fstream c++ code example

Example 1: c++ files

// basic file operations
#include <iostream>
#include <fstream>
using namespace std;

int main () {
  ofstream myfile;
  myfile.open ("example.txt");
  myfile << "Writing this to a file.\n";
  myfile.close();
  return 0;
}

Example 2: fstream in c++

#include<fstream>
int main()
{
  fstream file; 
  /*if we use fstream then we need to specify at least one 
  parameter mode like ios::out or ios::in else the file will not open */  
  file.open("filename.txt", ios::out|ios::in);
  /*all work with file*/
  file.close();
  return 0;
}

Example 3: opening file in c++

/ fstream::open / fstream::close
#include <fstream>      // std::fstream

int main () {

  std::fstream fs;
  fs.open ("test.txt", std::fstream::in | std::fstream::out | std::fstream::app);

  fs << " more lorem ipsum";

  fs.close();

  return 0;
}

Example 4: How to read a file in in C++

// io/read-file-sum.cpp - Read integers from file and print sum.
// Fred Swartz 2003-08-20

#include <iostream>
#include <iomanip>
#include <fstream>
using namespace std;

int main() {
    int sum = 0;
    int x;
    ifstream inFile;
    
    inFile.open("test.txt");
    if (!inFile) {
        cout << "Unable to open file";
        exit(1); // terminate with error
    }
    
    while (inFile >> x) {
        sum = sum + x;
    }
    
    inFile.close();
    cout << "Sum = " << sum << endl; 
    return 0;
}

Example 5: read text from file c++

#include<iostream>
#include<fstream>

using namespace std;

int main() {

 ifstream myReadFile;
 myReadFile.open("text.txt");
 char output[100];
 if (myReadFile.is_open()) {
 while (!myReadFile.eof()) {


    myReadFile >> output;
    cout<<output;


 }
}
myReadFile.close();
return 0;
}

Example 6: create file c++

// using ofstream constructors.
#include <iostream>
#include <fstream>  

std::ofstream outfile ("test.txt");

outfile << "my text here!" << std::endl;

outfile.close();