Working with processes in C

Question

Hi, just a quick question regarding C and processes. In my program, I create another child process and use a two-directional pipe to communicate between the child and parent. The child calls execl() to run yet another program.

My question is: I want the parent to wait n amount of seconds and then check if the program that the child has run has exited (and with what status). Something like waitpid() but if the child doesn't exit in n seconds, I'd like to do something different.

Answer 1

You can use waitpid() with WNOHANG as option to poll, or register a signal handler for SIGCHLD.

Answer 2

You can use an alarm to interrupt waitpid() after N seconds (don't use this approach in a multithreaded environment though)

   signal(SIGALRM,my_dummy_handler);
   alarm(10);

   pid_t p = waitpid(...);
   if(p == -1) {
     if(errno == EINTR) {
        //timeout occured
      } else {
        //handle other error
     }