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diff --git a/zdump.8.txt b/zdump.8.txt new file mode 100644 index 000000000000..a24d652deac3 --- /dev/null +++ b/zdump.8.txt @@ -0,0 +1,144 @@ +ZDUMP(8) System Manager's Manual ZDUMP(8) + +NAME + zdump - time zone dumper + +SYNOPSIS + zdump [ option ... ] [ zonename ... ] + +DESCRIPTION + Zdump prints the current time in each zonename named on the command + line. + + These options are available: + + --version + Output version information and exit. + + -i (This option is experimental: its behavior may change in future + versions.) Output a description of time intervals. For each + zonename on the command line, output an interval-format + description of the zone. See "INTERVAL FORMAT" below. + + -v Output a verbose description of time intervals. For each + 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 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 the times relative to the extreme time + 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. The lower bound + is exclusive and the upper is inclusive; for example, a loyear + of 1970 excludes a transition occurring at 1970-01-01 00:00:00 + UTC but a hiyear of 1970 includes the transition. 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 zonename determines whether the count includes leap + seconds. As with -c, the cutoff's lower bound is exclusive and + its upper bound is inclusive. + +INTERVAL FORMAT + This format is experimental: it may change in future versions. + + 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 zone name, 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" + - - -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 + + 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" + - - +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 + + 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 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 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 "UTC" for newer and "UT" for older time + stamps, partly because the exact date of the introduction of UTC is + problematic. + +SEE ALSO + newctime(3), tzfile(5), zic(8) + + ZDUMP(8) |