# Tmux Scripting

**Scripting** with tmux lets you automate session setup. Launch sessions with `tmux new-session`, create windows with `tmux new-window`, and send commands with `tmux send-keys`. This is useful for project-specific startup routines.

Basic session creation:

```bash
$ tmux new-session -d -s work          # create detached session (no attach)
$ tmux new-session -s work -c ~/proj   # create session in directory
$ tmux attach -t work                  # attach to session when ready
```

Send commands to a window:

```bash
$ tmux send-keys -t work "npm start" Enter
$ tmux send-keys -t work:1 "npm test" Enter  # window 1
```

Create windows and panes:

```bash
$ tmux new-window -t work -n build -c ~/build
$ tmux split-window -t work:build -v -c ~/build
```

## Example startup script

```bash
#!/bin/bash
# dev-setup.sh: create a project layout

SESSION="dev"
PROJECT_DIR="$HOME/myproject"

# Create session
tmux new-session -d -s $SESSION -c $PROJECT_DIR

# Editor window
tmux send-keys -t $SESSION "nvim" Enter

# Test window
tmux new-window -t $SESSION -n test -c $PROJECT_DIR
tmux send-keys -t $SESSION:test "npm test" Enter

# Build window
tmux new-window -t $SESSION -n build -c $PROJECT_DIR
tmux split-window -t $SESSION:build -v
tmux send-keys -t $SESSION:build.0 "npm run watch" Enter

# Attach to the first window
tmux attach -t $SESSION
```

Run it:

```bash
$ bash dev-setup.sh
```

Clean up:

```bash
$ tmux kill-session -t dev
```

Common patterns:

- `-d` flag creates the session detached (running in background)
- `-c` sets the starting directory for the window or pane
- `-n` names a window
- `-v` or `-h` split vertically or horizontally
- `Enter` sends the Enter key to execute a command

Use `tmux list-sessions` to check if a session exists before creating it:

```bash
tmux has-session -t work 2>/dev/null || tmux new-session -d -s work
```

This pattern is useful in scripts to avoid errors if the session already exists.