Toll Free Numbers
  • Last 5 Forum Topics
    Last post

The Web Only This Site



  • MARC

    Mailing list ARChives
    - Search by -


    Computing Dictionary

  • Text Link Ads
  • LINUX man pages
  • Linux Man Page Viewer

    The following form allows you to view linux man pages.





           #include <fcntl.h>
           int posix_fadvise(int fd, off_t offset, off_t len, int advice);
       Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
               _XOPEN_SOURCE >= 600 || _POSIX_C_SOURCE >= 200112L


           Programs  can  use  posix_fadvise()  to announce an intention to access
           file data in a specific pattern in the future, thus allowing the kernel
           to perform appropriate optimizations.
           The  advice  applies to a (not necessarily existent) region starting at
           offset and extending for len bytes (or until the end of the file if len
           is 0) within the file referred to by fd.  The advice is not binding; it
           merely constitutes an expectation on behalf of the application.
           Permissible values for advice include:
                  Indicates that the application has no advice to give  about  its
                  access  pattern  for  the specified data.  If no advice is given
                  for an open file, this is the default assumption.
                  The application expects to access  the  specified  data  sequen-
                  tially (with lower offsets read before higher ones).
                  The specified data will be accessed in random order.
                  The specified data will be accessed only once.
                  The specified data will be accessed in the near future.
                  The specified data will not be accessed in the near future.


           On success, zero is returned.  On error, an error number is returned.


           EBADF  The fd argument was not a valid file descriptor.
           EINVAL An invalid value was specified for advice.
           ESPIPE The  specified file descriptor refers to a pipe or FIFO.  (Linux
           and  POSIX_FADV_RANDOM disables file readahead entirely.  These changes
           affect the entire file, not just the specified region (but  other  open
           file handles to the same file are unaffected).
           POSIX_FADV_WILLNEED  initiates  a  nonblocking  read  of  the specified
           region into the page cache.  The amount of data read may  be  decreased
           by  the kernel depending on virtual memory load.  (A few megabytes will
           usually be fully satisfied, and more is rarely useful.)
           In kernels before 2.6.18, POSIX_FADV_NOREUSE had the same semantics  as
           POSIX_FADV_WILLNEED.   This  was  probably  a bug; since kernel 2.6.18,
           this flag is a no-op.
           POSIX_FADV_DONTNEED attempts to free cached pages associated  with  the
           specified  region.   This is useful, for example, while streaming large
           files.  A program may periodically request the kernel  to  free  cached
           data  that  has already been used, so that more useful cached pages are
           not discarded instead.
           Pages that have not yet been written out will be unaffected, so if  the
           application  wishes to guarantee that pages will be released, it should
           call fsync(2) or fdatasync(2) first.
       Architecture-specific variants
           Some architectures require 64-bit arguments to be aligned in a suitable
           pair  of registers (see syscall(2) for further detail).  On such archi-
           tectures, the call signature of posix_fadvise() shown in  the  SYNOPSIS
           would  force  a register to be wasted as padding between the fd and len
           arguments.  Therefore, these architectures define a version of the sys-
           tem call that orders the arguments suitably, but otherwise is otherwise
           exactly the same as posix_fadvise().
           For example, since Linux 2.6.14, ARM has the following system call:
               long arm_fadvise64_64(int fd, int advice,
                                     loff_t offset, loff_t len);
           These architecture-specific details are generally hidden from  applica-
           tions  by the glibc posix_fadvise() wrapper function, which invokes the
           appropriate architecture-specific system call.


           In kernels before 2.6.6, if len was  specified  as  0,  then  this  was
           interpreted  literally  as  "zero  bytes",  rather than as meaning "all
           bytes through to the end of the file".


           readahead(2), sync_file_range(2), posix_fallocate(3), posix_madvise(3)

    Linux 2013-04-01 POSIX_FADVISE(2)


  • Linux

    The Distributions


    The Software


    The News


  • Toll Free

Toll Free Numbers
Copyright © 1999 - 2016 by LinuxGuruz