world_writable?

If file_name is writable by others, returns an integer representing the file permission bits of file_name. Returns nil otherwise. The meaning of the bits is platform dependent; on Unix systems, see stat(2).

file_name can be an IO object.

File.world_writable?("/tmp")                  #=> 511
m = File.world_writable?("/tmp")
sprintf("%o", m)                              #=> "777"