How to wait for exit of non-children processes

Question

For child processes, the wait() and waitpid() functions can be used to suspends execution of the current process until a child has exited. But t

Answer 1

Nothing equivalent to wait(). The usual practice is to poll using kill(pid, 0) and looking for return value -1 and errno of ESRCH to indicate that the process is gone.

Update: Since linux kernel 5.3 there is a pidfd_open syscall, which creates an fd for a given pid, which can be polled to get notification when pid has exited.