Expose sched.h functions

Doc/library/os.rst

 :mod:`os` --- Miscellaneous operating system interfaces
 =======================================================
 
 .. module:: os
    :synopsis: Miscellaneous operating system interfaces.
 
 
 This module provides a portable way of using operating system dependent
 functionality.  If you just want to read or write a file see :func:`open`, if
 you want to manipulate paths, see the :mod:`os.path` module, and if you want to
@@ skipping 11 matching lines @@
   with the POSIX interface).
 
 * Extensions peculiar to a particular operating system are also available
   through the :mod:`os` module, but using them is of course a threat to
   portability.
 
 * All functions accepting path or file names accept both bytes and string
   objects, and result in an object of the same type, if a path or file name is
   returned.
 
-.. note::
-
-   If not separately noted, all functions that claim "Availability: Unix" are
-   supported on Mac OS X, which builds on a Unix core.
-
 * An "Availability: Unix" note means that this function is commonly found on
   Unix systems.  It does not make any claims about its existence on a specific
   operating system.
 
 * If not separately noted, all functions that claim "Availability: Unix" are
   supported on Mac OS X, which builds on a Unix core.
 
 .. Availability notes get their own line and occur at the end of the function
 .. documentation.
 
@@ skipping 47 matching lines @@
 
 .. _os-procinfo:
 
 Process Parameters
 ------------------
 
 These functions and data items provide information and operate on the current
 process and user.
 
 
+.. function:: ctermid()
+
+   Return the filename corresponding to the controlling terminal of the process.
+
+   Availability: Unix.
+
+
 .. data:: environ
 
    A mapping object representing the string environment. For example,
    ``environ['HOME']`` is the pathname of your home directory (on some platforms),
    and is equivalent to ``getenv("HOME")`` in C.
 
    This mapping is captured the first time the :mod:`os` module is imported,
    typically during Python startup as part of processing :file:`site.py`.  Changes
    to the environment made after this time are not reflected in ``os.environ``,
    except for changes made by modifying ``os.environ`` directly.
@@ skipping 57 matching lines @@
 
    .. versionadded:: 3.2
 
 
 .. function:: fsdecode(filename)
 
    Decode *filename* from the filesystem encoding with ``'surrogateescape'``
    error handler, or ``'strict'`` on Windows; return :class:`str` unchanged.
 
    :func:`fsencode` is the reverse function.
+
+   .. versionadded:: 3.2
+
+
+.. function:: getenv(key, default=None)
+
+   Return the value of the environment variable *key* if it exists, or
+   *default* if it doesn't. *key*, *default* and the result are str.
+
+   On Unix, keys and values are decoded with :func:`sys.getfilesystemencoding`
+   and ``'surrogateescape'`` error handler. Use :func:`os.getenvb` if you
+   would like to use a different encoding.
+
+   Availability: most flavors of Unix, Windows.
+
+
+.. function:: getenvb(key, default=None)
+
+   Return the value of the environment variable *key* if it exists, or
+   *default* if it doesn't. *key*, *default* and the result are bytes.
+
+   Availability: most flavors of Unix.
 
    .. versionadded:: 3.2
 
 
 .. function:: get_exec_path(env=None)
 
    Returns the list of directories that will be searched for a named
    executable, similar to a shell, when launching a process.
    *env*, when specified, should be an environment variable dictionary
    to lookup the PATH in.
    By default, when *env* is None, :data:`environ` is used.
 
    .. versionadded:: 3.2
 
 
-.. function:: ctermid()
-
-   Return the filename corresponding to the controlling terminal of the process.
-
-   Availability: Unix.
-
-
 .. function:: getegid()
 
    Return the effective group id of the current process.  This corresponds to the
    "set id" bit on the file being executed in the current process.
 
    Availability: Unix.
 
 
 .. function:: geteuid()
 
@@ skipping 23 matching lines @@
 
    .. versionadded:: 3.3
 
 
 .. function:: getgroups()
 
    Return list of supplemental group ids associated with the current process.
 
    Availability: Unix.
 
-
-.. function:: initgroups(username, gid)
-
-   Call the system initgroups() to initialize the group access list with all of
-   the groups of which the specified username is a member, plus the specified
-   group id.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.2
+   .. note:: On Mac OS X, :func:`getgroups` behavior differs somewhat from
+      other Unix platforms. If the Python interpreter was built with a
+      deployment target of :const:`10.5` or earlier, :func:`getgroups` returns
+      the list of effective group ids associated with the current user process;
+      this list is limited to a system-defined number of entries, typically 16,
+      and may be modified by calls to :func:`setgroups` if suitably privileged.
+      If built with a deployment target greater than :const:`10.5`,
+      :func:`getgroups` returns the current group access list for the user
+      associated with the effective user id of the process; the group access
+      list may change over the lifetime of the process, it is not affected by
+      calls to :func:`setgroups`, and its length is not limited to 16.  The
+      deployment target value, :const:`MACOSX_DEPLOYMENT_TARGET`, can be
+      obtained with :func:`sysconfig.get_config_var`.
 
 
 .. function:: getlogin()
 
    Return the name of the user logged in on the controlling terminal of the
    process.  For most purposes, it is more useful to use the environment variables
    :envvar:`LOGNAME` or :envvar:`USERNAME` to find out who the user is, or
    ``pwd.getpwuid(os.getuid())[0]`` to get the login name of the currently
    effective user id.
 
@@ skipping 26 matching lines @@
 
 
 .. function:: getppid()
 
    .. index:: single: process; id of parent
 
    Return the parent's process id.  When the parent process has exited, on Unix
    the id returned is the one of the init process (1), on Windows it is still
    the same id, which may be already reused by another process.
 
-   Availability: Unix, Windows
+   Availability: Unix, Windows.
 
    .. versionchanged:: 3.2
       Added support for Windows.
 
+
 .. function:: getpriority(which, who)
 
    .. index:: single: process; scheduling priority
 
-   Get program scheduling priority. The value *which* is one of
+   Get program scheduling priority.  The value *which* is one of
    :const:`PRIO_PROCESS`, :const:`PRIO_PGRP`, or :const:`PRIO_USER`, and *who*
    is interpreted relative to *which* (a process identifier for
    :const:`PRIO_PROCESS`, process group identifier for :const:`PRIO_PGRP`, and a
-   user ID for :const:`PRIO_USER`). A zero value for *who* denotes
+   user ID for :const:`PRIO_USER`).  A zero value for *who* denotes
    (respectively) the calling process, the process group of the calling process,
    or the real user ID of the calling process.
 
-   Availability: Unix
-
-   .. versionadded:: 3.3
-
-.. function:: getresuid()
-
-   Return a tuple (ruid, euid, suid) denoting the current process's
-   real, effective, and saved user ids.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.2
-
-
-.. function:: getresgid()
-
-   Return a tuple (rgid, egid, sgid) denoting the current process's
-   real, effective, and saved group ids.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.2
-
-
-.. function:: getuid()
-
-   .. index:: single: user; id
-
-   Return the current process's user id.
-
-   Availability: Unix.
-
-
-.. function:: getenv(key, default=None)
-
-   Return the value of the environment variable *key* if it exists, or
-   *default* if it doesn't. *key*, *default* and the result are str.
-
-   On Unix, keys and values are decoded with :func:`sys.getfilesystemencoding`
-   and ``'surrogateescape'`` error handler. Use :func:`os.getenvb` if you
-   would like to use a different encoding.
-
-   Availability: most flavors of Unix, Windows.
-
-
-.. function:: getenvb(key, default=None)
-
-   Return the value of the environment variable *key* if it exists, or
-   *default* if it doesn't. *key*, *default* and the result are bytes.
-
-   Availability: most flavors of Unix.
-
-   .. versionadded:: 3.2
+   Availability: Unix.
+
+   .. versionadded:: 3.3
+
 
 .. data:: PRIO_PROCESS
           PRIO_PGRP
           PRIO_USER
 
-   Parameters for :func:`getpriority` and :func:`setpriority` functions.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
+   Parameters for the :func:`getpriority` and :func:`setpriority` functions.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.3
+
+
+.. function:: getresuid()
+
+   Return a tuple (ruid, euid, suid) denoting the current process's
+   real, effective, and saved user ids.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.2
+
+
+.. function:: getresgid()
+
+   Return a tuple (rgid, egid, sgid) denoting the current process's
+   real, effective, and saved group ids.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.2
+
+
+.. function:: getuid()
+
+   .. index:: single: user; id
+
+   Return the current process's user id.
+
+   Availability: Unix.
+
+
+.. function:: initgroups(username, gid)
+
+   Call the system initgroups() to initialize the group access list with all of
+   the groups of which the specified username is a member, plus the specified
+   group id.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.2
+
 
 .. function:: putenv(key, value)
 
    .. index:: single: environment variables; setting
 
    Set the environment variable named *key* to the string *value*.  Such
    changes to the environment affect subprocesses started with :func:`os.system`,
    :func:`popen` or :func:`fork` and :func:`execv`.
 
    Availability: most flavors of Unix, Windows.
@@ skipping 31 matching lines @@
 
 
 .. function:: setgroups(groups)
 
    Set the list of supplemental group ids associated with the current process to
    *groups*. *groups* must be a sequence, and each element must be an integer
    identifying a group. This operation is typically available only to the superuser.
 
    Availability: Unix.
 
+   .. note:: On Mac OS X, the length of *groups* may not exceed the
+      system-defined maximum number of effective group ids, typically 16.
+      See the documentation for :func:`getgroups` for cases where it may not
+      return the same group list set by calling setgroups().
 
 .. function:: setpgrp()
 
    Call the system call :c:func:`setpgrp` or :c:func:`setpgrp(0, 0)` depending on
    which version is implemented (if any).  See the Unix manual for the semantics.
 
    Availability: Unix.
 
 
 .. function:: setpgid(pid, pgrp)
@@ skipping 103 matching lines @@
 
    Availability: Unix, Windows.
 
 
 .. function:: uname()
 
    .. index::
       single: gethostname() (in module socket)
       single: gethostbyaddr() (in module socket)
 
-   Return a 5-tuple containing information identifying the current operating
-   system.  The tuple contains 5 strings: ``(sysname, nodename, release, version,
-   machine)``.  Some systems truncate the nodename to 8 characters or to the
+   Returns information identifying the current operating system.
+   The return value is an object with five attributes:
+
+   * :attr:`sysname` - operating system name
+   * :attr:`nodename` - name of machine on network (implementation-defined)
+   * :attr:`release` - operating system release
+   * :attr:`version` - operating system version
+   * :attr:`machine` - hardware identifier
+
+   For backwards compatibility, this object is also iterable, behaving
+   like a five-tuple containing :attr:`sysname`, :attr:`nodename`,
+   :attr:`release`, :attr:`version`, and :attr:`machine`
+   in that order.
+
+   Some systems truncate :attr:`nodename` to 8 characters or to the
    leading component; a better way to get the hostname is
    :func:`socket.gethostname`  or even
    ``socket.gethostbyaddr(socket.gethostname())``.
 
    Availability: recent flavors of Unix.
+
+   .. versionchanged:: 3.3
+      Return type changed from a tuple to a tuple-like object
+      with named attributes.
 
 
 .. function:: unsetenv(key)
 
    .. index:: single: environment variables; deleting
 
    Unset (delete) the environment variable named *key*. Such changes to the
    environment affect subprocesses started with :func:`os.system`, :func:`popen` or
    :func:`fork` and :func:`execv`.
 
