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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 dif-
       fer (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 con-
       flict 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 defi-
       nition of seconds since the Epoch (see the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.14,  Sec-
       onds 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.

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(), strftime(), 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, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, 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)