Provided by: gammastep_2.0.9-1build2_amd64 
NAME
gammastep - set color temperature of display according to time of day
SYNOPSIS
gammastep [-l LAT:LON | -l PROVIDER:OPTIONS] [-t DAY:NIGHT] [OPTIONS...]
DESCRIPTION
gammastep adjusts the color temperature of your screen according to your surroundings.
This may help your eyes hurt less or reduce the risk for delayed sleep phase syndrome if
you are working in front of the screen at night.
The color temperature is set according to the position of the sun. A different color
temperature is set during night and daytime. During twilight and early morning, the color
temperature transitions smoothly from night to daytime temperature to allow your eyes to
slowly adapt over a period of about an hour. At night the color temperature should be set
to match the lamps in your room. This is typically a low temperature at around 3000K-4000K
(default is 4500K). During the day, the color temperature should match the light from
outside, typically around 5500K-6500K (default is 6500K). The light has a higher
temperature on an overcast day.
In addition to the command-line tool gammastep, the GUI gammastep-indicator provides an
alternative interface that shows up as a notification icon in the desktop environment.
OPTIONS
-h Display help message.
-v Enable verbose output.
-V Show program version.
-b DAY:NIGHT
Screen brightness to apply (between 0.1 and 1.0).
-c FILE
Load settings from specified configuration file.
-g R:G:B
Additional gamma correction to apply.
-l LAT:LON
Your current location, in degrees, given as floating point numbers, towards north
and east, with negative numbers representing south and west, respectively.
-l PROVIDER[:OPTIONS]
Select provider for automatic location updates (Use "-l list" to see available
providers).
-m METHOD[:OPTIONS]
Method to use to set color temperature (Use "-m list" to see available methods).
-o One-shot mode (do not continuously adjust color temperature). Use this with the -P
option to clear the existing gamma ramps before applying the new color temperature.
-O TEMP
One-shot manual mode (set color temperature). Use this with the -P option to clear
the existing gamma ramps before applying the new color temperature.
-p Print mode (only print parameters and exit).
-P Reset existing gamma ramps before applying new color effect.
-x Reset mode (remove adjustment from screen).
-r Disable fading between color temperatures.
-t DAY:NIGHT
Color temperature to set at daytime/night.
The neutral temperature is 6500K. Using this value will not change the color temperature
of the display. Setting the color temperature to a value higher than this results in more
blue light, and setting a lower value will result in more red light.
Default temperature values:
Daytime: 6500K, night: 4500K
CONFIGURATION FILE
A configuration file with the name config.ini can optionally be placed in
~/.config/gammastep/ (if the environment variable XDG_CONFIG_HOME is undefined) or
${XDG_CONFIG_HOME}/gammastep/ (if XDG_CONFIG_HOME is defined). The file has standard INI
format. General program options are placed under the general header, while options for
location providers and adjustment methods are placed under a header with the name of that
provider or method. General options are:
temp-day = integer
Daytime temperature
temp-night = integer
Night temperature
fade = 0 or 1
Disable or enable fading between color temperatures.
brightness-day = 0.1-1.0
Screen brightness at daytime
brightness-night = 0.1-1.0
Screen brightness at night
elevation-high = decimal
The solar elevation in degrees for the transition to daytime
elevation-low = decimal
The solar elevation in degrees for the transition to night
dawn-time = HH:MM[-HH:MM]
The custom time interval for the transition from night to day in the morning. When
specified, the solar elevation will not be used to determine the current
daytime/night period. If this option is set, dusk-time must also be specified.
dusk-time = HH:MM[-HH:MM]
The custom time interval for the transition from day to night in the evening. When
specified, the solar elevation will not be used to determine the current
daytime/night period. If this option is set, dawn-time must also be specified.
gamma = R:G:B
Gamma adjustment to apply (day and night)
gamma-day = R:G:B
Gamma adjustment to apply at daytime
gamma-night = R:G:B
Gamma adjustment to apply at night
adjustment-method = name
Select adjustment method. Options for the adjustment method can be given under the
configuration file heading of the same name.
location-provider = name
Select location provider. Options for the location provider can be given under the
configuration file heading of the same name.
Options for location providers and adjustment methods can be found in the help output of
the providers and methods.
EXAMPLE
Example for Copenhagen, Denmark:
$ gammastep -l 55.7:12.6 -t 5700:3600 -g 0.8 -m randr -v
An example configuration file with the same effect as the above command line:
[general]
temp-day=5700
temp-night=3600
gamma=0.8
adjustment-method=randr
location-provider=manual
[manual]
lat=55.7
lon=12.6
HOOKS
Executables (e.g. scripts) placed in folder ~/.config/gammastep/hooks will be run when a
certain event happens. The first parameter to the script indicates the event and further
parameters may indicate more details about the event. The event period-changed is
indicated when the period changes (night, daytime, transition). The second parameter is
the old period and the third is the new period. The event is also signaled at startup with
the old period set to none. Any dotfiles in the folder are skipped.
A simple script to handle these events can be written like this:
#!/bin/sh
case $1 in
period-changed)
exec notify-send "Gammastep" "Period changed to $3"
esac
AUTHOR
gammastep was written by Jon Lund Steffensen <jonlst@gmail.com>, and is now maintained by
Cameron Nemo <cam@nohom.org>.
Both gammastep and this manual page are released under the GNU General Public License,
version 3.
BUGS
Please report bugs to <https://gitlab.freedesktop.org/CameronNemo/gammastep/issues>
KNOWN ISSUES
gammastep will not affect the color of your cursor when your graphics driver is configured
to use hardware cursors. Some graphics drivers have an option to disable hardware cursors.
REDSHIFT(1)