I've written the sub below in order to return the signal level of wireless clients.

open TCPDUMP, "tcpdump -e -i $interface ether src $dst_hw_addr|" or di
+e "Can't open tcpdump.\n";

sub get_rssi {

    my $rssi = undef;
    while (!defined $rssi) {
        my $line = readline(TCPDUMP);
        if ( $line =~ m#(?<sig_level>-\d{1,3})dB signal.*QoS#ig ) {
            $rssi = $+{sig_level};
        }
    }
    $rssi;
}
[download]

The sub works fine except that perl seems to be playing a constant game of catchup with tcpdump. I have the sub running in a loop and it will freeze the loop for about 7 sec and then execute 6 loops in quick succession before freezing again. Since the purpose of the code is to output a tone based on the signal level, the freezing makes the tone useless.

I'm pretty new to perl and any help would be greatly appreciated. I thought about getting into the Net::Pcap mod, but using the file handle to open tcpdump just seemed so much simpler.

Thanks for any input