ibacklight.hs

#!/usr/bin/env nix-shell
#! nix-shell -i runhaskell -p "haskellPackages.ghcWithPackages (pkgs: [pkgs.shqq])"
{-# LANGUAGE QuasiQuotes #-}

import System.ShQQ (sh)
import System.Environment (getArgs)

parseOp :: Num a => Char -> a -> a -> a
parseOp '+' = (+)
parseOp '-' = (-)
parseOp '=' = flip const
parseOp op = error $ "invalid operation: " ++ [op]

main = do

  actBrightness <- read <$> readFile "/sys/class/backlight/intel_backlight/actual_brightness"
  maxBrightness <- read <$> readFile "/sys/class/backlight/intel_backlight/max_brightness"
  let curBrightness = actBrightness / maxBrightness

  args <- concat <$> getArgs
  if args == "-get"
      then print $ round $ curBrightness * 100
      else do
  (op:magn) <- [sh| echo ${args} | sed -e 's/-inc/+/g' -e 's/-dec/-/g' -e 's/-set/=/g'|]

  let newBrightness = round $ (maxBrightness *) $ parseOp op curBrightness (read magn/100) :: Int
  -- [sh| gksudo -\\- bash -c "echo ${newBrightness} > /sys/class/backlight/intel_backlight/brightness" |]
  writeFile "/sys/class/backlight/intel_backlight/brightness" (show newBrightness)

  return ()