5.3 KiB
====== The set builtin command ======
FIXME incomplete - text, examples, maybe extended description
===== Synopsis =====
set [--abefhkmnptuvxBCHP] <-o OPTIONNAME> [-][--]
===== Description =====
''set'' is primarily made to
- set the positional parameters (see handling positional parameters) to ''''
- 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