| 1.\" $Id: tzfile.5,v 1.6 1999/01/20 18:54:12 wollman Exp $
|
1.Dd September 13, 1994
2.Dt TZFILE 5
| 2.Dd September 13, 1994
3.Dt TZFILE 5
|
3.Os FreeBSD 2.0
| 4.Os FreeBSD 3.0
|
4.Sh NAME
5.Nm tzfile
6.Nd timezone information
7.Sh SYNOPSIS
| 5.Sh NAME
6.Nm tzfile
7.Nd timezone information
8.Sh SYNOPSIS
|
8.Fd #include <tzfile.h>
| 9.Fd #include "/usr/src/lib/libc/stdtime/tzfile.h"
|
9.Sh DESCRIPTION
10The time zone information files used by
11.Xr tzset 3
| 10.Sh DESCRIPTION
11The time zone information files used by
12.Xr tzset 3
|
12begin with bytes reserved for future use,
| 13begin with the magic characters
14.Dq Li TZif
15to identify them as
16time zone information files,
17followed by sixteen bytes reserved for future use,
|
13followed by four four-byte values
14written in a ``standard'' byte order
15(the high-order byte of the value is written first).
16These values are,
17in order:
18.Pp
19.Bl -tag -compact -width tzh_ttisstdcnt
| 18followed by four four-byte values
19written in a ``standard'' byte order
20(the high-order byte of the value is written first).
21These values are,
22in order:
23.Pp
24.Bl -tag -compact -width tzh_ttisstdcnt
|
20.It Li tzh_ttisstdcnt
| 25.It Va tzh_ttisgmtcnt
26The number of UTC/local indicators stored in the file.
27.It Va tzh_ttisstdcnt
|
21The number of standard/wall indicators stored in the file.
| 28The number of standard/wall indicators stored in the file.
|
22.It Li tzh_leapcnt
| 29.It Va tzh_leapcnt
|
23The number of leap seconds for which data is stored in the file.
| 30The number of leap seconds for which data is stored in the file.
|
24.It Li tzh_timecnt
| 31.It Va tzh_timecnt
|
25The number of ``transition times'' for which data is stored
26in the file.
| 32The number of ``transition times'' for which data is stored
33in the file.
|
27.It Li tzh_typecnt
| 34.It Va tzh_typecnt
|
28The number of ``local time types'' for which data is stored
29in the file (must not be zero).
| 35The number of ``local time types'' for which data is stored
36in the file (must not be zero).
|
30.It Li tzh_charcnt
| 37.It Va tzh_charcnt
|
31The number of characters of ``time zone abbreviation strings''
32stored in the file.
33.El
34.Pp
35The above header is followed by
| 38The number of characters of ``time zone abbreviation strings''
39stored in the file.
40.El
41.Pp
42The above header is followed by
|
36.Li tzh_timecnt
| 43.Va tzh_timecnt
|
37four-byte values of type
38.Fa long ,
39sorted in ascending order.
40These values are written in ``standard'' byte order.
41Each is used as a transition time (as returned by
42.Xr time 3 )
43at which the rules for computing local time change.
44Next come
| 44four-byte values of type
45.Fa long ,
46sorted in ascending order.
47These values are written in ``standard'' byte order.
48Each is used as a transition time (as returned by
49.Xr time 3 )
50at which the rules for computing local time change.
51Next come
|
45.Li tzh_timecnt
| 52.Va tzh_timecnt
|
46one-byte values of type
47.Fa "unsigned char" ;
48each one tells which of the different types of ``local time'' types
49described in the file is associated with the same-indexed transition time.
50These values serve as indices into an array of
51.Fa ttinfo
52structures that appears next in the file;
53these structures are defined as follows:
54.Pp
55.Bd -literal -offset indent
56struct ttinfo {
57 long tt_gmtoff;
58 int tt_isdst;
59 unsigned int tt_abbrind;
60};
61.Ed
62.Pp
63Each structure is written as a four-byte value for
| 53one-byte values of type
54.Fa "unsigned char" ;
55each one tells which of the different types of ``local time'' types
56described in the file is associated with the same-indexed transition time.
