title: What is the difference between a job pid and a process id in *nix?
body: <p>A job is a pipeline of processes. After I execute a command line, for example, <code>sleep 42 &amp;</code> , the terminal will give me some information like this</p>
  
  <pre><code>[1] 31562
  </code></pre>
  
  <p>Is this <code>31562</code> the "job pid" of this job? Is it the same as the process of the <code>ls</code> command?</p>
  
  <p>And if I have a command with a pipe, there will be more than one process created, is the job pid same as the process id of the first process of the pipeline?</p>