Listing 4.  Programs to Send and Receive SIGINT

#include <signal.h>

main ( ) {
    int process_id;
    printf ("Enter process_id which you want "
            "to send a signal : ");
    scanf ("%d", &process_id);

   if (!(kill ( process_id, SIGINT)))
       printf ("SIGINT sent to %d\n", process_id);
   else if (errno == EPERM)
       printf ("Operation not permitted.\n");
   else
       printf ("%d doesn't exist\n", process_id);
}

/* Listing 4a. This program will run until it
   receives SIGINT */

#include <signal.h>

 main ( ) {
   printf (" This process id is %d. "
   "Waiting for SIGINT.\n", getpid());
   for (;;);
}