如何使用数组接受命令行参数？

Question

So I'm trying to use cmd to take arguments while starting the program, but I keep running into issues from converting the variables from char to int, so they can be used with the rest of the program. Thanks for the help ahead of time.

int main(int argc, char* argv[]) {
    int n = 0, a = 0, b = 0, func = 0, choice = 0;
    double w;
    if(argc < 10)
    {
        cout << "The Program requires -f <Function> -a <Starting Point> -b <Ending Point> -m <Method> -n <Number of slices>" << endl;
        exit(0);
    }
    else
    {
        int func, a, b, choice, n;
        int i;
        for(int i = 1; i < argc - 1; i+=2)
        {
                if(argv[i] == "-f"){
                    func = *argv[i + 1];}
                else if(argv[i] == "-a"){
                    a = *argv[i + 1];}
                else if(argv[i] == "-b"){
                    b = *argv[i + 1];}
                else if(argv[i] == "-m"){
                    choice = *argv[i + 1];}
                else if(argv[i] == "-n"){
                    n = *argv[i + 1];}
                else {
                    cout << "Input is Invalid" << endl;
                    exit(0);}
                cout << argv[i] << endl;
        }
        w = (b-a)/double(n);
        next(n, a, b, w, func, choice);
    }
    return 0;
}

edit: So I have restructured my code to look like that above and it does compile, but I'm getting only the else statement. Such as when is start the program using a line like: ./a3 -f 5 -a 1 -b 10 -m 3 -n 100. I'm not sure why the program reverts to the else statement "input is Invalid" instead of the other if, if else statements.

Answer 1

Dude, you have to start with:

int n = 0, a = 0, b = 0, func = 0, choice = 0;

and then you have a character pointer to an integer type defined as

  char* func, a, b, choice, n;

I believe in the standard, pointer should point to their type and that is your problem.

Solution:

I guess you could use cast it to an char before you assign the ptrs..

Answer 2

you have problem with string comparing.

if(argv[i] == "-f")

don't check if argv[i] is equal to "-f" it check if the pointer value is the same as the pointer to the constants string "-f" with is wrong. you should use string compare methods like strcmp.

also is all flags require value why the loop is:

for(int i = 1; i < argc; i++)
    {
    if(i + 1 != argc)

because it pairs you can write it as:

for(int i = 1 ; i < argc - 1; i += 2)