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  man pages->Tru64 Unix man pages -> aio_read (3)              



NAME    [Toc]    [Back]

       aio_read - Queues a single asynchronous read request

SYNOPSIS    [Toc]    [Back]

       #include <aio.h>

       int aio_read (
            struct aiocb *aiocbp );

LIBRARY    [Toc]    [Back]

       Asynchronous I/O Library (libaio, libaio_raw)

PARAMETERS    [Toc]    [Back]

       A pointer to an aiocb structure.

DESCRIPTION    [Toc]    [Back]

       The  aio_read function allows the calling process to asynchronously
 read aiocbp->aio_nbytes from the  file  associated
 with aiocbp->aio_fildes into the buffer pointed to by

       The aio_read function issues a read  request  and  returns
       even when the data cannot be delivered immediately. If the
       request cannot be initiated, the aio_read function returns
       with  an error status. If an error condition occurs during
       queuing, the function call returns without initiating  the
       queue request. The aiocbp value may be used as an argument
       to the aio_error and aio_return functions to determine the
       error or return status of the asynchronous read operation.

       The requested operation takes place at the absolute  position
  in  the  file  as given by aio_offset, as if lseek()
       were called immediately prior to  the  operation  with  an
       offset equal to aio_offset and a whence equal to SEEK_SET.

       The aiocbp argument  points  to  an  asynchronous  control
       block  structure,  aiocb,  used  in  the  asynchronous I/O
       interfaces.  The  aiocb  structure  contains  asynchronous
       operation  information,  such  as  the file offset for the
       read operation. The aiocb structure has the following members:
   aio_fildes;   aio_offset;   *aio_buf;  aio_nbytes;
       aio_reqprio; aio_sigevent; aio_lio_opcode;

       The aio_fildes member is the file descriptor on which  the
       asynchronous operation is to be performed. After any asynchronous
 I/O operation, the aio_offset member is undefined
       and  must  be  set  explicitly  for every asynchronous I/O

       The aio_nbytes and aio_buf members are  the  same  as  the
       nbyte  and buf arguments defined by POSIX.1 read and write

       The aio_sigevent member of the aiocb structure defines the
       signal  generated  when  the I/O operation is complete. If
       aio_sigevent.sigev_notify    equals    SIGEV_SIGNAL    and
       aio_sigevent.sigev_signo  is  non-zero, a signal is generated
 when the asynchronous read operation has completed.

       The aio_lio_opcode and aio_reqprio members are ignored  by

       Pending  asynchronous  I/O  operations are handled as follows:
 On close, _exit, or exec, any I/O that was  directed
       to  a  file system file, a tty device, or a streams device
       is canceled. Any I/O that was directed to any raw  character
 device, excluding terminal and streams devices, is not
       canceled.  On fork, no asynchronous I/O is inherited.

RETURN VALUES    [Toc]    [Back]

       On an unsuccessful call, a value of  -1  is  returned  and
       errno  is set to indicate the type of error that occurred.

ERRORS    [Toc]    [Back]

       The aio_read function fails  under  the  following  conditions:
  The  requested  asynchronous I/O operation was not
       queued  due   to   system   resource   limitations.    The
       aiocbp->aio_fildes argument is not a valid file descriptor
       open for  reading.   The  file  offset  value  implied  by
       aiocbp->aio_offset would be invalid.

       On  a successful call, a value of 0 (zero) is returned and
       the I/O operation is queued. After successful  queuing  of
       aio_read,  return  and  error values are the same as for a
       call to the read function. One of the following additional
       errors  may  occur: The operation was canceled by aio_cancel.
  The offset in aio_offset is  invalid  for  the  file

SEE ALSO    [Toc]    [Back]

       Functions: close(2), exec(2), _exit(2), fork(2), lseek(2),
       read(2),    write(2),     aio_cancel(3),     aio_error(3),
       aio_group_completion_np(3),             aio_results_np(3),
       aio_return(3), aio_suspend(3), aio_write(3), lio_listio(3)

       Guide to Realtime Programming

[ Back ]
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