Find the most frequently occurring alphanumeric in a very large data file

alpha_max.rb

chars = Hash.new(0)
File.open("2019-annual/taxa.txt") do |f|
  f.each_char.lazy.each do |char|
    chars[char] += 1 if char.match(/^[[:alpha:]]$/)
  end
end
puts chars.to_a.max{ |a, b| a[1] <=> b[1] }