Format-token fields

Object fields expose values from tmux’s FORMATS, such as #pane_id, #window_zoomed_flag, and #session_name. The available fields depend on the accessor, object scope, tmux version, and data requested by the read.

A token needs the right scope and tmux version. For example, a pane token needs a pane context, and a token added after your tmux release may be absent. Check the accessor’s result before using a field that can be missing, as described below.

Handling an absent field¶

Accessors return a value and a boolean when a field can be unavailable. For example, mPane.DeadSignal returns (string, bool); check the boolean before using the string.

These examples read optional fields, including #pane_dead_signal on tmux 3.3 or newer:

signal, ok := pane.DeadSignal() // ok is false when the token isn't populated

Field availability¶

Field accessors retain the scope and version requirements of tmux tokens.

tmux/internal/generate/formats/ generates tmux/format_generated.go. Some accessors also parse the returned text: mPane.DeadTime returns (time.Time, bool), so the caller does not need to parse the timestamp.

Version gates describe tmux behavior: #pane_dead_signal and #pane_dead_time arrived in tmux 3.3, and a cluster of pane-geometry and floating-pane tokens (#pane_floating_flag, #pane_pb_progress, #pane_x, #pane_y, #pane_z, #pane_zoomed_flag, #bracket_paste_flag, #synchronized_output_flag, among others) arrived together in 3.7.

Fields promoted from the active child¶

tmux’s format engine includes active-child fields when listing a parent. A $list-sessions -F row can include #window_id and #pane_id for the active window and pane. Check the port reference for typed access to those fields, or use the explicit relationships described in Traversal.

A pane context can include parent window and session fields. A session cannot identify one attached client when several clients may be attached, so client tokens such as #client_name require a client context.