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.
22 == Establishing a connection
24 To establish a connection, simply open the IPC socket. The following code
25 snippet illustrates this in Perl:
27 -------------------------------------------------------------
29 chomp(my $path = qx(i3 --get-socketpath));
30 my $sock = IO::Socket::UNIX->new(Peer => $path);
31 -------------------------------------------------------------
33 == Sending messages to i3
35 To send a message to i3, you have to format in the binary message format which
36 i3 expects. This format specifies a magic string in the beginning to ensure
37 the integrity of messages (to prevent follow-up errors). Following the magic
38 string comes the length of the payload of the message as 32-bit integer, and
39 the type of the message as 32-bit integer (the integers are not converted, so
40 they are in native byte order).
42 The magic string currently is "i3-ipc" and will only be changed when a change
43 in the IPC API is done which breaks compatibility (we hope that we don’t need
46 Currently implemented message types are the following:
49 The payload of the message is a command for i3 (like the commands you
50 can bind to keys in the configuration file) and will be executed
51 directly after receiving it.
53 Gets the current workspaces. The reply will be a JSON-encoded list of
54 workspaces (see the reply section).
56 Subscribes your connection to certain events. See <<events>> for a
57 description of this message and the concept of events.
59 Gets the current outputs. The reply will be a JSON-encoded list of outputs
60 (see the reply section).
62 Gets the layout tree. i3 uses a tree as data structure which includes
63 every container. The reply will be the JSON-encoded tree (see the reply
66 Gets a list of marks (identifiers for containers to easily jump to them
67 later). The reply will be a JSON-encoded list of window marks (see
70 Gets the configuration (as JSON map) of the workspace bar with the
71 given ID. If no ID is provided, an array with all configured bar IDs is
74 So, a typical message could look like this:
75 --------------------------------------------------
76 "i3-ipc" <message length> <message type> <payload>
77 --------------------------------------------------
80 ------------------------------------------------------------------------------
81 00000000 69 33 2d 69 70 63 04 00 00 00 00 00 00 00 65 78 |i3-ipc........ex|
82 00000010 69 74 0a |it.|
83 ------------------------------------------------------------------------------
85 To generate and send such a message, you could use the following code in Perl:
86 ------------------------------------------------------------
87 sub format_ipc_command {
90 # Get the real byte count (vs. amount of characters)
91 { use bytes; $len = length($msg); }
92 return "i3-ipc" . pack("LL", $len, 0) . $msg;
95 $sock->write(format_ipc_command("exit"));
96 ------------------------------------------------------------------------------
98 == Receiving replies from i3
100 Replies from i3 usually consist of a simple string (the length of the string
101 is the message_length, so you can consider them length-prefixed) which in turn
102 contain the JSON serialization of a data structure. For example, the
103 GET_WORKSPACES message returns an array of workspaces (each workspace is a map
104 with certain attributes).
108 The reply format is identical to the normal message format. There also is
109 the magic string, then the message length, then the message type and the
112 The following reply types are implemented:
115 Confirmation/Error code for the COMMAND message.
117 Reply to the GET_WORKSPACES message.
119 Confirmation/Error code for the SUBSCRIBE message.
121 Reply to the GET_OUTPUTS message.
123 Reply to the GET_TREE message.
125 Reply to the GET_MARKS message.
127 Reply to the GET_BAR_CONFIG message.
131 The reply consists of a single serialized map. At the moment, the only
132 property is +success (bool)+, but this will be expanded in future versions.
141 The reply consists of a serialized list of workspaces. Each workspace has the
142 following properties:
145 The logical number of the workspace. Corresponds to the command
146 to switch to this workspace.
148 The name of this workspace (by default num+1), as changed by the
149 user. Encoded in UTF-8.
151 Whether this workspace is currently visible on an output (multiple
152 workspaces can be visible at the same time).
154 Whether this workspace currently has the focus (only one workspace
155 can have the focus at the same time).
