title: tcpdump: syntax error in filter expression: syntax error
body: <p>I'm trying to learn how to use tcpdump instead of airport to sniff packets, but I can't figure out a part of the code that I usually find around the internet. I've already been searching for about 2 days for someone that may have made a question similar to my needs, and I've decided to ask the question my self.</p>
  
  <pre><code>sudo tcpdump "type mgt subtype beacon and ether src $BSSID" -I -c 1 -i en0 -w beacon.cap
  </code></pre>
  
  <p>I figured out that it is a filter to not have a ton of garbage inside the packets .cap but I don't know why the command line Is returning me:</p>
  
  <pre><code>tcpdump: syntax error in filter expression: syntax error
  </code></pre>
  
  <p>Can someone explain me what the filter should do so that maybe I can start trying to figure out by myself how may I fix it, or at least have a different lead to follow to search on the internet</p>