1 # <a id="language-reference"></a> Language Reference
3 ## <a id="object-definition"></a> Object Definition
5 Icinga 2 features an object-based configuration format. You can define new
6 objects using the `object` keyword:
8 object Host "host1.example.org" {
11 address = "192.168.0.1"
15 In general you need to write each statement on a new line. Expressions started
16 with `{`, `(` and `[` extend until the matching closing character and can be broken
17 up into multiple lines.
19 Alternatively you can write multiple statements on a single line by separating
20 them with a semicolon:
22 object Host "host1.example.org" {
23 display_name = "host1"
25 address = "192.168.0.1"; address6 = "::1"
28 Each object is uniquely identified by its type (`Host`) and name
29 (`host1.example.org`). Some types have composite names, e.g. the
30 `Service` type which uses the `host_name` attribute and the name
31 you specified to generate its object name.
33 Exclamation marks (!) are not permitted in object names.
35 Objects can contain a comma-separated list of property
36 declarations. Instead of commas semicolons may also be used.
37 The following data types are available for property values:
39 All objects have at least the following attributes:
41 Attribute | Description
42 ---------------------|-----------------------------
43 name | The name of the object. This attribute can be modified in the object definition to override the name specified with the `object` directive.
44 type | The type of the object.
48 The following expressions can be used on the right-hand side of assignments.
50 ### <a id="numeric-literals"></a> Numeric Literals
52 A floating-point number.
58 ### <a id="duration-literals"></a> Duration Literals
60 Similar to floating-point numbers except for the fact that they support
61 suffixes to help with specifying time durations.
67 Supported suffixes include ms (milliseconds), s (seconds), m (minutes),
68 h (hours) and d (days).
70 Duration literals are converted to seconds by the config parser and
71 are treated like numeric literals.
73 ### <a id="string-literals"></a> String Literals
81 Certain characters need to be escaped. The following escape sequences
84 Character | Escape sequence
85 --------------------------|------------------------------------
89 <CARRIAGE-RETURN> | \\r
90 <LINE-FEED> | \\n
92 <FORM-FEED> | \\f
94 In addition to these pre-defined escape sequences you can specify
95 arbitrary ASCII characters using the backslash character (\\) followed
96 by an ASCII character in octal encoding.
98 ### <a id="multiline-string-literals"></a> Multi-line String Literals
100 Strings spanning multiple lines can be specified by enclosing them in
110 Unlike in ordinary strings special characters do not have to be escaped
111 in multi-line string literals.
113 ### <a id="boolean-literals"></a> Boolean Literals
115 The keywords `true` and `false` are used to denote truth values.
117 ### <a id="null-value"></a> Null Value
119 The `null` keyword can be used to specify an empty value.
121 ### <a id="dictionary"></a> Dictionary
123 An unordered list of key-value pairs. Keys must be unique and are
124 compared in a case-sensitive manner.
126 Individual key-value pairs must either be comma-separated or on separate lines.
127 The comma after the last key-value pair is optional.
132 address = "192.168.0.1"
