[atexit example]register a function to be called at normal process termination #atexit #interprocess

atexit_example.cpp

#include <iostream>
#include <cstdlib>
#include <unistd.h>
#include <cstring>
#include <cerrno>
#include <sys/types.h>
#include <sys/wait.h>

void parent_process_callback() {
  std::cout <<__func__ <<", pid: " <<getpid() <<std::endl;
}

void child_process_callback() {
  std::cout <<__func__ <<", pid: " <<getpid() <<std::endl;
}

int main(int argc, char **argv) {
  sem_child = new Semaphore;
  sem_parent = new Semaphore;
  
  setup_sigint_handler();
  
  pid_t pid = fork();
  switch (pid) {
    case 0: {
      std::cout <<"child process! pid:" <<getpid() <<std::endl;
      atexit(child_process_callback);
      break;
    }
    
    case -1: {
      std::cerr <<"fork failed, " <<strerror(errno) <<std::endl;
      break;
    }

    default: {
      std::cout <<"parent process! pid:" <<getpid() <<std::endl;
      atexit(parent_process_callback);
      while (pid = waitpid(-1, nullptr, 0)) {
        if (ECHILD == errno) {
          break;
        }
        std::cout <<"[" <<__func__ <<":" <<__LINE__ <<"]" <<"child " <<pid <<" terminated!" <<std::endl;
      }
      break;
    }
  }

  return 0;
}