Shutdown the Raspbian when GPIO24 is continuously HIGH for 5 seconds

crontab

@reboot /usr/local/bin/powerloss_watch &

gpio_shutdown.c

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <wiringPi.h>

#define PIN_POWERLOSS_IN (5)    // BCM GPIO24 (Header Pin 18)
#define READ_INTERVAL (100)     // msec
#define COUNT_TO_SHUTDOWN (50) // x {READ_INTERVAL}msec

void signal_handler(int signum);

void init()
{
	setenv("WIRINGPI_GPIOMEM", "1", 1);

	if(-1 == wiringPiSetup())
	{
		fprintf(stderr, "wiringPiSetup() failed\n");
		exit(1);
	}

	pinMode(PIN_POWERLOSS_IN, INPUT);
	pullUpDnControl(PIN_POWERLOSS_IN, PUD_DOWN);
}

void set_signal_handler(int signum)
{
	if(SIG_ERR == signal(signum, signal_handler))
	{
		fprintf(stderr, "set_signal_handler failed\n");
		exit(1);
	}
}

void signal_handler(int signum)
{
	fprintf(stderr, "signal_handler: got signal %d\n", signum);
	exit(1);
}

void run()
{
	int on_count = 0;
	int prev_in = 0;
	int current_in = 0;
	int prev_read_value = 0;

	while(1)
	{
		int read_value = digitalRead(PIN_POWERLOSS_IN);

		if(prev_read_value == read_value)
		{
			current_in = read_value;
		}		

		if(prev_in != current_in)
		{
			fprintf(stderr, "state changed %d to %d\n", prev_in, current_in);
		}

		if(1 == current_in)
		{
			on_count++;
			if(on_count >= COUNT_TO_SHUTDOWN)
			{
				break;
			}
		}
		else
		{
			on_count = 0;
		}
			
		prev_in = current_in;
		prev_read_value = read_value;
		delay(READ_INTERVAL);
	}
}

int main()
{
	set_signal_handler(SIGINT);
	set_signal_handler(SIGTERM);

	init();
	run();

	return 0;
}

Makefile

gpio_shutdown: gpio_shutdown.o
	cc -o $@ $^ -lwiringPi

.c.o:
	cc -c $<

clean:
	@rm gpio_shutdown
	@rm gpio_shutdown.o

powerloss_watch

#!/bin/sh
/usr/local/bin/gpio_shutdown
/sbin/shutdown -h now