title: how to get keys which does not match a particular pattern in redis?
body: <p>In Redis, <code>keys user*</code> will print all keys starting with <code>user</code>.
  For example:</p>
  
  <pre><code>keys user*
  1) "user2"
  2) "user1"
  </code></pre>
  
  <p>Now, I want all keys that don't start with <code>user</code> to be printed.
  How could I do that?</p>