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

In reply to online tcpdump filter by porpoise_paul

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.