timegm.c

   1 #include <sys/time.h>
   2 #include <unistd.h>
   3 #include <stdlib.h>
   4 #include <time.h>
   5 #include <stdio.h>
   6
   7  time_t timegm(struct tm *tm)
   8 {
   9         time_t t = mktime(tm);
  10         t -= mktime(gmtime(&t)) - (int)mktime(localtime(&t));
  11         return t;
  12 }
  13
  14 int get_time_zone(time_t t)
  15 {
  16         struct tm *tm = gmtime(&t);
  17         struct tm tm_utc;
  18         if (!tm)
  19                 return 0;
  20         tm_utc = *tm;
  21         tm = localtime(&t);
  22         if (!tm)
  23                 return 0;
  24         return mktime(&tm_utc) - mktime(tm);
  25 }
  26
  27 int main(void)
  28 {
  29         time_t t = time(NULL);
  30         struct tm *tm_local = localtime(&t);
  31         struct tm *tm_gmt   = gmtime(&t);
  32         int diff;
  33
  34         diff = timegm(tm_local) - (int)mktime(tm_local);
  35
  36         printf("gmt1=%d\n", t);
  37         printf("loc1=%d\n", t + 36000);
  38
  39         printf("loc2=%d\n", mktime(tm_local));
  40         printf("gmt2=%d\n", timegm(tm_local));
  41
  42         printf("diff=%d\n", diff);
  43
  44         printf("tz=%d\n", get_time_zone(t));
  45         return 0;
  46 }