Question

I see some code exp_send -i $bash_id "/bin/tcsh", what does the -i flag means? what is the meaning of -i flag after the exp_send?

Answer 1

Expect allows you to spawn multiple processes at once and then interact with them in a mixed way. This is a very powerful mechanism, but it does mean that when you are saying what to exp_send to or expect from, you have to say what you are talking about. That is done by using the -i flag to specify the spawn id, which is returned by spawn when a subprocess is created.

When there’s only a single subprocess, the -i can be omitted as the global spawn_id variable is used by default.