Idiomatic Rust would probably avoid allocations, which means something more like fn main() { if let Some(arg) = std::env::args().nth(1) {

Idiomatic Rust would probably avoid allocations, which means something more like fn main() { if let Some(arg) = std::env::args().nth(1) { println!("{}", { match arg.char_indices().nth(12) { Some((idx, _)) => &arg[..idx], None => &*arg } }); } } With the `unicode-segmentation` crate[1], you can just swap `char_indices()` with `grapheme_indices(true)`. [1] https://crates.io/crates/unicode-segmentation https://crates.io/crates/unicode-segmentation