posix_fadvise

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 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(3P)