Re: /usr/share/zoneinfo file formats
Re: /usr/share/zoneinfo file formats
- Subject: Re: /usr/share/zoneinfo file formats
- From: Chris Kane <email@hidden>
- Date: Tue, 31 Dec 2002 19:56:12 -0800
On Wednesday, December 18, 2002, at 01:14 PM, Todd Blanchard wrote:
I have a library that purports to be able to read timezone info from
any "standard" unix systems zoneinfo database.
It sez:
--------
"Time zone rules are loaded by reading compiled tzfile files from an
external source. Compiled tzfiles files are commonly distributed with
Unix and Linux systems.
A compiled tzfile is typically generated by the zic(1) compiler
distributed
as part of the public domain timezone database in the ~ftp/pub directory
of elsie.nci.nih.gov FTP server. Source code, documentation, and the
full (human readable) rule file source is available from
elsie.nci.nih.gov.
The tzfile data must be obtained separately. If you have a Unix-like
system, look in /usr/share/zoneinfo."
---------
'elsie' is where the data for the files in /usr/share/zoneinfo comes
from...
I find a bunch of promising looking files in /usr/share/zoneinfo. but
looking at the code, it tries to validate the files are of the correct
format by checking for the magic string 'TZif' in the first 4 bytes of
the file. This fails.
The first couple dozen bytes of each of these files on my Mac are all
zero. So does anybody know what format these files are in and why
they're different from other unixen?
The format is given in /usr/include/tzfile.h. These are basically just
compiled from the data files at elsie using the zic tool in the
distribution. I don't see an option for zic to include or not a magic
number. Historically, I don't remember ever seeing a 'TZif' magic
number on the zone info files. The data patterns in /etc/magic, which
describe to the 'file' command how to recognize different types of file
data, also does not specify any magic numbers for 'timezone data'. A
'TZif' magic number may be a relatively recent development.
Chris Kane
Cocoa Frameworks, Apple
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