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 single serialized map. At the moment, the only
144 property is +success (bool)+, but this will be expanded in future versions.
153 The reply consists of a serialized list of workspaces. Each workspace has the
154 following properties:
157 The logical number of the workspace. Corresponds to the command
158 to switch to this workspace.
160 The name of this workspace (by default num+1), as changed by the
161 user. Encoded in UTF-8.
163 Whether this workspace is currently visible on an output (multiple
164 workspaces can be visible at the same time).
166 Whether this workspace currently has the focus (only one workspace
167 can have the focus at the same time).
169 Whether a window on this workspace has the "urgent" flag set.
171 The rectangle of this workspace (equals the rect of the output it
172 is on), consists of x, y, width, height.
174 The video output this workspace is on (LVDS1, VGA1, …).
212 The reply consists of a single serialized map. The only property is
213 +success (bool)+, indicating whether the subscription was successful (the
214 default) or whether a JSON parse error occurred.
223 The reply consists of a serialized list of outputs. Each output has the
224 following properties:
227 The name of this output (as seen in +xrandr(1)+). Encoded in UTF-8.
229 Whether this output is currently active (has a valid mode).
230 current_workspace (integer)::
231 The current workspace which is visible on this output. +null+ if the
232 output is not active.
234 The rectangle of this output (equals the rect of the output it
235 is on), consists of x, y, width, height.
243 "current_workspace": 4,
254 "current_workspace": 1,
267 The reply consists of a serialized tree. Each node in the tree (representing
268 one container) has at least the properties listed below. While the nodes might
269 have more properties, please do not use any properties which are not documented
270 here. They are not yet finalized and will probably change!
273 The internal ID (actually a C pointer value) of this container. Do not
274 make any assumptions about it. You can use it to (re-)identify and
275 address containers when talking to i3.
277 The internal name of this container. For all containers which are part
278 of the tree structure down to the workspace contents, this is set to a
279 nice human-readable name of the container.
280 For all other containers, the content is not defined (yet).
282 Can be either "normal", "none" or "1pixel", dependending on the
283 container’s border style.
284 current_border_width (integer)::
285 Number of pixels of the border width.
287 Can be either "splith", "splitv", "stacked", "tabbed", "dockarea" or
289 Other values might be possible in the future, should we add new
291 orientation (string)::
292 Can be either "none" (for non-split containers), "horizontal" or
294 THIS FIELD IS OBSOLETE. It is still present, but your code should not
295 use it. Instead, rely on the layout field.
297 The percentage which this container takes in its parent. A value of
298 +null+ means that the percent property does not make sense for this
299 container, for example for the root container.
301 The absolute display coordinates for this container. Display
302 coordinates means that when you have two 1600x1200 monitors on a single
303 X11 Display (the standard way), the coordinates of the first window on
304 the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
307 The coordinates of the *actual client window* inside its container.
308 These coordinates are relative to the container and do not include the
309 window decoration (which is actually rendered on the parent container).
310 So, when using the +default+ layout, you will have a 2 pixel border on
311 each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
312 "height": 366 }+ (for example).
314 The original geometry the window specified when i3 mapped it. Used when
315 switching a window to floating mode, for example.
317 The X11 window ID of the *actual client window* inside this container.
318 This field is set to null for split containers or otherwise empty
319 containers. This ID corresponds to what xwininfo(1) and other
320 X11-related tools display (usually in hex).
322 Whether this container (window or workspace) has the urgency hint set.
324 Whether this container is currently focused.
326 Please note that in the following example, I have left out some keys/values
327 which are not relevant for the type of the node. Otherwise, the example would
328 be by far too long (it already is quite long, despite showing only 1 window and
331 It is useful to have an overview of the structure before taking a look at the
345 -----------------------
372 "layout": "dockarea",
373 "orientation": "vertical",
396 "orientation": "horizontal",
403 "floating_nodes": [],
427 "name": "bottomdock",
428 "layout": "dockarea",
429 "orientation": "vertical",
456 ------------------------
460 The reply consists of a single array of strings for each container that has a
461 mark. The order of that array is undefined. If more than one container has the
462 same mark, it will be represented multiple times in the reply (the array
463 contents are not unique).
465 If no window has a mark the response will be the empty array [].
469 This can be used by third-party workspace bars (especially i3bar, but others
470 are free to implement compatible alternatives) to get the +bar+ block
471 configuration from i3.
473 Depending on the input, the reply is either:
476 An array of configured bar IDs
478 A JSON map containing the configuration for the specified bar.
480 Each bar configuration has the following properties:
483 The ID for this bar. Included in case you request multiple
484 configurations and want to differentiate the different replies.
486 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
487 does not show unless a specific key is pressed).
489 Either +bottom+ or +top+ at the moment.
490 status_command (string)::
491 Command which will be run to generate a statusline. Each line on stdout
492 of this command will be displayed in the bar. At the moment, no
493 formatting is supported.
495 The font to use for text on the bar.
496 workspace_buttons (boolean)::
497 Display workspace buttons or not? Defaults to true.
499 Should the bar enable verbose output for debugging? Defaults to false.
501 Contains key/value pairs of colors. Each value is a color code in hex,
502 formatted #rrggbb (like in HTML).
