{"id":55,"description":"C: Get system time in epoch seconds (number of seconds since 1970-01-01 00:00:00 +0000 (UTC))","tags":["c","programming","datetime"],"contents":["time_t curtime = time(NULL); // time() included from time.h","(void)time(\u0026curtime); // also sets the seconds in the input buffer if given","// can also get the time in microsecond granularity with gettimeofday","struct timeval tm;","struct timezone tz","(void)gettimeofday(\u0026tm, \u0026tz); // included from sys/time.h","// tm.tv_sec - epoch time in seconds","// tm.tv_usec - microseconds","// tz.tz_dsttime - is Daylight Savings on?","// tz.tz_minuteswest - number of minutes from the GMT","printf(\"secs=%lu, msecs=%d, is_dst=%d, minutes_from_gmt=%d\n\", tm.tv_sec, tm.tv_usec, tz.tz_dsttime, tz.tz_minuteswest);","printf(\"timestamp=%s\", ctime(\u0026tm.tv_sec)); // get clock time as a readable string","// ctime returns a pointer to statically allocated buffer holding the stamp.","// Subsequent calls to ctime() would overwrite the buffer. Use ctime_r() to write the string to user provided buffer instead."]}