huschi.net

MKTIME(3P)                 POSIX Programmer's Manual                MKTIME(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
       mktime -- convert broken-down time into time since the Epoch
SYNOPSIS
       #include <time.h>
       time_t mktime(struct tm *timeptr);
DESCRIPTION
       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.1-2008
       defers to the ISO C standard.
       The  mktime() function shall convert the broken-down time, expressed as
       local time, in the structure pointed to by timeptr, into a  time  since
       the  Epoch  value with the same encoding as that of the values returned
       by time().  The original values of the tm_wday and  tm_yday  components
       of the structure are ignored, and the original values of the other com-
       ponents are not restricted to the ranges described in <time.h>.
       A positive or 0 value for tm_isdst shall cause mktime() to presume ini-
       tially that Daylight Savings Time, respectively, is or is not in effect
       for the specified time. A  negative  value  for  tm_isdst  shall  cause
       mktime()  to  attempt  to determine whether Daylight Savings Time is in
       effect for the specified time.
       Local timezone information shall  be  set  as  though  mktime()  called
       tzset().
       The  relationship  between  the  tm  structure (defined in the <time.h>
       header) and the time in seconds since the  Epoch  is  that  the  result
       shall be as specified in the expression given in the definition of sec-
       onds since the Epoch (see the Base Definitions volume of  POSIX.1-2008,
       Section  4.15,  Seconds Since the Epoch) corrected for timezone and any
       seasonal time adjustments, where the names in the structure and in  the
       expression correspond.
       Upon  successful completion, the values of the tm_wday and tm_yday com-
       ponents of the structure shall be set appropriately, and the other com-
       ponents  are  set  to represent the specified time since the Epoch, but
       with their values forced to the ranges indicated in the <time.h> entry;
       the  final  value  of tm_mday shall not be set until tm_mon and tm_year
       are determined.
RETURN VALUE
       The mktime() function shall return the specified time since  the  Epoch
       encoded  as a value of type time_t.  If the time since the Epoch cannot
       be represented, the function shall return the value (time_t)-1 and  set
       errno to indicate the error.
ERRORS
       The mktime() function shall fail if:
       EOVERFLOW
              The result cannot be represented.
       The following sections are informative.
EXAMPLES
       What day of the week is July 4, 2001?
           #include <stdio.h>
           #include <time.h>
           struct tm time_str;
           char daybuf[20];
           int main(void)
           {
               time_str.tm_year = 2001 -- 1900;
               time_str.tm_mon = 7 -- 1;
               time_str.tm_mday = 4;
               time_str.tm_hour = 0;
               time_str.tm_min = 0;
               time_str.tm_sec = 1;
               time_str.tm_isdst = -1;
               if (mktime(&time_str) == -1)
                   (void)puts("-unknown-");
               else {
                   (void)strftime(daybuf, sizeof(daybuf), "%A", &time_str);
                   (void)puts(daybuf);
               }
               return 0;
           }
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       asctime(),  clock(),  ctime(), difftime(), gmtime(), localtime(), strf-
       time(), strptime(), time(), tzset(), utime()
       The Base Definitions volume  of  POSIX.1-2008,  Section  4.15,  Seconds
       Since the Epoch, <time.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                           MKTIME(3P)