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1 perry 1 TZFILE
2 !!!TZFILE
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 SEE ALSO
7 ----
8 !!NAME
9
10
11 tzfile - time zone information
12 !!SYNOPSIS
13
14
15 __#include __
16 !!DESCRIPTION
17
18
19 The time zone information files used by tzset(3)
20 begin with the magic characters
21 ''long__, written in a ``standard'' byte
22 order (the high-order byte of the value is written first).
23 These values are, in order:
24
25
26 ''tzh_ttisgmtcnt''
27
28
29 The number of UTC/local indicators stored in the
30 file.
31
32
33 ''tzh_ttisstdcnt''
34
35
36 The number of standard/wall indicators stored in the
37 file.
38
39
40 ''tzh_leapcnt''
41
42
43 The number of leap seconds for which data is stored in the
44 file.
45
46
47 ''tzh_timecnt''
48
49
50 The number of
51
52
53 ''tzh_typecnt''
54
55
56 The number of
57
58
59 ''tzh_charcnt''
60
61
62 The number of characters of
63
64
65 The above header is followed by ''tzh_timecnt'' four-byte
66 values of type __long__, sorted in ascending order. These
67 values are written in ``standard'' byte order. Each is used
68 as a transition time (as returned by time(2)) at
69 which the rules for computing local time change. Next come
70 ''tzh_timecnt'' one-byte values of type __unsigned
71 char__; each one tells which of the different types of
72 ``local time'' types described in the file is associated
73 with the same-indexed transition time. These values serve as
74 indices into an array of ''ttinfo'' structures that
75 appears next in the file; these structures are defined as
76 follows:
77
78
79 struct ttinfo {
80 long tt_gmtoff;
81 int tt_isdst;
82 unsigned int tt_abbrind;
83 };
84 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.
85
86
87 Then there are ''tzh_leapcnt'' pairs of four-byte values,
88 written in standard byte order; the first value of each pair
89 gives the time (as returned by ''time(2))'' at which a
90 leap second occurs; the second gives the ''total'' number
91 of leap seconds to be applied after the given time. The
92 pairs of values are sorted in ascending order by
93 time.
94
95
96 Then there are ''tzh_ttisstdcnt'' standard/wall
97 indicators, each stored as a one-byte value; they tell
98 whether the transition times associated with local time
99 types were specified as standard time or wall clock time,
100 and are used when a time zone file is used in handling
101 POSIX-style time zone environment variables.
102
103
104 Finally there are ''tzh_ttisgmtcnt'' UTC/local
105 indicators, each stored as a one-byte value; they tell
106 whether the transition times associated with local time
107 types were specified as UTC or local time, and are used when
108 a time zone file is used in handling POSIX-style time zone
109 environment variables.
110
111
112 ''Localtime'' uses the first standard-time ''ttinfo''
113 structure in the file (or simply the first ''ttinfo''
114 structure in the absence of a standard-time structure) if
115 either ''tzh_timecnt'' is zero or the time argument is
116 less than the first transition time recorded in the
117 file.
118 !!SEE ALSO
119
120
121 newctime(3)
122 ----
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