There is a ruby gem for Linux called io_splice that does zero-copy IO. Hasn’t been updated in a while but it doesn’t have any dependencies other than modern Linux and doesn’t mean it won’t work. “Old” code that works still works, novelty, job-securitization and API churn be damned when it doesn’t add value.

https://rubygems.org/gems/io_splice/versions/4.4.0

http://www.bigfastblog.com/zero-copy-transfer-data-faster-in...

EDIT: source to current stable coreutils’ cat http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=blob_p...