一次结束一个C程序的多个实例？

Question

I was wondering what the best way is to go about exiting multiple C programs at once? I'm running the same C program in two different terminals (Linux) and they are communicating through an interim text file. When the user ends one of them, most likely using CTRL-C, I want them both to end at once. I've read that signals can be used to do capture the user interrupting a program, but how will the program running in the other terminal also know when to end?

A conceptual explanation is plenty, or a nudge in the right direction is all I need. Thank you!

Answer 1

Probably you are using threads to receive external connections from one or more remote access. Your system have to check a common point that we can call System Status (normally we use a separated thread to maintain the system status, information like number of remote users, and other procedures can be under constant validation by this thread), anyway, once you have a thread that are handling a remote user connection this thread can request information from a secondary thread (System Status), once any thread request to System Status Thread to kill the system, this start to disconnect all users by killing each connection thread.

I'm not sure if I was clear, anyway, if you need more explanation please let me know a little bit more about your program.

BR, Henrique Zenoni Machado

Answer 2

Pipes or sockets

What I'd suggest is the “right” thing to do, here, is to stop “communicating” through a text file, and rather, use a pipe, FIFO file, or UNIX-domain socket connection. Check out any “intro to POSIX programming” book in the chapters on “inter-process communications” (IPC), where there should be at least one example of doing that with a pipe, FIFO file, or socket; the manual page on pipe might give you a head start, as well. Then, you can detect a disconnection by the other process and react accordingly.

Signal Handling

Alternatively, you could catch the SIGINT (Signal: Interrupted) in each process, and write some flag to the text file to tell the other end to terminate in your signal handler. Since you're working in C, you can refer directly to the manual for signal for the gory details of registering signal handlers.

Parent/Child

If one of the processes is the parent of the other, you can also detect the death of a child process via SIGCHLD (Signal: Child Terminated), and use one of the wait system calls (eg, waitpid ) to reap it before terminating yourself. The parent's death is harder to detect, although the child can monitor its own parent process ID to determine if it has been orphaned.