how to install rubygems-1.4.2 to ruby 1.8.7 using rvm?

When I do ruby -v, I get

ruby 1.8.7 (2010-12-23 patchlevel 330) [i686-linux]

I want to install rubygems-1.4.2 to it, but the command:

rvm rubygems 1.4.2 

fails, it does not even fetch the rubygems as it fails in curl. So I downloaded the file from http://rubyforge.org/frs/?group_id=126, (http://rubyforge.org/frs/download.php/73882/rubygems-1.4.2.tgz), extracted it, and put it at ~/.rvm/src/, and then ran again:

rv开发者_高级运维m rubygems 1.4.2 

but it failed again. how can i install rubygems 1.4.2 to ruby-1.8.7@p330?

First switch to the correct ruby with rvm use 1.8.7@p330, then

gem install rubygems --version=1.4.2