mktime(3C)                     DG/UX 5.4R3.00                     mktime(3C)


NAME
       mktime - converts a tm structure to a calendar time

SYNOPSIS
       #include <time.h>

       timet mktime (struct tm *timeptr);

DESCRIPTION
       mktime converts the time represented by the tm structure pointed to
       by timeptr into a calendar time (the number of seconds since 00:00:00
       UTC, January 1, 1970).

       The tm structure has the following format.

       struct tm {
            int  tmsec;   /* seconds after the minute [0, 61]  */
            int  tmmin;   /* minutes after the hour [0, 59] */
            int  tmhour;  /* hour since midnight [0, 23] */
            int  tmmday;  /* day of the month [1, 31] */
            int  tmmon;   /* months since January [0, 11] */
            int  tmyear;  /* years since 1900 */
            int  tmwday;  /* days since Sunday [0, 6] */
            int  tmyday;  /* days since January 1 [0, 365] */
            int  tmisdst; /* flag for daylight savings time */
       };

       In addition to computing the calendar time, mktime normalizes the
       supplied tm structure.  The original values of the tmwday and
       tmyday components of the structure are ignored, and the original
       values of the other components are not restricted to the ranges
       indicated in the definition of the structure.  On successful
       completion, the values of the tmwday and tmyday components are set
       appropriately, and the other components are set to represent the
       specified calendar time, but with their values forced to be within
       the appropriate ranges.  The final value of tmmday is not set until
       tmmon and tmyear are determined.

       The original values of the components may be either greater than or
       less than the specified range.  For example, a tmhour of -1 means 1
       hour before midnight, tmmday of 0 means the day preceding the
       current month, and tmmon of -2 means 2 months before January of
       tmyear.

       If tmisdst is positive, the original values are assumed to be in the
       alternate timezone.  If it turns out that the alternate timezone is
       not valid for the computed calendar time, then the components are
       adjusted to the main timezone.  Likewise, if tmisdst is zero, the
       original values are assumed to be in the main timezone and are
       converted to the alternate timezone if the main timezone is not
       valid.  If tmisdst is negative, the correct timezone is determined
       and the components are not adjusted.

       Local timezone information is used as if mktime had called tzset.



Licensed material--property of copyright holder(s)                         1

mktime(3C)                     DG/UX 5.4R3.00                     mktime(3C)


       mktime returns the specified calendar time.  If the calendar time
       cannot be represented, the function returns the value (timet)-1.


   Considerations for Threads Programming
                     +---------+-----------------------------+
                     |         |                      async- |
                     |function | reentrant   cancel   cancel |
                     |         |              point    safe  |
                     +---------+-----------------------------+
                     |mktime   |     Y          N        N   |
                     +---------+-----------------------------+

EXAMPLE
       What day of the week is July 4, 2001?

                #include <stdio.h>
                #include <time.h>

                static char *const wday[] = {
                            "Sunday", "Monday", "Tuesday", "Wednesday",
                            "Thursday", "Friday", "Saturday", "-unknown-"
                };
                struct tm timestr;
                /*...*/
                timestr.tmyear     = 2001 - 1900;
                timestr.tmmon      = 7 - 1;
                timestr.tmmday     = 4;
                timestr.tmhour     = 0;
                timestr.tmmin      = 0;
                timestr.tmsec               = 1;
                timestr.tmisdst    = -1;
                if (mktime(&timestr)== -1)
                    timestr.tmwday=7;
                printf("%s\n", wday[timestr.tmwday]);


SEE ALSO
       reentrant(3), ctime(3C), getenv(3C), timezone(4).

NOTES
       tmyear of the tm structure must be for year 1970 or later.  Calendar
       times before 00:00:00 UTC, January 1, 1970 or after 03:14:07 UTC,
       January 19, 2038 cannot be represented.













Licensed material--property of copyright holder(s)                         2