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

.. module:: msvcrt :synopsis: Miscellaneous useful routines from the MS VC++ runtime.

Source code: :source:PC/msvcrtmodule.c

---

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.

.. availability:: Windows.

.. versionchanged:: 3.3 Operations in this module now raise :exc:OSError where :exc:IOError was raised.

.. _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: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.

.. audit-event:: msvcrt.locking fd,mode,nbytes msvcrt.locking

.. 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, :const:os.O_TEXT and :const:os.O_NOINHERIT. The returned file descriptor may be used as a parameter to :func:os.fdopen to create a file object.

The file descriptor is inheritable by default. Pass :const:os.O_NOINHERIT flag to make it non inheritable.

.. audit-event:: msvcrt.open_osfhandle handle,flags msvcrt.open_osfhandle

.. function:: get_osfhandle(fd)

Return the file handle for the file descriptor fd. Raises :exc:OSError if fd is not recognized.

.. audit-event:: msvcrt.get_osfhandle fd msvcrt.get_osfhandle

.. _msvcrt-console:

Console I/O

.. function:: kbhit()

Returns a nonzero value if a keypress is waiting to be read. Otherwise, return 0.

.. 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.

.. _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:OSError.

.. function:: set_error_mode(mode)

Changes the location where the C runtime writes an error message for an error that might end the program. mode must be one of the :const:!OUT_\* constants listed below or :const:REPORT_ERRMODE. Returns the old setting or -1 if an error occurs. Only available in :ref:debug build of Python <debug-build>.

.. data:: OUT_TO_DEFAULT

Error sink is determined by the app's type. Only available in :ref:debug build of Python <debug-build>.

.. data:: OUT_TO_STDERR

Error sink is a standard error. Only available in :ref:debug build of Python <debug-build>.

.. data:: OUT_TO_MSGBOX

Error sink is a message box. Only available in :ref:debug build of Python <debug-build>.

.. data:: REPORT_ERRMODE

Report the current error mode value. Only available in :ref:debug build of Python <debug-build>.

.. function:: CrtSetReportMode(type, mode)

Specifies the destination or destinations for a specific report type generated by :c:func:!_CrtDbgReport in the MS VC++ runtime. type must be one of the :const:!CRT_\* constants listed below. mode must be one of the :const:!CRTDBG_\* constants listed below. Only available in :ref:debug build of Python <debug-build>.

.. function:: CrtSetReportFile(type, file)

After you use :func:CrtSetReportMode to specify :const:CRTDBG_MODE_FILE, you can specify the file handle to receive the message text. type must be one of the :const:!CRT_\* constants listed below. file should be the file handle your want specified. Only available in :ref:debug build of Python <debug-build>.

.. data:: CRT_WARN

Warnings, messages, and information that doesn't need immediate attention.

.. data:: CRT_ERROR

Errors, unrecoverable problems, and issues that require immediate attention.

.. data:: CRT_ASSERT

Assertion failures.

.. data:: CRTDBG_MODE_DEBUG

Writes the message to the debugger's output window.

.. data:: CRTDBG_MODE_FILE

Writes the message to a user-supplied file handle. :func:CrtSetReportFile should be called to define the specific file or stream to use as the destination.

.. data:: CRTDBG_MODE_WNDW

Creates a message box to display the message along with the Abort, Retry, and Ignore buttons.

.. data:: CRTDBG_REPORT_MODE

Returns current mode for the specified type.

.. data:: CRT_ASSEMBLY_VERSION

The CRT Assembly version, from the :file:crtassem.h header file.

.. data:: VC_ASSEMBLY_PUBLICKEYTOKEN

The VC Assembly public key token, from the :file:crtassem.h header file.

.. data:: LIBRARIES_ASSEMBLY_NAME_PREFIX

The Libraries Assembly name prefix, from the :file:crtassem.h header file.