Section (1) uniq

Linux manual pages Section 1  


uniq — report or omit repeated lines


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


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


print all duplicate lines


like −D, but allow separating groups with an empty line; METHOD={none(default),prepend,separate}

−f, −−skip−fields=N/

avoid comparing the first N fields


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


display this help and exit


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] Note

_zsingle_quotesz_uniq_zsingle_quotesz_ does not detect repeated lines unless they are adjacent. You may want to sort the input first, or use _zsingle_quotesz_sort −u_zsingle_quotesz_ without _zsingle_quotesz_uniq_zsingle_quotesz_. Also, comparisons honor the rules specified by _zsingle_quotesz_LC_COLLATE_zsingle_quotesz_.


Written by Richard M. Stallman and David MacKenzie.


GNU coreutils online help: <>

Report any translation bugs to <>


comm(1), join(1), sort(1)

Full documentation <>

or available locally via: info _zsingle_quotesz_(coreutils) uniq invocation_zsingle_quotesz_


Copyright © 2019 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <>.

This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.