Fish Shell is Awesome

(when I switched my shell to zsh, I mentioned that I would try fish and report back: this is it.)

TLDR:

• fish shell is awesome!
• including features I didn’t know I wanted
• but, it’s not common – enjoy it on your own devices, but don’t expect it to be the default shell when you ssh somewhere

Truth in Advertising

The front page of the fish shell has a “sales pitch”

I rediscovered it while coming up with my own list of what makes fish great. But the pitch already has most of my points – fish shell had tried to tell me all along, I just hadn’t believed it!

Try Before You Buy

I think the biggest fears when switching shells come down to:

• how to try it without messing up your current setup?
• how much configuration/googling will you need before being productive?

For the first point, once installed (brew install fish, or equivalent), just type fish. You will be running fish without fiddling with your terminal or default shell. If you don’t like it, type exit to return to your “real” shell. This is low commitment!

For the second point, I have some good news:

• the fish config is sane by default!
  (a refreshing development over bash/zsh)
• there are surprisingly little knobs and settings to play with: trust the defaults!

If you want to customize the colors or the prompt, type fish_config and enjoy the browser-based config and preview.

All About Completion

The feature that makes or breaks a shell is what happens when you press TAB. I would NOT be talking about fish if its completion wasn’t excellent.

Let me try to summarize with a few examples:

• the red highlight had already told me that the command wouldn’t work…
• fish checks while you type

• valid commands are cyan (customizable)
• completed words are underlined (I pressed TAB to complete the filename)
• the grey text comes from the command history
• right-arrow will complete the grey text (not TAB)
• ctrl-f would grab the first word from the grey text (if there were multiple words)

Yes, other shells have history completion – the difference is that it shows up automatically. With bash/zsh, you have to remember that a command is in your history to want to grab it with ctrl-r.

More about command history:

• fish history in almost infinite (it stores 256k entries, in a LRU)
• history hints are directory-aware … offering you commands you would only type in certain directories!
• multi-shell histories are merged on shell exit: no clobbers, no worries

Other features worth mentioning:

• out-of-the-box installation comes with completions for most commands
• man page can be parsed to generate completions (as claimed in sales pitch)
• rsync/scp commands complete paths on the other side of an ssh connection (!)
• flag completion, with helpful text (below)

A few other things:

• case-insensitive (case-flexible?) completion – type it lowercase and TAB fix it!
• middle-of-text completion – you don’t have to type the beginning of a filename/directory, any unambiguous part will do

What’s the Catch?

The biggest catch is that it’s not default. You have to install it (probably) and enable it. Default choices are powerful, and that’s why bash/zsh still rule.

You can reduce the pain by “cheating”. Add fish to the bottom of your .bashrc/.zshrc

# pretty easy, no?
fish

Comment it out if you change your mind.

A few other things to know:

• fish syntax, if you are scripting, isn’t the same bash/zsh syntax – you might say it’s a good thing. I read through the language reference and found it reasonable. (better than sh’s CASE-ESAC, IF-FI, DO-DONE craziness…)
• it’s worth reading through Fish for bash users; it’s not too long

So, yes, fish will spoil you. And if you have to use other shells, you will miss its features.

Is that such a bad thing?

Final Worlds

Technology becomes truly useful when it becomes invisible.

I spent years trying to beat bash (and zsh) into shape. Many of my blog posts were about removing friction from the command-line experience. There is some joy in mastering complicated tools…

But fish allowed me to do everything I wanted, and more, without feeling like a struggle. (or worse: spending days/weeks/months getting my configuration just right)

Give fish a try and let me know what’s missing.