obra/using-tmux-for-interactive-commands

Using tmux for Interactive Commands

Overview

Interactive CLI tools (vim, interactive git rebase, REPLs, etc.) cannot be controlled through standard bash because they require a real terminal. tmux provides detached sessions that can be controlled programmatically via send-keys and capture-pane.

When to Use

Use tmux when:

• Running vim, nano, or other text editors programmatically
• Controlling interactive REPLs (Python, Node, etc.)
• Handling interactive git commands (git rebase -i, git add -p)
• Working with full-screen terminal apps (htop, etc.)
• Commands that require terminal control codes or readline

Don't use for:

• Simple non-interactive commands (use regular Bash tool)
• Commands that accept input via stdin redirection
• One-shot commands that don't need interaction

Quick Reference

| Task | Command | |------|---------| | Start session | tmux new-session -d -s <name> <command> | | Send input | tmux send-keys -t <name> 'text' Enter | | Capture output | tmux capture-pane -t <name> -p | | Stop session | tmux kill-session -t <name> | | List sessions | tmux list-sessions |

Core Pattern

Before (Won't Work)

# This hangs because vim expects interactive terminal
bash -c "vim file.txt"

After (Works)

# Create detached tmux session
tmux new-session -d -s edit_session vim file.txt

# Send commands (Enter, Escape are tmux key names)
tmux send-keys -t edit_session 'i' 'Hello World' Escape ':wq' Enter

# Capture what's on screen
tmux capture-pane -t edit_session -p

# Clean up
tmux kill-session -t edit_session

Implementation

Basic Workflow

1. Create detached session with the interactive command
2. Wait briefly for initialization (100-500ms depending on command)
3. Send input using send-keys (can send special keys like Enter, Escape)
4. Capture output using capture-pane -p to see current screen state
5. Repeat steps 3-4 as needed
6. Terminate session when done

Special Keys

Common tmux key names:

• Enter - Return/newline
• Escape - ESC key
• C-c - Ctrl+C
• C-x - Ctrl+X
• Up, Down, Left, Right - Arrow keys
• Space - Space bar
• BSpace - Backspace

Working Directory

Specify working directory when creating session:

tmux new-session -d -s git_session -c /path/to/repo git rebase -i HEAD~3

Helper Wrapper

For easier use, see /home/jesse/git/interactive-command/tmux-wrapper.sh:

# Start session
/path/to/tmux-wrapper.sh start <session-name> <command> [args...]

# Send input
/path/to/tmux-wrapper.sh send <session-name> 'text' Enter

# Capture current state
/path/to/tmux-wrapper.sh capture <session-name>

# Stop
/path/to/tmux-wrapper.sh stop <session-name>

Common Patterns

Python REPL

tmux new-session -d -s python python3 -i
tmux send-keys -t python 'import math' Enter
tmux send-keys -t python 'print(math.pi)' Enter
tmux capture-pane -t python -p  # See output
tmux kill-session -t python

Vim Editing

tmux new-session -d -s vim vim /tmp/file.txt
sleep 0.3  # Wait for vim to start
tmux send-keys -t vim 'i' 'New content' Escape ':wq' Enter
# File is now saved

Interactive Git Rebase

tmux new-session -d -s rebase -c /repo/path git rebase -i HEAD~3
sleep 0.5
tmux capture-pane -t rebase -p  # See rebase editor
# Send commands to modify rebase instructions
tmux send-keys -t rebase 'Down' 'Home' 'squash' Escape
tmux send-keys -t rebase ':wq' Enter

Common Mistakes

Not Waiting After Session Start

Problem: Capturing immediately after new-session shows blank screen

Fix: Add brief sleep (100-500ms) before first capture

tmux new-session -d -s sess command
sleep 0.3  # Let command initialize
tmux capture-pane -t sess -p

Forgetting Enter Key

Problem: Commands typed but not executed

Fix: Explicitly send Enter

tmux send-keys -t sess 'print("hello")' Enter  # Note: Enter is separate argument

Using Wrong Key Names

Problem: tmux send-keys -t sess '\n' doesn't work

Fix: Use tmux key names: Enter, not \n

tmux send-keys -t sess 'text' Enter  # ✓
tmux send-keys -t sess 'text\n'      # ✗

Not Cleaning Up Sessions

Problem: Orphaned tmux sessions accumulate

Fix: Always kill sessions when done

tmux kill-session -t session_name
# Or check for existing: tmux has-session -t name 2>/dev/null

Real-World Impact

• Enables programmatic control of vim/nano for file editing
• Allows automation of interactive git workflows (rebase, add -p)
• Makes REPL-based testing/debugging possible
• Unblocks any tool that requires terminal interaction
• No need to build custom PTY management - tmux handles it all