title: how to get output of rb_backtrace() in gdb for passenger process
body: <p>I'm trying to dump a backtrace of a passenger process in gdb. I know I should just execute</p>
  
  <pre><code>attach &lt;PID&gt;
  call rb_backtrace()
  </code></pre>
  
  <p>after starting gdb, but I can't figure out where the output is going, I've looked at rails production logs (set to info), nginx logs in /var/logs/nginx but I can't find the output. Any ideas?</p>