To adjust my backlight I'm using the command:

sudo bash -c "echo $backlight_value > /sys/class/backlight/apple_backlight/brightness;"

Now I want to setup a keybinding for the command above via shell script with openbox to adjust the backlight in my PC. To setup the keybinding I searched for the config file which is used by openbox:

 $ ps ax | grep openbox
 1194 ?        Sl     0:02 openbox --config-file /home/ubuntu/.config/openbox/lubuntu-rc.xml --sm-save-file /home/ubuntu/.cache/openbox/sessions/1478226066-1194-624962777.obs --sm-no-load
 1958 pts/0    S+     0:00 grep --color=auto openbox

Next I edited the config file lubuntu-rc.xml and it works (I tested it):

 <!-- My Keybindings -->
    <keybind key="0xC0">
      <action name="Execute">

Now I want to execute my custom shell script below. But in my shell script there are two commands (line 2 and 5) which needs addional permissions. How can I run them as root?

curr=`cat /sys/class/backlight/apple_backlight/brightness`
if [ $curr -gt 0 ]; then
   curr=$((curr - 1));
   echo $curr > /sys/class/backlight/apple_backlight/brightness;

I also changed privileges but the error is still there (permission denied):

ls -l /sys/class/backlight/apple_backlight/
total 0
-rwxrwxr-x 1 ubuntu ubuntu 4096 Nov  4 00:41 brightness

I tested only the script without binding and it works:

bash /home/ubuntu/Documents/CustomScripts/brightnessDown.sh

1 Answer 1


I had to setup the execution bit for both scripts:

-rw**x**r-**x**r-- 1 ubuntu ubuntu  189 Nov  4 15:34 brightnessDown.sh
-rw**x**r-**x**r-- 1 ubuntu ubuntu  191 Nov  4 15:36 brightnessUp.sh

So I entered:

sudo chmod 754 ~/Documents/CustomScripts/brightness*.sh

Now I can run both scripts via keyboard shortcuts.

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