oam/knowledge base/comm.md

comm

Compares two files line by line.

With no options, produces 3 columns in output:

• column 1 contains lines unique to file 1;
• column 2 contains lines unique to file 2;
• column 3 contains lines common to both files.

Comparisons honor the rules specified by 'LC_COLLATE'.

Table of contents

1. TL;DR
2. Further readings
3. Sources

TL;DR

# Print only lines present in both file1 and file2.
comm -12 'path/to/pre-sorted/file1' 'path/to/pre-sorted/file2'

# Print unique lines of file1 which are not present in file2.
comm -23 'path/to/pre-sorted/file1' 'path/to/pre-sorted/file2'
comm -23 <(sort -u 'path/to/file1') <(sort -u 'path/to/file2')

# Check the whole content of file1 is present in file2.
test $(comm -23 'path/to/pre-sorted/file1' <(sort -u 'path/to/file2') | wc -l) -eq 0
[[ $(comm -23 <(sort -u 'path/to/file1') 'path/to/pre-sorted/file2' | wc -l) -eq 0 ]]

Further readings

• cmp
• man page

Sources

All the references in the further readings section, plus the following:

• Check whether all lines of file occur in different file
• 6 more terminal commands you should know