tmux Skill

Use tmux to control interactive terminal applications by sending keystrokes and capturing output.

When to Use

• Running interactive REPLs (python, node, psql)
• Debugging with gdb/lldb
• Any CLI that requires TTY interaction
• Remote execution where you need to observe output

Core Pattern

# Create session
tmux new-session -d -s "$SESSION" -x 120 -y 40

# Send commands
tmux send-keys -t "$SESSION" "python3" Enter

# Capture output
tmux capture-pane -t "$SESSION" -p

# Wait for prompt (poll)
for i in {1..30}; do
  output=$(tmux capture-pane -t "$SESSION" -p)
  if echo "$output" | grep -q ">>>"; then break; fi
  sleep 0.5
done

# Cleanup
tmux kill-session -t "$SESSION"

Remote Execution (Codespaces/SSH)

For mise-installed tools, wrap in zsh:

# Non-interactive (won't hang)
ssh host 'zsh -c "source ~/.zshrc; tmux new-session -d -s mysession; tmux send-keys -t mysession python Enter"'

# Interactive (for tmux attach) - needs TTY
ssh host -t 'zsh -ilc "tmux attach -t mysession"'

Critical: Use zsh -c "source ~/.zshrc; ..." not zsh -lc to avoid hangs.

User Notification

After starting a session, ALWAYS print:

To monitor: tmux attach -t $SESSION
To capture: tmux capture-pane -t $SESSION -p

Tips

• Use -x 120 -y 40 for consistent pane size
• Poll with capture-pane -p rather than wait-for
• Send literal text with -l flag to avoid shell expansion
• Control keys: C-c (interrupt), C-d (EOF), Escape
• For Python REPL: set PYTHON_BASIC_REPL=1 to avoid fancy console interference

Helper Scripts

wait-for-text.sh

Poll tmux pane for a text pattern with timeout:

scripts/wait-for-text.sh -t session:0.0 -p '^>>>' -T 15

find-sessions.sh

List tmux sessions, optionally filtered:

scripts/find-sessions.sh -q claude  # filter by name
scripts/find-sessions.sh --all      # all sessions