xpath query to select element where attribute not present

Question

What should be xpath query to select an element where the attribute att not present.

<root>
  <elem att='the value' />
  <elem att='the value' />
  <elem att='the value' />
  **<elem />**
  <elem att='the value' />
  <elem att='the value' />
</root>

I want to update element where attribute att not present.

Thanks

Answer 1

You can use [@att] to test for the presence of an attribute, so you just need:

//elem[not(@att)]

... to test for the absence of it.

(Tested using xpathtester)

Answer 2

Also, you can use @* (the abbreviated form of attribute::*) to represent any attribute.

With any attribute example:

//elem[@*]

Without any attribute example:

//elem[not(@*)]