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UNIX in a Nutshell: System V Edition

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UNIX Commands
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uniq



uniq

 [

options

] [

file1

 [

file2

]]

Remove 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.

-u

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

- n

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

+ n

Ignore first n characters of a field.

Examples

Send one copy of each line from list to output file list.new :



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 | grep "3 "


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