Listing 1. Sample EVIOCGVERSION Function

/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or 
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */


#include <stdlib.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <asm/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/input.h>


int main (int argc, char **argv) {

  int fd = -1;
  int version;

  /* ioctl() requires a file descriptor, so we check we got one, and then open it */
  if (argc != 2) {
    fprintf(stderr, "usage: %s event-device - probably /dev/input/event0\n", argv[0]);
    exit(1);
  }
  if ((fd = open(argv[1], O_RDONLY)) < 0) {
    perror("evdev open");
    exit(1);
  }

  /* ioctl() accesses the underlying driver */
  if (ioctl(fd, EVIOCGVERSION, &version)) {
      perror("evdev ioctl");
  }

  /* the EVIOCGVERSION ioctl() returns an int */
  /* so we unpack it and display it */
  printf("evdev driver version is %d.%d.%d\n",
	 version >> 16, (version >> 8) & 0xff, version & 0xff);

  close(fd);

  exit(0);
}