.\"  -*- nroff -*-
.Dd August 4, 2018
.Os GNU/Linux
.Dt LIGHT 1 URM
.Sh NAME
.Nm light
.Nd a program to control backlight controllers
.Sh SYNOPSIS
.Nm light
.Op Fl abcGhHkIlLmOprV
.Op Fl s Ar ARG
.Op Fl v Ar LEVEL
.Op Fl A Ar VAL
.Op Fl S Ar VAL
.Op Fl U Ar VAL
.Sh DESCRIPTION
.Nm
is a program to control backlight display and keyboard controllers under
GNU/Linux.
.Pp
.Bl -bullet -compact
.It
Operates independently of X (X-Window)
.It
Can automatically figure out the best controller to use, making full use
of the underlying hardware
.It
Supports a minimum cap on the brightness value, as some controllers set
the display to be pitch black at a vaĺue of 0 (or higher)
.El
.Sh COMMANDS
The following unique commands are supported:
.Pp
.Bl -tag -width Ds
.It Fl A Ar VAL
Add value
.It Fl G
Get value, default
.It Fl H , Fl h
Show help text and exit
.It Fl I
Restore brightness
.It Fl L
List controllers
.It Fl O
Save brightness
.It Fl S Ar VAL
Set value
.It Fl U Ar VAL
Subtract value
.It Fl V
Show program version and exit
.El
.Sh OPTIONS
The behavior of the above commands can be modified using these options:
.Pp
.Bl -tag -width Ds
.It Fl b
Set
.Fl S ,
Get
.Fl G ,
Add
.Fl A ,
or Subtract
.Fl U
active brightness, default
.It Fl k
Act on keyboard backlight
.It Fl l
Act on display backlight, default
.It Fl m
Get 
.Fl G
maximum brightness
.It Fl c
Set
.Fl S
or get
.Fl G
minimum cap for brightness
.It Fl a
Select controller automatically, default
.It Fl p
Interpret input and output values in percent, default
.It Fl r
Interpret input and output values in raw mode
.It Fl s Ar ARG
Specify controller to use.  Use
.Fl L
to list available controllers
.It Fl v Ar ARG
Set verbosity level, by default
.Nm
only outputs read values:
.Pp
.Bl -tag -width 0: -compact
.It 0:
Read values
.It 1:
Read values, Errors
.It 2:
Read values, Errors, Warnings
.It 3:
Read values, Errors, Warnings, Notices
.El
.El
.Sh FILES
When run in its classic SUID root mode
.Nm
caches settings and current brightness in
.Pa /etc/light .
In its non-priviliged mode of operation the
.Pa ~/.cache/light
directory is used instead.
.Sh AUTHORS
Copyright \(co 2014 Fredrik Haikarainen
.Pp
This is free software, see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE