title: Extract number of variable length from string
body: <p>I want to extract a number of variable length from a string.</p>
  
  <p>The string looks like this:</p>
  
  <pre><code>used_memory:1775220696
  </code></pre>
  
  <p>I would like to have the <code>1775220696</code> part in a variable. There are a lot of questions about this, but I could not find a solution that suits my needs.</p>