title: Create a subdirectory for all directories in folder
body: <p>Suppose I have some directory, which contain a number of subdirectories, and in each of those subdirectories I want to create a directory with the same name:</p>
  
  <pre><code>./dir-1
  ./dir-2
  ...
  ./dir-n
  </code></pre>
  
  <p>I want to do <code>mkdir */new-dir</code></p>
  
  <p>but this throws an error. What's the best way of going about this?</p>