source: MondoRescue/branches/stable/mindi-busybox/miscutils/watchdog.c@ 821

/* vi: set sw=4 ts=4: */
/*
 * Mini watchdog implementation for busybox
 *
 * Copyright (C) 2003  Paul Mundt <lethal@linux-sh.org>
 * Copyright (C) 2006  Bernhard Fischer <busybox@busybox.net>
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */

#include "busybox.h"
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>

#define OPT_FOREGROUND 0x01
#define OPT_TIMER      0x02

/* Watchdog file descriptor */
static int fd;

static void watchdog_shutdown(int ATTRIBUTE_UNUSED unused)
{
    write(fd, "V", 1);  /* Magic, see watchdog-api.txt in kernel */
    close(fd);
    exit(0);
}

int watchdog_main(int argc, char **argv)
{
    unsigned long opts;
    unsigned long timer_duration = 30; /* Userspace timer duration, in seconds */
    char *t_arg;

    opts = bb_getopt_ulflags(argc, argv, "Ft:", &t_arg);

    if (opts & OPT_TIMER)
        timer_duration = bb_xgetlarg(t_arg, 10, 0, INT_MAX);

    /* We're only interested in the watchdog device .. */
    if (optind < argc - 1 || argc == 1)
        bb_show_usage();

#ifdef BB_NOMMU
    if (!(opts & OPT_FOREGROUND))
        vfork_daemon_rexec(0, 1, argc, argv, "-F");
#else
    bb_xdaemon(0, 1);
#endif

    signal(SIGHUP, watchdog_shutdown);
    signal(SIGINT, watchdog_shutdown);

    fd = bb_xopen(argv[argc - 1], O_WRONLY);

    while (1) {
        /*
         * Make sure we clear the counter before sleeping, as the counter value
         * is undefined at this point -- PFM
         */
        write(fd, "\0", 1);
        sleep(timer_duration);
    }

    watchdog_shutdown(0);

    return EXIT_SUCCESS;
}