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== Installation ==
== Installation ==


A basic user-specific installation with [[Home Manager]] may look like this:
=== NixOS System Installation ===


<syntaxhighlight lang="nix">
To install fish for a user on a regular nixos system:
home-manager.users.myuser = {
 
{{file|/etc/nixos/configuration.nix|nix|
<nowiki>
   programs.fish.enable = true;
   programs.fish.enable = true;
};
  users.extraUsers.myuser = {
</syntaxhighlight>
    ...
    shell = pkgs.fish;
  };
</nowiki>
}}
Replace <code>myuser</code> with the appropriate username.
 
{{warning| [https://fishshell.com/docs/current/index.html#default-shell As noted in the fish documentation], using fish as your *login* shell (via <code>/etc/passwd</code>) may cause issues, particularly for the <code>root</code> user, because fish is not POSIX compliant. While using fish as the default shell for regular users is generaly safe, caution is still advised. See [[#Setting fish as default shell]] for recommendations and mitigations.}}


Change <code>myuser</code> to the username of the user you want to configure.
=== Home Manager ===


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 <code>/etc/nixos/configuration.nix</code>:
For a user-specific installation managed by [[Home Manager]], use the following configuration:


<syntaxhighlight lang="nix">
{{file|home.nix|nix|
<nowiki>
home-manager.users.myuser = {
   programs.fish.enable = true;
   programs.fish.enable = true;
</syntaxhighlight>
};
</nowiki>
}}


== Setting fish as your shell ==
Replace <code>myuser</code> with the appropriate username.


Warning! [https://fishshell.com/docs/current/index.html#default-shell As noted in the fish documentation], using fish as your *login* shell (referenced in <code>/etc/passwd</code>) may cause issues because fish is not POSIX compliant. In particular, this author found systemd's emergency mode to be completely broken when fish was set as the login shell.
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:


This issue is discussed extensively on the [https://wiki.gentoo.org/wiki/Fish#Caveats Gentoo] and [https://wiki.archlinux.org/title/Fish#System_integration Arch] wikis. There they present an alternative, keeping bash as the system shell but having it exec fish when run interactively.
{{file|/etc/nixos/configuration.nix|nix|
<nowiki>
  programs.fish.enable = true;
</nowiki>
}}


Here is one solution, which launches fish unless the parent process is already fish:
== Configuration ==


<syntaxhighlight lang="nix">
Available fish plugins packaged in Nixpkgs can be found via the [https://search.nixos.org/packages?query=fishPlugins fishPlugins package set].
programs.bash = {
  interactiveShellInit = ''
    if [[ $(${pkgs.procps}/bin/ps --no-header --pid=$PPID --format=comm) != "fish" && -z ''${BASH_EXECUTION_STRING} ]]
    then
      shopt -q login_shell && LOGIN_OPTION='--login' || LOGIN_OPTION=""
      exec ${pkgs.fish}/bin/fish $LOGIN_OPTION
    fi
  '';
};
</syntaxhighlight>


If you still want to set fish as the login shell, see [[Command Shell#Changing default shell]].
=== NixOS System Configuration ===


== Configuration ==
To enable fish plugins system-wide, add your preferred plugins to `environment.systemPackages`:


=== System wide ===
{{file|/etc/nixos/configuration.nix|nix|
<nowiki>
  programs.fish = {
    enable = true;
    interactiveShellInit = ''
      set fish_greeting # Disable greeting
    '';
  };


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
    # Use 3rd-party fish plugins manually packaged.
    (pkgs.callPackage ../fish-colored-man.nix {buildFishPlugin = pkgs.fishPlugins.buildFishPlugin; } )
  ];
</nowiki>
|name=/etc/nixos/configuration.nix|lang=nix}}
Example of a file containing the definition of a fish plugin.
{{file|/etc/nixos/fish-colored-man.nix|nix|
<nowiki>
{
  lib,
  buildFishPlugin,
  fetchFromGitHub,
}:
buildFishPlugin {
  pname = "fish-colored-man";
  version = "0-unstable-20240416";
  src = fetchFromGitHub {
    owner = "decors";
    repo = "fish-colored-man";
    rev = "1ad8fff696d48c8bf173aa98f9dff39d7916de0e";
    hash = "sha256-uoZ4eSFbZlsRfISIkJQp24qPUNqxeD0JbRb/gVdRYlA=";
  };
}
</nowiki>
}}


