Playing with a new shell: fish

• Author: Solène
• Date: 05 September 2021
• Tags: openbsd shell

=> Comment on Mastodon

Introduction

Today I'll introduce you to the interactive shell fish. Usually, Linux distributions ships bash (which can be a hidden dash, a limited shell), MacOS is providing zsh and OpenBSD ksh. There are other shells around and fish is one of them.

But fish is not like the others.

=> fish shell project website

What make it special?

Here is a list of biggest changes:

• suggested input based on commands available
• suggested input based on history (even related to the current directory you are in!)
• not POSIX compatible (the usual shell syntax won't work)
• command completion works out of the box (no need for extensions like "ohmyzsh")
• interconnected processes: updating a variable can be done into every opened shells

=> Asciinema recording showing history features and also fzf integration

Making history more powerful with fzf

fzf is a simple utility for searching data among a file (the history file in that case) in fuzzy mode, meaning in not a strict matching, on OpenBSD I use the following configuration file in ~/.config/fish/config.fish to make fzf active.

When pressing ctrl+r with some history available, you can type any words you can think about an old command like "ssh bar" and it should return "ssh foobar" if it exists.

source /usr/local/share/fish/functions/fzf-key-bindings.fish
fzf_key_bindings

fzf is absolutely not related to fish, it can certainly be used in some other shells.

=> github: fzf project

Tips

Disable caret character for redirecting to stderr

The defaults works pretty well but as I said before, fish is not POSIX compatible, meaning some habits must be changed. By default, ^ character like in "grep ^foobar" is the equivalent of 2> which is very misleading.

# make typing ^ actually inserting a "^" and not stderr redirect
set -U fish_features stderr-nocaret qmark-noglob

Web GUI for customizing your shell

If you want to change behaviors or colors of your shell, just type "fish_config" while in a shell fish, it will run a local web server and open your web browser.

Validating a suggestion

When you type a command and you see more text suggested as you type the command you can press ctrl+e to validate the suggestion. If you don't care about the suggestion, continue typing your command.

Get the return value of latest command

In fish, you want to read $status and not $? , that variable doesn't exist in fish.

Syntax changes

Because it's not always easy to find what changed and how, here is a simple reminder that should cover most of your needs:

• loops (no do keyword, ends with end): for i in 1 2 3 ; echo $i ; end
• condition (no then, ends with end): if something ; echo true ; end
• inline command (no dollar sign): (date +%s)
• export a variable: set -x EDITOR kak
• return value of last command: $status

Conclusion

I love this shell. I've been using the shell that come with my system since forever, and a few months ago I wanted to try something different, it felt weird at first but over time I found it very convenient, especially for git commands or daily tasks, suggesting me exactly the command I wanted to type in that exact directory.

Obviously, as the usual syntax changes, it may not please everyone and it's totally fine.