Linux Access Control Lists library (libacl, -lacl).  The function
sets  the  permission set of the ACL entry indicated by the argu‐
ment to the permissions contained in the argument Any  ACL  entry
descriptors that refer to the entry containing the permission set
referred  to by shall continue to refer to those entries. Any ACL
entry descriptors that refer to the entry referred  to  by  shall
continue  to refer to that entry.  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 argument is not a  valid  descriptor  for  a  permission  set
within  an ACL entry.  The argument contains values which are not
valid values.  IEEE Std 1003.1e draft 17 (“POSIX.1e”,  abandoned)
Derived  from the FreeBSD manual pages written by and adapted for
Linux by