title: Can grep show only words that match search pattern?
body: <p>Is there a way to make grep output "words" from files that match the search expression?</p>
  
  <p>If I want to find all the instances of, say, "th" in a number of files, I can do:</p>
  
  <pre><code>grep "th" *
  </code></pre>
  
  <p>but the output will be something like (bold is by me);</p>
  
  <pre>
  some-text-file : <b>the</b> cat sat on <b>the</b> mat  
  some-other-text-file : <b>the</b> quick brown fox  
  yet-another-text-file : i hope <b>this</b> explains it <b>thoroughly</b> 
  </pre>
  
  <p>What I want it to output, using the same search, is:</p>
  
  <pre><code>the
  the
  the
  this
  thoroughly
  </code></pre>
  
  <p>Is this possible using grep? Or using another combination of tools?</p>