# API: base1

This package contains basic support API available to other packages.

## cockpit.js

Basic cockpit API to interact with the system

### Loading cockpit.js

`cockpit.js` should be loaded via a script tag.

    <script src="../base1/cockpit.js">

## cockpit.js: Object Caching

If the same information is displayed by multiple components in Cockpit, `cockpit.cache()` provides a way to share data between them. The shared data should be simple objects, arrays, and values, and not contain functions or other objects.

### cockpit.cache()

    cache = cockpit.cache(key, provider, consumer)

Create a new cache object. The `key` should be a globally unique string that describes the data being cached. This string must describe the data, across all machines and all versions of cockpit. It is customary to include a version number in the `key` string.

    function provider(result, key) {
        result("myvalue");

        return {
            close: function() {
                /* closed */
            }
        };
    }

The `provider` is a function that will be invoked to start retrieving data for the cache. It will be passed a `result` function as its first argument. The `result` should be invoked whenever new data is available. The `key` argument matches the key string the cache was created with.

The `provider` can return an object with a `close` method. This method will be invoked when the cache no longer needs data from the provider.

    function consumer(value, key) {
        /* ... */
    }

The `consumer` is a function that will be passed new values when they are available, whether they come from the `provider` or a source in a different component/frame.

### cache.close()

    cache.close()

Close a cache and stop calling its `consumer`. If the `provider` was invoked, then the `close()` method it returned will be invoked.

## cockpit.js: Raw Channels

At a low level Cockpit communicates with the system via messages passed through various channels. These are usually exposed via higher level APIs, such as the `cockpit.spawn()` function. It is rare to use raw channels directly.

### cockpit.channel()

    channel = cockpit.channel(options)

This function creates a new channel for communication with the system. It returns a new channel object. The `options` argument is a plain object. At least the `"payload"` option is required, and based on the payload type, other options may be required.

`"binary"`

  Set to `true` to transfer binary payloads. Both messages sent via `channel.send()` and those received via `channel.onmessage` should be arrays of bytes, either `Uint8Array` or `Array` depending on browser support.

`"payload"`

  The payload type for the channel. Only specific payload types are supported.

`"superuser"`

  Set to `"require"` to open this channel as root. If the currently logged in user is not permitted to become root (eg: via `pkexec`) then the `channel` will immediately be closed with a `"access-denied"` problem code. + Set to `"try"` to try to open the channel as root, but if that fails, then fall back to an unprivileged channel.

The channel object returned has the following fields and methods and events. You should call the `channel.close()` method when done with the channel.

A valid channel will always be returned and the is ready to `channel.send()`. The channel may close shortly afterword due to a failure.

### channel.binary

Will be `true` for an binary channel. Will be set to `false` if the channel is textual.

### channel.options

The options used to open this channel. This should not be changed.

### channel.valid

Will be `true` for an open channel. Will be set to `false` if the channel closes.

### channel.send()

    channel.send(data)

Send a message over the channel. The contents of the message depends on the payload type of the channel. If a binary channel, then `data` is expected to be an `Array` of bytes or a `Uint8Array`. If not binary, then the `data` will be converted to a string if not already a string.

### channel.control()

    channel.control(options)

Notify the channel to tune certain parameters on the fly. The `options` is a plain javascript object, and the contents depend on the `"payload"` of the channel.

One common operation is to set `"command"` to `"done"` in the options field. To indicate that no further messages will be sent through the channel.

### channel.wait()

    promise = channel.wait([callback])

Returns a `promise` that is ready when the channel is ready, or fails if the client closes. If a `callback` is specified, it is attached to the promise. The promise will be rejected or resolved with the contents `options` passed to the channel.onready and channel.onclose events respectively.

In general it’s not necessary to wait for the channel before starting to use the channel.

### channel.close()

    channel.close([options])

Close the channel.

If `options` is present it can be a plain javascript object containing additional channel close options to send to the peer. If closing for because of a problem, set the `"problem"` field to a problem code. If `options` is not an object it will be treated as a `"problem"`.

The close event will fire. A channel can also be closed by a peer or if the underlying transport closes.

### channel.onmessage

    channel.addEventListener("message", function(event, data) { ... })

An event triggered when the channel receives a message. The message is passed as a string to the handler in the `data`. In the case of binary channels `data` is an `Uint8Array` or an `Array` of bytes if the former is not supported by the browser. The contents of the message depends on the payload type of the channel.

### channel.oncontrol

    channel.addEventListener("control", function(event, options) { ... })

An event triggered when the channel receives an control message in the middle of the flow. One particular use is when the `command` is set to `"done"` then no further messages will be received in the channel. The exact form of these messages depend on the `"payload"` of the channel.

### channel.onready

    channel.addEventListener("ready", function(event, options) { ... })

An event triggered when the other end of the channel is ready to start processing messages. This indicates the channel is completely open. It is possible to start sending messages on the channel before this point.

### channel.onclose

    channel.addEventListener("close", function(event, options) { ... })

An event triggered when the channel closes. This can happen either because channel.close() function was called, or if the peer closed the channel, or the underlying transport closes.

The `options` will contain various close information, including a `"problem"` field which will be set if the channel was closed because of a problem.

### cockpit.transport.origin

    cockpit.transport.origin

The HTTP origin that is being used by the underlying channel transport. This is read-only, you should not assign a value. If the browser supports `window.location.origin` then this will be identical to that value.

### cockpit.transport.host

    cockpit.transport.host

The host that this transport is going to talk to by default. This is read-only, you should not assign a value. If the value is null that means that the transport has not been setup yet.

### cockpit.transport.csrf_token

    cockpit.transport.csrf_token

A cross site request forgery token for use with external channels. This becomes valid once the connection is properly established.

### cockpit.transport.options

    cockpit.transport.options

Initialization options received over the underlying channel transport. These will be empty until connection is properly established.

### cockpit.transport.wait()

    cockpit.transport.wait(callback)

Call the `callback` function once the underlying channel transport is initialized. This will start the initialization if not already in progress or completed. If the channel transport is already initialized, then `callback` will be called immediately.

In general it’s not necessary to wait for the transport before starting to open channels.

### cockpit.transport.close()

    cockpit.transport.close([problem])

Close the underlying channel transport. All channels open channels will close. The `problem` argument should be a problem code string. If not specified it will default to `"disconnected"`.

### cockpit.transport.filter()

    cockpit.transport.filter((message, channelid, control) =>  { ... })

Add a filter to the underlying channel transport. All incoming messages will be passed to each of the filter callbacks that are registered.

This function is rarely used.

Filter callbacks are called in the order they are registered. If a filter callback returns `false` then the message will not be dispatched further, whether to other filters, or to channels, etc.

The `message` is the string or array with the raw message including, the framing. The `channelid` is the channel identifier or an empty string for control messages. If `control` is set then this is a control message,d and the `control` argument contains the parsed JSON object of the control message.

### cockpit.transport.inject()

    cockpit.transport.inject(message, [out])

Inject a message into the underlying channel transport. The `message` should be a `string` or an array of bytes, and should be valid according to the Cockpit message protocol. If the `out` argument is equal to `false` then the message will be injected as an incoming message as if it was received on the underlying channel transport.

This function is rarely used. In general you should only `inject()` messages you got from a `filter()`.

### cockpit.base64_encode()

    string = cockpit.base64_encode(data)

Encode binary data into a string using the Base64 encoding. The `data` argument can either be a `string`, an `Array`, an `ArrayBuffer` or a `Uint8Array`. The return value is a string.

### cockpit.base64_decode()

    data = cockpit.base64_decode(string, [constructor])

Decode binary data from a Base64 encoded string. The `string` argument should be a javascript string. The returned `data`> will be an array of bytes.

You can pass `Uint8Array`, `Array` or `String` as an alternate `constructor` if you want the decoded data in an alternate form. The default is to return an `Array`. Note that if you use a `String` for the decoded data, then you must guarantee that the data does not contain bytes that would be invalid for a string.

## cockpit.js: DBus Client

Cockpit allows access to DBus services via this API.

### DBus Types

DBus values are represented as javascript values and objects as follows:

`BYTE 'y'`

  Javascript number.

`BOOLEAN 'b'`

  Javascript boolean.

