Originální popis anglicky:
gmtime, gmtime_r - convert a time value to a broken-down UTC time
Návod, kniha: POSIX Programmer's Manual
#include <time.h>
struct tm *gmtime(const time_t *
timer);
struct tm *gmtime_r(const time_t *restrict timer,
struct tm *restrict
result );
For
gmtime(): The functionality described on this reference page is
aligned with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This volume of
IEEE Std 1003.1-2001 defers to the ISO C standard.
The
gmtime() function shall convert the time in seconds since the Epoch
pointed to by
timer into a broken-down time, expressed as Coordinated
Universal Time (UTC).
The relationship between a time in seconds since the Epoch used as an argument
to
gmtime() and the
tm structure (defined in the
<time.h> header) is that the result shall be as specified in the
expression given in the definition of seconds since the Epoch (see the Base
Definitions volume of IEEE Std 1003.1-2001, Section 4.14,
Seconds Since the Epoch), where the names in the structure and in the
expression correspond.
The same relationship shall apply for
gmtime_r().
The
gmtime() function need not be reentrant. A function that is not
required to be reentrant is not required to be thread-safe.
The
asctime(),
ctime(),
gmtime(), and
localtime()
functions shall return values in one of two static objects: a broken-down time
structure and an array of type
char. Execution of any of the functions
may overwrite the information returned in either of these objects by any of
the other functions.
The
gmtime_r() function shall convert the time in seconds since the Epoch
pointed to by
timer into a broken-down time expressed as Coordinated
Universal Time (UTC). The broken-down time is stored in the structure referred
to by
result. The
gmtime_r() function shall also return the
address of the same structure.
Upon successful completion, the
gmtime() function shall return a pointer
to a
struct tm. If an error is detected,
gmtime() shall return a
null pointer and set
errno to indicate the error.
Upon successful completion,
gmtime_r() shall return the address of the
structure pointed to by the argument
result. If an error is detected,
gmtime_r() shall return a null pointer.
The
gmtime() function shall fail if:
- EOVERFLOW
- The result cannot be represented.
The following sections are informative.
None.
The
gmtime_r() function is thread-safe and returns values in a
user-supplied buffer instead of possibly using a static data area that may be
overwritten by each call.
None.
None.
asctime() ,
clock() ,
ctime() ,
difftime() ,
localtime() ,
mktime() ,
strftime() ,
strptime() ,
time() ,
utime() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<time.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
