ttscoff · July 8, 2019 16:20 · Jul 8, 2019
diff --git a/brightness.rb b/brightness.rb
@@ -0,0 +1,81 @@
+#!/usr/bin/env ruby
+# Brett Terpstra 2019
+# This script adds the ability to increment/decrement display brightness
+# levels to the nriley/brightness CLI (Copyright (c) 2014-2019, Nicholas Riley)
+# Requires CLI installation: `brew install brightness`
+# See https://github.com/nriley/brightness
+CMD = "/usr/local/bin/brightness"
+
+# Display usage and exit
+def usage(code)
+  puts "Usage: #{File.basename(__FILE__)} [+-=]X"
+  puts "  [+-]X increment/decrement by integer 0-100"
+  puts "  =X set brightness 0-100"
+  Process.exit code
+end
+
+# Returns current brightness of the first display as a percentage
+# (0-100). All displays will end up set to the same level, so we're only
+# checking for the first display.
+def get_brightness
+  details = %x{#{CMD} -l}
+
+  return (details.match(/display 0: brightness (\d\.\d+)/)[1].to_f.round(2) * 100).to_i
+end
+
+# Set brightness of all displays to a percentage (0-100)
+def set_brightness(level)
+  target = level * 0.01
+  return system %Q{"#{CMD}" #{target} &> /dev/null}
+end
+
+
+def main(arg)
+  # if the argument starts with =, set brightness
+  if arg =~ /^=(\d{1,3})/
+    target = $1.to_i
+
+    if target < 0 || target > 100
+      puts "Error: #{target} is out of range"
+      usage(1)
+    end
+
+  # if argument is a positive or negative integer, increment or decrement
+  # brightness
+  else
+    inc = arg.to_i
+    current = get_brightness
+    target = (current + inc)
+
+    # ensure the adjusted level is in range. Don't throw an error, allow
+    # overruns and just compensate
+    if target > 100
+      target = 100
+    elsif target < 0
+      target = 0
+    end
+  end
+
+  # Execute CLI
+  res = set_brightness(target)
+  if res
+    $stdout.print get_brightness
+  else
+    $stdout.puts "Error setting brightness"
+    Process.exit 1
+  end
+end
+
+# Ensure brightness CLI is installed
+unless File.executable?(CMD)
+  puts "Error: brightness executable missing"
+  puts "Requires brightness CLI (brew install brightness)"
+  Process.exit 1
+end
+
+# Ensure the argument is valid
+if ARGV.length != 1 || ARGV[0] !~ /^[+-=]?\d{1,3}$/
+  usage(1)
+else
+  main(ARGV[0])
+end
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