File.sub.gsub.rb

class File
  
  def self.gsub(path, regexp, &block)
    content = File.read(path).gsub(regexp, &block)
    File.open(path, 'wb') { |file| file.write(content) }
  end
  
  def self.sub(path, regexp, &block)
    content = File.read(path).sub(regexp, &block)
    File.open(path, 'wb') { |file| file.write(content) }
  end
  
end

# Examples

# This will look for the regular expression pattern 'class Awesome' inside the file.rb.
# Then it will replace 'class Awesome' with 'class Awesome\n\tinclude Awesomeness
# This will only occur on the first pattern that matches 'class Awesome'
File.sub('/path/to/file.rb', /class Awesome/) do |match|
  "#{match}\n\tinclude Awesomeness"
end

# This will look for the regular expression pattern 'class Awesome' inside the file.rb.
# Then it will replace 'class Awesome' with 'class Awesome\n\tinclude Awesomeness
# This will occur on any pattern that matches 'class Awesome'
File.gsub('/path/to/file.rb', /class Awesome/) do |match|
  "#{match}\n\tinclude Awesomeness"
end