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2d6c6dd1 | 1 | .\" %%%LICENSE_START(PUBLIC_DOMAIN) |
c3d92f8a | 2 | .\" This page is in the public domain |
2d6c6dd1 | 3 | .\" %%%LICENSE_END |
c3d92f8a | 4 | .\" |
734882f4 | 5 | .TH ZDUMP 8 2017-05-03 "" "Linux System Administration" |
fea681da | 6 | .SH NAME |
5b0dc1ba | 7 | zdump \- timezone dumper |
fea681da | 8 | .SH SYNOPSIS |
09c05a89 PE |
9 | .B zdump |
10 | [ | |
11 | .I option | |
12 | \&... ] [ | |
13 | .I timezone | |
14 | \&... ] | |
fea681da | 15 | .SH DESCRIPTION |
09c05a89 PE |
16 | .ie '\(lq'' .ds lq \&"\" |
17 | .el .ds lq \(lq\" | |
18 | .ie '\(rq'' .ds rq \&"\" | |
19 | .el .ds rq \(rq\" | |
20 | .de q | |
21 | \\$3\*(lq\\$1\*(rq\\$2 | |
22 | .. | |
23 | .ie \n(.g .ds - \f(CW-\fP | |
24 | .el ds - \- | |
7d92574b MK |
25 | The |
26 | .B zdump | |
27 | program prints the current time in each | |
09c05a89 | 28 | .I timezone |
fea681da | 29 | named on the command line. |
725399bb | 30 | .SH OPTIONS |
fea681da | 31 | .TP |
09c05a89 | 32 | .B \*-\*-version |
d0853a63 MK |
33 | Output version information and exit. |
34 | .TP | |
09c05a89 | 35 | .B \*-\*-help |
c28ca2ba | 36 | Output short usage message and exit. |
d0853a63 | 37 | .TP |
09c05a89 PE |
38 | .B \*-i |
39 | Output a description of time intervals. For each | |
40 | .I timezone | |
41 | on the command line, output an interval-format description of the | |
42 | timezone. See | |
43 | .q "INTERVAL FORMAT" | |
44 | below. | |
45 | .TP | |
46 | .B \*-v | |
47 | Output a verbose description of time intervals. | |
fea681da | 48 | For each |
09c05a89 | 49 | .I timezone |
fea681da MK |
50 | on the command line, |
51 | print the time at the lowest possible time value, | |
52 | the time one day after the lowest possible time value, | |
53 | the times both one second before and exactly at | |
54 | each detected time discontinuity, | |
55 | the time at one day less than the highest possible time value, | |
56 | and the time at the highest possible time value. | |
09c05a89 PE |
57 | Each line is followed by |
58 | .BI isdst= D | |
59 | where | |
60 | .I D | |
61 | is positive, zero, or negative depending on whether | |
62 | the given time is daylight saving time, standard time, | |
63 | or an unknown time type, respectively. | |
64 | Each line is also followed by | |
65 | .BI gmtoff= N | |
66 | if the given local time is known to be | |
67 | .I N | |
68 | seconds east of Greenwich. | |
fea681da | 69 | .TP |
09c05a89 PE |
70 | .B \*-V |
71 | Like | |
72 | .BR \*-v , | |
73 | except omit the times relative to the extreme time values. | |
74 | This generates output that is easier to compare to that of | |
75 | implementations with different time representations. | |
76 | .TP | |
77 | .BI "\*-c " \fR[\fIloyear , \fR]\fIhiyear | |
78 | Cut off interval output at the given year(s). | |
79 | Cutoff times are computed using the proleptic Gregorian calendar with year 0 | |
80 | and with Universal Time (UT) ignoring leap seconds. | |
81 | The lower bound is exclusive and the upper is inclusive; for example, a | |
82 | .I loyear | |
83 | of 1970 excludes a transition occurring at 1970-01-01 00:00:00 UTC but a | |
84 | .I hiyear | |
85 | of 1970 includes the transition. | |
86 | The default cutoff is | |
87 | .BR \*-500,2500 . | |
88 | .TP | |
89 | .BI "\*-t " \fR[\fIlotime , \fR]\fIhitime | |
90 | Cut off interval output at the given time(s), | |
91 | given in decimal seconds since 1970-01-01 00:00:00 | |
92 | Coordinated Universal Time (UTC). | |
93 | The | |
94 | .I timezone | |
95 | determines whether the count includes leap seconds. | |
96 | As with | |
97 | .BR \*-c , | |
98 | the cutoff's lower bound is exclusive and its upper bound is inclusive. | |
99 | .SH "INTERVAL FORMAT" | |
100 | The interval format is a compact text representation that is intended | |
101 | to be both human- and machine-readable. It consists of an empty line, | |
102 | then a line | |
103 | .q "TZ=\fIstring\fP" | |
104 | where | |
105 | .I string | |
106 | is a double-quoted string giving the timezone, a second line | |
107 | .q "\*- \*- \fIinterval\fP" | |
108 | describing the time interval before the first transition if any, and | |
109 | zero or more following lines | |
110 | .q "\fIdate time interval\fP", | |
111 | one line for each transition time and following interval. Fields are | |
112 | separated by single tabs. | |
113 | .PP | |
114 | Dates are in | |
115 | .IR yyyy - mm - dd | |
116 | format and times are in 24-hour | |
117 | .IR hh : mm : ss | |
118 | format where | |
119 | .IR hh <24. | |
120 | Times are in local time immediately after the transition. A | |
121 | time interval description consists of a UT offset in signed | |
