1 IPC interface (interprocess communication)
2 ==========================================
3 Michael Stapelberg <michael+i3@stapelberg.de>
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 SHM log markers for the current position, the last wrap, the
75 SHM segment name and segment size. This is necessary for tools like
76 i3-dump-log which want to display the SHM log.
78 So, a typical message could look like this:
79 --------------------------------------------------
80 "i3-ipc" <message length> <message type> <payload>
81 --------------------------------------------------
84 ------------------------------------------------------------------------------
85 00000000 69 33 2d 69 70 63 04 00 00 00 00 00 00 00 65 78 |i3-ipc........ex|
86 00000010 69 74 0a |it.|
87 ------------------------------------------------------------------------------
89 To generate and send such a message, you could use the following code in Perl:
90 ------------------------------------------------------------
91 sub format_ipc_command {
94 # Get the real byte count (vs. amount of characters)
95 { use bytes; $len = length($msg); }
96 return "i3-ipc" . pack("LL", $len, 0) . $msg;
99 $sock->write(format_ipc_command("exit"));
100 ------------------------------------------------------------------------------
102 == Receiving replies from i3
104 Replies from i3 usually consist of a simple string (the length of the string
105 is the message_length, so you can consider them length-prefixed) which in turn
106 contain the JSON serialization of a data structure. For example, the
107 GET_WORKSPACES message returns an array of workspaces (each workspace is a map
108 with certain attributes).
112 The reply format is identical to the normal message format. There also is
113 the magic string, then the message length, then the message type and the
116 The following reply types are implemented:
119 Confirmation/Error code for the COMMAND message.
121 Reply to the GET_WORKSPACES message.
123 Confirmation/Error code for the SUBSCRIBE message.
125 Reply to the GET_OUTPUTS message.
127 Reply to the GET_TREE message.
129 Reply to the GET_MARKS message.
131 Reply to the GET_BAR_CONFIG message.
133 Reply to the GET_LOG_MARKERS message.
137 The reply consists of a single serialized map. At the moment, the only
138 property is +success (bool)+, but this will be expanded in future versions.
147 The reply consists of a serialized list of workspaces. Each workspace has the
148 following properties:
151 The logical number of the workspace. Corresponds to the command
152 to switch to this workspace.
154 The name of this workspace (by default num+1), as changed by the
155 user. Encoded in UTF-8.
157 Whether this workspace is currently visible on an output (multiple
158 workspaces can be visible at the same time).
160 Whether this workspace currently has the focus (only one workspace
161 can have the focus at the same time).
163 Whether a window on this workspace has the "urgent" flag set.
165 The rectangle of this workspace (equals the rect of the output it
166 is on), consists of x, y, width, height.
168 The video output this workspace is on (LVDS1, VGA1, …).
206 The reply consists of a single serialized map. The only property is
207 +success (bool)+, indicating whether the subscription was successful (the
208 default) or whether a JSON parse error occurred.
215 === GET_OUTPUTS reply
217 The reply consists of a serialized list of outputs. Each output has the
218 following properties:
221 The name of this output (as seen in +xrandr(1)+). Encoded in UTF-8.
223 Whether this output is currently active (has a valid mode).
224 current_workspace (integer)::
225 The current workspace which is visible on this output. +null+ if the
226 output is not active.
228 The rectangle of this output (equals the rect of the output it
229 is on), consists of x, y, width, height.
237 "current_workspace": 4,
248 "current_workspace": 1,
261 The reply consists of a serialized tree. Each node in the tree (representing
262 one container) has at least the properties listed below. While the nodes might
263 have more properties, please do not use any properties which are not documented
264 here. They are not yet finalized and will probably change!
267 The internal ID (actually a C pointer value) of this container. Do not
268 make any assumptions about it. You can use it to (re-)identify and
269 address containers when talking to i3.
271 The internal name of this container. For all containers which are part
272 of the tree structure down to the workspace contents, this is set to a
273 nice human-readable name of the container.
