How do I execute an external program from Perl and have the perl script continue

Question

I am running a perl script from a cron job on Ubuntu. As part of the script it needs to execute an external program and not wait for the program to complete and also continue executing the script. I have tried the following but as near as I can tell it is not executing the program and also seams to not continue the script.

exec("/usr/bin/dotnet /usr/local/myprogram/myprogram.dll arg1, arg2, moreargs")
    or print STDERR "Couldn't exec myprogram";

Answer 1

• To call your program, you should pass the program arguments as separate arguments to exec. (See https://perldoc.perl.org/functions/exec.html.)
• Since you want the script to proceed without waiting for the program to return, you should use fork (see https://perldoc.perl.org/functions/fork.html) so that you have two separate processes running in parallel (one running the program, one running the rest of the script).

So:

my $child_pid = fork();
die "Couldn't fork" unless defined $child_pid;
if (! $child_pid) {
  exec '/usr/bin/dotnet', '/usr/local/myprogram/myprogram.dll', 'arg1', 'arg2', 'moreargs';
  die "Couldn't exec myprogram: $!";
}

# rest of script

wait();