Project: Icinga (Observability and Analysis / Observability)
File: 17-language-reference.md

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 = "2001:db8:1234::42" } ``` In general you need to write each statement on a new line. Expressions started with `{`, `(` and `[` extend until the matching closing character and can be broken up into multiple lines. Alternatively you can write multiple statements on a single line by separating them with a semicolon: ``` object Host "host1.example.org" { display_name = "host1" address = "192.168.0.1"; address6 = "2001:db8:1234::42" } ``` 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 semicolons may also be used. The following data types are available for property values: All objects have at least the following attributes: Attribute | Description |-- name | The name of the object. This attribute can be modified in the object definition to override the name specified with the `object` directive. type | The type of the object. The following expressions can be used on the right-hand side of assignments. A floating-point number. Example: ``` 27.3 ``` 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 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. 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. The keywords `true` and `false` are used to denote truth values. The `null` keyword can be used to specify an empty value. An unordered list of key-value pairs. Keys must be unique and are compared in a case-sensitive manner. Individual key-value pairs must either be comma-separated or on separate lines. 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 enclose the key in double quotes. An ordered list of values. Individual array elements must be comma-separated. 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. The following operators are supported in expressions. The operators are sorted by descending

Operator | Precedence | Examples (Result) | Description ||--|-- `()` | 1 | (3 + 3) * 5 | Groups sub-expressions `()` | 1 | Math.random() | Calls a function `[]` | 1 | a[3] | Array subscript `.` | 1 | a.b | Element access `!` | 2 | !"Hello" (false), !false (true) | Logical negation of the operand `~` | 2 | ~true (false) | Bitwise negation of the operand `+` | 2 | +3 | Unary plus `-` | 2 | -3 | Unary minus `&` | 2 | &var (reference to 'var') | Reference operator `` | 2 | var | Indirection operator `` | 3 | 5m 10 (3000) | Multiplies two numbers `/` | 3 | 5m / 5 (60) | Divides two numbers `%` | 3 | 17 % 12 (5) | Remainder after division `+` | 4 | 1 + 3 (4), "hello " + "world" ("hello world") | Adds two numbers; concatenates strings `-` | 4 | 3 - 1 (2) | Subtracts two numbers `<<` | 5 | 4 << 8 (1024) | Left shift `>>` | 5 | 1024 >> 4 (64) | Right shift `<` | 6 | 3 < 5 (true) | Less than `>` | 6 | 3 > 5 (false) | Greater than `<=` | 6 | 3 <= 3 (true) | Less than or equal `>=` | 6 | 3 >= 3 (true) | Greater than or equal `in` | 7 | "foo" in [ "foo", "bar" ] (true) | Element contained in array `!in` | 7 | "foo" !in [ "bar", "baz" ] (true) | Element not contained in array `==` | 8 | "hello" == "hello" (true), 3 == 5 (false) | Equal to `!=` | 8 | "hello" != "world" (true), 3 != 3 (false) | Not equal to `&` | 9 | 7 & 3 (3) | Binary AND `^` | 10 | 17 ^ 12 (29) | Bitwise XOR <code>&#124;</code> | 11 | 2 &#124; 3 (3) | Binary OR `&&` | 12 | true && false (false), 3 && 7 (7), 0 && 7 (0) | Logical AND <code>&#124;&#124;</code> | 13 | true &#124;&#124; false (true), 0 &#124;&#124; 7 (7)| Logical OR `=` | 14 | a = 3 | Assignment `=>` | 15 | x => x * x (function with arg x) | Lambda, for loop `?` | 16 | (2 * 3 > 5) ? 1 : 0 (1) | A reference to a value can be obtained using the `&` operator. The `*` operator can be used to dereference a reference: ``` var value = "Hello!" var p = &value / p refers to value / *p = "Hi!" log(value) // Prints "Hi!" because the variable was changed ``` Namespaces can be used to organize variables and functions. They are used to avoid name conflicts. The `namespace` keyword is used to create a new namespace: ``` namespace Utils { function calculate() { return 2 + 2 } } ``` The namespace is made available as a global variable which has the namespace's name (e.g. `Utils`): ``` Utils.calculate() ``` The `using` keyword can be used to make all attributes in a namespace available to a script without having to explicitly specify the namespace's name for each access: ``` using Utils calculate() ``` The `using` keyword only has an effect for the current file and only for code that follows the keyword: ``` calculate() // This will not

