Filterx function reference draft, part 1

content/filterx/_index.md

@@ -314,20 +314,20 @@ For details, see {{% xref "/filterx/operator-reference.md" %}}.
 Filterx has the following built-in functions.
 
 <!-- FIXME definitions/descriptions -->
-- "isset"
-- "unset"
-- "json"
-- "json_array"
-- "datetime"
-- "isodate"
-- "string"
+- [`datetime`]({{< relref "/filterx/function-reference.md#datetime" >}})
+- [`isodate`]({{< relref "/filterx/function-reference.md#isodate" >}})
+- [`isset`]({{< relref "/filterx/function-reference.md#isset" >}})
+- [`len`]({{< relref "/filterx/function-reference.md#len" >}}): Returns the length of an object.
+- [`json, json_object`]({{< relref "/filterx/function-reference.md#json" >}}): Convert a value into a JSON object.
+- [`json_array`]({{< relref "/filterx/function-reference.md#json-array" >}}): Convert a value into a JSON array.
+- [`string`]({{< relref "/filterx/function-reference.md#string" >}}): Convert a value into a string.
+- [`unset`]({{< relref "/filterx/function-reference.md#unset" >}})
+- [`vars`]({{< relref "/filterx/function-reference.md#vars" >}}): The variables defined in the filterx block.
 - "bytes"
 - "protobuf"
 - "bool"
 - "int"
 - "double"
-- "len"
-- "vars"
 - "lower"
 - "upper"
 - "regexp_search"

content/filterx/function-reference.md

@@ -10,6 +10,19 @@ weight: 4800
 sok egyszeru pelda az adott functionnel, a tmp/axosyslog/tests/light/functional_tests/filterx/test_filterx.py temakorei sok mindent lefednek 
 -->
 
+## datetime
+
+Cast a value into a datetime variable.
+
+Usage: `datetime(<string or expression to cast as datetime>)`
+
+For example:
+
+```shell
+date = datetime("1701350398.123000+01:00")
+```
+<!-- FIXME syntax for argument, timezone handling, etc. -->
+
 ## flatten
 
 Usage: `flatten(dict, separator=".")`
@@ -41,16 +54,52 @@ value_separator must be a string literal, and a single character
 pair_separator must be a string literal
 -->
 
+## isodate
+
+<!-- FIXME -->
+
+## isset
+
+Returns true if the argument exists and its value is not empty or null.
+
+Usage: `isset(<name of a variable, macro, or name-value pair>)`
+
 ## istype
 
 Usage: `istype(object, type_str)`
 <!-- FIXME include list of valid types -->
 
+## json, json_object {#json}
+
+Cast a value into a JSON object.
+
+Usage: `json(<string or expression to cast as json>)`
+
+For example:
+
+```shell
+js = json_object({"key": "value"})
+```
+
+## json_array {#json-array}
+
+Cast a value into a JSON array.
+
+Usage: `json_array(<string or expression to cast as json array>)`
+
+For example:
+
+```shell
+list = json_array(["first_element", "second_element", "third_element"]);
+```
+
 ## len
 
+Returns the number of items in an object. For example, the length of a string, or the number of elements in a list.
+
 Usage: `len(object)`
 
-<!-- FIXME mire van ertelmezve es mikor mit ad vissza? -->
+<!-- FIXME What does it return for different types? -->
 
 ## parse_csv
 
@@ -97,6 +146,20 @@ value_separator must be a string literal, and a single character
 pair_separator must be a string literal
 -->
 
+## regexp_search
+
+<!--     $MSG = json();
+    $MSG.unnamed = regexp_search("foobarbaz", /(foo)(bar)(baz)/);
+    $MSG.named = regexp_search("foobarbaz", /(?<first>foo)(?<second>bar)(?<third>baz)/);
+    $MSG.mixed = regexp_search("foobarbaz", /(?<first>foo)(bar)(?<third>baz)/);
+    $MSG.force_list = json_array(regexp_search("foobarbaz", /(?<first>foo)(bar)(?<third>baz)/));
+    $MSG.force_dict = json(regexp_search("foobarbaz", /(foo)(bar)(baz)/));
+
+    $MSG.no_match_unnamed = regexp_search("foobarbaz", /(almafa)/);
+    if (len($MSG.no_match_unnamed) == 0) {
+        $MSG.no_match_unnamed_handling = true;
+    }; -->
+
 ## regexp_subst
 
 <!-- 
@@ -108,12 +171,51 @@ pair_separator must be a string literal
 #define FILTERX_FUNC_REGEXP_SUBST_FLAG_NEWLINE_NAME "newline"
  -->
 
+## string
+
+Cast a value into a string.
+
+Usage: `string(<string or expression to cast>)`
+
+For example:
+
+```shell
+myvariable = string(${LEVEL_NUM});
+```
+
+Sometimes you have to explicitly cast values to strings, for example, when you want to concatenate them into a message using the `+` operator.
+
 ## strptime
 
 Usage: `strptime(time_str, format_str_1, ..., format_str_N)`
 
+## unset
+
+Deletes a variable, a name-value pair, or a key in a complex object (like JSON).
+
+<!-- FIXME What happens when trying to unset a hard macro? Error? -->
+
+See also {{% xref "/filterx/_index.md#delete-values" %}}.
+
 ## unset_empties
 
 Usage: `unset_empties(object, recursive=true)`
 
-Also unsets inner dicts' and lists' values is recursive is set.
+Also unsets inner dicts' and lists' values is recursive is set.
+
+## vars
+
+Returns the variables (including pipeline variables and name-value pairs) defined in the filterx block as a JSON object.
+
+For example:
+
+```shell
+filterx {
+  $logmsg_variable = "foo";
+  local_variable = "bar";
+  declare pipeline_level_variable = "baz";
+  ${MESSAGE} = vars();
+};
+```
+
+The value of `${MESSAGE}` will be: `{"logmsg_variable":"foo","pipeline_level_variable":"baz"}`