RegSetValue

The RegSetValue function sets the data for the default or unnamed value of a specified registry key. The data must be a text string.

This function is provided for compatibility with Windows version 3.1. Win32-based applications should use the RegSetValueEx function, which allows you to set any number of named values of any data type.

LONG RegSetValue(
  HKEY hKey,         // handle to key to set value for
  LPCTSTR lpSubKey,  // address of subkey name
  DWORD dwType,      // type of value
  LPCTSTR lpData,    // address of value data
  DWORD cbData       // size of value data
);
 

Parameters

hKey

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: HKEY_PERFORMANCE_DATA
Windows 95 and Windows 98: HKEY_DYN_DATA

lpSubKey

Pointer to a null-terminated string containing the name of a subkey of the hKey parameter. The function sets the default value of the specified subkey. If this parameter is NULL or points to an empty string, the function sets the default value of the key identified by hKey.

dwType

Specifies the type of information to be stored. This parameter must be the REG_SZ type. To store other data types, use the RegSetValueEx function.

lpData

Pointer to a null-terminated string containing the data to set for the default value of the specified key.

cbData

Specifies the length, in bytes, of the string pointed to by the lpData parameter, not including the terminating null character.

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

If the key specified by the lpSubKey parameter does not exist, the RegSetValue function creates it.

Value lengths are limited by available memory. Long values (more than 2048 bytes) should be stored as files with the filenames stored in the registry. This helps the registry perform efficiently.

The key identified by the hKey parameter must have been opened with KEY_SET_VALUE access. To open the key, use the RegCreateKeyEx or RegOpenKeyEx function. If the ANSI version of this function is used (either by explicitly calling RegSetValueA or by not defining UNICODE before including the WINDOWS.H file), the lpData parameter must be an ANSI character string. The string is converted to Unicode before it is stored in the registry.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  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, RegFlushKey, RegOpenKeyEx, RegQueryValue, RegQueryValueEx, RegSetValueEx