title: What do double curly braces do in a bash command?
body: <p>I am refactoring a script and I'm seeing this:</p>
  
  <pre><code>/bin/bash -c 'rm -rf directory/{{..?*,.[!.]*,*}}'
  </code></pre>
  
  <p>Googling "bash double curly braces" is strangely not getting my anywhere so far. What does this code do?</p>
  
  <p>EDIT: I didn't include enough details, apparently. It's actually a python command that was using <code>format()</code>, so the double curly braces were actually single curly braces being escaped for that. </p>
  
  <pre><code>subprocess.check_output(['/bin/bash', '-c', 'rm -rf {0}/{{..?*,.[!.]*,*}}'.format('directory')]
  </code></pre>
  
  <p>@thatotherguy nailed it in the comments.</p>