I posted some suggestion to improve robustness of shell scripts in https://endorama.dev/2022/making-your-shell-scripts-bulletproof/, but there are a few more that I usually use that I think may be useful, so here is part 2 of it.
Don’t split words on space
The Internal Field Separator that is used for word splitting after expansion and to split lines into words with the read builtin command. The default value is
<space><tab><newline>.
From BASH manual, under SHELL BUILTIN COMMANDS > Shell Variables.
The default value of this variable means BASH split lines on spaces too. Most of the time this is a very confusing behaviour, as we are not used to consider a space a sentence terminator or split point (compared to newline or tab character).
To change this to only newlines and tabs use:
IFS=$'\n\t'
99% of the time I never ever noticed the difference in my shell scripts, and if you really need splitting on space you can always prefix your command with IFS=$' '.
You may also want to save the original IFS value and you can do so by:
ORIGINAL_IFS=$IFS
IFS=$'\n\t'
This way you can still use the old IFS value by prefixing commands with IFS=$ORIGINAL_IFS.
Use traps
….
Use shellcheck
I don’t think I came across something more beneficial to my shell script writing than Shellcheck. Shellcheck is a static analysis tool for shell scripts (BASH is supported too).
The reason why you must run this is that will help you avoid all those errors you may be unconsciously making right now.
Stop formatting your code
…manually!. Use shfmt to do it automatically! shfmt is part of a Golang-based shell parser and interpreter, a really cool project.
Test BASH scripts with bats
Unit testing, in BASH. HELL YEAH! bats is a small framework to do unit testing in BASH (you can actually use it for any command that BASH can run, but let’s stay focused here).
Happy coding 😉
