What's the equivalent of python's __file__ in ruby?

Question

In python after imports, one can see the file, that has been loaded/where the module comes from.

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

What would be the equivalent in ruby?

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

Answer 1

There's nothing that's an exact match. It's easy to find it yourself, though:

# 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 2

There's nothing exactly equivalent.

All files that have been required are listed in $LOADED_FEATURES in the order they were required. So, if you want to know where a file came from directly after it was required, you simply need to look at the end:

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

However, unless you record every call to require it's going to be hard to figure out which entry corresponds to which call. Also, if a file is already in $LOADED_FEATURES, it will not get loaded again:

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

Also, many libraries aren't contained in a single file. So, the required files might themselves contain calls to require. In my case, for example, require 'yaml' not only loads yaml.rb but a whole bunch of files (15 to be exact):

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 3

Assuming you are using rubygems, you can find out which file it loads by using Gem.find_files(file).

e.g.:

>> 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

The first element of the array will be the file that is loaded by require 'active_record'.

Another way to find out which file is loaded by require, would be to call $ gem which foo from the command line.