A job is a command pipeline. You run a simple job whenever you give GNU/Linux a command (for example, type date on the command line and press RETURN: You have run a job). You can also create several jobs with multiple commands on a single command line:
$ find . –print | sort | lpr & grep –l alex /tmp/* > alexfiles &  18839  18876
The portion of the command line up to the first & is one job, consisting of three processes: (find [page 1165], sort [page 66], and lpr [page 63]) connected by pipes. The second job is a single process running grep. Both jobs have been put into the background by the trailing & characters, so bash does not wait for them to complete before giving you a prompt. Before the prompt, the shell displays information ...