mktime(3p) — Linux manual page


MKTIME(3P)                POSIX Programmer's Manual               MKTIME(3P)

PROLOG         top

       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         top

       mktime — convert broken-down time into time since the Epoch

SYNOPSIS         top

       #include <time.h>

       time_t mktime(struct tm *timeptr);

DESCRIPTION         top

       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 components are not restricted to the ranges described in

       A positive or 0 value for tm_isdst shall cause mktime() to presume
       initially 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

       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
       seconds 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
       components of the structure shall be set appropriately, and the other
       components 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         top

       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         top

       The mktime() function shall fail if:

              The result cannot be represented.

       The following sections are informative.

EXAMPLES         top

       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)
               else {
                   (void)strftime(daybuf, sizeof(daybuf), "%A", &time_str);
               return 0;



RATIONALE         top




SEE ALSO         top

       asctime(3p), clock(3p), ctime(3p), difftime(3p), gmtime(3p),
       localtime(3p), strftime(3p), strptime(3p), time(3p), tzset(3p),

       The Base Definitions volume of POSIX.1‐2008, Section 4.15, Seconds
       Since the Epoch, time.h(0p)

COPYRIGHT         top

       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 Electrical 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 .

       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 .

IEEE/The Open Group                 2013                          MKTIME(3P)

Pages that refer to this page: time.h(0p)asctime(3p)asctime_r(3p)clock(3p)ctime(3p)ctime_r(3p)difftime(3p)gmtime(3p)gmtime_r(3p)localtime(3p)localtime_r(3p)strftime(3p)strftime_l(3p)time(3p)tzname(3p)tzset(3p)