lubuntu - Openbox execute keybind - Ask Ubuntu

to adjust backlight i'm using command:

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

now want setup keybinding command above via shell script openbox adjust backlight in pc. setup keybinding searched config file used 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 edited config file lubuntu-rc.xml , works (i tested it):

 <!-- keybindings -->     <keybind key="0xc0">       <action name="execute">         <execute>lxterminal</execute>       </action>     </keybind> 

now want execute custom shell script below. in shell script there 2 commands (line 2 , 5) needs addional permissions. how can run them root?

#!/bin/bash curr=`cat /sys/class/backlight/apple_backlight/brightness` if [ $curr -gt 0 ];    curr=$((curr - 1));    echo $curr > /sys/class/backlight/apple_backlight/brightness; fi 

i changed privileges error 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 script without binding , works:

bash /home/ubuntu/documents/customscripts/brightnessdown.sh 

i had setup execution bit 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 entered:

sudo chmod 754 ~/documents/customscripts/brightness*.sh 

now can run both scripts via keyboard shortcuts.