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LIO_LISTIO
Section: POSIX Programmer's Manual (3P)
Updated: 2003
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PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
NAME
lio_listio - list directed I/O (REALTIME)
SYNOPSIS
#include <aio.h>
int lio_listio(int mode, struct aiocb *restrict const
list[restrict],
int nent, struct sigevent *restrict sig);
DESCRIPTION
The lio_listio() function shall 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.h> 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 shall wait until
all I/O is complete and the sig argument shall be ignored.
If the mode argument is LIO_NOWAIT, the function shall return
immediately, and asynchronous notification shall occur,
according to the sig argument, when all the I/O operations complete.
If sig is NULL, then no asynchronous
notification shall occur. If sig is not NULL, asynchronous notification
occurs as specified in Signal Generation and Delivery when all
the requests in list have
completed.
The I/O requests enumerated by list are submitted in an unspecified
order.
The list argument is an array of pointers to aiocb structures.
The array contains nent elements. The array
may contain NULL elements, which shall be 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.h>. 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() 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() with the aiocbp
equal to the
address of the aiocb structure.
The aio_fildes member specifies the file descriptor on which
the operation is to be performed.
The aio_buf member specifies the address of the buffer to or
from which the data is transferred.
The aio_nbytes member specifies the number of bytes of data
to be transferred.
The members of the aiocb structure further describe the I/O
operation to be performed, in a manner identical to that of
the corresponding aiocb structure when 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 behavior of this function is altered according to the definitions
of synchronized I/O data integrity completion and
synchronized I/O file integrity completion if synchronized I/O is
enabled on the file associated with aio_fildes.
For regular files, no data transfer shall occur past the offset maximum
established in the open file description associated with
aiocbp->aio_fildes.
RETURN VALUE
If the mode argument has the value LIO_NOWAIT, the lio_listio()
function shall return the value zero if the I/O
operations are successfully queued; otherwise, the function shall
return the value -1 and set errno to indicate the
error.
If the mode argument has the value LIO_WAIT, the lio_listio()
function shall return the value zero when all the
indicated I/O has completed successfully. Otherwise, lio_listio()
shall return a value of -1 and set 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
shall examine the error status associated with each aiocb control
block. The error statuses so returned are identical to
those returned as the result of an aio_read() or aio_write()
function.
ERRORS
The lio_listio() function shall fail if:
- 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, or 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 shall examine 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
may check 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. If the
lio_listio() function fails with an error code other than [EAGAIN],
[EINTR], or [EIO], no operations from the list shall
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 that 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.
- ECANCELED
-
The requested I/O was canceled before the I/O completed due to an
explicit aio_cancel() request.
- EFBIG
-
The aiocbp->aio_lio_opcode is LIO_WRITE, the file is a
regular file, aiocbp->aio_nbytes is
greater than 0, and the aiocbp->aio_offset is greater
than or equal to the offset maximum in the open file
description associated with aiocbp->aio_fildes.
- EINPROGRESS
-
The requested I/O is in progress.
- EOVERFLOW
-
The aiocbp->aio_lio_opcode is LIO_READ, the file is a
regular file, aiocbp->aio_nbytes is
greater than 0, and the aiocbp->aio_offset is before the
end-of-file and is greater than or equal to the offset
maximum in the open file description associated with aiocbp->aio_fildes.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
Although it may appear that there are inconsistencies in the specified
circumstances for error codes, the [EIO] error condition
applies when any circumstance relating to an individual operation
makes that operation fail. This might be due to a badly
formulated request (for example, the aio_lio_opcode field is
invalid, and aio_error() returns [EINVAL]) or might arise from
application behavior (for example, the
file descriptor is closed before the operation is initiated, and aio_error()
returns [EBADF]).
The limitation on the set of error codes returned when operations
from the list shall have been initiated enables applications
to know when operations have been started and whether aio_error()
is valid for a
specific operation.
FUTURE DIRECTIONS
None.
SEE ALSO
aio_read(), aio_write(), aio_error(), aio_return(),
aio_cancel(), close(), exec(), exit(),
fork(), lseek(), read(), the Base Definitions
volume of
IEEE Std 1003.1-2001, <aio.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- EXAMPLES
-
- APPLICATION USAGE
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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