Linux Access Control Lists library (libacl, -lacl).  The function
returns  if  the file or directory referred to by the argument is
associated with an extended access ACL, or if the  directory  re‐
ferred  to  by is associated with a default ACL. The function re‐
turns if the file has neither an extended access ACL  nor  a  de‐
fault ACL.  An extended ACL is an ACL that contains entries other
than  the  three  required  entries  of  tag  types ACL_USER_OBJ,
ACL_GROUP_OBJ and ACL_OTHER.  If the result of the function for a
file object is then ACLs define no  discretionary  access  rights
other  than those already defined by the traditional file permis‐
sion bits.  Access to the file object may be  further  restricted
by  other  mechanisms,  such as Mandatory Access Control schemes.
The system call can be used to check whether a given type of  ac‐
cess  to  a file object would be granted.  is identical to except
in the case of a symbolic link, where the link itself is interro‐
gated, not the file that it refers to.  Since symbolic links have
no ACL themselves, the operation is supposed to fail on them.  If
successful, the function returns if the file object  referred  to
by  has  an extended access ACL or a default ACL, and if the file
object referred to by has neither an extended access  ACL  nor  a
default  ACL.  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 corre‐
sponding value: Search permission is denied for  a  component  of
the  path  prefix.   The length of the argument is too long.  The
named object does not exist or the argument points  to  an  empty
string.   A component of the path prefix is not a directory.  The
file system on which the file identified by is located  does  not
support  ACLs,  or  ACLs  are  disabled.  This is a non‐portable,
Linux specific extension to the ACL  manipulation  functions  de‐
fined  in  IEEE  Std  1003.1e  draft  17 (“POSIX.1e”, abandoned).
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