Table of Contents
bash - GNU Bourne-Again SHell
bash [options] [file]
Bash is Copyright (C) 1989, 1991 by the Free Software Foundation,
Inc.
Bash is an sh-compatible command
language interpreter that executes commands read from the standard
input or from a file. Bash also incorporates
useful features from the Korn and C shells
(ksh and csh).
Bash is ultimately intended to be a conformant
implementation of the IEEE Posix Shell and Tools specification
(IEEE Working Group 1003.2).
In addition to the single-character shell options documented in the
description of the set builtin command,
bash interprets the following flags when it is
invoked:
-
-c string
-
If the -c flag is present, then commands are
read from string. If there are arguments after the
string, they are assigned to the positional
parameters, starting with $0.
-
-i
-
If the -i flag is present, the shell is
interactive.
-
-s
-
If the -s flag 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.
-
-
-
A single - 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 an argument of
-.
Bash also interprets a number of multi-character
options. These options must appear on the command line before the
single-character options to be recognized.
-
-norc
-
Do not read and execute the personal initialization file
~/.bashrc if the shell is interactive. This option is
on by default if the shell is invoked as sh.
-
-noprofile
-
Do not read either the system-wide startup file
/etc/profile or any of the personal initialization files
~/.bash_profile, ~/.bash_login, or
~/.profile. By default, bash normally
reads these files when it is invoked as a login shell (see
INVOCATION below).
-
-rcfile file
-
Execute commands from file instead of the standard
personal initialization file ~/.bashrc, if the shell
is interactive (see INVOCATION below).
-
-version
-
Show the version number of this instance of
bash when starting.
-
-quiet
-
Do not be verbose when starting up (do not show the shell
version or any other information). This is the default.
-
-login
-
Make bash act as if it had been invoked as a
login shell.
-
-nobraceexpansion
-
Do not perform curly brace expansion (see Brace
Expansion below).
-
-nolineediting
-
Do not use the GNU readline library to read command
lines if interactive.
-
-posix
-
Change the behavior of bash where the default operation differs
from the Posix 1003.2 standard to match the standard
If arguments remain after option processing, and neither the
-c nor the -s option has been
supplied, the first argument is assumed to be the name of a file
containing shell commands. If bash is invoked in
this fashion, $0 is set to the name of the file,
and the positional parameters are set to the remaining arguments.
Bash reads and executes commands from this file,
then exits. Bash's exit status is the exit status
of the last command executed in the script.
-
blank
-
A space or tab.
-
word
-
A sequence of characters considered as a single unit by the
shell. Also known as a token.
-
name
-
A word consisting only of alphanumeric characters and
underscores, and beginning with an alphabetic character or an
underscore. Also referred to as an identifier.
-
metacharacter
-
A character that, when unquoted, separates words. One of the
following:
| & ; ( ) < > space tab
-
control operator
-
A token that performs a control function. It is one of
the following symbols:
|| & && ; ;; ( ) | <newline>
Reserved words 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 command (see
SHELL GRAMMAR below) or the third word of a
case or for command:
! case do done elif else esac fi for function if in select then
until while { }
A simple command is a sequence of optional variable
assignments followed by blank-separated words and
redirections, and terminated by a control operator. The
first word specifies the command to be executed. The remaining
words are passed as arguments to the invoked command.
The return value of a simple command is its exit status,
or 128+n if the command is terminated by signal
n.
A pipeline is a sequence of one or more commands
separated by the character |. The format for a
pipeline is:
[ ! ] command [ | command2
... ]
The standard output of command is connected to the
standard input of command2. This connection is performed
before any redirections specified by the command (see
REDIRECTION below).
If the reserved word ! precedes a pipeline, the
exit status 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.
Each command in a pipeline is executed as a separate process
(i.e., in a subshell).
A list is a sequence of one or more pipelines separated
by one of the operators ;,
&, &&, or
, and terminated by one of ;,
&, or <newline>.
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
background in a subshell. 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
command && command2
command2 is executed if, and only if, command
returns an exit status of zero.
An OR list has the form
command command2
command2 is executed if and only if command
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.
A compound command is one of the following:
-
(list)
-
list is executed in a subshell. Variable assignments
and builtin commands that affect the shell's environment do not
remain in effect after the command completes. The return status
is the exit status of list.
-
{ list; }
-
list is simply executed in the current shell
environment. This is known as a group command. The
return status is the exit status of list.
-
for name [ in
word; ] do list ;
done
-
The list of words following in is expanded,
generating a list of items. The variable name is set
to each element of this list in turn, and list is
executed each time. If the in word is
omitted, the for command executes
list once for each positional parameter that is set
(see PARAMETERS below).
-
select name [ in
word; ] do list ;
done
-
The list of words following in is expanded,
generating a list of items. The set of expanded words is
printed on the standard error, each preceded by a number. If
the in word is omitted, the
positional parameters are printed (see
PARAMETERS below). The PS3
prompt is then displayed and a line read from the standard
input. If the line consists of the number corresponding to one
of the displayed words, then the value of name 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 name to be set to null. The
line read is saved in the variable REPLY. The
list is executed after each selection until a
break or return command is
executed. The exit status of select is the
exit status of the last command executed in list, or
zero if no commands were executed.
-
case word in [
pattern [ | pattern ]
-
A case command first expands word,
and tries to match it against each pattern in turn,
using the same matching rules as for pathname expansion (see
Pathname Expansion below). When a match is
found, the corresponding list is executed. After the
first match, no subsequent matches are attempted. The exit
status is zero if no patterns are matches. Otherwise, it is the
exit status of the last command executed in list.
-
if list then
list
-
[ elif list then
list ] ... [ else list ]
fi The if list is
executed. If its exit status is zero, the then
list is executed. Otherwise, each
elif list is executed in turn, and if
its exit status is zero, the corresponding
then list is executed and the command
completes. Otherwise, the else list
is executed, if present. The exit status is the exit status of
the last command executed, or zero if no condition tested true.
-
while list do
list done
-
until list do
list done
-
The while command continuously executes the
do list as long as the last command
in list returns an exit status of zero. The
until command is identical to the
while command, except that the test is
negated; the do list is executed as
long as the last command in list returns a non-zero
exit status. The exit status of the while and
until commands is the exit status of the last
do list command executed, or zero if
none was executed.
-
[ function ] name () { list;
}
-
This defines a function named name. The body
of the function is the list of commands between { and
}. This list is executed whenever name is specified 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
FUNCTIONS below.)
In a non-interactive shell, or an interactive shell in which the
-o interactive-comments option to the
set builtin is enabled, a word beginning with
# causes that word and all remaining characters on
that line to be ignored. An interactive shell without the
-o interactive-comments option enabled does not
allow comments.
Quoting is used to remove the special meaning of certain
characters or words to the shell. Quoting can be used to disable
special treatment for special characters, to prevent reserved words
from being recognized as such, and to prevent parameter expansion.
Each of the metacharacters listed above under
DEFINITIONS has special meaning to the shell and
must be quoted if they are to represent themselves. There are
three quoting mechanisms: the escape character, single
quotes, and double quotes.
A non-quoted backslash (\) is the escape
character. 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 quoted, the \<newline> is
treated as a line continuation (that is, it is effectively
ignored).
Enclosing characters in single quotes preserves the literal value
of each character within the quotes. A single quote may not occur
between single quotes, even when preceded by a backslash.
Enclosing characters in double quotes preserves the literal value
of all characters within the quotes, with the exception of
$, `, and \.
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
<newline>. A double quote may be quoted
within double quotes by preceding it with a backslash.
The special parameters * and @
have special meaning when in double quotes (see
PARAMETERS below).
A parameter is an entity that stores values, somewhat like
a variable in a conventional programming language. It can be a
name, a number, or one of the special characters listed
below under Special Parameters. For the shell's
purposes, a variable is a parameter denoted by a
name.
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 unset builtin command (see
SHELL BUILTIN COMMANDS below).
A variable may be assigned to by a statement of the form
name=[value]
If value is not given, the variable is assigned the null
string. All values undergo tilde expansion, parameter
and variable expansion, command substitution, arithmetic
expansion, and quote removal. If the variable has its
-i attribute set (see declare
below in SHELL BUILTIN COMMANDS) then
value is subject to arithmetic expansion even if the
$[...] syntax does not appear. Word splitting is not performed,
with the exception of "$@" as explained below
under Special Parameters. Pathname expansion is
not performed.
A positional parameter 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 set 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 FUNCTIONS
below).
When a positional parameter consisting of more than a single
digit is expanded, it must be enclosed in braces (see
EXPANSION below).
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 IFS special variable.
That is, ``$*'' is equivalent to
``$1c$2c...'',
where c is the first character of the value of the
IFS variable. If IFS is null
or unset, the parameters are separated by spaces.
-
@
-
Expands to the positional parameters, starting from one. When
the expansion occurs within double quotes, each parameter
expands as a separate word. That is, `` $@''
is equivalent to ``$1''
``$2'' ... When there are no positional
parameters, ``$@'' and $@
expand to nothing (i.e., they are removed).
-
#
-
Expands to the number of positional parameters in decimal.
-
?
-
Expands to the status of the most recently executed foreground
pipeline.
-
-
-
Expands to the current option flags as specified upon
invocation, by the set builtin command, or
those set by the shell itself (such as the -i
flag).
-
$
-
Expands to the process ID of the shell. In a () subshell, it
expands to the process ID of the current shell, not the
subshell.
-
!
-
Expands to the process ID of the most recently executed
background (asynchronous) command.
- Expands to the name of the shell or shell script. This is
set at shell initialization. If bash is
invoked with a file of commands, $0 is set
to the name of that file. If bash is started
with the -c option, then $0
is set to the first argument after the string to be executed,
if one is present. Otherwise, it is set to the pathname used
to invoke bash, as given by argument zero.
-
_
-
Expands to the last argument to the previous command, after
expansion. Also set to the full pathname of each command
executed and placed in the environment exported to that
command.
The following variables are set by the shell:
-
PPID
-
The process ID of the shell's parent.
-
PWD
-
The current working directory as set by the cd
command.
-
OLDPWD
-
The previous working directory as set by the
cd command.
-
REPLY
-
Set to the line of input read by the read
builtin command when no arguments are supplied.
-
UID
-
Expands to the user ID of the current user, initialized at
shell startup.
-
EUID
-
Expands to the effective user ID of the current user,
initialized at shell startup.
-
BASH
-
Expands to the full pathname used to invoke this instance of
bash.
-
BASH_VERSION
-
Expands to the version number of this instance of
bash.
-
SHLVL
-
Incremented by one each time an instance of
bash is started.
-
RANDOM
-
Each time this parameter is referenced, a random integer is
generated. The sequence of random numbers may be initialized by
assigning a value to RANDOM. If
RANDOM is unset, it loses its special
properties, even if it is subsequently reset.
-
SECONDS
-
Each time this parameter is referenced, the number of seconds
since shell invocation is returned. If a value is assigned to
SECONDS, the value returned upon subsequent
references is the number of seconds since the assignment plus
the value assigned. If SECONDS is unset, it
loses its special properties, even if it is subsequently reset.
