Converts the local time to a calendar value.
#include <time.h>
time_t mktime( struct tm *timeptr );
| timeptr | Pointer to time structure |
The mktime function converts the supplied time structure (possibly incomplete) pointed to by timeptr into a fully defined structure with “normalized” values and then converts it to a time_t calendar time value. The structure for the tm is described in the reference page for asctime.
The converted time has the same encoding as the values returned by the time function. The original values of the tm_wday and tm_yday components of the timeptr structure are ignored, and the original values of the other components are not restricted to their normal ranges.
If successful, mktime sets the values of tm_wday and tm_yday appropriately, and sets the other components to represent the specified calendar time, but with their values forced to the normal ranges; the final value of tm_mday is not set until tm_mon and tm_year are determined.
If timeptr references a date before midnight, December 31, 1899, mktime returns –1.
Note that the gmtime and localtime functions use a single statically allocated buffer for the conversion. If you supply this buffer to mktime, the previous contents will be destroyed.
The mktime function returns the specified calendar time encoded as a value of type time_t. If the calendar time cannot be represented, the function returns the value –1 cast to type time_t.
Standards:ANSI
16-Bit:DOS, QWIN, WIN, WIN DLL
32-Bit:DOS32X
asctime, gmtime, localtime, time
/* MKTIME.C: The example takes a number of days as input and returns
* the time, the current date, and the specified number of days.
*/
#include <time.h>
#include <stdio.h>
void main( void )
{
struct tm when;
time_t now, result;
int days;
time( &now );
when = *localtime( &now );
printf( "Current time is %s\n", asctime( &when ) );
printf( "How many days to look ahead: " );
scanf( "%d", &days );
when.tm_mday = when.tm_mday + days;
if( (result = mktime( &when )) != (time_t)-1 )
printf( "In %d days the time will be %s\n",
days, asctime( &when ) );
else
perror( "mktime failed" );
}
Current time is Sat Jun 19 11:45:20 1999
How many days to look ahead: 23
In 23 days the time will be Mon Jul 12 11:45:20 1999