell. The charac-
ter %% introduces a job specification (_j_o_b_s_p_e_c). Job number _n may be
referred to as %%nn. A job may also be referred to using a prefix of the
name used to start it, or using a substring that appears in its command
line. For example, %%ccee refers to a stopped job whose command name be-
gins with ccee. If a prefix matches more than one job, bbaasshh reports an
error. Using %%??ccee, on the other hand, refers to any job containing the
string ccee in its command line. If the substring matches more than one
job, bbaasshh reports an error. The symbols %%%% and %%++ refer to the shell's
notion of the _c_u_r_r_e_n_t _j_o_b, which is the last job stopped while it was
in the foreground or started in the background. The _p_r_e_v_i_o_u_s _j_o_b may
be referenced using %%--. If there is only a single job, %%++ and %%-- can
both be used to refer to that job. In output pertaining to jobs (e.g.,
the output of the jjoobbss command), the current job is always flagged with
a ++, and the previous job with a --. A single % (with no accompanying
job specification) also refers to the current job.
Simply naming a job can be used to bring it into the foreground: %%11 is
a synonym for ````ffgg %%11'''', bringing job 1 from the background into the
foreground. Similarly, ````%%11 &&'''' resumes job 1 in the background,
equivalent to ````bbgg %%11''''.
The shell learns immediately whenever a job changes state. Normally,
bbaasshh waits until it is about to print a prompt before reporting changes
in a job's status so as to not interrupt any other output. If the --bb
option to the sseett builtin command is enabled, bbaasshh reports such changes
immediately. Any trap on SSIIGGCCHHLLDD is executed for each child that ex-
its.
If an attempt to exit bbaasshh is made while jobs are stopped (or, if the
cchheecckkjjoobbss shell option has been enabled using the sshhoopptt builtin, run-
ning), the shell prints a warning message, and, if the cchheecckkjjoobbss option
is enabled, lists the jobs and their statuses. The jjoobbss command may
then be used to inspect their status. If a second attempt to exit is
made without an intervening command, the shell does not print another
warning, and any stopped jobs are terminated.
When the shell is waiting for a job or process using the wwaaiitt builtin,
and job control is enabled, wwaaiitt will return when the job changes
state. The --ff option causes wwaaiitt to wait until the job or process ter-
minates before returning.
PPRROOMMPPTTIINNGG
When executing interactively, bbaasshh displays the primary prompt PPSS11 when
it is ready to read a command, and the secondary prompt PPSS22 when it
needs more input to complete a command. BBaasshh displays PPSS00 after it
reads a command but before executing it. BBaasshh displays PPSS44 as de-
scribed above before tracing each command when the --xx option is en-
abled. BBaasshh allows these prompt strings to be customized by inserting
a number of backslash-escaped special characters that are decoded as
follows:
\\aa an ASCII bell character (07)
\\dd the date in "Weekday Month Date" format (e.g., "Tue May
26")
\\DD{{_f_o_r_m_a_t}}
the _f_o_r_m_a_t is passed to _s_t_r_f_t_i_m_e(3) and the result is in-
serted into the prompt string; an empty _f_o_r_m_a_t results in
a locale-specific time representation. The braces are
required
\\ee an ASCII escape character (033)
\\hh the hostname up to the first `.'
\\HH the hostname
\\jj the number of jobs currently managed by the shell
\\ll the basename of the shell's terminal device name
\\nn newline
\\rr carriage return
\\ss the name of the shell, the basename of $$00 (the portion
following the final slash)
\\tt the current time in 24-hour HH:MM:SS format
\\TT the current time in 12-hour HH:MM:SS format
\\@@ the current time in 12-hour am/pm format
\\AA the current time in 24-hour HH:MM format
\\uu the username of the current user
\\vv the version of bbaasshh (e.g., 2.00)
\\VV the release of bbaasshh, version + patch level (e.g., 2.00.0)
\\ww the current working directory, with $$HHOOMMEE abbreviated
with a tilde (uses the value of the PPRROOMMPPTT__DDIIRRTTRRIIMM vari-
able)
\\WW the basename of the current working directory, with $$HHOOMMEE
abbreviated with a tilde
\\!! the history number of this command
\\## the command number of this command
\\$$ if the effective UID is 0, a ##, otherwise a $$
\\_n_n_n the character corresponding to the octal number _n_n_n
\\\\ a backslash
\\[[ begin a sequence of non-printing characters, which could
be used to embed a terminal control sequence into the
prompt
\\]] end a sequence of non-printing characters
The command number and the history number are usually different: the
history number of a command is its position in the history list, which
may include commands restored from the history file (see HHIISSTTOORRYY be-
low), while the command number is the position in the sequence of com-
mands executed during the current shell session. After the string is
decoded, it is expanded via parameter expansion, command substitution,
arithmetic expansion, and quote removal, subject to the value of the
pprroommppttvvaarrss shell option (see the description of the sshhoopptt command under
SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). This can have unwanted side effects if
escaped portions of the string appear within command substitution or
contain characters special to word expansion.
RREEAADDLLIINNEE
This is the library that handles reading input when using an interac-
tive shell, unless the ----nnooeeddiittiinngg option is given at shell invocation.
Line editing is also used when using the --ee option to the rreeaadd builtin.
By default, the line editing commands are similar to those of Emacs. A
vi-style line editing interface is also available. Line editing can be
enabled at any time using the --oo eemmaaccss or --oo vvii options to the sseett
builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). To turn off line editing
after the shell is running, use the ++oo eemmaaccss or ++oo vvii options to the
sseett builtin.
RReeaaddlliinnee NNoottaattiioonn
In this section, the Emacs-style notation is used to denote keystrokes.
Control keys are denoted by C-_k_e_y, e.g., C-n means Control-N. Simi-
larly, _m_e_t_a keys are denoted by M-_k_e_y, so M-x means Meta-X. (On key-
boards without a _m_e_t_a key, M-_x means ESC _x, i.e., press the Escape key
then the _x key. This makes ESC the _m_e_t_a _p_r_e_f_i_x. The combination M-C-_x
means ESC-Control-_x, or press the Escape key then hold the Control key
while pressing the _x key.)
Readline commands may be given numeric _a_r_g_u_m_e_n_t_s, which normally act as
a repeat count. Sometimes, however, it is the sign of the argument
that is significant. Passing a negative argument to a command that
acts in the forward direction (e.g., kkiillll--lliinnee) causes that command to
act in a backward direction. Commands whose behavior with arguments
deviates from this are noted below.
When a command is described as _k_i_l_l_i_n_g text, the text deleted is saved
for possible future retrieval (_y_a_n_k_i_n_g). The killed text is saved in a
_k_i_l_l _r_i_n_g. Consecutive kills cause the text to be accumulated into one
unit, which can be yanked all at once. Commands which do not kill text
separate the chunks of text on the kill ring.
RReeaaddlliinnee IInniittiiaalliizzaattiioonn
Readline is customized by putting commands in an initialization file
(the _i_n_p_u_t_r_c file). The name of this file is taken from the value of
the IINNPPUUTTRRCC variable. If that variable is unset, the default is _~_/_._i_n_-
_p_u_t_r_c. If that file does not exist or cannot be read, the ultimate
default is _/_e_t_c_/_i_n_p_u_t_r_c. When a program which uses the readline li-
brary starts up, the initialization file is read, and the key bindings
and variables are set. There are only a few basic constructs allowed
in the readline initialization file. Blank lines are ignored. Lines
beginning with a ## are comments. Lines beginning with a $$ indicate
conditional constructs. Other lines denote key bindings and variable
settings.
The default key-bindings may be changed with an _i_n_p_u_t_r_c file. Other
programs that use this library may add their own commands and bindings.
For example, placing
M-Control-u: universal-argument
or
C-Meta-u: universal-argument
into the _i_n_p_u_t_r_c would make M-C-u execute the readline command _u_n_i_v_e_r_-
_s_a_l_-_a_r_g_u_m_e_n_t.
The following symbolic character names are recognized: _R_U_B_O_U_T, _D_E_L,
_E_S_C, _L_F_D, _N_E_W_L_I_N_E, _R_E_T, _R_E_T_U_R_N, _S_P_C, _S_P_A_C_E, and _T_A_B.
In addition to command names, readline allows keys to be bound to a
string that is inserted when the key is pressed (a _m_a_c_r_o).
RReeaaddlliinnee KKeeyy BBiinnddiinnggss
The syntax for controlling key bindings in the _i_n_p_u_t_r_c file is simple.
All that is required is the name of the command or the text of a macro
and a key sequence to which it should be bound. The name may be speci-
fied in one of two ways: as a symbolic key name, possibly with _M_e_t_a_- or
_C_o_n_t_r_o_l_- prefixes, or as a key sequence.
When using the form kkeeyynnaammee:_f_u_n_c_t_i_o_n_-_n_a_m_e or _m_a_c_r_o, _k_e_y_n_a_m_e is the name
of a key spelled out in English. For example:
Control-u: universal-argument
Meta-Rubout: backward-kill-word
Control-o: "> output"
In the above example, _C_-_u is bound to the function uunniivveerrssaall--aarrgguummeenntt,
_M_-_D_E_L is bound to the function bbaacckkwwaarrdd--kkiillll--wwoorrdd, and _C_-_o is bound to
run the macro expressed on the right hand side (that is, to insert the
text ``> output'' into the line).
