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bpo-16024: Doc cleanup regarding path_fd, dir_fd, follow_symlinks (GH-5505)
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Cheryl Sabella
larryhastings
parent
29500737d4
commit
e152169da9
@ -1453,16 +1453,19 @@ features:
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.. _path_fd:
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* **specifying a file descriptor:**
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For some functions, the *path* argument can be not only a string giving a path
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name, but also a file descriptor. The function will then operate on the file
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referred to by the descriptor. (For POSIX systems, Python will call the
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``f...`` version of the function.)
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Normally the *path* argument provided to functions in the :mod:`os` module
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must be a string specifying a file path. However, some functions now
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alternatively accept an open file descriptor for their *path* argument.
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The function will then operate on the file referred to by the descriptor.
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(For POSIX systems, Python will call the variant of the function prefixed
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with ``f`` (e.g. call ``fchdir`` instead of ``chdir``).)
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You can check whether or not *path* can be specified as a file descriptor on
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your platform using :data:`os.supports_fd`. If it is unavailable, using it
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will raise a :exc:`NotImplementedError`.
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You can check whether or not *path* can be specified as a file descriptor
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for a particular function on your platform using :data:`os.supports_fd`.
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If this functionality is unavailable, using it will raise a
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:exc:`NotImplementedError`.
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If the function also supports *dir_fd* or *follow_symlinks* arguments, it is
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If the function also supports *dir_fd* or *follow_symlinks* arguments, it's
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an error to specify one of those when supplying *path* as a file descriptor.
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.. _dir_fd:
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@ -1471,23 +1474,24 @@ features:
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should be a file descriptor referring to a directory, and the path to operate
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on should be relative; path will then be relative to that directory. If the
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path is absolute, *dir_fd* is ignored. (For POSIX systems, Python will call
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the ``...at`` or ``f...at`` version of the function.)
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the variant of the function with an ``at`` suffix and possibly prefixed with
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``f`` (e.g. call ``faccessat`` instead of ``access``).
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You can check whether or not *dir_fd* is supported on your platform using
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:data:`os.supports_dir_fd`. If it is unavailable, using it will raise a
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:exc:`NotImplementedError`.
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You can check whether or not *dir_fd* is supported for a particular function
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on your platform using :data:`os.supports_dir_fd`. If it's unavailable,
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using it will raise a :exc:`NotImplementedError`.
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.. _follow_symlinks:
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* **not following symlinks:** If *follow_symlinks* is
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``False``, and the last element of the path to operate on is a symbolic link,
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the function will operate on the symbolic link itself instead of the file the
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link points to. (For POSIX systems, Python will call the ``l...`` version of
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the function.)
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the function will operate on the symbolic link itself rather than the file
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pointed to by the link. (For POSIX systems, Python will call the ``l...``
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variant of the function.)
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You can check whether or not *follow_symlinks* is supported on your platform
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using :data:`os.supports_follow_symlinks`. If it is unavailable, using it
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will raise a :exc:`NotImplementedError`.
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You can check whether or not *follow_symlinks* is supported for a particular
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function on your platform using :data:`os.supports_follow_symlinks`.
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If it's unavailable, using it will raise a :exc:`NotImplementedError`.
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@ -1662,7 +1666,7 @@ features:
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.. availability:: Unix.
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.. versionadded:: 3.3
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Added support for specifying an open file descriptor for *path*,
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Added support for specifying *path* as an open file descriptor,
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and the *dir_fd* and *follow_symlinks* arguments.
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.. versionchanged:: 3.6
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@ -1781,7 +1785,7 @@ features:
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The *path* parameter became optional.
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.. versionadded:: 3.3
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Added support for specifying an open file descriptor for *path*.
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Added support for specifying *path* as an open file descriptor.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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@ -2593,7 +2597,7 @@ features:
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The :const:`ST_RDONLY` and :const:`ST_NOSUID` constants were added.
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.. versionadded:: 3.3
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Added support for specifying an open file descriptor for *path*.
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Added support for specifying *path* as an open file descriptor.
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.. versionchanged:: 3.4
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The :const:`ST_NODEV`, :const:`ST_NOEXEC`, :const:`ST_SYNCHRONOUS`,
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@ -2610,59 +2614,61 @@ features:
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.. data:: supports_dir_fd
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A :class:`~collections.abc.Set` object indicating which functions in the
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:mod:`os` module permit use of their *dir_fd* parameter. Different platforms
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provide different functionality, and an option that might work on one might
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be unsupported on another. For consistency's sakes, functions that support
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*dir_fd* always allow specifying the parameter, but will raise an exception
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if the functionality is not actually available.
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A :class:`set` object indicating which functions in the :mod:`os`
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module accept an open file descriptor for their *dir_fd* parameter.
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Different platforms provide different features, and the underlying
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functionality Python uses to implement the *dir_fd* parameter is not
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available on all platforms Python supports. For consistency's sake,
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functions that may support *dir_fd* always allow specifying the
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parameter, but will throw an exception if the functionality is used
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when it's not locally available. (Specifying ``None`` for *dir_fd*
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is always supported on all platforms.)
