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

int main(void) {
    FILE* fp = fopen("data.txt", "w");
    int fd = fileno(fp); // Retrieve file descriptor from FILE*
    fclose(stdout);
    dup2(fd, STDOUT_FILENO);
    printf("Hello!\n");
    fprintf(fp, "Hello_fprintf!\n");
    return 0;
}