Check if a file is real or a symbolic link
I have some source code for symlinks posted on my blog that will allow you to:
- create symlinks
- check whether a path is a symlink
- retrieve the target of a symlink
It also contains NUnit test cases, that you may wish to extend.
The meaty bit is:
private static SafeFileHandle getFileHandle(string path)
{
return CreateFile(path, genericReadAccess, shareModeAll, IntPtr.Zero, openExisting,
fileFlagsForOpenReparsePointAndBackupSemantics, IntPtr.Zero);
}
public static string GetTarget(string path)
{
SymbolicLinkReparseData reparseDataBuffer;
using (SafeFileHandle fileHandle = getFileHandle(path))
{
if (fileHandle.IsInvalid)
{
Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
}
int outBufferSize = Marshal.SizeOf(typeof(SymbolicLinkReparseData));
IntPtr outBuffer = IntPtr.Zero;
try
{
outBuffer = Marshal.AllocHGlobal(outBufferSize);
int bytesReturned;
bool success = DeviceIoControl(
fileHandle.DangerousGetHandle(), ioctlCommandGetReparsePoint, IntPtr.Zero, 0,
outBuffer, outBufferSize, out bytesReturned, IntPtr.Zero);
fileHandle.Close();
if (!success)
{
if (((uint)Marshal.GetHRForLastWin32Error()) == pathNotAReparsePointError)
{
return null;
}
Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
}
reparseDataBuffer = (SymbolicLinkReparseData)Marshal.PtrToStructure(
outBuffer, typeof(SymbolicLinkReparseData));
}
finally
{
Marshal.FreeHGlobal(outBuffer);
}
}
if (reparseDataBuffer.ReparseTag != symLinkTag)
{
return null;
}
string target = Encoding.Unicode.GetString(reparseDataBuffer.PathBuffer,
reparseDataBuffer.PrintNameOffset, reparseDataBuffer.PrintNameLength);
return target;
}
That is:
- Open the file with
CreateFile()
- Call
DeviceIoControl()
to get the reparse point data (NOTE: it could be a junction point!) - Check out the returned data structure to inspect. The reparse tag will tell you if it is a junction point or symbolic link. This may be all you want to do.
private bool IsSymbolic(string path)
{
FileInfo pathInfo = new FileInfo(path);
return pathInfo.Attributes.HasFlag(FileAttributes.ReparsePoint);
}