title: How do I retrieve the header when I want to look at grep output of something in bash?
body: <p>Let's suppose I pipe the output of a command and want to filter lines with grep but also keep the first one which is a header. I saw someone type something akin to this:</p>
  
  <pre><code>the command | (read l; echo$l) | grep bla | less
  </code></pre>
  
  <p>and it extracted the first line (header), then grepped the rest of the file for the lines matching bla and the output of that went to <code>less</code> for inspection. Of course the above command doesn't work but that's the idea, what part of it is wrong?</p>