-
LINENO
-
Each time this parameter is referenced, the shell substitutes a
decimal number representing the current sequential line number
(starting with 1) within a script or function. When not in a
script or function, the value substituted is not guaranteed to
be meaningful. When in a function, the value is not the number
of the source line that the command appears on (that
information has been lost by the time the function is
executed), but is an approximation of the number of
simple commands executed in the current function. If
LINENO is unset, it loses its special
properties, even if it is subsequently reset.
-
HISTCMD
-
The history number, or index in the history list, of the
current command. If HISTCMD is unset, it loses
its special properties, even if it is subsequently reset.
-
OPTARG
-
The value of the last option argument processed by the
getopts builtin command (see SHELL
BUILTIN COMMANDS below).
-
OPTIND
-
The index of the next argument to be processed by the
getopts builtin command (see SHELL
BUILTIN COMMANDS below).
-
HOSTTYPE
-
Automatically set to a string that uniquely describes the type
of machine on which bash is executing. The
default is system-dependent.
-
OSTYPE
-
Automatically set to a string that describes the operating
system on which bash is executing. The default
is system-dependent.
The following variables are used by the shell. In some cases,
bash assigns a default value to a variable;
these cases are noted below.
-
IFS
-
The Internal Field Separator that is used for word
splitting after expansion and to split lines into words with
the read builtin command. The default value is
``<space><tab><newline>''.
-
PATH
-
The search path for commands. It is a colon-separated list of
directories in which the shell looks for commands (see
COMMAND EXECUTION below). The default path is
system-dependent, and is set by the administrator who installs
bash. A common value is
``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin:.''.
-
HOME
-
The home directory of the current user; the default argument
for the cd builtin command.
-
CDPATH
-
The search path for the cd command. This is a
colon-separated list of directories in which the shell looks
for destination directories specified by the
cd command. A sample value is ``.:~:/usr''.
-
ENV
-
If this parameter is set when bash is
executing a shell script, its value is interpreted as a
filename containing commands to initialize the shell, as in
.bashrc. The value of ENV is
subjected to parameter expansion, command substitution, and
arithmetic expansion before being interpreted as a pathname.
PATH is not used to search for the resultant
pathname.
-
MAIL
-
If this parameter is set to a filename and the
MAILPATH variable is not set,
bash informs the user of the arrival of mail
in the specified file.
-
MAILCHECK
-
Specifies how often (in seconds) bash checks
for mail. The default is 60 seconds. When it is time to check
for mail, the shell does so before prompting. If this variable
is unset, the shell disables mail checking.
-
MAILPATH
-
A colon-separated list of pathnames to be checked for mail. The
message to be printed may be specified by separating the
pathname from the message with a `?'. $_ stands for the name of
the current mailfile. Example:
MAILPATH='/usr/spool/mail/bfox?"You have
mail":~/shell-mail?"$_ has mail!"'
Bash supplies a default value for this variable,
but the location of the user mail files that it uses is system
dependent (e.g., /usr/spool/mail/$USER).
-
MAIL_WARNING
-
If set, and a file that bash is checking for
mail has been accessed since the last time it was checked, the
message ``The mail in mailfile has been read'' is
printed.
-
PS1
-
The value of this parameter is expanded (see
PROMPTING below) and used as the primary
prompt string. The default value is ``bash\$
''.
-
PS2
-
The value of this parameter is expanded and used as the
secondary prompt string. The default is ``>
''.
-
PS3
-
The value of this parameter is used as the prompt for the
select command (see SHELL GRAMMAR
above).
-
PS4
-
The value of this parameter is expanded and the value is
printed before each command bash displays
during an execution trace. The first character of
PS4 is replicated multiple times, as
necessary, to indicate multiple levels of indirection. The
default is ``+ ''.
-
HISTSIZE
-
The number of commands to remember in the command history (see
HISTORY below). The default value is 500.
-
HISTFILE
-
The name of the file in which command history is saved. (See
HISTORY below.) The default value is
~/.bash_history. If unset, the command history is not
saved when an interactive shell exits.
-
HISTFILESIZE
-
The maximum number of lines contained in the history 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.
-
OPTERR
-
If set to the value 1, bash displays error
messages generated by the getopts builtin
command (see SHELL BUILTIN COMMANDS below).
OPTERR is initialized to 1 each time the shell
is invoked or a shell script is executed.
-
PROMPT_COMMAND
-
If set, the value is executed as a command prior to issuing
each primary prompt.
-
IGNOREEOF
-
Controls the action of the shell on receipt of an
EOF character as the sole input. If set, the
value is the number of consecutive EOF
characters typed as the first characters on an input line
before bash 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, EOF
signifies the end of input to the shell. This is only in effect
for interactive shells.
-
TMOUT
-
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. Bash terminates after waiting
for that number of seconds if input does not arrive.
-
FCEDIT
-
The default editor for the fc builtin command.
-
FIGNORE
-
A colon-separated list of suffixes to ignore when performing
filename completion (see READLINE below). A
filename whose suffix matches one of the entries in
FIGNORE is excluded from the list of matched
filenames. A sample value is ``.o:~''.
-
INPUTRC
-
The filename for the readline startup file, overriding the
default of ~/.inputrc (see READLINE
below).
-
notify
-
If set, bash reports terminated background
jobs immediately, rather than waiting until before printing the
next primary prompt (see also the -b option to
the set builtin command).
-
history_control
-
HISTCONTROL
-
If set to a value of ignorespace, lines which begin
with a space character are not entered on the
history list. If set to a value of ignoredups, lines
matching the last history line are not entered. A value of
ignoreboth 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.
-
command_oriented_history
-
If set, bash attempts to save all lines of a
multiple-line command in the same history entry. This allows
easy re-editing of multi-line commands.
-
glob_dot_filenames
-
If set, bash includes filenames beginning with
a `.' in the results of pathname expansion.
-
allow_null_glob_expansion
-
If set, bash allows pathname patterns which
match no files (see Pathname Expansion below)
to expand to a null string, rather than themselves.
-
histchars
-
The two or three characters which control history expansion and
tokenization (see HISTORY EXPANSION below).
The first character is the history expansion
character, that is, the character which signals the start
of a history expansion, normally `!'. The
second character is the quick substitution character,
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 signifies 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 necessarily cause the
shell parser to treat the rest of the line as a comment.
-
nolinks
-
If set, the shell does not follow symbolic links when executing
commands that change the current working directory. It uses the
physical directory structure instead. By default,
bash follows the logical chain of directories
when performing commands which change the current directory,
such as cd. See also the description of the
-P option to the set builtin
( SHELL BUILTIN COMMANDS below).
-
hostname_completion_file
-
HOSTFILE
-
Contains the name of a file in the same format as
/etc/hosts that should be read when the shell needs to
complete a hostname. The file may be changed interactively; the
next time hostname completion is attempted
bash adds the contents of the new file to the
already existing database.
-
noclobber
-
If set, bash does not overwrite an existing
file with the >,
>&, and <>
redirection operators. This variable may be overridden when
creating output files by using the redirection operator
>| instead of > (see
also the -C option to the set
builtin command).
-
auto_resume
-
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
name of a stopped job, in this context, is the command
line used to start it. If set to the value exact, the
string supplied must match the name of a stopped job exactly;
if set to substring, the string supplied needs to
match a substring of the name of a stopped job. The
substring value provides functionality analogous to
the %? job id (see JOB
CONTROL 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
id.
-
no_exit_on_failed_exec
-
If this variable exists, a non-interactive shell will not exit
if it cannot execute the file specified in the
exec builtin command. An interactive shell
does not exit if exec fails.
-
cdable_vars
-
If this is set, an argument to the cd builtin
command that is not a directory is assumed to be the name of a
variable whose value is the directory to change to.
Expansion is performed on the command line after it has been split
into words. There are seven kinds of expansion performed: brace
expansion, tilde expansion, parameter and
variable expansion, command substitution,
arithmetic expansion, word splitting, and
pathname expansion.
The order of expansions is: brace expansion, tilde expansion,
parameter, variable, command, and arithmetic 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: process substitution.
Only brace expansion, word splitting, and pathname expansion can
change the number of words of the expansion; other expansions
expand a single word to a single word. The single exception to
this is the expansion of ``$@'' as explained
above (see PARAMETERS).
Brace expansion is a mechanism by which arbitrary
strings may be generated. This mechanism is similar to
pathname expansion, but the filenames generated need not
exist. Patterns to be brace expanded take the form of an optional
preamble, followed by a series of comma-separated
strings between a pair of braces, followed by an optional
postamble. The preamble is prepended to each string
contained within the braces, and the postamble 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 preserved in the
result. It is strictly textual. Bash 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.
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
traditional versions of sh, the Bourne shell.
sh does not treat opening or closing braces
specially when they appear as part of a word, and preserves them
in the output. Bash removes braces from words as
a consequence of brace expansion. For example, a word entered to
sh as file{1,2} appears identically in
the output. The same word is output as file1 file2 after
expansion by bash. If strict compatibility with
sh is desired, start bash with
the -nobraceexpansion flag (see
OPTIONS above) or disable brace expansion with
the +o braceexpand option to the
set command (see SHELL BUILTIN
COMMANDS below).
If a word begins with a tilde character (`~'),
all of the characters preceding the first slash (or all
characters, if there is no slash) are treated as a possible
login name. If this login name is the null
string, the tilde is replaced with the value of the parameter
HOME. If HOME is unset, the
home directory of the user executing the shell is substituted
instead.
If a `+' follows the tilde, the value of PWD
replaces the tilde and `+'. If a `-' follows, the value of
OLDPWD is substituted. If the value following
the tilde is a valid login name, the tilde and login
name are replaced with the home directory associated with
that name. If the name is invalid, or the tilde expansion fails,
the word is unchanged.
Each variable assignment is checked for unquoted instances of
tildes following a : or =. In
these cases, tilde substitution is also performed. Consequently,
one may use pathnames with tildes in assignments to
PATH, MAILPATH, and
CDPATH, and the shell assigns the expanded
value.
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.
-
${parameter}
-
The value of parameter is substituted. The braces are
required when parameter is a positional parameter with
more than one digit, or when parameter is followed by
a character which is not to be interpreted as part of its name.
In each of the cases below, word is subject to tilde
expansion, parameter expansion, command substitution, and
arithmetic expansion. Bash tests for a parameter
that is unset or null; omitting the colon results in a test only
for a parameter that is unset.
-
${parameter:-word}
-
Use Default Values. If parameter is
unset or null, the expansion of word is substituted.
Otherwise, the value of parameter is substituted.
-
${parameter:=word}
-
Assign Default Values. If parameter
is unset or null, the expansion of word is assigned to
parameter. The value of parameter is then
substituted. Positional parameters and special parameters may
not be assigned to in this way.
-
${parameter:?word}
-
Display Error if Null or Unset. If
parameter is null or unset, the expansion of
word (or a message to that effect if word is
not present) is written to the standard error and the shell, if
it is not interactive, exits. Otherwise, the value of
parameter is substituted.
-
${parameter:+word}
-
Use Alternate Value. If parameter is
null or unset, nothing is substituted, otherwise the expansion
of word is substituted.