504 The following colors can be configured at the moment:
507 Background color of the bar.
509 Text color to be used for the statusline.
511 Text color to be used for the separator.
512 focused_workspace_text/focused_workspace_bg::
513 Text color/background color for a workspace button when the workspace
515 active_workspace_text/active_workspace_bg::
516 Text color/background color for a workspace button when the workspace
517 is active (visible) on some output, but the focus is on another one.
518 You can only tell this apart from the focused workspace when you are
519 using multiple monitors.
520 inactive_workspace_text/inactive_workspace_bg::
521 Text color/background color for a workspace button when the workspace
522 does not have focus and is not active (visible) on any output. This
523 will be the case for most workspaces.
524 urgent_workspace_text/urgent_workspace_bar::
525 Text color/background color for workspaces which contain at least one
526 window with the urgency hint set.
529 *Example of configured bars:*
534 *Example of bar configuration:*
539 "position": "bottom",
540 "status_command": "i3status",
541 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
542 "workspace_buttons": true,
545 "background": "#c0c0c0",
546 "statusline": "#00ff00",
547 "focused_workspace_text": "#ffffff",
548 "focused_workspace_bg": "#000000"
555 The reply consists of a single JSON dictionary with the following keys:
558 The major version of i3, such as +4+.
560 The minor version of i3, such as +2+. Changes in the IPC interface (new
561 features) will only occur with new minor (or major) releases. However,
562 bugfixes might be introduced in patch releases, too.
564 The patch version of i3, such as +1+ (when the complete version is
565 +4.2.1+). For versions such as +4.2+, patch will be set to +0+.
566 human_readable (string)::
567 A human-readable version of i3 containing the precise git version,
568 build date and branch name. When you need to display the i3 version to
569 your users, use the human-readable version whenever possible (since
570 this is what +i3 --version+ displays, too).
575 "human_readable" : "4.2-169-gf80b877 (2012-08-05, branch \"next\")",
586 To get informed when certain things happen in i3, clients can subscribe to
587 events. Events consist of a name (like "workspace") and an event reply type
588 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
589 as replies to specific commands. However, the highest bit of the message type
590 is set to 1 to indicate that this is an event reply instead of a normal reply.
592 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
593 that the requests to i3 are processed in order. This means, the following
594 situation can happen: You send a GET_WORKSPACES request but you receive a
595 "workspace" event before receiving the reply to GET_WORKSPACES. If your
596 program does not want to cope which such kinds of race conditions (an
597 event based library may not have a problem here), I suggest you create a
598 separate connection to receive events.
600 === Subscribing to events
602 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
603 you can register to an event.
606 ---------------------------------
608 payload: [ "workspace", "focus" ]
609 ---------------------------------
614 The numbers in parenthesis is the event type (keep in mind that you need to
615 strip the highest bit first).
618 Sent when the user switches to a different workspace, when a new
619 workspace is initialized or when a workspace is removed (because the
620 last client vanished).
622 Sent when RandR issues a change notification (of either screens,
623 outputs, CRTCs or output properties).
625 Sent whenever i3 changes its binding mode.
628 --------------------------------------------------------------------
629 # the appropriate 4 bytes read from the socket are stored in $input
631 # unpack a 32-bit unsigned integer
632 my $message_type = unpack("L", $input);
634 # check if the highest bit is 1
635 my $is_event = (($message_type >> 31) == 1);
638 my $event_type = ($message_type & 0x7F);
641 say "Received event of type $event_type";
643 --------------------------------------------------------------------
647 This event consists of a single serialized map containing a property
648 +change (string)+ which indicates the type of the change ("focus", "init",
651 Moreover, when the change is "focus", an +old (object)+ and a +current
652 (object)+ properties will be present with the previous and current
653 workspace respectively. When the first switch occurs (when i3 focuses
654 the workspace visible at the beginning) there is no previous
655 workspace, and the +old+ property will be set to +null+. Also note
656 that if the previous is empty it will get destroyed when switching,
657 but will still be present in the "old" property.
660 ---------------------
674 ---------------------
678 This event consists of a single serialized map containing a property
679 +change (string)+ which indicates the type of the change (currently only
683 ---------------------------
684 { "change": "unspecified" }
685 ---------------------------
689 This event consists of a single serialized map containing a property
690 +change (string)+ which holds the name of current mode in use. The name
691 is the same as specified in config when creating a mode. The default
692 mode is simply named default.
695 ---------------------------
696 { "change": "default" }
697 ---------------------------
699 == See also (existing libraries)
703 For some languages, libraries are available (so you don’t have to implement
704 all this on your own). This list names some (if you wrote one, please let me
708 i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
709 However, there is no library yet.
711 http://github.com/badboy/i3-ipc
713 https://metacpan.org/module/AnyEvent::I3
715 * https://github.com/whitelynx/i3ipc
716 * https://github.com/ziberna/i3-py (includes higher-level features)
718 * https://github.com/proxypoke/i3ipc