using Utils ``` The following namespaces are automatically imported as if by using the `using` keyword: System System.Configuration Types Icinga Functions can be called using the `()` operator: ``` const MyGroups = [ "test1", "test" ] { check_interval = len(MyGroups) * 1m } ``` A list of available functions is available in the chapter. In addition to the `=` operator shown above a number of other operators to manipulate attributes are supported. Here's a list of all available operators (the outermost `{` `}` stand for a local variable scope): Sets an attribute to the specified value. Example: ``` { a = 5 a = 7 } ``` In this example `a` has the value `7` after both instructions are executed. The += operator is a shortcut. The following expression: ``` { a = [ "hello" ] a += [ "world" ] } ``` is equivalent to: ``` { a = [ "hello" ] a = a + [ "world" ] } ``` The -= operator is a shortcut. The following expression: ``` { a = 10 a -= 5 } ``` is equivalent to: ``` { a = 10 a = a - 5 } ``` The *= operator is a shortcut. The following expression: ``` { a = 60 a *= 5 } ``` is equivalent to: ``` { a = 60 a = a * 5 } ``` The /= operator is a shortcut. The following expression: ``` { a = 300 a /= 5 } ``` is equivalent to: ``` { a = 300 a = a / 5 } ``` 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" } } ``` If the `hello` attribute does not already have a value, it is automatically initialized to an empty dictionary. Objects can import attributes from other objects. Example: ``` template Host "default-host" { vars.colour = "red" } template Host "test-host" { import "default-host" vars.colour = "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 variables and the custom variable `colour` has the value `"blue"`. Parent objects are resolved in the order they're specified using the `import` keyword. Default templates which are automatically imported into all object definitions can be specified using the `default` keyword: ``` template CheckCommand "plugin-check-command" default { // ... } ``` Default templates are imported before any other user-specified statement in an object definition is evaluated. If there are multiple default templates the order in which they are imported is unspecified. Global constants can be set using the `const` keyword: ``` const VarName = "some value" ``` Once defined a constant can be accessed from any file. Constants cannot be changed once they are set. Tip Best practice is to manage constants in the file. Icinga 2 provides a number of special global constants. These include directory paths, global configuration and runtime parameters for the application version and (build)

Constant | Description --|- ConfigDir |Read-only. Main configuration directory. Usually set to `/etc/icinga2`. DataDir |Read-only. Runtime data for the Icinga daemon. Usually set to `/var/lib/icinga2`. LogDir |Read-only. Logfiles from the daemon. Usually set to `/var/log/icinga2`. CacheDir |Read-only. Cached status information of the daemon. Usually set to `/var/cache/icinga2`. SpoolDir |Read-only. Spool directory for certain data outputs. Usually set to `/var/spool/icinga2`. InitRunDir |Read-only. Directory for PID files and sockets in daemon mode. Usually set to `/run/icinga2`. ZonesDir |Read-only. Contains the path of the zones.d directory. Defaults to `ConfigDir + "/zones.d"`. Constant | Description --|- Vars |Read-write. Contains a dictionary with global custom variables. Not set by default. NodeName |Read-write. Contains the cluster node name. Set to the local hostname by default. ReloadTimeout |Read-write. Defines the reload timeout for child processes. Defaults to `300s`. Environment |Read-write. The name of the Icinga environment. Included in the SNI host name for outbound connections. Not set by default. RunAsUser |Read-write. Defines the user the Icinga 2 daemon is running as. Set in the Icinga 2 sysconfig. RunAsGroup |Read-write. Defines the group the Icinga 2 daemon is running as. Set in the Icinga 2 sysconfig. MaxConcurrentChecks |Read-write. The number of max checks run simultaneously. Defaults to `512`. ApiBindHost |Read-write. Overrides the default value for the ApiListener `bind_host` attribute. Defaults to `::` if IPv6 is supported by the operating system and to `0.0.0.0` otherwise. ApiBindPort |Read-write. Overrides the default value for the ApiListener `bind_port` attribute. Not set by default. Constant | Description --|- PlatformName |Read-only. The name of the operating system, e.g. `Ubuntu`. PlatformVersion |Read-only. The version of the operating system, e.g. `14.04.3 LTS`. PlatformKernel |Read-only. The name of the operating system kernel, e.g. `Linux`. PlatformKernelVersion|Read-only. The version of the operating system kernel, e.g. `3.13.0-63-generic`. BuildCompilerName |Read-only. The name of the compiler Icinga was built with, e.g. `Clang`. BuildCompilerVersion|Read-only. The version of the compiler Icinga was built with, e.g. `7.3.0.7030031`. BuildHostName |Read-only. The name of the host Icinga was built on, e.g. `acheron`. ApplicationVersion |Read-only. The application version, e.g. `2.9.0`. Writable constants can be specified on the CLI using the `--define/-D` parameter. Note for v2.10+ Default paths which include `/etc` and `/var` as base directory continue to work based on the `SysconfDir` and `LocalStateDir` constants respectively. In