In the second form, ""kkeeyysseeqq"":_f_u_n_c_t_i_o_n_-_n_a_m_e or _m_a_c_r_o, kkeeyysseeqq differs
from kkeeyynnaammee above in that strings denoting an entire key sequence may
be specified by placing the sequence within double quotes. Some GNU
Emacs style key escapes can be used, as in the following example, but
the symbolic character names are not recognized.
"\C-u": universal-argument
"\C-x\C-r": re-read-init-file
"\e[11~": "Function Key 1"
In this example, _C_-_u is again bound to the function uunniivveerrssaall--aarrgguummeenntt.
_C_-_x _C_-_r is bound to the function rree--rreeaadd--iinniitt--ffiillee, and _E_S_C _[ _1 _1 _~ is
bound to insert the text ``Function Key 1''.
The full set of GNU Emacs style escape sequences is
\\CC-- control prefix
\\MM-- meta prefix
\\ee an escape character
\\\\ backslash
\\"" literal "
\\'' literal '
In addition to the GNU Emacs style escape sequences, a second set of
backslash escapes is available:
\\aa alert (bell)
\\bb backspace
\\dd delete
\\ff form feed
\\nn newline
\\rr carriage return
\\tt horizontal tab
\\vv vertical tab
\\_n_n_n the eight-bit character whose value is the octal value
_n_n_n (one to three digits)
\\xx_H_H the eight-bit character whose value is the hexadecimal
value _H_H (one or two hex digits)
When entering the text of a macro, single or double quotes must be used
to indicate a macro definition. Unquoted text is assumed to be a func-
tion name. In the macro body, the backslash escapes described above
are expanded. Backslash will quote any other character in the macro
text, including " and '.
BBaasshh allows the current readline key bindings to be displayed or modi-
fied with the bbiinndd builtin command. The editing mode may be switched
during interactive use by using the --oo option to the sseett builtin com-
mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
RReeaaddlliinnee VVaarriiaabblleess
Readline has variables that can be used to further customize its behav-
ior. A variable may be set in the _i_n_p_u_t_r_c file with a statement of the
form
sseett _v_a_r_i_a_b_l_e_-_n_a_m_e _v_a_l_u_e
or using the bbiinndd builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
Except where noted, readline variables can take the values OOnn or OOffff
(without regard to case). Unrecognized variable names are ignored.
When a variable value is read, empty or null values, "on" (case-insen-
sitive), and "1" are equivalent to OOnn. All other values are equivalent
to OOffff. The variables and their default values are:
bbeellll--ssttyyllee ((aauuddiibbllee))
Controls what happens when readline wants to ring the terminal
bell. If set to nnoonnee, readline never rings the bell. If set to
vviissiibbllee, readline uses a visible bell if one is available. If
set to aauuddiibbllee, readline attempts to ring the terminal's bell.
bbiinndd--ttttyy--ssppeecciiaall--cchhaarrss ((OOnn))
If set to OOnn, readline attempts to bind the control characters
treated specially by the kernel's terminal driver to their read-
line equivalents.
bblliinnkk--mmaattcchhiinngg--ppaarreenn ((OOffff))
If set to OOnn, readline attempts to briefly move the cursor to an
opening parenthesis when a closing parenthesis is inserted.
ccoolloorreedd--ccoommpplleettiioonn--pprreeffiixx ((OOffff))
If set to OOnn, when listing completions, readline displays the
common prefix of the set of possible completions using a differ-
ent color. The color definitions are taken from the value of
the LLSS__CCOOLLOORRSS environment variable.
ccoolloorreedd--ssttaattss ((OOffff))
If set to OOnn, readline displays possible completions using dif-
ferent colors to indicate their file type. The color defini-
tions are taken from the value of the LLSS__CCOOLLOORRSS environment
variable.
ccoommmmeenntt--bbeeggiinn ((````##''''))
The string that is inserted when the readline iinnsseerrtt--ccoommmmeenntt
command is executed. This command is bound to MM--## in emacs mode
and to ## in vi command mode.
ccoommpplleettiioonn--ddiissppllaayy--wwiiddtthh ((--11))
The number of screen columns used to display possible matches
when performing completion. The value is ignored if it is less
than 0 or greater than the terminal screen width. A value of 0
will cause matches to be displayed one per line. The default
value is -1.
ccoommpplleettiioonn--iiggnnoorree--ccaassee ((OOffff))
If set to OOnn, readline performs filename matching and completion
in a case-insensitive fashion.
ccoommpplleettiioonn--mmaapp--ccaassee ((OOffff))
If set to OOnn, and ccoommpplleettiioonn--iiggnnoorree--ccaassee is enabled, readline
treats hyphens (_-) and underscores (__) as equivalent when per-
forming case-insensitive filename matching and completion.
ccoommpplleettiioonn--pprreeffiixx--ddiissppllaayy--lleennggtthh ((00))
The length in characters of the common prefix of a list of pos-
sible completions that is displayed without modification. When
set to a value greater than zero, common prefixes longer than
this value are replaced with an ellipsis when displaying possi-
ble completions.
ccoommpplleettiioonn--qquueerryy--iitteemmss ((110000))
This determines when the user is queried about viewing the num-
ber of possible completions generated by the ppoossssiibbllee--ccoommppllee--
ttiioonnss command. It may be set to any integer value greater than
or equal to zero. If the number of possible completions is
greater than or equal to the value of this variable, readline
will ask whether or not the user wishes to view them; otherwise
they are simply listed on the terminal.
ccoonnvveerrtt--mmeettaa ((OOnn))
If set to OOnn, readline will convert characters with the eighth
bit set to an ASCII key sequence by stripping the eighth bit and
prefixing an escape character (in effect, using escape as the
_m_e_t_a _p_r_e_f_i_x). The default is _O_n, but readline will set it to
_O_f_f if the locale contains eight-bit characters.
ddiissaabbllee--ccoommpplleettiioonn ((OOffff))
If set to OOnn, readline will inhibit word completion. Completion
characters will be inserted into the line as if they had been
mapped to sseellff--iinnsseerrtt.
eecchhoo--ccoonnttrrooll--cchhaarraacctteerrss ((OOnn))
When set to OOnn, on operating systems that indicate they support
it, readline echoes a character corresponding to a signal gener-
ated from the keyboard.
eeddiittiinngg--mmooddee ((eemmaaccss))
Controls whether readline begins with a set of key bindings sim-
ilar to _E_m_a_c_s or _v_i. eeddiittiinngg--mmooddee can be set to either eemmaaccss or
vvii.
eemmaaccss--mmooddee--ssttrriinngg ((@@))
If the _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t variable is enabled, this string is
displayed immediately before the last line of the primary prompt
when emacs editing mode is active. The value is expanded like a
key binding, so the standard set of meta- and control prefixes
and backslash escape sequences is available. Use the \1 and \2
escapes to begin and end sequences of non-printing characters,
which can be used to embed a terminal control sequence into the
mode string.
eennaabbllee--bbrraacckkeetteedd--ppaassttee ((OOnn))
When set to OOnn, readline will configure the terminal in a way
that will enable it to insert each paste into the editing buffer
as a single string of characters, instead of treating each char-
acter as if it had been read from the keyboard. This can pre-
vent pasted characters from being interpreted as editing com-
mands.
eennaabbllee--kkeeyyppaadd ((OOffff))
When set to OOnn, readline will try to enable the application key-
pad when it is called. Some systems need this to enable the ar-
row keys.
eennaabbllee--mmeettaa--kkeeyy ((OOnn))
When set to OOnn, readline will try to enable any meta modifier
key the terminal claims to support when it is called. On many
terminals, the meta key is used to send eight-bit characters.
eexxppaanndd--ttiillddee ((OOffff))
If set to OOnn, tilde expansion is performed when readline at-
tempts word completion.
hhiissttoorryy--pprreesseerrvvee--ppooiinntt ((OOffff))
If set to OOnn, the history code attempts to place point at the
same location on each history line retrieved with pprreevviioouuss--hhiiss--
ttoorryy or nneexxtt--hhiissttoorryy.
hhiissttoorryy--ssiizzee ((uunnsseett))
Set the maximum number of history entries saved in the history
list. If set to zero, any existing history entries are deleted
and no new entries are saved. If set to a value less than zero,
the number of history entries is not limited. By default, the
number of history entries is set to the value of the HHIISSTTSSIIZZEE
shell variable. If an attempt is made to set _h_i_s_t_o_r_y_-_s_i_z_e to a
non-numeric value, the maximum number of history entries will be
set to 500.
hhoorriizzoonnttaall--ssccrroollll--mmooddee ((OOffff))
When set to OOnn, makes readline use a single line for display,
scrolling the input horizontally on a single screen line when it
becomes longer than the screen width rather than wrapping to a
new line. This setting is automatically enabled for terminals
of height 1.
iinnppuutt--mmeettaa ((OOffff))
If set to OOnn, readline will enable eight-bit input (that is, it
will not strip the eighth bit from the characters it reads), re-
gardless of what the terminal claims it can support. The name
mmeettaa--ffllaagg is a synonym for this variable. The default is _O_f_f,
but readline will set it to _O_n if the locale contains eight-bit
characters.
