lio_listio(3)lio_listio(3)NAMElio_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
Determines whether the lio_listio function returns when the I/O opera‐
tions are completed or as soon as the operations are queued. The mode
argument can have a value of either LIO_WAIT or LIO_NOWAIT. Specifies
a pointer to an array of pointers to aiocb structures. The array con‐
tains nent elements. 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. 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 deter‐
mines whether the function returns after the I/O operations are com‐
plete or as soon as they have been queued.
The list argument is a pointer to an array of pointers to aiocb struc‐
tures. 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 asynchro‐
nous 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 com‐
plete 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: 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. 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 func‐
tion 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. 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. The
mode argument is not a proper value. Nent was greater than AIO_LIS‐
TIO_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 addi‐
tional errors may occur: The requested I/O operation was not queued due
to resource limitations. The requested I/O operation was canceled by
aio_cancel. 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
lio_listio(3)