lio_listio - initiate a list of I/O requests
#include <aio.h>
int lio_listio(int mode, struct aiocb *const aiocb_list[],
int nitems, struct sigevent *sevp);
Link with -lrt.
The
lio_listio() function initiates the list of I/O operations described
by the array
aiocb_list.
The
mode operation has one of the following values:
- LIO_WAIT
- The call blocks until all operations are complete. The sevp
argument is ignored.
- LIO_NOWAIT
- The I/O operations are queued for processing and the call returns
immediately. When all of the I/O operations complete, asynchronous
notification occurs, as specified by the sevp argument; see
sigevent(7) for details. If sevp is NULL, no asynchronous
notification occurs.
The
aiocb_list argument is an array of pointers to
aiocb
structures that describe I/O operations. These operations are executed in an
unspecified order. The
nitems argument specifies the size of the array
aiocb_list. null pointers in
aiocb_list are ignored.
In each control block in
aiocb_list, the
aio_lio_opcode field
specifies the I/O operation to be initiated, as follows:
- LIO_READ
- Initiate a read operation. The operation is queued as for a call to
aio_read(3) specifying this control block.
- LIO_WRITE
- Initiate a write operation. The operation is queued as for a call to
aio_write(3) specifying this control block.
- LIO_NOP
- Ignore this control block.
The remaining fields in each control block have the same meanings as for
aio_read(3) and
aio_write(3). The
aio_sigevent fields of
each control block can be used to specify notifications for the individual I/O
operations (see
sigevent(7)).
If
mode is
LIO_NOWAIT,
lio_listio() returns 0 if all I/O
operations are successfully queued. Otherwise, -1 is returned, and
errno is set to indicate the error.
If
mode is
LIO_WAIT,
lio_listio() returns 0 when all of the
I/O operations have completed successfully. Otherwise, -1 is returned, and
errno is set to indicate the error.
The return status from
lio_listio() provides information only about the
call itself, not about the individual I/O operations. One or more of the I/O
operations may fail, but this does not prevent other operations completing.
The status of individual I/O operations in
aiocb_list can be determined
using
aio_error(3). When an operation has completed, its return status
can be obtained using
aio_return(3). Individual I/O operations can fail
for the reasons described in
aio_read(3) and
aio_write(3).
The
lio_listio() function may fail for the following reasons:
- EAGAIN
- Out of resources.
- EAGAIN
- The number of I/O operations specified by nitems would cause the
limit AIO_MAX to be exceeded.
- EINTR
- mode was LIO_WAIT and a signal was caught before all I/O
operations completed; see signal(7). (This may even be one of the
signals used for asynchronous I/O completion notification.)
- EINVAL
- mode is invalid, or nitems exceeds the limit
AIO_LISTIO_MAX.
- EIO
- One of more of the operations specified by aiocb_list failed. The
application can check the status of each operation using
aio_return(3).
If
lio_listio() fails with the error
EAGAIN,
EINTR, or
EIO, then some of the operations in
aiocb_list may have been
initiated. If
lio_listio() fails for any other reason, then none of the
I/O operations has been initiated.
The
lio_listio() function is available since glibc 2.1.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
lio_listio () |
Thread safety |
MT-Safe |
POSIX.1-2001, POSIX.1-2008.
It is a good idea to zero out the control blocks before use. The control blocks
must not be changed while the I/O operations are in progress. The buffer areas
being read into or written from must not be accessed during the operations or
undefined results may occur. The memory areas involved must remain valid.
Simultaneous I/O operations specifying the same
aiocb structure produce
undefined results.
aio_cancel(3),
aio_error(3),
aio_fsync(3),
aio_return(3),
aio_suspend(3),
aio_write(3),
aio(7)