count()

Description

count() evaluates an XPath expression, collects the resulting node-set (or sequence in XPath 2.0+), and returns the number of items as an integer. It is the standard way to determine how many elements match a given path without iterating over them.

Common use cases include:

• Conditionally processing content only if at least one element exists.
• Displaying totals (“5 items found”).
• Checking whether a repeated element has a specific number of occurrences.
• Using the count as a denominator or comparator in arithmetic expressions.

Parameters

Return value

xs:integer — the number of nodes or items in the argument.

Examples

Display item count

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<library>
  <book><title>XSLT Cookbook</title></book>
  <book><title>XML in a Nutshell</title></book>
  <book><title>Learning XML</title></book>
</library>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="text"/>

  <xsl:template match="/library">
    <xsl:value-of select="count(book)"/>
    <xsl:text> books in the library.</xsl:text>
  </xsl:template>
</xsl:stylesheet>

Output:

3 books in the library.

Conditional output based on count

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="/library">
    <result>
      <xsl:choose>
        <xsl:when test="count(book) = 0">
          <message>No books found.</message>
        </xsl:when>
        <xsl:otherwise>
          <message><xsl:value-of select="count(book)"/> book(s) found.</message>
        </xsl:otherwise>
      </xsl:choose>
    </result>
  </xsl:template>
</xsl:stylesheet>

Output:

<result>
  <message>3 book(s) found.</message>
</result>

Count elements matching a condition

<!-- Count books with more than 300 pages -->
<xsl:value-of select="count(book[@pages > 300])"/>

Notes

• count() counts nodes in the argument expression, not the context node’s children by default. Always specify the path explicitly.
• To count all descendants of a type, use count(.//element-name).
• count() always returns a non-negative integer; it returns 0 for an empty node-set, never an error.
• In XSLT 2.0+, you can use count() on any sequence, including sequences of atomic values.
• last() inside xsl:for-each gives the same number as count(select-expression) but only within the loop; count() can be used anywhere.

See also

• sum()
• last()