5-4-subreaper.c

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/wait.h>
#include <sys/prctl.h>

char* const argv_list[] = {
  "/bin/bash",
  NULL
};

int main()
{
  printf("Parent – ready to fork, current PID: %d\n", getpid());

  // 設定目前 process 的 child subreaper 屬性
  int ret = prctl(PR_SET_CHILD_SUBREAPER, 1, 0, 0, 0);
  if(ret < 0) {
    printf("can't set child subreaper\n");
    exit(EXIT_FAILURE);
  }

  pid_t pid = fork();

  if (pid == -1) {
    // pid == -1: error occurred
    printf("can't fork, error occurred\n");
    exit(EXIT_FAILURE);
  } else if (pid == 0) {
    // pid == 0: child process created
    printf("I am child process with PID: %d\n", getpid());
    execv(argv_list[0], argv_list);
    exit(0);
  } else {
    // pid > 0: a positive number is returned for the pid of parent process
    printf("I am parent process with PID %d and my child is %d\n", getpid(), pid);
    waitpid(pid, NULL, 0);
    // 不要讓 parent process 停下來
    while(1) {
      sleep(1);
    }
    printf("Parent - stopped!\n");
  }

  return 0;
}