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Thu, 20 Jun 2002 10:22:00 +0200 (CEST) |
NNAAMMEE
bash - GNU Bourne-Again SHell
SSYYNNOOPPSSIISS
bbaasshh [options] [file]
CCOOPPYYRRIIGGHHTT
Bash is Copyright (C) 1989-2001 by the Free Software FounÂ
dation, Inc.
DDEESSCCRRIIPPTTIIOONN
BBaasshh is an sshh-compatible command language interpreter that
executes commands read from the standard input or from a
file. BBaasshh also incorporates useful features from the
_K_o_r_n and _C shells (kksshh and ccsshh).
BBaasshh is intended to be a conformant implementation of the
IEEE POSIX Shell and Tools specification (IEEE Working
Group 1003.2).
OOPPTTIIOONNSS
In addition to the single-character shell options docuÂ
mented in the description of the sseett builtin command, bbaasshh
interprets the following options when it is invoked:
--cc _s_t_r_i_n_g If the --cc option is present, then
commands are
read from _s_t_r_i_n_g. If there are arguments after
the _s_t_r_i_n_g, they are assigned to the positional
parameters, starting with $$00.
--rr If the --rr option is present, the shell becomes
_r_e_s_t_r_i_c_t_e_d (see
RREESSTTRRIICCTTEEDD SSHHEELLLL below).
--ii If the --ii option is present, the shell is
_i_n_t_e_r_Â
_a_c_t_i_v_e.
--ss If the --ss option is present, or if no arguments
remain after option processing, then commands
are read from the standard input. This option
allows the positional parameters to be set when
invoking an interactive shell.
--vv Print shell input lines as they are read.
--xx Print commands and their arguments as they are
executed.
--DD A list of all double-quoted strings preceded by
$$ is printed on the standard ouput. These are
the strings that are subject to language transÂ
lation 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 valÂ
ues of the shell options accepted by sshhoopptt are
printed on the standard output. If the invocaÂ
tion 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 filenames and arguments.
An argument of -- is equivalent to ----.
BBaasshh also interprets a number of multi-character options.
These options must appear on the command line before the
single-character options in order for them to be recogÂ
nized.
----dduummpp--ppoo--ssttrriinnggss
Equivalent to --DD, but the output is in the GNU _g_e_t_Â
_t_e_x_t ppoo (portable object) file format.
----dduummpp--ssttrriinnggss
Equivalent to --DD.
----hheellpp Display a usage message on standard output and exit
successfully.
----iinniitt--ffiillee _f_i_l_e
----rrccffiillee _f_i_l_e
Execute commands from _f_i_l_e instead of the standard
personal initialization file _~_/_._b_a_s_h_r_c if the
shell
is interactive (see IINNVVOOCCAATTIIOONN below).
----llooggiinn
Make bbaasshh act as if it had been invoked as a login
shell (see IINNVVOOCCAATTIIOONN below).
----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_Â
_f_i_l_e. By default, bbaasshh reads these files when
it
is invoked as a login shell (see IINNVVOOCCAATTIIOONN
below).
----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 default if the shell is invoked as
sshh.
----ppoossiixx
Change the behavior of bbaasshh where the default operÂ
ation differs from the POSIX 1003.2 standard to
match the standard (_p_o_s_i_x _m_o_d_e).
----rreessttrriicctteedd
The shell becomes restricted (see RREESSTTRRIICCTTEEDD
SSHHEELLLL
below).
----vveerrbboossee
Equivalent to --vv.
----vveerrssiioonn
Show version information for this instance of bbaasshh
on the standard 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, $$00 is
set to the name of the file, and the positional parameters
are set to the remaining arguments. BBaasshh reads and exeÂ
cutes commands from this file, then exits. BBaasshh's exit
status is the exit status of the last command executed in
the script. If no commands are executed, the exit status
is 0. An attempt is first made to open the file in the
current directory, and, if no file is found, then the
shell searches the directories in PPAATTHH for the script.
IINNVVOOCCAATTIIOONN
A _l_o_g_i_n _s_h_e_l_l is one whose first character of
argument
zero is a --, or one started with the ----llooggiinn option.
An _i_n_t_e_r_a_c_t_i_v_e shell is one started without
non-option
arguments and without the --cc option whose standard input
and output are both connected to terminals (as determined
by _i_s_a_t_t_y(3)), or one started with the --ii option.
PPSS11 is
set and $$-- 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 file
names as described below under TTiillddee
EExxppaannssiioonn in the
EEXXPPAANNSSIIOONN section.
When bbaasshh is invoked as an interactive login shell, or as
a non-interactive shell with the ----llooggiinn option, it first
reads and executes commands 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 behavÂ
ior.
When a login shell exits, 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 example, 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 command
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 behavior of historical versions of sshh as closely
as possible, while conforming 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 inhibit 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 exeÂ
cute. Since a shell invoked as sshh does not attempt to
read and execute commands from any other startup files,
the ----rrccffiillee option has no effect. A
non-interactive
shell invoked with the name sshh does not attempt 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 by the
remote shell daemon, usually _r_s_h_d. If bbaasshh determines
it
is being run by _r_s_h_d, 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 _r_s_h_d does
not 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 funcÂ
tions are not inherited from the environment, the SSHHEELLÂÂ
LLOOPPTTSS variable, if it appears in the environment, is
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 document.
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 underscores, and beginning with an alphabetic
character or an underscore. Also referred to as an
iiddeennttiiffiieerr.
mmeettaacchhaarraacctteerr
A character that, when unquoted, separates words.
One of the following:
|| && ;; (( )) << >> ssppaaccee ttaabb
ccoonnttrrooll ooppeerraattoorr
A _t_o_k_e_n that performs a control function. It is
one of the following 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 simple comÂ
mand (see SSHHEELLLL GGRRAAMMMMAARR below) or the third word
of a ccaassee
or ffoorr command:
!! ccaassee 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 followed by bbllaannkk-separated words and redirecÂ
tions, 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 arguÂ
ments 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 the character ||. 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
perÂ
formed before any redirections specified by the command
(see RREEDDIIRREECCTTIIOONN below).
If the reserved word !! precedes a pipeline, the exit staÂ
tus of that pipeline is the logical NOT of the exit status
of the last command. Otherwise, the status of the
pipeline is the exit status of the last command. 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. 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.
Each command in a pipeline is executed as a separate proÂ
cess (i.e., in a subshell).
LLiissttss
A _l_i_s_t is a sequence of one or more pipelines separated by
one of the operators ;;, &&, &&&&, or ||||, and optionally terÂ
minated by one of ;;, &&, or <<nneewwlliinnee>>.
Of these list operators, &&&& and |||| have equal precedence,
followed by ;; and &&,, which have equal precedence.
If a command is terminated by the control operator &&, the
shell executes the command in the _b_a_c_k_g_r_o_u_n_d in
a subÂ
shell. The shell does not wait for the command to finish,
and the return status is 0. 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 executed.
The control operators &&&& and |||| denote AND lists and OR
lists, respectively. 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.
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:
(_l_i_s_t) _l_i_s_t is executed in a subshell. Variable
assignÂ
ments and builtin commands that affect the shell's
environment do not remain in effect after the comÂ
mand completes. The return status is the exit staÂ
tus of _l_i_s_t.
{ _l_i_s_t; }
_l_i_s_t is simply executed in the current shell enviÂ
ronment. _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.
((_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 below 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 evaluaÂ
tion 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 splitÂ
ting and pathname expansion are not performed on
the words between the [[[[ and ]]]]; tilde expansion,
parameter and variable expansion, arithmetic expanÂ
sion, command substitution, process substitution,
and quote removal are performed.
When the ==== and !!== operators are used, the string
to the right of the operator is considered a patÂ
tern and matched according to the rules described
below under PPaatttteerrnn MMaattcchhiinngg. The
return value is
0 if the string matches or does not match the patÂ
tern, respectively, and 1 otherwise. Any part of
the pattern may be quoted to force it to be matched
as a string.
Expressions may be combined using the following
operators, listed in decreasing order of preceÂ
dence:
(( _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 execute
_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 deterÂ
mine 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, generÂ
ating 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 exeÂ
cuted each time. If the iinn _w_o_r_d is omitted, the
ffoorr command executes _l_i_s_t once for each positional
parameter that is set (see PPAARRAAMMEETTEERRSS below).
The
return status is the exit status of the last comÂ
mand 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 AARRIITTHHÂÂ
MMEETTIICC 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 expresÂ
sion _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
expressions 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, generÂ
ating a list of items. The set of expanded words
is printed on the standard error, each preceded by
a number. If the iinn _w_o_r_d is omitted, the posiÂ
tional 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 comÂ
mands 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
same matching rules as for pathname expansion (see
PPaatthhnnaammee EExxppaannssiioonn below).
When a match is found,
the corresponding _l_i_s_t is executed. After the
first match, no subsequent matches are attempted.
The exit status is zero if no pattern matches.
Otherwise, it is the exit status of the last comÂ
mand 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
exeÂ
cuted and the command completes. Otherwise, the
eellssee _l_i_s_t is executed, if present. The exit
status
is the exit status of the last command executed, or
zero if no condition tested true.
wwhhiillee _l_i_s_t; ddoo _l_i_s_t; ddoonnee
uunnttiill _l_i_s_t; ddoo _l_i_s_t; ddoonnee
The wwhhiillee command continuously executes the ddoo
_l_i_s_t
as long as the last command in _l_i_s_t returns an exit
status of zero. The uunnttiill command is identical to
the wwhhiillee command, except that the test is negated;
the ddoo _l_i_s_t is executed as long as the last command
in _l_i_s_t returns a non-zero exit status. The exit
status of the wwhhiillee and uunnttiill commands is the
exit
status of the last ddoo _l_i_s_t command executed, or
zero if none was executed.
[ ffuunnccttiioonn ] _n_a_m_e () { _l_i_s_t; }
This defines a function named _n_a_m_e. The _b_o_d_y
of
the function is the _l_i_s_t of commands between { and
}. This list is executed whenever _n_a_m_e is speciÂ
fied as the name of a simple command. 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 iinntteerraaccttiivvee__ccoommmmeennttss
option to the sshhoopptt builtin
is enabled (see SSHHEELLLL BBUUIILLTTIINN
CCOOMMMMAANNDDSS below), a word
beginning with ## causes that word and all remaining charÂ
acters 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 interactive 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 preÂ
vent 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, 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 itself 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 litÂ
eral value of each character within the quotes. A single
quote may not occur between single quotes, even when preÂ
ceded by a backslash.
Enclosing characters in double quotes preserves the litÂ
eral value of all characters within the quotes, with the
exception of $$, ``, and \\. The characters $$ and `` retain
their special meaning within double quotes. The backslash
retains its special meaning only when followed by one of
the following characters: $$, ``, "", \\, or
<<nneewwlliinnee>>. A
double quote may be quoted within double quotes by precedÂ
ing it with a backslash.
The special parameters ** and @@ have special meaning when
in double quotes (see PPAARRAAMMEETTEERRSS below).
Words of the form $$'_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 specifed by the ANSI C standard. Backslash
escape sequences, if present, are decoded as follows:
\\aa alert (bell)
\\bb backspace
\\ee an escape character
\\ff form feed
\\nn new line
\\rr carriage return
\\tt horizontal tab
\\vv vertical tab
\\\\ backslash
\\'' single quote
\\_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)
The expanded result is single-quoted, as if the dollar
sign had not been present.
A double-quoted string preceded by a dollar sign ($$) will
cause the string to be translated according to the current
locale. If the current locale is CC or PPOOSSIIXX, the dollar
sign is ignored. If the string is translated and
replaced, 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 number, or one of the special characters listed
below under SSppeecciiaall PPaarraammeetteerrss. For
the shell's purposes,
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, command substitution, arithmetic
expansion, and quote removal (see EEXXPPAANNSSIIOONN below).
If
the variable has its iinntteeggeerr attribute set, then
_v_a_l_u_e is
subject to arithmetic expansion even if the $((...))
expansion is not used (see AArriitthhmmeettiicc
EExxppaannssiioonn below).
Word splitting is not performed, with the exception of
""address@hidden@"" as explained below under SSppeecciiaall
PPaarraammeetteerrss. PathÂ
name expansion is not performed. Assignment statements
may also appear as arguments to the ddeeccllaarree,
ttyyppeesseett,
eexxppoorrtt, rreeaaddoonnllyy, and llooccaall
builtin commands.
