如何从 Windows 注册表中读取值

小开

This gives the value if it exists, and returns an error code ERROR_FILE_NOT_FOUND if the key doesn't exist.

(I can't tell if my link is working or not, but if you just google for "RegQueryValueEx" the first hit is the msdn documentation.)

小开

The pair RegOpenKey and RegQueryKeyEx will do the trick.

If you use MFC CRegKey class is even more easier solution.

小开

const CString REG_SW_GROUP_I_WANT = _T("SOFTWARE\\My Corporation\\My Package\\Group I want");
const CString REG_KEY_I_WANT= _T("Key Name");


CRegKey regKey;
DWORD   dwValue = 0;


if(ERROR_SUCCESS != regKey.Open(HKEY_LOCAL_MACHINE, REG_SW_GROUP_I_WANT))
{
m_pobLogger->LogError(_T("CRegKey::Open failed in Method"));
regKey.Close();
goto Function_Exit;
}
if( ERROR_SUCCESS != regKey.QueryValue( dwValue, REG_KEY_I_WANT))
{
m_pobLogger->LogError(_T("CRegKey::QueryValue Failed in Method"));
regKey.Close();
goto Function_Exit;
}


// dwValue has the stuff now - use for further processing

小开

最佳答案

Here is some pseudo-code to retrieve the following:

If a registry key exists
What the default value is for that registry key
What a string value is
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;
}

小开

#include <windows.h>
#include <map>
#include <string>
#include <stdio.h>
#include <string.h>
#include <tr1/stdint.h>


using namespace std;


void printerr(DWORD dwerror) {
LPVOID lpMsgBuf;
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
dwerror,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
(LPTSTR) &lpMsgBuf,
0,
NULL
);
// Process any inserts in lpMsgBuf.
// ...
// Display the string.
if (isOut) {
fprintf(fout, "%s\n", lpMsgBuf);
} else {
printf("%s\n", lpMsgBuf);
}
// Free the buffer.
LocalFree(lpMsgBuf);
}






bool regreadSZ(string& hkey, string& subkey, string& value, string& returnvalue, string& regValueType) {
char s[128000];
map<string,HKEY> keys;
keys["HKEY_CLASSES_ROOT"]=HKEY_CLASSES_ROOT;
keys["HKEY_CURRENT_CONFIG"]=HKEY_CURRENT_CONFIG; //DID NOT SURVIVE?
keys["HKEY_CURRENT_USER"]=HKEY_CURRENT_USER;
keys["HKEY_LOCAL_MACHINE"]=HKEY_LOCAL_MACHINE;
keys["HKEY_USERS"]=HKEY_USERS;
HKEY mykey;


map<string,DWORD> valuetypes;
valuetypes["REG_SZ"]=REG_SZ;
valuetypes["REG_EXPAND_SZ"]=REG_EXPAND_SZ;
valuetypes["REG_MULTI_SZ"]=REG_MULTI_SZ; //probably can't use this.


LONG retval=RegOpenKeyEx(
keys[hkey],         // handle to open key
subkey.c_str(),  // subkey name
0,   // reserved
KEY_READ, // security access mask
&mykey    // handle to open key
);
if (ERROR_SUCCESS != retval) {printerr(retval); return false;}
DWORD slen=128000;
DWORD valuetype = valuetypes[regValueType];
retval=RegQueryValueEx(
mykey,            // handle to key
value.c_str(),  // value name
NULL,   // reserved
(LPDWORD) &valuetype,       // type buffer
(LPBYTE)s,        // data buffer
(LPDWORD) &slen      // size of data buffer
);
switch(retval) {
case ERROR_SUCCESS:
//if (isOut) {
//    fprintf(fout,"RegQueryValueEx():ERROR_SUCCESS:succeeded.\n");
//} else {
//    printf("RegQueryValueEx():ERROR_SUCCESS:succeeded.\n");
//}
break;
case ERROR_MORE_DATA:
//what do I do now?  data buffer is too small.
if (isOut) {
fprintf(fout,"RegQueryValueEx():ERROR_MORE_DATA: need bigger buffer.\n");
} else {
printf("RegQueryValueEx():ERROR_MORE_DATA: need bigger buffer.\n");
}
return false;
case ERROR_FILE_NOT_FOUND:
if (isOut) {
fprintf(fout,"RegQueryValueEx():ERROR_FILE_NOT_FOUND: registry value does not exist.\n");
} else {
printf("RegQueryValueEx():ERROR_FILE_NOT_FOUND: registry value does not exist.\n");
}
return false;
default:
if (isOut) {
fprintf(fout,"RegQueryValueEx():unknown error type 0x%lx.\n", retval);
} else {
printf("RegQueryValueEx():unknown error type 0x%lx.\n", retval);
}
return false;


}
retval=RegCloseKey(mykey);
if (ERROR_SUCCESS != retval) {printerr(retval); return false;}


returnvalue = s;
return true;
}

小开

Since Windows >=Vista/Server 2008, RegGetValue is available, which is a safer function than RegQueryValueEx. No need for RegOpenKeyEx, RegCloseKey or NUL termination checks of string values (ABC3, ABC4, REG_EXPAND_SZ).

