[tz] Version in zoneinfo files?

[Steven R. Loomis]

On 2/10/17 12:18 AM, Paul Eggert wrote:
> John Hawkinson wrote:
>> the idea is to have the string displayable using a semi-standard tool.
>
> On GNU/Linux a common tool for that is the 'file' command. For
> example, on Fedora 25:
>
> $ file /usr/share/zoneinfo/America/Los_Angeles
> /usr/share/zoneinfo/America/Los_Angeles: timezone data, version 2, 5
> gmt time flags, 5 std time flags, no leap seconds, 186 transition
> times, 5 abbreviation chars
>
> Here the string "America/Los_Angeles" is already part of the output.
Yes, but consider:
$ file /usr/share/zoneinfo/America/Los_Angeles
/usr/share/zoneinfo/America/Los_Angeles: timezone data, old version, 4
gmt time flags, 4 std time flags, no leap seconds, 185 transition times,
4 abbreviation chars
srl at filfla:/tmp/_
$ file /etc/localtime
/etc/localtime: timezone data, old version, 4 gmt time flags, 4 std time
flags, no leap seconds, 185 transition times, 4 abbreviation chars

Apparently 'file' didn't want to mess with readlink() either. I don't
blame it.
> Presumably the intended application for a change to the binary file
> format is when the binary file has been renamed or linked and someone
> wants to know the "originally-intended" or "canonical" name. 
Just so.
> tz follows the Unix tradition where files do not have canonical names
> - a design flaw to some, and a design feature to others.
but tz does have:

northamerica:  Zone America/Los_Angeles
backward: Link    America/Los_Angeles     US/Pacific

So, formally, what I am looking for is "the Zone entry of the stanza
which zic used to generate the tzfile output." I'm very happy to leave
filenames out of the definitional picture.

Steven


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