Background Job

Shell Programming and Scripting
1

Hello Everyody,
Having a doubt.
sort file1 &
when we sent a job to the background it returns
Job Number
PID
again if we want to put it into foreground we have to use
job number

                       WHY  NOT   PID ?
                      that is also unique  for the process .
2

The job is not only for one command, it can be shell scripting, which include thousands of commands, after you run it, it will generate different PIDs.

So which PID you need forground then?

To man jobs maybe give you full idea on the background and foreground jobs.