I've been trying to figure out a way to get some sort of ability to be able to return the true abspath of a symbolic link in Windows, under Python 2.7. (I cannot upgrade to 3.x, as most DCCs such as Maya/3ds max do not use that version of Python)
I've looked at the sid0 ntfs utils (whose islink() function works, but readlink() function always returns an empty unicode string for me for some reason), and the juntalis ntfs libs (which unfortunately, I couldn't get to work), along with a helpful script someone posted:
import os, ctypes, struct
from ctypes import windll, wintypes
FSCTL_GET_REPARSE_POINT = 0x900a8
FILE_ATTRIBUTE_READONLY = 0x0001
FILE_ATTRIBUTE_HIDDEN = 0x0002
FILE_ATTRIBUTE_DIRECTORY = 0x0010
FILE_ATTRIBUTE_NORMAL = 0x0080
FILE_ATTRIBUTE_REPARSE_POINT = 0x0400
GENERIC_READ = 0x80000000
GENERIC_WRITE = 0x40000000
OPEN_EXISTING = 3
FILE_READ_ATTRIBUTES = 0x80
FILE_FLAG_OPEN_REPARSE_POINT = 0x00200000
INVALID_HANDLE_VALUE = wintypes.HANDLE(-1).value
INVALID_FILE_ATTRIBUTES = 0xFFFFFFFF
FILE_FLAG_OPEN_REPARSE_POINT = 2097152
FILE_FLAG_BACKUP_SEMANTICS = 33554432
# FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTI
FILE_FLAG_REPARSE_BACKUP = 35651584
GetFileAttributes = windll.kernel32.GetFileAttributesW
_CreateFileW = windll.kernel32.CreateFileW
_DevIoCtl = windll.kernel32.DeviceIoControl
_DevIoCtl.argtypes = [
wintypes.HANDLE, #HANDLE hDevice
wintypes.DWORD, #DWORD dwIoControlCode
wintypes.LPVOID, #LPVOID lpInBuffer
wintypes.DWORD, #DWORD nInBufferSize
wintypes.LPVOID, #LPVOID lpOutBuffer
wintypes.DWORD, #DWORD nOutBufferSize
ctypes.POINTER(wintypes.DWORD), #LPDWORD lpBytesReturned
wintypes.LPVOID] #LPOVERLAPPED lpOverlapped
_DevIoCtl.restype = wintypes.BOOL
def islink(path):
# assert os.path.isdir(path), path
if GetFileAttributes(path) & FILE_ATTRIBUTE_REPARSE_POINT:
return True
else:
return False
def DeviceIoControl(hDevice, ioControlCode, input, output):
# DeviceIoControl Function
# http://msdn.microsoft.com/en-us/library/aa363216(v=vs.85).aspx
if input:
input_size = len(input)
else:
input_size = 0
if isinstance(output, int):
output = ctypes.create_string_buffer(output)
output_size = len(output)
assert isinstance(output, ctypes.Array)
bytesReturned = wintypes.DWORD()
status = _DevIoCtl(hDevice, ioControlCode, input,
input_size, output, output_size, bytesReturned, None)
print "status(%d)" % status
if status != 0:
return output[:bytesReturned.value]
else:
return None
def CreateFile(path, access, sharemode, creation, flags):
return _CreateFileW(path, access, sharemode, None, creation, flags, None)
SymbolicLinkReparseFormat = "LHHHHHHL"
SymbolicLinkReparseSize = struct.calcsize(SymbolicLinkReparseFormat);
def readlink(path):
""" Windows readlink implementation. """
# This wouldn't return true if the file didn't exist, as far as I know.
assert islink(path)
# assert type(path) == unicode
# Open the file correctly depending on the string type.
hfile = CreateFile(path, GENERIC_READ, 0, OPEN_EXISTING,
FILE_FLAG_REPARSE_BACKUP)
# MAXIMUM_REPARSE_DATA_BUFFER_SIZE = 16384 = (16*1024)
buffer = DeviceIoControl(hfile, FSCTL_GET_REPARSE_POINT, None, 16384)
windll.CloseHandle(hfile)
# Minimum possible length (assuming length of the target is bigger than 0)
if not buffer or len(buffer) < 9:
return None
# Only handle SymbolicLinkReparseBuffer
(tag, dataLength, reserver, SubstituteNameOffset, SubstituteNameLength,
PrintNameOffset, PrintNameLength,
Flags) = struct.unpack(SymbolicLinkReparseFormat,
buffer[:SymbolicLinkReparseSize])
print tag, dataLength, reserver, SubstituteNameOffset, SubstituteNameLength
start = SubstituteNameOffset + SymbolicLinkReparseSize
actualPath = buffer[start : start + SubstituteNameLength].decode("utf-16")
# This utf-16 string is null terminated
index = actualPath.find(u"")
assert index > 0
if index > 0:
actualPath = actualPath[:index]
if actualPath.startswith(u"?"):
return actualPath[2:]
else:
return actualPath
However, most of the time various solutions I've tried end up giving me:
[Error 126] The specified module could not be found
Even though I am able to import ctypes and do stuff such as importing cdll:
libc = cdll.msvcrt
libc.printf
<_FuncPtr object at 0x0000000002A9F388>
I'm pretty new to this part of Python and ctypes in general, so any pointers on dealing with symbolic links here would be very much appreciated!
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