Adding a Directory to the Path, export, command

Adding a Directory to the Path

<br />export PATH='/usr/local/lib/ruby/gems/1.8/bin':$PATH<br />

image_tag, path, url

http://api.rubyonrails.com/classes/ActionView/Helpers/AssetTagHelper.html


  ActionController::Base.asset_host = "assets.example.com"
  image_tag("rails.png")
    => <img src="http://assets.example.com/images/rails.png" alt="Rails" />
  stylesheet_link_tag("application")
    => <link href="http://assets.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />


  ActionController::Base.asset_host = Proc.new { |source| "http://assets#{rand(2) + 1}.example.com" }
  image_tag("rails.png")
    => <img src="http://assets2.example.com/images/rails.png" alt="Rails" />
  stylesheet_link_tag("application")
    => <link href="http://assets1.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />


  ActionController::Base.asset_host = Proc.new { |source|
     if source.starts_with?('/images')
       "http://images.example.com"
     else
       "http://assets.example.com"
     end
   }
  image_tag("rails.png")
    => <img src="http://images.example.com/images/rails.png" alt="Rails" />
  stylesheet_link_tag("application")
    => <link href="http://assets.example.com/stylesheets/application.css" media="screen" rel="stylesheet" type="text/css" />


  ActionController::Base.asset_host = Proc.new { |source, request|
    if request.ssl?
      "#{request.protocol}#{request.host_with_port}"
    else
      "#{request.protocol}assets.example.com"
    end
  }

File, Pathname, Dir

http://www.ruby-doc.org/core/classes/File.html
http://www.ruby-doc.org/core/classes/Pathname.html
http://www.ruby-doc.org/core/classes/Dir.html#M002347

join, dirname, __FILE__, RAILS_ROOT, directory?

require File.join(File.dirname(__FILE__), 'boot')

RAILS_ROOT = "#{File.dirname(__FILE__)}/.." unless defined?(RAILS_ROOT)


>> File.directory?("#{RAILS_ROOT}/app")
=> true
>> File.exist?("#{RAILS_ROOT}/app")
=> true

>> File.exist?("#{RAILS_ROOT}/app/controllers/application.rb")
=> true
>> File.directory?("#{RAILS_ROOT}/app/controllers/application.rb")
=> false

Dir is file, too


  Dir["config.?"]                     #=> ["config.h"]
  Dir.glob("config.?")                #=> ["config.h"]
  Dir.glob("*.[a-z][a-z]")            #=> ["main.rb"]
  Dir.glob("*.[^r]*")                 #=> ["config.h"]
  Dir.glob("*.{rb,h}")                #=> ["main.rb", "config.h"]
  Dir.glob("*")                       #=> ["config.h", "main.rb"]
  Dir.glob("*", File::FNM_DOTMATCH)   #=> [".", "..", "config.h", "main.rb"]