Linux Access Control Lists library (libacl, -lacl).  The function
obtains  a descriptor for an ACL entry as specified by within the
ACL indicated by the argument If the value of is ACL_FIRST_ENTRY,
then the function returns in a descriptor for the first ACL entry
within If the value of is ACL_NEXT_ENTRY, then the  function  re‐
turns  in a descriptor for the next ACL entry within If a call is
made to with set to ACL_NEXT_ENTRY when there has not been either
an initial successful call to or a previous  successful  call  to
following  a call to or then the effect is unspecified.  Calls to
do not modify any ACL entries. Subsequent  operations  using  the
returned ACL entry descriptor operate on the ACL entry within the
ACL  in working storage. The order of all existing entries in the
ACL remains unchanged.  Any existing ACL entry  descriptors  that
refer  to  entries  within the ACL continue to refer to those en‐
tries. Any existing ACL pointers that refer to the  ACL  referred
to by continue to refer to the ACL.  If the function successfully
obtains  an ACL entry, the function returns a value of If the ACL
has no ACL entries, the function returns the value If  the  value
of  is  ACL_NEXT_ENTRY  and the last ACL entry in the ACL has al‐
ready been returned by a previous call to  the  function  returns
the  value  until a successful call with an of ACL_FIRST_ENTRY is
made. Otherwise, the value is returned and 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 pointer to an ACL.  The argument is neither  ACL_NEXT_EN‐
TRY  nor ACL_FIRST_ENTRY.  IEEE Std 1003.1e draft 17 (“POSIX.1e”,
abandoned) Derived from the FreeBSD manual pages written  by  and
adapted for Linux by