crontab里设定一条：
0 12 28-31 * * sh /tmp/start.sh
start.sh 脚本如下：
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#!/usr/bin/ksh
#this script is used to start the xxx in the last day of every month
ym=`date +%m" "%Y`
if [ `date +%d` = `cal $ym|xargs|awk '{print $NF}'` ]
then
sh yourscripts
fi
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