Question

To be done in C for LINUX.

Write a simple test program to find out the parent process id of a process before and after its parent process terminates. Based on your test results, answer the following question: what is a process's parent process after its original parent process terminates?

Answer 1

// code

#include <pthread.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#define MAX 10
  
int main()
{
char turn = 'c';
int fd[2];
  
pipe(fd);
  
pid_t child_id = fork();
  
if(child_id > 0)
{
// Parent: reading only, so close the write-descriptor
close(fd[1]);
  
while(turn == 'c')
{

// now read the data (will block)
read(fd[0], &turn, sizeof(turn));
// close the read-descriptor
close(fd[0]);
}
  
  
printf("Parent is exiting");
}
else if(child_id == 0)
{
close(fd[0]);
pid_t parent_id = getppid();
pid_t new_parent_id = 0;
  
  
printf("\n Parent id is: %d", parent_id);
turn = 'p';
  
write(fd[1], &turn, sizeof(turn));
  
close(fd[1]);
  
printf("\nTurn is: %c", turn);
new_parent_id = getppid();
printf("\nNew parent_id: %d", new_parent_id);
}
else
{
perror("error\n"); //fork()
}
}

// After parent exit parent is now init that is pid = 1;