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 (con-
       sult 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 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.

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 Defini-
       tions 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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    GMTIME(3P)