title: Regex with min 8 digits, 20 characters
body: <p>I'm currently looking for a regex that verify's the following requirements:</p>
  
  <ul>
  <li>Should contain atleast 8 digits (0-9).</li>
  <li>Between the digits it is allowed to use other characters (a-z) (also upper case).</li>
  <li>It should contain max 20 characters (a-z 0-9).</li>
  </ul>
  
  <p><strong>example</strong>: </p>
  
  <pre><code>12345678: true
  123adafa45678: true
  123ab456: false (needs atleast 8 digits, now only 6)
  ab12345a678: true 
  ab123456789afgb2459a2: false (more then 20 characters)
  </code></pre>
  
  <p>I tried serveral things but if I use something like:
  <code>(\D*\d\D*){8,}</code> then it works but it doesn't meet the last requirement (up to 20 characters).</p>