`INT16 'n'`

  Javascript number.

`UINT16 'q'`

  Javascript number.

`INT32 'i'`

  Javascript number.

`UINT32 'u'`

  Javascript number.

`INT64 'x'`

  Javascript number.

`UINT64 't'`

  Javascript number.

`DOUBLE 'd'`

  Javascript number.

`STRING 's'`

  Javascript string.

`OBJECT_PATH 'o'`

  Javascript string.

`SIGNATURE 'g'`

  Javascript string.

`ARRAY of BYTE 'ay'`

  A string containing base64 encoded data.

`ARRAY of DICT_ENTRY with STRING keys 'a{s?}'`

  A javascript plain object with the keys as property names.

`ARRAY of DICT_ENTRY with other keys 'a{??}'`

  A javascript plain object each key JSON encoded into a string property name.

`ARRAY of other`

  A javascript array.

`VARIANT`

  A javascript plain object with the `"t"` property set to a DBus type string, and the `"v"` property set to a value.

`HANDLE 'h'`

  A javascript object that describes a cockpit channel which represents the passed file descriptor. The `payload` is always set to `stream`. Pass it to cockpit.channel() to create the channel and start reading or writing on it. Handles can only be received, not sent from within cockpit.

### cockpit.dbus()

    client = cockpit.dbus(name, [options])

Create a DBus client for the given bus `name` (eg: service name). Use the following functions to make DBus method calls, watch for events, etc. The optional `options` argument is a javascript plain object, and may include:

`"bus"`

  The DBus bus to connect to. Specifying `"session"` will connect to the DBus user session bus, `"user"` will connect to the user bus (on some systems this is identical to the session bus), `"system"` will connect to the DBus system bus, and `"none"` to the non-standard bus specified with the `address` option. This defaults to "system" if not present.

`"address"`

  The bus address to connect to in case `bus` is `"none"`.

`"superuser"`

  Set to `"require"` to talk to this service as root. The DBus service will see the DBus method calls and accesses as coming from root, rather than the logged in user. This is useful for talking to services that do not correctly use polkit to authorize administrative users. If the currently logged in user is not permitted to become root (eg: via `pkexec`) then the `client` will immediately be closed with a `"access-denied"` problem code. + Set to `"try"` to try to talk as root, but if that fails, fall back to unprivileged.

`"track"`

  It is valid for a DBus service to exit, and be restarted in such a way that clients continue to talk to it across the restart. Some services are not written with this in mind. If the `"track"` option is set to `true` then the channel will close when the service exits and/or disconnects from the DBus bus.

If the `name` argument is null, and no options other than `"bus"` are specified, then a shared DBus `client` is created. When using such a client with a DBus bus, a `"name"` option must be specified on various other methods in order to specify which client to talk to.

### client.wait()

    promise = client.wait([callback])

Returns a `promise` that is ready when the client is ready, or fails if the client closes. If a `callback` is specified, it is attached to the promise.

### client.close()

    client.close([problem])

Close the DBus client. If `problem` is specified it should be a problem code string.

### client.onclose

    client.addEventListener("close", options => { ... })

An event triggered when the DBus client closes. This can happen either because client.close() function was called, or the DBus service went away, or some other problem or disconnection.

The `options` will contain various close information, including a `"problem"` field which will be set if the channel was closed because of a problem.

### client.onowner

    client.addEventListener("owner", (event, owner) => { ... })

An event triggered when the owner of the DBus name changes. The owner value will be the id of the name owner on the bus or null if the name is unowned. The absence of an owner should not be treated as a disconnection. However this makes it possible to take some action based on the actual status of the service, for example disconnecting a pending signal handler.

### client.options

Set to the options used when creating the client. Will not change for the life of the client.

### client.unique_name

The unique DBus name of the client. Initially null, and becomes valid once the the client is ready.

### client.proxy()

    proxy = client.proxy([interface, path], [options])

Create proxy javascript object for a DBus `interface`. At the specified DBus object `path`. The proxy will have properties, methods and signals from to the DBus interface, and allows for natural interaction. If no `interface` is specified then the DBus bus name of the client is used. If no `path` is specified, then the DBus name of the client is converted to a path.

If creating lots of proxies for a given `interface` it is more efficient to use the `client.proxies()` function.

The proxy is loaded when the `proxy.valid` field is `true`, and it is set to `false` if the underlying `interface` and/or `path` don’t or no longer exist, or the `client` has closed. You can wait for proxy to become valid by passing a callback to its `proxy.wait()` function. The `proxy.onchanged` event will also fire when the proxy becomes valid or invalid. DBus properties and methods on the proxy are not defined until the proxy becomes valid.

    value = proxy.Prop1
    proxy.WritableProp = value

All DBus properties on the `interface` that start with an upper case letter (as is convention) will be automatically defined on this proxy, and will update their values as the DBus property values change. In addition the `proxy.onchanged` event will fire every time the properties change.

If you assign a value to a writable property on the proxy, the proxy will try to set that property on the DBus `interface` at `path`. The actual proxy property value will not update until the DBus service has notified the proxy of the change. If setting a property fails a warning will be logged. In order to have more reliable setting of properties, or track when they have been set, or if setting fails, use the `client.call()` directly. It should be noted that DBus service implementations may also be inconsistent in their behavior when setting a property fails.

You can access the raw property data using the `proxy.data` field, including data for properties that do not start with an upper case letter.

    proxy.Method(arg1, arg2)
        .then((retval1, retval2) => {
            ...
        })
        .catch(ex => {
            ...
        });

All DBus methods on the `interface` that start with an upper case letter (as is convention) will be automatically defined on this proxy. These methods are called with arguments as normal javascript arguments. A Promise that will complete successfully when the method returns, or fail if an error occurs. The return values from the DBus method will be passed to the `then` handler function directly.

Methods that do not start with an upper case letter can be invoked by using the usual `proxy.call()` directly.

    proxy.addEventListener("signal", (event, arg1, arg2) => {
        ...
    });

All DBus signals on the `interface` that start with an upper case letter (as is convention) will be automatically emit events on this proxy. These events will contain the signal arguments after the standard `event` argument.

Signals that do not start with an upper case letter can be subscribed to by using `proxy.onsignal` directly.

Usually a proxy asks the `client` to watch and notify it of changes to the relevant object or path. You can pass an `options` argument with the `watch` field set to `false` to prevent this.

### proxy.client

Set to the DBus client of the proxy. Will not change for the life of the proxy.

### proxy.path

Set to the DBus object path of the proxy. Will not change for the life of the proxy.

### proxy.iface

Set to the DBus interface name of the proxy. Will not change for the life of the proxy.

### proxy.valid

Set to `true` when the proxy’s DBus interface is present at its DBus path, and all information for the proxy has loaded. Is set to `false` while loading, and after the proxy no longer refers a DBus interface and path. Also set to `false` if the `client` closes.

Use the by `proxy.wait()` function to wait for a proxy to load. The `proxy.onchanged` event will also be emitted when the proxy becomes valid or invalid. DBus properties and methods on the proxy are not defined until the proxy becomes valid.

### proxy.data

A plain javascript object containing all the raw property data that this proxy has loaded. This will be updated automatically as the proxy is notified of property changes from the DBus service. The `proxy.onchanged` event will be emitted when it changes.

### proxy.call()

    invocation = proxy.call(method, args, [options])

Make a DBus method call on this proxy.

For DBus methods that start with an upper case letter, is usually more convenient to call the method directly on the proxy. However if methods that do not follow the usual DBus convention, or specify additional options, or the caller cannot be sure that the method actually exists, you can use this method.

This function also works on proxies that have are still loading and have not become valid yet.

The `method` should be a DBus method name, and the `args` should be an array of arguments to pass to the method. The `options` are described elsewhere.

The returned value is identical to the one returned from client.call(). It is a Promise that will complete successfully when the method returns, or fail if an error occurs.

### proxy.wait()

    promise = proxy.wait()
    proxy.wait(() => {
        ...
    });

Wait for a proxy to finish loading. This function returns a promise. If a callback function is passed as an argument then that function will be invoked when the proxy is ready. If this method is called after a proxy has already loaded, then the promise will be resolved immediately, and any callback will be invoked immediately. Use the promise or `proxy.valid` to determine whether the proxy is valid.

