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 Gets the version of i3. The reply will be a JSON-encoded dictionary
75 with the major, minor, patch and human-readable version.
77 So, a typical message could look like this:
78 --------------------------------------------------
79 "i3-ipc" <message length> <message type> <payload>
80 --------------------------------------------------
83 ------------------------------------------------------------------------------
84 00000000 69 33 2d 69 70 63 04 00 00 00 00 00 00 00 65 78 |i3-ipc........ex|
85 00000010 69 74 0a |it.|
86 ------------------------------------------------------------------------------
88 To generate and send such a message, you could use the following code in Perl:
89 ------------------------------------------------------------
90 sub format_ipc_command {
93 # Get the real byte count (vs. amount of characters)
94 { use bytes; $len = length($msg); }
95 return "i3-ipc" . pack("LL", $len, 0) . $msg;
98 $sock->write(format_ipc_command("exit"));
99 ------------------------------------------------------------------------------
101 == Receiving replies from i3
103 Replies from i3 usually consist of a simple string (the length of the string
104 is the message_length, so you can consider them length-prefixed) which in turn
105 contain the JSON serialization of a data structure. For example, the
106 GET_WORKSPACES message returns an array of workspaces (each workspace is a map
107 with certain attributes).
111 The reply format is identical to the normal message format. There also is
112 the magic string, then the message length, then the message type and the
115 The following reply types are implemented:
118 Confirmation/Error code for the COMMAND message.
120 Reply to the GET_WORKSPACES message.
122 Confirmation/Error code for the SUBSCRIBE message.
124 Reply to the GET_OUTPUTS message.
126 Reply to the GET_TREE message.
128 Reply to the GET_MARKS message.
130 Reply to the GET_BAR_CONFIG message.
132 Reply to the GET_VERSION message.
136 The reply consists of a single serialized map. At the moment, the only
137 property is +success (bool)+, but this will be expanded in future versions.
146 The reply consists of a serialized list of workspaces. Each workspace has the
147 following properties:
150 The logical number of the workspace. Corresponds to the command
151 to switch to this workspace.
153 The name of this workspace (by default num+1), as changed by the
154 user. Encoded in UTF-8.
156 Whether this workspace is currently visible on an output (multiple
157 workspaces can be visible at the same time).
159 Whether this workspace currently has the focus (only one workspace
160 can have the focus at the same time).
162 Whether a window on this workspace has the "urgent" flag set.
164 The rectangle of this workspace (equals the rect of the output it
165 is on), consists of x, y, width, height.
167 The video output this workspace is on (LVDS1, VGA1, …).
205 The reply consists of a single serialized map. The only property is
206 +success (bool)+, indicating whether the subscription was successful (the
207 default) or whether a JSON parse error occurred.
216 The reply consists of a serialized list of outputs. Each output has the
217 following properties:
220 The name of this output (as seen in +xrandr(1)+). Encoded in UTF-8.
222 Whether this output is currently active (has a valid mode).
223 current_workspace (integer)::
224 The current workspace which is visible on this output. +null+ if the
225 output is not active.
227 The rectangle of this output (equals the rect of the output it
228 is on), consists of x, y, width, height.
236 "current_workspace": 4,
247 "current_workspace": 1,
260 The reply consists of a serialized tree. Each node in the tree (representing
261 one container) has at least the properties listed below. While the nodes might
262 have more properties, please do not use any properties which are not documented
263 here. They are not yet finalized and will probably change!
266 The internal ID (actually a C pointer value) of this container. Do not
267 make any assumptions about it. You can use it to (re-)identify and
268 address containers when talking to i3.
270 The internal name of this container. For all containers which are part
271 of the tree structure down to the workspace contents, this is set to a
272 nice human-readable name of the container.
273 For all other containers, the content is not defined (yet).
275 Can be either "normal", "none" or "1pixel", dependending on the
276 container’s border style.
278 Can be either "splith", "splitv", "stacked", "tabbed", "dockarea" or
280 Other values might be possible in the future, should we add new
282 orientation (string)::
283 Can be either "none" (for non-split containers), "horizontal" or
285 THIS FIELD IS OBSOLETE. It is still present, but your code should not
286 use it. Instead, rely on the layout field.
288 The percentage which this container takes in its parent. A value of
289 +null+ means that the percent property does not make sense for this
290 container, for example for the root container.
292 The absolute display coordinates for this container. Display
293 coordinates means that when you have two 1600x1200 monitors on a single
294 X11 Display (the standard way), the coordinates of the first window on
295 the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
298 The coordinates of the *actual client window* inside its container.
299 These coordinates are relative to the container and do not include the
300 window decoration (which is actually rendered on the parent container).
301 So, when using the +default+ layout, you will have a 2 pixel border on
302 each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
303 "height": 366 }+ (for example).
305 The original geometry the window specified when i3 mapped it. Used when
306 switching a window to floating mode, for example.
308 The X11 window ID of the *actual client window* inside this container.
309 This field is set to null for split containers or otherwise empty
310 containers. This ID corresponds to what xwininfo(1) and other
311 X11-related tools display (usually in hex).
313 Whether this container (window or workspace) has the urgency hint set.
315 Whether this container is currently focused.
317 Please note that in the following example, I have left out some keys/values
318 which are not relevant for the type of the node. Otherwise, the example would
319 be by far too long (it already is quite long, despite showing only 1 window and
322 It is useful to have an overview of the structure before taking a look at the
336 -----------------------
363 "layout": "dockarea",
364 "orientation": "vertical",
387 "orientation": "horizontal",
394 "floating_nodes": [],
418 "name": "bottomdock",
419 "layout": "dockarea",
420 "orientation": "vertical",
447 ------------------------
451 The reply consists of a single array of strings for each container that has a
452 mark. The order of that array is undefined. If more than one container has the
453 same mark, it will be represented multiple times in the reply (the array
454 contents are not unique).
