Analog Moment

by James Cox-Morton (@th3james)

The shabby, productive glory of personal shell scripting

As professional engineers, we're taught to solve our problems robustly and generically.

We're discouraged from making assumptions about the environments our code will run in, as this can build coupling into the system which becomes intractable if those assumptions don't hold. We think hard about edge-cases where our string-parsing RegExp might not work. We don't couple our behaviour directly to our communication interfaces, as we may want to offer a different interface to that same behaviour later. We don't assume that we'll have access to certain libraries, so we use dependency management systems to declare and install our requirements.

The phrase "works on my machine" is viewed as the mark of an amateur.

This mindset is sensible in uncertain environments, where requirements can change, features are speculative, we can't anticipate the contexts in which our code will run, and where we have customers to whom we owe a good experience. And we've all been in codebases which are hard to maintain, extend and debug because they lack the qualities which come from these principles.

But it's not always much fun being a professional. Solving our problems generically takes longer. It requires us to think carefully about edge cases we'd rather not deal with. And sometimes, as an engineer, you just want to build things.

Personal Shell Scripting

Like many nerds, I maintain my dotfiles on GitHub, to allow me to version and sync my system configuration across my computers.

One of my long running frustrations has been that different machines often have different libraries and tools installed, so I ended up having lines of config which I comment out on machines where they're not relevant. This was annoying whenever I set up a new machine, and I'd always have to avoid committing uncommented lines whenever making changes to my config.

The straw that finally broke the camel's back was when I got an Apple Silicon Mac and discovered that homebrew paths were different. Now I also needed to conditionally modify my PATH specification depending on my architecture. Finally it became more lazy to not solve the problem. So I thought to myself, what's the easiest fix I can think of?

I use the delightful fish shell and had been looking for an excuse to learn a bit more about scripting with it. Some quick Googling and I had a simple function to string match on the result of a subshell to uname

function on_apple_silicon
  set -l system_arch_name (uname -m)
  if string match -q "x86_64" $system_arch_name 
    return 1
    return 0

Immediately, my "professional" programmer brain kicked in. There's probably a way to collapse lines 3-7 into a one-liner. Perhaps there are edge cases where the string match fails. What if I'm on a 32-bit system?

And then I realised: who cares? This code is for me and me only, and it works on every machine I own, so time to move on to the next problem. Now I can call this function to conditionally set my homebrew path.

Drunk on my new found productivity, born from ignoring the need to do things "properly", I set about solving my issue where I didn't want to install my direnv hooks on systems where direnv isn't installed. This time I didn't even need to do any Googling:

function is_installed -a executable_name
  set -l installed (which $executable_name)
  string length -q -- $installed

if is_installed direnv
  direnv hook fish | source

Is this the best way to see if a program is installed? I haven't even bothered to think about it since writing the function and finding it worked. And this is how the is_installed function shall stay until it doesn't work on one on my machines. Worst case scenario is that I annoy future me, and that guy is the worst.

Since making this selfish realisation, I've had much more fun with fish scripts. Liberated from the pressures of perfection, I've written loads of little ones and gradually replaced my notes library of shell snippets with custom functions. You can get a lot done when you truly embrace YAGNI.

Action matters

Professionalism was actually stopping me from solving my problems - I'd been working around the issue of different config on different machines for years but I'd not solved it as I mentally shrunk from the effort required to make it work "correctly". In the end, it turned out a 6 line function was good enough.

As someone who tries to have a bias towards action, this was a bit of a scary realisation. Building things and using them in anger is the ultimate feedback mechanism and it's a reminder that there is a balance to be struck between coding rigorously and learning by shipping. I won't go as far as to declare that you should Write Shitty Code, but as someone who takes pride in writing high-quality code, having these personal scripts as a space to explore a shabbier style of programming was a reminder of some of the benefits of the other side of that balance.

Now I'll try to catch myself if I'm procrastinating on solving a problem because I can't think of an elegant approach. Are there any little annoyances you haven't fixed because you couldn't get over the hump of solving it properly?

If you are so inclined, you can check my little collection of scripts here. They come with no warranty and they have no documentation, but guess what?

"Works on my machine"