Get the system time zone in Olson format using Ruby

there_i_fixed_it.rb

def get_local_timezone_str
  # Yes, this is actually a shell script…
  olsontz = `if [ -f /etc/timezone ]; then
    cat /etc/timezone
  elif [ -h /etc/localtime ]; then
    readlink /etc/localtime | sed "s/\\/usr\\/share\\/zoneinfo\\///"
  else
    checksum=\`md5sum /etc/localtime | cut -d' ' -f1\`
    find /usr/share/zoneinfo/ -type f -exec md5sum {} \\; | grep "^$checksum" | sed "s/.*\\/usr\\/share\\/zoneinfo\\///" | head -n 1
  fi`.chomp
  
  # …and it almost certainly won't work with Windows or weird *nixes
  throw "Olson time zone could not be determined" if olsontz.nil? || olsontz.empty?
  return olsontz
end

When using Rails, things only get worse—Rails gets the time zone from its configuration, so it's not useful for fetching the system's time zone.

Adding to the dissonance, Rails cleverly extends Time:

% rails console
Loading development environment (Rails 4.1.7)
irb(main):001:0> Time.now.zone
=> "PST"
irb(main):005:0> Time.now.zone.class
=> String
irb(main):002:0> Time.zone
=> #<ActiveSupport::TimeZone:0x00000101dae2b8 @name="UTC", @utc_offset=nil, @tzinfo=#<TZInfo::TimezoneProxy: Etc/UTC>, @current_period=#<TZInfo::TimezonePeriod: nil,nil,#<TZInfo::TimezoneOffset: 0,0,UTC>>>>
irb(main):003:0>