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

-D

print all duplicate lines

--all-repeated[=METHOD]

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

--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'.

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

Full documentation <https://www.gnu.org/software/coreutils/uniq>
or available locally via: info '(coreutils) uniq invocation'