shell判断文件是否有变化

#!/bin/bash
#
#通过比较五分钟前后，日志文件md5值是否相同，来判断日志文件是否有变化，从而判断java是否假死
#请根据实际情况，修改环境变量，项目路径
#加入计划任务执行
#
function RestartJava()
{
export  JAVA_HOME=/opt/apps/jdk1.6.0_41
export  PATH=$PATH:/opt/apps/jdk1.6.0_41/bin
export  CLASSPATH=.:$JAVA_HOME/lib/tools.jar:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/jre/lib/rt.jar
JavaPath="/opt/apps/apache-tomcat-6.0.37"
JavaId=$(ps -ef|grep java  |grep $JavaPath |grep -v "grep" |awk '{print $2}')

kill -9 $JavaId
cd $JavaPath/bin && /bin/bash startup.sh
}

#while [ 1 ]
#do
First=`md5sum /opt/shell/nohup.out |awk '{print $1}'`
sleep 300
Second=`md5sum /opt/shell/nohup.out |awk '{print $1}'`

if [[ $First == $Second ]]
then
echo "start restart java" >/dec/null 2>&1
RestartJava
fi

#done