To reverse a file

#If @ is used anywhere in the file to be reversed, use any other
special character that is not used 

ctr=`cat filename|wc -l `
line=`sed 's/$/@/g' filename |tr -d "\n"`
while test $ctr -ne 0
do
        echo $line|cut -d"@" -f$ctr
        ctr=`expr $ctr - 1`
done

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nl -ba FILE | sort -nr | cut -f2-