Problems with processing command-line arguments.

[Torin]

I'm a beginner to C++ and I'm trying to use if statements in a basic program to find out what command-line arguments were passed with the program. I have this:

#include <iostream>
#include <cstring>

using namespace std;

//void basicHelp();
//void detailedHelp();

int main(int argc, char** argv)
{
	if (argc < 2)
	{
		//cout << "\n\nPlease enter a valid option. Usage of this tool is as follows:";
		//basicHelp();
		cout << "\nYou used no parameters.\n";
		return 0;
	}
	if (argv[1] == (char*)"-h")
	{
		if (argv[2] == (char*)"-m")
		{
			//detailedHelp();
			cout << "\nYou used the parameters -h and -m.\n";
			return 0;
		}
		//basicHelp();
		cout << "\nYou only used the parameter -h.\n";
		return 0;
	}
	return 0;
}

All looked fine to me. The point was that if there were no additional arguments passed, "You used no parameters" would appear, and the other messages would appear if I used "-h", or if I used both "-h" and "-m" (in that order). But no, I get this:

main@bennun-ubuntu:~/Documents$ ./blah

You used no parameters.
main@bennun-ubuntu:~/Documents$ ./blah -h
main@bennun-ubuntu:~/Documents$ ./blah -h -m
main@bennun-ubuntu:~/Documents$

It doesn't see the other two parameters as "-h" and "-m". How can I make it do this? Is it a problem involving typecasting or something? I'm utterly confused.

Thanks in advance.

[Peter87]

Don't use type casting unless you know exactly what you are doing. It looks like you have used the cast here to get rid of a warning. The compiler tried to tell you something was wrong but you didn't listen. The problem is that you can't compare c strings with ==, because that will just compare the pointers. To compare two c strings you use std::strcmp instead.

[Torin]

Thanks very much for your reply. As I'm such a noob at C++, I was using typecasting so that I could make a comparison between two variables of the same type, but I didn't realise it was just comparing the pointers! I had no idea of strcmp's existence, and it has solved the problem. Thanks very much.

Here's the working code (working as far as I want it to currently) for anybody who's interested:

#include <iostream>
#include <cstring>

using namespace std;

//void basicHelp();
//void detailedHelp();

int main(int argc, char** argv)
{
	if (argc < 2)
	{
		//cout << "\n\nPlease enter a valid option. Usage of this tool is as follows:";
		//basicHelp();
		cout << "\nYou used no parameters.\n";
		return 0;
	}
	if (strcmp(argv[1],"-h") == 0)
	{
		if (argc >= 3)
		{
			if (strcmp(argv[2],"-m") == 0)
			{
				cout << "\nYou used -h and -m.\n";
				return 0;
			}
		}
		cout << "\nYou only used -h.\n";
	}
	return 0;
}

[Aramil of Elixia]

you can use command-line args in unix?

[Peter87]

@Aramil of Elixia, of course you can.

[Aramil of Elixia]

i didn't no that i thought you couldn't because its terminal

[Peter87]

Aramil of Elixia: Do you know what a terminal is? Terminals use a command-line interface so it makes very much sense to be able to pass command-line arguments from it.

[Aramil of Elixia]

i didnt know that thank you that is actually really helpful