home | help 
COMM(1) 		     General Commands Manual			 COMM(1)

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

SYNOPSIS
     comm [-123i] file1 file2

DESCRIPTION
     The  comm	utility reads file1 and file2, which should be sorted lexically,
     and produces three text columns as output: lines only in file1; lines  only
     in file2; and lines in both files.

     The filename ``-'' means the standard input.

     The following options are available:

     -1      Suppress printing of column 1, lines only in file1.

     -2      Suppress printing of column 2, lines only in file2.

     -3      Suppress printing of column 3, lines common to both.

     -i      Case insensitive comparison of lines.

     Each  column  will have a number of tab characters prepended to it equal to
     the number of lower numbered columns that are being printed.  For	example,
     if  column  number  two is being suppressed, lines printed in column number
     one will not have any tabs preceding them, and lines printed in column num-
     ber three will have one.

     The comm utility assumes that the files are lexically sorted;  all  charac-
     ters participate in line comparisons.

ENVIRONMENT
     The LANG, LC_ALL, LC_COLLATE, and LC_CTYPE environment variables affect the
     execution of comm as described in environ(7).

EXIT STATUS
     The comm utility exits 0 on success, and >0 if an error occurs.

EXAMPLES
     Assuming a file named example.txt with the following contents:

	   a
	   b
	   c
	   d

     Show lines only in example.txt, lines only in stdin and common lines:

	   $ echo -e "B\nc" | comm example.txt -
		   B
	   a
	   b
			   c
	   d

     Show only common lines doing case insensitive comparisons:

	   $ echo -e "B\nc" | comm -1 -2 -i example.txt -
	   b
	   c

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

STANDARDS
     The comm utility conforms to IEEE Std 1003.2-1992 ("POSIX.2").

     The -i option is an extension to the POSIX standard.

HISTORY
     A comm command appeared in Version 4 AT&T UNIX.

FreeBSD 15.1			  July 27, 2020 			 COMM(1)
home | help