1use std::ops::RangeInclusive;
2
3use clap::{arg, command};
4
5fn main() {
6 let matches = command!() // requires `cargo` feature
7 .arg(
8 arg!(<PORT>)
9 .help("Network port to use")
10 .value_parser(port_in_range),
11 )
12 .get_matches();
13
14 // Note, it's safe to call unwrap() because the arg is required
15 let port: u16 = *matches
16 .get_one::<u16>("PORT")
17 .expect("'PORT' is required and parsing will fail if its missing");
18 println!("PORT = {port}");
19}
20
21const PORT_RANGE: RangeInclusive<usize> = 1..=65535;
22
23fn port_in_range(s: &str) -> Result<u16, String> {
24 let port: usize = s
25 .parse()
26 .map_err(|_| format!("`{s}` isn't a port number"))?;
27 if PORT_RANGE.contains(&port) {
28 Ok(port as u16)
29 } else {
30 Err(format!(
31 "port not in range {}-{}",
32 PORT_RANGE.start(),
33 PORT_RANGE.end()
34 ))
35 }
36}
37