You can call COM from C. The syntax is somewhat less friendly than C ++, but it works. COM was originally designed to work with C or C ++, and native C language support is included in the COM and WMI header files. It will be a long time, but ... your program will be responsible for allocating all the necessary objects, checking the error conditions from each COM call and releasing the objects created by it.
When using documentation written with C ++ in mind, convert the form COM calls:
pSomething->Method(arg1, ...);
in
pSomething->lpVtbl->Method(pSomething, arg1, ...);
Below is the shortest C code snippet I could get in order to actually pull some information from WMI. If successful, he should list the processors on your computer, as well as their clock frequency in MHz. The program takes care of utilizing the resources that it allocates, but it does not check for errors at all (you must look at these hr values before continuing with each step).
This is the visual studio 2008 "Win32 Console Application" with the main file renamed to the .c extension and the additional stdafx files removed. To link the program, be sure to include wbemuuid.lib in the project properties in the "Configuration Properties" / "Linker / Input / Additional Dependencies" section. It worked successfully in my Vista folder.
#define _WIN32_WINNT 0x0400 #define _WIN32_DCOM #include <stdio.h> #include <tchar.h> #include <windows.h> #include <wbemidl.h> void _tmain(int argc, _TCHAR* argv[]) { // result code from COM calls HRESULT hr = 0; // COM interface pointers IWbemLocator *locator = NULL; IWbemServices *services = NULL; IEnumWbemClassObject *results = NULL; // BSTR strings we'll use (http://msdn.microsoft.com/en-us/library/ms221069.aspx) BSTR resource = SysAllocString(L"ROOT\\CIMV2"); BSTR language = SysAllocString(L"WQL"); BSTR query = SysAllocString(L"SELECT * FROM Win32_Processor"); // initialize COM hr = CoInitializeEx(0, COINIT_MULTITHREADED); hr = CoInitializeSecurity(NULL, -1, NULL, NULL, RPC_C_AUTHN_LEVEL_DEFAULT, RPC_C_IMP_LEVEL_IMPERSONATE, NULL, EOAC_NONE, NULL); // connect to WMI hr = CoCreateInstance(&CLSID_WbemLocator, 0, CLSCTX_INPROC_SERVER, &IID_IWbemLocator, (LPVOID *) &locator); hr = locator->lpVtbl->ConnectServer(locator, resource, NULL, NULL, NULL, 0, NULL, NULL, &services); // issue a WMI query hr = services->lpVtbl->ExecQuery(services, language, query, WBEM_FLAG_BIDIRECTIONAL, NULL, &results); // list the query results if (results != NULL) { IWbemClassObject *result = NULL; ULONG returnedCount = 0; // enumerate the retrieved objects while((hr = results->lpVtbl->Next(results, WBEM_INFINITE, 1, &result, &returnedCount)) == S_OK) { VARIANT name; VARIANT speed; // obtain the desired properties of the next result and print them out hr = result->lpVtbl->Get(result, L"Name", 0, &name, 0, 0); hr = result->lpVtbl->Get(result, L"MaxClockSpeed", 0, &speed, 0, 0); wprintf(L"%s, %dMHz\r\n", name.bstrVal, speed.intVal); // release the current result object result->lpVtbl->Release(result); } } // release WMI COM interfaces results->lpVtbl->Release(results); services->lpVtbl->Release(services); locator->lpVtbl->Release(locator); // unwind everything else we've allocated CoUninitialize(); SysFreeString(query); SysFreeString(language); SysFreeString(resource); }