multiprocessing - How to spawn other programs within perl script and immediately continue Perl processing?

Question

How to spawn other programs within perl script and immediately continue Perl processing (instead of halting until the spawned program terminates) ? Is it possible to process the output coming from the spawned program while it is running instead of waiting it to end?

Answer 1

You can use open for this (to run the program /bin/some/program with two command-line arguments):

open my $fh, "-|", "/bin/some/program", "cmdline_argument_1", "cmdline_argument_2";
while (my $line = readline($fh)) {
    print "Program said: $line";
}

Reading from $fh will give you the stdout of the program you're running.

The other way around works as well:

open my $fh, "|-", "/bin/some/program";
say $fh "Hello!";

This pipes everything you write on the filehandle to the stdin of the spawned process.

If you want to read and write to and from the same process, have a look at the IPC::Open3 and IPC::Cmd modules.