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

int
main(void)
{
    FILE *fp;
    off_t p, q;
    char c;

    long long size = 5000000000LL;
    int fd = open("junk", O_RDWR|O_CREAT, S_IREAD|S_IWRITE);
    lseek(fd, size, SEEK_SET);
    write(fd, "x", 1);
    close(fd);

    fp = fopen("junk", "r");

    p = fseeko(fp, size, SEEK_SET);
    fprintf(stderr, "%c ", fgetc(fp));
    q = ftello(fp);

    fprintf(stderr,"%llx %llx %llx\n",size,p, q);
}