57These values serve as indices into an array of
58.Fa ttinfo
59structures that appears next in the file;
60these structures are defined as follows:
61.Pp
62.Bd -literal -offset indent
63struct ttinfo {
64 long tt_gmtoff;
65 int tt_isdst;
66 unsigned int tt_abbrind;
67};
68.Ed
69.Pp
70Each structure is written as a four-byte value for
|
64.Li tt_gmtoff
| 71.Va tt_gmtoff
|
65of type
66.Fa long ,
67in a standard byte order, followed by a one-byte value for
| 72of type
73.Fa long ,
74in a standard byte order, followed by a one-byte value for
|
68.Li tt_isdst
| 75.Va tt_isdst
|
69and a one-byte value for
| 76and a one-byte value for
|
70.Li tt_abbrind .
| 77.Va tt_abbrind .
|
71In each structure,
| 78In each structure,
|
72.Li tt_gmtoff
73gives the number of seconds to be added to GMT,
| 79.Va tt_gmtoff
80gives the number of seconds to be added to UTC,
|
74.Li tt_isdst
75tells whether
76.Li tm_isdst
77should be set by
78.Xr localtime 3
79and
| 81.Li tt_isdst
82tells whether
83.Li tm_isdst
84should be set by
85.Xr localtime 3
86and
|
80.Li tt_abbrind
| 87.Va tt_abbrind
|
81serves as an index into the array of time zone abbreviation characters
82that follow the
83.Li ttinfo
84structure(s) in the file.
85.Pp
86Then there are
| 88serves as an index into the array of time zone abbreviation characters
89that follow the
90.Li ttinfo
91structure(s) in the file.
92.Pp
93Then there are
|
87.Li tzh_leapcnt
| 94.Va tzh_leapcnt
|
88pairs of four-byte values, written in standard byte order;
89the first value of each pair gives the time
90(as returned by
91.Xr time 3 )
92at which a leap second occurs;
93the second gives the
94.Em total
95number of leap seconds to be applied after the given time.
96The pairs of values are sorted in ascending order by time.
97.Pp
| 95pairs of four-byte values, written in standard byte order;
96the first value of each pair gives the time
97(as returned by
98.Xr time 3 )
99at which a leap second occurs;
100the second gives the
101.Em total
102number of leap seconds to be applied after the given time.
103The pairs of values are sorted in ascending order by time.
104.Pp
|
98Finally there are
99.Li tzh_ttisstdcnt
| 105Then there are
106.Va tzh_ttisstdcnt
|
100standard/wall indicators, each stored as a one-byte value;
101they tell whether the transition times associated with local time types
102were specified as standard time or wall clock time,
103and are used when a time zone file is used in handling POSIX-style
104time zone environment variables.
105.Pp
| 107standard/wall indicators, each stored as a one-byte value;
108they tell whether the transition times associated with local time types
109were specified as standard time or wall clock time,
110and are used when a time zone file is used in handling POSIX-style
111time zone environment variables.
112.Pp
|
| 113Finally there are
114.Va tzh_ttisgmtcnt
115UTC/local indicators, each stored as a one-byte value;
116they tell whether the transition times associated with local time types
117were specified as UTC or local time,
118and are used when a time zone file is used in handling POSIX-style
119time zone environment variables.
120.Pp
|
106.Nm localtime
107uses the first standard-time
108.Li ttinfo
109structure in the file
110(or simply the first
111.Li ttinfo
112structure in the absence of a standard-time structure)
113if either
114.Li tzh_timecnt
115is zero or the time argument is less than the first transition time recorded
116in the file.
117.Sh SEE ALSO
118.Xr ctime 3 ,
119.Xr time2posix 3 ,
120.Xr zic 8
121.\" @(#)tzfile.5 7.2
| 121.Nm localtime
122uses the first standard-time
123.Li ttinfo
124structure in the file
125(or simply the first
126.Li ttinfo
127structure in the absence of a standard-time structure)
128if either
129.Li tzh_timecnt
130is zero or the time argument is less than the first transition time recorded
131in the file.
132.Sh SEE ALSO
133.Xr ctime 3 ,
134.Xr time2posix 3 ,
135.Xr zic 8
136.\" @(#)tzfile.5 7.2
|
| 137.\" This file is in the public domain, so clarified as of
138.\" 1996-06-05 by Arthur David Olson (arthur_david_olson@nih.gov).
|
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