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- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <unistd.h>
-
- static char *argv0 = "./cpu-sleep";
- static char *cpu_file_template = "/sys/devices/system/cpu/cpu%d/online";
- static int cpu_min = 1;
- static int cpu_max = 3;
-
- void print_usage()
- {
- printf("usage: %s COMMAND\n", argv0);
- printf(" COMMAND = {get, enable, disable}\n");
- printf(" get ... prints the current sleep state: 'enabled' or 'disabled'\n");
- printf(" enable ... enables sleep mode\n");
- printf(" disable ... disables sleep mode\n");
- }
-
- void print_usage_and_fail()
- {
- print_usage();
- exit(EXIT_FAILURE);
- }
-
- void command_get()
- {
- char filename[256];
- sprintf(filename, cpu_file_template, 1);
- FILE *fp = fopen(filename, "r");
- if (fp == NULL) {
- fprintf(stderr, "Cannot open file '%s' for reading.\n", filename);
- exit(EXIT_FAILURE);
- }
- int buffer_length = 8;
- char buffer[buffer_length];
- fgets(buffer, buffer_length, fp);
- fclose(fp);
-
- if (strcmp(buffer, "1\n") == 0) {
- printf("disabled\n");
- } else {
- printf("enabled\n");
- }
- }
-
- void command_set(int value)
- {
- if (setuid(0)) {
- fprintf(stderr, "Cannot set root permissions via setuid(0).\n");
- exit(EXIT_FAILURE);
- }
-
- for (int cpu = cpu_min; cpu <= cpu_max; cpu++) {
- char filename[256];
- sprintf(filename, cpu_file_template, cpu);
- FILE *fp = fopen(filename, "w+");
- if (fp == NULL) {
- fprintf(stderr, "Cannot open file '%s' for writing.\n", filename);
- 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 != 2) {
- print_usage_and_fail();
- }
- char *command = argv[1];
- if (strcmp(command, "get") == 0) {
- command_get();
- } else if (strcmp(command, "enable") == 0) {
- command_set(0);
- } else if (strcmp(command, "disable") == 0) {
- command_set(1);
- } else {
- print_usage_and_fail();
- }
- exit(EXIT_SUCCESS);
- }
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