comm --version (return code: 0)
comm (GNU coreutils) 8.25 Copyright (C) 2016 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Written by Richard M. Stallman and David MacKenzie.
comm --help (return code: 0)
Usage: comm [OPTION]... FILE1 FILE2 Compare sorted files FILE1 and FILE2 line by line. When FILE1 or FILE2 (not both) is -, read standard input. With no options, produce three-column output. Column one contains lines unique to FILE1, column two contains lines unique to FILE2, and column three contains lines common to both files. -1 suppress column 1 (lines unique to FILE1) -2 suppress column 2 (lines unique to FILE2) -3 suppress column 3 (lines that appear in both files) --check-order check that the input is correctly sorted, even if all input lines are pairable --nocheck-order do not check that the input is correctly sorted --output-delimiter=STR separate columns with STR -z, --zero-terminated line delimiter is NUL, not newline --help display this help and exit --version output version information and exit Note, comparisons honor the rules specified by 'LC_COLLATE'. Examples: comm -12 file1 file2 Print only lines present in both file1 and file2. comm -3 file1 file2 Print lines in file1 not in file2, and vice versa. GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Full documentation at: <http://www.gnu.org/software/coreutils/comm> or available locally via: info '(coreutils) comm invocation'