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NAME
       posix_fadvise - file advisory information (ADVANCED REALTIME)


SYNOPSIS
       #include <fcntl.h>

       int posix_fadvise(int fd, off_t offset, size_t len, int advice);


DESCRIPTION
       The  posix_fadvise() function shall advise the implementation on the expected behavior of the application
       with respect to the data in the file associated with the open file descriptor, fd, starting at offset and
       continuing  for  len bytes. The specified range need not currently exist in the file. If len is zero, all
       data following offset is specified. The implementation may use this information to optimize  handling  of
       the  specified  data.  The  posix_fadvise()  function  shall  have  no  effect  on the semantics of other
       operations on the specified data, although it may affect the performance of other operations.

       The advice to be applied to the data is specified by the advice parameter and may be one of the following
       values:

       POSIX_FADV_NORMAL

              Specifies that the application has no advice to give on its behavior with respect to the specified
              data. It is the default characteristic if no advice is given for an open file.

       POSIX_FADV_SEQUENTIAL

              Specifies that the application expects to  access  the  specified  data  sequentially  from  lower
              offsets to higher offsets.

       POSIX_FADV_RANDOM

              Specifies that the application expects to access the specified data in a random order.

       POSIX_FADV_WILLNEED

              Specifies that the application expects to access the specified data in the near future.

       POSIX_FADV_DONTNEED

              Specifies  that  the  application  expects  that it will not access the specified data in the near
              future.

       POSIX_FADV_NOREUSE

              Specifies that the application expects to access the specified data once and  then  not  reuse  it
              thereafter.

       These values are defined in <fcntl.h>.


RETURN VALUE
       Upon  successful  completion,  posix_fadvise()  shall  return  zero;  otherwise, an error number shall be
       returned to indicate the error.


ERRORS
       The posix_fadvise() function shall fail if:

       EBADF  The fd argument is not a valid file descriptor.

       EINVAL The value of advice is invalid.

       ESPIPE The fd argument is associated with a pipe or FIFO.

       The following sections are informative.


EXAMPLES
       None.


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


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       posix_madvise() , the Base Definitions volume of IEEE Std 1003.1-2001, <fcntl.h>


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc and The Open Group. In the event of any discrepancy between this version and the  original  IEEE  and
       The  Open  Group  Standard,  the  original  IEEE and The Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .