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