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 sinÂ
gle 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 occurs within double
quotes, it expands to a single word with the value
of each parameter 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. When the expansion occurs within double
quotes, each parameter expands to a separate word.
That is, "address@hidden@" is equivalent to "$$11" "$$22"
... When
there are no positional parameters, "address@hidden@" and
address@hidden@
expand to nothing (i.e., they are removed).
## Expands to the number of positional parameters in
decimal.
?? Expands to the status of the most recently executed
foreground pipeline.
-- Expands to the current option flags as specified
upon invocation, by the sseett builtin command, or
those set by the shell itself (such as the --ii
option).
$$ Expands to the process ID of the shell. In a ()
subshell, it expands to the process ID of the curÂ
rent shell, not the subshell.
!! Expands to the process ID of the most recently exeÂ
cuted background (asynchronous) command.
00 Expands to the name of the shell or shell script.
This is set at shell initialization. If bbaasshh is
invoked with a file of commands, $$00 is set to the
name of that file. If bbaasshh is started with the --cc
option, then $$00 is set to the first argument after
the string to be executed, if one is present. OthÂ
erwise, it is set to the file name used to invoke
bbaasshh, as given by argument zero.
__ At shell startup, set to the absolute file name of
the shell or shell script being executed as passed
in the argument list. Subsequently, expands to the
last argument to the previous command, after expanÂ
sion. Also set to the full file name of each
command executed and placed in the environment
exported to that command. When checking mail, this
parameter holds the name of the mail file currently
being checked.
SShheellll VVaarriiaabblleess
The following variables are set by the shell:
BBAASSHH Expands to the full file name used to invoke this
instance of bbaasshh.
BBAASSHH__VVEERRSSIINNFFOO
A readonly array variable whose members hold verÂ
sion information for this instance of bbaasshh. The
values assigned to the array members are as folÂ
lows:
BBAASSHH__VVEERRSSIINNFFOO[[0]] The major
version number
(the _r_e_l_e_a_s_e).
BBAASSHH__VVEERRSSIINNFFOO[[1]] The minor
version number
(the _v_e_r_s_i_o_n).
BBAASSHH__VVEERRSSIINNFFOO[[2]] The patch
level.
BBAASSHH__VVEERRSSIINNFFOO[[3]] The build
version.
BBAASSHH__VVEERRSSIINNFFOO[[4]] The release
status (e.g.,
_b_e_t_a_1).
BBAASSHH__VVEERRSSIINNFFOO[[5]] The value
of MMAACCHHTTYYPPEE.
BBAASSHH__VVEERRSSIIOONN
Expands to a string describing the version of this
instance of bbaasshh.
CCOOMMPP__CCWWOORRDD
An index into $${{CCOOMMPP__WWOORRDDSS}} of the word
containing
the current cursor position. This variable is
available only in shell functions invoked by the
programmable completion facilities (see PPrrooÂÂ
ggrraammmmaabbllee CCoommpplleettiioonn below).
CCOOMMPP__LLIINNEE
The current command line. This variable is availÂ
able only in shell functions and external commands
invoked by the programmable completion facilities
(see PPrrooggrraammmmaabbllee
CCoommpplleettiioonn below).
CCOOMMPP__PPOOIINNTT
The index of the current cursor position relative
to the beginning of the current command. If the
current cursor position is at the end of the curÂ
rent 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 programmable completion facilities (see PPrrooÂÂ
ggrraammmmaabbllee CCoommpplleettiioonn below).
CCOOMMPP__WWOORRDDSS
An array variable (see AArrrraayyss below) consisting of
the individual words in the current command line.
This variable is available only in shell functions
invoked by the programmable completion facilities
(see PPrrooggrraammmmaabbllee
CCoommpplleettiioonn below).
DDIIRRSSTTAACCKK
An array variable (see AArrrraayyss below) containing the
current contents of the directory stack. DirectoÂ
ries appear in the stack in the order they are disÂ
played by the ddiirrss builtin. Assigning to members
of this array variable may be used to modify direcÂ
tories already in the stack, but the ppuusshhdd and
ppooppdd
builtins must be used to add and remove directoÂ
ries. Assignment to this variable will not change
the current directory. If DDIIRRSSTTAACCKK is unset,
it
loses its special properties, even if it is subseÂ
quently reset.
EEUUIIDD Expands to the effective user ID of the current
user, initialized at shell startup. This variable
is readonly.
FFUUNNCCNNAAMMEE
The name of any currently-executing shell function.
This variable exists only when a shell function is
executing. Assignments to FFUUNNCCNNAAMMEE have no
effect
and return an error status. If FFUUNNCCNNAAMMEE is
unset,
it loses its special properties, even if it is subÂ
sequently reset.
GGRROOUUPPSS An array variable containing the list of groups of
which the current user is a member. Assignments to
GGRROOUUPPSS have no effect and return an error status.
If GGRROOUUPPSS is unset, it loses its special properÂ
ties, even if it is subsequently reset.
HHIISSTTCCMMDD
The history number, or index in the history list,
of the current command. If HHIISSTTCCMMDD is unset, it
loses its special properties, even if it is subseÂ
quently 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 exeÂ
cuting. The default is system-dependent.
LLIINNEENNOO Each time this parameter is referenced, the shell
substitutes a decimal number representing the curÂ
rent sequential line number (starting with 1)
within a script or function. When not in a script
or function, the value substituted is not guaranÂ
teed to be meaningful. If LLIINNEENNOO is unset, it
loses its special properties, even if it is subseÂ
quently 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.
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 CCOOMMÂÂ
MMAANNDDSS below).
OOPPTTIINNDD The index of the next argument to be processed by
the ggeettooppttss builtin command (see SSHHEELLLL
BBUUIILLTTIINN CCOOMMÂÂ
MMAANNDDSS below).
OOSSTTYYPPEE Automatically set to a string that describes the
operating system on which bbaasshh is executing. The
default is system-dependent.
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 variÂ
able is readonly.
PPWWDD The current working directory as set by the ccdd comÂ
mand.
RRAANNDDOOMM Each time this parameter is referenced, a random
integer between 0 and 32767 is generated. The
sequence of random numbers may be initialized by
assigning a value to RRAANNDDOOMM. If RRAANNDDOOMM
is unset,
it loses its special properties, even if it is subÂ
sequently reset.
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. If
SSEECCOONNDDSS is unset, it loses its special properties,
even if it is subsequently 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.
UUIIDD Expands to the user ID of the current user, iniÂ
tialized at shell startup. This variable is readÂ
only.
The following variables are used by the shell. In some
cases, bbaasshh assigns a default value to a variable; these
cases are noted below.
BBAASSHH__EENNVV
If this parameter is set when bbaasshh is executing a
shell script, its value is interpreted as a fileÂ
name containing commands to initialize the shell,
as in _~_/_._b_a_s_h_r_c. The value of
BBAASSHH__EENNVV is subÂ
jected to parameter expansion, command substituÂ
tion, and arithmetic expansion before being interÂ
preted as a file name. PPAATTHH is not used to search
for the resultant file name.
CCDDPPAATTHH The search path for the ccdd command. This is
a
colon-separated list of directories in which the
shell looks for destination directories specified
by the ccdd command. A sample value is ``.:~:/usr''.
CCOOLLUUMMNNSS
Used by the sseelleecctt builtin command to determine the
terminal width when printing selection lists.
Automatically set upon receipt of a SIGWINCH.
CCOOMMPPRREEPPLLYY
An array variable from which bbaasshh reads the possiÂ
ble completions generated by a shell function
invoked by the programmable completion facility
(see PPrrooggrraammmmaabbllee
CCoommpplleettiioonn below).
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 suffix matches one of the
entries in FFIIGGNNOORREE is excluded from the list of
matched filenames. A sample value is ``.o:~''
(Quoting is needed when assigning a value to this
variable, which contains tildes).
GGLLOOBBIIGGNNOORREE
A colon-separated list of patterns defining the set
of filenames to be ignored by pathname expansion.
If a filename matched by a pathname expansion patÂ
tern also matches one of the patterns in GGLLOOBBIIGGÂÂ
NNOORREE, it is removed from the list of matches.
HHIISSTTCCOONNTTRROOLL
If set to a value of _i_g_n_o_r_e_s_p_a_c_e, lines
which begin
with a ssppaaccee character are not entered on the hisÂ
tory list. If set to a value of _i_g_n_o_r_e_d_u_p_s,
lines
matching the last history line are not entered. A
value of _i_g_n_o_r_e_b_o_t_h combines the two
options. If
unset, or if set to any other value than those
above, all lines read by the parser are saved on
the history list, subject to the value of HHIISSTTIIGGÂÂ
NNOORREE. This variable's function is superseded by
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 HHIISSTTOORRYY 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 an interactive shell exits.
HHIISSTTFFIILLEESSIIZZEE
The maximum number of lines contained in the hisÂ
tory file. When this variable is assigned a value,
the history file is truncated, if necessary, to
contain no more than that number of lines. The
default value is 500. The history file is also
truncated to this size after writing it when an
interactive shell exits.
HHIISSTTIIGGNNOORREE
A colon-separated list of patterns used to decide
which command lines should be saved on the history
list. Each pattern is anchored 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 characters, `&&' matches the
previous history line. `&&' may be escaped using a
backslash; the backslash is removed before attemptÂ
ing a match. 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
HHIISSTTIIGGNNOORREE.
HHIISSTTSSIIZZEE
The number of commands to remember in the command
history (see HHIISSTTOORRYY below). The default value is
500.
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 hostÂ
name completions may be changed while the shell is
running; the next time hostname completion is
attempted 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, bbaasshh
attempts to
read _/_e_t_c_/_h_o_s_t_s to obtain the list of
possible
hostname completions. 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 after expansion and to split lines into
words with the rreeaadd builtin command. The default
value is ``<space><tab><newline>''.
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 characÂ
ters 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,
overÂ
riding the default of _~_/_._i_n_p_u_t_r_c (see
RREEAADDLLIINNEE
below).
LLAANNGG Used to determine the locale category for any cateÂ
gory 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 sequences 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 transÂ
late double-quoted strings preceded by a $$.
LLCC__NNUUMMEERRIICC
This variable determines the locale category used
for number formatting.
LLIINNEESS Used by the sseelleecctt builtin command to
determine the
column length for printing selection lists. AutoÂ
matically set upon receipt of a SIGWINCH.
MMAAIILL If this parameter is set to a file name and the
MMAAIILLPPAATTHH variable is not set, bbaasshh
informs the user
of the arrival of mail in the specified file.
MMAAIILLCCHHEECCKK
Specifies how often (in seconds) bbaasshh checks for
mail. The default is 60 seconds. When it is time
to check for mail, the shell does so before disÂ
playing 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 file names to be checked
for mail. The message to be printed when mail
arrives in a particular file may be specified by
separating the file name from the message with a
`?'. When used in the text of the message, $$__
expands to the name of the current mailfile. ExamÂ
ple:
MMAAIILLPPAATTHH='/var/mail/bfox?"You
have
mail":~/shell-mail?"$_ has mail!"'
BBaasshh supplies a default value for this variable,
but the location of the user mail files that it
uses is system dependent (e.g., /var/mail/$$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-sepaÂ
rated list of directories in which the shell looks
for commands (see CCOOMMMMAANNDD
EEXXEECCUUTTIIOONN below). The
default path is system-dependent, and is set by the
administrator who installs bbaasshh. A common value is
``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.''.
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.
PPRROOMMPPTT__CCOOMMMMAANNDD
If set, the value is executed as a command prior to
issuing each primary prompt.
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 execution trace. The first
character of PPSS44 is replicated multiple times, as
necessary, to indicate multiple levels of indirecÂ
tion. The default is ``++ ''.
TTIIMMEEFFOORRMMAATT
The value of this parameter is used as a format
string specifying how the timing information for
pipelines prefixed with the ttiimmee reserved word
should be displayed. The %% character introduces 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 specÂ
ified, 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%%33llSS''.
If
the value is null, no timing information is disÂ
played. A trailing newline is added when the forÂ
mat string is displayed.
