4.2. String[] args

When a user launches a program using a shell command (i.e., when they type the command into the prompt that appears in their terminal emulator), any command-line arguments that the user includes after the program name are passed into the program. How do they get in? In Java, they are placed into an array of String objects that can be referred to using the main method’s args parameter.

The main method for a Java program.

public static void main(String[] args) {
    ...
} // main

This is a fairly common approach. Something very similar happens when command-line arguments are supplied to programs written in C, C++, and several other programming languages. The Python programming doesn’t use main as a method or function name like the other languages mentioned so far do; however, it does place the command-line arguments into a Python list that is accessible using Python’s sys.argv variable.

The function main for a C or C++ program.

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

The special name __main__ for a Python program.

if __name__ == '__main__':
    args: list = sys.argv
    ...