[tz] Version in zoneinfo files?

[Guy Harris]

On Oct 27, 2015, at 8:19 AM, Bradley White <bww at acm.org> wrote:

> On Tue, Oct 27, 2015 at 7:40 AM, Guy Harris <guy at alum.mit.edu> wrote:
> 
>> On Oct 26, 2015, at 2:50 PM, Bradley White <bww at acm.org> wrote:
>> 
>>> On Sun, Oct 25, 2015 at 2:30 PM, Guy Harris <guy at alum.mit.edu> wrote:
>>> 
>>>> Is this just something to let people know whether they have an up-to-date version of the tzdb files or not?
>>> 
>>> Yes, although I think of it simply as let people know what version of a tzdb file they have.  (Whether that is the latest version is a separate question.)
>> 
>> Which version they have, or which version of the IANA tzdb the version they have is based on? :-)
> 
> The version of the data file that was passed to zic to produce the zoneinfo file in question.

"The version of the data file that was passed to zic to produce the zoneinfo file in question" presumably means, here, "The version string, which was passed as one of the arguments to zic", as the text files don't themselves include version numbers.

> (If someone downstream wants to modify data files and recompile them, then sub-versioning is up to them.)

And they can pass any version string they choose.

>>> Then you could tell, for example, where /etc/localtime came from.
>> 
>> Well, on my system, it came from a symlink() call:
>> 
>> $ ls -l /etc/localtime
>> lrwxr-xr-x  1 root  wheel  39 Oct 10 21:20 /etc/localtime -> /usr/share/zoneinfo/America/Los_Angeles
> 
> And on others it is a copy.  It seems preferable to have the data be self identifying rather than assuming anything about symlinks.

Presumably, then, by "where /etc/localtime came from" you meant "the tzdb name for the default time zone".