gmtime(3p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

GMTIME(3P)              POSIX Programmer's Manual             GMTIME(3P)

PROLOG         top

       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.

NAME         top

       gmtime, gmtime_r — convert a time value to a broken-down UTC time

SYNOPSIS         top

       #include <time.h>

       struct tm *gmtime(const time_t *timer);
       struct tm *gmtime_r(const time_t *restrict timer,
           struct tm *restrict result);

DESCRIPTION         top

       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.

RETURN VALUE         top

       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.

ERRORS         top

       The gmtime() and gmtime_r() functions shall fail if:

       EOVERFLOW
              The result cannot be represented.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       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.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       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)

COPYRIGHT         top

       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)