What is the idiomatic approach to obtain accurate outcome messages from std::io?

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The idiomatic approach to obtain accurate outcome messages from std::io is to use Result, which is a type that represents either success or failure, including an associated value or error message. For example, instead of directly reading from a file and printing error messages if the operation fails, you can wrap the operation in a Result and handle the different cases separately:

use std::fs::File;
use std::io::{Error, Read, Result};

fn read_file(filename: &str) -> Result<String> {
    let mut file = File::open(filename)?;
    let mut contents = String::new();
    file.read_to_string(&mut contents)?;
    Ok(contents)
}

fn main() -> Result<()> {
    match read_file("input.txt") {
        Ok(contents) => println!("{}", contents),
        Err(error) => match error.kind() {
            ErrorKind::NotFound => println!("File not found"),
            _ => println!("Error reading file"),
        }
    }
    Ok(())
}

In this example, read_file returns a Result<string>, which indicates whether the operation was successful (Ok) and returns the file contents, or failed (Err) and returns an Error object. The error handling is done in main, where the different cases are matched and appropriate messages are printed.