1 IPC interface (interprocess communication)
2 ==========================================
3 Michael Stapelberg <michael@i3wm.org>
6 This document describes how to interface with i3 from a separate process. This
7 is useful for example to remote-control i3 (to write test cases for example) or
8 to get various information like the current workspaces to implement an external
11 The method of choice for IPC in our case is a unix socket because it has very
12 little overhead on both sides and is usually available without headaches in
13 most languages. In the default configuration file, the ipc-socket gets created
14 in +/tmp/i3-%u.XXXXXX/ipc-socket.%p+ where +%u+ is your UNIX username, +%p+ is
15 the PID of i3 and XXXXXX is a string of random characters from the portable
16 filename character set (see mkdtemp(3)). You can get the socketpath from i3 by
17 calling +i3 --get-socketpath+.
19 All i3 utilities, like +i3-msg+ and +i3-input+ will read the +I3_SOCKET_PATH+
20 X11 property, stored on the X11 root window.
23 .Use an existing library!
24 There are existing libraries for many languages. You can have a look at
25 <<libraries>> or search the web if your language of choice is not mentioned.
26 Usually, it is not necessary to implement low-level communication with i3
29 == Establishing a connection
31 To establish a connection, simply open the IPC socket. The following code
32 snippet illustrates this in Perl:
34 -------------------------------------------------------------
36 chomp(my $path = qx(i3 --get-socketpath));
37 my $sock = IO::Socket::UNIX->new(Peer => $path);
38 -------------------------------------------------------------
40 == Sending messages to i3
42 To send a message to i3, you have to format in the binary message format which
43 i3 expects. This format specifies a magic string in the beginning to ensure
44 the integrity of messages (to prevent follow-up errors). Following the magic
45 string comes the length of the payload of the message as 32-bit integer, and
46 the type of the message as 32-bit integer (the integers are not converted, so
47 they are in native byte order).
49 The magic string currently is "i3-ipc" and will only be changed when a change
50 in the IPC API is done which breaks compatibility (we hope that we don’t need
53 Currently implemented message types are the following:
56 The payload of the message is a command for i3 (like the commands you
57 can bind to keys in the configuration file) and will be executed
58 directly after receiving it.
60 Gets the current workspaces. The reply will be a JSON-encoded list of
61 workspaces (see the reply section).
63 Subscribes your connection to certain events. See <<events>> for a
64 description of this message and the concept of events.
66 Gets the current outputs. The reply will be a JSON-encoded list of outputs
67 (see the reply section).
69 Gets the layout tree. i3 uses a tree as data structure which includes
70 every container. The reply will be the JSON-encoded tree (see the reply
73 Gets a list of marks (identifiers for containers to easily jump to them
74 later). The reply will be a JSON-encoded list of window marks (see
77 Gets the configuration (as JSON map) of the workspace bar with the
78 given ID. If no ID is provided, an array with all configured bar IDs is
81 Gets the version of i3. The reply will be a JSON-encoded dictionary
82 with the major, minor, patch and human-readable version.
84 So, a typical message could look like this:
85 --------------------------------------------------
86 "i3-ipc" <message length> <message type> <payload>
87 --------------------------------------------------
90 ------------------------------------------------------------------------------
91 00000000 69 33 2d 69 70 63 04 00 00 00 00 00 00 00 65 78 |i3-ipc........ex|
93 ------------------------------------------------------------------------------
95 To generate and send such a message, you could use the following code in Perl:
96 ------------------------------------------------------------
97 sub format_ipc_command {
100 # Get the real byte count (vs. amount of characters)
101 { use bytes; $len = length($msg); }
102 return "i3-ipc" . pack("LL", $len, 0) . $msg;
105 $sock->write(format_ipc_command("exit"));
106 ------------------------------------------------------------------------------
108 == Receiving replies from i3
110 Replies from i3 usually consist of a simple string (the length of the string
111 is the message_length, so you can consider them length-prefixed) which in turn
112 contain the JSON serialization of a data structure. For example, the
113 GET_WORKSPACES message returns an array of workspaces (each workspace is a map
114 with certain attributes).
