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 .

IEEE/The Open Group                                   2003                                      POSIX_FADVISE(P)