TRUE
on success and FALSE on failure, by default generating an
exception. The flags argument is a bitwise disjunction of
these flags:
SIO_INPUTSIO_OUTPUTSIO_INPUT for details.
If neither SIO_OUTPUT nor SIO_INPUT is given t
may not be a pair.SIO_TRYLOCKFALSE if the stream cannot be locked immediately. No
error is generated.SIO_NOERRORThe returned stream is owned by the calling thread using PL_acquire_stream().