/etc/shutdown-at-night/clients-generator is in debian-edu-config 1.818+deb8u2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 | #!/usr/bin/perl
use strict;
use warnings;
use Socket;
use SiteSummary;
use vars qw(%hostmap);
$ENV{PATH} .= ':/usr/sbin';
my @hostlist = `netgroup -h shutdown-at-night-hosts`;
chomp @hostlist;
map { $hostmap{$_} = 1; } @hostlist;
for_all_hosts(\&host_handler);
exit(0);
sub host_handler {
    my $hostid = shift;
    my $ipaddr = SiteSummary::get_primary_ip_address($hostid);
    my $fqdn = scalar gethostbyaddr(inet_aton($ipaddr), AF_INET);
    if ($fqdn) {
        my $mac = (get_ether_hwaddr($hostid))[0];
        if (exists $hostmap{$fqdn}) {
            print "$fqdn $mac\n";
        }
    }
}
sub get_ether_hwaddr {
    my $hostid = shift;
    my $path = get_filepath_current($hostid, "/system/ifconfig-a");
    if (open(FILE, "<", $path)) {
        my $sysinfo = 0;
        my @hwaddr = ();
        while (<FILE>) {
            chomp;
            if (m/Link encap:Ethernet  HWaddr (.+\S)\s*$/) {
                push(@hwaddr, $1);
            }
        }
        close(FILE);
        return @hwaddr;
    } else {
        return undef;
    }
}
 |