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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 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  compo-
       nents 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
       IEEE Std 1003.1-2001, Section 4.14, 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.
ERRORS
       No errors are defined.
       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(), 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                           MKTIME(3P)