TTMMOOUUTT If set to a value greater than zero, the value is
interpreted as the number of seconds to wait for
input after issuing the primary prompt. BBaasshh terÂ
minates after waiting for that number of seconds if
input does not arrive.
aauuttoo__rreessuummee
This variable controls how the shell interacts with
the user and job control. If this variable is set,
single word simple commands without redirections
are treated as candidates for resumption 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
analoÂ
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 %% 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_Â
_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 characÂ
ter, which is used as shorthand for re-running the
previous command entered, substituting one string
for another in the command. The default is `^^'.
The optional third character is the character which
indicates that the remainder of the line is a
comment when found as the first character of a
word, normally `##'. The history comment character
causes history substitution to be skipped for the
remaining words on the line. It does not necessarÂ
ily cause the shell parser to treat the rest of the
line as a comment.
AArrrraayyss
BBaasshh provides one-dimensional array variables. Any variÂ
able may be used as an 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 contiguously. Arrays are indexed
using integers and are zero-based.
An 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 greater than or equal to zero. To
explicitly declare an array, use ddeeccllaarree --aa
_n_a_m_e (see
SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS 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.
Attributes
may be specified for an array variable using the ddeeccllaarree
and rreeaaddoonnllyy builtins. Each attribute applies to all
memÂ
bers 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 is of the
form [_s_u_b_s_c_r_i_p_t]=_s_t_r_i_n_g. Only
_s_t_r_i_n_g is required. 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. This syntax is also
accepted by the ddeeccllaarree builtin. Individual array eleÂ
ments 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 introduced above.
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 conÂ
flicts 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 sinÂ
gle word with the value of each array member separated by
the first character of the IIFFSS special variable, and
address@hidden expands each element of _n_a_m_e to a separate
word. When there are no array members, address@hidden expands
to nothing. 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_Â
_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 array. Referencing an array
variable without a subscript is equivalent to referencing
element zero.
The uunnsseett builtin is used to destroy arrays.
uunnsseett
_n_a_m_e[_s_u_b_s_c_r_i_p_t] destroys the array element
at index _s_u_b_Â
_s_c_r_i_p_t. 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.
The ddeeccllaarree, llooccaall, and rreeaaddoonnllyy
builtins each accept a --aa
option to specify an array. 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 expanÂ
sion, parameter, variable and arithmetic expansion and
command substitution (done in a left-to-right fashion),
word splitting, and pathname expansion.
On systems that can support it, there is an additional
expansion available: _p_r_o_c_e_s_s
_s_u_b_s_t_i_t_u_t_i_o_n.
Only brace expansion, word splitting, and pathname expanÂ
sion can change the number of words of the expansion;
other expansions expand a single word to a single word.
The only exceptions to this are the expansions of "address@hidden@" and
"address@hidden@]]}}" 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 generated. This mechanism is similar to
_p_a_t_h_n_a_m_e
_e_x_p_a_n_s_i_o_n, but the filenames 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 a series of comma-separated
strings
between a pair of braces, followed by an optional
_p_o_s_t_s_c_r_i_p_t. The preamble is prefixed to each
string conÂ
tained 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'.
Brace expansion is performed before any other expansions,
and any characters special to other expansions are preÂ
served 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. 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 expansion, the string $${{
is not considered eligible for brace expansion.
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 compatiÂ
bility with sshh is desired, start bbaasshh with the ++BB
option
or disable brace expansion with the ++BB option to the sseett
command (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 directory of the user executing
the shell is substituted instead. Otherwise, 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 replaces the tilde-prefix. If the tilde-preÂ
fix is a `~-', the value of the shell variable OOLLDDPPWWDD, if
it is set, is substituted. If the characters 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 argument. If the
characters following the tilde in the tilde-prefix consist
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 immediately following a :: or ==. In these cases,
tilde expansion is also performed. Consequently, one may
use file names with tildes in assignments to PPAATTHH,
MMAAIILLÂÂ
PPAATTHH, and CCDDPPAATTHH, and the shell assigns the
expanded
value.
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 embedded arithmetic expansion,
command substitution, or paramter expansion.
${_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
parameÂ
ter 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 interÂ
preted as part of its name.
If the first character of _p_a_r_a_m_e_t_e_r is an
exclamation
point, a level of variable indirection is introduced.
BBaasshh uses the value of the variable formed from the rest
of _p_a_r_a_m_e_t_e_r as the name of the variable; this
variable is
then expanded and that value is used in the rest of the
substitution, rather than the value of _p_a_r_a_m_e_t_e_r
itself.
This is known as _i_n_d_i_r_e_c_t _e_x_p_a_n_s_i_o_n.
The exception to
this is the expansion of ${!_p_r_e_f_i_x*} described below.
In each of the cases below, _w_o_r_d is subject to tilde
expansion, parameter expansion, command substitution, and
arithmetic expansion. When not performing substring
expansion, bbaasshh tests for a parameter that is unset or
null; omitting the colon results in a test only for a
parameter that is unset.
${_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 expansion 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 expansion of _w_o_r_d is assigned to
_p_a_r_a_m_e_Â
_t_e_r. The value of _p_a_r_a_m_e_t_e_r is then
substituted.
Positional parameters and special parameters 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_Â
_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 expanÂ
sion 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 charÂ
acters of _p_a_r_a_m_e_t_e_r starting at the character
specÂ
ified by _o_f_f_s_e_t. If _l_e_n_g_t_h is omitted,
expands to
the substring of _p_a_r_a_m_e_t_e_r starting at the
characÂ
ter specified by _o_f_f_s_e_t. _l_e_n_g_t_h and
_o_f_f_s_e_t are
arithmetic expressions (see AARRIITTHHMMEETTIICC
EEVVAALLUUAATTIIOONN
below). _l_e_n_g_t_h must evaluate to a number greater
than or equal to zero. If _o_f_f_s_e_t evaluates to a
number less than zero, the value is used as an offÂ
set from the end of the value of _p_a_r_a_m_e_t_e_r.
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. If
_p_a_r_a_m_e_t_e_r is an
array name indexed by @ or *, the result is the
_l_e_n_g_t_h members of the array beginning with
${_p_a_r_a_m_Â
_e_t_e_r[_o_f_f_s_e_t]}. Substring indexing is
zero-based
unless the positional parameters are used, in which
case the indexing starts at 1.
${!!_p_r_e_f_i_x**}
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.
${##_p_a_r_a_m_e_t_e_r}
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
substituted 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.
${_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}
The _w_o_r_d is expanded to produce a pattern just as
in pathname expansion. 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 operation is applied to each posiÂ
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 pattern removal operaÂ
tion 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}
The _w_o_r_d is expanded to produce a pattern just as
in pathname expansion. If the pattern matches a
trailing portion of the expanded value of _p_a_r_a_m_e_Â
_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
operation
is applied to each positional parameter in turn,
and the expansion is the resultant list. If _p_a_r_a_m_Â
_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}
${_p_a_r_a_m_e_t_e_r////_p_a_t_t_e_r_n//_s_t_r_i_n_g}
The _p_a_t_t_e_r_n is expanded to produce a pattern 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. In the first form, only
the first match is replaced. The second form
causes all matches of _p_a_t_t_e_r_n to be replaced with
_s_t_r_i_n_g. 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 //
folÂ
lowing _p_a_t_t_e_r_n may be omitted. If
_p_a_r_a_m_e_t_e_r is @@
or **, the substitution 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
variÂ
able subscripted with @@ or **, the substitution
operation is applied to each member of the array in
turn, and the expansion is the resultant list.
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 command 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 and
replacing the command substitution with the standard outÂ
put of the command, with any trailing newlines deleted.
Embedded newlines are not deleted, but they may be removed
during word splitting. The command 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 $$, ``, or \\. The first backquote not preceded by a
backslash terminates the command substitution. When using
the $(_c_o_m_m_a_n_d) form, all characters between the parentheÂ
ses make up the command; none are treated specially.
Command substitutions may be nested. To nest when using
the backquoted form, escape the inner backquotes with
backslashes.
If the substitution appears within double quotes, word
splitting and pathname expansion are not performed on the
results.
AArriitthhmmeettiicc EExxppaannssiioonn
Arithmetic expansion allows the evaluation of an arithÂ
metic expression and the substitution of the result. The
format for arithmetic expansion is:
$$((((_e_x_p_r_e_s_s_i_o_n))))
The old format $$[[[[_e_x_p_r_e_s_s_i_o_n]]]] is
deprecated and will be
removed in upcoming versions of bash.
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 tokens in the expression undergo
parameter expansion, string expansion, command substituÂ
tion, and quote removal. Arithmetic substitutions 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 is supported
on systems that support
named pipes (_F_I_F_O_s) or the //ddeevv//ffdd method of
naming open
files. It takes the form of <<((_l_i_s_t)) or
>>((_l_i_s_t)). The proÂ
cess _l_i_s_t is run with its input or output connected to a
_F_I_F_O or some file in //ddeevv//ffdd. The name of this
file is
passed as an argument to the current command 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.
When available, process substitution is performed simultaÂ
neously with parameter and variable expansion, command
substitution, and arithmetic expansion.
WWoorrdd SSpplliittttiinngg
The shell scans the results of parameter expansion, comÂ
mand substitution, 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 on
these characters. If IIFFSS is unset, or its value is
exactly
<<ssppaaccee>><<ttaabb>><<nneewwlliinnee>>, the default,
then any
sequence of IIFFSS characters serves to delimit words. If
IIFFSS has a value other than the default, then sequences of
the whitespace characters ssppaaccee and ttaabb are ignored at
the
beginning and end of the word, as long as the whitespace
character is in the value of IIFFSS (an IIFFSS whitespace charÂ
acter). Any character in IIFFSS that is not IIFFSS whitespace,
along with any adjacent IIFFSS whitespace characters, delimÂ
its 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. Unquoted
implicit null arguments, resulting from the expansion of
parameters that have no values, are removed. If a parameÂ
ter with no value is expanded within double quotes, a null
argument results and is retained.
Note that if no expansion occurs, no splitting is perÂ
formed.
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, then the word is regarded
as a _p_a_t_t_e_r_n, and replaced with an alphabetically sorted
list of file names matching the pattern. If no matching
file names are found, and the shell option nnuullllgglloobb
is
disabled, the word is left unchanged. If the
nnuullllgglloobb
option is set, and no matches are found, the word is
removed. If the shell option nnooccaasseegglloobb is
enabled, the
match is performed without regard to the case of alphaÂ
betic 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 explicitly,
unless the shell option ddoottgglloobb is set. When matching a
pathname, the slash character must always be matched
explicitly. In other cases, the ````..'''' character is not
treated specially. See the description of sshhoopptt below
under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS
for a description of the
nnooccaasseegglloobb, nnuullllgglloobb, 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. The file names ````..'''' and ````....'''' are
always
ignored, even when GGLLOOBBIIGGNNOORREE is set. However,
setting
GGLLOOBBIIGGNNOORREE has the effect of enabling the
ddoottgglloobb shell
option, so all other file names beginning with a ````..''''
will match. To get the old behavior of ignoring file
names beginning with a ````..'''', make ````..**'''' one of
the patÂ
terns in GGLLOOBBIIGGNNOORREE. The ddoottgglloobb
option is disabled when
GGLLOOBBIIGGNNOORREE is unset.
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.
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.
?? 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 sorts between
those
two characters, inclusive, using the current
locale's collating sequence and character set, is
matched. If the first character 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 value of the LLCC__CCOOLLLLAATTEE shell variable,
if set.
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.2 stanÂ
dard:
aallnnuumm aallpphhaa aasscciiii
bbllaannkk ccnnttrrll ddiiggiitt ggrraapphh lloowweerr
pprriinntt ppuunncctt ssppaaccee uuppppeerr
xxddiiggiitt
A character class matches any character belonging
to that class.
Within [[ and ]], an _e_q_u_i_v_a_l_e_n_c_e
_c_l_a_s_s can be speciÂ
fied using the syntax [[==_c==]], which matches all
characters with the same collation weight (as
defined by the current locale) as the character _c.
Within [[ and ]], the syntax [[.._s_y_m_b_o_l..]]
matches the
collating 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 ||. ComÂ
posite patterns may be formed using one or more of the
following 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 exactly one of the given patterns
!!((_p_a_t_t_e_r_n_-_l_i_s_t))
Matches anything except one of the given
patterns
QQuuoottee RReemmoovvaall
After the preceding expansions, all unquoted occurrences
of the characters \\, '', 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 may also be used to open and close
files for the current shell execution environment. The
following redirection operators may precede or appear anyÂ
where within a _s_i_m_p_l_e _c_o_m_m_a_n_d or may follow
a _c_o_m_m_a_n_d.
