RubyGems的功能类似于Linux下的apt-get。使用它可以方便第从远程服务器下载并安装Rails。

# 安装指定gem包，程序先从本机查找gem包并安装，如果本地没有，则从远程gem安装。
gem install [gemname]

# 仅从本机安装gem包
gem install -l [gemname]

# 仅从远程安装gem包
gem install -r [gemname]

Ruby’s package management system is known as RubyGems, and packages or modules
distributed using RubyGems are called “gems.” RubyGems makes it easy to install Ruby
software and can automatically manage complex dependencies between packages.
The frontend script for RubyGems is gem, and it’s distributed with Ruby 1.9 just as
irb and ri are. In Ruby 1.8, you must install it separately—see http://rubygems.org. Once
the gem program is installed, you might use it like this:
# gem install rails
Successfully installed activesupport-1.4.4
Successfully installed activerecord-1.15.5
Successfully installed actionpack-1.13.5
Successfully installed actionmailer-1.3.5
Successfully installed actionwebservice-1.2.5
Successfully installed rails-1.2.5
6 gems installed
Installing ri documentation for activesupport-1.4.4...
Installing ri documentation for activerecord-1.15.5...
...etc...
As you can see, the gem install command installs the most recent version of the gem
you request and also installs any gems that the requested gem requires. gem has other
useful subcommands as well. Some examples:

gem list # List installed gems

gem enviroment # Display RubyGems configuration information

gem update rails # Update a named gem
gem update # Update all installed gems

gem使用参考手册：http://guides.rubygems.org/

列出远程可安装的gems

*** REMOTE GEMS ***
 
 activerecord (0.8.4, 0.8.3, 0.8.2, 0.8.1, 0.8.0, 0.7.6, 0.7.5)
  Implements the ActiveRecord pattern for ORM.
 
 BlueCloth (0.0.4, 0.0.3, 0.0.2)
  BlueCloth is a Ruby implementation of Markdown, a
  text-to-HTML conversion tool for web writers.
  Markdown allows you to write using an easy-to-read,
  easy-to-write plain text format, then convert it to
  structurally valid XHTML (or HTML).
 ..........
.

 gem query --remote --name-matches doom
  # 快捷方式: gem q -R -n doom

*** REMOTE GEMS ***
 
 ruby-doom (0.8, 0.0.7)
  Ruby-DOOM provides a scripting API for creating DOOM
  maps. It also provides higher-level APIs to make map
  creation easier.

gem install --remote progressbar
 # 快捷方式: gem i -r progressbar

gem ins -r progressbar-0.0.3

gem ins -r progressbar --version ‘> 0.0.1‘

2.5 查看已经安装的gem

gem specification progressbar
 # 快捷方式: gem spec progressbar

 --- !ruby/object:Gem::Specification
  rubygems_version:"1.0\"
  name: progressbar
  version: !ruby/object:Gem::Version
  version: 0.0.3
  date: 2004-03-20 20:03:00.679937 +11:00
  platform:
  summary: "Ruby/ProgressBar is a text progress bar library for Ruby. It can
  indicate progress with percentage, a progress bar, and estimated
  remaining time."
  require_paths:
  - lib
  files:
  - sample/test.rb
  - lib/progressbar.rb
  - docs/progressbar.en.rd
  - docs/progressbar.ja.rd
  - ChangeLog
  autorequire: progressbar
  author: Satoru Takabayashi
  email: satoru@namazu.org
  homepage: http://namazu.org/~satoru/ruby-progressbar/
 

gem query --local
 # 快捷方式: ‘gem q -L‘

gem: --rdoc --test