XPath

External

• https://www.baeldung.com/linux/evaluate-xpath
• https://www.w3schools.com/xml/xpath_intro.asp
• https://www.w3schools.com/xml/xpath_syntax.asp

Internal

• XML
• XSL

Overview

XPath is a specification language that allows specifying parts of an XML structure. It is part of XSL. An XPath expression can be thought as an address of a part of an XML document.

TODO: https://docs.oracle.com/javase/tutorial/jaxp/xslt/xpath.html

Command Line Tooling

• XMLStarlet
• xmllint
• xidel
• xpath

Java Support

https://www.baeldung.com/java-xpath

Syntax

https://www.w3schools.com/xml/xpath_syntax.asp

Example

<books>
    <book id="1" category="linux">
        <title lang="en">Linux Device Drivers</title>
        <year>2003</year>
        <author>Jonathan Corbet</author>
        <author>Alessandro Rubini</author>
    </book>
    <book id="2" category="linux">
        <title lang="en">Understanding the Linux Kernel</title>
        <year>2005</year>
        <author>Daniel P. Bovet</author>
        <author>Marco Cesati</author>
    </book>
    <book id="3" category="novel">
        <title lang="en">A Game of Thrones</title>
        <year>2013</year>
        <author>George R. R. Martin</author>
    </book>
    <book id="4" category="novel">
        <title lang="fr">The Little Prince</title>
        <year>1990</year>
        <author>Antoine de Saint-Exupéry</author>
    </book>
</books>

Node Selection

XPath uses path expressions to select nodes in an XML document. The node is selected by following a path (or steps):

nodename

Select the node (or nodes) with the given nodename. If multiple nodes with the same node match, they're all selected.

xml sel -t -v "/books/book/title" ./books.xml

/

Select from the root node.

xml sel -t -v "/books/book/title" ./books.xml

//

Selects nodes in the document from the current node that match the selection no matter where they are/

xml sel -t -v "//title" ./books.xml

.

Selects the current node

..

Selects the parent of the current node

@

Selects attributes.

To get the value of a specific attribute, use /@<attribute-name> as below:

/books/book[@id='1']/@category

Predicates

Predicates are used to find a specific node or a node that contains a specific value. Predicates are always embedded in square brackets.

element-name[@attribute-name='value']
element-name[sub-element-expression]

Select an Element based on Two Attributes

/box/object[@name='D' and @color='yellow']

Note that and is case sensitive.

Select an Element based on Value/Attribute of Sub-Element

Select the <books>/<book> element whose sub-element <year> is 2003, and display the <title> sub-element of the element.

/books/book[year=2003]/title

Select the <books>/<book> element whose sub-element <title> has a "fr" 'lang' attribute, and display the <author> sub-element of the selected <book> element.

/books/book/title[@lang='fr']/../author