在我的 ubuntu 机器上，当我尝试使用 mechanize gem 时，irb (ruby) 会给出 NameError：
$ irb
irb(main):001:0> require 'mechanize'
=> true
irb(main):002:0> Mechanize.new
NameError: uninitialized constant Mechanize
from (irb):2
from :0
gem env 显示了这一点：
RubyGems Environment:
- RUBYGEMS VERSION: 1.3.7
- RUBY VERSION: 1.8.7 (2010-01-10 patchlevel 249) [x86_64-linux]
- INSTALLATION DIRECTORY: /usr/lib/ruby/gems/1.8
- RUBY EXECUTABLE: /usr/bin/ruby1.8
- EXECUTABLE DIRECTORY: /usr/bin
- RUBYGEMS PLATFORMS:
- ruby
- x86_64-linux
- GEM PATHS:
- /usr/lib/ruby/gems/1.8
- /var/lib/gems/1.8
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :benchmark => false
- :backtrace => false
- :bulk_threshold => 1000
- :gempath => ["/var/lib/gems/1.8", "/usr/lib/ruby/gems/1.8"]
- REMOTE SOURCES:
- http://rubygems.org/
gem list 显示它已安装：
$ gem list mech
*** LOCAL GEMS ***
mechanize (1.0.0)
它在文件系统的两个路径中：
$ ls -1 /var/lib/gems/1.8/gems/ |grep mech
mechanize-1.0.0
$ ls -1 /usr/lib/ruby/gems/1.8/gems |grep mech
mechanize-1.0.0
RubyGems 是最新的：
$ gem update --system
Updating RubyGems
Nothing to update
# gem list rubygems
*** LOCAL GEMS ***
rubygems-update (1.3.7)
我有一个最新的红宝石：
ruby 1.8.7 (2010-01-10 patchlevel 249) [x86_64-linux]
这是我拥有的 ubuntu gems 包（请注意，我安装了 rubygems-update 并运行了 update_rubygems）：
# dpkg -l rubygems*
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Description
+++-==================-==================-====================================================
ii rubygems 1.3.5-1ubuntu2 package management framework for Ruby libraries/appl
ii rubygems-doc 1.3.5-1ubuntu2 package management framework for Ruby libraries/appl
ii rubygems1.8 1.3.5-1ubuntu2 package management framework for Ruby libraries/appl