Question

What “nonblocking” command makes tcsh wait until a specific background
task completes and then “alerts” me by running a command of my choosing?

I want “wait %3 && xmessage job completed &” to wait until background
job [3] is finished and then xmessage me “job completed”, but want
this command itself to return immediately, not “block” the terminal.

Obviously, my syntax above doesn’t work. What does?

I’ve written a Perl program that can do this, but surely tcsh can do
it natively?

Answer 1

You may be able to do something like (untested):

while (! $?)
    kill -s 0 $!
    sleep 1
end

Or take a look at the notify command. I’m not sure if it would do what you want.