Redshift (software)

Redshift is an application that adjusts the computer display's color temperature based upon the time of day. The program is free software, and is intended to reduce eye strain as well as insomnia.
Redshift transitions the computer display's color temperature evenly between daytime and night temperatures to allow the user's eyes to slowly adapt. At night, the color temperature is low and is typically 3000–4000 K, preferably matching the room's lighting temperature. Typical color temperature during the daytime is 5500–6500 K.
Features.
Redshift is primarily distributed for and used on the Linux operating system.
Redshift can be used to set a single color temperature and brightness ("one shot mode") or can adjust the temperature and brightness continuously to follow the sun's elevation, in which case it will transition to the night color temperature settings near twilight. The temperature and brightness settings for daytime and night can be user-configured.
To determine the Sun's elevation the software requires the user's location in form of latitude and longitude.
On Linux and BSD operating systems, Redshift supports multiple monitors through the X extensions RandR (preferred) or VidMode, or through the Direct Rendering Manager. Because Redshift can only be configured to use the same gamma correction on all monitors it controls, it is usually desirable to run one instance of the program per monitor.
Interfaces.
Redshift originally possessed only a command-line interface, but now has graphical user interfaces (GUIs) that support most Linux desktop environments. Those GUIs include redshift-gtk, redshift-plasmoid, and nightshift.
redshift-gtk is included in Redshift's source tree. In addition to a windowed interface, it provides a tray status icon that can enable or disable Redshift or adjust the screen's color temperature automatically.
Redshift can be opened with the use of terminal, panel launchers or startup commands: the command 'redshift -O #TEMP' (#TEMP being a number from 1000-25000) will set the temperature and the command 'redshift -x' to exit Redshift.
A simple script can be made and called upon to set the colour temp manually via a shortcut or panel launcher:
shouldloop=true;
while $shouldloop; do
 read -p "What temp would you like? 1000-25000K: " scale
 if "$scale" -ge 1000 && "$scale" -le 25000; then
 redshift -O $scale
 shouldloop=false;
 elif $scale = "x"; then
 exit
 elif $scale = "X"; then
 exit
 else
 echo "Invalid value or outside range. x to exit..."
 fi
done
Reviews.
Redshift has been positively reviewed by Linux users, who note that Redshift has some installation and user interface advantages compared to the f.lux Linux port xflux. However, f.lux's systems have since been updated to enhance its dimmed display.
Ubuntu MATE provides Redshift installed by default since their 17.10 release.
Linux Mint Cinnamon provides Redshift installed by default since their 18.3 release.