A timer in a thread does not tally with the runtime of the program?

[diskhub]

I am trying to create a game with a few threads running.
And i have create a thread to store the time since the process has run.

The code is:

void * clock_timer(void *arg){
    while(!menuExit){
        tstop = (double)clock()/CLOCKS_PER_SEC;
        ttime= tstop-tstart; /*ttime is how long your code run */
    }
}

But this clock does not sync with the reading i get when i timed my program.

It took 74.44 secnds.
Simulator Bot Exit
Program Destroyed.

real    0m45.061s
user    0m49.338s
sys     0m25.120s

Can anyone tell me how they implement a timer in a thread which can sync with the runtime of the program?

[helios]

Under Linux (and possibly POSIX in general), clock() returns the amount of CPU time used by the process, not any value based on real time. Note that user+sys=74.458 s.
I can't seem to find any way to get the real value.

[Athar]

For measuring real time, there is clock_gettime:
http://linux.die.net/man/3/clock_gettime

[diskhub]

I need some help or advice here:
My intention is clear:
a) I have a thread which does some object creation and i wish to store the time it has been created. Do I use sys, user or real time to store this value?

b) another timer thread will continue to run and if it checks and finds out that a object is outdated (by comparing the date), it will trigger another thread to do something else.

So what kind of time should i store?

thanks in advance

[Athar]

That's rather obvious, assuming you know the difference. So read this:
http://stackoverflow.com/questions/556405/what-do-real-user-and-sys-mean-in-the-output-of-time1

[diskhub]

Sorry, i have read that but i am still confused.
When we use usleep() and sleep(), are they related to REAL or USER time?

[Athar]

Real time... real time is just that, real time.
user+sys time is the time your program spends actually doing something (i.e. not sleeping).