Redirections are processed in the order they appear, from
left to right.
In the following descriptions, if the file descriptor numÂ
ber is omitted, and the first character of the redirection
operator is <<, the redirection 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 followÂ
ing descriptions, unless otherwise noted, is subjected to
brace expansion, tilde expansion, parameter 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 as standard output
before the standard output was redirected to _d_i_r_l_i_s_t.
BBaasshh handles several filenames specially when they are
used in redirections, as described in the following table:
//ddeevv//ffdd//_f_d
If _f_d is a valid integer, file descriptor _f_d
is duplicated.
//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 a TCP
connection to the corresponding 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 a UDP
connection to the corresponding socket.
A failure to open or create a file causes the redirection
to fail.
RReeddiirreeccttiinngg IInnppuutt
Redirection of input causes the file whose name results
from the expansion 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 expansion 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 redirection 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 results from the expansion of _w_o_r_d to be opened
for appending 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.
The general format for appending output is:
[_n]>>>>_w_o_r_d
RReeddiirreeccttiinngg SSttaannddaarrdd
OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr
BBaasshh 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
with this construct.
There are two formats for redirecting standard output and
standard error:
&&>>_w_o_r_d
and
>>&&_w_o_r_d
Of the two forms, the first is preferred. This is semanÂ
tically equivalent to
>>_w_o_r_d 2>>&&1
HHeerree DDooccuummeennttss
This type of redirection instructs the shell to read input
from the current source until a line containing only _w_o_r_d
(with no trailing blanks) is seen. All of the lines read
up to that point are then used as the standard input for a
command.
The format of here-documents is as follows:
<<<<[--]_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 expansion, command substitution, arithmetic
expansion, or pathname expansion is performed on _w_o_r_d. If
any characters in _w_o_r_d are 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 unquoted, all
lines of the here-document are subjected to parameter
expansion, command substitution, and arithmetic expansion.
In the latter case, the character sequence
\\<<nneewwlliinnee>> is
ignored, and \\ must be used to quote the characters \\, $$,
and ``.
If the redirection operator is <<<<--, then all leading tab
characters are stripped from input lines and the line conÂ
taining _d_e_l_i_m_i_t_e_r. This allows here-documents
within
shell scripts to be indented in a natural fashion.
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 descriptor 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 descripÂ
tor 1) is used. If the digits in _w_o_r_d do not specify a
file descriptor open for output, a redirection error
occurs. As a special case, if _n is omitted, and _w_o_r_d does
not expand to one or more digits, the standard output and
standard error are redirected as described previously.
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
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 alias name and the replacement text may conÂ
tain any valid shell input, including the
_m_e_t_a_c_h_a_r_a_c_t_e_r_s
listed above, with the exception that the alias name may
not contain _=. 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 replaceÂ
ment text. If arguments are needed, a shell function
should be used (see FFUUNNCCTTIIOONNSS below).
Aliases are not expanded when the shell is not interacÂ
tive, 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 comÂ
plete line of input before executing any of the commands
on that line. Aliases are expanded when a command is
read, not when it is executed. Therefore, an alias defiÂ
nition 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
compound command. As a consequence, aliases defined in a
function are not available until after that function is
executed. To be safe, always put alias definitions 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 comÂ
mand name, the list of commands associated with that funcÂ
tion name is executed. Functions are executed in the conÂ
text of the current shell; no new process is created to
interpret 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. Positional parameter 0 is unchanged.
The FFUUNNCCNNAAMMEE variable is set to the name of the
function
while the function is executing. All other aspects of the
shell execution environment are identical between a funcÂ
tion and its caller with the exception that the DDEEBBUUGG trap
(see the description of the ttrraapp builtin under
SSHHEELLLL
BBUUIILLTTIINN CCOOMMMMAANNDDSS below) is not inherited.
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 the builtin command rreettuurrnn is executed in a function,
the function completes and execution resumes with the next
command after the function call. When a function comÂ
pletes, 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 ttyyppeesseett will list the
function names
only. Functions may be exported so that subshells autoÂ
matically have them defined with the --ff option to the
eexxppoorrtt builtin.
Functions may be recursive. No limit is imposed on the
number of recursive calls.
AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN
The shell allows arithmetic expressions to be evaluated,
under certain circumstances (see the lleett builtin command
and AArriitthhmmeettiicc EExxppaannssiioonn).
Evaluation is done in long
integers with no check for overflow, though division by 0
is trapped and flagged as an error. The operators and
their precedence and associativity are the same as in the
C language. The following list of operators is grouped
into levels of equal-precedence operators. The levels are
listed in order of decreasing precedence.
_i_d++++ _i_d----
variable post-increment and post-decrement
++++_i_d ----_i_d
variable pre-increment and pre-decrement
-- ++ unary minus and plus
!! ~~ 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 evaluation
== **== //== %%== ++== --== <<<<== >>>>== &&== ^^==
||==
assignment
_e_x_p_r_1 ,, _e_x_p_r_2
comma
Shell variables are allowed as operands; parameter expanÂ
sion is performed before the expression is evaluated.
Within an expression, shell variables may also be referÂ
enced by name without using the parameter expansion synÂ
tax. The value of a variable is evaluated as an arithÂ
metic expression when it is referenced. A shell variable
need not have its integer attribute turned on to be used
in an expression.
Constants with a leading 0 are interpreted as octal numÂ
bers. A leading 0x or 0X denotes hexadecimal. Otherwise,
numbers take the form [_b_a_s_e_#]n, where _b_a_s_e is a
decimal
number between 2 and 64 representing the arithmetic base,
and _n is a number in that base. If _b_a_s_e_# is omitted, then
base 10 is used. The digits greater than 9 are repreÂ
sented 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 uppercase letters may be used
interchangably to represent numbers between 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 comÂ
mand and the tteesstt and [[ builtin commands to test file
attributes and perform string and arithmetic comparisons.
Expressions are formed from the following unary or binary
primaries. If any _f_i_l_e argument to one of the primaries
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.
--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.
--OO _f_i_l_e
True if _f_i_l_e exists and is owned by the effective
user id.
--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.
--SS _f_i_l_e
True if _f_i_l_e exists and is a socket.
--NN _f_i_l_e
True if _f_i_l_e exists and has been modified since it
was last read.
_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.
_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.
_f_i_l_e_1 --eeff _f_i_l_e_2
True if _f_i_l_e_1 and _f_i_l_e_2 have the same
device and
inode numbers.
--oo _o_p_t_n_a_m_e
True if 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.
--zz _s_t_r_i_n_g
True if the length of _s_t_r_i_n_g is zero.
--nn _s_t_r_i_n_g
_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
True if the strings are equal. == may be used in
place of ====.
_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
lexicographiÂ
cally in the current locale.
_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
lexicographiÂ
cally in the current locale.
_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.
SSIIMMPPLLEE CCOOMMMMAANNDD EEXXPPAANNSSIIOONN
When a simple command is executed, the shell performs the
following expansions, assignments, and redirections, from
left to right.
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 variÂ
able.
If no command name results, the variable assignments
affect the current shell environment. Otherwise, the
variables are added to the environment of the executed
command and do not affect the current shell environment.
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 affect the current shell environment. A rediÂ
rection 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 expansions contained a command subÂ
stitution, the exit status of the command is the exit staÂ
tus 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 containing an executable file by that
name. BBaasshh uses a hash table to remember the full pathÂ
names 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 prints an
error message and returns an exit status of 127.
If the search is successful, or if the command name conÂ
tains one or more slashes, the shell executes the named
program in a separate execution environment. Argument 0
is set to the name given, and the remaining arguments to
the command are set to the arguments given, if any.
If this execution fails because the file is not in exeÂ
cutable 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 comÂ
mands. A subshell is spawned to execute it. This subÂ
shell 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 under 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 proÂ
gram. The shell executes the specified interpreter on
operating systems that do not handle this executable forÂ
mat 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 following:
· open files inherited by the shell at invocation, as
modified by redirections supplied to the eexxeecc
builtin
· the current working directory as set by ccdd, ppuusshhdd,
or ppooppdd, or inherited by the shell at invocation
· the file creation mode mask as set by uummaasskk or
inherited from the shell's parent
· current traps set by ttrraapp
· shell parameters that are set by variable assignÂ
ment or with sseett or inherited from the shell's parÂ
ent in the environment
· shell functions defined during execution or inherÂ
ited from the shell's parent in the environment
· options enabled at invocation (either by default or
with command-line arguments) or by sseett
· options enabled by sshhoopptt
· shell aliases defined with aalliiaass
· 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 funcÂ
tion is to be executed, it is invoked in a separate execuÂ
tion environment that consists of the following. Unless
otherwise noted, the values are inherited from the shell.
· the shell's open files, plus any modifications and
additions specified by redirections to the command
· the current working directory
· the file creation mode mask
· shell variables marked for export, along with variÂ
ables exported for the command, passed in the enviÂ
ronment
· traps caught by the shell are reset to the values
the 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 and asynchronous commands are invoked
in a subshell environment that is a duplicate of the shell
environment, except that traps caught by the shell are
reset to the values that the shell inherited from its parÂ
ent at invocation. Builtin commands that are invoked as
part of a pipeline are also executed in a subshell enviÂ
ronment. Changes made to the subshell environment cannot
affect the shell's execution environment.
If a command is followed by a && and job control is not
active, the default standard input for the command is the
empty file _/_d_e_v_/_n_u_l_l. Otherwise, the invoked
command
inherits the file descriptors of the calling shell as modÂ
ified 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 environÂ
ment. On invocation, 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 processes. Executed comÂ
mands inherit the environment. The eexxppoorrtt and
ddeeccllaarree --xx
commands allow parameters and functions to be added to and
deleted from the environment. If the value of a parameter
in the environment is modified, the new value becomes part
of the environment, replacing the old. The environment
inherited by any executed command consists of the shell's
initial environment, whose values may be modified 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 environment 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 file name of the command and passed to
that command in its environment.
EEXXIITT SSTTAATTUUSS
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 failÂ
ure. 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 returns 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 sucÂ
cessful, 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.
BBaasshh itself returns the exit status of the last command
executed, unless 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 interacÂ
tive 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
ignores SSIIGGTTTTIINN, SSIIGGTTTTOOUU, and
SSIIGGTTSSTTPP.
Synchronous jobs started by bbaasshh have signal handlers set
to the values inherited by the shell from its parent.
When job control is not in effect, asynchronous commands
ignore SSIIGGIINNTT and SSIIGGQQUUIITT as well. Commands
run as a
result of command substitution ignore the keyboard-generÂ
ated job control signals SSIIGGTTTTIINN, SSIIGGTTTTOOUU,
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 SSIIGGÂÂ
CCOONNTT 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 using 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.
When bbaasshh receives a signal for which a trap has been set
while waiting for a command to complete, the trap will not
be executed until the command 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 status 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 execution 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 interface supÂ
plied jointly by the system'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
asynÂ
chronously (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 proÂ
cess 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 proÂ
cess 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-generated signals.
Only foreground processes are allowed to read from or
write to the terminal. Background processes which attempt
to read from (write to) the terminal are sent a SSIIGGTTTTIINN
((SSIIGGTTTTOOUU)) signal by the 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 (typically ^^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 charÂ
acter (typically ^^YY, Control-Y) causes the process to be
stopped when it attempts to read input from the terminal,
and control to be returned 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 disÂ
carded.
There are a number of ways to refer to a job in the shell.
The character %% introduces a job name. 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 subÂ
string that appears in its command line. For example, %%ccee
refers to a stopped ccee job. 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 %%--.
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 --.
Simply naming a job can be used to bring it into the foreÂ
ground: %%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 exits.
If an attempt to exit bbaasshh is made while jobs are stopped,
the shell prints a warning message. 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 the stopped jobs are
terminated.
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 allows these prompt strings to be cusÂ
tomized 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")
\\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 $$00
(the portion following the final slash)
\\tt the current time in 24-hour HH:MM:SS format
\\TT the current time in 12-hour HH:MM:SS format
address@hidden@ the current time in 12-hour am/pm format
\\AA the current time in 24-hour HH:MM format
\\uu the username of the current user
\\vv the version of bbaasshh (e.g., 2.00)
\\VV the release of bbaasshh, version + patchelvel
(e.g., 2.00.0)
\\ww the current working directory
\\WW the basename of the current working direcÂ
tory
\\!! the history number of this command
\\## the command number of this command
\\$$ 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 conÂ
trol sequence into the prompt
\\]] end a sequence of non-printing characters
The command number and the history number are usually difÂ
ferent: the history number of a command is its position in
the history list, which may include commands restored from
the history file (see HHIISSTTOORRYY below), while the command
number is the position in the sequence of commands exeÂ
cuted during the current shell session. After the string
is decoded, it is expanded via parameter expansion, comÂ
mand 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).
