How do I do a one way diff in Linux?

Question

How do I do a one way diff in Linux?

Normal behavior of diff:

Normally, diff will tell you all the differences between a two files. For e

Answer 1

An alternative, if your files consist of single-line entities only, and the output order doesn't matter (the question as worded is unclear on this), would be:

comm -23 <(sort A) <(sort B)

comm requires its inputs to be sorted, and the -2 means "don't show me the lines that are unique to the second file", while -3 means "don't show me the lines that are common between the two files".

If you need the "differences" to be presented in the order they occur, though, the above diff / awk solution is ok (although the grep bit isn't really necessary - it could be diff A B | awk '/^.

EDIT: fixed which set of lines to report - I read it backwards originally...