/*
 * progrsm to demonstrate how to get time
 * get time first, wait 10 seconds, then get time, compare to first
 * demonstrates how the *time() functions use static storage and
 * return pointers
 *
 * Matt Bishop, ECS 36A, Fall Quarter 2019
 */
#include <stdio.h>
#include <unistd.h>
#include <time.h>

/*
 * print the given time structure
 */
void prboard(struct tm *tock)
{
        printf("In detail . . .\n");
        printf("\tYear: %d\n", tock->tm_year + 1900);
        printf("\tMonth: %d\n", tock->tm_mon + 1);
        printf("\tDay: %d\n", tock->tm_mday);
        printf("\tDay of week: %d\n", tock->tm_wday);
        printf("\tDay of year: %d\n", tock->tm_yday);
        printf("\tHour: %d\n", tock->tm_hour);
        printf("\tMinute: %d\n", tock->tm_min);
        printf("\tSecond: %d\n", tock->tm_sec);
	printf("\t%s daylight savings time\n", tock->tm_isdst ? "On" : "Off");
	printf("---------------------------\n");
}

/*
 * get the current time, then print it
 */
time_t getime(void)
{
	time_t tick;	/* current time since the epoch */

	/*
	 * get the current time
	 */
        if ((tick = time(NULL)) == -1){
                perror("time");
                return(1);
        }

	/*
	 * now print it; note it has a trailing newline
	 */
        printf("%s", ctime(&tick));

	/* return the time */
	return(tick);
}

/*
 * the main routine
 */
int main(int argc, char *argv[])
{
	struct tm *tod1;	/* current time as structure */
	struct tm *tod2;	/* time 10 seconds later  as structure */
	time_t tick, newtick;

	/*
	 * get program start time
	 */
	printf("The initial time ...\n");
	if ((tick = getime()) == -1)
		return(1);
	tod1 = localtime(&tick);
	prboard(tod1);

	/*
	 * make sure you get a different time
	 */
	printf("Now a 10-second pause ...\n");
	(void) sleep(10);

	/*
	 * noiw get the later time
	 */
	printf("Now the new time ...\n");
	if ((newtick = getime()) == -1)
		return(1);
	tod2 = localtime(&newtick);
	prboard(tod2);

	/*
	 * now compare the new time with the old one
	 * they should be different but are not!
	 */
	printf("Now we check the original time\n");
	prboard(tod1);
	printf("Here's why:\n");
	printf(" * pointer to original time: %p\n", (void *) tod1);
	printf(" * pointer to new time:      %p\n", (void *) tod2);

	/*
	 * bye!
	 */
	return(0);
}