Linux Access Control Lists library (libacl, -lacl).  The function
associates  an access ACL with a file or directory, or associates
a default ACL with a directory. The pathname for the file or  di‐
rectory  is  pointed  to by the argument The effective user ID of
the process must match the owner of the file or directory or  the
process  must  have  the CAP_FOWNER capability for the request to
succeed.  The value of the argument is used to  indicate  whether
the  access  ACL or the default ACL associated with is being set.
If the parameter is ACL_TYPE_ACCESS, the access ACL of  shall  be
set.  If  the  parameter  is ACL_TYPE_DEFAULT, the default ACL of
shall be set. If the argument specifies a type of ACL that cannot
be associated with then the function fails.  The  parameter  must
reference  a  valid  ACL  according to the rules described on the
manual page if the parameter is ACL_TYPE_ACCESS, and must  either
reference  a valid ACL or an ACL with zero ACL entries if the pa‐
rameter is ACL_TYPE_DEFAULT. If the parameter references an empty
ACL, then the function removes any default  ACL  associated  with
the  directory  referred to by the parameter.  If any of the fol‐
lowing conditions occur, the function returns  and  sets  to  the
corresponding  value: Search permission is denied for a component
of the path prefix or the object exists and the process does  not
have appropriate access rights.  Argument specifies a type of ACL
that  cannot  be associated with The argument does not point to a
valid ACL.  The ACL has more entries than the file referred to by
can obtain.  The parameter is not ACL_TYPE_ACCESS or ACL_TYPE_DE‐
FAULT.  The parameter is ACL_TYPE_DEFAULT, but the file  referred
to  by  is  not  a  directory.  The length of the argument is too
long.  The named object does not exist or the argument points  to
an empty string.  The directory or file system that would contain
the  new ACL cannot be extended or the file system is out of file
allocation resources.  A component of the path prefix  is  not  a
directory.   The file identified by cannot be associated with the
ACL because the file system on which the file is located does not
support this.  The process does not have appropriate privilege to
perform the operation to set the  ACL.   This  function  requires
modification of a file system which is currently read‐only.  IEEE
Std 1003.1e draft 17 (“POSIX.1e”, abandoned) The behavior of when
the  parameter  refers  to  an  empty  ACL  and  the parameter is
ACL_TYPE_DEFAULT is an extension in the Linux implementation,  in
order  that  all values returned by can be passed to The POSIX.1e
function for removing a default ACL is Derived from  the  FreeBSD
manual pages written by and adapted for Linux by