osarg

osarg is a tiny, zero-dependency, borrow-first CLI parser for Rust binaries.

It is built for size-sensitive tools that want explicit control flow, OS-native argument handling, and enough ergonomics for real --help, --version, options, values, and positionals.

osarg is not a CLI framework. It does not use derive macros, schemas, or generated help text.

Supported Forms

• -v
• -abc
• --verbose
• --port=8080
• --port 8080
• -p 8080
• -p8080
• --
• positional arguments
• repeated options
• passthrough via Parser::current_value_and_remaining() / into_remaining() / remaining_vec()

Example

use osarg::{Arg, Parser};
use std::path::PathBuf;

fn main() -> Result<(), osarg::Error> {
    let mut parser = Parser::from_args(["-p", "8080", "./data"]);

    let mut port = 8080;
    let mut path: Option<PathBuf> = None;

    while let Some(arg) = parser.next()? {
        match arg {
            Arg::Short('p') | Arg::Long("port") => {
                port = parser.parse::<u16>()?;
            }
            Arg::Value(value) => {
                value.store_path_buf(&mut path)?;
            }
            other => return Err(other.unexpected()),
        }
    }

    let path = osarg::required(path, "<PATH>")?;
    let _ = (port, path);
    Ok(())
}

Examples

See examples/ for:

• basic single-command parsing
• optional values
• repeated options
• passthrough wrappers

Benchmarks

Size benchmark:

bash ./scripts/size-bench.sh

Runtime benchmark:

cargo bench --bench parse -- --quick