Given the following example html:
<products>
<product>
<sku>10021</sku>
</product>
<product>
<sku>10021</sku>
</product>
<product>
<sku>10022</sku>
</product>
<product>
<sku>10023</sku>
</product>
<product>
<sku>10023</sku>
</product>
</products>
I know how to find distinct sku values with xpath: distinct-values(//sku), which will output:
10021
10022
10023
But how would I get the ones that are not distinct, so:
10021
10023
I am using xidel, so XPath 3 is fine. But if it can be done somehow with XPath 1, preferably without XSLT, I would very much like to read about that as well.