7.2 uniq: Uniquify files

uniq writes the unique lines in the given `input', or standard input if nothing is given or for an input name of `-'. Synopsis:

uniq [option]... [input [output]]

By default, uniq prints the unique lines in a sorted file, i.e., discards all but one of identical successive lines. Optionally, it can instead show only lines that appear exactly once, or lines that appear more than once.

The input must be sorted. If your input is not sorted, perhaps you want to use sort -u.

If no output file is specified, uniq writes to standard output.

The program accepts the following options. Also see 2. Common options.

`-n'

`-f n'

`--skip-fields=n'

Skip n fields on each line before checking for uniqueness. Fields are sequences of non-space non-tab characters that are separated from each other by at least one spaces or tabs.

`+n'

`-s n'

`--skip-chars=n'

Skip n characters before checking for uniqueness. If you use both the field and character skipping options, fields are skipped over first.

`-c'

`--count'

Print the number of times each line occurred along with the line.

`-i'

`--ignore-case'

Ignore differences in case when comparing lines.

`-d'

`--repeated'

Print only duplicate lines.

`-D'

`--all-repeated'

Print all duplicate lines and only duplicate lines. This option is useful mainly in conjunction with other options e.g., to ignore case or to compare only selected fields. This is a GNU extension.

`-u'

`--unique'

Print only unique lines.

`-w n'

`--check-chars=n'

Compare n characters on each line (after skipping any specified fields and characters). By default the entire rest of the lines are compared.