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


/*! \brief                          Returns a value from HKLM as string.
\exception  std::runtime_error  Replace with your error handling.
*/
std::wstring GetStringValueFromHKLM(const std::wstring& regSubKey, const std::wstring& regValue)
{
size_t bufferSize = 0xFFF; // If too small, will be resized down below.
std::wstring valueBuf; // Contiguous buffer since C++11.
valueBuf.resize(bufferSize);
auto cbData = static_cast<DWORD>(bufferSize * sizeof(wchar_t));
auto rc = RegGetValueW(
HKEY_LOCAL_MACHINE,
regSubKey.c_str(),
regValue.c_str(),
RRF_RT_REG_SZ,
nullptr,
static_cast<void*>(valueBuf.data()),
&cbData
);
while (rc == ERROR_MORE_DATA)
{
// Get a buffer that is big enough.
cbData /= sizeof(wchar_t);
if (cbData > static_cast<DWORD>(bufferSize))
{
bufferSize = static_cast<size_t>(cbData);
}
else
{
bufferSize *= 2;
cbData = static_cast<DWORD>(bufferSize * sizeof(wchar_t));
}
valueBuf.resize(bufferSize);
rc = RegGetValueW(
HKEY_LOCAL_MACHINE,
regSubKey.c_str(),
regValue.c_str(),
RRF_RT_REG_SZ,
nullptr,
static_cast<void*>(valueBuf.data()),
&cbData
);
}
if (rc == ERROR_SUCCESS)
{
cbData /= sizeof(wchar_t);
valueBuf.resize(static_cast<size_t>(cbData - 1)); // remove end null character
return valueBuf;
}
else
{
throw std::runtime_error("Windows system error code: " + std::to_string(rc));
}
}


int main()
{
std::wstring regSubKey;
#ifdef _WIN64 // Manually switching between 32bit/64bit for the example. Use dwFlags instead.
regSubKey = L"SOFTWARE\\WOW6432Node\\Company Name\\Application Name\\";
#else
regSubKey = L"SOFTWARE\\Company Name\\Application Name\\";
#endif
std::wstring regValue(L"MyValue");
std::wstring valueFromRegistry;
try
{
valueFromRegistry = GetStringValueFromHKLM(regSubKey, regValue);
}
catch (std::exception& e)
{
std::cerr << e.what();
}
std::wcout << valueFromRegistry;
}

Its parameter dwFlags supports flags for type restriction, filling the value buffer with zeros on failure (RRF_ZEROONFAILURE) and 32/64bit registry access (RRF_SUBKEY_WOW6464KEY, RRF_SUBKEY_WOW6432KEY) for 64bit programs.

小开

This console app will list all the values and their data from a registry key for most of the potential registry values. There's some weird ones not often used. If you need to support all of them, expand from this example while referencing this Registry Value Type documentation.

Let this be the registry key content you can import from a .reg file format:

Windows Registry Editor Version 5.00


[HKEY_CURRENT_USER\added\subkey]
"String_Value"="hello, world!"
"Binary_Value"=hex:01,01,01,01
"Dword value"=dword:00001224
"QWord val"=hex(b):24,22,12,00,00,00,00,00
"multi-line val"=hex(7):4c,00,69,00,6e,00,65,00,20,00,30,00,00,00,4c,00,69,00,\
6e,00,65,00,20,00,31,00,00,00,4c,00,69,00,6e,00,65,00,20,00,32,00,00,00,00,\
00
"expanded_val"=hex(2):25,00,55,00,53,00,45,00,52,00,50,00,52,00,4f,00,46,00,49,\
00,4c,00,45,00,25,00,5c,00,6e,00,65,00,77,00,5f,00,73,00,74,00,75,00,66,00,\
66,00,00,00

The console app itself:

#include <Windows.h>
#include <iostream>
#include <string>
#include <locale>
#include <vector>
#include <iomanip>


int wmain()
{
const auto hKey = HKEY_CURRENT_USER;
constexpr auto lpSubKey = TEXT("added\\subkey");
auto openedKey = HKEY();
auto status = RegOpenKeyEx(hKey, lpSubKey, 0, KEY_READ, &openedKey);


if (status == ERROR_SUCCESS) {
auto valueCount = static_cast<DWORD>(0);
auto maxNameLength = static_cast<DWORD>(0);
auto maxValueLength = static_cast<DWORD>(0);
status = RegQueryInfoKey(openedKey, NULL, NULL, NULL, NULL, NULL, NULL,
&valueCount, &maxNameLength, &maxValueLength, NULL, NULL);


