How can I tell that a directory is really a recycle bin?
Here's a question inspired by an actual customer question:
I need a function that, given a path, tells me whether it is
a Recycle Bin folder.
I tried using functions like SHGetSpecialFolderPath
with CSIDL_BITBUCKET, but that doesn't work because
the Recycle Bin is a virtual folder that is the union of the
Recycle Bins of all drives.
The customer noted that they don't want to hard-code the words
RECYCLED and RECYCLER,
which is a good decision because
the name of the directory
depends on many things.
I mentioned earlier that
it depends on the file system.
It also depends on whether the drive is accessed locally or remotely;
network-based Recycle Bin folders follow yet another naming scheme.
It may even depend on what operating system the user is running.
No, hard-coding the name of the Recycle Bin folders is not a good idea.
The SHDESCRIPTIONID structure tells you a little more
about a shell folder.
In addition to the "description ID", it also gives you a CLSID,
and it is the CLSID that is relevant here.
#include <windows.h>
#include <shlobj.h>
#include <tchar.h>
#include <stdio.h>
HRESULT
GetFolderDescriptionId(LPCWSTR pszPath, SHDESCRIPTIONID *pdid)
{
HRESULT hr;
LPITEMIDLIST pidl;
if (SUCCEEDED(hr = SHParseDisplayName(pszPath, NULL,
&pidl, 0, NULL))) {
IShellFolder *psf;
LPCITEMIDLIST pidlChild;
if (SUCCEEDED(hr = SHBindToParent(pidl, IID_IShellFolder,
(void**)&psf, &pidlChild))) {
hr = SHGetDataFromIDList(psf, pidlChild,
SHGDFIL_DESCRIPTIONID, pdid, sizeof(*pdid));
psf->Release();
}
CoTaskMemFree(pidl);
}
return hr;
}
int __cdecl wmain(int argc, WCHAR **argv)
{
SHDESCRIPTIONID did;
if (SUCCEEDED(GetFolderDescriptionId(argv[1], &did)) &&
did.clsid == CLSID_RecycleBin) {
printf("is a recycle bin\n");
} else {
printf("is not a recycle bin\n");
}
return 0;
}
The GetFolderDescriptionId function
takes the path to a folder
and converts it to an ITEMIDLIST
just so it can call SHGetDataFromIDList
to obtain the SHDESCRIPTIONID.
All we care about in this case
is whether the CLSID
is the Recycle Bin or not.
C:\> checkrecycle C:\Windows
is not a recycle bin
C:\> checkrecycle C:\RECYCLER\S-1-5-21-2127521184-1604012920-1887927527-72713
is a recycle bin
Of course, now that I told you how to do it, I have to tell
you that this is not how to do it.
This is another example of a customer having a problem,
solving half of it, and
asking for help with the other half,
unaware that they are approaching the problem from the wrong
direction.
Next time, we'll look at the customer's real problem.
