Is behavior of expect_after/expect_background in p

Question

I'm automating some work with expect, and have something like the following:

# procedure to set background and after patterns
proc foo {} {
    expect_after {
        -re $regex1 {puts "Matched regex1"; send $command_to_run; exp_continue}
        timeout {exp_continue}
    }
    expect_background {
        -re $regex2 {do other things; exp_continue}
        -re $regex3 {and more different things; exp_continue}
        timeout {exp_continue}
    }
}

spawn $thing
foo
expect_user {
    -ex "stahp" {exit}
}

This hangs indefinitely after expect_after pattern is matched (and the associated body is run). However, if I move the expect_after and expect_background patterns out of the procedure, then it runs as I, well, expected.

Why does it behave differently when put in a procedure?

Answer 1

Thanks to glenn jackman for the idea! It seems that when called in a procedure, expect_after, expect_background, and probably expect_before not only look for the spawn_id which is in the global scope, but need it specified.

This works:

proc foo {} {
    namespace eval global {
        expect_after {
            -i $spawn_id -re $regex1 {do things}
        }
        expect_background {
            -i $spawn_id -re $regex2 {do more different things}
            -i $spawn_id ...
        }
    }
}

If anyone can explain why it needs -i $spawn_id that would be great, but here's a fix for anyone running into the same problem. Adding a global spawn_id should also work, but I ended up using this as I have about 5-6 variables, half of which I modify in foo.