title: Diff inside if-statement condition - how to make it true?
body: <p>I have </p>
  
  <p><code>diff &lt;file1&gt; &lt;file2&gt;</code> which returns nothing</p>
  
  <p>I want it inside condition which is true when diff returns nothing. I tried it in several ways, but all the time I had else-commands executed.</p>