136 Identifiers may not contain certain characters (e.g. space) or start
137 with certain characters (e.g. digits). If you want to use a dictionary
138 key that is not a valid identifier you can enclose the key in double
141 ### <a id="array"></a> Array
143 An ordered list of values.
145 Individual array elements must be comma-separated.
146 The comma after the last element is optional.
152 An array may simultaneously contain values of different types, such as
155 ### <a id="expression-operators"></a> Operators
157 The following operators are supported in expressions. The operators are by descending precedence.
159 Operator | Precedence | Examples (Result) | Description
160 ---------|------------|-----------------------------------------------|--------------------------------
161 () | 1 | (3 + 3) * 5 | Groups sub-expressions
162 () | 1 | Math.random() | Calls a function
163 [] | 1 | a[3] | Array subscript
164 . | 1 | a.b | Element access
165 ! | 2 | !"Hello" (false), !false (true) | Logical negation of the operand
166 ~ | 2 | ~true (false) | Bitwise negation of the operand
167 + | 2 | +3 | Unary plus
168 - | 2 | -3 | Unary minus
169 * | 3 | 5m * 10 (3000) | Multiplies two numbers
170 / | 3 | 5m / 5 (60) | Divides two numbers
171 % | 3 | 17 % 12 (5) | Remainder after division
172 + | 4 | 1 + 3 (4), "hello " + "world" ("hello world") | Adds two numbers; concatenates strings
173 - | 4 | 3 - 1 (2) | Subtracts two numbers
174 << | 5 | 4 << 8 (1024) | Left shift
175 >> | 5 | 1024 >> 4 (64) | Right shift
176 < | 6 | 3 < 5 (true) | Less than
177 > | 6 | 3 > 5 (false) | Greater than
178 <= | 6 | 3 <= 3 (true) | Less than or equal
179 >= | 6 | 3 >= 3 (true) | Greater than or equal
180 in | 7 | "foo" in [ "foo", "bar" ] (true) | Element contained in array
181 !in | 7 | "foo" !in [ "bar", "baz" ] (true) | Element not contained in array
182 == | 8 | "hello" == "hello" (true), 3 == 5 (false) | Equal to
183 != | 8 | "hello" != "world" (true), 3 != 3 (false) | Not equal to
184 & | 9 | 7 & 3 (3) | Binary AND
185 ^ | 10 | 17 ^ 12 (29) | Bitwise XOR
186 | | 11 | 2 | 3 (3) | Binary OR
187 && | 13 | true && false (false), 3 && 7 (7), 0 && 7 (0) | Logical AND
188 || | 14 | true || false (true), 0 || 7 (7)| Logical OR
189 = | 12 | a = 3 | Assignment
190 => | 15 | x => x * x (function with arg x) | Lambda, for loop
192 ### <a id="function-calls"></a> Function Calls
194 Functions can be called using the `()` operator:
196 const MyGroups = [ "test1", "test" ]
199 check_interval = len(MyGroups) * 1m
202 A list of available functions is available in the [Library Reference](20-library-reference.md#library-reference) chapter.
204 ## <a id="dictionary-operators"></a> Assignments
206 In addition to the `=` operator shown above a number of other operators
207 to manipulate attributes are supported. Here's a list of all
210 ### <a id="operator-assignment"></a> Operator =
212 Sets an attribute to the specified value.
221 In this example `a` has the value `7` after both instructions are executed.
223 ### <a id="operator-additive-assignment"></a> Operator +=
225 The += operator is a shortcut. The following expression:
239 ### <a id="operator-substractive-assignment"></a> Operator -=
241 The -= operator is a shortcut. The following expression:
255 ### <a id="operator-multiply-assignment"></a> Operator \*=
257 The *= operator is a shortcut. The following expression:
271 ### <a id="operator-dividing-assignment"></a> Operator /=
273 The /= operator is a shortcut. The following expression:
287 ## <a id="indexer"></a> Indexer
289 The indexer syntax provides a convenient way to set dictionary elements.
297 Example (alternative syntax):
300 hello["key"] = "world"
303 This is equivalent to writing:
311 If the `hello` attribute does not already have a value it is automatically initialized to an empty dictionary.
313 ## <a id="template-imports"></a> Template Imports
315 Objects can import attributes from other objects.
319 template Host "default-host" {
323 template Host "test-host" {
324 import "default-host"
329 object Host "localhost" {
332 address = "127.0.0.1"
336 The `default-host` and `test-host` objects are marked as templates
337 using the `template` keyword. Unlike ordinary objects templates are not
338 instantiated at run-time. Parent objects do not necessarily have to be
339 templates, however in general they are.
341 The `vars` dictionary for the `localhost` object contains all three
342 custom attributes and the custom attribute `colour` has the value `"blue"`.
344 Parent objects are resolved in the order they're specified using the
347 ## <a id="constants"></a> Constants
349 Global constants can be set using the `const` keyword:
351 const VarName = "some value"
353 Once defined a constant can be accessed from any file. Constants cannot be changed
356 Icinga 2 provides a number of special global constants. Some of them can be overridden using the `--define` command line parameter:
358 Variable |Description
359 --------------------|-------------------
360 PrefixDir |**Read-only.** Contains the installation prefix that was specified with cmake -DCMAKE_INSTALL_PREFIX. Defaults to "/usr/local".
361 SysconfDir |**Read-only.** Contains the path of the sysconf directory. Defaults to PrefixDir + "/etc".
362 ZonesDir |**Read-only.** Contains the path of the zones.d directory. Defaults to SysconfDir + "/zones.d".
363 LocalStateDir |**Read-only.** Contains the path of the local state directory. Defaults to PrefixDir + "/var".
364 RunDir |**Read-only.** Contains the path of the run directory. Defaults to LocalStateDir + "/run".
365 PkgDataDir |**Read-only.** Contains the path of the package data directory. Defaults to PrefixDir + "/share/icinga2".
