wait - check child process status
wait_nohang looks for zombies (child processes that have
exited). If it sees a zombie, it eliminates the zombie,
puts the zombie's exit status into wstat, and returns the
zombie's process ID. If there are several zombies,
wait_nohang picks one. If there are children but no
zombies, wait_nohang returns 0. If there are no children,
wait_nohang returns -1, setting errno appropriately.
wait_stopnohang is similar to wait_nohang, but it also looks
for children that have stopped.
wait_stop is similar to wait_stopnohang, but if there are
children it will pause waiting for one of them to stop or
wait_pid waits for child process pid to exit. It eliminates
any zombie that shows up in the meantime, discarding the
wait_stop and wait_pid retry upon error_intr.
If the child stopped, wait_stopped is nonzero; wait_stopsig
is the signal that caused the child to stop.
If the child exited by crashing, wait_stopped is zero;
wait_crashed is nonzero.
If the child exited normally, wait_stopped is zero;
wait_crashed is zero; and wait_exitcode is the child's exit
Man(1) output converted with