find lines that matches on 2 different sorted file

Supposed we have 2 sorted files:
file1
1
2
3
4
5
file2
3
4
5
6
7
comm is a utility for finding lines that appear (or not) between 2 files. The normal output are 3 column.
  1. 1.
    Lines that is unique on file 1
  2. 2.
    Lines that is unique on file 2
  3. 3.
    Lines that are appear on both

Examples

$ comm file1 file2
1
2
3
4
5
6
7

Find lines that on both file only

$ comm -12 file1 file2
3
4
5
-12 supresses (do not include) colunm 1 & 2

Fine line that is unique on first file

$ comm -23 file1 file2
1
2

For file that is not uniq or sorted

If file is not sorted, you can use the <(..) operator
$ comm <(sort -u file1) <(sort -u file2)
1
2
3
4
5
6
7