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(5).

ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|MT-Level | MT-Safe |
+--------------------+-------------------+
|Standard | See standards(5). |
+--------------------+-------------------+

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(5), lf64(5), standards(5)


February 5, 2008 LIO_LISTIO(3C)