Time Conversion

[moni]

I have 2 time values:


System time and an input from the user.


1) System time is in the form of seconds from 1/1/1970 calculated by
using


time_t secs;
SYSTEMTIME stime;


time(&secs);


2) The input from the user is in form hr:min:sec which is a string
value.


But the seperate values have been obtained by using


sscanf(storedTi meValue, "%d:%d:%d", &hour,&minutes, &seconds);


So now I have 3 integer values for hour,minutes and seconds.


3) I have a function which calculates the time difference between 2
time values,
but both these time values need to be seconds from 1/1/1970.


Is there any way by which,I could convert the user given time into time

in seconds from 1/1/1970,
so that I can get the difference between the system time and the user
given time.

[Richard Bos]

Re: Time Conversion

"moni" <mons.2110@gmai l.comwrote:

I have 2 time values: System time and an input from the user.

1) System time is in the form of seconds from 1/1/1970

ISO C doesn't guarantee that. Nor does it give you any way to do maths
on time_t. But all is not lost...

time_t secs;
SYSTEMTIME stime;

This type doesn't exist in C. It's also not necessary.

time(&secs);

2) The input from the user is in form hr:min:sec which is a string
value. But the seperate values have been obtained by using

sscanf(storedTi meValue, "%d:%d:%d", &hour,&minutes, &seconds);

So now I have 3 integer values for hour,minutes and seconds.

Good. Note that you'll still need the relevant date, but that can be had
from the time_t you got from time().

3) I have a function which calculates the time difference between 2
time values, but both these time values need to be seconds from 1/1/1970.

Then you have the wrong function. The right function to calculate the
difference between two time_t's is in <time.h>, and it's called
difftime(). This must work regardless of the format of a time_t, and is
therefore superior to a home-made function which assumes an epoch of
1970/01/01 and a resolution of 1 second.

Is there any way by which,I could convert the user given time into time
in seconds from 1/1/1970,

No. However, there _is_ a way to convert it into a time_t. It's a bit
roundabout, but it does work anywhere.
First you convert your time_t into a struct tm, using either gmtime() or
localtime(). Next you set the tm_hour, tm_min and tm_sec members of this
struct tm to the values you got from sscanf(). Then you convert this
struct tm back to a second time_t, using mktime(). Finally you subtract
both time_t's using difftime(), and Bob's your uncle. All of these
functions are ISO Standard C, and all (except sscanf(), obviously) can
be found in <time.h>.

Richard

[Richard Heathfield]

Re: Time Conversion

Richard Bos said:

<snip>

ISO C doesn't [...] give you any way to do maths on time_t.

....except for difftime.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

[moni]

Re: Time Conversion


struct tm *newtime, *oldtime;

time_t result;
time_t long_time;
double elapsed_time;


sscanf(stringto convert, "%d:%d:%d", &hour,&minutes, &seconds);


time( &long_time ); /* Get time as long integer. */

newtime = localtime( &long_time ); /* Convert to local time. */
oldtime = localtime( &long_time );




newtime->tm_isdst = 0;
newtime->tm_hour = hour;
newtime->tm_min = minutes;
newtime->tm_sec = seconds;
//newtime->tm_year = 2006;

result = mktime(&newtime );



elapsed_time = difftime( result, long_time );
printf("time is %d, %d", result, long_time);



Here the result always come s to -1, ie. mktime is always returning -1.

Can you tell me the reason?

Thanx alot..

Richard Heathfield wrote:

Richard Bos said:
>
<snip>
>

ISO C doesn't [...] give you any way to do maths on time_t.

>
...except for difftime.
>
--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

[attn.steven.kuo@gmail.com]

Re: Time Conversion

moni wrote:

struct tm *newtime, *oldtime;
>
time_t result;
time_t long_time;
double elapsed_time;
>
>
sscanf(stringto convert, "%d:%d:%d", &hour,&minutes, &seconds);
>
>
time( &long_time ); /* Get time as long integer. */
>
newtime = localtime( &long_time ); /* Convert to local time. */
oldtime = localtime( &long_time );
>
>
>
>
newtime->tm_isdst = 0;
newtime->tm_hour = hour;
newtime->tm_min = minutes;
newtime->tm_sec = seconds;
//newtime->tm_year = 2006;
>
result = mktime(&newtime );
>
>
>
elapsed_time = difftime( result, long_time );
printf("time is %d, %d", result, long_time);
>
>
>
Here the result always come s to -1, ie. mktime is always returning -1.
>
Can you tell me the reason?

The argument to mktime is a pointer to struct tm:

So try:

result = mktime(newtime) ;

instead of

result = mktime(&newtime );

If you want to throw in error checking, then:

if ( (result = mktime(newtime) ) == (time_t)-1)
{
fprintf(stderr, "Bad mktime\n");
return EXIT_FAILURE;
}

--
Hope this helps,
Steven

[moni]

Re: Time Conversion

hey...

Thanx alot...

that worked..!


attn.steven.kuo @gmail.com wrote:

moni wrote:

struct tm *newtime, *oldtime;

time_t result;
time_t long_time;
double elapsed_time;


sscanf(stringto convert, "%d:%d:%d", &hour,&minutes, &seconds);


time( &long_time ); /* Get time as long integer. */

newtime = localtime( &long_time ); /* Convert to local time. */
oldtime = localtime( &long_time );




newtime->tm_isdst = 0;
newtime->tm_hour = hour;
newtime->tm_min = minutes;
newtime->tm_sec = seconds;
//newtime->tm_year = 2006;

result = mktime(&newtime );



elapsed_time = difftime( result, long_time );
printf("time is %d, %d", result, long_time);



Here the result always come s to -1, ie. mktime is always returning -1.

Can you tell me the reason?

