I'm avoiding system calls in this perl program I'm writing and I need to check to see if some pid is currently active.. I'd prefer to do this without modules (cuz it seems simple) so here's what I came up with: 
#!/usr/bin/perl
use strict;

my $pid = $ARGV[0] or die "usage: $0 pid\n";
my $group = getpgrp $pid;

print "$pid\'s group is $group\n";
if($group >= 0) {
        print "$pid is active\n";
} else {
        print "$pid doesn't exist\n";
}

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Because what I noticed during some testing is that getpgrp returns -1 if the pid doesn't exist, a number > 0 if pid exists, and 0 if the pid is 1 (init). Anyone else played with this and have any advice/warnings about doing it this way?

In reply to Checking PIDs without system calls by reyjrar

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