[tz] Getting current tzdb version in use

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Fri Jul 20 21:18:07 UTC 2018

On 2018-07-20 12:35, Paul Eggert wrote:
> Robert Elz wrote:
>> test for what you need to know - exactly - never simply
>> assume that if X is detected, then (an unrelated) Y will also exist
> This is good advice. It's a primary design philosophy of Autoconf: test for what
> you need, not for version numbers. Although you can't always do it, it's better
> to do it when you can.

Expecting distributors to change their packaging scripts, except when you make a
change which breaks the process, won't happen: some distros package only the
.tab files and the zic binaries, some include the changelog, Debian etc. still
include leap-seconds.list, others include leapseconds, some include tzdata.zi,
some include various selections of uppercase named and .html docs, none include

Only zic knows what build selections are made, and assuming that has not been
customized, it could generate say a VERSION file on mass rebuilds.

Of course that does not handle when distros revert name or abbreviation changes
to maintain consistent backwards compatibility, or cherry pick zones to package
in their own manner; and each DB vendor has their own unique approaches.

If their customers cared enough, they'd complain more, and be unsatisfied with
workarounds of picking some other zone with the desired offset - oh - and don't
forget to change back in a few months: missing the whole point of the project!

Perhaps we need a bug reporting campaign to distros, to complain about lack of
project docs, other distributed files, and detailed build version info.

>> saving a few bytes of
>> download time in an environment when half the world are streaming
>> movies (or porn) and the rest are trying to download kde or openoffice
>> just isn't an objective that matters.
> Admittedly it's not a big deal, but if we're upgrading tzdata in 5 billion
> mobile devices ten times per year and saving 50 kB per upgrade, that's 250 TB of
> mobile data and Internet traffic saved worldwide per year. Although this is only
> a tiny fraction of total use (Cisco predicts 200 EB for such traffic in 2018),
> even a 1 part-per-million decrease would be a (tiny) win.
> It'd be like Hogan's Heroes vs the German army; you get only small victories,
> but you do what you can and every bit helps.
> My source for traffic estimates is the last page of:
> https://www.cisco.com/c/en/us/solutions/collateral/service-provider/visual-networking-index-vni/complete-white-paper-c11-481360.pdf

I certainly expect Android/iOS/BB and downstream mobile vendors to distribute
only changed binaries (or just deltas) of a few KB, rather than the whole 1.5MB
of unique files each time, saving a lot more traffic per upgrade.
Given that the vendors are telcos, that would be naive, why would they?
Are mobile updates free anywhere?

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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