mirror of
https://github.com/clap-rs/clap
synced 2024-12-14 06:42:33 +00:00
40 lines
2 KiB
Rust
40 lines
2 KiB
Rust
extern crate clap;
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use clap::{App, Arg};
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fn main() {
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// There are two ways in which to get a default value, one is to use claps Arg::default_value
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// method, and the other is to use Rust's built in Option::unwrap_or method.
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//
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// I'll demo both here.
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//
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// First, we'll use clap's Arg::default_value with an "INPUT" file.
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let matches = App::new("myapp").about("does awesome things")
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.arg(Arg::with_name("INPUT")
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.help("The input file to use") // Note, we don't need to specify
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// anything like, "Defaults to..."
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// because clap will automatically
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// generate that for us, and place
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// it in the help text
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.default_value("input.txt")
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.index(1))
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// Next we'll use the Option::unwrap_or method on this "CONFIG" option
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.arg(Arg::with_name("CONFIG")
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// Note that we have to manaully include some verbage to the user
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// telling them what the default will be.
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.help("The config file to use (default is \"config.json\")")
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.short('c')
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.takes_value(true))
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.get_matches();
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// It's safe to call unwrap because the value with either be what the user input at runtime
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// or "input.txt"
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let input = matches.value_of("INPUT").unwrap();
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// Using Option::unwrap_or we get the same affect, but without the added help text injection
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let config_file = matches.value_of("CONFIG").unwrap_or("config.json");
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println!("The input file is: {}", input);
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println!("The config file is: {}", config_file);
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}
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