Question

How do I add additional command line arguments in C++? I am working on a programming assignment that has the user input a file into the command line and then they have the option to also add a series of other arguments to the command line. I know how to accept the text file from the command line by using:

int main(int argc, char *argv[]) { /.../ }

Then filename(argv[1]) would be the text file that they put into the command line. The part I am confused how to do is the additional command line arguments and the syntax on how to use it. It is asking to add:

-LL=t which The line length should be set to t. The value of t must be a positive integer greater than 0.Default value of t = 20.

-IN=n which The indentation should be set to n. The value of n must be a positive integer greater than 0.Default value of n =5.

and there are a few more which I should be able to do once I understand how to add this option to add to the command line. Not sure how to add these arguments so they'll be accepted to the command line or how to set their default values. Also, do the dashes '-' make a difference in handling the additional commands?

Would I have to add something like ", int -LL=t)* or something like that after argv[], where I declared the main function?

Hopefully that made sense and I appreciate any help to understand how to do this.

Answer 1

As far as I can understand your question, below are my take on this:

Pro tip: Try to look into this more simply. These command-line arguments can be very complex if handled in the wrong way.

1. We take the command line arguments - only two things matter - number of arguments and arguments itself.
2. For simplicity, you can consider, the arguments which we get is simply an array of string and nothing else( In reality it's not a simple array of string, please keep this in mind).
3. So providing -argument or argument doesn't matter in terms of arguments handling and conditional checking. These "-" are often used for visual benefits in simple terms.
4. Also, for giving any argument any default value, simply treat the argv as a simple array of strings or integers and you will be good to go.

Please look at the comments of the program for more clarity.

#include<bits/stdc++.h>
using namespace std;

int main(int argc, char** argv)
{
    cout << "Total number of entered arguments: " << argc << "\n"; // argc will hold the number of command line arguments entered.

    /*
     Now for the default value which we want to have a default value

     Lets us suppose a, we are running the program as
     "multiple_command_line_arguments hey 1 -t a.txt".
     Here, for the third argument we want to have a default value as 5
    */
    int thirdValue = 5; // Setting the default value
    for (int i = 0; i < argc; ++i)  // Now here, we are looping through the entire given arguments.
        {
                                    // Our given arguments will start from index-1 and will go till index (argc-1)
            if(i==2 && argv[i]>0)   // argv[0] will have the name of the file
                cout << thirdValue << "\n";
            else
                cout << argv[i] << "\n";
        }

    return 0;
}

Sample Input-Output/Code-run:

Input: multiple_command_line_arguments hey 1 -t a.txt

Input: multiple_command_line_arguments hey 10 -t a.txt

Please let me know in the comments in case of any confusion. Also, please upvote if you like.