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 list of serialized maps for each command that was
144 parsed. Each has the property +success (bool)+ and may also include a
145 human-readable error message in the property +error (string)+.
149 [{ "success": true }]
154 The reply consists of a serialized list of workspaces. Each workspace has the
155 following properties:
158 The logical number of the workspace. Corresponds to the command
159 to switch to this workspace. For named workspaces, this will be -1.
161 The name of this workspace (by default num+1), as changed by the
162 user. Encoded in UTF-8.
164 Whether this workspace is currently visible on an output (multiple
165 workspaces can be visible at the same time).
167 Whether this workspace currently has the focus (only one workspace
168 can have the focus at the same time).
170 Whether a window on this workspace has the "urgent" flag set.
172 The rectangle of this workspace (equals the rect of the output it
173 is on), consists of x, y, width, height.
175 The video output this workspace is on (LVDS1, VGA1, …).
213 The reply consists of a single serialized map. The only property is
214 +success (bool)+, indicating whether the subscription was successful (the
215 default) or whether a JSON parse error occurred.
224 The reply consists of a serialized list of outputs. Each output has the
225 following properties:
228 The name of this output (as seen in +xrandr(1)+). Encoded in UTF-8.
230 Whether this output is currently active (has a valid mode).
231 current_workspace (string)::
232 The name of the current workspace that is visible on this output. +null+ if
233 the output is not active.
235 The rectangle of this output (equals the rect of the output it
236 is on), consists of x, y, width, height.
244 "current_workspace": "4",
255 "current_workspace": "1",
268 The reply consists of a serialized tree. Each node in the tree (representing
269 one container) has at least the properties listed below. While the nodes might
270 have more properties, please do not use any properties which are not documented
271 here. They are not yet finalized and will probably change!
274 The internal ID (actually a C pointer value) of this container. Do not
275 make any assumptions about it. You can use it to (re-)identify and
276 address containers when talking to i3.
278 The internal name of this container. For all containers which are part
279 of the tree structure down to the workspace contents, this is set to a
280 nice human-readable name of the container.
281 For containers that have an X11 window, the content is the title
282 (_NET_WM_NAME property) of that window.
283 For all other containers, the content is not defined (yet).
285 Type of this container. Can be one of "root", "output", "con",
286 "floating_con", "workspace" or "dockarea".
288 Can be either "normal", "none" or "1pixel", dependending on the
289 container’s border style.
290 current_border_width (integer)::
291 Number of pixels of the border width.
293 Can be either "splith", "splitv", "stacked", "tabbed", "dockarea" or
295 Other values might be possible in the future, should we add new
297 orientation (string)::
298 Can be either "none" (for non-split containers), "horizontal" or
300 THIS FIELD IS OBSOLETE. It is still present, but your code should not
301 use it. Instead, rely on the layout field.
303 The percentage which this container takes in its parent. A value of
304 +null+ means that the percent property does not make sense for this
305 container, for example for the root container.
307 The absolute display coordinates for this container. Display
308 coordinates means that when you have two 1600x1200 monitors on a single
309 X11 Display (the standard way), the coordinates of the first window on
310 the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
313 The coordinates of the *actual client window* inside its container.
314 These coordinates are relative to the container and do not include the
315 window decoration (which is actually rendered on the parent container).
316 So, when using the +default+ layout, you will have a 2 pixel border on
317 each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
318 "height": 366 }+ (for example).
320 The coordinates of the *window decoration* inside its container. These
321 coordinates are relative to the container and do not include the actual
324 The original geometry the window specified when i3 mapped it. Used when
325 switching a window to floating mode, for example.
327 The X11 window ID of the *actual client window* inside this container.
328 This field is set to null for split containers or otherwise empty
329 containers. This ID corresponds to what xwininfo(1) and other
330 X11-related tools display (usually in hex).
332 Whether this container (window or workspace) has the urgency hint set.
334 Whether this container is currently focused.
336 Please note that in the following example, I have left out some keys/values
337 which are not relevant for the type of the node. Otherwise, the example would
338 be by far too long (it already is quite long, despite showing only 1 window and
341 It is useful to have an overview of the structure before taking a look at the
355 -----------------------
382 "layout": "dockarea",
383 "orientation": "vertical",
406 "orientation": "horizontal",
413 "floating_nodes": [],
437 "name": "bottomdock",
438 "layout": "dockarea",
439 "orientation": "vertical",
466 ------------------------
470 The reply consists of a single array of strings for each container that has a
471 mark. A mark can only be set on one container, so the array is unique.
