title: Way to output differences between two files (preferably using command line)
body: <p>I am familiar with tools such as tkDiff and WinMerge and am aware of how to see the difference between two files.</p>
  
  <p>What I'm looking to do is to produce a report of elements in one file that are not present in another.</p>
  
  <p>For example:</p>
  
  <p>File1 contains:</p>
  
  <pre><code>apple
  cool
  dude
  flan
  </code></pre>
  
  <p>File2 contains:</p>
  
  <pre><code>apple
  ball
  cool
  dude
  elephant
  </code></pre>
  
  <p>I want to produce a report that contains:</p>
  
  <pre><code>ball
  elephant
  </code></pre>
  
  <p>Or, better yet, a report like this:</p>
  
  <pre><code>+ball
  +elephant
  -flan
  </code></pre>
  
  <p>Does anybody know of a tool that can do this?  Preferably with command line options.</p>
  
  <p>The report feature in WinMerge isn't too far off what I'd like but there is no command line option to do this (as far as I know).</p>
  
  <p>Thanks in advance.</p>