#include <fcntl.h>
#include <stdio.h>
#include <sys/mman.h>

char buf[4096];
int main(int argc, char* argv[])
{
  int fd;
  char *start;

  if (argc < 2) {
	printf("Usage: %s <filename>\n", argv[0]);
	exit(1);
  }
  fd = open(argv[1], O_RDWR | O_CREAT , 0644);
  if (fd < 0) {
	perror("open");
	exit(1);
  }
  if (write(fd, buf, 4096) < 0) {
	perror("write");
	exit(2);
  } 
  start = (char *)mmap64(0, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
  if (!start) {
	perror("mmap64");
	exit(2);
  }
  memset(start, 0, 4096);
  exit(0);	
}