Listing 7 mktime.c

/*
 * mktime.c
 * pass the month, day, and year;  return
 * the number of seconds from the Epoch
 */
#include <stdio.h>
#include <time.h>

void main(int argc, char **argv)
{
int mm, dd, yy;
struct tm rettm;
time_t tloc;

if(argc != 4)
   {
   printf("-1");
   exit(1);
   }
if ( (mm=atoi(argv[1])) == NULL)
   {
   printf("-2");
   exit(1);
   }
if ( (dd=atoi(argv[2])) == NULL)
   {
   printf("-3");
   exit(1);
   }
if ( (yy=atoi(argv[3])) == NULL)
   {
   printf("-4");
   exit(1);
   } 
/* populate the tm structure with todays data */
time(&tloc); 
rettm=*localtime(&tloc);
/* change values from passed parameters */
rettm.tm_year=yy-1900;
rettm.tm_mon=mm-1;
rettm.tm_mday=dd;

printf("%ld", mktime(&rettm));
exit(0);
}