How to Change the Monitor Brightness on Linux

Possible to change screen brightness with C?

I'd start with selecting from the following list of ubuntu pacakges, the tool that allows you to manage your screen's brightness (hint: it depends on the brand)

nvidia-settings - Tool of configuring the NVIDIA graphics driver
smartdimmer - Change LCD brightness on Geforce cards
armada-backlight - adjust backlight of Compaq Armada laptops (E300, M500, M700)
ddccontrol - a program to control monitor parameters
eeepc-acpi-scripts - Scripts to support suspend and hotkeys on the Asus Eee PC laptop
fnfxd - ACPI and hotkey daemon for Toshiba laptops
gddccontrol - a program to control monitor parameters
spicctrl - Sony Vaio controller program to set LCD backlight brightness
tpb - program to use the IBM ThinkPad(tm) special keys
xfce4-power-manager - power manager for Xfce desktop
xfce4-power-manager-plugins - power manager plugins for Xfce panel
xvattr - Utility to change Xv attributes

Once you have selected it,

sudo apt-get build-dep <pkgname>
apt-get source --compile <pkgname> 

should get you on the right track

How to control backlight by terminal command

There are many possibilities. Just to name a few:

1.Bare echo

echo 8 > /sys/class/backlight/intel_backlight/brightness

For this to work, the user must be in the video group.

Look at /sys/class/backlight/intel_backlight/max_brightness to see what maximum brightness is supported.

2.The simplest to use

Install xbacklight package and then try

 xbacklight -inc 20     # increase backlight by 20%
 xbacklight -dec 30     # decrease by 30%
 xbacklight -set 80     # set to 80% of max value
 xbacklight -get        # get the current level

3.Over sophisticated

Run xrandr --verbose and look for a line with resolution like LVDS1 connected 1024x600+0+0. The name of your display (LVDS1 in this example) is needed here. Now you are ready to set brightness

xrandr --output LVDS1 --brightness 0.4

But this sets only software, not hardware brightness so you can exceed the limits (in both directons). Don't expect beautiful results but if you are brave enough to experiment a little bit then fasten your seatbelt and run

xrandr --output LVDS1 --brightness 1.7
xrandr --output LVDS1 --brightness -0.4  #yes, negative value is possible
xrandr --output LVDS1 --brightness 1

You can torture more your display with xrandr, but be ready to reboot your computer if something goes wrong. For example play with the following

xrandr --output LVDS1 --reflect x
xrandr --output LVDS1 --reflect xy
xrandr --output LVDS1 --reflect normal     # return to normal state
xrandr --output LVDS1 --rotate left
xrandr --output LVDS1 --rotate inverted
xrandr --output LVDS1 --rotate normal      # again, back to normal

Changing monitor brightness programatically in Ubuntu 11.10

I'm not sure that it's possible to go lower than what the laptop controls get you, but you can programatically change brightness by echoing a value to /sys/class/backlight/<something>/brightness. On my netbook the 'something' is acpi_video0.

$ cat /sys/class/backlight/acpi_video0/brightness
10
$ sudo sh -c 'echo 0 > /sys/class/backlight/acpi_video0/brightness'
$ cat /sys/class/backlight/acpi_video0/brightness
0

Edit: There's also xbacklight, which uses XRandr.

How can i change the screen brightness of my laptop in ubuntu?

sudo gedit /etc/default/grub

And then type your root password and insert these lines:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
GRUB_CMDLINE_LINUX="acpi_osi=Linux"

Save and exit.

sudo update-grub

Restart your laptop and then it should work by the "Fn" + left and right arrows.

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