Dir.tmpdir

# File tmp/rubies/ruby-3.3.0/lib/tmpdir.rb, line 26
def self.tmpdir
  ['TMPDIR', 'TMP', 'TEMP', ['system temporary path', SYSTMPDIR], ['/tmp']*2, ['.']*2].find do |name, dir|
    unless dir
      next if !(dir = ENV[name] rescue next) or dir.empty?
    end
    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
      break dir
    end
  end or raise ArgumentError, "could not find a temporary directory"
end