Opens the specified registry key. Note that key names are not case sensitive.

To perform transacted registry operations on a key, call the RegOpenKeyTransacted function.

Syntax

LONG WINAPI RegOpenKeyEx(
  __in        HKEY hKey,
  __in_opt    LPCTSTR lpSubKey,
  __reserved  DWORD ulOptions,
  __in        REGSAM samDesired,
  __out       PHKEY phkResult
);

Parameters

hKey [in]

A handle to an open registry key. This handle is returned by the RegCreateKeyEx or RegOpenKeyEx function, or it can be one of the following predefined keys:

HKEY_CLASSES_ROOT

HKEY_CURRENT_USER

HKEY_LOCAL_MACHINE

HKEY_USERS

lpSubKey [in, optional]

The name of the registry subkey to be opened.

Key names are not case sensitive.

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.

For more information, see Registry Element Size Limits.

ulOptions

This parameter is reserved and must be zero.

samDesired [in]

A mask that specifies the desired access rights to the key. The function fails if the security descriptor of the key does not permit the requested access for the calling process. For more information, see Registry Key Security and Access Rights.

phkResult [out]

A pointer to a variable that receives a handle to the opened key. If the key is not one of the predefined registry keys, call the RegCloseKey function after you have finished using the handle.

Return Value

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.

If your service or application impersonates different users, do not use this function with HKEY_CURRENT_USER. Instead, call the RegOpenCurrentUser function.

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 Deleting a Key with Subkeys.

Requirements

See Also

RegCloseKey

RegCreateKeyEx

RegDeleteKey

Registry Functions

Registry Overview

RegOpenKeyTransacted

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Build date: 11/19/2009