newlib/libc/time/tzset.c

   1 /*
   2 FUNCTION
   3 <<tzset>>---set timezone characteristics from <[TZ]> environment variable
   4
   5 INDEX
   6         tzset
   7 INDEX
   8         _tzset_r
   9
  10 SYNOPSIS
  11         #include <time.h>
  12         void tzset(void);
  13         void _tzset_r (struct _reent *<[reent_ptr]>);
  14
  15 DESCRIPTION
  16 <<tzset>> examines the <[TZ]> environment variable and sets up the three
  17 external variables: <<_timezone>>, <<_daylight>>, and <<tzname>>.
  18 The value of <<_timezone>> shall be the offset from the current time
  19 to Universal Time.
  20 The value of <<_daylight>> shall be 0 if there is no daylight savings
  21 time for the current time zone, otherwise it will be non-zero.
  22 The <<tzname>> array has two entries: the first is the designation of the
  23 standard time period, the second is the designation of the alternate time
  24 period.
  25
  26 The <[TZ]> environment variable is expected to be in the following POSIX
  27 format (spaces inserted for clarity):
  28
  29     <[std]> <[offset1]> [<[dst]> [<[offset2]>] [,<[start]> [/<[time1]>], <[end]> [/<[time2]>]]]
  30
  31 where:
  32
  33 <[std]> is the designation for the standard time period (minimum 3,
  34 maximum <<TZNAME_MAX>> bytes) in one of two forms:
  35
  36 *- quoted within angle bracket '<' '>' characters: portable numeric
  37 sign or alphanumeric characters in the current locale; the
  38 quoting characters are not included in the designation
  39
  40 *- unquoted: portable alphabetic characters in the current locale
  41
  42 <[offset1]> is the value to add to local standard time to get Universal Time;
  43 it has the format:
  44
  45     [<[S]>]<[hh]>[:<[mm]>[:<[ss]>]]
  46
  47     where:
  48
  49     <[S]> is an optional numeric sign character; if negative '-', the
  50     time zone is East of the International Reference
  51     Meridian; else it is positive and West, and '+' may be used
  52
  53     <[hh]> is the required numeric hour between 0 and 24
  54
  55     <[mm]> is the optional numeric minute between 0 and 59
  56
  57     <[ss]> is the optional numeric second between 0 and 59
  58
  59 <[dst]> is the designation of the alternate (daylight saving or
  60 summer) time period, with the same limits and forms as
  61 the standard time period designation
  62
  63 <[offset2]> is the value to add to local alternate time to get
  64 Universal Time; it has the same format as <[offset1]>
  65
  66 <[start]> is the date in the year that alternate time starts;
  67 the form may be one of:
  68 (quotes "'" around characters below are used only to distinguish literals)
  69
  70     <[n]>       zero based Julian day (0-365), counting February 29 Leap days
  71
  72     'J'<[n]>    one based Julian day (1-365), not counting February 29 Leap
  73     days; in all years day 59 is February 28 and day 60 is March 1
  74
  75     'M'<[m]>'.'<[w]>'.'<[d]>
  76     month <[m]> (1-12) week <[w]> (1-5) day <[d]> (0-6) where week 1 is
  77     the first week in month <[m]> with day <[d]>; week 5 is the last
  78     week in the month; day 0 is Sunday
  79
  80 <[time1]> is the optional local time that alternate time starts, in
  81 the same format as <[offset1]> without any sign, and defaults
  82 to 02:00:00
  83
  84 <[end]> is the date in the year that alternate time ends, in the same
  85 forms as <[start]>
  86
  87 <[time2]> is the optional local time that alternate time ends, in
  88 the same format as <[offset1]> without any sign, and
  89 defaults to 02:00:00
  90
  91 Note that there is no white-space padding between fields. Also note that
  92 if <[TZ]> is null, the default is Universal Time which has no daylight saving
  93 time. If <[TZ]> is empty, the default EST5EDT is used.
  94
  95 The function <<_tzset_r>> is identical to <<tzset>> only it is reentrant
  96 and is used for applications that use multiple threads.
  97
  98 RETURNS
  99 There is no return value.
 100
 101 PORTABILITY
 102 <<tzset>> is part of the POSIX standard.
 103
 104 Supporting OS subroutine required: None
 105 */
 106
 107 #include <_ansi.h>
 108 #include <reent.h>
 109 #include <time.h>
 110 #include "local.h"
 111
 112 void
 113 _tzset_unlocked (void)
 114 {
 115   _tzset_unlocked_r (_REENT);
 116 }
 117
 118 void
 119 tzset (void)
 120 {
 121   TZ_LOCK;
 122   _tzset_unlocked_r (_REENT);
 123   TZ_UNLOCK;
 124 }