|
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <unistd.h>
- #include <stdbool.h>
-
- static char *argv0 = "./backlight";
- static char *backlight_file = "/sys/devices/platform/backlight/backlight/backlight/brightness";
- static char *max_backlight_file = "/sys/devices/platform/backlight/backlight/backlight/max_brightness";
-
- int max_brightness = 10;
-
- void print_usage()
- {
- printf("usage: %s COMMAND [VALUE]\n", argv0);
- printf(" COMMAND = {get, set}\n");
- printf(" get ... prints current raw backlight level\n");
- printf(" get_percent ... prints current percentage backlight level\n");
- printf(" set ... sets backlight level to raw VALUE_RAW\n");
- printf(" set_percent ... sets backlight level to percentage VALUE_PCT\n");
- printf(" VALUE_RAW = [0..%d]\n", max_brightness);
- printf(" VALUE_PCT = [0..100]\n");
- }
-
- void print_usage_and_fail()
- {
- print_usage();
- exit(EXIT_FAILURE);
- }
-
- void read_max_brightness()
- {
- FILE *fp = fopen(max_backlight_file, "r");
- if (fp == NULL) {
- fprintf(stderr, "Cannot open file '%s' for reading. Using the default max brightness '%d'.\n",
- max_backlight_file, max_brightness);
- return;
- }
- fscanf(fp, "%d", &max_brightness);
- fclose(fp);
- }
-
- void command_get(bool percent)
- {
- FILE *fp = fopen(backlight_file, "r");
- if (fp == NULL) {
- fprintf(stderr, "Cannot open file '%s' for reading.\n", backlight_file);
- exit(EXIT_FAILURE);
- }
- int buffer_length = 255;
- char buffer[buffer_length];
- fgets(buffer, buffer_length, fp);
- if (percent) {
- int value = atoi(buffer);
- printf("%d\n", value * 100 / max_brightness);
- } else {
- printf("%s", buffer);
- }
- fclose(fp);
- }
-
- void command_set(int value, bool percent)
- {
- if (setuid(0)) {
- fprintf(stderr, "Cannot set root permissions via setuid(0).\n");
- exit(EXIT_FAILURE);
- }
-
- FILE *fp = fopen(backlight_file, "w+");
- if (fp == NULL) {
- fprintf(stderr, "Cannot open file '%s' for writing.\n", backlight_file);
- exit(EXIT_FAILURE);
- }
- int raw = percent ? (value * max_brightness / 100) : value;
- fprintf(fp, "%d\n", raw);
- fclose(fp);
- }
-
- int main(int argc, char *argv[])
- {
- read_max_brightness();
- if (argc < 1) {
- print_usage_and_fail();
- }
- argv0 = argv[0];
- if (argc < 2) {
- print_usage_and_fail();
- }
- char *command = argv[1];
- if ((strcmp(command, "get") == 0) && (argc == 2)) {
- command_get(false);
- } else if ((strcmp(command, "get_percent") == 0) && (argc == 2)) {
- command_get(true);
- } else if ((strcmp(command, "set") == 0) && (argc == 3)) {
- int value = atoi(argv[2]);
- if (value < 0 || value > max_brightness) {
- print_usage_and_fail();
- }
- command_set(value, false);
- } else if ((strcmp(command, "set_percent") == 0) && (argc == 3)) {
- int value = atoi(argv[2]);
- if (value < 0 || value > 100) {
- print_usage_and_fail();
- }
- command_set(value, true);
- } else {
- print_usage_and_fail();
- }
- exit(EXIT_SUCCESS);
- }
|