Nix Tmux

A quick blog post on using nix with Tmux.

Tmux is one of my favourite tools. Recently I have been playing with Go Networking which often requires multiple terminals. Fortunately Tmux is great for this experience, but I often want to have a pre-defined setup.

Enter Nix and Tmux to manage the environment effortlessly. You can amend the configuration used to setup the screen however you wish. Just amend the dev.tmux script to realign your screen layout however you want.

Nix Scripts

We can define a script to represent the environment requirement.

1. Lets create a tmux layout script dev.tmux:

    1# dev.tmux
    2SESSION="go-dev"
    3
    4# Check if the session already exists
    5tmux has-session -t $SESSION 2>/dev/null
    6
    7if [ $? != 0 ]; then
    8  # Create session, split panes
    9  tmux new-session -d -s $SESSION
   10  tmux split-window -h -t $SESSION
   11  tmux split-window -v -t $SESSION
   12fi
   13
   14# Attach
   15tmux attach-session -t $SESSION
   

   In the above dev.tmux script we create a new session, then split the window both vertically and horizontally.

2. We need to tell Nix to add the dev.tmux external script as a dependency.

   1let
   2  # External Script: This reads './dev.tmux' and puts it into a binary named 'dev-tmux'
   3  tmuxLayout   = pkgs.writeShellScriptBin "dev-tmux" (builtins.readFile ./dev.tmux);
   4in
   

   writeShellScriptBin lets us define dev-tmux wrapping the local script dev.tmux

3. Now we can create a shell.nix script:

    1with import <nixpkgs> {};
    2
    3let
    4  # External Script: This reads './dev.tmux' and puts it into a binary named 'dev-tmux'
    5  tmuxLayout   = pkgs.writeShellScriptBin "dev-tmux" (builtins.readFile ./dev.tmux);
    6in
    7pkgs.mkShell {
    8
    9  name = "go-dev";
   10  nativeBuildInputs = with pkgs; [
   11    go
   12    tmux
   13    tmuxLayout   # Custom script with Tmux layout 
   14  ];
   15
   16  LANGUAGE = "Go";
   17  VERSION  = "go version";
   18
   19  shellHook = ''
   20    # Optional: Script environment start up
   21    echo "Welcome to $LANGUAGE Development Environment"
   22    $VERSION
   23
   24    # The Trap: This kills the tmux session as soon as you exit the nix-shell
   25    # It ensures no "ghost" sessions stay running in the background.
   26    trap "tmux kill-session -t go-dev" EXIT
   27
   28    # Perform Tmux Dev Layout
   29    dev-tmux
   30  '';
   31}
   

   The above script will still give us a tmux environment. When the nix script executes it will automatically call the dev-tmux to handle the screen layout. In addition there is a trap defined to kill existing sessions on exit.

4. Run the script:

   1nix-shell --pure
   

   Remember a pure environment tries to ignore the existing host configuration 😂 Nix will automatically look for the file shell.nix so you dont need to added this parameter 🥰

   Expected Output:

   1Welcome to Go Development Environment
   2go version go1.25.5 darwin/arm64
   

   Awesome, Tmux is configured and ready to go!

5. Exit the Nix Shell

   To exit, you will need to exit each screen individually.

   1exit
   

Nice we now have a super easy way to run Tmux on a Nix machine.