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.TH UNIQ 1 "May 23, 2021"
.SH NAME
uniq \- report or filter out repeated lines in a file
.SH SYNOPSIS
.SS "/usr/bin/uniq"
.nf
\fB/usr/bin/uniq\fR [\fB-c\fR | \fB-d\fR | \fB-u\fR] [\fB-f\fR \fIfields\fR] [\fB-s\fR \fIchar\fR]
     [\fIinput_file\fR [\fIoutput_file\fR]]
.fi

.LP
.nf
\fB/usr/bin/uniq\fR [\fB-c\fR | \fB-d\fR | \fB-u\fR] [\fB-n\fR] [+ \fIm\fR] [\fIinput_file\fR [\fIoutput_file\fR]]
.fi

.SS "ksh93"
.nf
\fBuniq\fR [\fB-cdiu\fR] [\fB-D\fR[\fIdelimit\fR]] [\fB-f\fR \fIfields\fR] [\fB-s\fR \fIchars\fR] [\fB-w\fR \fIchars\fR]
     [\fIinput_file\fR [\fIoutput_file\fR]]
.fi

.LP
.nf
\fBuniq\fR [\fB-cdiu\fR] [\fB-D\fR[\fIdelimit\fR]] [\fB-n\fR] [\fB+m\fR] [\fB-w\fR \fIchars\fR] [\fIinput_file\fR [\fIoutput_file\fR]]
.fi

.SH DESCRIPTION
.SS "/usr/bin/uniq"
The \fBuniq\fR utility reads an input file comparing adjacent lines and writes
one copy of each input line on the output. The second and succeeding copies of
repeated adjacent input lines are not written.
.sp
.LP
Repeated lines in the input are not detected if they are not adjacent.
.SS "ksh93"
The \fBuniq\fR built-in in \fBksh93\fR is associated with the \fB/bin\fR or
\fB/usr/bin path\fR. It is invoked when \fBuniq\fR is executed without a
pathname prefix and the pathname search finds a \fB/bin/uniq\fR or
\fB/usr/bin/uniq\fR executable.
.sp
.LP
\fBuniq\fR reads an input, comparing adjacent lines, and writing one copy of
each input line on the output. The second and succeeding copies of the repeated
adjacent lines are not written.
.sp
.LP
If \fIoutput_file\fR is not specified, \fBuniq\fR writes to standard output. If
\fIinput_file\fR is not specified, or if \fIinput_file\fR is \fB-\fR,
\fBuniq\fR reads from standard input, and the start of the file is defined as
the current offset.
.SH OPTIONS
.SS "/usr/bin/uniq"
The following options are supported by \fB/usr/bin/uniq\fR:
.sp
.ne 2
.na
\fB\fB-c\fR\fR
.ad
.RS 13n
Precedes each output line with a count of the number of times the line occurred
in the input.
.RE

.sp
.ne 2
.na
\fB\fB-d\fR\fR
.ad
.RS 13n
Suppresses the writing of lines that are not repeated in the input.
.RE

.sp
.ne 2
.na
\fB\fB-f\fR \fIfields\fR\fR
.ad
.RS 13n
Ignores the first \fIfields\fR fields on each input line when doing
comparisons, where \fIfields\fR is a positive decimal integer. A field is the
maximal string matched by the basic regular expression:
.sp
.in +2
.nf
[[:blank:]]*[^[:blank:]]*
.fi
.in -2
.sp

If \fIfields\fR specifies more fields than appear on an input line, a null
string is used for comparison.
.RE

.sp
.ne 2
.na
\fB\fB+\fR\fIm\fR\fR
.ad
.RS 13n
Equivalent to \fB-s\fR \fIchars\fR with \fIchars\fR set to \fIm\fR.
.RE

.sp
.ne 2
.na
\fB\fB\(mi\fR\fIn\fR\fR
.ad
.RS 13n
Equivalent to \fB-f\fR \fIfields\fR with \fIfields\fR set to \fIn\fR.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR \fIchars\fR\fR
.ad
.RS 13n
Ignores the first \fIchars\fR characters when doing comparisons, where
\fIchars\fR is a positive decimal integer. If specified in conjunction with the
\fB-f\fR option, the first \fIchars\fR characters after the first \fIfields\fR
fields is ignored. If \fIchars\fR specifies more characters than remain on an
input line, a null string is used for comparison.
.RE

.sp
.ne 2
.na
\fB\fB-u\fR\fR
.ad
.RS 13n
Suppresses the writing of lines that are repeated in the input.
.RE

.SS "ksh93"
The following options are supported by the \fBuniq\fR built-in command is
\fBksh93\fR:
.sp
.ne 2
.na
\fB\fB-c\fR\fR
.ad
.br
.na
\fB\fB--count\fR\fR
.ad
.RS 28n
Outputs the number of times each line occurred along with the line.
.RE

.sp
.ne 2
.na
\fB\fB-d\fR\fR
.ad
.br
.na
\fB\fB--repeated | duplicates\fR\fR
.ad
.RS 28n
Outputs only duplicate lines.
.RE