    When :func:`unsetenv` is supported, deletion of items in ``os.environ`` is
    automatically translated into a corresponding call to :func:`unsetenv`; however,
    calls to :func:`unsetenv` don't update ``os.environ``, so it is actually
    preferable to delete items of ``os.environ``.
 
    Availability: most flavors of Unix, Windows.
 
 
 .. _os-newstreams:
 
 File Object Creation
 --------------------
 
-These functions create new :term:`file objects <file object>`. (See also :func:`open`.)
-
-
-.. function:: fdopen(fd[, mode[, bufsize]])
-
-   .. index:: single: I/O control; buffering
-
-   Return an open file object connected to the file descriptor *fd*.  The *mode*
-   and *bufsize* arguments have the same meaning as the corresponding arguments to
-   the built-in :func:`open` function.
-
-   When specified, the *mode* argument must start with one of the letters
-   ``'r'``, ``'w'``, or ``'a'``, otherwise a :exc:`ValueError` is raised.
-
-   On Unix, when the *mode* argument starts with ``'a'``, the *O_APPEND* flag is
-   set on the file descriptor (which the :c:func:`fdopen` implementation already
-   does on most platforms).
-
-   Availability: Unix, Windows.
+This function creates new :term:`file objects <file object>`.  (See also
+:func:`~os.open` for opening file descriptors.)
+
+
+.. function:: fdopen(fd, *args, **kwargs)
+
+   Return an open file object connected to the file descriptor *fd*.  This is an
+   alias of the :func:`open` built-in function and accepts the same arguments.
+   The only difference is that the first argument of :func:`fdopen` must always
+   be an integer.
 
 
 .. _os-fd-ops:
 
 File Descriptor Operations
 --------------------------
 
 These functions operate on I/O streams referenced using file descriptors.
 
 File descriptors are small integers corresponding to a file that has been opened
 by the current process.  For example, standard input is usually file descriptor
 0, standard output is 1, and standard error is 2.  Further files opened by a
 process will then be assigned 3, 4, 5, and so forth.  The name "file descriptor"
 is slightly deceptive; on Unix platforms, sockets and pipes are also referenced
 by file descriptors.
 
 The :meth:`~file.fileno` method can be used to obtain the file descriptor
 associated with a :term:`file object` when required.  Note that using the file
 descriptor directly will bypass the file object methods, ignoring aspects such
 as internal buffering of data.
 
-.. data:: AT_SYMLINK_NOFOLLOW
-          AT_EACCESS
-          AT_FDCWD
-          AT_REMOVEDIR
-          AT_SYMLINK_FOLLOW
-          UTIME_NOW
-          UTIME_OMIT
-
-   These parameters are used as flags to the \*at family of functions.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
 
 .. function:: close(fd)
 
    Close file descriptor *fd*.
 
    Availability: Unix, Windows.
 
    .. note::
 
       This function is intended for low-level I/O and must be applied to a file
       descriptor as returned by :func:`os.open` or :func:`pipe`.  To close a "file
       object" returned by the built-in function :func:`open` or by :func:`popen` or
       :func:`fdopen`, use its :meth:`~file.close` method.
 
 
 .. function:: closerange(fd_low, fd_high)
 
    Close all file descriptors from *fd_low* (inclusive) to *fd_high* (exclusive),
-   ignoring errors. Equivalent to::
+   ignoring errors. Equivalent to (but much faster than)::
 
       for fd in range(fd_low, fd_high):
           try:
               os.close(fd)
           except OSError:
               pass
 
    Availability: Unix, Windows.
 
 
@@ skipping 10 matching lines @@
    Availability: Unix, Windows.
 
 
 .. function:: dup2(fd, fd2)
 
    Duplicate file descriptor *fd* to *fd2*, closing the latter first if necessary.
 
    Availability: Unix, Windows.
 
 
-.. function:: faccessat(dirfd, path, mode, flags=0)
-
-   Like :func:`access` but if *path* is relative, it is taken as relative to *dirfd*.
-   *flags* is optional and can be constructed by ORing together zero or more
-   of these values: :data:`AT_SYMLINK_NOFOLLOW`, :data:`AT_EACCESS`.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
 .. function:: fchmod(fd, mode)
 
-   Change the mode of the file given by *fd* to the numeric *mode*.  See the docs
-   for :func:`chmod` for possible values of *mode*.
-
-   Availability: Unix.
-
-
-.. function:: fchmodat(dirfd, path, mode, flags=0)
-
-   Like :func:`chmod` but if *path* is relative, it is taken as relative to *dirfd*.
-   *flags* is optional and may be 0 or :data:`AT_SYMLINK_NOFOLLOW`.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
+   Change the mode of the file given by *fd* to the numeric *mode*.  See the
+   docs for :func:`chmod` for possible values of *mode*.  As of Python 3.3, this
+   is equivalent to ``os.chmod(fd, mode)``.
+
+   Availability: Unix.
 
 
 .. function:: fchown(fd, uid, gid)
 
    Change the owner and group id of the file given by *fd* to the numeric *uid*
-   and *gid*.  To leave one of the ids unchanged, set it to -1.
-
-   Availability: Unix.
-
-
-.. function:: fchownat(dirfd, path, uid, gid, flags=0)
-
-   Like :func:`chown` but if *path* is relative, it is taken as relative to *dirfd*.
-   *flags* is optional and may be 0 or :data:`AT_SYMLINK_NOFOLLOW`.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
+   and *gid*.  To leave one of the ids unchanged, set it to -1.  See
+   :func:`chown`.  As of Python 3.3, this is equivalent to ``os.chown(fd, uid,
+   gid)``.
+
+   Availability: Unix.
 
 
 .. function:: fdatasync(fd)
 
    Force write of file with filedescriptor *fd* to disk. Does not force update of
    metadata.
 
    Availability: Unix.
 
    .. note::
       This function is not available on MacOS.
-
-
-.. function:: fdlistdir(fd)
-
-   Like :func:`listdir`, but uses a file descriptor instead and always returns
-   strings.  After execution of this function, *fd* will be closed.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: fexecve(fd, args, env)
-
-   Execute the program specified by a file descriptor *fd* with arguments given
-   by *args* and environment given by *env*, replacing the current process.
-   *args* and *env* are given as in :func:`execve`.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
 
 
 .. function:: fpathconf(fd, name)
 
    Return system configuration information relevant to an open file. *name*
    specifies the configuration value to retrieve; it may be a string which is the
    name of a defined system value; these names are specified in a number of
    standards (POSIX.1, Unix 95, Unix 98, and others).  Some platforms define
    additional names as well.  The names known to the host operating system are
    given in the ``pathconf_names`` dictionary.  For configuration variables not
    included in that mapping, passing an integer for *name* is also accepted.
 
    If *name* is a string and is not known, :exc:`ValueError` is raised.  If a
    specific value for *name* is not supported by the host system, even if it is
    included in ``pathconf_names``, an :exc:`OSError` is raised with
    :const:`errno.EINVAL` for the error number.
 
+   As of Python 3.3, this is equivalent to ``os.pathconf(fd, name)``.
+
    Availability: Unix.
 
 
 .. function:: fstat(fd)
 
-   Return status for file descriptor *fd*, like :func:`~os.stat`.
-
-   Availability: Unix, Windows.
-
-.. function:: fstatat(dirfd, path, flags=0)
-
-   Like :func:`stat` but if *path* is relative, it is taken as relative to *dirfd*.
-   *flags* is optional and may be 0 or :data:`AT_SYMLINK_NOFOLLOW`.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
+   Return status for file descriptor *fd*, like :func:`~os.stat`.  As of Python
+   3.3, this is equivalent to ``os.stat(fd)``.
+
+   Availability: Unix, Windows.
 
 
 .. function:: fstatvfs(fd)
 
-   Return information about the filesystem containing the file associated with file
-   descriptor *fd*, like :func:`statvfs`.
+   Return information about the filesystem containing the file associated with
+   file descriptor *fd*, like :func:`statvfs`.  As of Python 3.3, this is
+   equivalent to ``os.statvfs(fd)``.
 
    Availability: Unix.
 
 
 .. function:: fsync(fd)
 
    Force write of file with filedescriptor *fd* to disk.  On Unix, this calls the
    native :c:func:`fsync` function; on Windows, the MS :c:func:`_commit` function.
 
    If you're starting with a buffered Python :term:`file object` *f*, first do
    ``f.flush()``, and then do ``os.fsync(f.fileno())``, to ensure that all internal
    buffers associated with *f* are written to disk.
 
-   Availability: Unix, and Windows.
+   Availability: Unix, Windows.
 
 
 .. function:: ftruncate(fd, length)
 
-   Truncate the file corresponding to file descriptor *fd*, so that it is at most
-   *length* bytes in size.
-
-   Availability: Unix.
-
-
-.. function:: futimesat(dirfd, path, (atime, mtime))
-              futimesat(dirfd, path, None)
-
-   Like :func:`utime` but if *path* is relative, it is taken as relative to *dirfd*.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: futimens(fd, (atime_sec, atime_nsec), (mtime_sec, mtime_nsec))
-              futimens(fd, None, None)
-
-   Updates the timestamps of a file specified by the file descriptor *fd*, with
-   nanosecond precision.
-   The second form sets *atime* and *mtime* to the current time.
-   If *atime_nsec* or *mtime_nsec* is specified as :data:`UTIME_NOW`, the corresponding
-   timestamp is updated to the current time.
-   If *atime_nsec* or *mtime_nsec* is specified as :data:`UTIME_OMIT`, the corresponding
-   timestamp is not updated.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. data:: UTIME_NOW
-          UTIME_OMIT
-
-   Flags used with :func:`futimens` to specify that the timestamp must be
-   updated either to the current time or not updated at all.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: futimes(fd, (atime, mtime))
-              futimes(fd, None)
-
-   Set the access and modified time of the file specified by the file
-   descriptor *fd* to the given values. If the second form is used, set the
-   access and modified times to the current time.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
+   Truncate the file corresponding to file descriptor *fd*, so that it is at
+   most *length* bytes in size.  As of Python 3.3, this is equivalent to
+   ``os.truncate(fd, length)``.
+
+   Availability: Unix.
 
 
 .. function:: isatty(fd)
 
    Return ``True`` if the file descriptor *fd* is open and connected to a
    tty(-like) device, else ``False``.
 
    Availability: Unix.
-
-
-.. function:: linkat(srcfd, srcpath, dstfd, dstpath, flags=0)
-
-   Like :func:`link` but if *srcpath* is relative, it is taken as relative to *srcfd*
-   and if *dstpath* is relative, it is taken as relative to *dstfd*.
-   *flags* is optional and may be 0 or :data:`AT_SYMLINK_FOLLOW`.
-   If *srcpath* is relative and *srcfd* is the special value :data:`AT_FDCWD`, then
-   *srcpath* is interpreted relative to the current working directory. This
-   also applies for *dstpath*.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
 
 
 .. function:: lockf(fd, cmd, len)
 
    Apply, test or remove a POSIX lock on an open file descriptor.
    *fd* is an open file descriptor.
    *cmd* specifies the command to use - one of :data:`F_LOCK`, :data:`F_TLOCK`,
    :data:`F_ULOCK` or :data:`F_TEST`.
    *len* specifies the section of the file to lock.
 
    Availability: Unix.
 
    .. versionadded:: 3.3
 
 
 .. data:: F_LOCK
           F_TLOCK
           F_ULOCK
           F_TEST
 
    Flags that specify what action :func:`lockf` will take.
 
    Availability: Unix.
 
