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extern crate clap;
use clap::{App, AppSettings, SubCommand};
fn main() {
// You can use AppSettings to change the application level behavior of clap. .setting() function
// of App struct takes AppSettings enum as argument. There is also .settings() function which
// takes slice of AppSettings enum. You can learn more about AppSettings in the documentation,
// which also has examples on each setting.
//
// This example will only show usage of one AppSettings setting. See documentation for more
// information.
let matches = App::new("myapp")
.setting(AppSettings::SubcommandsNegateReqs)
// Negates requirement of parent command.
.arg_from_usage("<input> 'input file to use'")
// Required positional argument called input. This
// will be only required if subcommand is not present.
.subcommand(SubCommand::with_name("test")
.about("does some testing"))
// if program is invoked with subcommand, you do not
// need to specify the <input> argument anymore due to
// the AppSettings::SubcommandsNegateReqs setting.
.get_matches();
// Calling unwrap() on "input" would not be advised here, because although it's required,
// if the user uses a subcommand, those requirements are no longer required. Hence, we should
// use some sort of 'if let' construct
if let Some(inp) = matches.value_of("input") {
println!("The input file is: {}", inp);
}
match matches.subcommand() {
("test", _) => println!("The 'test' subcommand was used"),
_ => unreachable!()
}
}
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