RegEnumKeyEx

The RegEnumKeyEx function enumerates subkeys of the specified open registry key. The function retrieves information about one subkey each time it is called. Unlike the RegEnumKey function, RegEnumKeyEx retrieves the class name of the subkey and the time it was last modified.

LONG RegEnumKeyEx(
  HKEY hKey,          // handle to key to enumerate
  DWORD dwIndex,      // index of subkey to enumerate
  LPTSTR lpName,      // address of buffer for subkey name
  LPDWORD lpcbName,   // address for size of subkey buffer
  LPDWORD lpReserved, // reserved
  LPTSTR lpClass,     // address of buffer for class string
  LPDWORD lpcbClass,  // address for size of class buffer
  PFILETIME lpftLastWriteTime 
                      // address for time key last written to
);
 

Parameters

hKey

Handle to a currently open key or one 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 enumerated keys are subkeys of the key identified by hKey.

dwIndex

Specifies the index of the subkey to retrieve. This parameter should be zero for the first call to the RegEnumKeyEx function and then incremented for subsequent calls.

Because subkeys are not ordered, any new subkey will have an arbitrary index. This means that the function may return subkeys in any order.

lpName

Pointer to a buffer that receives the name of the subkey, including the terminating null character. The function copies only the name of the subkey, not the full key hierarchy, to the buffer.

lpcbName

Pointer to a variable that specifies the size, in characters, of the buffer specified by the lpName parameter. This size should include the terminating null character. When the function returns, the variable pointed to by lpcbName contains the number of characters stored in the buffer. The count returned does not include the terminating null character.

lpReserved

Reserved; must be NULL.

lpClass

Pointer to a buffer that contains the class of the enumerated subkey when the function returns. This parameter can be NULL if the class is not required.

lpcbClass

Pointer to a variable that specifies the size, in characters, of the buffer specified by the lpClass parameter. The size should include the terminating null character. When the function returns, lpcbClass contains the number of characters stored in the buffer. The count returned does not include the terminating null character. This parameter can be NULL only if lpClass is NULL.

lpftLastWriteTime

Pointer to a variable that receives the time the enumerated subkey was last written to.

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

To enumerate subkeys, an application should initially call the RegEnumKeyEx function with the dwIndex parameter set to zero. The application should then increment the dwIndex parameter and call RegEnumKeyEx until there are no more subkeys (until the function returns ERROR_NO_MORE_ITEMS).

The application can also set dwIndex to the index of the last subkey on the first call to the function and decrement the index until the subkey with the index 0 is enumerated. To retrieve the index of the last subkey, use the RegQueryInfoKey function.

While an application is using the RegEnumKeyEx function, it should not make calls to any registration functions that might change the key being enumerated.

The key identified by hKey must have been opened with KEY_ENUMERATE_SUB_KEYS access (KEY_READ includes KEY_ENUMERATE_SUB_KEYS). Use the RegCreateKeyEx or RegOpenKeyEx function to open the key.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  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, RegCreateKeyEx, RegDeleteKey, RegEnumKey, RegOpenKeyEx, RegQueryInfoKey