    .. versionadded:: 3.3
 
+
 .. function:: lseek(fd, pos, how)
 
    Set the current position of file descriptor *fd* to position *pos*, modified
    by *how*: :const:`SEEK_SET` or ``0`` to set the position relative to the
    beginning of the file; :const:`SEEK_CUR` or ``1`` to set it relative to the
    current position; :const:`os.SEEK_END` or ``2`` to set it relative to the end of
-   the file.
+   the file. Return the new cursor position in bytes, starting from the beginning.
 
    Availability: Unix, Windows.
 
 
 .. data:: SEEK_SET
           SEEK_CUR
           SEEK_END
 
    Parameters to the :func:`lseek` function. Their values are 0, 1, and 2,
-   respectively. Availability: Windows, Unix.
-
-
-.. function:: mkdirat(dirfd, path, mode=0o777)
-
-   Like :func:`mkdir` but if *path* is relative, it is taken as relative to *dirfd*.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: mkfifoat(dirfd, path, mode=0o666)
-
-   Like :func:`mkfifo` but if *path* is relative, it is taken as relative to *dirfd*.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: mknodat(dirfd, path, mode=0o600, device=0)
-
-   Like :func:`mknod` but if *path* is relative, it is taken as relative to *dirfd*.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: open(file, flags[, mode])
+   respectively.
+
+   Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+      Some operating systems could support additional values, like
+      :data:`os.SEEK_HOLE` or :data:`os.SEEK_DATA`.
+
+
+.. function:: open(file, flags, mode=0o777, *, dir_fd=None)
 
    Open the file *file* and set various flags according to *flags* and possibly
-   its mode according to *mode*.  The default *mode* is ``0o777`` (octal), and
-   the current umask value is first masked out.  Return the file descriptor for
-   the newly opened file.
+   its mode according to *mode*.  When computing *mode*, the current umask value
+   is first masked out.  Return the file descriptor for the newly opened file.
 
    For a description of the flag and mode values, see the C run-time documentation;
    flag constants (like :const:`O_RDONLY` and :const:`O_WRONLY`) are defined in
    this module too (see :ref:`open-constants`).  In particular, on Windows adding
    :const:`O_BINARY` is needed to open files in binary mode.
 
+   This function can support :ref:`paths relative to directory descriptors
+   <dir_fd>`.
+
    Availability: Unix, Windows.
 
    .. note::
 
       This function is intended for low-level I/O.  For normal usage, use the
       built-in function :func:`open`, which returns a :term:`file object` with
       :meth:`~file.read` and :meth:`~file.write` methods (and many more).  To
       wrap a file descriptor in a file object, use :func:`fdopen`.
 
-
-.. function:: openat(dirfd, path, flags, mode=0o777)
-
-   Like :func:`open` but if *path* is relative, it is taken as relative to *dirfd*.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
+   .. versionadded:: 3.3
+      The *dir_fd* argument.
 
 
 .. function:: openpty()
 
    .. index:: module: pty
 
    Open a new pseudo-terminal pair. Return a pair of file descriptors ``(master,
    slave)`` for the pty and the tty, respectively. For a (slightly) more portable
    approach, use the :mod:`pty` module.
 
@@ skipping 85 matching lines @@
 
    Read at most *n* bytes from file descriptor *fd*. Return a bytestring containing the
    bytes read.  If the end of the file referred to by *fd* has been reached, an
    empty bytes object is returned.
 
    Availability: Unix, Windows.
 
    .. note::
 
       This function is intended for low-level I/O and must be applied to a file
-      descriptor as returned by :func:`os.open` or :func:`pipe`.  To read a "file object"
-      returned by the built-in function :func:`open` or by :func:`popen` or
-      :func:`fdopen`, or :data:`sys.stdin`, use its :meth:`~file.read` or
-      :meth:`~file.readline` methods.
+      descriptor as returned by :func:`os.open` or :func:`pipe`.  To read a
+      "file object" returned by the built-in function :func:`open` or by
+      :func:`popen` or :func:`fdopen`, or :data:`sys.stdin`, use its
+      :meth:`~file.read` or :meth:`~file.readline` methods.
 
 
 .. function:: sendfile(out, in, offset, nbytes)
               sendfile(out, in, offset, nbytes, headers=None, trailers=None, flags=0)
 
    Copy *nbytes* bytes from file descriptor *in* to file descriptor *out*
    starting at *offset*.
    Return the number of bytes sent. When EOF is reached return 0.
 
    The first function notation is supported by all platforms that define
@@ skipping 23 matching lines @@
           SF_SYNC
 
    Parameters to the :func:`sendfile` function, if the implementation supports
    them.
 
    Availability: Unix.
 
    .. versionadded:: 3.3
 
 
-.. function:: readlinkat(dirfd, path)
-
-   Like :func:`readlink` but if *path* is relative, it is taken as relative to *dirfd*.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: renameat(olddirfd, oldpath, newdirfd, newpath)
-
-   Like :func:`rename` but if *oldpath* is relative, it is taken as relative to
-   *olddirfd* and if *newpath* is relative, it is taken as relative to *newdirfd*.
-   If *oldpath* is relative and *olddirfd* is the special value :data:`AT_FDCWD`, then
-   *oldpath* is interpreted relative to the current working directory. This
-   also applies for *newpath*.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: symlinkat(src, dstfd, dst)
-
-   Like :func:`symlink` but if *dst* is relative, it is taken as relative to *dstfd*.
-   If *dst* is relative and *dstfd* is the special value :data:`AT_FDCWD`, then *dst*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
 .. function:: readv(fd, buffers)
 
    Read from a file descriptor into a number of writable buffers. *buffers* is
    an arbitrary sequence of writable buffers. Returns the total number of bytes
    read.
 
    Availability: Unix.
 
    .. versionadded:: 3.3
 
@@ skipping 14 matching lines @@
    Availability: Unix.
 
 
 .. function:: ttyname(fd)
 
    Return a string which specifies the terminal device associated with
    file descriptor *fd*.  If *fd* is not associated with a terminal device, an
    exception is raised.
 
    Availability: Unix.
-
-
-.. function:: unlinkat(dirfd, path, flags=0)
-
-   Like :func:`unlink` but if *path* is relative, it is taken as relative to *dirfd*.
-   *flags* is optional and may be 0 or :data:`AT_REMOVEDIR`. If :data:`AT_REMOVEDIR` is
-   specified, :func:`unlinkat` behaves like :func:`rmdir`.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: utimensat(dirfd, path, (atime_sec, atime_nsec), (mtime_sec, mtime_nsec), flags)
-              utimensat(dirfd, path, None, None, flags)
-
-   Updates the timestamps of a file with nanosecond precision.
-   The second form sets *atime* and *mtime* to the current time.
-   If *atime_nsec* or *mtime_nsec* is specified as :data:`UTIME_NOW`, the corresponding
-   timestamp is updated to the current time.
-   If *atime_nsec* or *mtime_nsec* is specified as :data:`UTIME_OMIT`, the corresponding
-   timestamp is not updated.
-   If *path* is relative, it is taken as relative to *dirfd*.
-   *flags* is optional and may be 0 or :data:`AT_SYMLINK_NOFOLLOW`.
-   If *path* is relative and *dirfd* is the special value :data:`AT_FDCWD`, then *path*
-   is interpreted relative to the current working directory.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
 
 
 .. function:: write(fd, str)
 
    Write the bytestring in *str* to file descriptor *fd*. Return the number of
    bytes actually written.
 
    Availability: Unix, Windows.
 
    .. note::
 
       This function is intended for low-level I/O and must be applied to a file
       descriptor as returned by :func:`os.open` or :func:`pipe`.  To write a "file
       object" returned by the built-in function :func:`open` or by :func:`popen` or
       :func:`fdopen`, or :data:`sys.stdout` or :data:`sys.stderr`, use its
       :meth:`~file.write` method.
 
 
 .. function:: writev(fd, buffers)
 
-   Write the the contents of *buffers* to file descriptor *fd*, where *buffers*
+   Write the contents of *buffers* to file descriptor *fd*, where *buffers*
    is an arbitrary sequence of buffers.
    Returns the total number of bytes written.
 
    Availability: Unix.
 
    .. versionadded:: 3.3
 
 
 .. _open-constants:
 
@@ skipping 23 matching lines @@
           O_SYNC
           O_NDELAY
           O_NONBLOCK
           O_NOCTTY
           O_SHLOCK
           O_EXLOCK
           O_CLOEXEC
 
    These constants are only available on Unix.
 
+   .. versionchanged:: 3.3
+      Add :data:`O_CLOEXEC` constant.
 
 .. data:: O_BINARY
           O_NOINHERIT
           O_SHORT_LIVED
           O_TEMPORARY
           O_RANDOM
           O_SEQUENTIAL
           O_TEXT
 
    These constants are only available on Windows.
 
 
 .. data:: O_ASYNC
           O_DIRECT
           O_DIRECTORY
           O_NOFOLLOW
           O_NOATIME
 
    These constants are GNU extensions and not present if they are not defined by
    the C library.
 
 
+.. data:: RTLD_LAZY
+          RTLD_NOW
+          RTLD_GLOBAL
+          RTLD_LOCAL
+          RTLD_NODELETE
+          RTLD_NOLOAD
+          RTLD_DEEPBIND
+
+   See the Unix manual page :manpage:`dlopen(3)`.
+
+   .. versionadded:: 3.3
+
+
+.. _terminal-size:
+
+Querying the size of a terminal
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. versionadded:: 3.3
+
+.. function:: get_terminal_size(fd=STDOUT_FILENO)
+
+   Return the size of the terminal window as ``(columns, lines)``,
+   tuple of type :class:`terminal_size`.
+
+   The optional argument ``fd`` (default ``STDOUT_FILENO``, or standard
+   output) specifies which file descriptor should be queried.
+
+   If the file descriptor is not connected to a terminal, an :exc:`OSError`
+   is thrown.
+
+   :func:`shutil.get_terminal_size` is the high-level function which
+   should normally be used, ``os.get_terminal_size`` is the low-level
+   implementation.
+
+   Availability: Unix, Windows.
+
+.. class:: terminal_size
+
+   A subclass of tuple, holding ``(columns, lines)`` of the terminal window size.
+
+   .. attribute:: columns
+
+      Width of the terminal window in characters.
+
+   .. attribute:: lines
+
+      Height of the terminal window in characters.
+
+
 .. _os-file-dir:
 
 Files and Directories
 ---------------------
 
-.. function:: access(path, mode)
+On some Unix platforms, many of these functions support one or more of these
+features:
+
+.. _path_fd:
+
+* **specifying a file descriptor:**
+  For some functions, the *path* argument can be not only a string giving a path
+  name, but also a file descriptor.  The function will then operate on the file
+  referred to by the descriptor.  (For POSIX systems, Python will call the
+  ``f...`` version of the function.)
+
+  You can check whether or not *path* can be specified as a file descriptor on
+  your platform using :data:`os.supports_fd`.  If it is unavailable, using it
+  will raise a :exc:`NotImplementedError`.
+
+  If the function also supports *dir_fd* or *follow_symlinks* arguments, it is
+  an error to specify one of those when supplying *path* as a file descriptor.
+
+.. _dir_fd:
+
+* **paths relative to directory descriptors:** If *dir_fd* is not ``None``, it
+  should be a file descriptor referring to a directory, and the path to operate
+  on should be relative; path will then be relative to that directory.  If the
+  path is absolute, *dir_fd* is ignored.  (For POSIX systems, Python will call
+  the ``...at`` or ``f...at`` version of the function.)
+
+  You can check whether or not *dir_fd* is supported on your platform using
+  :data:`os.supports_dir_fd`.  If it is unavailable, using it will raise a
+  :exc:`NotImplementedError`.
+
+.. _follow_symlinks:
+
+* **not following symlinks:** If *follow_symlinks* is
+  ``False``, and the last element of the path to operate on is a symbolic link,
+  the function will operate on the symbolic link itself instead of the file the
+  link points to.  (For POSIX systems, Python will call the ``l...`` version of
+  the function.)
+
+  You can check whether or not *follow_symlinks* is supported on your platform
+  using :data:`os.supports_follow_symlinks`.  If it is unavailable, using it
+  will raise a :exc:`NotImplementedError`.
+
+
+
+.. function:: access(path, mode, *, dir_fd=None, effective_ids=False, follow_symlinks=True)
 
    Use the real uid/gid to test for access to *path*.  Note that most operations
    will use the effective uid/gid, therefore this routine can be used in a
    suid/sgid environment to test if the invoking user has the specified access to
    *path*.  *mode* should be :const:`F_OK` to test the existence of *path*, or it
    can be the inclusive OR of one or more of :const:`R_OK`, :const:`W_OK`, and
    :const:`X_OK` to test permissions.  Return :const:`True` if access is allowed,
    :const:`False` if not. See the Unix man page :manpage:`access(2)` for more
    information.
 
