The clap crate implements built-in behaviour for the -h
option, but it doesn't seem to do the same for -?
. Is there a way to tell it to do so?
I had opened an issue at the clap repository. The author / main contributor has answered there. Here is a copy of the code, which answers the question:
extern crate clap;
use std::env;
use std::process;
use clap::{App, Arg};
fn main() {
// We build the App instance and save it, so we can
// use it later if needed
let mut app = App::new("prog").arg(
Arg::with_name("help")
.short("?")
.help("Also prints the help message"),
);
// We call this method which will do all the
//parsing, but not consume our App instance
let res = app.get_matches_from_safe_borrow(env::args_os());
// This calls all the normal clap error messages
// if one should exist
let matches = res.unwrap_or_else(|e| e.exit());
// Now we check for ?
if matches.is_present("help") {
let _ = app.print_help();
println!(""); // adds a newline
process::exit(0);
}
// Now we can use matches like normal...
}