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mktime() returns -1

Posted on 2000-03-01
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Last Modified: 2010-04-02
Hi

Here's my code,

------
#include <iostream>
#include <time.h>

struct tm tm_str ;

int main(int argc, char* argv[])
{
  tm_str.tm_mday  = (int) argv[1] ;
  tm_str.tm_mon   = (int) argv[2] ;
  tm_str.tm_year  = (int) argv[3] ;

  tm_str.tm_mon   -= 1 ;
  cout << mktime(&tm_str) << endl ;  
}
------

when i compile and execute this i get the output as -1, instead i need to get the number of seconds since from jan 1, 1970. please help me how should i get this.

--gsbabu
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Question by:gsbabu
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9 Comments
 
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Expert Comment

by:Jan Louwerens
ID: 2573764
make sure that the year you're passing in is actually the number of years since 1900. So, for year 2001, tm_year should be 101.
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Author Comment

by:gsbabu
ID: 2573822
Even though the year has been passed correctly, i get -1 as output.
more helps expected.
--gsbabu
0
 
LVL 22

Accepted Solution

by:
nietod earned 10 total points
ID: 2573862
The entries in argv will be strings (char *).  but the members in the tm structure are integers.  These are different types.  Code like

 tm_str.tm_mday  = (int) argv[1] ;

will just set the tm_mday data member to garbage.

You need to set it to the proper integer value _represented_ by the string.  You can use the atoi() funciton for this, like

 tm_str.tm_mday  = atoi(argv[1]);
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Expert Comment

by:Jan Louwerens
ID: 2573880
oh!! the argv[] array returns char*. You can't just cast the char* to an int. try this instead:


tm_str.tm_mday  = atoi(argv[1]) ;
tm_str.tm_mon   = atoi(argv[2]) ;
tm_str.tm_year  = atoi(argv[3]) ;
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Expert Comment

by:Jan Louwerens
ID: 2573881
Here's a snippet of code I use as a utility:

      int year;
      int month;
      int day;
      int hour;
      int minute;
      int second;

....
  year = atoi(argv[0]);
   if ((year < 1900) || (year > 9999))
   {
      cerr << "year must be in range (1900 - 9999)" << endl;
      resultCode = 1;
   }
   year -= 1900; // struct tm stores as years since 1900

   month = atoi(argv[1]);
   if ((month < 1) || (month > 12))
   {
      cerr << "month must be in range (1 - 12)" << endl;
      resultCode = 1;
   }
   month--; // struct tm stores months as 0-11

   day = atoi(argv[2]);
   if ((day < 1) || (day > 31))
   {
      cerr << "day must be in range (1 - 31)" << endl;
      resultCode = 1;
   }

   if (argc >= 4)
      hour = atoi(argv[3]);
   if ((hour < 0) || (hour > 23))
   {
      cerr << "hour must be in range (0 - 23)" << endl;
      resultCode = 1;
   }

   if (argc >= 5)
      minute = atoi(argv[4]);
   if ((minute < 0) || (minute > 59))
   {
      cerr << "minute must be in range (0 - 59)" << endl;
      resultCode = 1;
   }

   if (argc >= 6)
      second = atoi(argv[5]);
   if ((second < 0) || (second > 59))
   {
      cerr << "second must be in range (0 - 59)" << endl;
      resultCode = 1;
   }

....

   struct tm tmDate;

   tmDate.tm_year = year;
   tmDate.tm_mon = month;
   tmDate.tm_mday = day;
   tmDate.tm_hour = hour;
   tmDate.tm_min = minute;
   tmDate.tm_sec = second;

   cout << mktime(&tmDate);

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Expert Comment

by:Jan Louwerens
ID: 2573886
oops! sorry, nietod, guess you beat me to the punch...
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Expert Comment

by:nietod
ID: 2573901
Your code is a little better though.  Much much more than I woudl do for 10 points.
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Expert Comment

by:Jan Louwerens
ID: 2573947
yeah, well, it was already written... I just cut and pasted it...
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Author Comment

by:gsbabu
ID: 2574011
thanks to both
--gsbabu
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