how to make program send SIGINT to itself in C?

Question

I want to know what happens to this program at POSITION A, POSITION B and POSITION C if one were to press CTRL-C at those positions. I know that you are supposed to implement a SIGINT, but I am not sure how exactly to implement it. Please help.

#include<stdio.h> 
#include<signal.h> 
#include<wait.h> 
int x = 5;

void handler(int sig) {
    x += 3;
    fprintf(stderr, "inside %d ", x);
}

int main() {
    fprintf(stderr, "start ");
    //                             POSITION A
    struct sigaction act;
    act.sa_handler = handler;
    act.sa_flags = 0;
    sigemptyset(&act.sa_mask);
    sigaction(SIGINT,&act,NULL);

    //                             POSITION B
    x += 2;

    //                             POSITION C
    fprintf(stderr, "outside %d", x);

    return 0;
}

Answer 1

You can send yourself a signal with kill and getpid .

$ gcc -o t2 t.c && ./t2
signal 2
sent signal

#include<stdio.h>
#include<unistd.h>
#include<signal.h>

void handler(int sig) {
    fprintf(stderr, "signal %d \n", sig);
}

int main() {
    struct sigaction act;
    act.sa_handler = handler;
    act.sa_flags = 0;
    sigemptyset(&act.sa_mask);
    sigaction(SIGINT,&act,NULL);
    kill(getpid(),SIGINT);
    fprintf(stderr,"sent signal\n");
}

Answer 2

Use the kill system call.

kill(getpid(), SIGINT);