How to Retrieve Registry Key and Value in C ?

How to Retrieve Registry Key and Value

Determining Key Existence

To safely check for the existence of a registry key, use RegOpenKeyExW with the KEY_READ access flag. If the function returns ERROR_SUCCESS, the key exists.

Getting Key Value

Pseudo-Code

<code class="pseudo-code">if (key exists) {
    get default value of key
    get string value of key
    get DWORD value of key
}</code>

Example Code

<code class="cpp">#include <windows.h>

int main() {
    // Open the registry key
    HKEY hKey;
    LONG lRes = RegOpenKeyExW(HKEY_LOCAL_MACHINE, L"SOFTWARE\Perl", 0, KEY_READ, &hKey);
    // Check if the key exists
    bool bExistsAndSuccess = (lRes == ERROR_SUCCESS);
    // Get the default value of the key
    std::wstring strKeyDefaultValue;
    GetStringRegKey(hKey, L"", strKeyDefaultValue, L"bad");
    return 0;
}

// Function to get a string value from the registry
LONG GetStringRegKey(HKEY hKey, const std::wstring &strValueName, std::wstring &strValue, const std::wstring &strDefaultValue) {
    strValue = strDefaultValue;
    WCHAR szBuffer[512];
    DWORD dwBufferSize = sizeof(szBuffer);
    ULONG nError;
    nError = RegQueryValueExW(hKey, strValueName.c_str(), 0, NULL, (LPBYTE)szBuffer, &dwBufferSize);
    if (ERROR_SUCCESS == nError) {
        strValue = szBuffer;
    }
    return nError;
}</code>

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