Can you install documentation for existing gems?

Question

Rubyinside mentioned a blog post on how to speed up gem installation by not installing RI or RDoc.

Is it possible to install a gem and subsequently install documentation at a later date, so you can hack in haste and RTFM at leisure?

Answer 1

> gem help rdoc

Usage: gem rdoc [args] [options]
Options:
      --all                        Generate RDoc/RI documentation for all
                                   installed gems
      --[no-]rdoc                  Include RDoc generated documents
      --[no-]ri                    Include RI generated documents
  -v, --version VERSION            Specify version of gem to rdoc
Arguments:
  GEMNAME       gem to generate documentation for (unless --all)
Summary:
  Generates RDoc for pre-installed gems
Defaults:
  --version '>= 0' --rdoc --ri