uniq

uniq
Original author(s)	Ken Thompson; (AT&T Bell Laboratories)
Developer(s)	Various open-source and commercial developers
Initial release	February 1973; 51 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 4 from The Open Group
^ uniq(1) – Linux General Commands Manual
^ MSX-DOS2 Tools User's Manual by ASCII Corporation
^ CoreUtils for Windows
^ Native Win32 ports of some GNU utilities
^ IBM. "IBM System i Version 7.2 Programming Qshell" (PDF). IBM. Retrieved 2020-09-05.

External links

uniq(1) – Linux User Manual – User Commands
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 4 from The Open Group

[3] uniq(1) – Linux General Commands Manual

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

[5] CoreUtils for Windows

[6] Native Win32 ports of some GNU utilities

[7] IBM. "IBM System i Version 7.2 Programming Qshell" (PDF). IBM. Retrieved 2020-09-05.

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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
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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
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Overview

History

See also

References

External links