title: Windows CMD's FINDSTR wrong regexp matching
body: <p>I need to check if a string contains anything except the digit. But I've got a problem.</p>
  
  <pre><code>echo bdfbdfd | findstr /R [^0123456789]
  </code></pre>
  
  <p>returns nothing, but it should return bdfbdfd. 
  But </p>
  
  <p><code>echo 123 | findstr /R [^0123456789]</code></p>
  
  <p>returns '123'. Why? It should work vice versa.</p>