[tz] Getting current tzdb version in use

Paul Eggert eggert at cs.ucla.edu
Thu Jul 19 14:51:28 UTC 2018

Martin Burnicki wrote:
> So the*implementation*  of this feature in the lib would also be easier
> if tzdb provided a standard way to get the version.

/usr/share/zoneinfo/tzdata.zi contains a "# version" line. Though this is 
reasonably recent in tzdb, and many distributions don't install that file, and 
it's not part of the stable API.

I have my doubts about the version info. Many distributions apply local changes 
to their tzdb data, and I expect that they're not updating the version line 
appropriately. So all you have is some sort of vague good-faith attempt at 
version info; it doesn't guarantee that you have a particular tzdb release. That 
is, the version info is not something that a portable program should rely on; 
all it's really good for is as a string that the program can report to the user 
so that the user can try to debug whatever goes wrong.

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