uniq

uniq
uniq
Original authors	Ken Thompson; (AT&T Bell Laboratories)
Developers	Various open-source and commercial developers
Release	February 1973; 53 years ago
Written in	C
Operating system	Unix, Unix-like, Plan 9, Inferno, MSX-DOS, IBM i
Platform	Cross-platform
Type	Command
License	coreutils: GPLv3+; Plan 9: MIT License
Website	man7.org/linux/man-pages/man1/uniq.1.html

uniq is a utility command on Unix, Plan 9, Inferno, and Unix-like operating systems which, when fed a text file or standard input, outputs the text with adjacent identical lines collapsed to one, unique line of text.

Overview

The command is a kind of filter program. Typically it is used after sort. It can also output only the duplicate lines (with the -d option), or add the number of occurrences of each line (with the -c option). For example, the following command lists the unique lines in a file, sorted by the number of times each occurs:

$ sort file | uniq -c | sort -n

Using uniq like this is common when building pipelines in shell scripts.

History

First appearing in Version 3 Unix,^[1] uniq is now available for a number of different Unix and Unix-like operating systems. It is part of the X/Open Portability Guide since issue 2 of 1987. It was inherited into the first version of POSIX and the Single Unix Specification.^[2]

The version bundled in GNU coreutils was written by Richard Stallman and David MacKenzie.^[3]

A uniq command is also part of ASCII's MSX-DOS2 Tools for MSX-DOS version 2.^[4]

The command is available as a separate package for Microsoft Windows as part of the GnuWin32 project^[5] and the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities.^[6]

The uniq command has also been ported to the IBM i operating system.^[7]

References

↑ McIlroy, M. D. (1987). A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 (PDF) (Technical report). CSTR. Bell Labs. 139.
↑ uniq – Shell and Utilities Reference, The Single UNIX Specification, Version 5 from The Open Group
↑ uniq(1) – Linux General Commands Manual from ManKier.com
↑ MSX-DOS2 Tools User's Manual by ASCII Corporation
↑ "CoreUtils for Windows". Archived from the original on 2025-07-30. Retrieved 2026-02-03.
↑ "Native Win32 ports of some GNU utilities". Archived from the original on 2006-02-09. Retrieved 2026-02-03.
↑ IBM. "IBM System i Version 7.2 Programming Qshell" (PDF). IBM. Archived (PDF) from the original on 2020-09-18. Retrieved 2020-09-05.

External links

uniq(1) – Linux User Manual – User Commands from Manned.org
uniq(1) – Plan 9 Programmer's Manual, Volume 1
uniq(1) – Inferno General commands Manual
SourceForge UnxUtils – Port of several GNU utilities to Windows

[reader-1] McIlroy, M. D. (1987). A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 (PDF) (Technical report). CSTR. Bell Labs. 139.

[2] uniq – Shell and Utilities Reference, The Single UNIX Specification, Version 5 from The Open Group

[3] uniq(1) – Linux General Commands Manual from ManKier.com

[4] MSX-DOS2 Tools User's Manual by ASCII Corporation

[5] "CoreUtils for Windows". Archived from the original on 2025-07-30. Retrieved 2026-02-03.

[6] "Native Win32 ports of some GNU utilities". Archived from the original on 2006-02-09. Retrieved 2026-02-03.

[7] IBM. "IBM System i Version 7.2 Programming Qshell" (PDF). IBM. Archived (PDF) from the original on 2020-09-18. Retrieved 2020-09-05.

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v t e Unix command-line utilities and shell builtins
File system	cat chattr chmod chown chgrp cksum cmp cp dd du df file fuser ln ls mkdir mv pax pwd rm rmdir split tee touch type umask
Processes	at bg crontab fg kill nice ps time
User environment	env exit logname mesg talk tput uname who write
Text processing	awk basename comm csplit cut diff dirname ed ex fold head iconv join m4 more nl paste patch printf read sed sort strings tail tr troff uniq vi wc xargs
Shell builtins	alias cd echo test unset wait
Searching	find grep
Documentation	man
Software development	ar ctags lex make nm strip yacc
Miscellaneous	bc cal dc expr lp od sleep true and false
Categories Standard Unix programs Unix SUS2008 utilities List

v t e Plan 9 command-line interface programs and shell builtins
File system	chmod chgrp cmp cp dd du file gzip ls mkdir pwd rm split tee touch
Processes	kill ps
User environment	passwd who
Text processing	awk basename comm diff ed eqn join sed sort spell strings tail tr troff uniq wc
Shell builtins	echo test
Networking	ip/ipconfig ip/ping netstat
Searching	grep
Software development	ar hoc lex nm strip yacc
Miscellaneous	bc cal fortune sleep
Category

v t e GNU Core Utilities command-line interface programs
File system	chcon chmod chown chgrp cksum cp dd df dir dircolors install ln ls mkdir mkfifo mknod mktemp mv realpath rm rmdir shred sync touch truncate vdir
Text utilities	b2sum base32 base64 cat cksum comm csplit cut expand fmt fold head join md5sum nl numfmt od paste ptx pr sha1sum shuf sort split sum tac tail tr tsort unexpand uniq wc
Shell utilities	arch basename chroot date dirname du echo env expr factor false groups hostid id link logname nice nohup nproc pathchk pinky printenv printf pwd readlink runcon seq sleep stat stdbuf stty tee test timeout true tty uname unlink uptime users who whoami yes

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uniq

Overview

History

See also

References

External links