title: difference between pipelining and redirection in linux
body: <p>Can anyone tell me the difference? for example:<br>
  if I have a file <code>a.txt</code> with the following content:  </p>
  
  <blockquote>
    <p>a<br>
    b<br>
    c</p>
  </blockquote>
  
  <p>what would be the difference between <code>cat a.txt | cat</code> and <code>cat &lt; a.txt</code><br>
  It seems to me that they all simulate STDIN, is that correct, or are there differences? Thanks a lot.</p>