Ohai plug-in to get the public ip address

public_ip.rb

Ohai.plugin(:PublicIp) do
  provides 'public_ip'

  collect_data do
    public_ip Mash.new
    public_ip[:public_ip] = `curl -s http://whatismyip.akamai.com/`
  end
end

Usage

$ ohai public_ip
{
  "public_ip": "1.2.3.4"
}