title: How to output tcpdump with grep expression to stdout / file?
body: <p>I am trying to output the following tcpdump grep expression to a file :</p>
  
  <p>tcpdump -vvvs 1024 -l -A tcp port 80 | grep -E 'X-Forwarded-For:' --line-buffered | awk '{print $2}</p>
  
  <p>I understand it is  related to the line-buffered option, that sends the output to stdin. However, if I don't use --line-buffered I don't get any output at all from my tcpdump.</p>
  
  <p>How can I use grep so that it will send my output directly to stdout / file in this case ? </p>