+   This function can support specifying :ref:`paths relative to directory
+   descriptors <dir_fd>` and :ref:`not following symlinks <follow_symlinks>`.
+
+   If *effective_ids* is ``True``, :func:`access` will perform its access
+   checks using the effective uid/gid instead of the real uid/gid.
+   *effective_ids* may not be supported on your platform; you can check whether
+   or not it is available using :data:`os.supports_effective_ids`.  If it is
+   unavailable, using it will raise a :exc:`NotImplementedError`.
+
    Availability: Unix, Windows.
 
    .. note::
 
       Using :func:`access` to check if a user is authorized to e.g. open a file
       before actually doing so using :func:`open` creates a security hole,
       because the user might exploit the short time interval between checking
       and opening the file to manipulate it. It's preferable to use :term:`EAFP`
       techniques. For example::
 
          if os.access("myfile", os.R_OK):
              with open("myfile") as fp:
                  return fp.read()
          return "some default data"
 
       is better written as::
 
          try:
              fp = open("myfile")
-         except IOError as e:
-             if e.errno == errno.EACCESS:
-                 return "some default data"
-             # Not a permission error.
-             raise
+         except PermissionError:
+             return "some default data"
          else:
              with fp:
                  return fp.read()
 
    .. note::
 
       I/O operations may fail even when :func:`access` indicates that they would
       succeed, particularly for operations on network filesystems which may have
       permissions semantics beyond the usual POSIX permission-bit model.
 
+   .. versionchanged:: 3.3
+      Added the *dir_fd*, *effective_ids*, and *follow_symlinks* parameters.
+
 
 .. data:: F_OK
-
-   Value to pass as the *mode* parameter of :func:`access` to test the existence of
-   *path*.
-
-
-.. data:: R_OK
-
-   Value to include in the *mode* parameter of :func:`access` to test the
-   readability of *path*.
-
-
-.. data:: W_OK
-
-   Value to include in the *mode* parameter of :func:`access` to test the
-   writability of *path*.
-
-
-.. data:: X_OK
-
-   Value to include in the *mode* parameter of :func:`access` to determine if
-   *path* can be executed.
+          R_OK
+          W_OK
+          X_OK
+
+   Values to pass as the *mode* parameter of :func:`access` to test the
+   existence, readability, writability and executability of *path*,
+   respectively.
 
 
 .. function:: chdir(path)
 
    .. index:: single: directory; changing
 
    Change the current working directory to *path*.
 
-   Availability: Unix, Windows.
-
-
-.. function:: fchdir(fd)
-
-   Change the current working directory to the directory represented by the file
-   descriptor *fd*.  The descriptor must refer to an opened directory, not an open
-   file.
-
-   Availability: Unix.
-
-
-.. function:: getcwd()
-
-   Return a string representing the current working directory.
-
-   Availability: Unix, Windows.
-
-
-.. function:: getcwdb()
-
-   Return a bytestring representing the current working directory.
-
-   Availability: Unix, Windows.
-
-
-.. function:: chflags(path, flags)
+   This function can support :ref:`specifying a file descriptor <path_fd>`.  The
+   descriptor must refer to an opened directory, not an open file.
+
+   Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+      Added support for specifying *path* as a file descriptor
+      on some platforms.
+
+
+.. function:: chflags(path, flags, *, follow_symlinks=True)
 
    Set the flags of *path* to the numeric *flags*. *flags* may take a combination
    (bitwise OR) of the following values (as defined in the :mod:`stat` module):
 
    * :data:`stat.UF_NODUMP`
    * :data:`stat.UF_IMMUTABLE`
    * :data:`stat.UF_APPEND`
    * :data:`stat.UF_OPAQUE`
    * :data:`stat.UF_NOUNLINK`
    * :data:`stat.UF_COMPRESSED`
    * :data:`stat.UF_HIDDEN`
    * :data:`stat.SF_ARCHIVED`
    * :data:`stat.SF_IMMUTABLE`
    * :data:`stat.SF_APPEND`
    * :data:`stat.SF_NOUNLINK`
    * :data:`stat.SF_SNAPSHOT`
 
-   Availability: Unix.
-
-
-.. function:: chroot(path)
-
-   Change the root directory of the current process to *path*. Availability:
-   Unix.
-
-
-.. function:: chmod(path, mode)
+   This function can support :ref:`not following symlinks <follow_symlinks>`.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.3
+      The *follow_symlinks* argument.
+
+
+.. function:: chmod(path, mode, *, dir_fd=None, follow_symlinks=True)
 
    Change the mode of *path* to the numeric *mode*. *mode* may take one of the
    following values (as defined in the :mod:`stat` module) or bitwise ORed
    combinations of them:
 
    * :data:`stat.S_ISUID`
    * :data:`stat.S_ISGID`
    * :data:`stat.S_ENFMT`
    * :data:`stat.S_ISVTX`
    * :data:`stat.S_IREAD`
    * :data:`stat.S_IWRITE`
    * :data:`stat.S_IEXEC`
    * :data:`stat.S_IRWXU`
    * :data:`stat.S_IRUSR`
    * :data:`stat.S_IWUSR`
    * :data:`stat.S_IXUSR`
    * :data:`stat.S_IRWXG`
    * :data:`stat.S_IRGRP`
    * :data:`stat.S_IWGRP`
    * :data:`stat.S_IXGRP`
    * :data:`stat.S_IRWXO`
    * :data:`stat.S_IROTH`
    * :data:`stat.S_IWOTH`
    * :data:`stat.S_IXOTH`
 
+   This function can support :ref:`specifying a file descriptor <path_fd>`,
+   :ref:`paths relative to directory descriptors <dir_fd>` and :ref:`not
+   following symlinks <follow_symlinks>`.
+
    Availability: Unix, Windows.
 
    .. note::
 
-      Although Windows supports :func:`chmod`, you can only  set the file's read-only
-      flag with it (via the ``stat.S_IWRITE``  and ``stat.S_IREAD``
-      constants or a corresponding integer value).  All other bits are
-      ignored.
-
-
-.. function:: chown(path, uid, gid)
-
-   Change the owner and group id of *path* to the numeric *uid* and *gid*. To leave
-   one of the ids unchanged, set it to -1.
-
-   Availability: Unix.
+      Although Windows supports :func:`chmod`, you can only set the file's
+      read-only flag with it (via the ``stat.S_IWRITE`` and ``stat.S_IREAD``
+      constants or a corresponding integer value).  All other bits are ignored.
+
+   .. versionadded:: 3.3
+      Added support for specifying *path* as an open file descriptor,
+      and the *dir_fd* and *follow_symlinks* arguments.
+
+
+.. function:: chown(path, uid, gid, *, dir_fd=None, follow_symlinks=True)
+
+   Change the owner and group id of *path* to the numeric *uid* and *gid*.  To
+   leave one of the ids unchanged, set it to -1.
+
+   This function can support :ref:`specifying a file descriptor <path_fd>`,
+   :ref:`paths relative to directory descriptors <dir_fd>` and :ref:`not
+   following symlinks <follow_symlinks>`.
+
+   See :func:`shutil.chown` for a higher-level function that accepts names in
+   addition to numeric ids.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.3
+      Added support for specifying an open file descriptor for *path*,
+      and the *dir_fd* and *follow_symlinks* arguments.
+
+
+.. function:: chroot(path)
+
+   Change the root directory of the current process to *path*.
+
+   Availability: Unix.
+
+
+.. function:: fchdir(fd)
+
+   Change the current working directory to the directory represented by the file
+   descriptor *fd*.  The descriptor must refer to an opened directory, not an
+   open file.  As of Python 3.3, this is equivalent to ``os.chdir(fd)``.
+
+   Availability: Unix.
+
+
+.. function:: getcwd()
+
+   Return a string representing the current working directory.
+
+   Availability: Unix, Windows.
+
+
+.. function:: getcwdb()
+
+   Return a bytestring representing the current working directory.
+
+   Availability: Unix, Windows.
 
 
 .. function:: lchflags(path, flags)
 
-   Set the flags of *path* to the numeric *flags*, like :func:`chflags`, but do not
-   follow symbolic links.
+   Set the flags of *path* to the numeric *flags*, like :func:`chflags`, but do
+   not follow symbolic links.  As of Python 3.3, this is equivalent to
+   ``os.chflags(path, flags, follow_symlinks=False)``.
 
    Availability: Unix.
 
 
 .. function:: lchmod(path, mode)
 
    Change the mode of *path* to the numeric *mode*. If path is a symlink, this
-   affects the symlink rather than the target. See the docs for :func:`chmod`
-   for possible values of *mode*.
+   affects the symlink rather than the target.  See the docs for :func:`chmod`
+   for possible values of *mode*.  As of Python 3.3, this is equivalent to
+   ``os.chmod(path, mode, follow_symlinks=False)``.
 
    Availability: Unix.
 
 
 .. function:: lchown(path, uid, gid)
 
-   Change the owner and group id of *path* to the numeric *uid* and *gid*. This
-   function will not follow symbolic links.
-
-   Availability: Unix.
-
-
-.. function:: link(source, link_name)
-
-   Create a hard link pointing to *source* named *link_name*.
+   Change the owner and group id of *path* to the numeric *uid* and *gid*.  This
+   function will not follow symbolic links.  As of Python 3.3, this is equivalent
+   to ``os.chown(path, uid, gid, follow_symlinks=False)``.
+
+   Availability: Unix.
+
+
+.. function:: link(src, dst, *, src_dir_fd=None, dst_dir_fd=None, follow_symlinks=True)
+
+   Create a hard link pointing to *src* named *dst*.
+
+   This function can support specifying *src_dir_fd* and/or *dst_dir_fd* to
+   supply :ref:`paths relative to directory descriptors <dir_fd>`, and :ref:`not
+   following symlinks <follow_symlinks>`.
 
    Availability: Unix, Windows.
 
    .. versionchanged:: 3.2
       Added Windows support.
 
+   .. versionadded:: 3.3
+      Added the *src_dir_fd*, *dst_dir_fd*, and *follow_symlinks* arguments.
+
 
 .. function:: listdir(path='.')
 
    Return a list containing the names of the entries in the directory given by
-   *path* (default: ``'.'``).  The list is in arbitrary order.  It does not include the special
+   *path*.  The list is in arbitrary order, and does not include the special
    entries ``'.'`` and ``'..'`` even if they are present in the directory.
 
