`comm`

Select or reject lines common to two files (POSIX)

Syntax:

comm [-1] [-2] [-3] file1 file2

Options:

-1: (the number one) Suppress writing of lines found only in file1.
-2: Suppress writing of lines found only in file2.
-3: Suppress writing of lines found in both file1 & file2.
file1: A pathname of the first file to be compared. If file1 is -, the standard input is used.
file2: A pathname of the second file to be compared. If file2 is -, the standard input is used.

Description:

The comm utility reads file1 and file2, which must be ordered in collating sequence (see the sort utility), and produces three text columns as output.

This column:	Contains:
1	lines found only in file1
2	lines found only in file2
3	lines found in both files

Examples:

Print only the lines common to both files:

comm -12 test.dat save.dat

Files:

The standard input is used only if specified as a dash (-) command-line file parameter.

All input files must be text files for comm to produce a meaningful result.

The results of the comparison will be written to standard output.

Errors will result in diagnostic messages being written to standard error.

Exit status:

0: All input files were successfully output as specified.
>0: An error occurred.