I switched to the fish shell a while ago and it’s great. The sntax is sane and understandable, tab completions work pretty well, history completions save you a lot of time and my shell feels faster to me now.

It’s super easy to create a custom shell prompt:

function fish_prompt
  set_color red -o
  echo -n ">> "
  set_color cyan -o
  if test $PWD = $HOME
    echo -n "~"
  else
    echo -n (basename $PWD)
  end
  echo -n " "
  if git status >/dev/null ^/dev/null
    set_color red -o
    echo -n (git branch | grep '*' | cut -c3-)
    echo -n " "
    if not test (git status | tail -1) = "nothing to commit, working directory clean"
      set_color yellow -o
      echo -n "× "
    end
  end
end

This displays the current working directory, then the current git branch if one exists, then an ×, if there are uncommitted changes in the git repository.

My right prompt displays the ruby version currently in use

function fish_right_prompt
  set_color white -o
  rbenv version | cut -d ' ' -f 1
end

All you need to do is create two files, name them fish_prompt.fish, fish_right_prompt.fish and place them in ~/.config/fish/functions.

Adding your own tab-completions is also pretty easy. Here’s a simple example:

complete -f -c jekyll -a 'build doctor help import new serve'
complete -f -c jekyll -s w -l 'watch'

The first line will tab-complete jekyll’s build, doctor, help, import, new and serve commands. The second line will complete the -w or --watch option. Of course, Jekyll has many more commands and options and writing the whole thing would be much longer, but you get the idea. Put these lines in .config/fish/completions into a file named jekyll.fish and you’ll be good to go.

I highly encourage you to at least read through the introductory fish tutorial.