gmtime

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
       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
       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
       The gmtime() and gmtime_r() functions 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 POSIX.1‐2017, Section 4.16, Seconds Since
       the Epoch, <time.h>

COPYRIGHT
       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)