Text processing

Linux uniq command

Report or remove adjacent repeated lines; sort first to group matches.

Availability: Common Linux commands; shell built-ins and external implementations may differ by distribution.中文

Syntax

uniq [OPTION]... [INPUT [OUTPUT]]

Examples

Count each distinct line; uniq compares adjacent lines.

sort names.txt | uniq -c

Print values that occur more than once.

sort names.txt | uniq -d

Parameters, options and clauses

Option / clause	Description
`-c, --count`	Prefix each output line with its number of occurrences.
`-d, --repeated`	Print only repeated lines.
`-u, --unique`	Print only lines that occur once.
`-i, --ignore-case`	Ignore case when comparing lines.
`-f, --skip-fields=N`	Skip N fields before comparing.
`-s, --skip-chars=N`	Skip N characters before comparing.

Safety note

Review a command and its target before running it. Commands that alter files, services, accounts, disks, permissions or databases may be difficult to reverse. Test in a safe environment and keep backups.

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