Use wait() system call for the parent process to wait for the child to terminate.
#include<unistd.h>
#include<sys/types.h>
#include<stdio.h>
#include<sys/wait.h>
int main()
{
pid_t p;
printf("before fork\n");
p=fork();
if(p==0)//child
{
printf("I am child having id %d\n",getpid());
printf("My parent's id is %d\n",getppid());
}
else//parent
{
wait(NULL);
printf("My child's id is %d\n",p);
printf("I am parent having id %d\n",getpid());
}
printf("Common\n");
}