-   This function can be called with a bytes or string argument, and returns
-   filenames of the same datatype.
+   *path* may be either of type ``str`` or of type ``bytes``.  If *path*
+   is of type ``bytes``, the filenames returned will also be of type ``bytes``;
+   in all other circumstances, they will be of type ``str``.
+
+   This function can also support :ref:`specifying a file descriptor
+   <path_fd>`; the file descriptor must refer to a directory.
+
+   .. note::
+      To encode ``str`` filenames to ``bytes``, use :func:`~os.fsencode`.
 
    Availability: Unix, Windows.
 
    .. versionchanged:: 3.2
       The *path* parameter became optional.
 
-.. function:: lstat(path)
+   .. versionadded:: 3.3
+      Added support for specifying an open file descriptor for *path*.
+
+
+.. function:: lstat(path, *, dir_fd=None)
 
    Perform the equivalent of an :c:func:`lstat` system call on the given path.
    Similar to :func:`~os.stat`, but does not follow symbolic links.  On
    platforms that do not support symbolic links, this is an alias for
-   :func:`~os.stat`.
+   :func:`~os.stat`.  As of Python 3.3, this is equivalent to ``os.stat(path,
+   dir_fd=dir_fd, follow_symlinks=False)``.
+
+   This function can also support :ref:`paths relative to directory descriptors
+   <dir_fd>`.
 
    .. versionchanged:: 3.2
       Added support for Windows 6.0 (Vista) symbolic links.
 
-
-.. function:: lutimes(path, (atime, mtime))
-              lutimes(path, None)
-
-   Like :func:`utime`, but if *path* is a symbolic link, it is not
-   dereferenced.
-
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: mkfifo(path[, mode])
-
-   Create a FIFO (a named pipe) named *path* with numeric mode *mode*.  The
-   default *mode* is ``0o666`` (octal).  The current umask value is first masked
-   out from the mode.
-
-   FIFOs are pipes that can be accessed like regular files.  FIFOs exist until they
-   are deleted (for example with :func:`os.unlink`). Generally, FIFOs are used as
-   rendezvous between "client" and "server" type processes: the server opens the
-   FIFO for reading, and the client opens it for writing.  Note that :func:`mkfifo`
-   doesn't open the FIFO --- it just creates the rendezvous point.
-
-   Availability: Unix.
-
-
-.. function:: mknod(filename[, mode=0o600[, device]])
-
-   Create a filesystem node (file, device special file or named pipe) named
-   *filename*. *mode* specifies both the permissions to use and the type of node
-   to be created, being combined (bitwise OR) with one of ``stat.S_IFREG``,
-   ``stat.S_IFCHR``, ``stat.S_IFBLK``, and ``stat.S_IFIFO`` (those constants are
-   available in :mod:`stat`).  For ``stat.S_IFCHR`` and ``stat.S_IFBLK``,
-   *device* defines the newly created device special file (probably using
-   :func:`os.makedev`), otherwise it is ignored.
-
-
-.. function:: major(device)
-
-   Extract the device major number from a raw device number (usually the
-   :attr:`st_dev` or :attr:`st_rdev` field from :c:type:`stat`).
-
-
-.. function:: minor(device)
-
-   Extract the device minor number from a raw device number (usually the
-   :attr:`st_dev` or :attr:`st_rdev` field from :c:type:`stat`).
-
-
-.. function:: makedev(major, minor)
-
-   Compose a raw device number from the major and minor device numbers.
-
-
-.. function:: mkdir(path[, mode])
-
-   Create a directory named *path* with numeric mode *mode*. The default *mode*
-   is ``0o777`` (octal).  On some systems, *mode* is ignored.  Where it is used,
-   the current umask value is first masked out.  If the directory already
-   exists, :exc:`OSError` is raised.
+   .. versionchanged:: 3.3
+      Added the *dir_fd* parameter.
+
+
+.. function:: mkdir(path, mode=0o777, *, dir_fd=None)
+
+   Create a directory named *path* with numeric mode *mode*.
+
+   On some systems, *mode* is ignored.  Where it is used, the current umask
+   value is first masked out.  If the directory already exists, :exc:`OSError`
+   is raised.
+
+   This function can also support :ref:`paths relative to directory descriptors
+   <dir_fd>`.
 
    It is also possible to create temporary directories; see the
    :mod:`tempfile` module's :func:`tempfile.mkdtemp` function.
 
    Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+      The *dir_fd* argument.
 
 
 .. function:: makedirs(path, mode=0o777, exist_ok=False)
 
    .. index::
       single: directory; creating
       single: UNC paths; and os.makedirs()
 
    Recursive directory creation function.  Like :func:`mkdir`, but makes all
    intermediate-level directories needed to contain the leaf directory.  If
    the target directory with the same mode as specified already exists,
    raises an :exc:`OSError` exception if *exist_ok* is False, otherwise no
    exception is raised.  If the directory cannot be created in other cases,
    raises an :exc:`OSError` exception.  The default *mode* is ``0o777`` (octal).
    On some systems, *mode* is ignored.  Where it is used, the current umask
    value is first masked out.
 
    .. note::
 
       :func:`makedirs` will become confused if the path elements to create
       include :data:`pardir`.
 
    This function handles UNC paths correctly.
 
    .. versionadded:: 3.2
       The *exist_ok* parameter.
 
 
+.. function:: mkfifo(path, mode=0o666, *, dir_fd=None)
+
+   Create a FIFO (a named pipe) named *path* with numeric mode *mode*.
+   The current umask value is first masked out from the mode.
+
+   This function can also support :ref:`paths relative to directory descriptors
+   <dir_fd>`.
+
+   FIFOs are pipes that can be accessed like regular files.  FIFOs exist until they
+   are deleted (for example with :func:`os.unlink`). Generally, FIFOs are used as
+   rendezvous between "client" and "server" type processes: the server opens the
+   FIFO for reading, and the client opens it for writing.  Note that :func:`mkfifo`
+   doesn't open the FIFO --- it just creates the rendezvous point.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.3
+      The *dir_fd* argument.
+
+
+.. function:: mknod(filename, mode=0o600, device=0, *, dir_fd=None)
+
+   Create a filesystem node (file, device special file or named pipe) named
+   *filename*. *mode* specifies both the permissions to use and the type of node
+   to be created, being combined (bitwise OR) with one of ``stat.S_IFREG``,
+   ``stat.S_IFCHR``, ``stat.S_IFBLK``, and ``stat.S_IFIFO`` (those constants are
+   available in :mod:`stat`).  For ``stat.S_IFCHR`` and ``stat.S_IFBLK``,
+   *device* defines the newly created device special file (probably using
+   :func:`os.makedev`), otherwise it is ignored.
+
+   This function can also support :ref:`paths relative to directory descriptors
+   <dir_fd>`.
+
+   .. versionadded:: 3.3
+      The *dir_fd* argument.
+
+
+.. function:: major(device)
+
+   Extract the device major number from a raw device number (usually the
+   :attr:`st_dev` or :attr:`st_rdev` field from :c:type:`stat`).
+
+
+.. function:: minor(device)
+
+   Extract the device minor number from a raw device number (usually the
+   :attr:`st_dev` or :attr:`st_rdev` field from :c:type:`stat`).
+
+
+.. function:: makedev(major, minor)
+
+   Compose a raw device number from the major and minor device numbers.
+
+
 .. function:: pathconf(path, name)
 
    Return system configuration information relevant to a named file. *name*
    specifies the configuration value to retrieve; it may be a string which is the
    name of a defined system value; these names are specified in a number of
    standards (POSIX.1, Unix 95, Unix 98, and others).  Some platforms define
    additional names as well.  The names known to the host operating system are
    given in the ``pathconf_names`` dictionary.  For configuration variables not
    included in that mapping, passing an integer for *name* is also accepted.
 
    If *name* is a string and is not known, :exc:`ValueError` is raised.  If a
    specific value for *name* is not supported by the host system, even if it is
    included in ``pathconf_names``, an :exc:`OSError` is raised with
    :const:`errno.EINVAL` for the error number.
 
+   This function can support :ref:`specifying a file descriptor
+   <path_fd>`.
+
    Availability: Unix.
 
 
 .. data:: pathconf_names
 
    Dictionary mapping names accepted by :func:`pathconf` and :func:`fpathconf` to
    the integer values defined for those names by the host operating system.  This
-   can be used to determine the set of names known to the system. Availability:
-   Unix.
-
-
-.. function:: readlink(path)
+   can be used to determine the set of names known to the system.
+
+   Availability: Unix.
+
+
+.. function:: readlink(path, *, dir_fd=None)
 
    Return a string representing the path to which the symbolic link points.  The
-   result may be either an absolute or relative pathname; if it is relative, it may
-   be converted to an absolute pathname using ``os.path.join(os.path.dirname(path),
-   result)``.
+   result may be either an absolute or relative pathname; if it is relative, it
+   may be converted to an absolute pathname using
+   ``os.path.join(os.path.dirname(path), result)``.
 
    If the *path* is a string object, the result will also be a string object,
    and the call may raise an UnicodeDecodeError. If the *path* is a bytes
    object, the result will be a bytes object.
 
+   This function can also support :ref:`paths relative to directory descriptors
+   <dir_fd>`.
+
    Availability: Unix, Windows
 
    .. versionchanged:: 3.2
       Added support for Windows 6.0 (Vista) symbolic links.
 
-
-.. function:: remove(path)
+   .. versionadded:: 3.3
+      The *dir_fd* argument.
+
+
+.. function:: remove(path, *, dir_fd=None)
 
    Remove (delete) the file *path*.  If *path* is a directory, :exc:`OSError` is
-   raised; see :func:`rmdir` below to remove a directory.  This is identical to
-   the :func:`unlink` function documented below.  On Windows, attempting to
-   remove a file that is in use causes an exception to be raised; on Unix, the
-   directory entry is removed but the storage allocated to the file is not made
-   available until the original file is no longer in use.
-
-   Availability: Unix, Windows.
+   raised.  Use :func:`rmdir` to remove directories.
+
+   This function can support :ref:`paths relative to directory descriptors
+   <dir_fd>`.
+
+   On Windows, attempting to remove a file that is in use causes an exception to
+   be raised; on Unix, the directory entry is removed but the storage allocated
+   to the file is not made available until the original file is no longer in use.
+
+   This function is identical to :func:`unlink`.
+
+   Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+      The *dir_fd* argument.
 
 
 .. function:: removedirs(path)
 
    .. index:: single: directory; deleting
 
    Remove directories recursively.  Works like :func:`rmdir` except that, if the
    leaf directory is successfully removed, :func:`removedirs`  tries to
    successively remove every parent directory mentioned in  *path* until an error
    is raised (which is ignored, because it generally means that a parent directory
    is not empty). For example, ``os.removedirs('foo/bar/baz')`` will first remove
    the directory ``'foo/bar/baz'``, and then remove ``'foo/bar'`` and ``'foo'`` if
    they are empty. Raises :exc:`OSError` if the leaf directory could not be
    successfully removed.
 
 
-.. function:: rename(src, dst)
+.. function:: rename(src, dst, *, src_dir_fd=None, dst_dir_fd=None)
 
    Rename the file or directory *src* to *dst*.  If *dst* is a directory,
    :exc:`OSError` will be raised.  On Unix, if *dst* exists and is a file, it will
    be replaced silently if the user has permission.  The operation may fail on some
    Unix flavors if *src* and *dst* are on different filesystems.  If successful,
    the renaming will be an atomic operation (this is a POSIX requirement).  On
    Windows, if *dst* already exists, :exc:`OSError` will be raised even if it is a
-   file; there may be no way to implement an atomic rename when *dst* names an
-   existing file.
-
-   Availability: Unix, Windows.
+   file.
+
+   This function can support specifying *src_dir_fd* and/or *dst_dir_fd* to
+   supply :ref:`paths relative to directory descriptors <dir_fd>`.
+
+   If you want cross-platform overwriting of the destination, use :func:`replace`.
+
+   Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+      The *src_dir_fd* and *dst_dir_fd* arguments.
 
