1.\" $OpenBSD: uniq.1,v 1.22 2021/11/02 15:12:09 millert Exp $ 2.\" $NetBSD: uniq.1,v 1.5 1994/12/06 07:51:15 jtc Exp $ 3.\" 4.\" Copyright (c) 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" This code is derived from software contributed to Berkeley by 8.\" the Institute of Electrical and Electronics Engineers, Inc. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)uniq.1 8.1 (Berkeley) 6/6/93 35.\" 36.Dd $Mdocdate: November 2 2021 $ 37.Dt UNIQ 1 38.Os 39.Sh NAME 40.Nm uniq 41.Nd report or filter out repeated lines in a file 42.Sh SYNOPSIS 43.Nm uniq 44.Op Fl ci 45.Op Fl d | u 46.Op Fl f Ar fields 47.Op Fl s Ar chars 48.Oo 49.Ar input_file 50.Op Ar output_file 51.Oc 52.Sh DESCRIPTION 53The 54.Nm 55utility reads the standard input comparing adjacent lines and writes 56a copy of each unique input line to the standard output. 57The second and succeeding copies of identical adjacent input lines are 58not written. 59Repeated lines in the input will not be detected if they are not adjacent, 60so it may be necessary to sort the files first. 61.Pp 62The options are as follows: 63.Bl -tag -width Ds 64.It Fl c 65Precede each output line with the count of the number of times the line 66occurred in the input, followed by a single space. 67.It Fl d 68Only output lines which have duplicates. 69.It Fl f Ar fields 70Ignore the first 71.Ar fields 72in each input line when doing comparisons. 73A field is a string of non-blank characters separated from adjacent fields 74by blanks, with blanks considered part of the following field. 75Field numbers are one based, i.e., the first field is field one. 76.It Fl i 77Regard lower and upper case ASCII characters as identical. 78.It Fl s Ar chars 79Ignore the first 80.Ar chars 81characters in each input line when doing comparisons. 82If specified in conjunction with the 83.Fl f 84option, the first 85.Ar chars 86characters after the first 87.Ar fields 88fields will be ignored. 89Character numbers are one based, i.e., the first character is character one. 90.It Fl u 91Only output lines which are unique. 92.\".It Fl Ns Ar n 93.\"(Deprecated; replaced by 94.\".Fl f ) . 95.\"Ignore the first n 96.\"fields on each input line when doing comparisons, 97.\"where n is a number. 98.\"A field is a string of non-blank 99.\"characters separated from adjacent fields 100.\"by blanks. 101.\".It Cm \&\(pl Ns Ar n 102.\"(Deprecated; replaced by 103.\".Fl s ) . 104.\"Ignore the first 105.\".Ar m 106.\"characters when doing comparisons, where 107.\".Ar m 108.\"is a 109.\"number. 110.El 111.Pp 112If additional arguments are specified on the command line, the first 113such argument is used as the name of an input file, the second is used 114as the name of an output file. 115A file name of 116.Ql - 117denotes the standard input or the standard output 118.Pq depending on its position on the command line . 119.Sh ENVIRONMENT 120.Bl -tag -width LC_CTYPE 121.It Ev LC_CTYPE 122The character encoding 123.Xr locale 1 . 124It decides which byte sequences form characters 125and which characters are considered blank. 126If unset or set to 127.Qq C , 128.Qq POSIX , 129or an unsupported value, each byte is treated as a character, 130and only space and tab are considered blank. 131.Pp 132This variable is ignored for case comparisons. 133Lower and upper case versions of non-ASCII characters are always 134considered different. 135.El 136.Sh EXIT STATUS 137.Ex -std uniq 138.Sh SEE ALSO 139.Xr sort 1 140.Sh STANDARDS 141The 142.Nm 143utility is compliant with the 144.St -p1003.1-2008 145specification. 146.Pp 147The 148.Fl i 149option and the use of 150.Fl c 151in conjunction with 152.Fl d 153or 154.Fl u 155are extensions to that specification. 156.Pp 157The historic 158.Cm + Ns Ar number 159and 160.Fl Ns Ar number 161options have been deprecated but are still supported in this implementation. 162.Sh HISTORY 163A 164.Nm 165utility first appeared in 166.At v3 . 167