Question

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

void sigint_handler(int);

int  main()
{
    signal(SIGINT, sigint_handler);

     while (1){
         pause();
     }
    printf("Out..\n");
    return 0;
}

 void sigint_handler(int sig)
{

    printf("killing process %d\n",getpid());
    exit(0);
}

I dont get: Out… after ctrl+c
So never returns on while or getting out. How can i fix it, to continiue in main, and print “Out…”?

Answer 1

I dont get: Out… after ctrl+c

Because the signal handler immediately ends the process so main never gets the chance of actually doing the printf. I suspect you don’t actually want to exit in the handler. You should take the pause out of the loop and wait until the signal gets delivered.

This isn’t the best way of waiting for a signal. For starters it is conceivable that the user could send the SIGINT before you get the chance to pause. The signal would be lost and pause(2) would block until the end of time.

You should probably use sigsuspend or the simpler sigpause.