signal handler does not print

Dear all:

How come the program below returns alarm clock but does not print "signal sent!!"?What did I do wrong?

Thanks

Code:

---

/* Using a signal handler */

#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>

sig_atomic_t sigusr1_count = 1;

void handler (int signal_number) {
        printf("signal sent!!\n");
}

int main () {
        int i;
        struct sigaction sa;
        memset (&sa, 0, sizeof(sa));
        sa.sa_handler = handler;
        sigaction (SIGUSR1, &sa, NULL);

        alarm(1);
        //kill (getpid(), SIGUSR1);
        while (1) {
                printf("Hello\n");
        }

        return 0;
}

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Your handler is listening for SIGUSR1, but alarm sends SIGALRM.

alarm
Try "SIGALRM".

sigaction
Note the example code. That may not be the same as memset'ing to 0.

gg

I think I misunderstand the usage of alarm(), is there a way I can make SIGUSR1 to behave like SIGALRM?

Thanks.

Quote:

---

Originally Posted by Codeplug

alarm
Try "SIGALRM".

sigaction
Note the example code. That may not be the same as memset'ing to 0.

gg

---

Install a handler for SIGALRM and have that handler call kill(getpid(), SIGUSR1);

EDIT: This could potentially get you into some serious race conditions if you have your SIGUSR1 handler reset the alarm in return. Also, be careful in using sleep, usleep or the setitimer/getitimer functions as they may conflict with alarm().