122 | .RI \(+- hhmmss | |
123 | format, a time zone abbreviation, and an isdst flag. An abbreviation | |
124 | that equals the UT offset is omitted; other abbreviations are | |
125 | double-quoted strings unless they consist of one or more alphabetic | |
126 | characters. An isdst flag is omitted for standard time, and otherwise | |
127 | is a decimal integer that is unsigned and positive (typically 1) for | |
128 | daylight saving time and negative for unknown. | |
129 | .PP | |
130 | In times and in UT offsets with absolute value less than 100 hours, | |
131 | the seconds are omitted if they are zero, and | |
132 | the minutes are also omitted if they are also zero. Positive UT | |
133 | offsets are east of Greenwich. The UT offset \*-00 denotes a UT | |
134 | placeholder in areas where the actual offset is unspecified; by | |
135 | convention, this occurs when the UT offset is zero and the time zone | |
136 | abbreviation begins with | |
137 | .q "\*-" | |
138 | or is | |
139 | .q "zzz". | |
140 | .PP | |
141 | In double-quoted strings, escape sequences represent unusual | |
142 | characters. The escape sequences are \es for space, and \e", \e\e, | |
143 | \ef, \en, \er, \et, and \ev with their usual meaning in the C | |
144 | programming language. E.g., the double-quoted string | |
145 | \*(lq"CET\es\e"\e\e"\*(rq represents the character sequence \*(lqCET | |
146 | "\e\*(rq.\"" | |
147 | .PP | |
148 | .ne 9 | |
149 | Here is an example of the output, with the leading empty line omitted. | |
150 | (This example is shown with tab stops set far enough apart so that the | |
151 | tabbed columns line up.) | |
152 | .nf | |
153 | .sp | |
154 | .if \n(.g .ft CW | |
155 | .if t .in +.5i | |
156 | .if n .in +2 | |
157 | .nr w \w'1896-01-13 'u | |
158 | .ta \nwu +\nwu +\nwu +\nwu | |
159 | TZ="Pacific/Honolulu" | |
160 | - - -10:31:26 LMT | |
161 | 1896-01-13 12:01:26 -10:30 HST | |
162 | 1933-04-30 03 -09:30 HDT 1 | |
163 | 1933-05-21 11 -10:30 HST | |
164 | 1942-02-09 03 -09:30 HDT 1 | |
165 | 1945-09-30 01 -10:30 HST | |
166 | 1947-06-08 02:30 -10 HST | |
167 | .in | |
168 | .if \n(.g .ft | |
169 | .sp | |
170 | .fi | |
171 | Here, local time begins 10 hours, 31 minutes and 26 seconds west of | |
172 | UT, and is a standard time abbreviated LMT. Immediately after the | |
173 | first transition, the date is 1896-01-13 and the time is 12:01:26, and | |
174 | the following time interval is 10.5 hours west of UT, a standard time | |
175 | abbreviated HST. Immediately after the second transition, the date is | |
176 | 1933-04-30 and the time is 03:00:00 and the following time interval is | |
177 | 9.5 hours west of UT, is abbreviated HDT, and is daylight saving time. | |
178 | Immediately after the last transition the date is 1947-06-08 and the | |
179 | time is 02:30:00, and the following time interval is 10 hours west of | |
180 | UT, a standard time abbreviated HST. | |
181 | .PP | |
182 | .ne 10 | |
183 | Here are excerpts from another example: | |
184 | .nf | |
185 | .sp | |
186 | .if \n(.g .ft CW | |
187 | .if t .in +.5i | |
188 | .if n .in +2 | |
189 | TZ="Europe/Astrakhan" | |
190 | - - +03:12:12 LMT | |
191 | 1924-04-30 23:47:48 +03 | |
192 | 1930-06-21 01 +04 | |
193 | 1981-04-01 01 +05 1 | |
194 | 1981-09-30 23 +04 | |
195 | \&... | |
196 | 2014-10-26 01 +03 | |
197 | 2016-03-27 03 +04 | |
198 | .in | |
199 | .if \n(.g .ft | |
200 | .sp | |
201 | .fi | |
202 | This time zone is east of UT, so its UT offsets are positive. Also, | |
203 | many of its time zone abbreviations are omitted since they duplicate | |
204 | the text of the UT offset. | |
205 | .SH LIMITATIONS | |
206 | Time discontinuities are found by sampling the results returned by localtime | |
207 | at twelve-hour intervals. | |
208 | This works in all real-world cases; | |
209 | one can construct artificial time zones for which this fails. | |
210 | .PP | |
211 | In the | |
212 | .B \*-v | |
213 | and | |
214 | .B \*-V | |
215 | output, | |
216 | .q "UT" | |
217 | denotes the value returned by | |
218 | .IR gmtime (3), | |
219 | which uses UTC for modern timestamps and some other UT flavor for | |
220 | timestamps that predate the introduction of UTC. | |
221 | No attempt is currently made to have the output use | |
222 | .q "UTC" | |
223 | for newer and | |
224 | .q "UT" | |
225 | for older timestamps, partly because the exact date of the | |
226 | introduction of UTC is problematic. | |
47297adb | 227 | .SH SEE ALSO |
46f5295b MK |
228 | .BR tzfile (5), |
229 | .BR zic (8) | |
09c05a89 PE |
230 | .\" This file is in the public domain, so clarified as of |
231 | .\" 2009-05-17 by Arthur David Olson. |