#! /usr/bin/perl
use strict;
use warnings;

if (scalar @ARGV < 1) {
        die "Usage: $0 <lowest_gid>";
}

my $LOWEST_PVV_GID = int($ARGV[0]);

my @lines = ();

# Read old group file
open(IN, "/etc/group") || die "Unable to open /etc/group: $!";
while(<IN>) {
        my @parts = split(":");
        if ($parts[2] < $LOWEST_PVV_GID || $parts[0] eq "nogroup") {
                push @lines, $_;
        }
}
close IN || die "Unable to close /etc/group: $!";

# Read pvv group file
my $groupcount = 0;
open(PVV, "/etc/group.pvv") || die "Unable to open /etc/group.pvv: $!";
while(<PVV>) {
        ++$groupcount;
        push @lines, $_;
}
close PVV || die "Unable to close /etc/group.pvv: $!";

if ($groupcount < 200) {
        die "/etc/group.pvv has less than 200 groups, something went wrong";
}

open(OUT, ">/etc/group.tmp") || die "Unable to open /etc/group.tmp for writing: $!";
foreach (@lines) {
        print OUT $_ || die "Can't write to /etc/group.tmp: $!";
}
close OUT || die "Unable to close /etc/group.tmp: $!";

rename "/etc/group.tmp", "/etc/group" || die "Unable to move /etc/group.tmp to /etc/group: $!";