wait

cyber-mux wait <pane> (--match <text> | --regex <pattern>) [--timeout <ms>] [--lines <n>]

Block until the pane’s output matches, then exit 0. If the deadline passes first, exit 1 — the verdict rides the exit code, so a shell caller branches on it without parsing anything.

Pass exactly one pattern. --match <text> is a literal substring and is the portable form: it means the same on every backend. --regex <pattern> is matched by the backend’s own engine (Rust’s regex on herdr, ECMAScript elsewhere), so the portable subset is what both accept — character classes, quantifiers, alternation, anchors. Prefer --match whenever a literal will do.

--timeout <ms> defaults to 30000. --lines <n> restricts the searched snapshot to the trailing n lines, exactly as read --lines does.

The snapshot searched is the same one read returns, and it is searched immediately — output already on screen when the command starts counts as a match, so a wait cannot lose a race to text that arrived a moment early.

A timeout is a normal answer and still prints the pane’s output, so a caller that guessed the wrong pattern sees what the pane actually said. A pane that is gone is not a timeout: it fails with pane-not-found rather than quietly waiting out the deadline. Neither is a wait that never ran — on a herdr older than 0.7.5, which has no pane wait-output, the command fails loudly instead of reporting an instant false timeout.

<pane> takes either a pane id or a label — see Pane for resolution rules.

Examples

# Wait for a harness to finish booting
cyber-mux wait %3 --match 'ready'

# Branch on the verdict
if cyber-mux wait logs --match 'listening on' --timeout 10000; then
  echo up
else
  echo still not up
fi

# A regex, scoped to the last 20 lines, as JSON
cyber-mux wait %3 --regex 'on [0-9]+' --lines 20 --format json