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 |
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.
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
pipelines in
shell 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]
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]