C++ putchar() function except the output goes to a designated output file?

Question

I'm working on an exercise in my C++ textbook that asks me to create a program to "encrypt" a given input text file and print the encrypted text to an output file. The "encryption" is fairly simplistic and just consist of moving every alphabetical character two places down the list in the alphabet. So, a would be encrypted as c, e would be encrypted as g, etc.

My approach has been to assign a declared integer object "converter" to the value "input +2" where "input" is the character read from the file. I use a switch statement to ensure that grammatical characters like period, comma, etc, are copied with no transformation.

I am having the damndest time trying to figure out how I can then print "converter" as a character rather than an integer. It's not that I don't know how to use the putchar() function - it's that I can't get this function to write the output to my output text file rather than stream it to the standard output!

Does anybody know how to manipulate this function to print to an output file rather than standard output? Is there perhaps another function that I am not aware of which I should be using? Here is my code:

/******************************************************************************

Problem 5-18

*******************************************************************************/
#include <iostream>
#include <string>
#include <fstream>
#include <cmath>
#include <iomanip>

using namespace std;

int main()
{
    //Declare and Initialize Objects
    
    char input, output;
    int converter;
    string filename;
    ifstream fin;
    ofstream fout;
    
    //Collect Name of Input File
    
    cout << "Enter filename: \n" << endl;
    cin >> filename;
    
    //Open Input File and Check for Errors
    
    fin.open(filename);
    
    if(fin.fail())
    {
        cerr << "Error opening file " << filename << endl;
        exit(1);
    }
    
    //Open Output filename
    
    fout.open("Report.txt");
    
    //Read Input File and Transcribe to Code
    
    while(!fin.eof())
    {
        fin >> input;
        
        switch(input)
        {
            case ' ':
            fout << input;
            break;
            
            case '.':
            fout << input;
            break;
            
            case ',':
            fout << input;
            break;
            
            default:
            converter = (input + 2);
            fout << putchar(converter);
            break;
        }
        
        
    }

    return 0;

Your help would be greatly appreciated!

`while(!fin.eof())` [does not do what you think it does](https://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-i-e-while-stream-eof-cons). — Sam Varshavchik, Jan 27 '22 at 22:58

score 0 · Answer 1 · answered Jan 27 '22 at 22:48

Use fout << converter; instead of fout << putchar(converter);.

It's due to the fact that putchar is the function - that prints to the standard output - defined in the C library <stdio.h>. Whereas you are using object oriented C++ library . These are two different language even though C++ is mostly backward-compatible with C. The C language handles files very differently (mostly using FILE struct and pointers defined in the <stdio.h> library) as it lacks object oriented features present in C++.

If you wanted to use C-like way to accomplish the task, you would have to rewrite the entire source code.

C++ putchar() function except the output goes to a designated output file?

1 Answers1