title: grep with regex functionality in linux
body: <pre><code>$ echo 'HI' | grep '\w*'
  HI
  $ echo 'HI' | grep '\w+'
  $ echo 'HI' | grep '\w{2}'
  </code></pre>
  
  <p>For cases 2 &amp; 3, grep must have returned 'HI', but is returning nothing. Is there something wrong in what I am grepping for?</p>