-
${#parameter}
-
The length in characters of the value of parameter is
substituted. If parameter is * or
@, the length substituted is the length of
* expanded within double quotes.
-
${parameter#word}
-
${parameter##word}
-
The word is expanded to produce a pattern just as in
pathname expansion. If the pattern matches the beginning of the
value of parameter, then the expansion is the value of
parameter with the shortest matching pattern deleted
(the ``#'' case) or the longest matching
pattern deleted (the ``##'' case).
-
${parameter%word}
-
${parameter%%word}
-
The word is expanded to produce a pattern just as in
pathname expansion. If the pattern matches a trailing portion
of the value of parameter, then the expansion is the
value of parameter with the shortest matching pattern
deleted (the ``%'' case) or the longest
matching pattern deleted (the ``%%'' case).
Command substitution allows the output of a command to
replace the command name. There are two forms:
$(command )
or
`command`
Bash performs the expansion by executing
command and replacing the command substitution with the
standard output of the command, with any trailing newlines
deleted.
When the old-style backquote form of substitution is used,
backslash retains its literal meaning except when followed by
$, `, or \.
When using the $(command ) form, all characters between
the parentheses make up the command; none are treated specially.
Command substitutions may be nested. To nest when using the old
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.
Arithmetic expansion allows the evaluation of an arithmetic
expression and the substitution of the result. There are two
formats for arithmetic expansion:
$[expression]
$((expression))
The expression is treated as if it were within double
quotes, but a double quote inside the braces or parentheses is
not treated specially. All tokens in the expression undergo
parameter expansion, command substitution, and quote removal.
Arithmetic substitutions may be nested.
The evaluation is performed according to the rules listed below
under ARITHMETIC EVALUATION. If
expression is invalid, bash prints a
message indicating failure and no substitution occurs.
Process substitution is supported on systems that
support named pipes (FIFOs) or the
/dev/fd method of naming open files. It takes
the form of <(list)
or >(list). The
process list is run with its input or output connected
to a FIFO or some file in /dev/fd. The
name of this file is passed as an argument to the current command
as the result of the expansion. If the
>(list) form is
used, writing to the file will provide input for list.
If the <(list) form
is used, the file passed as an argument should be read to obtain
the output of list.
On systems that support it, process substitution is
performed simultaneously with parameter and variable
expansion, command substitution, and arithmetic
expansion.
The shell scans the results of parameter expansion, command
substitution, and arithmetic expansion that did not occur within
double quotes for word splitting.
The shell treats each character of IFS as a
delimiter, and splits the results of the other expansions into
words on these characters. If the value of IFS
is exactly
<space><tab><newline>, the
default, then any sequence of IFS characters
serves to delimit words. If IFS has a value
other than the default, then sequences of the whitespace
characters space and tab are
ignored at the beginning and end of the word, as long as the
whitespace character is in the value of IFS (an
IFS whitespace character). Any character in
IFS that is not IFS whitespace,
along with any adjacent IFS whitespace
characters, delimits a field. A sequence of IFS
whitespace characters is also treated as a delimiter. If the
value of IFS is null, no word splitting occurs.
IFS cannot be unset.
Explicit null arguments ("" or
'') are retained. Implicit null arguments,
resulting from the expansion of parameters that have no
values, are removed.
Note that if no expansion occurs, no splitting is performed.
After word splitting, unless the -f option has
been set, bash scans each word for the
characters *, ?, and
[. If one of these characters appears, then the
word is regarded as a pattern, and replaced with an
alphabetically sorted list of pathnames matching the pattern. If
no matching pathnames are found, and the shell variable
allow_null_glob_expansion is unset, the word is
left unchanged. If the variable is set, and no matches are found,
the word is removed. When a pattern is used for pathname
generation, the character ``.'' at the start of
a name or immediately following a slash must be matched
explicitly, unless the shell variable
glob_dot_filenames is set. The slash character
must always be matched explicitly. In other cases, the
``.'' character is not treated specially.
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 minus sign denotes a range;
any character lexically between those two characters,
inclusive, is matched. If the first character following the
[ is a ! or a
^ then any character not enclosed is matched.
A - or ] may be matched by
including it as the first or last character in the set.
After the preceding expansions, all unquoted occurrences of the
characters \, `, and
" are removed.
Before a command is executed, its input and output may be
redirected 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 anywhere within a simple
command or may follow a command. Redirections are
processed in the order they appear, from left to right.
In the following descriptions, if the file descriptor number 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 that follows the redirection operator in the following
descriptions is subjected to brace expansion, tilde expansion,
parameter expansion, command substitution, arithmetic expansion,
quote removal, and pathname expansion. If it expands to more than
one word, bash 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
dirlist, while the command
ls 2>&1 > dirlist
directs only the standard output to file dirlist,
because the standard error was duplicated as standard output
before the standard output was redirected to dirlist.
Redirection of input causes the file whose name results from the
expansion of word 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]<word
Redirection of output causes the file whose name results from the
expansion of word 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]>word
If the redirection operator is >|, then the
value of the -C option to the
set builtin command is not tested, and file
creation is attempted. (See also the description of
noclobber under Shell Variables
above.)
Redirection of output in this fashion causes the file whose name
results from the expansion of word 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]>>word
Bash 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
word with this construct.
There are two formats for redirecting standard output and
standard error:
&>word
and
>&word
Of the two forms, the first is preferred. This is semantically
equivalent to
>word 2>&1
This type of redirection instructs the shell to read input from
the current source until a line containing only word
(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:
<<[-]word
here-document
delimiter
No parameter expansion, command substitution, pathname expansion,
or arithmetic expansion is performed on word. If any
characters in word are quoted, the delimiter is
the result of quote removal on word, and the lines in
the here-document are not expanded. Otherwise, all lines of the
here-document are subjected to parameter expansion, command
substitution, and arithmetic expansion. In the latter case, the
pair \<newline> 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 containing delimiter. This allows here-documents
within shell scripts to be indented in a natural fashion.
The redirection operator
[n]<&word
is used to duplicate input file descriptors. If word
expands to one or more digits, the file descriptor denoted by
n is made to be a copy of that file descriptor. If
word evaluates to -, file descriptor
n is closed. If n is not specified, the
standard input (file descriptor 0) is used.
The operator
[n]>&word
is used similarly to duplicate output file descriptors. If
n is not specified, the standard output (file descriptor
1) is used. As a special case, if n is omitted, and
word does not expand to one or more digits, the standard
output and standard error are redirected as described previously.
The redirection operator
[n]<>word
causes the file whose name is the expansion of word to
be opened for both reading and writing on file descriptor
n, or as the standard input and standard output if
n is not specified. If the file does not exist, it is
created.
A shell function, defined as described above under SHELL
GRAMMAR, stores a series of commands for later execution.
Functions are executed in the context 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.
Variables local to the function may be declared with the
local builtin command. Ordinarily, variables and
their values are shared between the function and its caller.
If the builtin command return is executed in a
function, the function completes and execution resumes with the
next command after the function call. When a function completes,
the values of the positional parameters and the special parameter
# are restored to the values they had prior to
function execution.
Function names and definitions may be listed with the
-f option to the declare or
typeset builtin commands. Functions may be
exported so that subshells automatically have them defined with
the -f option to the export
builtin.
Functions may be recursive. No limit is imposed on the number of
recursive calls.
The shell maintains a list of aliases that may be set and
unset with the alias and unalias
builtin commands (see SHELL BUILTIN COMMANDS
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 contain any
valid shell input, including the metacharacters 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
ls to ls -F, for instance, and
bash does not try to recursively expand the
replacement text. If the last character of the alias value is a
blank, then the next command word following the alias is
also checked for alias expansion.
Aliases are created and listed with the alias
command, and removed with the unalias command.
There is no mechanism for using arguments in the replacement
text, as in csh. If arguments are needed, a
shell function should be used.
Aliases are not expanded when the shell is not interactive.
The rules concerning the definition and use of aliases are
somewhat confusing. Bash always reads at least
one complete 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 definition appearing on
the same line as another command does not take effect until the
next line of input is read. This means that 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 the 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 alias in
compound commands.
Note that for almost every purpose, aliases are superseded by
shell functions.
Job control refers to the ability to selectively stop
(suspend) the execution of processes and continue
(resume) their execution at a later point. A user
typically employs this facility via an interactive interface
supplied jointly by the system's terminal driver and
bash.
The shell associates a job with each pipeline. It keeps
a table of currently executing jobs, which may be listed with the
jobs command. When bash starts
a job asynchronously (in the background), it prints a
line that looks like:
[1] 25647
indicating that this job is job number 1 and that the process ID
of the last process in the pipeline associated with this job is
25647. All of the processes in a single pipeline are members of
the same job. Bash uses the job
abstraction as the basis for job control.
To facilitate the implementation of the user interface to job
control, the system maintains the notion of a current
terminal process group ID. Members of this process group
(processes whose process group ID is equal to the current
terminal process group ID) receive keyboard-generated signals
such as SIGINT. These processes are said to be
in the foreground. Background 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 SIGTTIN (SIGTTOU)
signal by the terminal driver, which, unless caught, suspends the
process.
If the operating system on which bash is running
supports job control, bash allows you to use it.
Typing the suspend character (typically
^Z, Control-Z) while a process is running causes
that process to be stopped and returns you to
bash. Typing the delayed suspend
character (typically ^Y, Control-Y) causes the
process to be stopped when it attempts to read input from the
terminal, and control to be returned to bash.
You may then manipulate the state of this job, using the
bg command to continue it in the background, the
fg command to continue it in the foreground, or
the kill command to kill it. A
^Z takes effect immediately, and has the
additional side effect of causing pending output and typeahead to
be discarded.
There are a number of ways to refer to a job in the shell. The
character % introduces a job name. Job number
n may be referred to as %n. A job may
also be referred to using a prefix of the name used to start it,
or using a substring that appears in its command line. For
example, %ce refers to a stopped
ce job. If a prefix matches more than one job,
bash reports an error. Using
%?ce, on the other hand, refers to any job
containing the string ce in its command line. If
the substring matches more than one job, bash
reports an error. The symbols %% and
%+ refer to the shell's notion of the
current job, which is the last job stopped while it was
in the foreground. The previous job may be referenced
using %-. In output pertaining to jobs (e.g.,
the output of the jobs 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 foreground:
%1 is a synonym for ``fg %1'',
bringing job 1 from the background into the foreground.
Similarly, ``%1 &'' resumes job 1 in the
background, equivalent to ``bg %1''.
The shell learns immediately whenever a job changes state.
Normally, bash 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 -b option to
the set builtin command is set,
bash reports such changes immediately. (See also
the description of notify variable under
Shell Variables above.)
If you attempt to exit bash while jobs are
stopped, the shell prints a message warning you. You may then use
the jobs command to inspect their status. If you
do this, or try to exit again immediately, you are not warned
again, and the stopped jobs are terminated.
When bash is interactive, it ignores
SIGTERM (so that kill 0 does not
kill an interactive shell), and SIGINT is caught
and handled (so that the wait builtin is
interruptible). In all cases, bash ignores
SIGQUIT. If job control is in effect,
bash ignores SIGTTIN,
SIGTTOU, and SIGTSTP.
