监控配置文件变化，并且执行对应的操作。 monitoring file changed, and do some action

filemoniter.sh

#!/bin/bash
#author: orangleliu@gmail.com
#use this shell script with cron 
file=/home/ftp/rulebase/rules.list
md5checkfile=/tmp/rulebase.md5

if [ ! -f $file ]
    then
	echo "$file not exist .."
        exit 1
fi

filemd5=`md5sum $file |cut -d " " -f1`
echo "filemd5 $filemd5"

if [ -z $filemd5 ]
    then
	echo "the $file is empty"
	exit 1
fi

if [ -f $md5checkfile ]
    then
	savedmd5=`cat $md5checkfile`
	echo "saved md5 $savemd5"

	if [ "$savedmd5" = "$filemd5" ]
	    then
		echo "not changed"
	    else
		echo "File has ben changed"
		#restart some service 
		/bin/sh /home/ftp/rulebase/udpserver.sh restart
	fi
fi

echo $filemd5 > $md5checkfile