(bsd)tar is broken on 6.1
Patrick M. Hausen
hausen at punkt.de
Sat May 27 01:32:45 PDT 2006
On Fri, May 26, 2006 at 08:58:01PM +1000, Peter Jeremy wrote:
> On Fri, 2006-May-26 11:34:43 +0200, Patrick M. Hausen wrote:
> >> > -rw-r--r-- 1 jmz jmz 4312 Apr 16 1947 supclkrd.prg
> >Since there cannot be a date before January 1st 1970, 0:00 on
> >any Unix system, i guess there's something seriously broken here.
> Why do you say that? time_t is signed so it can represent a date
> prior to 1970. In theory, a file prepared on an earlier computer
> could have been transferred onto a Unix system whilst retaining
> its original modification time.
If I'm not mistaken, the signedness of time_t is merely historical.
time_t predates explicitely unsigned integer data types in C.
The historical definition seems to have been "long".
Dates before the Epoch are undefined.
I mean, which part of "seconds since the Epoch" implies time
values _before_ the Epoch?
You are not supposed to do calculations subtractions with time_t
but use difftime(), for example.
POSIX.1-1990. Section 184.108.40.206: seconds since the Epoch
"If the year < 1970 or the value [of seconds since the Epoch] is
negative, the relationship is undefined. If the year >= 1970 and the
value is non-negative, the value is related to a Coordinated Universal
Time name ..."
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