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 original geometry the window specified when i3 mapped it. Used when
321 switching a window to floating mode, for example.
323 The X11 window ID of the *actual client window* inside this container.
324 This field is set to null for split containers or otherwise empty
325 containers. This ID corresponds to what xwininfo(1) and other
326 X11-related tools display (usually in hex).
328 Whether this container (window or workspace) has the urgency hint set.
330 Whether this container is currently focused.
332 Please note that in the following example, I have left out some keys/values
333 which are not relevant for the type of the node. Otherwise, the example would
334 be by far too long (it already is quite long, despite showing only 1 window and
337 It is useful to have an overview of the structure before taking a look at the
351 -----------------------
378 "layout": "dockarea",
379 "orientation": "vertical",
402 "orientation": "horizontal",
409 "floating_nodes": [],
433 "name": "bottomdock",
434 "layout": "dockarea",
435 "orientation": "vertical",
462 ------------------------
466 The reply consists of a single array of strings for each container that has a
467 mark. A mark can only be set on one container, so the array is unique.
468 The order of that array is undefined.
470 If no window has a mark the response will be the empty array [].
474 This can be used by third-party workspace bars (especially i3bar, but others
475 are free to implement compatible alternatives) to get the +bar+ block
476 configuration from i3.
478 Depending on the input, the reply is either:
481 An array of configured bar IDs
483 A JSON map containing the configuration for the specified bar.
485 Each bar configuration has the following properties:
488 The ID for this bar. Included in case you request multiple
489 configurations and want to differentiate the different replies.
491 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
492 does not show unless a specific key is pressed).
494 Either +bottom+ or +top+ at the moment.
495 status_command (string)::
496 Command which will be run to generate a statusline. Each line on stdout
497 of this command will be displayed in the bar. At the moment, no
498 formatting is supported.
500 The font to use for text on the bar.
501 workspace_buttons (boolean)::
502 Display workspace buttons or not? Defaults to true.
503 binding_mode_indicator (boolean)::
504 Display the mode indicator or not? Defaults to true.
506 Should the bar enable verbose output for debugging? Defaults to false.
508 Contains key/value pairs of colors. Each value is a color code in hex,
509 formatted #rrggbb (like in HTML).
511 The following colors can be configured at the moment:
514 Background color of the bar.
516 Text color to be used for the statusline.
518 Text color to be used for the separator.
519 focused_workspace_text/focused_workspace_bg::
520 Text color/background color for a workspace button when the workspace
522 active_workspace_text/active_workspace_bg::
523 Text color/background color for a workspace button when the workspace
524 is active (visible) on some output, but the focus is on another one.
525 You can only tell this apart from the focused workspace when you are
526 using multiple monitors.
527 inactive_workspace_text/inactive_workspace_bg::
528 Text color/background color for a workspace button when the workspace
529 does not have focus and is not active (visible) on any output. This
530 will be the case for most workspaces.
531 urgent_workspace_text/urgent_workspace_bar::
532 Text color/background color for workspaces which contain at least one
533 window with the urgency hint set.
536 *Example of configured bars:*
541 *Example of bar configuration:*
546 "position": "bottom",
547 "status_command": "i3status",
548 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
549 "workspace_buttons": true,
550 "binding_mode_indicator": true,
553 "background": "#c0c0c0",
554 "statusline": "#00ff00",
555 "focused_workspace_text": "#ffffff",
556 "focused_workspace_bg": "#000000"
563 The reply consists of a single JSON dictionary with the following keys:
566 The major version of i3, such as +4+.
568 The minor version of i3, such as +2+. Changes in the IPC interface (new
569 features) will only occur with new minor (or major) releases. However,
570 bugfixes might be introduced in patch releases, too.
572 The patch version of i3, such as +1+ (when the complete version is
573 +4.2.1+). For versions such as +4.2+, patch will be set to +0+.
574 human_readable (string)::
575 A human-readable version of i3 containing the precise git version,
576 build date and branch name. When you need to display the i3 version to
577 your users, use the human-readable version whenever possible (since
578 this is what +i3 --version+ displays, too).
583 "human_readable" : "4.2-169-gf80b877 (2012-08-05, branch \"next\")",
594 To get informed when certain things happen in i3, clients can subscribe to
595 events. Events consist of a name (like "workspace") and an event reply type
596 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
597 as replies to specific commands. However, the highest bit of the message type
598 is set to 1 to indicate that this is an event reply instead of a normal reply.
600 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
601 that the requests to i3 are processed in order. This means, the following
602 situation can happen: You send a GET_WORKSPACES request but you receive a
603 "workspace" event before receiving the reply to GET_WORKSPACES. If your
604 program does not want to cope which such kinds of race conditions (an
605 event based library may not have a problem here), I suggest you create a
606 separate connection to receive events.
608 === Subscribing to events
610 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
611 you can register to an event.
