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.
83 GET_BINDING_MODES (8)::
84 Gets a list of currently configured binding modes.
86 So, a typical message could look like this:
87 --------------------------------------------------
88 "i3-ipc" <message length> <message type> <payload>
89 --------------------------------------------------
92 ------------------------------------------------------------------------------
93 00000000 69 33 2d 69 70 63 04 00 00 00 00 00 00 00 65 78 |i3-ipc........ex|
95 ------------------------------------------------------------------------------
97 To generate and send such a message, you could use the following code in Perl:
98 ------------------------------------------------------------
99 sub format_ipc_command {
102 # Get the real byte count (vs. amount of characters)
103 { use bytes; $len = length($msg); }
104 return "i3-ipc" . pack("LL", $len, 0) . $msg;
107 $sock->write(format_ipc_command("exit"));
108 ------------------------------------------------------------------------------
110 == Receiving replies from i3
112 Replies from i3 usually consist of a simple string (the length of the string
113 is the message_length, so you can consider them length-prefixed) which in turn
114 contain the JSON serialization of a data structure. For example, the
115 GET_WORKSPACES message returns an array of workspaces (each workspace is a map
116 with certain attributes).
120 The reply format is identical to the normal message format. There also is
121 the magic string, then the message length, then the message type and the
124 The following reply types are implemented:
127 Confirmation/Error code for the COMMAND message.
129 Reply to the GET_WORKSPACES message.
131 Confirmation/Error code for the SUBSCRIBE message.
133 Reply to the GET_OUTPUTS message.
135 Reply to the GET_TREE message.
137 Reply to the GET_MARKS message.
139 Reply to the GET_BAR_CONFIG message.
141 Reply to the GET_VERSION message.
143 Reply to the GET_BINDING_MODES message.
147 The reply consists of a list of serialized maps for each command that was
148 parsed. Each has the property +success (bool)+ and may also include a
149 human-readable error message in the property +error (string)+.
153 [{ "success": true }]
158 The reply consists of a serialized list of workspaces. Each workspace has the
159 following properties:
162 The logical number of the workspace. Corresponds to the command
163 to switch to this workspace. For named workspaces, this will be -1.
165 The name of this workspace (by default num+1), as changed by the
166 user. Encoded in UTF-8.
168 Whether this workspace is currently visible on an output (multiple
169 workspaces can be visible at the same time).
171 Whether this workspace currently has the focus (only one workspace
172 can have the focus at the same time).
174 Whether a window on this workspace has the "urgent" flag set.
176 The rectangle of this workspace (equals the rect of the output it
177 is on), consists of x, y, width, height.
179 The video output this workspace is on (LVDS1, VGA1, …).
217 The reply consists of a single serialized map. The only property is
218 +success (bool)+, indicating whether the subscription was successful (the
219 default) or whether a JSON parse error occurred.
228 The reply consists of a serialized list of outputs. Each output has the
229 following properties:
232 The name of this output (as seen in +xrandr(1)+). Encoded in UTF-8.
234 Whether this output is currently active (has a valid mode).
235 current_workspace (string)::
236 The name of the current workspace that is visible on this output. +null+ if
237 the output is not active.
239 The rectangle of this output (equals the rect of the output it
240 is on), consists of x, y, width, height.
248 "current_workspace": "4",
259 "current_workspace": "1",
272 The reply consists of a serialized tree. Each node in the tree (representing
273 one container) has at least the properties listed below. While the nodes might
274 have more properties, please do not use any properties which are not documented
275 here. They are not yet finalized and will probably change!
278 The internal ID (actually a C pointer value) of this container. Do not
279 make any assumptions about it. You can use it to (re-)identify and
280 address containers when talking to i3.
282 The internal name of this container. For all containers which are part
283 of the tree structure down to the workspace contents, this is set to a
284 nice human-readable name of the container.
285 For containers that have an X11 window, the content is the title
286 (_NET_WM_NAME property) of that window.
287 For all other containers, the content is not defined (yet).
289 Type of this container. Can be one of "root", "output", "con",
290 "floating_con", "workspace" or "dockarea".
