Not specifically answering your question, but be
aware that Perl has a number of built-in functions
relating to users and groups, for
example: getlogin, getpwnam, getgrent.
See Perl functions for fetching user and group info.
And it is usually preferable to use the Perl builtin
function rather than an external command
(for why, see Unix shell versus Perl).
Though I am not aware of a Perl builtin function
that can add a Unix group, you could use them to
help you verify the changes you make.
To illustrate, the test program below prints
all groups on the system along with which users
are in each group:
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();
