Pathname#world_readable?

If the entry at the path in self exists and is readable by others, returns the integer permissions for the entry; otherwise, returns nil:

pn = Pathname('/tmp/t.tmp')
pn.world_readable?                    # => nil    # Does not exist.
pn.write('foo')                                   # Create file.
pn.world_readable?.to_s(8)            # => "664"  # World-readable.
pn.chmod(0o000)                                   # Change to unreadable.
pn.world_readable?                    # => nil    # Not readable.
pn.delete                                         # Clean up.
Pathname('.').world_readable?.to_s(8) # => "775"  # Directory.