/* Includes */
#include <unistd.h>     /* Symbolic Constants */
//#include <sys/types.h>  /* Primitive System Data Types */
//#include <errno.h>      /* Errors */
#include <stdio.h>      /* Input/Output */
//#include <sys/wait.h>   /* Wait for Process Termination */
#include <stdlib.h>     /* General Utilities */
#define MAXLINE 80

int main() {
    int n;
    int fd[2];
    pid_t pid;
    char line[MAXLINE];
    
    if ( pipe( fd ) < 0 ) {
        perror("pipe fail");
        exit(1);
    }
    
    if ( (pid = fork()) < 0 ) {
        perror("fork");
        exit(1);
    }
        
    if ( pid > 0 ) {
        close( fd[0] );
        write( fd[1], "hello world\n", 12);
        wait(NULL);
    } else {
        close( fd[1] );
        n = read(fd[0], line, MAXLINE);
        
        printf("I am the child process\n");
        write( STDOUT_FILENO, line, n );
    }
    
    return 0;
}