RREEAADDLLIINNEE
This is the library that handles reading input when using
an interactive shell, unless the ----nnooeeddiittiinngg
option is
given at shell invocation. By default, the line editing
commands are similar to those of emacs. A vi-style line
editing interface is also available. To turn off line
editing after the shell is running, use the ++oo eemmaaccss or
++oo
vvii options to the sseett builtin (see SSHHEELLLL
BBUUIILLTTIINN CCOOMMMMAANNDDSS
below).
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. Similarly, _m_e_t_a keys are
denoted by M-_k_e_y, so M-x means Meta-X. (On keyboards
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_Â
_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 arguÂ
ments 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 initialÂ
ization 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. When
a proÂ
gram which uses the readline library starts up, the iniÂ
tialization file is read, and the key bindings and variÂ
ables 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 specified 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_Â
_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
uunniivveerrÂÂ
ssaall--aarrgguummeenntt, _M_-_D_E_L is bound to
the function bbaacckkÂÂ
wwaarrdd--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, kkeeyyÂÂ
sseeqq 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 uunniiÂÂ
vveerrssaall--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 function name. In the macro body,
the backslash escapes described above are expanded. BackÂ
slash will quote any other character in the macro text,
including " and '.
BBaasshh allows the current readline key bindings to be disÂ
played or modified with the bbiinndd builtin command. The
editing mode may be switched during interactive use by
using the --oo option to the sseett builtin command (see
SSHHEELLLL
BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
RReeaaddlliinnee VVaarriiaabblleess
Readline has variables that can be used to further cusÂ
tomize its behavior. 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
Except where noted, readline variables can take the values
OOnn or 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 aauuddiiÂÂ
bbllee, readline attempts to ring the terminal's bell.
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 comÂ
mand mode.
ccoommpplleettiioonn--iiggnnoorree--ccaassee
((OOffff))
If set to OOnn, readline performs filename matching
and completion in a case-insensitive fashion.
ccoommpplleettiioonn--qquueerryy--iitteemmss
((110000))
This determines when the user is queried about
viewing the number of possible completions generÂ
ated by the
ppoossssiibbllee--ccoommpplleettiioonnss 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 variÂ
able, the user is asked whether or not he 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_Â
_f_i_x).
ddiissaabbllee--ccoommpplleettiioonn ((OOffff))
If set to OOnn, readline will inhibit word compleÂ
tion. Completion characters will be inserted into
the line as if they had been mapped to
sseellff--iinnsseerrtt.
eeddiittiinngg--mmooddee ((eemmaaccss))
Controls whether readline begins with a set of key
bindings similar to _e_m_a_c_s or _v_i.
eeddiittiinngg--mmooddee can
be set to either eemmaaccss or vvii.
eennaabbllee--kkeeyyppaadd ((OOffff))
When set to OOnn, readline will try to enable the
application keypad when it is called. Some systems
need this to enable the arrow keys.
eexxppaanndd--ttiillddee ((OOffff))
If set to oonn, tilde expansion is performed when
readline attempts word completion.
hhiissttoorryy--pprreesseerrvvee--ppooiinntt
If set to oonn, the history code attempts to place
point at the same location on each history line
retrived with pprreevviioouuss--hhiissttoorryy or
nneexxtt--hhiissttoorryy.
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.
iinnppuutt--mmeettaa ((OOffff))
If set to OOnn, readline will enable eight-bit input
(that is, it will not strip the high bit from the
characters it reads), regardless of what the termiÂ
nal claims it can support. The name mmeettaa--ffllaagg
is a
synonym for this variable.
iisseeaarrcchh--tteerrmmiinnaattoorrss
((````CC--[[CC--JJ''''))
The string of characters that should terminate an
incremental search without subsequently executing
the character as a command. If this variable has
not been given a value, the characters _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.
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 displayed with a preceding asterisk (**).
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, unless
the leading `.' is supplied by the user in the
filename to be completed.
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.
pprriinntt--ccoommpplleettiioonnss--hhoorriizzoonnttaallllyy
((OOffff))
If set to OOnn, readline will display completions
with matches sorted horizontally in alphabetical
order, rather than down the screen.
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.
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 completions.
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 perÂ
formed as the result of tests. There are four parser
directives used.
$$iiff The $$iiff construct allows bindings to be made based
on the editing mode, the terminal being used, or
the application using readline. The text of the
test extends to the end of the line; no characters
are required to isolate it.
mmooddee The mmooddee== form of the $$iiff
directive is used
to test whether readline is in emacs or vi
mode. This may be used in conjunction with
the sseett kkeeyymmaapp command, for instance, to
set
bindings in the
_e_m_a_c_s_-_s_t_a_n_d_a_r_d and
_e_m_a_c_s_-_c_t_l_x keymaps only if
readline is
starting out in emacs mode.
tteerrmm The tteerrmm== form may be used to include
termiÂ
nal-specific key bindings, perhaps to bind
the key sequences output by the terminal's
function keys. The word on the right side
of the == is tested against the both full
name of the terminal and the portion of the
terminal name before the first --. This
allows _s_u_n to match both _s_u_n and
_s_u_n_-_c_m_d,
for instance.
aapppplliiccaattiioonn
The aapppplliiccaattiioonn construct is used to
include
application-specific settings. Each program
using the readline library sets the
_a_p_p_l_i_c_a_Â
_t_i_o_n _n_a_m_e, and an initialization file
can
test for a particular value. This could be
used to bind key sequences to functions useÂ
ful for a specific program. For instance,
the following command adds a key sequence
that quotes the current or previous word in
Bash:
$$iiff Bash
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
$$eennddiiff
$$eennddiiff This command, as seen in the previous example, terÂ
minates 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 arguÂ
ment and reads commands and bindings from that
file. For example, the following 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 comÂ
mand 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, readline 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 terÂ
minate 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 containÂ
ing 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 terminate 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 characÂ
ters 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. ComÂ
mand names without an accompanying key sequence are
unbound by default. In the following descriptions, _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 characÂ
ters (letters and digits).
cclleeaarr--ssccrreeeenn ((CC--ll))
Clear the screen leaving the current 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, movÂ
ing 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.
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 previÂ
ous command begin with word 0). A negative arguÂ
ment inserts the _nth word from the end of the preÂ
vious command.
yyaannkk--llaasstt--aarrgg ((MM--..,, MM--__))
Insert the last argument to the previous command
(the last word of the previous history entry).
With an argument, behave exactly like
yyaannkk--nntthh--aarrgg.
Successive calls to yyaannkk--llaasstt--aarrgg move
back through
the history list, inserting the last argument of
each line in turn.
sshheellll--eexxppaanndd--lliinnee ((MM--CC--ee))
Expand the line as the shell does. This performs
alias and history 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 EEXXPPAANNSSIIOONN below for a
description of hisÂ
tory 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. Any argument is ignored.
CCoommmmaannddss ffoorr CChhaannggiinngg TTeexxtt
ddeelleettee--cchhaarr ((CC--dd))
Delete the character at point. If point is at the
beginning of the line, there are no characters in
the line, and the last character typed was not
bound to ddeelleettee--cchhaarr, then return EEOOFF.
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 cursor 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. NegaÂ
tive 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 argument, uppercase the previous word, but
do not move point.
ddoowwnnccaassee--wwoorrdd ((MM--ll))
Lowercase the current (or following) word. With a
negative argument, lowercase the previous word, but
do not move point.
ccaappiittaalliizzee--wwoorrdd ((MM--cc))
Capitalize the current (or following) word. With a
negative argument, capitalize the previous word,
but do not move point.
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 ffoorrÂÂ
wwaarrdd--wwoorrdd.
bbaacckkwwaarrdd--kkiillll--wwoorrdd
((MM--RRuubboouutt))
Kill the word behind point. Word boundaries are
the same as those used by bbaacckkwwaarrdd--wwoorrdd.
uunniixx--wwoorrdd--rruubboouutt ((CC--ww))
Kill the word behind point, using white space as a
word boundary. 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 boundaries 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 following yyaannkk or yyaannkk--ppoopp.
NNuummeerriicc AArrgguummeennttss
ddiiggiitt--aarrgguummeenntt ((MM--00,, MM--11,,
......,, MM----))
Add this digit to the argument already accumulatÂ
ing, or start a new argument. M-- starts a negaÂ
tive 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 followed by
digits, executing
uunniivveerrssaall--aarrgguummeenntt again ends the
numeric argument, but is otherwise ignored. As a
special case, if this command is immediately folÂ
lowed by a character that is neither a digit or
minus sign, the argument count for the next command
is multiplied by four. The argument count is iniÂ
tially one, so executing this function the first
time makes the argument 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--ccoommpplleeÂÂ
ttiioonnss.
mmeennuu--ccoommpplleettee
Similar to ccoommpplleettee, but replaces the word to
be
completed with a single match from the list of posÂ
sible completions. Repeated execution of
mmeennuu--ccoommÂÂ
pplleettee steps through the list of possible compleÂ
tions, 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 argument
may be used to move backward through the list.
This command is intended to be bound to TTAABB, but 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, treatÂ
ing 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--$$))
Attempt completion on the text before point, treatÂ
ing it as a shell variable.
ppoossssiibbllee--vvaarriiaabbllee--ccoommpplleettiioonnss
((CC--xx $$))
List the possible completions of the text before
point, treating it as a shell variable.
ccoommpplleettee--hhoossttnnaammee ((address@hidden@))
Attempt completion on the text before point, treatÂ
ing 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, treatÂ
ing 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, comÂ
paring 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 completions 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 makÂ
ing the characters in the macro appear as if typed
at the keyboard.
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 terÂ
minal's bell (subject to the setting of
bbeellll--ssttyyllee).
ddoo--uuppppeerrccaassee--vveerrssiioonn
((MM--aa,, MM--bb,, MM--_x,, ......))
If the metafied character _x is lowercase, run the
command that is bound to the corresponding upperÂ
case character.
pprreeffiixx--mmeettaa ((EESSCC))
Metafy the next character typed. EESSCC ff is equivaÂ
lent 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 ((address@hidden@,,
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 occurrences.
cchhaarraacctteerr--sseeaarrcchh--bbaacckkwwaarrdd
((MM--CC--]]))
A character is read and point is moved to the preÂ
vious occurrence of that character. A negative
count searches for subsequent occurrences.
iinnsseerrtt--ccoommmmeenntt ((MM--##))
The value of the readline ccoommmmeenntt--bbeeggiinn
variable is
inserted at the beginning of the current line, and
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 comÂ
ment.
gglloobb--eexxppaanndd--wwoorrdd ((CC--xx **))
The word before point is treated as a pattern for
pathname expansion, and the list of matching file
names is inserted, replacing the word.
gglloobb--lliisstt--eexxppaannssiioonnss
((CC--xx gg))
The list of expansions that would have been generÂ
ated by gglloobb--eexxppaanndd--wwoorrdd is
displayed, and the line
is redrawn.
dduummpp--ffuunnccttiioonnss
Print all of the functions and their key bindings
to the readline output stream. If a numeric arguÂ
ment 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--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 formatÂ
ted 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 ouput. 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
programmable completion
facilities are invoked.
First, the command name is identified. 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.
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 completion as described above under
CCoommpplleettÂÂ
iinngg is performed.
First, the actions specified by the compspec are used.
Only matches which are prefixed by the word being comÂ
pleted 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 filename expansion pattern
to the --GG option 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 considered. The string is first split using the
characters in the IIFFSS special variable as delimiters.
Shell quoting is honored. Each word is then expanded
using brace expansion, tilde expansion, parameter and
variable expansion, command substitution, arithmetic
expansion, and pathname 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 comÂ
pleted, and the matching words become the possible compleÂ
tions.
