Enumerating Registry Subkeys

The following example uses the RegQueryInfoKey, RegEnumKeyEx, and RegEnumValue functions to enumerate the subkeys of the specified key. The hKey parameter passed to each function is a handle to an open key. This key must be opened before the function call and closed afterward.

// QueryKey - Enumerates the subkeys of key and its associated values.
// hKey - Key whose subkeys and values are to be enumerated.

#include <windows.h>
#include <stdio.h>
#include <tchar.h>

#define MAX_KEY_LENGTH 255
#define MAX_VALUE_NAME 16383

void QueryKey(HKEY hKey)
{
 TCHAR achKey[MAX_KEY_LENGTH]; // buffer for subkey name
 DWORD cbName = 0; // 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 = 0; // longest subkey size 
 DWORD cchMaxClass = 0; // longest class string 
 DWORD cValues = 0; // number of values for key 
 DWORD cchMaxValue = 0; // longest value name 
 DWORD cbMaxValueData = 0; // longest value data 
 DWORD cbSecurityDescriptor = 0; // size of security descriptor 
 FILETIME ftLastWriteTime; // last write time 

 DWORD i = 0, j = 0, retCode = 0;

 TCHAR achValue[MAX_VALUE_NAME] = {'\0'};
 DWORD cchValue = MAX_VALUE_NAME;

 // Get the class name and the value count. 
 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 



 // Enumerate the subkeys, until RegEnumKeyEx fails.

 if (cSubKeys)
 {
 printf("\nNumber of subkeys: %d\n", cSubKeys);

 for (i = 0; i < cSubKeys; i++)
 {
 cbName = MAX_KEY_LENGTH;
 retCode = ::RegEnumKeyEx(hKey, i,
 achKey,
 &cbName,
 NULL,
 NULL,
 NULL,
 &ftLastWriteTime);

 if (retCode == ERROR_SUCCESS)
 {
 _tprintf(TEXT("(%d) %s\n"), i + 1, achKey);
 }
 }
 }

 // Enumerate the key values. 

 if (cValues)
 {
 printf("\nNumber of values: %d\n", cValues);

 for (i = 0; i < cValues; i++)
 {
 cchValue = MAX_VALUE_NAME;
 achValue[0] = '\0';
 retCode = ::RegEnumValue(hKey, i,
 achValue,
 &cchValue,
 NULL,
 NULL,
 NULL,
 NULL);

 if (retCode == ERROR_SUCCESS)
 {
 _tprintf(TEXT("(%d) %s\n"), i + 1, achValue);
 }
 }
 }
}

int __cdecl _tmain()
{
 HKEY hTestKey = 0;

 if (::RegOpenKeyEx(HKEY_CURRENT_USER,
 TEXT("SOFTWARE\\Microsoft"),
 0,
 KEY_READ,
 &hTestKey) == ERROR_SUCCESS
 )
 {
 QueryKey(hTestKey);
 }

 ::RegCloseKey(hTestKey);

 return 0;
}