RegQueryValue

The RegQueryValue function retrieves the data associated with the default or unnamed value of a specified registry key. The data must be a null-terminated string.

Note  This function is provided only for compatibility with 16-bit versions of Windows. Win32-based applications should use the RegQueryValueEx function.

LONG RegQueryValue(
  HKEY hKey,        // handle to key to query
  LPCTSTR lpSubKey, // subkey name
  LPTSTR lpValue,   // string buffer
  PLONG lpcbValue   // size of returned string
);

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 of the hKey parameter for which the default value is retrieved. If this parameter is NULL or points to an empty string, the function retrieves the default value for the key identified by hKey.

lpValue

[out] Pointer to a buffer that receives the null-terminated string associated with the default value of the specified key.

If lpValue is NULL, and lpcbValue is non-NULL, the function returns ERROR_SUCCESS, and stores the size of the data, in bytes, in the variable pointed to by lpcbValue. This lets an application determine the best way to allocate a buffer for the value's data.

lpcbValue

[in/out] Pointer to a variable that specifies the size, in bytes, of the buffer pointed to by the lpValue parameter. When the function returns, this variable contains the size of the data copied to lpValue, including the terminating null character.

If the buffer specified by lpValue parameter is not large enough to hold the data, the function returns the value ERROR_MORE_DATA, and stores the required buffer size, in bytes, into the variable pointed to by lpcbValue. In this case, the contents of the lpValue buffer are undefined.

In all cases the value returned in lpcbValue includes the size of the terminating null character in the string.

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

The key identified by the hKey parameter must have been opened with KEY_QUERY_VALUE access (KEY_READ access includes KEY_QUERY_VALUE access).

If the ANSI version of this function is used (either by explicitly calling RegQueryValueA or by not defining UNICODE before including the Windows.h file), this function converts the stored Unicode string to an ANSI string before copying it to the buffer specified by the lpValue parameter.

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, RegEnumKey, RegEnumKeyEx, RegEnumValue, RegQueryInfoKey, RegQueryValueEx, RegSetValue, RegSetValueEx