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75 lines
5.3 KiB
Plaintext
75 lines
5.3 KiB
Plaintext
====== The set builtin command ======
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FIXME incomplete - text, examples, maybe extended description
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===== Synopsis =====
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<code>
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set [--abefhkmnptuvxBCHP] <-o OPTIONNAME> [-][--] <POSPARAMS>
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</code>
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===== Description =====
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''set'' is primarily made to
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* set the positional parameters (see [[scripting:posparams | handling positional parameters]]) to ''<POSPARAMS>''
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* set shell attributes with short options (see below)
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* set shell attributes with long option names (see below)
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Without any options, ''set'' displays all shell- and environment-variables (only is POSIX-mode) in a re-usable format ''NAME=VALUE''.
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==== Attributes ====
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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)).
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^Flag^Optionname^Description^
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|''-a''|''allexport''|Automatically mark new and altered variables to be exported to subsequent environments.|
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|''-b''|''notify''|Don't wait for the next prompt to print when showing the reports for a terminated background job (only with job control)|
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|''-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'', ''<nowiki>||</nowiki>'', ''<nowiki>&&</nowiki>'')|
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|''-f''|''noglob''|Disable [[syntax:expansion:globs | pathname expansion]] (globbing)|
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|''-h''|''hashall''|Remembers the location of commands when they're called (hashing). Enabled by default.|
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|''-k''|''keyword''|Allows to place environment-assignments everywhere in the commandline, not only infront of the called command.|
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|''-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).|
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|''-n''|''noexec''|Read and parse but **do not execute commands** - useful for checking scripts for syntax errors. Ignored by interactive shells.|
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|''-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.|
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|''-p''|''privileged''|Turn on privileged mode.|
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|''-t''|''onecmd''|Exit after reading and executing **one** command.|
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|''-u''|''nounset''|Treat unset variables as an error when performing parameter expansion. Non-interactive shells exit on this error.|
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|''-v''|''verbose''|Print shell input lines as they are read - useful for debugging.|
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|''-x''|''xtrace''|Print commands just before execution - with all expansions and substitutions done, and words marked - useful for debugging.|
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|''-B''|''braceexpand''|The shell performs [[syntax:expansion:brace | brace expansion]] This is on by default.|
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|''-C''|<BOOKMARK:tag_noclobber>''noclobber''|Don't overwrite files on redirection operations. You can override that by specifying the ''>|'' redirection operator when needed. See [[syntax:redirection | redirection]]|
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|''-E''|''errtrace''|''ERR''-traps are inherited by by shell functions, command substitutions, and commands executed in a subshell environment.|
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|''-H''|''histexpand''|Enable ''!''-style history expansion. Defaults to ''on'' for interactive shells.|
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|''-P''|''physical''|Don't follow symlinks when changing directories - use the physical filesystem structure.|
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|''-T''|''functrace''|''DEBUG''- and ''RETURN''-traps are inherited by subsequent environments, like ''-E'' for ''ERR'' trap.|
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|''-''| |"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 ''<nowiki>--</nowiki>''!) when no further arguments are given.|
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|''<nowiki>--</nowiki>''| |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.|
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^^Long options usable with ''-o'' without a short equivalent ^^
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| |''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.|
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| |''history''|If set, command historization is done (enabled by default on interactive shells)|
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| |''ignoreeof''|The effect is as if the shell command ''IGNOREEOF=10'' had been executed. See [[syntax:shellvars | shell variables]].|
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| |''nolog''|**(currently ignored)**|
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| |''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)|
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| |''posix''|When set, Bash runs in POSIX mode.|
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| |''vi''|Enables a ''vi''-style command line editing interface.|
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===== Examples =====
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Tag a part of a shell script to output debugging information (''-x''):
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<code bash>
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#!/bin/bash
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...
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set -x # on
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...
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set +x # off
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...
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</code>
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===== Portability considerations =====
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''set'' and its basic behaviour and options are specified by POSIX(r). However, options that influence Bash-specific things are not portable, naturally.
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===== See also =====
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* Internal: [[commands:builtin:shopt | The shopt builtin command]]
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