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Tutorial: Getting started with ydotool to automate key presses (or mouse movements) in Linux

14 minute read

ydotool works well in both the X11 and Wayland window managers to press any keys, including Windows + D, for example

Here is a full tutorial.

Note: ydotool is a universal replacement of xdotool, which is a tool to move the mouse and do keypresses in the X11 window manager. The ydotool program was created because xdotool doesn’t work in Wayland, which is the new window manager that Ubuntu is slowly moving towards, even though Wayland currently is still very buggy should be turned off in most cases.

Tested on Ubuntu 22.04.2 with both the X11 and Wayland window managers (for how to change between the two, see my notes and screenshots in my answer here).

1. Build and install ydotool:

See: https://github.com/ReimuNotMoe/ydotool#build.

First, build and install it:

# install dependencies
sudo apt update
sudo apt install git cmake scdoc

# build ydotool
# See: https://github.com/ReimuNotMoe/ydotool#build
git clone https://github.com/ReimuNotMoe/ydotool.git
cd ydotool
mkdir build
cd build
cmake ..                 # takes < 1 second
time make -j "$(nproc)"  # takes < 1 second
sudo make install
# Note: the install command installs here:
#
#       -- Install configuration: ""
#       -- Installing: /usr/local/bin/ydotoold
#       -- Installing: /usr/local/bin/ydotool
#       -- Installing: /usr/lib/systemd/user/ydotool.service
#       -- Installing: /usr/local/share/man/man1/ydotool.1
#       -- Installing: /usr/local/share/man/man8/ydotoold.8

# See the man pages for help, and to prove to yourself it is installed
man ydotool   # for the main program
man ydotoold  # for the background daemon process
# help menu
ydotool -h    # for the main program
ydotoold -h   # for the background daemon process [VERY HELPFUL MENU!]

# check the version; my output is `v1.0.4-0-g57ba7d0`
ydotoold --version

2. Now, use it: have ydotool press Windows + D

Quick summary:

# 1. start the `ydotoold` background daemon (`sudo -b` runs it in the
# background; see `sudo -h`).
# - It takes a couple seconds to fully start up and print "READY". Once it does
#   that, hit Enter a couple times to clear out the command line.
sudo -b ydotoold --socket-path="$HOME/.ydotool_socket" --socket-own="$(id -u):$(id -g)"

# 2. Use `ydotool`
# - Have ydotool press Windows + D once to hide all windows, then make it wait 2
#   seconds, then have it press Windows + D again to show all windows:
YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool key 125:1 32:1 32:0 125:0; \
    sleep 2; \
    YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool key 125:1 32:1 32:0 125:0

# 3. Additional commands you may need: to show, kill, and help

# See the `ydotoold` background running processes
ps auxf | grep ydotoold

# Kill the `ydotoold` background running processes
sudo pkill ydotoold

# View the `ydotool` main help menu, including a list of all sub-commands.
ydotool -h

# View the `ydotool` sub-command help menus. 
# - Bug ( https://github.com/ReimuNotMoe/ydotool/issues/206 ): the daemon *must*
#   be running first to see these help menus!
YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool key -h
YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool click -h
YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool mousemove -h
# etc. 

# Open the Linux C header file containing all available key codes that `ydotool`
# can press
gedit /usr/include/linux/input-event-codes.h

Details:

# In one terminal, start the required background daemon process as root, but
# setting its socket file to be accessible by your main user withOUT `sudo`. 
# - Allowing our user to access this daemon withOUT running it as `root` is
#   accomplished by setting the owner of the socket file to our own user via
#   the `--socket-path="$HOME/.ydotool_socket" --socket-own="$(id -u):$(id -g)"` 
#   options.
# - It takes a couple seconds to fully start up and print "READY". Once it does
#   that, hit Enter a couple times to clear out the command line.
sudo -b ydotoold --socket-path="$HOME/.ydotool_socket" --socket-own="$(id -u):$(id -g)"

# In the same terminal, or another terminal, send a signal to this running
# background daemon via the open socket inter-process-communication
# (IPC) pseudo-file. Here, we send the Windows + D shortcut key:
#
# Windows + D press and release: window toggle: this hides all windows.
YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool key 125:1 32:1 32:0 125:0

The 125:1 32:1 32:0 125:0 key codes tell the program to, in this order: “press the Windows key, press the D key, release the D key, release the Windows key”.

That’s it!

Manually press Windows + D now to show all windows again so you can see your terminal.

I’ll talk about what the key 125:1 32:1 32:0 125:0 part means farther below.

Note that sudo -b runs this daemon as a background process. If you leave off -b, then you’ll have to use two separate terminals, as the daemon will take up the first terminal.

