CPU governor changer for Network UPS Tools

nut-governor.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

const char basepath[] = "/sys/devices/system/cpu/cpu%d/cpufreq/%s";

void update_governor(int cpu, char *gov) {
    FILE *fp;
    char path[64];
    sprintf(path, basepath, cpu, "scaling_governor");

    fp = fopen(path, "a");
    if (!fp) {
        return;
    }
    fwrite(gov, 1, 9, fp);
    fclose(fp);
}

int main(int argc, char *argv[]) {
    char *type;
    int cpus = sysconf(_SC_NPROCESSORS_CONF);

    if (!(type = getenv("NOTIFYTYPE"))) {
        return 1;
    }

    for (int i = 0; i < cpus; i++) {
        if (!strcmp(type, "ONLINE")) {
            update_governor(i, "schedutil");
        } else if (!strcmp(type, "ONBATT")) {
            update_governor(i, "powersave");
        } else {
            return 1;
        }
    }

    return 0;
}