原来是lazy写的，我做了一些改动

oldfile="/home/backup/`date --date='2 days ago' '+%Y-%m-%d'`.tar.gz"
filename="/home/backup/`date '+%Y-%m-%d'`.tar.gz"
oldsrc="/home/backup/src`date --date='2 days ago' '+%Y-%m-%d'`.tar.gz"
srcname="/home/backup/src`date '+%Y-%m-%d'`.tar.gz"


if [ -f $oldfile ]; then
        echo "Deleting old backup file of three days ago..."
        rm -f $oldfile
fi
if [ -f $filename ]; then
        echo "File $filename existed. Exiting..."
        exit 1
fi

#echo "Start backuping BBS system..."
cd /home
tar vzcf $filename bbs/


if [ -f $oldsrc ]; then
        echo "Deleting old backup file of two days ago..."
        rm -f $oldsrc
fi

if [ -f $srcname ]; then
        echo "File $srcname existed. Exiting..."
        exit 1
fi

cd /home
tar vzcf $srcname bbssrc/

#echo "Done."
--
FROM 202.200.235.53