fu_test.rb

require 'fileutils'

source_path = "/Users/kencollins/Desktop/source.txt"
move_path = "/Users/kencollins/Desktop/move.txt"

FileUtils.rm move_path if File.exists?(move_path)
File.open(source_path,'w') { |f| 30000.times{f.write("#{'x'*70}\n")} }

FileUtils.move source_path, move_path

while File.size?(move_path) == nil do
 sleep 0.25
 puts "loop"
end

puts IO.read(move_path)

gistfile2.txt

# With and without sleep has same output.

$ /opt/local/bin/ruby1.9 fu_test.rb | wc
   30000   30000 2130000


# Now with 300_000 and toggle sleep.

$ /opt/local/bin/ruby1.9 fu_test.rb | wc
  300000  300000 21300000

$ /opt/local/bin/ruby1.9 fu_test.rb | wc
  300000  300000 21300000