Uniq

Last updated
uniq
Original authors Ken Thompson
(AT&T Bell Laboratories)
Developers Various open-source and commercial developers
Initial releaseFebruary 1973;52 years ago (1973-02)
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.

Contents

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:

$sortfile|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]

See also

References

  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
  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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