如何只读取xml属性的第一叶

Question

I have Powershell code like this:

$Xml = @"
<?xml version="1.0" encoding="utf-8"?>
<DisplayDefinitionTable>
    <columns>
        <column_entry order_num="0" relation_to_base="Item.current_name">current_name</column_entry>
    </columns>
    <rows>
        <row>
            <object_tag tag="91859" uid="TdjJhBMdpQNFhC"/>
            <object_tag tag="86504" uid="TtvJBp53pQNFhC"/>
            <row_element column="0" component_tag="91859" property_name="current_name">EAUX</row_element>
        </row>
        <row>
            <object_tag tag="92069" uid="DCuJhBMdpQNFhC"/>
            <object_tag tag="86504" uid="TtvJBp53pQNFhC"/>
            <row_element column="0" component_tag="92069" property_name="current_name">VISS</row_element>
        </row>
    </rows>
</DisplayDefinitionTable>

"@

Select-Xml -Content $Xml -XPath "//object_tag" | foreach {$_.node.uid}

And results:

Select-Xml -Content $Xml -XPath "//object_tag" | foreach {$_.node.uid}


TdjJhBMdpQNFhC
TtvJBp53pQNFhC
DCuJhBMdpQNFhC
TtvJBp53pQNFhC

PS C:\Windows\system32> 

The main goal is to take only first uid value of every leaf in the file so proper answer should looks like this:

TdjJhBMdpQNFhC
DCuJhBMdpQNFhC


PS C:\Windows\system32> 

How to do this?? Thanks

Answer 1

Try specifying your command as:

Select-Xml -Content $Xml -XPath "//object_tag[1]" | foreach {$_.node.uid}

Note, the addition of the [1] to the XPath to specifically pull just the first instance.

Or you also could have your command like the below to save piping to the foreach:

(Select-Xml -Content $Xml -XPath "//object_tag[1]").node.uid

Both variations above give you the results you're looking for.

Also, this great cheat sheet on XPath has some further information on indexing, etc...

Answer 2

It is probably easier use the (accelerated) standard .Net xml parser this will also better target the specific row/object_tag uid s and not all other possible uid at other levels:

$Xml = [xml]@'
<?xml version="1.0" encoding="utf-8"?>
<DisplayDefinitionTable>
    <columns>
        <column_entry order_num="0" relation_to_base="Item.current_name">current_name</column_entry>
    </columns>
    <rows>
        <row>
            <object_tag tag="91859" uid="TdjJhBMdpQNFhC"/>
            <object_tag tag="86504" uid="TtvJBp53pQNFhC"/>
            <row_element column="0" component_tag="91859" property_name="current_name">EAUX</row_element>
        </row>
        <row>
            <object_tag tag="92069" uid="DCuJhBMdpQNFhC"/>
            <object_tag tag="86504" uid="TtvJBp53pQNFhC"/>
            <row_element column="0" component_tag="92069" property_name="current_name">VISS</row_element>
        </row>
    </rows>
</DisplayDefinitionTable>
'@

and the PowerShell Xml dot notation syntax:

$xml.DisplayDefinitionTable.Rows.Row.ForEach{ $_.object_tag[0].uid }
TdjJhBMdpQNFhC
DCuJhBMdpQNFhC