title: Checking file permissions in linux
body: <p>I need to change the permissions of files within a directory, such as :</p>
  
  <ul>
  <li>if the group has no permissions, others should have no permissions either</li>
  <li>if the group has permissions, nothing should change</li>
  </ul>
  
  <p>But in a single command.</p>
  
  <p>I'm pretty sure I have to use <code>chmod</code> for the change itself.
  My biggest problem is actually how to know if the group has permissions or not? thereafter, use this information in a single command</p>