установить информацию о преобразовании часового пояса (set timezone conversion information)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
daylight, timezone, tzname, tzset — set timezone conversion
information
Синопсис (Synopsis)
#include <time.h>
extern int daylight;
extern long timezone;
extern char *tzname[2];
void tzset(void);
Описание (Description)
The tzset() function shall use the value of the environment
variable TZ to set time conversion information used by ctime(3p),
localtime(3p), mktime(3p), and strftime(3p). If TZ is absent
from the environment, implementation-defined default timezone
information shall be used.
The tzset() function shall set the external variable tzname as
follows:
tzname[0] = "std";
tzname[1] = "dst";
where std and dst are as described in the Base Definitions volume
of POSIX.1‐2017, Chapter 8, Environment Variables.
The tzset() function also shall set the external variable
daylight to 0 if Daylight Savings Time conversions should never
be applied for the timezone in use; otherwise, non-zero. The
external variable timezone shall be set to the difference, in
seconds, between Coordinated Universal Time (UTC) and local
standard time.
If a thread accesses tzname, daylight, or timezone directly while
another thread is in a call to tzset(), or to any function that
is required or allowed to set timezone information as if by
calling tzset(), the behavior is undefined.
Возвращаемое значение (Return value)
The tzset() function shall not return a value.
Ошибки (Error)
No errors are defined.
The following sections are informative.
Примеры (Examples)
Example TZ variables and their timezone differences are given in
the table below:
┌───────────┬────────────┐
│ TZ │ timezone │
├───────────┼────────────┤
│EST5EDT │ 5*60*60 │
│GMT0 │ 0*60*60 │
│JST-9 │ -9*60*60 │
│MET-1MEST │ -1*60*60 │
│MST7MDT │ 7*60*60 │
│PST8PDT │ 8*60*60 │
└───────────┴────────────┘
Использование в приложениях (Application usage)
Since the ctime(), localtime(), mktime(), strftime(), and
strftime_l() functions are required to set timezone information
as if by calling tzset(), there is no need for an explicit
tzset() call before using these functions. However, portable
applications should call tzset() explicitly before using
ctime_r() or localtime_r() because setting timezone information
is optional for those functions.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
ctime(3p), localtime(3p), mktime(3p), strftime(3p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, time.h(0p)
