Chapter 9.1 IO stream: too many open files

[dotm]

in the first example code, if you just run it as is, it will return this error messages:

STDOUT:
class: Errno::EMFILE
message: Too many open files - new-fd
backtrace: RubyMonk:4:in `sysopen'

Clearly, this ruby primer book has a lot of user (which is good).
Unfortunately, this can be very confusing to beginner, like me, who are just trying to learn about io stream and fd (which is bad).
Please fix this for clarity and thanks for the awesome book.