title: delete all directories except one
body: <p>So using the shell, and having a directory:</p>
  
  <pre><code>./parent
  ./parent/one
  ./parent/two
  ./parent/three
  ./parent/four
  </code></pre>
  
  <p>i want to do something like <code>rm -rf parent/*</code> in one command, but keeping one directory, for example 'four', so the end result would be</p>
  
  <pre><code>./parent
  ./parent/four
  </code></pre>