Linux/Unix Command: uniq - Removes Duplicate Lines

Woman and two men at a table working
vgajic/E+/Getty Images


uniq - remove duplicate lines from a sorted file.


uniq [OPTION]... [INPUT [OUTPUT]]  


Discard all but one of successive identical lines from INPUT (or standard input), writing to OUTPUT (or standard output).

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


Prefix lines by the number of occurrences.


Only print duplicate lines.

-D--all-repeated [=delimit-method] print all duplicate lines.

Delimit-method={none(default),prepend,separate} Delimiting is done with blank lines.


Avoid comparing the first N fields.


Ignore differences in case when comparing.


Avoid comparing the first N characters.


Only print unique lines.


Compare no more than N characters in lines.


Display this help and exit.


Output version information and exit.

A field is a run of whitespace, then non-whitespace characters. Fields are skipped before chars.  

See Also

The full documentation for uniq is maintained as a Texinfo manual. If the info and uniq programs are properly installed at your site, the command info uniq should give you access to the complete manual.