LIO_LISTIO(3C) Standard C Library Functions LIO_LISTIO(3C)
NAME
lio_listio - list directed I/O
SYNOPSIS
#include <aio.h>
int lio_listio(
int mode,
struct aiocb *restrict const list[],
int nent,
struct sigevent *restrict sig);
DESCRIPTION
The
lio_listio() function allows the calling process, LWP, or thread, to
initiate a list of I/O requests within 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 waits until all
I/O is complete and the
sig argument is ignored.
If the
mode argument is
LIO_NOWAIT, the function returns immediately, and
asynchronous notification occurs, according to the
sig argument, when all
the I/O operations complete. If
sig is
NULL, no asynchronous notification
occurs. If
sig is not
NULL, asynchronous notification occurs as specified
in
signal.h(3HEAD) 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 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.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(3C) 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(3C) 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 to be 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(3C) and
aio_write(3C) 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. See
fcntl.h(3HEAD) definitions of
O_DSYNC and
O_SYNC.
For regular files, no data transfer will occur past the offset maximum
established in the open file description associated with
aiocbp->
aio_fildes.
RETURN VALUES
If the
mode argument has the value
LIO_NOWAIT, and the I/O operations
are successfully queued,
lio_listio() returns
0; otherwise, it returns
-1, and sets
errno to indicate the error.
If the
mode argument has the value
LIO_WAIT, and all the indicated I/O
has completed successfully,
lio_listio() returns
0; otherwise, it
returns
-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 must examine the error status
associated with each
aiocb control block. Each error status so returned
is identical to that returned as a result of an
aio_read(3C) or
aio_write(3C) function.
ERRORS
The
lio_listio() function will fail if:
EAGAIN The resources necessary to queue all the I/O requests were not
available. The error status for each request is recorded in the
aio_error member of the corresponding
aiocb structure, and can
be retrieved using
aio_error(3C).
EAGAIN The number of entries indicated by
nent would cause the system-
wide limit
AIO_MAX to be exceeded.
EINVAL The
mode argument is an improper value, or the value of
nent is
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 can use
aio_fsync(3C) to determine if any
request was initiated;
aio_return(3C) to determine if any
request has completed; or
aio_error(3C) to determine if any
request was canceled.
EIO One or more of the individual I/O operations failed. The
application can use
aio_error(3C) to 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 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(2) or
write(2) 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(3C) 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.USAGE
The
lio_listio() function has a transitional interface for 64-bit file
offsets. See
lf64(7).
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|MT-Level | MT-Safe |
+--------------------+-------------------+
|Standard | See
standards(7). |
+--------------------+-------------------+
SEE ALSO
close(2),
exec(2),
exit(2),
fork(2),
lseek(2),
read(2),
write(2),
aio_cancel(3C),
aio_error(3C),
aio_fsync(3C),
aio_read(3C),
aio_return(3C),
aio_write(3C),
aio.h(3HEAD),
fcntl.h(3HEAD),
siginfo.h(3HEAD),
signal.h(3HEAD),
attributes(7),
lf64(7),
standards(7) February 5, 2008
LIO_LISTIO(3C)