Bash Control Scripts
Bash works great for "control" scripts, as part of the unix philosophy, to glue a series of steps together and play with the filesystem - try to avoid using it to implement computation directly, there are loads of gotchas that are hard to prevent or identify.
Useful Snippets
What follows are a selection of snippets I find useful, some have their caveats. Feel like something important is missing? Contact me and tell me.
Work Locally
This is incredibly useful for build or run scripts, which need to execute on items relative to where the script itself is.
source_dir="$(cd $(dirname ${BASH_SOURCE[0]}) && pwd)"
cd $source_dir
At any later point you can cd $source_dir to reset yourself without having to worry about where you have managed to end up. Useful when running intermediate scripts and working inside repositories or in other 'relative path' situations.
Fail Fast
Missing errors introduces bugs. Strict mode is useful but not perfect, read the blog post where I first found it here (by Aaron Maxwell).
set -euo pipefail
$IFS=$'\n\t'
The following assumes you have at least skimmed the blog :- I use -uo pipefail at all times and will toggle -e for times when I am expecting an error code. The IFS change is not actually something I will implement until using a loop - I prefer to set it for the specific code than as a general case.
Change the input
Sometimes you want to pretend things were different:
#!/bin/bash
echo "Input: \"$@\""
set -- "Three blind mice"
echo "Out: \"$@\""
Here we manipulate the calling arguments, useful with getopt and getopts