[root@SZDB ~]# more purge_datedir.sh  
#!/bin/bash 
# Author: Leshami 
# Blog : http://blog.csdn.net/leshami 
 
RemoveDir=/log/hotbak/physical 
dt=`date +%Y%m%d -d "3 day ago"` 
 
for subdir in `ls $RemoveDir`; 
do 
  if [ "${subdir}" < "${dt}" ]; 
    then  
    rm -rf $RemoveDir/$subdir >/dev/null 
    echo "The directory $RemoveDir/$subdir has been removed." 
  fi 
done 

[root@SZDB ~]# ls /log/hotbak/physical 
20141203 20141210 20141217 20141224 20141231 20150107 20150114 20150125 tmp.sh 
20141207 20141214 20141221 20141228 20150104 20150111 20150121 20150128 
 
[root@SZDB ~]# ./purge_datedir.sh  
The directory /log/hotbak/physical/20141203 has been removed. 
The directory /log/hotbak/physical/20141207 has been removed. 
The directory /log/hotbak/physical/20141210 has been removed. 
The directory /log/hotbak/physical/20141214 has been removed. 
The directory /log/hotbak/physical/20141217 has been removed. 
The directory /log/hotbak/physical/20141221 has been removed. 
The directory /log/hotbak/physical/20141224 has been removed. 
The directory /log/hotbak/physical/20141228 has been removed. 
The directory /log/hotbak/physical/20141231 has been removed. 
The directory /log/hotbak/physical/20150104 has been removed. 
The directory /log/hotbak/physical/20150107 has been removed. 
The directory /log/hotbak/physical/20150111 has been removed. 
The directory /log/hotbak/physical/20150114 has been removed. 
The directory /log/hotbak/physical/20150121 has been removed. 
 
[root@SZDB ~]# ls /log/hotbak/physical 
20150125 20150128