title: How do I determine what hostnames do not resolve to an IP address?
body: <p>I'm using bash shell on Mac 10.9.1.  Given a file of hostnames, which might ocntain entries like</p>
  
  <pre><code>dave.mydomain.com
  dave2.otherdomain.com
  somethingelse.whatever.com
  </code></pre>
  
  <p>How can I determine which of the host names in the file does not resolve to an IP address?</p>