PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult 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, off_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, or the value of len is less than zero.

       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 POSIX.1‐2008, <fcntl.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2013 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .