## <a id="configuration-syntax"></a> Configuration Syntax

### <a id="object-definition"></a> Object Definition

Icinga 2 features an object-based configuration format. In order to
define objects the `object` keyword is used:

    object Host "host1.example.org" {
      display_name = "host1",

      macros = {
        address = "192.168.0.1"
      }
    }

> **Note**
>
> The Icinga 2 configuration format is agnostic to white space characters and
> new-lines.

> **Note**
>
> Exclamation marks (!) are not permitted in object names.

Each object is uniquely identified by its type (`Host`) and name
(`host1.example.org`). Objects can contain a comma-separated list of
property declarations. The following data types are available for
property values:

### Expressions

The following expressions can be used in the right-hand side of dictionary
values.

#### <a id="numeric-literals"></a> Numeric Literals

A floating-point number.

Example:

    -27.3

#### <a id="duration-literals"></a> Duration Literals

Similar to floating-point numbers except for the fact that they support
suffixes to help with specifying time durations.

Example:

    2.5m

Supported suffixes include ms (milliseconds), s (seconds), m (minutes),
h (hours) and d (days).

#### <a id="string-literals"></a> String Literals

A string.

Example:

    "Hello World!"

Certain characters need to be escaped. The following escape sequences
are supported:

  Character                           |Escape sequence
  ------------------------------------|------------------------------------
  "                                   |\\"
  \\                                  |\\\\
  \<TAB\>                             |\\t
  \<CARRIAGE-RETURN\>                 |\\r
  \<LINE-FEED\>                       |\\n
  \<BEL\>                             |\\b
  \<FORM-FEED\>                       |\\f

In addition to these pre-defined escape sequences you can specify
arbitrary ASCII characters using the backslash character (\\) followed
by an ASCII character in octal encoding.

#### <a id="multiline-string-literals"></a> Multi-line String Literals

Strings spanning multiple lines can be specified by enclosing them in
{{{ and }}}.

Example.

    {{{This
    is
    a multi-line
    string.}}}

> **Note**
>
> Unlike in ordinary strings special characters do not have to be escaped
> in multi-line string literals.

#### <a id="boolean-literals"></a> Boolean Literals

The keywords `true` and `false` are equivalent to 1 and 0 respectively.

#### <a id="null-value"></a> Null Value

The `null` keyword can be used to specify an empty value.

#### <a id="dictionary"></a> Dictionary

An unordered list of key-value pairs. Keys must be unique and are
compared in a case-insensitive manner.

Individual key-value pairs must be separated from each other with a
comma. The comma after the last key-value pair is optional.

Example:

    {
      address = "192.168.0.1",
      port = 443
    }

> **Note**
>
> Identifiers may not contain certain characters (e.g. space) or start
> with certain characters (e.g. digits). If you want to use a dictionary
> key that is not a valid identifier you can put the key in double
> quotes.

> **Note**
>
> Setting a dictionary key to null causes the key and its value to be
> removed from the dictionary.

#### <a id="array"></a> Array

An ordered list of values.

Individual array elements must be separated from each other with a
comma. The comma after the last element is optional.

Example:

    [ "hello", 42 ]

> **Note**
>
> An array may simultaneously contain values of different types, such as
> strings and numbers.

#### <a id="constant-expressions"></a> Operators

The following operators are supported in expressions:

Operator | Examples (Result)                             | Description
---------|-----------------------------------------------|--------------------------------
!, ~     | ~true (false)                                 | Bitwise negation of the operand
+        | 1 + 3 (4), "hello " + "world" ("hello world") | Adds two numbers; concatenates strings
-        | 3 - 1 (2)                                     | Subtracts two numbers
*        | 5m * 10 (3000)                                | Multiplies two numbers
/        | 5m / 5 (60)                                   | Divides two numbers
&        | 7 & 3 (3)                                     | Binary AND
\|       | 2 \| 3 (3)                                    | Binary OR
<        | 3 < 5 (true)                                  | Less than
>        | 3 > 5 (false)                                 | Greater than
<=       | 3 <= 3 (true)                                 | Less than or equal
>=       | 3 >= 3 (true)                                 | Greater than or equal
<<       | 4 << 8 (1024)                                 | Left shift
>>       | 1024 >> 4 (64)                                | Right shift
==       | "hello" == "hello" (true), 3 == 5 (false)     | Equal to
!=       | "hello" != "world" (true), 3 != 3 (false)     | Not equal to
in       | "foo" in [ "foo", "bar" ] (true)              | Element contained in array
!in      | "foo" !in [ "bar", "baz" ] (true)             | Element not contained in array
()       | (3 + 3) * 5                                   | Groups sub-expressions