iisseeaarrcchh--tteerrmmiinnaattoorrss ((````CC--[[CC--JJ''''))
The string of characters that should terminate an incremental
search without subsequently executing the character as a com-
mand. If this variable has not been given a value, the charac-
ters _E_S_C and _C_-_J will terminate an incremental search.
kkeeyymmaapp ((eemmaaccss))
Set the current readline keymap. The set of valid keymap names
is _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_-_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; _e_m_a_c_s is
equivalent to _e_m_a_c_s_-_s_t_a_n_d_a_r_d. The default value is _e_m_a_c_s; the
value of eeddiittiinngg--mmooddee also affects the default keymap.
kkeeyysseeqq--ttiimmeeoouutt ((550000))
Specifies the duration _r_e_a_d_l_i_n_e will wait for a character when
reading an ambiguous key sequence (one that can form a complete
key sequence using the input read so far, or can take additional
input to complete a longer key sequence). If no input is re-
ceived within the timeout, _r_e_a_d_l_i_n_e will use the shorter but
complete key sequence. The value is specified in milliseconds,
so a value of 1000 means that _r_e_a_d_l_i_n_e will wait one second for
additional input. If this variable is set to a value less than
or equal to zero, or to a non-numeric value, _r_e_a_d_l_i_n_e will wait
until another key is pressed to decide which key sequence to
complete.
mmaarrkk--ddiirreeccttoorriieess ((OOnn))
If set to OOnn, completed directory names have a slash appended.
mmaarrkk--mmooddiiffiieedd--lliinneess ((OOffff))
If set to OOnn, history lines that have been modified are dis-
played with a preceding asterisk (**).
mmaarrkk--ssyymmlliinnkkeedd--ddiirreeccttoorriieess ((OOffff))
If set to OOnn, completed names which are symbolic links to direc-
tories have a slash appended (subject to the value of mmaarrkk--ddii--
rreeccttoorriieess).
mmaattcchh--hhiiddddeenn--ffiilleess ((OOnn))
This variable, when set to OOnn, causes readline to match files
whose names begin with a `.' (hidden files) when performing
filename completion. If set to OOffff, the leading `.' must be
supplied by the user in the filename to be completed.
mmeennuu--ccoommpplleettee--ddiissppllaayy--pprreeffiixx ((OOffff))
If set to OOnn, menu completion displays the common prefix of the
list of possible completions (which may be empty) before cycling
through the list.
oouuttppuutt--mmeettaa ((OOffff))
If set to OOnn, readline will display characters with the eighth
bit set directly rather than as a meta-prefixed escape sequence.
The default is _O_f_f, but readline will set it to _O_n if the locale
contains eight-bit characters.
ppaaggee--ccoommpplleettiioonnss ((OOnn))
If set to OOnn, readline uses an internal _m_o_r_e-like pager to dis-
play a screenful of possible completions at a time.
pprriinntt--ccoommpplleettiioonnss--hhoorriizzoonnttaallllyy ((OOffff))
If set to OOnn, readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the
screen.
rreevveerrtt--aallll--aatt--nneewwlliinnee ((OOffff))
If set to OOnn, readline will undo all changes to history lines
before returning when aacccceepptt--lliinnee is executed. By default, his-
tory lines may be modified and retain individual undo lists
across calls to rreeaaddlliinnee.
sshhooww--aallll--iiff--aammbbiigguuoouuss ((OOffff))
This alters the default behavior of the completion functions.
If set to OOnn, words which have more than one possible completion
cause the matches to be listed immediately instead of ringing
the bell.
sshhooww--aallll--iiff--uunnmmooddiiffiieedd ((OOffff))
This alters the default behavior of the completion functions in
a fashion similar to sshhooww--aallll--iiff--aammbbiigguuoouuss. If set to OOnn, words
which have more than one possible completion without any possi-
ble partial completion (the possible completions don't share a
common prefix) cause the matches to be listed immediately in-
stead of ringing the bell.
sshhooww--mmooddee--iinn--pprroommpptt ((OOffff))
If set to OOnn, add a string to the beginning of the prompt indi-
cating the editing mode: emacs, vi command, or vi insertion.
The mode strings are user-settable (e.g., _e_m_a_c_s_-_m_o_d_e_-_s_t_r_i_n_g).
sskkiipp--ccoommpplleetteedd--tteexxtt ((OOffff))
If set to OOnn, this alters the default completion behavior when
inserting a single match into the line. It's only active when
performing completion in the middle of a word. If enabled,
readline does not insert characters from the completion that
match characters after point in the word being completed, so
portions of the word following the cursor are not duplicated.
vvii--ccmmdd--mmooddee--ssttrriinngg ((((ccmmdd))))
If the _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t variable is enabled, this string is
displayed immediately before the last line of the primary prompt
when vi editing mode is active and in command mode. The value
is expanded like a key binding, so the standard set of meta- and
control prefixes and backslash escape sequences is available.
Use the \1 and \2 escapes to begin and end sequences of non-
printing characters, which can be used to embed a terminal con-
trol sequence into the mode string.
vvii--iinnss--mmooddee--ssttrriinngg ((((iinnss))))
If the _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t variable is enabled, this string is
displayed immediately before the last line of the primary prompt
when vi editing mode is active and in insertion mode. The value
is expanded like a key binding, so the standard set of meta- and
control prefixes and backslash escape sequences is available.
Use the \1 and \2 escapes to begin and end sequences of non-
printing characters, which can be used to embed a terminal con-
trol sequence into the mode string.
vviissiibbllee--ssttaattss ((OOffff))
If set to OOnn, a character denoting a file's type as reported by
_s_t_a_t(2) is appended to the filename when listing possible com-
pletions.
RReeaaddlliinnee CCoonnddiittiioonnaall CCoonnssttrruuccttss
Readline implements a facility similar in spirit to the conditional
compilation features of the C preprocessor which allows key bindings
and variable settings to be performed as the result of tests. There
are four parser directives used.
$$iiff The $$iiff construct allows bindings to be made based on the edit-
ing mode, the terminal being used, or the application using
readline. The text of the test, after any comparison operator,
extends to the end of the line; unless otherwise noted, no
characters are required to isolate it.
mmooddee The mmooddee== form of the $$iiff directive is used to test
whether readline is in emacs or vi mode. This may be
used in conjunction with the sseett kkeeyymmaapp command, for in-
stance, to set bindings in the _e_m_a_c_s_-_s_t_a_n_d_a_r_d and
_e_m_a_c_s_-_c_t_l_x keymaps only if readline is starting out in
emacs mode.
tteerrmm The tteerrmm== form may be used to include terminal-specific
key bindings, perhaps to bind the key sequences output by
the terminal's function keys. The word on the right side
of the == is tested against both the full name of the ter-
minal and the portion of the terminal name before the
first --. This allows _s_u_n to match both _s_u_n and _s_u_n_-_c_m_d,
for instance.
vveerrssiioonn
The vveerrssiioonn test may be used to perform comparisons
against specific readline versions. The vveerrssiioonn expands
to the current readline version. The set of comparison
operators includes ==, (and ====), !!==, <<==, >>==, <<, and >>.
The version number supplied on the right side of the op-
erator consists of a major version number, an optional
decimal point, and an optional minor version (e.g., 77..11).
If the minor version is omitted, it is assumed to be 00.
The operator may be separated from the string vveerrssiioonn and
from the version number argument by whitespace.
aapppplliiccaattiioonn
The aapppplliiccaattiioonn construct is used to include application-
specific settings. Each program using the readline li-
brary sets the _a_p_p_l_i_c_a_t_i_o_n _n_a_m_e, and an initialization
file can test for a particular value. This could be used
to bind key sequences to functions useful for a specific
program. For instance, the following command adds a key
sequence that quotes the current or previous word in
bbaasshh:
$$iiff Bash
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
$$eennddiiff
_v_a_r_i_a_b_l_e
The _v_a_r_i_a_b_l_e construct provides simple equality tests for
readline variables and values. The permitted comparison
operators are _=, _=_=, and _!_=. The variable name must be
separated from the comparison operator by whitespace; the
operator may be separated from the value on the right
hand side by whitespace. Both string and boolean vari-
ables may be tested. Boolean variables must be tested
against the values _o_n and _o_f_f.
$$eennddiiff This command, as seen in the previous example, terminates an $$iiff
command.
$$eellssee Commands in this branch of the $$iiff directive are executed if the
test fails.
$$iinncclluuddee
This directive takes a single filename as an argument and reads
commands and bindings from that file. For example, the follow-
ing directive would read _/_e_t_c_/_i_n_p_u_t_r_c:
$$iinncclluuddee _/_e_t_c_/_i_n_p_u_t_r_c
SSeeaarrcchhiinngg
Readline provides commands for searching through the command history
(see HHIISSTTOORRYY below) for lines containing a specified string. There are
two search modes: _i_n_c_r_e_m_e_n_t_a_l and _n_o_n_-_i_n_c_r_e_m_e_n_t_a_l.
