ls -la /sys/class/backlight/acpi_video0/
totale 0
drwxr-xr-x 3 root root    0 feb 24 02:01 .
drwxr-xr-x 3 root root    0 feb 24 02:01 ..
-r--r--r-- 1 root root 4096 feb 24 02:01 actual_brightness
-rw-r--r-- 1 root root 4096 feb 24 02:04 bl_power
-rw-r--r-- 1 root root 4096 feb 24 02:01 brightness
lrwxrwxrwx 1 root root    0 feb 24 02:04 device -> ../../../0000:00:02.0
-r--r--r-- 1 root root 4096 feb 24 02:01 max_brightness
drwxr-xr-x 2 root root    0 feb 24 02:04 power
lrwxrwxrwx 1 root root    0 feb 24 02:04 subsystem -> ../../../../../class/backlight
-r--r--r-- 1 root root 4096 feb 24 02:01 type
-rw-r--r-- 1 root root 4096 feb 24 02:01 uevent