Command executed through Proc::Async is not "tapped" correctly

Question

I have a good like this... straight from the documentation

my $proc = Proc::Async.new: ‘raku’, ‘script.raku’;
$proc.stdout.tap(-> $v { print "Output: $v" }, quit => { say 'caught exception ' ~ .^name });
$proc.stderr.tap(-> $v { print "Error:  $v" });
my $promise = $proc.start;
Thread.start: {  await $promise;}
sleep 30;

The script produces data on stdout and stderr. But it only prints one line .. Output:something

It stops printing information out... The script produces much more output.. What could be the problem?

Answer 1

You need an await $promise at the end of your program, otherwise it might just exit before the program you call has finished running.

Update (after OP edited his post).

OP also said off stackoverflow:

The full output is printed when the program ends.. with a considerable delay.

If that's the case, the problem is likely with the program that is called, that it buffers its STDOUT (and possible STDERR), and so the observing program doesn't even have early access to its output.

Calling flush on the appropriate handle in the called program might help.