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README.md

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  • infos = Information about the spec plugin is in keys below
  • infos/author = Thomas Waser thomas.waser@libelektra.org
  • infos/licence = BSD
  • infos/needs =
  • infos/provides = check apply
  • infos/placements = postgetstorage presetstorage
  • infos/status = maintained nodep configurable global preview
  • infos/description = copies metadata from spec namespace to other namespaces

Introduction

The spec plugin is a global plugin that copies metadata from the spec-namespace to other namespaces using their key names as globbing expressions. Globbing resembles regular expressions. They do not have the same expressive power, but are easier to use. The semantics are more suitable to match path names:

  • _ matches any key name of just one hierarchy. This means it complies with any character except slash or null.
  • ? satisfies single characters with the same exclusion.
  • # matches Elektra array elements.
  • Additionally, there are ranges and character classes. They can also be inverted.

The plugin copies the metadata of the corresponding spec key to every matching key in the other namespaces.

The spec plugin also provides basic validation and structural checking. Specifically it supports:

  • detection of invalid array key names
  • detection of missing keys
  • validation of array ranges
  • validating the number of subkeys

Configuration

Actions

  • ERROR yields an error when a conflict occurs
  • WARNING adds a warning when a conflict occurs
  • INFO adds a metakey logs/spec/info which can be used by logging plugins
  • IGNORE ignores the conflict, this is the default value

Conflicts

  • Invalid array member: an invalid array key has been detected. e.g. /#abc
  • Out of range: the array has more or less elements than specified by the array option.
  • Invalid number of subkeys count: a key matching a _ expression has more or less subkeys than specified by the required option.
  • Conflicting metadata collision: the metakey that's supposed to be added already exists.
  • Missing keys missing: the key structure doesn't contain the required subkeys flagged with the require metakey in the spec namespace.
  • Invalid keys invalid: keys that are subkeys of an invalid array member. e.g. /#abc/key

Basic Configuration

conflict/set and conflict/get are used to specify what actions should be taken on conflicts. e.g. conflict/get = ERROR yields an error on every conflict.

Per Conflict Configuration

Actions can also be specified on a per conflict basis. Those actions take precedence over basic configuration options.

Examples:

conflict/get/member = WARNING
conflict/set/range = ERROR

Per Key Configuration

Actions can also be specified per-key. Those will take precedence over basic and per-conflict configurations.

Example:

spec/test/#
    conflict/get/member = INFO

Examples

Ini files can be found in /examples/spec which should be PWD so that the example works:

cd ~e/examples/spec
kdb global-mount        # mounts spec plugin by default
kdb mount $PWD/spec.ini spec ni
kdb mount $PWD/spectest.ini /testkey ni
kdb export /testkey ni     # note: spec can only applied on cascading access

With spec mount one can use (in this case battery.ini needs to be installed in kdb file spec (this should be preferred on non-development machines so that everything still works after the source is removed):

cp battery.ini $(dirname $(kdb file spec))
kdb mount battery.ini spec/example/battery ni
kdb spec-mount /example/battery
kdb lsmeta /example/battery/level    # we see it has a check/enum
kdb getmeta /example/battery/level check/enum    # now we know allowed values
kdb set /example/battery/level low   # success, low is ok!
kdb set /example/battery/level x     # fails, not one of the allowed values!

cp openicc.ini $(dirname $(kdb file spec))
kdb mount openicc.ini spec/freedesktop/openicc ni
kdb spec-mount /freedesktop/openicc

kdb ls /freedesktop/openicc # lets see the whole configuration
kdb export spec/freedesktop/openicc ni   # give us details about the specification
kdb lsmeta /freedesktop/openicc/device/camera/#0/EXIF_serial   # seems like there is a check/type
kdb set "/freedesktop/openicc/device/camera/#0/EXIF_serial" 203     # success, is a long
kdb set "set "/freedesktop/openicc/device/camera/#0/EXIF_serial" x   # fails, not a long