Writing Performance Data to a Log File

#define UNICODE
#define _UNICODE

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

void
DisplayCommandLineHelp ()
{
   _tprintf (TEXT("\n\nOne or more valid log names must be")); 
   _tprintf (TEXT("specified as a command line argument. The"));
   _tprintf (TEXT("\nlog file will be in the CSV log file format."));
   return;
}

int __cdecl _tmain (int argc, TCHAR **argv)
{

   HQUERY          hQuery;
   HLOG            hLog;
   PDH_STATUS      pdhStatus;
   DWORD           dwLogType = PDH_LOG_TYPE_CSV;
   HCOUNTER        hCounter;
   CHAR            szCounterPath[45] = 
                    TEXT("\\Processor(0)\\% Processor Time");
   DWORD           dwCount;

   if (argc != 2) {
      DisplayCommandLineHelp ();
      return -1;
   }

   // Open a query object.
   pdhStatus = PdhOpenQuery (0, 
                             0, 
                             &hQuery);

   // Add one counter that will provide the data.
   pdhStatus = PdhAddCounter (hQuery,
                              szCounterPath,
                              0,
                              &hCounter);

   // Open the log file for write access.
   pdhStatus = PdhOpenLog (argv[1], 
                           PDH_LOG_WRITE_ACCESS | 
                           PDH_LOG_CREATE_ALWAYS,
                           &dwLogType,
                           hQuery,
                           0, 
                           NULL,
                           &hLog);

   // Write 50 records to the log file.
   for (dwCount = 0; dwCount <= 50; dwCount++) {
       pdhStatus = PdhUpdateLog (hLog, TEXT("This is a comment."));
       Sleep(1000);      // Wait one second between samples for 
                         //  the counter to be updated.
   }

   // Close the query object.
   pdhStatus = PdhCloseQuery (hQuery);

   // Close the log file.
   pdhStatus = PdhCloseLog (hLog, 
                            PDH_FLAGS_CLOSE_QUERY);

   return 0;
}