614 ---------------------------------
616 payload: [ "workspace", "focus" ]
617 ---------------------------------
622 The numbers in parenthesis is the event type (keep in mind that you need to
623 strip the highest bit first).
626 Sent when the user switches to a different workspace, when a new
627 workspace is initialized or when a workspace is removed (because the
628 last client vanished).
630 Sent when RandR issues a change notification (of either screens,
631 outputs, CRTCs or output properties).
633 Sent whenever i3 changes its binding mode.
635 Sent when a client's window is successfully reparented (that is when i3
636 has finished fitting it into a container), when a window received input
637 focus or when certain properties of the window have changed.
638 barconfig_update (4)::
639 Sent when the hidden_state or mode field in the barconfig of any bar
640 instance was updated and when the config is reloaded.
642 Sent when a configured command binding is triggered with the keyboard or
646 --------------------------------------------------------------------
647 # the appropriate 4 bytes read from the socket are stored in $input
649 # unpack a 32-bit unsigned integer
650 my $message_type = unpack("L", $input);
652 # check if the highest bit is 1
653 my $is_event = (($message_type >> 31) == 1);
656 my $event_type = ($message_type & 0x7F);
659 say "Received event of type $event_type";
661 --------------------------------------------------------------------
665 This event consists of a single serialized map containing a property
666 +change (string)+ which indicates the type of the change ("focus", "init",
669 Moreover, when the change is "focus", an +old (object)+ and a +current
670 (object)+ properties will be present with the previous and current
671 workspace respectively. When the first switch occurs (when i3 focuses
672 the workspace visible at the beginning) there is no previous
673 workspace, and the +old+ property will be set to +null+. Also note
674 that if the previous is empty it will get destroyed when switching,
675 but will still be present in the "old" property.
678 ---------------------
692 ---------------------
696 This event consists of a single serialized map containing a property
697 +change (string)+ which indicates the type of the change (currently only
701 ---------------------------
702 { "change": "unspecified" }
703 ---------------------------
707 This event consists of a single serialized map containing a property
708 +change (string)+ which holds the name of current mode in use. The name
709 is the same as specified in config when creating a mode. The default
710 mode is simply named default.
713 ---------------------------
714 { "change": "default" }
715 ---------------------------
719 This event consists of a single serialized map containing a property
720 +change (string)+ which indicates the type of the change
722 * +new+ - the window has become managed by i3
723 * +close+ - the window has closed
724 * +focus+ - the window has received input focus
725 * +title+ - the window's title has changed
726 * +fullscreen_mode+ - the window has entered or exited fullscreen mode
727 * +move+ - the window has changed its position in the tree
728 * +floating+ - the window has transitioned to or from floating
729 * +urgent+ - the window has become urgent or lost its urgent status
731 Additionally a +container (object)+ field will be present, which consists
732 of the window's parent container. Be aware that for the "new" event, the
733 container will hold the initial name of the newly reparented window (e.g.
734 if you run urxvt with a shell that changes the title, you will still at
735 this point get the window title as "urxvt").
738 ---------------------------
747 ---------------------------
749 === barconfig_update event
751 This event consists of a single serialized map reporting on options from the
752 barconfig of the specified bar_id that were updated in i3. This event is the
753 same as a +GET_BAR_CONFIG+ reply for the bar with the given id.
757 This event consists of a single serialized map reporting on the details of a
758 binding that ran a command because of user input. The +change (sring)+ field
759 indicates what sort of binding event was triggered (right now it will always be
760 +"run"+ but may be expanded in the future).
762 The +binding (object)+ field contains details about the binding that was run:
765 The i3 command that is configured to run for this binding.
766 mods (array of strings)::
767 The modifier keys that were configured with this binding.
768 input_code (integer)::
769 If the binding was configured with +bindcode+, this will be the key code
770 that was given for the binding. If the binding is a mouse binding, it will be
771 the number of the mouse button that was pressed. Otherwise it will be 0.
772 symbol (string or null)::
773 If this is a keyboard binding that was configured with +bindsym+, this
774 field will contain the given symbol. Otherwise it will be +null+.
775 input_type (string)::
776 This will be +"keyboard"+ or +"mouse"+ depending on whether or not this was
777 a keyboard or a mouse binding.
780 ---------------------------
791 "input_type": "keyboard"
794 ---------------------------
796 == See also (existing libraries)
800 For some languages, libraries are available (so you don’t have to implement
801 all this on your own). This list names some (if you wrote one, please let me
805 * i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
806 * https://github.com/acrisci/i3ipc-glib
808 * https://github.com/proxypoke/i3ipc
810 * https://github.com/acrisci/i3ipc-gjs
812 * https://github.com/acrisci/i3ipc-lua
814 * https://metacpan.org/module/AnyEvent::I3
816 * https://github.com/acrisci/i3ipc-python
817 * https://github.com/whitelynx/i3ipc (not maintained)
818 * https://github.com/ziberna/i3-py (not maintained)
820 * http://github.com/badboy/i3-ipc
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