### proxy.onchanged

    proxy.addEventListener("changed", (event, data) => {
        ...
    });

This event is emitted when the proxy’s properties change.

The `data` has the following form, and will only include properties that have changed:

    {
        "Prop1": "value",
        "Prop2": 5
    }

### proxy.onsignal

    proxy.addEventListener("signal", (event, name, args) => {
        ...
    });

This event is emitted when the proxy’s emits an event.

For most events, that have names which start with an upper case letter, you can just connect to that event as a signal directly. However if you wish to be notified when any signal is emitted, or for signals that do not follow the usual DBus convention, you can connect to this event.

The `name` is the DBus signal name, and the `args` is an array of arguments that were emitted with the signal.

### client.proxies()

    proxies = client.proxies([interface], [path_namespace], [options])

Create proxy javascript objects for a DBus interfaces. The proxies will have properties, methods and signals from the DBus `interface`, and allow for natural interaction. If no `interface` is specified then the DBus bus name of the client is used. If no `path_namespace` is provided then `"/"` will be used.

Proxies will be automatically created for instances of the `interface` available at the DBus service. The optional `path_namespace` argument can be used to restrict the proxies for instances that have DBus paths which have the namespace path prefix.

    proxy1 = proxies["/dbus/path1"];
    proxy2 = proxies["/dbus/path2"];
    for (proxy in proxies) {
        ...
    }

The returned `proxies` object will is used as a dictionary, and will have values containing proxies for DBus interface instances, with the keys being the DBus paths of those instances. It is possible to enumerate over the returned `proxies`.

Proxies will be automatically added and removed from the `proxies` object as they appear and disappear in the service. The `proxies.onadded` and `proxies.onremoved` events will be emitted. DBus services may not support notifications of paths disappearing.

Use the `proxies.wait()` function to be notified when the initial set of proxies has been populated.

Usually a proxies ask the `client` to watch and be notified of changes to the relevant object or path. You can pass an `options` argument with the `watch` field set to `false` to prevent this.

### proxies.wait()

    promise = proxies.wait()
    proxies.wait(() => {
        ...
    });

Wait for a `proxies` object to populate its initial set of proxies. This function returns a promise. If a callback function is passed as an argument then that function will be invoked when the proxies are ready. If this method is called after the proxies have populated, then the promise will be resolved immediately, and any callback will be invoked immediately.

### proxies.client

Set to the DBus client of the proxies. Will not change.

### proxies.iface

Set to the DBus interface name of the proxies. Will not change.

### proxies.path_namespace

Set to the DBus path namespace used which the proxies must have as a DBus path prefix. Will not change.

### proxies.onadded

    proxies.addEventListener("added", (event, proxy) => {
        ...
    })

This event is emitted when a proxy is added to the `proxies` object. The proxy will already have loaded.

### proxies.onchanged

    proxies.addEventListener("changed", (event, proxy) => {
        ...
    })

This event is emitted when one of the proxy in the `proxies` object changes its properties.

### proxies.onremoved

    proxies.addEventListener("removed", (event, proxy) => {
        ...
    })

This event is emitted when a proxy is removed to the `proxies` object.

### client.call()

    invocation = client.call(path, interface, method, args, [options])

Make a DBus method call.

The `path` is the DBus object path to make the call on, `interface` is the DBus interface for the method and `method` is the name of the method to call. The `args` is an array of arguments to pass to the method, each of which must be appropriate for the expected DBus type of that argument. The `args` may be `null` if no arguments are to be sent.

The returned value is a Promise that will complete successfully when the method returns, or fail if an error occurs.

If `options` is specified it should be a plain javascript object, which may contain the following properties:

`flags`

  A string containing DBus message flags. The character `"i"` indicates to the dbus service that interactive authentication is allowed. If the entire `flags` field is missing, then `"i"` is set by default.

`type`

  A valid DBus type signature to use when calling the method. In the absence of this, the DBus service will be introspected (and the result cached) to ask what the method type signature is.

`timeout`

  The timeout of the call in milliseconds. The call will fail with the `"timeout"` problem code. If "timeout" is not given, the call will never time out.

### invocation.then()

    invocation.then((args, options) => { ... })

This is a standard Promise method. It sets up a handler to be called when the DBus method call finishes successfully.

The `args` argument is an array of return values from the DBus method. Each of them will be converted to an appropriate javascript type.

The `options` argument may contain additional information about the reply. If the `type` option was specified when performing the method call, then the `options` in the reply here will also contain a `type` field containing the DBus type signature of the output. If the `flags` option was specified when performing the call then the `options` in the reply here will contain message flags. Possible out message flags are:

`>`

  A big endian message.

`<`

  A little endian message.

### invocation.catch()

    invocation.catch(exception => { ... })

This is a standard Promise method. It sets up a handler to be called when the DBus method call fails.

The `exception` object passed to the handler can have the following properties:

`problem`

  A problem code string when a problem occurred starting or communicating with the DBus service. This is `null` in the cases where an actual DBus error was occurred.

`name`

  The DBus error name. This will be `null` in cases where the failure was not due to a DBus error.

`message`

  A DBus error message. This will be `null` in cases where the failure was not due to a DBus error.

### client.subscribe()

    subscription = client.subscribe(match, (path, interface, signal, args) => { ... })

Subscribe to signals. The `match` argument is a javascript plain object which defines what signals to subscribe to. Each property in the `match` argument restricts signals subscribed to. If a property is not present then it is treated as a wildcard, matching anything. If an empty object is specified as `match` then all signals will be subscribed to. The `match` argument may contain the following properties:

`interface`

  A DBus interface to match.

`path`

  A DBus object path to match. May not be used together with the `path_namespace` property. It should be a valid DBus object path, that is, it should have no trailing slash.

`path_namespace`

  A DBus object path prefix to match. Any paths in the hierarchy below this top path will match. May not be used together with the `path` property.

`member`

  The DBus signal name to match.

`arg0`

  Matches the first argument of a DBus message, which must be a string.

The handler passed as the second argument will be invoked when the signal is received. A `subscription` is returned which can be used to remove the subscription by calling its `subscription.remove()` method.

It is not a problem to subscribe to the same signals more than once, with identical or slightly different `match` arguments.

### subscription.remove()

    subscription.remove()

Unsubscribe from the DBus signal subscription.

### client.watch()

    watch = client.watch(path)
    watch = client.watch({ "path_namespace": path_namespace, "interface": interface })

Watch for property and interface changes on the given DBus object `path` DBus `path_namespace`. If `interface` is specified only properties on that DBus interface will be watched.

The `client.proxy()` and `client.proxies()` functions and the objects they return are high level wrappers around `client.watch()`.

The property and interface changes will be available in raw form on the `client.onnotify` event.

Property and interface changes that are caused by a method call or signal will show up before that method call reply is received, or signal event is triggered. It should be possible to rely on this guarantee, unless the DBus service in question behaves incorrectly. Internally these watches work well with code that implements the ObjectManager portion of the DBus specification. If no ObjectManager implementation is available, the watch falls back to using DBus Introspection along with the usual PropertiesChanged signal. If the DBus service implements none of these, or implements them in an inconsistent manner, then this function will provide inconsistent or unexpected results.

The parameter is either a DBus `path` or a plain javascript object with zero or more of the following fields. If an empty javascript object is used as an argument, then all paths, interfaces and properties will be watched.

`interface`

  Watch properties on this DBus interface.

`path`

  Watch interfaces and properties at this DBus path. May not be used together with the `path_namespace` property.

`path_namespace`

  Watch interfaces and properties under this DBus path. It should be a valid DBus object path, that is, it should have no trailing slash. If an ObjectManager implementation is available at this interface, then it is used. May not be used together with the `path` property.

The returned value is a Promise that will complete successfully when the watch has populated its initial set of properties and interfaces, and these have been notified via `client.onnotify`.

A watch can be removed by calling the `watch.remove()` method on the returned value. If identical watches are added more than once, then they must also be removed the same number of times before the removal takes effect.

### watch.then()

    watch.then(() => { ... })

This is a standard Promise method. It sets up a handler to be called when the watch has populated its initial properties and interfaces.

