Solution for Exercise 21-8

ex2108

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

int main()
{
    time_t tictoc;
    struct tm *today;

    time(&tictoc);
    today = localtime(&tictoc);
    printf("It's now ");
    if( today->tm_hour > 12 )
        printf("%d:",today->tm_hour-12);
    else
        printf("%d:",today->tm_hour);
    printf("%02d:%02d ",
            today->tm_min,
            today->tm_sec
          );
    printf("%s\n",
            today->tm_hour > 11 ?
            "P.M." : "A.M."
          );
    return(0);
}

Output

It's now 5:01:03 PM

Notes

* To make the output work without creating a new variable, I split the printf() statement into several chunks:

Line 11 handles the initial string output, It's now

Lines 12 through 15 use an if-else decision to output AM and PM hours. Line 13 subtracts 12 from the tm_hour value when tm_hour is greater than 12.

Line 16 outputs the minute and second values, same as for Exercise 21-7.

The printf() statement split between Lines 20 and 23 uses sorcery to output the A.M. and P.M. strings. A ternary operator tests whether tm_hour is greater than 11. If so, string "P.M." is returned, otherwise "A.M." This string is output by the printf() statement.

* Click here to see my solution from this book's previous edition.

Exercise ex2109 →