Fish

fish, the Friendly Interactive Shell, is a command shell designed around user-friendliness.

Installation

For setting fish as the default shell system wide, see Command Shell#Changing default shell.

A basic user-specific installation with Home Manager may look like this:

home-manager.users.myuser = {
  programs.fish.enable = true;
};

Change myuser to the username of the user you want to configure.

You can enable the fish shell and manage fish configuration and plugins with Home Manager, but to enable vendor fish completions provided by Nixpkgs you will also want to enable the fish shell in /etc/nixos/configuration.nix:

  programs.fish.enable = true;

Configuration

System wide

To enable fish plugins, add your preferred plugins to `environment.systemPackages`:

environment.systemPackages = with pkgs; [
  fishPlugins.done
  fishPlugins.fzf-fish
  fishPlugins.forgit
  fishPlugins.hydro
  fzf
  fishPlugins.grc
  grc
];

programs.fish.enable = true;

Home Manager

An example configuration in Home Manager for adding plugins and changing options could look like this:

home-manager.users.myuser = {
  programs.fish = {
    enable = true;
    interactiveShellInit = ''
      set fish_greeting # Disable greeting
    '';
    plugins = [
      # Enable a plugin (here grc for colorized command output) from nixpkgs
      { name = "grc"; src = pkgs.fishPlugins.grc.src; }
      # Manually packaging and enable a plugin
      {
      name = "z";
      src = pkgs.fetchFromGitHub {
        owner = "jethrokuan";
        repo = "z";
        rev = "e0e1b9dfdba362f8ab1ae8c1afc7ccf62b89f7eb";
        sha256 = "0dbnir6jbwjpjalz14snzd3cgdysgcs3raznsijd6savad3qhijc";
      };
    }
  ];
};

See fishPlugins package set for available plugins in nixpkgs.

Useful scripts

Show that you are in a nix-shell

Add this to the fish_prompt function (usually placed in ~/.config/fish/functions/fish_prompt.fish):

set -l nix_shell_info (
  if test -n "$IN_NIX_SHELL"
    echo -n "<nix-shell> "
  end
)

and $nix_shell_info to the echo in that function, e.g.:

echo -n -s "$nix_shell_info ~>"

Now your prompt looks like this:

• outside: ~>
• inside: <nix-shell> ~>

You can directly start nix-shell in fish with nix-shell --run fish.

Environments

Here are some examples of helper functions that put you in a nix-shell with the given packages installed.

You can either put these in programs.fish.functions with home-manager or in ~/.config/fish/functions/fish_prompt.fish without.

haskellEnv

function haskellEnv
  nix-shell -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [ $argv ])"
end

# Invocation: haskellEnv package1 packages2 .. packageN

pythonEnv

function pythonEnv --description 'start a nix-shell with the given python packages' --argument pythonVersion
  if set -q argv[2]
    set argv $argv[2..-1]
  end
 
  for el in $argv
    set ppkgs $ppkgs "python"$pythonVersion"Packages.$el"
  end
 
  nix-shell -p $ppkgs
end

# Invocation: pythonEnv 3 package1 package2 .. packageN
# or:         pythonEnv 2 ..

See also

• Command Shell