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Diffstat (limited to 'Doc/library/os.rst')
| -rw-r--r-- | Doc/library/os.rst | 83 |
1 files changed, 76 insertions, 7 deletions
diff --git a/Doc/library/os.rst b/Doc/library/os.rst index 82d05ed..848fd16 100644 --- a/Doc/library/os.rst +++ b/Doc/library/os.rst @@ -685,17 +685,30 @@ as internal buffering of data. .. function:: dup(fd) - Return a duplicate of file descriptor *fd*. + Return a duplicate of file descriptor *fd*. The new file descriptor is + :ref:`non-inheritable <fd_inheritance>`. + + On Windows, when duplicating a standard stream (0: stdin, 1: stdout, + 2: stderr), the new file descriptor is :ref:`inheritable + <fd_inheritance>`. Availability: Unix, Windows. + .. versionchanged:: 3.4 + The new file descriptor is now non-inheritable. + -.. function:: dup2(fd, fd2) +.. function:: dup2(fd, fd2, inheritable=True) Duplicate file descriptor *fd* to *fd2*, closing the latter first if necessary. + The file descriptor *fd2* is :ref:`inheritable <fd_inheritance>` by default, + or non-inheritable if *inheritable* is ``False``. Availability: Unix, Windows. + .. versionchanged:: 3.4 + Add the optional *inheritable* parameter. + .. function:: fchmod(fd, mode) @@ -848,6 +861,7 @@ as internal buffering of data. Open the file *file* and set various flags according to *flags* and possibly 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. + The new file descriptor is :ref:`non-inheritable <fd_inheritance>`. 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 @@ -859,6 +873,9 @@ as internal buffering of data. Availability: Unix, Windows. + .. versionchanged:: 3.4 + The new file descriptor is now non-inheritable. + .. note:: This function is intended for low-level I/O. For normal usage, use the @@ -933,20 +950,28 @@ or `the MSDN <http://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Window .. 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. + Open a new pseudo-terminal pair. Return a pair of file descriptors + ``(master, slave)`` for the pty and the tty, respectively. The new file + descriptors are :ref:`non-inheritable <fd_inheritance>`. For a (slightly) more + portable approach, use the :mod:`pty` module. Availability: some flavors of Unix. + .. versionchanged:: 3.4 + The new file descriptors are now non-inheritable. + .. function:: pipe() - Create a pipe. Return a pair of file descriptors ``(r, w)`` usable for reading - and writing, respectively. + Create a pipe. Return a pair of file descriptors ``(r, w)`` usable for + reading and writing, respectively. The new file descriptor are + :ref:`non-inheritable <fd_inheritance>`. Availability: Unix, Windows. + .. versionchanged:: 3.4 + The new file descriptors are now non-inheritable. + .. function:: pipe2(flags) @@ -1178,6 +1203,50 @@ Querying the size of a terminal Height of the terminal window in characters. +.. _fd_inheritance: + +Inheritance of File Descriptors +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +A file descriptor has a inheritable flag which indicates if the file descriptor +can be inherited or not in child processes. Since Python 3.4, file descriptors +created by Python are non-inheritable by default. + +On UNIX, non-inheritable file descriptors are closed in child processes at the +execution of a new program, other file descriptors are inherited. + +On Windows, non-inheritable handles and file descriptors are closed in child +processes, except standard streams (file descriptors 0, 1 and 2: stdin, stdout +and stderr) which are always inherited. Using :func:`os.spawn*` functions, +all inheritable handles and all inheritable file descriptors are inherited. +Using the :mod:`subprocess` module, all file descriptors except standard +streams are closed, inheritable handles are only inherited if the *close_fds* +parameter is ``False``. + +.. versionadded:: 3.4 + +.. function:: get_inheritable(fd) + + Get the `inheritable flag <fd_inheritance>`_ of the specified file + descriptor. Return a :class:`bool`. + +.. function:: set_inheritable(fd, inheritable) + + Set the `inheritable flag <fd_inheritance>`_ of the specified file descriptor. + +.. function:: get_handle_inheritable(handle) + + Get the `inheritable flag <fd_inheritance>`_ of the specified handle. Return a :class:`bool`. + + Availability: Windows. + +.. function:: set_handle_inheritable(handle, inheritable) + + Set the `inheritable flag <fd_inheritance>`_ of the specified handle. + + Availability: Windows. + + .. _os-file-dir: Files and Directories |