Thread: wierd results

How come this is not returning the desired outcome?

Code:

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

int main(int argc, char **argv) {
        time_t c_time, a_time;
        char buffer[256];
        struct tm a_time_struct;

        printf("Enter the time in which you want to wake up.\n");
        printf("In this format: (MM DD YYYY hh mm).\n");
        fgets(buffer, sizeof buffer, stdin);
        sscanf(buffer, "%i %i %i %i %i", &a_time_struct.tm_mon, &a_time_struct.tm_mday, &a_time_struct.tm_year
                                        ,&a_time_struct.tm_hour, &a_time_struct.tm_min);
        printf("%i = mon, %i = day, %i = year, %i = hour, %i = min.\n", a_time_struct.tm_mon, a_time_struct.tm_mday, a_time_struct.tm_year, a_time_struct.tm_hour, a_time_struct.tm_min);
/* . . . */
return 0;
}

Here is my test run.

Enter the time in which you want to wake up.
In this format: (MM DD YYYY hh mm).
03 09 2004 10 56
3 = mon, 0 = day, 9 = year, 2004 = hour, 10 = min.

Perhaps you would have better results with this?

Code:

sscanf(buffer, "%02d%02d%04d%02d%02d",
               &a_time_struct.tm_mon,
               &a_time_struct.tm_mday,
               &a_time_struct.tm_year,
               &a_time_struct.tm_hour,
               &a_time_struct.tm_min);

and apply the same solution as above to printing the output too.

figured it, when looking at your code, I saw you used %d, not %i. I told myself a long time ago from a problem like this never to use %i, but I fell back into. Thanx for the help.

>I told myself a long time ago from a problem like this never to use %i
With the printf family %d and %i are the same. This breeds confusion because the scanf family makes an important but subtle distinction between the two. For the scanf family, %d reads a signed decimal value equivalent to a strtol call with 10 as the base. %i on the other hand, reads a signed integer value equivalent to a strtol call with 0 as the base. In other words, %i reads hexadecimal and octal as well as decimal. %i is choking on 09, an invalid octal value, so it takes input to mean that the 0 and 9 are distinct values and reads them separately, resulting in your odd output.

So the thing to remember is not that you should avoid %i, but that you should recognize and understand the differences between similar flags in the scanf and printf families.

thanx for the distinction, I always used to just remembered to avoid %i.