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Mac OS X Tiger in a Nutshell by Jason McIntosh, Chuck Toporek, Chris Stone, Andy Lester

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Name

uniq

Synopsis

uniq [options] [file1 [file2]]

Removes duplicate adjacent lines from sorted file1, sending one copy of each line to file2 (or to standard output). Often used as a filter. Specify only one of -c, -d, or -u. See also comm and sort .

Options

-c

Print each line once, counting instances of each.

-d

Print duplicate lines once, but no unique lines.

-f n

Ignore the first n fields of a line. Fields are separated by spaces or by tabs.

-s n

Ignore the first n characters of a field.

-u

Print only unique lines (no copy of duplicate entries is kept).

- n

Ignore the first n fields of a line. Fields are separated by spaces or by tabs.

+ n

Ignore the first n characters of a field. Both [-/+]n have been deprecated but are still in this version.

Examples

Send one copy of each line from list to output file list.new(list must be sorted):

$ uniq list list.new

Show which names appear more than once:

$ sort names | uniq -d

Show which lines appear exactly three times:

$ sort names | uniq -c | awk '$1 =  = 3'

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