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.

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