The `wait` program

wait waits for a set of children, then executes a program.

Interface

In an execlineb script:

     wait [ -r ] { [ pids... ] } prog...

wait reads a list of pids in a (possibly empty) block, and unquotes it.
wait waits for every child whose pid is listed in pids.... If pids... is an empty list, it waits for every child process it has.
wait then execs into prog....

-r : reap mode. Do not pause until a child has exited; only reap all pending zombies. The read block must be empty for that option to be effective.