test.c

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>

const char stringToPrint[] = "Hello, world!\n";

int main() {
    int pipes[2];
    assert(pipe(pipes) != -1);

    pid_t pid = fork();
    if (pid == 0) {
        close(pipes[0]);
        assert(dup2(pipes[1], fileno(stdout)) != -1);
        assert(dup2(pipes[1], fileno(stderr)) != -1);

        write(fileno(stdout), stringToPrint, strlen(stringToPrint));
        _exit(0);
    }

    close(pipes[1]);

    while(1) {
        char buf[sizeof(stringToPrint) - 1];
        memset(buf, 0, sizeof(buf));
        ssize_t err = read(pipes[0], buf, sizeof(buf));

        if (err == -1) {
            fprintf(stderr, "could not read from pipe: %s", strerror(errno));
            return 1;
        }
        if (err > 0)
            puts(buf);
        else
            break;

        fflush(stdout);
    }

    int status;
    assert(waitpid(pid, &status, 0) != -1);
    printf("child exited: %d" , WEXITSTATUS(status));
    return 0;
}