I was writing a -kind of - server that works io thru files. When I tried to append a string to the file, (I at the time did not know about ios::app, so I used a very unconventional way of doing it) it would not behave as I expected ( I tried the append function without the loop, and it worked every time):
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <string>
using namespace std;
ofstream* open(string fileName)
{ // opens a file and returns a pointer to the object ready for writing
vector<string> contents;
ifstream f(fileName.c_str());
if (!f)
{
cout << "No File Found";
exit(-1);
}
while (!f.eof())
{ //read
string temp;
getline(f, temp);
contents.push_back(temp);
}
f.close();
ofstream* out = new ofstream(fileName.c_str());
for (int i = 1; i < contents.size(); i++)
{ // write previous contents
*out << contents[i] << endl << flush;
}
return out;
}
void apend(string text, string fileName)
{
ofstream* file = open(fileName);
*file << text << endl << flush; // insert text
file->close();
}
string stringify(int in)
{ // converts an integer to a string
stringstream x;
x << in;
string out;
x >> out;
return out;
}
int main()
{
cout << "Welcome to the cgs v1.0 ... loading files ... " << endl;
for (int i = 0; i < 10; i++)
apend(stringify(i), "server1.txt");
return 0;
}
Upon running this I got : server1.txt :
5
6
7
8
9
And if I ran the program again : server1.txt:
0
1
2
3
4
5
6
7
8
9
My question is, if I used std::flush why did it somehow not write the whole file, and then when it was re-run, write the rest of the first cycle and none of the second? - This is just curiosity. I will now move to ios::app. Thanks for any explanations.