274 For all other containers, the content is not defined (yet).
276 Can be either "normal", "none" or "1pixel", dependending on the
277 container’s border style.
279 Can be either "default", "stacked", "tabbed", "dockarea" or "output".
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
286 The percentage which this container takes in its parent. A value of
287 +null+ means that the percent property does not make sense for this
288 container, for example for the root container.
290 The absolute display coordinates for this container. Display
291 coordinates means that when you have two 1600x1200 monitors on a single
292 X11 Display (the standard way), the coordinates of the first window on
293 the second monitor are +{ "x": 1600, "y": 0, "width": 1600, "height":
296 The coordinates of the *actual client window* inside its container.
297 These coordinates are relative to the container and do not include the
298 window decoration (which is actually rendered on the parent container).
299 So, when using the +default+ layout, you will have a 2 pixel border on
300 each side, making the window_rect +{ "x": 2, "y": 0, "width": 632,
301 "height": 366 }+ (for example).
303 The original geometry the window specified when i3 mapped it. Used when
304 switching a window to floating mode, for example.
306 Whether this container (window or workspace) has the urgency hint set.
308 Whether this container is currently focused.
310 Please note that in the following example, I have left out some keys/values
311 which are not relevant for the type of the node. Otherwise, the example would
312 be by far too long (it already is quite long, despite showing only 1 window and
315 It is useful to have an overview of the structure before taking a look at the
329 -----------------------
356 "layout": "dockarea",
357 "orientation": "vertical",
380 "orientation": "horizontal",
387 "floating_nodes": [],
411 "name": "bottomdock",
412 "layout": "dockarea",
413 "orientation": "vertical",
440 ------------------------
444 The reply consists of a single array of strings for each container that has a
445 mark. The order of that array is undefined. If more than one container has the
446 same mark, it will be represented multiple times in the reply (the array
447 contents are not unique).
449 If no window has a mark the response will be the empty array [].
453 This can be used by third-party workspace bars (especially i3bar, but others
454 are free to implement compatible alternatives) to get the +bar+ block
455 configuration from i3.
457 Depending on the input, the reply is either:
460 An array of configured bar IDs
462 A JSON map containing the configuration for the specified bar.
464 Each bar configuration has the following properties:
467 The ID for this bar. Included in case you request multiple
468 configurations and want to differentiate the different replies.
470 Either +dock+ (the bar sets the dock window type) or +hide+ (the bar
471 does not show unless a specific key is pressed).
473 Either +bottom+ or +top+ at the moment.
474 status_command (string)::
475 Command which will be run to generate a statusline. Each line on stdout
476 of this command will be displayed in the bar. At the moment, no
477 formatting is supported.
479 The font to use for text on the bar.
480 workspace_buttons (boolean)::
481 Display workspace buttons or not? Defaults to true.
483 Should the bar enable verbose output for debugging? Defaults to false.
485 Contains key/value pairs of colors. Each value is a color code in hex,
486 formatted #rrggbb (like in HTML).
488 The following colors can be configured at the moment:
491 Background color of the bar.
493 Text color to be used for the statusline.
494 focused_workspace_text/focused_workspace_bg::
495 Text color/background color for a workspace button when the workspace
497 active_workspace_text/active_workspace_bg::
498 Text color/background color for a workspace button when the workspace
499 is active (visible) on some output, but the focus is on another one.
500 You can only tell this apart from the focused workspace when you are
501 using multiple monitors.
502 inactive_workspace_text/inactive_workspace_bg::
503 Text color/background color for a workspace button when the workspace
504 does not have focus and is not active (visible) on any output. This
505 will be the case for most workspaces.
506 urgent_workspace_text/urgent_workspace_bar::
507 Text color/background color for workspaces which contain at least one
508 window with the urgency hint set.
