TopolearnFormats are how scripts ask tmux questions and how you build an informative status bar.
A format is a string with #{variable} placeholders that tmux expands. Hundreds of variables exist: session_name, window_index, window_name, pane_index, pane_id (stable ids like %3), pane_current_path, pane_current_command, pane_pid, client_prefix, window_zoomed_flag...
Where formats are used:
display-message -p '#{...}'prints a format for the current pane: the standard way for a script to ask "where am I?".list-sessions,list-windows,list-panestake-F format;-alists across all sessions. Combine with-f filterto select.- Options such as
status-left,status-right,window-status-formatand the-cofsplit-windoware expanded as formats.
Formats have operators:
- Conditionals:
#{?client_prefix,PREFIX,}shows text only while the prefix is pressed;#{?window_zoomed_flag,[Z],}. - Comparisons:
#{==:#{pane_current_command},vim},#{m:*.log,#{pane_title}}(glob match). - Modifiers:
#{=10:pane_title}truncates,#{b:pane_current_path}is the basename,#{t:...}formats a timestamp.
In status options, %H:%M style strftime codes are also expanded, and #[fg=yellow] sets styles. Use stable ids (%3, @2, $1) rather than indexes in scripts: indexes change as windows are moved or renumbered.
Example
tmux display -p '#{session_name}:#{window_index}.#{pane_index}' # dev:1.0
tmux display -p '#{pane_current_path}' # /home/me/code
tmux list-panes -a -F '#{pane_id} #{session_name} #{pane_current_command}'
# %0 dev vim
# %1 dev node
tmux list-panes -a -f '#{==:#{pane_current_command},node}' -F '#{pane_id}'
# ~/.tmux.conf
set -g status-right '#{?client_prefix,#[reverse]PREFIX#[noreverse] ,}#{b:pane_current_path} %H:%M'
setw -g window-status-current-format '#I:#W#{?window_zoomed_flag, [Z],}'Remember
- display -p and list-* -F print formats for scripts
- #{?cond,yes,no}, #{==:a,b}, #{b:path} and other operators
- Prefer stable ids (%pane, @window, $session) over indexes in scripts
Watch out for
- Using single-character aliases like #W without knowing them; the long #{window_name} form is clearer.