RegOpenKeyEx

The RegOpenKeyEx function opens the specified registry key.

LONG RegOpenKeyEx(
  HKEY hKey,         // handle to open key
  LPCTSTR lpSubKey,  // subkey name
  DWORD ulOptions,   // reserved
  REGSAM samDesired, // security access mask
  PHKEY phkResult    // handle to open key
);

Parameters

hKey

[in] 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/2000: HKEY_PERFORMANCE_DATA
Windows 95/98: HKEY_DYN_DATA

lpSubKey

[in] Pointer to a null-terminated string containing the name of the subkey to open. If this parameter is NULL or a pointer to an empty string, the function will open a new handle to the key identified by the hKey parameter. In this case, the function will not close the handles previously opened.

ulOptions

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

Unlike the RegCreateKeyEx function, the RegOpenKeyEx function does not create the specified key if the key does not exist in the registry.

Windows 95/98: No registry subkey or value name may exceed 255 characters.

Requirements

  Windows NT/2000: Requires Windows NT 3.1 or later.
  Windows 95/98: Requires Windows 95 or later.
  Header: Declared in Winreg.h; include Windows.h.
  Library: Use Advapi32.lib.
  Unicode: Implemented as Unicode and ANSI versions on Windows NT/2000.

See Also

Registry Overview, Registry Functions, RegCloseKey, RegCreateKeyEx, RegDeleteKey, RegOpenKey