RPI status led showing system load

statusled.c

#define _DEFAULT_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <sys/sysinfo.h>

#define LEDCTL "/sys/class/leds/led0/brightness"

float getload()
{
	static int ncpus = -1;
	if (ncpus < 0)
		ncpus = get_nprocs_conf();
	FILE *f = fopen("/proc/loadavg", "r");
	if (f == NULL)
		return -1;
	float r;
	fscanf(f, "%f", &r);
	fclose(f);
	return r / ncpus;
}

void ledctl(int ctl) {
	FILE *f = fopen(LEDCTL, "w");
	if (f == NULL)
		return;
	fputs(ctl ? "1" : "0", f);
	fclose(f);
}

void ledtoggle() {
	static int stat = 0;
	ledctl((stat = !stat));
}

void cleanup(int sig) {
	ledctl(0);
	exit(0);
}

int main() {
	signal(SIGINT, cleanup);
	signal(SIGTERM, cleanup);
	for (;;) {
		ledtoggle();
		float w = 1 - getload();
		usleep(100000);
		usleep(w * 1000000);
	};
	return 0;
}