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 increasing collating sequence (see sort(1) and Environment Variables below), and produces a three-column output:

Column 1: Lines that appear only in file1,

Column 2: Lines that appear only in file2,

Column 3: Lines that appear in both files. 

If - is used for file1 or file2, the standard input is used.

Options 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 does nothing useful. 

EXTERNAL INFLUENCES

Environment Variables

LC_COLLATE determines the collating sequence comm expects from the input files. 

LANG determines the language in which messages are displayed. 

If LC_COLLATE is not specified in the environment or is set to the empty string, the value of LANG is used as a default.  If LANG is not specified or is set to the empty string, a default of “C” (see lang(5)) is used instead of LANG.  If any internationalization variable contains an invalid setting, comm behaves as if all internationalization variables are set to “C”.  See environ(5).

International Code Set Support

Single- and multi-byte character code sets are supported with the exception that multi-byte character file names are not supported. 

EXAMPLES

The following examples assume that file1 and file2 have been ordered in the collating sequence defined by the LC_COLLATE or LANG environment variable. 

Print all lines common to file1 and file2 (in other words, print column 3):

comm -12 file1 file2

Print all lines that appear in file1 but not in file2 (in other words, print column 1):

comm -23 file1 file2

Print all lines that appear in file2 but not in file1 (in other words, print column 2):

comm -13 file1 file2

SEE ALSO

cmp(1), diff(1), sdiff(1), sort(1), uniq(1). 

STANDARDS CONFORMANCE

comm: SVID2, XPG2, XPG3, POSIX.2

Hewlett-Packard Company  —  HP-UX Release 9.0: August 1992