apt-get cannnot clean cache files

[Kuang He <icrazy@gmail.com>]

Hello, everyone!

I want to achieve the effects of ``apt-get clean'' after each 'apt-get
install foo' and I've put ``ATP::APT::Get::Clean "always";'' in
/etc/apt/apt.conf, but it seems not to work. What can I do?

Thank you very much!

James He