title: Remove everything except a certain pattern
body: <p>I have a log file with lots of strings. 
  I would like to remove everything from this file (find &amp; replace) except any string that starts with: <code>phone=</code> and ended with <code>Digits=1</code></p>
  
  <p>for example: <code>phone=97212345678&amp;step=1&amp;digits=1</code></p>
  
  <p>To find that string I am using <code>(phone=.*digits=1)</code> and it works! but I did not manage to find the regex the select everything but this string and to clear them all.</p>
  
  <p><a href="http://admin.customee.com/sample.txt" rel="noreferrer">sample file</a>.</p>