title: Why grep \n matches every line
body: <p>I found that <code>grep $'xxx\nxxx' file</code>, where <code>xxx</code> can be anything, prints every line of <code>file</code>. I'm a little confused about that. Does anyone get any clues? Thanks.</p>
  
  <p>The grep version is "GNU grep 2.6.3"</p>