Tribblix: manual page: zdump.8

ZDUMP(8) Maintenance Commands and Procedures ZDUMP(8)

NAME

zdump - time zone dumper

SYNOPSIS

zdump [--version] [-i] [-v] [-V]
[-c [loyear,]hiyear] [-t [lotime,]hitime]
[zonename]...

DESCRIPTION

The zdump command prints the current time for each time zone
(zonename) listed on the command line. Specify zonename as the name
of the time zone database file relative to /usr/share/lib/zoneinfo.
A timezone of - is treated as if it were /dev/stdin; this can be used
to pipe TZif data into zdump.

OPTIONS

The following options are supported:

--version
Output version information and exit.

--help Output short usage message and exit.

-i Output a description of time intervals. For each timezone on
the command line, output an interval-format description of the
timezone. See "INTERVAL FORMAT" below.

-v Output a verbose description of time intervals. For each
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 localtime(3) and gmtime(3) can
represent, and the times both one second before and exactly at
each detected time discontinuity. Each line is followed by
isdst=D where 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 gmtoff=N if the given local time is known to be N
seconds east of Greenwich.

-V Like -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.

-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. Cutoffs
are at the start of each year, where the lower-bound timestamp
is inclusive and the upper is exclusive; for example, -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
-500,2500.

-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 timezone determines whether the count includes
leap seconds. As with -c, the cutoff's lower bound is
inclusive and its upper bound is exclusive.

EXIT STATUS

The following exit values are returned:

0
Successful completion.

1
An error occurred.

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 "TZ=string" where string is a double-quoted string
giving the timezone, a second line "- - interval" describing the time
interval before the first transition if any, and zero or more
following lines "date time interval", one line for each transition
time and following interval. Fields are separated by single tabs.

Dates are in yyyy-mm-dd format and times are in 24-hour hh:mm:ss
format where hh<24. Times are in local time immediately after the
transition. A time interval description consists of a UT offset in
signed +-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.

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 "-" or
is "zzz".

In double-quoted strings, escape sequences represent unusual
characters. The escape sequences are \s for space, and \", \\, \f,
\n, \r, \t, and \v with their usual meaning in the C programming
language. E.g., the double-quoted string ""CET\s\"\\"" represents
the character sequence "CET "\".

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.)

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

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.

Here are excerpts from another example:

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

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.

LIMITATIONS

Time discontinuities are found by sampling the results returned by
localtime(3) at twelve-hour intervals. This works in all real-world
cases; one can construct artificial time zones for which this fails.

In the -v and -V output, "UT" denotes the value returned by
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 "UTC" for newer and
"UT" for older timestamps, partly because the exact date of the
introduction of UTC is problematic.

FILES

/usr/share/lib/zoneinfo
Standard zone information directory

INTERFACE STABILITY

Uncommitted

The zdump utility is not maintained directly by illumos.