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From:David Della Vecchia Date:December 21 2006 8:39pm
Subject:Buffer Problems?
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Hi, ive been having this problem, and I believe i've narrowed it down to  
something im doing wrong with mysqlpp.

I've asked on other forums and they told me they dont know whats wrong  
because, barring mysqlpp, my code is fine.

The problem is: This loop runs every 5 seconds and my intention is to  
write to a file the results of the query each iteration, however, this  
file keeps growing bigger and bigger instead of being truncated to 0 each  
time and starting over from scratch. I've tried flushing the file, using  
ofstream::trunc while opening, and as far as i know, the ofstream handler  
is doing its job. The file is opened and truncated, however when i write  
to the file (using <<), it writes all data that has been written in the  
past as well as any new data (i assume there is some buffer that never  
gets cleared), this is my problem.

I know it may seem confusing, maybe my spaghetti code will clear things up  

#include "util.h"
#include <mysql++.h>
#include <custom.h>
#include "tastatus_ssqls.h"
#include <iostream>
#include <iomanip>
#include <vector>
#include <fstream>

using namespace std;
using namespace mysqlpp;

int main(int argc, const char *argv[]) {
   vector<tastatus> ta;
   char delim[5] = ",";
   cout << "Connecting to MySQL...";
   Connection conn("--EDITED--","--EDITED--","--EDITED--","--EDITED--");
   cout << "success!" << endl;
   Query ta_status = conn.query();
   string query = "SELECT * FROM --EDITED--";
   int run = 0;
   while (run < 1) { //Run forever
     ofstream tafile("tafile.txt");
     //ofstream tafile("tafile.txt", ofstream::out | ofstream::trunc); //  
This doesnt make a difference
     ta_status << query;
     for (vector<tastatus>::iterator it = ta.begin(); it != ta.end(); ++it)  
       tafile << it->address << delim << it->status << delim
it->last_req << delim << it->last_command << delim <<
it->updated << endl;  
//basically creating a CSV
     sleep(5); //Loop every 5 seconds...
     //tafile.flush(); //no difference
     //cout.flush(); //no difference
     //tafile.close(); // This doesnt make a difference either
   return 0;

Here is my SSQLS declaration (inside "tastatus_ssqls.h"):

sql_create_6(tastatus, 1, 0,
             mysqlpp::sql_char, address,
             mysqlpp::sql_char, host,
             mysqlpp::sql_char, status,
             mysqlpp::sql_int, last_req,
             mysqlpp::sql_char, last_command,
             mysqlpp::sql_char, updated)

Thanks for any help!,
David Della Vecchia
Vacation Express
Buffer Problems?David Della Vecchia21 Dec
  • Re: Buffer Problems?Warren Young22 Dec
    • Re: Buffer Problems?Warren Young22 Dec