How to make child process die after parent exits?

Child can ask kernel to deliver SIGHUP (or other signal) when parent dies by specifying option PR_SET_PDEATHSIG in prctl() syscall like this:

prctl(PR_SET_PDEATHSIG, SIGHUP);

See man 2 prctl for details.

Edit: This is Linux-only

I'm trying to solve the same problem, and since my program must run on OS X, the Linux-only solution didn't work for me.

I came to the same conclusion as the other people on this page -- there isn't a POSIX-compatible way of notifying a child when a parent dies. So I kludged up the next-best thing -- having the child poll.

When a parent process dies (for any reason) the child's parent process becomes process 1. If the child simply polls periodically, it can check if its parent is 1. If it is, the child should exit.

This isn't great, but it works, and it's easier than the TCP socket/lockfile polling solutions suggested elsewhere on this page.

I have achieved this in the past by running the "original" code in the "child" and the "spawned" code in the "parent" (that is: you reverse the usual sense of the test after fork()). Then trap SIGCHLD in the "spawned" code...

May not be possible in your case, but cute when it works.