How to read two files simultaneously in linux

i have two sorted files of images(ls -l),i have to compare these two files and check each line are same if it same move to next line if not same i have to rechange it to equal.
bt for me not executing properly
my codings are below
while read line
do
while read lline
do
if [ "$line"=="$lline" ]
then
break
else
sudo cp -r /digital_images/local1/00/00_sortedlist.txt/$line /digital_images local1/00/00_localsortedlist.txt/$lline
fi
done </digital_images local1/00/00_localsortedlist.txt
done </digital_images/local1/00/00_sortedlist.txt
Any one pls give me suggestion for this
Thanks in advance