Обработка сигналов в линуксе

#include <stdio.h>
#include <signal.h>
#include <sys/time.h>

static int count = 0;

struct itimerval timer;

int in = 1;

void sighandler(int sig)
{
    if (sig == SIGALRM)
    {
        count++;
        printf("%d\n", count);

        if (count % 3 == 0)
        {
            timer.it_interval.tv_sec = 0;
            timer.it_value.tv_sec = 0;
            setitimer(ITIMER_REAL, &timer, NULL);
            in = 1;
        }
    }
}
int main()
{
    signal(SIGALRM, sighandler);

    char ch = '0';
    while (1)
    {
        if (in == 1)
        {
            printf("input> ");
            scanf("%c", &ch);
            switch (ch)
            {
                case 's':
                {
                    timer.it_interval.tv_sec = 1;
                    timer.it_value.tv_sec = 1;
                    setitimer(ITIMER_REAL, &timer, NULL);
                    in = 0;
                    break;
                }
                default: break;
            }
        }   
    }
    
    return 0;
}