Constants may be used in constant expressions:

    const MyCheckInterval = 10m

    ...

    {
      check_interval = MyCheckInterval / 2.5
    }

#### Function Calls

Functions can be called using the `()` operator:

    const MyGroups = [ "test1", "test" ]

    {
      check_interval = len(MyGroups) * 1m
    }

Function             | Description
---------------------|-----------------------
regex(pattern, text) | Returns true if the regex pattern matches the text, false otherwise.
match(pattern, text) | Returns true if the wildcard pattern matches the text, false otherwise.
len(value)           | Returns the length of the value, i.e. the number of elements for an array or dictionary, or the length of the string in bytes.

### <a id="operators"></a> Dictionary Operators

In addition to the `=` operator shown above a number of other operators
to manipulate dictionary elements are supported. Here's a list of all
available operators:

#### <a id="operator-assignment"></a> Operator =

Sets a dictionary element to the specified value.

Example:

    {
      a = 5,
      a = 7
    }

In this example a has the value 7 after both instructions are executed.

#### <a id="operator-additive-assignment"></a> Operator +=

Modifies a dictionary or array by adding new elements to it.

Example:

    {
      a = [ "hello" ],
      a += [ "world" ]
    }

In this example a contains both `"hello"` and `"world"`. This currently
only works for dictionaries and arrays.

<!--

#### <a id="operator-substractive-assignment"></a> Operator -=

Removes elements from a dictionary.

Example:

    {
      a = { "hello", "world" },
      a -= [ "world" ]
    }

In this example a contains `"hello"`. Trying to remove an item that does
not exist is not an error. Not implemented yet.

#### <a id="operator-multiply-assignment"></a> Operator \*=

Multiplies an existing dictionary element with the specified number. If
the dictionary element does not already exist 0 is used as its value.

Example:

    {
      a = 60,
      a *= 5
    }

In this example a is 300. This only works for numbers. Not implemented
yet.

#### <a id="operator-dividing-assignment"></a> Operator /=

Divides an existing dictionary element by the specified number. If the
dictionary element does not already exist 0 is used as its value.

Example:

    {
      a = 300,
      a /= 5
    }

In this example a is 60. This only works for numbers. Not implemented
yet.

-->

### <a id="indexer"></a> Indexer

The indexer syntax provides a convenient way to set dictionary elements.

Example:

    {
      hello["key"] = "world"
    }

This is equivalent to writing:

    {
      hello += {
        key = "world"
      }
    }

### <a id="object-inheritance"></a> Object Inheritance

Objects can inherit attributes from other objects.

Example:

    template Host "default-host" {
      macros["color"] = "red"
    }

    template Host "test-host" inherits "default-host" {
      macros["color"] = "blue"
    }

    object Host "localhost" inherits "test-host" {
      macros["address"] = "127.0.0.1",
      macros["address6"] = "::1"
    }

The `default-host` and `test-host` objects are marked as templates
using the `template` keyword. Unlike ordinary objects templates are not
instantiated at run-time. Parent objects do not necessarily have to be
templates though in general they are.

> **Note**
>
> The final macros dictionary contains all three macros and the macro
> `color` has the value `"blue"`.

Parent objects are resolved in the order they're specified using the
`inherits` keyword.