157 Whether a window on this workspace has the "urgent" flag set.
159 The rectangle of this workspace (equals the rect of the output it
160 is on), consists of x, y, width, height.
162 The video output this workspace is on (LVDS1, VGA1, …).
200 The reply consists of a single serialized map. The only property is
201 +success (bool)+, indicating whether the subscription was successful (the
202 default) or whether a JSON parse error occurred.
209 === GET_OUTPUTS reply
211 The reply consists of a serialized list of outputs. Each output has the
212 following properties:
215 The name of this output (as seen in +xrandr(1)+). Encoded in UTF-8.
217 Whether this output is currently active (has a valid mode).
218 current_workspace (integer)::
219 The current workspace which is visible on this output. +null+ if the
220 output is not active.
222 The rectangle of this output (equals the rect of the output it
223 is on), consists of x, y, width, height.
231 "current_workspace": 4,
242 "current_workspace": 1,
255 The reply consists of a serialized tree. Each node in the tree (representing
256 one container) has at least the properties listed below. While the nodes might
257 have more properties, please do not use any properties which are not documented
258 here. They are not yet finalized and will probably change!
261 The internal ID (actually a C pointer value) of this container. Do not
262 make any assumptions about it. You can use it to (re-)identify and
263 address containers when talking to i3.
265 The internal name of this container. For all containers which are part
266 of the tree structure down to the workspace contents, this is set to a
267 nice human-readable name of the container.
268 For all other containers, the content is not defined (yet).
270 Can be either "normal", "none" or "1pixel", dependending on the
271 container’s border style.
273 Can be either "default", "stacked", "tabbed", "dockarea" or "output".
274 Other values might be possible in the future, should we add new
276 orientation (string)::
277 Can be either "none" (for non-split containers), "horizontal" or
280 The percentage which this container takes in its parent. A value of
281 +null+ means that the percent property does not make sense for this
282 container, for example for the root container.
284 The absolute display coordinates for this container. Display
285 coordinates means that when you have two 1600x1200 monitors on a single
286 X11 Display (the standard way), the coordinates of the first window on
287 the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
290 The coordinates of the *actual client window* inside its container.
291 These coordinates are relative to the container and do not include the
292 window decoration (which is actually rendered on the parent container).
293 So, when using the +default+ layout, you will have a 2 pixel border on
294 each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
295 "height": 366 }+ (for example).
297 The original geometry the window specified when i3 mapped it. Used when
298 switching a window to floating mode, for example.
300 Whether this container (window or workspace) has the urgency hint set.
302 Whether this container is currently focused.
304 Please note that in the following example, I have left out some keys/values
305 which are not relevant for the type of the node. Otherwise, the example would
306 be by far too long (it already is quite long, despite showing only 1 window and
309 It is useful to have an overview of the structure before taking a look at the
323 -----------------------
350 "layout": "dockarea",
351 "orientation": "vertical",
374 "orientation": "horizontal",
381 "floating_nodes": [],
405 "name": "bottomdock",
406 "layout": "dockarea",
407 "orientation": "vertical",
434 ------------------------
438 The reply consists of a single array of strings for each container that has a
439 mark. The order of that array is undefined. If more than one container has the
440 same mark, it will be represented multiple times in the reply (the array
441 contents are not unique).
443 If no window has a mark the response will be the empty array [].
447 This can be used by third-party workspace bars (especially i3bar, but others
448 are free to implement compatible alternatives) to get the +bar+ block
449 configuration from i3.
451 Depending on the input, the reply is either:
454 An array of configured bar IDs
456 A JSON map containing the configuration for the specified bar.
458 Each bar configuration has the following properties:
461 The ID for this bar. Included in case you request multiple
462 configurations and want to differentiate the different replies.
464 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
465 does not show unless a specific key is pressed).