472 The order of that array is undefined.
474 If no window has a mark the response will be the empty array [].
478 This can be used by third-party workspace bars (especially i3bar, but others
479 are free to implement compatible alternatives) to get the +bar+ block
480 configuration from i3.
482 Depending on the input, the reply is either:
485 An array of configured bar IDs
487 A JSON map containing the configuration for the specified bar.
489 Each bar configuration has the following properties:
492 The ID for this bar. Included in case you request multiple
493 configurations and want to differentiate the different replies.
495 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
496 does not show unless a specific key is pressed).
498 Either +bottom+ or +top+ at the moment.
499 status_command (string)::
500 Command which will be run to generate a statusline. Each line on stdout
501 of this command will be displayed in the bar. At the moment, no
502 formatting is supported.
504 The font to use for text on the bar.
505 workspace_buttons (boolean)::
506 Display workspace buttons or not? Defaults to true.
507 binding_mode_indicator (boolean)::
508 Display the mode indicator or not? Defaults to true.
510 Should the bar enable verbose output for debugging? Defaults to false.
512 Contains key/value pairs of colors. Each value is a color code in hex,
513 formatted #rrggbb (like in HTML).
515 The following colors can be configured at the moment:
518 Background color of the bar.
520 Text color to be used for the statusline.
522 Text color to be used for the separator.
523 focused_workspace_text/focused_workspace_bg::
524 Text color/background color for a workspace button when the workspace
526 active_workspace_text/active_workspace_bg::
527 Text color/background color for a workspace button when the workspace
528 is active (visible) on some output, but the focus is on another one.
529 You can only tell this apart from the focused workspace when you are
530 using multiple monitors.
531 inactive_workspace_text/inactive_workspace_bg::
532 Text color/background color for a workspace button when the workspace
533 does not have focus and is not active (visible) on any output. This
534 will be the case for most workspaces.
535 urgent_workspace_text/urgent_workspace_bar::
536 Text color/background color for workspaces which contain at least one
537 window with the urgency hint set.
540 *Example of configured bars:*
545 *Example of bar configuration:*
550 "position": "bottom",
551 "status_command": "i3status",
552 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
553 "workspace_buttons": true,
554 "binding_mode_indicator": true,
557 "background": "#c0c0c0",
558 "statusline": "#00ff00",
559 "focused_workspace_text": "#ffffff",
560 "focused_workspace_bg": "#000000"
567 The reply consists of a single JSON dictionary with the following keys:
570 The major version of i3, such as +4+.
572 The minor version of i3, such as +2+. Changes in the IPC interface (new
573 features) will only occur with new minor (or major) releases. However,
574 bugfixes might be introduced in patch releases, too.
576 The patch version of i3, such as +1+ (when the complete version is
577 +4.2.1+). For versions such as +4.2+, patch will be set to +0+.
578 human_readable (string)::
579 A human-readable version of i3 containing the precise git version,
580 build date and branch name. When you need to display the i3 version to
581 your users, use the human-readable version whenever possible (since
582 this is what +i3 --version+ displays, too).
587 "human_readable" : "4.2-169-gf80b877 (2012-08-05, branch \"next\")",
598 To get informed when certain things happen in i3, clients can subscribe to
599 events. Events consist of a name (like "workspace") and an event reply type
600 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
601 as replies to specific commands. However, the highest bit of the message type
602 is set to 1 to indicate that this is an event reply instead of a normal reply.
604 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
605 that the requests to i3 are processed in order. This means, the following
606 situation can happen: You send a GET_WORKSPACES request but you receive a
607 "workspace" event before receiving the reply to GET_WORKSPACES. If your
608 program does not want to cope which such kinds of race conditions (an
609 event based library may not have a problem here), I suggest you create a
610 separate connection to receive events.
612 === Subscribing to events
614 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
615 you can register to an event.
618 ---------------------------------
620 payload: [ "workspace", "output" ]
621 ---------------------------------
626 The numbers in parenthesis is the event type (keep in mind that you need to
627 strip the highest bit first).
630 Sent when the user switches to a different workspace, when a new
631 workspace is initialized or when a workspace is removed (because the
632 last client vanished).
634 Sent when RandR issues a change notification (of either screens,
635 outputs, CRTCs or output properties).
637 Sent whenever i3 changes its binding mode.
639 Sent when a client's window is successfully reparented (that is when i3
640 has finished fitting it into a container), when a window received input
641 focus or when certain properties of the window have changed.
