Simple C/C++ time question

bpalmer · 03-09-2006, 10:58 AM

Hi,

Recently I started putting together some simple OpenGL code. I'm up to the part where I want to do smooth time-based movement. Unfortunately, I had no clue how to work with time/timers on linux.

I looked at the linux port of this tutorial: http://nehe.gamedev.net/data/lessons....asp?lesson=21 , and it used the following code:

Code:

#include <sys/timeb.h>
#include <stdio.h>

unsigned int getMilliSeconds()
{
    struct timeb tb;
    ftime(&tb);
    return tb.time * 1000 + tb.millitm;
}

However, simply displaying the result of a call to getMilliSeconds() shows a negative number!

Is that supposed to be the number of milliseconds since the system was booted? What is the linux equivalent of GetTickCount() on Windows?

Thank you reading this

cppkid · 03-09-2006, 11:04 AM

Time is never negative, its just because you must be storing the value in some signed variable, and if the value is large then it will set the sign bit and when you display the result, it will give you the negative number....

like if you are using
long t = getMilliSeconds();
try using
unsigned long t = getMilliSeconds();

cppkid · 03-09-2006, 11:06 AM

And i missed one thing...
Sorry there is no alternative to GetTickCount() in linux... You have to do the work some other way... But linux will give you more precision with the timer...

bpalmer · 03-09-2006, 11:14 AM

Ok, I tried storing it into a unsigned long, and it works great!

One more simple question, what is the code for displaying a long in printf() ?

When I do printf("Time: %i\n", timer); it shows a negative number, but cout << timer; shows it correctly.

cppkid · 03-09-2006, 11:27 AM

Printf use following formats...

%d for double
%u for unsigned long
%c for char
%x for displaying HEX
and so on.....

So to print unsigned long you have to use...

printf("Time: %u\n", timer);

bpalmer · 03-09-2006, 11:39 AM

Excellent, thanks alot for the assistance!

cppkid · 03-09-2006, 11:52 AM

Quote:

Originally Posted by bpalmer

Excellent, thanks alot for the assistance!

No problem. Always there...
Just wanted to say that, like my post helped you... So you also try if you can help anyone... That's make a community...

All the best....