如何在Ruby中知道文件是否已完全下载

require 'net/http'

# 下载文件
url = 'https://example.com/file.txt'
file_name = 'file.txt'

uri = URI(url)
Net::HTTP.start(uri.host, uri.port, :use_ssl => uri.scheme == 'https') do |http|
  request = Net::HTTP::Get.new(uri)
  http.request(request) do |response|
    open(file_name, 'wb') do |io|
      response.read_body do |chunk|
        io.write(chunk)
      end
    end
  end
end

# 检查文件是否已完全下载
if File.exist?(file_name)
  expected_size = Net::HTTP.get_response(URI(url)).content_length
  actual_size = File.size(file_name)

  if expected_size == actual_size
    puts "文件已完全下载"
  else
    puts "文件未完全下载"
  end
else
  puts "文件不存在"
end