title: Filter function for less +F
body: <p>When watching a growing log file with e.g. "less -iS +F service.log" I want
  to limit the display to lines matching a certain pattern.</p>
  
  <p>I tried something like</p>
  
  <pre><code>less +F service.log | grep &lt;pattern&gt; | less +F
  </code></pre>
  
  <p>which doesn't work. Also</p>
  
  <pre><code>cat &lt; service.log | grep &lt;pattern&gt; | less +F
  </code></pre>
  
  <p>doesn't do what I want. It looks like the input is already closed and
  less doesn't show changes.</p>
  
  <p>How can I limit the display to lines matching a certain pattern?</p>