642 barconfig_update (4)::
643 Sent when the hidden_state or mode field in the barconfig of any bar
644 instance was updated and when the config is reloaded.
646 Sent when a configured command binding is triggered with the keyboard or
650 --------------------------------------------------------------------
651 # the appropriate 4 bytes read from the socket are stored in $input
653 # unpack a 32-bit unsigned integer
654 my $message_type = unpack("L", $input);
656 # check if the highest bit is 1
657 my $is_event = (($message_type >> 31) == 1);
660 my $event_type = ($message_type & 0x7F);
663 say "Received event of type $event_type";
665 --------------------------------------------------------------------
669 This event consists of a single serialized map containing a property
670 +change (string)+ which indicates the type of the change ("focus", "init",
673 Moreover, when the change is "focus", an +old (object)+ and a +current
674 (object)+ properties will be present with the previous and current
675 workspace respectively. When the first switch occurs (when i3 focuses
676 the workspace visible at the beginning) there is no previous
677 workspace, and the +old+ property will be set to +null+. Also note
678 that if the previous is empty it will get destroyed when switching,
679 but will still be present in the "old" property.
682 ---------------------
696 ---------------------
700 This event consists of a single serialized map containing a property
701 +change (string)+ which indicates the type of the change (currently only
705 ---------------------------
706 { "change": "unspecified" }
707 ---------------------------
711 This event consists of a single serialized map containing a property
712 +change (string)+ which holds the name of current mode in use. The name
713 is the same as specified in config when creating a mode. The default
714 mode is simply named default.
717 ---------------------------
718 { "change": "default" }
719 ---------------------------
723 This event consists of a single serialized map containing a property
724 +change (string)+ which indicates the type of the change
726 * +new+ - the window has become managed by i3
727 * +close+ - the window has closed
728 * +focus+ - the window has received input focus
729 * +title+ - the window's title has changed
730 * +fullscreen_mode+ - the window has entered or exited fullscreen mode
731 * +move+ - the window has changed its position in the tree
732 * +floating+ - the window has transitioned to or from floating
733 * +urgent+ - the window has become urgent or lost its urgent status
735 Additionally a +container (object)+ field will be present, which consists
736 of the window's parent container. Be aware that for the "new" event, the
737 container will hold the initial name of the newly reparented window (e.g.
738 if you run urxvt with a shell that changes the title, you will still at
739 this point get the window title as "urxvt").
742 ---------------------------
751 ---------------------------
753 === barconfig_update event
755 This event consists of a single serialized map reporting on options from the
756 barconfig of the specified bar_id that were updated in i3. This event is the
757 same as a +GET_BAR_CONFIG+ reply for the bar with the given id.
761 This event consists of a single serialized map reporting on the details of a
762 binding that ran a command because of user input. The +change (sring)+ field
763 indicates what sort of binding event was triggered (right now it will always be
764 +"run"+ but may be expanded in the future).
766 The +binding (object)+ field contains details about the binding that was run:
769 The i3 command that is configured to run for this binding.
770 mods (array of strings)::
771 The modifier keys that were configured with this binding.
772 input_code (integer)::
773 If the binding was configured with +bindcode+, this will be the key code
774 that was given for the binding. If the binding is a mouse binding, it will be
775 the number of the mouse button that was pressed. Otherwise it will be 0.
776 symbol (string or null)::
777 If this is a keyboard binding that was configured with +bindsym+, this
778 field will contain the given symbol. Otherwise it will be +null+.
779 input_type (string)::
780 This will be +"keyboard"+ or +"mouse"+ depending on whether or not this was
781 a keyboard or a mouse binding.
784 ---------------------------
795 "input_type": "keyboard"
798 ---------------------------
800 == See also (existing libraries)
804 For some languages, libraries are available (so you don’t have to implement
805 all this on your own). This list names some (if you wrote one, please let me
809 * i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
810 * https://github.com/acrisci/i3ipc-glib
812 * https://github.com/proxypoke/i3ipc
814 * https://github.com/acrisci/i3ipc-gjs
816 * https://github.com/acrisci/i3ipc-lua
818 * https://metacpan.org/module/AnyEvent::I3
820 * https://github.com/acrisci/i3ipc-python
821 * https://github.com/whitelynx/i3ipc (not maintained)
822 * https://github.com/ziberna/i3-py (not maintained)
824 * http://github.com/badboy/i3-ipc
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