Synchronous jobs started by bash have signals
set to the values inherited by the shell from its parent. When
job control is not in effect, background jobs (jobs started with
&) ignore SIGINT and
SIGQUIT. Commands run as a result of command
substitution ignore the keyboard-generated job control signals
SIGTTIN, SIGTTOU, and
SIGTSTP.
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
FUNCTIONS. 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, bash searches each element
of the PATH for a directory containing an
executable file by that name. If the search is unsuccessful, the
shell prints an error message and returns a nonzero exit status.
If the search is successful, or if the command name contains one
or more slashes, the shell executes the named program. 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 executable
format, and the file is not a directory, it is assumed to be a
shell script, a file containing shell commands. A
subshell is spawned to execute it. This subshell reinitializes
itself, so that the effect is as if a new shell had been invoked
to handle the script, with the exception that the locations of
commands remembered by the parent (see hash
below under SHELL BUILTIN COMMANDS) are retained
by the child.
If the program is a file beginning with #!, the
remainder of the first line specifies an interpreter for the
program. The shell executes the specified interpreter on
operating systems that do not handle this executable format
themselves. The arguments to the interpreter consist of a single
optional argument following the interpreter name on the first
line of the program, followed by the name of the program,
followed by the command arguments, if any.
When a program is invoked it is given an array of strings called
the environment. This is a list of
name-value pairs, of the form
name=value.
The shell allows you to manipulate the environment in several
ways. On invocation, the shell scans its own environment and
creates a parameter for each name found, automatically marking it
for export to child processes. Executed commands inherit
the environment. The export and declare
-x 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 unset command, plus any additions via the
export and declare -x commands.
The environment for any simple command or function may
be augmented temporarily by prefixing it with parameter
assignments, as described above in PARAMETERS.
These assignment statements affect only the environment seen by
that command.
If the -k flag is set (see the
set builtin command below), then all
parameter assignments are placed in the environment for a
command, not just those that precede the command name.
When bash invokes an external command, the
variable _ is set to the full path name of the
command and passed to that command in its environment.
For the purposes of the shell, a command which exits with a zero
exit status has succeeded. An exit status of zero indicates
success. A non-zero exit status indicates failure. When a command
terminates on a fatal signal, bash uses the value
of 128+signal 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.
Bash 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 exit
builtin command below.
When executing interactively, bash displays the
primary prompt PS1 when it is ready to read a
command, and the secondary prompt PS2 when it
needs more input to complete a command. Bash
allows these prompt strings to be customized by inserting a number
of backslash-escaped special characters that are decoded as
follows:
-
\t
-
the current time in HH:MM:SS format
-
\d
-
the date in "Weekday Month Date" format (e.g., "Tue May 26")
-
\n
-
newline
-
\s
-
the name of the shell, the basename of $0
(the portion following the final slash)
-
\w
-
the current working directory
-
\W
-
the basename of the current working directory
-
\u
-
the username of the current user
-
\h
-
the hostname
-
\#
-
the command number of this command
-
\!
-
the history number of this command
-
\$
-
if the effective UID is 0, a #, otherwise a
$
-
\nnn
-
the character corresponding to the octal number
nnn
-
\\
-
a backslash
-
\[
-
begin a sequence of non-printing characters, which could be
used to embed a terminal control sequence into the prompt
-
\]
-
end a sequence of non-printing characters
The command number and the history number are usually different:
the history number of a command is its position in the history
list, which may include commands restored from the history file
(see HISTORY below), while the command number is
the position in the sequence of commands executed during the
current shell session. After the string is decoded, it is
expanded via parameter expansion, command substitution,
arithmetic expansion, and word splitting.
This is the library that handles reading input when using an
interactive shell, unless the -nolineediting
option is given. By default, the line editing commands are similar
to those of emacs. A vi-style line editing interface is also
available.
In this section, the emacs-style notation is used to denote
keystrokes. Control keys are denoted by C-key, e.g., C-n
means Control-N. Similarly, meta keys are denoted by
M-key, so M-x means Meta-X. (On keyboards without a
meta key, M-x means ESC x, i.e., press
the Escape key then the x key. This makes ESC the
meta prefix. The combination M-C-x means
ESC-Control-x, or press the Escape key then hold the
Control key while pressing the x key.)
The default key-bindings may be changed with an ~/.inputrc
file. The value of the shell variable
INPUTRC, if set, is used instead of
~/.inputrc. 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 ~/.inputrc would make M-C-u execute the
readline command universal-argument.
The following symbolic character names are recognized:
RUBOUT, DEL, ESC, LFD,
NEWLINE, RET, RETURN, SPC,
SPACE, and TAB. In addition to command names,
readline allows keys to be bound to a string that is inserted
when the key is pressed (a macro).
Readline is customized by putting commands in an initialization
file. The name of this file is taken from the value of the
INPUTRC variable. If that variable is unset, the
default is ~/.inputrc. When a program which uses the
readline library starts up, the init file is read, and the key
bindings and variables are set. There are only a few basic
constructs allowed in the readline init 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 syntax for controlling key bindings in the
~/.inputrc 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 Meta- or
Control- prefixes, or as a key sequence. When using the
form keyname:function-name or
macro, keyname 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
universal-argument, M-DEL is bound to
the function backward-kill-word, 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,
"keyseq":function-name or
macro, keyseq differs from
keyname 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.
"\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
universal-argument. C-x C-r is bound to
the function re-read-init-file, and ESC [ 1
1 ~ is bound to insert the text Function Key
1. The full set of escape sequences is
-
\C-
-
control prefix
-
\M-
-
meta prefix
-
\e
-
an escape character
-
\\
-
backslash
-
\"
-
literal "
-
\'
-
literal '
When entering the text of a macro, single or double quotes should
be used to indicate a macro definition. Unquoted text is assumed
to be a function name. Backslash will quote any character in the
macro text, including " and '.
Bash allows the current readline key bindings to
be displayed or modified with the bind builtin
command. The editing mode may be switched during interactive use
by using the -o option to the
set builtin command (see SHELL BUILTIN
COMMANDS below).
Readline has variables that can be used to further customize its
behavior. A variable may be set in the inputrc file with
a statement of the form
set variable-name value
Except where noted, readline variables can take the values
On or Off. The variables and
their default values are:
-
horizontal-scroll-mode (Off)
-
When set to On, 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.
-
editing-mode (emacs)
-
Controls whether readline begins with a set of key bindings
similar to emacs or vi.
editing-mode can be set to either
emacs or vi.
-
mark-modified-lines (Off)
-
If set to On, history lines that have been
modified are displayed with a preceding asterisk
(*).
-
bell-style (audible)
-
Controls what happens when readline wants to ring the terminal
bell. If set to none, readline never rings the
bell. If set to visible, readline uses a
visible bell if one is available. If set to
audible, readline attempts to ring the
terminal's bell.
-
comment-begin (``#'')
-
The string that is inserted in vi mode when
the vi-comment command is executed.
-
meta-flag (Off)
-
If set to On, readline will enable eight-bit
input (that is, it will not strip the high bit from the
characters it reads), regardless of what the terminal claims it
can support.
-
convert-meta (On)
-
If set to On, readline will convert characters
with the eighth bit set to an ASCII key sequence by stripping
the eighth bit and prepending an escape character (in effect,
using escape as the meta prefix).
-
output-meta (Off)
-
If set to On, readline will display characters
with the eighth bit set directly rather than as a meta-prefixed
escape sequence.
-
completion-query-items (100)
-
This determines when the user is queried about viewing the
number of possible completions generated by the
possible-completions command. It may be set to
any integer value greater than or equal to zero. If the number
of possible completions is greater than or equal to the value
of this variable, the user is asked whether or not he wishes to
view them; otherwise they are simply listed on the terminal.
-
keymap (emacs)
-
Set the current readline keymap. The set of legal keymap names
is emacs, emacs-standard, emacs-meta, emacs-ctlx, vi,
vi-move, vi-command, and vi-insert. vi
is equivalent to vi-command; emacs is
equivalent to emacs-standard. The default value is
emacs; the value of editing-mode also
affects the default keymap.
-
show-all-if-ambiguous (Off)
-
This alters the default behavior of the completion functions.
If set to on, words which have more than one
possible completion cause the matches to be listed immediately
instead of ringing the bell.
-
expand-tilde (Off)
-
If set to on, tilde expansion is performed
when readline attempts word completion.
Readline implements a facility similar in spirit to the
conditional compilation features of the C preprocessor which
allows key bindings and variable settings to be performed as the
result of tests. There are three parser directives used.
-
$if
-
The $if 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.
-
mode
-
The mode= form of the $if
directive is used to test whether readline is in emacs or vi
mode. This may be used in conjunction with the set
keymap command, for instance, to set bindings in the
emacs-standard and emacs-ctlx keymaps only if
readline is starting out in emacs mode.
-
term
-
The term= form may be used to include
terminal-specific key bindings, perhaps to bind the key
sequences output by the terminal's function keys. The word on
the right side of the = is tested against the
full name of the terminal and the portion of the terminal name
before the first -. This allows sun
to match both sun and sun-cmd, for instance.
-
application
-
The application construct is used to include
application-specific settings. Each program using the readline
library sets the application name, and an
initialization file can test for a particular value. This could
be used to bind key sequences to functions useful for a
specific program. For instance, the following command adds a
key sequence that quotes the current or previous word in Bash:
$if Bash
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
$endif
-
$endif
-
This command, as you saw in the previous example, terminates an
$if command.
-
$else
-
Commands in this branch of the $if directive
are executed if the test fails.
Readline commands may be given numeric arguments, 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.,
kill-line) causes that command to act in a
backward direction. Commands whose behavior with arguments
deviates from this are noted.
When a command is described as killing text, the text
deleted is saved for possible future retrieval
(yanking). The killed text is saved in a
kill-ring. 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.
The following is a list of the names of the commands and the
default key sequences to which they are bound.
-
beginning-of-line (C-a)
-
Move to the start of the current line.
-
end-of-line (C-e)
-
Move to the end of the line.
-
forward-char (C-f)
-
Move forward a character.
-
backward-char (C-b)
-
Move back a character.
-
forward-word (M-f)
-
Move forward to the end of the next word. Words are composed of
alphanumeric characters (letters and digits).
-
backward-word (M-b)
-
Move back to the start of this, or the previous, word. Words
are composed of alphanumeric characters (letters and digits).
-
clear-screen (C-l)
-
Clear the screen leaving the current line at the top of the
screen. With an argument, refresh the current line without
clearing the screen.
-
redraw-current-line
-
Refresh the current line. By default, this is unbound.
-
accept-line (Newline, Return)
-
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 HISTCONTROL variable. If the line is a
modified history line, then restore the history line to its
original state.
-
previous-history (C-p)
-
Fetch the previous command from the history list, moving back
in the list.
-
next-history (C-n)
-
Fetch the next command from the history list, moving forward in
the list.
-
beginning-of-history (M-<)
-
Move to the first line in the history.