>
>
The argument to mktime is a pointer to struct tm:
>
So try:
>
result = mktime(newtime) ;
>
instead of
>
result = mktime(&newtime );
>
If you want to throw in error checking, then:
>
if ( (result = mktime(newtime) ) == (time_t)-1)
{
fprintf(stderr, "Bad mktime\n");
return EXIT_FAILURE;
}
>
--
Hope this helps,
Steven

[Jordan Abel]

Re: Time Conversion

2006-11-07 <1162926494.233 238.42790@i42g2 000cwa.googlegr oups.com>,
moni wrote:

hey...
>
Thanx alot...
>
that worked..!

Top-posting isn't good.

Anyway - you should be aware a tm_year value of 2006 refers to the year
3906. The proper tm_year value for this year is 106.

[moni]

Re: Time Conversion

Why is that?

i dint get it...

thanx..


Jordan Abel wrote:

2006-11-07 <1162926494.233 238.42790@i42g2 000cwa.googlegr oups.com>,
moni wrote:

hey...

Thanx alot...

that worked..!

>
Top-posting isn't good.
>
Anyway - you should be aware a tm_year value of 2006 refers to the year
3906. The proper tm_year value for this year is 106.

[Asbjørn Sæbø]

OT: Q: C Unleashed - availability


The book "C Unleashed" seems to be out of print and somewhat hard to
come by. Can anybody (Mr. Heathfield, for example) tell me whether
there are any plans for a reprint or a new edition?

(Sorry for the somewhat off-topic post. I tried to contact
Mr. Heathfield at the email address he specifies at the bottom of his
posts, but it came back with a message saying:
"Your message cannot be delivered to the following recipients:

Recipient address: <xxx>@<xxxx>.or g.uk
Reason: Illegal host/domain name found")

Asbjørn Sæbø
--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[John Gordon]

Re: Time Conversion

In <1162933374.209 969.30560@k70g2 000cwa.googlegr oups.com"moni" <mons.2110@gmai l.comwrites:

Anyway - you should be aware a tm_year value of 2006 refers to the year
3906. The proper tm_year value for this year is 106.

Why is that?
i dint get it...

Because the definition of the tm_year field is "years since 1900", not
"years since 0".

--
John Gordon "... What with you being his parents and all,
gordon@panix.co m I think that you could be trusted not to shaft
him." -- Robert Chang, rec.games.board

[Richard Heathfield]

Re: OT: Q: C Unleashed - availability

Asbj?rn Sæb? said:

>
The book "C Unleashed" seems to be out of print and somewhat hard to
come by.

Yes, I'm afraid that's true. "C Unleashed" went out of print earlier this
year IIRC, and as far as I know there are no plans for a re-print or a new
edition. :-(

(Sorry for the somewhat off-topic post. I tried to contact
Mr. Heathfield at the email address he specifies at the bottom of his
posts, but it came back with a message saying:
"Your message cannot be delivered to the following recipients:

Mea culpa. The mail forwarding is broken at present, and I haven't got
around to contacting the forwarder to find out why. I'll try to remember to
do that tomorrow.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: er, none at the moment.

[Asbjørn Sæbø]

Re: OT: Q: C Unleashed - availability

Richard Heathfield <invalid@invali d.invalidwrites :

Asbj?rn Sæb? said:
>

The book "C Unleashed" seems to be out of print and somewhat hard to
come by.

>
Yes, I'm afraid that's true. "C Unleashed" went out of print earlier this
year IIRC, and as far as I know there are no plans for a re-print or a new
edition. :-(

OK, thanks for the information. I'll have to look around for a bit,
then.

Asbjørn
--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Andrew Poelstra]

Re: OT: Q: C Unleashed - availability

On Tue, 2006-11-07 at 22:23 +0100, Asbjørn Sæbø wrote:

The book "C Unleashed" seems to be out of print and somewhat hard to
come by. Can anybody (Mr. Heathfield, for example) tell me whether
there are any plans for a reprint or a new edition?

(Sorry for the somewhat off-topic post. I tried to contact
Mr. Heathfield at the email address he specifies at the bottom of his
posts, but it came back with a message saying:
"Your message cannot be delivered to the following recipients:

Recipient address: <xxx>@<xxxx>.or g.uk
Reason: Illegal host/domain name found")

I got my copy at Half Price Computer Books. I had requested it
from my library, but they denied it on the grounds that it was
"older" and "high priced".

You may find that contacting Sams Publishing will get you a
better answer than this group will.

--
Andrew Poelstra <http://www.wpsoftware. net>
For email, use 'apoelstra' at the above site.
"You're only smart on the outside." -anon.

[Keith Thompson]

Re: Time Conversion

"moni" <mons.2110@gmai l.comwrites:

Why is that?
>
i dint get it...

You didn't get what? If you didn't get Jordan's advice to avoid
top-posting, read the following:

http://www.caliburn.nl/topposting.html

http://www.cpax.org.uk/prg/writings/topposting.php

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <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.

[Nelu]

Re: OT: Q: C Unleashed - availability



On Nov 7, 5:53 pm, Asbjørn Sæbø <a...@stud.ntnu .nowrote:

Richard Heathfield <inva...@invali d.invalidwrites :

Asbj?rn Sæb? said:

>

The book "C Unleashed" seems to be out of print and somewhat hard to
come by.

>

Yes, I'm afraid that's true. "C Unleashed" went out of print earlier this
year IIRC, and as far as I know there are no plans for a re-print or a new
edition. :-(

OK, thanks for the information. I'll have to look around for a bit,
then.

They still have it on Amazon if you have nothing against used books.

--
Ioan - Ciprian Tandau
tandau _at_ freeshell _dot_ org (hope it's not too late)
(... and that it still works...)