Signal handler using sigaction and instruction SIGINT. fail with struct variable: no storage size of sa is known

Question

I'm a noob with C programming. I'm just trying to make a program that registers if the user taps three times CRTL+C in three seconds. My problem is that the terminal says always that: no storage size of 'sa' is known. I searched for many examples in the web but it appears always the same problem. Maybe it's a problem withe the include section so I post all my code.

#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include  <stdlib.h>


int counter=0;
int counter2=0;
//time timestart;
//time timeend;
void signalHandler(int signum);
void  ALARMhandler(int sig);
void SIGHUPhandler();
void SIGUSR1handler();


void signalHandler(int signum){ 
alarm(3);
//printf("the signal caught %d\n", signum);
if (signum == SIGUSR1){
        printf("received SIGUSR1\n");
    signal(SIGUSR1, SIGUSR1handler);
    counter++;
    }else if (signum == SIGKILL){
        printf("received SIGKILL\n");
    counter++;
    }else if (signum == SIGSTOP){
        printf("received SIGSTOP\n");
    counter++;
}else if(counter>=3){
    printf("shut program");

}else if (signum == SIGINT){// sorry sigint can't be handled
        printf("received SIGint\n");
    counter++;
}else if(signum== SIGALRM ){
    printf("recived SIGALRM\n");
    signal(SIGALRM, ALARMhandler);
    counter++;
}else if(signum== SIGHUP){
    printf("recived SIGHUP\n");
    signal(SIGHUP, SIGHUPhandler);
}
//exit(signum);
  }


  int main( void )
  {
/* Place your handler somewhere around here */
clock_t timeStart, timeEnd;
printf( "Hello World!\n" );
//for ( ;; )
//{
    /* infinite loop */
//}

struct sigaction sa;
memset (&sa, 0, sizeof(sa));
sa.sa_handler = signalHandler;
//sigemptyset(&sa.sa_mask);
//sa.sa_flags = SA_RESTART;


counter++;

while(counter2<3){
    printf("please press CRTL+C\n");
    timeStart=clock();
    //sigaction(SIGINT, &sa, NULL);
    pause();
    timeEnd=clock();
    if (timeEnd - timeStart < 3){
        counter++;
    }else if(timeEnd - timeStart ==3){
        printf("shutting down\n");
        exit(1);
    }//end esle if


    counter2++;

}
printf("shutting down\n");
return 0;

}

The problem seems to be in this declaration: struct sigaction sa; The terminal says: no storage size of 'sa' is known.

I know that the parameters of struct must be declared but I've seen many examples on the net that doesn't have this declaration. What I'm doing wrong?

Answer 1

I'm guessing that you're compiling under C99. If you are, you need to #define the macro _XOPEN_SOURCE for sigaction and friends to be available. If you compile with the option -D_XOPEN_SOURCE it should work.