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

#define MY_MACIG 'G'
#define READ_IOCTL _IOR(MY_MACIG, 0, int)
#define WRITE_IOCTL _IOW(MY_MACIG, 1, int)


int main(){
	char buf[200];
	int fd = -1;
	if ((fd = open("/dev/cdev_example", O_RDWR)) < 0) {
		perror("open");
		return -1;
	}
	if(ioctl(fd, WRITE_IOCTL, "hello world") < 0)
		perror("first ioctl");
	if(ioctl(fd, READ_IOCTL, buf) < 0)
		perror("second ioctl");

	printf("message: %s\n", buf);
	return 0;

}