NAME

       md_src_plugins_glob_README - README

       • infos = Information about glob plugin is in keys below

       • infos/author = Felix Berlakovich elektra@berlakovich.net

       • infos/licence = BSD

       • infos/needs =

       • infos/ordering = check keytometa

       • infos/stacking = no

       • infos/provides =

       • infos/placements = presetstorage postgetstorage

       • infos/description = copies metadata to keys with the help of globbing

       The  glob  plugin  provides  coping metadata given by the plugin's configuration to keys identified using
       glob 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 with any key name of just one hierarchy. This means it complies  with  any  character  except
         slash or null.

       • ? satisfies single characters with the same exclusions.

       • Additionally, there are ranges and character classes. They can also be inverted.

       So  this  plugin adds metadata to keys identified by globbing expressions. The plugin copies the metadata
       of the corresponding globbing keys in its configuration. Globbing can be applied in get and set direction
       or both.

   GLOBBING KEYS
       The plugin is configured with globbing keys in its configuration. Each key  below  the  configuration  is
       interpreted as a globbing key. The value of the key contains the globbing expression. When a key matching
       the  glob  expression  contained  in one of the globbing keys is found, the metakeys of the corresponding
       globbing key are copied.

   GLOBBING DIRECTION
       Globbing keys located  directly  below  the  configuration  (e.g  config/glob/#1)  are  applied  in  both
       directions  (get  and  set).  Keys  below  'get'  (e.g.  config/glob/get/#1)  are applied only in the get
       direction and keys below set (e.g. config/glob/set/#1) are applied only in the set direction.

       So the glob plugin iterates over a list of glob expressions for every key. Metadata is applied  only  for
       the first expression that matches. So later expressions can be used as default values.

   GLOBBING FLAGS
       Globbing  keys  may  contain a subkey named 'flags'. This optional key contains the flags to be passed to
       the globbing function (currently fnmatch). If the key does not exist or if the value of the key cannot be
       converted into a number, FNM_PATHNAME is used as a default (see fnmatch(3) for more details).

   Contracts
       Glob statements are very useful together with contracts. Storage plugins can request the glob  plugin  to
       fill up metadata before they receive the keys in elektraPluginSet(). In config/needs, the plugin declares
       which keys should obtain which metadata. If the glob expression starts with a slash, the contract checker
       will automatically prepend the mount point.

       For example, the hosts plugin contract contains:

           keyNew ("system/elektra/modules/hosts/config/needs/glob/#1",
                   KEY_VALUE, "/*",
                   KEY_META, "check/ipaddr", "", /* Preferred way to check */
                           /* Can be checked additionally */
                   KEY_META, "check/validation", "^[0-9.:]+$",
                   KEY_META, "check/validation/message",
                           "Character present not suitable for ip address",
                   KEY_END),
           keyNew ("system/elektra/modules/hosts/config/needs/glob/#2",
                   KEY_VALUE, "/*/*",
                           /* Strict character validation */
                   KEY_META, "check/validation", "^[0-9a-zA-Z.:]+$",
                   KEY_META, "check/validation/message",
                           "Character present not suitable for host address",
                   KEY_END),

       We see that the hosts plugin adds two glob statements with the clause config/needs. The first one matches
       with hostnames, the second with aliases.

       The  glob  plugin  only  fills the metadata in kdbSet(). This makes a difference compared with adding the
       metadata already in kdbGet(). Using the glob plugin, the user  will  not  see  the  metadata,  but  later
       plugins in kdbSet() will.

       To  sum up, the glob plugin replenishes the keys with metadata. The plugin applies metadata in a flexible
       way. This metadata can be used for later checks. Limited configuration storage plugins,  like  the  hosts
       plugin,  use  this  feature.  They  need it because they are not able to store metadata themselves. It is
       obviously not possible to apply values to non-existing keys.

Version 0.8.14                                   Tue Dec 15 2015            md_src_plugins_glob_README(3elektra)