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lio_listio(3)
NAME
lio_listio - Initiates a list of asynchronous I/O requests
SYNOPSIS
#include <aio.h>
int lio_listio (
int mode,
struct aiocb *list,
int nent,
struct sigevent *sig );
LIBRARY
Asynchronous I/O Library (libaio, libaio_raw)
PARAMETERS
mode
Determines whether the lio_listio function returns when the I/O
operations are completed or as soon as the operations are queued. The
mode argument can have a value of either LIO_WAIT or LIO_NOWAIT.
list
Specifies a pointer to an array of pointers to aiocb structures. The
array contains nent elements.
nent
Specifies the length of the array pointed to by the list argument. The
nent argument also specifies the number of I/O operations potentially
performed by the lio_listio function.
*sig
Specifies a pointer to a sigevent structure.
DESCRIPTION
The lio_listio function allows the calling process to initiate a list of
I/O requests with a single function call. The mode argument determines
whether the function returns after the I/O operations are complete or as
soon as they have been queued.
The list argument is a pointer to an array of pointers to aiocb structures.
The aio_lio_opcode field of each aiocb structure specifies the operation to
be performed and can take any one of three values; LIO_READ, LIO_WRITE, and
LIO_NOP as defined in the <aio.h> header file. Whether the operation is
specified as a read or write operation, the list array element contains the
address of the aiocb structure for that operation. If the list array
element is NULL, that array element will be skipped. If the aio_lio_opcode
is LIO_READ, the I/O operation is submitted as an aio_read operation. If
the aio_lio_opcode is LIO_WRITE, the I/O operation is submitted as an
aio_write operation. If the aio_lio_opcode is LIO_NOP, the list entry is
skipped.
The aio_fildes member of the aiocb structure specifies the file descriptor
for the operation. The aio_buf member specifies the address of the data
transfer buffer. The number of bytes to be transferred is specified in the
aio_nbytes member.
The sig argument points to a sigevent structure, which contains the signal
number of the signal to be sent upon completion of the asynchronous I/O
operation. If you specify LIO_WAIT, the function waits until all I/O
operations are completed, and the sig argument is ignored. If you specify
LIO_NOWAIT, and the sigev_notify element of the sigevent structure equals
SIGEV_SIGNAL and sigev_signo does not equal 0 (zero), the signal is
generated.
RETURN VALUES
If the mode argument has the value LIO_NOWAIT, the lio_listio function
returns the value 0 (zero) if the I/O operations are successfully queued.
Otherwise, the function returns -1 and sets errno to indicate the error
type.
If the mode argument has the value LIO_WAIT, the lio_listio function
returns the value 0 (zero) when all the indicated I/O operations complete
successfully. Otherwise, the function returns -1 and sets errno to indicate
the error type.
In either case, the return value indicates only the success or failure of
the lio_listio function call, not the status of 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, examine
the error status associated with each lio_aiocb control block. These error
statuses are identical to those returned as the result of an aio_read or
aio_write function.
The address of the aiocb structure is used as a handle for retrieving the
error and return status of the asynchronous operation while it is in
progress (equal to [EINPROGRESS]). The error codes returned are identical
to those returned as the result of an aio_read or aio_write function.
If an error occurs, the only way to determine which operations were
initiated is to check the aiocb by using the aio_error function.
ERRORS
The lio_listio function fails under the following conditions:
[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 requests that failed. The number of entries
indicated by nent would exceed the system limit of AIO_MAX.
[EINTR]
A signal or event was delivered while waiting for all I/O requests to
complete during a LIO_WAIT operation. Each I/O operation invoked by the
lio_listio function may send a signal when it completes. Therefore,
this error may be caused by the completion of one or more of the very
operations being awaited. Outstanding I/O requests are not canceled,
and the application must examine each list element to determine whether
the request was initiated, interrupted, or completed.
[EIO]
One or more of the individual I/O operations failed. The application
may check error status for each aiocb structure to determine the
individual requests that failed.
[EINVAL]
The mode argument is not a proper value. Nent was greater than
AIO_LISTIO_MAX. aio_lio opcode is invalid.
If the aio_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
asociated error code. These error codes are the same as for a call to the
read or write function. One of the following additional errors may occur:
[EGAIN]
The requested I/O operation was not queued due to resource limitations.
[ECANCELED]
The requested I/O operation was canceled by aio_cancel.
[EINPROGRESS]
The requested I/O is in progress.
SEE ALSO
Functions: close(2), exec(2), _exit(2), fork(2), lseek(2), read(2),
write(2), aio_cancel(3), aio_error(3), aio_group_completion_np(3),
aio_read(3), aio_results_np(3), aio_return(3), aio_write(3)
Guide to Realtime Programming
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Index for
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Alphabetical
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Top of
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