How to Load Development environment in Rails

I am using rails 3 on ubuntu 10. When i trying to load rails
development environment using Rails Runner command

i am getting this:

Usage: runner [options] (‘Some.ruby(code)’ or a filename)

-e, --environment=name Specifies the environment for the
runner to operate under (test/development/production).
Default: development

-h, --help Show this help message.

You can also use runner as a shebang line for your scripts like this:

#!/usr/bin/env /root/workspace/anurag/script/rails runner

Product.all.each { |p| p.price *= 2 ;! }

I also tried rails console command then i get this error:

usr/local/lib/ruby/1.9.1/irb/completion.rb:9:in require': cannot load such file -- readline (LoadError) from /usr/local/lib/ruby/1.9.1/irb/completion.rb:9:in<top
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.0/lib/
commands/console.rb:3:in require' from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.0/lib/ rails/ commands/console.rb:3:in<top (required)>’
from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.0/lib/
commands.rb:38:in require' from /usr/local/lib/ruby/gems/1.9.1/gems/railties-3.2.0/lib/ rails/ commands.rb:38:in<top (required)>’
from script/rails:6:in require' from script/rails:6:in

Anyone please tell how to load Development environment.