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✏️ Editing: msvcrt.rst.txt

:mod:`msvcrt` --- Useful routines from the MS VC++ runtime
==========================================================

.. module:: msvcrt
   :platform: Windows
   :synopsis: Miscellaneous useful routines from the MS VC++ runtime.
.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>

These functions provide access to some useful capabilities on Windows platforms.
Some higher-level modules use these functions to build the  Windows
implementations of their services.  For example, the :mod:`getpass` module uses
this in the implementation of the :func:`getpass` function.

Further documentation on these functions can be found in the Platform API
documentation.

The module implements both the normal and wide char variants of the console I/O
api. The normal API deals only with ASCII characters and is of limited use
for internationalized applications. The wide char API should be used where
ever possible.

.. _msvcrt-files:

File Operations
---------------

.. function:: locking(fd, mode, nbytes)

Lock part of a file based on file descriptor *fd* from the C runtime.  Raises
   :exc:`IOError` on failure.  The locked region of the file extends from the
   current file position for *nbytes* bytes, and may continue beyond the end of the
   file.  *mode* must be one of the :const:`LK_\*` constants listed below. Multiple
   regions in a file may be locked at the same time, but may not overlap.  Adjacent
   regions are not merged; they must be unlocked individually.

.. data:: LK_LOCK
          LK_RLCK

Locks the specified bytes. If the bytes cannot be locked, the program
   immediately tries again after 1 second.  If, after 10 attempts, the bytes cannot
   be locked, :exc:`IOError` is raised.

.. data:: LK_NBLCK
          LK_NBRLCK

Locks the specified bytes. If the bytes cannot be locked, :exc:`IOError` is
   raised.

.. data:: LK_UNLCK

Unlocks the specified bytes, which must have been previously locked.

.. function:: setmode(fd, flags)

Set the line-end translation mode for the file descriptor *fd*. To set it to
   text mode, *flags* should be :const:`os.O_TEXT`; for binary, it should be
   :const:`os.O_BINARY`.

.. function:: open_osfhandle(handle, flags)

Create a C runtime file descriptor from the file handle *handle*.  The *flags*
   parameter should be a bitwise OR of :const:`os.O_APPEND`, :const:`os.O_RDONLY`,
   and :const:`os.O_TEXT`.  The returned file descriptor may be used as a parameter
   to :func:`os.fdopen` to create a file object.

.. function:: get_osfhandle(fd)

Return the file handle for the file descriptor *fd*.  Raises :exc:`IOError` if
   *fd* is not recognized.

.. _msvcrt-console:

Console I/O
-----------

.. function:: kbhit()

Return true if a keypress is waiting to be read.

.. function:: getch()

Read a keypress and return the resulting character.  Nothing is echoed to the
   console.  This call will block if a keypress is not already available, but will
   not wait for :kbd:`Enter` to be pressed. If the pressed key was a special
   function key, this will return ``'\000'`` or ``'\xe0'``; the next call will
   return the keycode.  The :kbd:`Control-C` keypress cannot be read with this
   function.

.. function:: getwch()

Wide char variant of :func:`getch`, returning a Unicode value.

.. versionadded:: 2.6

.. function:: getche()

Similar to :func:`getch`, but the keypress will be echoed if it  represents a
   printable character.

.. function:: getwche()

Wide char variant of :func:`getche`, returning a Unicode value.

.. versionadded:: 2.6

.. function:: putch(char)

Print the character *char* to the console without buffering.

.. function:: putwch(unicode_char)

Wide char variant of :func:`putch`, accepting a Unicode value.

.. versionadded:: 2.6

.. function:: ungetch(char)

Cause the character *char* to be "pushed back" into the console buffer; it will
   be the next character read by :func:`getch` or :func:`getche`.

.. function:: ungetwch(unicode_char)

Wide char variant of :func:`ungetch`, accepting a Unicode value.

.. versionadded:: 2.6

.. _msvcrt-other:

Other Functions
---------------

.. function:: heapmin()

Force the :c:func:`malloc` heap to clean itself up and return unused blocks to
   the operating system.  On failure, this raises :exc:`IOError`.

MR SKB