 
 .. function:: renames(old, new)
 
    Recursive directory or file renaming function. Works like :func:`rename`, except
    creation of any intermediate directories needed to make the new pathname good is
    attempted first. After the rename, directories corresponding to rightmost path
    segments of the old name will be pruned away using :func:`removedirs`.
 
    .. note::
 
       This function can fail with the new directory structure made if you lack
       permissions needed to remove the leaf directory or file.
 
 
-.. function:: rmdir(path)
+.. function:: replace(src, dst, *, src_dir_fd=None, dst_dir_fd=None)
+
+   Rename the file or directory *src* to *dst*.  If *dst* is a directory,
+   :exc:`OSError` will be raised.  If *dst* exists and is a file, it will
+   be replaced silently if the user has permission.  The operation may fail
+   if *src* and *dst* are on different filesystems.  If successful,
+   the renaming will be an atomic operation (this is a POSIX requirement).
+
+   This function can support specifying *src_dir_fd* and/or *dst_dir_fd* to
+   supply :ref:`paths relative to directory descriptors <dir_fd>`.
+
+   Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+
+
+.. function:: rmdir(path, *, dir_fd=None)
 
    Remove (delete) the directory *path*.  Only works when the directory is
    empty, otherwise, :exc:`OSError` is raised.  In order to remove whole
    directory trees, :func:`shutil.rmtree` can be used.
 
-   Availability: Unix, Windows.
-
-
-.. function:: stat(path)
+   This function can support :ref:`paths relative to directory descriptors
+   <dir_fd>`.
+
+   Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+      The *dir_fd* parameter.
+
+
+.. function:: stat(path, *, dir_fd=None, follow_symlinks=True)
 
    Perform the equivalent of a :c:func:`stat` system call on the given path.
-   (This function follows symlinks; to stat a symlink use :func:`lstat`.)
-
-   The return value is an object whose attributes correspond to the members
-   of the :c:type:`stat` structure, namely:
+   *path* may be specified as either a string or as an open file descriptor.
+   (This function normally follows symlinks; to stat a symlink add the argument
+   ``follow_symlinks=False``, or use :func:`lstat`.)
+
+   The return value is an object whose attributes correspond roughly
+   to the members of the :c:type:`stat` structure, namely:
 
    * :attr:`st_mode` - protection bits,
    * :attr:`st_ino` - inode number,
    * :attr:`st_dev` - device,
    * :attr:`st_nlink` - number of hard links,
    * :attr:`st_uid` - user id of owner,
    * :attr:`st_gid` - group id of owner,
    * :attr:`st_size` - size of file, in bytes,
-   * :attr:`st_atime` - time of most recent access,
-   * :attr:`st_mtime` - time of most recent content modification,
-   * :attr:`st_ctime` - platform dependent; time of most recent metadata change on
-     Unix, or the time of creation on Windows)
+   * :attr:`st_atime` - time of most recent access expressed in seconds,
+   * :attr:`st_mtime` - time of most recent content modification
+     expressed in seconds,
+   * :attr:`st_ctime` - platform dependent; time of most recent metadata
+     change on Unix, or the time of creation on Windows, expressed in seconds
+   * :attr:`st_atime_ns` - time of most recent access
+     expressed in nanoseconds as an integer,
+   * :attr:`st_mtime_ns` - time of most recent content modification
+     expressed in nanoseconds as an integer,
+   * :attr:`st_ctime_ns` - platform dependent; time of most recent metadata
+     change on Unix, or the time of creation on Windows,
+     expressed in nanoseconds as an integer
 
    On some Unix systems (such as Linux), the following attributes may also be
    available:
 
    * :attr:`st_blocks` - number of blocks allocated for file
    * :attr:`st_blksize` - filesystem blocksize
    * :attr:`st_rdev` - type of device if an inode device
    * :attr:`st_flags` - user defined flags for file
 
    On other Unix systems (such as FreeBSD), the following attributes may be
    available (but may be only filled out if root tries to use them):
 
    * :attr:`st_gen` - file generation number
    * :attr:`st_birthtime` - time of file creation
 
    On Mac OS systems, the following attributes may also be available:
 
    * :attr:`st_rsize`
    * :attr:`st_creator`
    * :attr:`st_type`
 
    .. note::
 
       The exact meaning and resolution of the :attr:`st_atime`,
       :attr:`st_mtime`, and :attr:`st_ctime` attributes depend on the operating
       system and the file system. For example, on Windows systems using the FAT
       or FAT32 file systems, :attr:`st_mtime` has 2-second resolution, and
       :attr:`st_atime` has only 1-day resolution.  See your operating system
       documentation for details.
-
-   For backward compatibility, the return value of :func:`~os.stat` is also accessible
-   as a tuple of at least 10 integers giving the most important (and portable)
-   members of the :c:type:`stat` structure, in the order :attr:`st_mode`,
-   :attr:`st_ino`, :attr:`st_dev`, :attr:`st_nlink`, :attr:`st_uid`,
-   :attr:`st_gid`, :attr:`st_size`, :attr:`st_atime`, :attr:`st_mtime`,
-   :attr:`st_ctime`. More items may be added at the end by some implementations.
+      Similarly, although :attr:`st_atime_ns`, :attr:`st_mtime_ns`,
+      and :attr:`st_ctime_ns` are always expressed in nanoseconds, many
+      systems do not provide nanosecond precision.  On systems that do
+      provide nanosecond precision, the floating-point object used to
+      store :attr:`st_atime`, :attr:`st_mtime`, and :attr:`st_ctime`
+      cannot preserve all of it, and as such will be slightly inexact.
+      If you need the exact timestamps you should always use
+      :attr:`st_atime_ns`, :attr:`st_mtime_ns`, and :attr:`st_ctime_ns`.
+
+   For backward compatibility, the return value of :func:`~os.stat` is also
+   accessible as a tuple of at least 10 integers giving the most important (and
+   portable) members of the :c:type:`stat` structure, in the order
+   :attr:`st_mode`, :attr:`st_ino`, :attr:`st_dev`, :attr:`st_nlink`,
+   :attr:`st_uid`, :attr:`st_gid`, :attr:`st_size`, :attr:`st_atime`,
+   :attr:`st_mtime`, :attr:`st_ctime`. More items may be added at the end by
+   some implementations.
+
+   This function can support :ref:`specifying a file descriptor
+   <path_fd>`, :ref:`specifying a file descriptor <path_fd>` and :ref:`not
+   following symlinks <follow_symlinks>`.
 
    .. index:: module: stat
 
    The standard module :mod:`stat` defines functions and constants that are useful
    for extracting information from a :c:type:`stat` structure. (On Windows, some
    items are filled with dummy values.)
 
    Example::
 
       >>> import os
       >>> statinfo = os.stat('somefile.txt')
       >>> statinfo
       posix.stat_result(st_mode=33188, st_ino=7876932, st_dev=234881026,
       st_nlink=1, st_uid=501, st_gid=501, st_size=264, st_atime=1297230295,
       st_mtime=1297230027, st_ctime=1297230027)
       >>> statinfo.st_size
       264
 
    Availability: Unix, Windows.
 
+   .. versionadded:: 3.3
+      Added the *dir_fd* and *follow_symlinks* arguments,
+      specifying a file descriptor instead of a path,
+      and the :attr:`st_atime_ns`, :attr:`st_mtime_ns`,
+      and :attr:`st_ctime_ns` members.
+
 
 .. function:: stat_float_times([newvalue])
 
    Determine whether :class:`stat_result` represents time stamps as float objects.
    If *newvalue* is ``True``, future calls to :func:`~os.stat` return floats, if it is
    ``False``, future calls return ints. If *newvalue* is omitted, return the
    current setting.
 
    For compatibility with older Python versions, accessing :class:`stat_result` as
    a tuple always returns integers.
 
    Python now returns float values by default. Applications which do not work
    correctly with floating point time stamps can use this function to restore the
    old behaviour.
 
    The resolution of the timestamps (that is the smallest possible fraction)
    depends on the system. Some systems only support second resolution; on these
    systems, the fraction will always be zero.
 
    It is recommended that this setting is only changed at program startup time in
    the *__main__* module; libraries should never change this setting. If an
    application uses a library that works incorrectly if floating point time stamps
    are processed, this application should turn the feature off until the library
    has been corrected.
+
+   .. deprecated:: 3.3
 
 
 .. function:: statvfs(path)
 
    Perform a :c:func:`statvfs` system call on the given path.  The return value is
    an object whose attributes describe the filesystem on the given path, and
    correspond to the members of the :c:type:`statvfs` structure, namely:
    :attr:`f_bsize`, :attr:`f_frsize`, :attr:`f_blocks`, :attr:`f_bfree`,
    :attr:`f_bavail`, :attr:`f_files`, :attr:`f_ffree`, :attr:`f_favail`,
    :attr:`f_flag`, :attr:`f_namemax`.
 
    Two module-level constants are defined for the :attr:`f_flag` attribute's
    bit-flags: if :const:`ST_RDONLY` is set, the filesystem is mounted
    read-only, and if :const:`ST_NOSUID` is set, the semantics of
    setuid/setgid bits are disabled or not supported.
 
+   This function can support :ref:`specifying a file descriptor <path_fd>`.
+
    .. versionchanged:: 3.2
       The :const:`ST_RDONLY` and :const:`ST_NOSUID` constants were added.
 
    Availability: Unix.
 
-
-.. function:: symlink(source, link_name)
-              symlink(source, link_name, target_is_directory=False)
+   .. versionadded:: 3.3
+      Added support for specifying an open file descriptor for *path*.
+
+
+.. data:: supports_dir_fd
+
+   A :class:`~collections.Set` object indicating which functions in the
+   :mod:`os` module permit use of their *dir_fd* parameter.  Different platforms
+   provide different functionality, and an option that might work on one might
+   be unsupported on another.  For consistency's sakes, functions that support
+   *dir_fd* always allow specifying the parameter, but will throw an exception
+   if the functionality is not actually available.
+
+   To check whether a particular function permits use of its *dir_fd*
+   parameter, use the ``in`` operator on ``supports_dir_fd``.  As an example,
+   this expression determines whether the *dir_fd* parameter of :func:`os.stat`
+   is locally available::
+
+       os.stat in os.supports_dir_fd
+
+   Currently *dir_fd* parameters only work on Unix platforms; none of them work
+   on Windows.
+
+   .. versionadded:: 3.3
+
+
+.. data:: supports_effective_ids
+
+   A :class:`~collections.Set` object indicating which functions in the
+   :mod:`os` module permit use of the *effective_ids* parameter for
+   :func:`os.access`.  If the local platform supports it, the collection will
+   contain :func:`os.access`, otherwise it will be empty.
+
+   To check whether you can use the *effective_ids* parameter for
+   :func:`os.access`, use the ``in`` operator on ``supports_dir_fd``, like so::
+
+       os.access in os.supports_effective_ids
+
+   Currently *effective_ids* only works on Unix platforms; it does not work on
+   Windows.
+
+   .. versionadded:: 3.3
+
+
+.. data:: supports_fd
+
+   A :class:`~collections.Set` object indicating which functions in the
+   :mod:`os` module permit specifying their *path* parameter as an open file
+   descriptor.  Different platforms provide different functionality, and an
+   option that might work on one might be unsupported on another.  For
+   consistency's sakes, functions that support *fd* always allow specifying
+   the parameter, but will throw an exception if the functionality is not
+   actually available.
+
+   To check whether a particular function permits specifying an open file
+   descriptor for its *path* parameter, use the ``in`` operator on
+   ``supports_fd``. As an example, this expression determines whether
+   :func:`os.chdir` accepts open file descriptors when called on your local
+   platform::
+
+       os.chdir in os.supports_fd
+
+   .. versionadded:: 3.3
+
+
+.. data:: supports_follow_symlinks
+
+   A :class:`~collections.Set` object indicating which functions in the
+   :mod:`os` module permit use of their *follow_symlinks* parameter.  Different
+   platforms provide different functionality, and an option that might work on
+   one might be unsupported on another.  For consistency's sakes, functions that
+   support *follow_symlinks* always allow specifying the parameter, but will
+   throw an exception if the functionality is not actually available.
+
+   To check whether a particular function permits use of its *follow_symlinks*
+   parameter, use the ``in`` operator on ``supports_follow_symlinks``.  As an
+   example, this expression determines whether the *follow_symlinks* parameter
+   of :func:`os.stat` is locally available::
+
+       os.stat in os.supports_follow_symlinks
+
+   .. versionadded:: 3.3
+
+
+.. function:: symlink(source, link_name, target_is_directory=False, *, dir_fd=None)
 
    Create a symbolic link pointing to *source* named *link_name*.
 
