aio_read(3)

1AIO_READ(3)                Linux Programmer's Manual               AIO_READ(3)
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NAME

6       aio_read - asynchronous read
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SYNOPSIS

9       #include <aio.h>
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11       int aio_read(struct aiocb *aiocbp);
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DESCRIPTION

15       The  aio_read()  function  requests  an asynchronous "n = read(fd, buf,
16       count)"   with   fd,   buf,   count   given   by    aiocbp->aio_fildes,
17       aiocbp->aio_buf,  aiocbp->aio_nbytes, respectively. The return status n
18       can be retrieved upon completion using aio_return(3).
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20       The data is read starting at the absolute file offset  aiocbp->aio_off‐
21       set,  regardless  of the current file position. After this request, the
22       value of the current file position is unspecified.
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24       The "asynchronous" means that this call returns as soon as the  request
25       has been enqueued; the read may or may not have completed when the call
26       returns. One tests for completion using aio_error(3).
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28       If _POSIX_PRIORITIZED_IO is defined, and this file  supports  it,  then
29       the  asynchronous operation is submitted at a priority equal to that of
30       the calling process minus aiocbp->aio_reqprio.
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32       The field aiocbp->aio_lio_opcode is ignored.
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34       No data is read from a regular file beyond its maximum offset.
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RETURN VALUE

37       On success, 0 is returned. On error the request is not enqueued, -1  is
38       returned, and errno is set appropriately. If an error is first detected
39       later, it will be reported via aio_return(3) (returns  status  -1)  and
40       aio_error(3)  (error  status  whatever  one would have gotten in errno,
41       such as EBADF).
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ERRORS

44       EAGAIN Out of resources.
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46       EBADF  aio_fildes is not a valid file descriptor open for reading.
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48       EINVAL One or more of aio_offset, aio_reqprio, aio_nbytes are invalid.
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50       ENOSYS This function is not supported.
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52       EOVERFLOW
53              The file is a regular file, we start reading before  end-of-file
54              and  want  at  least one byte, but the starting position is past
55              the maximum offset for this file.
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NOTES

58       It is a good idea to zero out the control block before use.  This  con‐
59       trol block must not be changed while the read operation is in progress.
60       The buffer area being read into must not be accessed during the  opera‐
61       tion  or  undefined  results  may occur. The memory areas involved must
62       remain valid.
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CONFORMING TO

66       POSIX.1-2001
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