-
end-of-history (M->)
-
Move to the end of the input history, i.e., the line currently
being entered.
-
reverse-search-history (C-r)
-
Search backward starting at the current line and moving `up'
through the history as necessary. This is an incremental
search.
-
forward-search-history (C-s)
-
Search forward starting at the current line and moving `down'
through the history as necessary. This is an incremental
search.
-
non-incremental-reverse-search-history (M-p)
-
Search backward through the history starting at the current
line using a non-incremental search for a string supplied by
the user.
-
non-incremental-forward-search-history (M-n)
-
Search forward through the history using a non-incremental
search for a string supplied by the user.
-
history-search-forward
-
Search forward through the history for the string of characters
between the start of the current line and the current point.
This is a non-incremental search. By default, this command is
unbound.
-
history-search-backward
-
Search backward through the history for the string of
characters between the start of the current line and the
current point. This is a non-incremental search. By default,
this command is unbound.
-
yank-nth-arg (M-C-y)
-
Insert the first argument to the previous command (usually the
second word on the previous line) at point (the current cursor
position). With an argument n, insert the nth
word from the previous command (the words in the previous
command begin with word 0). A negative argument inserts the
nth word from the end of the previous command.
-
yank-last-arg (M-., M-_)
-
Insert the last argument to the previous command (the last word
on the previous line). With an argument, behave exactly like
yank-nth-arg.
-
shell-expand-line (M-C-e)
-
Expand the line the way the shell does when it reads it. This
performs alias and history expansion as well as all of the
shell word expansions. See HISTORY EXPANSION
below for a description of history expansion.
-
history-expand-line (M-^)
-
Perform history expansion on the current line. See
HISTORY EXPANSION below for a description of
history expansion.
-
insert-last-argument (M-., M-_)
-
A synonym for yank-last-arg.
-
operate-and-get-next (C-o)
-
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.
-
delete-char (C-d)
-
Delete the character under the cursor. If point is at the
beginning of the line, there are no characters in the line, and
the last character typed was not C-d, then
return EOF.
-
backward-delete-char (Rubout)
-
Delete the character behind the cursor. When given a numeric
argument, save the deleted text on the kill-ring.
-
quoted-insert (C-q, C-v)
-
Add the next character that you type to the line verbatim. This
is how to insert characters like C-q, for
example.
-
tab-insert (C-v TAB)
-
Insert a tab character.
-
self-insert (a, b, A, 1, !, ...)
-
Insert the character typed.
-
transpose-chars (C-t)
-
Drag the character before point forward over the character at
point. Point moves forward as well. If point is at the end of
the line, then transpose the two characters before point.
Negative arguments don't work.
-
transpose-words (M-t)
-
Drag the word behind the cursor past the word in front of the
cursor moving the cursor over that word as well.
-
upcase-word (M-u)
-
Uppercase the current (or following) word. With a negative
argument, do the previous word, but do not move point.
-
downcase-word (M-l)
-
Lowercase the current (or following) word. With a negative
argument, do the previous word, but do not move point.
-
capitalize-word (M-c)
-
Capitalize the current (or following) word. With a negative
argument, do the previous word, but do not move point.
-
kill-line (C-k)
-
Kill the text from the current cursor position to the end of
the line.
-
backward-kill-line (C-x C-Rubout)
-
Kill backward to the beginning of the line.
-
unix-line-discard (C-u)
-
Kill backward from point to the beginning of the line.
-
kill-whole-line
-
Kill all characters on the current line, no matter where the
cursor is. By default, this is unbound.
-
kill-word (M-d)
-
Kill from the cursor 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 forward-word.
-
backward-kill-word (M-Rubout)
-
Kill the word behind the cursor. Word boundaries are the same
as those used by backward-word.
-
unix-word-rubout (C-w)
-
Kill the word behind the cursor, using white space as a word
boundary. The word boundaries are different from
backward-kill-word.
-
delete-horizontal-space
-
Delete all spaces and tabs around point. By default, this is
unbound.
-
yank (C-y)
-
Yank the top of the kill ring into the buffer at the cursor.
-
yank-pop (M-y)
-
Rotate the kill-ring, and yank the new top. Only works
following yank or yank-pop.
-
digit-argument (M-0, M-1, ..., M--)
-
Add this digit to the argument already accumulating, or start a
new argument. M-- starts a negative argument.
-
universal-argument
-
Each time this is executed, the argument count is multiplied by
four. The argument count is initially one, so executing this
function the first time makes the argument count four. By
default, this is not bound to a key.
-
complete (TAB)
-
Attempt to perform completion on the text before point.
Bash attempts completion treating the text as
a variable (if the text begins with $),
username (if the text begins with ~), hostname
(if the text begins with @), or command
(including aliases and functions) in turn. If none of these
produces a match, filename completion is attempted.
-
possible-completions (M-?)
-
List the possible completions of the text before point.
-
insert-completions
-
Insert all completions of the text before point that would have
been generated by possible-completions. By
default, this is not bound to a key.
-
complete-filename (M-/)
-
Attempt filename completion on the text before point.
-
possible-filename-completions (C-x /)
-
List the possible completions of the text before point,
treating it as a filename.
-
complete-username (M-~)
-
Attempt completion on the text before point, treating it as a
username.
-
possible-username-completions (C-x ~)
-
List the possible completions of the text before point,
treating it as a username.
-
complete-variable (M-$)
-
Attempt completion on the text before point, treating it as a
shell variable.
-
possible-variable-completions (C-x $)
-
List the possible completions of the text before point,
treating it as a shell variable.
-
complete-hostname (M-@)
-
Attempt completion on the text before point, treating it as a
hostname.
-
possible-hostname-completions (C-x @)
-
List the possible completions of the text before point,
treating it as a hostname.
-
complete-command (M-!)
-
Attempt completion on the text before point, treating it as a
command name. Command completion attempts to match the text
against aliases, reserved words, shell functions, builtins, and
finally executable filenames, in that order.
-
possible-command-completions (C-x !)
-
List the possible completions of the text before point,
treating it as a command name.
-
dynamic-complete-history (M-TAB)
-
Attempt completion on the text before point, comparing the text
against lines from the history list for possible completion
matches.
-
complete-into-braces (M-{)
-
Perform filename completion and return the list of possible
completions enclosed within braces so the list is available to
the shell (see Brace Expansion above).
-
start-kbd-macro (C-x ()
-
Begin saving the characters typed into the current keyboard
macro.
-
end-kbd-macro (C-x ))
-
Stop saving the characters typed into the current keyboard
macro and save the definition.
-
call-last-kbd-macro (C-x e)
-
Re-execute the last keyboard macro defined, by making the
characters in the macro appear as if typed at the keyboard.
-
re-read-init-file (C-x C-r)
-
Read in the contents of your init file, and incorporate any
bindings or variable assignments found there.
-
abort (C-g)
-
Abort the current editing command and ring the terminal's bell
(subject to the setting of bell-style).
-
do-uppercase-version (M-a, M-b, ...)
-
Run the command that is bound to the corresponding uppercase
character.
-
prefix-meta (ESC)
-
Metafy the next character typed. ESC
f is equivalent to Meta-f.
-
undo (C-_, C-x C-u)
-
Incremental undo, separately remembered for each line.
-
revert-line (M-r)
-
Undo all changes made to this line. This is like typing the
undo command enough times to return the line
to its initial state.
-
tilde-expand (M-~)
-
Perform tilde expansion on the current word.
-
dump-functions
-
Print all of the functions and their key bindings to the
readline output stream. If a numeric argument is supplied, the
output is formatted in such a way that it can be made part of
an inputrc file.
-
display-shell-version (C-x C-v)
-
Display version information about the current instance of
bash.
When interactive, the shell provides access to the command
history, the list of commands previously typed. The text of
the last HISTSIZE commands (default 500) is saved
in a history list. The shell stores each command in the history
list prior to parameter and variable expansion (see
EXPANSION above) but after history expansion is
performed, subject to the values of the shell variables
command_oriented_history and
HISTCONTROL. On startup, the history is
initialized from the file named by the variable
HISTFILE (default ~/.bash_history).
HISTFILE is truncated, if necessary, to contain no
more than HISTFILESIZE lines. The builtin command
fc (see SHELL BUILTIN COMMANDS
below) may be used to list or edit and re-execute a portion of the
history list. The history builtin can be used to
display the history list and manipulate the history file. When
using the command-line editing, search commands are available in
each editing mode that provide access to the history list. When an
interactive shell exits, the last HISTSIZE lines
are copied from the history list to HISTFILE. If
HISTFILE is unset, or if the history file is
unwritable, the history is not saved.
The shell supports a history expansion feature that is similar to
the history expansion in csh. This section
describes what syntax features are available. This feature is
enabled by default for interactive shells, and can be disabled
using the +H option to the set
builtin command (see SHELL BUILTIN COMMANDS
below). Non-interactive shells do not perform history expansion.
History expansion is performed immediately after a complete 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 previous
history to use during substitution. The second is to select
portions of that line for inclusion into the current one. The
line selected from the previous history is the event,
and the portions of that line that are acted upon are
words. The line is broken into words in the same fashion
as when reading input, so that several
metacharacter-separated words surrounded by quotes are
considered as one word. Only backslash (\) and
single quotes can quote the history escape character, which is
! by default.
The shell allows control of the various characters used by the
history expansion mechanism (see the description of
histchars above under Shell
Variables).
An event designator is a reference to a command line entry in the
history list.
-
!
-
Start a history substitution, except when followed by a
blank, newline, = or (.
-
!!
-
Refer to the previous command. This is a synonym for `!-1'.
-
!n
-
Refer to command line n.
-
!-n
-
Refer to the current command line minus n.
-
!string
-
Refer to the most recent command starting with string.
-
!?string[?]
-
Refer to the most recent command containing string.
-
d^ustring1d^ustring2d^u
-
Quick substitution. Repeat the last command, replacing
string1 with string2. Equivalent to
``!!:s/string1/string2/'' (see
Modifiers below).
-
!#
-
The entire command line typed so far.
A : separates the event specification from the
word designator. It can 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 a 0 (zero).
-
0 (zero)
-
The zeroth word. For the shell, this is the command word.
-
n
-
The nth word.
-
^
-
The first argument. That is, word 1.
-
$
-
The last argument.
-
%
-
The word matched by the most recent `?string?' search.
-
x-y
-
A range of words; `-y' abbreviates `0-y'.
-
*
-
All of the words but the zeroth. This is a synonym for `1-$'.
It is not an error to use * if there is just
one word in the event; the empty string is returned in that
case.
-
x*
-
Abbreviates x-$.
-
x-
-
Abbreviates x-$ like x*, but omits
the last word.
After the optional word designator, you can add a sequence of one
or more of the following modifiers, each preceded by a `:'.
-
h
-
Remove a trailing pathname component, leaving only the head.
-
r
-
Remove a trailing suffix of the form .xxx, leaving the
basename.
-
e
-
Remove all but the trailing suffix.
-
t
-
Remove all leading pathname components, leaving the tail.
-
p
-
Print the new command but do not execute it.
-
q
-
Quote the substituted words, escaping further substitutions.