366 StatePath |**Read-write.** Contains the path of the Icinga 2 state file. Defaults to LocalStateDir + "/lib/icinga2/icinga2.state".
367 ObjectsPath |**Read-write.** Contains the path of the Icinga 2 objects file. Defaults to LocalStateDir + "/cache/icinga2/icinga2.debug".
368 PidPath |**Read-write.** Contains the path of the Icinga 2 PID file. Defaults to RunDir + "/icinga2/icinga2.pid".
369 Vars |**Read-write.** Contains a dictionary with global custom attributes. Not set by default.
370 NodeName |**Read-write.** Contains the cluster node name. Set to the local hostname by default.
371 EnableNotifications |**Read-write.** Whether notifications are globally enabled. Defaults to true.
372 EnableEventHandlers |**Read-write.** Whether event handlers are globally enabled. Defaults to true.
373 EnableFlapping |**Read-write.** Whether flap detection is globally enabled. Defaults to true.
374 EnableHostChecks |**Read-write.** Whether active host checks are globally enabled. Defaults to true.
375 EnableServiceChecks |**Read-write.** Whether active service checks are globally enabled. Defaults to true.
376 EnablePerfdata |**Read-write.** Whether performance data processing is globally enabled. Defaults to true.
377 UseVfork |**Read-write.** Whether to use vfork(). Only available on *NIX. Defaults to true.
378 RunAsUser |**Read-write.** Defines the user the Icinga 2 daemon is running as. Used in the `init.conf` configuration file.
379 RunAsGroup |**Read-write.** Defines the group the Icinga 2 daemon is running as. Used in the `init.conf` configuration file.
381 ## <a id="apply"></a> Apply
383 The `apply` keyword can be used to create new objects which are associated with
384 another group of objects.
386 apply Service "ping" to Host {
387 import "generic-service"
389 check_command = "ping4"
391 assign where host.name == "localhost"
394 In this example the `assign where` condition is a boolean expression which is
395 evaluated for all objects of type `Host` and a new service with name "ping"
396 is created for each matching host. [Expression operators](19-language-reference.md#expression-operators)
397 may be used in `assign where` conditions.
399 The `to` keyword and the target type may be omitted if there is only one target
400 type, e.g. for the `Service` type.
402 Depending on the object type used in the `apply` expression additional local
403 variables may be available for use in the `where` condition:
405 Source Type | Target Type | Variables
406 ------------------|-------------|--------------
407 Service | Host | host
408 Dependency | Host | host
409 Dependency | Service | host, service
410 Notification | Host | host
411 Notification | Service | host, service
412 ScheduledDowntime | Host | host
413 ScheduledDowntime | Service | host, service
415 Any valid config attribute can be accessed using the `host` and `service`
416 variables. For example, `host.address` would return the value of the host's
417 "address" attribute - or null if that attribute isn't set.
419 ## <a id="group-assign"></a> Group Assign
421 Group objects can be assigned to specific member objects using the `assign where`
422 and `ignore where` conditions.
424 object HostGroup "linux-servers" {
425 display_name = "Linux Servers"
427 assign where host.vars.os == "Linux"
430 In this example the `assign where` condition is a boolean expression which is evaluated
431 for all objects of the type `Host`. Each matching host is added as member to the host group
432 with the name "linux-servers". Membership exclusion can be controlled using the `ignore where`
433 condition. [Expression operators](19-language-reference.md#expression-operators) may be used in `assign where` and
434 `ignore where` conditions.
436 Source Type | Variables
437 ------------------|--------------
439 ServiceGroup | host, service
443 ## <a id="boolean-values"></a> Boolean Values
445 The `assign where`, `ignore where`, `if` and `while` statements, the `!` operator as
446 well as the `bool()` function convert their arguments to a boolean value based on the
449 Description | Example Value | Boolean Value
450 ---------------------|-------------------|--------------
451 Empty value | null | false
453 Non-zero integer | -23945 | true
454 Empty string | "" | false
455 Non-empty string | "Hello" | true
456 Empty array | [] | false
457 Non-empty array | [ "Hello" ] | true
458 Empty dictionary | {} | false
459 Non-empty dictionary | { key = "value" } | true
461 For a list of supported expression operators for `assign where` and `ignore where`
462 statements, see [expression operators](19-language-reference.md#expression-operators).
