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Rust provides two methods for handling unrecoverable errors unwrap and expect, they can be used on both Result and Option types, they will trigger a panic! if the value is an Err(E) variant for Result<T, E> or a None variant for Option<T>

These methods extract the inner value but terminate the program if the operation fails. They are particularly useful for quick prototyping or situations where an error is truly unrecoverable.

In this challenge, you will interact with file operations to demonstrate the use of unwrap and expect. Instead of directly working with Result or Option, you will use standard library functions that return these types and handle their results using unwrap and expect.

Your Task

Implement the following functions:

  1. read_file_to_string: This function takes a file path as input, attempts to read its contents, and returns the contents as a String. Use expect to handle any file I/O errors with a custom error message of exactly Failed to read file: <path>.
  2. get_env_variable: This function retrieves the value of an environment variable by name. Use unwrap to panic if the variable is not set.

Notes

  • expect provides a way to add context to your panics, which can help with debugging.
  • unwrap is more concise but less descriptive when errors occur.

Hints

If you're stuck, here are some hints to help you solve the challenge:

<details> <summary>Click here to reveal hints</summary>
  • Use std::fs::read_to_string(path) to read the contents of a file. It returns a Result<String, std::io::Error>.
  • Use std::env::var(key) to retrieve an environment variable. It returns a Result<String, std::env::VarError>.
  • Use .expect() to add a custom error message when handling a Result.
  • Use .unwrap() for a quick, less descriptive error handling method.
</details>
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pub fn read_file_to_string(path: &str) -> String {
    // 1. Implement the function
}


pub fn get_env_variable(key: &str) -> String {
    // 2. Implement the function
}


/// Example usage
pub fn main() {
    // Example 1: Using read_file_to_string
    let file_content = read_file_to_string("example.txt");
    println!("File content: {}", file_content);


    // Example 2: Using get_env_variable
    std::env::set_var("EXAMPLE_KEY", "example_value");
    let value = get_env_variable("EXAMPLE_KEY");
    println!("Environment variable value: {}", value);


    // Must panic
    read_file_to_string("nonexistent.txt");
    get_env_variable("MISSING_KEY");
}