How to Write to a Text File from a C++ Program - Article on SQLNetHub

How to Write to a Text File from a C++ Program

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Writing to a text file from a C++ Program is very easy. In this example, which is part of my online course on Udemy titled “The Philosophy and Fundamentals of Computer Programming“, I will show you step by step, how to write to a text file from a sample C++ program that generates an array of 10 strings, and then it writes these values into a text file.

Note: In this example I’m using the c:\demosdirectory for exporting my file into.

The process of writing to a text file from a C++ program has five main steps in your code:

  1. Include the proper libraries
  2. Decide the data to be written into the file
  3. Open (create) the new file for writing
  4. Write the data
  5. Close the file

 

Include the proper libraries

The libraries to be included in the program are the below:

#include <iostream>
#include <string>
#include <fstream>

 

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Decide the data to be written into the file

This is something that is totally up to to you. In this example, I’m writing to the file, an array of 10 strings:

//define array of strings
string vehiclesList[10] = { "value0", "value1", "value2","value3", "value4", "value5","value6", "value7","value8", "value9" };

 

Open (create) the new file for writing

In this example, I’m writing into the file c:\demos\CPlusPlusSampleFile.txt, therefore, that is the file I’m opening/creating for writing:

//open file for writing
ofstream fw("c:\\demos\\CPlusPlusSampleFile.txt", std::ofstream::out);

 

Write the data

Prior to writing the data, first I’m checking if the file is actually open and ready for writing, then I proceed and write the data using the file handler and the bitwise left shift operators:

//check if file was successfully opened for writing
if (fw.is_open())
{
  //store array contents to text file
  for (int i = 0; i < arraySize; i++) {
    fw << vehiclesList[i] << "\n";
  }
  fw.close();
}
else cout << "Problem with opening file";

 

Close the file

Even though I closed the file after writing in the previous step, I also wanted to talk about this as a separate step, because I would like to stress out the importance of closing the file. This is very important, because if you don’t close the file, the operation will not be completed. Therefore, after writing all the data in the file, make sure that you close the file with the below command (based on my example):

//close the file after the writing operation is completed
fw.close();

 

Sample code for writing to a text file from a C++ program

Below, you can find the full sample code I prepared, for showcasing a simple example of writing an array of 10 strings into a text file.

// Sample C++ App that Writes Sample Data to Text File
//
// Created for the online course on Udemy: "The Philosophy and Fundamentals 
// of Computer Programming"
//
// Course URL: 
// https://www.udemy.com/course/philosophy-fundamentals-computer-programming/ 
//
// Author/Instructor: Artemakis Artemiou
//
// Disclaimer: This source code which is part of the online course on Udemy "The Philosophy and 
// Fundamentals of Computer Programming", is intended to be used only for demo purposes. Do not 
// use it for Production systems as it is simplified for demo purposes.
//
#include <iostream>
#include <string>
#include <fstream>

using namespace std;

int main()
{

  //define array of strings
  string vehiclesList[10] = { "value0", "value1", "value2","value3", "value4", "value5","value6", "value7","value8", "value9" };

  //get array size
  int arraySize = *(&vehiclesList + 1) - vehiclesList;

  //exception handling
  try {

    cout << "\nWriting  array contents to file...";

    //open file for writing
    ofstream fw("c:\\demos\\CPlusPlusSampleFile.txt", std::ofstream::out);

    //check if file was successfully opened for writing
    if (fw.is_open())
    {
      //store array contents to text file
      for (int i = 0; i < arraySize; i++) {
        fw << vehiclesList[i] << "\n";
      }
      fw.close();
    }
    else cout << "Problem with opening file";

  }
  catch (const char* msg) {
    cerr << msg << endl;
  }

  cout << "\nDone!";
  cout << "\nPress any key to exit...";
  getchar();

}

 

Watch the video tutorial: How to Write to a Text File Using C++

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