uniq is a utility command (computing), command on Unix, Plan 9 from Bell Labs, Plan 9, Inferno (operating system), Inferno, and Unix-like operating systems 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),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:
uniq like this is common when building pipeline (software), pipelines in shell scripts.
History
First appearing in Version 3 Unix,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.
The version bundled in GNU coreutils was written by Richard Stallman and David MacKenzie.
A uniq command is also part of ASCII Corporation, ASCII's ''MSX-DOS2 Tools'' for MSX-DOS version 2.
The command is available as a separate package for Microsoft Windows as part of the GnuWin32 project and the UnxUtils collection of Native (computing), native Windows API, Win32 porting, ports of common GNU Unix-like utilities.
The command has also been ported to the IBM i operating system.
See also
* List of Unix commandsReferences
External links
* * *