clap/examples/tutorial_builder/04_02_validate.rs

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// Note: this requires the `cargo` feature
use std::ops::RangeInclusive;
use clap::{arg, command};
fn main() {
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let matches = command!()
.arg(
arg!(<PORT>)
.help("Network port to use")
.validator(port_in_range),
)
.get_matches();
// Note, it's safe to call unwrap() because the arg is required
let port: usize = matches
.value_of_t("PORT")
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.expect("'PORT' is required and parsing will fail if its missing");
println!("PORT = {}", port);
}
const PORT_RANGE: RangeInclusive<usize> = 1..=65535;
fn port_in_range(s: &str) -> Result<(), String> {
let port: usize = s
.parse()
.map_err(|_| format!("`{}` isn't a port number", s))?;
if PORT_RANGE.contains(&port) {
Ok(())
} else {
Err(format!(
"Port not in range {}-{}",
PORT_RANGE.start(),
PORT_RANGE.end()
))
}
}