#include <fcntl.h>
#include <unistd.h>
#include <assert.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <string.h>

#define BLOCK_SIZE 1

int main(int argc, char *argv[])
{
    int fin,
        fout;
    char buf[BLOCK_SIZE];
    struct stat st;

    assert( argc == 3 );

    fin = open(argv[1],O_RDONLY);
    assert( fin >= 0 );

    fstat(fin, &st);

    char *src = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fin, 0);
    assert(src != MAP_FAILED);

    fout = open(argv[2],O_CREAT|O_RDWR|O_TRUNC,0600);
    assert( fout >= 0 );

    ftruncate(fout, st.st_size);

    char *dst = mmap(NULL, st.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fout, 0);
    assert(dst != MAP_FAILED);

    memcpy(dst, src, st.st_size);

    munmap(src, st.st_size);
    munmap(dst, st.st_size);

    close(fin);
    close(fout);

    return 0;

}