class String

def shell_split
  out = [String.new("")]
  state = :none
  escape_next = false
  quote = String.new("")
  strip.split(//).each do |char|
    case state
    when :none, :space
      case char
      when /\s/
        out << String.new("") unless state == :space
        state = :space
        escape_next = false
      when "\\"
        if escape_next
          out.last << char
          escape_next = false
        else
          escape_next = true
        end
      when '"', "'"
        if escape_next
          out.last << char
          escape_next = false
        else
          state = char
          quote = String.new("")
        end
      else
        state = :none
        out.last << char
        escape_next = false
      end
    when '"', "'"
      case char
      when '"', "'"
        if escape_next
          quote << char
          escape_next = false
        elsif char == state
          out.last << quote
          state = :none
        else
          quote << char
        end
      when '\\'
        if escape_next
          quote << char
          escape_next = false
        else
          escape_next = true
        end
      else
        quote << char
        escape_next = false
      end
    end
  end
  out
end