118 The reply format is identical to the normal message format. There also is
119 the magic string, then the message length, then the message type and the
122 The following reply types are implemented:
125 Confirmation/Error code for the COMMAND message.
127 Reply to the GET_WORKSPACES message.
129 Confirmation/Error code for the SUBSCRIBE message.
131 Reply to the GET_OUTPUTS message.
133 Reply to the GET_TREE message.
135 Reply to the GET_MARKS message.
137 Reply to the GET_BAR_CONFIG message.
139 Reply to the GET_VERSION message.
143 The reply consists of a single serialized map. At the moment, the only
144 property is +success (bool)+, but this will be expanded in future versions.
153 The reply consists of a serialized list of workspaces. Each workspace has the
154 following properties:
157 The logical number of the workspace. Corresponds to the command
158 to switch to this workspace.
160 The name of this workspace (by default num+1), as changed by the
161 user. Encoded in UTF-8.
163 Whether this workspace is currently visible on an output (multiple
164 workspaces can be visible at the same time).
166 Whether this workspace currently has the focus (only one workspace
167 can have the focus at the same time).
169 Whether a window on this workspace has the "urgent" flag set.
171 The rectangle of this workspace (equals the rect of the output it
172 is on), consists of x, y, width, height.
174 The video output this workspace is on (LVDS1, VGA1, …).
212 The reply consists of a single serialized map. The only property is
213 +success (bool)+, indicating whether the subscription was successful (the
214 default) or whether a JSON parse error occurred.
223 The reply consists of a serialized list of outputs. Each output has the
224 following properties:
227 The name of this output (as seen in +xrandr(1)+). Encoded in UTF-8.
229 Whether this output is currently active (has a valid mode).
230 current_workspace (integer)::
231 The current workspace which is visible on this output. +null+ if the
232 output is not active.
234 The rectangle of this output (equals the rect of the output it
235 is on), consists of x, y, width, height.
243 "current_workspace": 4,
254 "current_workspace": 1,
267 The reply consists of a serialized tree. Each node in the tree (representing
268 one container) has at least the properties listed below. While the nodes might
269 have more properties, please do not use any properties which are not documented
270 here. They are not yet finalized and will probably change!
273 The internal ID (actually a C pointer value) of this container. Do not
274 make any assumptions about it. You can use it to (re-)identify and
275 address containers when talking to i3.
277 The internal name of this container. For all containers which are part
278 of the tree structure down to the workspace contents, this is set to a
279 nice human-readable name of the container.
280 For containers that have an X11 window, the content is the title
281 (_NET_WM_NAME property) of that window.
282 For all other containers, the content is not defined (yet).
284 Type of this container. Can be one of "root", "output", "con",
285 "floating_con", "workspace" or "dockarea".
287 Can be either "normal", "none" or "1pixel", dependending on the
288 container’s border style.
289 current_border_width (integer)::
290 Number of pixels of the border width.
292 Can be either "splith", "splitv", "stacked", "tabbed", "dockarea" or
294 Other values might be possible in the future, should we add new
296 orientation (string)::
297 Can be either "none" (for non-split containers), "horizontal" or
299 THIS FIELD IS OBSOLETE. It is still present, but your code should not
300 use it. Instead, rely on the layout field.
302 The percentage which this container takes in its parent. A value of
303 +null+ means that the percent property does not make sense for this
304 container, for example for the root container.
306 The absolute display coordinates for this container. Display
307 coordinates means that when you have two 1600x1200 monitors on a single
308 X11 Display (the standard way), the coordinates of the first window on
309 the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
312 The coordinates of the *actual client window* inside its container.
313 These coordinates are relative to the container and do not include the
314 window decoration (which is actually rendered on the parent container).
315 So, when using the +default+ layout, you will have a 2 pixel border on
316 each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
317 "height": 366 }+ (for example).
319 The original geometry the window specified when i3 mapped it. Used when
320 switching a window to floating mode, for example.
