====== Bash ======

The **__B__ourne __A__gain __Sh__ell** is the default command language / shell in [[Linux]], and I've never bothered to try any other. You type stuff in (or paste it from stackexchange...) and useful stuff happens.

===== Features =====

==== Arguments ====

You can use [[getopts]] to read arguments attached to the command. You use a ''while'' loop and a ''case'' statement to figure out what to do with the arguments/flags entered.

In this example you can use ''-i'' and ''-o'' arguments to specify file names and they will be stored in variables ''input'' and ''output''.

<code bash>
while getopts :io flag
do
	case $flag in
		i) input=${OPTARG} ;;
		o) output=${OPTARG} ;;
	esac
done
</code>

==== Conditional Constructs ====

=== if ===


-n string True if the length of string is non-zero. -a file True if file exists. DPMT USE -a, it's weird

In the documentation of test you will also see a the switch -e. This switch tests the following argument and evaluates to true if that argument is a file or directory that exists. More useful still is the -f switch which evaluates to true if the following argument exists and is a regular file (as opposed to a directory or a block device, or whatever).

=== case ===

===== Examples =====

==== Randomised file names ====

  * https://askubuntu.com/questions/1107016/how-to-change-names-of-files-in-a-directory-to-random-generated-names

<code bash>
for file in *.jpeg; do
	mv -- "$file" "$RANDOM.jpeg"
done
</code>

<code bash>
for file in *.jpeg; do
	mv -- "$file" "$(mktemp --dry-run XXXXXXXX.jpeg)"
done
</code>

==== Move all files in subdirectories to parent ====

  * https://unix.stackexchange.com/questions/358284/move-all-files-inside-sub-folders-to-parent-folder

<code bash>
find . -mindepth 2 -type f -print -exec mv {} . \;
</code>

==== See Also ====

Bash examples elsewhere on the wiki:

  * [[ffmpeg]]
  * [[imagemagick]]
  * [[tumbler]]

===== See Also =====

  * [[wp>Bash (Unix shell)]]
  * [[https://www.gnu.org/software/bash/|GNU Bash]] - Homepage

{{tag>guide language Linux}}