class File
U_R = 0400
U_W = 0200
U_X = 0100
G_R = 0040
G_W = 0020
G_X = 0010
O_R = 0004
O_W = 0002
O_X = 0001
A_R = 0444
A_W = 0222
A_X = 0111
end
new_permission = File.lstat("my_file").mode ^ File::O_R
File.chmod(new_permission, "my_file")