comm.md

comm

common

compare two sorted files line by line

---

References

• man comm

Quickstart

comm file1 file2        # Compare file1 with file2
comm -12 file1 file2    # Print lines in both file1 & file2
comm -23 file1 file2    # Lines unique to file1
comm -13 file1 file2    # Lines unique to file2

Options

Column

Meanings of Column N to FILE N

• Column 1 contains lines unique to FILE1.
• Column 2 contains lines unique to FILE2.
• Column 3 contains lines common to both files.

How to use options -1, -2, -3 ?

• -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)
• With no options, produce three-column output.

Others

• --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

Usage

Sample

$ cat file1
1
2
3

$ cat file2
2
3
4

Default

$ comm file1 file2
# column : 1 , 2 , 3
1
                2
                3
        4

Column N

Suppress Column 1

Print only lines present in both file1 and file2.

$ comm -1 file1 file2
        2
        3
4

Suppress Column 2

Print lines in file2 not in file1, and vice versa.

$ comm -2 file1 file2
1
        2
        3

Suppress Column 3

Print lines in file1 not in file2, and vice versa.

$ comm -3 file1 file2
1
        4

Trim Leading Whitespace

comm -3 file1 file2 | sed 's/^\s*//g'
1
4

Set

Intersection

$ comm -12 file1 file2
2
3

Difference Set

File1 - File2

$ comm -23 file1 file2
1

File2 - File1

$ comm -13 file1 file2
4