/***********************************************************************                    linux watchdog demo hacking* 说明：*     本文主要解析linux watchdog大概应该如何操作。**                                    2016-3-28 深圳 南山平山村 曾剑锋*********************************************************************/#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/watchdog.h>int fd;/** This function simply sends an IOCTL to the driver, which in turn ticks* the PC Watchdog card to reset its internal timer so it doesn't trigger* a computer reset.* 这个函数仅仅是发送一个IOCTL命令给驱动，重新启动Watchdog的内部时钟计数器，* 这样就不会导致系统重启。*/
static void keep_alive(void)
{int dummy;ioctl(fd, WDIOC_KEEPALIVE, &dummy);
}/** The main program.  Run the program with "-d" to disable the card,* or "-e" to enable the card.* 主程序，通过传递参数-d来关闭watchdog，-e来打开watchdog。*/
int main(int argc, char *argv[])
{int flags;// 打开设备节点fd = open("/dev/watchdog", O_WRONLY);if (fd == -1) {fprintf(stderr, "Watchdog device not enabled.\n");fflush(stderr);exit(-1);}if (argc > 1) {// 关闭watchdogif (!strncasecmp(argv[1], "-d", 2)) {flags = WDIOS_DISABLECARD;ioctl(fd, WDIOC_SETOPTIONS, &flags);fprintf(stderr, "Watchdog card disabled.\n");fflush(stderr);exit(0);// 使能watchdog} else if (!strncasecmp(argv[1], "-e", 2)) {flags = WDIOS_ENABLECARD;ioctl(fd, WDIOC_SETOPTIONS, &flags);fprintf(stderr, "Watchdog card enabled.\n");fflush(stderr);exit(0);} else {fprintf(stderr, "-d to disable, -e to enable.\n");fprintf(stderr, "run by itself to tick the card.\n");fflush(stderr);exit(0);}} else {fprintf(stderr, "Watchdog Ticking Away!\n");fflush(stderr);}while(1) {// 每一秒喂狗一次
        keep_alive();sleep(1);}
}