0 Indicates success.
-1 Indicates failure, the named shared memory
object is not changed by the function call,
and errno is set to indicate the error:
o EACCES - Permission is denied to unlink the
named shared memory object.
o ENAMETOOLONG - The length of the name
argument exceeds PATH_MAX or a pathname
component is longer than NAME_MAX.
o ENOENT - The named shared memory object
does not exist.