1 /* 2 用户层 3 4 ./a.out stat 5 */ 6 #include <sys/stat.h> 7 #include <fcntl.h> 8 #include <stdio.h> 9 #include <stdlib.h> 10 11 12 int main(int argc, char const *argv[]) 13 { 14 /* code */ 15 16 if(argc != 3) { 17 printf("Usage: ./a.out file<device file> <led status> "); 18 return -1; 19 } 20 21 int fd = open(argv[1], O_RDWR); 22 if(fd < 0 ) { 23 perror("open"); 24 goto err_open; 25 } 26 27 unsigned char led_status = atoi(argv[2]); 28 write(fd, &led_status, 1); 29 30 31 close(fd); 32 return 0; 33 34 err_open: 35 return -1; 36 }