Ruby require

Ruby
#1

Got a Question to $LOAD_PATH.

When using require ‘mygem’ in the ruby documentation is written:

“If the filename does not resolve to an absolute path, it will be
searched for in the directories listed in $LOAD_PATH”

But when i output the $LOAD_PATH before the require statement on mri
2.1.1 i got following:

/home/benny/.rubies/mri-2.1.1/lib/ruby/site_ruby/2.1.0
/home/benny/.rubies/mri-2.1.1/lib/ruby/site_ruby/2.1.0/x86_64-linux
/home/benny/.rubies/mri-2.1.1/lib/ruby/site_ruby
/home/benny/.rubies/mri-2.1.1/lib/ruby/vendor_ruby/2.1.0
/home/benny/.rubies/mri-2.1.1/lib/ruby/vendor_ruby/2.1.0/x86_64-linux
/home/benny/.rubies/mri-2.1.1/lib/ruby/vendor_ruby
/home/benny/.rubies/mri-2.1.1/lib/ruby/2.1.0
/home/benny/.rubies/mri-2.1.1/lib/ruby/2.1.0/x86_64-linux

After the require statment for example i wanna use stackprof the
$LOAD_PATH is:

/home/benny/.gem/ruby/2.1.1/extensions/x86_64-linux/2.1.0-static/stackprof-0.2.6
/home/benny/.gem/ruby/2.1.1/gems/stackprof-0.2.6/lib
/home/benny/.rubies/mri-2.1.1/lib/ruby/site_ruby/2.1.0
/home/benny/.rubies/mri-2.1.1/lib/ruby/site_ruby/2.1.0/x86_64-linux
/home/benny/.rubies/mri-2.1.1/lib/ruby/site_ruby
/home/benny/.rubies/mri-2.1.1/lib/ruby/vendor_ruby/2.1.0
/home/benny/.rubies/mri-2.1.1/lib/ruby/vendor_ruby/2.1.0/x86_64-linux
/home/benny/.rubies/mri-2.1.1/lib/ruby/vendor_ruby
/home/benny/.rubies/mri-2.1.1/lib/ruby/2.1.0
/home/benny/.rubies/mri-2.1.1/lib/ruby/2.1.0/x86_64-linux

This is kinda weird for me because in the documentation there is said a
require statement tries to load a library from the $LOAD_PATH when it’s
not a absolute path and doesn’t modify it?

Is there anything else going on?
Maybe rubygems itself just includes gems to the load path if they are
required explicitly?

#2

Adding the lib directory of a required gem to $LOAD_PATH is documented
by rubygems:

=====
Loading code

At its core, RubyGems exists to help you manage Ruby’s $LOAD_PATH, which
is how the require statement picks up new code. There’s several things
you can do to make sure you’re loading code the right way.

…
…

Mangling the load path

Gems should not change the $LOAD_PATH variable. RubyGems manages this
for you. Code like this should not be necessary:

lp = File.expand_path(File.dirname(FILE))
unless $LOAD_PATH.include?(lp)
$LOAD_PATH.unshift(lp)
end

Or:

DIR = File.dirname(FILE)

$LOAD_PATH.unshift DIR unless
$LOAD_PATH.include?(DIR) ||
$LOAD_PATH.include?(File.expand_path(DIR))

When RubyGems activates a gem, it adds your package’s lib folder to the
$LOAD_PATH ready to be required normally by another lib or application.
It is safe to assume you can then require any file in your lib folder.

http://guides.rubygems.org/patterns/

#3

Found the interesting part for me:
https://github.com/rubygems/rubygems/blob/master/lib/rubygems/core_ext/kernel_require.rb#L38https://github.com/rubygems/rubygems/blob/master/lib/rubygems/core_ext/kernel_require.rb#L38

Just if anyone needs this too :slight_smile:

#4

okay thx to clear this up :slight_smile:
just wondered how the $LOAD_PATH got modified by requiring a gem

i’ll dig into the rubygems source to make it more clearer to me