292 Can be either "normal", "none" or "pixel", depending on the
293 container’s border style.
294 current_border_width (integer)::
295 Number of pixels of the border width.
297 Can be either "splith", "splitv", "stacked", "tabbed", "dockarea" or
299 Other values might be possible in the future, should we add new
301 orientation (string)::
302 Can be either "none" (for non-split containers), "horizontal" or
304 THIS FIELD IS OBSOLETE. It is still present, but your code should not
305 use it. Instead, rely on the layout field.
307 The percentage which this container takes in its parent. A value of
308 +null+ means that the percent property does not make sense for this
309 container, for example for the root container.
311 The absolute display coordinates for this container. Display
312 coordinates means that when you have two 1600x1200 monitors on a single
313 X11 Display (the standard way), the coordinates of the first window on
314 the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
317 The coordinates of the *actual client window* inside its container.
318 These coordinates are relative to the container and do not include the
319 window decoration (which is actually rendered on the parent container).
320 So, when using the +default+ layout, you will have a 2 pixel border on
321 each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
322 "height": 366 }+ (for example).
324 The coordinates of the *window decoration* inside its container. These
325 coordinates are relative to the container and do not include the actual
328 The original geometry the window specified when i3 mapped it. Used when
329 switching a window to floating mode, for example.
331 The X11 window ID of the *actual client window* inside this container.
332 This field is set to null for split containers or otherwise empty
333 containers. This ID corresponds to what xwininfo(1) and other
334 X11-related tools display (usually in hex).
336 Whether this container (window or workspace) has the urgency hint set.
338 Whether this container is currently focused.
340 Please note that in the following example, I have left out some keys/values
341 which are not relevant for the type of the node. Otherwise, the example would
342 be by far too long (it already is quite long, despite showing only 1 window and
345 It is useful to have an overview of the structure before taking a look at the
359 -----------------------
386 "layout": "dockarea",
387 "orientation": "vertical",
410 "orientation": "horizontal",
417 "floating_nodes": [],
441 "name": "bottomdock",
442 "layout": "dockarea",
443 "orientation": "vertical",
470 ------------------------
474 The reply consists of a single array of strings for each container that has a
475 mark. A mark can only be set on one container, so the array is unique.
476 The order of that array is undefined.
478 If no window has a mark the response will be the empty array [].
482 This can be used by third-party workspace bars (especially i3bar, but others
483 are free to implement compatible alternatives) to get the +bar+ block
484 configuration from i3.
486 Depending on the input, the reply is either:
489 An array of configured bar IDs
491 A JSON map containing the configuration for the specified bar.
493 Each bar configuration has the following properties:
496 The ID for this bar. Included in case you request multiple
497 configurations and want to differentiate the different replies.
499 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
500 does not show unless a specific key is pressed).
502 Either +bottom+ or +top+ at the moment.
503 status_command (string)::
504 Command which will be run to generate a statusline. Each line on stdout
505 of this command will be displayed in the bar. At the moment, no
506 formatting is supported.
508 The font to use for text on the bar.
509 workspace_buttons (boolean)::
510 Display workspace buttons or not? Defaults to true.
511 binding_mode_indicator (boolean)::
512 Display the mode indicator or not? Defaults to true.
514 Should the bar enable verbose output for debugging? Defaults to false.
516 Contains key/value pairs of colors. Each value is a color code in hex,
517 formatted #rrggbb (like in HTML).
519 The following colors can be configured at the moment:
522 Background color of the bar.
524 Text color to be used for the statusline.
526 Text color to be used for the separator.
528 Background color of the bar on the currently focused monitor output.
530 Text color to be used for the statusline on the currently focused
533 Text color to be used for the separator on the currently focused
535 focused_workspace_text/focused_workspace_bg/focused_workspace_border::
536 Text/background/border color for a workspace button when the workspace
538 active_workspace_text/active_workspace_bg/active_workspace_border::
539 Text/background/border color for a workspace button when the workspace
540 is active (visible) on some output, but the focus is on another one.