Incremental searches begin before the user has finished typing the
search string. As each character of the search string is typed, read-
line displays the next entry from the history matching the string typed
so far. An incremental search requires only as many characters as
needed to find the desired history entry. The characters present in
the value of the iisseeaarrcchh--tteerrmmiinnaattoorrss variable are used to terminate an
incremental search. If that variable has not been assigned a value the
Escape and Control-J characters will terminate an incremental search.
Control-G will abort an incremental search and restore the original
line. When the search is terminated, the history entry containing the
search string becomes the current line.
To find other matching entries in the history list, type Control-S or
Control-R as appropriate. This will search backward or forward in the
history for the next entry matching the search string typed so far.
Any other key sequence bound to a readline command will terminate the
search and execute that command. For instance, a _n_e_w_l_i_n_e will termi-
nate the search and accept the line, thereby executing the command from
the history list.
Readline remembers the last incremental search string. If two Control-
Rs are typed without any intervening characters defining a new search
string, any remembered search string is used.
Non-incremental searches read the entire search string before starting
to search for matching history lines. The search string may be typed
by the user or be part of the contents of the current line.
RReeaaddlliinnee CCoommmmaanndd NNaammeess
The following is a list of the names of the commands and the default
key sequences to which they are bound. Command names without an accom-
panying key sequence are unbound by default. In the following descrip-
tions, _p_o_i_n_t refers to the current cursor position, and _m_a_r_k refers to
a cursor position saved by the sseett--mmaarrkk command. The text between the
point and mark is referred to as the _r_e_g_i_o_n.
CCoommmmaannddss ffoorr MMoovviinngg
bbeeggiinnnniinngg--ooff--lliinnee ((CC--aa))
Move to the start of the current line.
eenndd--ooff--lliinnee ((CC--ee))
Move to the end of the line.
ffoorrwwaarrdd--cchhaarr ((CC--ff))
Move forward a character.
bbaacckkwwaarrdd--cchhaarr ((CC--bb))
Move back a character.
ffoorrwwaarrdd--wwoorrdd ((MM--ff))
Move forward to the end of the next word. Words are composed of
alphanumeric characters (letters and digits).
bbaacckkwwaarrdd--wwoorrdd ((MM--bb))
Move back to the start of the current or previous word. Words
are composed of alphanumeric characters (letters and digits).
sshheellll--ffoorrwwaarrdd--wwoorrdd
Move forward to the end of the next word. Words are delimited
by non-quoted shell metacharacters.
sshheellll--bbaacckkwwaarrdd--wwoorrdd
Move back to the start of the current or previous word. Words
are delimited by non-quoted shell metacharacters.
pprreevviioouuss--ssccrreeeenn--lliinnee
Attempt to move point to the same physical screen column on the
previous physical screen line. This will not have the desired
effect if the current Readline line does not take up more than
one physical line or if point is not greater than the length of
the prompt plus the screen width.
nneexxtt--ssccrreeeenn--lliinnee
Attempt to move point to the same physical screen column on the
next physical screen line. This will not have the desired effect
if the current Readline line does not take up more than one
physical line or if the length of the current Readline line is
not greater than the length of the prompt plus the screen width.
cclleeaarr--ddiissppllaayy ((MM--CC--ll))
Clear the screen and, if possible, the terminal's scrollback
buffer, then redraw the current line, leaving the current line
at the top of the screen.
cclleeaarr--ssccrreeeenn ((CC--ll))
Clear the screen, then redraw the current line, leaving the cur-
rent line at the top of the screen. With an argument, refresh
the current line without clearing the screen.
rreeddrraaww--ccuurrrreenntt--lliinnee
Refresh the current line.
CCoommmmaannddss ffoorr MMaanniippuullaattiinngg tthhee HHiissttoorryy
aacccceepptt--lliinnee ((NNeewwlliinnee,, RReettuurrnn))
Accept the line regardless of where the cursor is. If this line
is non-empty, add it to the history list according to the state
of the HHIISSTTCCOONNTTRROOLL variable. If the line is a modified history
line, then restore the history line to its original state.
pprreevviioouuss--hhiissttoorryy ((CC--pp))
Fetch the previous command from the history list, moving back in
the list.
nneexxtt--hhiissttoorryy ((CC--nn))
Fetch the next command from the history list, moving forward in
the list.
bbeeggiinnnniinngg--ooff--hhiissttoorryy ((MM--<<))
Move to the first line in the history.
eenndd--ooff--hhiissttoorryy ((MM-->>))
Move to the end of the input history, i.e., the line currently
being entered.
rreevveerrssee--sseeaarrcchh--hhiissttoorryy ((CC--rr))
Search backward starting at the current line and moving `up'
through the history as necessary. This is an incremental
search.
ffoorrwwaarrdd--sseeaarrcchh--hhiissttoorryy ((CC--ss))
Search forward starting at the current line and moving `down'
through the history as necessary. This is an incremental
search.
nnoonn--iinnccrreemmeennttaall--rreevveerrssee--sseeaarrcchh--hhiissttoorryy ((MM--pp))
Search backward through the history starting at the current line
using a non-incremental search for a string supplied by the
user.
nnoonn--iinnccrreemmeennttaall--ffoorrwwaarrdd--sseeaarrcchh--hhiissttoorryy ((MM--nn))
Search forward through the history using a non-incremental
search for a string supplied by the user.
hhiissttoorryy--sseeaarrcchh--ffoorrwwaarrdd
Search forward through the history for the string of characters
between the start of the current line and the point. This is a
non-incremental search.
hhiissttoorryy--sseeaarrcchh--bbaacckkwwaarrdd
Search backward through the history for the string of characters
between the start of the current line and the point. This is a
non-incremental search.
hhiissttoorryy--ssuubbssttrriinngg--sseeaarrcchh--bbaacckkwwaarrdd
Search backward through the history for the string of characters
between the start of the current line and the current cursor po-
sition (the _p_o_i_n_t). The search string may match anywhere in a
history line. This is a non-incremental search.
hhiissttoorryy--ssuubbssttrriinngg--sseeaarrcchh--ffoorrwwaarrdd
Search forward through the history for the string of characters
between the start of the current line and the point. The search
string may match anywhere in a history line. This is a non-in-
cremental search.
yyaannkk--nntthh--aarrgg ((MM--CC--yy))
Insert the first argument to the previous command (usually the
second word on the previous line) at point. With an argument _n,
insert the _nth word from the previous command (the words in the
previous command begin with word 0). A negative argument in-
serts the _nth word from the end of the previous command. Once
the argument _n is computed, the argument is extracted as if the
"!_n" history expansion had been specified.
yyaannkk--llaasstt--aarrgg ((MM--..,, MM--__))
Insert the last argument to the previous command (the last word
of the previous history entry). With a numeric argument, behave
exactly like yyaannkk--nntthh--aarrgg. Successive calls to yyaannkk--llaasstt--aarrgg
move back through the history list, inserting the last word (or
the word specified by the argument to the first call) of each
line in turn. Any numeric argument supplied to these successive
calls determines the direction to move through the history. A
negative argument switches the direction through the history
(back or forward). The history expansion facilities are used to
extract the last word, as if the "!$" history expansion had been
specified.
sshheellll--eexxppaanndd--lliinnee ((MM--CC--ee))
Expand the line as the shell does. This performs alias and his-
tory expansion as well as all of the shell word expansions. See
HHIISSTTOORRYY EEXXPPAANNSSIIOONN below for a description of history expansion.
hhiissttoorryy--eexxppaanndd--lliinnee ((MM--^^))
Perform history expansion on the current line. See HHIISSTTOORRYY EEXX--
PPAANNSSIIOONN below for a description of history expansion.
mmaaggiicc--ssppaaccee
Perform history expansion on the current line and insert a
space. See HHIISSTTOORRYY EEXXPPAANNSSIIOONN below for a description of history
expansion.
aalliiaass--eexxppaanndd--lliinnee
Perform alias expansion on the current line. See AALLIIAASSEESS above
for a description of alias expansion.
hhiissttoorryy--aanndd--aalliiaass--eexxppaanndd--lliinnee
Perform history and alias expansion on the current line.
iinnsseerrtt--llaasstt--aarrgguummeenntt ((MM--..,, MM--__))
A synonym for yyaannkk--llaasstt--aarrgg.
ooppeerraattee--aanndd--ggeett--nneexxtt ((CC--oo))
Accept the current line for execution and fetch the next line
relative to the current line from the history for editing. A
numeric argument, if supplied, specifies the history entry to
use instead of the current line.
eeddiitt--aanndd--eexxeeccuuttee--ccoommmmaanndd ((CC--xx CC--ee))
Invoke an editor on the current command line, and execute the
result as shell commands. BBaasshh attempts to invoke $$VVIISSUUAALL, $$EEDD--
IITTOORR, and _e_m_a_c_s as the editor, in that order.
