CODEWITHSUNDEEP
c
d12985
d12985

Reputation: 31

Using Ctrl+C multiple times in C

I'm currently trying to use Ctrl+C to terminate individual while loops. However when I press Ctrl+C it is currently terminating both while loops. Is there a way I can make these individual?

This is how I currently have it setup:

volatile sig_atomic_t exitSig = 0;
volatile sig_atomic_t feedExitSig = 0;

void signal_handler(int signum){
    exitSig = 1;
    livefeedExitSig =1;
}

int main(int argc, char *argv[]){
    while (!exitSig){
         //complete task

         while (!feedExitSig){
               //complete task
         }

         //complete task
    }
}

If I press Ctrl+C while I'm in the feedExitSig loop I want it to only exit that loop and not the exitSig loop.

Upvotes: 2

Views: 727

Answers (2)

David C. Rankin
David C. Rankin

Reputation: 84579

In addition to the correct catch by @lenik that signal is not called registering your signal_handler() function, you need to only set exitSig if feedExitSig is already set. You can do that with a simple conditional in your signal_handler(), e.g.

void signal_handler(int signum)
{
    if (signum == SIGINT) {
        if (feedExitSig)        /* only if feedExitSig already set */
            exitSig = 1;        /* set exitSig - requires 2nd ctrl+c */
        feedExitSig = 1;
    }
}

A complete example requiring Ctrl+c to be pressed to break the inner loop and then pressed again to break the outer loop ending the program could be similar to:

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

volatile sig_atomic_t exitSig = 0;
volatile sig_atomic_t feedExitSig = 0;

void signal_handler(int signum)
{
    if (signum == SIGINT) {
        if (feedExitSig)        /* only if feedExitSig already set */
            exitSig = 1;        /* set exitSig - requires 2nd ctrl+c */
        feedExitSig = 1;
    }
}

int main (void) {

    signal (SIGINT, signal_handler);

    while (!exitSig){
        puts ("outer");

        while (!feedExitSig){
            puts ("  inner");
            sleep(1);
        }

        sleep(1);
    }
}

Look things over and let me know if you have further questions.

Upvotes: 3

lenik
lenik

Reputation: 23556

In your main() you have to use signal(SIGINT, signal_handler); to let the system know you're about to handle Ctrl/C presses.

Once that done, you may want to set only one variable in the handler, not both, because right now you're terminating both loops at the same time.

Upvotes: 2

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