Create an MD5 hash (checksum) for an external file

checksum.rb

require 'tempfile'
require 'net/http'
require 'digest/md5'

file = Tempfile.new('temp_file')

begin
  Net::HTTP.start("domain.tld") { |http|
    resp = http.get("/02185773dcb5a468df6b.pdf")
    file.write(resp.body)
  }
  hash = Digest::MD5.hexdigest(File.read(file))
  puts hash
ensure
  file.close
  file.unlink
end