467 Either +bottom+ or +top+ at the moment.
468 status_command (string)::
469 Command which will be run to generate a statusline. Each line on stdout
470 of this command will be displayed in the bar. At the moment, no
471 formatting is supported.
473 The font to use for text on the bar.
474 workspace_buttons (boolean)::
475 Display workspace buttons or not? Defaults to true.
477 Should the bar enable verbose output for debugging? Defaults to false.
479 Contains key/value pairs of colors. Each value is a color code in hex,
480 formatted #rrggbb (like in HTML).
482 The following colors can be configured at the moment:
485 Background color of the bar.
487 Text color to be used for the statusline.
488 focused_workspace_text/focused_workspace_bg::
489 Text color/background color for a workspace button when the workspace
491 active_workspace_text/active_workspace_bg::
492 Text color/background color for a workspace button when the workspace
493 is active (visible) on some output, but the focus is on another one.
494 You can only tell this apart from the focused workspace when you are
495 using multiple monitors.
496 inactive_workspace_text/inactive_workspace_bg::
497 Text color/background color for a workspace button when the workspace
498 does not have focus and is not active (visible) on any output. This
499 will be the case for most workspaces.
500 urgent_workspace_text/urgent_workspace_bar::
501 Text color/background color for workspaces which contain at least one
502 window with the urgency hint set.
505 *Example of configured bars:*
510 *Example of bar configuration:*
515 "position": "bottom",
516 "status_command": "i3status",
517 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
518 "workspace_buttons": true,
521 "background": "#c0c0c0",
522 "statusline": "#00ff00",
523 "focused_workspace_text": "#ffffff",
524 "focused_workspace_bg": "#000000"
533 To get informed when certain things happen in i3, clients can subscribe to
534 events. Events consist of a name (like "workspace") and an event reply type
535 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
536 as replies to specific commands. However, the highest bit of the message type
537 is set to 1 to indicate that this is an event reply instead of a normal reply.
539 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
540 that the requests to i3 are processed in order. This means, the following
541 situation can happen: You send a GET_WORKSPACES request but you receive a
542 "workspace" event before receiving the reply to GET_WORKSPACES. If your
543 program does not want to cope which such kinds of race conditions (an
544 event based library may not have a problem here), I suggest you create a
545 separate connection to receive events.
547 === Subscribing to events
549 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
550 you can register to an event.
553 ---------------------------------
555 payload: [ "workspace", "focus" ]
556 ---------------------------------
561 The numbers in parenthesis is the event type (keep in mind that you need to
562 strip the highest bit first).
565 Sent when the user switches to a different workspace, when a new
566 workspace is initialized or when a workspace is removed (because the
567 last client vanished).
569 Sent when RandR issues a change notification (of either screens,
570 outputs, CRTCs or output properties).
573 --------------------------------------------------------------------
574 # the appropriate 4 bytes read from the socket are stored in $input
576 # unpack a 32-bit unsigned integer
577 my $message_type = unpack("L", $input);
579 # check if the highest bit is 1
580 my $is_event = (($message_type >> 31) == 1);
583 my $event_type = ($message_type & 0x7F);
586 say "Received event of type $event_type";
588 --------------------------------------------------------------------
592 This event consists of a single serialized map containing a property
593 +change (string)+ which indicates the type of the change ("focus", "init",
597 ---------------------
598 { "change": "focus" }
599 ---------------------
603 This event consists of a single serialized map containing a property
604 +change (string)+ which indicates the type of the change (currently only
608 ---------------------------
609 { "change": "unspecified" }
610 ---------------------------
614 For some languages, libraries are available (so you don’t have to implement
615 all this on your own). This list names some (if you wrote one, please let me
619 i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
620 However, there is no library yet.
622 http://github.com/badboy/i3-ipc
624 http://search.cpan.org/search?query=AnyEvent::I3
626 https://github.com/whitelynx/i3ipc
627 https://github.com/ziberna/i3-py (includes higher-level features)