C Linux Signal Handler for the Main Process Only

Question

I am making a program that creates numerous processes using fork() , which then calls an exec function to the same program (this is required by the professor).

I need it to react to CTRL+C (SIGINT) and ask the user if he/she wants to leave. The problem is that the signal handler is implemented in all the child processes too, so, when the signal is sent, the user has to answer the same amount of times as the number of processes.

I only want it to ask the user once per CTRL+C.

What solutions can I implement?

Answer 1

When you call fork() , the parent process will get back the pid of the child. You can send a SIGTERM or SIGKILL signal to the children through the kill syscall when the parent receives the SIGINT signal.

Answer 2

You can set a global variable pid and populate it with the result of getpid() on launch. And inside the signal handler test getpid() against pid then execute your code. Something like, if you are the main process please proceed, if not exit!

End result: You will have a signal handler that is run once by the main process....