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Diffstat (limited to 'clap/examples/03_args.rs')
| -rw-r--r-- | clap/examples/03_args.rs | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/clap/examples/03_args.rs b/clap/examples/03_args.rs new file mode 100644 index 0000000..c62d576 --- /dev/null +++ b/clap/examples/03_args.rs @@ -0,0 +1,84 @@ +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" +} |