Original author(s) | Ken Thompson (AT&T Bell Laboratories) |
---|---|
Developer(s) | Various open-source and commercial developers |
Initial release | February 1973; 51 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 |
uniq
is a utility commandonUnix, Plan 9, Inferno, and Unix-like operating systems which, when fed a text fileorstandard input, outputs the text with adjacent identical lines collapsed to one, unique line of text.
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 pipelinesinshell scripts.
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]
Auniq
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]
uniq
– Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group
uniq(1)
– Linux General Commands Manual
uniq(1)
– Linux User Manual – User Commandsuniq(1)
– Plan 9 Programmer's Manual, Volume 1uniq(1)
– Inferno General commands Manual
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