CODEWITHSUNDEEP
c++parameters
Yetoo
Yetoo

Reputation: 47

Comparing an Argument with an Integer in C++

I'm playing around with command line arguments and I've been trying to have a comparison between the argument number and the input. So if someone input 1 then the output would be "The difficulty level is 1". 

#include <iostream>
#include <cstring>
using namespace std;
int main(ijnt argc, char* argv[])
{
int a; 
if (argc[1] == '1')
    {
    cout << "The difficulty level is " << argv[1] << endl;
    return 1;
    }
}

I made the comparing 1 a char but I get the error "ISO C++ forbids comparison between pointer and integer [-fpermissive]" and says that the error is 

if (argv[1] == '1')

How do I get the 1 that is getting compared to, to be accepted as a char?

Upvotes: 1

Views: 565

Answers (3)

Andreas DM
Andreas DM

Reputation: 10998

I think what you want is if (*argv[1] == '1')

Upvotes: 1

Galik
Galik

Reputation: 48615

The command line arguments are character arrays and so you need to use something like std::strcmp() to compare them like this:

int main(int argc, char* argv[])
{
    // check argument exists ...

    if(!std::strcmp(argv[1], "1")) // 0 when equal
    {
        // they are the same here
    }

    // ...
}

It may be simpler to just create a `std::string out of the arg

    if(std::string(argv[1]) == "1")
    {
        // they are the same here
    }

In all cases make sure you check whether or not the argument is present:

int main(int argc, char* argv[])
{
    if(!argv[1]) // argument not present (null terminated array)
    {
         std::cerr << "Expected an argument." << std::endl;
         return EXIT_FAILURE;
    }

    // process arg here

    // ...
}

Upvotes: 0

WhiZTiM
WhiZTiM

Reputation: 21576

argv is an array of character array...

So, use strcmp and compare, or better still, convert it to an std::string and compare... But also make sure that argc is greater than 1. Example:

#include <iostream>
#include <cstring>
using namespace std;
int main(int argc, char* argv[])
{
int a; 
if (argc > 1 && strcmp(argv[1], "1") == 0)
    {
    cout << "The difficulty level is " << argv[1] << endl;
    return 1;
    }
}

or

#include <iostream>
#include <string>
using namespace std;
int main(int argc, char* argv[])
{
int a; 
if (argc > 1 && string(argv[1]) == "1")
    {
    cout << "The difficulty level is " << argv[1] << endl;
    return 1;
    }
}

Upvotes: 1

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