use strict;
use warnings;

my $user = getlogin();
my ($uid, $primarygid, $home, $shell) = (getpwnam($user))[2,3,7,8];
defined($uid) or die "$0: error user '$user' does not exist\n";
print "user='$user' primary gid=$primarygid\n\n";

while (my ($name, $pw, $gid, $members) = getgrent) {
   print "gid        : $gid\n";
   print "group name : $name\n";
   print "members    : $members\n\n";
}
endgrent();