uniq(1) — Linux manual pages

Linux manual pages	Section 1

DESCRIPTION

Filter adjacent matching lines from INPUT (or standard input), writing to OUTPUT (or standard output).

With no options, matching lines are merged to the first occurrence.

Mandatory arguments to long options are mandatory for short options too.

−c, −−count: prefix lines by the number of occurrences
−d, −−repeated: only print duplicate lines, one for each group
−D, −−all−repeated[=METHOD]: print all duplicate lines; groups can be delimited with an empty line; METHOD={none(default),prepend,separate}
−f, −−skip−fields=N: avoid comparing the first N fields
−−group[=METHOD]: show all items, separating groups with an empty line; METHOD={separate(default),prepend,append,both}
−i, −−ignore−case: ignore differences in case when comparing
−s, −−skip−chars=N: avoid comparing the first N characters
−u, −−unique: only print unique lines
−z, −−zero−terminated: line delimiter is NUL, not newline
−w, −−check−chars=N: compare no more than N characters in lines
−−help: display this help and exit
−−version: output version information and exit

A field is a run of blanks (usually spaces and/or TABs), then non−blank characters. Fields are skipped before chars.

	Note
	'uniq' does not detect repeated lines unless they are adjacent. You may want to sort the input first, or use 'sort `−u`' without 'uniq'. Also, comparisons honor the rules specified by 'LC_COLLATE'.

Written by Richard M. Stallman and David MacKenzie.