int pfork(int);
void process_join(int,int);
 
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
#include<stdio.h>
 
int main()
{
 
        int sum=0,fsum;
        int *a3,shmid,id;
        int i,n,a1[15],a2[15];
 
        printf("enter how many nos\n");
        scanf("%d",&n);
 
        for(i=0;i<n;i++)
        {
                printf("enter number for 1st array:\n");
                scanf("%d",&a1[i]);
        }
 
        for(i=0;i<n;i++)
        {
                printf("enter number for 2nd array:\n");
                scanf("%d",&a2[i]);
        }
 
        shmid=shmget(IPC_PRIVATE,4,0666|IPC_CREAT);
         
        a3=(int *)shmat(shmid,0,0);
 
        if(shmid < 0)
        {
                printf("Error\n");
        }
 
        for(i=0;i<n;i++)
        {
                *(a3+i)=0;
        }
 
        id=pfork(2);
 
        if(id==0)
        {
 
                for(i=0;i<n;i+=2)
                {
                        *(a3+i)=a1[i]+a2[i];
                }
 
                printf("parent doing sum\n");
                for(i=0;i<n;i+=2)
                {
                        printf("sum by parent %d\n",*(a3+i));
                }
                printf("\n");
        }
 
        else
        {
                if(id==1)
                {
 
                        for(i=1;i<n;i+=2)
                        {
 
                                *(a3+i)=a1[i]+a2[i];
                        }
                        printf("child doing sum\n");
                        for(i=1;i<n;i+=2)
                        {
                                printf("Sum by child %d\n",*(a3+i));
                        }
 
                        printf("\n");
                }
        }
 
 
        //printf("Calling process join for id %d\n",id);
        process_join(2,id);
 
        printf("The final sum array is : \n");
        for(i=0;i<n;i++)
        {
                printf(" %d ",*(a3+i));
 
        }
 
        printf("\n");
        printf("End Parent\n");
        return 1;
}
 
 
int pfork(int x)
{
        int j;
        for(j=1;j<=(x-1);j++)
        {
                if((fork())==0)
                        return j;
        }
 
        return 0;
}
 
void process_join(int x,int id)
{
        int j,val;
        if(id==0)
        {
                for(j=1;j<=(x-1);j++)
                {
                        printf("parent process id %d\n\n",getpid());
                        printf("Parent calling wait:blocked state\n");
 
                        val=wait(0);
                        printf("The child deleted is : %d\n",val);
                }
        }
        else
        {
                printf("child pid %d\n",getpid());
                exit(0);
        }
        printf("after exit %d\n",getpid());
 
 
}


Output:

[04mca8@LINTEL 04mca8]$ cc add3arr.c
[04mca8@LINTEL 04mca8]$ ./a.out
enter how many nos
5
enter number for 1st array:
1
enter number for 1st array:
3
enter number for 1st array:
5
enter number for 1st array:
7
enter number for 1st array:
9
enter number for 2nd array:
2
enter number for 2nd array:
4
enter number for 2nd array:
6
enter number for 2nd array:
8
enter number for 2nd array:
10
child doing sum
Sum by child 7
Sum by child 15
 
child pid 18249
parent doing sum
sum by parent 3
sum by parent 11
sum by parent 19
 
parent process id 18248
 
Parent calling wait:blocked state
The child deleted is : 18249
after exit 18248
The final sum array is :
 3  7  11  15  19
End Parent