posix_fadvise(3c)

1posix_fadvise(3C)        Standard C Library Functions        posix_fadvise(3C)
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NAME

6       posix_fadvise - file advisory information
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SYNOPSIS

9       #include <fcntl.h>
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11       int posix_fadvise(int fd, off_t offset, off_t len, int advice);
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DESCRIPTION

15       The  posix_fadvise() function advises the system on the expected behav‐
16       ior of the application with respect to the data in the file  associated
17       with  the  open  file descriptor, fd, starting at offset and continuing
18       for len bytes. The specified range need  not  currently  exist  in  the
19       file.  If len is zero, all data following offset is specified. The sys‐
20       tem may use this information to  optimize  handling  of  the  specified
21       data.  The  posix_fadvise()  function has no effect on the semantics of
22       other operations on the specified data, although it may affect the per‐
23       formance of other operations.
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26       The advice to be applied to the data is specified by the advice parame‐
27       ter and may be one of the following values:
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29       POSIX_FADV_NORMAL        Specifies that the application has  no  advice
30                                to  give  on  its behavior with respect to the
31                                specified data. It is the default characteris‐
32                                tic if no advice is given for an open file.
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35       POSIX_FADV_SEQUENTIAL    Specifies  that  the  application  expects  to
36                                access the specified  data  sequentially  from
37                                lower offsets to higher offsets.
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40       POSIX_FADV_RANDOM        Specifies  that  the  application  expects  to
41                                access the specified data in a random order.
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44       POSIX_FADV_WILLNEED      Specifies  that  the  application  expects  to
45                                access the specified data in the near future.
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48       POSIX_FADV_DONTNEED      Specifies that the application expects that it
49                                will not access the specified data in the near
50                                future.
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53       POSIX_FADV_NOREUSE       Specifies  that  the  application  expects  to
54                                access the specified data once  and  then  not
55                                reuse it thereafter.
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59       These values are defined in <fcntl.h>
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RETURN VALUES

62       Upon successful completion, posix_fadvise() returns zero. Otherwise, an
63       error number is returned to indicate the error.
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ERRORS

66       The posix_fadvise() function will fail if:
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68       EBADF     The fd argument is not a valid file descriptor.
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71       EINVAL    The value of advice is invalid, or the value of len  is  less
72                 than zero.
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75       ESPIPE    The fd argument is associated with a pipe or FIFO.
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USAGE

79       The  posix_fadvise()  function  has a transitional interface for 64-bit
80       file offsets. See lf64(5).
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ATTRIBUTES

83       See attributes(5) for descriptions of the following attributes:
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88       ┌─────────────────────────────┬─────────────────────────────┐
89       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
90       ├─────────────────────────────┼─────────────────────────────┤
91       │Interface Stability          │Committed                    │
92       ├─────────────────────────────┼─────────────────────────────┤
93       │MT-Level                     │MT-Safe                      │
94       ├─────────────────────────────┼─────────────────────────────┤
95       │Standard                     │See standards(5).            │
96       └─────────────────────────────┴─────────────────────────────┘
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