c - Detect death of parent process

Question

How can I detect parent process death in Linux OS?

If in parent process called fork(), that create child process. In the parent process I can use system call wait() for waiting terminated child process, and getting its status.

But, I can't find info about how child process can detect parent process' death?

Answer 1

You can get the parent process id by calling getppid() and then sending signal 0 via kill(). A return code of 0 will indicate that the process is still alive.

As mentioned by @Ariel, getppid() will either return the pid of the original parent or that of init, which will be pid 1. So you either have to store the parent pid by calling getppid() at startup or later check if your parent has pid 1.

According to this answer on Linux you can also detect the death of the parent via prctl()'s PR_SET_PDEATHSIG option and a self-chosen signal.