Trouble with fstream, not able to write properly to a file to exact position as speci

[mksakeesh]

Hi,
I have an text file "CD details" with content as below

1~ Cast Away~ English~ Thriller~ U~
2~ Titanic~ English~ Romance~ A~
3~ Forest Gump~ English~ Life~ U~

I am trying to add some additional data to the start of each line by using a code as below

#include<iostream>
#include<fstream.h>
#include<string>
#include<istream.h>
#include<conio.h>
#include <stdio.h>
using namespace std;

class CD_data_search
{
	public:
		void find_file(int search_option,string search_string);
};
void CD_data_search::find_file(int search_option,string search_string)
{
	string s;
	char p;
	int find_count=0,find_spport=0, loop_count=0,searchVar_temp;
	long pntr_postg=0,pntr_postp=0;
	searchVar_temp = search_option;
	search_option--;//To appropriately choose the correct field.
	fstream RW_myfile("CD Details",ios::in | ios::out);
	if (RW_myfile.is_open())
	{
		while (getline(RW_myfile,s))
		{
			pntr_postg=RW_myfile.tellg();
			pntr_postp=RW_myfile.tellp();
			cout<<"pntr_post_G:"<<pntr_postg<<"\n";
			cout<<"pntr_post_P:"<<pntr_postp<<"\n";
			RW_myfile.seekp(pntr_postg, ios::beg);
			pntr_postp=RW_myfile.tellp();
			RW_myfile << "TEST";
		}//end of while loop to read the file line by line

	}//End of IF loop opening the file
	else
	{
		cout<<"error in opening file";
	}
	RW_myfile.close();
	cout<<"\n"<<"Exit Search Mode\n";
	
}//End of find_file(int , string)
int main()
{
	int a=0;
	string f;
	cout<<"enter choose ID:-\t";
	cin>>a;
	cout<<"Enter string:-\t";
	cin>>f;
	cin.get();
	CD_data_search *search_D;
	search_D= new CD_data_search;
	search_D->find_file(a,f);
	return 0;
}

But this is not working as expected, it is writing at some other position, Do any body suggest me WHY is it behaving so?

[Ancient Dragon]

You can not simply insert stuff into existing lines of a text file. Instead, you have to completely rewrite the file. Open the original file for reading, open a new temp file for writing. In a loop, read each line of the original file and rewrite it with desired changes to the output file. After that is done, close both files, delete the original, and rename the temp to be the same name as the original.

[mksakeesh]

You can not simply insert stuff into existing lines of a text file. Instead, you have to completely rewrite the file. Open the original file for reading, open a new temp file for writing. In a loop, read each line of the original file and rewrite it with desired changes to the output file. After that is done, close both files, delete the original, and rename the temp to be the same name as the original.

Are you suggesting that the above said is the exact way to edit file.
I have test this, if we can exactly point the tellp pointer to the exact location where we need to edit and then if we insert the new word then the line get edited. I had trouble while using fstream class. If I use ifstream and ofstream separately, then I am able to do it(i.e., edit the Existing file itself).