lio_listio(S)
lio_listio --
list directed I/O
Syntax
cc . . . -lsuds
#include <aio.h>
int lio_listio(int mode, struct aiocb * const list[], int nent,
struct sigevent *sig);
Description
The
lio_listio(S)
function allows the calling process to initiate a list of
I/O requests with a single function call.
The mode argument takes one of the values
LIO_WAIT or LIO_NOWAIT declared in
aio(FP)
and determines whether the function returns when the I/O
operations have been completed, or as soon as the operations have
been queued. If the mode argument is LIO_WAIT,
the function waits until all I/O is complete and the
sig argument is ignored.
If the mode argument is LIO_NOWAIT, the function
returns immediately after
all the I/O operations are complete.
The list argument is an array of pointers to
aiocb structures. The array contains nent
elements. The array may contain NULL elements which are
ignored.
The aio_lio_opcode field of each aiocb structure
specifies the operation to be performed. The supported operations
are LIO_READ, LIO_WRITE, and LIO_NOP;
these symbols are defined in
aio(FP).
The LIO_NOP operation causes the list entry to be
ignored. If the aio_lio_opcode element is equal to
LIO_READ, then an I/O operation is submitted as
if by a call to
aio_read(S)
with the aiocbp equal to the address of the
aiocb structure. If the aio_lio_opcode element
is equal to LIO_WRITE, then an I/O operation is
submitted as if by a call to
aio_write(S)
with the aiocbp equal to the address of the
aiocb structure.
The aio_files member specifies the file descriptor on
which the operation is to be performed. It must refer to a raw
device.
The aio_buf member specifies the address of the buffer to
or from which the data is to be transferred. It must be 512 byte
aligned.
The aio_nbytes member specifies the number of bytes of
data to be transferred. It must be a multiple of 512.
The lio_aiocb element further describes the I/O
operation to be performed, in the identical manner that the
corresponding aiocb structure is used by the
aio_read and aio_write functions.
The nent argument specifies how many elements are members
of the list, that is, the length of the array.
The sig argument is a pointer to a signal control
structure, used when the mode argument has the value
LIO_NOWAIT, which defines the signal to be generated when
the entire list of I/O requests have been completed.
Return values
If the mode argument has the value LIO_NOWAIT,
the lio_listio function returns the value zero if the
I/O operations are successfully queued; otherwise, the
function returns the value -1 and sets errno to indicate
the error.
If the mode argument has the value LIO_WAIT, the
lio_listio function returns the value zero when all the
indicated I/O has completed successfully. Otherwise,
lio_listio returns a value of -1 and sets errno
to indicate the error.
In either case, the return value only indicates the success or
failure of the lio_listio call itself, not the status of
the individual I/O requests. In some cases one or more of
the I/O requests contained in the list may fail. Failure of
an individual request does not prevent completion of any other
individual request. To determine the outcome of each I/O
request, the application examines the error status associated with
each lio_aiocb control block. The error statuses so
returned are identical to those returned as the result of an
aio_read or aio_write function.
Diagnostics
If any of the following conditions occur, the lio_listio
function returns -1 and sets errno to the corresponding
value:
[EAGAIN]-
The resources necessary to queue all the I/O requests were
not available. The application may check the error status for each
aiocb to determine the individual request(s) that failed.
[EAGAIN]-
The number of entries indicated by nent would cause the
system-wide limit {AIO_MAX} to be exceeded.
[EINVAL]-
The mode argument is not a proper value.
The value of nent was greater than
{AIO_LISTIO_MAX}.
[EINTR]-
A signal was delivered while waiting for all I/O requests
to complete during an LIO_WAIT operation. Note that, since
each I/O operation invoked by lio_listio may
possibly provoke a signal when it completes, this error return may
be caused by the completion of one (or more) of the very
I/O operations being awaited. Outstanding I/O
requests are not canceled, and the application examines each list
element to determine whether the request was initiated, canceled, or
completed.
[EIO]-
One or more of the individual I/O operations failed. The
application checks the error status for each aiocb
structure to determine the individual request(s) that failed.
In addition to the errors returned by the lio_listio
function, if the lio_listio function succeeds or fails
with errors of [EAGAIN], [EINTR], or [EIO],
then some of the I/O specified by the list may have been
initiated. The I/O operation indicated by each list
element can encounter errors specific to the individual read or
write function being performed. In this event, the error status for
each aiocb control block contains the associated error
code. The error codes which can be set are the same as would be set
by a read or write function, with the following additional error
codes possible:
[EAGAIN]-
The requested I/O operation was not queued due to resource
limitations.
[EINPROGRESS]-
The requested I/O is in process.
See also
aio(FP),
aio_error(S),
aio_mkcbs(S),
aio_read(S),
aio_return(S),
aio_write(S),
close(S),
_exit(S),
exec(S),
fork(S),
lseek(S),
read(S)
Standards conformance
Text reprinted and/or adapted from IEEE Std 1003.1b-1993,
IEEE Standard for Information Technology, POSIX
Part 1: System Application Program Interface (API)
Amendment 1: Realtime Extensions [C Language], copyright © 1993
by the Institute of Electrical and Electronics Engineers, Inc. The
IEEE takes no responsibility for and will assume no
liability for damages resulting from the reader's misinterpretation
of said information resulting from the placement and context in this
publication. Information is reproduced with the permission of the
IEEE.
© 2003 Caldera International, Inc. All rights reserved.
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