Question

I like to compare two text files and save the difference under linux.

I know there are tools like kdiff, diff vimdiff etc. but my expectation are as follows.

1. Output should be in a separate file
2. The difference should be quoted with colours, ex: delete line in red and added line in green something like that
3. It should ignore space differences
4. It should be an opensource tool

Answer 1

use tkdiff4 -w file-name1 file-name2

It fulfills all your requirements. Specific color might be an issue.