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

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.
NAME
       gmtime, gmtime_r - convert a time value to a broken-down UTC time
SYNOPSIS
       #include <time.h>
       struct tm *gmtime(const time_t *timer);

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

DESCRIPTION
       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  Defi-
       nitions volume of IEEE Std 1003.1-2001, Section 4.14, Seconds Since the
       Epoch), where the names in the structure and in the  expression  corre-
       spond.
       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 struc-
       ture 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 Coordi-
       nated 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
       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.
ERRORS
       The gmtime() function shall fail if:
       EOVERFLOW
              The result cannot be represented.

       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       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
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       asctime(), clock(), ctime(), difftime(), localtime(),  mktime(),  strf-
       time(),  strptime(),  time(),  utime(),  the Base Definitions volume of
       IEEE Std 1003.1-2001, <time.h>
COPYRIGHT
       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 .

IEEE/The Open Group                  2003                           GMTIME(3P)