addition to that, the constants below are used to define specific file paths. You should never need to change them, as they are pre-compiled based on the constants above. Variable |Description --|- StatePath |Read-write. Contains the path of the Icinga 2 state file. Defaults to `DataDir + "/icinga2.state"`. ObjectsPath |Read-write. Contains the path of the Icinga 2 objects file. Defaults to `CacheDir + "/icinga2.debug"`. PidPath |Read-write. Contains the path of the Icinga 2 PID file. Defaults to `InitRunDir + "/icinga2.pid"`. PkgDataDir |Read-only. Contains the path of the package data directory. Defaults to `PrefixDir + "/share/icinga2"`. The constants below have been used until Icinga v2.10, and are still intact. You don't need them for future builds and configuration based on the newly available constants above. Variable |Description --|- PrefixDir |Read-only. Contains the installation prefix that was specified with `cmake -DCMAKEINSTALLPREFIX`. `Defaults to "/usr/local"`. SysconfDir |Read-only. Contains the path of the sysconf directory. Defaults to `PrefixDir + "/etc"`. LocalStateDir |Read-only. Contains the path of the local state directory. Defaults to `PrefixDir + "/var"`. RunDir |Read-only. Contains the path of the run directory. Defaults to `LocalStateDir + "/run"`. Advanced runtime constants. Please only use them if advised by support or developers. Variable | Description |- EventEngine

The name of the socket event engine, can be `poll` or `epoll`. The epoll interface is only supported on Linux. AttachDebugger |Read-write. Whether to attach a debugger when Icinga 2 crashes. Defaults to `false`. Advanced sysconfig environment variables, defined in `/etc/sysconfig/icinga2` (RHEL/SLES) or `/etc/default/icinga2` (Debian/Ubuntu). Variable | Description |- ICINGA2\RLIMIT\FILES |Read-write. Defines the resource limit for `RLIMIT_NOFILE` that should be set at start-up. Value cannot be set lower than the default `16 * 1024`. 0 disables the setting. Set in Icinga 2 sysconfig. ICINGA2\RLIMIT\PROCESSES |Read-write. Defines the resource limit for `RLIMIT_NPROC` that should be set at start-up. Value cannot be set lower than the default `16 * 1024`. 0 disables the setting. Set in Icinga 2 sysconfig. ICINGA2\RLIMIT\STACK |Read-write. Defines the resource limit for `RLIMIT_STACK` that should be set at start-up. Value cannot be set lower than the default `256 * 1024`. 0 disables the setting. Set in Icinga 2 sysconfig. These constants are only available in debug builds for developers and help with tracing messages and attaching to debuggers. Variable | Description |- Internal.DebugJsonRpc | Read-write. Setting this to `1` prints the raw JSON-RPC message to STDOUT. Internal.DebugWorkerDelay | Read-write. Delays the main worker process by X seconds after forked from the umbrella process. This helps with attaching LLDB which cannot follow child forks like GDB. Example: ``` $ icinga2 daemon -DInternal.DebugWorkerDelay=120 Closed FD 6 which we inherited from our parent process. [2020-01-29 12:22:33 +0100] information/cli: Icinga application loader (version: v2.11.0-477-gfe8701d77; debug) [2020-01-29 12:22:33 +0100] information/RunWorker: DEBUG: Current PID: 85253. Sleeping for 120 seconds to allow lldb/gdb -p <PID> attachment. $ lldb -p 85253 (lldb) b icinga::Checkable::ProcessCheckResult (lldb) c ``` The `apply` keyword can be used to create new objects which are associated with another group of objects. ``` 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. may be used in `assign where` conditions. The `to` keyword and the target type may be omitted if there is only one 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. More usage examples are documented in the chapter. rules can be extended with the keyword. ``` apply Service "prefix-" for (key => value in host.vars.dictionary) to Host { import "generic-service" check_command = "ping4" vars.host_value = value } ``` Any valid config attribute can be accessed using the `host` and `service` variables. The attribute must be of the Array or Dictionary type. In this example `host.vars.dictionary` is of the Dictionary type which needs a key-value-pair as iterator. In this example all generated service object names consist of `prefix-` and the value of the `key`

