How to Read a Value from the Windows Registry

How to read a value from the Windows registry

Here is some pseudo-code to retrieve the following:

1. If a registry key exists
2. What the default value is for that registry key
3. What a string value is
4. What a DWORD value is

Example code:

Include the library dependency: Advapi32.lib

HKEY hKey;
LONG lRes = RegOpenKeyExW(HKEY_LOCAL_MACHINE, L"SOFTWARE\\Perl", 0, KEY_READ, &hKey);
bool bExistsAndSuccess (lRes == ERROR_SUCCESS);
bool bDoesNotExistsSpecifically (lRes == ERROR_FILE_NOT_FOUND);
std::wstring strValueOfBinDir;
std::wstring strKeyDefaultValue;
GetStringRegKey(hKey, L"BinDir", strValueOfBinDir, L"bad");
GetStringRegKey(hKey, L"", strKeyDefaultValue, L"bad");

LONG GetDWORDRegKey(HKEY hKey, const std::wstring &strValueName, DWORD &nValue, DWORD nDefaultValue)
{
    nValue = nDefaultValue;
    DWORD dwBufferSize(sizeof(DWORD));
    DWORD nResult(0);
    LONG nError = ::RegQueryValueExW(hKey,
        strValueName.c_str(),
        0,
        NULL,
        reinterpret_cast<LPBYTE>(&nResult),
        &dwBufferSize);
    if (ERROR_SUCCESS == nError)
    {
        nValue = nResult;
    }
    return nError;
}


LONG GetBoolRegKey(HKEY hKey, const std::wstring &strValueName, bool &bValue, bool bDefaultValue)
{
    DWORD nDefValue((bDefaultValue) ? 1 : 0);
    DWORD nResult(nDefValue);
    LONG nError = GetDWORDRegKey(hKey, strValueName.c_str(), nResult, nDefValue);
    if (ERROR_SUCCESS == nError)
    {
        bValue = (nResult != 0) ? true : false;
    }
    return nError;
}


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;
}

How to read integer value from Windows registry using Java?

I have found the solution:

import java.io.IOException;
import java.io.InputStream;
import java.io.StringWriter;

public class ReadRegistry
{
    public static final String readRegistry(String location, String key){
        try {
            // Run reg query, then read output with StreamReader (internal class)
            Process process = Runtime.getRuntime().exec("reg query " +
                    '"'+ location + "\" /v " + key);

            StreamReader reader = new StreamReader(process.getInputStream());
            reader.start();
            process.waitFor();
            reader.join();

            // Parse out the value
            // String[] parsed = reader.getResult().split("\\s+");

            String s1[];
            try{
             s1=reader.getResult().split("REG_SZ|REG_DWORD");
            }
            catch(Exception e)
            {
                return " ";
            }
           //MK System.out.println(s1[1].trim());

            return s1[1].trim();
        } catch (Exception e) {
        }

        return null;
    }
     static class StreamReader extends Thread {
        private InputStream is;
        private StringWriter sw= new StringWriter();

        public StreamReader(InputStream is) {
            this.is = is;
        }

        public void run() {
            try {
                int c;
                while ((c = is.read()) != -1)
                    //System.out.println(c);
                    sw.write(c);
            } catch (IOException e) {
            }
        }

        public String getResult() {
            return sw.toString();
        }
    }
}

You have to use it like this:

Registry2.readRegistry("HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Services\\LanmanWorkstation\\Parameters", "EnableSecuritySignature");

The class was taken from here.

C++ Can't read registry value data

The value MachineGuid in the key SOFTWARE\Microsoft\Cryptography in my environment is a string longer than 4 characters, not a DWORD value.

You have to allocate enough resion to read the value. Otherwise, ERROR_MORE_DATA will be returned as documented.

#include <cstdio>
#include <cstdlib>
#include <Windows.h>
int main()
{
    char val[128];
    DWORD dataSize = sizeof(val);
    if (ERROR_SUCCESS == RegGetValueA(HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Cryptography", "MachineGuid", RRF_RT_ANY, nullptr, &val, &dataSize))
    {
        printf("Value is %.*s\n", (int)dataSize, val);
    }
    else
    {
        printf("Read Error");
    };
    system("pause");
    return 1;
}

How to read (Default) value from registry and put into a variable within a batch file?

From the cmd line:

for /f "tokens=3*" %a in ('reg query "HKLM\SOFTWARE\Wow6432Node\Notepad++"') do echo %a %b

if you want to do it in script, double the %'s

Getting REG_DWORD from windows registry as a wstring

if (type != REG_SZ && type != REG_DWORD) ...

You just have to treat REG_SZ and REG_DWORD differently.

Also add an extra +1 for the null terminator to be safe.

wstring ReadRegValue(HKEY root, wstring key, wstring name)
{
    HKEY hKey;
    if (RegOpenKeyEx(root, key.c_str(), 0, KEY_READ, &hKey) != ERROR_SUCCESS)
        throw "Could not open registry key";
    DWORD type;
    DWORD cbData;
    if (RegQueryValueEx(hKey, 
            name.c_str(), NULL, &type, NULL, &cbData) != ERROR_SUCCESS)
    {
        RegCloseKey(hKey);
        throw "Could not read registry value";
    }

    std::wstring value;
    if (type == REG_SZ)
    {
        value.resize(1 + (cbData / sizeof(wchar_t)), L'\0');
        if (0 == RegQueryValueEx(hKey, name.c_str(), NULL, NULL,
            reinterpret_cast<BYTE*>(value.data()), &cbData))
        { //okay 
        }
    }
    else if (type == REG_DWORD)
    {
        DWORD dword;
        if (0 == RegQueryValueEx(hKey, name.c_str(), NULL, &type,
            reinterpret_cast<BYTE*>(&dword), &cbData))
            value = std::to_wstring(dword);
    }
    RegCloseKey(hKey);
    return value;
}

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