### <a id="disable-override-objects-attributes"></a> Disable/Override Objects and Attributes

Object attributes can be overridden by defining the additional changed attribute
directly on the object. Use the `+=` operator for the inline services dictionary.

    services["overridden-custom-attr"] += {
      custom = {
        notes = "disabled all custom attr"
      }
    }

If you don't require an attribute inherited from templates, you can simply
override its value by setting it explicitely to `null`.

    services["no-custom-attr"] += {
      custom = null
    }


The same method applies for disabling services defined in the inline `services`
dictionary by explicitly overriding their value with `null`.

    services["ping6"] = null


### <a id="constants"></a> Constants

Global constants can be set using the `const` keyword:

    const VarName = "some value"

The value can be a string, number, array, or a dictionary.

Constants cannot be changed once they are set.

> **Note**
>
> The `set` and `var` keywords are an alias for `const` and are available
> in order to provide compatibility with older versions. Their use is
> deprecated.

### <a id="apply"></a> Apply

The `apply` keyword can be used to associate a template with another group of
objects. The exact effect of this association depends on the two object types.

    template Service "ping-service" {
      short_name = "ping",
      check_command = "ping4"
    }

    apply template Service "ping-service" to Host where (host == "localhost")

In this example the `where` condition is a constant expression which is
evaluated for all objects of type Host and a new service is created for each
matching host.

Depending on the object types used in the `apply` expression additional local
variables may be available for use in the `where` condition.

### <a id="comments"></a> Comments

The Icinga 2 configuration format supports C/C++-style comments.

Example:

    /*
     This is a comment.
     */
    object Host "localhost" {
      check_interval = 30, // this is also a comment.
      retry_interval = 15
    }

### <a id="includes"></a> Includes

Other configuration files can be included using the `include` directive.
Paths must be relative to the configuration file that contains the
`include` directive.

Example:

    include "some/other/file.conf"
    include "conf.d/*.conf"

> **Note**
>
> Wildcard includes are not recursive.

Icinga also supports include search paths similar to how they work in a
C/C++ compiler:

    include <itl/itl.conf>

Note the use of angle brackets instead of double quotes. This causes the
config compiler to search the include search paths for the specified
file. By default $PREFIX/icinga2 is included in the list of search
paths. Additional include search paths can be added using
[command-line options](#cmdline).

Wildcards are not permitted when using angle brackets.

### <a id="recursive-includes"></a> Recursive Includes

The `include_recursive` directive can be used to recursively include all
files in a directory which match a certain pattern.

Example:

    include_recursive "conf.d" "*.conf"
    include_recursive "templates"

The first parameter specifies the directory from which files should be
recursively included.

The file names need to match the pattern given in the second parameter.
When no pattern is specified the default pattern "*.conf" is used.

### <a id="library"></a> Library directive

The `library` directive can be used to manually load additional
libraries. Libraries can be used to provide additional object types and
methods.

Example:

    library "snmphelper"

> **Note**
>
> The `icinga` library is automatically loaded at startup. You don't need
> to load it manually.

<!--

### <a id="type-definition"></a> Type Definition

By default Icinga has no way of semantically verifying its configuration
objects. This is where type definitions come in. Using type definitions
you can specify which attributes are allowed in an object definition.

Example:

    type Pizza {
            %require "radius",
            %attribute number "radius",

            %attribute dictionary "ingredients" {
                    %validator "ValidateIngredients",

                    %attribute string "*",

                    %attribute dictionary "*" {
                            %attribute number "quantity",
                            %attribute string "name"
                    }
            },

            %attribute any "custom::*"
    }

The Pizza definition provides the following validation rules:

-   Pizza objects must contain an attribute `radius` which has to be a
    number.

-   Pizza objects may contain an attribute `ingredients` which has to be
    a dictionary.

-   Elements in the ingredients dictionary can be either a string or a
    dictionary.

-   If they're a dictionary they may contain attributes `quantity` (of
    type number) and `name` (of type string).

-   The script function `ValidateIngredients` is run to perform further
    validation of the ingredients dictionary.

-   Pizza objects may contain attribute matching the pattern
    `custom::*` of any type.

Valid types for type rules include:

* any
* number
* string
* scalar (an alias for string)
* dictionary

-->