afork_pipe.c

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

int ChildProcess(void);
int ParentProcess(void);
int pid;
int i,len;
int parent_pid;
int child_pid;
int the_pid;
int pipe_read=0,pipe_write=1;
int p_parent[2],p_child[2];
int main(void){
    pipe(p_parent);
    pipe(p_child);
    parent_pid=getpid();
    child_pid=fork(); /*Returns child_pid to parent*/
    if (getpid()==parent_pid) {
        ParentProcess();
    } else {
        ChildProcess();
    }
    return 0;
}

int ChildProcess(void)
{
    char parent_said[5];
    close(p_child[pipe_read]);
    close(p_parent[pipe_write]);
    while (i<2) {
        len=read(p_parent[pipe_read], parent_said, 1024);
        printf("    parent just wrote %s\n",parent_said);
        printf ("The child with pid %d is doing some work and the present value of i=%d\n", getpid(),i);
        i++;
        if (i==2) {
            write(p_child[pipe_write], "done", 5);
            sleep(3);
            break;
        }
        write(p_child[pipe_write], "next", 5);

        sleep(3);
    }
    return 0;
}

int ParentProcess(void){
    char child_said[5];
    close(p_child[pipe_write]);
    close(p_parent[pipe_read]);
    while (i<2) {
        printf ("The parent with pid %d is doing some work and the present value of i=%d\n", getpid(),i);
        write(p_parent[pipe_write],"next", 5);
        i++;
        sleep(1);
        len=read(p_child[pipe_read], child_said, 1024);
        printf("   the child just wrote %s\n",child_said);
    }
    len=read(p_child[pipe_read], &child_said, 1024);
    printf("just heard from child, it is %s.\n",child_said);
    return 0;
}

Note: There is an assumption that after the fork the parent is before the child in the queue.