I think the terminal emulator I use does keep a file. I'll look into that. It would be cool if every screen write tripped a flag somewhere tho, then it would be easy. Tx.
Depending on what exactly you want to do, you could probably achieve this using tmux and some combination of its hooks, pane flags and/or pipe-pane. I recommend searching for "monitor-", "-hook" and "pipe-pane" in tmux(1). Whether this would be better than Expect would depend on the task at hand. If you don't already use tmux and aren't interested in using it, Expect is probably better.
Eric