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UNIQ(1) BSD General Commands Manual UNIQ(1)
uniq -- report or filter out repeated lines in a file
uniq [-c | -d | -u] [-i] [-f num] [-s chars] [input_file [output_file]]
The uniq utility reads the specified input_file comparing adjacent lines, and writes a copy
of each unique input line to the output_file. If input_file is a single dash ('-') or
absent, the standard input is read. If 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 nec-
essary 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 single space.
-d Only output lines that are repeated in the input.
-f num Ignore the first 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 num-
bers 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 num fields will be ignored. Character numbers are one based, i.e. the first
character is character one.
-u Only output lines that are not repeated in the input.
-i Case insensitive comparison of 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
The uniq utility is expected to be IEEE Std 1003.2 (``POSIX.2'') compatible.
A uniq command appeared in Version 3 AT&T UNIX.
BSD June 6, 1993 BSD
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