Changing effecive user id

astroboy has asked for the wisdom of the Perl Monks concerning the following question:

I'm trying to run a script that changes my effective user id. The permissions are 6550 (-r-sr-s---) owner = root, and I'm running the script as a member of the group that is given group execute permissions.

#!/usr/bin/perl -T
use strict;

my $user  = 'etl';
my $group = 'etl';
my $uid = getpwnam($user) || die "Cannot identify uid";
my $gid = getgrnam($group) || die "Cannot identify gid";

printf("Current Effective User ID: %s\n", $>);
printf("Current Effective Group IDs: %s\n", $));
printf("Requested User ID: %s\n", $uid);
printf("Requested Group ID: %s\n", $gid);

print "Changing Effective IDs\n";

$> = $uid;
$) = $gid;

printf("Current Effective User ID: %s\n", $>);
printf("Current Effective Group IDs: %s\n", $));
[download]

When the script as run as myself, the output is:

Current Effective User ID: 500
Current Effective Group IDs: 500 500
Requested User ID: 502
Requested Group ID: 503
Changing Effective IDs
Current Effective User ID: 500
Current Effective Group IDs: 500 500
[download]

Note the effective ids haven't changed. However, when I run the script as root, the effective user id is what I requested, although the group ids haven't changed

Current Effective User ID: 0
Current Effective Group IDs: 0 0 1 2 3 4 6 10
Requested User ID: 502
Requested Group ID: 503
Changing Effective IDs
Current Effective User ID: 502
Current Effective Group IDs: 0 0 1 2 3 4 6 10
[download]

So my question is: how do I change my effective user id? I'm using Perl 5.10.0 on Centos 5.3 Thnanks

Back to Seekers of Perl Wisdom