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To check whether a particular function permits use of its *dir_fd*
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parameter, use the ``in`` operator on ``supports_dir_fd``. As an example,
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this expression determines whether the *dir_fd* parameter of :func:`os.stat`
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is locally available::
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To check whether a particular function accepts an open file descriptor
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for its *dir_fd* parameter, use the ``in`` operator on ``supports_dir_fd``.
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As an example, this expression evaluates to ``True`` if :func:`os.stat`
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accepts open file descriptors for *dir_fd* on the local platform::
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os.stat in os.supports_dir_fd
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Currently *dir_fd* parameters only work on Unix platforms; none of them work
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on Windows.
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Currently *dir_fd* parameters only work on Unix platforms;
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none of them work on Windows.
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.. versionadded:: 3.3
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.. data:: supports_effective_ids
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A :class:`~collections.abc.Set` object indicating which functions in the
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:mod:`os` module permit use of the *effective_ids* parameter for
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:func:`os.access`. If the local platform supports it, the collection will
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contain :func:`os.access`, otherwise it will be empty.
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A :class:`set` object indicating whether :func:`os.access` permits
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specifying ``True`` for its *effective_ids* parameter on the local platform.
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(Specifying ``False`` for *effective_ids* is always supported on all
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platforms.) If the local platform supports it, the collection will contain
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:func:`os.access`; otherwise it will be empty.
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To check whether you can use the *effective_ids* parameter for
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:func:`os.access`, use the ``in`` operator on ``supports_effective_ids``,
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like so::
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This expression evaluates to ``True`` if :func:`os.access` supports
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``effective_ids=True`` on the local platform::
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os.access in os.supports_effective_ids
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Currently *effective_ids* only works on Unix platforms; it does not work on
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Windows.
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Currently *effective_ids* is only supported on Unix platforms;
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it does not work on Windows.
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.. versionadded:: 3.3
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.. data:: supports_fd
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A :class:`~collections.abc.Set` object indicating which functions in the
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A :class:`set` object indicating which functions in the
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:mod:`os` module permit specifying their *path* parameter as an open file
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descriptor. Different platforms provide different functionality, and an
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option that might work on one might be unsupported on another. For
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consistency's sakes, functions that support *fd* always allow specifying
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the parameter, but will raise an exception if the functionality is not
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actually available.
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descriptor on the local platform. Different platforms provide different
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features, and the underlying functionality Python uses to accept open file
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descriptors as *path* arguments is not available on all platforms Python
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supports.
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To check whether a particular function permits specifying an open file
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To determine whether a particular function permits specifying an open file
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descriptor for its *path* parameter, use the ``in`` operator on
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``supports_fd``. As an example, this expression determines whether
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:func:`os.chdir` accepts open file descriptors when called on your local
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``supports_fd``. As an example, this expression evaluates to ``True`` if
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:func:`os.chdir` accepts open file descriptors for *path* on your local
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platform::
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os.chdir in os.supports_fd
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@ -2672,17 +2678,21 @@ features:
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.. data:: supports_follow_symlinks
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A :class:`~collections.abc.Set` object indicating which functions in the
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:mod:`os` module permit use of their *follow_symlinks* parameter. Different
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platforms provide different functionality, and an option that might work on
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one might be unsupported on another. For consistency's sakes, functions that
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support *follow_symlinks* always allow specifying the parameter, but will
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raise an exception if the functionality is not actually available.
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A :class:`set` object indicating which functions in the :mod:`os` module
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accept ``False`` for their *follow_symlinks* parameter on the local platform.
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Different platforms provide different features, and the underlying
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functionality Python uses to implement *follow_symlinks* is not available
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on all platforms Python supports. For consistency's sake, functions that
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may support *follow_symlinks* always allow specifying the parameter, but
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will throw an exception if the functionality is used when it's not locally
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available. (Specifying ``True`` for *follow_symlinks* is always supported
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on all platforms.)
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To check whether a particular function permits use of its *follow_symlinks*
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parameter, use the ``in`` operator on ``supports_follow_symlinks``. As an
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example, this expression determines whether the *follow_symlinks* parameter
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of :func:`os.stat` is locally available::
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To check whether a particular function accepts ``False`` for its
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*follow_symlinks* parameter, use the ``in`` operator on
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``supports_follow_symlinks``. As an example, this expression evaluates
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to ``True`` if you may specify ``follow_symlinks=False`` when calling
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:func:`os.stat` on the local platform::
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os.stat in os.supports_follow_symlinks
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@ -2801,7 +2811,7 @@ features:
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following symlinks <follow_symlinks>`.
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.. versionadded:: 3.3
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Added support for specifying an open file descriptor for *path*,
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Added support for specifying *path* as an open file descriptor,
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and the *dir_fd*, *follow_symlinks*, and *ns* parameters.
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.. versionchanged:: 3.6
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@ -3162,7 +3172,7 @@ to be ignored.
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.. availability:: Unix, Windows.
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.. versionadded:: 3.3
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Added support for specifying an open file descriptor for *path*
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Added support for specifying *path* as an open file descriptor
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for :func:`execve`.
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.. versionchanged:: 3.6
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