1POSIX_FADVISE(3P)          POSIX Programmer's Manual         POSIX_FADVISE(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.
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NAME

12       posix_fadvise - file advisory information (ADVANCED REALTIME)
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SYNOPSIS

15       #include <fcntl.h>
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17       int posix_fadvise(int fd, off_t offset, size_t len, int advice);
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DESCRIPTION

21       The posix_fadvise() function shall advise  the  implementation  on  the
22       expected  behavior  of  the application with respect to the data in the
23       file associated with the open file descriptor, fd, starting  at  offset
24       and  continuing  for  len bytes. The specified range need not currently
25       exist in the file. If len is zero, all data following offset is  speci‐
26       fied.  The implementation may use this information to optimize handling
27       of the specified data.  The  posix_fadvise()  function  shall  have  no
28       effect  on  the  semantics  of  other operations on the specified data,
29       although it may affect the performance of other operations.
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31       The advice to be applied to the data is specified by the advice parame‐
32       ter and may be one of the following values:
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34       POSIX_FADV_NORMAL
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36              Specifies  that  the  application  has  no advice to give on its
37              behavior with respect to the specified data. It is  the  default
38              characteristic if no advice is given for an open file.
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40       POSIX_FADV_SEQUENTIAL
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42              Specifies  that  the application expects to access the specified
43              data sequentially from lower offsets to higher offsets.
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45       POSIX_FADV_RANDOM
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47              Specifies that the application expects to access  the  specified
48              data in a random order.
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50       POSIX_FADV_WILLNEED
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52              Specifies  that  the application expects to access the specified
53              data in the near future.
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55       POSIX_FADV_DONTNEED
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57              Specifies that the application expects that it will  not  access
58              the specified data in the near future.
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60       POSIX_FADV_NOREUSE
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62              Specifies  that  the application expects to access the specified
63              data once and then not reuse it thereafter.
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66       These values are defined in <fcntl.h>.
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RETURN VALUE

69       Upon successful completion, posix_fadvise() shall return  zero;  other‐
70       wise, an error number shall be returned to indicate the error.
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ERRORS

73       The posix_fadvise() function shall fail if:
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75       EBADF  The fd argument is not a valid file descriptor.
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77       EINVAL The value of advice is invalid.
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79       ESPIPE The fd argument is associated with a pipe or FIFO.
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82       The following sections are informative.
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EXAMPLES

85       None.
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APPLICATION USAGE

88       The posix_fadvise() function is part of the Advisory Information option
89       and need not be provided on all implementations.
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RATIONALE

92       None.
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FUTURE DIRECTIONS

95       None.
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SEE ALSO

98       posix_madvise(), the Base Definitions volume  of  IEEE Std 1003.1-2001,
99       <fcntl.h>
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102       Portions  of  this text are reprinted and reproduced in electronic form
103       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
104       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
105       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
106       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
107       event of any discrepancy between this version and the original IEEE and
108       The  Open Group Standard, the original IEEE and The Open Group Standard
109       is the referee document. The original Standard can be  obtained  online
110       at http://www.opengroup.org/unix/online.html .
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114IEEE/The Open Group                  2003                    POSIX_FADVISE(3P)
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