Dir.tmpdir

# File tmp/rubies/ruby-3.0.5/lib/tmpdir.rb, line 21
def self.tmpdir
  tmp = nil
  ['TMPDIR', 'TMP', 'TEMP', ['system temporary path', @@systmpdir], ['/tmp']*2, ['.']*2].each do |name, dir = ENV[name]|
    next if !dir
    dir = File.expand_path(dir)
    stat = File.stat(dir) rescue next
    case
    when !stat.directory?
      warn "#{name} is not a directory: #{dir}"
    when !stat.writable?
      warn "#{name} is not writable: #{dir}"
    when stat.world_writable? && !stat.sticky?
      warn "#{name} is world-writable: #{dir}"
    else
      tmp = dir
      break
    end
  end
  raise ArgumentError, "could not find a temporary directory" unless tmp
  tmp
end