/* test to see how mmap works on kernel level */
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#ifndef O_LARGEFILE
 /* don't use it if the kernel can't use it */
 #define O_LARGEFILE 0
#endif
int main(int argc, char **argv) {
 void *start = 0;
 size_t length = 1024;
 int flags = MAP_SHARED;
 int fd = 0;
 off_t offset = 0;
 struct stat statbuffer;
 fd = open("mmaptest.c", O_RDONLY | O_LARGEFILE, 0);
 fprintf(stderr, "File descriptor obtained: 0x%x\n", fd);
 if (fstat(fd, &statbuffer) < 0) {
  fprintf(stderr, "cannot stat: %s\n", strerror(errno));
  _exit(1);
 }
 length = (size_t)(statbuffer.st_size);
 fprintf(stderr, "Before calling mmap, start = 0x%x\n", (int)start);
 start = mmap(start, length, statbuffer.st_mode & 7, flags, fd, offset);
 fprintf(stderr, "After calling mmap, start = 0x%x\n", (int)start);
 return 0;
}