Editing Uniq

{{short description|Unix text filtering utility}}
{{about|the command-line utility|other uses|Uniq (disambiguation)}}
{{lowercase title}}
{{Infobox software
| name                   = uniq
| logo                   = 
| screenshot             = 
| screenshot size        = 
| caption                = 
| author                 = [[Ken Thompson]]<br />([[AT&T Bell Laboratories]])
| developer              = Various [[open-source software|open-source]] and [[commercial software|commercial]] developers
| released               = {{Start date and age|1973|2}}
| latest release version = 
| latest release date    = 
| programming language   = [[C (programming language)|C]]
| operating system       = [[Unix]], [[Unix-like]], [[Plan 9 from Bell Labs|Plan 9]], [[Inferno (operating system)|Inferno]], [[MSX-DOS]], [[IBM i]]
| platform               = [[Cross-platform]]
| genre                  = [[Command (computing)|Command]]
| license                = [[coreutils]]: [[GPLv3+]]<br />Plan 9: [[MIT License]]
| website                = {{URL|http://man7.org/linux/man-pages/man1/uniq.1.html}}
}}
<code>'''uniq'''</code> is a utility [[command (computing)|command]] on [[Unix]], [[Plan 9 from Bell Labs|Plan 9]], [[Inferno (operating system)|Inferno]], and [[Unix-like]] [[operating system]]s which, when fed a [[text file]] or [[Standard streams#Standard input (stdin)|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 (Unix)|<code>sort</code>]]. It can also output only the duplicate lines (with the <code>-d</code> option), or add the number of occurrences of each line (with the <code>-c</code> option). For example, the following command lists the unique lines in a file, sorted by the number of times each occurs:

<syntaxhighlight lang="sh">
$ sort file | uniq -c | sort -n
</syntaxhighlight>

Using <code>uniq</code> like this is common when building [[pipeline (software)|pipelines]] in [[shell script]]s.

==History==
First appearing in [[Version 3 Unix]],<ref name="reader">{{cite tech report
 | first1      = M. D.
 | last1       = McIlroy
 | authorlink1 = Doug McIlroy
 | year        = 1987
 | url         = https://www.cs.dartmouth.edu/~doug/reader.pdf
 | title       = A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986
 | series      = CSTR
 | number      = 139
 | institution = Bell Labs}}</ref> <code>uniq</code> is now available for a number of different [[Unix]] and [[Unix-like]] [[operating system]]s. 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]].<ref>{{man|cu|uniq|SUS}}</ref>

The version bundled in [[GNU]] [[coreutils]] was written by [[Richard Stallman]] and David MacKenzie.<ref>{{man|1|uniq|ManKier}}</ref>

A <code>uniq</code> command is also part of [[ASCII Corporation|ASCII]]'s ''MSX-DOS2 Tools'' for [[MSX-DOS]] version 2.<ref>[https://archive.org/details/MSXDOS2TOOLS MSX-DOS2 Tools User's Manual by ASCII Corporation]</ref>

The command is available as a separate package for [[Microsoft Windows]] as part of the [[GnuWin32]] project<ref>[http://gnuwin32.sourceforge.net/packages/coreutils.htm CoreUtils for Windows]</ref> and the [[UnxUtils]] collection of [[Native (computing)|native]] [[Windows API|Win32]] [[porting|ports]] of common GNU Unix-like utilities.<ref>[http://unxutils.sourceforge.net/ Native Win32 ports of some GNU utilities]</ref>

The {{Mono|uniq}} command has also been ported to the [[IBM i]] operating system.<ref>{{cite web |title=IBM System i Version 7.2 Programming Qshell |language=en |author=IBM |website=[[IBM]] |author-link=IBM |url=https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_74/rzahz/rzahzpdf.pdf?view=kc |access-date=2020-09-05 }}</ref>

==See also==
* [[List of Unix commands]]

==References==
{{Reflist}}

==External links==
{{Wikibooks|Guide to Unix|Commands}}
* {{man|1|uniq|Linux}}
* {{man|1|uniq|Plan 9}}
* {{man|1|uniq|Inferno}}
* [https://sourceforge.net/projects/unxutils/ SourceForge UnxUtils – Port of several GNU utilities to Windows]

{{Unix commands}}
{{Plan 9 commands}}
{{Core Utilities commands}}

[[Category:Unix text processing utilities]]
[[Category:Unix SUS2008 utilities]]
[[Category:Plan 9 commands]]
[[Category:Inferno (operating system) commands]]
[[Category:IBM i Qshell commands]]