Linux Access Control Lists library (libacl, -lacl).  The function
retrieves the qualifier from the ACL entry indicated by the argu‐
ment  into working storage and returns a pointer to that storage.
If the value of the tag type in the ACL entry referred to  by  is
ACL_USER,  then the value returned by is a pointer to type If the
value of the tag  type  in  the  ACL  entry  referred  to  by  is
ACL_GROUP, then the value returned by is a pointer to type If the
tag  type in the ACL entry referred to by is a tag type for which
a qualifier is not supported, returns a value of and the function
fails. Subsequent operations using the returned  pointer  operate
on  an  independent copy of the qualifier in working storage, and
will not change the qualifier of the ACL  entry.   This  function
may  cause memory to be allocated. The caller should free any re‐
leasable memory, when the new qualifier is no longer required, by
calling with the value returned by as an argument.  The  argument
and  any other ACL entry descriptors that refer to entries within
the ACL containing the entry referred to by continue to refer  to
those  entries. The order of all existing entries in the ACL con‐
taining the entry referred to by remains unchanged.  On  success,
the  function returns a pointer to the tag qualifier that was re‐
trieved into ACL working storage. On error, a  value  of  is  re‐
turned  and is set appropriately.  If any of the following condi‐
tions occur, the function returns and sets to  the  corresponding
value:  The  argument is not a valid descriptor for an ACL entry.
The value of the tag type in the ACL entry referenced by the  ar‐
gument  is  neither  ACL_USER nor ACL_GROUP.  The value to be re‐
turned requires more memory than is allowed by  the  hardware  or
system‐imposed  memory  management constraints.  IEEE Std 1003.1e
draft 17 (“POSIX.1e”, abandoned) Derived from the FreeBSD  manual
pages written by and adapted for Linux by