uniq-(1) manual page


uniq – report or omit repeated lines




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.

-c, –count
prefix lines by the number of occurrences
-d, –repeated
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.
-f, –skip-fields=N
avoid comparing the first N fields
-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
end lines with 0 byte, 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 whitespace, then non-whitespace 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’.


Written by Richard Stallman and David MacKenzie.

Reporting Bugs

Report bugs to <bug-coreutils@gnu.org>.


Copyright © 2008 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html >
This is free software:you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

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.