C++:Storing a text file - c++

Question

i wrote a simple program(C++) that take 20 numbers and sort them into ascending order.Now i want to save the actions in the program in a file like "num.txt" with . Can you explain me what changes should i do?
#include <iostream>
#include <iomanip>
#include <conio.h>
using namespace std;
int main() {
int x[21], s;
int j,i;
for (int i = 1; i < 21; i++)
{
cout << setw(11) << i << ": ";
cin >> x[i];
}
for (int i = 1; i < 21; i++)
{
for (int j = i+1; j < 21; j++)
{
if (x[j] < x[i])
{
s = x[j];
x[j] = x[i];
x[i] = s;
}
}
}
cout << endl;
for (int i = 1; i < 21; i++)
{
cout << i << ": ";
cout << x[i] << "\t";
if (i % 5 == 0)
{
cout << endl;
}
}
getch();
return 0;
}
i know it's simple but i just started since few days ago and i'm novice.

Answer 1

To output the numbers to a file you can use std::ofstream for the output stream and replace cout with the variable name you use for the stream.
std::ofstream outfile;
outfile.open("num.txt");
for (int i = 1; i < 21; i++)
{
outfile << i << ": ";
outfile << x[i] << "\t";
if (i % 5 == 0)
{
outfile << std::endl;
}
}
outfile.close();
You can also take it a step further and add input validation and use components from the Standard Library to handle most of what you are trying to accomplish. For instance instead of storing the numbers in an array I suggest using std::vector instead. You can also use std::sort to sort the data instead of implementing it yourself.
#include <vector> // vector
#include <fstream> // fstream
#include <algorithm> // sort
#include <iostream>
int main()
{
std::vector<int> numbers;
while(numbers.size() != 20)
{
int value;
if(!(std::cin >> value))
{
std::cout << "you must enter a number" << std::endl;
}
else
{
numbers.push_back(value);
}
}
// Do the sort. Pretty easy huh!
std::sort(numbers.begin(), numbers.end());
std::ofstream outfile;
outfile.open("num.txt");
if(outfile.is_open() == false)
{
std::cout << "Unable to open num.txt" << std::endl;
}
else
{
for(size_t i = 0; i < numbers.size(); i++)
{
outfile << i << ": ";
outfile << numbers[i] << "\t";
if (i % 5 == 0)
{
outfile << std::endl;
}
}
outfile.close();
}
}

Answer 2

Use this in your code
#include <fstream>
ofstream outputFile;
outputFile.open("outputfile.txt");
outputFile << value << endl;
outputFile.close();

Answer 3

One solution is to use ofstream (in "fstream.h", very similar to std::cout):
ofstream out("num.txt");
if (out.is_open() == false)
{
cout << "Error! Couldn't open file!" << endl;
}
else
{
out << "\n";
for (int i = 1; i < 21; i++)
{
out << i << ": ";
out << x[i] << "\t";
if (i % 5 == 0)
{
out << "\n";
}
}
out.close();
}

Answer 4

If you're running your program from the command line, type the following(when you run it) to forward the output to a file:
myApp > num.txt
you can also use the < switch to specify a file to get input from too
You can find more information here.

Answer 5

here is your code with all the changes
now you just need to copy paste (i have made a comment on line i added )
#include <iostream>
#include <iomanip>
#include <conio.h>
#include <fstream>//file stream
using namespace std;
int main() {
int x[21], s;
int j,i;
for (int i = 1; i < 21; i++)
{
cout << setw(11) << i << ": ";
cin >> x[i];
}
for (int i = 1; i < 21; i++)
{
for (int j = i+1; j < 21; j++)
{
if (x[j] < x[i])
{
s = x[j];
x[j] = x[i];
x[i] = s;
}
}
}
ofstream out; //output file stream
out.open("num.txt"); //opening (and creating output file named out
//cout << endl;
for (int i = 1; i < 21; i++)
{
//cout << i << ": ";
out << i << ": "; //printing in output file
// cout << x[i] << "\t";
out << x[i] << "\t"; //printing in output file
if (i % 5 == 0)
{
//cout << endl;
out << endl; //printing in output file
}
}
//getch();
out.close(); //closing output file
return 0;
}