title: cp: silence "omitting directory" warning
body: <p>I'm using the command <code>cp ./* "backup_$timestamp"</code> in a bash script to backup all files in directory into a backup folder in a subdirectory. This works fine, but the script keeps outputting warning messages:</p>
  
  <pre><code>cp: omitting directory `./backup_1364935268'
  </code></pre>
  
  <p>How do I tell cp to shut up without silencing any other warnings that I might want to know about?</p>