# Tmux

> Manages background processes, captures command output, and handles session multiplexing. Use when running long-running commands, capturing output from detached processes, or managing concurrent tasks in headless environments.

- Skill: `knoopx/tmux` (Agent Skill)
- Install (CLI): `npx skillmds@latest add knoopx/tmux`
- Raw SKILL.md: https://api.skillmd.com/api/skills/knoopx/tmux/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: knoopx (https://skillmd.com/u/knoopx)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/knoopx/tmux

---


# tmux

Terminal multiplexer for background processes, output capture, and session management. Every process runs in a named session you can inspect later.

## Running Background Processes

Start a command in a named detached session:

```bash
tmux new-session -d -s myserver 'python -m http.server 8080'
tmux new-session -d -s build -c /path/to/project 'make build'
```

Keep a session alive after the command completes:

```bash
tmux new-session -d -s task 'command; exec bash'
```

Only create if it doesn't exist:

```bash
tmux has -t myserver || tmux new-session -d -s myserver 'command'
```

## Capturing Output

Get the output from a running session:

```bash
tmux capture-pane -t mysession -p           # Visible output only
tmux capture-pane -t mysession -p -S -      # Full scrollback history
tmux capture-pane -t mysession -p -S -100   # Last 100 lines
tmux capture-pane -t mysession -p > file.txt  # Save to file
```

## Sending Input

Send keystrokes to a session:

```bash
tmux send-keys -t mysession 'echo hello' Enter    # Type and press Enter
tmux send-keys -t mysession C-c                    # Send Ctrl+C
```

## Waiting for Completion

Signal when a job finishes, then wait for it:

```bash
tmux new-session -d -s job 'command; tmux wait-for -S job-done'
tmux wait-for job-done
```

## Session Management

```bash
tmux ls                                    # List all sessions
tmux kill-session -t myserver              # Kill specific session
tmux kill-server                           # Kill all sessions
```

## Common Patterns

**Development servers:**

```bash
tmux new-session -d -s backend 'bun run backend'
tmux new-session -d -s frontend 'bun run frontend'
```

**Run and capture output in a script:**

```bash
tmux new-session -d -s job 'command'
sleep 0.5
output=$(tmux capture-pane -t job -p)
echo "$output"
```

## Tips

- Use `-c /path` to set working directory when creating a session
- Use `exec bash` to keep sessions alive after commands finish
- Use `-S -` with `capture-pane` to get full scrollback history