.TH "md_doc_help_elektra-cascading" 3elektra "Sun May 29 2016" "Version 0.8.14" "Elektra" \" -*- nroff -*-
.ad l
.nh
.SH NAME
md_doc_help_elektra-cascading \- elektra-cascading(7) -- of key names 
\fBCascading\fP is the triggering of secondary actions\&. For configuration it means that first the user configuration is read and if this attempt fails, the system configuration is used as fallback\&.
.PP
The idea is that the application installs a configuration storage with default settings that can only be changed by the administrator\&. But every user has the possibility to override parts of this \fIsystem configuration\fP regarding the user's needs in the *user configuration\&. To sum up, besides system configuration, users have their own key databases that can override the settings according to their preferences\&.
.PP
Thus when a key starts with \fC/\fP such cascading will automatically performed\&.
.PP
Keys in \fCspec\fP 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 \fCksLookup\fP\&. When cascading keys (those starting with \fC/\fP) are used following features are available (in the meta data of respective \fCspec\fP-keys):
.PP
.IP "\(bu" 2
\fCoverride/#\fP: use these keys \fIin favour\fP of the key itself (note that \fC#\fP is the syntax for arrays, e\&.g\&. \fC#0\fP for the first element, \fC#_10\fP for the 11th and so on)
.IP "\(bu" 2
\fCnamespace/#\fP: instead of using all namespaces in the predefined order, one can specify which namespaces should be searched in which order
.IP "\(bu" 2
\fCfallback/#\fP: when no key was found in any of the (specified) namespaces the \fCfallback\fP-keys will be searched
.IP "\(bu" 2
\fCdefault\fP: this value will be used if nothing else was found
.PP
.PP
.SS "CASCADING"
.PP
When cascading keys (those starting with \fC/\fP) the lookup will work in the following way (it can be debugged with \fCkdb get -v\fP):
.PP
1\&.) In the \fCspec\fP-key the \fCoverride/#\fP keys will be considered\&. 2\&.) If, in the \fCspec\fP-key, a \fCnamespace/#\fP exist, those namespaces will be used\&. 3\&.) Otherwise, all namespaces will be considered, see \fBhere\&.\fP 4\&.) In the \fCspec\fP-key the \fCfallback/#\fP keys will be considered\&. 5\&.) In the \fCspec\fP-key the \fCdefault\fP value will be returned\&.
.PP
See \fBapplication integration\fP for how to use cascading names in the context of applications\&.
.PP
\fBRead more about namespaces\&.\fP