检查是否已安装服务

Created: November-22, 2018

此示例显示如何检查服务是否已存在（即，是否已安装在计算机上）。此代码仅需要最低权限，因此每个进程都可以执行检查，无论它运行的安全级别如何。

#define UNICODE
#define _UNICODE
#include <Windows.h>
#include <string>
#include <iostream>

enum Result
{
   unknown,
   serviceManager_AccessDenied,
   serviceManager_DatabaseDoesNotExist,
   service_AccessDenied,
   service_InvalidServiceManagerHandle,
   service_InvalidServiceName,
   service_DoesNotExist,
   service_Exist
};

Result ServiceExists(const std::wstring &serviceName)
{
   Result r = unknown;

   // Get a handle to the SCM database
   SC_HANDLE manager = OpenSCManager(NULL, SERVICES_ACTIVE_DATABASE, GENERIC_READ);
   
   if (manager == NULL)
   {
      DWORD lastError = GetLastError();
      
      // At this point, we can return directly because no handles need to be closed.
      if (lastError == ERROR_ACCESS_DENIED)
         return serviceManager_AccessDenied;
      else if (lastError == ERROR_DATABASE_DOES_NOT_EXIST)
         return serviceManager_DatabaseDoesNotExist;
      else
         return unknown;
   }

   SC_HANDLE service = OpenService(manager, serviceName.c_str(), GENERIC_READ);
   
   if (service == NULL)
   {
      DWORD error = GetLastError();
      
      if (error == ERROR_ACCESS_DENIED)
         r = service_AccessDenied;
      else if (error == ERROR_INVALID_HANDLE)
         r = service_InvalidServiceManagerHandle;
      else if (error == ERROR_INVALID_NAME)
         r = service_InvalidServiceName;
      else if (error == ERROR_SERVICE_DOES_NOT_EXIST)
         r = service_DoesNotExist;
      else
         r = unknown;
   }
   else
      r = service_Exist;

   if (service != NULL)
      CloseServiceHandle(service);

   if (manager != NULL)
      CloseServiceHandle(manager);
   
   return r;
}

int main()
{
   std::wstring serviceName = L"MSSQL$SQLEXPRESS";  // name of the service to check
   Result result = ServiceExists(serviceName);
   if (result == service_Exist)
      std::wcout << L"The service '" << serviceName << "' exists." << std::endl;
   else if (result == service_DoesNotExist)
      std::wcout << L"The service '" << serviceName << "' does not exist." << std::endl;
   else
      std::wcout << L"An error has occurred, and it could not be determined whether the service '" << serviceName << "' exists or not." << std::endl;
}

API 参考：