Linux Access Control Lists library (libacl, -lacl).  The function
clears all permissions from the permission set referred to by the
argument Any existing descriptors that refer to shall continue to
refer to that permission set.  If any of the following conditions
occur,  the function returns and sets to the corresponding value:
The argument is not a  valid  descriptor  for  a  permission  set
within  an  ACL  entry.   IEEE  Std 1003.1e draft 17 (“POSIX.1e”,
abandoned) Derived from the FreeBSD manual pages written  by  and
adapted for Linux by