No, they really are not the same thing, not even nearly. You yourself mention one class of handles for which Unix has no equivalent. (FreeBSD process descript

No, they really are not the same thing, not even nearly. You yourself mention one class of handles for which Unix has no equivalent. (FreeBSD process descriptors have some gotchas that make them significiantly different; and Linux procfs descriptors do not match behaviours when it comes to the object lifetimes and handle waitability.)