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UNIQ(1) BSD General Commands Manual UNIQ(1)
uniq -- report or filter out repeated lines in a file
uniq [-cdu] [-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 identi-
cal 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 single space.
-d Don't output lines that are not repeated 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 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 fields fields will be ignored. Character numbers are one based, i.e. the
first character is character one.
-u Don't output lines that are repeated in the input.
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.
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.
BSD January 6, 2007 BSD
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