Registry Management API Reference

This section provides details on the Windows Registry API, enabling developers to programmatically access and manipulate the system registry.

Overview

The Windows Registry is a hierarchical database that stores low-level settings for the operating system and for applications that opt to use the registry to store configuration data.

Important: Incorrectly modifying the registry can cause serious system problems. Always back up your registry before making changes.

Key Concepts

Hives: Top-level registry keys (e.g., HKEY_CLASSES_ROOT, HKEY_CURRENT_USER).
Keys: Folders within the registry hierarchy.
Values: Data entries associated with keys. Values have a name, a type, and data.
Value Types: REG_SZ (string), REG_DWORD (32-bit integer), REG_BINARY (binary data), etc.

Core Functions

The following functions are commonly used for registry management:

Opening and Closing Keys

RegOpenKeyEx: Opens an existing registry key.
RegCreateKeyEx: Creates a new registry key or opens an existing one.
RegCloseKey: Closes an open registry key handle.

Reading Values

RegQueryValueEx: Retrieves the data and type for a specified registry value.
RegEnumKeyEx: Enumerates the subkeys of a specified registry key.
RegEnumValue: Enumerates the values of a specified registry key.

Writing Values

RegSetValueEx: Sets the data and type for a specified registry value.
RegDeleteKey: Deletes a subkey and its values from the registry.
RegDeleteValue: Deletes a named entry (value) from a registry key.

Example: Reading a Registry Value

The following C++ code snippet demonstrates how to read a string value from the registry:


#include <windows.h>
#include <iostream>

int main() {
    HKEY hKey;
    LONG result;
    DWORD type = REG_SZ;
    CHAR value[256];
    DWORD dataSize = sizeof(value);

    // Open the key
    result = RegOpenKeyEx(
        HKEY_CURRENT_USER,
        TEXT("Software\\MyApp"),
        0,
        KEY_READ,
        &hKey);

    if (result == ERROR_SUCCESS) {
        // Query the value
        result = RegQueryValueEx(
            hKey,
            TEXT("SettingName"),
            NULL,
            &type,
            (LPBYTE)value,
            &dataSize);

        if (result == ERROR_SUCCESS && type == REG_SZ) {
            std::wcout << L"Value: " << value << std::endl;
        } else {
            std::cerr << "Failed to query value or incorrect type." << std::endl;
        }

        RegCloseKey(hKey);
    } else {
        std::cerr << "Failed to open registry key." << std::endl;
    }

    return 0;
}

Registry Viewer Tools

For manual inspection and editing, the built-in Windows Registry Editor (regedit.exe) is available.

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