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.
277 current_border_width (integer)::
278 Number of pixels of the border width.
280 Can be either "splith", "splitv", "stacked", "tabbed", "dockarea" or
282 Other values might be possible in the future, should we add new
284 orientation (string)::
285 Can be either "none" (for non-split containers), "horizontal" or
287 THIS FIELD IS OBSOLETE. It is still present, but your code should not
288 use it. Instead, rely on the layout field.
290 The percentage which this container takes in its parent. A value of
291 +null+ means that the percent property does not make sense for this
292 container, for example for the root container.
294 The absolute display coordinates for this container. Display
295 coordinates means that when you have two 1600x1200 monitors on a single
296 X11 Display (the standard way), the coordinates of the first window on
297 the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
300 The coordinates of the *actual client window* inside its container.
301 These coordinates are relative to the container and do not include the
302 window decoration (which is actually rendered on the parent container).
303 So, when using the +default+ layout, you will have a 2 pixel border on
304 each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
305 "height": 366 }+ (for example).
307 The original geometry the window specified when i3 mapped it. Used when
308 switching a window to floating mode, for example.
310 The X11 window ID of the *actual client window* inside this container.
311 This field is set to null for split containers or otherwise empty
312 containers. This ID corresponds to what xwininfo(1) and other
313 X11-related tools display (usually in hex).
315 Whether this container (window or workspace) has the urgency hint set.
317 Whether this container is currently focused.
319 Please note that in the following example, I have left out some keys/values
320 which are not relevant for the type of the node. Otherwise, the example would
321 be by far too long (it already is quite long, despite showing only 1 window and
324 It is useful to have an overview of the structure before taking a look at the
338 -----------------------
365 "layout": "dockarea",
366 "orientation": "vertical",
389 "orientation": "horizontal",
396 "floating_nodes": [],
420 "name": "bottomdock",
421 "layout": "dockarea",
422 "orientation": "vertical",
449 ------------------------
453 The reply consists of a single array of strings for each container that has a
454 mark. The order of that array is undefined. If more than one container has the
455 same mark, it will be represented multiple times in the reply (the array
456 contents are not unique).
458 If no window has a mark the response will be the empty array [].
462 This can be used by third-party workspace bars (especially i3bar, but others
463 are free to implement compatible alternatives) to get the +bar+ block
464 configuration from i3.
466 Depending on the input, the reply is either:
469 An array of configured bar IDs
471 A JSON map containing the configuration for the specified bar.
473 Each bar configuration has the following properties:
476 The ID for this bar. Included in case you request multiple
477 configurations and want to differentiate the different replies.
479 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
480 does not show unless a specific key is pressed).
482 Either +bottom+ or +top+ at the moment.
483 status_command (string)::
484 Command which will be run to generate a statusline. Each line on stdout
485 of this command will be displayed in the bar. At the moment, no
486 formatting is supported.
488 The font to use for text on the bar.
489 workspace_buttons (boolean)::
490 Display workspace buttons or not? Defaults to true.
492 Should the bar enable verbose output for debugging? Defaults to false.
494 Contains key/value pairs of colors. Each value is a color code in hex,
495 formatted #rrggbb (like in HTML).
497 The following colors can be configured at the moment:
500 Background color of the bar.
502 Text color to be used for the statusline.
503 focused_workspace_text/focused_workspace_bg::
504 Text color/background color for a workspace button when the workspace
506 active_workspace_text/active_workspace_bg::
507 Text color/background color for a workspace button when the workspace
508 is active (visible) on some output, but the focus is on another one.
509 You can only tell this apart from the focused workspace when you are
510 using multiple monitors.
511 inactive_workspace_text/inactive_workspace_bg::
512 Text color/background color for a workspace button when the workspace
513 does not have focus and is not active (visible) on any output. This
514 will be the case for most workspaces.
515 urgent_workspace_text/urgent_workspace_bar::
516 Text color/background color for workspaces which contain at least one
517 window with the urgency hint set.
520 *Example of configured bars:*
525 *Example of bar configuration:*
530 "position": "bottom",
531 "status_command": "i3status",
532 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
533 "workspace_buttons": true,
536 "background": "#c0c0c0",
537 "statusline": "#00ff00",
538 "focused_workspace_text": "#ffffff",
539 "focused_workspace_bg": "#000000"
546 The reply consists of a single JSON dictionary with the following keys:
549 The major version of i3, such as +4+.
551 The minor version of i3, such as +2+. Changes in the IPC interface (new
552 features) will only occur with new minor (or major) releases. However,
553 bugfixes might be introduced in patch releases, too.
555 The patch version of i3, such as +1+ (when the complete version is
556 +4.2.1+). For versions such as +4.2+, patch will be set to +0+.
557 human_readable (string)::
558 A human-readable version of i3 containing the precise git version,
559 build date and branch name. When you need to display the i3 version to
560 your users, use the human-readable version whenever possible (since
561 this is what +i3 --version+ displays, too).
566 "human_readable" : "4.2-169-gf80b877 (2012-08-05, branch \"next\")",
577 To get informed when certain things happen in i3, clients can subscribe to
578 events. Events consist of a name (like "workspace") and an event reply type
579 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
580 as replies to specific commands. However, the highest bit of the message type
581 is set to 1 to indicate that this is an event reply instead of a normal reply.
583 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
584 that the requests to i3 are processed in order. This means, the following
585 situation can happen: You send a GET_WORKSPACES request but you receive a
586 "workspace" event before receiving the reply to GET_WORKSPACES. If your
587 program does not want to cope which such kinds of race conditions (an
588 event based library may not have a problem here), I suggest you create a
589 separate connection to receive events.
591 === Subscribing to events
593 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
594 you can register to an event.
597 ---------------------------------
599 payload: [ "workspace", "focus" ]
600 ---------------------------------
605 The numbers in parenthesis is the event type (keep in mind that you need to
606 strip the highest bit first).
609 Sent when the user switches to a different workspace, when a new
610 workspace is initialized or when a workspace is removed (because the
611 last client vanished).
613 Sent when RandR issues a change notification (of either screens,
614 outputs, CRTCs or output properties).
616 Sent whenever i3 changes its binding mode.
619 --------------------------------------------------------------------
620 # the appropriate 4 bytes read from the socket are stored in $input
622 # unpack a 32-bit unsigned integer
623 my $message_type = unpack("L", $input);
625 # check if the highest bit is 1
626 my $is_event = (($message_type >> 31) == 1);
629 my $event_type = ($message_type & 0x7F);
632 say "Received event of type $event_type";
634 --------------------------------------------------------------------
638 This event consists of a single serialized map containing a property
639 +change (string)+ which indicates the type of the change ("focus", "init",
643 ---------------------
644 { "change": "focus" }
645 ---------------------
649 This event consists of a single serialized map containing a property
650 +change (string)+ which indicates the type of the change (currently only
654 ---------------------------
655 { "change": "unspecified" }
656 ---------------------------
660 This event consists of a single serialized map containing a property
661 +change (string)+ which holds the name of current mode in use. The name
662 is the same as specified in config when creating a mode. The default
663 mode is simply named default.
666 ---------------------------
667 { "change": "default" }
668 ---------------------------
672 For some languages, libraries are available (so you don’t have to implement
673 all this on your own). This list names some (if you wrote one, please let me
677 i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
678 However, there is no library yet.
680 http://github.com/badboy/i3-ipc
682 https://metacpan.org/module/AnyEvent::I3
684 * https://github.com/whitelynx/i3ipc
685 * https://github.com/ziberna/i3-py (includes higher-level features)