Select first instance only with XPath?

Question

I am parsing some XML something like this:

<root>     <some_gunk/>     <dupe_node>         ...         stuff I want         ...     </dupe_node>     <bits_and_pieces/>     <other_gunk/>     <dupe_node>         ...         stuff I don't want         ...     </dupe_node>     <more_gunk/> </root> 

An XPath of '//dupe_node' will give me two instances of dupe_node to play with. I only want to traverse the first. Can I do this with XPath?

Answer 1

/descendant::dupe_node[1] 

//dupe_node[1] is generally wrong, although it produces an identical result in this particular case. See docs:

The location path //para[1] does not mean the same as the location path /descendant::para[1]. The latter selects the first descendant para element; the former selects all descendant para elements that are the first para children of their parents.

Given the following XML:

<foo>     <bar/>     <foo>         <bar/>     </foo> </foo> 

//bar[1] will produce two nodes, because both bars are first children of their respective parents.

/descendant::bar[1] will give only one node, which is the first of all the bars in the document.

Answer 2

//dupe_node[1] 

XPath counts from 1, not 0 in this case. You can use this tool to try things out in your browser:

http://www.xmlme.com/XpathTool.aspx?mid=82