After these matches have been generated, any shell funcÂ
tion or command specified with the --FF and --CC options is
invoked. When the command or function is invoked, the
CCOOMMPP__LLIINNEE and CCOOMMPP__PPOOIINNTT
variables are assigned values as
described above under SShheellll VVaarriiaabblleess. If a
shell funcÂ
tion is being invoked, the CCOOMMPP__WWOORRDDSS and
CCOOMMPP__CCWWOORRDD variÂ
ables are also set. When the function or command is
invoked, the first argument is the name of the command
whose arguments are being completed, the second argument
is the word being completed, and the third argument is the
word preceding the word being completed on the current
command line. No filtering of the generated completions
against the word being completed is performed; the funcÂ
tion 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 CCOOMMÂÂ
PPRREEPPLLYY array variable.
Next, any command specified with the --CC option is invoked
in an environment 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 newÂ
line, if necessary.
After all of the possible completions are generated, any
filter specified with the --XX option is applied to the
list. The filter is a pattern as used for pathname expanÂ
sion; 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 matching the pattern will
be removed.
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 compleÂ
tion 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 ccoommÂÂ
pplleettee when the compspec was defined, directory name comÂ
pletion is attempted.
By default, if a compspec is found, whatever it generates
is returned to the completion code as the full set of posÂ
sible completions. The default bbaasshh completions are not
attempted, and the readline default of filename completion
is disabled. If the --oo ddeeffaauulltt option was
supplied to
ccoommpplleettee when the compspec was defined, readline's
default
completion will be performed if the compspec generates no
matches.
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
commands
(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
perÂ
formed, subject to the values of the shell variables
HHIISSTTIIGGNNOORREE and HHIISSTTCCOONNTTRROOLL.
On startup, the history is initialized from the file named
by the variable HHIISSTTFFIILLEE (default
_~_/_._b_a_s_h___h_i_s_t_o_r_y). The
file named by the value of HHIISSTTFFIILLEE is truncated, if
necÂ
essary, to contain no more than the number of lines speciÂ
fied by the value of HHIISSTTFFIILLEESSIIZZEE. When an
interactive
shell 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
unwritable, the history is not saved. After saving the
history, the history file is truncated to contain no more
than HHIISSTTFFIILLEESSIIZZEE lines. If
HHIISSTTFFIILLEESSIIZZEE is not set, no
truncation is performed.
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 hhiissttoorryy builtin may be used to disÂ
play or modify the history list and manipulate 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 variÂ
ables 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 correctÂ
ness. 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 options.
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 feaÂ
ture is enabled by default for interactive shells, and can
be disabled using the ++HH option to the sseett builtin command
(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 curÂ
rent input line, or fix errors in previous commands
quickly.
History expansion is performed immediately after a comÂ
plete line is read, before the shell breaks it into words.
It takes place in two parts. The first is to determine
which line from the history list to use during substituÂ
tion. 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
available 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 surÂ
rounded by quotes are considered one word. History expanÂ
sions are introduced by the appearance of the history
expansion character, which is !! by default. Only backÂ
slash (\\) and single quotes can quote the history expanÂ
sion character.
Several shell options settable with the sshhoopptt builtin may
be used to tailor the behavior of history expansion. If
the hhiissttvveerriiffyy shell option is enabled (see the
descripÂ
tion of the sshhoopptt builtin), 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).
EEvveenntt DDeessiiggnnaattoorrss
An event designator is a reference to a command line entry
in the history list.
!! Start a history substitution, except when followed
by a bbllaannkk, newline, = or (.
!!_n Refer to command line _n.
!!--_n Refer to the current command line 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 starting with
_s_t_r_i_n_g.
!!??_s_t_r_i_n_g[[??]]
Refer to the most recent command 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.
^^_s_t_r_i_n_g_1^^_s_t_r_i_n_g_2^^
Quick substitution. Repeat the last 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 ^^, $$, **, --, or %%. Words are numbered from
the beginning of the line, with the first word being
denoted by 0 (zero). Words are inserted into the current
line separated by single spaces.
00 ((zzeerroo))
The zeroth word. For the shell, this is the comÂ
mand word.
_n The _nth word.
^^ The first argument. That is, word 1.
$$ The last argument.
%% The word matched by the most recent `?_s_t_r_i_n_g?'
search.
_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 a word designator is supplied without an event specifiÂ
cation, 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 `:'.
hh Remove a trailing file name component, leaving only
the head.
tt Remove all leading file name 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 subÂ
stitutions.
xx Quote the substituted words as with qq, but break
into words at bbllaannkkss and newlines.
ss//_o_l_d//_n_e_w//
Substitute _n_e_w for the first occurrence of _o_l_d in
the event line. Any delimiter can be used 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 backÂ
slash. 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 substitutions took place, the
last _s_t_r_i_n_g in a !!??_s_t_r_i_n_g[[??]]
search.
&& 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.
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.
:: [_a_r_g_u_m_e_n_t_s]
No effect; the command does nothing beyond expandÂ
ing _a_r_g_u_m_e_n_t_s and performing any specified
redirecÂ
tions. A zero exit code is returned.
.. _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
curÂ
rent shell environment and return the exit status
of the last command executed from _f_i_l_e_n_a_m_e.
If
_f_i_l_e_n_a_m_e does not contain a slash, file names
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 positional parameters when _f_i_l_e_n_a_m_e
is
executed. Otherwise the positional parameters are
unchanged. The return status is the status of the
last command exited within the script (0 if no comÂ
mands 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 supplied, the
name and value of the alias is printed. AAlliiaass
returns 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 the 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, if _j_o_b_s_p_e_c was not found or started withÂ
out job control.
bbiinndd [--mm _k_e_y_m_a_p] [--llppssvvPPSSVV]
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
Display current rreeaaddlliinnee key and function
bindings,
or bind a key sequence to a rreeaaddlliinnee function
or
macro. The binding syntax accepted is identical to
that of _._i_n_p_u_t_r_c, but each binding must be
passed
as a separate argument; e.g., '"\C-x\C-r":
re-read-init-file'. Options, 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;
_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.
--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.
--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.
--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 entered.
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 exited.
The return value is 0 unless the shell is not
executing a loop when bbrreeaakk is executed.
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 functionalÂ
ity 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.
ccdd [--LLPP] [_d_i_r]
Change the current directory to _d_i_r. The variable
HHOOMMEE is the default _d_i_r. The variable
CCDDPPAATTHH
defines the search path for the directory containÂ
ing _d_i_r. Alternative directory 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 says to use the physical
directory structure instead of following symbolic
links (see also the --PP option to the sseett builtin
command); the --LL option forces symbolic links to be
followed. An argument of -- is equivalent to $$OOLLDDÂÂ
PPWWDD. 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 option is supplied, a description of
_c_o_m_m_a_n_d is
printed. The --vv option causes a single word indiÂ
cating the command or file name used to invoke _c_o_m_Â
_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 cannot be found,
the exit status is 127. Otherwise, the exit status
of the ccoommmmaanndd builtin is the exit status of
_c_o_m_Â
_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 variÂ
ous shell variables set by the programmable compleÂ
tion facilities, while available, will not have
useful values.
The matches will be generated in the same way as if
the programmable completion code had generated them
directly from a completion specification with the
same flags. If _w_o_r_d is specified, only those comÂ
pletions 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 [--aabbccddeeffggjjkkssvvuu]
[--oo _c_o_m_p_-_o_p_t_i_o_n] [--AA _a_c_t_i_o_n] [--GG
_g_l_o_b_p_a_t] [--WW _w_o_r_d_l_i_s_t] [--PP
_p_r_e_f_i_x] [--SS _s_u_f_f_i_x]
[--XX _f_i_l_t_e_r_p_a_t] [--FF
_f_u_n_c_t_i_o_n] [--CC _c_o_m_m_a_n_d] _n_a_m_e
[_n_a_m_e _._._.]
ccoommpplleettee --pprr [_n_a_m_e ...]
Specify how arguments to each _n_a_m_e should be comÂ
pleted. If the --pp option is supplied, or if no
options are supplied, existing completion specifiÂ
cations are printed in a way that allows them to be
reused as input. The --rr option removes a compleÂ
tion specification for each _n_a_m_e, or, if no
_n_a_m_es
are supplied, all completion specifications.
The process of applying these completion specificaÂ
tions when word completion is attempted is
described above under PPrrooggrraammmmaabbllee
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 expansion
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 compspec's behavior beyond the simple
generation of completions.
_c_o_m_p_-_o_p_t_i_o_n may
be one of:
ddeeffaauulltt Use readline's default completion
if the compspec generates no
matches.
ddiirrnnaammeess
Perform directory name completion
if the compspec generates no
matches.
ffiilleennaammeess
Tell readline that the compspec
generates filenames, so it can perÂ
form any filename-specific processÂ
ing (like adding a slash to direcÂ
tory names or suppressing trailing
spaces). Intended to be used with
shell functions.
--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 speciÂ
fied as --cc.
ddiirreeccttoorryy
Directory names. May also be specÂ
ified 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 conÂ
trol is active.
sseerrvviiccee Service names. May also be speciÂ
fied 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 conÂ
trol is active.
uusseerr User names. May also be specified
as --uu.
vvaarriiaabbllee
Names of all shell variables. May
also be specified as --vv.
--GG _g_l_o_b_p_a_t
The filename expansion pattern _g_l_o_b_p_a_t is
expanded to generate the possible compleÂ
tions.
--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. The
possible completions are the members of the
resultant list which match the word being
completed.
--CC _c_o_m_m_a_n_d
_c_o_m_m_a_n_d is executed in a subshell environÂ
ment, and its output is used as the possiÂ
ble 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 it
finishes, the possible completions are
retrieved from the value of the
CCOOMMPPRREEPPLLYY
array variable.
--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
filename
expansion. It is applied to the list of
possible completions generated by the preÂ
ceding options and arguments, and each comÂ
pletion 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.
--PP _p_r_e_f_i_x
_p_r_e_f_i_x is added at the beginning of each
possible completion 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.
The return value is true unless an invalid option
is supplied, an option other than --pp or --rr is supÂ
plied without a _n_a_m_e argument, 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.
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 enclosing loops,
the last enclosing loop (the ``top-level'' loop) is
resumed. The return value is 0 unless the shell is
not executing a loop when ccoonnttiinnuuee is executed.
ddeeccllaarree [--aaffFFiirrxx] [--pp]
[_n_a_m_e[=_v_a_l_u_e]]
ttyyppeesseett [--aaffFFiirrxx] [--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 variÂ
ables. The --pp option will display the attributes
and values of each _n_a_m_e. When --pp is used, addiÂ
tional options are ignored. The --FF option inhibits
the display of function definitions; only the funcÂ
tion name and attributes are printed. The --FF
option implies --ff. The following options can be
used to restrict output to variables with the specÂ
ified attribute or to give variables attributes:
--aa Each _n_a_m_e is an array variable (see
AArrrraayyss
above).
--ff Use function names only.
--ii The variable is treated as an integer;
arithmetic evaluation (see AARRIITTHHMMEETTIICC
EEVVAALLUUÂÂ
AATTIIOONN )) is performed when the variable is
assigned a value.
--rr Make _n_a_m_es readonly. These names cannot
then be assigned values by subsequent
assignment statements or unset.
--xx Mark _n_a_m_es for export to subsequent commands
via the environment.
Using `+' instead of `-' turns off the attribute
instead, with the exception that ++aa may not be used
to destroy an array variable. When used in a funcÂ
tion, makes each _n_a_m_e local, as with the llooccaall
comÂ
mand. 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 assign a value to an array variÂ
able without using the compound assignment 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
readonly status for a readonly variable, an attempt
is made to turn off array status for an array variÂ
able, or an attempt is made to display a non-exisÂ
tent function with --ff.
ddiirrss [[--ccllppvv]] [[++_n]] [[--_n]]
Without options, displays the list of currently
remembered directories. The default display is on
a single line with directory names separated by
spaces. Directories are added to the list with the
ppuusshhdd command; the ppooppdd command removes
entries
from the list.
++_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.
--cc Clears the directory stack by deleting all
of the entries.
--ll Produces a longer listing; the default listÂ
ing 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, prefixing each entry with its index in
the stack.
The return value is 0 unless an invalid option is
supplied or _n indexes beyond the end of the direcÂ
tory stack.
ddiissoowwnn [--aarr] [--hh] [_j_o_b_s_p_e_c ...]
