You must use tethereal 
      instead of ethereal. There's an autostop condition -a and you can fix a 
      limit in time or size. For example, to capture just 1kB in "file.pcap" 
      from the default interface use :
      tethereal -a filesize:1 -w 
      file.pcap 
      
      
see http://www.ethereal.com/tethereal.1.html 
      for more info 
      
      
      
-----Original Message----- 
From: Venkatesh, Susheel [mailto:susheel@xxxxxx] 
      
Sent:Wednesday, June 25, 
      20033:19 
      PM 
To: 'ethereal-dev@xxxxxxxxxxxx'; 
      'ethereal-users@xxxxxxxxxxxx' 
Subject: [Ethereal-dev] Help!! 
      
      
Hi, 
      
I am trying to develop a Automated test-suite which would require 
      controlling Ethereal. I was just wondering if I can get custom-made 
      executable that would allow me to control Ethereal (start, stop and save 
      ethereal capture in text format from an external application) or if 
      someone could suggest how to add this functionality into 
      Ethereal. 
      
The sequence of steps during a typical test is as follows. These 
      steps are to be executed using an external application (the automation 
      test tool):- 
      
1) Launch ethereal and start (this can be done from the 
      command-line and there is no problem with this step) 
      
2) Run a test-script 
      
3) Stop capture and save the capture in 
      text-format (there is a problem here; there is no way I can control 
      ethereal from an external application and there is no command-line option 
      to stop and save capture in text-format) 
      
I am using Windows 2K. What all do I require to take the ethereal 
      source code and compile it on my PC? 
      
I would appreciate some help on this. 
      
Thanks, 
Susheel