-   On Windows, symlink version takes an additional optional parameter,
-   *target_is_directory*, which defaults to ``False``.
-
-   On Windows, a symlink represents a file or a directory, and does not morph to
-   the target dynamically.  For this reason, when creating a symlink on Windows,
-   if the target is not already present, the symlink will default to being a
-   file symlink.  If *target_is_directory* is set to ``True``, the symlink will
-   be created as a directory symlink.  This parameter is ignored if the target
-   exists (and the symlink is created with the same type as the target).
+   On Windows, a symlink represents either a file or a directory, and does not
+   morph to the target dynamically.  If *target_is_directory* is set to ``True``,
+   the symlink will be created as a directory symlink, otherwise as a file symlink
+   (the default).  On non-Window platforms, *target_is_directory* is ignored.
 
    Symbolic link support was introduced in Windows 6.0 (Vista).  :func:`symlink`
    will raise a :exc:`NotImplementedError` on Windows versions earlier than 6.0.
 
+   This function can support :ref:`paths relative to directory descriptors
+   <dir_fd>`.
+
    .. note::
 
-      The *SeCreateSymbolicLinkPrivilege* is required in order to successfully
-      create symlinks. This privilege is not typically granted to regular
-      users but is available to accounts which can escalate privileges to the
-      administrator level. Either obtaining the privilege or running your
+      On Windows, the *SeCreateSymbolicLinkPrivilege* is required in order to
+      successfully create symlinks. This privilege is not typically granted to
+      regular users but is available to accounts which can escalate privileges
+      to the administrator level. Either obtaining the privilege or running your
       application as an administrator are ways to successfully create symlinks.
-
 
       :exc:`OSError` is raised when the function is called by an unprivileged
       user.
 
    Availability: Unix, Windows.
 
    .. versionchanged:: 3.2
       Added support for Windows 6.0 (Vista) symbolic links.
 
+   .. versionadded:: 3.3
+      Added the *dir_fd* argument, and now allow *target_is_directory*
+      on non-Windows platforms.
+
 
 .. function:: sync()
 
    Force write of everything to disk.
 
    Availability: Unix.
 
    .. versionadded:: 3.3
 
 
 .. function:: truncate(path, length)
 
    Truncate the file corresponding to *path*, so that it is at most
    *length* bytes in size.
 
-   Availability: Unix.
-
-   .. versionadded:: 3.3
-
-
-.. function:: unlink(path)
-
-   Remove (delete) the file *path*.  This is the same function as
-   :func:`remove`; the :func:`unlink` name is its traditional Unix
-   name.
-
-   Availability: Unix, Windows.
-
-
-.. function:: utime(path, times)
-
-   Set the access and modified times of the file specified by *path*. If *times*
-   is ``None``, then the file's access and modified times are set to the current
-   time. (The effect is similar to running the Unix program :program:`touch` on
-   the path.)  Otherwise, *times* must be a 2-tuple of numbers, of the form
-   ``(atime, mtime)`` which is used to set the access and modified times,
-   respectively. Whether a directory can be given for *path* depends on whether
-   the operating system implements directories as files (for example, Windows
-   does not).  Note that the exact times you set here may not be returned by a
-   subsequent :func:`~os.stat` call, depending on the resolution with which your
-   operating system records access and modification times; see :func:`~os.stat`.
-
-   Availability: Unix, Windows.
+   This function can support :ref:`specifying a file descriptor <path_fd>`.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.3
+
+
+.. function:: unlink(path, *, dir_fd=None)
+
+   Remove (delete) the file *path*.  This function is identical to
+   :func:`remove`; the ``unlink`` name is its traditional Unix
+   name.  Please see the documentation for :func:`remove` for
+   further information.
+
+   Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+      The *dir_fd* parameter.
+
+
+.. function:: utime(path, times=None, *, ns=None, dir_fd=None, follow_symlinks=True)
+
+   Set the access and modified times of the file specified by *path*.
+
+   :func:`utime` takes two optional parameters, *times* and *ns*.
+   These specify the times set on *path* and are used as follows:
+
+   - If *ns* is not ``None``,
+     it must be a 2-tuple of the form ``(atime_ns, mtime_ns)``
+     where each member is an int expressing nanoseconds.
+   - If *times* is not ``None``,
+     it must be a 2-tuple of the form ``(atime, mtime)``
+     where each member is an int or float expressing seconds.
+   - If *times* and *ns* are both ``None``,
+     this is equivalent to specifying ``ns=(atime_ns, mtime_ns)``
+     where both times are the current time.
+     (The effect is similar to running the Unix program
+     :program:`touch` on *path*.)
+
+   It is an error to specify tuples for both *times* and *ns*.
+
+   Whether a directory can be given for *path*
+   depends on whether the operating system implements directories as files
+   (for example, Windows does not).  Note that the exact times you set here may
+   not be returned by a subsequent :func:`~os.stat` call, depending on the
+   resolution with which your operating system records access and modification
+   times; see :func:`~os.stat`.  The best way to preserve exact times is to
+   use the *st_atime_ns* and *st_mtime_ns* fields from the :func:`os.stat`
+   result object with the *ns* parameter to `utime`.
+
+   This function can support :ref:`specifying a file descriptor <path_fd>`,
+   :ref:`paths relative to directory descriptors <dir_fd>` and :ref:`not
+   following symlinks <follow_symlinks>`.
+
+   Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+      Added support for specifying an open file descriptor for *path*,
+      and the *dir_fd*, *follow_symlinks*, and *ns* parameters.
 
 
 .. function:: walk(top, topdown=True, onerror=None, followlinks=False)
 
    .. index::
       single: directory; walking
       single: directory; traversal
 
    Generate the file names in a directory tree by walking the tree
    either top-down or bottom-up. For each directory in the tree rooted at directory
@@ skipping 15 matching lines @@
 
    When *topdown* is ``True``, the caller can modify the *dirnames* list in-place
    (perhaps using :keyword:`del` or slice assignment), and :func:`walk` will only
    recurse into the subdirectories whose names remain in *dirnames*; this can be
    used to prune the search, impose a specific order of visiting, or even to inform
    :func:`walk` about directories the caller creates or renames before it resumes
    :func:`walk` again.  Modifying *dirnames* when *topdown* is ``False`` is
    ineffective, because in bottom-up mode the directories in *dirnames* are
    generated before *dirpath* itself is generated.
 
-   By default errors from the :func:`listdir` call are ignored.  If optional
+   By default, errors from the :func:`listdir` call are ignored.  If optional
    argument *onerror* is specified, it should be a function; it will be called with
    one argument, an :exc:`OSError` instance.  It can report the error to continue
    with the walk, or raise the exception to abort the walk.  Note that the filename
    is available as the ``filename`` attribute of the exception object.
 
    By default, :func:`walk` will not walk down into symbolic links that resolve to
    directories. Set *followlinks* to ``True`` to visit directories pointed to by
    symlinks, on systems that support them.
 
    .. note::
 
-      Be aware that setting *followlinks* to ``True`` can lead to infinite recursion if a
-      link points to a parent directory of itself. :func:`walk` does not keep track of
-      the directories it visited already.
+      Be aware that setting *followlinks* to ``True`` can lead to infinite
+      recursion if a link points to a parent directory of itself. :func:`walk`
+      does not keep track of the directories it visited already.
 
    .. note::
 
       If you pass a relative pathname, don't change the current working directory
       between resumptions of :func:`walk`.  :func:`walk` never changes the current
       directory, and assumes that its caller doesn't either.
 
    This example displays the number of bytes taken by non-directory files in each
    directory under the starting directory, except that it doesn't look under any
    CVS subdirectory::
@@ skipping 15 matching lines @@
       # CAUTION:  This is dangerous!  For example, if top == '/', it
       # could delete all your disk files.
       import os
       for root, dirs, files in os.walk(top, topdown=False):
           for name in files:
               os.remove(os.path.join(root, name))
           for name in dirs:
               os.rmdir(os.path.join(root, name))
 