Without options, each _j_o_b_s_p_e_c is removed from the
table of active jobs. 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 receives a SSIIGGHHUUPP. If no _j_o_b_s_p_e_c
is 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 no
_j_o_b_s_p_e_c is supÂ
plied, the --aa option means to remove or mark all
jobs; the --rr option without a _j_o_b_s_p_e_c
argument
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 always 0. If --nn is
specified, the trailing newline is suppressed. If
the --ee option is given, interpretation of the folÂ
lowing backslash-escaped characters is enabled.
The --EE option disables the interpretation 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 escape characters by default.
eecchhoo does not interpret ---- to mean the end of
options. eecchhoo interprets the following escape
sequences:
\\aa alert (bell)
\\bb backspace
\\cc suppress trailing newline
\\ee an escape character
\\ff form feed
\\nn new line
\\rr carriage return
\\tt horizontal tab
\\vv vertical tab
\\\\ backslash
\\_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)
eennaabbllee [--aaddnnppss] [--ff
_f_i_l_e_n_a_m_e] [_n_a_m_e ...]
Enable and disable builtin shell commands. DisÂ
abling 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 enabled. 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 supÂ
plied, a list of shell builtins is printed. With
no other option arguments, the list consists of all
enabled shell builtins. If --nn is supplied, only
disabled builtins are printed. If --aa is supplied,
the list printed includes all builtins, with an
indication 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 command. This command is then read and exeÂ
cuted 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
supÂ
plied, the shell places a dash at the beginning of
the zeroth arg 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 supÂ
plied, the shell passes _n_a_m_e as the zeroth argument
to the executed command. If _c_o_m_m_a_n_d cannot be exeÂ
cuted for some reason, a non-interactive shell
exits, unless the shell option eexxeeccffaaiill is
enabled,
in which case it returns failure. An interactive
shell returns failure if the file cannot be exeÂ
cuted. If _c_o_m_m_a_n_d is not specified, any redirecÂ
tions 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 environment of subsequently executed comÂ
mands. 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 all names that are
exported in this shell is printed. The --nn option
causes the export property to be removed from the
named variables. 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 supplied with a _n_a_m_e that is not a function.
ffcc [--ee _e_n_a_m_e] [--nnllrr] [_f_i_r_s_t]
[_l_a_s_t]
ffcc --ss [_p_a_t=_r_e_p] [_c_m_d]
Fix Command. In the first form, a range of comÂ
mands from _f_i_r_s_t to _l_a_s_t is selected from the
hisÂ
tory list. _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 hisÂ
tory list, where a negative number is used as an
offset from the current command number). 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. Otherwise, the ediÂ
tor 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 complete, 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. A useful
alias to use with this is ``r=fc -s'', so that typÂ
ing ``r cc'' runs the last command beginning with
``cc'' and typing ``r'' re-executes the last comÂ
mand.
If the first form is used, the return value is 0
unless an invalid 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-executed, unless _c_m_d does not specÂ
ify 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 specify a valid job or
_j_o_b_s_p_e_c
specifies a job that was started without job conÂ
trol.
ggeettooppttss _o_p_t_s_t_r_i_n_g _n_a_m_e
[_a_r_g_s]
ggeettooppttss is used by shell procedures to parse posiÂ
tional parameters. _o_p_t_s_t_r_i_n_g contains the
option
characters to be recognized; if a character is folÂ
lowed by a colon, the option is expected to have an
argument, which should be separated from it by
white space. The colon and question mark characÂ
ters 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 option 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 return value greater than zero.
OOPPTTIINNDD is set to the index of the first non-option
argument, and nnaammee is set to ?.
ggeettooppttss normally parses the positional parameters,
but if more arguments are given in _a_r_g_s,
ggeettooppttss
parses those instead.
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 diagÂ
nostic 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 displayed, even if the first character of _o_p_t_Â
_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 OOPPTTAARRGG 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 [--rr] [--pp _f_i_l_e_n_a_m_e] [--tt]
[_n_a_m_e]
For each _n_a_m_e, the full file name of the command is
determined by searching the directories in $$PPAATTHH
and remembered. 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 file name of the command. The --rr option
causes the shell to forget all remembered locaÂ
tions. 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 pathÂ
name. If no arguments are given, 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 [--ss] [_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. The --ss option restricts the informaÂ
tion displayed to a short usage synopsis. The
return status is 0 unless no command matches _p_a_t_Â
_t_e_r_n.
hhiissttoorryy [[_n]]
hhiissttoorryy --cc
hhiissttoorryy --dd _o_f_f_s_e_t
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 numbers. Lines listed with a ** have been
modified. An argument of _n lists only the last _n
lines. 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.
--aa Append the ``new'' history lines (history
lines entered since the beginning of the
current bbaasshh session) to the history file.
--nn Read the history lines not already read from
the history file into the current history
list. These are lines appended to the hisÂ
tory file since the beginning of the current
bbaasshh session.
--rr Read the contents of the history file and
use them as the current history.
--ww Write the current history to the history
file, overwriting the history file's conÂ
tents.
--pp Perform history substitution on the followÂ
ing _a_r_g_s and display the result on the stanÂ
dard 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 sinÂ
gle entry. The last command in the history
list is removed before the _a_r_g_s are added.
The return value is 0 unless an invalid option is
encountered, an error occurs while reading or writÂ
ing the history file, an invalid _o_f_f_s_e_t is supplied
as an argument to --dd, or the history expansion supÂ
plied 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 following meanings:
--ll List process IDs in addition to the normal
information.
--pp List only the process ID of the job's proÂ
cess group leader.
--nn Display information only about jobs that
have changed status since the user was last
notified of their status.
--rr Restrict output to running jobs.
--ss Restrict output to stopped jobs.
If _j_o_b_s_p_e_c is given, output is restricted to inforÂ
mation 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 correÂ
sponding process group ID, and executes _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 [_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 signal name such as SSIIGGKKIILLLL or a signal
number; _s_i_g_n_u_m is a signal number. If
_s_i_g_s_p_e_c is a
signal name, the name may be given with or without
the SSIIGG prefix. 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 staÂ
tus of a process terminated by a signal. kkiillll
returns true if at least one signal was successÂ
fully sent, or false if an error occurs or an
invalid option is encountered.
lleett _a_r_g [_a_r_g ...]
Each _a_r_g is an arithmetic expression to be evaluÂ
ated (see AARRIITTHHMMEETTIICC
EEVVAALLUUAATTIIOONN). If the last _a_r_g
evaluates to 0, lleett returns 1; 0 is returned otherÂ
wise.
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 function
and its children. 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 funcÂ
tion. 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.
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 following meanÂ
ings:
++_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.
--nn Suppresses the normal change of directory
when removing directories from the stack, so
that only the stack is manipulated.
If the ppooppdd command is successful, a ddiirrss is
perÂ
formed as well, and the return status is 0. ppooppdd
returns false if an invalid option is encountered,
the directory stack is empty, a non-existent direcÂ
tory stack entry is specified, or the directory
change fails.
pprriinnttff _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
outÂ
put under the control of the _f_o_r_m_a_t. 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 outÂ
put, 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) formats,
%%bb
causes pprriinnttff to expand backslash escape sequences
in the corresponding _a_r_g_u_m_e_n_t, and %%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.
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_Â
_m_e_n_t_s than are supplied, the extra format specifiÂ
cations 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] [_d_i_r]
ppuusshhdd [--nn] [+_n] [-_n]
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 arguÂ
ments, exchanges the top two directories and
returns 0, unless the directory stack is empty.
Arguments, if supplied, have the following meanÂ
ings:
++_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.
--nn Suppresses the normal change of directory
when adding directories to the stack, so
that only the stack is manipulated.
_d_i_r Adds _d_i_r to the directory stack at the top,
making it the new current working directory.
If the ppuusshhdd command is successful, a ddiirrss is
perÂ
formed 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 directory
stack is empty, a non-existent directory stack eleÂ
ment 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 symÂ
bolic 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 invalid
option is supplied.
rreeaadd [--eerrss] [--tt _t_i_m_e_o_u_t] [--aa
_a_n_a_m_e] [--pp _p_r_o_m_p_t] [--nn
_n_c_h_a_r_s] [--dd _d_e_l_i_m] [_n_a_m_e ...]
One line is read from the standard input, and the
first word is assigned to the first _n_a_m_e, the secÂ
ond word to the second _n_a_m_e, and so on, with leftÂ
over words and their intervening separators
assigned to the last _n_a_m_e. If there are fewer
words read from the standard input than names, the
remaining names are assigned empty values. The
characters in IIFFSS are used to split the line into
words. The backslash character (\\) may be used to
remove any special meaning for the next character
read and for line continuation. Options, if supÂ
plied, 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 ignored.
--dd _d_e_l_i_m
The first character of _d_e_l_i_m is used to terÂ
minate the input line, rather than newline.
--ee If the standard input is coming from a terÂ
minal, rreeaaddlliinnee (see
RREEAADDLLIINNEE above) is used
to obtain the line.
--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.
--pp _p_r_o_m_p_t
Display _p_r_o_m_p_t on standard error, without a
trailing newline, 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 characÂ
ter. The backslash is considered to be part
of the line. In particular, a backslash-
newline pair may not be used as a line conÂ
tinuation.
--ss Silent mode. If input is coming from a terÂ
minal, characters 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 is not read within
_t_i_m_e_o_u_t seconds. This option has no effect
if rreeaadd is not reading input from the termiÂ
nal or a pipe.
If no _n_a_m_e_s are supplied, the line read is assigned
to the variable RREEPPLLYY. The return code is zero,
unless end-of-file is encountered or rreeaadd times
out.
rreeaaddoonnllyy [--aappff] [_n_a_m_e ...]
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 arrays.
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 --pp option causes output to be disÂ
played in a format that may be reused as input.
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 exit with the return value
specified by _n. If _n is omitted, the return status
is that of the last command executed in the funcÂ
tion body. If 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 staÂ
tus of the script. If used outside a function and
not during execution of a script by .., the return
status is false.
sseett [----aabbeeffhhkkmmnnppttuuvvxxBBCCHHPP]
[--oo _o_p_t_i_o_n] [_a_r_g ...]
Without options, the name and value of each shell
variable are displayed in a format that can be
reused as input. The output is sorted according to
the current locale. When options are specified,
they set or unset shell attributes. Any arguments
remaining after the options are processed are
treated as values for the positional parameters and
are assigned, in order, to $$11, $$22, ......
$$_n.
Options, if specified, have the following meanings:
--aa Automatically mark variables and functions
which are modified or created for export to
the environment of subsequent commands.
--bb Report the status of terminated background
jobs immediately, rather than before the
next primary prompt. This is effective
only when job control is enabled.
--ee Exit immediately if a _s_i_m_p_l_e
_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 an _u_n_t_i_l or
_w_h_i_l_e loop, part of an _i_f statement, part
of a &&&& or |||| list, or if the command's
return value is being inverted via !!. A
trap on EERRRR, if set, is executed before the
shell exits.
--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 interacÂ
tive shells on systems that support it (see
JJOOBB CCOONNTTRROOLL above). Background
processes
run in a separate process group and a line
containing their exit status is printed
upon their completion.
--nn Read commands but do not execute them.
This may be used to check a shell script
for syntax errors. This is ignored 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
followÂ
ing:
aalllleexxppoorrtt
Same as --aa.
bbrraacceeeexxppaanndd
Same as --BB.
eemmaaccss Use an emacs-style command line
editing interface. This is enabled
by default when the shell is interÂ
active, unless the shell is started
with the ----nnooeeddiittiinngg option.
eerrrreexxiitt Same as --ee.
hhaasshhaallll Same as --hh.
hhiisstteexxppaanndd
Same as --HH.
hhiissttoorryy Enable command history, as
described above under HHIISSTTOORRYY.
This option is on by default in
interactive shells.
iiggnnoorreeeeooff
The effect is as if the shell comÂ
mand ``IGNOREEOF=10'' had been exeÂ
cuted (see SShheellll
VVaarriiaabblleess 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.
ppoossiixx Change the behavior of bbaasshh
where
the default operation differs from
the POSIX 1003.2 standard to match
the standard (_p_o_s_i_x _m_o_d_e).
pprriivviilleeggeedd
Same as --pp.
vveerrbboossee Same as --vv.
vvii Use a vi-style command line editing
interface.
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 curÂ
rent 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
variable, if
it appears in the environment, is 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 supÂ
plied, these actions are taken and the
effective user id is set to the real user
id. If the --pp option is supplied 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 comÂ
mand.
