How to detect server network status in Linux

 #!/bin/bash

# 检测服务器是否连接着网络,如果网络不通 则 3次后 关机
# crontab -e
# */5 * * * * ./check.sh

echo "Starting test network was clear..."

if test -e ./checkInfo
 then
 echo "CheckInfo File Exist..."
else
 cat /dev/null > ./checkInfo
fi

last_res=`head -1 ./checkInfo`

checkInternet(){
 ping_res=1

 for url in "8.8.8.8" "61.139.2.69" "114.114.114.114" "168.95.1.1" "223.5.5.5" "180.76.76.76"
 do
 echo "PING ${url}"

 ping=`ping -c 3 ${url}|awk 'NR==7 {print $4}'`

 if [ ${ping} -eq 0 ]
  then
  ping_res=1
  else
  ping_res=2
 fi

 if [ ${ping_res} -eq 2 ]
  then
  break
 fi
 done

 return ${ping_res}
}

checkInternet

result="$?"

if [ ${result} -eq 1 ]
 then
 if [ "${last_res}" = "1" ]
  then
  echo "2" > ./checkInfo
 elif [ "${last_res}" = "2" ]
  then
  cat /dev/null > ./checkInfo
  init 0
  else
  echo "1" > ./checkInfo
 fi
 else
 cat /dev/null > ./checkInfo
fi