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C++ Simple Posix Timer

Posted on 2010-09-01
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Last Modified: 2013-11-17
Hey guys,

What's the simplest bare bones method of creating a timer to handle this situation:

I have a program running that will always be getting messages and doing internal processing.  Every 10 seconds on top of this (or some other arbitrary number), I would like to get a signal from a timer which calls one of the methods on a singleton class within the program (just a callback really).

Anyway, I'm aware of the thread synch issues and all, but it's been a while since I've made a timer in a Unix/Linux environment so some code would be useful. :)

Thanks!

-w00te
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Question by:w00te
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Accepted Solution

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jkr earned 500 total points
ID: 33577127
You could use 'setitimer()', which would be used like follows (code taken from http://www.cs.uaf.edu/~olawlor/ref/examples/unix/setitimer.c - see also http://www.cs.uaf.edu/~olawlor/ref/examples/unix/setitimer_pc.c)
/* Orion Lawlor's Short UNIX Examples, olawlor@acm.org 2004/3/5



Shows how to use setitimer to get periodic interrupts.

*/

#include <stdio.h>

#include <stdlib.h>

#include <signal.h>

#include <sys/time.h>

#ifdef SOLARIS /* needed with at least Solaris 8 */

#include <siginfo.h>

#endif



void printStack(const char *where) {

	printf("%s stack: %p\n",where,&where);

}



void signalHandler(int cause, siginfo_t *HowCome, void *ucontext) {

	printStack("signal handler");

}



int main(){ 

	int i;

	struct itimerval itimer;

	

/* Install our SIGPROF signal handler */

        struct sigaction sa;

	

        sa.sa_sigaction = signalHandler;

        sigemptyset( &sa.sa_mask );

        sa.sa_flags = SA_SIGINFO; /* we want a siginfo_t */

        if (sigaction (SIGPROF, &sa, 0)) {

		perror("sigaction");

		exit(1);

        }

	

	printStack("main routine");



/* Request SIGPROF */

	itimer.it_interval.tv_sec=0;

	itimer.it_interval.tv_usec=10*1000;

	itimer.it_value.tv_sec=0;

	itimer.it_value.tv_usec=10*1000;

	setitimer(ITIMER_PROF, &itimer, NULL); 

	

/* Just wait a bit, which should get a few SIGPROFs */

	for (i=0;i<1000*1000*10;i++) {

	}



        return(0);

}

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Expert Comment

by:simoesp
ID: 33577722
You can do something like this:

while (true)
{
while (pendingEvents () )
handleEvens ();
sleep (10);
}
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LVL 12

Author Closing Comment

by:w00te
ID: 33578275
Thanks JKR - worked great.
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LVL 12

Author Comment

by:w00te
ID: 33578280
Oh and thanks for the other answer too, I just didn't want to touch the sleep function if I didnt have to. :)
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