Hi there!

I want to write a script that

- captures the output of tcpdump

- deposits the PID of the tcpdump process in $pid

- kills the tcpdump after some time

I tried running this code:

#!/usr/local/bin/perl -w

use warnings;
use strict;

$|=1;

my $output;
my $pid;

$pid = open (STDIN,"sudo /usr/sbin/tcpdump -n -e -i mon_wlan0 -c 100|"
+);

while ($output=<>){
    print "$output\n";
}

print "pid = $pid\n";

[download]

while running top | grep tcpdump on another terminal

but the PID returned by the script is different(larger) from the one in the terminal

So my questions are:

---why do i have 2 process id-s? (parent&child maybe?)

---how do i fix the script to be able to stop the tcpdump with kill -9 $pid before the packet counter expires ?

Any help would be appreciated. Thank you!

In reply to capture output of tcpdump and PID by mike928

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