I'm trying to make a program that reads input from a file (it is named grades.txt) and make an output of (image attached)

.

Apparently, I'm converting strings to char arrays and my program's output quite unexpected (image attached) I have checked twice, the IDE doesn't show any errors as well.

I'm using this as the source code.

#pragma warning(disable:4996)
#include <fstream>
#include <string>
#include <iostream>
using namespace std;

//Author: Hidden for privacy

const int MAXNAME = 20;

int main()
{
    ifstream inData;
    inData.open("grades.txt");
    string rawInputString;

    char name[MAXNAME   1]; // holds student name 
    float average;          // holds student average

    inData.get(name, MAXNAME   1);
    while (inData)
    {
        bool firstSpace = false;
        bool secondSpace = false;
        char converter[23];
            getline(inData, rawInputString, '\n');
            strcpy(converter, rawInputString.c_str());
            for (int a = 0; a <= 22; a  ) {
                if (converter[a] != ' ') {
                    cout << converter[a];
                }
                if (converter[a] == ' ') {
                    if (!firstSpace) {
                        firstSpace = true;
                        continue;
                    }
                    if (!secondSpace) {
                        secondSpace = true;
                        continue;
                    }
                }
                if (firstSpace) {
                    cout << converter[a];
                    if (secondSpace) {
                        cout << converter[a];
                    }
                }
            }
    }
    inData.close();
    return 0;
}

Here is the grades.txt file:

Adara Starr          94
David Starr          91
Sophia Starr         94
Maria Starr          91
Danielle DeFino      94
Dominic DeFino       98
McKenna DeFino       92
Taylor McIntire      99
Torrie McIntire      91
Emily Garrett        97
Lauren Garrett       92
Marlene Starr        83
Donald DeFino        73

What I've tried: As seen in the source code, I tried to make the program print the output char by char. But apparently, the first few characters printed are not even in the file where the program is taking input from. I know that float average and char array name are uninitiated, but it doesn't affect the rest of the code (too much), so I'm just leaving those there. I tried reading the fstream library to maybe figure out if this was something caused by the ifstream, but that doesn't seem to be the case either.

CodePudding user response：

There are a few different problems in your code, but the main ones is that:

• You start with inData.get(name, MAXNAME 1) which reads only a part of the first line
• You iterate over the whole array no matter its string length
• The character array converter is just too small to fit a full line including the null-terminator

Among the other problems is that you read from the input file before checking its status; You use while (inData) which is not correct; You use a C-style character array when there's no need; And you forget to print a newline.

There are also better ways to handle the input and output, like using an input string stream to parse out the fields, and use standard I/O manipulators for your output.

If we put it all together I would recommend something like this instead:

#include <iostream>
#include <sstream>
#include <iomanip>
#include <fstream>

int main()
{
    std::ifstream infile("grades.txt");

    std::string inputline;

    // Read line by line from the input, includes error checking
    // Also includes checking if the file was opened or not
    while (std::getline(infile, inputline))
    {
        // An input stream to parse out the data we need
        std::istringstream parser(inputline);

        std::string firstname;
        std::string lastname;
        int         value;

        parser >> firstname >> lastname >> value;

        // Just construct a simple string of the name
        // To simplify "pretty" output
        std::string fullname = firstname   ' '   lastname;

        // And finally the output with the name in one column and the value in another        
        std::cout << std::left << std::setw(20) << fullname << value << '\n';
    }
}