Shell脚本检测URL可用性

#!/bin/bash
#自动检测URL是否挂了

while true
do
URL=" http://bbs.example.cn"
RETURN=`curl -o /dev/null -s -w "%{http_code}" "${URL}"`
if [ $RETURN != '200' ];then
/data/sh/fastcgi_restart
fi
sleep 12
done