The prefix string can be omitted if not required. The `key` and `value` variables can be used for object attribute assignment, e.g. for setting the `check_command` attribute or custom variables as command parameters. `apply for` rules are first evaluated against all objects matching the `for loop` list and afterwards the `assign where` and `ignore where` conditions are evaluated. It is not necessary to check attributes referenced in the `for loop` expression for their existance using an additional `assign where` condition. More usage examples are documented in the chapter. Group objects can be assigned to specific member objects using the `assign where` and `ignore where` conditions. ``` object HostGroup "linux-servers" { display_name = "Linux Servers" assign where host.vars.os == "Linux" } ``` In this example the `assign where` condition is a boolean expression which is evaluated for all objects of the type `Host`. Each matching host is added as member to the host group with the name "linux-servers". Membership exclusion can be controlled using the `ignore where` condition. may be used in `assign where` and `ignore where` conditions. Source Type | Variables |-- HostGroup | host ServiceGroup | host, service UserGroup | user The `assign where`, `ignore where`, `if` and `while` statements, the `!` operator 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 For a list of supported expression operators for `assign where` and `ignore where` statements, see . 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 } ``` 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> ``` 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/include is included in the list of search paths. Additional include search paths can be added using . Wildcards are not permitted when using angle brackets. 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. Note This is an internal functionality consumed by Icinga itself. The preferred way for users managing configuration files in zones is to use the or . The `include_zones` recursively includes all subdirectories for the given

In addition to that it sets the `zone` attribute for all objects created in these subdirectories to the name of the subdirectory. Example: ``` include_zones "etc", "zones.d", "*.conf" include_zones "puppet", "puppet-zones" ``` The first parameter specifies a tag name for this directive. Each `include_zones` invocation should use a unique tag name. When copying the zones' configuration files Icinga uses the tag name as the name for the destination directory in `/var/lib/icinga2/api/config`. The second parameter specifies the directory which contains the subdirectories. The file names need to match the pattern given in the third parameter. When no pattern is specified the default pattern "*.conf" is used. The `library` directive was used to manually load additional libraries. Starting with version 2.9 it is no longer necessary to explicitly load libraries and this directive has no effect. Functions can be defined using the `function` keyword. Example: ``` function multiply(a, b) { return a * b } ``` When encountering the `return` keyword further execution of the function is terminated and the specified value is supplied to the caller of the function: ``` log(multiply(3, 5)) ``` In this example the `multiply` function we declared earlier is invoked with two arguments (3 and 5). The function computes the product of those arguments and makes the result available to the function's caller. When no value is supplied for the `return` statement the function returns `null`. Functions which do not have a `return` statement have their return value set to the value of the last expression which was performed by the function. For example, we could have also written our `multiply` function like this: ``` function multiply(a, b) { a * b } ``` Anonymous functions can be created by omitting the name in the function definition. The resulting function object can be used like any other value: ``` var fn = function() { 3 } fn() / Returns 3 / ``` Functions can also be declared using the alternative lambda syntax. Example: ``` f = (x) => x * x ``` Multiple statements can be used by putting the function body into braces: ``` f = (x) => { log("Lambda called") x * x } ``` Just like with ordinary functions the return value is the value of the last statement. For lambdas which take exactly one argument the braces around the arguments can be omitted: ``` f = x => x * x ``` Lambda expressions which take a given number of arguments may need additional variable values from the outer scope. When the lambda expression does not allow to change the interface, come into play. ``` var y f = ((x) use(y) => x == y) ``` Note that the braces around arguments are always required when using closures. A more concrete example: Within the DSL, you want to an array of HostGroup objects by their name. The filter function takes one argument being a function callback which either returns `true` or `false`. Matching items are collected into the result set. ``` get_objects(HostGroup).filter((hg) => hg.name == "linux-servers") ``` Instead of hardcoding the matching hostgroup name into the lambda scope, you want to control the value from the outside configuration values, e.g. in a custom variable or global constant. ``` var hgfiltername = "linux-servers" getobjects(HostGroup).filter((hg) use(hgfiltername) => hg.name == hgfilter_name) ``` You can also use this example vice versa and extract host object matching a specific host group name. ``` var hgfiltername = "linux-servers" getobjects(Host).filter((h) use (hgsearchname) => hgsearch_name in h.groups).map(h =>

