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83 lines
5.0 KiB
Markdown
83 lines
5.0 KiB
Markdown
# The set builtin command
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!!! warning "FIXME"
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incomplete text, examples, maybe extended description
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## Synopsis
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set [--abefhkmnptuvxBCHP] <-o OPTIONNAME> [-][--] <POSPARAMS>
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## Description
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`set` is primarily made to
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- set the positional parameters (see [handling positional
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parameters](../../scripting/posparams.md)) 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
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(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
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using `+X`. This is done because of the historical meaning of the `-` to
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set flags (true for most commands on UNIX(r)).
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|Flag|Optionname|Description|
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|----|----------|-----------|
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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`, `||`, `&&`)|
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|`-f`|`noglob`|Disable [pathname expansion](../../syntax/expansion/globs.md) (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 [brace expansion](../../syntax/expansion/brace.md) This is on by default.|
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|`-C`|`noclobber`|Don't overwrite files on redirection operations. You can override that by specifying the `>|` redirection operator when needed. See [redirection](../../syntax/redirection.md)|
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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 `--`!) when no further arguments are given.|
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|`--`||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 [shell variables](../../syntax/shellvars.md).|
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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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``` 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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```
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## Portability considerations
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`set` and its basic behaviour and options are specified by POSIX(r).
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However, options that influence Bash-specific things are not portable,
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naturally.
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## See also
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- Internal: [The shopt builtin command](../../commands/builtin/shopt.md)
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