title: What's the pid represent for when using eval
body: <p>In bash shell, I wrote a function a, and in function b I used eval to call function a dynamically. But I found when using <code>echo $(sh -c 'echo $PPID')</code> in function a, it returned a pid, but I can't find this process by using <code>ps -p pidno</code>. So was it a pid number? Or what else the number represent for ?
  Thanks for answering. </p>