world_writable?

        # File::Stat.world_writable?

(from ruby core)
### Implementation from Stat
---
    stat.world_writable?  ->  integer or nil

---

If *stat* is writable 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("/tmp").world_writable?         #=> 511
    sprintf("%o", m)                              #=> "777"