541 You can only tell this apart from the focused workspace when you are
542 using multiple monitors.
543 inactive_workspace_text/inactive_workspace_bg/inactive_workspace_border::
544 Text/background/border color for a workspace button when the workspace
545 does not have focus and is not active (visible) on any output. This
546 will be the case for most workspaces.
547 urgent_workspace_text/urgent_workspace_bg/urgent_workspace_border::
548 Text/background/border color for workspaces which contain at least one
549 window with the urgency hint set.
550 binding_mode_text/binding_mode_bg/binding_mode_border::
551 Text/background/border color for the binding mode indicator.
554 *Example of configured bars:*
559 *Example of bar configuration:*
564 "position": "bottom",
565 "status_command": "i3status",
566 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
567 "workspace_buttons": true,
568 "binding_mode_indicator": true,
571 "background": "#c0c0c0",
572 "statusline": "#00ff00",
573 "focused_workspace_text": "#ffffff",
574 "focused_workspace_bg": "#000000"
581 The reply consists of a single JSON dictionary with the following keys:
584 The major version of i3, such as +4+.
586 The minor version of i3, such as +2+. Changes in the IPC interface (new
587 features) will only occur with new minor (or major) releases. However,
588 bugfixes might be introduced in patch releases, too.
590 The patch version of i3, such as +1+ (when the complete version is
591 +4.2.1+). For versions such as +4.2+, patch will be set to +0+.
592 human_readable (string)::
593 A human-readable version of i3 containing the precise git version,
594 build date and branch name. When you need to display the i3 version to
595 your users, use the human-readable version whenever possible (since
596 this is what +i3 --version+ displays, too).
597 loaded_config_file_name (string)::
598 The current config path.
603 "human_readable" : "4.2-169-gf80b877 (2012-08-05, branch \"next\")",
604 "loaded_config_file_name" : "/home/hwangcc23/.i3/config",
611 === BINDING_MODES reply
613 The reply consists of an array of all currently configured binding modes.
616 ---------------------
617 ["default", "resize"]
618 ---------------------
624 To get informed when certain things happen in i3, clients can subscribe to
625 events. Events consist of a name (like "workspace") and an event reply type
626 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
627 as replies to specific commands. However, the highest bit of the message type
628 is set to 1 to indicate that this is an event reply instead of a normal reply.
630 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
631 that the requests to i3 are processed in order. This means, the following
632 situation can happen: You send a GET_WORKSPACES request but you receive a
633 "workspace" event before receiving the reply to GET_WORKSPACES. If your
634 program does not want to cope which such kinds of race conditions (an
635 event based library may not have a problem here), I suggest you create a
636 separate connection to receive events.
638 === Subscribing to events
640 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
641 you can register to an event.
644 ---------------------------------
646 payload: [ "workspace", "output" ]
647 ---------------------------------
652 The numbers in parenthesis is the event type (keep in mind that you need to
653 strip the highest bit first).
656 Sent when the user switches to a different workspace, when a new
657 workspace is initialized or when a workspace is removed (because the
658 last client vanished).
660 Sent when RandR issues a change notification (of either screens,
661 outputs, CRTCs or output properties).
663 Sent whenever i3 changes its binding mode.
665 Sent when a client's window is successfully reparented (that is when i3
666 has finished fitting it into a container), when a window received input
667 focus or when certain properties of the window have changed.
668 barconfig_update (4)::
669 Sent when the hidden_state or mode field in the barconfig of any bar
670 instance was updated and when the config is reloaded.
