125 lines
3.7 KiB
C
125 lines
3.7 KiB
C
/*
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FUNCTION
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<<tzset>>---set timezone characteristics from <[TZ]> environment variable
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INDEX
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tzset
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INDEX
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_tzset_r
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SYNOPSIS
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#include <time.h>
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void tzset(void);
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void _tzset_r (struct _reent *<[reent_ptr]>);
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DESCRIPTION
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<<tzset>> examines the <[TZ]> environment variable and sets up the three
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external variables: <<_timezone>>, <<_daylight>>, and <<tzname>>.
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The value of <<_timezone>> shall be the offset from the current time
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to Universal Time.
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The value of <<_daylight>> shall be 0 if there is no daylight savings
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time for the current time zone, otherwise it will be non-zero.
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The <<tzname>> array has two entries: the first is the designation of the
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standard time period, the second is the designation of the alternate time
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period.
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The <[TZ]> environment variable is expected to be in the following POSIX
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format (spaces inserted for clarity):
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<[std]> <[offset1]> [<[dst]> [<[offset2]>] [,<[start]> [/<[time1]>], <[end]> [/<[time2]>]]]
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where:
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<[std]> is the designation for the standard time period (minimum 3,
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maximum <<TZNAME_MAX>> bytes) in one of two forms:
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*- quoted within angle bracket '<' '>' characters: portable numeric
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sign or alphanumeric characters in the current locale; the
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quoting characters are not included in the designation
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*- unquoted: portable alphabetic characters in the current locale
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<[offset1]> is the value to add to local standard time to get Universal Time;
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it has the format:
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[<[S]>]<[hh]>[:<[mm]>[:<[ss]>]]
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where:
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<[S]> is an optional numeric sign character; if negative '-', the
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time zone is East of the International Reference
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Meridian; else it is positive and West, and '+' may be used
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<[hh]> is the required numeric hour between 0 and 24
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<[mm]> is the optional numeric minute between 0 and 59
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<[ss]> is the optional numeric second between 0 and 59
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<[dst]> is the designation of the alternate (daylight saving or
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summer) time period, with the same limits and forms as
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the standard time period designation
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<[offset2]> is the value to add to local alternate time to get
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Universal Time; it has the same format as <[offset1]>
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<[start]> is the date in the year that alternate time starts;
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the form may be one of:
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(quotes "'" around characters below are used only to distinguish literals)
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<[n]> zero based Julian day (0-365), counting February 29 Leap days
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'J'<[n]> one based Julian day (1-365), not counting February 29 Leap
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days; in all years day 59 is February 28 and day 60 is March 1
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'M'<[m]>'.'<[w]>'.'<[d]>
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month <[m]> (1-12) week <[w]> (1-5) day <[d]> (0-6) where week 1 is
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the first week in month <[m]> with day <[d]>; week 5 is the last
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week in the month; day 0 is Sunday
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<[time1]> is the optional local time that alternate time starts, in
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the same format as <[offset1]> without any sign, and defaults
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to 02:00:00
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<[end]> is the date in the year that alternate time ends, in the same
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forms as <[start]>
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<[time2]> is the optional local time that alternate time ends, in
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the same format as <[offset1]> without any sign, and
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defaults to 02:00:00
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Note that there is no white-space padding between fields. Also note that
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if <[TZ]> is null, the default is Universal Time which has no daylight saving
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time. If <[TZ]> is empty, the default EST5EDT is used.
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The function <<_tzset_r>> is identical to <<tzset>> only it is reentrant
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and is used for applications that use multiple threads.
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RETURNS
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There is no return value.
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PORTABILITY
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<<tzset>> is part of the POSIX standard.
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Supporting OS subroutine required: None
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*/
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#include <_ansi.h>
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#include <reent.h>
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#include <time.h>
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#include "local.h"
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void
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_tzset_unlocked (void)
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{
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_tzset_unlocked_r (_REENT);
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}
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void
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tzset (void)
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{
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TZ_LOCK;
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_tzset_unlocked_r (_REENT);
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TZ_UNLOCK;
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}
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