* Replay 2010[acflm] which had been merged but not recorded. * Merge 2010n. * Reorganize (unsplit) the code to match the upstream layout. * Merge 2022[cdefg]. MFC after: 1 week Sponsored by: Klara, Inc.
232 lines
6.4 KiB
Groff
232 lines
6.4 KiB
Groff
.\" This file is in the public domain, so clarified as of
|
|
.\" 2009-05-17 by Arthur David Olson.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd December 15, 2022
|
|
.Dt ZDUMP 8
|
|
.Os
|
|
.Sh NAME
|
|
.Nm zdump
|
|
.Nd timezone dumper
|
|
.Sh SYNOPSIS
|
|
.Nm
|
|
.Op Fl -help
|
|
.Op Fl -version
|
|
.Op Fl ivV
|
|
.Oo
|
|
.Fl c
|
|
.Op Ar loyear , Ns
|
|
.Ar hiyear
|
|
.Oc
|
|
.Oo
|
|
.Fl t
|
|
.Op Ar lotime , Ns
|
|
.Ar hitime
|
|
.Oc
|
|
.Op Ar timezone ...
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
program prints the current time in each
|
|
.Ar timezone
|
|
named on the command line.
|
|
.Pp
|
|
The following options are available:
|
|
.Bl -tag -width indent
|
|
.It Fl -version
|
|
Output version information and exit.
|
|
.It Fl -help
|
|
Output short usage message and exit.
|
|
.It Fl i
|
|
Output a description of time intervals.
|
|
For each
|
|
.Ar timezone
|
|
on the command line, output an interval-format description of the
|
|
timezone.
|
|
See
|
|
.Sx "INTERVAL FORMAT"
|
|
below.
|
|
.It Fl v
|
|
Output a verbose description of time intervals.
|
|
For each
|
|
.Ar timezone
|
|
on the command line,
|
|
print the times at the two extreme time values,
|
|
the times (if present) at and just beyond the boundaries of years that
|
|
.Xr localtime 3
|
|
and
|
|
.Xr gmtime 3
|
|
can represent, and
|
|
the times both one second before and exactly at
|
|
each detected time discontinuity.
|
|
Each line is followed by
|
|
.Cm isdst= Ns Ar D
|
|
where
|
|
.Ar 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
|
|
.Cm gmtoff= Ns Ar N
|
|
if the given local time is known to be
|
|
.Ar N
|
|
seconds east of Greenwich.
|
|
.It Fl V
|
|
Like
|
|
.Fl v ,
|
|
except omit output concerning extreme time and year values.
|
|
This generates output that is easier to compare to that of
|
|
implementations with different time representations.
|
|
.It Fl c Oo Ar loyear , Oc Ns Ar 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.
|
|
Cutoffs are at the start of each year, where the lower-bound
|
|
timestamp is inclusive and the upper is exclusive; for example,
|
|
.Ql "-c 1970,2070"
|
|
selects transitions on or after 1970-01-01 00:00:00 UTC
|
|
and before 2070-01-01 00:00:00 UTC.
|
|
The default cutoff is
|
|
.Ql -500,2500 .
|
|
.It Fl t Oo Ar lotime , Oc Ns Ar 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
|
|
.Ar timezone
|
|
determines whether the count includes leap seconds.
|
|
As with
|
|
.Fl c ,
|
|
the cutoff's lower bound is inclusive and its upper bound is exclusive.
|
|
.El
|
|
.Sh "INTERVAL FORMAT"
|
|
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
|
|
.Dq "TZ=\fIstring\fP"
|
|
where
|
|
.Ar string
|
|
is a double-quoted string giving the timezone, a second line
|
|
.Dq "\*- \*- \fIinterval\fP"
|
|
describing the time interval before the first transition if any, and
|
|
zero or more following lines
|
|
.Dq "\fIdate time interval\fP",
|
|
one line for each transition time and following interval.
|
|
Fields are
|
|
separated by single tabs.
|
|
.Pp
|
|
Dates are in
|
|
.Ql "yyyy - mm - dd"
|
|
format and times are in 24-hour
|
|
.Ql "hh : mm : ss"
|
|
format where
|
|
.Ql "hh <24" .
|
|
Times are in local time immediately after the transition.
|
|
A
|
|
time interval description consists of a UT offset in signed
|
|
.Ql "\(+- 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
|
|
.Dq "-"
|
|
or is
|
|
.Dq "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
|
|
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.)
|
|
.Bd -literal -offset indent
|
|
TZ="Pacific/Honolulu"
|
|
- - -103126 LMT
|
|
1896-01-13 12:01:26 -1030 HST
|
|
1933-04-30 03 -0930 HDT 1
|
|
1933-05-21 11 -1030 HST
|
|
1942-02-09 03 -0930 HWT 1
|
|
1945-08-14 13:30 -0930 HPT 1
|
|
1945-09-30 01 -1030 HST
|
|
1947-06-08 02:30 -10 HST
|
|
.Ed
|
|
.Pp
|
|
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
|
|
Here are excerpts from another example:
|
|
.Bd -literal -offset indent
|
|
TZ="Europe/Astrakhan"
|
|
- - +031212 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
|
|
.Ed
|
|
.Pp
|
|
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
|
|
.Xr localtime 3
|
|
at twelve-hour intervals.
|
|
This works in all real-world cases;
|
|
one can construct artificial time zones for which this fails.
|
|
.Pp
|
|
In the
|
|
.Fl v
|
|
and
|
|
.Fl V
|
|
output,
|
|
.Dq "UT"
|
|
denotes the value returned by
|
|
.Xr gmtime 3 ,
|
|
which uses UTC for modern timestamps and some other UT flavor for
|
|
timestamps that predate the introduction of UTC.
|
|
No attempt is currently made to have the output use
|
|
.Dq "UTC"
|
|
for newer and
|
|
.Dq "UT"
|
|
for older timestamps, partly because the exact date of the
|
|
introduction of UTC is problematic.
|
|
.Sh SEE ALSO
|
|
.Xr tzfile 5 ,
|
|
.Xr zic 8
|