/* NOTE: Like the code in lecture, this code omits error checks when
 * calling the various library and system calls.  Your MP code should
 * check for errors.  We omit it here so that the main steps of the
 * code are more clearly illustrated.
 */

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

/* Our signal handler:  We will set it up so that this function
 * is called whenever the program receives a SIGINT (which is
 * caused by the user pressing control-c).
 */
void handle(int sig) {
    char handmsg[] = "Ha! Handled!!!\n";
    int msglen = sizeof(handmsg);

    /* Note we have to use `write' here, not printf(), because
     * write is safe to use in a signal handler (printf might
     * cause problems if another signal handler is called
     * while we are executing this one. */
    write(2, handmsg, msglen);       
}

int main(int argc, char** argv) {
    /* We will use sigaction() to set up our signal handler.
     * It has us put some of its arguments inside a structure
     * `struct sigaction'.  So here we are really just setting
     * up arguments to sigaction -- kind of annoying that we
     * have to give the arguments this way rather than just
     * passing them in directly, but that's life.
     */
    struct sigaction sa;
    sa.sa_handler = handle;   /* the most important argument: the handler function */
    sa.sa_flags = 0;          /* no special options */
    sigemptyset(&sa.sa_mask); /* sa_mask is the set of signals to block while in
                               * the signal handler `handle'.  Here we block none, i.e.,
                               * the empty set of signals. */

    /* Finally, we actually install the signal handler for
     * the signal SIGINT. The second argument is the options
     * we set above.  The third is used for sigaction() to tell
     * us what the old signal handler used to be, but we don't
     * care about that so we pass in NULL (which in this case
     * is a valid thing to pass in -- see the sigaction man page).
     */
    sigaction(SIGINT, &sa, NULL);

    /* Print some miscellaneous output... try pressing control-c
     * while this happens. */
    while (1) {
        printf("Fish.\n");
        sleep(1);
    }
}