BACKLIGHT(1) - General Commands Manual
backlight - adjust screen brightness
backlight decrease [amount]
backlight increase [amount]
backlight set percentage
The backlight tool adjust the brightness on your screen using direct access to ACPI video extension.
The following commands are available:
Decrease the specific amount percentage value (default: 10).
Get the current level scaled to a percentage range.
Increase the specific amount percentage value (default: 10).
Set brightness to the percentage value.
On Linux, you need to have ACPI Video support either as module or built-in the kernel.
You may use backlight as non-root user if you create appropriate udev rules to make files under /sys/class/backlight writable by a group or per user.
The source package comes with an example of udev rule that can be installed in /usr/lib/udev/rules.d.
Access to brightness under FreeBSD requires super-user, you may need to run backlight as root or use setuid permission for non-root users.
You also need to load acpi_video(4) module at boot by adding acpi_video_load=“YES” in /boot/loader.conf.
On OpenBSD, the device /dev/ttyC0 must be writable in your user but this is normally the case when you login. Otherwise you may simply run the program as root.
Note: you may need to specify a bigger amount with the increase, decrease commands if your system use small percentages.
backlight was written by David Demelier <email@example.com>
Mac OS X 10.15 - September 16, 2019