322 The X11 window ID of the *actual client window* inside this container.
323 This field is set to null for split containers or otherwise empty
324 containers. This ID corresponds to what xwininfo(1) and other
325 X11-related tools display (usually in hex).
327 Whether this container (window or workspace) has the urgency hint set.
329 Whether this container is currently focused.
331 Please note that in the following example, I have left out some keys/values
332 which are not relevant for the type of the node. Otherwise, the example would
333 be by far too long (it already is quite long, despite showing only 1 window and
336 It is useful to have an overview of the structure before taking a look at the
350 -----------------------
377 "layout": "dockarea",
378 "orientation": "vertical",
401 "orientation": "horizontal",
408 "floating_nodes": [],
432 "name": "bottomdock",
433 "layout": "dockarea",
434 "orientation": "vertical",
461 ------------------------
465 The reply consists of a single array of strings for each container that has a
466 mark. A mark can only be set on one container, so the array is unique.
467 The order of that array is undefined.
469 If no window has a mark the response will be the empty array [].
473 This can be used by third-party workspace bars (especially i3bar, but others
474 are free to implement compatible alternatives) to get the +bar+ block
475 configuration from i3.
477 Depending on the input, the reply is either:
480 An array of configured bar IDs
482 A JSON map containing the configuration for the specified bar.
484 Each bar configuration has the following properties:
487 The ID for this bar. Included in case you request multiple
488 configurations and want to differentiate the different replies.
490 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
491 does not show unless a specific key is pressed).
493 Either +bottom+ or +top+ at the moment.
494 status_command (string)::
495 Command which will be run to generate a statusline. Each line on stdout
496 of this command will be displayed in the bar. At the moment, no
497 formatting is supported.
499 The font to use for text on the bar.
500 workspace_buttons (boolean)::
501 Display workspace buttons or not? Defaults to true.
502 binding_mode_indicator (boolean)::
503 Display the mode indicator or not? Defaults to true.
505 Should the bar enable verbose output for debugging? Defaults to false.
507 Contains key/value pairs of colors. Each value is a color code in hex,
508 formatted #rrggbb (like in HTML).
510 The following colors can be configured at the moment:
513 Background color of the bar.
515 Text color to be used for the statusline.
517 Text color to be used for the separator.
518 focused_workspace_text/focused_workspace_bg::
519 Text color/background color for a workspace button when the workspace
521 active_workspace_text/active_workspace_bg::
522 Text color/background color for a workspace button when the workspace
523 is active (visible) on some output, but the focus is on another one.
524 You can only tell this apart from the focused workspace when you are
525 using multiple monitors.
526 inactive_workspace_text/inactive_workspace_bg::
527 Text color/background color for a workspace button when the workspace
528 does not have focus and is not active (visible) on any output. This
529 will be the case for most workspaces.
530 urgent_workspace_text/urgent_workspace_bar::
531 Text color/background color for workspaces which contain at least one
532 window with the urgency hint set.
535 *Example of configured bars:*
540 *Example of bar configuration:*
545 "position": "bottom",
546 "status_command": "i3status",
547 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
548 "workspace_buttons": true,
549 "binding_mode_indicator": true,
552 "background": "#c0c0c0",
553 "statusline": "#00ff00",
554 "focused_workspace_text": "#ffffff",
555 "focused_workspace_bg": "#000000"
562 The reply consists of a single JSON dictionary with the following keys:
565 The major version of i3, such as +4+.
567 The minor version of i3, such as +2+. Changes in the IPC interface (new
568 features) will only occur with new minor (or major) releases. However,
569 bugfixes might be introduced in patch releases, too.
571 The patch version of i3, such as +1+ (when the complete version is
572 +4.2.1+). For versions such as +4.2+, patch will be set to +0+.
573 human_readable (string)::
574 A human-readable version of i3 containing the precise git version,
575 build date and branch name. When you need to display the i3 version to
576 your users, use the human-readable version whenever possible (since
577 this is what +i3 --version+ displays, too).
582 "human_readable" : "4.2-169-gf80b877 (2012-08-05, branch \"next\")",
593 To get informed when certain things happen in i3, clients can subscribe to
594 events. Events consist of a name (like "workspace") and an event reply type
595 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
596 as replies to specific commands. However, the highest bit of the message type
597 is set to 1 to indicate that this is an event reply instead of a normal reply.