-
x
-
Quote the substituted words as with q, but
break into words at blanks and newlines.
-
s/old/new/
-
Substitute new for the first occurrence of
old 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
old and new with a single backslash. If &
appears in new, it is replaced by old. A
single backslash will quote the &.
-
&
-
Repeat the previous substitution.
-
g
-
Cause changes to be applied over the entire event line. This is
used in conjunction with `:s' (e.g.,
`:gs/old/new/') or `:&'. If used with
`:s', any delimiter can be used in place of /, and the final
delimiter is optional if it is the last character of the event
line.
The shell allows arithmetic expressions to be evaluated, under
certain circumstances (see the let builtin command
and Arithmetic Expansion). Evaluation is done in
long integers with no check for overflow, though division by 0 is
trapped and flagged as an error. The following list of operators is
grouped into levels of equal-precedence operators. The levels are
listed in order of decreasing precedence.
-
- +
-
unary minus and plus
-
! ~
-
logical and bitwise negation
-
* / %
-
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
-
= *= /= %= += -= <<= >>= &= ^=
|=
-
assignment
Shell variables are allowed as operands; parameter expansion is
performed before the expression is evaluated. The value of a
parameter is coerced to a long integer within an expression. 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 numbers. A
leading 0x or 0X denotes hexadecimal. Otherwise, numbers take the
form [base#]n, where base is a decimal number
between 2 and 36 representing the arithmetic base, and n
is a number in that base. If base is omitted, then base
10 is used.
Operators are evaluated in order of precedence. Sub-expressions
in parentheses are evaluated first and may override the
precedence rules above.
-
: [arguments]
-
No effect; the command does nothing beyond expanding
arguments and performing any specified redirections. A
zero exit code is returned.
-
. filename [arguments]
-
source filename [arguments]
-
Read and execute commands from filename in the current
shell environment and return the exit status of the last
command executed from filename. If filename
does not contain a slash, pathnames in PATH
are used to find the directory containing filename.
The file searched for in PATH need not be
executable. The current directory is searched if no file is
found in PATH. If any arguments are
supplied, they become the positional parameters when
file 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 commands are
executed), and false if filename is not found.
-
alias [name[=value] ...]
-
Alias with no arguments prints the list of
aliases in the form name=value on standard
output. When arguments are supplied, an alias is defined for
each name whose value is given. A trailing
space in value causes the next word to be checked for
alias substitution when the alias is expanded. For each
name in the argument list for which no value
is supplied, the name and value of the alias is printed.
Alias returns true unless a name is
given for which no alias has been defined.
-
bg [jobspec]
-
Place jobspec in the background, as if it had been
started with &. If jobspec is not
present, the shell's notion of the current job is
used. bg jobspec returns 0 unless run
when job control is disabled or, when run with job control
enabled, if jobspec was not found or started without
job control.
-
bind [-m keymap]
[-lvd] [-q name]
-
bind [-m keymap]
-f filename
-
bind [-m keymap]
keyseq:function-name
-
Display current readline key and function
bindings, or bind a key sequence to a readline
function or macro. The binding syntax accepted is identical to
that of .inputrc, 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:
-
-m keymap
-
Use keymap as the keymap to be affected by the
subsequent bindings. Acceptable keymap names are
emacs, emacs-standard, emacs-meta, emacs-ctlx, vi, vi-move,
vi-command, and vi-insert. vi is
equivalent to vi-command; emacs is equivalent
to emacs-standard.
-
-l
-
List the names of all readline functions
-
-v
-
List current function names and bindings
-
-d
-
Dump function names and bindings in such a way that they can be
re-read
-
-f filename
-
Read key bindings from filename
-
-q function
-
Query about which keys invoke the named function
The return value is 0 unless an unrecognized option is given or
an error occurred.
-
break [n]
-
Exit from within a for,
while, or until 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
break is executed.
-
builtin shell-builtin
[arguments]
-
Execute the specified shell builtin, passing it
arguments, and return its exit status. This is useful
when you wish to define a function whose name is the same as a
shell builtin, but need the functionality of the builtin within
the function itself. The cd builtin is
commonly redefined this way. The return status is false if
shell-builtin is not a shell builtin command.
-
cd [dir]
-
Change the current directory to dir. The variable
HOME is the default dir. The variable
CDPATH defines the search path for the
directory containing dir. Alternative directory names
are separated by a colon (:). A null directory name in
CDPATH is the same as the current directory,
i.e., ``.''. If dir begins with a
slash (/), then CDPATH is not used. An
argument of - is equivalent to
$OLDPWD. The return value is true if the
directory was successfully changed; false otherwise.
-
command [-pVv]
command [arg ...]
-
Run command with args suppressing the normal
shell function lookup. Only builtin commands or commands found
in the PATH are executed. If the
-p option is given, the search for
command is performed using a default value for
PATH that is guaranteed to find all of the
standard utilities. If either the -V or
-v option is supplied, a description of
command is printed. The -v option
causes a single word indicating the command or pathname used to
invoke command to be printed; the -V
option produces a more verbose description. An argument of
-- disables option checking for the rest of
the arguments. If the -V or
-v option is supplied, the exit status is 0 if
command was found, and 1 if not. If neither option is
supplied and an error occurred or command cannot be
found, the exit status is 127. Otherwise, the exit status of
the command builtin is the exit status of
command.
-
continue [n]
-
Resume the next iteration of the enclosing
for, while, or
until 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
continue is executed.
-
declare [-frxi]
[name[=value]]
-
typeset [-frxi]
[name[=value]]
-
Declare variables and/or give them attributes. If no
names are given, then display the values of variables
instead. The options can be used to restrict output to
variables with the specified attribute.
-
-f
-
Use function names only
-
-r
-
Make names readonly. These names cannot then be
assigned values by subsequent assignment statements.
-
-x
-
Mark names for export to subsequent commands via the
environment.
-
-i
-
The variable is treated as an integer; arithmetic evaluation
(see ARITHMETIC EVALUATION ") " is performed
when the variable is assigned a value.
Using `+' instead of `-' turns off the attribute instead. When
used in a function, makes names local, as with the
local command. The return value is 0 unless an
illegal option is encountered, an attempt is made to define a
function using "-f foo=bar", one of the names is not a
legal shell variable name, an attempt is made to turn off
readonly status for a readonly variable, or an attempt is made to
display a non-existant function with -f.
-
dirs [-l] [+/-n]
-
Display the list of currently remembered directories.
Directories are added to the list with the
pushd command; the popd
command moves back up through the list.
-
+n
-
displays the nth entry counting from the left of the
list shown by dirs when invoked without
options, starting with zero.
-
-n
-
displays the nth entry counting from the right of the
list shown by dirs when invoked without
options, starting with zero.
-
-l
-
produces a longer listing; the default listing format uses a
tilde to denote the home directory.
The return value is 0 unless an illegal option is supplied or
n indexes beyond the end of the directory stack.
-
echo [-neE] [arg
...]
-
Output the args, separated by spaces. The return
status is always 0. If -n is specified, the
trailing newline is suppressed. If the -e
option is given, interpretation of the following
backslash-escaped characters is enabled. The
-E option disables the interpretation of these
escape characters, even on systems where they are interpreted
by default.
-
\a
-
alert (bell)
-
\b
-
backspace
-
\c
-
suppress trailing newline
-
\f
-
form feed
-
\n
-
new line
-
\r
-
carriage return
-
\t
-
horizontal tab
-
\v
-
vertical tab
-
\\
-
backslash
-
\nnn
-
the character whose ASCII code is nnn (octal)
-
enable [-n]
[-all] [name ...]
-
Enable and disable builtin shell commands. This allows the
execution of a disk command which has the same name as a shell
builtin without specifying a full pathname. If
-n is used, each name is disabled;
otherwise, names are enabled. For example, to use the
test binary found via the
PATH instead of the shell builtin version,
type ``enable -n test''. If no arguments are given, a list of
all enabled shell builtins is printed. If only
-n is supplied, a list of all disabled
builtins is printed. If only -all is supplied,
the list printed includes all builtins, with an indication of
whether or not each is enabled. enable accepts
-a as a synonym for -all. The
return value is 0 unless a name is not a shell
builtin.
-
eval [arg ...]
-
The args are read and concatenated together into a
single command. This command is then read and executed by the
shell, and its exit status is returned as the value of the
eval command. If there are no args,
or only null arguments, eval returns true.
-
exec [[-] command
[arguments]]
-
If command is specified, it replaces the shell. No new
process is created. The arguments become the arguments
to command. If the first argument is
-, the shell places a dash in the zeroth arg
passed to command. This is what login does. If the
file cannot be executed for some reason, a non-interactive
shell exits, unless the shell variable
no_exit_on_failed_exec exists, in which case
it returns failure. An interactive shell returns failure if the
file cannot be executed. If command is not specified,
any redirections take effect in the current shell, and the
return status is 0.
-
exit [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 EXIT is executed
before the shell terminates.
-
export [-nf]
[name[=word]] ...
-
export -p
-
The supplied names are marked for automatic export to
the environment of subsequently executed commands. If the
-f option is given, the names refer
to functions. If no names are given, or if the
-p option is supplied, a list of all names
that are exported in this shell is printed. The
-n option causes the export property to be
removed from the named variables. An argument of
-- disables option checking for the rest of
the arguments. export returns an exit status
of 0 unless an illegal option is encountered, one of the
names is not a legal shell variable name, or
-f is supplied with a name that is
not a function.
-
fc [-e ename]
[-nlr] [first] [last]
-
fc -s
[pat=rep] [cmd]
-
Fix Command. In the first form, a range of commands from
first to last is selected from the history
list. First and last may be specified as a
string (to locate the last command beginning with that string)
or as a number (an index into the history list, where a
negative number is used as an offset from the current command
number). If last is not specified it is set to the
current command for listing (so that fc -l -10
prints the last 10 commands) and to first otherwise.
If first is not specified it is set to the previous
command for editing and -16 for listing.
The -n flag suppresses the command numbers
when listing. The -r flag reverses the order
of the commands. If the -l flag is given,
the commands are listed on standard output. Otherwise, the
editor given by ename is invoked on a file
containing those commands. If ename is not given,
the value of the FCEDIT variable is used,
and the value of EDITOR if
FCEDIT is not set. If neither variable is
set, vi is used. When editing is complete, the
edited commands are echoed and executed.
In the second form, command is re-executed after
each instance of pat is replaced by rep. A
useful alias to use with this is ``r=fc -s'', so that typing
``r cc'' runs the last command beginning with ``cc'' and
typing ``r'' re-executes the last command.
If the first form is used, the return value is 0 unless an
illegal option is encountered or first or
last specify history lines out of range. If the
-e 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 cmd does not specify a valid
history line, in which case fc returns
failure.
-
fg [jobspec]
-
Place jobspec in the foreground, and make it the
current job. If jobspec is not present, the shell's
notion of the current job 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 jobspec does not specify a valid job or
jobspec specifies a job that was started without job
control.
