RegOpenKey

The RegOpenKey function opens the specified key. This function is provided for compatibility with Windows version 3.1. Win32-based applications should use the RegOpenKeyEx function.

LONG RegOpenKey(
  HKEY hKey,        // handle to open key
  LPCTSTR lpSubKey, // address of name of subkey to open
  PHKEY phkResult   // address of handle to open key
);
 

Parameters

hKey

Handle to a currently open key or any of the following predefined reserved handle values:

HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
Windows NT: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

The key opened by the RegOpenKey function is a subkey of the key identified by hKey.

lpSubKey

Pointer to a null-terminated string containing the name of the key to open. This key must be a subkey of the key identified by the hKey parameter. If this parameter is NULL or a pointer to an empty string, the function returns the same handle that was passed in.

phkResult

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 RegOpenKey function uses the default security access mask to open a key. If opening the key requires a different mask, the function fails, returning ERROR_ACCESS_DENIED. An application should use the RegOpenKeyEx function to specify an access mask in this situation.

Unlike the RegCreateKey function, RegOpenKey does not create the specified key if the key does not exist in the database.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in winreg.h.
  Import Library: Use advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT.

See Also

Registry Overview, Registry Functions, RegCloseKey, RegCreateKey, RegCreateKeyEx, RegDeleteKey, RegOpenKeyEx