C++ Opening a txt file using argc and argv

[Joon]

Homework Statement

I have a complete code that calculates distances between point 1(x1,y1,z1) and other points(from 2nd up to more than 100) and the nth point that results in minimum distance and the minimum distance between point 1 and nth point. The code is below.

The code is 100% correct, but it doesn't work when I run on Debugger. I think it is because the code has no access to the actual txt file. How do I pass the filename or the actual file as argv?

Thank you.

Homework Equations

The Attempt at a Solution

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cmath>
#include <limits>
using namespace std;

struct Point3d {
    double x, y, z;
};

ostream& operator << (ostream& os, const Point3d& p) {
    os << "(" << p.x << ", " << p.y << ", " << p.z << ")";
    return os;
}

istream& operator >> (istream& is, Point3d& p) {
    is >> p.x >> p.y >> p.z;
    return is;
}

double distance(const Point3d &a, const Point3d &b) {
    auto squared = pow(a.x - b.x, 2) +
        pow(a.y - b.y, 2) +
        pow(a.z - b.z, 2);
    return sqrt(squared);
}

int main(int argc, char **argv) {
    if (argc != 2) {
        cerr << "Exactly one argument expected, got " << argc << "\n";
        return 1;
    }
      ifstream inFile(argv[1]);
    if (!inFile.is_open()) {
        cerr << "error: failed to open '" << argv[1] << "'\n";
        return 1;
    }

    // discard the header line
    inFile.ignore(numeric_limits<streamsize>::max(), '\n');
  

    Point3d first_pt;
    if (!(inFile >> first_pt)) {  // read the first point
        cerr << "error: failed read of the first point\n";
        return 1;
    }

    bool other_points = false;
    double dist_min = numeric_limits<double>::max();
    Point3d closest, current;
    while (inFile >> current) {  // loop through the other points
        other_points = true;
        double dist = distance(first_pt, current);
        if (dist < dist_min) {
            dist_min = dist;
            closest = current;
        }
    }
    inFile.close();

    if (other_points) {
        cout << "closest point to " << first_pt <<
            " is " << closest << " [distance: " << dist_min << "]\n";
    }
    else {
        cout << "There was only one point in the file\n";
    }
    system("pause");

}

 

[Mark44]

Homework Statement

I have a complete code that calculates distances between point 1(x1,y1,z1) and other points(from 2nd up to more than 100) and the nth point that results in minimum distance and the minimum distance between point 1 and nth point. The code is below.

The code is 100% correct, but it doesn't work when I run on Debugger. I think it is because the code has no access to the actual txt file. How do I pass the filename or the actual file as argv?

Are you using Visual Studio? And are passing just the file name without its full path? If so, the debugger looks for input files in the same directory as the source code. If the file isn't there, the ifstream constructor will fail. If you run you program from a command prompt window (i.e., outside of the debugger) the file will need to be in the same directory as your executable.
As an alternative, you could pass the full path of the file as one of the arguments in the argv vector.

Thank you.

Homework Equations

The Attempt at a Solution

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cmath>
#include <limits>
using namespace std;

struct Point3d {
    double x, y, z;
};

ostream& operator << (ostream& os, const Point3d& p) {
    os << "(" << p.x << ", " << p.y << ", " << p.z << ")";
    return os;
}

istream& operator >> (istream& is, Point3d& p) {
    is >> p.x >> p.y >> p.z;
    return is;
}

double distance(const Point3d &a, const Point3d &b) {
    auto squared = pow(a.x - b.x, 2) +
        pow(a.y - b.y, 2) +
        pow(a.z - b.z, 2);
    return sqrt(squared);
}

int main(int argc, char **argv) {
    if (argc != 2) {
        cerr << "Exactly one argument expected, got " << argc << "\n";
        return 1;
    }
     ifstream inFile(argv[1]);
    if (!inFile.is_open()) {
        cerr << "error: failed to open '" << argv[1] << "'\n";
        return 1;
    }

    // discard the header line
    inFile.ignore(numeric_limits<streamsize>::max(), '\n');
 

    Point3d first_pt;
    if (!(inFile >> first_pt)) {  // read the first point
        cerr << "error: failed read of the first point\n";
        return 1;
    }

    bool other_points = false;
    double dist_min = numeric_limits<double>::max();
    Point3d closest, current;
    while (inFile >> current) {  // loop through the other points
        other_points = true;
        double dist = distance(first_pt, current);
        if (dist < dist_min) {
            dist_min = dist;
            closest = current;
        }
    }
    inFile.close();

    if (other_points) {
        cout << "closest point to " << first_pt <<
            " is " << closest << " [distance: " << dist_min << "]\n";
    }
    else {
        cout << "There was only one point in the file\n";
    }
    system("pause");

}

 

[Joon]

Thank you, that's solved the problem.
I saw you've replied to my another approach to this problem, I think that one could be a lot simpler than the code written here. Could you have a look at the other one?