How do you use "not" in xpath

Question

I want to write something of the sort:

//a[not contains(@id, 'xx')]

(meaning all the links that there 'id' attribute doesn't contain the string 'xx')

I can't find the right syntax.

Thanks

Answer 1

not() is a function in xpath (as opposed to an operator), so

//a[not(contains(@id, 'xx'))]

Answer 2

You should also check out the false() function which works in much the same way.