pipe_close_on_exec_bug.rb

#!/usr/bin/env ruby
r, w = IO.pipe

# exec on ruby 2.0 closes the fds and so cat fails with "Bad file descriptor"
# on ree this works as expected.
#
# I thought close_on_exec was the issue, but this doesn't fix it at all.
# Perhaps it is not being respected?
#
# r.close_on_exec = false
# w.close_on_exec = false
#
# Maybe related:
# * https://www.ruby-forum.com/topic/566695
#

if Process.fork
  r.close
  w.puts "echo hello"
  w.close
else
  w.close
  exec "cat <&#{r.fileno}"
end

https://github.com/ruby/ruby/blob/trunk/io.c#L4023