RegSetValueA function (winreg.h)

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

Syntax

LSTATUS RegSetValueA(
  [in]           HKEY   hKey,
  [in, optional] LPCSTR lpSubKey,
  [in]           DWORD  dwType,
  [in]           LPCSTR lpData,
  [in]           DWORD  cbData
);

Parameters

[in] hKey

A handle to an open registry key. The key must have been opened with the KEY_SET_VALUE 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, optional] lpSubKey

The name of a subkey of the hKey parameter. The function sets the default value of the specified subkey. If lpSubKey does not exist, the function creates it.

Key names are not case sensitive.

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

For more information, see Registry Element Size Limits.

[in] dwType

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

[in] lpData

The data to be stored. This parameter cannot be NULL.

[in] cbData

This parameter is ignored. The function calculates this value based on the size of the data in the lpData parameter.

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

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

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.

Requirements

See also

RegCreateKeyEx

RegFlushKey

RegOpenKeyEx

RegQueryValueEx

RegSetValueEx

Registry Functions

Registry Overview