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| <h3 class="section">8.11 <code>tzset</code>—set timezone characteristics from TZ environment variable</h3> |
| |
| <p><a name="index-tzset-443"></a><a name="index-g_t_005ftzset_005fr-444"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <time.h> |
| void tzset(void); |
| void _tzset_r (struct _reent *); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| <code>tzset</code> examines the TZ environment variable and sets up the three |
| external variables: <code>_timezone</code>, <code>_daylight</code>, and <code>tzname</code>. The |
| value of <code>_timezone</code> shall be the offset from the current time zone |
| to GMT. The value of <code>_daylight</code> shall be 0 if there is no daylight |
| savings time for the current time zone, otherwise it will be non-zero. |
| The <code>tzname</code> array has two entries: the first is the name of the |
| standard time zone, the second is the name of the daylight-savings time |
| zone. |
| |
| <p>The TZ environment variable is expected to be in the following POSIX |
| format: |
| |
| <p>stdoffset1[dst[offset2][,start[/time1],end[/time2]]] |
| |
| <p>where: std is the name of the standard time-zone (minimum 3 chars) |
| offset1 is the value to add to local time to arrive at Universal time |
| it has the form: hh[:mm[:ss]] |
| dst is the name of the alternate (daylight-savings) time-zone (min 3 chars) |
| offset2 is the value to add to local time to arrive at Universal time |
| it has the same format as the std offset |
| start is the day that the alternate time-zone starts |
| time1 is the optional time that the alternate time-zone starts |
| (this is in local time and defaults to 02:00:00 if not specified) |
| end is the day that the alternate time-zone ends |
| time2 is the time that the alternate time-zone ends |
| (it is in local time and defaults to 02:00:00 if not specified) |
| |
| <p>Note that there is no white-space padding between fields. Also note that |
| if TZ is null, the default is Universal GMT which has no daylight-savings |
| time. If TZ is empty, the default EST5EDT is used. |
| |
| <p>The function <code>_tzset_r</code> is identical to <code>tzset</code> only it is reentrant |
| and is used for applications that use multiple threads. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| There is no return value. |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| <code>tzset</code> is part of the POSIX standard. |
| |
| <p>Supporting OS subroutine required: None |
| |
| <p><br> |
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