-
getopts optstring name
[args]
-
getopts is used by shell procedures to parse
positional parameters. optstring contains the option
letters to be recognized; if a letter is followed by a colon,
the option is expected to have an argument, which should be
separated from it by white space. Each time it is invoked,
getopts places the next option in the shell
variable name, initializing name if it does
not exist, and the index of the next argument to be processed
into the variable OPTIND.
OPTIND is initialized to 1 each time the shell
or a shell script is invoked. When an option requires an
argument, getopts places that argument into
the variable OPTARG. The shell does not reset
OPTIND automatically; it must be manually
reset between multiple calls to getopts within
the same shell invocation if a new set of parameters is to be
used.
getopts can report errors in two ways. If
the first character of optstring is a colon,
silent error reporting is used. In normal operation
diagnostic messages are printed when illegal options or
missing option arguments are encountered. If the variable
OPTERR is set to 0, no error message will be
displayed, even if the first character of optstring
is not a colon.
If an illegal option is seen, getopts places
? into name and, if not silent, prints an error
message and unsets OPTARG. If
getopts is silent, the option character
found is placed in OPTARG and no diagnostic
message is printed.
If a required argument is not found, and
getopts is not silent, a question mark
(?) is placed in name,
OPTARG is unset, and a diagnostic message is
printed. If getopts is silent, then a colon
(:) is placed in name and OPTARG is
set to the option character found.
getopts normally parses the positional
parameters, but if more arguments are given in args,
getopts parses those instead.
getopts returns true if an option, specified
or unspecified, is found. It returns false if the end of
options is encountered or an error occurs.
-
hash [-r] [name]
-
For each name, the full pathname of the command is
determined and remembered. The -r option
causes the shell to forget all remembered locations. If no
arguments are given, information about remembered commands is
printed. An argument of -- disables option
checking for the rest of the arguments. The return status is
true unless a name is not found or an illegal option
is supplied.
-
help [pattern]
-
Display helpful information about builtin commands. If
pattern is specified, help gives
detailed help on all commands matching pattern;
otherwise a list of the builtins is printed. The return status
is 0 unless no command matches pattern.
-
history [n]
-
history -rwan
[filename]
-
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 a non-option argument is supplied, it is
used as the name of the history file; if not, the value of
HISTFILE is used. Options, if supplied, have
the following meanings:
-
-a
-
Append the ``new'' history lines (history lines entered since
the beginning of the current bash session) to
the history file
-
-n
-
Read the history lines not already read from the history file
into the current history list. These are lines appended to the
history file since the beginning of the current
bash session.
-
-r
-
Read the contents of the history file and use them as the
current history
-
-w
-
Write the current history to the history file, overwriting the
history file's contents.
The return value is 0 unless an illegal option is encountered or
an error occurs while reading or writing the history file.
-
jobs [-lnp] [
jobspec ... ]
-
jobs -x command [
args ... ]
-
The first form lists the active jobs. The -l
option lists process IDs in addition to the normal information;
the -p option lists only the process ID of the
job's process group leader. The -n option
displays only jobs that have changed status since last
notified. If jobspec is given, output is restricted to
information about that job. The return status is 0 unless an
illegal option is encountered or an illegal jobspec is
supplied.
If the -x option is supplied,
jobs replaces any jobspec found in
command or args with the corresponding
process group ID, and executes command passing it
args, returning its exit status.
-
kill [-s sigspec |
-sigspec] [pid | jobspec]
...
-
kill -l [signum]
-
Send the signal named by sigspec to the processes
named by pid or jobspec. sigspec is
either a signal name such as SIGKILL or a
signal number. If sigspec is a signal name, the name
is case insensitive and may be given with or without the
SIG prefix. If sigspec is not
present, then SIGTERM is assumed. An argument
of -l lists the signal names. If any arguments
are supplied when -l is given, the names of
the specified signals are listed, and the return status is 0.
An argument of -- disables option checking for
the rest of the arguments. kill returns true
if at least one signal was successfully sent, or false if an
error occurs or an illegal option is encountered.
-
let arg [arg ...]
-
Each arg is an arithmetic expression to be evaluated
(see ARITHMETIC EVALUATION). If the last
arg evaluates to 0, let returns 1; 0
is returned otherwise.
-
local [name[=value] ...]
-
For each argument, create a local variable named name,
and assign it value. When local is
used within a function, it causes the variable name to
have a visible scope restricted to that function and its
children. With no operands, local writes a
list of local variables to the standard output. It is an error
to use local when not within a function. The
return status is 0 unless local is used
outside a function, or an illegal name is supplied.
-
logout
-
Exit a login shell.
-
popd [+/-n]
-
Removes entries from the directory stack. With no arguments,
removes the top directory from the stack, and performs a
cd to the new top directory.
-
+n
-
removes the nth entry counting from the left of the
list shown by dirs, 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 dirs, starting with zero. For
example: ``popd -0'' removes the last directory, ``popd -1''
the next to last.
If the popd command is successful, a
dirs is performed as well, and the return status
is 0. popd returns false if an illegal option is
encountered, the directory stack is empty, a non-existent
directory stack entry is specified, or the directory change
fails.
-
pushd [dir]
-
pushd +/-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 arguments, exchanges the top two directories
and returns 0, unless the directory stack is empty.
-
+n
-
Rotates the stack so that the nth directory (counting
from the left of the list shown by dirs) is at
the top.
-
-n
-
Rotates the stack so that the nth directory (counting
from the right) is at the top.
-
dir
-
adds dir to the directory stack at the top, making it
the new current working directory.
If the pushd command is successful, a
dirs is performed as well. If the first form is
used, pushd returns 0 unless the cd to
dir fails. With the second form, pushd
returns 0 unless the directory stack is empty, a non-existant
directory stack element is specified, or the directory change to
the specified new current directory fails.
-
pwd
-
Print the absolute pathname of the current working directory.
The path printed contains no symbolic links if the
-P option to the set builtin
command is set. See also the description of
nolinks under Shell Variables
above). The return status is 0 unless an error occurs while
reading the pathname of the current directory.
-
read [-r] [name ...]
-
One line is read from the standard input, and the first word is
assigned to the first name, the second word to the
second name, and so on, with leftover words assigned
to the last name. Only the characters in
IFS are recognized as word delimiters. If no
names are supplied, the line read is assigned to the
variable REPLY. The return code is zero,
unless end-of-file is encountered. If the -r
option is given, a backslash-newline pair is not ignored, and
the backslash is considered to be part of the line.
-
readonly [-f] [name
...]
-
readonly -p
-
The given names are marked readonly and the values of
these names may not be changed by subsequent
assignment. If the -f option is supplied, the
functions corresponding to the names are so marked. If
no arguments are given, or if the -p option is
supplied, a list of all readonly names is printed. An argument
of -- disables option checking for the rest of
the arguments. The return status is 0 unless an illegal option
is encountered, one of the names is not a legal shell
variable name, or -f is supplied with a
name that is not a function.
-
return [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 function body. If used
outside a function, but during execution of a script by the
. (source) command, it causes
the shell to stop executing that script and return either
n or the exit status of the last command executed
within the script as the exit status of the script. If used
outside a function and not during execution of a script by
., the return status is false.
-
set [--abefhkmnptuvxldCHP]
[-o option] [arg ...]
-
-a
-
Automatically mark variables which are modified or created for
export to the environment of subsequent commands.
-
-b
-
Cause the status of terminated background jobs to be reported
immediately, rather than before the next primary prompt. (Also
see notify under Shell
Variables above).
-
-e
-
Exit immediately if a simple-command (see
SHELL GRAMMAR above) exits with a non-zero
status. The shell does not exit if the command that fails is
part of an until or while loop, part of an
if statement, part of a && or
list, or if the command's return value is
being inverted via !.
-
-f
-
Disable pathname expansion.
-
-h
-
Locate and remember function commands as functions are defined.
Function commands are normally looked up when the function is
executed.
-
-k
-
All keyword arguments are placed in the environment for a
command, not just those that precede the command name.
-
-m
-
Monitor mode. Job control is enabled. This flag is on by
default for interactive shells on systems that support it (see
JOB CONTROL above). Background processes run
in a separate process group and a line containing their exit
status is printed upon their completion.
-
-n
-
Read commands but do not execute them. This may be used to
check a shell script for syntax errors. This is ignored for
interactive shells.
-
-o option-name
-
The option-name can be one of the following:
-
allexport
-
Same as -a.
-
braceexpand
-
The shell performs brace expansion (see Brace
Expansion above). This is on by default.
-
emacs
-
Use an emacs-style command line editing interface. This is
enabled by default when the shell is interactive, unless the
shell is started with the -nolineediting
option.
-
errexit
-
Same as -e.
-
histexpand
-
Same as -H.
-
ignoreeof
-
The effect is as if the shell command `IGNOREEOF=10' had been
executed (see Shell Variables above).
-
interactive-comments
-
Allow a word beginning with # to cause that
word and all remaining characters on that line to be ignored in
an interactive shell (see COMMENTS above).
-
monitor
-
Same as -m.
-
noclobber
-
Same as -C.
-
noexec
-
Same as -n.
-
noglob
-
Same as -f.
-
nohash
-
Same as -d.
-
notify
-
Same as -b.
-
nounset
-
Same as -u.
-
physical
-
Same as -P.
-
posix
-
Change the behavior of bash where the default operation differs
from the Posix 1003.2 standard to match the standard.
-
privileged
-
Same as -p.
-
verbose
-
Same as -v.
-
vi
-
Use a vi-style command line editing interface.
-
xtrace
-
Same as -x.
If no option-name is supplied, the values of the current
options are printed.
-
-p
-
Turn on privileged mode. In this mode, the
$ENV file is not processed, and shell
functions are not inherited from the environment. This is
enabled automatically on startup if the effective user (group)
id is not equal to the real user (group) id. Turning this
option off causes the effective user and group ids to be set to
the real user and group ids.
-
-t
-
Exit after reading and executing one command.
-
-u
-
Treat unset variables as an error when performing 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.
-
-v
-
Print shell input lines as they are read.
-
-x
-
After expanding each simple-command,
bash displays the expanded value of
PS4, followed by the command and its expanded
arguments.
-
-l
-
Save and restore the binding of name in a
for name [in word]
command (see SHELL GRAMMAR above).
-
-d
-
Disable the hashing of commands that are looked up for
execution. Normally, commands are remembered in a hash table,
and once found, do not have to be looked up again.
-
-C
-
The effect is as if the shell command `noclobber=' had been
executed (see Shell Variables above).
-
-H
-
Enable ! style history substitution. This flag
is on by default when the shell is interactive.
-
-P
-
If set, do not follow symbolic links when performing commands
such as cd which change the current directory.
The physical directory is used instead.
-
--
-
If no arguments follow this flag, then the positional
parameters are unset. Otherwise, the positional parameters are
set to the args, even if some of them begin with a
-.
-
-
-
Signal the end of options, cause all remaining args to
be assigned to the positional parameters. The
-x and -v options are turned
off. If there are no args, the positional parameters
remain unchanged.
The flags are off by default unless otherwise noted. Using +
rather than - causes these flags to be turned off. The flags can
also be specified as options to an invocation of the shell. The
current set of flags may be found in $-. After
the option arguments are processed, the remaining n
args are treated as values for the positional parameters
and are assigned, in order, to $1,
$2, ...
