title: Grep in multiple files prints matches line with file name
body: <p>I'm using grep to found matching lines from a file in two different files. It finds the matching files just fine from <code>File1</code> into <code>File2</code> and <code>File3</code>, but from the moment there is more than one file, it prints the file name in which it was found next to the line. </p>
  
  <pre><code>grep -w -f File1 File2 File3
  </code></pre>
  
  <p>Output:</p>
  
  <p><code>File2: pattern</code></p>
  
  <p><code>File2: pattern</code></p>
  
  <p><code>File3: pattern</code></p>
  
  <p>Is there an option to avoid the print of <code>File2:</code> and <code>File3:</code>?</p>