Testing if fsync(dup(1)) flushes stdout!

testflush.c

/* testflush.c
 * Expected Output:
 *    Goodbye World!Hello World!
 *
 * Testing for Output:
 *    Hello World!Goodbye World!
 * 
 * Actual Output:
 *    Goodbye World!Hello World!
 */

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

int fsync(int fd);

void xwrite(int fd, const char *buf)
{
        if(write(fd, buf, strlen(buf)) < 0) {
                perror(buf);
                exit(errno);
        }
}


int main()
{
        int fd;

        fd = dup(1);
        if(fd < 0) {
                perror("Failed to duplicate stdout");
                return errno;
        }

        xwrite(1, "Goodbye, World!");
        xwrite(fd, "Hello, World!");

        fsync(fd);
        fsync(1);

        close(fd);

        xwrite(1, "\n");
        return 0;
}