title: How can I tell if a file is older than 30 minutes from /bin/sh?
body: <p>How do I write a script to determine if a file is older than 30 minutes in /bin/sh?</p>
  
  <p>Unfortunately does not the <code>stat</code> command exist in the system. It is an old Unix system, <a href="http://en.wikipedia.org/wiki/Interactive_Unix" rel="noreferrer">http://en.wikipedia.org/wiki/Interactive_Unix</a></p>
  
  <p>Perl is unfortunately not installed on the system and the customer does not want to install it, and nothing else either.</p>