[ snip ]
>> paste listing1.txt listing2.txt | while read f1 f2
>> do
>> diff $f1 $f2
>> done
>>
>
> Only if file name contain no space, or you have to let paste -dX where X
> is a char that never appears in filename.
I think the OP can work out that detail by reading the man page;
you're not really adding to the value of Barry's answer.
Anyway, whereas simpleton end users may be forgiven for using spaces in file
names, the same cannot be said about users of version control, whom we
should be able to count on to be more disciplined.