Yesterday, I had a problem. I had two files that were almost the same, but one of them had a few chunks of new data in it, and there were a couple of places where there were lines that only had a word or two changed in them. What I wanted was just the new data in the second file, and I didn’t care about the stuff that had just changed a bit.

Obviously, this sounded like a job for the diff command.

Unfortunately, I found the man page a little more difficult than normal to decipher and had to call upon the massively oversized brain of Ben Hawkes-Lewis to see if we could work out together how to do what I wanted. After a bit of fumbling, it turned out that we wanted to use the line group format options. Here’s what we came up with that solved my problem:

diff --new-group-format="%>" --old-group-format="" \
--changed-group-format="" --unchanged-group-format="" \
original.file file-with-extra-data.file

Hopefully this will be of use to someone else at some point too.

Tags: diff, feci

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