title: wget: Checking for file timestamp and overwriting
body: <p>How can I get <code>wget</code> to do this:</p>
  
  <p>Download a file from a location say <code>x</code>, only if the local copy of the file has an older time stamp than that of the file's time stamp on <code>x</code>. That means, it should download a file from a given location, only if there is a newer version of the file.</p>
  
  <p>In case there is a newer version of the file, <code>wget</code> should overwrite the file. </p>
  
  <p>Is it possible to do this?</p>