title: how to "grep" text in the middle with special chars
body: <pre><code>Unexpected header.nextMessage.response.statusLine.statusCode := 403 with 180 unmatched
  </code></pre>
  
  <p>I want to grep the following text into var: <code>nextMessage.response.statusLine.statusCode := 403</code></p>
  
  <p>I used this command: <code>exp=$(grep -oP '(?&lt;=header).+(?=with)' text.txt)</code> but it fetched only this part:<code>.nextMessage.response.statusLine.statusCode</code> without 403.</p>