456 If no window has a mark the response will be the empty array [].
460 This can be used by third-party workspace bars (especially i3bar, but others
461 are free to implement compatible alternatives) to get the +bar+ block
462 configuration from i3.
464 Depending on the input, the reply is either:
467 An array of configured bar IDs
469 A JSON map containing the configuration for the specified bar.
471 Each bar configuration has the following properties:
474 The ID for this bar. Included in case you request multiple
475 configurations and want to differentiate the different replies.
477 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
478 does not show unless a specific key is pressed).
480 Either +bottom+ or +top+ at the moment.
481 status_command (string)::
482 Command which will be run to generate a statusline. Each line on stdout
483 of this command will be displayed in the bar. At the moment, no
484 formatting is supported.
486 The font to use for text on the bar.
487 workspace_buttons (boolean)::
488 Display workspace buttons or not? Defaults to true.
490 Should the bar enable verbose output for debugging? Defaults to false.
492 Contains key/value pairs of colors. Each value is a color code in hex,
493 formatted #rrggbb (like in HTML).
495 The following colors can be configured at the moment:
498 Background color of the bar.
500 Text color to be used for the statusline.
501 focused_workspace_text/focused_workspace_bg::
502 Text color/background color for a workspace button when the workspace
504 active_workspace_text/active_workspace_bg::
505 Text color/background color for a workspace button when the workspace
506 is active (visible) on some output, but the focus is on another one.
507 You can only tell this apart from the focused workspace when you are
508 using multiple monitors.
509 inactive_workspace_text/inactive_workspace_bg::
510 Text color/background color for a workspace button when the workspace
511 does not have focus and is not active (visible) on any output. This
512 will be the case for most workspaces.
513 urgent_workspace_text/urgent_workspace_bar::
514 Text color/background color for workspaces which contain at least one
515 window with the urgency hint set.
518 *Example of configured bars:*
523 *Example of bar configuration:*
528 "position": "bottom",
529 "status_command": "i3status",
530 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
531 "workspace_buttons": true,
534 "background": "#c0c0c0",
535 "statusline": "#00ff00",
536 "focused_workspace_text": "#ffffff",
537 "focused_workspace_bg": "#000000"
544 The reply consists of a single JSON dictionary with the following keys:
547 The major version of i3, such as +4+.
549 The minor version of i3, such as +2+. Changes in the IPC interface (new
550 features) will only occur with new minor (or major) releases. However,
551 bugfixes might be introduced in patch releases, too.
553 The patch version of i3, such as +1+ (when the complete version is
554 +4.2.1+). For versions such as +4.2+, patch will be set to +0+.
555 human_readable (string)::
556 A human-readable version of i3 containing the precise git version,
557 build date and branch name. When you need to display the i3 version to
558 your users, use the human-readable version whenever possible (since
559 this is what +i3 --version+ displays, too).
564 "human_readable" : "4.2-169-gf80b877 (2012-08-05, branch \"next\")",
575 To get informed when certain things happen in i3, clients can subscribe to
576 events. Events consist of a name (like "workspace") and an event reply type
577 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
578 as replies to specific commands. However, the highest bit of the message type
579 is set to 1 to indicate that this is an event reply instead of a normal reply.
581 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
582 that the requests to i3 are processed in order. This means, the following
583 situation can happen: You send a GET_WORKSPACES request but you receive a
584 "workspace" event before receiving the reply to GET_WORKSPACES. If your
585 program does not want to cope which such kinds of race conditions (an
586 event based library may not have a problem here), I suggest you create a
587 separate connection to receive events.
589 === Subscribing to events
591 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
592 you can register to an event.
595 ---------------------------------
597 payload: [ "workspace", "focus" ]
598 ---------------------------------
603 The numbers in parenthesis is the event type (keep in mind that you need to
604 strip the highest bit first).
607 Sent when the user switches to a different workspace, when a new
608 workspace is initialized or when a workspace is removed (because the
609 last client vanished).
611 Sent when RandR issues a change notification (of either screens,
612 outputs, CRTCs or output properties).
614 Sent whenever i3 changes its binding mode.
617 --------------------------------------------------------------------
618 # the appropriate 4 bytes read from the socket are stored in $input
620 # unpack a 32-bit unsigned integer
621 my $message_type = unpack("L", $input);
623 # check if the highest bit is 1
624 my $is_event = (($message_type >> 31) == 1);
627 my $event_type = ($message_type & 0x7F);
630 say "Received event of type $event_type";
632 --------------------------------------------------------------------
636 This event consists of a single serialized map containing a property
637 +change (string)+ which indicates the type of the change ("focus", "init",
641 ---------------------
642 { "change": "focus" }
643 ---------------------
647 This event consists of a single serialized map containing a property
648 +change (string)+ which indicates the type of the change (currently only
652 ---------------------------
653 { "change": "unspecified" }
654 ---------------------------
658 This event consists of a single serialized map containing a property
659 +change (string)+ which holds the name of current mode in use. The name
660 is the same as specified in config when creating a mode. The default
661 mode is simply named default.
664 ---------------------------
665 { "change": "default" }
666 ---------------------------
670 For some languages, libraries are available (so you don’t have to implement
671 all this on your own). This list names some (if you wrote one, please let me
675 i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
676 However, there is no library yet.
678 http://github.com/badboy/i3-ipc
680 https://metacpan.org/module/AnyEvent::I3
682 * https://github.com/whitelynx/i3ipc
683 * https://github.com/ziberna/i3-py (includes higher-level features)