RegOpenUserClassesRoot

The RegOpenUserClassesRoot function retrieves a handle to the HKEY_CLASSES_ROOT key for a specified user. The user is identified by an access token. The returned key has a view of the registry that merges the contents of the HKEY_LOCAL_MACHINE\Software\Classes key with the contents of the Software\Classes keys in the user's registry hive. For more information, see The HKEY_CLASSES_ROOT Key.

LONG RegOpenUserClassesRoot(
  HANDLE hToken,      // token 
  DWORD  dwOptions,   // reserved; must be zero
  REGSAM samDesired,  // security access mask
  PHKEY  phkResult    // receives key handle 
);

Parameters

hToken

[in] Handle to a primary or impersonation access token that identifies the user of interest. This can be a token handle returned by a call to LogonUser, CreateRestrictedToken, DuplicateToken, DuplicateTokenEx, OpenProcessToken, or OpenThreadToken functions. The handle must have TOKEN_QUERY access.

dwOptions

Reserved; must be zero.

samDesired

[in] An access mask that specifies the desired access rights to the key. This parameter can be a combination of the following values.

Value	Meaning
KEY_CREATE_LINK	Permission to create a symbolic link.
KEY_CREATE_SUB_KEY	Permission to create subkeys.
KEY_ENUMERATE_SUB_KEYS	Permission to enumerate subkeys.
KEY_EXECUTE	Permission for read access.
KEY_NOTIFY	Permission for change notification.
KEY_QUERY_VALUE	Permission to query subkey data.
KEY_SET_VALUE	Permission to set subkey data.
KEY_ALL_ACCESS	Combines the KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS, KEY_NOTIFY, KEY_CREATE_SUB_KEY, KEY_CREATE_LINK, and KEY_SET_VALUE access rights, plus all the standard access rights except SYNCHRONIZE.
KEY_READ	Combines the STANDARD_RIGHTS_READ, KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS, and KEY_NOTIFY access rights.
KEY_WRITE	Combines the STANDARD_RIGHTS_WRITE, KEY_SET_VALUE, and KEY_CREATE_SUB_KEY access rights.

phkResult

[out] Pointer to a variable that receives a handle to the opened key. When you no longer need the returned handle, call the RegCloseKey function to close it.

Return Values

If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a nonzero error code defined in Winerror.h. You can use the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag to get a generic description of the error.

Remarks

The RegOpenUserClassesRoot function enables you to retrieve the merged HKEY_CLASSES_ROOT information for users other than the interactive user. For example, the server component of a client/server application could use RegOpenUserClassesRoot to retrieve the merged information for a client.

RegOpenUserClassesRoot fails if the user profile for the specified user is not loaded. When a user logs on interactively, the system automatically loads the user's profile. For other users, you can call the LoadUserProfile function to load the user's profile. However, LoadUserProfile can be very time-consuming, so do not call it for this purpose unless it is absolutely necessary to have the user's merged HKEY_CLASSES_ROOT information.

Applications running in the security context of the interactively logged-on user do not need to use RegOpenUserClassesRoot. These applications can call the RegOpenKeyEx function to retrieve a merged view of the HKEY_CLASSES_ROOT key for the interactive user.

Requirements

  Windows NT/2000: Requires Windows 2000.
  Windows 95/98: Unsupported.
  Header: Declared in Winreg.h; include Windows.h.
  Library: Use Advapi32.lib.

See Also

Registry Overview, Registry Functions, LoadUserProfile, RegCloseKey, RegOpenKeyEx