### watch.catch()

    watch.catch(ex => { ... })

This is a standard Promise method. It sets up a handler to be called if the watch fails to populate its initial properties and interfaces. Note that a watch will only fail if the DBus client closes or is somehow disconnected. It does not fail in the case of missing interfaces or properties.

### watch.remove()

    watch.remove()

Remove the watch. This may not have any immediate effect if other watches are in place. In particular, if identical watches are added more than once, then they must also be removed the same number of times before the removal takes effect.

### client.onnotify

    client.addEventListener("notify", data => { ... })

An event triggered when watched properties or interfaces change.

The `client.proxy()` and `client.proxies()` functions and the objects they return are high level wrappers around the `data` provided by this event.

The `data` has the following form:

    {
        "/path1": {
            "org.Interface1": {
                "Prop1": "value",
                "Prop2": 5
            },
            "org.Interface2": null
        }
    }

Multiple paths may be present, each of which may have multiple interfaces, each of which may have multiple properties. The first time a given path and interface is emitted from this signal, it will have all its properties and interfaces. Thereafter only changes are noted. If an interface is set to `null`, then that interface has disappeared.

### client.notify()

    client.notify(data)

Emits a synthetic `notify` event. The `data` argument should follow the same layout as described for the `notify` event.

### client.onmeta

    client.onmeta = (ev, data) => { ... }

An event triggered when the meta data about watched interfaces is loaded.

The `client.proxy()` and `client.proxies()` functions and the objects they return are high level wrappers around the `data` provided by this event.

The `data` has the following form:

      {
          "org.Interface": {
              "methods": {
                  "Method1": {
                      "in": [ "s", "v" ],
                      "out": [ "i" ]
                  },
                  "Method2": { }
              },
              "signals": {
                  "Signal": {
                      "in": [ "b", "s" ]
                  }
              },
              "properties": {
                  "Prop1": {
                      "flags": "rw",
                      "type": "s"
                  },
                  "Prop2": {
                      "flags": "r",
                      "type": "b"
                  }
              }
          }
      }

Multiple interfaces may be present, each of which may have methods and properties. This is emitted before the first `client.onnotify` event for the relevant interface.

### cockpit.variant()

    variant = cockpit.variant(type, value)

A DBus variant is represented as a plain javascript object with a `"t"` property represesting the full DBus type of the variant, and a `"v"` property containing the variant value.

This is a helper function for creating such a variant object.

## cockpit.js: Errors

cockpit.js: Errors

Problem codes and messages

### Problem Codes

Cockpit represents problems with standardized problem string codes.

`"access-denied"`

  The user is not permitted to perform the action in question.

`"authentication-failed"`

  User authentication failed.

`"internal-error"`

  An unexpected internal error without further info. This should not happen during the normal course of operations.

`"no-cockpit"`

  The system does not have a compatible version of Cockpit installed or installed properly.

`"no-session"`

  Cockpit is not logged in.

`"not-found"`

  Something specifically requested was not found, such as a file, executable etc.

`"terminated"`

  Something was terminated forcibly, such as a connection, process session, etc.

`"timeout"`

  Something timed out.

`"unknown-hostkey"`

  The remote host had an unexpected or unknown key.

`"no-forwarding"`

  Could not forward authentication credentials to the remote host.

### cockpit.message()

    message = cockpit.message(problem)
    message = cockpit.message(exception)

Return a message for the `exception` or `problem` code passed as an argument. If the argument is an object with a `"message"` property, as is the case with most exceptions, that will be returned directly. If the argument is an object with a `"problem"` property, then it will be used as the problem code. An appropriate message will be returned for problem codes.

## cockpit.js: File Access

The `cockpit.file` API lets you read, write, and watch regular files in their entirety. It cannot efficiently do random access in a big file or read non-regular files such as `/dev/random`.

    file = cockpit.file(path,
                        { syntax: syntax_object,
                          binary: boolean,
                          max_read_size: int,
                          superuser: string,
                        })

    promise = file.read()
    promise
        .then((content, tag) => { ... })
        .catch(error => { ... })

    promise = file.replace(content, [ expected_tag ])
    promise
        .then(new_tag => { ... })
        .catch(error => { ... })

    promise = file.modify(callback, [ initial_content, initial_tag ]
    promise
        .then((new_content, new_tag) => { ... })
        .catch(error => { ... })

    file.watch((content, tag, [error]) => { }, [ { read: boolean } ])

    file.close()

### Simple reading and writing

You can read a file with code like this:

    cockpit.file("/path/to/file").read()
        .then((content, tag) => {
            ...
        })
        .catch(error => {
            ...
        });

It is recommended to use absolute paths. Relative paths are resolved against `/`. To work with the current user’s files cockpit.user() can be used to get the user’s home directory.

The `read()` method returns a Promise.

When successful, the promise will be resolved with the content of the file. Unless you specify options to change this (see below), the file is assumed to be text in the UTF-8 encoding, and `content` will be a string.

The tag that is passed to the `then()` callback is a short string that is associated with the file and changes whenever the content of the file changes. It is meant to be used with `replace()`.

It is not an error when the file does not exist. In this case, the `then()` callback will be called with a `null` value for `content` and `tag` is `"-"`.

The `superuser` option can be used the same way as described in the cockpit.channel() to provide a different access level to the file.

You can use the `max_read_size` option to limit the amount of data that is read. If the file is larger than the given number of bytes, no data is read and the channel is closed with problem code `too-large`. The default limit is 16 MiB. The limit can be completely removed by setting it to -1.

To write to a file, use code like this:

    cockpit.file("/path/to/file").replace("my new content\n")
        .then(tag => {
            ...
        })
        .catch(error => {
            ...
        });

The `replace()` method returns a Promise.

When the promise is resolved, the file has been atomically replaced (via the `rename()` syscall) with the new content. As with `read()`, by default the new content is a string and will be written to the file as UTF-8. The returned tag corresponds to the new content of the file.

When the promise is rejected because of an error, the file or its meta data has not been changed in any way.

As a special case, passing the value `null` to `replace()` will remove the file.

The `replace()` method can also check for conflicting changes to a file. You can pass a tag (as returned by `read()` or `replace()`) to `replace()`, and the file will only be replaced if it still has the given tag. If the tag of the file has changed, `replace()` will fail with an error object that has `error.problem == "change-conflict"`. See `modify()` below for a convenient way to achieve transactional updates to a file.

### File format

By default, a file is assumed to be text encoded in UTF-8, and the `read()` and `replace()` functions use strings to represent the content.

By specifying the `syntax.parser()` and `syntax.stringify()` options, you can cause `read()` to parse the content before passing it back to you, and `replace()` to unparse it before writing.

The main idea is to be able to write `{ syntax: JSON }`, of course, but you can easily pass in individual functions or make your own parser/unparser object:

    cockpit.file("/path/to/file.json", { syntax: JSON })

    var syntax_object = {
        parse:     my_parser,
        stringify: my_unparser
    };

    cockpit.file("/path/to/file", { syntax: syntax_object })

Any exceptions thrown by the `parse()` and `stringify()` functions are caught and reported as read or write errors.

The `null` value that is used to represent the content of a non-existing file (see "Simple reading and writing", above) is not passed through the `parse()` and `stringify()` functions.

### Binary files

By default the content of the file is assumed to be text encoded as UTF-8 and it can not contain zero bytes. The content is represented as a JavaScript string with `read()`, `replace()`, etc. By setting the `binary` option to true when creating the proxy, no assumptions are placed on the content, and it is represented as a `Uint8Array` in JavaScript.

### Atomic modifications

Use `modify()` to modify the content of the file safely. A call to `modify()` will read the content of the file, call `callback` on the content, and then replace the content of the file with the return value of the callback.

The `modify()` method uses the `read()` and `replace()` methods internally in the obvious way. Thus, the `syntax.parse()` and `syntax.stringify()` options work as expected, `null` represents a non-existing file, and the watch callbacks are fired.

It will do this one or more times, until no other conflicting changes have been made to the file between reading and replacing it.

The callback is called like this

    new_content = callback (old_content)

The callback is allowed to mutate `old_content`, but note that this will also mutate the objects that are passed to the watch callbacks. Returning `undefined` from the proxy is the same as returning `old_content`.