CCoommmmaannddss ffoorr CChhaannggiinngg TTeexxtt
_e_n_d_-_o_f_-_f_i_l_e ((uussuuaallllyy CC--dd))
The character indicating end-of-file as set, for example, by
``stty''. If this character is read when there are no charac-
ters on the line, and point is at the beginning of the line,
Readline interprets it as the end of input and returns EEOOFF.
ddeelleettee--cchhaarr ((CC--dd))
Delete the character at point. If this function is bound to the
same character as the tty EEOOFF character, as CC--dd commonly is, see
above for the effects.
bbaacckkwwaarrdd--ddeelleettee--cchhaarr ((RRuubboouutt))
Delete the character behind the cursor. When given a numeric
argument, save the deleted text on the kill ring.
ffoorrwwaarrdd--bbaacckkwwaarrdd--ddeelleettee--cchhaarr
Delete the character under the cursor, unless the cursor is at
the end of the line, in which case the character behind the cur-
sor is deleted.
qquuootteedd--iinnsseerrtt ((CC--qq,, CC--vv))
Add the next character typed to the line verbatim. This is how
to insert characters like CC--qq, for example.
ttaabb--iinnsseerrtt ((CC--vv TTAABB))
Insert a tab character.
sseellff--iinnsseerrtt ((aa,, bb,, AA,, 11,, !!,, ......))
Insert the character typed.
ttrraannssppoossee--cchhaarrss ((CC--tt))
Drag the character before point forward over the character at
point, moving point forward as well. If point is at the end of
the line, then this transposes the two characters before point.
Negative arguments have no effect.
ttrraannssppoossee--wwoorrddss ((MM--tt))
Drag the word before point past the word after point, moving
point over that word as well. If point is at the end of the
line, this transposes the last two words on the line.
uuppccaassee--wwoorrdd ((MM--uu))
Uppercase the current (or following) word. With a negative ar-
gument, uppercase the previous word, but do not move point.
ddoowwnnccaassee--wwoorrdd ((MM--ll))
Lowercase the current (or following) word. With a negative ar-
gument, lowercase the previous word, but do not move point.
ccaappiittaalliizzee--wwoorrdd ((MM--cc))
Capitalize the current (or following) word. With a negative ar-
gument, capitalize the previous word, but do not move point.
oovveerrwwrriittee--mmooddee
Toggle overwrite mode. With an explicit positive numeric argu-
ment, switches to overwrite mode. With an explicit non-positive
numeric argument, switches to insert mode. This command affects
only eemmaaccss mode; vvii mode does overwrite differently. Each call
to _r_e_a_d_l_i_n_e_(_) starts in insert mode. In overwrite mode, charac-
ters bound to sseellff--iinnsseerrtt replace the text at point rather than
pushing the text to the right. Characters bound to bbaacckk--
wwaarrdd--ddeelleettee--cchhaarr replace the character before point with a
space. By default, this command is unbound.
KKiilllliinngg aanndd YYaannkkiinngg
kkiillll--lliinnee ((CC--kk))
Kill the text from point to the end of the line.
bbaacckkwwaarrdd--kkiillll--lliinnee ((CC--xx RRuubboouutt))
Kill backward to the beginning of the line.
uunniixx--lliinnee--ddiissccaarrdd ((CC--uu))
Kill backward from point to the beginning of the line. The
killed text is saved on the kill-ring.
kkiillll--wwhhoollee--lliinnee
Kill all characters on the current line, no matter where point
is.
kkiillll--wwoorrdd ((MM--dd))
Kill from point to the end of the current word, or if between
words, to the end of the next word. Word boundaries are the
same as those used by ffoorrwwaarrdd--wwoorrdd.
bbaacckkwwaarrdd--kkiillll--wwoorrdd ((MM--RRuubboouutt))
Kill the word behind point. Word boundaries are the same as
those used by bbaacckkwwaarrdd--wwoorrdd.
sshheellll--kkiillll--wwoorrdd
Kill from point to the end of the current word, or if between
words, to the end of the next word. Word boundaries are the
same as those used by sshheellll--ffoorrwwaarrdd--wwoorrdd.
sshheellll--bbaacckkwwaarrdd--kkiillll--wwoorrdd
Kill the word behind point. Word boundaries are the same as
those used by sshheellll--bbaacckkwwaarrdd--wwoorrdd.
uunniixx--wwoorrdd--rruubboouutt ((CC--ww))
Kill the word behind point, using white space as a word bound-
ary. The killed text is saved on the kill-ring.
uunniixx--ffiilleennaammee--rruubboouutt
Kill the word behind point, using white space and the slash
character as the word boundaries. The killed text is saved on
the kill-ring.
ddeelleettee--hhoorriizzoonnttaall--ssppaaccee ((MM--\\))
Delete all spaces and tabs around point.
kkiillll--rreeggiioonn
Kill the text in the current region.
ccooppyy--rreeggiioonn--aass--kkiillll
Copy the text in the region to the kill buffer.
ccooppyy--bbaacckkwwaarrdd--wwoorrdd
Copy the word before point to the kill buffer. The word bound-
aries are the same as bbaacckkwwaarrdd--wwoorrdd.
ccooppyy--ffoorrwwaarrdd--wwoorrdd
Copy the word following point to the kill buffer. The word
boundaries are the same as ffoorrwwaarrdd--wwoorrdd.
yyaannkk ((CC--yy))
Yank the top of the kill ring into the buffer at point.
yyaannkk--ppoopp ((MM--yy))
Rotate the kill ring, and yank the new top. Only works follow-
ing yyaannkk or yyaannkk--ppoopp.
NNuummeerriicc AArrgguummeennttss
ddiiggiitt--aarrgguummeenntt ((MM--00,, MM--11,, ......,, MM----))
Add this digit to the argument already accumulating, or start a
new argument. M-- starts a negative argument.
uunniivveerrssaall--aarrgguummeenntt
This is another way to specify an argument. If this command is
followed by one or more digits, optionally with a leading minus
sign, those digits define the argument. If the command is fol-
lowed by digits, executing uunniivveerrssaall--aarrgguummeenntt again ends the nu-
meric argument, but is otherwise ignored. As a special case, if
this command is immediately followed by a character that is nei-
ther a digit nor minus sign, the argument count for the next
command is multiplied by four. The argument count is initially
one, so executing this function the first time makes the argu-
ment count four, a second time makes the argument count sixteen,
and so on.
CCoommpplleettiinngg
ccoommpplleettee ((TTAABB))
Attempt to perform completion on the text before point. BBaasshh
attempts completion treating the text as a variable (if the text
begins with $$), username (if the text begins with ~~), hostname
(if the text begins with @@), or command (including aliases and
functions) in turn. If none of these produces a match, filename
completion is attempted.
ppoossssiibbllee--ccoommpplleettiioonnss ((MM--??))
List the possible completions of the text before point.
iinnsseerrtt--ccoommpplleettiioonnss ((MM--**))
Insert all completions of the text before point that would have
been generated by ppoossssiibbllee--ccoommpplleettiioonnss.
mmeennuu--ccoommpplleettee
Similar to ccoommpplleettee, but replaces the word to be completed with
a single match from the list of possible completions. Repeated
execution of mmeennuu--ccoommpplleettee steps through the list of possible
completions, inserting each match in turn. At the end of the
list of completions, the bell is rung (subject to the setting of
bbeellll--ssttyyllee) and the original text is restored. An argument of _n
moves _n positions forward in the list of matches; a negative ar-
gument may be used to move backward through the list. This com-
mand is intended to be bound to TTAABB, but is unbound by default.
mmeennuu--ccoommpplleettee--bbaacckkwwaarrdd
Identical to mmeennuu--ccoommpplleettee, but moves backward through the list
of possible completions, as if mmeennuu--ccoommpplleettee had been given a
negative argument. This command is unbound by default.
ddeelleettee--cchhaarr--oorr--lliisstt
Deletes the character under the cursor if not at the beginning
or end of the line (like ddeelleettee--cchhaarr). If at the end of the
line, behaves identically to ppoossssiibbllee--ccoommpplleettiioonnss. This command
is unbound by default.
ccoommpplleettee--ffiilleennaammee ((MM--//))
Attempt filename completion on the text before point.
ppoossssiibbllee--ffiilleennaammee--ccoommpplleettiioonnss ((CC--xx //))
List the possible completions of the text before point, treating
it as a filename.
ccoommpplleettee--uusseerrnnaammee ((MM--~~))
Attempt completion on the text before point, treating it as a
username.
ppoossssiibbllee--uusseerrnnaammee--ccoommpplleettiioonnss ((CC--xx ~~))
List the possible completions of the text before point, treating
it as a username.
ccoommpplleettee--vvaarriiaabbllee ((MM--$$))
Attempt completion on the text before point, treating it as a
shell variable.
ppoossssiibbllee--vvaarriiaabbllee--ccoommpplleettiioonnss ((CC--xx $$))
List the possible completions of the text before point, treating
it as a shell variable.
ccoommpplleettee--hhoossttnnaammee ((MM--@@))
Attempt completion on the text before point, treating it as a
hostname.
ppoossssiibbllee--hhoossttnnaammee--ccoommpplleettiioonnss ((CC--xx @@))
List the possible completions of the text before point, treating
it as a hostname.
ccoommpplleettee--ccoommmmaanndd ((MM--!!))
Attempt completion on the text before point, treating it as a
command name. Command completion attempts to match the text
against aliases, reserved words, shell functions, shell
builtins, and finally executable filenames, in that order.
ppoossssiibbllee--ccoommmmaanndd--ccoommpplleettiioonnss ((CC--xx !!))
