===================================================
[oracle@localhost export]$ vi backup_oracle.sh
rq=`date '+%Y%m%d%H%M'`
su - oracle -c "exp system/123@cci owner=liu file=/liu/export/liu_$rq.dmp"
~
~
~
~
===================================================
[root@localhost oracle]# crontab -e
no crontab for root - using an empty one
31 16 * * * /liuhongtao/export/backup_oracle.sh
31 16 * * * echo "good liuhongtao" >> /liuhongtao/export/test.txt