464 ## <a id="comments"></a> Comments
466 The Icinga 2 configuration format supports C/C++-style and shell-style comments.
473 object Host "localhost" {
474 check_interval = 30 // this is also a comment.
475 retry_interval = 15 # yet another comment
478 ## <a id="includes"></a> Includes
480 Other configuration files can be included using the `include` directive.
481 Paths must be relative to the configuration file that contains the
486 include "some/other/file.conf"
487 include "conf.d/*.conf"
489 Wildcard includes are not recursive.
491 Icinga also supports include search paths similar to how they work in a
496 Note the use of angle brackets instead of double quotes. This causes the
497 config compiler to search the include search paths for the specified
498 file. By default $PREFIX/share/icinga2/include is included in the list of search
499 paths. Additional include search paths can be added using
500 [command-line options](8-cli-commands.md#config-include-path).
502 Wildcards are not permitted when using angle brackets.
504 ## <a id="recursive-includes"></a> Recursive Includes
506 The `include_recursive` directive can be used to recursively include all
507 files in a directory which match a certain pattern.
511 include_recursive "conf.d", "*.conf"
512 include_recursive "templates"
514 The first parameter specifies the directory from which files should be
515 recursively included.
517 The file names need to match the pattern given in the second parameter.
518 When no pattern is specified the default pattern "*.conf" is used.
520 ## <a id="library"></a> Library directive
522 The `library` directive can be used to manually load additional
523 libraries. Libraries can be used to provide additional object types and
530 ## <a id="functions"></a> Functions
532 Functions can be defined using the `function` keyword.
536 function multiply(a, b) {
540 When encountering the `return` keyword further execution of the function is terminated and
541 the specified value is supplied to the caller of the function:
545 In this example the `multiply` function we declared earlier is invoked with two arguments (3 and 5).
546 The function computes the product of those arguments and makes the result available to the
549 When no value is supplied for the `return` statement the function returns `null`.
551 Functions which do not have a `return` statement have their return value set to the value of the
552 last expression which was performed by the function. For example, we could have also written our
553 `multiply` function like this:
555 function multiply(a, b) {
559 Anonymous functions can be created by omitting the name in the function definition. The
560 resulting function object can be used like any other value:
562 var fn = function() { 3 }
566 ## <a id="lambdas"></a> Lambda Expressions
568 Functions can also be declared using the alternative lambda syntax.
574 Multiple statements can be used by putting the function body into braces:
581 Just like with ordinary functions the return value is the value of the last statement.
583 For lambdas which take exactly one argument the braces around the arguments can be omitted:
587 ## <a id="nullary-lambdas"></a> Abbreviated Lambda Syntax
589 Lambdas which take no arguments can also be written using the abbreviated lambda syntax.
595 This creates a new function which returns the value 3.
597 ## <a id="variable-scopes"></a> Variable Scopes
599 When setting a variable Icinga checks the following scopes in this order whether the variable
600 already exists there:
606 The local scope contains variables which only exist during the invocation of the current function,
607 object or apply statement. Local variables can be declared using the `var` keyword:
609 function multiply(a, b) {
614 Each time the `multiply` function is invoked a new `temp` variable is used which is in no way
615 related to previous invocations of the function.
617 When setting a variable which has not previously been declared as local using the `var` keyword
618 the `this` scope is used.
620 The `this` scope refers to the current object which the function or object/apply statement
623 object Host "localhost" {
627 In this example the `this` scope refers to the "localhost" object. The `check_interval` attribute
628 is set for this particular host.
630 You can explicitly access the `this` scope using the `this` keyword:
632 object Host "localhost" {
633 var check_interval = 5m
635 /* This explicitly specifies that the attribute should be set
636 * for the host, if we had omitted `this.` the (poorly named)
637 * local variable `check_interval` would have been modified instead.
639 this.check_interval = 1m
642 Similarly the keywords `locals` and `globals` are available to access the local and global scope.
644 Functions also have a `this` scope. However unlike for object/apply statements the `this` scope for
645 a function is set to whichever object was used to invoke the function. Here's an example:
650 function init(word) {
655 /* Let's invoke the init() function */
658 We're using `hm.init` to invoke the function which causes the value of `hm` to become the `this`
659 scope for this function call.
661 ## <a id="closures"></a> Closures
663 By default `function`s, `object`s and `apply` rules do not have access to variables declared
664 outside of their scope (except for global variables).
