C ++程序不会打印命令行参数

Question

I have decided to get back into programming (specifically C++) and to that end I have started working on a command-line parser. The goal is, eventually, to turn it into a simple class that I can import in some future projects.

This test program is simply supposed to list the number of arguments it received, then print them out, one per line, then exit.

Here is my code:

#include <iostream>
#include <cstdlib>

using namespace std;

int main(int argc, char* argv[]){
    cout << "Es gibt " << argc << " Argumente." << endl;
    for(int i=0; i << argc; i++){
        cout << "Argument " << i << ": " << argv[i] << endl;
    }
    return 0;
}

Here is what happens in the terminal:

[user@dx4320 cmdline-parser]$ g++ cmdline-parser-test.cpp -o parsetest
[user@dx4320 cmdline-parser]$ ./parsetest eins zwei
Es gibt 3 Argumente.
[user@dx4320 cmdline-parser]$ 

Why doesn't it print the arguments as it is supposed to? It clearly recognizes the arguments, so what is the problem? I'm sure I am missing something obvious here.

Answer 1

You have the wrong operator, you need:

for(int i=0; i < argc; i++){
   // only one ^ is correct here

otherwise you'd have the operator << (aka "left shift") and as a result, the expression i << argc (where i is initially 0 ) always evaluates to false and the loop's body is never executed.