wait - await completion of process
Wait until all processes started with & have completed, and report on
abnormal terminations.
Because wait(II) must be executed in the parent process,
the Shell itself executes wait, without creating a new process.
After executing wait you are committed to waiting until termination,
because interrupts and quits are ignored by all processes concerned. The only
out, if the process does not terminate, is to kill it from another
terminal or to hang up.