: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. <firstname.lastname@example.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.
.. versionchanged:: 3.3 Operations in this module now raise :exc:`OSError` where :exc:`IOError` was raised.
.. function:: locking(fd, mode, nbytes) Lock part of a file based on file descriptor *fd* from the C runtime. Raises :exc:`OSError` 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:`OSError` is raised.
.. data:: LK_NBLCK LK_NBRLCK Locks the specified bytes. If the bytes cannot be locked, :exc:`OSError` 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:`OSError` if *fd* is not recognized.
.. function:: kbhit() Return true if a keypress is waiting to be read.
.. function:: getch() Read a keypress and return the resulting character as a byte string. 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.
.. 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.
.. function:: putch(char) Print the byte string *char* to the console without buffering.
.. function:: putwch(unicode_char) Wide char variant of :func:`putch`, accepting a Unicode value.
.. function:: ungetch(char) Cause the byte string *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.
.. 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:`OSError`.