在ruby中，python的__file__等價於什麼？

Question

在python導入後，可以看到已加載的文件/模塊的來源。

>>> import os 
>>> os.__file__ 
'/Users/tm/lib/python2.6/os.pyc' 

在紅寶石中有什麼等價物？

>> require 'xmlrpc/client' 
=> true 
>> ... 

Answer 1

沒有什麼完全相同的。

required的所有文件在$LOADED_FEATURES中按照他們的順序排列爲require d。所以，如果你想知道一個文件直接後，這是require d來了，你只需要在最後一下：

$LOADED_FEATURES.last if require 'yaml' 
# => 'C:/Program Files/Ruby/lib/ruby/1.9.1/yaml.rb' 

但是，除非你記錄每次調用require這將是很難找出哪個條目對應哪個呼叫。另外，如果一個文件已在$LOADED_FEATURES，它不會再次加載：

require 'yaml' 
# => true 
# true means: the file was loaded 

$LOADED_FEATURES.last 
# => 'C:/Program Files/Ruby/lib/ruby/1.9.1/yaml.rb' 

require 'json' 
$LOADED_FEATURES.last 
# => 'C:/Program Files/Ruby/lib/ruby/1.9.1/json.rb' 

require 'yaml' 
# => false 
# false means: the file wasn't loaded again, because it has already been loaded 

$LOADED_FEATURES.last 
# => 'C:/Program Files/Ruby/lib/ruby/1.9.1/json.rb' 
# Last loaded feature is still JSON, because YAML wasn't actually loaded twice 

另外，許多庫不包含在一個單一的文件。因此，require d文件本身可能包含對require的調用。在我的情況下，例如，require 'yaml'不僅加載yaml.rb但文件一大堆（15確切）：

1. C:/Program Files/Ruby/lib/ruby/1.9.1/i386-mingw32/stringio.so
2. C:/Program Files/Ruby/lib/ruby/1.9.1/i386-mingw32/syck.so
3. C:/Program Files/Ruby/lib/ruby/1.9.1/syck/error.rb
4. C:/Program Files/Ruby/lib/ruby/1.9.1/syck/basenode.rb
5. C:/Program Files/Ruby/lib/ruby/1.9.1/syck/syck.rb
6. C:/Program Files/Ruby/lib/ruby/1.9.1/syck/tag.rb
7. C:/Program Files/Ruby/lib/ruby/1.9.1/syck/stream.rb
8. C:/Program Files/Ruby/lib/ruby/1.9.1/syck/constants.rb
9. C:/Program Files/Ruby/lib/ruby/1.9.1/date/format.rb
10. C:/Program Files/Ruby/lib/ruby/1.9.1/date.rb
11. C:/Program Files/Ruby/lib/ruby/1.9.1/syck/rubytypes.rb
12. C:/Program Files/Ruby/lib/ruby/1.9.1/syck/types.rb
13. C:/Program Files/Ruby/lib/ruby/1.9.1/yaml/syck.rb
14. C:/Program Files/Ruby/lib/ruby/1.9.1/syck.rb
15. C:/Program Files/Ruby/lib/ruby/1.9.1/yaml.rb

Answer 2

沒有什麼是完全匹配的。但是，您可以很容易地找到它：

# Find where a path `p` was loaded from. 
def locate(p) 
    # Find the first path in your load-paths that contains a file matching `p`. 
    $:.find { |l| 
    File.exists?(File.join(l, p)) 
    } 
end 

ruby-1.9.1-p378 > locate('yaml') 
=> "/home/johnf/.rvm/rubies/ruby-1.9.1-p378/lib/ruby/1.9.1" 
# --> This tells you that 'yaml.rb' was loaded from here. 

ruby-1.9.1-p378 > locate('zzz') 
=> nil 
# --> There's no matches for this library. 

ruby-1.9.1-p378 > locate('haml') 
=> "/home/johnf/.rvm/gems/ruby-1.9.1-p378@standard/gems/haml-3.0.12/bin" 
# --> Here's a third-party library from my gems. 

Answer 3

假設你正在使用rubygems，你可以通過使用Gem.find_files(file)找出它加載哪個文件。

例如爲：

>> puts Gem.find_files('active_record') 
/Library/Ruby/Gems/1.8/gems/activerecord-3.0.0.beta2/lib/active_record.rb 
/Library/Ruby/Gems/1.8/gems/activerecord-2.3.8/lib/active_record.rb 
/Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record.rb 
/Library/Ruby/Gems/1.8/gems/activerecord-2.3.4/lib/active_record.rb 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record.rb 
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activerecord-1.15.6/lib/active_record.rb 

數組的第一元素是由require 'active_record'加載的文件。

找出哪個文件按要求加載的另一種方法是從命令行調用$ gem which foo。