#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#define bufsize 20

int fildes[2];
char buffer[bufsize];
void error(void)
{
 printf("unable to create a new process - job terminated \n");
 fflush(stdout);
}
void child(void)
{
 int pm, i;
 printf("child starts working.\n");
 close(fildes[1]);
 for (i = 0; i<5; i++)
 {
 printf("in child i = %d \n", i);
 pm = read(fildes[0],&buffer,20);
 printf ("child received %d chars from parent\n",pm);
 printf ("message received is: %s ",buffer);
 fflush(stdout);
 sleep(1);
 }
 exit(0);
}
void parent(void)
{
 int i, pm;
 printf("parent starts working.\n");
 close(fildes[0]);
 for (i = 0; i < 5 ; i++)
 {
 switch(i){
 case 0:
    pm = write(fildes[1], "first message \n", 20);
 printf("characters written by parent = %d \n", pm);
    fflush(stdout);
 break;
case 1:
    pm = write(fildes[1], "second message \n", 20);
    printf("characters written by parent = %d \n", pm);
    fflush(stdout);
 break;
 case 2:
    pm = write(fildes[1], "third message \n", 20);
    printf("characters written by parent = %d \n", pm);
    fflush(stdout);
 break;
case 3:
    pm = write(fildes[1], "fourth message \n", 20);
    printf("characters written by parent = %d \n", pm);
    fflush(stdout);
break;
case 4:
    pm = write(fildes[1], "fifth message \n", 20);
    printf("characters written by parent = %d \n", pm);
    fflush(stdout);
 }
 }
 wait(NULL);
 printf("parent terminating\n");
 exit(0);
}
int main(void)
{
 int pp, pid;

 pp = pipe (fildes);
 printf("pipe opened with pp = %d \n", pp);
 fflush(stdout);
 pid = fork();
 if (pid == 0)
 child();
 else if (pid == -1)
 error();
 else parent();
}