You can leave the background ydotoold background daemon running forever, but if you’d like to kill it, here’s how:

  1. Kill ydotoold: 
     sudo pkill ydotoold
  2. (Optional) see if ydotoold is running: 
     ps auxf | grep ydotoold

    Example run and output before killing ydotoold. As you can see, my single call to ydotoold above actually spawned 3 ydotoold processes, because the one I called spawned a sub process, which spawned a sub sub process.

     $ ps auxf | grep ydotoold
 root     1772293  0.0  0.0  23004  5952 pts/4    S    22:00   0:00  |   |   \_ sudo ydotoold --socket-path=/home/gabriel/.ydotool_socket --socket-own=1000:1000
 root     1772304  0.0  0.0  23004   944 pts/6    Ss+  22:00   0:00  |   |   |   \_ sudo ydotoold --socket-path=/home/gabriel/.ydotool_socket --socket-own=1000:1000
 root     1772305  0.0  0.0   2776   956 pts/6    S    22:00   0:00  |   |   |       \_ ydotoold --socket-path=/home/gabriel/.ydotool_socket --socket-own=1000:1000
 gabriel+ 1792351  0.0  0.0  17864  2476 pts/4    S+   22:09   0:00  |   |   \_ grep --color=auto ydotoold
  3. Here is what the main ydotool help menu looks like. It shows the various sub-commands available: 
     $ ydotool -h
 Usage: ydotool <cmd> <args>
 Available commands:
   click
   mousemove
   type
   key
   debug
   bakers
 Use environment variable YDOTOOL_SOCKET to specify daemon socket.
  4. Here are some of the sub-command menus. Note that due to this bug, you must have the ydotoold daemon running first in order for the sub-command help menus to show up:
    1. key: YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool key -h 
       $ YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool key -h
 Usage: key [OPTION]... [KEYCODES]...
 Emit key events.

 Options:
   -d, --key-delay=N          Delay N milliseconds between key events
   -h, --help                 Display this help and exit

 Since there's no way to know how many keyboard layouts are there in the world,
 we're using raw keycodes now.

 Syntax: <keycode>:<pressed>
 e.g. 28:1 28:0 means pressing on the Enter button on a standard US keyboard.
      (where :1 for pressed means the key is down and then :0 means the key is released)     
      42:1 38:1 38:0 24:1 24:0 38:1 38:0 42:0 - "LOL"

 Non-interpretable values, such as 0, aaa, l0l, will only cause a delay.

 See `/usr/include/linux/input-event-codes.h' for available key codes (KEY_*).
    2. click: YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool click -h 
       $ YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool click -h
 Usage: click [OPTION]... [BUTTONS]...
 Click mouse buttons.

 Options:
   -r, --repeat=N             Repeat entire sequence N times
   -D, --next-delay=N         Delay N milliseconds between input events (up/down,                                
                              a complete click means doubled time)
   -h, --help                 Display this help and exit

 How to specify buttons:
   Now all mouse buttons are represented using hexadecimal numeric values, with an optional
 bit mask to specify if mouse up/down needs to be omitted.
   0x00 - LEFT
   0x01 - RIGHT
   0x02 - MIDDLE
   0x03 - SIDE
   0x04 - EXTR
   0x05 - FORWARD
   0x06 - BACK
   0x07 - TASK
   0x40 - Mouse down
   0x80 - Mouse up
   Examples:
     0x00: chooses left button, but does nothing (you can use this to implement extra sleeps)
     0xC0: left button click (down then up)
     0x41: right button down
     0x82: middle button up
   The '0x' prefix can be omitted if you want.
    3. mousemove: YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool mousemove -h 
       $ YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool mousemove -h
 Usage: mousemove [OPTION]... [-x <xpos> -y <ypos>] [-- <xpos> <ypos>]
 Move mouse pointer or wheel.

 Options:
   -w, --wheel                Move mouse wheel relatively
   -a, --absolute             Use absolute position, not applicable to wheel
   -x, --xpos                 X position
   -y, --ypos                 Y position
   -h, --help                 Display this help and exit

 You need to disable mouse speed acceleration for correct absolute movement.

Voila! I’m so happy I got this working! I now have a viable means of getting my “show desktop” button to work again once I am forced to use Wayland, and once it is less buggy and actually functions right.

What do keycodes 125:1 32:1 32:0 125:0 mean, and how do I find key codes I want to use?

See the YDOTOOL_SOCKET="$HOME/.ydotool_socket" ydotool key -h help menu above. It states:

Syntax: <keycode>:<pressed>
e.g. 28:1 28:0 means pressing on the Enter button on a standard US keyboard.
     (where :1 for pressed means the key is down and then :0 means the key is released)     
     42:1 38:1 38:0 24:1 24:0 38:1 38:0 42:0 - "LOL"

Non-interpretable values, such as 0, aaa, l0l, will only cause a delay.

