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>

COPYRIGHT

       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 .