Linux Access Control Lists library (libacl, -lacl).  The function
checks  if  the  ACL pointed to by the argument contains only the
required ACL entries of tag  types  ACL_USER_OBJ,  ACL_GROUP_OBJ,
and  ACL_OTHER,  and contains no permissions other that ACL_READ,
ACL_WRITE or ACL_EXECUTE.  If the ACL has this form, it  can  can
be  fully  represented with the traditional file permission bits,
and is considered equivalent with the traditional file permission
bits.  If is an equivalent ACL and the pointer is not  the  value
pointed  to  by  is set to the value that defines the same owner,
group and other permissions as contained in the ACL.  On success,
this function returns the value if is an equivalent ACL, and  the
value  if  is  not  an equivalent ACL. On error, the value is re‐
turned, and is set appropriately.  If any of the following condi‐
tions occur, the function returns the value and sets to the  cor‐
responding  value: The argument is not a valid pointer to an ACL.
This is a non‐portable, Linux specific extension to the  ACL  ma‐
nipulation  functions  defined  in  IEEE  Std  1003.1e  draft  17
(“POSIX.1e”, abandoned).  Written by