Comparing two unsorted lists in linux, listing the unique in the second file

Question

I have 2 files with a list of numbers (telephone numbers).

I\'m looking for a method of listing the numbers in the second file that is not present in the first file.

Answer 1

You need to use comm:

comm -13 first.txt second.txt

will do the job.

ps. order of first and second file in command line matters.

also you may need to sort files before:

comm -13 <(sort first.txt) <(sort second.txt)

in case files are numerical add -n option to sort.