[SOLVED] Help: C++ program not giving expected output ( timer )

[kingsmasher1]

Hi All,
i have this C++ program. It has a simple for loop which prints numbers from 1 to 20. Between this, execution, the timer expires multiple times, and each time it expires, it should print an output from signal handler.

Unfortunately i am not getting this output. And it is just simply printing the numbers from 1 to 20. Can someone please help me?

Thanks in advance,

kingsmasher1

    #include <stdlib.h>
    #include <unistd.h>
    #include <stdio.h>
    #include <signal.h>
    #include <time.h>
    #define CLOCKID CLOCK_REALTIME
    #define SIG SIGRTMIN
    #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \
    } while (0)
    #include <iostream>

    using namespace std;

    static int flag=0;
    class timer{

    static void
    handler(int sig) {
      printf("Caught signal %d\n", sig);
      ::flag=1;
      signal(sig, handler);
    }

    public:

    void timer_func()
    {
    timer_t timerid;
    struct sigevent sev;
    struct itimerspec its;
    long long freq_nanosecs=1; // The timer frequency in nanosecs
    sigset_t mask;
    struct sigaction sa;

    /* Establish handler for timer signal */

    printf("Establishing handler for signal %d\n", SIG);

    sa.sa_flags = SA_RESETHAND;
    sa.sa_handler = handler;


     /* Create the timer */

     sev.sigev_notify = SIGEV_SIGNAL;
     sev.sigev_signo = SIG;
     sev.sigev_value.sival_ptr = &timerid;

     if (timer_create(CLOCKID, &sev, &timerid) == -1)
       errExit("timer_create");

     printf("timer ID is 0x%lx\n", (long) timerid);

     /* Start the timer */

     its.it_value.tv_sec = freq_nanosecs / 1000000000;
     its.it_value.tv_nsec = freq_nanosecs % 1000000000;
     its.it_interval.tv_sec = its.it_value.tv_sec;
     its.it_interval.tv_nsec = its.it_value.tv_nsec;

     if (timer_settime(timerid, 0, &its, NULL) == -1)
       errExit("timer_settime");
      }
     };

     int main() {
      
       timer ob;
       ob.timer_func();

       for(int i=0; i<20; i++) {
         sleep(1);
       if(flag) {
         cout << "Timer called" << endl;
         flag=0;
        }
       cout << "Printing i: " << i << endl;
      }
     }

But if i set "long long freq_nanosecs = 1" in that also the output is only once from the timer. It should be repeated

[Rubberman]

I don't see where you are calling the sigaction() function in order to enable the handler for the timer signal.

[kingsmasher1]

I don't see where you are calling the sigaction() function in order to enable the handler for the timer signal.

Thanks Rubberman, i just got it correct.