waiter.c

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#include <sys/time.h>
#include <assert.h>

int
main(int argc, char *argv[])
{
	int i;
	struct timeval now;
	struct timeval alarm;
	struct timeval to;
	assert(argc == 2);
	i = atoi(argv[1]);
	gettimeofday(&now, NULL);
	alarm.tv_sec = now.tv_sec + i + (now.tv_sec % i);
	alarm.tv_usec = 0;
	to.tv_sec = alarm.tv_sec - now.tv_sec;
	to.tv_usec = alarm.tv_usec - now.tv_usec;
	if (to.tv_usec < 0) {
		to.tv_usec += 1000000;
		to.tv_sec -= 1;
	}
	select(1, NULL, NULL, NULL, &to);
	return 0;
}