.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "LIO_LISTIO" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" lio_listio 
.SH 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.
.SH NAME
lio_listio \- list directed I/O (\fBREALTIME\fP)
.SH SYNOPSIS
.LP
\fB#include <aio.h>
.br
.sp
int lio_listio(int\fP \fImode\fP\fB, struct aiocb *restrict const\fP
\fIlist\fP\fB[restrict],
.br
\ \ \ \ \ \  int\fP \fInent\fP\fB, struct sigevent *restrict\fP \fIsig\fP\fB);
\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIlio_listio\fP() function shall initiate a list of I/O requests
with a single function call.
.LP
The \fImode\fP argument takes one of the values LIO_WAIT or LIO_NOWAIT
declared in \fI<aio.h>\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 \fImode\fP
argument is LIO_WAIT, the function shall wait until
all I/O is complete and the \fIsig\fP argument shall be ignored.
.LP
If the \fImode\fP argument is LIO_NOWAIT, the function shall return
immediately, and asynchronous notification shall occur,
according to the \fIsig\fP argument, when all the I/O operations complete.
If \fIsig\fP is NULL, then no asynchronous
notification shall occur. If \fIsig\fP is not NULL, asynchronous notification
occurs as specified in \fISignal Generation and Delivery\fP when all
the requests in \fIlist\fP have
completed.
.LP
The I/O requests enumerated by \fIlist\fP are submitted in an unspecified
order.
.LP
The \fIlist\fP argument is an array of pointers to \fBaiocb\fP structures.
The array contains \fInent\fP elements. The array
may contain NULL elements, which shall be ignored.
.LP
The \fIaio_lio_opcode\fP field of each \fBaiocb\fP structure specifies
the operation to be performed. The supported operations
are LIO_READ, LIO_WRITE, and LIO_NOP; these symbols are defined in
\fI<aio.h>\fP. The
LIO_NOP operation causes the list entry to be ignored. If the \fIaio_lio_opcode\fP
element is equal to LIO_READ, then an I/O
operation is submitted as if by a call to \fIaio_read\fP() with the
\fIaiocbp\fP equal
to the address of the \fBaiocb\fP structure. If the \fIaio_lio_opcode\fP
element is equal to LIO_WRITE, then an I/O operation is
submitted as if by a call to \fIaio_write\fP() with the \fIaiocbp\fP
equal to the
address of the \fBaiocb\fP structure.
.LP
The \fIaio_fildes\fP member specifies the file descriptor on which
the operation is to be performed.
.LP
The \fIaio_buf\fP member specifies the address of the buffer to or
from which the data is transferred.
.LP
The \fIaio_nbytes\fP member specifies the number of bytes of data
to be transferred.
.LP
The members of the \fBaiocb\fP structure further describe the I/O
operation to be performed, in a manner identical to that of
the corresponding \fBaiocb\fP structure when used by the \fIaio_read\fP()
and \fIaio_write\fP() functions.
.LP
The \fInent\fP argument specifies how many elements are members of
the list; that is, the length of the array.
.LP
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 \fIaio_fildes\fP.
.LP
For regular files, no data transfer shall occur past the offset maximum
established in the open file description associated with
\fIaiocbp\fP->\fIaio_fildes\fP.
.SH RETURN VALUE
.LP
If the \fImode\fP argument has the value LIO_NOWAIT, the \fIlio_listio\fP()
function shall return the value zero if the I/O
operations are successfully queued; otherwise, the function shall
return the value -1 and set \fIerrno\fP to indicate the
error.
.LP
If the \fImode\fP argument has the value LIO_WAIT, the \fIlio_listio\fP()
function shall return the value zero when all the
indicated I/O has completed successfully. Otherwise, \fIlio_listio\fP()
shall return a value of -1 and set \fIerrno\fP to
indicate the error.
.LP
In either case, the return value only indicates the success or failure
of the \fIlio_listio\fP() 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 \fBaiocb\fP control
block. The error statuses so returned are identical to
those returned as the result of an \fIaio_read\fP() or \fIaio_write\fP()
function.
.SH ERRORS
.LP
The \fIlio_listio\fP() function shall fail if:
.TP 7
.B EAGAIN
The resources necessary to queue all the I/O requests were not available.
The application may check the error status for each
\fBaiocb\fP to determine the individual request(s) that failed.
.TP 7
.B EAGAIN
The number of entries indicated by \fInent\fP would cause the system-wide
limit {AIO_MAX} to be exceeded.
.TP 7
.B EINVAL
The \fImode\fP argument is not a proper value, or the value of \fInent\fP
was greater than {AIO_LISTIO_MAX}.
.TP 7
.B 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 \fIlio_listio\fP() 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.
.TP 7
.B EIO
One or more of the individual I/O operations failed. The application
may check the error status for each \fBaiocb\fP structure
to determine the individual request(s) that failed.
.sp
.LP
In addition to the errors returned by the \fIlio_listio\fP() function,
if the \fIlio_listio\fP() 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
\fIlio_listio\fP() 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
\fBaiocb\fP control block contains the associated error code.
The error codes that can be set are the same as would be set by a
\fIread\fP() or \fIwrite\fP() function, with the following additional
error codes possible:
.TP 7
.B EAGAIN
The requested I/O operation was not queued due to resource limitations.
.TP 7
.B ECANCELED
The requested I/O was canceled before the I/O completed due to an
explicit \fIaio_cancel\fP() request.
.TP 7
.B EFBIG
The \fIaiocbp\fP->\fIaio_lio_opcode\fP is LIO_WRITE, the file is a
regular file, \fIaiocbp\fP->\fIaio_nbytes\fP is
greater than 0, and the \fIaiocbp\fP->\fIaio_offset\fP is greater
than or equal to the offset maximum in the open file
description associated with \fIaiocbp\fP->\fIaio_fildes\fP.
.TP 7
.B EINPROGRESS
The requested I/O is in progress.
.TP 7
.B EOVERFLOW
The \fIaiocbp\fP->\fIaio_lio_opcode\fP is LIO_READ, the file is a
regular file, \fIaiocbp\fP->\fIaio_nbytes\fP is
greater than 0, and the \fIaiocbp\fP->\fIaio_offset\fP is before the
end-of-file and is greater than or equal to the offset
maximum in the open file description associated with \fIaiocbp\fP->\fIaio_fildes\fP.
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
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 \fIaio_lio_opcode\fP field is
invalid, and \fIaio_error\fP() returns [EINVAL]) or might arise from
application behavior (for example, the
file descriptor is closed before the operation is initiated, and \fIaio_error\fP()
returns [EBADF]).
.LP
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 \fIaio_error\fP()
is valid for a
specific operation.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIaio_read\fP(), \fIaio_write\fP(), \fIaio_error\fP(), \fIaio_return\fP(),
\fIaio_cancel\fP(), \fIclose\fP(), \fIexec\fP(), \fIexit\fP(),
\fIfork\fP(), \fIlseek\fP(), \fIread\fP(), the Base Definitions
volume of
IEEE\ Std\ 1003.1-2001, \fI<aio.h>\fP
.SH 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 .