Vagrant (v1.1+) snippet to set VirtualBox guest CPU count to the number of host cores on Linux or OS X

Vagrantfile

# -*- mode: ruby -*-
# vi: set ft=ruby :

if not RUBY_PLATFORM.downcase.include?("mswin")
  config.vm.provider "virtualbox" do |v|
    v.customize ["modifyvm", :id, "--cpus",
      `awk "/^processor/ {++n} END {print n}" /proc/cpuinfo 2> /dev/null || sh -c 'sysctl hw.logicalcpu 2> /dev/null || echo ": 2"' | awk \'{print \$2}\' | cut -d' ' -f2 `.chomp ]
  end
end