Thoughts on shells

I have been using fish as my shell for a while now and I am a bit conflicted on whether or not to continue using it. This post is essentially a ramble for me to organize my thoughts and perhaps make a decision eventually.

My early days

I started my shell journey with bash way back when I didn’t even know what a shell was, nor the distinction between the shell and the terminal (emulator). It came installed by default on my first Linux distribution (I believe it was Ubuntu 8.04? It was more than half my lifetime ago, anyway), and basically just used it for installing some programs and running commands I found on different fora when I had a problem that needed fixing. Coming from Windows, doing anything non-graphical was a bit foreign and mystical.

Eventually I grew comfortable with moving around my system and doing things in the shell sometimes rather than always through a graphical file manager or other applications, though it took a good while and I often reached for graphical tools when unsure.

Then one day - I can’t say when - something switched and I preferred doing most things in the shell, only opening graphical programs when needed¹. I started automating some tasks, writing shell scripts to type repetitive or difficult to remember commands less. I wasn’t proficient yet by any stretch, but I wasn’t entirely new at it like when I was fresh from Windows. The shell became comfortable. Or, to be more precise: bash became comfortable.

There are other shells?

In university a friend introduced me to zsh. At this point I hadn’t even realized that there were other shells. I hadn’t figured out that I was using a specific one called bash; I was just doing things “in the terminal”! I was also shown oh my zsh and it was just so cool and shiny that I had to have it. I still base my shell prompts, no matter what shell I use, on the ys theme. I really like having a multi-line prompt so that any commands I type are always the first thing on the line (save for the starting $).

Of course, zsh having a bunch of fancy plugins and eye-candy wasn’t the only good² thing about it. Oh my zsh is often the thing listed online in articles and blog posts as the reason to switch to zsh, but I don’t think that’s even the most compelling reason. zsh just has some saner defaults and configurations that bash either lacks, or does a poor job recreating.

One thing that comes to mind is how zsh handles tab-completion. If a completion is ambiguous, the possible completions are listed below the prompt and can be moved around with using <Tab> and <Shift-Tab>, or the arrow keys. The auto-completion in bash, on the other hand is crude in comparison. When hitting <Tab> when completions are ambiguous, it just spits out the list of possible completions, shoving your prompt down in the terminal window, and leaving it up to you to type enough that the match is no longer ambiguous. You can sort of get slightly nicer tab-completion in bash with something like:

bind 'TAB:menu-complete'
bind 'set show-all-if-ambiguous on'

but this just feels like a crude approximation of zsh’s nice version.

Another nice feature of zsh is the recursive path expansion and automatic cd. To move into a directory, you just need to type the path, and to move deep into a file tree you don’t even have to type (or repeatedly tab-complete!) the full path. Hitting <Tab> after an abbreviated path expands to the full path, for example /u/l/s/f expands to /usr/local/share/fonts on my system.

There are many other features that just gel better with who I am and how I use the shell in zsh than in bash. This became a long tangent on zsh, and I’m not even planning on talking about fish next. Interesting how you can just continue writing sometimes once you’ve started.

POSIX-noncompliance? Ew.

Both bash and zsh are POSIX-compatible, and their syntaxes similar enough that switching between the two is in most cases painless. The first non-POSIX-ish shell I ran into was tcsh and my god did (do) I dislike it strongly. I realize this is mostly inertia and not being used to it, but it lacking simple things like redirecting stdout and stderr to different places, and redirection in general being a bit weird. I sometimes run into tcsh-scripts and the syntax is… not horrifying, but bad enough that my eyes glaze over. It feels like taking C and trying to cram it into some form of shell language³ to make it suck less. But all shell languages suck, and so (t)csh does too.

There were lots of other little things that just bothered me so much about using tcsh interactively that I began believing (wrongly) that POSIX-noncompliant shells are awful by default.

POSIX-noncompliance is good, actually.

Enter fish. It is not POSIX-compliant, but it is a good shell. A great shell, even. It corrected my belief that POSIX-noncompliance is bad by default, and it is a joy to use interactively. It has a ton of the features and eye-candy that zsh has by default, and more! Its completion hinting⁴ where a context-aware completion is shown dimly after your cursor is very cool. Hitting the right arrow key will usually complete almost exactly the command you’re after, drawing from the command history.

And POSIX-noncompliance is mostly a non-issue. Why should the shell be beholden to the rules of POSIX anyway? Why should it have to behave like sh? Some may say it’s for portability, others may say it’s stifling innovation. I’m not going to make a judgement call on that. I can see the merit of both sides on this issue.

To summarize, here’s a short list of what fish does compared to zsh:

• Recursive path expansion like zsh? Check.
• Automatic cd like zsh? Check.
• Cool eye-candy like zsh? Check.
• Completion hinting, unlike zsh? Pretty cool!
• A joy to use interactively? Absolutely!
• Configurable in a nice way, like zsh? About that…

POSIX-noncompliance is bad, actually.

fish is very opinionated⁵. “Configurability is the root of all evil” is one of the core beliefs of fish’s design philosophy. The way you configure fish is via a web interface, for some reason. On its own, not a terrible idea perhaps. But to me⁶ it feels… opaque? I don’t know how to describe it. Sure, there’s text configuration in the bottom of it somewhere if you wanted to configure it with text, like most other shells, but it feels like it’s discouraged to do so.

It also bothers me that aliases as such don’t really exist in fish, and you don’t just configure them in something like a .fishrc file. Instead, you create functions, and each function gets its own file in ~/.config/fish/functions/. Aliases are pretty short and concise; it is completely reasonable to keep most of them in the same file. And since fish has its own language and syntax, I have to keep looking it up whenever I want to do some text config. POSIX skills are non-transferrable here. And only useful with this particular shell. I know I said up above that I wasn’t going to make a judgement call for or against POSIX, but I do feel like I’m leaning slightly towards POSIX. And again, I know that it’s force of habit, but oh boy is that a strong force.

Switching back to zsh?

Typing all of this out, I think I will be going back to zsh pretty soon. fish has been great to use, but I have had some issues with it. The completion hinting sometimes simply does not work or doesn’t do what I expect/want it do to and is frankly distracting sometimes. Tab-completion sometimes hits some weird recursion depth that I haven’t managed to get to the bottom of. I have to look up syntax whenever I have to do something that is slightly more complicated than piping and redirecting some commands, but which isn’t complicated enough to warrant a script.

It is very possible (even likely) that I just don’t appreciate fish because I don’t understand it yet. It’s different, in both good and bad ways. But I recently learned that you can bring some fish into your zsh. With both shells having plugin systems, making one behave a bit more like the other shouldn’t be too hard.

Conclusion

In the end, which shell you use interactively largely doesn’t matter. Use whatever suits best. The differences are pretty small, but can for exactly that reason be a bit jarring. I may revisit fish in the future, and try to gain some more appreciation for it. But until then, I’ll be happy in zsh. Or maybe I’ll go all out and try out something like nushell. We’ll see.