The example is confusing, as it just happens to result in 1 2 3, $ printf '%s\n' 1 2 3 4 > file1 $ printf '%s\n' 2 3 4 5 6 > file2 $ comm --total -123 file1 file2 1 2 3 total
So please use $ printf '%s\n' 0 2 3 5 6 > file1 $ printf '%s\n' 1 2 4 6 7 8 9 > file2 $ comm --total -123 file1 file2 3 5 2 total Also add a note "However --total is a GNU extension. For a portable way to make totals, use wc: $ echo Lines only in 1st = $(comm -23 file1 file2 | wc -l) $ echo Lines only in 2nd = $(comm -13 file1 file2 | wc -l) $ echo Lines in both = $(comm -12 file1 file2 | wc -l)
