==== ignore subdirectories ====
One way is to call diff without the --recursive (-r) option and use grep to filter out the unwanted messages:

<code>
 % diff dir1 dir2 | grep -v "^Only in "
</code>
or
<code>
 % diff -q dir1 dir2 | grep -v "^Only in "
</code>

See https://stackoverflow.com/questions/30446490/diff-only-compare-files-and-ignore-subdirectories/ for some sample tests using this idea.

==== diff word by word ====
<code>
git diff --word-diff --no-index -- foo bar
</code>
or
<code>
git diff -U0 --word-diff --no-index -- foo bar
</code>

You can run this command even if the files are not part of a git repository.

Ref:- https://unix.stackexchange.com/a/330807/198064

Related commands:
  * ''<nowiki>git diff --no-index --color-words -- foo bar</nowiki>'' - to diff word by word
  * ''<nowiki>git diff --no-index --color-words=. -- foo bar</nowiki>'' - to diff character by character

==== head and diff ====
To diff headers of two files without creating any temporary files
<code>
% diff <(head -n 1 foo.20170102) <(head -n 1 foo.20170104)
</code>

==== ignore newline endings ====
tags | ignore line endings

<code>
diff --strip-trailing-cr file1 file2
</code>

<code>
$ diff --help | grep -i strip
      --strip-trailing-cr         strip trailing carriage return on input
</code>

Ref:- https://stackoverflow.com/questions/40974170/how-can-i-ignore-line-endings-when-comparing-files