RegQueryValue info  Overview  Group

The RegQueryValue function retrieves the value associated with the unnamed value for a specified key in the registry. Values in the registry have name, type, and data components. This function retrieves the data for a key’s first value that has a NULL name. This function is provided for compatibility with Windows version 3.1. Win32-based applications should use the RegQueryValueEx function.

LONG RegQueryValue(

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

Parameters

hKey

Identifies 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 only: HKEY_PERFORMANCE_DATA 
Windows 95 only: HKEY_DYN_DATA 

lpSubKey

Points to a null-terminated string containing the name of the subkey of the hKey parameter for which a value is to be retrieved. If this parameter is NULL or points to an empty string, the function retrieves the value set by the RegSetValue function for the key identified by hKey.

lpValue

Points to a buffer that receives the value associated with the lpSubKey parameter. The buffer should be big enough to contain the terminating null character. This parameter can be NULL if the data is not required.

If lpValue is NULL, and lpcbValue is not NULL, the function places the size in bytes of the data referenced by the value key, including the terminating null character, into the variable pointed to by lpcbValue. This lets an application determine how to best preallocate a buffer for the value key’s data.

lpcbValue

Points to a variable specifying 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.

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

In all cases the value returned in lpcbValue always 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.

See Also

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