The `modify()` method returns a Promise.

The promise will be resolved with the new content and its tag, like so

    function shout(old_content) {
        return old_content.toUpperCase();
    }

    cockpit.file("/path/to/file").modify(shout)
        .then((content, tag) => {
            ...
        })
        .catch(error => {
            ...
        });

If you have cached the last content and tag results of the `read()` or `modify()` method, or the last values passed to a watch callback, you can pass them to `modify()` as the second and third argument. In this case, `modify()` will skip the initial read and start with the given values.

### Change notifications

Calling `watch()` will start monitoring the file for external changes.

    handle = file.watch(callback);

    handle_no_read = file.watch(callback, { read: false });

Whenever a change occurs, the `callback()` is called with the new content and tag of the file. This might happen because of external changes, but also as part of calls to `read()`, `replace()`, and `modify()`.

When a read error occurs, the `callback()` is called with an error as a third argument. Write errors are not reported via the watch callback.

Calling `watch()` will also automatically call `read()` to get the initial content of the file. Thus, you normally don’t need to call `read()` at all when using `watch()`.

To disable the automatic reading, e.g. for large files or unreadable file system objects, set the `read` option to `false`. The first `content` argument of the callback will then always be `null`.

To free the resources used for monitoring, call `handle.remove()`.

### file.path

A string containing the path that was passed to the `cockpit.file()` method.

### Closing

Call the `close()` method on a file proxy to cancel all ongoing operations, such as reading, writing, and monitoring. The proxy should not be used after closing it.

## cockpit.js: HTTP Client

Cockpit allows access to local HTTP and REST services via this API.

### cockpit.http()

    http = cockpit.http(endpoint, [options])
    http = cockpit.http(options)

Create a new HTTP client. The `endpoint` can be a file path starting with `/` to connect to a unix socket, or it can be a port number to connect to. The optional `options` argument is a javascript plain object, and may include:

`"address"`

  Connect to an address other than localhost. Must be a valid host name or IP address. To use this option you also must provide a port number.

`"port"`

  Port number to use with "address" option, when not given in `endpoint`.

`"tls"`

  Object properties for an https connection. See `http-stream2 TLS options`.

`"headers"`

  Additional HTTP headers to include with the HTTP request. This is a plain javascript object with each key as a header name, and each value as the header value.

`"superuser"`

  Set to `"require"` to open this channel as root. If the currently logged in user is not permitted to become root (eg: via `pkexec`) then the `channel` will immediately be closed with a `"access-denied"` problem code. + Set to `"try"` to try to make the request as root, but if that fails, fall back to perform an unprivileged request.

`"tls"`

  If set to a plain javascript object, then the connection will be an HTTPS connection and include TLS encryption. The fields of the `tls` object declare various TLS configuration and data. All fields are optional: +

  - `"authority"`: Certificate authority(s) to expect as signers of the server’s TLS certificate, represented as a plain javascript object. It should have either a `"file"` field containing a readable PEM file on the system containing authorities, or a `"data"` with PEM encoded certificate data.

  - `"certificate"`: A client certificate to use, represented as a plain javascript object. It should have either a `"file"` field containing a readable PEM file on the system to use as a certificate, or a `"data"` with PEM encoded certificate data.

  - `"key"`: A client key to use, represented as a plain javascript object. It should have either a `"file"` field containing a readable PEM file on the system to use as a key, or a `"data"` with PEM encoded key data.

  - `"validate"`: A boolean that describes whether to validate the server’s TLS certificate or not. By default local connections are not validated, and remote connections are validated.

Here is a somewhat complex example of using most of the above `options` when when calling `cockpit.http()`:

    http = cockpit.http({
        "address": "localhost",
        "headers": {
            "Authorization": "Basic dXNlcjpwYXNzd29yZA=="
        },
        "port": 443,
        "tls": {
            "validate": true,
            "authority": {
                "file": "/etc/pki/tls/certs/ca-bundle.crt",
            },
            "certificate": {
                "data": "-----BEGIN CERTIFICATE-----\nMIIDsDCCA..."
            },
            "key": {
                "data": "-----BEGIN RSA PRIVATE KEY-----\nMIIEogIBA..."
            }
        }
    });

### http.get()

    request = http.get(path, [params, [headers]])

Perform an HTTP GET request for the given `path`. If the `params` is specified it should be a plain javascript object, which will be turned into a query string.

Optionally a plain javascript object containing headers can be included in the `headers` argument.

The return value is a Promise that will complete if the request happens successfully, or fail if there’s a problem.

### http.post()

    request = http.post(path, body, [headers])

Perform an HTTP POST request for the given `path`. The `body` can be a string, or a javascript plain object, which will be encoded as JSON data. If `body` is `undefined` or `null` then an empty HTTP body will be sent.

Optionally a plain javascript object containing headers can be included in the `headers` argument.

The return value is a Promise that will complete if the request happens successfully, or fail if there’s a problem.

### http.request()

    request = http.request(options)

Perform an HTTP request. The `options` can contain the following:

`"body"`

  The HTTP request body. If you do not specify a body, then you must call request.input() to complete the body and allow the request to start.

`"headers"`

  A javascript plain object containing HTTP headers.

`"method"`

  The HTTP method. Defaults to `"GET"`.

`"params"`

  A javascript plain object containing query string parameters.

`"path"`

  The HTTP path. Defaults to `/`.

The return value is a Promise that will complete if the request happens successfully, or fail if there’s a problem.

### request.then()

    request.then(data => { ... })

This is a standard Promise method. It sets up a handler to be called when the request finishes successfully.

The `data` argument contains the body result of the request. If it a string, unless the process was opened in binary mode, in which case the `data` is an array of bytes. If a `request.stream()` handler is set up, then any standard output data consumed by the handler will not be included in the `data` argument.

### request.catch()

    request.catch((exception[, data]) => { ... })

This is a standard Promise method. It sets up a handler to be called when the request fails, or returns an error code.

The `exception` object passed to the handler can have the following fields:

`problem`

  A problem code string when a problem occurred starting or communicating with the server. This is `null` if the process exited or was terminated.

`status`

  The numeric status of the response. This is `null` if no response was received.

`reason`

  A string reason returned in the response. This is `null` if no response was received.

`message`

  A string message returned in the response. This is `null` if no response was received.

If the request returned a response body, it will be available in the `data` argument. Otherwise this argument will be `undefined`.

### request.response()

    request.response((status, headers) => { ... })

This sets up a handler to be called when the HTTP request gets the initial response from the server. The `status` argument is the HTTP status integer, and the `headers` is a plain javascript object containing the headers of the response.

### request.stream()

    request.stream(data => { ... })

This sets up a handler to be called when the request returns output data. The handler will be called multiple times.

Only one handler may be registered at a time. Registering an additional handler replaces the previous one. The handler receives either string `data` or an array of binary bytes as its argument. A stream handler may return a number, which indicates the number of characters or bytes consumed from `data`. Any data not consumed will be included again the next time the handler is called.

If a `request.stream()` handler is set up, then the `request.then()` handlers will only get any remaining data not consumed by the stream handler.

### request.input()

    request.input(data, [stream])

This method writes `data` to the HTTP request body. It is only valid if no `"body"` has been specified in http.request() options. If `stream` is `true` then this function can be called again to provide further data.

### request.close()

    request.close([problem])

Cancel the request. If `problem` is specified it should be a standard problem code string.

### http.close()

    http.close([problem])

Cancel all outstanding requests with the given problem code. This is useful when you know that the server is going down soon.

## cockpit.js: Localization

Cockpit provides a `gettext()` like API for easy translation of strings.

### cockpit.language

The current locale language code. This is set based on the `cockpit.locale()` data loaded.

### cockpit.locale()

    cockpit.locale(po)

Load locale information for a given `po` data. The data should be JSON data in the po2json format. The data will be loaded globally. If `po` data has already been loaded, then this will extend that loaded data with additional strings. Any identical translations strings will be replaced with the new strings. A `null` argument clears all the locale information previously loaded.

Various methods such as `cockpit.gettext()` make use of the loaded data.

