1 #include <sys/types.h>
 2 #include <sys/stat.h>
 3 #include <fcntl.h>
 4 #include <stdio.h>
 5 
 6 /* led_test on
 7  * led_test off
 8  */
 9 int main(int argc, char **argv)
10 {
11     int fd;
12     int val = 1;
13     fd = open("/dev/led", O_RDWR);
14     if (fd < 0)
15     {
16         printf("can't open!\n");
17     }
18     if (argc != 2)
19     {
20         printf("Usage :\n");
21         printf("%s <on|off>\n", argv[0]);
22         return 0;
23     }
24 
25     if (strcmp(argv[1], "on") == 0)
26     {
27         val  = 1;
28     }
29     else
30     {
31         val = 0;
32     }
33     
34     write(fd, &val, 4);
35     return 0;
36 }