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

#include <sys/ioctl.h>

#define BLKGETLASTSECT  _IO(0x12,108) /* get last sector of block device */
#define BLKSETLASTSECT  _IO(0x12,109) /* get last sector of block device */
#define BLKSSZGET  _IO(0x12,104)/* get block device sector size */

struct blkdev_ioctl_param {
	unsigned int block;
	size_t content_length;
	char * block_contents;
};

main(int argc, char *argv[])
{
  int filedes, rc=0, blksz=0;
  char *lastblock, newchar = 'a';
  struct blkdev_ioctl_param ioctl_param;
  
  if( argc > 1 ) newchar = argv[1][0];

  ioctl_param.block = 0;

  filedes = open("/dev/sdb", O_RDONLY );
  printf("  open filedes: %d\n", filedes);

  rc = ioctl(filedes, BLKSSZGET, &blksz) ;
  lastblock = (char *) malloc( blksz + 2 );
  ioctl_param.content_length = blksz ;
  printf("  block size appears to be %d\n", blksz );

  memset( lastblock, newchar, blksz + 2 );
  ioctl_param.block_contents = lastblock;

  rc = ioctl(filedes, BLKSETLASTSECT, &ioctl_param) ;
  printf("  last sect ioctl rc: %d\n", rc);

  return 0;
}