XPath is a (read-only) subset of the
XQuery language. So, an XPath expression is also an XQuery expression.
Some XPath expressions
/ | represents the root of the XML element tree. |
/xyz | navigates to the node named xyz immediately below the root of the XML element tree. |
/abc/*/xyz | navigates to node xyz which is below any single node that is below abc immediately under the root element. |
//N | navigates to any node N below the «actual context» |
//N//M | navigates to any node N below any node M below the «actual context» |
.. | get «actual node's» parent node |
@foo | evaluate to the value of the attribute named @foo (For example //someNode/@theAttribute) |
[…] | apply a filter, on child node value: //parentNode[childNode = 'xyz'] or on node's attribute: //node[@attr = 'bla']). Some operators include =, !=, or, and, not() |
/node/subnode
/node/subnode… traverses the XML document from the root to select one or more nodes:
[xml] $doc = @"
<root>
<abc>one </abc>
<def>two </def>
<abc>three <xyz>nine</xyz> </abc>
</root>
"@
foreach ($node in (select-xml -xml $doc -xPath '/root/abc').node) {
"$($node.InnerText) ($($node.InnerXml))"
}
#
# one (one )
# three nine (three <xyz>nine</xyz>)
@attr
@attr is applied on one (or more?) nodes to return the value of the attribute named attr:
[xml] $doc = @"
<root>
<foo id='1'>one</foo>
<bar id='2'>two</bar>
<baz id='3'>baz</baz>
</root>
"@
$found = select-xml -xml $doc -xPath '/root/bar/@id'
write-host "The id is $($found.node.Value)"
Filters
Find an alement with a given attribute-value:
[xml] $doc = @"
<root>
<elem id='99'>ninety-nine</elem>
<elem id='42'>forty-two</elem>
<elem id='17'>seventeen</elem>
</root>
"@
$found = select-xml -xml $doc -xPath '/root/elem[@id="42"]'
$found.Node.InnerText
[]
Find an element (here: <item>) with a child element named <name> whose content is bar, then print the content of another child element of the found element (<value>):
[xml] $doc = @"
<root>
<item id='1'>
<name>foo</name>
<value>42</value>
</item>
<item id='2'>
<name>bar</name>
<value>99</value>
</item>
<item id='3'>
<name>baz</name>
<value>7</value>
</item>
</root>
"@
$item_bar = select-xml -xml $doc -xPath "//item[name='bar']"
write-host "The value of the item whose name is bar is $($item_bar.node.value)"