ruby require './blahblah.rb' vs require File.expand_path('../blahblah', __FILE__)

Question

What is the difference between

require 'blahblahlblah.rb'

vs

require './blahblah.rb'

vs

require File.expand_path('../blahblah', __FILE__)

I see both of them being used. Wondering what's better, and under what circumstance is one better than the other.

Thanks!

Answer 1

• require blaba.rb is searching to your default gem path to load the file, which depends on the ruby version you are using. For example RVM will search in $HOME/.rvm/rubies/... while a system wide ruby will search in the distribution's default path. Note that this is where gems are located, but you could manually add a library say mylibrary.rb in the same path and use it in any of your programs. However, that's an awful thing to do, it's a much cleaner procedure to create gems and install them in your system.

• require ./blabla.rb loads a file that is sitting in your working directory. You could add the full path like require /home/username/library/myproject/models/sample.rb. It will work just about the same. In the UNIX-like world the ./ sign means current directory. This solution is often used in irb to load say a rails Model i.e. users.rb into irb or pry and work with it. To give you an example in a shell environment (if you are familiar with UNIX shells, you'll figure it out):

  GreyJewel ~ » ls myports.txt                                                                                                                                                         
  myports.txt
  
  GreyJewel ~ » ls ./myports.txt                                                                                                                                                       
  ./myports.txt
  

• The third solution require File.expand_path('../sample.rb', __FILE__) is used in programs, because it explicitly creates a full path using as an anchor the directory which the file holding the line sits, which is a much more secure approach compared to require ./sample.rb. Note that when you load a ruby file, you can omit the file extension .rb.

Hope this clarifies a bit the situation.