UNIQ(1) Commands and Applications UNIQ(1)
uniq - report or filter out repeated lines in a file
uniq [-c | -du] [-i] [-f fields] [-s chars] [input [output]]
uniq [-fields] [+chars] [input [output]]
The uniq utility reads the standard input comparing adjacent lines, and
writes a copy of each unique input line to the standard 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.
The following options are available:
-c Precede each output line with the count of the number of
times the line occurred in the input, followed by a sin-
-d Print one copy of each repeated line in the input.
Ignore the first 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.
Ignore the first chars characters in each input line when
doing comparisons. If specified in conjunction with the
-f option, the first chars characters after the first
fields fields will be ignored. Character numbers are one
based, i.e. the first character is character one.
-u Print lines that are not repeated in the input.
-i Case insensitive comparison of lines.
If additional arguments are specified on the command line, the first
such argument is used as the name of an input file, the second is used
as the name of an output file.
If neither of the options d or u are specified on the command line,
uniq behaves as if both d and u are set, printing a single copy of
repeated lines as well as unrepeated lines.
The uniq utility exits 0 on success, and >0 if an error occurs.
The historic +number and -number options have been deprecated but are
still supported in this implementation.
This manual page documents uniq version 2.0.
This command was ported from FreeBSD source code for distribution with
A version of uniq written in 1992 was distributed with earlier releases
The uniq utility is expected to be POSIX-2 compatible.
GNO November 1997 UNIQ(1)
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