Linux Access Control Lists library (libacl, -lacl).  The function
tests  if  the  permission  specified  by  the  argument  (one of
ACL_READ, ACL_WRITE, ACL_EXECUTE) is contained in the ACL permis‐
sion set pointed to by the argument Any existing descriptors that
refer to continue to refer to that permission set.   If  success‐
ful,  the function returns if the permission specified by is con‐
tained in the ACL permission set and if  the  permission  is  not
contained in the permission set. Otherwise, the value is returned
and  the global variable is set to indicate the error.  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.  The argument is not  a
valid value.  This is a non‐portable, Linux specific extension to
the  ACL manipulation functions defined in IEEE Std 1003.1e draft
17 (“POSIX.1e”, abandoned).  Written by