#include <stdlib.h>
#include <iostream>
#include <string>
#include <sstream>
#include <sys/types.h>

using namespace std;

int main ()
{

/*
 Pipes are similar to files, and establish uni-directional communication.  Each pipe has two file descriptors, one for read (0) and the other for write (1) operation.
 Here we create two pipes, to establish bidirectional communication. For uni-directional communication, only one pipe is sufficient.

To compile:

g++ unnamed-pipe.cpp -o unnamed-pipe
*/
       int     parent2child[2], child2parent[2];  
       pid_t   childpid;
 
       pipe(parent2child);
       pipe(child2parent);
        
       childpid = fork();
                 

       if(childpid == 0)
        {
                char    readbuffer[80];
		char str1[] = "Hello Parent! \n";
                /* Child process closes up the ones used by the parent */
                close(child2parent[0]);
                close(parent2child[1]);

                /* Send a string through the output side of pipe */
                write(child2parent[1], str1 , (strlen(str1)+1));
		cout << "Child sent " << str1 << endl;
               

	      /* Read in a string from the pipe */
                read(parent2child[0], readbuffer, sizeof(readbuffer));
                cout << "Child received "<< readbuffer << endl;;
 
       }
        else
        {
                char    readbuffer[80];
		stringstream ss;
		ss << "Hello child #" << childpid << "!";
		char* str2 = (char*) ss.str().c_str();
               /* Parent process closes up the ones used by the child */
                close(child2parent[1]);
                close(parent2child[0]);

                /* Read in a string from the pipe */
                read(child2parent[0], readbuffer, sizeof(readbuffer));
                cout << "Parent received "<< readbuffer << endl;;
            	

               /* Send a string through the output side of pipe */
 		write(parent2child[1], str2 , (strlen(str2)+1));
		cout << "Parent sent " << str2 << endl;
 
          }
  return 0;
}