[coreutils] How to check uniqueness on one or multiple columns in a table and print the duplicated rows?

[Peng Yu]

Hi,

Uniq doesn't have an option to check the uniqueness for a given column
(although it can exclude the first a few columns). It will need 'cut'
to check uniqueness on a give number of columns and print the
duplicated rows. This is not convenient. I'm wondering if there is a
better way to do so.

-- 
Regards,
Peng