#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
main()
{
pid_t A, B, C;
int fd[2];
int fd2[2];

if (pipe(fd) == -1)
{
    perror("pipe");
    exit(1);
}
B = fork();
if (B == -1)
{
    perror("fork");
    exit(2);
}
if (B == 0)
{
    if (pipe(fd2) == -1)
    {
        perror("pipe");
        exit(11);
    }
    C=fork();
    if(C == -1)
    {
        perror("fork 2");
        exit(22);
    }
    if (C == 0)
    {
        //i am C
        //do some stuff
    }
    else
    {
        //i am B
        //do some stuff
    }
}
else
{
    //i am A
    //do some stuff
}