Comment by raggi

it does an ok job with this task:

    use std::fs::File;
    use std::io::{self, BufReader, Read};

    fn read_file_character_by_character(path: &str) -> io::Result<()> {
        // Open the file in read-only mode.
        let file = File::open(path)?;

        // Create a buffered reader to read the file more efficiently.
        let reader = BufReader::new(file);

        // `chars` method returns an iterator over the characters of the input.
        // Note that it returns a Result<(char, usize), io::Error>, where usize is the byte length of the char.
        for char_result in reader.chars() {
            match char_result {
                Ok(c) => print!("{}", c),
                Err(e) => return Err(e),
            }
        }

        Ok(())
    }

    fn main() {
        let path = "path/to/your/file.txt";

        if let Err(e) = read_file_character_by_character(path) {
            eprintln!("Error reading file: {}", e);
        }
    }