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LIO_LISTIO(3P)             POSIX Programmer's Manual            LIO_LISTIO(3P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (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 asyn-
       chronous 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  opera-
       tions  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 sub-
       mitted  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  com-
       pletion  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  descrip-
       tion 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 deter-
       mine 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 descrip-
              tion 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 maxi-
              mum 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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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 .



IEEE/The Open Group                  2003                       LIO_LISTIO(3P)