toggle_lcd_backlight.hs

{-# LANGUAGE OverloadedStrings #-}

module Main (main) where

import Turtle hiding (x)
import Prelude hiding (FilePath)
import qualified Data.Text as T
import qualified Data.Text.IO as TIO
import Filesystem.Path.CurrentOS (encodeString)

main :: IO ()
main = do
  let a = "/tmp/lcd_backlight_last_value" :: Turtle.FilePath
  exists <- testfile a
  if exists then do
    v <- TIO.readFile $ encodeString a
    proc "xbacklight" ["-set", v] empty
    rm a
  else do
    output a (inproc "xbacklight" ["-get"] empty)
    void $ proc "xbacklight" ["-set", "0"] empty