Using ZSH with grml config, and nix-shell prompt indicator

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I use the GRML zshrc for more than 10 years, and still find it better than the oh-my-zsh prompts especially regarding version control integration (e.g. it shows cleanly whether you are in a git rebase or git cherry-pick).

Here’s how I use it on NixOS, based on my previous post on reddit (which I cannot update any more because Reddit crappily forbids that).

It explains some pitfalls I encountered, and also features showing (nix-shell) in the prompt when I’m in nix-shell.

{
    # zsh
    programs.zsh.enable = true;
    programs.zsh.interactiveShellInit = ''
      # Note that loading grml's zshrc here will override NixOS settings such as
      # `programs.zsh.histSize`, so they will have to be set again below.
      source ${pkgs.grml-zsh-config}/etc/zsh/zshrc

      alias d='ls -lah'
      alias g=git

      # Increase history size.
      HISTSIZE=10000000

      # Prompt modifications.
      #
      # In current grml zshrc, changing `$PROMPT` no longer works,
      # and `zstyle` is used instead, see:
      # https://unix.stackexchange.com/questions/656152/why-does-setting-prompt-have-no-effect-in-grmls-zshrc

      # Disable the grml `sad-smiley` on the right for exit codes != 0;
      # it makes copy-pasting out terminal output difficult.
      # Done by setting the `items` of the right-side setup to the empty list
      # (as of writing, the default is `items sad-smiley`).
      # See: https://bts.grml.org/grml/issue2267
      zstyle ':prompt:grml:right:setup' items

      # Add nix-shell indicator that makes clear when we're in nix-shell.
      # Set the prompt items to include it in addition to the defaults:
      # Described in: http://bewatermyfriend.org/p/2013/003/
      function nix_shell_prompt () {
        REPLY=''${IN_NIX_SHELL+"(nix-shell) "}
      }
      grml_theme_add_token nix-shell-indicator -f nix_shell_prompt '%F{magenta}' '%f'
      zstyle ':prompt:grml:left:setup' items rc nix-shell-indicator change-root user at host path vcs percent
    '';
    programs.zsh.promptInit = ""; # otherwise it'll override the grml prompt

    users.users.root.shell = pkgs.zsh;
}

PS:

  • The code highlighting here on Discourse is broken, it does not understand the ''$VARIABLE escape to write a verbatim $ into the config in Nix multi-line strings ('').
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