bsd man page for comm

COMM(1) 						      General Commands Manual							   COMM(1)

NAME
       comm - select or reject lines common to two sorted files

SYNOPSIS
       comm [ - [ 123 ] ] file1 file2

DESCRIPTION
       Comm  reads  file1 and file2, which should be ordered in ASCII collating sequence, and produces a three column output: lines only in file1;
       lines only in file2; and lines in both files.  The filename `-' means the standard input.

       Flags 1, 2, or 3 suppress printing of the corresponding column.	Thus comm -12 prints only the lines common to  the  two  files;  comm  -23
       prints only lines in the first file but not in the second; comm -123 is a no-op.

SEE ALSO
       cmp(1), diff(1), uniq(1)

7th Edition							  April 29, 1985							   COMM(1)