``` Note that this example makes use of the method for the Array type which extracts the host name attribute from the full object into a new array. Lambdas which take no arguments can also be written using the abbreviated lambda syntax. Example: ``` f = {{ 3 }} ``` This creates a new function which returns the value 3. When setting a variable Icinga checks the following scopes in this order whether the variable already exists there: Local Scope `this` Scope Global Scope The local scope contains variables which only exist during the invocation of the current function, object or apply statement. Local variables can be declared using the `var` keyword: ``` function multiply(a, b) { var temp = a * b return temp } ``` Each time the `multiply` function is invoked a new `temp` variable is used which is in no way related to previous invocations of the function. When setting a variable which has not previously been declared as local using the `var` keyword the `this` scope is used. The `this` scope refers to the current object which the function or object/apply statement operates on. ``` object Host "localhost" { check_interval = 5m } ``` In this example the `this` scope refers to the "localhost" object. The `check_interval` attribute is set for this particular host. You can explicitly access the `this` scope using the `this` keyword: ``` object Host "localhost" { var check_interval = 5m /* This explicitly specifies that the attribute should be set for the host, if we had omitted `this.` the (poorly named) local variable `check_interval` would have been modified instead. */ this.check_interval = 1m } ``` Similarly the keywords `locals` and `globals` are available to access the local and global scope. Functions also have a `this` scope. However unlike for object/apply statements the `this` scope for a function is set to whichever object was used to invoke the function. Here's an example: ``` hm = { h_word = null function init(word) { h_word = word } } / Let's invoke the init() function / hm.init("hello") ``` We're using `hm.init` to invoke the function which causes the value of `hm` to become the `this` scope for this function call. By default `function`s, `object`s and `apply` rules do not have access to variables declared outside of their scope (except for global variables). In order to access variables which are defined in the outer scope the `use` keyword can be used: ``` function MakeHelloFunction(name) { return function() use(name) { log("Hello, " + name) } } ``` In this case a new variable `name` is created inside the inner function's scope which has the value of the `name` function argument. Alternatively a different value for the inner variable can be specified: ``` function MakeHelloFunction(name) { return function() use (greeting = "Hello, " + name) { log(greeting) } } ``` Sometimes it can be desirable to only evaluate statements when certain conditions are met. The if/else construct can be used to accomplish this. Example: ``` a = 3 if (a < 5) { a *= 7 } else if (a > 10) { a *= 5 } else { a *= 2 } ``` An if/else construct can also be used in place of any other

The value of an if/else statement is the value of the last statement which was evaluated for the branch which was taken: ``` a = if (true) { log("Taking the 'true' branch") 7 * 3 } else { log("Taking the 'false' branch") 9 } ``` This example prints the log message "Taking the 'true' branch" and the `a` variable is set to 21 (7 * 3). The value of an if/else construct is null if the condition evaluates to false and no else branch is given. Instead of if/else condition chains, you can also use the ternary operator `?` with assignments. Values are separated with a colon `:` character. ``` cond ? condvaltrue : condvalfalse ``` Whether the first condition matches, the first value is returned, if not, the else and second branch value is returned. The following example evaluates a condition and either assigns `1` or `0` to the local variable. ``` <1> => var x = (2 * 3 > 5) ? 1 : 0 null <2> => x 1.000000 <3> => var x = (2 * 3 > 7) ? 1 : 0 null <4> => x 0.000000 ``` Additional examples with advanced condition chaining: ``` <1> => 1 ? 2 : 3 ? 4 : 5 ? 6 : 7 2.000000 <2> => 0 ? 2 : 3 ? 4 : 5 ? 6 : 7 4.000000 <3> => 0 ? 2 : 0 ? 4 : 5 ? 6 : 7 6.000000 <4> => 0 ? 2 : 0 ? 4 : 0 ? 6 : 7 7.000000 <5> => 1 + 0 ? 2 : 3 + 4 2.000000 <6> => 0 + 0 ? 2 : 3 + 4 7.000000 <7> => (()=>{ return 1 ? 2 : 3 })() 2.000000 <8> => var x = 1 ? 