lio_listio(3)

NAME#

lio_listio - initiate a list of I/O requests

LIBRARY#

Real-time library (librt, -lrt)

SYNOPSIS#

#include <aio.h>

int lio_listio(int \nmode\n,\n
\n               struct aiocb *restrict const \naiocb_list\n[restrict],\n
\n               int \nnitems\n, struct sigevent *restrict \nsevp\n);

DESCRIPTION#

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(3type) 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)).

RETURN VALUE#

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).

ERRORS#

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.

ATTRIBUTES#

For an explanation of the terms used in this section, see attributes(7).

STANDARDS#

POSIX.1-2008.

HISTORY#

glibc 2.1. POSIX.1-2001.

NOTES#

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.

SEE ALSO#

aio_cancel(3), aio_error(3), aio_fsync(3), aio_return(3), aio_suspend(3), aio_write(3), aio(7)