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



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

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.1-2017, <fcntl.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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 .



IEEE/The Open Group                  2017                     POSIX_FADVISE(3)
