title: Using grep to match md5 hashes
body: <p>How can I match md5 hashes with the grep command?</p>
  
  <p>In php I used this regular expression pattern in the past: </p>
  
  <pre><code>/^[0-9a-f]{32}$/i
  </code></pre>
  
  <p>But I tried:</p>
  
  <pre><code>grep '/^[0-9a-f]{32}$/i' filename
  grep '[0-9a-f]{32}$/' filename
  grep '[0-9a-f]{32}' filename
  </code></pre>
  
  <p>And other variants, but I am not getting anything as output, and i know for sure the file contains md5 hashes. </p>