### cockpit.gettext()

    translated = cockpit.gettext([context], string)
    var _ = cockpit.gettext
    var C_ = cockpit.gettext
    translated = _("string")
    translated = C_("context", "string")

Lookup `string` for translation in the loaded locale data. The translated string will be returned, or `string` will be returned if no such translated string is present. The `context` argument is an optional string used to qualify the string.

This function can be assigned to a variable called `_` (underscore) which will make your code work with the typical `_("string")` syntax.

### cockpit.noop()

    var N_ = cockpit.noop
    var NC_ = cockpit.noop

A noop function suitable for assigning to `N_` or `NC_` so that gettext scanners will be able to find translatable strings. More specifically this function returns its last argument.

### cockpit.ngettext()

    translated = cockpit.ngettext([context], string1, stringN, number)

Lookup a string appropriate for a pluralization form of the `number`. Various languages have complex pluralization forms that go far between the singular and plural forms speakers of English are familiar with. If no such translated string is found then either one of `string1` or `stringN` is returned according to simple pluralization rules.

The `context` argument is an optional string used to qualify the string.

### cockpit.translate()

    cockpit.translate()
    cockpit.translate(element, ...)
    cockpit.translate(selection)

The document will be scanned for `translate` tags and they will be translated according to the strings in loaded locale data. One or more `element` arguments may be specified. These are DOM elements for specific parts of the document to be translated. If no `element` is specified then the entire document is translated.

If an array or array-like object is passed as a `selection` then all DOM elements in the array will be treated as parts of the document to be translated.

## cockpit.js: Page Location and Jumping

Page location and navigation between components

### Page location

    location = cockpit.location
    cockpit.location = "/path"

Cockpit components often have different views, without changing the HTML file that is being viewed. These are known as pages. `cockpit.location` is an object that can be used to read the current page and to navigate to a different page location. It works by updating `window.location.hash`.

The `cockpit.location` looks like a HTTP path with a possible query string:

    /path/sub/page?option=value,option2

The `location.path` and `location.options` contain a parsed form of the location. While the location cannot be modified in place, a new one can be created by assigning a string to `cockpit.location` or by calling the `location.go()` function.

`cockpit.location` is designed similarly to `window.location` in that the location object is preplaced whenever the current page location changes. To be aware of when the page location changes listen for the `cockpit.onlocationchanged` event.

Using the location object as a string will result in the `location.href`.

#### location.href

The string representation of this page location, including any options.

#### location.path

An array of path segments, parsed and decoded appropriately. An empty array denotes the root path.

#### location.options

A javascript object containing the various options present in the location.

If an option appears more than once, its value will be an array.

#### location.go()

    location.go(path, [options])

Changes the current location to the given `path` and `options`. If the `path` argument is a string, it will be parsed into a path. If it is a relative path, then the result will be relative to the current `location.path`. If the `path` argument is an array of path segments, it will be treated as a full parsed absolute path.

Any options found in a `path` will be added to those in the optional `options` argument, and used in the result.

The location change will only take effect if the location has not changed in the meantime. This can be to good effect by saving a `cockpit.location` object and doing a conditional navigation, by calling the saved `location.go()` method later. This will only navigate if the user or other code has not navigated in the meantime.

#### location.replace()

    location.replace(path, [options])

Similar to `location.go()` except the location change will not result in a navigation change in the browser’s history.

#### location.decode()

    path = location.decode(href, [options])

Decode a cockpit href into its `path` array. If the `options` argument is specified, then it will be populated with options found in the href.

If href is a relative path it will be resolved relative to `location.href`.

#### location.encode()

    href = location.encode(path, [options])

Encode the given `path` and `options` into a cockpit href. The `path` argument may be an array of path segments, or a string path. If a relative path is passed, it will be resolved relative to `location.href`.

#### cockpit.onlocationchanged

    cockpit.addEventListener("locationchanged", function() { ... })

An event emitted when over the `cockpit.location` changes. Typically a component reacts to this event by updating its interface to reflect the new `cockpit.location.path` and `cockpit.location.options`.

This event is not triggered immediately during a `location.go()` or similar call. It will be triggered asynchronously at a later time.

### Jumping between components

    cockpit.jump("/system/log")

In Cockpit in there multiple components shown. In order to tell Cockpit to jump to and show another component and a certain location within that component, use the `cockpit.jump()` function. Stable component paths are documented. Don’t assume you can navigate into paths that are not stable API.

#### cockpit.jump()

    cockpit.jump(path, [ host ])

Ask Cockpit to jump to another component. The location of the current component will not be affected. The `path` argument can be a string path, starting with `/` or an array containing the parts of a path that will be joined to create a path. If `host` is not specified, then the component on the same host as the caller will be displayed. If host is null, then the host portion of the path will be removed, displaying the component on the host that cockpit is connected directly to.

If the calling component is not running within Cockpit, or the calling component is not currently displayed, then the jump will not happen, and this function has no effect.

#### cockpit.hidden

A boolean property that indicates if the current component page is visible or hidden. When the code or user jumps to another component, the prior one remains loaded and initialized but is hidden. Use this property together with the `cockpit.onvisibilitychange` event to decide whether or not to perform expensive tasks to update the interface.

This property is analogous to the `document.hidden` page visibility API, but works with the document and frame implementation of Cockpit.

#### cockpit.onvisibilitychange

    cockpit.onvisibilitychange = function() { ... }

This event is emitted when the `cockpit.hidden` property changes. This event is similar to the `document.onvisibilitychange` API, but works with the document and frame implementation of Cockpit.

## cockpit.js: User Session

User information and login session state

### cockpit.logout()

    cockpit.logout([reload])

Logout of Cockpit. Unless `reload` is `false` this will also cause the page to be reloaded, so that the user can see the logged out state.

### cockpit.user()

    var promise = cockpit.user();
    promise.then(user => { ... });

This object contains information about the user that’s currently logged into cockpit. The following fields are defined:

`"id"`

  This is unix user id.

`"gid"`

  This is unix user group id.

`"name"`

  This is the unix user name like `"root"`.

`"full_name"`

  This is a readable name for the user.

`"groups"`

  This is an array of group names to which the user belongs. Since version 318, the first item in this list is the primary group.

`"home"`

  This is user’s home directory.

`"shell"`

  This is unix user shell.

Returns a promise that completes once the user information is available.

Warning | `cockpit.user()` is soft-deprecated since Cockpit 336, if your page does not need to maintain compatibility with older Cockpit versions you can usecockpit.info to obtain the user information.

### Permission lookup

Cockpit provides a mechanism for checking if the current user satisfies a given criteria. This is meant for updating UI elements based on what actions the user can perform. It is not an access control mechanism.

#### cockpit.permission()

    permission = cockpit.permission([options])

Create a new permission object to check if the current user has a particular permission specified by `options`:

`admin: true`

  True if the session has superuser privileges, i.e. can run channels as root with `{ superuser: "require" }`.

`group:` name

  True if the currently logged user is a member of group name.

The permission result is always true for the "root" user. When `options` is not given, check if the current user is root.

#### permission.allowed

A boolean value which indicates if the permission is allowed or not. This will be `null` if the permission is unknown, or there was an error checking the permission or the permission data has not yet loaded. This property will update asynchronously and if you wish to be notified of changes connect to the permission.onchanged event.

#### permission.onchanged

    permission.addEventListener("changed", function() { ... })

This event is fired when the permission changes. In particular the permission.allowed property.

#### permission.close()

    permission.close()

Closes the permission object and tears down any registered callbacks and dbus subscriptions.

## cockpit.js: Manifests

### Loading Manifests

For a convenient access to all page manifests, include `<script src="../manifests.js"></script>` into your page to register the manifests at the `cockpit.manifests` global variable.

You can also load `../manifests.json` directly in your page, with `fetch()`.

## cockpit.js: Metrics

Metrics about the system can be retrieved from several sources using `cockpit.metrics()` metrics channels. The metrics are made available as series data, and can be used with the `cockpit.series()` and `cockpit.grid()` facilities.

### cockpit.metrics()

    metrics = cockpit.metrics(interval, options, cache)

Opens a new metrics channel. The data retrieved will be available in the `metrics.series` series sink, and can be used together with `cockpit.grid()` objects.

The `interval` is in milliseconds, and is the granularity of the series data retrieved. Any grids consuming the data must have the same interval.

