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#!/usr/bin/env python3
'''
brightness.py
Usage:
brightness.py [show]
brightness.py set [--] <value>
'''
import re
import docopt
backlight_prefix_path = '/sys/class/backlight/intel_backlight'
def read_brightness():
'''
Return the current brightness value as reported by the driver.
'''
# We can use either the `brightness' file or `actual_brightness'.
# The differences are documented in the linux kernel tree at
# Documentation/sysfs-class-backlight.txt
# Briefly speaking, reading the `brigthness' file returns the
# brightness as reported by the driver whereas reading
# `actual_brigthess` returns the value queried directly from the
# hardware.
with open(backlight_prefix_path + '/brightness') as fd:
return int(fd.read())
def read_max_brightness():
'''
Return the maximum brightness value that is supported.
'''
with open(backlight_prefix_path + '/max_brightness') as fd:
return int(fd.read())
def print_current_brightness():
'''
Output the current brightness first as a value over the maximum
value, then as a percentage.
'''
max_brightness = read_max_brightness()
cur_brightness = read_brightness()
percentage_brightness = cur_brightness * 100 / max_brightness
output = 'Current brightness: {cur}/{max} ({percentage:.2f}%)'.format(
cur=cur_brightness, max=max_brightness,
percentage=percentage_brightness)
print(output)
def set_current_brightness(value):
'''
Set the current brightness value according to the parameter.
The parameter can take multiple forms:
1) a number (e.g. 650);
2) a number followed by the '%' sign (e.g. 70%);
3) a number preceded by a '+' or '-' sign (e.g. +30);
4) a number number preceded by a '+' or '-' sign and followed by a '%' sign
(e.g. +10%).
'''
matches = re.fullmatch('([+-])?(\d+)(%)?', value)
if matches is None:
raise ValueError()
groups = matches.groups()
# The first group is either '+', '-' or None.
# The second group is a number.
# The third group is either '%' or None.
max_brightness = None
cur_brightness = None
new_brightness = None
# If we are going to increment / decrement the the value, we need to know
# what the current value is.
if groups[0] is not None:
cur_brightness = read_brightness()
# If we want to play around with percentage values, we need to know what
# the maximum value is.
if groups[2] is not None:
max_brightness = read_max_brightness()
# option 1)
if groups[0] is None and groups[2] is None:
new_brightness = int(groups[1])
# option 2)
elif groups[0] is None and groups[2] is not None:
new_brightness = round(int(groups[1]) * max_brightness / 100)
# option 3)
elif groups[0] is not None and groups[2] is None:
if groups[0] == '+':
new_brightness = cur_brightness + int(groups[1])
else:
new_brightness = cur_brightness - int(groups[1])
# option 4)
else:
delta = round(int(groups[1]) * max_brightness / 100)
if groups[0] == '+':
new_brightness = cur_brightness + delta
else:
new_brightness = cur_brightness - delta
with open(backlight_prefix_path + '/brightness', mode='w') as fd:
print(new_brightness, file=fd)
def main(argv=None):
args = docopt.docopt(__doc__, version='1', argv=argv)
try:
if args['set']:
set_current_brightness(args['<value>'])
else:
print_current_brightness()
except ValueError as e:
raise docopt.DocoptExit(str(e))
if __name__ == '__main__':
main()
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