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 position aiocbp->aio_offset,
27       regardless of the file offset.  After the call, the value of  the  file
28       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
47       is  returned,  and errno is set appropriately.  If an error is detected
48       only later, it will be reported via aio_return(3) (returns  status  -1)
49       and 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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ATTRIBUTES

71       For   an   explanation   of   the  terms  used  in  this  section,  see
72       attributes(7).
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74       ┌───────────┬───────────────┬─────────┐
75       │Interface  │ Attribute     │ Value   │
76       ├───────────┼───────────────┼─────────┤
77       │aio_read() │ Thread safety │ MT-Safe │
78       └───────────┴───────────────┴─────────┘

CONFORMING TO

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

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

93       See aio(7).
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COLOPHON

100       This page is part of release 5.04 of the Linux  man-pages  project.   A
101       description  of  the project, information about reporting bugs, and the
102       latest    version    of    this    page,    can     be     found     at
103       https://www.kernel.org/doc/man-pages/.
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107                                  2017-09-15                       AIO_READ(3)