output_confirms

Description#

Waiting for a pane to say something is the first thing a supervising program needs and the easiest to get wrong, because a capture shows two things that are not output. The first is a command still sitting on the prompt: it has been typed, nothing has run it, and searching for it succeeds immediately. The second is its echo. A shell echoes typed input at least once — the kernel's own cooked-mode echo — and often twice more before anything runs, from the line editor's redisplay and from any unrelated repaint. None of those are output, however many rows they end up spread across.

sent is what the calling program itself typed into this pane and has not had confirmed. Every whole occurrence of every entry is masked before wanted is looked for, so an echo cannot be credited to the pane no matter where a redraw moved it, and a short entry cannot corrupt a longer real word that merely contains it. That is the check row position alone misses: the same unsubmitted line, unchanged, after something else pushed it off the last row without the pane having produced anything.