1AIO_READ(3P)               POSIX Programmer's Manual              AIO_READ(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
10

NAME

12       aio_read — asynchronous read from a file
13

SYNOPSIS

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

20       The aio_read() function shall read  aiocbp->aio_nbytes  from  the  file
21       associated  with  aiocbp->aio_fildes  into  the  buffer  pointed  to by
22       aiocbp->aio_buf. The function call shall return when the  read  request
23       has  been initiated or queued to the file or device (even when the data
24       cannot be delivered immediately).
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26       If prioritized I/O is supported for this file,  then  the  asynchronous
27       operation  shall  be submitted at a priority equal to a base scheduling
28       priority minus aiocbp->aio_reqprio. If Thread Execution  Scheduling  is
29       not supported, then the base scheduling priority is that of the calling
30       process;
31       otherwise, the base scheduling priority is that of the calling thread.
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33       The aiocbp value  may  be  used  as  an  argument  to  aio_error()  and
34       aio_return()  in order to determine the error status and return status,
35       respectively, of the asynchronous operation while it is proceeding.  If
36       an  error  condition  is  encountered during queuing, the function call
37       shall return without  having  initiated  or  queued  the  request.  The
38       requested operation takes place at the absolute position in the file as
39       given by aio_offset, as if lseek() were called immediately prior to the
40       operation  with  an  offset  equal  to aio_offset and a whence equal to
41       SEEK_SET.  After a successful call to enqueue an asynchronous I/O oper‐
42       ation, the value of the file offset for the file is unspecified.
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44       The  aio_sigevent  member  specifies the notification which occurs when
45       the request is completed.
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47       The aiocbp->aio_lio_opcode field shall be ignored by aio_read().
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49       The aiocbp argument points to an aiocb structure. If the buffer pointed
50       to by aiocbp->aio_buf or the control block pointed to by aiocbp becomes
51       an illegal address prior  to  asynchronous  I/O  completion,  then  the
52       behavior is undefined.
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54       Simultaneous  asynchronous  operations  using  the  same aiocbp produce
55       undefined results.
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57       If  synchronized  I/O  is  enabled  on   the   file   associated   with
58       aiocbp->aio_fildes, the behavior of this function shall be according to
59       the definitions of synchronized I/O data integrity completion and  syn‐
60       chronized I/O file integrity completion.
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62       For  any  system  action that changes the process memory space while an
63       asynchronous I/O is outstanding to the address range being changed, the
64       result of that action is undefined.
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66       For regular files, no data transfer shall occur past the offset maximum
67       established   in   the   open   file   description   associated    with
68       aiocbp->aio_fildes.
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RETURN VALUE

71       The  aio_read()  function shall return the value zero if the I/O opera‐
72       tion is successfully queued; otherwise, the function shall  return  the
73       value -1 and set errno to indicate the error.
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ERRORS

76       The aio_read() function shall fail if:
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78       EAGAIN The  requested  asynchronous I/O operation was not queued due to
79              system resource limitations.
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81       Each of the following conditions may be detected synchronously  at  the
82       time of the call to aio_read(), or asynchronously. If any of the condi‐
83       tions below are detected synchronously, the aio_read()  function  shall
84       return  -1 and set errno to the corresponding value. If any of the con‐
85       ditions below are detected asynchronously, the  return  status  of  the
86       asynchronous  operation is set to -1, and the error status of the asyn‐
87       chronous operation is set to the corresponding value.
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89       EBADF  The aiocbp->aio_fildes argument is not a valid  file  descriptor
90              open for reading.
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92       EINVAL The  file  offset  value  implied by aiocbp->aio_offset would be
93              invalid,
94              aiocbp->aio_reqprio is not a valid value, or  aiocbp->aio_nbytes
95              is an invalid value.
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97       In  the  case that the aio_read() successfully queues the I/O operation
98       but the operation is subsequently canceled or encounters an error,  the
99       return  status  of the asynchronous operation is one of the values nor‐
100       mally returned by the read() function call. In addition, the error sta‐
101       tus  of  the asynchronous operation is set to one of the error statuses
102       normally set by the read() function call, or one of the following  val‐
103       ues:
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105       EBADF  The  aiocbp->aio_fildes  argument is not a valid file descriptor
106              open for reading.
107
108       ECANCELED
109              The requested I/O was canceled before the I/O completed  due  to
110              an explicit aio_cancel() request.
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112       EINVAL The  file  offset  value  implied by aiocbp->aio_offset would be
113              invalid.
114
115       The  following  condition  may  be  detected  synchronously  or   asyn‐
116       chronously:
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118       EOVERFLOW
119              The  file  is a regular file, aiobcp->aio_nbytes is greater than
120              0, and the starting offset in aiobcp->aio_offset is  before  the
121              end-of-file  and  is at or beyond the offset maximum in the open
122              file description associated with aiocbp->aio_fildes.
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124       The following sections are informative.
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EXAMPLES

127       None.
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APPLICATION USAGE

130       None.
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RATIONALE

133       None.
134

FUTURE DIRECTIONS

136       None.
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SEE ALSO

139       aio_cancel(),  aio_error(),  lio_listio(),  aio_return(),  aio_write(),
140       close(), exec, exit(), fork(), lseek(), read()
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142       The Base Definitions volume of POSIX.1‐2017, <aio.h>
143
145       Portions  of  this text are reprinted and reproduced in electronic form
146       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
147       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
148       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
149       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
150       event of any discrepancy between this version and the original IEEE and
151       The  Open Group Standard, the original IEEE and The Open Group Standard
152       is the referee document. The original Standard can be  obtained  online
153       at http://www.opengroup.org/unix/online.html .
154
155       Any  typographical  or  formatting  errors that appear in this page are
156       most likely to have been introduced during the conversion of the source
157       files  to  man page format. To report such errors, see https://www.ker
158       nel.org/doc/man-pages/reporting_bugs.html .
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162IEEE/The Open Group                  2017                         AIO_READ(3P)
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