title: Remove newlines (\n) if they are followed by a string - using SED
body: <p>I have a text file and I need to remove newlines if they are followed by the string "fox"</p>
  
  <pre><code>the 
  brown 
  fox 
  jumps 
  </code></pre>
  
  <p>will become</p>
  
  <pre><code>the 
  brown fox 
  jumps 
  </code></pre>
  
  <p>I would like to do it in SED, but the AWK solution would be useful too.</p>