/*************************************************************************\
*                  Copyright (C) Michael Kerrisk, 2026.                   *
*                                                                         *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU General Public License as published by the   *
* Free Software Foundation, either version 3 or (at your option) any      *
* later version. This program is distributed without any warranty.  See   *
* the file COPYING.gpl-v3 for details.                                    *
\*************************************************************************/

/* intquit.c

   Catch the SIGINT and SIGQUIT signals, which are normally generated
   by the control-C (^C) and control-\ (^\) keys respectively.

   Note that although we use signal() to establish signal handlers in this
   program, the use of sigaction() is always preferable for this task.
*/
#include <signal.h>
#include "tlpi_hdr.h"

static void
sigHandler(int sig)
{
    static int count = 0;

    /* UNSAFE: This handler uses non-async-signal-safe functions
       (printf(), exit(); see Section 21.1.2) */

    if (sig == SIGINT) {
        count++;
        printf("Caught SIGINT (%d)\n", count);
        return;                 /* Resume execution at point of interruption */
    }

    /* Must be SIGQUIT - print a message and terminate the process */

    printf("Caught SIGQUIT - that's all folks!\n");
    exit(EXIT_SUCCESS);
}

int
main(int argc, char *argv[])
{
    /* Establish same handler for SIGINT and SIGQUIT. Here we use the
       simpler signal() API to establish a signal handler, but for the
       reasons described in Section 22.7 of TLPI, sigaction() is the
       (strongly) preferred API for this task. */

    if (signal(SIGINT, sigHandler) == SIG_ERR)
        errExit("signal");
    if (signal(SIGQUIT, sigHandler) == SIG_ERR)
        errExit("signal");

    for (;;)                    /* Loop forever, waiting for signals */
        pause();                /* Block until a signal is caught */
}