599 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
600 that the requests to i3 are processed in order. This means, the following
601 situation can happen: You send a GET_WORKSPACES request but you receive a
602 "workspace" event before receiving the reply to GET_WORKSPACES. If your
603 program does not want to cope which such kinds of race conditions (an
604 event based library may not have a problem here), I suggest you create a
605 separate connection to receive events.
607 === Subscribing to events
609 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
610 you can register to an event.
613 ---------------------------------
615 payload: [ "workspace", "focus" ]
616 ---------------------------------
621 The numbers in parenthesis is the event type (keep in mind that you need to
622 strip the highest bit first).
625 Sent when the user switches to a different workspace, when a new
626 workspace is initialized or when a workspace is removed (because the
627 last client vanished).
629 Sent when RandR issues a change notification (of either screens,
630 outputs, CRTCs or output properties).
632 Sent whenever i3 changes its binding mode.
634 Sent when a client's window is successfully reparented (that is when i3
635 has finished fitting it into a container).
636 barconfig_update (4)::
637 Sent when the hidden_state or mode field in the barconfig of any bar
638 instance was updated.
641 --------------------------------------------------------------------
642 # the appropriate 4 bytes read from the socket are stored in $input
644 # unpack a 32-bit unsigned integer
645 my $message_type = unpack("L", $input);
647 # check if the highest bit is 1
648 my $is_event = (($message_type >> 31) == 1);
651 my $event_type = ($message_type & 0x7F);
654 say "Received event of type $event_type";
656 --------------------------------------------------------------------
660 This event consists of a single serialized map containing a property
661 +change (string)+ which indicates the type of the change ("focus", "init",
664 Moreover, when the change is "focus", an +old (object)+ and a +current
665 (object)+ properties will be present with the previous and current
666 workspace respectively. When the first switch occurs (when i3 focuses
667 the workspace visible at the beginning) there is no previous
668 workspace, and the +old+ property will be set to +null+. Also note
669 that if the previous is empty it will get destroyed when switching,
670 but will still be present in the "old" property.
673 ---------------------
687 ---------------------
691 This event consists of a single serialized map containing a property
692 +change (string)+ which indicates the type of the change (currently only
696 ---------------------------
697 { "change": "unspecified" }
698 ---------------------------
702 This event consists of a single serialized map containing a property
703 +change (string)+ which holds the name of current mode in use. The name
704 is the same as specified in config when creating a mode. The default
705 mode is simply named default.
708 ---------------------------
709 { "change": "default" }
710 ---------------------------
714 This event consists of a single serialized map containing a property
715 +change (string)+ which currently can indicate only that a new window
716 has been successfully reparented (the value will be "new").
718 Additionally a +container (object)+ field will be present, which consists
719 of the window's parent container. Be aware that the container will hold
720 the initial name of the newly reparented window (e.g. if you run urxvt
721 with a shell that changes the title, you will still at this point get the
722 window title as "urxvt").
725 ---------------------------
734 ---------------------------
736 === barconfig_update event
738 This event consists of a single serialized map reporting on options from the
739 barconfig of the specified bar_id that were updated in i3. The map always
740 consists of a property +id (string)+, which specifies to which bar instance the
741 sent config update belongs, a property +hidden_state (string)+, which indicates
742 the hidden_state of an i3bar instance, and a property +mode (string)+, which
743 corresponds to the current mode.
746 ---------------------------
749 "hidden_state": "hide"
752 ---------------------------
754 == See also (existing libraries)
758 For some languages, libraries are available (so you don’t have to implement
759 all this on your own). This list names some (if you wrote one, please let me
763 i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
764 However, there is no library yet.
766 http://github.com/badboy/i3-ipc
768 https://metacpan.org/module/AnyEvent::I3
770 * https://github.com/whitelynx/i3ipc
771 * https://github.com/ziberna/i3-py (includes higher-level features)
773 * https://github.com/proxypoke/i3ipc