List the possible completions of the text before point, treating
it as a command name.
ddyynnaammiicc--ccoommpplleettee--hhiissttoorryy ((MM--TTAABB))
Attempt completion on the text before point, comparing the text
against lines from the history list for possible completion
matches.
ddaabbbbrreevv--eexxppaanndd
Attempt menu completion on the text before point, comparing the
text against lines from the history list for possible completion
matches.
ccoommpplleettee--iinnttoo--bbrraacceess ((MM--{{))
Perform filename completion and insert the list of possible com-
pletions enclosed within braces so the list is available to the
shell (see BBrraaccee EExxppaannssiioonn above).
KKeeyybbooaarrdd MMaaccrrooss
ssttaarrtt--kkbbdd--mmaaccrroo ((CC--xx (())
Begin saving the characters typed into the current keyboard
macro.
eenndd--kkbbdd--mmaaccrroo ((CC--xx ))))
Stop saving the characters typed into the current keyboard macro
and store the definition.
ccaallll--llaasstt--kkbbdd--mmaaccrroo ((CC--xx ee))
Re-execute the last keyboard macro defined, by making the char-
acters in the macro appear as if typed at the keyboard.
pprriinntt--llaasstt--kkbbdd--mmaaccrroo (())
Print the last keyboard macro defined in a format suitable for
the _i_n_p_u_t_r_c file.
MMiisscceellllaanneeoouuss
rree--rreeaadd--iinniitt--ffiillee ((CC--xx CC--rr))
Read in the contents of the _i_n_p_u_t_r_c file, and incorporate any
bindings or variable assignments found there.
aabboorrtt ((CC--gg))
Abort the current editing command and ring the terminal's bell
(subject to the setting of bbeellll--ssttyyllee).
ddoo--lloowweerrccaassee--vveerrssiioonn ((MM--AA,, MM--BB,, MM--_x,, ......))
If the metafied character _x is uppercase, run the command that
is bound to the corresponding metafied lowercase character. The
behavior is undefined if _x is already lowercase.
pprreeffiixx--mmeettaa ((EESSCC))
Metafy the next character typed. EESSCC ff is equivalent to MMeettaa--ff.
uunnddoo ((CC--__,, CC--xx CC--uu))
Incremental undo, separately remembered for each line.
rreevveerrtt--lliinnee ((MM--rr))
Undo all changes made to this line. This is like executing the
uunnddoo command enough times to return the line to its initial
state.
ttiillddee--eexxppaanndd ((MM--&&))
Perform tilde expansion on the current word.
sseett--mmaarrkk ((CC--@@,, MM--<<ssppaaccee>>))
Set the mark to the point. If a numeric argument is supplied,
the mark is set to that position.
eexxcchhaannggee--ppooiinntt--aanndd--mmaarrkk ((CC--xx CC--xx))
Swap the point with the mark. The current cursor position is
set to the saved position, and the old cursor position is saved
as the mark.
cchhaarraacctteerr--sseeaarrcchh ((CC--]]))
A character is read and point is moved to the next occurrence of
that character. A negative count searches for previous occur-
rences.
cchhaarraacctteerr--sseeaarrcchh--bbaacckkwwaarrdd ((MM--CC--]]))
A character is read and point is moved to the previous occur-
rence of that character. A negative count searches for subse-
quent occurrences.
sskkiipp--ccssii--sseeqquueennccee
Read enough characters to consume a multi-key sequence such as
those defined for keys like Home and End. Such sequences begin
with a Control Sequence Indicator (CSI), usually ESC-[. If this
sequence is bound to "\[", keys producing such sequences will
have no effect unless explicitly bound to a readline command,
instead of inserting stray characters into the editing buffer.
This is unbound by default, but usually bound to ESC-[.
iinnsseerrtt--ccoommmmeenntt ((MM--##))
Without a numeric argument, the value of the readline ccoomm--
mmeenntt--bbeeggiinn variable is inserted at the beginning of the current
line. If a numeric argument is supplied, this command acts as a
toggle: if the characters at the beginning of the line do not
match the value of ccoommmmeenntt--bbeeggiinn, the value is inserted, other-
wise the characters in ccoommmmeenntt--bbeeggiinn are deleted from the begin-
ning of the line. In either case, the line is accepted as if a
newline had been typed. The default value of ccoommmmeenntt--bbeeggiinn
causes this command to make the current line a shell comment.
If a numeric argument causes the comment character to be re-
moved, the line will be executed by the shell.
gglloobb--ccoommpplleettee--wwoorrdd ((MM--gg))
The word before point is treated as a pattern for pathname ex-
pansion, with an asterisk implicitly appended. This pattern is
used to generate a list of matching filenames for possible com-
pletions.
gglloobb--eexxppaanndd--wwoorrdd ((CC--xx **))
The word before point is treated as a pattern for pathname ex-
pansion, and the list of matching filenames is inserted, replac-
ing the word. If a numeric argument is supplied, an asterisk is
appended before pathname expansion.
gglloobb--lliisstt--eexxppaannssiioonnss ((CC--xx gg))
The list of expansions that would have been generated by
gglloobb--eexxppaanndd--wwoorrdd is displayed, and the line is redrawn. If a
numeric argument is supplied, an asterisk is appended before
pathname expansion.
dduummpp--ffuunnccttiioonnss
Print all of the functions and their key bindings to the read-
line output stream. If a numeric argument is supplied, the out-
put is formatted in such a way that it can be made part of an
_i_n_p_u_t_r_c file.
dduummpp--vvaarriiaabblleess
Print all of the settable readline variables and their values to
the readline output stream. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an _i_n_p_u_t_r_c file.
dduummpp--mmaaccrrooss
Print all of the readline key sequences bound to macros and the
strings they output. If a numeric argument is supplied, the
output is formatted in such a way that it can be made part of an
_i_n_p_u_t_r_c file.
ddiissppllaayy--sshheellll--vveerrssiioonn ((CC--xx CC--vv))
Display version information about the current instance of bbaasshh.
PPrrooggrraammmmaabbllee CCoommpplleettiioonn
When word completion is attempted for an argument to a command for
which a completion specification (a _c_o_m_p_s_p_e_c) has been defined using
the ccoommpplleettee builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below), the program-
mable completion facilities are invoked.
First, the command name is identified. If the command word is the
empty string (completion attempted at the beginning of an empty line),
any compspec defined with the --EE option to ccoommpplleettee is used. If a
compspec has been defined for that command, the compspec is used to
generate the list of possible completions for the word. If the command
word is a full pathname, a compspec for the full pathname is searched
for first. If no compspec is found for the full pathname, an attempt
is made to find a compspec for the portion following the final slash.
If those searches do not result in a compspec, any compspec defined
with the --DD option to ccoommpplleettee is used as the default. If there is no
default compspec, bbaasshh attempts alias expansion on the command word as
a final resort, and attempts to find a compspec for the command word
from any successful expansion.
Once a compspec has been found, it is used to generate the list of
matching words. If a compspec is not found, the default bbaasshh comple-
tion as described above under CCoommpplleettiinngg is performed.
First, the actions specified by the compspec are used. Only matches
which are prefixed by the word being completed are returned. When the
--ff or --dd option is used for filename or directory name completion, the
shell variable FFIIGGNNOORREE is used to filter the matches.
Any completions specified by a pathname expansion pattern to the --GG op-
tion are generated next. The words generated by the pattern need not
match the word being completed. The GGLLOOBBIIGGNNOORREE shell variable is not
used to filter the matches, but the FFIIGGNNOORREE variable is used.
Next, the string specified as the argument to the --WW option is consid-
ered. The string is first split using the characters in the IIFFSS spe-
cial variable as delimiters. Shell quoting is honored. Each word is
then expanded using brace expansion, tilde expansion, parameter and
variable expansion, command substitution, and arithmetic expansion, as
described above under EEXXPPAANNSSIIOONN. The results are split using the rules
described above under WWoorrdd SSpplliittttiinngg. The results of the expansion are
prefix-matched against the word being completed, and the matching words
become the possible completions.
After these matches have been generated, any shell function or command
specified with the --FF and --CC options is invoked. When the command or
function is invoked, the CCOOMMPP__LLIINNEE, CCOOMMPP__PPOOIINNTT, CCOOMMPP__KKEEYY, and CCOOMMPP__TTYYPPEE
variables are assigned values as described above under SShheellll VVaarriiaabblleess.
If a shell function is being invoked, the CCOOMMPP__WWOORRDDSS and CCOOMMPP__CCWWOORRDD
variables are also set. When the function or command is invoked, the
first argument ($$11) is the name of the command whose arguments are be-
ing completed, the second argument ($$22) is the word being completed,
and the third argument ($$33) is the word preceding the word being com-
pleted on the current command line. No filtering of the generated com-
pletions against the word being completed is performed; the function or
command has complete freedom in generating the matches.
Any function specified with --FF is invoked first. The function may use
any of the shell facilities, including the ccoommppggeenn builtin described
below, to generate the matches. It must put the possible completions
in the CCOOMMPPRREEPPLLYY array variable, one per array element.
Next, any command specified with the --CC option is invoked in an envi-
ronment equivalent to command substitution. It should print a list of
completions, one per line, to the standard output. Backslash may be
used to escape a newline, if necessary.
