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

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

Icinga 2 features an object-based configuration format. You can define new
objects using the `object` keyword:

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

      address = "192.168.0.1"
      address6 = "::1"
    }

In general you need to write each statement on a new line. Expressions started
with `{`, `(` and `[` extend until the matching closing brace and can be broken
up into multiple lines.

Alternatively you can write multiple statements in a single line by separating
them with a semi-colon:

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

      address = "192.168.0.1"; address6 = "::1"
    }

Each object is uniquely identified by its type (`Host`) and name
(`host1.example.org`). Some types have composite names, e.g. the
`Service` type which uses the `host_name` attribute and the name
you specified to generate its object name.

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

Objects can contain a comma-separated list of property
declarations. Instead of commas semi-colons may also be used.
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).

Duration literals are converted to seconds by the config parser and
are treated like numeric literals.

#### <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
--------------------------|------------------------------------
"                         | \\"
\\                        | \\\\
&lt;TAB&gt;               | \\t
&lt;CARRIAGE-RETURN&gt;   | \\r
&lt;LINE-FEED&gt;         | \\n
&lt;BEL&gt;               | \\b
&lt;FORM-FEED&gt;         | \\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.}}}

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
    }

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.

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 ]

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

#### <a id="expression-operators"></a> Operators

The following operators are supported in expressions:

Operator | Examples (Result)                             | Description
---------|-----------------------------------------------|--------------------------------
!        | !"Hello" (false), !false (true)               | Log<!-- ignore BLACKLIST -->ical negation of the operand
~        | ~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
&#124;   | 2 &#124; 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 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.
union(array, array, ...)        | Returns an array containing all unique elements from the specified arrays.
intersection(array, array, ...) | Returns an array containing all unique elements which are common to all specified arrays.
string(value)                   | Converts the value to a string.
number(value)                   | Converts the value to a number.
bool(value)                     | Converts to value to a bool.
log(value)                      | Writes a message to the log. Non-string values are converted to a JSON string.
log(severity, facility, value)  | Writes a message to the log. `severity` can be one of `LogDebug`, `LogInformation`, `LogWarning` and `LogCritical`. Non-string values are converted to a JSON string.
exit(integer)                   | Terminates the application.

### <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 +=

The += operator is a shortcut. The following expression:

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

is equivalent to:

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

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

The -= operator is a shortcut. The following expression:

    {
      a = 10
      a -= 5
    }

is equivalent to:

    {
      a = 10
      a = a - 5
    }

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

The *= operator is a shortcut. The following expression:

    {
      a = 60
      a *= 5
    }

is equivalent to:

    {
      a = 60
      a = a * 5
    }

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

The /= operator is a shortcut. The following expression:

    {
      a = 300
      a /= 5
    }

is equivalent to:

    {
      a = 300
      a = a / 5
    }

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

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

Example:

    {
      hello.key = "world"
    }

Example (alternative syntax):

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

This is equivalent to writing:

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

### <a id="template-imports"></a> Template Imports

Objects can import attributes from other objects.

Example:

    template Host "default-host" {
      vars.color = "red"
    }

    template Host "test-host" {
      import "default-host"

      vars.color = "blue"
    }

    object Host "localhost" {
      import "test-host"

      address = "127.0.0.1"
      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, however in general they are.

The `vars` dictionary for the `localhost` object contains all three
custom attributes and the custom attribute `color` has the value `"blue"`.

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

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

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

    const VarName = "some value"

Once defined a constant can be access from any file. Constants cannot be changed
once they are set.

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

The `apply` keyword can be used to create new objects which are associated with
another group of objects.
Applying group membership for objects can be done in a similar way using [group apply](#group-apply)

    apply Service "ping" to Host {
      import "generic-service"
 
      check_command = "ping4"
  
      assign where host.name == "localhost"
    }

In this example the `assign where` condition is a boolean expression which is
evaluated for all objects of type `Host` and a new service with name "ping"
is created for each matching host.

The `to` keyword and the target type may be omitted if there is only target
type, e.g. for the `Service` type.

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

Source Type       | Target Type | Variables
------------------|-------------|--------------
Service           | Host        | host
Dependency        | Host        | host
Dependency        | Service     | host, service
Notification      | Host        | host
Notification      | Service     | host, service
ScheduledDowntime | Host        | host
ScheduledDowntime | Service     | host, service

Any valid config attribute can be accessed using the `host` and `service`
variables. For example, `host.address` would return the value of the host's
"address" attribute - or null if that attribute isn't set.

#### <a id="group-membership-apply"></a> Group Membership Apply

The `apply` keyword can be used for groups too. Instead of creating a new object
(for example a new `HostGroup` object for every matching `Host`) it will create
the group object only once and add the membership for the matching rule object.

    apply HostGroup "www" to Host {
      display_name = "Web Server"

      assign where match("*www*", host.name)
    }

In this example the `assign where` condition is a boolean expression which is
evaluated for all object of type `Host`. A new host group with name "www" is created
and each matching host is added to this host group.

Depending on the group object type used in the `apply` expression additional local
variables may be available for use in the `where` condition:

Source Type       | Target Type | Variables
------------------|-------------|--------------
HostGroup         | Host        | host
ServiceGroup      | Service     | host, service
UserGroup         | User        | user

Any valid config attribute can be accessed using the `host`, `service` and `user`
variables. For example, `user.vars.sla` would return the value of the user's custom
attribute "sla" - or null if that attribute isn't set.

### <a id="boolean-values"></a> Boolean Values

The `assign where` and `ignore where` statements, the `!`, `&&` and `||`
operators as well as the `bool()` function convert their arguments to a
boolean value based on the following rules:

Description          | Example Value     | Boolean Value
---------------------|-------------------|--------------
Empty value          | null              | false
Zero                 | 0                 | false
Non-zero integer     | -23945            | true
Empty string         | ""                | false
Non-empty string     | "Hello"           | true
Empty array          | []                | false
Non-empty array      | [ "Hello" ]       | true
Empty dictionary     | {}                | false
Non-empty dictionary | { key = "value" } | true

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

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

Example:

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

### <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"

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/share/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
functions.

Example:

    library "snmphelper"

<!--

### <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 s
-   cript 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
* %array

-->