The `cache` argument is a cache identifier. If specified, then this metrics channel will share data with other metrics channels of the same identifier. Make sure to use a globally unique string.

The `options` argument is either a javascript plain object, or an array of those. Each object can have the following fields.

`"metrics"`

  An array of full metric descriptions, as javascript objects. The specifics of these, and how to determine which ones to use, can unfortunately only be found in the low-level protocol documentation. This option is required.

`"source"`

  The source to use for real-time data. This is used by the `follow` method, see below. Set to `"internal"` to retrieve internal metrics read by the bridge. If set to `"direct"` or `"pmcd"` then data will be retrieved from PCPif it is available. The default is `"internal"`.

`"archive_source"`

  The source to use for retrieving historical data. This is used by the `fetch` method, see below. Set to `"pcp-archive"` to retrieve data from PCP archives. The default is not to try to retrieve historical data.

When the `options` argument is an array of javascript objects, then the metrics channel tries to use them in order until one succeeds. This way, you can prefer PCP as the source but fall back to internal metrics when PCP is not available, for example. The channel gives no indication which of the options has been used, and `fetch` and `follow` might use different entries from the list.

### metrics.fetch()

    metrics.fetch(beg, end)

Retrieve archived metrics data between `beg` and `end`. The arguments can either be numbers, in which case they are interval based offsets, or they can be javascript Date objects.

### metrics.follow()

    metrics.follow()

Start retrieving live metrics data as it become available.

### metrics.close()

    metrics.close()

Stop the retrieval of metrics and release resources.

### metrics.series

The series sink where data retrieved data will be processed.

### metrics.meta

The metrics meta data last received.

### metrics.onchanged

    metrics.onchanged = function() { }

An event triggered when one of the properties on this metrics object changes.

## cockpit.js: Series Data

Series data consists of values along a continuous (usually time) axis. We can place these in grids which expose a distinct subset of these values. These are the underlying mechanism for displaying metrics data in graphs.

### cockpit.grid()

    grid = cockpit.grid(interval, [beg, end])

Creates a grid object to contain series data.

The `interval` is the granularity of the grid. Usually this is a number of milliseconds, when used with time series data. The `beg` and `end` are the bounds of the grid. If omitted they will be set to zero for an initially empty grid.

If `beg` and/or `end` are negative (including negative zero) then they are interpreted in number of intervals relative to the current time. Thus cockpit.grid(1000, -300, -0) will create a grid for the most recent 5 minutes.

### grid.add()

    row = grid.add(series, path)
    row = grid.add(callback, [early])
    row = grid.add()

Adds a row to the grid. The returned `row` is a Javascript array that will contain series data. The arguments control how the row is populated from the series data. The `row` is a sparse array. Its `row.length` will not match the expected size of the grid, unless and until the row has been completely filled in. The first index of the `row` will contain the data from the series data at the `grid.beg` offset.

When no arguments are passed, an empty row is added, and it is not populated with data.

When called with a `series` and `path` argument then the row will be populated directly with series data. The `series` can either be a series object or an object that has an `obj.series` property. The series interval must match the interval of this grid. If `path` is missing or empty, then the series data is placed into the row directly. Otherwise `path` indicates which part of the series data to place in the row. When `path` is an array, it is used as a set of property names or array indexes to follow into nested series data. When `path` is a dotted string, it is split and used the same way to locate the correct value in nested series data. The exact format of the series data depends on its producer, and relevant paths will be documented there.

If a `callback` function is specified, then it will be invoked to provide series data for the row. The function is invoked as `callback(row, index, count)`, where the `row` is the row to fill in, the `index` is the index to start filling in and `count` is the number of items to fill in. The `this` variable will be set to the grid while invoking the `callback`. The callback is called after other data rows for a given series have been filled in. Callbacks are called in the order added, unless the `early` argument is set to `true`, in which case the callback is called earlier than callbacks without the `early` argument set.

To remove the row use the `grid.remove()` method.

The row will start being populated with data when the `series` produces data. To make this happen right away, use the `grid.sync()` method.

### grid.remove()

    grid.remove(row)

Remove a previously added `row` from the grid. The row will no longer be updated with series data.

### grid.sync()

    grid.sync()

Load or reload data from the series into the rows. This does not clear the rows before populating them. Some data may be populated immediately, others may have to wait until data can be loaded. Internally this function calls `series.load()` for each series.

All rows with callbacks will be invoked to regenerate all the data. The `grid.onnotify` event will be triggered. It is not necessary to call this function after a call of the `grid.move()` method.

### grid.move()

    grid.move(beg[, end])

Move the grid to new `beg` and `end` range. Data will be discarded from the rows and `grid.sync()` will be called to load or reload series data for the new range of offsets.

If `end` is not specified it will be set to `beg`. If `beg` and/or `end` are negative (including negative zero) then they will be set to the number of intervals prior to the current time taken as an interval.

If `beg` and/or `end` are negative (including negative zero) then they are interpreted in number of intervals relative to the current time. Thus cockpit.grid(1000, -300, -0) will create a grid for the most recent 5 minutes.

### grid.walk()

    grid.walk()

Move the grid forward every `grid.interval` milliseconds. To stop moving forward, call `grid.move()`.

### grid.notify()

    grid.notify(index, count)

This function is called to have rows with callbacks recalculate their data. It is not normally necessary to call this function, as it will be invoked automatically when new series data is available or has been loaded. This function triggers the `grid.onnotify` event.

### grid.onnotify

    grid.addEventListener("notify", function(index, count) { ... });

An event that is triggered when some part of the series data in grid changes. The `index` is the row index where things changed, and the `count` is the length of the data that changed.

### grid.close()

    grid.close()

Close the grid, and stop updating the rows.

### grid.interval

The granularity of the grid. For time series data this is an interval in milliseconds. In order to use a given grid and series together, their interval properties must match.

### grid.beg

The beginning offset of the series data in the grid. Do not set this property directly. Use the grid.move() method instead.

### grid.end

The ending offset of the series data in the grid. Do not set this property directly. Use the grid.move() method instead.

### cockpit.series()

    series = cockpit.series(interval, [cache, fetch])

Create a new sink of series data. This is usually done by producers of series data, and it is rare to invoke this function directly.

The `interval` is the granularity of the series data. For time series data this is an interval in milliseconds. If a `cache` string is specified, series data will be cached across frames for series with the same `cache` cache identifier to load and/or reload.

If a `fetch` callback is specified, then it will be invoked when grids request certain ranges of data. The `fetch` callback is invoked with `function fetch(beg, end) { ... }` range offsets. The series.input() should be called with data retrieved, either immediately or at a later time. The callback may be called multiple times for the same ranges of data. It is up to the callback to determine when or whether it should retrieve the data more than once.

A producer of series data, usually calls this function and creates itself a `obj.series` property containing this series object.

### series.input()

    series.input(beg, items[, mapping])

Send series data into the series sink. Any grids that have added rows based on this series, will have data filled in. The `beg` is the beginning offset of `items`. The `items` are an array one or more series data items.

Producers may wish to provide additional properties that can be used in lookup paths that rows can pull from. This is done in the `mapping` argument. If specified it is a tree of objects. Each sub object should have a property with the name `""` empty string, which will be used as the property name or index in place of the one used in the lookup path.

### series.load()

    series.load(beg, end)

Load data from the series into any grids that have rows based on this series data. Any cached data will be filled in immediately. Any data not cached, will be requested from the producer, if possible, and may arrive at a later time.

The `beg` and `end` denote the range of data to load.

### series.interval

The granularity of the series. For time series data this is an interval in milliseconds. In order to use a given grid and series together, their interval properties must match.

### series.limit

The maximum number of items to cache for loading and/or reloading. You can change this value to a different number. Having a number close to zero will break certain usage of grids, such as `grid.walk()`.

## cockpit.js: Spawning Processes

This is the API for spawning a process and receiving its output, as well as exit codes.

### cockpit.spawn()

    process = cockpit.spawn(args, [options])

Spawns a process on the system.

The `args` should be an array starting with the executable and containing all the arguments to pass on the command line. If `args` is a string then it is interpreted as an executable name. The optional `options` argument is a javascript plain object and can contain any of the following fields:

`"binary"`

  If set to `true` then handle the input and output of the process as arrays of binary bytes.

