I'm trying to do something simple with alarms, however the printf is never executing after I do the alarm, why's that?
#include <stdio.h>
#include <signal.h>
int main() {
alarm(3);
printf("Hello...\n");
alarm(6);
while(1);
printf("Hello2\n");
}
I want hello and hello2 to be printed, only hello is being printed for now
You didn't specify a handler for SIGALRM
, and its default behavior (per man 7 signal
) is to terminate the program. Even if you did specify a handler, after it ran, you'd still be in the while(1)
loop.
Here's how you'd modify your program to fix both of those problems:
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
volatile sig_atomic_t got_sigalrm = 0;
void handle_sigalrm(int signum) {
got_sigalrm = 1;
}
int main() {
struct sigaction act = { .sa_handler = handle_sigalrm };
sigaction(SIGALRM, &act, NULL);
alarm(3);
printf("Hello...\n");
alarm(6);
while(!got_sigalrm);
printf("Hello2\n");
}
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