C Read values from the registry-CodePudding

I want to display these registry key values:

MSSQL12.MSSQLSERVER
MSSQL15.SQLEXPRESS
MSSQL11.TEW_SQLEXPRESS

Code:

if (RegOpenKeyEx(HKEY_LOCAL_MACHINE,
        TEXT("SOFTWARE\\Microsoft\\Microsoft SQL Server\\Instance Names\\SQL"),
        0,
        KEY_READ | KEY_WOW64_64KEY,
        &hKey) == ERROR_SUCCESS){
    DWORD i, retCode, cchName, buflen;

    TCHAR    achKey[MAX_KEY_LENGTH];            // buffer for subkey name
    DWORD    cbName;                            // size of name string 
    TCHAR    achClass[MAX_PATH] = TEXT("");     // buffer for class name 
    DWORD    cchClassName = MAX_PATH;           // size of class string 
    DWORD    cSubKeys = 0;                      // number of subkeys 
    DWORD    cbMaxSubKey;                       // longest subkey size 
    DWORD    cchMaxClass;                       // longest class string 
    DWORD    cValues;                           // number of values for key 
    DWORD    cchMaxValue;                       // longest value name 
    DWORD    cbMaxValueData;                    // longest value data 
    DWORD    cbSecurityDescriptor;              // size of security descriptor 
    FILETIME ftLastWriteTime;                   // last write time 

    retCode = RegQueryInfoKey(
        hKey,                    // key handle 
        achClass,                // buffer for class name 
        &cchClassName,           // size of class string 
        NULL,                    // reserved 
        &cSubKeys,               // number of subkeys 
        &cbMaxSubKey,            // longest subkey size 
        &cchMaxClass,            // longest class string 
        &cValues,                // number of values for this key 
        &cchMaxValue,            // longest value name 
        &cbMaxValueData,         // longest value data 
        &cbSecurityDescriptor,   // security descriptor 
        &ftLastWriteTime);       // last write time 

   
    result = RegGetValue(
                hKey, NULL, L"MSSQLSERVER",                    
                RRF_RT_REG_SZ, 0, buf, &bufsz);
    if (result != ERROR_SUCCESS) {
                printf("Failed read value");
                _getch();
                return -1;
            }
    wprintf(L"%s\n", buf);
}

I need to replace L"MSSQLSERVER" with the variable keyName, but I don't understand how to do that. I'm trying to write the name of the key to a variable.

LPWSTR aResult;
LPSTR  keyName;
RegEnumKeyExA(hKey, i, keyName, &cchName, NULL, NULL, NULL, NULL);
MultiByteToWideChar(0, 0, keyName, -1, aResult, 0);
result = RegGetValue(
            hKey, NULL, aResult,                    
            RRF_RT_REG_SZ, 0, buf, &bufsz);

But I think it's wrong. Here keyName is NULL. And keyName is LPSTR, but RegGetValue() needs LPCWSTR.

CodePudding user response：

It turned out that my task needed names, not values. And only SQL Express. Here is the code:

if (RegOpenKeyEx(HKEY_LOCAL_MACHINE,
        L"SOFTWARE\\Microsoft\\Microsoft SQL Server\\Instance Names\\SQL",
        0,
        KEY_READ | KEY_WOW64_64KEY,
        &hTestKey) == ERROR_SUCCESS
        )
while (RegEnumValueW(hTestKey, index, (wchar_t*)valueName.c_str(), &lppchValueName, 0, 0, 0, 0) == ERROR_SUCCESS) 
        {
            lppchValueName = MAX_PATH;
            buffSize = MAX_PATH;
            if (RegQueryValueExW(hTestKey, valueName.c_str(), 0, 0, (LPBYTE)value.c_str(), &buffSize) == ERROR_SUCCESS)
            {
                if (value.find(L"Express") != std::wstring::npos || value.find(L"EXPRESS") != std::wstring::npos || value.find(L"express") != std::wstring::npos)
                {
                    // Here is an array entry.
                }
            }
            index  ;
            memset((void*)valueName.c_str(), 0, MAX_PATH);
            memset((void*)value.c_str(), 0, MAX_PATH);
        }

CodePudding user response：

Looks like have to use unicode, pay attention on L"...." and LPWSTR

    LPWSTR  keyName = L"MSSQL12.MSSQLSERVER";
    result = RegGetValue(
                hKey, NULL, keyName ,                    
                RRF_RT_REG_SZ, 0, buf, &bufsz);