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TZFILE
!!!TZFILE
NAME
SYNOPSIS
DESCRIPTION
SEE ALSO
----
!!NAME


tzfile - time zone information
!!SYNOPSIS


__#include __
!!DESCRIPTION


The time zone information files used by tzset(3)
begin with the magic characters
''long__, written in a ``standard'' byte
order (the high-order byte of the value is written first).
These values are, in order:


''tzh_ttisgmtcnt''


The number of UTC/local indicators stored in the
file.


''tzh_ttisstdcnt''


The number of standard/wall indicators stored in the
file.


''tzh_leapcnt''


The number of leap seconds for which data is stored in the
file.


''tzh_timecnt''


The number of


''tzh_typecnt''


The number of


''tzh_charcnt''


The number of characters of


The above header is followed by ''tzh_timecnt'' four-byte
values of type __long__, sorted in ascending order. These
values are written in ``standard'' byte order. Each is used
as a transition time (as returned by time(2)) at
which the rules for computing local time change. Next come
''tzh_timecnt'' one-byte values of type __unsigned
char__; each one tells which of the different types of
``local time'' types described in the file is associated
with the same-indexed transition time. These values serve as
indices into an array of ''ttinfo'' structures that
appears next in the file; these structures are defined as
follows:


struct ttinfo {
long          tt_gmtoff;
int           tt_isdst;
unsigned int  tt_abbrind;
};
Each structure is written as a four-byte value for ''tt_gmtoff'' of type __long__, in a standard byte order, followed by a one-byte value for ''tt_isdst'' and a one-byte value for ''tt_abbrind''. In each structure, ''tt_gmtoff'' gives the number of seconds to be added to UTC, ''tt_isdst'' tells whether ''tm_isdst'' should be set by ''localtime (3)'' and ''tt_abbrind'' serves as an index into the array of time zone abbreviation characters that follow the ''ttinfo'' structure(s) in the file.


Then there are ''tzh_leapcnt'' pairs of four-byte values,
written in standard byte order; the first value of each pair
gives the time (as returned by ''time(2))'' at which a
leap second occurs; the second gives the ''total'' number
of leap seconds to be applied after the given time. The
pairs of values are sorted in ascending order by
time.


Then there are ''tzh_ttisstdcnt'' standard/wall
indicators, each stored as a one-byte value; they tell
whether the transition times associated with local time
types were specified as standard time or wall clock time,
and are used when a time zone file is used in handling
POSIX-style time zone environment variables.


Finally there are ''tzh_ttisgmtcnt'' UTC/local
indicators, each stored as a one-byte value; they tell
whether the transition times associated with local time
types were specified as UTC or local time, and are used when
a time zone file is used in handling POSIX-style time zone
environment variables.


''Localtime'' uses the first standard-time ''ttinfo''
structure in the file (or simply the first ''ttinfo''
structure in the absence of a standard-time structure) if
either ''tzh_timecnt'' is zero or the time argument is
less than the first transition time recorded in the
file.
!!SEE ALSO


newctime(3)
----
5 pages link to tzfile(5):
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Last edited on Tuesday, June 4, 2002 12:30:41 am by "perry"
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