title: How to 'grep' a continuous stream?
body: <p>Is that possible to use <code>grep</code> on a continuous stream?</p>
  
  <p>What I mean is sort of a <code>tail -f &lt;file&gt;</code> command, but with <code>grep</code> on the output in order to keep only the lines that interest me.</p>
  
  <p>I've tried <code>tail -f &lt;file&gt; | grep pattern</code> but it seems that <code>grep</code> can only be executed once <code>tail</code> finishes, that is to say never.</p>