Library

• <ofstream>: Output file stream that creates and writes information to files.
• <ifstream>: Input file stream that reads information from files.
• <fstream>: General file stream, with both ofstream and ifstream capabilities that allow it to create, read, and write information to files.

To perform file processing in C++, header files <iostream> and <fstream> must be includedin the C++ source file.

Example

PS: ofstream MyFile;, the class name is still ofstream for write or ifstream for read, not fstream(it is the name of library, not the class)

#include <iostream>
#include <fstream>
using namespace std;
int main()
{
    ofstream MyFile;
    if(MyFile.is_open()){
        MyFile.open("test.txt");
        MyFile << "Some text! \n";
    }else{
        cout << "open error!\n";
    }
    MyFile.close();
}

#include <iostream>
#include <fstream>
using namespace std;
int main()
{
    ifstream MyFile("file/test.txt");
    string line;
    while(getline(MyFile, line)){
        cout << line << endl;
    }
    MyFile.close();
}

constructor

constructor can replace open()

ofstream MyFile("test.txt");

file opening modes

MyFile.open("file.txt", ios::out | ios:: trunc)