clap/examples/05_flag_args.rs

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use clap::{App, Arg};
fn main() {
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// Of the three argument types, flags are the most simple. Flags are simple switches which can
// be either "on" or "off"
//
// clap also supports multiple occurrences of flags, the common example is "verbosity" where a
// user could want a little information with "-v" or tons of information with "-v -v" or "-vv"
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let matches = App::new("MyApp")
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// Regular App configuration goes here...
// We'll add a flag that represents an awesome meter...
//
// I'll explain each possible setting that "flags" accept. Keep in mind
// that you DO NOT need to set each of these for every flag, only the ones
// you want for your individual case.
.arg(
Arg::new("awesome")
.about("turns up the awesome") // Displayed when showing help info
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.short('a') // Trigger this arg with "-a"
.long("awesome") // Trigger this arg with "--awesome"
.multiple(true) // This flag should allow multiple
// occurrences such as "-aaa" or "-a -a"
.requires("config") // Says, "If the user uses -a, they MUST
// also use this other 'config' arg too"
// Can also specify a list using
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// requires_all(Vec<&str>)
.conflicts_with("output"), // Opposite of requires(), says "if the
// user uses -a, they CANNOT use 'output'"
// also has a conflicts_with_all(Vec<&str>)
// and an exclusive(true)
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)
// NOTE: In order to compile this example, comment out requires() and
// conflicts_with() because we have not defined an "output" or "config"
// argument.
.get_matches();
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// We can find out whether or not awesome was used
if matches.is_present("awesome") {
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println!("Awesomeness is turned on");
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}
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// If we set the multiple() option of a flag we can check how many times the user specified
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//
// Note: if we did not specify the multiple() option, and the user used "awesome" we would get
// a 1 (no matter how many times they actually used it), or a 0 if they didn't use it at all
match matches.occurrences_of("awesome") {
0 => println!("Nothing is awesome"),
1 => println!("Some things are awesome"),
2 => println!("Lots of things are awesome"),
_ => println!("EVERYTHING is awesome!"),
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}
// Continued program logic goes here...
}