.TH "md_src_plugins_README" 3elektra "Sun May 29 2016" "Version 0.8.14" "Elektra" \" -*- nroff -*-
.ad l
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.SH NAME
md_src_plugins_README \- elektra-plugins(7) -- plugins overview 
Plugins can be mounted into the KDB and can access or manipulate the KeySet on every access\&.
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Multiple plugins can be mounted into the \fBkey data base\fP\&. On every access to the key data base they are executed and thus can change the functionality\&.
.SH "Introduction"
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Elektra already has a wide range of different plugins\&. The plugin folders should contain a README\&.md with further information\&. (Or follow links below\&.) The plugins are:
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Overview Plugins For background information see \fBelektra-plugins-framework(7)\fP\&.
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.SS "C-Interface"
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All plugins implement the same interface:
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.IP "\(bu" 2
\fC\fBkdbOpen()\fP\fP calls \fCelektraPluginOpen()\fP of every plugin to let them do their initialisation\&.
.IP "\(bu" 2
\fC\fBkdbGet()\fP\fP requests \fCelektraPluginGet()\fP of every plugin in the queried backends to return a key set\&.
.IP "\(bu" 2
\fC\fBkdbSet()\fP\fP usually calls \fCelektraPluginSet()\fP of every plugin in the queried backends to store the configuration\&.
.IP "\(bu" 2
\fC\fBkdbSet()\fP\fP also calls \fCelektraPluginError()\fP for every plugin when an error happens\&. Because of \fCelektraPluginError()\fP, plugins are guaranteed to have their chance for necessary cleanups\&.
.IP "\(bu" 2
\fC\fBkdbClose()\fP\fP makes sure that plugins can finally free their own resources in \fCelektraPluginClose()\fP\&.
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.SS "KDB-Interface"
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.IP "\(bu" 2
To list all plugins use \fBkdb-list(1)\fP\&.
.IP "\(bu" 2
To check a plugin use \fBkdb-check(1)\fP\&.
.IP "\(bu" 2
For information on a plugin use \fBkdb-info(1)\fP\&.
.IP "\(bu" 2
For mount plugin(s) use \fBkdb-mount(1)\fP\&.
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.SS "See also"
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For an easy introduction, see \fBthis tutorial how to write a storage plugin\fP\&. For more background information of the \fBplugin framework, continue here\fP\&. Otherwise, you can visit the \fCthe API documentation\fP\&.
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.SH "Plugins"
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.SS "Resolver"
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Before configuration is actually written, the file name needs to be determined (will be automatically added by kdb mount):
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.IP "\(bu" 2
\fBresolver\fP uses POSIX APIs to handle conflicts gracefully
.IP "\(bu" 2
\fBwresolver\fP minimalistic resolver for non-POSIX systems
.IP "\(bu" 2
\fBnoresolver\fP does not resolve, but can act as one
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and afterwards the configuration file must be synced with harddisc (recommended to add at every kdb mount):
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.IP "\(bu" 2
\fBsync\fP uses POSIX APIs to sync configuration file with harddisc
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.SS "Storage"
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Are responsible for reading writing the configuration to configuration files\&.
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Read and write everything a KeySet might contain:
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.IP "\(bu" 2
\fBdump\fP makes a dump of a KeySet in an Elektra-specific format
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Read (and write) standard config files of /etc:
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.IP "\(bu" 2
\fBaugeas\fP parses and generates many different configuration files using the augeas library
.IP "\(bu" 2
\fBhosts\fP read/write hosts files
.IP "\(bu" 2
\fBline\fP reads any file line by line
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Using semi-structured data for config files:
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.IP "\(bu" 2
\fBtcl\fP-like config files (including meta data)\&.
.IP "\(bu" 2
\fBni\fP parses INI files based on \fCni\fP\&.
.IP "\(bu" 2
\fBini\fP parses INI files based on \fCinih\fP\&.
.IP "\(bu" 2
\fBxmltool\fP uses XML\&.
.IP "\(bu" 2
\fByajl\fP uses JSON\&.
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Plugins that just show some functionality, (currently) not intended for productive use:
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.IP "\(bu" 2
\fBfstab\fP reads fstab files\&.
