require 'fileutils'
def test mask
  File.umask mask
  result = File.umask
  puts "Umask is #{result.to_s(8)}"
  result
end

def test_file mask
  test mask
  File.open("temp.txt#{mask.to_s(8)}", 'w') {|f| f << "boo"}
  puts File.stat("temp.txt#{mask.to_s(8)}").mode.to_s(8)
end

test_file 0
test_file 0200
test_file 0400
test_file 0600