comm flags & options

Basic usage

Compare two sorted files. Outputs three columns: lines unique to file1, lines unique to file2, lines in both.

comm file1.txt file2.txt

-1

Suppress column 1 (lines unique to file1).

comm -1 file1.txt file2.txt

-2

Suppress column 2 (lines unique to file2).

comm -2 file1.txt file2.txt

-3

Suppress column 3 (lines common to both files).

comm -3 file1.txt file2.txt

Lines only in file1

Suppress columns 2 and 3.

comm -23 file1.txt file2.txt

Lines only in file2

Suppress columns 1 and 3.

comm -13 file1.txt file2.txt

Lines common to both

Suppress columns 1 and 2.

comm -12 file1.txt file2.txt

With unsorted input

Sort files inline using process substitution.

comm -12 <(sort file1.txt) <(sort file2.txt)

--check-order

Verify that input is sorted and fail if not.

comm --check-order file1.txt file2.txt