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



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       lio_listio -- list directed I/O

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 Section 2.4.1, 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.

       If the buffer pointed to by list or the aiocb structures pointed to by
       the elements of the array list become illegal addresses before all
       asynchronous I/O completed and, if necessary, the notification is sent,
       then the behavior is undefined. If the buffers pointed to by the
       aio__buf member of the aiocb structure pointed to by the elements of the
       array list become illegal addresses prior to the asynchronous I/O
       associated with that aiocb structure being completed, the behavior is
       undefined.

       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 associated with
       aiocbp->aio__fildes.

       If sig->sigev__notify is SIGEV_THREAD and sig->sigev__notify__attributes
       is a non-null pointer and the block pointed to by this pointer becomes
       an illegal address prior to all asynchronous I/O being completed, then
       the behavior is undefined.

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 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 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 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 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 POSIX.1-2017, <aio.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                        LIO_LISTIO(3)