After all of the possible completions are generated, any filter speci-
fied with the --XX option is applied to the list. The filter is a pat-
tern as used for pathname expansion; a && in the pattern is replaced
with the text of the word being completed. A literal && may be escaped
with a backslash; the backslash is removed before attempting a match.
Any completion that matches the pattern will be removed from the list.
A leading !! negates the pattern; in this case any completion not match-
ing the pattern will be removed. If the nnooccaasseemmaattcchh shell option is
enabled, the match is performed without regard to the case of alpha-
betic characters.
Finally, any prefix and suffix specified with the --PP and --SS options are
added to each member of the completion list, and the result is returned
to the readline completion code as the list of possible completions.
If the previously-applied actions do not generate any matches, and the
--oo ddiirrnnaammeess option was supplied to ccoommpplleettee when the compspec was de-
fined, directory name completion is attempted.
If the --oo pplluussddiirrss option was supplied to ccoommpplleettee when the compspec
was defined, directory name completion is attempted and any matches are
added to the results of the other actions.
By default, if a compspec is found, whatever it generates is returned
to the completion code as the full set of possible completions. The
default bbaasshh completions are not attempted, and the readline default of
filename completion is disabled. If the --oo bbaasshhddeeffaauulltt option was sup-
plied to ccoommpplleettee when the compspec was defined, the bbaasshh default com-
pletions are attempted if the compspec generates no matches. If the --oo
ddeeffaauulltt option was supplied to ccoommpplleettee when the compspec was defined,
readline's default completion will be performed if the compspec (and,
if attempted, the default bbaasshh completions) generate no matches.
When a compspec indicates that directory name completion is desired,
the programmable completion functions force readline to append a slash
to completed names which are symbolic links to directories, subject to
the value of the mmaarrkk--ddiirreeccttoorriieess readline variable, regardless of the
setting of the mmaarrkk--ssyymmlliinnkkeedd--ddiirreeccttoorriieess readline variable.
There is some support for dynamically modifying completions. This is
most useful when used in combination with a default completion speci-
fied with ccoommpplleettee --DD. It's possible for shell functions executed as
completion handlers to indicate that completion should be retried by
returning an exit status of 124. If a shell function returns 124, and
changes the compspec associated with the command on which completion is
being attempted (supplied as the first argument when the function is
executed), programmable completion restarts from the beginning, with an
attempt to find a new compspec for that command. This allows a set of
completions to be built dynamically as completion is attempted, rather
than being loaded all at once.
For instance, assuming that there is a library of compspecs, each kept
in a file corresponding to the name of the command, the following de-
fault completion function would load completions dynamically:
_completion_loader()
{
. "/etc/bash_completion.d/$1.sh" >/dev/null 2>&1 && return 124
}
complete -D -F _completion_loader -o bashdefault -o default
HHIISSTTOORRYY
When the --oo hhiissttoorryy option to the sseett builtin is enabled, the shell
provides access to the _c_o_m_m_a_n_d _h_i_s_t_o_r_y, the list of commands previously
typed. The value of the HHIISSTTSSIIZZEE variable is used as the number of
commands to save in a history list. The text of the last HHIISSTTSSIIZZEE com-
mands (default 500) is saved. The shell stores each command in the
history list prior to parameter and variable expansion (see EEXXPPAANNSSIIOONN
above) but after history expansion is performed, subject to the values
of the shell variables HHIISSTTIIGGNNOORREE and HHIISSTTCCOONNTTRROOLL.
On startup, the history is initialized from the file named by the vari-
able HHIISSTTFFIILLEE (default _~_/_._b_a_s_h___h_i_s_t_o_r_y). The file named by the value
of HHIISSTTFFIILLEE is truncated, if necessary, to contain no more than the
number of lines specified by the value of HHIISSTTFFIILLEESSIIZZEE. If HHIISSTTFFIILLEE--
SSIIZZEE is unset, or set to null, a non-numeric value, or a numeric value
less than zero, the history file is not truncated. When the history
file is read, lines beginning with the history comment character fol-
lowed immediately by a digit are interpreted as timestamps for the fol-
lowing history line. These timestamps are optionally displayed depend-
ing on the value of the HHIISSTTTTIIMMEEFFOORRMMAATT variable. When a shell with
history enabled exits, the last $$HHIISSTTSSIIZZEE lines are copied from the
history list to $$HHIISSTTFFIILLEE. If the hhiissttaappppeenndd shell option is enabled
(see the description of sshhoopptt under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below), the
lines are appended to the history file, otherwise the history file is
overwritten. If HHIISSTTFFIILLEE is unset, or if the history file is un-
writable, the history is not saved. If the HHIISSTTTTIIMMEEFFOORRMMAATT variable is
set, time stamps are written to the history file, marked with the his-
tory comment character, so they may be preserved across shell sessions.
This uses the history comment character to distinguish timestamps from
other history lines. After saving the history, the history file is
truncated to contain no more than HHIISSTTFFIILLEESSIIZZEE lines. If HHIISSTTFFIILLEESSIIZZEE
is unset, or set to null, a non-numeric value, or a numeric value less
than zero, the history file is not truncated.
The builtin command ffcc (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) may be used
to list or edit and re-execute a portion of the history list. The hhiiss--
ttoorryy builtin may be used to display or modify the history list and ma-
nipulate the history file. When using command-line editing, search
commands are available in each editing mode that provide access to the
history list.
The shell allows control over which commands are saved on the history
list. The HHIISSTTCCOONNTTRROOLL and HHIISSTTIIGGNNOORREE variables may be set to cause the
shell to save only a subset of the commands entered. The ccmmddhhiisstt shell
option, if enabled, causes the shell to attempt to save each line of a
multi-line command in the same history entry, adding semicolons where
necessary to preserve syntactic correctness. The lliitthhiisstt shell option
causes the shell to save the command with embedded newlines instead of
semicolons. See the description of the sshhoopptt builtin below under SSHHEELLLL
BBUUIILLTTIINN CCOOMMMMAANNDDSS for information on setting and unsetting shell op-
tions.
HHIISSTTOORRYY EEXXPPAANNSSIIOONN
The shell supports a history expansion feature that is similar to the
history expansion in ccsshh. This section describes what syntax features
are available. This feature is enabled by default for interactive
shells, and can be disabled using the ++HH option to the sseett builtin com-
mand (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below). Non-interactive shells do not
perform history expansion by default.
History expansions introduce words from the history list into the input
stream, making it easy to repeat commands, insert the arguments to a
previous command into the current input line, or fix errors in previous
commands quickly.
History expansion is performed immediately after a complete line is
read, before the shell breaks it into words, and is performed on each
line individually without taking quoting on previous lines into ac-
count. It takes place in two parts. The first is to determine which
line from the history list to use during substitution. The second is
to select portions of that line for inclusion into the current one.
The line selected from the history is the _e_v_e_n_t, and the portions of
that line that are acted upon are _w_o_r_d_s. Various _m_o_d_i_f_i_e_r_s are avail-
able to manipulate the selected words. The line is broken into words
in the same fashion as when reading input, so that several _m_e_t_a_c_h_a_r_a_c_-
_t_e_r-separated words surrounded by quotes are considered one word. His-
tory expansions are introduced by the appearance of the history expan-
sion character, which is !! by default. Only backslash (\\) and single
quotes can quote the history expansion character, but the history ex-
pansion character is also treated as quoted if it immediately precedes
the closing double quote in a double-quoted string.
Several characters inhibit history expansion if found immediately fol-
lowing the history expansion character, even if it is unquoted: space,
tab, newline, carriage return, and ==. If the eexxttgglloobb shell option is
enabled, (( will also inhibit expansion.
Several shell options settable with the sshhoopptt builtin may be used to
tailor the behavior of history expansion. If the hhiissttvveerriiffyy shell op-
tion is enabled (see the description of the sshhoopptt builtin below), and
rreeaaddlliinnee is being used, history substitutions are not immediately
passed to the shell parser. Instead, the expanded line is reloaded
into the rreeaaddlliinnee editing buffer for further modification. If rreeaaddlliinnee
is being used, and the hhiissttrreeeeddiitt shell option is enabled, a failed
history substitution will be reloaded into the rreeaaddlliinnee editing buffer
for correction. The --pp option to the hhiissttoorryy builtin command may be
used to see what a history expansion will do before using it. The --ss
option to the hhiissttoorryy builtin may be used to add commands to the end of
the history list without actually executing them, so that they are
available for subsequent recall.
The shell allows control of the various characters used by the history
expansion mechanism (see the description of hhiissttcchhaarrss above under SShheellll
VVaarriiaabblleess). The shell uses the history comment character to mark his-
tory timestamps when writing the history file.
EEvveenntt DDeessiiggnnaattoorrss
An event designator is a reference to a command line entry in the his-
tory list. Unless the reference is absolute, events are relative to
the current position in the history list.
!! Start a history substitution, except when followed by a bbllaannkk,
newline, carriage return, = or ( (when the eexxttgglloobb shell option
is enabled using the sshhoopptt builtin).
!!_n Refer to command line _n.
!!--_n Refer to the current command minus _n.
