title: 6 digits regular expression
body: <p>I need a regular expression that requires at least ONE digits and SIX maximum. </p>
  
  <p>I've worked out this, but neither of them seems to work.</p>
  
  <pre><code>^[0-9][0-9]\?[0-9]\?[0-9]\?[0-9]\?[0-9]\?$
  
  ^[0-999999]$
  </code></pre>
  
  <p>Any other suggestion?</p>