Question

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C String — Using Equality Operator == for comparing two strings for equality

Basic question here. I’m compiling this program in g++ and running it with a single -r argument, (./a.out -r) however it does not output the specified cout statement below. Is there anything wrong with this code?

#include <string>
using namespace std;

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

    if (argv[1] == "-r" ) {
        cout << "First arg is -r" << endl;
    }

    return 0;
}  

Answer 1

You cannot compare string literals using ==, because what that does is compare pointers (i.e., memory addresses, which in this case are always going to be different).

Use strcmp or compare std::string objects instead:

if (strcmp(argv[1], "-r") == 0) { ... }

or

if (std::string(argv[1]) == "-r") { ... }