Simple getopt alternative.

Construct a vector of options, either by using reqopt, optopt, and optflag or by building them from components yourself, and pass them to getopts, along with a vector of actual arguments (not including argv[0]). You'll either get a failure code back, or a match. You'll have to verify whether the amount of 'free' arguments in the match is what you expect. Use opt_* accessors to get argument values out of the matches object.

Single-character options are expected to appear on the command line with a single preceding dash; multiple-character options are expected to be proceeded by two dashes. Options that expect an argument accept their argument following either a space or an equals sign. Single-character options don't require the space.

Example

The following example shows simple command line parsing for an application that requires an input file to be specified, accepts an optional output file name following -o, and accepts both -h and --help as optional flags.

extern crate getopts;
use getopts::{optopt,optflag,getopts,OptGroup};
use std::os;

fn do_work(inp: &str, out: Option<~str>) {
    println!("{}", inp);
    match out {
        Some(x) => println!("{}", x),
        None => println!("No Output"),
    }
}

fn print_usage(program: &str, _opts: &[OptGroup]) {
    println!("Usage: {} [options]", program);
    println!("-o\t\tOutput");
    println!("-h --help\tUsage");
}

fn main() {
    let args = os::args();

    let program = args[0].clone();

    let opts = ~[
        optopt("o", "", "set output file name", "NAME"),
        optflag("h", "help", "print this help menu")
    ];
    let matches = match getopts(args.tail(), opts) {
        Ok(m) => { m }
        Err(f) => { fail!(f.to_err_msg()) }
    };
    if matches.opt_present("h") {
        print_usage(program, opts);
        return;
    }
    let output = matches.opt_str("o");
    let input: &str = if !matches.free.is_empty() {
        (*matches.free.get(0)).clone()
    } else {
        print_usage(program, opts);
        return;
    };
    do_work(input, output);
}