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 The X11 window ID of the *actual client window* inside this container.
301 This field is set to null for split containers or otherwise empty
302 containers. This ID corresponds to what xwininfo(1) and other
303 X11-related tools display (usually in hex).
305 Whether this container (window or workspace) has the urgency hint set.
307 Whether this container is currently focused.
309 Please note that in the following example, I have left out some keys/values
310 which are not relevant for the type of the node. Otherwise, the example would
311 be by far too long (it already is quite long, despite showing only 1 window and
314 It is useful to have an overview of the structure before taking a look at the
328 -----------------------
355 "layout": "dockarea",
356 "orientation": "vertical",
379 "orientation": "horizontal",
386 "floating_nodes": [],
410 "name": "bottomdock",
411 "layout": "dockarea",
412 "orientation": "vertical",
439 ------------------------
443 The reply consists of a single array of strings for each container that has a
444 mark. The order of that array is undefined. If more than one container has the
445 same mark, it will be represented multiple times in the reply (the array
446 contents are not unique).
448 If no window has a mark the response will be the empty array [].
452 This can be used by third-party workspace bars (especially i3bar, but others
453 are free to implement compatible alternatives) to get the +bar+ block
454 configuration from i3.
456 Depending on the input, the reply is either:
459 An array of configured bar IDs
461 A JSON map containing the configuration for the specified bar.
463 Each bar configuration has the following properties:
466 The ID for this bar. Included in case you request multiple
467 configurations and want to differentiate the different replies.
469 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
470 does not show unless a specific key is pressed).
472 Either +bottom+ or +top+ at the moment.
473 status_command (string)::
474 Command which will be run to generate a statusline. Each line on stdout
475 of this command will be displayed in the bar. At the moment, no
476 formatting is supported.
478 The font to use for text on the bar.
479 workspace_buttons (boolean)::
480 Display workspace buttons or not? Defaults to true.
482 Should the bar enable verbose output for debugging? Defaults to false.
484 Contains key/value pairs of colors. Each value is a color code in hex,
485 formatted #rrggbb (like in HTML).
487 The following colors can be configured at the moment:
490 Background color of the bar.
492 Text color to be used for the statusline.
493 focused_workspace_text/focused_workspace_bg::
494 Text color/background color for a workspace button when the workspace
496 active_workspace_text/active_workspace_bg::
497 Text color/background color for a workspace button when the workspace
498 is active (visible) on some output, but the focus is on another one.
499 You can only tell this apart from the focused workspace when you are
500 using multiple monitors.
501 inactive_workspace_text/inactive_workspace_bg::
502 Text color/background color for a workspace button when the workspace
503 does not have focus and is not active (visible) on any output. This
504 will be the case for most workspaces.
505 urgent_workspace_text/urgent_workspace_bar::
506 Text color/background color for workspaces which contain at least one
507 window with the urgency hint set.
510 *Example of configured bars:*
515 *Example of bar configuration:*
520 "position": "bottom",
521 "status_command": "i3status",
522 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
523 "workspace_buttons": true,
526 "background": "#c0c0c0",
527 "statusline": "#00ff00",
528 "focused_workspace_text": "#ffffff",
529 "focused_workspace_bg": "#000000"
538 To get informed when certain things happen in i3, clients can subscribe to
539 events. Events consist of a name (like "workspace") and an event reply type
540 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
541 as replies to specific commands. However, the highest bit of the message type
542 is set to 1 to indicate that this is an event reply instead of a normal reply.
544 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
545 that the requests to i3 are processed in order. This means, the following
546 situation can happen: You send a GET_WORKSPACES request but you receive a
547 "workspace" event before receiving the reply to GET_WORKSPACES. If your
548 program does not want to cope which such kinds of race conditions (an
549 event based library may not have a problem here), I suggest you create a
550 separate connection to receive events.
552 === Subscribing to events
554 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
555 you can register to an event.
558 ---------------------------------
560 payload: [ "workspace", "focus" ]
561 ---------------------------------
566 The numbers in parenthesis is the event type (keep in mind that you need to
567 strip the highest bit first).
570 Sent when the user switches to a different workspace, when a new
571 workspace is initialized or when a workspace is removed (because the
572 last client vanished).
574 Sent when RandR issues a change notification (of either screens,
575 outputs, CRTCs or output properties).
578 --------------------------------------------------------------------
579 # the appropriate 4 bytes read from the socket are stored in $input
581 # unpack a 32-bit unsigned integer
582 my $message_type = unpack("L", $input);
584 # check if the highest bit is 1
585 my $is_event = (($message_type >> 31) == 1);
588 my $event_type = ($message_type & 0x7F);
591 say "Received event of type $event_type";
593 --------------------------------------------------------------------
597 This event consists of a single serialized map containing a property
598 +change (string)+ which indicates the type of the change ("focus", "init",
602 ---------------------
603 { "change": "focus" }
604 ---------------------
608 This event consists of a single serialized map containing a property
609 +change (string)+ which indicates the type of the change (currently only
613 ---------------------------
614 { "change": "unspecified" }
615 ---------------------------
619 For some languages, libraries are available (so you don’t have to implement
620 all this on your own). This list names some (if you wrote one, please let me
624 i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
625 However, there is no library yet.
627 http://github.com/badboy/i3-ipc
629 http://search.cpan.org/search?query=AnyEvent::I3
631 https://github.com/whitelynx/i3ipc
632 https://github.com/ziberna/i3-py (includes higher-level features)