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Control OSX Screen Brightness from Ubuntu 14.04 (on a USB stick!)

After trawling here and there and trying lots of different things, for me this works on my late 2012 21″ iMac with an ACPI card.

It’s best to put the script into a file, make sure the file is discoverable on PATH.

All details are in the folder: 
/sys/class/backlight/acpi_video0
which on my machine looks like this:
ubuntu@ubuntu:~/mc2$ cd /sys/class/backlight/acpi_video0
ubuntu@ubuntu:/sys/class/backlight/acpi_video0$ ls -l
total 0
-r--r--r-- 1 root root 4096 Oct 7 08:29 actual_brightness
-rw-r--r-- 1 root root 4096 Oct 7 08:29 bl_power
-rw-r--r-- 1 root root 4096 Oct 7 08:28 brightness
lrwxrwxrwx 1 root root 0 Oct 7 08:29 device -> ../../../0000:01:00.0
-r--r--r-- 1 root root 4096 Oct 7 08:03 max_brightness
drwxr-xr-x 2 root root 0 Oct 7 08:29 power
lrwxrwxrwx 1 root root 0 Oct 7 08:29 subsystem -> ../../../../../../class/backlight
-r--r--r-- 1 root root 4096 Oct 7 08:03 type
-rw-r--r-- 1 root root 4096 Oct 7 08:03 uevent
WARNING: If you use values higher than the maximum allowed for your card you *MAY* cause damage. The limit on my machine is 15 as indicated in the file
echo $1 | sudo tee /sys/class/backlight/acpi_video0/max_brightness
There are more exhaustive solutions out there including one I saw that didn’t work first time for me that limits the value but for me, being a hacker, I only needed a one liner. YMMV.

 DISCLAIMER: If you damage your machine, that’s your fault not mine!!!
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