set LEDS on your keyboard

main.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/input.h>
#include <sys/ioctl.h>

struct leds {
  const char *name;
  int value;
} ks[] = {
{ .name="LED_NUML",     .value=LED_NUML     },
{ .name="LED_CAPSL",    .value=LED_CAPSL    },
{ .name="LED_SCROLLL",  .value=LED_SCROLLL  },
{ .name="LED_COMPOSE",  .value=LED_COMPOSE  },
{ .name="LED_KANA",     .value=LED_KANA     },
{ .name="LED_SLEEP",    .value=LED_SLEEP    },
{ .name="LED_SUSPEND",  .value=LED_SUSPEND  },
{ .name="LED_MUTE",     .value=LED_MUTE     },
{ .name="LED_MISC",     .value=LED_MISC     },
{ .name="LED_MAIL",     .value=LED_MAIL     },
{ .name="LED_CHARGING", .value=LED_CHARGING },
{NULL, 0}
};

int get_led_value(const char *val) {
  if (strcmp(val, "true") == 0) {
    return 1;
  } else if (strcmp(val, "false") == 0) {
    return 0;
  }
  return -1;
}

int get_led_code(const char *led) {
  for (struct leds *k = ks; k->name; k+=1) {
    if (strcmp(k->name, led) == 0) {
      return k->value;
    }
  }
  return -1;
}

void usage(char **argv) {
    printf("USAGE: %s DEVICE LED true\n", argv[0]);
    printf("USAGE: %s DEVICE LED false\n", argv[0]);
    printf("supported LEDs are:\n");
    for (struct leds *k = ks; k->name; k+=1) {
      printf("0x%02X %s\n", k->value, k->name);
    }
}

int main(int argc, char **argv) {
  if (argc != 4) {
    usage(argv);
    return -1;
  }
  
  const char *dev = argv[1];
  const int val = get_led_value(argv[3]);
  const int lednum = get_led_code(argv[2]);
  
  if (val == -1) {
    usage(argv);
    return -1;
  }
  if (lednum == -1) {
    usage(argv);
    return -1;
  }
  
  int kb = open(dev, O_RDWR );
  if (kb < 0) {
    printf("unable to open device file");
    return -1;
  }
  //char kbname [256] = "key-x123";
  char LedStatus = 0;

//  ioctl (kb, EVIOCGBIT (EV_LED,sizeof (LedStatus)), &LedStatus);
//  printf("EVENT BITS: 0x%08X\n", LedStatus);

  ioctl (kb, EVIOCGLED (sizeof (LedStatus)), &LedStatus);
  printf("LED STATUS: 0x%08X\n", LedStatus);
  
  struct input_event event;
  event.type  = EV_LED;
  event.code  = lednum; 
  event.value = val;
  
  for (int x = 0; x < sizeof(event); x++) {
    printf("\\x%02x", ((unsigned char *)&event)[x]);
  }
  printf("\n");

  if (write(kb, &event, sizeof (struct input_event)) < 0) {
    printf("some error\n");
  }
  
  return 0;
}