eintr.c

#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
#include <errno.h>
#include <stdbool.h>

int number = 0;
bool running = true;

void do_nothing(int s) {
    if (number < 0) {
        running = false;
    }
    printf ("Inside signal handler %d %d\n", running, number);
}

void skip_input() {
    printf ("Skipping invalid input...\n");
    int c;
    do {
        c = getchar();
    } while (c != EOF && c != '\n');
    // c is EOF or newline
}
int main() {
    struct sigaction z;
    sigemptyset(&z.sa_mask);
    z.sa_handler = do_nothing;
    sigaction(SIGINT, &z, NULL);

    number = 47;
    do {
        printf ("Enter a number: ");
        errno = 0;
        int how_many_items = scanf("%d", &number);
        if (errno == EINTR) {
            perror("What?");
            printf ("I did not get your input. Last value was %d\n", number);
        } else {
            if (how_many_items == 0) {
                skip_input();
            }
            printf ("You entered %d\n", number);
        }
    } while (number != 0 && running);
    printf ("\nEnd of program\n");
    return 0;
}