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.
Examples:
Print only the lines common to both files:
comm -12 test.dat save.dat
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 |
Exit status:
- 0
- All input files were successfully output as specified.
- >0
- An error occurred.
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.
See also:
- cmp utility (Compare two binary files)
- diff utility (Report the differences between two text files)
- sort utility (Sort, merge or sequence-check text files)
- uniq utility (Report or filter out repeated lines in a file)