POSIX_FADVISE(3P)                                   POSIX Programmer's Manual                                  POSIX_FADVISE(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

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 imple-
       mentation 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 opera-
       tions.

       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 off-
              sets.

       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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                             POSIX_FADVISE(3P)