http://stackoverflow.com/questions/19378734/how-to-make-chil

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

int  a;
pid_t pid;
int main(void)
{

a=10;
//declare and create 2 pipes
int p1[2], p2[2];
pipe(p1);
pipe(p2);
int ra;
 for(int i=0;i<3;i++)
 {
   pid = fork();
   if (pid==0)
   {
      close(p1[1]);
      close(p2[0]);
      if (read(p1[0],&ra,sizeof(int)) != sizeof(int))
       _exit(0);
      while(ra>0)
      {
        ra-=1;
        printf("%i a are available, reported by process %i\n",ra,getpid());
        write(p2[1],&ra,sizeof(int));
        sched_yield();
        if (read(p1[0],&ra,sizeof(int)) != sizeof(int))
         _exit(0);
      }
      close(p2[1]);
      close(p1[0]);
      _exit(0);
   }
 }

 if(pid>0)    //parent process outside for loop
 {
    close(p1[0]);
    close(p2[1]);
    while (a>0)
    {
        write(p1[1],&a,sizeof(int));
        read(p2[0],&a,sizeof(int));
    }
    close(p2[0]);
    close(p1[1]);

 }
}