Printing System time and 30 minute alarm

I am trying to figure out how to get C to set an alarm for 30 minutes ahead of whatever the displayed time is. I got the rough draft of displaying the system time (although it does prompt me to input a new system time which im not too fond of) but unsure of what my options are when it comes to the 30 minute alarm timer.

Here is the system time code

Code:

---


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

int main(void)
{
string thirty;
time_t now;
time(&now);
alarm(&thirty)= time + 30;
printf("%s", ctime(&now));
printf("%s", alarm(&thirty));

return EXIT_SUCCESS;
}

---

Does that even compile ?

It does not compile. It did until I tried to put the thirty statement in there and then kind of got stuck.

Ok, well now stores the time in seconds. So then calculate how many seconds in 30 minutes.

Then :

Code:

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while(time(NULL)  - null < secondsin30mins)
{
    //  Countdown to 30 minutes
}
//  Sound alarm.

---

You may want to check this out.

okay so the while statement starts the countdown? how would i get the program to display that the timer was set when the program was run and will go off at time 11:00pm (if program is run at 10:30)

Kevin

The while loop doesn't so much start the countdown as it just counts the seconds that go by. To show what time it started and what time it will finish you would have to use other commands. Look at the link I provided.

thanks for the link although I think it might be written a little over my head..

Work at it. Once you understand it, your program will be a cinch.

Lookup localtime() and mktime()

It also doesnt seem to really matter what other code I program into it because all my program ends up doing is compiling and then when it is run it tells you the current time and allows input for a new time and then stops running regardless of everything else i have. Even tested it with printf("SAY SOMETHING"); code to no avail.


Kev

Then it's time for you to show us some code. And check to see if this is the problem.

here is the code

Code:

---


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

int main( void )
{
    time_t t1;                               
    struct tm *tptr;
    clock_t ticks;                           
    char *s;

    if ( ( t1 = time(( time_t * ) 0 )) != ( time_t )-1 )
        {
        s = ctime( &t1 );
        printf( "Current time is %s", s );
        tptr = localtime( &t1 );
        printf( "You have an appointment in 30 minutes at time %d:%d:%d.\n",             
                                      tptr->tm_hour,
                                      tptr->tm_min+30,
                                      tptr->tm_sec );
      }
    else
        printf( "Error with the time() function\n" );

                                                         
   
    return 0;
}

---

Now it compiles just fine but running the program it only displays the current time and than asks the user for the new time. And these words aren't coming from my program. No matter what I have printf say it still says

The current time is 21:21:06
Enter new time:
<USER INPUT>
and then ends the program.

You've called your program "time.exe"
Which is the same name as an existing command on your system (which is the one you're getting).

Try perhaps (from the directory where your .exe exists)
./time.exe

This should run your version rather than the system version.

thanks now it works and im trying to figure how to carry over 30 minutes to the next hour
for example 18:45 30 minutes later it says 18:75 and i want it to read 19:15.

if statement? not sure where to start.


kevin

The mktime() function sorts out all the rounding necessary following things like
tptr->tm_min += 30;

well this is what i got and the code compiles but and gives me the current time and then gives me an error and boots out.

Code:

---

{
    time_t t1;                               
    struct tm *tptr;
    clock_t ticks;                           
    char *s;
    struct tm *ntptr;

    if ( ( t1 = time(( time_t * ) 0 )) != ( time_t )-1 )
        {
        s = ctime( &t1 );
        printf( "Current time is %s", s );
        tptr = localtime( &t1 );
        ntptr->tm_min = mktime(tptr->tm_min += 30);
        printf( "You have an appointment in 30 minutes at time %d:%d:%d.\n",             
                                      ntptr->tm_hour,
                                      ntptr->tm_min,         
                                      ntptr->tm_sec );
     
      }
    else
        printf( "Error with the time() function\n" );

                                                         
   
    return 0;
}

---

Erm, try reading the manual page?

time_t
mktime(struct tm *tm);

Code:

---

time_t now = time(NULL);
struct tm tnow = localtime( &now );
tnow.tm_min += 30;
time_t later = mktime( &tnow );

---