#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#define NOKEY 0int main(){	int key7_fd;	        char ret[2];               key7_fd = open("/dev/key7", O_RDONLY);	if(key7_fd<0)	{                printf("open key7 device error!\n");		return 0;	}        else{              printf("key7 is opened!");           }	while(1)	{	                read(key7_fd,ret,1);		if (ret[0] != NOKEY)		{			printf("key = %c\n",ret[0]);					}		usleep(100000);	}		close(key7_fd);	        return 0;}