{ ... }:
{
  programs.bash.shellInit = ''
      download_nixpkgs_cache_index () {
        filename="index-$(uname -m)-$(uname | tr A-Z a-z)"
        mkdir -p ~/.cache/nix-index && cd ~/.cache/nix-index
        # -N will only download a new version if there is an update.
        wget -q -N https://github.com/Mic92/nix-index-database/releases/latest/download/$filename
        ln -f $filename files
    }
  '';
}