The sortu program is a replacement for the sort and uniq programs. It is
common for Unix script writers to want to count how many separate patterns
are in a file.  For example, if you have a list of addresses, you may want
to see how many are from each state. So you cut out the state part, sort
these, and then pass them through uniq -c. Sortu does all this for you in a
fraction of the time.

Sortu uses a hash table and some decent line processing to provide this
functionality.  For a relatively small number of keys, it can be signifcantly
smaller than using sort, because it does not have to keep temporary files.
If you are dealing with a large number of unique keys then sortu will run out
of memory and stop. Sortu has some basic field and delimiter handling which
should do most basic awk or cut features to separate out the field that you
are sorting on.

WWW: http://256.com/sources/sortu/