Not every library has a strict mapping between the name of the gem and the name of the file you need to require. First you should check to see if the files match correctly:

$ gem list RedCloth

*** LOCAL GEMS ***

RedCloth (4.1.1)
$ ruby -rubygems -e 'require "RedCloth"'
/Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `gem_original_require': no such file to load -- RedCloth (LoadError)
	from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:31:in `require'
	from -e:1
$ gem contents --no-prefix RedCloth | grep lib
lib/case_sensitive_require/RedCloth.rb
lib/redcloth/erb_extension.rb
lib/redcloth/formatters/base.rb
lib/redcloth/formatters/html.rb
lib/redcloth/formatters/latex.rb
lib/redcloth/formatters/latex_entities.yml
lib/redcloth/textile_doc.rb
lib/redcloth/version.rb
lib/redcloth.rb
$ ruby -rubygems -e 'require "redcloth"'
$ # success!

If you’re requiring the correct file, maybe `gem` is using a different ruby than `ruby`:

$ which ruby
/usr/local/bin/ruby
$ gem env | grep 'RUBY EXECUTABLE'
   - RUBY EXECUTABLE: /usr/local/bin/ruby1.9

In this instance we’ve got two ruby installations so that `gem` uses a different version than `ruby`. You can probably fix this by adjusting a symlink:

$ ls -l /usr/local/bin/ruby*
lrwxr-xr-x  1 root  wheel       76 Jan 20  2010 /usr/local/bin/ruby@ -> /usr/local/bin/ruby1.8
-rwxr-xr-x  1 root  wheel  1213160 Jul 15 16:36 /usr/local/bin/ruby1.8*
-rwxr-xr-x  1 root  wheel  2698624 Jul  6 19:30 /usr/local/bin/ruby1.9*
$ ls -l /usr/local/bin/gem*
lrwxr-xr-x  1 root  wheel   76 Jan 20  2010 /usr/local/bin/gem@ -> /usr/local/bin/gem1.9
-rwxr-xr-x  1 root  wheel  550 Jul 15 16:36 /usr/local/bin/gem1.8*
-rwxr-xr-x  1 root  wheel  550 Jul  6 19:30 /usr/local/bin/gem1.9*

You may also need to give `irb` the same treatment.

Require returns false when loading a file from a gem. Usually require will return true when it has loaded correctly. What’s wrong?

Answer

Nothing. Well, something. But nothing you need to worry about.

A false return from the require method does not indicate an error. It just means that the file has already been loaded.

RubyGems has a feature that allows a file to be automatically loaded when a gem is activated (i.e. selected). When you require a file that is in an inactive gem, the RubyGems software will activate that gem for you. During that activation, any autoloaded files will be loaded for you.

So, by the time your require statement actually does the work of loading the file, it has already been autoloaded via the gem activation, and therefore it returns false.

When I run the gem command, I get the following error message:

 ruby: No such file to load -- rubygems (LoadError)

What’s wrong?

Answer

It looks like executing copy of Ruby does not have the RubyGems library installed. RubyGems was probably installed at one time (because the gem command is recognized), but it may have been installed on a different installation of Ruby than the one you are currently running.

Things to check

• Check that the installation of Ruby that is running is the same one that has RubyGems installed. On a unix system, the which command (or type command) will help figure this out.

• Verify that the currently running installation of Ruby does indeed have the RubyGems library installed. You should find a “rubygems.rb” file in the site_ruby/1.8 directory of the Ruby installation.

These mixup can easily happen after installing a new instance of Ruby, but the old instance preceeds the new one in the PATH list.

You can submit bug reports in the RubyGems bug tracker

You will need a RubyForge account.

If you take a look at the RubyGems bug list to see if the bug has already been filed the maintainers will really appreciate it.

I have a problem with RubyGems. It doesn’t matter what I try to install with, it freezes.

Particulary I tried to execute:

gem install rails —include-dependencies

but the command freezes at the following message:

“Updating Gem source index for: http://gems.rubyforge.org”

Answer

You’ll need to upgrade RubyGems to a modern version. You can find instructions in the Downloads link at the top of this page.