Feb 03, 2026 • 3 min read

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.

Lets create a tmux layout script dev.tmux:

# dev.tmux
SESSION="go-dev"

# Check if the session already exists
tmux has-session -t $SESSION 2>/dev/null

if [ $? != 0 ]; then
  # Create session, split panes
  tmux new-session -d -s $SESSION
  tmux split-window -h -t $SESSION
  tmux split-window -v -t $SESSION
fi

# Attach
tmux attach-session -t $SESSION

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

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

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

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

Now we can create a shell.nix script:

with import <nixpkgs> {};

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

  name = "go-dev";
  nativeBuildInputs = with pkgs; [
    go
    tmux
    tmuxLayout   # Custom script with Tmux layout 
  ];

  LANGUAGE = "Go";
  VERSION  = "go version";

  shellHook = ''
    # Optional: Script environment start up
    echo "Welcome to $LANGUAGE Development Environment"
    $VERSION

    # The Trap: This kills the tmux session as soon as you exit the nix-shell
    # It ensures no "ghost" sessions stay running in the background.
    trap "tmux kill-session -t go-dev" EXIT

    # Perform Tmux Dev Layout
    exec dev-tmux
  '';
}

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. Finally we use exec to initiate an isolated session.

Run the script:
```
nix-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:
```
Welcome to Go Development Environment
go version go1.25.5 darwin/arm64
```
Awesome, Tmux is configured and ready to go!
Exit the Nix Shell

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

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