diff <(echo -e "foo\n123") <(echo -e "foo\n123" | tr '[:upper:][:lower:]' '[:lower:][:upper:]')
wdiff <(echo foo bar) <(echo foo xyz)
HOWTO Compare directories 2010630474 1862711630
diff --recursive --brief ~/dir1 ~/dir2 | grep Only
colordiff --recursive path/to/dir1 path/to/dir2
colordiff --ignore-space-change path/to/1.file path/to/2.file