title: Using \d{1,3} when creating regex to find IPs
body: <p>Why would one use <code>{1,3}</code> in <code>\d{1,3}</code> when catching an IP with <code>grep</code>? For example:</p>
  
  <pre><code>grep -Po 'inet addr:\K(?!127\.)\d{1,3}.\d{1,3}\.\d{1,3}\.\d{1,3}'
  </code></pre>
  
  <p>\K removes <code>inet addr:</code>, and <code>(?!127\.)</code>, AFAIU, removes any address that starts with 127 (the loopback in that case), but what are the <code>{1,3}</code> after <code>\d</code>?</p>
  
  <p>Clearly, we don't only want IP calsses that starts in 1 and end with 2 or 3 so the purpose there is unclear to me.</p>
  
  <p>Note: <code>inet addr:</code> is part of the <code>ifconfig</code> Linux utility.</p>