C++/File/File End EOF

ios::ate places the get-position pointer at the file end, enable tellg() to return the size of the file

<source lang="cpp">

1. include <fstream>
2. include <iostream>
3. include <cstdlib>

using namespace std; void print_error(const char* p1, const char* p2 = 0); int main(int argc, char* argv[]) {

    if (3 != argc)
       print_error("usage: function input_file output_file");
    ifstream in(argv[1], ios::binary | ios::ate);                     
    if (!in) print_error("cannot open input file", argv[1]);
    long N = in.tellg();                                              
    char buffer[N];                                                   
    in.seekg(ios::beg);                                               
    ofstream out(argv[2], ios::binary);                               
    if (!out) print_error("cannot open output file", argv[2]);
    in.read(buffer, N);                                               
    out.write(buffer, N);                                             
    if (!in.good()) {
       print_error("something strange happened");
       exit(1);
    }
    in.close();
    out.close();
    return 0;

} void print_error(const char* p1, const char* p2) {

    if (p2) 
       cerr << p1 << " " << p2 << endl;
    else 
       cerr << p1 << endl;
    exit(1);

}

 </source>

Use eof() to read and display a text file.

<source lang="cpp">

1. include <iostream>
2. include <fstream>

using namespace std; int main(int argc, char *argv[]) {

 char ch;
 ifstream fin("text.txt");
 if(!fin) {
   cout << "Cannot open file.\n";
   return 1;
 }
 do {
   fin.get(ch);
   if(!fin.eof() && (fin.fail() || fin.bad())) {
     cout << "Input Error\n";
     fin.close();
     return 1;
   }
   if(!fin.eof()) cout << ch;
 } while(!fin.eof());
 fin.clear();
 fin.close();
 if(!fin.good()) {
   cout << "Error closing file.";
   return 1;
 }
 return 0;

}

 </source>

While it is not the end of a file, output file line by line

<source lang="cpp">

1. include <iostream>
2. include <fstream>

using namespace std; int main () {

char buffer[256];
ifstream myfile ("test.txt");
while (! myfile.eof() )
{
  myfile.getline (buffer,100);
  cout << buffer << endl;
}
return 0;

}

 </source>