diff options
Diffstat (limited to 'zdump.8')
| -rw-r--r-- | zdump.8 | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/zdump.8 b/zdump.8 new file mode 100644 index 0000000000000..ef611db7cf9e1 --- /dev/null +++ b/zdump.8 @@ -0,0 +1,226 @@ +.TH ZDUMP 8 +.SH NAME +zdump \- time zone dumper +.SH SYNOPSIS +.B zdump +[ +.I option +\&... ] [ +.I zonename +\&... ] +.SH DESCRIPTION +.ie '\(lq'' .ds lq \&"\" +.el .ds lq \(lq\" +.ie '\(rq'' .ds rq \&"\" +.el .ds rq \(rq\" +.de q +\\$3\*(lq\\$1\*(rq\\$2 +.. +.ie \n(.g .ds - \f(CW-\fP +.el ds - \- +.I Zdump +prints the current time in each +.I zonename +named on the command line. +.PP +These options are available: +.TP +.BI "\*-\*-version" +Output version information and exit. +.TP +.B \*-i +.I "(This option is experimental: its behavior may change in future versions.)" +Output a description of time intervals. For each +.I zonename +on the command line, output an interval-format description of the +zone. See +.q "INTERVAL FORMAT" +below. +.TP +.B \*-v +Output a verbose description of time intervals. +For each +.I zonename +on the command line, +print the time at the lowest possible time value, +the time one day after the lowest possible time value, +the times both one second before and exactly at +each detected time discontinuity, +the time at one day less than the highest possible time value, +and the time at the highest possible time value. +Each line is followed by +.BI isdst= D +where +.I D +is positive, zero, or negative depending on whether +the given time is daylight saving time, standard time, +or an unknown time type, respectively. +Each line is also followed by +.BI gmtoff= N +if the given local time is known to be +.I N +seconds east of Greenwich. +.TP +.B \*-V +Like +.BR \*-v , +except omit the times relative to the extreme time values. +This generates output that is easier to compare to that of +implementations with different time representations. +.TP +.BI "\*-c " [loyear,]hiyear +Cut off interval output at the given year(s). +Cutoff times are computed using the proleptic Gregorian calendar with year 0 +and with Universal Time (UT) ignoring leap seconds. +The lower bound is exclusive and the upper is inclusive; for example, a +.I loyear +of 1970 excludes a transition occurring at 1970-01-01 00:00:00 UTC but a +.I hiyear +of 1970 includes the transition. +The default cutoff is +.BR \*-500,2500 . +.TP +.BI "\*-t " [lotime,]hitime +Cut off interval output at the given time(s), +given in decimal seconds since 1970-01-01 00:00:00 +Coordinated Universal Time (UTC). +The +.I zonename +determines whether the count includes leap seconds. +As with +.BR \*-c , +the cutoff's lower bound is exclusive and its upper bound is inclusive. +.SH "INTERVAL FORMAT" +.I "This format is experimental: it may change in future versions." +.PP +The interval format is a compact text representation that is intended +to be both human- and machine-readable. It consists of an empty line, +then a line +.q "TZ=\fIstring\fP" +where +.I string +is a double-quoted string giving the zone name, a second line +.q "\*- \*- \fIinterval\fP" +describing the time interval before the first transition if any, and +zero or more following lines +.q "\fIdate time interval\fP", +one line for each transition time and following interval. Fields are +separated by single tabs. +.PP +Dates are in +.IR yyyy - mm - dd +format and times are in 24-hour +.IR hh : mm : ss +format where +.IR hh <24. +Times are in local time immediately after the transition. A +time interval description consists of a UT offset in signed +.RI \(+- hhmmss +format, a time zone abbreviation, and an isdst flag. An abbreviation +that equals the UT offset is omitted; other abbreviations are +double-quoted strings unless they consist of one or more alphabetic +characters. An isdst flag is omitted for standard time, and otherwise +is a decimal integer that is unsigned and positive (typically 1) for +daylight saving time and negative for unknown. +.PP +In times and in UT offsets with absolute value less than 100 hours, +the seconds are omitted if they are zero, and +the minutes are also omitted if they are also zero. Positive UT +offsets are east of Greenwich. The UT offset \*-00 denotes a UT +placeholder in areas where the actual offset is unspecified; by +convention, this occurs when the UT offset is zero and the time zone +abbreviation begins with +.q "\*-" +or is +.q "zzz". +.PP +In double-quoted strings, escape sequences represent unusual +characters. The escape sequences are \es for space, and \e", \e\e, +\ef, \en, \er, \et, and \ev with their usual meaning in the C +programming language. E.g., the double-quoted string +\*(lq"CET\es\e"\e\e"\*(rq represents the character sequence \*(lqCET +"\e\*(rq.\"" +.PP +.ne 9 +Here is an example of the output, with the leading empty line omitted. +(This example is shown with tab stops set far enough apart so that the +tabbed columns line up.) +.nf +.sp +.if \n(.g .ft CW +.if t .in +.5i +.if n .in +2 +.nr w \w'1896-01-13 'u +.ta \nwu +\nwu +\nwu +\nwu +TZ="Pacific/Honolulu" +- - -10:31:26 LMT +1896-01-13 12:01:26 -10:30 HST +1933-04-30 03 -09:30 HDT 1 +1933-05-21 11 -10:30 HST +1942-02-09 03 -09:30 HDT 1 +1945-09-30 01 -10:30 HST +1947-06-08 02:30 -10 HST +.in +.if \n(.g .ft +.sp +.fi +Here, local time begins 10 hours, 31 minutes and 26 seconds west of +UT, and is a standard time abbreviated LMT. Immediately after the +first transition, the date is 1896-01-13 and the time is 12:01:26, and +the following time interval is 10.5 hours west of UT, a standard time +abbreviated HST. Immediately after the second transition, the date is +1933-04-30 and the time is 03:00:00 and the following time interval is +9.5 hours west of UT, is abbreviated HDT, and is daylight saving time. +Immediately after the last transition the date is 1947-06-08 and the +time is 02:30:00, and the following time interval is 10 hours west of +UT, a standard time abbreviated HST. +.PP +.ne 10 +Here are excerpts from another example: +.nf +.sp +.if \n(.g .ft CW +.if t .in +.5i +.if n .in +2 +TZ="Europe/Astrakhan" +- - +03:12:12 LMT +1924-04-30 23:47:48 +03 +1930-06-21 01 +04 +1981-04-01 01 +05 1 +1981-09-30 23 +04 +\&... +2014-10-26 01 +03 +2016-03-27 03 +04 +.in +.if \n(.g .ft +.sp +.fi +This time zone is east of UT, so its UT offsets are positive. Also, +many of its time zone abbreviations are omitted since they duplicate +the text of the UT offset. +.SH LIMITATIONS +Time discontinuities are found by sampling the results returned by localtime +at twelve-hour intervals. +This works in all real-world cases; +one can construct artificial time zones for which this fails. +.PP +In the +.B \*-v +and +.B \*-V +output, +.q "UT" +denotes the value returned by +.IR gmtime (3), +which uses UTC for modern time stamps and some other UT flavor for +time stamps that predate the introduction of UTC. +No attempt is currently made to have the output use +.q "UTC" +for newer and +.q "UT" +for older time stamps, partly because the exact date of the +introduction of UTC is problematic. +.SH "SEE ALSO" +newctime(3), tzfile(5), zic(8) +.\" This file is in the public domain, so clarified as of +.\" 2009-05-17 by Arthur David Olson. |