G'day ajose,

I'm unclear on how A "triggers" B, B "invokes" C, what type of scripts those are and whether any of that matters.

However, your requirement for capturing output and periodic "Waiting ..." messages when no output has been found, seems very similar to a question from a few weeks ago.

Take a look at my initial response to Check for a new line, the follow-up questions, and then my subsequent response.

My solution (using alarm) has similarities to what you appear to attempting with your "$timeout=1000; ..." code. You may be able to modify it directly to do what you want or use it as the basis for a new solution.