main function and entry point in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the main entry point of a Rust program.

Rust

fn [1]() {
    println!("Hello, world!");
}

Drag options to blanks, or click blank then click option'

Amain

Bstart

Crun

Dbegin

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name other than 'main' for the entry point.

Forgetting to define a function at all.

The main function is the entry point of every Rust program.

2fill in blank

medium

Complete the code to print a message inside the main function.

Rust

fn main() {
    [1]!("Welcome to Rust!");
}

Drag options to blanks, or click blank then click option'

Aecho

Bprintln

Cprint

Dwrite

Attempts:

3 left

💡 Hint

Common Mistakes

Using print which does not add a newline.

Using functions that do not exist in Rust.

The println! macro prints text to the console with a newline.

3fill in blank

hard

Fix the error in the main function declaration.

Rust

fn [1](args: Vec<String>) {
    println!("Arguments count: {}", args.len());
}

Drag options to blanks, or click blank then click option'

Astart

Brun

Centry

Dmain

Attempts:

3 left

💡 Hint

Common Mistakes

Adding parameters to the main function.

Using a different function name for the entry point.

The Rust entry point main function cannot have parameters like args.

4fill in blank

hard

Fill both blanks to create a main function that returns a result.

Rust

fn main() -> [1] {
    println!("Program started");
    [2]
}

Drag options to blanks, or click blank then click option'

AResult<(), Box<dyn std::error::Error>>

Bi32

COk(())

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Returning an integer when a Result is expected.

Not returning anything from a function with a return type.

Rust's main can return a Result to handle errors gracefully. Returning Ok(()) means success.

5fill in blank

hard

Fill the blanks to create a main function that reads command line arguments and prints the first one.

Rust

fn main() {
    let args: Vec<String> = std::env::[1]().collect();
    if args.len() > 1 {
        println!("First argument: {}", args[[2]]);
    } else {
        println!("No arguments provided.");
    }
}

Drag options to blanks, or click blank then click option'

Aargs

B1

C0

Denv

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong function to get arguments.

Accessing the wrong index for the first user argument.

std::env::args() returns an iterator over command line arguments. The first argument is at index 1 because index 0 is the program name.