Redshift and dim/undim your screens with easy to use commands.

dim.sh

#!/bin/bash
#
# This script can be used to set the Monitor temperatur and 
# brightness to nighttime and eye friendly values
# Author: c.stein@keyboardinterrupt.com
# Usage:
# `dim.sh 1` = normal brightness
# `dim.sh .5` = half brightness 
for display in $(xrandr --listmonitors | cut -d " " -f 6) ; do
  xrandr --output $display --brightness ${1} --gamma 1:.8:.7
done

undim.sh

#!/bin/bash
# This script sets the brightness and gamma of every monitor to *normal* 1
# Usage:
# `undim.sh`
for display in $(xrandr --listmonitors | cut -d " " -f 6) ; do
  xrandr --output $display --brightness 1 --gamma 1:1:1
done