Manual browser: uniq(1)

UNIQ(1) General Commands Manual UNIQ(1)


uniqreport 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 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:

Precede each output line with the count of the number of times the line occurred in the input, followed by a single space.
Don't output lines that are not repeated in the input.
-f fields
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.
-s chars
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.
Don't output lines that are repeated in the input.

Additional arguments input_file and output_file may be specified on the command line, where the former is then used as the name of an input file, and the latter 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 this implementation.




The uniq utility is expected to be IEEE Std 1003.2 (“POSIX.2”) compatible.
August 26, 2012 NetBSD 7.0