How can I get the most bang for my buck with the “diff” command?

Question

I have tried using the linux diff command in the past without much luck or patience. I usually end up using a GUI utility like DiffMerge or Kdiff.

Recently I started trying to use diff again to compare files on remote systems via ssh, and I have found the -y / --side-by-side option to be very useful, but I still feel like I'm not making this most of this utility.

So I'm curious of how to achieve the following things:

1. Highlight changes or use color-coding to make the output more readable
2. Merge - Select lines with differences and effect the changes into one of the files

Also, I haven't found many good examples when googling, so if you have some linux-fu secrets for getting the most out of diff, could you please share? I will mainly be comparing text-based configuration files but any tricks and tips would be wonderful.

For Reference - The DiffMerge utility easily shows changes side by side with color highlighting. Icons at the top allow you to switch between views of "show all," "show differences," and "show differences with context." Would love some of this functionality at the command prompt.

ps: I should also note that one other option that I find quite useful is --suppress-common-lines which I learned about on this concise and readable blog post.

Answer 1

In no particular sequence:

• meld is a very nice diff program which does very nice diffs and three-way merges.
• git config --global merge.conflictstyle diff3 gets you three-way merge output for use with tools like meld.
• wdiff does word diffs, very nice if colored: wdiff -w "$(tput bold;tput setaf 1)" -x "$(tput sgr0)" -y "$(tput bold;tput setaf 2)" -z "$(tput sgr0)" ...
• To minimize cruft in the diff output, I usually use the --ignore-all-space (-w) option
• diff-ignore-moved-lines* does what it says on the label.
• difff* can be used to diff only lines which match in given fields.

* Disclaimer: I'm the author, and developed these to help with CLI and GUI diffing and merging.

Answer 2

I've found vimdiff to be very useful.

Answer 3

To get coloring in the diff you should look at http://colordiff.sourceforge.net/ . This is just a wrapper around diff and, as such, all the command options still work.

In case you have ubuntu just write:

    # sudo apt-get install colordiff

Running the risk of not meeting your use case, git is a very nice VCS that integrates well with many diffing and merging tools (both command line and GUI ones). Give it a try if it is an option.

Answer 4

Try sdiff

diff also has options (-e or -ed) to create a merge script for use with ed

sdiff, diff and ed should be part of your shell where ever you go.

Your version control software probably also has a diff and merge tool built in.