Ruby 2.3.0 リファレンスマニュアル > ライブラリ一覧 > 組み込みライブラリ > File::Statクラス > world_readable?
world_readable? -> Integer | nil
[permalink][rdoc]If stat is readable by others, returns an integer representing the file permission bits of stat. Returns nil otherwise. The meaning of the bits is platform dependent; on Unix systems, see stat(2).
m = File.stat("/etc/passwd").world_readable? # => 420 sprintf("%o", m) # => "644"