How do I install the Ruby ri documentation?

Question

I\'ve recently installed Ruby 1.9.1 on Windows 7, and apparently it doesn\'t come with the standard ri documentation. So when I do \'ri Array\', I get:

C:\\         


        

Answer 1

Things are still largely the same with Ruby Installer 2.4.1.2 (year 2017). If I run ri Array, it shows Array < Object and nothing else. If I run ri "Array#each", I get the familiar "Nothing known..." message. In short, the ri-format documentation on Ruby core and standard libraries are missing.

Here's how I got my copy of core/stdlib ri-documentation. Of course, Ruby must be installed prior to this.

1. Get ruby's source code that most closely matches my version from their Github releases page.
2. Extract the .zip or .tar.gz archive to some folder
3. Open cmd.exe/Powershell, cd to that folder and run rdoc --all --ri
   • This command parses .c files, .rb files, and a few other file types in the current directory recursively and generates ri-documentation to ~/.rdoc directory.
   • Took about 5 minutes on my laptop with i7-3520M processor to complete, with no errors.
4. Delete the archive and the directory containing the source code because we don't need them anymore.

Now if you try running ri Array or ri "Array#each" you'll get the documentation in all its glory.

tl;dr

Run rdoc --all --ri on directory containing source code for same ruby version as your installed version.

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Appendix Z: Comments on other answers

1. The rvm docs generate-ri could work, but you have to use Cygwin or Ubuntu on Windows (if on Windows 10) to use rvm.
2. gem rdoc --all --ri --no-rdoc installs ri-documentation for all your gems. It doesn't install the core/stdlib documentations.
3. gem install rdoc-data followed by rdoc-data --install only works for Ruby versions up to 2.3.0.