.. _signal:

Handling Signals
================================================

.. figure:: sig_handle.png
   :align: center    

   Signals other that SIG_KILL and SIG_STOP may be caught and execute a defined
   signal handler function.

::

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

    static void sig_handler(int);

    int main ()
    {
        int i, parent_pid, child_pid, status;

        if(signal(SIGUSR1, sig_handler) == SIG_ERR)
            printf("Parent: Unable to create handler for SIGUSR1\n");
        if(signal(SIGUSR2, sig_handler) == SIG_ERR)
            printf("Parent: Unable to create handler for SIGUSR2\n");
        parent_pid = getpid();

        if((child_pid = fork()) == 0) {
            kill(parent_pid, SIGUSR1);
            for (;;) pause();
        }
        else {
            kill(child_pid, SIGUSR2);
            sleep(3);
            printf("Parent: Terminating child ...\n");
            kill(child_pid, SIGTERM);
            wait(&status);
            printf("done\n");
        }
    }

    static void sig_handler(int signo) {
        switch(signo) {
            case SIGUSR1:  /* Incoming SIGUSR1 */
                printf("Parent: Received SIGUSER1\n");
                break;
            case SIGUSR2:  /* Incoming SIGUSR2 */
                printf("Child: Received SIGUSER2\n");
                break;
            default: break;
        }
        return;
    }