💻 Shell Scripting Advice

First Published: 2024-01-14

Shell is an untyped, interpreted "programming language" ubiquitous since the 80s. It comes with no package manager of its own and is weak in isolation. It hinges on the operating system to do what the language can't: almost everything. When I'm talking about shell scripting I'm assuming a gnu (or busybox) environment to go along with it.

My authority on the matter comes primarily from two years leading ani-cli development. Ani-cli is an incredibly cross-plattform and featureful cli tool to browse and play anime.

When Not To Use Shell

If your application needs to do math, use python instead. Sure you can do some basic math in shell scripts, but when you can anticipate in advance that a lot of your program data will consist of numbers, pick sth else. My heuristic: if it needs to do more than count, do it in python.

Shell Scripts are manageable up to around a thousand LoC. Shell has significantly more footguns than Python. Use Python if you need to frequently collaborate with noobs.

Dev Tools

Shellcheck is a linter for shell that catches many common pitfalls.
Shfmt is a formatter for shell. I like to use it with the -i 4 -ci options.
I don't use LSP, but a shell language server is available via bash lsp.
For CI I like to use the sh-checker by luizm. It combines shellcheck and shfmt.

Debugging & Profiling

Just run your script with sh -x to get pretty verbose runtime output.
Ideally, cook up increments of your program in an interactive shell of your choice, this speeds up the feedback loop. For benchmarking, use time or hyperfine.
For pinpointing bottlenecks it can be useful to put date +%S:%N statements near I/O areas or borders of code segments, this prints seconds and nanoseconds.
For advanced debugging and profiling, strace can be useful.

Useful External Programs

Further Reading

Read through the lists of all the available programs in the GNU Coreutils and util-linux.
If you want to deploy via docker, busybox too.
Read the manuals for find, grep and sed in depth.
I won't stop you from checking out awk for sake of completeness, but haven't found it very fruitful myself.

After picking up the tools of this article and reading the recommended manuals, you will soon write better shell scripts than 90% of shell programmers out there, you're welcome.


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