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    brightlight v4
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Overview
========

This is brightlight, version v4. brightlight is a program that can get and
set the screen backlight brightness on Linux systems using the kernel sysfs 
interface. I wrote this program because the backlight keys on my laptop's 
keyboard didn't work after I installed Linux on it, and the bash script I was 
using to perform the task wasn't very flexible nor portable.

This program requires libbsd or a BSD-compatible implementation of strlcpy() 
and strlcat().


Installation
============

brightlight can be compiled by issuing 'make'. Compiler options can be changed
by editing the Makefile. The default compiler is gcc, however clang works too.
You can then place the resulting binary somewhere in your $PATH.

You can change the path #defined by the preprocessor macro BACKLIGHT_PATH to 
suit your own system. It must point to the directory where the files 
'brightness' and 'max_brightness' reside. On my laptop, for example, this path 
is "/sys/class/backlight/intel_backlight/", however yours may be different. 
The compile-time default can always be overridden using the -f flag (see below).


Usage
=====

Options:

  -v, --version          Print program version and exit.
  -h, --help             Show this help message.
  -p, --percentage       Read or write the brightness level as a percentage 
                         (0 to 100) instead of the internal scale the kernel 
                         uses (such as e.g. 0 to 7812).
  -r, --read             Read the backlight brightness level.
  -w, --write <val>      Set the backlight brightness level to <val>, where
                         <val> is a positive integer.
  -i, --increment <val>  Increment/increase the backlight brightness level by
                         <val>, where <val> is a positive integer. 
      --increase <val>   Same as --increment.
  -d, --decrement <val>  Decrement/decrease the backlight brightness level by
                         <val>, where <val> is a positive integer.
      --decrease <val>   Same as --decrement.
  -f, --file <path>      Specify alternative path to backlight control
                         directory. This is likely to be a subdirectory under
                         \"/sys/class/backlight/\".
  -m, --maximum          Show maximum brightness level of the screen
                         backlight on the kernel's scale. The compile-time
                         default control directory is used if -f or --file is
                         not specified. The -p and --percentage flags are 
                         ignored when this option is specified.

The flags -r, -w, -m, -i, -d and their corresponding long options are mutually
exclusive however one of them is required.


Changelog:
==========

v1, 07/02/2016 - First version of brighlight.
v2, 26/04/2016 - Tidied up program internals, added new operations
                 and long options.
v3, 31/07/2016 - Tidied up program logic and internals, added build system.
v4, 08/01/2017 - Minor changes to fix bugs found by clang static analyzer.

License
=======

Copyright (C) 2016, 2017 multiplex'd <[email protected]>

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
file LICENSE for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.