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124 lines
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124 lines
5.3 KiB
HTML
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<a name="tzset"></a>
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<div class="header">
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<p>
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Previous: <a href="_005f_005ftz_005flock.html#g_t_005f_005ftz_005flock" accesskey="p" rel="prev">__tz_lock</a>, Up: <a href="Timefns.html#Timefns" accesskey="u" rel="up">Timefns</a> [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
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<a name="tzset_002d_002d_002dset-timezone-characteristics-from-TZ-environment-variable"></a>
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<h3 class="section">8.11 <code>tzset</code>—set timezone characteristics from TZ environment variable</h3>
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<a name="index-tzset"></a>
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<a name="index-_005ftzset_005fr"></a>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">#include <time.h>
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void tzset(void);
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void _tzset_r (struct _reent *<var>reent_ptr</var>);
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</pre></div>
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<p><strong>Description</strong><br>
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<code>tzset</code> examines the TZ environment variable and sets up the three
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external variables: <code>_timezone</code>, <code>_daylight</code>, and <code>tzname</code>. The
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value of <code>_timezone</code> shall be the offset from the current time zone
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to GMT. The value of <code>_daylight</code> shall be 0 if there is no daylight
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savings time for the current time zone, otherwise it will be non-zero.
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The <code>tzname</code> array has two entries: the first is the name of the
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standard time zone, the second is the name of the daylight-savings time
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zone.
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</p>
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<p>The TZ environment variable is expected to be in the following POSIX
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format:
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</p>
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<p>stdoffset1[dst[offset2][,start[/time1],end[/time2]]]
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</p>
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<p>where: std is the name of the standard time-zone (minimum 3 chars)
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offset1 is the value to add to local time to arrive at Universal time
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it has the form: hh[:mm[:ss]]
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dst is the name of the alternate (daylight-savings) time-zone (min 3 chars)
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offset2 is the value to add to local time to arrive at Universal time
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it has the same format as the std offset
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start is the day that the alternate time-zone starts
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time1 is the optional time that the alternate time-zone starts
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(this is in local time and defaults to 02:00:00 if not specified)
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end is the day that the alternate time-zone ends
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time2 is the time that the alternate time-zone ends
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(it is in local time and defaults to 02:00:00 if not specified)
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</p>
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<p>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 GMT which has no daylight-savings
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time. If TZ is empty, the default EST5EDT is used.
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</p>
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<p>The function <code>_tzset_r</code> is identical to <code>tzset</code> only it is reentrant
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and is used for applications that use multiple threads.
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</p>
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<br>
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<p><strong>Returns</strong><br>
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There is no return value.
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</p>
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<br>
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<p><strong>Portability</strong><br>
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<code>tzset</code> is part of the POSIX standard.
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</p>
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<p>Supporting OS subroutine required: None
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</p>
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<br>
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<p>
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Previous: <a href="_005f_005ftz_005flock.html#g_t_005f_005ftz_005flock" accesskey="p" rel="prev">__tz_lock</a>, Up: <a href="Timefns.html#Timefns" accesskey="u" rel="up">Timefns</a> [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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