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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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GMTIME(3P) POSIX Programmer's Manual GMTIME(3P)
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.
gmtime, gmtime_r — convert a time value to a broken-down UTC time
#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 POSIX.1‐2017 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 POSIX.1‐2017, Section 4.16,
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 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 and set errno
to indicate the error.
The gmtime() and gmtime_r() functions 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(3p), clock(3p), ctime(3p), difftime(3p), localtime(3p),
mktime(3p), strftime(3p), strptime(3p), time(3p), utime(3p)
The Base Definitions volume of POSIX.1‐2017, Section 4.16,
Seconds Since the Epoch, time.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 GMTIME(3P)
Pages that refer to this page: time.h(0p), asctime(3p), clock(3p), ctime(3p), difftime(3p), localtime(3p), mktime(3p), strftime(3p), time(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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