#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <ctype.h>

int main(int argc, char **argv) {
    int fd1 = open(argv[1], O_RDONLY);
    int fd2 = open(argv[2], O_RDWR | O_CREAT, 0666);
    int flength = lseek(fd1, 0, SEEK_END);
    write(fd1, "\0", 1);
    lseek(fd1, 0, SEEK_SET);
    char *mapped_mem = (char *)mmap(NULL, flength, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd1, 0);
    char *p = mapped_mem;
    for (int i = 0; i <= flength; i++) {
        if (*p >= 'a' && *p <= 'z')
            *p = toupper(*p);
        p++;
    }
    p = mapped_mem + flength;
    for (int i = flength; i >= 0; i--) {
        write(fd2, p, 1);
        p--;
    }
    printf("%s\n", mapped_mem);
    munmap(mapped_mem, flength + 1);
    close(fd1);
    close(fd2);
    return 0;
}