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¶

Ordinary calls use subprocesses. mServer.connected(attachingTo:_:) provides a persistent connection, and mControlConnection.watch(_:) receives events.

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

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.

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 LibTmux

// One-shot: every call underneath this handle spawns a `tmux` process.
let server = try Server(socketName: "default")
let session = try await server.newSession(named: "work", windowName: "editor")
let window = try await server.newWindow(in: session, named: "logs").window
let pane = try await server.splitWindow(window, direction: .right)
try await server.run("echo hello", in: pane)

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

$ tmux -C attach-session -t work