How do you diff a directory for only files of a specific type?

Question

I have a question about the diff command if I want a recursive directory diff but only for a specific file type, how to do that?

I tried using the exclude option but can

Answer 1

Taken from ( a version of) the man page:

-x PAT  --exclude=PAT
  Exclude files that match PAT.

-X FILE    --exclude-from=FILE
  Exclude files that match any pattern in FILE.

So it looks like -x only accepts one pattern as you report but if you put all the patterns you want to exclude in a file (presumably one per line) you could use the second flag like so:

$ diff /destination/dir/1 /destination/dir/2 -r -X exclude.pats

where exclude.pats is:

*.jpg
*.JPG
*.xml
*.XML
*.png
*.gif