`"directory"`

  The directory to spawn the process in.

`"err"`

  Controls where the standard error is sent. By default it is logged to the journal. If set to `"out"` it is included in with the output data. If set to `"ignore"` then the error output is discarded. If set to `"message"`, then it will be returned as the error message. When the `"pty"` field is set, this field has no effect.

`"environ"`

  An optional array that contains strings to be used as additional environment variables for the new process. These are `"NAME=VALUE"` strings.

`"pty"`

  Launch the process in its own PTY terminal, and send/receive terminal input and output.

`"batch"`

  Batch data coming from the process in blocks of at least this size. This is not a guarantee. After a short timeout the data will be sent even if the data doesn’t match the batch size. Defaults to zero.

`"latency"`

  The timeout for flushing any cached data in milliseconds.

`"superuser"`

  Set to `"require"` to spawn the process as root instead of the logged in user. If the currently logged in user is not permitted to become root (eg: via `pkexec`) then the `client` will immediately be closed with a `"access-denied"` problem code. + Set to `"try"` to try to run the process as root, but if that fails, fall back to an unprivileged process.

The spawned process is a promise that will complete if the process exits successfully, or fail if there’s a problem. Some additional methods besides the standard promise methods are documented below.

The standard output of the process is made available via the spawned process object. Any non-UTF8 output from the process will be coerced into textual form. It is highly recommended that only textual output be produced by the command. The standard error is logged to the journal.

### cockpit.script()

    process = cockpit.script(script, [args], [options])

Run a shell script on the system.

This function spawns a Bourne shell script process. The full text of the `/bin/sh` shell script should be passed in as the first argument. The `args` can be an array of arguments, not including the executable, which are passed to the script as `$1`, `$2` and so on. Shebang options are not used or respected.

The `options` is an optional javascript plain object and can include any of the fields listed for the `cockpit.spawn()` function.

The spawned process is a promise that will complete if the script exits successfully, or fail if there’s a problem. Some additional methods besides the standard promise methods are documented below.

The standard output of the process is made available via the spawned process object. Any non-UTF8 output from the process will be coerced into textual form. It is highly recommended that only textual output be produced by the command. The standard error is logged to the journal by default.

### process.then()

    process.then((data[, message]) => { ... })

This is a standard promise method. It sets up a handler to be called when the process finishes successfully.

The `data` argument contains the standard output of the process. If it a string, unless the process was opened in binary mode, in which case the `data` is an array of bytes. If a `process.stream()` handler is set up, then any standard output data consumed by the handler will not be included in the `data` argument.

If the process was spawned with the `"err"` option set to `"message"` then the second argument will contain the standard error output of the process.

### process.catch()

    process.catch((exception[, data]) => { ... })

This is a standard Promise method. It sets up a handler to be called when the process fails, terminates or exits.

The `exception` object passed to the handler can have the following fields:

`message`

  A message describing the exception. If the process was spawned with the `"err"` option set to `"message"` then the second argument will contain the standard error output of the process.

`problem`

  A problem code string when a problem occurred starting or communicating with the process. This is `null` if the process exited or was terminated.

`exit_status`

  The numeric exit status of the process. This is `null` if the process did not exit.

`exit_signal`

  A string representing a unix signal that caused the process to terminate. This is `null` if the process did not terminate because of a signal.

If the process actually ran and produced output before failing, it will be available in the `data` argument. Otherwise this argument will be `undefined`.

### process.stream()

    process.stream(data => { ... })

This sets up a handler to be called when the process has standard output. The handler will be called multiple times. The handler will be called regardless of whether the process ends up exiting successfully or not.

Only one handler may be registered at a time. Registering an additional handler replaces the previous one. The handler receives either string `data` or an array of binary bytes as its argument. A stream handler may return a number, which indicates the number of characters or bytes consumed from `data`. Any data not consumed will be included again the next time the handler is called.

If a `process.stream()` handler is set up, then the `process.then()` handlers will only get any remaining data not consumed by the stream handler.

### process.input()

    process.input(data, [stream])

This method writes `data` to the standard input of the process. If `data` is `null` or `undefined` it is not sent. The `data` should be a string or an array of bytes if the process was opened in binary mode.

If `stream` is set to `true` then this function may be called again with further input. Otherwise the standard input of the process is closed.

### process.close()

    process.close([problem])

Close the process by closing its standard input and output. If `problem` is specified it should be a standard problem code string. In this case the process will be terminated with a signal.

## cockpit.js: Utilities

Various utility functions

### cockpit.format()

    string = cockpit.format(template, args)
    string = cockpit.format(template, [arg, ...])

Format a string interpolating `args` into `template` using shell like syntax. The `args` may be either an array or javascript object. The `template` can contain fields that look like `$name` or `${name}` or `$0`. Numeric fields are used with array `args` and start at zero.

In the second form, multiple `arg` arguments may be passed directly, and interpolated as as numeric fields in the `template`.

All falsy arguments except the numbers `0` and `0.0`are replaced by an empty string.

### cockpit.format_number()

    string = cockpit.format_number(number, [precision])

Formats `number` into a displayable `string`. If the number is not an integer, it is rounded to the given number of decimal places, defaulting to 3. If the number is near zero, but not quite zero it is rounded to the smallest non-zero value of the given precision; i.e. ±0.001 for default precision 3.

If `number` is `null` or `undefined` an empty string will be returned.

### cockpit.format_bytes()

    string = cockpit.format_bytes(number, [options])

Formats `number` into a displayable `string` with a suffix, such as kB or MB.

By default, SI units are used. IEC units (1024-based) can be requested by including `base2: true` in `options`.

By default, non-integer numbers will be formatted with 3 digits of precision. This can be changed with `options.precision`.

If `number` is `null` or `undefined` an empty string will be returned.

### cockpit.format_bytes_per_sec()

    string = cockpit.format_bytes_per_sec(number, [options])

Format `number` of bytes into a displayable speed `string`.

This function is mostly equivalent to `cockpit.format_bytes()` but the returned value contains a unit like kB/s or MB/s.

### cockpit.format_bits_per_sec()

    string = cockpit.format_bits_per_sec(number, [options])

Format `number` of bits into a displayable speed `string`.

This function is mostly equivalent to `cockpit.format_bytes()` but the returned value contains a unit like kbps or Mbps.

This function does not support IEC units. `base2` may not be passed as part of `options`.

### cockpit.init()

    await cockpit.init();

    cockpit.init().then(() => { ... });

Requests initialization of the Cockpit client library. This will ensure that the transport is connected and we are ready to create channels. It also populates the `cockpit.info` field.

This function returns a promise. Initialization isn’t complete until the promise has resolved. You can either `await` it or call `.then()` on it.

### cockpit.info

    cockpit.info.channels[payload]

    cockpit.info.os_release[field]

    cockpit.info.user

    cockpit.info.ws.version

This object contains information about Cockpit itself. It is only available after cockpit.init() has been called and awaited.

`channels`

  This is a mapping of channel payload types (keys, strings) supported by the bridge to capabilities advertised by those channels (values, lists of strings). Channels are listed even if they don’t advertise any capabilities, making this useful as a way to determine which channel types are supported by the bridge.

`os_release`

  This is the data from the `/etc/os-release` or `/usr/lib/os-release` on the system that the bridge is running on. It is a mapping from the key names to their values. See the os-release Specification for information about the available keys.

`user`

  Contains information about the user we’re logged in as.

  `uid`

    This is unix user id as an integer.

  `gid`

    This is unix user group id as an integer.

  `name`

    This is the unix user name like `"root"`.

  `fullname`

    This is a readable name for the user, from the GECOS field.

  `group`

    This is the primary group name of the user.

  `groups`

    This is an array of group names to which the user belongs. The first item in this list is the primary group.

  `home`

    This is user’s home directory.

  `shell`

    This is unix user shell.

`ws`

  Contains information about the webserver Cockpit is being served with.

  `version`

    The version of the webserver.

### cockpit.event_target

    cockpit.event_target(object, [handlers])

Adds an EventTarget implementation to the `object`. Optionally store the handlers in `handlers` if its specified.