How to properly use %USERPROFILE% inside code?

Is my co开发者_JAVA技巧de correct? It seems can compile but does not work properly..

CString testing = _T(" --url=") + cstring + _T(" --out=%USERPROFILE%\\snapshot.png");

I want to point it to user's folder..but still cannot work.

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The answer is that you don't use environment variables at all. Rather, you use the shell functions specifically designed to retrieve the path of special folders.

On Windows Vista and later, that function is SHGetKnownFolderPath. It takes KNOWNFOLDERID values to identify the folder whose path you wish to retrieve. In your case, that would be FOLDERID_Profile.

If you need to target earlier versions of Windows (such as XP), you will need to use the SHGetSpecialFolderPath function, instead. It takes a CSIDL value identifying the folder whose path you wish to retrieve. Again, in your case, that would be CSIDL_PROFILE.

Of course, you should never store data directly in the user's profile folder. So hopefully the bit of code that you've shown is for demonstration purposes only. Applications should only create files in the specific locations under the user profile folder, designed for application data storage.

These locations are CSIDL_APPDATA or CSIDL_LOCAL_APPDATA. If you are creating data that the user should be able to modify and should treat as his/her own, then it would be appropriate to store that data in the user's documents folder (CSIDL_MYDOCUMENTS).

More usage information is available in my answer here.

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Sample code:

TCHAR szFolderPath[MAX_PATH];
if (!SHGetSpecialFolderPath(NULL, szFolderPath, CSIDL_APPDATA, FALSE))
{
    // Uh-oh! An error occurred; handle it.
}

Or, using MFC's CString class:

CString buffer;
BOOL bRet = SHGetSpecialFolderPath(NULL, buffer.GetBuffer(MAX_PATH), CSIDL_APPDATA, FALSE);
buffer.ReleaseBuffer();
if (!bRet)
{
    // Uh-oh! An error occurred; handle it.
}

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As Cody suggested, it's better to use the SHGetSpecialFolderPath function. However, you could use the GetEnvironmentVariable function to get that and other variables set in the system.

TCHAR szBuf[MAX_PATH] = {0};
::GetEnvironmentVariable(_T( "USERPROFILE" ), szBuf, MAX_PATH);