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

#include <signal.h>
#include <time.h>

struct timespec *start_time, *stop_time;
int done;

void handle_start() {

	if(clock_gettime(CLOCK_MONOTONIC, start_time) == -1) {

		printf("failed to get start time.\n");
		exit(1);
	}

	pause();
}

void handle_stop() {

	long int start_sec, stop_sec, delta;

	if(clock_gettime(CLOCK_MONOTONIC, stop_time) == -1) {

		printf("failed to get stop time.\n");
		exit(1);
	}

	start_sec = ((long int) start_time->tv_sec);
	stop_sec  = ((long int) stop_time->tv_sec);

	delta = stop_sec - start_sec;

	printf("%ld seconds elapsed between signals.\n", delta);

	done = 1;
}

int main(int argc, char *argv[]) {

	done = 0;

	start_time = (struct timespec *) calloc(1, sizeof(struct timespec));
	stop_time  = (struct timespec *) calloc(1, sizeof(struct timespec));

	if(signal(SIGTSTP, handle_start) == SIG_ERR ||
	   signal(SIGCONT, handle_stop)  == SIG_ERR) {

		printf("could not bind signal handlers\n");
		return 1;
	} 

	terminate_check:

	pause();

	if(!done)
		goto terminate_check;

	free(start_time);
	free(stop_time);

	return 0;
}