gpg utility for encrypting and decrypting files

gpg_utility.rb

# encoding: utf-8

require 'io/console'
require 'optparse'

def show_wait_spinner(fps=10)
  chars = %w[| / - \\]
  delay = 1.0/fps
  iter = 0
  spinner = Thread.new do
    while iter do  # Keep spinning until told otherwise
      print chars[(iter+=1) % chars.length]
      sleep delay
      print "\b"
    end
  end
  yield.tap{       # After yielding to the block, save the return value
    iter = false   # Tell the thread to exit, cleaning up after itself…
    spinner.join   # …and wait for it to do so.
  }                # Use the block's return value as the method's
end

opts = {}

OptionParser.new do |opt|
  opt.on('-e', '--encrypt [file]',  'Encrypt the given file') { |o| opts[:encrypt] = true; opts[:file] = o; }
  opt.on('-d', '--decrypt [file]',  'Decrypt the given file') { |o| opts[:encrypt] = false; opts[:file] = o; }
  opt.on('-o', '--output [file]',   'Specify the output of the encrypted/decrypted file') { |o| opts[:output] = o }
end.parse!

# Check mandatory values
unless (opts.keys.length == 3)
  raise Exception.new('Not enough options to execute this script were given. Try to run this script with [-h || --help] argument to learn more.')
end

# Check gpg command exists
if `which gpg`.chomp.length.zero?
  raise Exception.new("gpg utility is not installed.")
end

# Check file exists
unless File.exists?(opts[:file])
  raise Exception.new("Input file '#{opts[:file]}' does not exists.")
end
# Check output does not exists
if File.exists?(opts[:output])
  raise Exception.new("Output file '#{opts[:output]}' already exists.")
end

if opts[:encrypt]
  puts 'Enter the password to encrypt the file: '
  password  = STDIN.noecho(&:gets).chomp
  
  show_wait_spinner do
    `gpg --yes --batch --passphrase=\"#{password}\" --output #{opts[:output]} -c #{opts[:file]}`
  end
else
  puts 'Enter the password to decrypt the file: '
  password  = STDIN.noecho(&:gets).chomp
  
  show_wait_spinner do
    `gpg --yes --batch --passphrase=\"#{password}\" --output #{opts[:output]} -d #{opts[:file]}`
  end
end

puts "**** DONE! ****"