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(bashref.info)The Set Builtin
The Set Builtin
===============
This builtin is so complicated that it deserves its own section.
`set'
set [--abefhkmnptuvxBCHP] [-o OPTION] [ARGUMENT ...]
If no options or arguments are supplied, `set' displays the names
and values of all shell variables and functions, sorted according
to the current locale, in a format that may be reused as input.
When options are supplied, they set or unset shell attributes.
Options, if specified, have the following meanings:
`-a'
Mark variables and function 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 printing the next primary
prompt.
`-e'
Exit immediately if a simple command (Note: Simple
Commands) exits with a non-zero status, unless 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 status is being inverted using `!'. A trap
on `ERR', if set, is executed before the shell exits.
`-f'
Disable file name generation (globbing).
`-h'
Locate and remember (hash) commands as they are looked up for
execution. This option is enabled by default.
`-k'
All arguments in the form of assignment statements are placed
in the environment for a command, not just those that precede
the command name.
`-m'
Job control is enabled (Note: Job Control).
`-n'
Read commands but do not execute them; this may be used to
check a script for syntax errors. This option is ignored by
interactive shells.
`-o OPTION-NAME'
Set the option corresponding to OPTION-NAME:
`allexport'
Same as `-a'.
`braceexpand'
Same as `-B'.
`emacs'
Use an `emacs'-style line editing interface (Note:
Command Line Editing).
`errexit'
Same as `-e'.
`hashall'
Same as `-h'.
`histexpand'
Same as `-H'.
`history'
Enable command history, as described in Note: Bash
History Facilities. This option is on by default in
interactive shells.
`ignoreeof'
An interactive shell will not exit upon reading EOF.
`keyword'
Same as `-k'.
`monitor'
Same as `-m'.
`noclobber'
Same as `-C'.
`noexec'
Same as `-n'.
`noglob'
Same as `-f'.
`nolog'
Currently ignored.
`notify'
Same as `-b'.
`nounset'
Same as `-u'.
`onecmd'
Same as `-t'.
`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 (Note: Bash POSIX Mode). This is intended to
make Bash behave as a strict superset of that standard.
`privileged'
Same as `-p'.
`verbose'
Same as `-v'.
`vi'
Use a `vi'-style line editing interface.
`xtrace'
Same as `-x'.
`-p'
Turn on privileged mode. In this mode, the `$BASH_ENV' and
`$ENV' files are not processed, shell functions are not
inherited from the environment, and the `SHELLOPTS' variable,
if it appears in the environment, is ignored. If the shell
is started with the effective user (group) id not equal to the
real user (group) id, and the `-p' option is not supplied,
these actions are taken and the effective user id is set to
the real user id. If the `-p' option is supplied at startup,
the effective user id is not reset. Turning this option off
causes the effective user and group ids to be set to the real
user and group ids.
`-t'
Exit after reading and executing one command.
`-u'
Treat unset variables as an error when performing parameter
expansion. An error message will be written to the standard
error, and a non-interactive shell will exit.
`-v'
Print shell input lines as they are read.
`-x'
Print a trace of simple commands and their arguments after
they are expanded and before they are executed.
`-B'
The shell will perform brace expansion (Note: Brace
Expansion). This option is on by default.
`-C'
Prevent output redirection using `>', `>&', and `<>' from
overwriting existing files.
`-H'
Enable `!' style history substitution (Note: History
Interaction). This option is on by default for interactive
shells.
`-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. By default, Bash follows
the logical chain of directories when performing commands
which change the current directory.
For example, if `/usr/sys' is a symbolic link to
`/usr/local/sys' then:
$ cd /usr/sys; echo $PWD
/usr/sys
$ cd ..; pwd
/usr
If `set -P' is on, then:
$ cd /usr/sys; echo $PWD
/usr/local/sys
$ cd ..; pwd
/usr/local
`--'
If no arguments follow this option, then the positional
parameters are unset. Otherwise, the positional parameters
are set to the ARGUMENTS, even if some of them begin with a
`-'.
`-'
Signal the end of options, cause all remaining ARGUMENTS to
be assigned to the positional parameters. The `-x' and `-v'
options are turned off. If there are no arguments, the
positional parameters remain unchanged.
Using `+' rather than `-' causes these options to be turned off.
The options can also be used upon invocation of the shell. The
current set of options may be found in `$-'.
The remaining N ARGUMENTS are positional parameters and are
assigned, in order, to `$1', `$2', ... `$N'. The special
parameter `#' is set to N.
The return status is always zero unless an invalid option is
supplied.
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