title: What is the file extension of a file called "foo.tar.bz2"?
body: <p>Considering the file named:</p>
  
  <pre><code>foo.tar.bz2
  </code></pre>
  
  <p>What is the file extension? Is it <code>.tar.bz2</code> or <code>.bz2</code>? Is it well defined?</p>
  
  <p>Edit: The question here is one of the definition of a "file extension", or where the separation is between the file's name and its extension: is it "foo|.tar.bz2" or "foo.tar|.bz2"</p>