!!!! Refer to the previous command. This is a synonym for `!-1'.
!!_s_t_r_i_n_g
Refer to the most recent command preceding the current position
in the history list starting with _s_t_r_i_n_g.
!!??_s_t_r_i_n_g[[??]]
Refer to the most recent command preceding the current position
in the history list containing _s_t_r_i_n_g. The trailing ?? may be
omitted if _s_t_r_i_n_g is followed immediately by a newline. If
_s_t_r_i_n_g is missing, the string from the most recent search is
used; it is an error if there is no previous search string.
^^_s_t_r_i_n_g_1^^_s_t_r_i_n_g_2^^
Quick substitution. Repeat the previous command, replacing
_s_t_r_i_n_g_1 with _s_t_r_i_n_g_2. Equivalent to ``!!:s^_s_t_r_i_n_g_1^_s_t_r_i_n_g_2^''
(see MMooddiiffiieerrss below).
!!## The entire command line typed so far.
WWoorrdd DDeessiiggnnaattoorrss
Word designators are used to select desired words from the event. A ::
separates the event specification from the word designator. It may be
omitted if the word designator begins with a ^^, $$, **, --, or %%. Words
are numbered from the beginning of the line, with the first word being
denoted by 0 (zero). Words are inserted into the current line sepa-
rated by single spaces.
00 ((zzeerroo))
The zeroth word. For the shell, this is the command word.
_n The _nth word.
^^ The first argument. That is, word 1.
$$ The last word. This is usually the last argument, but will ex-
pand to the zeroth word if there is only one word in the line.
%% The first word matched by the most recent `?_s_t_r_i_n_g?' search, if
the search string begins with a character that is part of a
word.
_x--_y A range of words; `-_y' abbreviates `0-_y'.
** All of the words but the zeroth. This is a synonym for `_1_-_$'.
It is not an error to use ** if there is just one word in the
event; the empty string is returned in that case.
xx** Abbreviates _x_-_$.
xx-- Abbreviates _x_-_$ like xx**, but omits the last word. If xx is miss-
ing, it defaults to 0.
If a word designator is supplied without an event specification, the
previous command is used as the event.
MMooddiiffiieerrss
After the optional word designator, there may appear a sequence of one
or more of the following modifiers, each preceded by a `:'. These mod-
ify, or edit, the word or words selected from the history event.
hh Remove a trailing filename component, leaving only the head.
tt Remove all leading filename components, leaving the tail.
rr Remove a trailing suffix of the form _._x_x_x, leaving the basename.
ee Remove all but the trailing suffix.
pp Print the new command but do not execute it.
qq Quote the substituted words, escaping further substitutions.
xx Quote the substituted words as with qq, but break into words at
bbllaannkkss and newlines. The qq and xx modifiers are mutually exclu-
sive; the last one supplied is used.
ss//_o_l_d//_n_e_w//
Substitute _n_e_w for the first occurrence of _o_l_d in the event
line. Any character may be used as the delimiter in place of /.
The final delimiter is optional if it is the last character of
the event line. The delimiter may be quoted in _o_l_d and _n_e_w with
a single backslash. If & appears in _n_e_w, it is replaced by _o_l_d.
A single backslash will quote the &. If _o_l_d is null, it is set
to the last _o_l_d substituted, or, if no previous history substi-
tutions took place, the last _s_t_r_i_n_g in a !!??_s_t_r_i_n_g[[??]] search.
If _n_e_w is null, each matching _o_l_d is deleted.
&& Repeat the previous substitution.
gg Cause changes to be applied over the entire event line. This is
used in conjunction with `::ss' (e.g., `::ggss//_o_l_d//_n_e_w//') or `::&&'.
If used with `::ss', any delimiter can be used in place of /, and
the final delimiter is optional if it is the last character of
the event line. An aa may be used as a synonym for gg.
GG Apply the following `ss' or `&&' modifier once to each word in the
event line.
SSHHEELLLL 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 above under CCOONNDDIITTIIOONNAALL 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.
RREESSTTRRIICCTTEEDD SSHHEELLLL
If bbaasshh is started with the name rrbbaasshh, or the --rr option is supplied at
invocation, the shell becomes restricted. A restricted shell is used
to set up an environment more controlled than the standard shell. It
behaves identically to bbaasshh with the exception that the following are
disallowed or not performed:
+o changing directories with ccdd
+o setting or unsetting the values of SSHHEELLLL, PPAATTHH, HHIISSTTFFIILLEE, EENNVV,
or BBAASSHH__EENNVV
+o specifying command names containing //
+o specifying a filename containing a // as an argument to the ..
builtin command
+o specifying a filename containing a slash as an argument to the
hhiissttoorryy builtin command
+o specifying a filename containing a slash as an argument to the
--pp option to the hhaasshh builtin command
+o importing function definitions from the shell environment at
startup
+o parsing the value of SSHHEELLLLOOPPTTSS from the shell environment at
startup
+o redirecting output using the >, >|, <>, >&, &>, and >> redirect-
ion operators
+o using the eexxeecc builtin command to replace the shell with another
command
+o adding or deleting builtin commands with the --ff and --dd options
to the eennaabbllee builtin command
+o using the eennaabbllee builtin command to enable disabled shell
builtins
+o specifying the --pp option to the ccoommmmaanndd builtin command
+o turning off restricted mode with sseett ++rr or sseett ++oo rreessttrriicctteedd.
These restrictions are enforced after any startup files are read.
When a command that is found to be a shell script is executed (see CCOOMM--
MMAANNDD EEXXEECCUUTTIIOONN above), rrbbaasshh turns off any restrictions in the shell
spawned to execute the script.
SSEEEE AALLSSOO
_B_a_s_h _R_e_f_e_r_e_n_c_e _M_a_n_u_a_l, Brian Fox and Chet Ramey
_T_h_e _G_n_u _R_e_a_d_l_i_n_e _L_i_b_r_a_r_y, Brian Fox and Chet Ramey
_T_h_e _G_n_u _H_i_s_t_o_r_y _L_i_b_r_a_r_y, Brian Fox and Chet Ramey
_P_o_r_t_a_b_l_e _O_p_e_r_a_t_i_n_g _S_y_s_t_e_m _I_n_t_e_r_f_a_c_e _(_P_O_S_I_X_) _P_a_r_t _2_: _S_h_e_l_l _a_n_d _U_t_i_l_i_-
_t_i_e_s, IEEE --
http://pubs.opengroup.org/onlinepubs/9699919799/
http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
_s_h(1), _k_s_h(1), _c_s_h(1)
_e_m_a_c_s(1), _v_i(1)
_r_e_a_d_l_i_n_e(3)
FFIILLEESS
_/_b_i_n_/_b_a_s_h
The bbaasshh executable
_/_e_t_c_/_p_r_o_f_i_l_e
The systemwide initialization file, executed for login shells
_~_/_._b_a_s_h___p_r_o_f_i_l_e
The personal initialization file, executed for login shells
_~_/_._b_a_s_h_r_c
The individual per-interactive-shell startup file
_~_/_._b_a_s_h___l_o_g_o_u_t
The individual login shell cleanup file, executed when a login
shell exits
_~_/_._i_n_p_u_t_r_c
Individual _r_e_a_d_l_i_n_e initialization file
AAUUTTHHOORRSS
Brian Fox, Free Software Foundation
bfox@gnu.org
Chet Ramey, Case Western Reserve University
chet.ramey@case.edu
BBUUGG RREEPPOORRTTSS
If you find a bug in bbaasshh,, you should report it. But first, you should
make sure that it really is a bug, and that it appears in the latest
version of bbaasshh. The latest version is always available from
_f_t_p_:_/_/_f_t_p_._g_n_u_._o_r_g_/_p_u_b_/_g_n_u_/_b_a_s_h_/.
Once you have determined that a bug actually exists, use the _b_a_s_h_b_u_g
command to submit a bug report. If you have a fix, you are encouraged
to mail that as well! Suggestions and `philosophical' bug reports may
be mailed to _b_u_g_-_b_a_s_h_@_g_n_u_._o_r_g or posted to the Usenet newsgroup
ggnnuu..bbaasshh..bbuugg.
ALL bug reports should include:
The version number of bbaasshh
The hardware and operating system
The compiler used to compile
A description of the bug behaviour
A short script or `recipe' which exercises the bug
_b_a_s_h_b_u_g inserts the first three items automatically into the template
it provides for filing a bug report.
Comments and bug reports concerning this manual page should be directed
to _c_h_e_t_._r_a_m_e_y_@_c_a_s_e_._e_d_u.
BBUUGGSS
It's too big and too slow.
There are some subtle differences between bbaasshh and traditional versions
of sshh, mostly because of the PPOOSSIIXX specification.
Aliases are confusing in some uses.
Shell builtin commands and functions are not stoppable/restartable.
Compound commands and command sequences of the form `a ; b ; c' are not
handled gracefully when process suspension is attempted. When a
process is stopped, the shell immediately executes the next command in
the sequence. It suffices to place the sequence of commands between
parentheses to force it into a subshell, which may be stopped as a
unit.
Array variables may not (yet) be exported.
There may be only one active coprocess at a time.
GNU Bash 5.1 2020 October 29 BASH(1)