RegEnumKeyW function (winreg.h)

Article
02/09/2023

Enumerates the subkeys of the specified open registry key. The function retrieves the name of one subkey each time it is called.

Note This function is provided only for compatibility with 16-bit versions of Windows. Applications should use the RegEnumKeyEx function.

Syntax

LSTATUS RegEnumKeyW(
  [in]  HKEY   hKey,
  [in]  DWORD  dwIndex,
  [out] LPWSTR lpName,
  [in]  DWORD  cchName
);

Parameters

[in] hKey

A handle to an open registry key. The key must have been opened with the KEY_ENUMERATE_SUB_KEYS access right. For more information, see Registry Key Security and Access Rights.

This handle is returned by the RegCreateKeyEx, RegCreateKeyTransacted, RegOpenKeyEx, or RegOpenKeyTransacted function. It can also be one of the following predefined keys:

HKEY_CLASSES_ROOT

HKEY_CURRENT_CONFIG

HKEY_CURRENT_USER

HKEY_LOCAL_MACHINE

HKEY_USERS

[in] dwIndex

The index of the subkey of hKey to be retrieved. This value should be zero for the first call to the RegEnumKey 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.

[out] lpName

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

For more information, see Registry Element Size Limits.

[in] cchName

The size of the buffer pointed to by the lpName parameter, in TCHARs. To determine the required buffer size, use the RegQueryInfoKey function to determine the size of the largest subkey for the key identified by the hKey parameter.

Return value

If the function succeeds, the return value is ERROR_SUCCESS.

If the function fails, the return value is a system error code. If there are no more subkeys available, the function returns ERROR_NO_MORE_ITEMS.

If the lpName buffer is too small to receive the name of the key, the function returns ERROR_MORE_DATA.

Remarks

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

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

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

Note

The winreg.h header defines RegEnumKey as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	winreg.h (include Windows.h)
Library	Advapi32.lib
DLL	Advapi32.dll