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📛 NAME

comm - compare two sorted files line by line

🚀 Quick Reference

Use Case	Command	Description
🔹 Common lines only	comm -12 file1 file2	Suppress columns 1 & 2 (unique lines), leaving only lines present in both files
🔹 Lines unique to FILE1	comm -23 file1 file2	Suppress columns 2 & 3, showing lines only in FILE1
🔹 Lines unique to FILE2	comm -13 file1 file2	Suppress columns 1 & 3, showing lines only in FILE2
🔹 Lines unique to either file (no common lines)	comm -3 file1 file2	Suppress column 3 (common lines), showing lines unique to each file
🔹 Verify sorted order	comm --check-order file1 file2	Check that input files are correctly sorted
🔹 NUL‑terminated lines	comm -z file1 file2	Use NUL as line delimiter
🔹 Summary only	comm --total file1 file2	Output a summary of counts

📖 Synopsis

comm [OPTION]... FILE1 FILE2

📝 Description

Compare sorted files FILE1 and FILE2 line by line.

When FILE1 or FILE2 (not both) is -, read standard input.

With no options, produce three‑column output. Column one contains lines unique to FILE1, column two contains lines unique to FILE2, and column three contains lines common to both files.

⚙️ Options

🔸 -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)

🔸 --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

🔸 --total

output a summary

🔸 -z, --zero-terminated

line delimiter is NUL, not newline

🔸 --help

display this help and exit

🔸 --version

output version information and exit

Note: comparisons honor the rules specified by 'LC_COLLATE'.

📋 Examples

comm -12 file1 file2

🔹 Print only lines present in both file1 and file2.

comm -3 file1 file2

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

✍️ Author

Written by Richard M. Stallman and David MacKenzie.

🐛 Reporting Bugs

GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>

©️ Copyright

Copyright © 2020 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

📚 See Also

join(1), uniq(1)

Full documentation <https://www.gnu.org/software/coreutils/comm>
or available locally via: info '(coreutils) comm invocation'

📛 NAME 🚀 Quick Reference 📖 Synopsis 📝 Description ⚙️ Options 📋 Examples ✍️ Author 🐛 Reporting Bugs ©️ Copyright 📚 See Also