From: Brian Candler <b.candler@...>
Date: 2011-10-07T18:11:54+09:00
Subject: Re: don't understand -r

Thomas Sawyer wrote in post #1025489:
> Can anyone explain to me why, with RUBYOPT="-rubgems"

The difference is not whether you provide -rubygems on the command line 
or in an environment variable. The difference is whether you use -ransi 
or -e'require "ansi"'

Note that none of these work:

$ ruby -rbundler -e 'puts "hello"'
ruby: no such file to load -- bundler (LoadError)
$ ruby -rubygems -rbundler -e 'puts "hello"'
ruby: no such file to load -- bundler (LoadError)
$ env RUBYOPT="-rubygems" ruby -rbundler -e 'puts "hello"'
ruby: no such file to load -- bundler (LoadError)

But it works this way if you have -rubygems:

$ ruby -e 'require "bundler"; puts "hello"'
-e:1:in `require': no such file to load -- bundler (LoadError)
  from -e:1
$ ruby -rubygems -e 'require "bundler"; puts "hello"'
hello
$ env RUBYOPT="-rubygems" ruby -e 'require "bundler"; puts "hello"'hello
hello

This is with ruby 1.8.7 (2010-08-16 patchlevel 302) [x86_64-linux]

I imagine it's because rubygems redefines Kernel#require, but using -r 
on the command line calls the internal require function directly. If -r 
doesn't do a full method dispatch, then rubygems can't override what it 
does.

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