elektra-cascading(7) of key names


Keys in spec allow us to specify which keys are read by the application, which fallback it might have and which is the default value using meta data. The implementation of these features happened in ksLookup. When cascading keys (those starting with /) are used following features are available (in the meta data of respective spec-keys):
override/#: use these keys in favour of the key itself (note that # is the syntax for arrays, e.g. #0 for the first element, #_10 for the 11th and so on)
namespace/#: instead of using all namespaces in the predefined order, one can specify which namespaces should be searched in which order
fallback/#: when no key was found in any of the (specified) namespaces the fallback-keys will be searched
default: this value will be used if nothing else was found


When cascading keys (those starting with /) the lookup will work in the following way (it can be debugged with kdb get -v):

1.) In the spec-key the override/# keys will be considered. 2.) If, in the spec-key, a namespace/# exist, those namespaces will be used. 3.) Otherwise, all namespaces will be considered, see here. /doc/help/elektra-namespaces.md 4.) In the spec-key the fallback/# keys will be considered. 5.) In the spec-key the default value will be returned.

See application integration /doc/tutorials/application-integration.md for how to use cascading names in the context of applications.

Read more about namespaces. /doc/help/elektra-namespaces.md