Parent Terminates Before Child Code In Linux Operating System

Parent Terminates Before Child: Scenario-1

#include <unistd.h>

int main() {
  int ret;
  printf("welcome..pid=%d\n", getpid());
  ret = fork();
  if (ret < 0) {
    perror("fork");
    exit(1);
  }
  if (ret == 0) {
    printf("child--welcome,pid=%d,ppid=%d\n", getpid(), getppid());
    sleep(2);  //Intentional delay in child
    printf("wakes up,pid=%d,ppid=%d\n", getpid(), getppid());
    exit(0);
  } else // ret>0
  {
    printf("parent--hello,pid=%d,ppid=%d\n", getpid(), getppid());
  }
  return 0;
}

 
Parent Terminates Before Child: Scenario-2

#include <unistd.h>
#include <stdio.h>

int main() {
  pid_t ret
  int i, max = 100;
  printf("welcome..pid=%d\n", getpid());
  ret = fork();
  if (ret < 0) {
    perror("fork");
    exit(1);
  }
  if (ret == 0) {
    printf("child--welcome,pid=%d,ppid=%d\n", getpid(), getppid());
    for (i = 1; i <= max+5; i++) {
      printf("wakes up,pid=%d,ppid=%d\n", getpid(), getppid());
      sleep(1); //usleep(1000*100)
    }
    exit(0);
  } else // ret>0
  {
    printf("parent--hello,pid=%d,ppid=%d\n", getpid(), getppid());
    for (i = 1; i <= max; i++) {
      printf("parent--%d\n", i);
      sleep(1);
    }
  }
  return 0;
}

 
Observations & Understanding
 

• What is the ppid of child
  • After wake up from sleep (Post parent termination) in first examples
  • Towards last 4-5 iterations in child’s for loop in second example (max vs max + 5)
• Have you observed that shell prompt came in between, before the completion of child’s output
• Any disadvantages of parent terminates before child process?
• Is it possible to prevent parent termination before the completion of child process?