Documentation is sparse on this and it doesn't help that Apple's version differs from POSIX.
I know to specify ACL_TYPE_EXTENDED for acl_get_file() and know how to cycle through entries. From what I can tell, the tag is either ALLOW or DENY and you can check the permset for which actions the tag applies to.
I can't figure out how get the group or user the entry applies to. The only way I've been able to get this info is by using acl_to_text and scraping that output. Anyone know how to do this using the acl APIs?