wait.ch

Wait for a child matching PID to die. If PID is greater than 0, match any process whose process ID is PID. If PID is (pid_t) -1, match any process. If PID is (pid_t) 0, match any process with the same process group as the current process. If PID is less than -1, match any process whose process group is the absolute value of PID. If the WNOHANG bit is set in OPTIONS, and that child is not already dead, return (pid_t) 0. If successful, return PID and store the dead child's status in STAT_LOC. Return (pid_t) -1 for errors. If the WUNTRACED bit is set in OPTIONS, return status for stopped children; otherwise don't. This function is a cancellation point and therefore not marked with __THROW.