I wrote a simple program to calculate the hypotenuse length of a triangle. My question is, how can I give variables "side1" and "side2" values while executing the main function from the terminal? Code below:

#include <iostream>
#include <cmath>

int main(int side1, int side2) {

    int c2 = (pow(side1, 2))   (pow(side2, 2));
    
    std::cout << sqrt(c2) << std::endl;

    return 0;
}

The function compiles without error, so normally I would execute the function from terminal using "./main.exe", but is there a way to pass values to variables side1 & side2 while executing? (ex: ./main.exe "5" "5"). I don't want to go the std::cin route because I already know how to do that. For the same reason, I don't want to assign values to the variables within the function (ex: int side1 {5};).

I don't know if this is possible to do or not, but sites like Leetcode have their functions set up this way, and I have no clue how they input values for test cases.

CodePudding user response：

The signature of the main function can be

int main(int argc, char *argv[])

so you get an argument count and a "string" array. Note that argv[0] is the executable name, so side1 would be argv[1] and side2 is argv[2].

CodePudding user response：

You need to get the command line argument strings and convert them to integers. Alas, this does increase the complexity of your program a little if you want to catch errors.

#include <cmath>
#include <iostream>
#include <string>

int help()
{
  std::cerr << 
    "usage:\n"
    "  a.exe SIDE1 SIDE2\n\n"
    "Where SIDE1 and SIDE2 are integers.\n";
  return 1;
}

int main( int argc, char ** argv )
{
  int side1, side2;
  if (argc != 3) return help();
  try {
    side1 = std::stoi( argv[1] );
    side2 = std::stoi( argv[2] );
  }
  catch (...)
  {
    return help();
  }

  int c2 = side1*side1   side2*side2;
  std::cout << std::sqrt( c2 ) << "\n";
}

You could leave a lot of that error checking out and just let the program crash without explanation, but IMHO it is always worth adding a usage clause to your program to help users (including yourself two months from now) figure out how to run the program.

CodePudding user response：

As noted previously, your function signature for main is incorrect. The correct signature when you want to access command line arguments is:

int main(int argc, char **argv)

argc is the count of arguments, the first being the name of the executable. argv is an array of those arguments. We can:

• Check that the right number of arguments have been passed in, and print an error if not.
• Use std::atoi to convert those inputs into ints, at which point we can use them as we please.

#include <iostream>
#include <cstdlib>

int main(int argc, char **argv) {
  if (argc != 3) {
    std::cerr << "Usage: "<< argv[0] 
              << " val1 val2" << std::endl;
    return 1;
  }

  auto v1 = std::atoi(argv[1]);
  auto v2 = std::atoi(argv[2]);

  std::cout << v1 << ", " << v2 << std::endl;

  return 0;
}

CodePudding user response：

Your main signature is wrong. See https://en.cppreference.com/w/cpp/language/main_function.