Save data to your local filesystem by posting to your webserver.

bjorx.rb

require "sinatra"

configure do
  set :root, "."
  set :public_folder, "."
end

# Any post to /save will write data to the path provided.
post '/save' do
  data = params["data"]
  path = params["path"]

  # Ensure directory exists
  FileUtils.mkdir_p File.dirname(path)

  File.open(path, 'w') do |file|
    file.write(data)
  end

  200
end