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extern crate clap;
use clap::{App, Arg};
fn main() {
// Args describe a possible valid argument which may be supplied by the user at runtime. There
// are three different types of arguments (flags, options, and positional) as well as a fourth
// special type of argument, called SubCommands (which will be discussed separately).
//
// Args are described in the same manner as Apps using the "builder pattern" with multiple
// methods describing various settings for the individual arguments. Or by supplying a "usage"
// string. Both methods have their pros and cons.
//
// Arguments can be added to applications in two manners, one at a time with the arg(), and
// arg_from_usage() method, or multiple arguments at once via a Vec<Arg> inside the args() method,
// or a single &str describing multiple Args (one per line) supplied to args_from_usage().
//
// There are various options which can be set for a given argument, some apply to any of the
// three types of arguments, some only apply one or two of the types. *NOTE* if you set
// incompatible options on a single argument, clap will panic! at runtime. This is by design,
// so that you know right away an error was made by the developer, not the end user.
//
// # Help and Version
// clap automatically generates a help and version flag for you, unless you specify your
// own. By default help uses "-h" and "--help", and version uses "-V" and "--version". You can
// safely override "-V" and "-h" to your own arguments, and "--help" and "--version" will still
// be automatically generated for you.
let matches = App::new("MyApp")
// All application settings go here...
// A simple "Flag" argument example (i.e. "-d") using the builder pattern
.arg(Arg::with_name("debug")
.help("turn on debugging information")
.short("d"))
// Two arguments, one "Option" argument (i.e. one that takes a value) such
// as "-c some", and one positional argument (i.e. "myapp some_file")
.args(&[
Arg::with_name("config")
.help("sets the config file to use")
.takes_value(true)
.short("c")
.long("config"),
Arg::with_name("input")
.help("the input file to use")
.index(1)
.required(true)
])
// *Note* the following two examples are convenience methods, if you wish
// to still get the full configurability of Arg::with_name() and the readability
// of arg_from_usage(), you can instantiate a new Arg with Arg::from_usage() and
// still be able to set all the additional properties, just like Arg::with_name()
//
//
// One "Flag" using a usage string
.arg_from_usage("--license 'display the license file'")
// Two args, one "Positional", and one "Option" using a usage string
.args_from_usage("[output] 'Supply an output file to use'
-i, --int=[IFACE] 'Set an interface to use'")
.get_matches();
// Here are some examples of using the arguments defined above. Keep in mind that this is only
// an example, and may be somewhat contrived
//
// First we check if debugging should be on or not
println!("Debugging mode is: {}", if matches.is_present("debug") { "ON" } else { "OFF" });
// Next we print the config file we're using, if any was defined with either -c <file> or
// --config <file>
if let Some(config) = matches.value_of("config") {
println!("A config file was passed in: {}", config);
}
// Let's print the <INPUT> file the user passed in. We can use .unwrap() here becase the arg is
// required, and parsing would have failed if the user forgot it
println!("Using input file: {}", matches.value_of("input").unwrap());
// We could continue checking for and using arguments in this manner, such as "license",
// "output", and "interface". Keep in mind that "output" and "interface" are optional, so you
// shouldn't call .unwrap(). Instead, prefer using an 'if let' expression as we did with
// "config"
}
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