title: Regex that matches a string that starts with whitespace and has only digits after
body: <p>I need a regex that will match lines like:</p>
  
  <pre><code>    123
    12345
  1234567
  </code></pre>
  
  <p>So I know the maximum length of a string (7) and that string can contain only digits and whitespaces at the beginning.</p>
  
  <p>I have tried this one: <code>[ 0-9]{7}</code> but this one will match strings like <code>12 34</code></p>