title: Average and maximum size of directories
body: <p>I have a directory and a bunch of sub-directories like this:
  - <strong>directory1</strong> (<em>sub-dir1</em>, <em>sub-dir2</em>, <em>sub-dir3</em>, <em>sub-dir4</em>, <em>sub-dir5</em>...........and so on, hundreds of them...)</p>
  
  <p>How do I find out what is average size of the sub-directories?
  And how do I find what is the maximum size of the sub-directories?</p>
  
  <p>All using Unix commands...</p>
  
  <p>Thanks.</p>