Opens the specified registry key. Note that key names are not case sensitive.
To perform transacted registry operations on a key, call the RegOpenKeyTransacted function.
LONG WINAPI RegOpenKeyEx( _In_ HKEY hKey, _In_opt_ LPCTSTR lpSubKey, _In_ DWORD ulOptions, _In_ REGSAM samDesired, _Out_ PHKEY phkResult );
- hKey [in]
- lpSubKey [in, optional]
The name of the registry subkey to be opened.
Key names are not case sensitive.
The lpSubKey parameter can be a pointer to an empty string. If lpSubKey is a pointer to an empty string and hKey is HKEY_CLASSES_ROOT, phkResult receives the same hKey handle passed into the function. Otherwise, phkResult receives a new handle to the key specified by hKey.
The lpSubKey parameter can be NULL only if hKey is one of the predefined keys. If lpSubKey is NULL and hKey is HKEY_CLASSES_ROOT, phkResult receives a new handle to the key specified by hKey. Otherwise, phkResult receives the same hKey handle passed in to the function.
For more information, see Registry Element Size Limits.
- ulOptions [in]
Specifies the option to apply when opening the key. Set this parameter to zero or the following:
The key is a symbolic link. Registry symbolic links should only be used when absolutely necessary.
- samDesired [in]
A mask that specifies the desired access rights to the key to be opened. The function fails if the security descriptor of the key does not permit the requested access for the calling process. For more information, see Registry Key Security and Access Rights.
- phkResult [out]
A pointer to a variable that receives a handle to the opened key. If the key is not one of the predefined registry keys, call the RegCloseKey function after you have finished using the handle.
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.
Unlike the RegCreateKeyEx function, the RegOpenKeyEx function does not create the specified key if the key does not exist in the registry.
Certain registry operations perform access checks against the security descriptor of the key, not the access mask specified when the handle to the key was obtained. For example, even if a key is opened with a samDesired of KEY_READ, it can be used to create registry keys if the key's security descriptor permits. In contrast, the RegSetValueEx function specifically requires that the key be opened with the KEY_SET_VALUE access right.
If your service or application impersonates different users, do not use this function with HKEY_CURRENT_USER. Instead, call the RegOpenCurrentUser function.
Note that operations that access certain registry keys are redirected. For more information, see Registry Virtualization and 32-bit and 64-bit Application Data in the Registry.
For an example, see Deleting a Key with Subkeys.
Minimum supported client
|Windows 2000 Professional [desktop apps only]|
Minimum supported server
|Windows 2000 Server [desktop apps only]|
Unicode and ANSI names
|RegOpenKeyExW (Unicode) and RegOpenKeyExA (ANSI)|