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 (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	speci-
       fied.  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 parame-
       ter 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;	other-
       wise, 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 Electri-
       cal  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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group		     2013		     POSIX_FADVISE(3P)