I need a script, that will run tcpdump with timeout and then exit. Here is what i have. 
#!/usr/bin/perl
use strict;

my $pid = 0;
my $cmd = $ARGV[0];

eval {
        my $process;
    local $SIG{ALRM} = sub { kill 'INT', $pid; close $process; die "ti
+meout\n" };
    alarm( 5 );
        $pid = open $process, "$cmd |";
    while (<$process>) {
        chomp ($_);
        print $_, "\n";
    }   
};

[download]
usage: perl timeout 'tcpdump -n -i em0' It works perfectly. Runs tcpdump command and kills the perl script and tcpdump after 5 seconds. The main problem is buffering. When i have not a lot of captured packets, script doesn't show them. Could u please help me with that? I tried to do 
select $process;
$|=1;
select $process;

[download]
doesn't help.

In reply to cmd timeout by pronini

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.