xpath find if node exists

Question

Using a xpath query how do you find if a node (tag) exists at all?

For example if I needed to make sure a website page has the correct basic structure like /html/bod

Answer 1

I work in Ruby and using Nokogiri I fetch the element and look to see if the result is nil.

require 'nokogiri'

url = "http://somthing.com/resource"

resp = Nokogiri::XML(open(url))

first_name = resp.xpath("/movies/actors/actor[1]/first-name")

puts "first-name not found" if first_name.nil?