shell regular backup script

#!/bin/bash
SOURCE_DIR=(
$*
)
TARGET_DIR=/data
YEAR=`date +%Y`
MONTH=`date +%m`
DAY=`date +%d`
WEEK=`date +%u`
FILES=system_backup.tgz
CODE=$?
if [ -z "$*" ];then
echo -e "Please Enter Your Backup Files or Directories\n--------------------------------------------\nExample $0 /boot /etc ......"
exit
fi
#Determine Whether the Target Directory Exists
if [ ! -d $TARGET_DIR/$YEAR/$MONTH/$DAY ];then
mkdir -p $TARGET_DIR/$YEAR/$MONTH/$DAY
echo "This $TARGET_DIR is Created Successfully !"
fi
#EXEC Full_Backup Function Command""
Full_Backup()
{
if [ "$WEEK" -eq "7" ];then
rm -rf $TARGET_DIR/snapshot
cd $TARGET_DIR/$YEAR/$MONTH/$DAY
tar -g $TARGET_DIR/snapshot -czvf $FILES `echo ${SOURCE_DIR[@]}`
[ "$CODE" == "0" ]&&echo -e "--------------------------------------------\nThese Full_Backup System Files Backup Successfully !"
fi
}
#Perform incremental BACKUP Function Command
Add_Backup()
{
cd $TARGET_DIR/$YEAR/$MONTH/$DAY ;
if [ -f $TARGET_DIR/$YEAR/$MONTH/$DAY/$FILES ];then
read -p "These $FILES Already Exists, overwrite confirmation yes or no ? : " SURE
if [ $SURE == "no" -o $SURE == "n" ];then
sleep 1 ;exit 0
fi
#Add_Backup Files System
if [ $WEEK -ne "7" ];then
cd $TARGET_DIR/$YEAR/$MONTH/$DAY ;tar -g $TARGET_DIR/snapshot -czvf $$_$FILES `echo ${SOURCE_DIR[@]}`
[ "$CODE" == "0" ]&&echo -e "-----------------------------------------\nThese Add_Backup System Files Backup Successfully !"
fi
else
if [ $WEEK -ne "7" ];then
cd $TARGET_DIR/$YEAR/$MONTH/$DAY ;tar -g $TARGET_DIR/snapshot -czvf $FILES `echo ${SOURCE_DIR[@]}`
[ "$CODE" == "0" ]&&echo -e "-------------------------------------------\nThese Add_Backup System Files Backup Successfully !"
fi
fi
}
Full_Backup;Add_Backup