C言語でlinuxの下でマウスポインタの相対位置を取得する

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


int main(int argc,char **argv)
{
	int fd, retval;
	char buf[6];
	fd_set readfds;
	struct timeval tv;
	//       
	fd = open( "/dev/input/mice", O_RDONLY );
	//         
	if(fd<0) {
		printf("Failed to open \"/dev/input/mice\".
");
		exit(1);
	} else {
		printf("open \"/dev/input/mice\" successfuly.
");
	}

	while(1) {
		//         
		tv.tv_sec = 5;
		tv.tv_usec = 0;

		FD_ZERO( &readfds );
		FD_SET( fd, &readfds );

		retval = select( fd+1, &readfds, NULL, NULL, &tv );
		if(retval==0) {
			printf( "Time out!
" );
		}
		if(FD_ISSET(fd,&readfds)) {
			//           
			if(read(fd, buf, 6) <= 0) {
				continue;
			}
			//                
			printf("Button type = %d, X = %d, Y = %d, Z = %d
", (buf[0] & 0x07), buf[1], buf[2],   buf[3]);
		}
	}
	close(fd);
	return 0;
}