file - Why is seekp not doing its job? C++/CLI -

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my function "writetofile" writing piece of data file @ end of line indicated int variable zone. file set @ beginning text indicate put data, seekp() doesn't seem placing output marker need go.

can point out i'm missing please?

this file creation in main function:

string myfilename = txtboxcont; myfilename.append(".txt"); myfilename="test.txt"; //temporary name, delete before publish <<.  ofstream prefile(myfilename, ios::trunc); int i; (i=1;i<=4;i++)  prefile << "dc" << << "\n"; prefile << "junk:"; prefile.flush(); prefile.close();  fstream myfile(myfilename,ios::in | ios::out | ios::ate); if (!myfile.is_open())     throw;

and writetofile function: (fyi: data "0.95" or "623")

    void writetofile(fstream &myfile, string& data, int zone) {     data = numbercheck(data); //filters out non-numeric data, returns "null" if nothing left.     if (data=="null")       //if filter leaves no valid output, no need write.         return;      myfile.seekg(0, ios::beg);   //set initial position @ start?     string fileline, srch="dc";     stringstream ss; //for int string conversion     ss << zone;     srch.append(ss.str());     int fs=1, marker=string::npos;     while(!myfile.eof())        //test each line if begins dc(zone)     {         getline(myfile, fileline);         marker = marker + fileline.length();         if (srch==fileline.substr(0,3))             break;     }     marker++;      //can't avoid overwriting so... gon' suck...     string temp;     myfile.seekg(0,ios::end);     int length = myfile.tellg(), curiosity;     length = length - marker;     temp.resize(length);     myfile.seekg(marker);     curiosity = myfile.tellg();     myfile.read(&temp[0],temp.size()); //####  here's problem  ####     myfile.seekp(marker);     curiosity = myfile.tellp();     myfile << ',' << data << temp;      myfile.flush();     myfile.clear();     data.clear(); }

(the curisity variable says on tin , helping me debug) the problem is after curiosity = myfile.tellg();, bit @ correct point in file seems. after curiosity = myfile.tellp();, put bit @ -1 (or std::npos assume). file never writes @ myfile << ',' << data << temp; don't why.


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