compare two files in UNIX

Question

I would like to compare two files [ unsorted ] file1 and file2. I would like to do file2 - file1 [ the difference ] irrespective of the line number? diff is not working.

Answer 1

I got the solution by using comm

comm -23 file1 file2  

will give you the desired output.

The files need to be sorted first anyway.

Answer 2

Well, you can just sort the files first, and diff the sorted files.

sort file1 > file1.sorted
sort file2 > file2.sorted
diff file1.sorted file2.sorted

You can also filter the output to report lines in file2 which are absent from file1:

diff -u file1.sorted file2.sorted | grep "^+" 

As indicated in comments, you in fact do not need to sort the files. Instead, you can use a process substitution and say:

diff <(sort file1) <(sort file2)