Linux Access Control Lists library (libacl, -lacl).  The function
calculates  and sets the permissions associated with the ACL_MASK
ACL entry of the ACL referred to by The value of the new  permis‐
sions  is  the union of the permissions granted by all entries of
tag type ACL_GROUP, ACL_GROUP_OBJ, or ACL_USER.  If the  ACL  re‐
ferred  to by already contains an ACL_MASK entry, its permissions
are overwritten; if it does not contain an ACL_MASK entry, one is
added.  If the ACL referred to by does not contain  enough  space
for the new ACL entry, then additional working storage may be al‐
located.  If  the working storage cannot be increased in the cur‐
rent location, then it may be relocated and the previous  working
storage  is  released and a pointer to the new working storage is
returned via The order of existing entries in the  ACL  is  unde‐
fined  after  this  function.  Any existing ACL entry descriptors
that refer to entries in 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 any of the following con‐
ditions occur, the function returns and sets to the corresponding
value: The argument is not a valid pointer to an ACL.  The  func‐
tion  is  unable  to allocate the memory required for an ACL_MASK
ACL entry.  IEEE Std 1003.1e draft 17 (“POSIX.1e”, abandoned) De‐
rived from the FreeBSD manual pages written by  and  adapted  for
Linux by