/**
 * Example program demonstrating UNIX pipes.
 *
 * Figures 3.23 & 3.24
 *
 * @author Gagne, Galvin, Silberschatz
 * Operating System Concepts  - Eighth Edition
 * Copyright John Wiley & Sons - 2008.
 */

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <string.h>

#define BUFFER_SIZE 25
#define READ_END	0
#define WRITE_END	1

int main(void)
{
    char write_msg[BUFFER_SIZE] = "Greetings";
    char read_msg[BUFFER_SIZE];
    pid_t pid;
    int fd[2];

    /* create the pipe */
    if (pipe(fd) == -1) {
	fprintf(stderr,"Pipe failed");
	return 1;
    }

    /* now fork a child process */
    pid = fork();

    if (pid < 0) {
	fprintf(stderr, "Fork failed");
	return 1;
    }

    if (pid > 0) {  /* parent process */
	/* close the unused end of the pipe */
	close(fd[READ_END]);

	/* write to the pipe, including the terminating \0 */
	write(fd[WRITE_END], write_msg, strlen(write_msg) + 1); 

	/* close the write end of the pipe */
	close(fd[WRITE_END]);
    }
    else { /* child process */
	/* close the unused end of the pipe */
	close(fd[WRITE_END]);

	/* read from the pipe */
	read(fd[READ_END], read_msg, BUFFER_SIZE);
	printf("child read \"%s\"\n",read_msg);

	/* close the write end of the pipe */
	close(fd[READ_END]);
    }

    return 0;
}