How to replace a list of strings by another list

It would be easier to create a file with both the input and replacement strings on the same line (assuming that neither input nor replacement strings contain spaces). Then you can do so something simple like:

while read n k; do sed -i "s/$n/$k/g" file1; done < fileA

EDIT:

After seeing Nykakin's answer, I realized you can do the same thing with the two files you have combining his suggestion with mine:

paste fileA fileB | while read n k; do sed -i "s/$n/$k/g" file1; done 

This is basically your first idea, but with the substitution commands put into a file, so they’re more manageable:

tmpfile=/tmp/Asasuser.$$
exec 3< fileA
exec 4< fileB
while read –r astring <&3
do
        read –r bstring <&4
        echo "s/$astring/$bstring/" >> "$tmpfile"
done
exec 3<&- 4<&-
sed –f "$tmpfile" file1 > out
rm –f "$tmpfile"

This assumes that fileA and fileB have the same number of lines (and that that number is greater than zero) and that neither of them has any unescaped / characters.

We can just generate command that we need. Let's say that files with lists are called lista and listb. Then we can use:

$ for i in $(paste lista listb -d/); do echo -n "-e 's/$i/g' "; done

to generate option for sed. Now we can use it with eval. Let's say our file is called test. We use:

$ eval "sed" $(for i in $(paste lista listb -d/); do echo -n "-e 's/$i/g' "; done) "test"