 
+.. function:: fwalk(top='.', topdown=True, onerror=None, *, follow_symlinks=False, dir_fd=None)
+
+   .. index::
+      single: directory; walking
+      single: directory; traversal
+
+   This behaves exactly like :func:`walk`, except that it yields a 4-tuple
+   ``(dirpath, dirnames, filenames, dirfd)``, and it supports ``dir_fd``.
+
+   *dirpath*, *dirnames* and *filenames* are identical to :func:`walk` output,
+   and *dirfd* is a file descriptor referring to the directory *dirpath*.
+
+   This function always supports :ref:`paths relative to directory descriptors
+   <dir_fd>` and :ref:`not following symlinks <follow_symlinks>`.  Note however
+   that, unlike other functions, the :func:`fwalk` default value for
+   *follow_symlinks* is ``False``.
+
+   .. note::
+
+      Since :func:`fwalk` yields file descriptors, those are only valid until
+      the next iteration step, so you should duplicate them (e.g. with
+      :func:`dup`) if you want to keep them longer.
+
+   This example displays the number of bytes taken by non-directory files in each
+   directory under the starting directory, except that it doesn't look under any
+   CVS subdirectory::
+
+      import os
+      for root, dirs, files, rootfd in os.fwalk('python/Lib/email'):
+          print(root, "consumes", end="")
+          print(sum([os.stat(name, dir_fd=rootfd).st_size for name in files]),
+                end="")
+          print("bytes in", len(files), "non-directory files")
+          if 'CVS' in dirs:
+              dirs.remove('CVS')  # don't visit CVS directories
+
+   In the next example, walking the tree bottom-up is essential:
+   :func:`unlinkat` doesn't allow deleting a directory before the directory is
+   empty::
+
+      # Delete everything reachable from the directory named in "top",
+      # assuming there are no symbolic links.
+      # CAUTION:  This is dangerous!  For example, if top == '/', it
+      # could delete all your disk files.
+      import os
+      for root, dirs, files, rootfd in os.fwalk(top, topdown=False):
+          for name in files:
+              os.unlinkat(rootfd, name)
+          for name in dirs:
+              os.unlinkat(rootfd, name, os.AT_REMOVEDIR)
+
+   Availability: Unix.
+
+   .. versionadded:: 3.3
+
+
+Linux extended attributes
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. versionadded:: 3.3
+
+These functions are all available on Linux only.
+
+.. function:: getxattr(path, attribute, *, follow_symlinks=True)
+
+   Return the value of the extended filesystem attribute *attribute* for
+   *path*. *attribute* can be bytes or str. If it is str, it is encoded
+   with the filesystem encoding.
+
+   This function can support :ref:`specifying a file descriptor <path_fd>` and
+   :ref:`not following symlinks <follow_symlinks>`.
+
+
+.. function:: listxattr(path=None, *, follow_symlinks=True)
+
+   Return a list of the extended filesystem attributes on *path*.  The
+   attributes in the list are represented as strings decoded with the filesystem
+   encoding.  If *path* is ``None``, :func:`listxattr` will examine the current
+   directory.
+
+   This function can support :ref:`specifying a file descriptor <path_fd>` and
+   :ref:`not following symlinks <follow_symlinks>`.
+
+
+.. function:: removexattr(path, attribute, *, follow_symlinks=True)
+
+   Removes the extended filesystem attribute *attribute* from *path*.
+   *attribute* should be bytes or str. If it is a string, it is encoded
+   with the filesystem encoding.
+
+   This function can support :ref:`specifying a file descriptor <path_fd>` and
+   :ref:`not following symlinks <follow_symlinks>`.
+
+
+.. function:: setxattr(path, attribute, value, flags=0, *, follow_symlinks=True)
+
+   Set the extended filesystem attribute *attribute* on *path* to *value*.
+   *attribute* must be a bytes or str with no embedded NULs. If it is a str,
+   it is encoded with the filesystem encoding.  *flags* may be
+   :data:`XATTR_REPLACE` or :data:`XATTR_CREATE`. If :data:`XATTR_REPLACE` is
+   given and the attribute does not exist, ``EEXISTS`` will be raised.
+   If :data:`XATTR_CREATE` is given and the attribute already exists, the
+   attribute will not be created and ``ENODATA`` will be raised.
+
+   This function can support :ref:`specifying a file descriptor <path_fd>` and
+   :ref:`not following symlinks <follow_symlinks>`.
+
+   .. note::
+
+      A bug in Linux kernel versions less than 2.6.39 caused the flags argument
+      to be ignored on some filesystems.
+
+
+.. data:: XATTR_SIZE_MAX
+
+   The maximum size the value of an extended attribute can be. Currently, this
+   is 64 kilobytes on Linux.
+
+
+.. data:: XATTR_CREATE
+
+   This is a possible value for the flags argument in :func:`setxattr`. It
+   indicates the operation must create an attribute.
+
+
+.. data:: XATTR_REPLACE
+
+   This is a possible value for the flags argument in :func:`setxattr`. It
+   indicates the operation must replace an existing attribute.
+
+
 .. _os-process:
 
 Process Management
 ------------------
 
 These functions may be used to create and manage processes.
 
 The various :func:`exec\*` functions take a list of arguments for the new
 program loaded into the process.  In each case, the first of these arguments is
 passed to the new program as its own name rather than as an argument a user may
@@ skipping 53 matching lines @@
    locate the executable; *path* must contain an appropriate absolute or relative
    path.
 
    For :func:`execle`, :func:`execlpe`, :func:`execve`, and :func:`execvpe` (note
    that these all end in "e"), the *env* parameter must be a mapping which is
    used to define the environment variables for the new process (these are used
    instead of the current process' environment); the functions :func:`execl`,
    :func:`execlp`, :func:`execv`, and :func:`execvp` all cause the new process to
    inherit the environment of the current process.
 
-   Availability: Unix, Windows.
-
+   For :func:`execve` on some platforms, *path* may also be specified as an open
+   file descriptor.  This functionality may not be supported on your platform;
+   you can check whether or not it is available using :data:`os.supports_fd`.
+   If it is unavailable, using it will raise a :exc:`NotImplementedError`.
+
+   Availability: Unix, Windows.
+
+   .. versionadded:: 3.3
+      Added support for specifying an open file descriptor for *path*
+      for :func:`execve`.
 
 .. function:: _exit(n)
 
    Exit the process with status *n*, without calling cleanup handlers, flushing
    stdio buffers, etc.
 
    Availability: Unix, Windows.
 
    .. note::
 
@@ skipping 361 matching lines @@
    The :mod:`subprocess` module provides more powerful facilities for spawning
    new processes and retrieving their results; using that module is preferable
    to using this function.  See the :ref:`subprocess-replacements` section in
    the :mod:`subprocess` documentation for some helpful recipes.
 
    Availability: Unix, Windows.
 
 
 .. function:: times()
 
-   Return a 5-tuple of floating point numbers indicating accumulated (processor
-   or other) times, in seconds.  The items are: user time, system time,
-   children's user time, children's system time, and elapsed real time since a
-   fixed point in the past, in that order.  See the Unix manual page
+   Returns the current global process times.
+   The return value is an object with five attributes:
+
+   * :attr:`user` - user time
+   * :attr:`system` - system time
+   * :attr:`children_user` - user time of all child processes
+   * :attr:`children_system` - system time of all child processes
+   * :attr:`elapsed` - elapsed real time since a fixed point in the past
+
+   For backwards compatibility, this object also behaves like a five-tuple
+   containing :attr:`user`, :attr:`system`, :attr:`children_user`,
+   :attr:`children_system`, and :attr:`elapsed` in that order.
+
+   See the Unix manual page
    :manpage:`times(2)` or the corresponding Windows Platform API documentation.
-   On Windows, only the first two items are filled, the others are zero.
-
-   Availability: Unix, Windows
+   On Windows, only :attr:`user` and :attr:`system` are known; the other
+   attributes are zero.
+   On OS/2, only :attr:`elapsed` is known; the other attributes are zero.
+
+   Availability: Unix, Windows.
+
+   .. versionchanged:: 3.3
+      Return type changed from a tuple to a tuple-like object
+      with named attributes.
 
 
 .. function:: wait()
 
    Wait for completion of a child process, and return a tuple containing its pid
    and exit status indication: a 16-bit number, whose low byte is the signal number
    that killed the process, and whose high byte is the exit status (if the signal
    number is zero); the high bit of the low byte is set if a core file was
    produced.
 
@@ skipping 108 matching lines @@
    is available immediately. The function returns ``(0, 0)`` in this case.
 
    Availability: Unix.
 
 
 .. data:: WCONTINUED
 
    This option causes child processes to be reported if they have been continued
    from a job control stop since their status was last reported.
 
-   Availability: Some Unix systems.
+   Availability: some Unix systems.
 
 
 .. data:: WUNTRACED
 
    This option causes child processes to be reported if they have been stopped but
    their current state has not been reported since they were stopped.
 
    Availability: Unix.
 
 
@@ skipping 100 matching lines @@
 
    A round-robin scheduling policy.
 
 .. data:: SCHED_RESET_ON_FORK
 
    This flag can OR'ed with any other scheduling policy. When a process with
    this flag set forks, its child's scheduling policy and priority are reset to
    the default.
 
 
-.. class:: sched_param(sched_prioirity)

[Charles-François Natali, 2011/07/31 00:37:27]

typo: priority

+.. class:: sched_param(sched_priority)
 
    This class represents tunable scheduling parameters used in
    :func:`sched_setparam`, :func:`sched_setscheduler`, and
    :func:`sched_getparam`. It is immutable.
 
    At the moment, there is only one possible parameter:
 
    .. attribute:: sched_priority
 
       The scheduling priority for a scheduling policy.
@@ skipping 41 matching lines @@
 
    Return the round-robin quantum in seconds for the process with PID *pid*. A
    *pid* of 0 means the calling process.
 
 
 .. function:: sched_yield()
 
    Voluntarily relinquish the CPU.
 
 
-.. class:: cpu_set(ncpus)
-
-   :class:`cpu_set` represents a set of CPUs on which a process runs. *ncpus* is

[Charles-François Natali, 2011/07/31 00:37:27]

It's not really a "set of CPUs on which a process runs", but rather "set of CPUs
on which a process is eligible to run".

-   the number of CPUs the set should describe. Methods on :class:`cpu_set` allow
-   CPUs to be add or removed.
-
-   :class:`cpu_set` supports the AND, OR, and XOR bitwise operations. For
-   example, given two cpu_sets, ``one`` and ``two``, ``one | two`` returns a
-   :class:`cpu_set` containing the cpus enabled both in ``one`` and ``two``.
-
-   .. method:: set(i)
-
-      Enable CPU *i*.
-
-   .. method:: clear(i)
-
-      Remove CPU *i*.
-
-   .. method:: isset(i)
-
-      Return ``True`` if CPU *i* is enabled in the set.
-
-   .. method:: count()
-
-      Return the number of enabled CPUs in the set.
-
-   .. method:: zero()
-
-      Clear the set completely.
-
-
 .. function:: sched_setaffinity(pid, mask)
 
-   Restrict the process with PID *pid* to a set of CPUs. *mask* is a
-   :class:`cpu_set` instance.
-
-
-.. function:: sched_getaffinity(pid, size)
-
-   Return the :class:`cpu_set` the process with PID *pid* is restricted to. The
-   result will contain *size* CPUs.
+   Restrict the process with PID *pid* (or the current process if zero) to a
+   set of CPUs.  *mask* is an iterable of integers representing the set of
+   CPUs to which the process should be restricted.
+
+
+.. function:: sched_getaffinity(pid)
+
+   Return the set of CPUs the process with PID *pid* (or the current process
+   if zero) is restricted to.
 

[Charles-François Natali, 2011/07/31 00:37:27]

Thos functions accept too a PID of 0 to denote the calling process (to be
consistent with the other funtions).

 
 .. _os-path:
 
 Miscellaneous System Information
 --------------------------------
 
 
 .. function:: confstr(name)
 
    Return string-valued system configuration values. *name* specifies the
    configuration value to retrieve; it may be a string which is the name of a
    defined system value; these names are specified in a number of standards (POSIX,
    Unix 95, Unix 98, and others).  Some platforms define additional names as well.
    The names known to the host operating system are given as the keys of the
    ``confstr_names`` dictionary.  For configuration variables not included in that
    mapping, passing an integer for *name* is also accepted.
 
    If the configuration value specified by *name* isn't defined, ``None`` is
    returned.
 
    If *name* is a string and is not known, :exc:`ValueError` is raised.  If a
    specific value for *name* is not supported by the host system, even if it is
    included in ``confstr_names``, an :exc:`OSError` is raised with
    :const:`errno.EINVAL` for the error number.
 
-   Availability: Unix
+   Availability: Unix.
 
 
 .. data:: confstr_names
 
    Dictionary mapping names accepted by :func:`confstr` to the integer values
    defined for those names by the host operating system. This can be used to
    determine the set of names known to the system.
 
    Availability: Unix.
 
@@ skipping 101 matching lines @@
 Miscellaneous Functions
 -----------------------
 
 
 .. function:: urandom(n)
 
    Return a string of *n* random bytes suitable for cryptographic use.
 
    This function returns random bytes from an OS-specific randomness source.  The
    returned data should be unpredictable enough for cryptographic applications,
-   though its exact quality depends on the OS implementation.  On a UNIX-like
+   though its exact quality depends on the OS implementation.  On a Unix-like
    system this will query /dev/urandom, and on Windows it will use CryptGenRandom.
    If a randomness source is not found, :exc:`NotImplementedError` will be raised.