--uu Treat unset variables as an error when perÂ
forming parameter expansion. If expansion
is attempted on an unset variable, 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, disÂ
play the expanded value of PPSS44, followed by
the command and its expanded arguments.
--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 redirecÂ
tion operator >>|| instead of >>.
--HH Enable !! style history substitution. This
option is on by default when the shell is
interactive.
--PP If set, the shell does not follow 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 logÂ
ical chain of directories when performing
commands which change the current direcÂ
tory.
---- If no arguments follow this option, then
the positional parameters are unset. OthÂ
erwise, the positional parameters 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 posiÂ
tional parameters. The --xx and --vv options
are turned off. If there are no _a_r_gs, the
positional parameters remain unchanged.
The options are off by default unless otherwise
noted. Using + rather than - causes these options
to be turned off. The options can also be speciÂ
fied as arguments to an invocation of the shell.
The current set of options may be found in $$--. The
return status is always true unless an invalid
option is encountered.
sshhiifftt [_n]
The positional parameters from _n+1 ... are renamed
to $$11 ........ Parameters represented by the numbers
$$## down to $$##-_n+1 are unset. _n must be a non-negaÂ
tive number less than or equal to $$##. If _n is 0,
no parameters are changed. If _n is not given, it
is assumed to be 1. If _n is greater than $$##, the
positional parameters are not changed. The return
status is greater than zero if _n is greater than $$##
or less than zero; otherwise 0.
sshhoopptt [--ppqqssuu] [--oo] [_o_p_t_n_a_m_e ...]
Toggle the values of variables controlling optional
shell behavior. With no options, or with the --pp
option, a list of all settable options is disÂ
played, with an indication of whether or not each
is set. The --pp option causes output to be disÂ
played in a form that may be reused as input.
Other options 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 multiple _o_p_t_n_a_m_e arguÂ
ments are given with --qq, the return status
is zero if all _o_p_t_n_a_m_e_s are enabled;
non-
zero otherwise.
--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 arguÂ
ments, the display is limited to those options
which are set or unset, respectively. Unless othÂ
erwise 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 options, 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:
ccddaabbllee__vvaarrss
If set, an argument to the ccdd builtin comÂ
mand 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 component in a ccdd command will be
corrected. The errors checked for are
transposed characters, a missing character,
and one character too many. If a correcÂ
tion is found, the corrected file name is
printed, and the command proceeds. This
option is only used by interactive shells.
cchheecckkhhaasshh
If set, bbaasshh checks that a command found in
the hash table exists before trying to exeÂ
cute it. If a hashed command no longer
exists, a normal path search is performed.
cchheecckkwwiinnssiizzee
If set, bbaasshh checks the window size after
each command and, if necessary, updates the
values of LLIINNEESS and CCOOLLUUMMNNSS.
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.
ddoottgglloobb If set, bbaasshh includes filenames
beginning
with a `.' in the results of pathname
expansion.
eexxeeccffaaiill
If set, a non-interactive shell will not
exit if it cannot execute the file speciÂ
fied 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 interactive shells.
eexxttgglloobb If set, the extended pattern matching feaÂ
tures described above under PPaatthhnnaammee
EExxppaannÂÂ
ssiioonn are enabled.
hhiissttaappppeenndd
If set, the history list is appended to the
file named by the value of the
HHIISSTTFFIILLEE
variable when the shell exits, 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 history substitution are not
immediately passed to the shell parser.
Instead, the resulting line is loaded into
the rreeaaddlliinnee editing buffer, allowing
furÂ
ther modification.
hhoossttccoommpplleettee
If set, and rreeaaddlliinnee is being used,
bbaasshh
will attempt to perform hostname completion
when a word containing a @@ is being comÂ
pleted (see CCoommpplleettiinngg under
RREEAADDLLIINNEE
above). This is enabled by default.
hhuuppoonneexxiitt
If set, bbaasshh will send SSIIGGHHUUPP to all
jobs
when an interactive login shell exits.
iinntteerraaccttiivvee__ccoommmmeennttss
If set, allow a word beginning with ## to
cause that word and all remaining characÂ
ters on that line to be ignored in an
interactive shell (see CCOOMMMMEENNTTSS
above).
This option is enabled by default.
lliitthhiisstt If set, and the ccmmddhhiisstt
option is enabled,
multi-line commands are saved to the hisÂ
tory with embedded newlines rather than
using semicolon separators where possible.
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 displayed.
nnoo__eemmppttyy__ccmmdd__ccoommpplleettiioonn
If set, and rreeaaddlliinnee is being used,
bbaasshh
will not attempt 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).
nnuullllgglloobb
If set, bbaasshh allows patterns which match no
files (see PPaatthhnnaammee
EExxppaannssiioonn above) to
expand to a null string, rather than themÂ
selves.
pprrooggccoommpp
If set, the programmable completion faciliÂ
ties (see PPrrooggrraammmmaabbllee
CCoommpplleettiioonn above)
are enabled. This option is enabled by
default.
pprroommppttvvaarrss
If set, prompt strings undergo variable and
parameter expansion 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 restricted 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
discover 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 parameters.
ssoouurrcceeppaatthh
If set, the ssoouurrccee (..) builtin uses the
value of PPAATTHH to find the directory conÂ
taining the file supplied as an argument.
This option is enabled by default.
xxppgg__eecchhoo
If set, the eecchhoo builtin expands backslash-
escape sequences by default.
ssuussppeenndd [--ff]
Suspend the execution of this shell until it
receives a SSIIGGCCOONNTT signal. The --ff option says
not
to complain if this is a login shell; just suspend
anyway. The return status is 0 unless the shell is
a login shell and --ff is not supplied, or if job
control is not enabled.
tteesstt _e_x_p_r
[[ _e_x_p_r ]]
Return a status of 0 or 1 depending on the evaluaÂ
tion of the conditional expression _e_x_p_r. Each
operator and operand must be a separate argument.
Expressions are composed of the primaries described
above under CCOONNDDIITTIIOONNAALL
EEXXPPRREESSSSIIOONNSS.
Expressions may be combined using the following
operators, listed in decreasing order of preceÂ
dence.
!! _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 operaÂ
tors.
_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 argument is one of
the unary conditional operators listed above
under CCOONNDDIITTIIOONNAALL
EEXXPPRREESSSSIIOONNSS, the expresÂ
sion is true if the unary test is true. If
the first argument is not a valid unary conÂ
ditional operator, the expression is false.
3 arguments
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. 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 arguÂ
ment. Otherwise, the expression is false.
The --aa and --oo operators are considered
binary operators in this case.
4 arguments
If the first argument is !!, the result is
the negation of the three-argument expresÂ
sion composed of the remaining arguments.
Otherwise, the expression is parsed and
evaluated 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.
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 receives signal(s) _s_i_g_s_p_e_c. If _a_r_g is
absent
or --, all specified signals are reset to their
original values (the values they had upon entrance
to the shell). If _a_r_g is the null string the sigÂ
nal 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 disÂ
played. If no arguments are supplied or if only --pp
is given, ttrraapp prints the list of commands associÂ
ated with each signal number. 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. If a _s_i_g_s_p_e_c is EEXXIITT (0)
the comÂ
mand _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 executed after
every _s_i_m_p_l_e _c_o_m_m_a_n_d (see
SSHHEELLLL GGRRAAMMMMAARR above). If
a _s_i_g_s_p_e_c is EERRRR, the command _a_r_g is
executed whenÂ
ever a simple command has a non-zero exit status.
The EERRRR trap is not executed if the failed command
is part of an _u_n_t_i_l or _w_h_i_l_e loop, part of
an _i_f
statement, part of a &&&& or |||| list, or if the comÂ
mand's return value is being inverted via !!. The
--ll option causes the shell to print a list of sigÂ
nal names and their corresponding numbers. Signals
ignored upon entry to the shell cannot be trapped
or reset. Trapped signals are reset to their origÂ
inal values in a child process when it is created.
The return status is false if any _s_i_g_s_p_e_c is
invalid; otherwise ttrraapp returns true.
ttyyppee [--aattpp] _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 returned. 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 return _f_i_l_e. If a command is hashed, --pp prints
the hashed value, not necessarily the file that
appears first in PPAATTHH. If the --aa option is used,
ttyyppee prints all of the places that contain an exeÂ
cutable 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 conÂ
sulted when using --aa. ttyyppee returns true if any of
the arguments are found, false if none are found.
uulliimmiitt [--SSHHaaccddffllmmnnppssttuuvv
[_l_i_m_i_t]]
Provides control over the resources available to
the shell and to processes started by it, on sysÂ
tems 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 once it is set; a soft limit may be
increased up to the value of the hard limit. If
neither --HH nor --SS is specified, 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, respectively. 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 are printed before the
value. Other options are interpreted as follows:
--aa All current limits are reported
--cc The maximum size of core files created
--dd The maximum size of a process's data segment
--ff The maximum size of files created by the
shell
--ll The maximum size that may be locked into
memory
--mm The maximum resident set size
--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)
--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 availÂ
able to the shell
If _l_i_m_i_t is given, it is the new value of the specÂ
ified resource (the --aa option is display only). If
no option is given, then --ff is assumed. Values are
in 1024-byte increments, except for --tt, which is in
seconds, --pp, which is in units of 512-byte blocks,
and --nn and --uu, which are unscaled values. The
return status is 0 unless an invalid option or
argument is supplied, or an error occurs while setÂ
ting 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 symÂ
bolic 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 symbolic 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 supÂ
plied _n_a_m_e is not a defined alias.
uunnsseett [-ffvv] [_n_a_m_e ...]
For each _n_a_m_e, remove the corresponding variable or
function. If no options are supplied, or the --vv
option is given, each _n_a_m_e refers to a shell variÂ
able. Read-only variables may not be unset. If --ff
is specifed, each _n_a_m_e refers to a shell function,
and the function definition is removed. Each unset
variable or function is removed from the environÂ
ment passed to subsequent commands. If any of RRAANNÂÂ
DDOOMM, SSEECCOONNDDSS, LLIINNEENNOO,
HHIISSTTCCMMDD, FFUUNNCCNNAAMMEE, GGRROOUUPPSS, or
DDIIRRSSTTAACCKK are unset, they lose their special
properÂ
ties, even if they are subsequently reset. The
exit status is true unless a _n_a_m_e does not exist or
is readonly.
wwaaiitt [_n]
Wait for the specified process and return its terÂ
mination status. _n may be a process ID or a job
specification; if a job spec is given, all proÂ
cesses in that job's pipeline are waited for. If _n
is not given, all currently active child processes
are waited for, and the return status is zero. If
_n 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.
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 identiÂ
cally to bbaasshh with the exception that the following are
disallowed or not performed:
· changing directories with ccdd
· setting or unsetting the values of SSHHEELLLL,
PPAATTHH,
EENNVV, or BBAASSHH__EENNVV
· specifying command names containing //
· specifying a file name containing a // as an arguÂ
ment to the .. builtin command
· Specifying a filename containing a slash as an
argument to the --pp option to the hhaasshh builtin comÂ
mand
· importing function definitions from the shell enviÂ
ronment at startup
· parsing the value of SSHHEELLLLOOPPTTSS from the shell
enviÂ
ronment at startup
· redirecting output using the >, >|, <>, >&, &>, and
>> redirection operators
· using the eexxeecc builtin command to replace the shell
with another command
· adding or deleting builtin commands with the --ff and
--dd options to the eennaabbllee builtin command
· specifying the --pp option to the ccoommmmaanndd
builtin
command
· 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 exeÂ
cuted (see CCOOMMMMAANNDD 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
_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
address@hidden
Chet Ramey, Case Western Reserve University
address@hidden
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 that you
have.
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_-
address@hidden 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 address@hidden
BBUUGGSS
It's too big and too slow.
There are some subtle differences between bbaasshh and tradiÂ
tional versions of sshh, mostly because of the PPOOSSIIXX speciÂ
fication.
Aliases are confusing in some uses.
Shell builtin commands and functions are not stopÂ
pable/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 immediÂ
ately executes the next command in the sequence. It sufÂ
fices to place the sequence of commands between parentheÂ
ses to force it into a subshell, which may be stopped as a
unit.
Commands inside of $$((...)) command substitution are not
parsed until substitution is attempted. This will delay
error reporting until some time after the command is
entered.
Array variables may not (yet) be exported.
GNU Bash-2.05a 2001 November 13 BASH(1)