<syntaxhighlight lang="nix">
For a full list of fish module options, refer to [https://search.nixos.org/options?query=programs.fish programs.fish].
environment.systemPackages = with pkgs; [
  fishPlugins.done
  fishPlugins.fzf-fish
  fishPlugins.forgit
  fishPlugins.hydro
  fzf
  fishPlugins.grc
  grc
];
 
programs.fish.enable = true;
</syntaxhighlight>


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


<syntaxhighlight lang="nix">
{{file|home.nix|nix|
<nowiki>
home-manager.users.myuser = {
home-manager.users.myuser = {
   programs.fish = {
   programs.fish = {
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   };
   };
};
};
</syntaxhighlight>
</nowiki>
Full list of home-manager options for fish can be found  See also [https://github.com/nix-community/home-manager/blob/master/modules/programs/fish.nix here].
}}
 
For the full list of available home-manager options for fish, refer to the [https://github.com/nix-community/home-manager/blob/master/modules/programs/fish.nix module source].
 
== Tips and tricks ==
 
=== Setting fish as default shell ===
 
Using fish as the the login shell can cause compatibility issues. For example, certain recovery environments such as systemd's emergency mode to be completely broken when fish was set as the login shell. This  limitation is noted on the [https://wiki.gentoo.org/wiki/Fish#Caveats Gentoo] wiki. There they present an alternative, keeping bash as the system shell but having it exec fish when run interactively.
 
Here is one solution, which launches fish unless the parent process is already fish:
 
{{file|/etc/nixos/configuration.nix|nix|
<nowiki>
programs.bash = {
  interactiveShellInit = ''
    if [[ $(${pkgs.procps}/bin/ps --no-header --pid=$PPID --format=comm) != "fish" && -z ''${BASH_EXECUTION_STRING} ]]
    then
      shopt -q login_shell && LOGIN_OPTION='--login' || LOGIN_OPTION=""
      exec ${pkgs.fish}/bin/fish $LOGIN_OPTION
    fi
  '';
};
</nowiki>
}}
 
'''Setting fish as default for Gnome Console'''
 
It is possible to set fish as the interactive non-login shell for Gnome Console without setting fish as the login shell (the login shell in /etc/passwd for your user will not be fish).
 
{{File|3=home-manager.users.myuser = {
    dconf = {
        enable = true;
        settings."org/gnome/console" = {
            shell = [ "FISH" ];
        };
    };
};|name=home.nix|lang=nix}}
 
 
If you still want to set fish as the login shell, see [[Command Shell#Changing the default shell]].
 
==== Disable man page generation ====
Some users suffer from slow build due to fish enabling `documentation.man.generateCaches`. You may force false.
documentation.man.generateCaches = false'';''
 
==== Running fish interactively with zsh as system shell on darwin ====


See [https://search.nixos.org/packages?channel=unstable&from=0&size=50&buckets=%7B%22package_attr_set%22%3A%5B%22fishPlugins%22%5D%2C%22package_license_set%22%3A%5B%5D%2C%22package_maintainers_set%22%3A%5B%5D%2C%22package_platforms%22%3A%5B%5D%7D&sort=relevance&query=fishPlugins fishPlugins package set] for available plugins in nixpkgs.
Zsh users on darwin will need to use a modified version of the above snippet. As written, it presents two incompatibilities. First, being BSD-derived, MacOS's <code>ps</code> command accepts different options. Second, this is a script intended for bash, not zsh. MacOS uses zsh as its default shell.


== Useful scripts ==
<syntaxhighlight lang="nix">
programs.zsh = {
  initExtra = ''
    if [[ $(ps -o command= -p "$PPID" | awk '{print $1}') != 'fish' ]]
    then
        exec fish -l
    fi
  ''
};
</syntaxhighlight>


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


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* [[Command Shell]]
* [[Command Shell]]


[[Category:Applications]]
 
[[Category:Shell]]
[[Category:Shell]]
Retrieved from "https://wiki.nixos.org/wiki/Fish"