UNIQ(1) General Commands Manual UNIQ(1)
uniq - report or filter out repeated lines in a file
uniq [-ci] [-d | -u] [-f fields] [-s chars] [input_file [output_file]]
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 options are as follows:
-c Precede each output line with the count of the number of times
the line occurred in the input, followed by a single space.
-d Only output lines which have duplicates.
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, with blanks considered
part of the following field. Field numbers are one based, i.e.,
the first field is field one.
-i Regard lower and upper case ASCII characters as identical.
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 Only output lines which are unique.
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. A file name of `-' denotes the standard input or
the standard output (depending on its position on the command line).
LC_CTYPE The character encoding locale(1). It decides which byte
sequences form characters and which characters are considered
blank. If unset or set to "C", "POSIX", or an unsupported
value, each byte is treated as a character, and only space and
tab are considered blank.
This variable is ignored for case comparisons. Lower and upper
case versions of non-ASCII characters are always considered
The uniq utility exits 0 on success, and >0 if an error occurs.
The uniq utility is compliant with the IEEE Std 1003.1-2008 ("POSIX.1")
The -i option and the use of -c in conjunction with -d or -u are
extensions to that specification.
The historic +number and -number options have been deprecated but are
still supported in this implementation.
OpenBSD 6.4 December 23, 2017 OpenBSD 6.4
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