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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13       Link with -lrt.
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DESCRIPTION

16       The  aio_read() function queues the I/O request described by the buffer
17       pointed to by aiocbp.  This function  is  the  asynchronous  analog  of
18       read(2).  The arguments of the call
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20           read(fd, buf, count)
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22       correspond (in order) to the fields aio_fildes, aio_buf, and aio_nbytes
23       of the structure pointed to by aiocbp.  (See aio(7) for  a  description
24       of the aiocb structure.)
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26       The  data is read starting at the absolute file offset aiocbp->aio_off‐
27       set, regardless of the current file offset.  After the call, the  value
28       of the current file offset is unspecified.
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30       The  "asynchronous" means that this call returns as soon as the request
31       has been enqueued; the read may or may not have completed when the call
32       returns.  One tests for completion using aio_error(3).  The return sta‐
33       tus of a completed I/O operation  can  be  obtained  by  aio_return(3).
34       Asynchronous  notification of I/O completion can be obtained by setting
35       aiocbp->aio_sigevent appropriately; see sigevent(7) for details.
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37       If _POSIX_PRIORITIZED_IO is defined, and this file  supports  it,  then
38       the  asynchronous operation is submitted at a priority equal to that of
39       the calling process minus aiocbp->aio_reqprio.
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41       The field aiocbp->aio_lio_opcode is ignored.
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43       No data is read from a regular file beyond its maximum offset.
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RETURN VALUE

46       On success, 0 is returned.  On error the request is not enqueued, -1 is
47       returned, and errno is set appropriately.  If an error is detected only
48       later, it will be reported via aio_return(3) (returns  status  -1)  and
49       aio_error(3)  (error  status—whatever  one  would have gotten in errno,
50       such as EBADF).
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ERRORS

53       EAGAIN Out of resources.
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55       EBADF  aio_fildes is not a valid file descriptor open for reading.
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57       EINVAL One or  more  of  aio_offset,  aio_reqprio,  or  aio_nbytes  are
58              invalid.
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60       ENOSYS aio_read() is not implemented.
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62       EOVERFLOW
63              The  file is a regular file, we start reading before end-of-file
64              and want at least one byte, but the starting  position  is  past
65              the maximum offset for this file.
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VERSIONS

68       The aio_read() function is available since glibc 2.1.
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CONFORMING TO

71       POSIX.1-2001, POSIX.1-2008.
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NOTES

74       It  is  a good idea to zero out the control block before use.  The con‐
75       trol block must not be changed while the read operation is in progress.
76       The  buffer area being read into must not be accessed during the opera‐
77       tion or undefined results may occur.  The memory  areas  involved  must
78       remain valid.
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80       Simultaneous I/O operations specifying the same aiocb structure produce
81       undefined results.
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EXAMPLE

84       See aio(7).
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COLOPHON

91       This  page  is  part of release 3.53 of the Linux man-pages project.  A
92       description of the project, and information about reporting  bugs,  can
93       be found at http://www.kernel.org/doc/man-pages/.
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97                                  2012-05-08                       AIO_READ(3)