Control mode vs one-shot

libtmux sends commands to tmux through subprocesses or persistent control-mode connections. tmux also accepts several commands in one invocation:

1. One-shot subprocess. Each command spawns a fresh tmux process, which sends the request to the server, prints the result, and exits.
2. A persistent control-mode client. $tmux -C attach-session starts one long-lived tmux process that stays attached and speaks a line-oriented protocol over its stdout: commands go in, replies and asynchronous notifications (%window-add, %output, …) come out, without starting a process per call.
3. One invocation, several commands. tmux accepts more than one command per invocation (;-joined, or one -F-tagged list-* per line). Grouping operations this way reduces process starts without opening a control-mode connection.

Available transports¶

Commands use a subprocess by default. mpipeline() and mbatch() group operations. mconnect() and mwatch() keep a connection for notifications; ordinary commands still use separate processes.

Choose based on whether you need command results, notifications, or a batch of changes.

Notifications and commands are separable¶

TypeScript’s mconnect() adds an event observer while commands such as msession.newWindow(...) and mpane.sendKeys(...) continue to run as separate tmux processes. A dedicated process provides a completion boundary for output from alias-expanded or waiting commands.

A control client is a real client¶

A persistent control connection attaches a tmux client. It appears in $list-clients, increments #session_attached, and affects odestroy-unattached, client hooks, and idle-client accounting. Each connection counts separately.

Why fold several commands into one invocation¶

Creating an object can require a second command to read its resulting state. Batching can reduce repeated reads and process starts.

mbatch() resolves planned mutations from one final snapshot.

What this costs in practice¶

A persistent connection avoids starting a client for each command. A chain groups a known sequence into one invocation. For occasional commands, use the default subprocess transport; measure your workload before changing transports for performance. Use a notification stream when your program needs tmux events.

Sending a command¶

The example uses the subprocess API. See the reference for batching and control-mode setup.

import { Server } from "libtmux";

// Each awaited command uses a tmux subprocess.
const server = new Server();
const session = await server.newSession({ name: "work" });
const editor = await session.newWindow({ name: "editor" });
await editor.panes.at(0)?.sendKeys("echo hello");

To inspect tmux’s control protocol, attach a control client:

$ tmux -C attach-session -t work