Q:

Are ruby command line switches -rubygems & -r incompatible?

I recently converted a ruby library to a gem, which seemed to break the command line usability
Worked fine as a library
  $ ruby -r foobar -e 'p FooBar.question' # => "answer"

And as a gem, irb knows how to require a gem from command-line switches
  $ irb -rubygems -r foobar
  irb(main):001:0> FooBar.question # => "answer"

But the same fails for ruby itself:
  $ ruby -rubygems -r foobar -e 'p FooBar.question'
  ruby: no such file to load -- foobar (LoadError)

must I now do this, which seems ugly: 
  ruby -rubygems -e 'require "foobar"; p FooBar.question' # => "answer"

Or is there a way to make the 2 switches work?
Note: I know the gem could add a bin/program for every useful method but I don't like to pollute the command line namespace unnecessarily

A:

-rubygems is actually the same as -r ubygems.
It doesn't mess with your search path, as far as I understand, but I think it doesn't add anything to your -r search path either. I was able to do something like this:
ruby -rubygems -r /usr/lib/ruby/gems/myhelpfulclass-0.0.1/lib/MyHelpfulClass -e "puts MyHelpfulClass"

MyHelpfulClass.rb exists in the lib directory specified above.
That kind of sucks, but it at least demonstrates that you can have multiple -r equire directives.
As a slightly less ugly workaround, you can add additional items to the ruby library search path (colon delimited in *nix, semicolon delimited in windows).
export RUBYLIB=/usr/lib/ruby/gems/1.8/gems/myhelpfulclass-0.0.1/lib
ruby -rubygems -r MyHelpfulClass -e "puts MyHelpfulClass"

If you don't want to mess with the environment variable, you can add something to the load path yourself: 
ruby -I /usr/lib/ruby/gems/1.8/gems/myhelpfulclass-0.0.1/lib \
   -rubygems -r MyHelpfulClass -e "puts MyHelpfulClass"

