Human readable display of hours:minutes

I have a C program that logs the duration of a process (substituted with sleep for illustrative purposes):

// Compilation: gcc time.c -lm -Wall -o time
// Execution: ./time
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <math.h>
#include <unistd.h>

int main (void) {
  time_t begin = time(NULL);
  sleep(4);
  time_t end = time(NULL);

  char buffer_hours[3];
  int hours = floor((end-begin) / 3600);
  sprintf(buffer_hours, "%d", hours);
  if (hours < 10) strcat(buffer_hours, "0");

  char buffer_minutes[3];
  int minutes = round(hours / 60);
  sprintf(buffer_minutes, "%d", minutes);
  if (minutes < 10) strcat(buffer_minutes, "0");

  printf("Time elapsed: %ld seconds (%s:%s hh:mm).\n\a", (end - begin), buffer_hours, buffer_minutes);

  return 0;
}

The purpose is to show time in seconds as well as hours and minutes, but with a zero prefixed for when either is less than 10. This seems like an inefficient way of doing it, as 4 new variables are introduced as well as 4 lines of string handling. Can someone suggest a refactored way of how this could be done?

Hi @technossomy,

you can use printf's format capacity, see man 3 printf. Here is a simple version that also prints the other time intervals:

#include <stdio.h> // printf()
#include <stdlib.h> // atoi()
#include <time.h> // time()
#include <unistd.h> // sleep()

int main(int argc, char **argv) {
    time_t beg = time(NULL);
    sleep(atoi(argv[1]));
    time_t end = time(NULL);

    int secs = end - beg;
    printf("Time elapsed: %d seconds (%d-%02d:%02d:%02d d-hh:mm:ss).\n", \
           secs, secs/86400, secs/3600%24, secs/60%60, secs%60);

    return 0;
}

For testing different time intervals, comment out the sleep call and replace int secs ... by int secs = atoi(argv[1]);. Start the prog via ./time seconds.

see the below .... , with or without minute/hour variables, no intermediate strings, and minimum 2 digit precision on number of ... seconds/minutes/hours.
you can pass a sleep delay on the command line ... if none supplied it'll waste 5 seconds of your valuable time

#include <stdlib.h>
#include <stdio.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <math.h>
#include <unistd.h>

int main (int argc, char **argv )
{
        int secs=5;

        secs = (argc == 2) ? atoi(argv[1]) : 5;
        time_t begin = time(NULL);
        printf(" sleeping for %d seconds \n", secs );
        sleep(secs);
        time_t end = time(NULL);

        printf( " without any additional variables \n" );
        printf("Time elapsed: %.2ld seconds (%.2ld:%.2ld hh:mm).\n\a", (end - begin), (long)floor((end-begin) / 3600), (long)( floor((end-begin) / 3600) / 60 ) );


        int hours = floor((end-begin) / 3600);
        int minutes = round(hours / 60);
        printf( "\nwith minute and hour variables \n" );
        printf("Time elapsed: %.2ld seconds (%.2d:%.2d hh:mm).\n\a", (end - begin), hours, minutes);

        return 0;
}

use of "%.2ld" or "%.2d" - guarantees at least 2 digits

@technossomy,

fyi -
you can do away with the sleep (and save yourself some time ... just add the #seconds passed in to the end variable.

time_t end = time(NULL) + atoi(argv[1]);

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