672 Sent when a configured command binding is triggered with the keyboard or
676 --------------------------------------------------------------------
677 # the appropriate 4 bytes read from the socket are stored in $input
679 # unpack a 32-bit unsigned integer
680 my $message_type = unpack("L", $input);
682 # check if the highest bit is 1
683 my $is_event = (($message_type >> 31) == 1);
686 my $event_type = ($message_type & 0x7F);
689 say "Received event of type $event_type";
691 --------------------------------------------------------------------
695 This event consists of a single serialized map containing a property
696 +change (string)+ which indicates the type of the change ("focus", "init",
697 "empty", "urgent"). A +current (object)+ property will be present with the
698 affected workspace whenever the type of event affects a workspace (otherwise,
701 When the change is "focus", an +old (object)+ property will be present with the
702 previous workspace. When the first switch occurs (when i3 focuses the
703 workspace visible at the beginning) there is no previous workspace, and the
704 +old+ property will be set to +null+. Also note that if the previous is empty
705 it will get destroyed when switching, but will still be present in the "old"
709 ---------------------
723 ---------------------
727 This event consists of a single serialized map containing a property
728 +change (string)+ which indicates the type of the change (currently only
732 ---------------------------
733 { "change": "unspecified" }
734 ---------------------------
738 This event consists of a single serialized map containing a property
739 +change (string)+ which holds the name of current mode in use. The name
740 is the same as specified in config when creating a mode. The default
741 mode is simply named default. It contains a second property, +pango_markup+, which
742 defines whether pango markup shall be used for displaying this mode.
745 ---------------------------
750 ---------------------------
754 This event consists of a single serialized map containing a property
755 +change (string)+ which indicates the type of the change
757 * +new+ - the window has become managed by i3
758 * +close+ - the window has closed
759 * +focus+ - the window has received input focus
760 * +title+ - the window's title has changed
761 * +fullscreen_mode+ - the window has entered or exited fullscreen mode
762 * +move+ - the window has changed its position in the tree
763 * +floating+ - the window has transitioned to or from floating
764 * +urgent+ - the window has become urgent or lost its urgent status
766 Additionally a +container (object)+ field will be present, which consists
767 of the window's parent container. Be aware that for the "new" event, the
768 container will hold the initial name of the newly reparented window (e.g.
769 if you run urxvt with a shell that changes the title, you will still at
770 this point get the window title as "urxvt").
773 ---------------------------
782 ---------------------------
784 === barconfig_update event
786 This event consists of a single serialized map reporting on options from the
787 barconfig of the specified bar_id that were updated in i3. This event is the
788 same as a +GET_BAR_CONFIG+ reply for the bar with the given id.
792 This event consists of a single serialized map reporting on the details of a
793 binding that ran a command because of user input. The +change (sring)+ field
794 indicates what sort of binding event was triggered (right now it will always be
795 +"run"+ but may be expanded in the future).
797 The +binding (object)+ field contains details about the binding that was run:
800 The i3 command that is configured to run for this binding.
801 event_state_mask (array of strings)::
802 The group and modifier keys that were configured with this binding.
803 input_code (integer)::
804 If the binding was configured with +bindcode+, this will be the key code
805 that was given for the binding. If the binding is a mouse binding, it will be
806 the number of the mouse button that was pressed. Otherwise it will be 0.
807 symbol (string or null)::
808 If this is a keyboard binding that was configured with +bindsym+, this
809 field will contain the given symbol. Otherwise it will be +null+.
810 input_type (string)::
811 This will be +"keyboard"+ or +"mouse"+ depending on whether or not this was
812 a keyboard or a mouse binding.
815 ---------------------------
820 "event_state_mask": [
826 "input_type": "keyboard"
829 ---------------------------
831 == See also (existing libraries)
835 For some languages, libraries are available (so you don’t have to implement
836 all this on your own). This list names some (if you wrote one, please let me
840 * i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
841 * https://github.com/acrisci/i3ipc-glib
843 * https://github.com/drmgc/i3ipcpp
845 * https://github.com/proxypoke/i3ipc
847 * https://github.com/acrisci/i3ipc-gjs
849 * https://github.com/acrisci/i3ipc-lua
851 * https://metacpan.org/module/AnyEvent::I3
853 * https://github.com/acrisci/i3ipc-python
854 * https://github.com/whitelynx/i3ipc (not maintained)
855 * https://github.com/ziberna/i3-py (not maintained)
857 * https://github.com/veelenga/i3ipc-ruby
858 * https://github.com/badboy/i3-ipc (not maintained)
860 * https://github.com/tmerr/i3ipc-rs