if (status == ERROR_SUCCESS) {
DWORD type = 0;
DWORD index = 0;
std::vector<wchar_t> valueName = std::vector<wchar_t>(maxNameLength + 1);
std::vector<BYTE> dataBuffer = std::vector<BYTE>(maxValueLength);


for (DWORD index = 0; index < valueCount; index++) {
DWORD charCountValueName = static_cast<DWORD>(valueName.size());
DWORD charBytesData = static_cast<DWORD>(dataBuffer.size());
status = RegEnumValue(openedKey, index, valueName.data(), &charCountValueName,
NULL, &type, dataBuffer.data(), &charBytesData);


if (type == REG_SZ) {
const auto reg_string = reinterpret_cast<wchar_t*>(dataBuffer.data());
std::wcout << L"Type: REG_SZ" << std::endl;
std::wcout << L"\tName: " << valueName.data() << std::endl;
std::wcout << L"\tData : " << reg_string << std::endl;
}
else if (type == REG_EXPAND_SZ) {
const auto casted = reinterpret_cast<wchar_t*>(dataBuffer.data());
TCHAR buffer[32000];
ExpandEnvironmentStrings(casted, buffer, 32000);
std::wcout << L"Type: REG_EXPAND_SZ" << std::endl;
std::wcout << L"\tName: " << valueName.data() << std::endl;
std::wcout << L"\tData: " << buffer << std::endl;
}
else if (type == REG_MULTI_SZ) {
std::vector<std::wstring> lines;
const auto str = reinterpret_cast<wchar_t*>(dataBuffer.data());
auto line = str;
lines.emplace_back(line);
for (auto i = 0; i < charBytesData / sizeof(wchar_t) - 1; i++) {
const auto c = str[i];
if (c == 0) {
line = str + i + 1;
const auto new_line = reinterpret_cast<wchar_t*>(line);
if (wcsnlen_s(new_line, 1024) > 0)
lines.emplace_back(new_line);
}
}
std::wcout << L"Type: REG_MULTI_SZ" << std::endl;
std::wcout << L"\tName: " << valueName.data() << std::endl;
std::wcout << L"\tData: " << std::endl;
for (size_t i = 0; i < lines.size(); i++) {
std::wcout << L"\t\tLine[" << i + 1 << L"]: " << lines[i] << std::endl;
}
}
if (type == REG_DWORD) {
const auto dword_value = reinterpret_cast<unsigned long*>(dataBuffer.data());
std::wcout << L"Type: REG_DWORD" << std::endl;
std::wcout << L"\tName: " << valueName.data() << std::endl;
std::wcout << L"\tData : " << std::to_wstring(*dword_value) << std::endl;
}
else if (type == REG_QWORD) {
const auto qword_value = reinterpret_cast<unsigned long long*>(dataBuffer.data());
std::wcout << L"Type: REG_DWORD" << std::endl;
std::wcout << L"\tName: " << valueName.data() << std::endl;
std::wcout << L"\tData : " << std::to_wstring(*qword_value) << std::endl;
}
else if (type == REG_BINARY) {
std::vector<uint16_t> bins;
for (auto i = 0; i < charBytesData; i++) {
bins.push_back(static_cast<uint16_t>(dataBuffer[i]));
}
std::wcout << L"Type: REG_BINARY" << std::endl;
std::wcout << L"\tName: " << valueName.data() << std::endl;
std::wcout << L"\tData:";
for (size_t i = 0; i < bins.size(); i++) {
std::wcout << L" " << std::uppercase << std::hex << \
std::setw(2) << std::setfill(L'0') << std::to_wstring(bins[i]);
}
std::wcout << std::endl;
}
}
}
}


RegCloseKey(openedKey);
return 0;
}

Expected console output:

Type: REG_SZ
Name: String_Value
Data : hello, world!
Type: REG_BINARY
Name: Binary_Value
Data: 01 01 01 01
Type: REG_DWORD
Name: Dword value
Data : 4644
Type: REG_DWORD
Name: QWord val
Data : 1188388
Type: REG_MULTI_SZ
Name: multi-line val
Data:
Line[1]: Line 0
Line[2]: Line 1
Line[3]: Line 2
Type: REG_EXPAND_SZ
Name: expanded_val
Data: C:\Users\user name\new_stuff

小开

Typically the register key and value are constants in the program. If so, here is an example how to read a DWORD registry value Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem\LongPathsEnabled:

#include <windows.h>


DWORD val;
DWORD dataSize = sizeof(val);
if (ERROR_SUCCESS == RegGetValueA(HKEY_LOCAL_MACHINE, "SYSTEM\\CurrentControlSet\\Control\\FileSystem", "LongPathsEnabled", RRF_RT_DWORD, nullptr /*type not required*/, &val, &dataSize)) {
printf("Value is %i\n", val);
// no CloseKey needed because it is a predefined registry key
}
else {
printf("Error reading.\n");
}

To adapt for other value types, see https://learn.microsoft.com/en-us/windows/win32/api/winreg/nf-winreg-reggetvaluea for complete spec.