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I was wondering if there is any way in C to read the date and time
(either system time or from the keyboard) and see if it falls between
certain date and time? I am not sure how to compare the 2 entries of
date/time. Any help on this would be great.

Thanks

wrote On 02/01/06 16:31,:
> I was wondering if there is any way in C to read the date and time
> (either system time or from the keyboard) and see if it falls between
> certain date and time? I am not sure how to compare the 2 entries of
> date/time. Any help on this would be great.

You can get the current time as a time_t value by
calling the time() function.

You can construct the time_t value for a given
date and time by inserting values in a struct tm and
calling mktime().

You can compare two time_t values by passing them
to difftime() and checking the sign of the result.

Error-checking omitted:

time_t early, later, now;
struct tm when;

/* Get the early time: 2006-Mar-01 12:34:56 (local) */
when.tm_year = 2006 - 1900; /* years since 1900 */
when.tm_mon = 3 - 1; /* months since January */
when.tm_mday = 1;
when.tm_hour = 12;
when.tm_min = 34;
when.tm_sec = 56;
when.tm_isdst = -1; /* DST status unknown */
early = mktime(&when);

/* Get the later time: 2006-May-07 08:09:10 (local) */
when.tm_year = 2006 - 1900;
when.tm_mon = 5 - 1;
when.tm_mday = 7;
when.tm_hour = 8;
when.tm_min = 9;
when.tm_sec = 10;
when.tm_isdst = -1;
later = mktime(&when);

now = time(NULL);
if (difftime(now, early) < 0)
printf ("Earlier than early\n");
else if (difftime(now, later) > 0)
printf ("Later than late\n");
else
printf ("Now is the time for all good parties\n"
"to come to the aid of Man.\n");

--

In article < .com>,
<> wrote:
>I was wondering if there is any way in C to read the date and time
>(either system time or from the keyboard) and see if it falls between
>certain date and time? I am not sure how to compare the 2 entries of
>date/time. Any help on this would be great.

time_t currenttime = time();
if (currenttime != (time_t)-1) {
struct tm *tf = localtime(currenttime);
/* now examine tf->tm_year tm_mon tm_hour tm_min tm_sec,
taking into account that tm_year is relative to 1900
and tm_mon is 0 for january */
}


Be careful, though, to take into account the timezone and the
"daylight savings time". You need to precisely define what it means
for a particular time to fall between two other times considering
these factors. Suppose for example that a reference time falls
within the hour that daylight time is changing -- there might not
*be* a 01:15 on a particular day, so what do you do if you
are given that as a reference time? Or there might be -two- 01:15's
on a day about 6 months later.

Oh yes, and also watch out for Feb 29th
--
All is vanity. -- Ecclesiastes

Hi,

you can get the time using time_t structure included in time.h. Here is
code to read the current time from your system.

#include <stdio.h>
#include <time.h>
#include<conio.h>
int main ()
{
time_t rawtime;
time ( &rawtime );
printf ( "Current date and time are: %s", ctime(&rawtime));
getch();
return 0;
}

Cheers
Shastri




wrote:
> I was wondering if there is any way in C to read the date and time
> (either system time or from the keyboard) and see if it falls between
> certain date and time? I am not sure how to compare the 2 entries of
> date/time. Any help on this would be great.
>
> Thanks

"Shastri" <> writes:
> you can get the time using time_t structure included in time.h. Here is
> code to read the current time from your system.
>
> #include <stdio.h>
> #include <time.h>
> #include<conio.h>
> int main ()
> {
> time_t rawtime;
> time ( &rawtime );
> printf ( "Current date and time are: %s", ctime(&rawtime));
> getch();
> return 0;
> }

Please don't top-post. Your response goes below, or interspersed
with, any quoted text.

<conio.h> is not a standard C function, and getch() is not a standard
C function.

Your output should be terminated with a '\n'; otherwise it's not
guaranteed to appear.

--
Keith Thompson (The_Other_Keith) kst- <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

Keith Thompson wrote:
> "Shastri" <> writes:
> > you can get the time using time_t structure included in time.h. Here is
> > code to read the current time from your system.
> >
> > #include <stdio.h>
> > #include <time.h>
> > #include<conio.h>
> > int main ()
> > {
> > time_t rawtime;
> > time ( &rawtime );
> > printf ( "Current date and time are: %s", ctime(&rawtime));
> > getch();
> > return 0;
> > }

[snip]

> Your output should be terminated with a '\n'; otherwise it's not
> guaranteed to appear.

The string formed by ctime contains a newline.

Robert Gamble

"Robert Gamble" <> writes:
> Keith Thompson wrote:
>> "Shastri" <> writes:
[...]
>> > printf ( "Current date and time are: %s", ctime(&rawtime));
[snip]
>> Your output should be terminated with a '\n'; otherwise it's not
>> guaranteed to appear.
>
> The string formed by ctime contains a newline.

So it does. Thanks.

--
Keith Thompson (The_Other_Keith) kst- <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.