#!/usr/bin/perl -w
#<UnusedGrp.pl> Find unused Groups in /etc/group
use strict;

my $GROUPfile="/etc/group";
my $PASSWD="/etc/passwd";

open my $gh, "<", $GROUPfile or die "$GROUPfile Open failed: $!\n";
open my $ph , "<", $PASSWD or die "$PASSWD Open failed: $!\n";

my %gids = map { (split /:/)[3] => 1 } <$ph>;

while (<$gh>) {
    my @fields = split /:/;

    next if length $fields[3] > 1;
    next if $gids{$fields[2]};
    print "$fields[0] has no users and no GID references\n"
}