GNU Info
(libc.info)Status of AIO Operations
Getting the Status of AIO Operations
------------------------------------
As already described in the documentation of the functions in the
last section, it must be possible to get information about the status
of an I/O request. When the operation is performed truly
asynchronously (as with `aio_read' and `aio_write' and with
`lio_listio' when the mode is `LIO_NOWAIT'), one sometimes needs to
know whether a specific request already terminated and if so, what the
result was. The following two functions allow you to get this kind of
information.
- Function: int aio_error (const struct aiocb *AIOCBP)
This function determines the error state of the request described
by the `struct aiocb' variable pointed to by AIOCBP. If the
request has not yet terminated the value returned is always
`EINPROGRESS'. Once the request has terminated the value
`aio_error' returns is either 0 if the request completed
successfully or it returns the value which would be stored in the
`errno' variable if the request would have been done using `read',
`write', or `fsync'.
The function can return `ENOSYS' if it is not implemented. It
could also return `EINVAL' if the AIOCBP parameter does not refer
to an asynchronous operation whose return status is not yet known.
When the sources are compiled with `_FILE_OFFSET_BITS == 64' this
function is in fact `aio_error64' since the LFS interface
transparently replaces the normal implementation.
- Function: int aio_error64 (const struct aiocb64 *AIOCBP)
This function is similar to `aio_error' with the only difference
that the argument is a reference to a variable of type `struct
aiocb64'.
When the sources are compiled with `_FILE_OFFSET_BITS == 64' this
function is available under the name `aio_error' and so
transparently replaces the interface for small files on 32 bit
machines.
- Function: ssize_t aio_return (const struct aiocb *AIOCBP)
This function can be used to retrieve the return status of the
operation carried out by the request described in the variable
pointed to by AIOCBP. As long as the error status of this request
as returned by `aio_error' is `EINPROGRESS' the return of this
function is undefined.
Once the request is finished this function can be used exactly
once to retrieve the return value. Following calls might lead to
undefined behavior. The return value itself is the value which
would have been returned by the `read', `write', or `fsync' call.
The function can return `ENOSYS' if it is not implemented. It
could also return `EINVAL' if the AIOCBP parameter does not refer
to an asynchronous operation whose return status is not yet known.
When the sources are compiled with `_FILE_OFFSET_BITS == 64' this
function is in fact `aio_return64' since the LFS interface
transparently replaces the normal implementation.
- Function: int aio_return64 (const struct aiocb64 *AIOCBP)
This function is similar to `aio_return' with the only difference
that the argument is a reference to a variable of type `struct
aiocb64'.
When the sources are compiled with `_FILE_OFFSET_BITS == 64' this
function is available under the name `aio_return' and so
transparently replaces the interface for small files on 32 bit
machines.
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