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.
| Original author(s) | Ken Thompson (AT&T Bell Laboratories) |
|---|---|
| Developer(s) | Various open-source and commercial developers |
| Initial release | February 1973 |
| 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 |
Overview
editThe 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
editFirst 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
editReferences
edit- ^ McIlroy, M. D. (1987). A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 (PDF) (Technical report). CSTR. Bell Labs. 139.
- ^ – Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group
- ^ – 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
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