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cwindowswinapi

FindFirstFile and Junctions

I use this go get the content of directory foo: FindFirstFile(L"foo\\*", &findData). It works great when foo is a regular directory. However when foo is a junction pointing to another directory (created with mklink /j foo C:\gah) FindFirstFile fails.

The docs have this to say: "If the path points to a symbolic link, the WIN32_FIND_DATA buffer contains information about the symbolic link, not the target." But when I run it the debugger I just get an INVALID_HANDLE_VALUE and findData remains untouched.

So, how do I work around this?

Solution

  • Raymond Chen has an answer for you.

    Functions like GetFileAttributes and FindFirstFile, when asked to provide information about a symbolic link, returns information about the link itself and not the link destination. If you use the FindFirstFile function, you can tell that you have a symbolic link because the file attributes will have the FILE_ATTRIBUTES_REPARSE_POINT flag set, and the dwReserved0 member will contain the special value IO_REPARSE_TAG_SYMLINK.

    Okay, great, so now I know I have a symbolic link, but what if I want information about the link target? For example, I want to know the size of the link target, its last-modified time, and its name.

    To do this, you open the symbolic link. The I/O manager dereferences the symbolic link and gives you a handle to the link destination. You can then call functions like GetFileSize, GetFileInformationByHandleEx, or GetFinalPathNameByHandle to obtain information about the symbolic link target.