666 In order to access variables which are defined in the outer scope the `use` keyword can be used:
668 function MakeHelloFunction(name) {
669 return function() use(name) {
670 log("Hello, " + name)
674 In this case a new variable `name` is created inside the inner function's scope which has the
675 value of the `name` function argument.
677 Alternatively a different value for the inner variable can be specified:
679 function MakeHelloFunction(name) {
680 return function() use (greeting = "Hello, " + name) {
685 ## <a id="conditional-statements"></a> Conditional Statements
687 Sometimes it can be desirable to only evaluate statements when certain conditions are met. The if/else
688 construct can be used to accomplish this.
702 An if/else construct can also be used in place of any other value. The value of an if/else statement
703 is the value of the last statement which was evaluated for the branch which was taken:
706 log("Taking the 'true' branch")
709 log("Taking the 'false' branch")
713 This example prints the log message "Taking the 'true' branch" and the `a` variable is set to 21 (7 * 3).
715 The value of an if/else construct is null if the condition evaluates to false and no else branch is given.
717 ## <a id="while-loops"></a> While Loops
719 The `while` statement checks a condition and executes the loop body when the condition evaluates to `true`.
720 This is repeated until the condition is no longer true.
731 The `continue` and `break` keywords can be used to control how the loop is executed: The `continue` keyword
732 skips over the remaining expressions for the loop body and begins the next loop evaluation. The `break` keyword
733 breaks out of the loop.
735 ## <a id="for-loops"></a> For Loops
737 The `for` statement can be used to iterate over arrays and dictionaries.
741 var list = [ "a", "b", "c" ]
747 The loop body is evaluated once for each item in the array. The variable `item` is declared as a local
748 variable just as if the `var` keyword had been used.
750 Iterating over dictionaries can be accomplished in a similar manner:
752 var dict = { a = 3, b = 7 }
754 for (key => value in dict) {
755 log("Key: " + key + ", Value: " + value)
758 The `continue` and `break` keywords can be used to control how the loop is executed: The `continue` keyword
759 skips over the remaining expressions for the loop body and begins the next loop evaluation. The `break` keyword
760 breaks out of the loop.
762 ## <a id="types"></a> Types
764 All values have a static type. The `typeof` function can be used to determine the type of a value:
766 typeof(3) /* Returns an object which represents the type for numbers */
768 The following built-in types are available:
770 Type | Examples | Description
771 -----------|-------------------|------------------------
772 Number | 3.7 | A numerical value.
773 Boolean | true, false | A boolean value.
774 String | "hello" | A string.
775 Array | [ "a", "b" ] | An array.
776 Dictionary | { a = 3 } | A dictionary.
778 Depending on which libraries are loaded additional types may become available. The `icinga`
779 library implements a whole bunch of other types, e.g. Host, Service, CheckCommand, etc.
781 Each type has an associated type object which describes the type's semantics. These
782 type objects are made available using global variables which match the type's name:
784 /* This logs 'true' */
785 log(typeof(3) == Number)
787 The type object's `prototype` property can be used to find out which methods a certain type
790 /* This returns: ["find","len","lower","replace","split","substr","to_string","upper"] */
791 keys(String.prototype)
793 ## <a id="reserved-keywords"></a> Reserved Keywords
795 These keywords are reserved and must not be used as constants or custom attributes.
822 You can escape reserved keywords using the `@` character. The following example
823 tries to set `vars.include` which references a reserved keyword and generates
826 [2014-09-15 17:24:00 +0200] critical/config: Location:
827 /etc/icinga2/conf.d/hosts/localhost.conf(13): vars.sla = "24x7"
828 /etc/icinga2/conf.d/hosts/localhost.conf(14):
829 /etc/icinga2/conf.d/hosts/localhost.conf(15): vars.include = "some cmdb export field"
831 /etc/icinga2/conf.d/hosts/localhost.conf(16): }
832 /etc/icinga2/conf.d/hosts/localhost.conf(17):
834 Config error: in /etc/icinga2/conf.d/hosts/localhost.conf: 15:8-15:14: syntax error, unexpected include (T_INCLUDE), expecting T_IDENTIFIER
835 [2014-09-15 17:24:00 +0200] critical/config: 1 errors, 0 warnings.
837 You can escape the `include` keyword by prefixing it with an additional `@` character:
839 object Host "localhost" {
840 import "generic-host"
842 address = "127.0.0.1"
848 vars.@include = "some cmdb export field"