How can I get diff to show only added and deleted lines

How can I get the unix command diff show only added and deleted lines? If diff can't do it, what tool can?

Solution 1:

I'm not sure this is possible as it will be hard to differentiate between changed, added and deleted lines.

Consider this file:

start
old
old
old
end

We edit it so it looks like this:

start
old
old but now new
new
new
end

If we diff it we get this output:

< old
< old
---
> old but now new
> new
> new

This is straightforward to generate. But if you ask diff to only print added and deleted line I think it becomes a matter of opinion which lines have been added and deleted and which have been changed. For example, did I delete the the last line that said old and replace it with a line that said new or did I edit it?

Solution 2:

Does diff -u0 do what you want?