instance method REXML::DocType#external_id

external_id -> String | nil[permalink][rdoc][edit]

DTD が外部サブセットを用いている場合は "SYSTEM", "PUBLIC" のいずれかの文字列を返します。

それ以外の場合は nil を返します。 

require 'rexml/document'
doctype = REXML::Document.new(<<EOS).doctype
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
         "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
EOS
doctype.name # => "html"
doctype.external_id  # => "PUBLIC"

doctype = REXML::Document.new(<<EOS).doctype
<!DOCTYPE books [
  <!ELEMENT books (book+)>
  <!ELEMENT book (title,author)>
  <!ELEMENT title (#PCDATA)>
  <!ELEMENT author (#PCDATA)>
]>
EOS
doctype.name # => "books"
doctype.external_id # => nil