.sp
.ne 2
.na
\fB\fB-D\fR\fR
.ad
.br
.na
\fB\fB--all-repeated\fR[\fB=\fR\fIdelimit\fR]\fR
.ad
.RS 28n
Outputs all duplicate lines as a group with an empty line delimiter specified
by \fIdelimit\fR.
.sp
Specify \fIdelimit\fR as one of the following:
.sp
.ne 2
.na
\fB\fBnone\fR\fR
.ad
.RS 12n
Do not delimit duplicate groups.
.RE

.sp
.ne 2
.na
\fB\fBprepend\fR\fR
.ad
.RS 12n
Prepend an empty line before each group.
.RE

.sp
.ne 2
.na
\fB\fBseparate\fR\fR
.ad
.RS 12n
Separate each group with an empty line.
.RE

The value for \fIdelimit\fR can be omitted. The default value is \fBnone\fR.
.RE

.sp
.ne 2
.na
\fB\fB-f\fR\fR
.ad
.br
.na
\fB\fB--skip-fields=\fR\fIfields\fR\fR
.ad
.RS 28n
Skips over \fIfields\fR number of fields before checking for uniqueness. A
field is the minimal string matching the \fBBRE
[[:\fR\fIblank\fR\fB:]]*[^[:\fR\fIblank\fR\fB:]]*\fR.
.RE

.sp
.ne 2
.na
\fB\fB-i\fR\fR
.ad
.br
.na
\fB\fB--ignore-case\fR\fR
.ad
.RS 28n
Ignore case in comparisons.
.RE

.sp
.ne 2
.na
\fB\fB+\fR\fIm\fR\fR
.ad
.RS 28n
Equivalent to the \fB-s\fR \fIchars\fR option, with \fIchars\fR set to \fIm\fR.
.RE

.sp
.ne 2
.na
\fB\fB-\fR\fIn\fR\fR
.ad
.RS 28n
Equivalent to the \fB-f\fR \fIfields\fR option, with \fIfields\fR set to
\fIn\fR.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR\fR
.ad
.br
.na
\fB\fB--skip-chars=\fR\fIchars\fR\fR
.ad
.RS 28n
Skips over \fIchars\fR number of characters before checking for uniqueness.
.sp
If specified with the \fB-f\fR option, the first \fIchars\fR after the first
fields are ignored. If the \fIchars\fR specifies more characters than are on
the line, an empty string is used for comparison.
.RE

.sp
.ne 2
.na
\fB\fB-u\fR\fR
.ad
.br
.na
\fB\fB--uniq\fR\fR
.ad
.RS 28n
Outputs unique lines.
.RE

.sp
.ne 2
.na
\fB\fB-w\fR\fR
.ad
.br
.na
\fB\fB--check-chars=\fR\fIchars\fR\fR
.ad
.RS 28n
Skips over any specified fields and characters, then compares \fIchars\fR
number of characters.
.RE

.SH OPERANDS
The following operands are supported:
.sp
.ne 2
.na
\fB\fIinput_file\fR\fR
.ad
.RS 15n
A path name of the input file. If \fIinput_file\fR is not specified, or if the
\fIinput_file\fR is \fB\(mi\fR, the standard input is used.
.RE

.sp
.ne 2
.na
\fB\fIoutput_file\fR\fR
.ad
.RS 15n
A path name of the output file. If \fIoutput_file\fR is not specified, the
standard output is used. The results are unspecified if the file named by
\fIoutput_file\fR is the file named by \fIinput_file\fR.
.RE

.SH EXAMPLES
\fBExample 1 \fRUsing the \fBuniq\fR Command
.sp
.LP
The following example lists the contents of the \fBuniq.test\fR file and
outputs a copy of the repeated lines.

.sp
.in +2
.nf
example% \fBcat uniq.test\fR
This is a test.
This is a test.
TEST.
Computer.
TEST.
TEST.
Software.

example% \fBuniq -d uniq.test\fR
This is a test.
TEST.
example%
.fi
.in -2
.sp

.sp
.LP
The next example outputs just those lines that are not repeated in the
\fBuniq.test\fR file.

.sp
.in +2
.nf
example% \fBuniq -u uniq.test\fR
TEST.
Computer.
Software.
example%
.fi
.in -2
.sp

.sp
.LP
The last example outputs a report with each line preceded by a count of the
number of times each line occurred in the file:

.sp
.in +2
.nf
example% \fBuniq -c uniq.test\fR
   2 This is a test.
   1 TEST.
   1 Computer.
   2 TEST.
   1 Software.
example%
.fi
.in -2
.sp

.SH ENVIRONMENT VARIABLES
See \fBenviron\fR(7) for descriptions of the following environment variables
that affect the execution of \fBuniq\fR: \fBLANG\fR, \fBLC_ALL\fR,
\fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
.SH EXIT STATUS
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 6n
Successful completion.
.RE

.sp
.ne 2
.na
\fB\fB>0\fR\fR
.ad
.RS 6n
An error occurred.
.RE

.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.SS "/usr/bin/uniq"
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
CSI	Enabled
_
Interface Stability	Committed
_
Standard	See \fBstandards\fR(7).
.TE

.SS "ksh93"
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	See below.
.TE

.sp
.LP
The \fBksh93\fR built-in binding to \fB/bin\fR and \fB/usr/bin\fR is Volatile.
The built-in interfaces are Uncommitted.
.SH SEE ALSO
.BR comm (1),
.BR ksh93 (1),
.BR sort (1),
.BR attributes (7),
.BR environ (7),
.BR standards (7)