Controls and displays volume settings on the Mac command line.

vol.rb

#!/usr/bin/env ruby

# This file's home is at https://gist.github.com/keithrbennett/fcf8d1511a430dd2cbc3bafdfe81ba59.

# With a numeric argument from 0 to 100, 
# sets volume to that %, and outputs new volume settings.
#
# Without any argument, outputs volume settings.

# Author: Keith Bennett (keithrbennett on Github)

# Strangely, the argument to "osascript -e 'set volume..." is in the range
# 0 to 7, where 0 is 0% volume and 7 is 100% volume, while
# the utility that prints the volume prints the percent: 

#  osascript -e 'get volume settings'
# output volume:50, input volume:100, alert volume:100, output muted:false

# We need to round the percent numbers because the underlying Mac utility
# returns integral percents (i.e. 33%, not 33.3%).


def percent_to_range_0_7(percent)
  percent / (100 / 7.0)
end


def current_volume_percent
  text = `osascript -e 'get volume settings'`
  text.split(',').first.split(':').last.to_f.round(0)
end


def set_volume(percent)
  arg_0_to_7 = percent_to_range_0_7(percent)
  cmd = "osascript -e 'set volume #{arg_0_to_7}'"
  `#{cmd} 2>&1`
end


def main
  old_volume = current_volume_percent

  volume_change_requested = (ARGV.length > 0)

  if volume_change_requested
    requested_volume = ARGV[0].to_f.round(0)

    if old_volume == requested_volume
      puts "No need to change volume. Already at #{old_volume}%."
    else
      set_volume(requested_volume)
      new_volume = current_volume_percent
      puts "Changed volume from #{old_volume}% to #{new_volume}%."
    end
  else
    puts "Volume is currently at #{old_volume}%."
  end
end


main