+add the `-S` and `-C` options for the configuration parser as described
+in <<config:>>. These options are handled internally by @cf_getopt().
+
+You can rely on the configuration files having been loaded before the
+first of your program's options is parsed.
+
+[[deep]]
+Getting deeper
+--------------
+
+Since the configuration system is somehow complicated, this part gives
+you a little overview of what you can find and where.
+
+[[conf_multi]]
+Arrays and lists
+~~~~~~~~~~~~~~~~
+
+It is sometime needed to have multiple items of the same type. There
+are three ways to do that:
+
+*Static arrays*::
+ An array with fixed maximum length. You provide
+ the length and already allocated array which is filled with items.
+ The configuration may contain less than the maximum length items.
++
+For example, you can have an static array of five unsigned integers:
++
+ static uns array[] = { 1, 2, 3, 4, 5 };
++
+ static struct cf_section section = {
+ CF_ITEMS {
+ CF_UNS_ARY("array", array, 5),
+ CF_END
+ }
+ };
+
+*Dynamic arrays*::
+ Similar to static array, but you provide pointer
+ to pointer to the given item (eg. if you want dynamic array of
+ integers, you give `**int`). The parser allocates an array of needed
+ size. You can use the <<def_DARY_LEN,`DARY_LEN`>> macro to find out
+ the number of elements actually loaded.
++
+If you want dynamic array of strings, you would use:
++
+ static char *array[];
++
+ static struct cf_section section = {
+ CF_ITEMS {
+ CF_STRING_DYN("array", &array, CF_ANY_NUM),
+ CF_END
+ }
+ };
+
+*Lists*::
+ Linked lists based on <<clist:>>. You provide description
+ of single node and pointer to the
+ <<clist:struct_clist,`struct clist`>> variable. All the nodes will
+ be created dynamically and put there.
++
+First element of your structure must be <<clist:type_cnode,`cnode`>>.
++
+The first example is list of strings and uses <<clist:simple,simple
+lists>>:
++
+ static struct clist list;
++
+ static struct cf_section section = {
+ CF_ITEMS {
+ CF_LIST("list", &list, &cf_string_list_config),
+ CF_END
+ }
+ };
++
+Another example, describing how to create more complicated list node
+than just a string can be found at the <<def_CF_TYPE,`CF_TYPE`>> macro.
+
+[[reload]]
+Reloading configuration
+~~~~~~~~~~~~~~~~~~~~~~~
+
+The configuration system allows you to reload configuration at
+runtime. The new config changes the values against the default values.
+It means, if the default value for variable `A` is `10`, the currently
+loaded config sets it to `42` and the new config does not talk about
+this variable, `A` will have a value of `10` after a successful load.
+
+Furthermore, if the loading of a new configuration fails, the current
+configuration is preserved.
+
+All this is done with <<journal,config journaling>>. The load of the
+first config creates a journal entry. If you try to load some new
+configuration, it is partially rolled back to defaults (the rollback
+happens, but instead of removing the journal entry, another journal
+entry is added for the rollback). If the loading succeeds, the two
+journal entries are removed and a new one, for the new configuration,
+is added. If it fails, the first one is replayed and the rollback
+entry is removed.
+
+See <<cf_reload()>>.
+
+[[custom_parser]]
+Creating custom parsers
+~~~~~~~~~~~~~~~~~~~~~~~
+
+If you need to parse some data type the configuration system can't
+handle, you can write your own parser. But before you start, you
+should know a few things.
+
+The parser needs to support <<journal,journaling>>. To accomplish that,
+you have to use the <<alloc,configuration mempool>> for memory allocation.
+
+Now, you need a function with the same signature as
+<<type_cf_parser1,`cf_parser1`>>. Parse the first parameter (the
+string) and store the data in the second parameter. You may want to
+write a dumper function, with signature of
+<<type_cf_dumper1,`cf_dumper1`>> (needed for debug dumps).
+
+Fill in a structure <<struct_cf_user_type,cf_user_type>> and use the
+new data type in your configuration description with
+<<def_CF_USER,`CF_USER`>> macro as its @t parameter.
+
+You do not need to call @cf_journal_block() on the variable you store
+the result. It is true you change it, but it was stored to journal
+before your parser function was called.
+
+[[hooks]]
+Hooks
+~~~~~
+
+The configuration system supports hooks. They are used to initialize the
+configuration (if simple default value of variable is not enough) and
+to check the sanity of loaded data.
+
+Each hook is of type <<type_cf_hook,`cf_hook`>> and you can include
+them in configuration description using <<def_CF_INIT,`CF_INIT`>> and
+<<def_CF_COMMIT,`CF_COMMIT`>> macros.
+
+The hooks should follow similar guidelines as custom parsers (well,
+init hooks do not need to call @cf_journal_block()) to support
+journaling. If you change nothing in the commit hook, you do not need
+to care about the journaling either.
+
+You may use the return value to inform about errors. Just return the
+error message, or NULL if everything went well.
+
+Another similar function is a copy function. It is very similar to a
+hook and is used when the item is copied and is too complicated to use
+simple memcpy(). Its type is <<type_cf_copier,`cf_copier`>> and is
+specified by the <<def_CF_COPY,`CF_COPY`>> macro. It's return value is
+the same as the one of a hook.
+
+[[conf_h]]
+ucw/conf.h
+----------
+
+Use this file if you want define a configuration section, request
+loading of some variables or create new item type.
+
+!!ucw/conf.h
+
+[[getopt_h]]
+ucw/getopt.h
+------------
+
+This header contains routines for parsing command line arguments and
+loading the configuration.
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