Home / ubuntu / Questions / 1234742
Accepted
Gregory Opera
Asked: 2020-05-04 04:17:52 +0800 CST

Automatic Light / Dark Mode?

  • 772

Has anyone found a way to automatically switch between "light" and "dark" modes yet, with regards to the "Window Theme" in Ubuntu's settings (Settings → Appearance → Window Theme → Light / Standard / Dark)?

Digging into the settings every morning or evening is a real pain. It'd be great to be able to automatically switch to "dark" mode at sunset, and automatically switch to "light" mode at sunrise.

gnome gnome-shell

3 Answers

  1. Best Answer

    For GNOME, this shell extension exists: Night Theme Switcher

    It has quite a lot of options and already works out of the box, without having to configure anything, but the configuration is straight forward as well!

    Screenshot of the Schedule tab

    Screenshot of the GTK theme tab

    • 18

  2. The terminal command for changing theme is:

    gsettings set org.gnome.desktop.interface gtk-theme Yaru-dark

    for the Yaru-dark theme, and

    gsettings set org.gnome.desktop.interface gtk-theme Yaru-light

    for the Yaru-light theme.

    Now, there's something called cron-job for scheduling jobs (basically executing something, repeatedly at specific time). So, you can write a cron-job to execute these commands at specified times (something like change to dark theme at 9 PM and light theme at 6 AM).

    Add the following to a file named script.sh:

    #!/bin/bash
echo export DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS > lightscript.sh
echo export DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS > darkscript.sh
echo "gsettings set org.gnome.desktop.interface gtk-theme Yaru-light" >> lightscript.sh
echo "gsettings set org.gnome.desktop.interface gtk-theme Yaru-dark" >> darkscript.sh
chmod 755 lightscript.sh
chmod 755 darkscript.sh

currenttime=$(date +%H:%M)
if [[ "$currenttime" > "21:00" ]] || [[ "$currenttime" < "06:00" ]]; then
  ./darkscript.sh
else
  ./lightscript.sh
fi

    Make the file executable running:

    chmod 755 /path/to/script.sh

    or:

    chmod +x /path/to/script.sh

    Run gnome-session-properties in terminal. Add a new start up program by clicking add on right side and selecting the script.sh file by browsing and save it with some name and comment. This will tell GNOME to create lightscript.sh and darkscript.sh whenever you login through GUI.

    Add your job (change theme) to crontab by using the command:

    crontab -e

    and choosing a suitable editor or you can go to /var/spool/cron/crontabs and edit the file with your username. Accessing the file this way requires sudo privileges. Add the following two lines (with /path/to/ replaced by actual path):

    0 6 * * * /path/to/lightscript.sh
0 21 * * * /path/to/darkscript.sh

    It will say:

    crontab: installing new crontab

    after exiting the command. You can also check with:

    crontab -l

    This should do it. The above two lines tell cron to execute lightscript.sh at 6:00 AM and darkscript.sh at 9:00 PM everyday.

    We are taking this detour instead of just adding:

    0 6 * * * gsettings set org.gnome.desktop.interface gtk-theme Yaru-light

    to crontab because this requires the DBUS_SESSION_BUS_ADDRESS variable to be set correctly.

    • 9

  3. We can achieve this with the help of crontab and @shubhzgang's answer.

    #!/bin/bash

# Script that auto switches Ubuntu themes to Dark or Light, 
# depending on the time of day

# Copy this script file to /usr/local/bin/my-auto-theme
# Add following lines to crontab -e
# 0 9 * * * bash /usr/bin/local/my-auto-theme light
# 0 17 * * * bash /usr/bin/local/my-auto-theme dark
# @reboot bash /usr/bin/local/my-auto-theme

set_theme() {
    if [[ "$1" == "dark" ]]; then
        new_gtk_theme="Yaru-dark"
    elif [[ "$1" == "light" ]]; then
        new_gtk_theme="Yaru-light"
    else
        echo "[!] Unsupported theme: $1"
        return
    fi
    
    # https://askubuntu.com/a/1234819/895417
    export DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS
    current_gtk_theme=$(gsettings get org.gnome.desktop.interface gtk-theme)
    # echo "[.] Currently using ${current_gtk_theme}"
    if [[ "${current_gtk_theme}" == "'${new_gtk_theme}'" ]]; then
        echo "[i] Already using gtk '${new_gtk_theme}' theme"
    else
        echo "[-] Setting gtk theme to ${new_gtk_theme}"
        gsettings set org.gnome.desktop.interface gtk-theme ${new_gtk_theme}
        echo "[✓] gtk theme changed to ${new_gtk_theme}"
    fi
}

# If script run without argument
if [[ -z "$1" ]]; then
    currenttime=$(date +%H:%M)
    if [[ "$currenttime" > "17:00" || "$currenttime" < "09:00" ]]; then
        set_theme dark
    else
        set_theme light
    fi
else
    set_theme $1
fi

    We added @reboot so that script runs even if PC was shut down at cron trigger time.

    • 1