CS452 Lab04 - Pipes - Sample 2

lab03_b.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#define READ 0
#define WRITE 1
#define MAX 1024

int main () {
    int fd[2];
    ssize_t num;
    pid_t pid;
    char str[MAX];

    if (pipe (fd) < 0) {
        perror ("plumbing problem");
        exit (1);
    }
    // point A

    if ((pid = fork ()) < 0) {
        perror ("fork failed");
        exit (1);
    }

    // point B
    else if (!pid) {
        dup2 (fd[WRITE], fileno(stdout));
        // point C 
        close (fd[READ]);
        close (fd[WRITE]);

        //point D
        fgets (str, MAX, stdin);
        write (fileno(stdout), (const void *) str, (size_t) strlen (str) + 1);
        exit (0);
    }

    dup2 (fd[READ], fileno(stdin));

    //point C 
    close (fd[READ]);
    close (fd[WRITE]);

    //point D 
    num = read (fileno(stdin), (void *) str, (size_t) sizeof (str));
    if (num > MAX) {
        perror ("pipe read error\n");
        exit (1);
    }
    printf ("By %d: %s", getpid(), str);
    return 0;
}