use std::error::Error; use std::io::{self, BufRead, Write}; fn main() -> Result<(), Box> { let stdin = io::stdin(); let mut stdin = stdin.lock(); let mut stdout = io::BufWriter::new(io::stdout()); let mut line = String::new(); while stdin.read_line(&mut line)? > 0 { stdout.write_all(line.to_uppercase().as_bytes())?; line.clear(); } Ok(()) }