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 differ (con-
       sult 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  associ-
       ated 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 opera-
       tions 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 associ-
       ated 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 appli-
       cations 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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                LIO_LISTIO(3P)