Duplicate stdio handles on Windows using ctypes

handles.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
#
# Copyright (C) 2021 Red Dove Consultants Limited. BSD-3-Clause licensed.
#
from ctypes import *
from ctypes.wintypes import BYTE,WORD,DWORD,LPWSTR,LPCWSTR,HANDLE,LPVOID,BOOL
import os
import sys

DEBUGGING = 'PY_DEBUG' in os.environ

LPBYTE = POINTER(BYTE)

STD_INPUT_HANDLE = -10
STD_OUTPUT_HANDLE = -11
STD_ERROR_HANDLE = -12
TRUE = 1
DUPLICATE_SAME_ACCESS = 2

class STARTUPINFOW(Structure):
    _fields_ = [('cb', DWORD),
                ('lpReserved', LPWSTR),
                ('lpDesktop', LPWSTR),
                ('lpTitle', LPWSTR),
                ('dwX', DWORD),
                ('dwY', DWORD),
                ('dwXSize', DWORD),
                ('dwYSize', DWORD),
                ('dwXCountChars', DWORD),
                ('dwYCountChars', DWORD),
                ('dwFillAttribute',DWORD),
                ('dwFlags', DWORD),
                ('wShowWindow', WORD),
                ('cbReserved2', WORD),
                ('lpReserved2', LPBYTE),
                ('hStdInput', HANDLE),
                ('hStdOutput', HANDLE),
                ('hStdError', HANDLE)]

GetStdHandle = windll.kernel32.GetStdHandle

GetCurrentProcess = windll.kernel32.GetCurrentProcess
GetCurrentProcess.restype = HANDLE

DuplicateHandle = windll.kernel32.DuplicateHandle
DuplicateHandle.restype = BOOL
DuplicateHandle.argtypes = (HANDLE, HANDLE, HANDLE, POINTER(HANDLE),
                            DWORD, BOOL, DWORD)

def main():
    si = STARTUPINFOW()
    si.cb = sizeof(STARTUPINFOW)
    process = GetCurrentProcess()
    for ih in (STD_INPUT_HANDLE, STD_OUTPUT_HANDLE, STD_ERROR_HANDLE):
        h = GetStdHandle(ih)
        if ih == STD_INPUT_HANDLE:
            f = STARTUPINFOW.hStdInput
            addr = pointer(HANDLE.from_buffer(si, f.offset))
        elif ih == STD_OUTPUT_HANDLE:
            f = STARTUPINFOW.hStdOutput
            addr = pointer(HANDLE.from_buffer(si, f.offset))
        else:
            f = STARTUPINFOW.hStdError
            addr = pointer(HANDLE.from_buffer(si, f.offset))
        ok = DuplicateHandle(process, h, process, addr, 0, TRUE, DUPLICATE_SAME_ACCESS)
        print(ok)

if __name__ == '__main__':
    try:
        rc = main()
    except KeyboardInterrupt:
        rc = 2
    except Exception as e:
        if DEBUGGING:
            s = ' %s:' % type(e).__name__
        else:
            s = ''
        sys.stderr.write('Failed:%s %s\n' % (s, e))
        if DEBUGGING: import traceback; traceback.print_exc()
        rc = 1
    sys.exit(rc)