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XPath operator

comment() node test

Selects XML comment nodes. Their delimiters are syntax; the node's string-value is only the content between them.

comment() selects comments on the chosen axis. A comment is a node in the XPath data model even though it is not an element and never appears in an element-only wildcard.

Comments cannot nest and cannot contain --. If the parser preserves them, their string-value is the text between <!-- and -->.

Syntax
child::comment() — usually comment()
Returns
node-set
Kind
Operator
Version
XPath 1.0 (libxml2)

Worked examples

Each result below is what the evaluator returned, asserted on every test run. An empty result means an empty node-set — which is an answer, not an error.

  • count(/order/comment())on order.xmlRun
    1
  • normalize-space(string(/order/comment()))on order.xmlRun
    priority customer
  • count(/order/*[self::comment()])on order.xmlRun
    0

Run your own expression

What catches people out

  • * selects elements, so */comment() and *[self::comment()] ask very different questions.
  • Some application pipelines discard comments before XPath runs; an empty result may describe the tree you were given rather than the source file.
  • Comments carry no namespace and have no element name.

The sample documents

Every example on this page runs against this document. The sitemap one is namespaced on purpose — almost every real XML document is, and that changes which expressions match.

order.xml
<?xml version="1.0" encoding="UTF-8"?>
<order id="A-1001" tier="gold">
  <customer country="NO">Ada Lovelace</customer>
  <!-- priority customer -->
  <?audit retained?>
  <lines>
    <line sku="WIDGET-1" qty="2"><price>14.50</price></line>
    <line sku="WIDGET-2" qty="1"><price>39.00</price></line>
    <line sku="GIFT-WRAP" qty="1"><price>0.00</price></line>
  </lines>
  <note>  Deliver after 09:00  </note>
</order>

Related

All 40 XPath entries

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