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]

"moni" <mo*******@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]

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]

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]

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]

hey...

Thanx alot...

that worked..!
at************* @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]

2006-11-07 <11************ *********@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]

Why is that?

i dint get it...

thanx..
Jordan Abel wrote:

2006-11-07 <11************ *********@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]

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]

In <11************ *********@k70g2 000cwa.googlegr oups.com"moni" <mo*******@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,
go****@panix.co m I think that you could be trusted not to shaft
him." -- Robert Chang, rec.games.board