See `/usr/include/linux/input-event-codes.h' for available key codes (KEY_*).

So, open up your Linux /usr/include/linux/input-event-codes.h file to see all key codes:

# (my preference) open in the Sublime Text GUI
subl /usr/include/linux/input-event-codes.h
# open in the gedit GUI
gedit /usr/include/linux/input-event-codes.h
# open in nano (Ctrl + x to exit)
nano /usr/include/linux/input-event-codes.h
# open in vim (:q then Enter to exit)
vi /usr/include/linux/input-event-codes.h

You can see what appears to be a more-recent version of this file online in the Linux kernel here: https://github.com/torvalds/linux/blob/master/include/uapi/linux/input-event-codes.h.

As you can see in that file here, key code 125 is the KEY_LEFTMETA:

#define KEY_LEFTMETA      125

Key code 32 is KEY_D:

#define KEY_D         32

A Google search for “input-event-codes.h which is the super or windows key?” helped me find this, where @hasimsait said it was KEY_LEFTMETA. That’s how I knew to use that key for the Windows (Super) key.

From the ydotool key -h help menu above, we learned: Syntax: <keycode>:<pressed>, where 1 is pressed, and 0 is not pressed. So, 32:1 32:0 means to press and then release the D key. That would type a lower-case d if your cursor was in a text editor.

Therefore, 125:1 32:1 32:0 125:0 means, in this order: “press the Windows key, press the D key, release the D key, release the Windows key”.

Notice that to activate the Windows + D shortcut key, you must release the buttons in the opposite order they were pressed! You hold the Windows key while pressing and releasing the D key. So, be sure to release the buttons with <keycode>:0 in the opposite order that you pressed them.

Warnings in Wayland

Note that I see this in the output when I run my ydotoold command above in Wayland only:

WARNING: running xinput against an Xwayland server. See the xinput man page for details.
unable to find device pointer:ydotoold virtual device

I don’t really know what it means, but it seems important. Here is the full run and output:

$ sudo ydotoold --socket-path="$HOME/.ydotool_socket" --socket-own="$(id -u):$(id -g)"
[sudo] password for gabriel: 
Socket path: /home/gabriel/.ydotool_socket
Removing old stale socket
Socket permission: 0600
Socket ownership: UID=1000, GID=1000
READY
WARNING: running xinput against an Xwayland server. See the xinput man page for details.
unable to find device pointer:ydotoold virtual device

man xinput shows the following, but again, I don’t really understand what this means either:

XWAYLAND

Xwayland is an X server that uses a Wayland Compositor as backend. Xwayland acts as translation layer between the X protocol and the Way‐ land protocol but does not have direct access to the hardware. The X Input Extension devices created by Xwayland (“xwayland-pointer”, “xway‐ land-keyboard”, etc.) map to the Wayland protocol devices, not to phys‐ ical devices.

These X Input Extension devices are only visible to other X clients connected to the same Xwayland process. Changing properties on Xwayland devices only affects the behavior of those clients. For example, dis‐ abling an Xwayland device with xinput does not disable the device in Wayland-native applications. Other changes may not have any effect at all.

In most instances, using xinput with an Xwayland device is indicative of a bug in a shell script and xinput will print a warning. Use the Wayland Compositor’s native device configuration methods instead.

In X11, I don’t get the warning. Here is the output when I run the daemon:

$ sudo ydotoold --socket-path="$HOME/.ydotool_socket" --socket-own="$(id -u):$(id -g)"
[sudo] password for gabriel: 
Socket path: /home/gabriel/.ydotool_socket
Removing old stale socket
Socket permission: 0600
Socket ownership: UID=1000, GID=1000
READY

References:

  1. The comment from @Rinzwind where I first found out about ydotool
  2. https://github.com/ReimuNotMoe/ydotool - official repository for ydotool
  3. Ask Ubuntu Equivalent to xdotool for Wayland - mentions ydotool
  4. [my answer] Bugs in Wayland, and how to change between the X11 and Wayland window managers in Ubuntu: Ask Ubuntu: “failed to enable link training” when resuming from suspend
  5. [my answer] Ask Ubuntu: How can I add “Show desktop” to the GNOME dash or Ubuntu Dock?
  6. [my answer] Get the User ID (UID) and Group ID (GID) for the running user
  7. Where I learned about sudo -b: Running a program in the background as sudo
  8. Where I learned about the -f part of ps auxf to graphically show the process hierarchy (previously I just used ps aux): Unix & Linux: How to view the names all child processes spawned by a program

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