6.8 KiB
The set builtin command
FIXME incomplete - text, examples, maybe extended description
Synopsis
set [--abefhkmnptuvxBCHP] <-o OPTIONNAME> [-][--] <POSPARAMS>
Description
set is primarily made to
- set the positional parameters (see handling positional
parameters) to
<POSPARAMS> - set shell attributes with short options (see below)
- set shell attributes with long option names (see below)
Without any options, set displays all shell- and environment-variables
(only is POSIX-mode) in a re-usable format NAME=VALUE.
Attributes
All attributes below can be switched on using -X and switched off
using +X. This is done because of the historical meaning of the - to
set flags (true for most commands on UNIX(r)).
Flag Optionname Description
-a allexport Automatically mark new and altered variables to be exported to subsequent environments.
-b notify Don't wait for the next prompt to print when showing the reports for a terminated background job (only with job control)
-e errexit When set, the shell exits when a simple command in a command list exits non-zero (FALSE). This is not done in situations, where the exit code is already checked (if, while, until, ||, &&)
-f noglob Disable pathname expansion (globbing)
-h hashall Remembers the location of commands when they're called (hashing). Enabled by default.
-k keyword Allows to place environment-assignments everywhere in the commandline, not only infront of the called command.
-m monitor Monitor mode. With job control, a short descriptive line is printed when a backgroud job ends. Default is "on" for interactive shells (with job control).
-n noexec Read and parse but do not execute commands - useful for checking scripts for syntax errors. Ignored by interactive shells.
-o Set/unset attributes with long option names, e.g. set -o noglob. The long option names are in the second column of this table. If no option name is given, all options are printed with their current status.
-p privileged Turn on privileged mode.
-t onecmd Exit after reading and executing one command.
-u nounset Treat unset variables as an error when performing parameter expansion. Non-interactive shells exit on this error.
-v verbose Print shell input lines as they are read - useful for debugging.
-x xtrace Print commands just before execution - with all expansions and substitutions done, and words marked - useful for debugging.
-B braceexpand The shell performs brace expansion This is on by default.
-C <BOOKMARK:tag_noclobber>noclobber Don't overwrite files on redirection operations. You can override that by specifying the >| redirection operator when needed. See redirection
-E errtrace ERR-traps are inherited by by shell functions, command substitutions, and commands executed in a subshell environment.
-H histexpand Enable !-style history expansion. Defaults to on for interactive shells.
-P physical Don't follow symlinks when changing directories - use the physical filesystem structure.
-T functrace DEBUG- and RETURN-traps are inherited by subsequent environments, like -E for ERR trap.
- "End of options" - all following arguments are assigned to the positional parameters, even when they begin with a dash. -x and -v options are turned off. Positional parameters are unchanged (unlike using --!) when no further arguments are given.
-- If no arguments follow, the positional parameters are unset. With arguments, the positional parameters are set, even if the strings begin with a - (dash) like an option.
Long options usable with -o without a short equivalent
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 --noediting option.
history If set, command historization is done (enabled by default on interactive shells)
ignoreeof The effect is as if the shell command IGNOREEOF=10 had been executed. See shell variables.
nolog (currently ignored)
pipefail If set, the exit code from a pipeline is different from the normal ("last command in pipeline") behaviour: TRUE when no command failed, FALSE when something failed (code of the rightmost command that failed)
posix When set, Bash runs in POSIX mode.
vi Enables a vi-style command line editing interface.
Examples
Tag a part of a shell script to output debugging information (-x):
#!/bin/bash
...
set -x # on
...
set +x # off
...
Portability considerations
set and its basic behaviour and options are specified by POSIX(r).
However, options that influence Bash-specific things are not portable,
naturally.
See also
- Internal: The shopt builtin command