Show nodes where certname and fqdn are not the same

find_certname_fqdn_mismatches.rb

#!/opt/puppetlabs/puppet/bin/ruby
#
# This script will find any Puppet agent whose certname does NOT match the agent's FQDN.
#
require 'json'

fqdn_values = JSON.parse(`/opt/puppetlabs/puppet/bin/puppet query 'facts[certname,value] { name = "fqdn" }'`)

fqdn_values.each do |result|
  puts result['certname'] if result['certname'] != result['value']
end