C:/Users/Lenovo/rubycode/test1 下有两个文件：max.rb 和 a.rb

# 情况1
# Code in max.rb:
puts __FILE__
puts $0

require "./a"

puts __FILE__
puts $0

# Code in a.rb
puts __FILE__
puts $0

C:/Users/Lenovo/rubycode/test1 ruby max.rb
# 输出如下：
test1/max.rb
test1/max.rb
C:/Users/Lenovo/rubycode/test1/a.rb
test1/max.rb
test1/max.rb
test1/max.rb
# 但是，若
C:/Users/Lenovo/rubycode ruby test1/max.rb
# 则会输出错误
test1/max.rb
test1/max.rb
Traceback (most recent call last):
        2: from test1/max.rb:5:in `<main>'
        1: from C:/Ruby25-x64/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require'
C:/Ruby25-x64/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:59:in `require': cannot load such file -- ./a (LoadError)

# 情况2
# Code in max.rb:
puts __FILE__
puts $0

require_relative "a"

puts __FILE__
puts $0

# Code in a.rb
puts __FILE__
puts $0

C:/Users/Lenovo/rubycode/test1 ruby max.rb 及 C:/Users/Lenovo/rubycode ruby test1/max.rb
# 输出皆如下：
test1/max.rb
test1/max.rb
C:/Users/Lenovo/rubycode/test1/a.rb
test1/max.rb
test1/max.rb
test1/max.rb