BrightnessControl

Shell script to control screen brightness in Ubuntu Linux.

Usage

$ sudo backlight.sh -u | -d

-u Increases brightness
-d Decrease brightness

Move the script backlight.sh to /usr/bin/
$ sudo mv backlight.sh /usr/bin/backlight
Now its possible to execute the script from anywhere in the commandline without the .sh extension
$ sudo backlight -u | -d

As the script requires more privileges, we have to run it with sudo and type in the password
To avoid this lets modify the sudoers file to allow the current user to execute the command without password
Open the sudoers file:
$ sudo visudo
Add the following line to the file
username ALL=(ALL) NOPASSWD: /usr/bin/backlight
where username is your username
Press Control + X to save the file and reboot your system
After the reboot you can run the command without entering the password

It makes our life easier if we are able to raise/lower brightness using keyboard. It's very easy.
Install xbindkeys using the following command:
$ sudo apt-get install xbindkeys
Next we have to create a configuration file for xbindkeys in the home directory
$ xbindkeys --defaults > $HOME/.xbindkeysrc
where $HOME referes to your home directory
Open the configuration file:
$ nano .xbindkeysrc
Add your configuration which is a pair of key and a command to execute on pressing that key.

"sudo backlight -u"
    Control + Right
"sudo backlight -d"
    Control + Left

Save the file and close it.
Run xbindkeys
$ xbindkeys
Now pressing Control + Right should increase the brightness and Control + Right decreases it.
To make xbindkeys stop listening to key presses:
$ killall -HUP xbindkeys

Checked in Ubuntu 14.04 64-bit Linux on Dell Inspiron N4010. It will work in all Dell Inspirons I guess. About other laptops I don't know SORRY!