How to change "Global Dark Theme" on and off through Terminal?

I know how to set and display most themes, however I can find anything about how to turn the Global Dark Theme on and off through Terminal, I can only find the option in the gnome-tweak-tool. So is there not a way to turn it on and off through Terminal? I am running Ubuntu GNOME 15.10 with GNOME 3.18.

Solution 1:

To set the global dark theme from the command line, first navigate to a Terminal of your choice and then from within the shell emulator ...

Navigate to your home directory:

 cd ~

Create a new file called settings.ini inside of the GTK 4 directory:

 nano ~/.config/gtk-4.0/settings.ini

Enter the following fields into the configuration file:

[Settings]
gtk-application-prefer-dark-theme=1

Write the changes to disk by pressing control + x, then press y, then enter.

Solution 2:

For modern Gnome desktops:

Tested: Ubuntu 18.04, 20.04; Fedora 27, 32

Default dark mode:

gsettings set org.gnome.desktop.interface gtk-theme 'Adwaita-dark'

Default light mode:

gsettings set org.gnome.desktop.interface gtk-theme 'Adwaita'

Getting a list of available base theme names:

ls -d /usr/share/themes/* |xargs -L 1 basename

Caveats:

Some existing limitations to changing the theme: https://bugzilla.gnome.org/show_bug.cgi?id=783666 (bug conversation mentions them)
It appears that there's some variance in how this is adopted with Adwaita being the currently accepted default, but the tweak tool will also attempt to write to the settings.ini files.
Furthemore, applications provided as snaps may ship with their own settings.ini files making a command line solution much more difficult than a one-liner.

Ideally, a technique to invoke gnome-tweak-tool through CLI would cover most scenarios holistically. Gnome-tweak-tool is written in python3, so this should be theoretically possible to someone familiar with Python.