/* 
 * The text on p.273 reads:
 * 
 *     We invoke the program in the background and use the kill(1) command
 *     to send it signals.  Note that the term "kill" in Unix is a misnomer.
 *     The kill(1) command the kill(2) function just send a signal to a 
 *     process or process group.  Whether or not that signal terminates
 *     the process depends on which signal is sent and whether the process
 *     has arranged to catch the signal
 *   
 *                                   | 
 *     $ a.out &                     | start process in background
 *     [1]       4720                | job-control shell prints job# and PID
 *     $ kill -USR1 4720             | send it SIGUSR1
 *     received SIGUSR1              |
 *     $ kill -USR2 4720             | send it SIGUSR2
 *     received SIGUSR2              | 
 *     $ kill 4720                   | now send it SIGTERM
 *     [1] + Terminated     a.out &  |
 *                                   | 
 *
 *     When we send the SIGTERM signal the process is terminated, since it 
 *     doesn't catch the signal and the default action for the signal
 *     is termination.
 *
 * Note: The above example interaction with the program never sent
 *       the same signal twice.   The action for a signal gets reset to it's
 *       default each time the signal occurs.  Since our program doesn't
 *       explicitly reset the signal handler once it executes, a second
 *       signal of the same type would not be caught by our handler.
 *       (instead, the signal's default action would be executed)
 *
 * Modified Feb 18/99: removed dependency on ourhdr.h
 */

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

static void sig_usr (int);   /* one handler for both signals */

int main (void)
{
    if (signal (SIGUSR1, sig_usr) == SIG_ERR)
    {
        fprintf(stderr, "can't catch SIGUSR1"); exit(1);
    }
    if (signal (SIGUSR2, sig_usr) == SIG_ERR)
    {
        fprintf(stderr, "can't catch SIGUSR2"); exit(1);
    }

    for ( ; ; )
        pause();
}

static void
sig_usr (int signo)          /* argument is signal number    */
{
    if (signo == SIGUSR1)
        printf("received SIGUSR1\n");
    else if (signo == SIGUSR2)
        printf("received SIGUSR2\n");
    else
    {
        fprintf(stderr, "received signal %d\n", signo); exit(1);
    }

    return;
}