On Mon, Nov 10, 2003 at 11:22:11AM -0800, Wolfgang  S. Rupprecht wrote:
  | 
  | > On a related note, a function similar to tzset(3) that took a
  | > timezone argument rather than requiring the $TZ environment to be
  | > modified would allow mktime(3) to be used.
  | 
  | I don't yet understand all that is going on, but
  | /usr/src/lib/libc/time/localtime.c:mktime() sure looks more
  | heavyweight than timegm() with extra locking and TZ string malloc-ing
  | and copying.  I'm not sure I really want to do that on a per
  | invocation basis when I convert a few thousand lines in a text file
  | that have a UTC timestamp up front.

Right, and that's what I used timegm() for.

In my case, I had a datestamp in the format that `date -u` returns.
I parse it with something like:

		char		*timestamp;
		struct tm	newtm;
		time_t		ntime;

		timestamp = get_timestamp_string();
			// timestamp is of the form:
			//	Tue Nov 11 01:24:38 UTC 2003
		if (strptime(timestamp, "%a %b %d %T UTC %Y", &newtm) == NULL)
			barf();
		if ((ntime = timegm(&newtm)) == -1)
			barf();
		printf("parsed `%s' as %ld `%.24s'\n",
		    timestamp, (long)ntime, asctime(&newtm));


Cheers,
Luke.