BRIGHTNESS(1)

# NAME

brightness - adjust brightness via sysfs

# SYNOPSIS

*brightness* [*-h*] [*-m* _minimum_[*%*]] [*-M* _maximum_[*%*]]  _backlight_ [*+*|*-*]_adjustment_

# DESCRIPTION

The *brightness* utility is used to perform log-scale brightness adjustments of
a sysfs exposed backlight.

The options are as follows:

*-m* _minimum_[*%*] or *--min* _minimum_[*%*]
	Specify an artificial minimum raw value or log-scale percentage.

*-M* _maximum_[*%*] or *--max* _maximum_[*%*]
	Specify an artificial maximum raw value or log-scale percentage.

*-h* or *--help*
	Print out the *brightness* help text and exit.

_backlight_ must be the path to the directory of a backlight exposed over sysfs.

_adjustment_ is a real number optionally prefixed by a sign. Numbers prefixed
with either a *+* or a *-* are relative percentage changes and un-prefixed
numbers are treated as absolute percentages. If *--max* or *--min* are
specified, the meanings of a percent of change and a percentage setpoint are
unaffected. This means that attempting to set 15% brightness when a 10% is set
will set the brightness to 15%, not 23.5%.

# EXAMPLES

Increase the brightness by 10%:

```
$ brightness /sys/class/backlight/amdgpu_bl0 +10
```

Decrease the brightness by 6.25%:

```
$ brightness /sys/class/backlight/amdgpu_bl0 -6.25
```

Set the backlight to maximum brightness:

```
$ brightness /sys/class/backlight/amdgpu_bl0 100
```

This tool is best paired with _acpid_(8) and used as part of an event handler.
For example:

```
#!/bin/sh
backlight=/sys/class/backlight/amdgpu_bl0
pct=6.25
case "$1" in
video/brightnessup*)   brightness "$backlight" "+$pct" ;;
video/brightnessdown*) brightness "$backlight" "-$pct" ;;
esac
```

# SEE ALSO

_sysfs_(5), _acpid_(8)