[augeas-devel] Distinguishing empty string from no value in path expressions

[David Lutterkort]

Hi Michael,

On Wed, 2011-09-28 at 14:33 +1000, Michael Chapman wrote:
> With Augeas's path expressions, is it possible to distinguish a node whose 
> value is an empty string from one that has no value? At the moment, nodes 
> with no value appear to be treated the same as those with an empty string:

Currently, there is no way to do that. When path expressions are
evaluated, NULL's are automatically converted to the empty string to
avoid funky tri-state logic.

So far, nobody has needed that distinction, but it would be easy enough
to add a null function to the language so that you could pick out nodes
with null values, i.e. something like

   match test/*[null(.)]

which, in your example, would match /test/b

Would that be good enough for your purposes ?

David