title: What is the difference between ‘catalina.out’ and ‘catalina.YYYY-MM-DD.log’ log files in tomcat webapp server?
body: <p>In a tomcat server, logs folder contains files like these</p>
  
  <ul>
  <li><strong>localhost.YYYY-MM-DD.log</strong>: the log of the host<br></li>
  <li><strong>host-manager.YYYY-MM-DD.log</strong> and <strong>manager.YYYY-MM-DD.log</strong>: the logs of the related web applications <br></li>
  <li><strong>catalina.YYYY-MM-DD.log:</strong>: the container log file</li>
  <li><strong>catalina.out</strong>: ??</li>
  </ul>
  
  <p>I have an understanding about all the log files other than "catalina.out". I was looking for an explanation in the documentation but couldn't find different between "catalina.out" and "catalina.YYYY-MM-DD.log". When I go through the content, both seem similar. Can someone please help me to differentiate them?</p>
  
  <p><strong>Note</strong>: Reason I'm digging into this is my productions servers, "catalina.out" file is becoming bulkier(around 12 GB now). This can crash my application at any time since tomcat will not guarantee for application crashes after "catalina.out" become more than 2gb (as the Tomcat reference). Remaining options are rotating "catalina.out" using 3rd party tool like Logrotate or clean the "catalina.out".
  I'm using sl4j with log4j as the logging toolkit.</p>