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RegEnumKeyEx function

Applies to: desktop apps only

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

Syntax

Copy

LONG WINAPI RegEnumKeyEx(
  __in         HKEY hKey,
  __in         DWORD dwIndex,
  __out        LPTSTR lpName,
  __inout      LPDWORD lpcName,
  __reserved   LPDWORD lpReserved,
  __inout      LPTSTR lpClass,
  __inout_opt  LPDWORD lpcClass,
  __out_opt    PFILETIME lpftLastWriteTime
);

Parameters

hKey [in]

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_PERFORMANCE_DATA

HKEY_USERS

dwIndex [in]

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 [out]

A 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. If the function fails, no information is copied to this buffer.

For more information, see Registry Element Size Limits.

lpcName [in, out]

A pointer to a variable that specifies the size of the buffer specified by the lpName parameter, in characters. This size should include the terminating null character. If the function succeeds, the variable pointed to by lpcName contains the number of characters stored in the buffer, not including the terminating null character.

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.

lpReserved

This parameter is reserved and must be NULL.

lpClass [in, out]

A pointer to a buffer that receives the user-defined class of the enumerated subkey. This parameter can be NULL.

lpcClass [in, out, optional]

A pointer to a variable that specifies the size of the buffer specified by the lpClass parameter, in characters. The size should include the terminating null character. If the function succeeds, lpcClass contains the number of characters stored in the buffer, not including the terminating null character. This parameter can be NULL only if lpClass is NULL.

lpftLastWriteTime [out, optional]

A pointer to FILETIME structure that receives the time at which the enumerated subkey was last written. This parameter can be NULL.

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 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 (meaning 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.

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.

Examples

For an example, see Enumerating Registry Subkeys.

Requirements

Minimum supported client	Windows 2000 Professional
Minimum supported server	Windows 2000 Server
Header	Winreg.h (include Windows.h)
Library	Advapi32.lib
DLL	Advapi32.dll
Unicode and ANSI names	RegEnumKeyExW (Unicode) and RegEnumKeyExA (ANSI)

In 32-bit code on a 64-bit system do not recurse into HKLM\Software\Wow6432Node. It acts like a symbolic link that loops back to HKLM\Software in the same 32-bit hive. It does not map into the 'other' hive (64-bit) as you might think. The result is infinite recursion: HKLM\Software\Wow6432Node\Wow6432Node\Wow6432Node\..., etc. (All of these are the same 32-bit key.)

You should ignore any result from RegEnumKeyEx that returns "Wow6432Node". It is a magic name that triggers special behavior by the registry API. See http://msdn2.microsoft.com/en-us/library/ms724072.aspx

Windows Server 2008: In the 32-bit hive the registry key HKLM\Software\Wow6432Node is hidden from RegEnumKeyEx. This fixes the infinite recursion bug described above. The hidden key still exists and the infinite recursion can still happen, but only if you explicitly open it.

History

3/26/2008
Gideon7

5/4/2008
Gideon7

WOW64 RegEnumKeyEx does not enumerate shared keys

Note: If RegEnumKeyEx is called on the 32-bit view of the registry it will sometimes omit registry keys that are shared between the 32-bit and 64-bit registry hives. For example, the enumeration of HKLM\Software\Microsoft\Windows\CurrentVersion will not list the child keys 'Group Policy', 'Policies', and 'Tablet PC'.

The workaround is to open the parent handle using KEY_WOW64_64KEY.