Automating back up of database tables

Hi all, i would like to set a cronjob to back up my db tables.
I have written the par file, i would like to know how can i execute a exp command in a shell script.
my par file

userid=admin/password
file=backup.dmp
log=backupLOG.log
tables=
(Tables 1,
Tables 2)

My cron job script will be something like

#execute the command to run the par file
#capture current sysdate to a variable
#rename backup.dmp to sysdate_backup.dmp
#execute the command in shell pine -attach yyyymmdd_backup.dmp me@domain.com

would anyone be able to advise me on the systax?

This thread for Oracle backup script may help - read the fix issue before attempting to use/modify.