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.

Answer 2

None I am aware of. Apart from the solution from chaos, you can use semaphores if you can change the program you want to wait for.

The library functions are sem_open(3), sem_init(3), sem_wait(3), ...

sem_wait(3) performs a wait, so you don´t have to do busy waiting as in chaos´ solution. Of course, using semaphores makes your programs more complex and it may not be worth the trouble.

Answer 3

On BSDs and OS X, you can use kqueue with EVFILT_PROC+NOTE_EXIT to do exactly that. No polling required. Unfortunately there's no Linux equivalent.