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- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <unistd.h>
-
- static char *argv0 = "./led";
- static char *led_file_template = "/sys/class/leds/%s:%s/brightness";
-
- void print_usage()
- {
- printf("usage: %s COMMAND COLOR [VALUE]\n", argv0);
- printf(" COMMAND = {get, set}\n");
- printf(" get ... prints LED level\n");
- printf(" set ... sets LED level to VALUE\n");
- printf(" COLOR = {red, green, blue, flash}\n");
- printf(" red ... red:indicator LED\n");
- printf(" green ... green:indicator LED\n");
- printf(" blue ... blue:indicator LED\n");
- printf(" flash ... white:flash LED\n");
- printf(" VALUE = [0..255] ... light level\n");
- }
-
- void print_usage_and_fail()
- {
- print_usage();
- exit(EXIT_FAILURE);
- }
-
- void command_get(char *filepath)
- {
- FILE *fp = fopen(filepath, "r");
- if (fp == NULL) {
- fprintf(stderr, "Cannot open file '%s' for reading.\n", filepath);
- exit(EXIT_FAILURE);
- }
- int buffer_length = 255;
- char buffer[buffer_length];
- while (fgets(buffer, buffer_length, fp)) {
- printf("%s", buffer);
- }
- fclose(fp);
- }
-
- void command_set(char *filepath, int value)
- {
- if (setuid(0)) {
- fprintf(stderr, "Cannot set root permissions via setuid(0).\n");
- exit(EXIT_FAILURE);
- }
-
- FILE *fp = fopen(filepath, "w+");
- if (fp == NULL) {
- fprintf(stderr, "Cannot open file '%s' for writing.\n", filepath);
- exit(EXIT_FAILURE);
- }
- fprintf(fp, "%d\n", value);
- fclose(fp);
- }
-
- int main(int argc, char *argv[])
- {
- if (argc < 1) {
- print_usage_and_fail();
- }
- argv0 = argv[0];
- if (argc < 3) {
- print_usage_and_fail();
- }
- char *command = argv[1];
- char *led = argv[2];
- if (strcmp(led, "red") != 0
- && strcmp(led, "blue") != 0
- && strcmp(led, "green") != 0
- && strcmp(led, "flash")) {
- print_usage_and_fail();
- }
- char *type = "indicator";
- if (strcmp(led, "flash") == 0) {
- led = "white";
- type = "flash";
- }
- char filename[255];
- sprintf(filename, led_file_template, led, type);
- if ((strcmp(command, "get") == 0) && (argc == 3)) {
- command_get(filename);
- } else if ((strcmp(command, "set") == 0) && (argc == 4)) {
- int value = atoi(argv[3]);
- if (value < 0 || value > 255) {
- print_usage_and_fail();
- }
- command_set(filename, value);
- } else {
- print_usage_and_fail();
- }
- exit(EXIT_SUCCESS);
- }
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