How do you detect an end of file in c plus plus?

Answer 1

The following code demonstrates how the end of file can be detected. Note that you do not test std::istream::eof() directly. The eof flag is only set when you read past the end of a file, not when you read the last character in a file. That is, if the file has three characters and you extract three characters, eof is not set at that point. It is only set when you attempt to read another character and there is no character there. At that point you are past the end of the file and the flag is set.

#include<iostream>

#include<fstream>

int main()

{

char * filename = "test.txt";

// create a 3-character file

std::ofstream outfile;

outfile.open (filename, std::ios::out);

outfile << "ABC";

outfile.close();

std::ifstream infile;

infile.open (filename, std::ios::in);

char ch;

while (infile.get(ch))

{

std::cout << ch;

std::cout << "\tEOF flag is " << (infile.eof()?"":"not") << " set\n";

}

std::cout << "EOF flag is " << (infile.eof()?" ":"not ") << "set\n";

infile.close();

}