Shell Programming and Scripting

/*
** DIFFDATE     F.P.Murphy Feb 26th, 2008
**
** USAGE: diffdate [-d] -f dateformat startdate finishdate
**
**        -d turn on debugging
**        -f format strings per strptime(2) to match inputted start and finish dates
**
** OUTPUT:  Prints difference between startdate and finishdate as HH:MM:SS
**          Handles up to 99 hrs difference as currently written
**
** EXAMPLE: diffdate -f "%a, %b %d, %Y %T %p" "Tue, Feb 19, 2008 08:00:02 PM" "Wed, Feb 20, 2008 02:19:09 AM"
*/

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


int
main(int argc, char* argv[])
{
   struct tm tm1, tm2;

   char buf[50];
   char format[50];
   char startdate[80];
   char finishdate[80];

   time_t t1, t2;
   long diff;
   int secs;
   int mins;
   int hours;

   int c;
   extern char *optarg;
   extern int optind, optopt;
   int debug = 0;
   int errflg = 0;

   while ((c = getopt(argc, argv, "df:h")) != -1) {
        switch(c) {
        case 'd':
            debug = 1;
            break;
        case 'f':
            strcpy(format, optarg);
            break;
        case 'h':
            errflg++;
            break;
        case '?':
            fprintf(stderr, "Unknown option: -%c\n", optopt);
            errflg++;
        }
   }
   if (errflg || (argc - optind != 2)) {
       fprintf(stderr, "Usage: diffdate [-d] -f format startdate finishdate\n");
       exit(2);
   }

   strcpy(startdate, argv[optind]);
   optind++;
   strcpy(finishdate, argv[optind]);

   if (debug) {
       fprintf(stderr, "Format: %s\n", format);
       fprintf(stderr, "Start Date: %s\n", startdate);
       fprintf(stderr, "Finish Date: %s\n", finishdate);
   }

   if (!strptime(startdate, format, &tm1)) {
       fprintf(stderr, "strptime() error\n");
       exit(1);
   }
   strftime(buf, 50, "%a %Y %H:%M:%S", &tm1);

   if (!strptime(finishdate, format, &tm2)) {
      fprintf(stderr, "strptime() error\n");
      exit(1);
   }
   strftime(buf, 50, "%a %Y %H:%M:%S", &tm2);

   if (((t1 = mktime(&tm1)) == -1) || ((t2 = mktime(&tm2)) == -1)) {
      fprintf(stderr, "mktime() error\n");
      exit(1);
   }

   diff = t2 - t1;
   if (diff < 0)
      diff = t1 - t2;

   if (debug) {
      printf("Start Date: seconds since Epoch:  %ld\n", (long) t1);
      printf("Finish Date: seconds since Epoch:  %ld\n", (long) t2);
      printf("Difference in seconds: %ld\n", (long) diff);
   }

   secs  = diff % 60;
   mins  = diff % (60 * 60) / 60;
   hours = diff / (60 * 60);

   printf("%02d:%02d:%02d\n", hours, mins, secs);
}

$./diffdate -f "%a, %b %d, %Y %T %p" "Tue, Feb 19, 2008 08:00:02 PM" "Wed, Feb 20, 2008 02:19:09 AM"
06:19:07
$