Change screen color temperature and brightness using the Xrandr extension
The original program was written by Ted Unangst (see http://www.tedunangst.com/flak/post/sct-set-color-temperature) who was so kind to put it under public domain.
In contrast to other programs that adapt color temperature, this programs minimizes the required dependencies to an absolute minimum.
I simply added the option to change the brightness, too. The arguments are as follows:
./sct TEMPERATURE BRIGHTNESS
where TEMPERATURE is given between 1000K and 10000K (default 6500K)
and BRIGHTNESS between 0.1 and 1.0 (default 1.0).
To compile, you must specify the location of libX11, libXrandr and the required include files, e.g.,
gcc -I/usr/local/include -L/usr/local/lib sct.c -o sct -lXrandr -lX11
or adapt it to your OS.
On Devuan (and probably other Debian derived distributions) you will need to
install the additional packages libxrandr-dev and libc6-dev.