string-length()

Description

string-length() returns the number of characters in its string argument. The argument is first converted to a string using string() rules. When called without an argument, it returns the character count of the context node’s string value.

In XPath 1.0, “characters” means Unicode code points. Surrogate pairs and multi-byte UTF-8 sequences each count as however many code points they represent (a supplementary character represented by two UTF-16 code units may count as one or two depending on the processor).

string-length() is useful for validation (checking minimum or maximum field lengths), for computing substring offsets, and for filtering elements whose content exceeds or falls below a threshold.

Parameters

Return value

xs:double — the number of characters in the string (a non-negative integer represented as a double).

Examples

Filter elements by content length

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<words>
  <word>hi</word>
  <word>hello</word>
  <word>extraordinary</word>
  <word>ok</word>
</words>

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="/words">
    <long-words>
      <xsl:for-each select="word[string-length(.) &gt; 4]">
        <item><xsl:value-of select="."/></item>
      </xsl:for-each>
    </long-words>
  </xsl:template>
</xsl:stylesheet>

Output:

<long-words>
  <item>hello</item>
  <item>extraordinary</item>
</long-words>

Report field lengths

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<form>
  <field name="username">alice</field>
  <field name="email">alice@example.com</field>
</form>

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="/form">
    <lengths>
      <xsl:for-each select="field">
        <field name="{@name}" length="{string-length(.)}"/>
      </xsl:for-each>
    </lengths>
  </xsl:template>
</xsl:stylesheet>

Output:

<lengths>
  <field name="username" length="5"/>
  <field name="email" length="17"/>
</lengths>

Notes

• string-length('') returns 0. An empty element with no text children has string-length() of 0.
• The return value is a number (double), not an integer, although it will always be a whole number in practice.
• string-length() counts the string value of the context node when called with no argument — for an element, that is all descendant text nodes concatenated.
• For computing a right-aligned substring (e.g. the last N characters), combine with substring(): substring($s, string-length($s) - N + 1).
• In XSLT 2.0+, fn:string-length() operates identically but the argument must be a single string; passing a sequence of more than one item raises a type error.

See also

• string()
• normalize-space()
• substring()