.IP "\(bu" 2
\fBregexstore\fP
.IP "\(bu" 2
\fBsimpleini\fP is ini without sections
.IP "\(bu" 2
\fBcsvstorage\fP for csv files
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.SS "System Information"
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Information compiled in Elektra:
.IP "\(bu" 2
\fBversion\fP is a build-in plugin directly within the core so that it cannot give wrong version information
.IP "\(bu" 2
\fBconstants\fP various constants, including version information
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Providing information found on the system not available in persistent files:
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.IP "\(bu" 2
\fBuname\fP information from the uname syscall\&.
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.SS "Filter"
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\fIFilter plugins\fP process keys and their values in both directions\&. In one direction they undo what they do in the other direction\&. Most filter plugins available now encode and decode values\&. Storage plugins that use characters to separate key names, values or metadata will not work without them\&.
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.SS "Encoding"
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Rewrite unwanted characters with different techniques:
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.IP "\(bu" 2
\fBccode\fP using the technique from arrays in the programming language C
.IP "\(bu" 2
\fBhexcode\fP using hex codes
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Transformations:
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.IP "\(bu" 2
\fBkeytometa\fP transforms keys to metadata
.IP "\(bu" 2
\fBrename\fP renames keys according to different rules
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Doing other stuff:
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.IP "\(bu" 2
\fBcrypto\fP encrypts / decrypts confidential values
.IP "\(bu" 2
\fBiconv\fP make sure the configuration will have correct character encoding
.IP "\(bu" 2
\fBhidden\fP hides keys whose names start with a \fC\&.\fP\&.
.IP "\(bu" 2
\fBnull\fP takes care of null values and other binary specialities
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.SS "Notification and Logging"
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Log/Send out all changes to configuration to:
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.IP "\(bu" 2
\fBdbus\fP
.IP "\(bu" 2
\fBjournald\fP
.IP "\(bu" 2
\fBsyslog\fP
.IP "\(bu" 2
\fBlogchange\fP prints the change of every key on the console
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.SS "Debug"
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Trace everything that happens within KDB:
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.IP "\(bu" 2
\fBtimeofday\fP print timestamps
.IP "\(bu" 2
\fBtracer\fP
.IP "\(bu" 2
\fBcounter\fP count and print how often plugin is used
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.SS "Checker"
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Copies meta data to keys:
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.IP "\(bu" 2
\fBglob\fP using globbing techniques
.IP "\(bu" 2
\fBstruct\fP using a defined structure (may also reject configuration not conforming to that structure)
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Plugins that check if values are valid based on meta data (typically copied by another plugin just before):
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.IP "\(bu" 2
\fBvalidation\fP by using regex
.IP "\(bu" 2
\fBnetwork\fP by using network APIs
.IP "\(bu" 2
\fBpath\fP by checking files on filesystem
.IP "\(bu" 2
\fBtype\fP using runtime type checking (CORBA types/)
.IP "\(bu" 2
\fBenum\fP compares the keyvalue against a list of valid values
.IP "\(bu" 2
\fBmathcheck\fP by mathematical expressions using keysvalues as operants
.IP "\(bu" 2
\fBconditionals\fP by using if-then-else like statements
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.SS "Interpreter"
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These plugins start an interpreter and allow you to use a bindings\&.
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.IP "\(bu" 2
\fBjni\fP java plugins started by jni, works with jna plugins
.IP "\(bu" 2
\fBpython\fP Python 3 plugins (technical preview/)
.IP "\(bu" 2
\fBpython2\fP Python 2 plugins (technical preview, deprecated/)
.IP "\(bu" 2
\fBlua\fP Lua plugins (technical preview/)
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.SS "Others"
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.IP "\(bu" 2
\fBdoc\fP contains the documentation of the plugin interface
.IP "\(bu" 2
\fBerror\fP yields errors as described in metadata (handy for test purposes)
.IP "\(bu" 2
\fBtemplate\fP to be copied for new plugins
.IP "\(bu" 2
\fBlineendings\fP tests file for consistent line endings
.IP "\(bu" 2
\fBlist\fP loads other plugins
.IP "\(bu" 2
\fBfilecheck\fP does sanity checks on a file
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To add a new plugin you can copy the template plugin\&. Please make sure to add your plugin:
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.IP "\(bu" 2
to this list, at least in Others
.IP "\(bu" 2
to \fBcmake\fP, at least in ALL 
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