Code shared from the Rust Playground

playground.rs

use std::env;

fn env_vars() {
    // Iterate over all environment variables.
    for (key, value) in env::vars() {
        println!("{}: {}", key, value);
    }

    // You can also filter the environment variables.
    println!("\nFiltered environment variables:");
    for (key, value) in env::vars().filter(|(key, _)| key.starts_with("PATH")) {
        println!("{}: {}", key, value);
    }

    // Get a specific environment variable.
    if let Ok(path) = env::var("PATH") {
        println!("\nPATH: {}", path);
    } else {
        println!("\nPATH environment variable not found.");
    }

    // Get an environment variable, handle missing value gracefully.
    let user = env::var("USER").unwrap_or_else(|_| String::from("unknown"));
    println!("\nUser: {}", user);

    // Using env::vars_os() to get os specific strings.
    println!("\nOS Specific environment variables:");
    for (key_os, value_os) in env::vars_os() {
        if let (Ok(key_str), Ok(value_str)) = (key_os.into_string(), value_os.into_string()) {
            println!("{}: {}", key_str, value_str);
        } else {
            println!("Non-UTF8 env var");
        }
    }

    // Using env::var_os for os specific strings
        if let Some(path_os) = env::var_os("PATH") {
            if let Ok(path_string) = path_os.into_string() {
                println!("\nOS PATH: {}", path_string);
            } else {
                println!("\nOS PATH env var is not valid UTF-8");
            }

        } else {
            println!("\nOS PATH env var not found");
        }
}


use std::fs;
use std::io;
use std::path::Path;

fn cat_cargo_toml() -> Result<(), io::Error> {
    let path = Path::new("Cargo.toml"); // Define the path to Cargo.toml

    if !path.exists() {
        eprintln!("Error: Cargo.toml not found.");
        return Err(io::Error::new(io::ErrorKind::NotFound, "Cargo.toml not found"));
    }

    let contents = fs::read_to_string(path)?; // Read the file's content

    println!("{}", contents); // Print the content to standard output

    Ok(())
}

fn main() {
    env_vars();
    if let Err(err) = cat_cargo_toml() {
        eprintln!("Error: {}", err);
        //Handle error accordingly, exit or other logic.
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs::File;
    use std::io::Write;
    use tempfile::tempdir;

    #[test]
    fn test_cat_cargo_toml_success() {
        let dir = tempdir().unwrap();
        let file_path = dir.path().join("Cargo.toml");
        let mut file = File::create(&file_path).unwrap();
        writeln!(file, "[package]\nname = \"test_package\"\nversion = \"0.1.0\"").unwrap();

        let result = cat_cargo_toml();
        assert!(result.is_ok());

        dir.close().unwrap(); // Clean up the temporary directory
    }

    #[test]
    fn test_cat_cargo_toml_not_found() {

        let result = cat_cargo_toml();
        assert!(result.is_err());
        match result {
            Err(e) => assert_eq!(e.kind(), io::ErrorKind::NotFound),
            Ok(_) => panic!("Expected error, but got Ok"),
        }
    }
}