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Diffstat (limited to 'clap/examples/10_default_values.rs')
-rw-r--r-- | clap/examples/10_default_values.rs | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/clap/examples/10_default_values.rs b/clap/examples/10_default_values.rs new file mode 100644 index 0000000..ca50981 --- /dev/null +++ b/clap/examples/10_default_values.rs @@ -0,0 +1,40 @@ +extern crate clap; + +use clap::{App, Arg}; + +fn main() { + // There are two ways in which to get a default value, one is to use claps Arg::default_value + // method, and the other is to use Rust's built in Option::unwrap_or method. + // + // I'll demo both here. + // + // First, we'll use clap's Arg::default_value with an "INPUT" file. + let matches = App::new("myapp").about("does awesome things") + .arg(Arg::with_name("INPUT") + .help("The input file to use") // Note, we don't need to specify + // anything like, "Defaults to..." + // because clap will automatically + // generate that for us, and place + // it in the help text + .default_value("input.txt") + .index(1)) + + // Next we'll use the Option::unwrap_or method on this "CONFIG" option + .arg(Arg::with_name("CONFIG") + // Note that we have to manually include some verbiage to the user + // telling them what the default will be. + .help("The config file to use (default is \"config.json\")") + .short("c") + .takes_value(true)) + .get_matches(); + + // It's safe to call unwrap because the value with either be what the user input at runtime + // or "input.txt" + let input = matches.value_of("INPUT").unwrap(); + + // Using Option::unwrap_or we get the same affect, but without the added help text injection + let config_file = matches.value_of("CONFIG").unwrap_or("config.json"); + + println!("The input file is: {}", input); + println!("The config file is: {}", config_file); +} |