Table of contents📚
Commant line arguments💬
What are command line arguments ❓
Commant line arguments are the keywords after the program name when you start it from a terminal.
Here, we start cow-translator
Here we start the program with two command line arguments.
--bonjour
Arguments are separated by a space.
The env module
To access command line arguments from a rust program, we need to import the env module.
use std::env;
The env module allows us to access environment variables.
Storing arguments in a vector
To store the arguments, we will use a String vector, to get the arguments we use the args method.
let mut args: Vec<String> = env::args().collect();
We use the collect method to store the arguments in a vector because args() returns an iterator. The collect method will convert the iterator into a vector.
Now let’s see what our vector looks like.
let mut args: Vec<String> = env::args().collect();
println!("{:?}", args);
$ cargo run
["myProgram"]
We have the program name in the vector because it is always the 0th element.
We can remove it with the remove(0) method.
let mut args: Vec<String> = env::args().collect();
args.remove(0);
println!("{:?}", args);
$ cargo run
[]
We have an empty vector because we didn’t pass any argument.
To pass arguments whan we use the cargo run command, we need to pass the arguments as arguments to the cargo run command after --
$ cargo run -- hello
["hello"]
We can now see that hello is in the arguments vector.
Exemple
We will now create a simple program that says hello {name} and name is the first argument.
use std::env;
fn main(){
let mut args: Vec<String> = env::args().collect();
args.remove(0);
println!("Hello {}", args[0]);
}
$ cargo run -- Skwal
Hello Skwal