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

int main(int argc, char **argv) {

    int pipe_ends [2];
    if (pipe(pipe_ends) == -1)
        perror("pipe"), exit(1);

    char msg [] = { "Hi\n" };

    if (write(pipe_ends[1], msg, sizeof msg - 1) == -1)
        perror("write");

    close(pipe_ends[1]);

    char pipe_buf[128];

    size_t n;
    while ((n = read(pipe_ends[0], pipe_buf, sizeof pipe_buf)) > 0)
        if (write(1, pipe_buf, n) != n)
            perror("write");
}