$n. If no options or args are
supplied, all shell variables are printed. The return status is
always true unless an illegal option is encountered.
-
shift [n]
-
The positional parameters from n+1 ... are renamed to
$1 .... Parameters
represented by the numbers $# down to
$#-n+1 are unset. If n is 0,
no parameters are changed. If n is not given, it is
assumed to be 1. n must be a non-negative number less
than or equal to $#. If n is greater
than $#, the positional parameters are not
changed. The return status is greater than 0 if n is
greater than $# or less than 0; otherwise 0.
-
suspend [-f]
-
Suspend the execution of this shell until it receives a
SIGCONT signal. The -f 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 -f is not supplied, or if job
control is not enabled.
-
test expr
-
[ expr ]
-
Return a status of 0 (true) or 1 (false) depending on the
evaluation of the conditional expression expr.
Expressions may be unary or binary. Unary expressions are often
used to examine the status of a file. There are string
operators and numeric comparison operators as well. Each
operator and operand must be a separate argument. If
file is of the form /dev/fd/n, then file
descriptor n is checked.
-
-b file
-
True if file exists and is block special.
-
-c file
-
True if file exists and is character special.
-
-d file
-
True if file exists and is a directory.
-
-e file
-
True if file exists.
-
-f file
-
True if file exists and is a regular file.
-
-g file
-
True if file exists and is set-group-id.
-
-k file
-
True if file has its ``sticky'' bit set.
-
-L file
-
True if file exists and is a symbolic link.
-
-p file
-
True if file exists and is a named pipe.
-
-r file
-
True if file exists and is readable.
-
-s file
-
True if file exists and has a size greater than zero.
-
-S file
-
True if file exists and is a socket.
-
-t fd
-
True if fd is opened on a terminal.
-
-u file
-
True if file exists and its set-user-id bit is set.
-
-w file
-
True if file exists and is writable.
-
-x file
-
True if file exists and is executable.
-
-O file
-
True if file exists and is owned by the effective user
id.
-
-G file
-
True if file exists and is owned by the effective
group id.
-
file1 -nt file2
-
True if file1 is newer (according to modification
date) than file2.
-
file1 -ot file2
-
True if file1 is older than file2.
-
file1 -ef file
-
True if file1 and file2 have the same device
and inode numbers.
-
-z string
-
True if the length of string is zero.
-
-n string
-
string
-
True if the length of string is non-zero.
-
string1 = string2
-
True if the strings are equal.
-
string1 != string2
-
True if the strings are not equal.
-
! expr
-
True if expr is false.
-
expr1 -a expr2
-
True if both expr1 AND expr2 are true.
-
expr1 -o expr2
-
True if either expr1 OR expr2 is true.
-
arg1 OP arg2
-
OP is one of -eq,
-ne, -lt,
-le, -gt, or
-ge. These arithmetic binary operators return
true if arg1 is equal, not-equal, less-than,
less-than-or-equal, greater-than, or greater-than-or-equal than
arg2, respectively. Arg1 and arg2
may be positive integers, negative integers, or the special
expression -l string, which evaluates
to the length of string.
-
times
-
Print the accumulated user and system times for the shell and
for processes run from the shell. The return status is 0.
-
trap [-l] [arg]
[sigspec]
-
The command arg is to be read and executed when the
shell receives signal(s) sigspec. If arg is
absent or -, all specified signals are reset
to their original values (the values they had upon entrance to
the shell). If arg is the null string this signal is
ignored by the shell and by the commands it invokes.
sigspec is either a signal name defined in
<signal.h>, or a signal number. If
sigspec is EXIT (0) the command
arg is executed on exit from the shell. With no
arguments, trap prints the list of commands
associated with each signal number. The -l
option causes the shell to print a list of signal names and
their corresponding numbers. An argument of --
disables option checking for the rest of the arguments. Signals
ignored upon entry to the shell cannot be trapped or reset.
Trapped signals are reset to their original values in a child
process when it is created. The return status is false if
either the trap name or number is invalid; otherwise
trap returns true.
-
type [-all]
[-type | -path] name
[name ...]
-
With no options, indicate how each name would be
interpreted if used as a command name. If the
-type flag is used, type
prints a phrase which is one of alias,
keyword, function, builtin, or
file if name is an alias, shell reserved
word, function, builtin, or disk file, respectively. If the
name is not found, then nothing is printed, and an exit status
of false is returned. If the -path flag is
used, type either returns the name of the disk
file that would be executed if name were specified as
a command name, or nothing if -type would not
return file. If a command is hashed,
-path prints the hashed value, not necessarily
the file that appears first in PATH. If the
-all flag is used, type
prints all of the places that contain an executable named
name. This includes aliases and functions, if and only
if the -path flag is not also used. The table
of hashed commands is not consulted when using
-all. type accepts
-a, -t, and
-p in place of -all,
-type, and -path,
respectively. An argument of -- disables
option checking for the rest of the arguments.
type returns true if any of the arguments are
found, false if none are found.
-
ulimit [-SHacdfmstpnuv
[limit]]
-
Ulimit provides control over the resources
available to the shell and to processes started by it, on
systems that allow such control. The value of limit
can be a number in the unit specified for the resource, or the
value unlimited. The H and
S 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 H nor
S is specified, the command applies to the
soft limit. If limit is omitted, the current value of
the soft limit of the resource is printed, unless the
H option is given. When more than one resource
is specified, the limit name and unit is printed before the
value. Other options are interpreted as follows:
-
-a
-
all current limits are reported
-
-c
-
the maximum size of core files created
-
-d
-
the maximum size of a process's data segment
-
-f
-
the maximum size of files created by the shell
-
-m
-
the maximum resident set size
-
-s
-
the maximum stack size
-
-t
-
the maximum amount of cpu time in seconds
-
-p
-
the pipe size in 512-byte blocks (this may not be set)
-
-n
-
the maximum number of open file descriptors (most systems do
not allow this value to be set, only displayed)
-
-u
-
the maximum number of processes available to a single user
-
-v
-
The maximum amount of virtual memory available to the shell
An argument of -- disables option checking for
the rest of the arguments. If limit is given, it is the
new value of the specified resource (the -a
option is display only). If no option is given, then
-f is assumed. Values are in 1024-byte
increments, except for -t, which is in seconds,
-p, which is in units of 512-byte blocks, and
-n and -u, which are unscaled
values. The return status is 0 unless an illegal option is
encountered, a non-numeric argument other than
unlimited is supplied as limit, or an
error occurs while setting a new limit.
-
umask [-S] [mode]
-
The user file-creation mask is set to mode. If
mode begins with a digit, it is interpreted as an
octal number; otherwise it is interpreted as a symbolic mode
mask similar to that accepted by
chmod(1) . If mode is omitted, or if the
-S option is supplied, the current value of
the mask is printed. The -S option causes the
mask to be printed in symbolic form; the default output is an
octal number. An argument of -- disables
option checking for the rest of the arguments. The return
status is 0 if the mode was successfully changed or if no mode
argument was supplied, and false otherwise.
-
unalias [-a] [name
...]
-
Remove names from the list of defined aliases. If
-a is supplied, all alias definitions are
removed. The return value is true unless a supplied
name is not a defined alias.
-
unset [-fv] [name
...]
-
For each name, remove the corresponding variable or,
given the -f option, function. An argument of
-- disables option checking for the rest of
the arguments. Note that PATH,
IFS, PPID,
PS1, PS2,
UID, and EUID cannot be
unset. If any of RANDOM,
SECONDS, LINENO, or
HISTCMD are unset, they lose their special
properties, even if they are subsequently reset. The exit
status is true unless a name does not exist or is
non-unsettable.
-
wait [n]
-
Wait for the specified process and return its termination
status. n may be a process ID or a job specification;
if a job spec is given, all processes in that job's pipeline
are waited for. If n is not given, all currently
active child processes are waited for, and the return status is
zero. If n specifies a non-existant process or job,
the return status is 127. Otherwise, the return status is the
exit status of the last process or job waited for.
A login shell is one whose first character of argument
zero is a -, or one started with the
-login flag.
An interactive shell is one whose standard input and
output are both connected to terminals (as determined by
isatty(3) ), or one started with the -i
option. PS1 is set and $-
includes i if bash is
interactive, allowing a shell script or a startup file to test
this state.
Login shells:
On login (subject to the -noprofile option):
if /etc/profile exists, source it.
if ~/.bash_profile exists, source it,
else if ~/.bash_login exists, source it,
else if ~/.profile exists, source it.
On exit:
if ~/.bash_logout exists, source it.
Non-login interactive shells:
On startup (subject to the -norc and
-rcfile options):
if ~/.bashrc exists, source it.
Non-interactive shells:
On startup:
if the environment variable ENV is non-null,
expand
it and source the file it names, as if the command
if [ "$ENV" ]; then . $ENV; fi
had been executed, but do not use PATH to search
for the pathname. When not started in Posix mode, bash
looks for BASH_ENV before ENV.
If Bash is invoked as sh, it tries to mimic the
behavior of sh as closely as possible. For a
login shell, it attempts to source only /etc/profile and
~/.profile, in that order. The
-noprofile option may still be used to disable
this behavior. A shell invoked as sh does not
attempt to source any other startup files.
When bash is started in posix mode, as
with the -posix command line option, it follows
the Posix standard for startup files. In this mode, the
ENV variable is expanded and that file sourced;
no other startup files are read.
-
Bash Features, Brian Fox and Chet Ramey
-
The Gnu Readline Library, Brian Fox and Chet Ramey
-
The Gnu History Library, Brian Fox and Chet Ramey
-
A System V Compatible Implementation of 4.2BSD Job
Control, David Lennert
-
Portable Operating System Interface (POSIX) Part 2: Shell
and Utilities, IEEE
-
sh(1) ,
ksh(1) ,
csh(1)
-
emacs(1) ,
vi(1)
-
readline(3)
-
/bin/bash
-
The bash executable
-
/etc/profile
-
The systemwide initialization file, executed for login shells
-
~/.bash_profile
-
The personal initialization file, executed for login shells
-
~/.bashrc
-
The individual per-interactive-shell startup file
-
~/.inputrc
-
Individual readline initialization file
Brian Fox, Free Software Foundation (primary author)
bfox@ai.MIT.Edu
Chet Ramey, Case Western Reserve University
chet@ins.CWRU.Edu
If you find a bug in bash, 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 bash that you
have.
Once you have determined that a bug actually exists, use the
bashbug command to submit a bug report. If you have a
fix, you are welcome to mail that as well! Suggestions and
`philosophical' bug reports may be mailed to
bug-bash@prep.ai.MIT.Edu or posted to the Usenet
newsgroup gnu.bash.bug.
ALL bug reports should include:
-
The version number of bash
-
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
bashbug 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 chet@ins.CWRU.Edu.
It's too big and too slow.
There are some subtle differences between bash
and traditional versions of sh, mostly because
of the POSIX specification.
Aliases are confusing in some uses.
Table of Contents
This work is licensed under a
Creative
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