CLI Arguments

CLI Arguments stands for Command Line Interface Arguments. CLI arguments describe the act of passing in arguments to a program when executing said program, just like executing a function and passing in the arguments to the function. In fact, many programs can be thought of as "functions" in the Linux world, where you pass in data to a function and get something from it in return.

Here is an example of CLI arguments in action:

use Core.print

def main(str[] args):
    for (idx, elem) in args:
        print($"args[{idx}] = {elem}\n");

Note how the signature of the main function has changed. The main function is allowed to have a parameter of type str[] or to have no parameter. All other cases will lead to an compile error.

This program will print different lines to the console, depending on how we execute it. If we execute the built program (for example the main binary) with this command:

./main

we will see this line being printed to the console:

args[0] = ./main

If we execute the program like so:

./main someargument somethingelse third-thing

we will se theese lines being printed to the console instead:

args[0] = ./main
args[1] = someargument
args[2] = somethingelse
args[3] = third-thing

As you can see, the first argument is always the command with which the program was executed with. If the built binary is in a subdirectory, for example, and you execute it with this command:

./somedirectory/main

you will see this line being printed to the console in this case:

args[0] = ./somedirectory/main

So, if you execute a program with the absolute path to said program, the first CLI argument will contain the command used to execute the program.