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aio_read (2)
  • >> aio_read (2) ( FreeBSD man: Системные вызовы )
  • aio_read (3) ( Solaris man: Библиотечные вызовы )
  • aio_read (3) ( Linux man: Библиотечные вызовы )
  • aio_read (3) ( POSIX man: Библиотечные вызовы )

  • BSD mandoc
     

    NAME

    
    
    aio_read
    
     - asynchronous read from a file (REALTIME)
    
     
    

    LIBRARY

    Lb libc
    
     
    

    SYNOPSIS

       #include <aio.h>
    int aio_read (struct aiocb *iocb);
     

    DESCRIPTION

    The aio_read ();
    system call allows the calling process to read Fa iocb->aio_nbytes from the descriptor Fa iocb->aio_fildes beginning at the offset Fa iocb->aio_offset into the buffer pointed to by Fa iocb->aio_buf . The call returns immediately after the read request has been enqueued to the descriptor; the read may or may not have completed at the time the call returns.

    If _POSIX_PRIORITIZED_IO is defined, and the descriptor supports it, then the enqueued operation is submitted at a priority equal to that of the calling process minus Fa iocb->aio_reqprio .

    The Fa iocb->aio_lio_opcode argument is ignored by the aio_read ();
    system call.

    The Fa iocb pointer may be subsequently used as an argument to aio_return ();
    and aio_error ();
    in order to determine return or error status for the enqueued operation while it is in progress.

    If the request could not be enqueued (generally due to invalid arguments), then the call returns without having enqueued the request.

    If the request is successfully enqueued, the value of Fa iocb->aio_offset can be modified during the request as context, so this value must not be referenced after the request is enqueued.  

    RESTRICTIONS

    The Asynchronous I/O Control Block structure pointed to by Fa iocb and the buffer that the Fa iocb->aio_buf member of that structure references must remain valid until the operation has completed. For this reason, use of auto (stack) variables for these objects is discouraged.

    The asynchronous I/O control buffer Fa iocb should be zeroed before the aio_read ();
    call to avoid passing bogus context information to the kernel.

    Modifications of the Asynchronous I/O Control Block structure or the buffer contents after the request has been enqueued, but before the request has completed, are not allowed.

    If the file offset in Fa iocb->aio_offset is past the offset maximum for Fa iocb->aio_fildes , no I/O will occur.  

    RETURN VALUES

    Rv -std aio_read  

    DIAGNOSTICS

    None.  

    ERRORS

    The aio_read ();
    system call will fail if:

    Bq Er EAGAIN
    The request was not queued because of system resource limitations.
    Bq Er ENOSYS
    The aio_read ();
    system call is not supported.

    The following conditions may be synchronously detected when the aio_read ();
    system call is made, or asynchronously, at any time thereafter. If they are detected at call time, aio_read ();
    returns -1 and sets errno appropriately; otherwise the aio_return ();
    system call must be called, and will return -1, and aio_error ();
    must be called to determine the actual value that would have been returned in errno

    Bq Er EBADF
    The Fa iocb->aio_fildes argument is invalid.
    Bq Er EINVAL
    The offset Fa iocb->aio_offset is not valid, the priority specified by Fa iocb->aio_reqprio is not a valid priority, or the number of bytes specified by Fa iocb->aio_nbytes is not valid.
    Bq Er EOVERFLOW
    The file is a regular file, Fa iocb->aio_nbytes is greater than zero, the starting offset in Fa iocb->aio_offset is before the end of the file, but is at or beyond the Fa iocb->aio_fildes offset maximum.

    If the request is successfully enqueued, but subsequently cancelled or an error occurs, the value returned by the aio_return ();
    system call is per the read(2) system call, and the value returned by the aio_error ();
    system call is either one of the error returns from the read(2) system call, or one of:

    Bq Er EBADF
    The Fa iocb->aio_fildes argument is invalid for reading.
    Bq Er ECANCELED
    The request was explicitly cancelled via a call to aio_cancel (.);
    Bq Er EINVAL
    The offset Fa iocb->aio_offset would be invalid.

     

    SEE ALSO

    aio_cancel2, aio_error2, aio_return2, aio_suspend2, aio_waitcomplete2, aio_write2, siginfo(3), aio(4)  

    STANDARDS

    The aio_read ();
    system call is expected to conform to the St -p1003.1 standard.  

    HISTORY

    The aio_read ();
    system call first appeared in Fx 3.0 .  

    AUTHORS

    This manual page was written by An Terry Lambert Aq [email protected] .  

    BUGS

    Invalid information in Fa iocb->_aiocb_private may confuse the kernel.


     

    Index

    NAME
    LIBRARY
    SYNOPSIS
    DESCRIPTION
    RESTRICTIONS
    RETURN VALUES
    DIAGNOSTICS
    ERRORS
    SEE ALSO
    STANDARDS
    HISTORY
    AUTHORS
    BUGS


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