title: What exactly does a non-shallow filecmp.cmp do?
body: <p>I'm using Python 2.6.2. The <a href="http://docs.python.org/release/2.6.5/library/filecmp.html" rel="noreferrer">docs for the filecmp module</a> say:</p>
  
  <blockquote>
    <p>The filecmp module defines functions to compare files and directories, with various optional time/correctness trade-offs.</p>
  </blockquote>
  
  <p>and, of the filecmp.cmp function:</p>
  
  <blockquote>
    <p>filecmp.cmp(f1, f2[, shallow])</p>
    
    <p>Compare the files named f1 and f2, returning True if they seem equal, False otherwise.</p>
    
    <p>Unless shallow is given and is false, files with identical os.stat() signatures are taken to be equal.</p>
  </blockquote>
  
  <p>What they don't do is specify just what is the correctness level one obtains with <code>shallow=False</code>. So, what does <code>shallow=False</code> do? How correct is it?</p>