连续4个小时ping不通远端主机，则本机关机

 #!/bin/bash
 #连续4个小时ping不通远端主机，则本机关机。

 begin_time=$(date "+%s")
 while true;do
     sleep 2
     ping -c 1 172.16.160.1 > /dev/null
     if [ $? != 0 ];then
         end_time=$(date "+%s")
     else
         begin_time=$(date "+%s")
     fi
     if [ $end_time -gt $begin_time ] ; then
         time_difference=$(($end_time - $begin_time))
         echo $time_difference
         if [ $time_difference -gt 14400 ]; then
         shutdown -h now
         fi
     fi
 done