511 *Example of configured bars:*
516 *Example of bar configuration:*
521 "position": "bottom",
522 "status_command": "i3status",
523 "font": "-misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1",
524 "workspace_buttons": true,
527 "background": "#c0c0c0",
528 "statusline": "#00ff00",
529 "focused_workspace_text": "#ffffff",
530 "focused_workspace_bg": "#000000"
535 === LOG_MARKERS reply
537 Gets the SHM log markers for the current position, the last wrap, the
538 SHM segment name and segment size. This is necessary for tools like
539 i3-dump-log which want to display the SHM log.
541 The reply is a JSON map with the following entries:
544 The name of the SHM segment, will be of the format +/i3-log-<pid>+.
546 The size (in bytes) of the SHM segment. If this is 0, SHM logging is
548 offset_next_write (integer)::
549 The offset in the SHM segment at which the next write will happen.
550 Tools should start printing lines from here, since the bytes following
551 this offset are the oldest log lines. However, the first line might be
552 garbled, so it makes sense to skip all bytes until the first \0.
553 offset_last_wrap (integer)::
554 The offset in the SHM segment at which the last wrap occured. i3 only
555 stores entire messages in the SHM log, so it might waste a few bytes at
556 the end to be more efficient. Tools should not print content after the
560 -----------------------------
562 "offset_next_write":132839,
563 "offset_last_wrap":26214400,
564 "shmname":"/i3-log-3392",
567 -----------------------------
573 To get informed when certain things happen in i3, clients can subscribe to
574 events. Events consist of a name (like "workspace") and an event reply type
575 (like I3_IPC_EVENT_WORKSPACE). The events sent by i3 are in the same format
576 as replies to specific commands. However, the highest bit of the message type
577 is set to 1 to indicate that this is an event reply instead of a normal reply.
579 Caveat: As soon as you subscribe to an event, it is not guaranteed any longer
580 that the requests to i3 are processed in order. This means, the following
581 situation can happen: You send a GET_WORKSPACES request but you receive a
582 "workspace" event before receiving the reply to GET_WORKSPACES. If your
583 program does not want to cope which such kinds of race conditions (an
584 event based library may not have a problem here), I suggest you create a
585 separate connection to receive events.
587 === Subscribing to events
589 By sending a message of type SUBSCRIBE with a JSON-encoded array as payload
590 you can register to an event.
593 ---------------------------------
595 payload: [ "workspace", "focus" ]
596 ---------------------------------
601 The numbers in parenthesis is the event type (keep in mind that you need to
602 strip the highest bit first).
605 Sent when the user switches to a different workspace, when a new
606 workspace is initialized or when a workspace is removed (because the
607 last client vanished).
609 Sent when RandR issues a change notification (of either screens,
610 outputs, CRTCs or output properties).
613 --------------------------------------------------------------------
614 # the appropriate 4 bytes read from the socket are stored in $input
616 # unpack a 32-bit unsigned integer
617 my $message_type = unpack("L", $input);
619 # check if the highest bit is 1
620 my $is_event = (($message_type >> 31) == 1);
623 my $event_type = ($message_type & 0x7F);
626 say "Received event of type $event_type";
628 --------------------------------------------------------------------
632 This event consists of a single serialized map containing a property
633 +change (string)+ which indicates the type of the change ("focus", "init",
637 ---------------------
638 { "change": "focus" }
639 ---------------------
643 This event consists of a single serialized map containing a property
644 +change (string)+ which indicates the type of the change (currently only
648 ---------------------------
649 { "change": "unspecified" }
650 ---------------------------
654 For some languages, libraries are available (so you don’t have to implement
655 all this on your own). This list names some (if you wrote one, please let me
659 i3 includes a headerfile +i3/ipc.h+ which provides you all constants.
660 However, there is no library yet.
662 http://github.com/badboy/i3-ipc
664 http://search.cpan.org/search?query=AnyEvent::I3
666 http://github.com/thepub/i3ipc