2 : 3 null <9> => x 2.000000 ``` The `while` statement checks a condition and executes the loop body when the condition evaluates to `true`. This is repeated until the condition is no longer true. Example: ``` var num = 5 while (num > 5) { log("Test") num -= 1 } ``` The `continue` and `break` keywords can be used to control how the loop is executed: The `continue` keyword skips over the remaining expressions for the loop body and begins the next loop evaluation. The `break` keyword breaks out of the loop. The `for` statement can be used to iterate over arrays and dictionaries. Example: ``` var list = [ "a", "b", "c" ] for (var item in list) { log("Item: " + item) } ``` The loop body is evaluated once for each item in the array. The variable `item` is declared as a local variable just as if the `var` keyword had been used. Iterating over dictionaries can be accomplished in a similar manner: ``` var dict = { a = 3, b = 7 } for (var key => var value in dict) { log("Key: " + key + ", Value: " + value) } ``` The `continue` and `break` keywords can be used to control how the loop is executed: The `continue` keyword skips over the remaining expressions for the loop body and begins the next loop evaluation. The `break` keyword breaks out of the loop. The `var` keyword is optional when declaring variables in the loop's header. Variables declared without the `var` keyword are nonetheless local to the function. In order to create a new value of a specific type constructor calls may be used. Example: ``` var pd = PerfdataValue() pd.label = "test"

= 10 ``` You can also try to convert an existing value to another type by specifying it as an argument for the constructor call. Example: ``` var s = String(3) / Sets s to "3". / ``` Built-in commands may throw exceptions to signal errors such as invalid arguments. User scripts can throw exceptions using the `throw` keyword. Example: ``` throw "An error occurred." ``` Exceptions can be handled using the `try` and `except` keywords. When an exception occurs while executing code in the `try` clause no further statements in the `try` clause are evaluated and the `except` clause is executed instead. Example: ``` try { throw "Test" log("This statement won't get executed.") } except { log("An error occurred in the try clause.") } ``` The `debugger` keyword can be used to insert a breakpoint. It may be used at any place where an assignment would also be a valid expression. By default breakpoints have no effect unless Icinga is started with the `--script-debugger` command-line option. When the script debugger is enabled Icinga stops execution of the script when it encounters a breakpoint and spawns a console which lets the user inspect the current state of the execution environment. All values have a static type. The `typeof` function can be used to determine the type of a value: ``` typeof(3) / Returns an object which represents the type for numbers / ``` The following built-in types are available: Type | Examples | Description --|-| Number | 3.7 | A numerical value. Boolean | true, false | A boolean value. String | "hello" | A string. Array | [ "a", "b" ] | An array. Dictionary | { a = 3 } | A dictionary. Depending on which libraries are loaded additional types may become available. The `icinga` library implements a whole bunch of other , e.g. Host, Service, CheckCommand, etc. Each type has an associated type object which describes the type's semantics. These type objects are made available using global variables which match the type's name: ``` / This logs 'true' / log(typeof(3) == Number) ``` The type object's `prototype` property can be used to find out which methods a certain type supports: ``` / This returns: ["contains","find","len","lower","replace","reverse","split","substr","to_string","trim","upper"] / keys(String.prototype) ``` Additional documentation on type methods is available in the . The location of the currently executing script can be obtained using the `currentfilename` and `currentline` keywords. Example: ``` log("Hello from '" + currentfilename + "' in line " + currentline) ``` These keywords are reserved and must not be used as constants or custom variables. ``` object template include include_recursive include_zones library null true false const var this globals locals use default ignoreonerror current_filename current_line apply to where import assign ignore function return break continue for if else while throw try except in using namespace ``` You can escape reserved keywords using the `@` character. The following example tries to set `vars.include` which references a reserved keyword and generates an error: ``` [2014-09-15 17:24:00 +0200] critical/config: Location: /etc/icinga2/conf.d/hosts/localhost.conf(13): vars.sla = "24x7" /etc/icinga2/conf.d/hosts/localhost.conf(14): /etc/icinga2/conf.d/hosts/localhost.conf(15): vars.include = "some cmdb export field" ^^^^^^^ /etc/icinga2/conf.d/hosts/localhost.conf(16): } /etc/icinga2/conf.d/hosts/localhost.conf(17): Config error: in /etc/icinga2/conf.d/hosts/localhost.conf: 15:8-15:14: syntax error, unexpected include (TINCLUDE), expecting TIDENTIFIER [2014-09-15 17:24:00 +0200] critical/config: 1 errors, 0 warnings. ``` You can escape the `include` keyword by prefixing it with an additional `@` character: ``` object Host "localhost" { import "generic-host" address = "127.0.0.1" address6 = "::1" vars.os = "Linux" vars.sla = "24x7" vars.@include = "some cmdb export field" } ```