Index: head/usr.bin/uniq/uniq.1
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--- head/usr.bin/uniq/uniq.1	(revision 361890)
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 .\" Copyright (c) 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
 .\"
 .\" This code is derived from software contributed to Berkeley by
 .\" the Institute of Electrical and Electronics Engineers, Inc.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\" 3. Neither the name of the University nor the names of its contributors
 .\"    may be used to endorse or promote products derived from this software
 .\"    without specific prior written permission.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
 .\"     From: @(#)uniq.1	8.1 (Berkeley) 6/6/93
 .\" $FreeBSD$
 .\"
-.Dd December 15, 2019
+.Dd June 7, 2020
 .Dt UNIQ 1
 .Os
 .Sh NAME
 .Nm uniq
 .Nd report or filter out repeated lines in a file
 .Sh SYNOPSIS
 .Nm
 .Op Fl c | Fl d | Fl D | Fl u
 .Op Fl i
 .Op Fl f Ar num
 .Op Fl s Ar chars
 .Oo
 .Ar input_file
 .Op Ar output_file
 .Oc
 .Sh DESCRIPTION
 The
 .Nm
 utility reads the specified
 .Ar input_file
 comparing adjacent lines, and writes a copy of each unique input line to
 the
 .Ar output_file .
 If
 .Ar input_file
 is a single dash
 .Pq Sq Fl
 or absent, the standard input is read.
 If
 .Ar output_file
 is absent, standard output is used for output.
 The second and succeeding copies of identical adjacent input lines are
 not written.
 Repeated lines in the input will not be detected if they are not adjacent,
 so it may be necessary to sort the files first.
 .Pp
 The following options are available:
 .Bl -tag -width Ds
 .It Fl c , Fl -count
 Precede each output line with the count of the number of times the line
 occurred in the input, followed by a single space.
 .It Fl d , Fl -repeated
 Output a single copy of each line that is repeated in the input.
 .It Fl D , Fl -all-repeated Op Ar septype
 Output all lines that are repeated (like
 .Fl d ,
 but each copy of the repeated line is written).
 The optional
 .Ar septype
 argument controls how to separate groups of repeated lines in the output;
 it must be one of the following values:
 .Pp
 .Bl -tag -compact -width separate
 .It none
 Do not separate groups of lines (this is the default).
 .It prepend
 Output an empty line before each group of lines.
 .It separate
 Output an empty line after each group of lines.
 .El
 .It Fl f Ar num , Fl -skip-fields Ar num
 Ignore the first
 .Ar num
 fields in each input line when doing comparisons.
 A field is a string of non-blank characters separated from adjacent fields
 by blanks.
 Field numbers are one based, i.e., the first field is field one.
 .It Fl i , Fl -ignore-case
 Case insensitive comparison of lines.
 .It Fl s Ar chars , Fl -skip-chars Ar chars
 Ignore the first
 .Ar chars
 characters in each input line when doing comparisons.
 If specified in conjunction with the
 .Fl f , Fl -unique
 option, the first
 .Ar chars
 characters after the first
 .Ar num
 fields will be ignored.
 Character numbers are one based, i.e., the first character is character one.
 .It Fl u , Fl -unique
 Only output lines that are not repeated in the input.
 .\".It Fl Ns Ar n
 .\"(Deprecated; replaced by
 .\".Fl f ) .
 .\"Ignore the first n
 .\"fields on each input line when doing comparisons,
 .\"where n is a number.
 .\"A field is a string of non-blank
 .\"characters separated from adjacent fields
 .\"by blanks.
 .\".It Cm \&\(pl Ns Ar n
 .\"(Deprecated; replaced by
 .\".Fl s ) .
 .\"Ignore the first
 .\".Ar m
 .\"characters when doing comparisons, where
 .\".Ar m
 .\"is a
 .\"number.
 .El
 .Sh ENVIRONMENT
 The
 .Ev LANG ,
 .Ev LC_ALL ,
 .Ev LC_COLLATE
 and
 .Ev LC_CTYPE
 environment variables affect the execution of
 .Nm
 as described in
 .Xr environ 7 .
 .Sh EXIT STATUS
 .Ex -std
+.Sh EXAMPLES
+Assuming a file named cities.txt with the following content:
+.Bd -literal -offset indent
+Madrid
+Lisbon
+Madrid
+.Ed
+.Pp
+The following command reports three different lines since identical elements
+are not adjacent:
+.Bd -literal -offset indent
+$ uniq -u cities.txt
+Madrid
+Lisbon
+Madrid
+.Ed
+.Pp
+Sort the file and count the number of identical lines:
+.Bd -literal -offset indent
+$ sort cities.txt | uniq -c
+	1 Lisbon
+	2 Madrid
+.Ed
+.Pp
+Assuming the following content for the file cities.txt:
+.Bd -literal -offset indent
+madrid
+Madrid
+Lisbon
+.Ed
+.Pp
+Show repeated lines ignoring case sensitiveness:
+.Bd -literal -offset indent
+$ uniq -d -i cities.txt
+madrid
+.Ed
+.Pp
+Same as above but showing the whole group of repeated lines:
+.Bd -literal -offset indent
+$ uniq -D -i cities.txt
+madrid
+Madrid
+.Ed
+.Pp
+Report the number of identical lines ignoring the first character of every line:
+.Bd -literal -offset indent
+$ uniq -s 1 -c cities.txt
+	2 madrid
+	1 Lisbon
+.Ed
 .Sh COMPATIBILITY
 The historic
 .Cm \&\(pl Ns Ar number
 and
 .Fl Ns Ar number
 options have been deprecated but are still supported in this implementation.
 .Sh SEE ALSO
 .Xr sort 1
 .Sh STANDARDS
 The
 .Nm
 utility conforms to
 .St -p1003.1-2001
 as amended by Cor.\& 1-2002.
 .Sh HISTORY
 A
 .Nm
 command appeared in
 .At v3 .