#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;	}	while(1)	{	                read(keys4_fd,ret,1);		if (ret[0] != NOKEY)		{			printf("key = %c\n",ret[0]);					}		usleep(100000);	}		close(keys4_fd);	        return 0;}