34.2. "msvcrt" — Useful routines from the MS VC++ runtime
*********************************************************

======================================================================

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 "getpass"
module uses this in the implementation of the "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.

Changed in version 3.3: Operations in this module now raise "OSError"
where "IOError" was raised.


34.2.1. File Operations
=======================

msvcrt.locking(fd, mode, nbytes)

   Lock part of a file based on file descriptor *fd* from the C
   runtime.  Raises "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
   "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.

msvcrt.LK_LOCK
msvcrt.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, "OSError" is raised.

msvcrt.LK_NBLCK
msvcrt.LK_NBRLCK

   Locks the specified bytes. If the bytes cannot be locked, "OSError"
   is raised.

msvcrt.LK_UNLCK

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

msvcrt.setmode(fd, flags)

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

msvcrt.open_osfhandle(handle, flags)

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

msvcrt.get_osfhandle(fd)

   Return the file handle for the file descriptor *fd*.  Raises
   "OSError" if *fd* is not recognized.


34.2.2. Console I/O
===================

msvcrt.kbhit()

   Return true if a keypress is waiting to be read.

msvcrt.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 "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 "Control-C" keypress cannot be read with this
   function.

msvcrt.getwch()

   Wide char variant of "getch()", returning a Unicode value.

msvcrt.getche()

   Similar to "getch()", but the keypress will be echoed if it
   represents a printable character.

msvcrt.getwche()

   Wide char variant of "getche()", returning a Unicode value.

msvcrt.putch(char)

   Print the byte string *char* to the console without buffering.

msvcrt.putwch(unicode_char)

   Wide char variant of "putch()", accepting a Unicode value.

msvcrt.ungetch(char)

   Cause the byte string *char* to be “pushed back” into the console
   buffer; it will be the next character read by "getch()" or
   "getche()".

msvcrt.ungetwch(unicode_char)

   Wide char variant of "ungetch()", accepting a Unicode value.


34.2.3. Other Functions
=======================

msvcrt.heapmin()

   Force the "malloc()" heap to clean itself up and return unused
   blocks to the operating system.  On failure, this raises "OSError".
