Getting Started

Question 1

Does Rust require a Linker installed on your system?

Answer 1

Yes. C compilers usually come with the correct linker. Also, some common Rust packages depend on C code and will need a C compiler

Question 2

What is the command to update rust to the latest stable version?

Answer 2

rustup update stable

Question 3

Rustup installs local documentation. What is the command to open it?

Answer 3

rustup doc

This will open the documentation in your browser.

Question 4

What is the extension for Rust files?

Answer 4

*.rs

By convention, Rust filenames use snake case with underscores between words.

Question 5

What function runs first when a Rust program is executed?

Answer 5

main(), though there is a small Rust “runtime” which runs before this, then calls main() as the first function to execute. The body of main() must be surrounded by curly braces.

Question 6

What is the tool to format Rust code in the established style?

Answer 6

rustfmt

Question 7

Does Rust indent code with tabs or spaces?

Answer 7

The Rust convention is to indent with 4 spaces.

Question 8

What is println!() an example of?

Answer 8

A macro.

Question 9

What character ends an expression?

Answer 9

The semicolon (;) character indicates that an expression is over and the next one is ready to begin.

Question 10

How do you compile a Rust file using the Rust compiler?

Answer 10

Enter: rustc file_name.rs

Question 11

What is the output of the Rust compiler?

Answer 11

A binary executable.

Question 12

Rust is an ahead-of-time compiled language. What does this mean?

Answer 12

You can compile an executable and give it to someone else, and they can run it without having Rust installed.

Question 13

What is Rust’s build system and package manager called?

Answer 13

Cargo

Question 14

What is the name for libraries your code needs?

Answer 14

Dependencies

Question 15

What does the command “cargo new hello_world” do?

Answer 15

It initialises a new Rust executable package. It will create a directory called “hello_world”. In this directory it will create a Cargo.toml file and a src directory containing the file main.rs. It will also create a .gitignore file unless the –vcs switch is used to use another VCS or none at all.

Question 16

What does TOML stand for?

Answer 16

Tom’s Obvious, Minimal Language. It is Cargo’s configuration format.

Question 17

What is the [package] section of Cargo.toml?

Answer 17

[package] is a section heading indicating that the following statements are configuring a package.

Question 18

What are the 4 minimum pieces of information in Cargo.toml needed for Cargo to compile a package?

Answer 18

name, version, authors, edition

Question 19

Where does Cargo get your name and email information from?

Answer 19

Your environment

Question 20

What is the [dependencies] section of the Cargo.toml file?

Answer 20

It is the start of the section to list any of your project’s dependencies. In Rust, packages of code are referred to as crates.

Question 21

Where does Cargo expect to find an executable’s source files?

Answer 21

In the src directory.

Question 22

What type of files should go in a project’s top-level directory?

Answer 22

README files, license information, configuration files and anything else not related to your code.

Question 23

If you started a project that doesn’t use Cargo, how do you convert it to a project which does?

Answer 23

Move the project source code to a src directory, and create a Cargo.toml file in the top level directory.

Question 24

Running the command ‘cargo build’ causes Cargo to create the Cargo.lock file. What does this file do?

Answer 24

Cargo.lock is created in the top-level directory and keeps track of the exact version of project dependencies. You won’t ever need to change this file manually.

Question 25

What does running the command ‘cargo check’ do?

Answer 25

It checks your code to ensure it compiles, but doesn’t create an executable. It is often much faster than ‘cargo build’ because it doesn’t create the executable.

Question 26

What does the command: ‘cargo build –release’ do?

Answer 26

It build the executable with optimisations in the target/release folder. Optimisations make Rust code run faster but increase build time. It should always be used when benchmarking code’s running time.

Question 27

What are the 2 standard build profiles?

Answer 27

development and release

Question 28

How do you make the Cargo output less verbose?

Answer 28

Use the -q | –quiet option

Question 29

What is the Rust unit type?

Answer 29

The unit type is like an empty value and is signified with a set of empty parentheses: (). It is used when there is no other meaningful value that could be returned. A function without a return type eg main() returns the unit type.

Question 30

Who created Rust?

Answer 30

First appearing in 2010 out of a personal project started in 2006, Rust was designed by Graydon Hoare at Mozilla Research with contributions from Dave Herman, Brendan Eich, and others.

Question 31

In Rust, is if an expression or a statement?

Answer 31

In Rust, if is an expression, not a statement. An expression returns a value, but a statement does not. An if without an else will return the unit type.

Question 32

What does the ? operator do?

Answer 32

Where a function returns a Result, the ? operator will unpack an Ok value or propagate the Err value to the return type.

Question 33

What is the idiomatic way to return a value from a function?

Answer 33

Whilst Rust does have the return keyword to return a value from a function, the idiom is to omit the semicolon from the last expression to implicitly return that result.

Question 34

How do you separate flags meant for cargo from flags meant for the binary it will run?

Answer 34

Use a pair of dashes:

Cargo run -q — -n

Question 35

Where does cargo place downloaded source code?

Answer 35

Into the .cargo/registry/sec/ folder in your home directory.

Question 36

Where does cargo build the dependencies?

Answer 36

In the project’s target/debug/deps directory.

Question 37

How do you delete the target directory?

Answer 37

cargo clean will delete the target directories, including all the built dependencies. This can free up disk space for projects no being worked on.

Question 38

What is the purpose of a leading underscore in a variable name?

Answer 38

It suppresses compiler warnings that the variable is unused, which is useful during development.

Question 39

What are the Rust release channels

Answer 39

Stable, Beta and Nightly