clap/examples/07_option_args.rs
Ed Page bfa02fd418 test: More thoroughly test examples
This ports our example testing over to [trycmd](https://docs.rs/) so
we can:
- More thoroughly test our examples
- Provide always-up-to-date example usage

The old way of testing automatically picked up examples.  This new way
requires we have a `.md` file that uses the example in some way.

Notes:
- Moved overall example description to the `.md` file
- I added cross-linking between related examples
- `14_groups` had a redundant paragraph (twice talked about "one and
  only one"
2021-11-23 13:13:41 -06:00

71 lines
3 KiB
Rust

use clap::{arg, App, Arg};
fn main() {
let matches = App::new("MyApp")
// Regular App configuration goes here...
// Assume we have an application that accepts an input file via the "-i file"
// or the "--input file" (as well as "--input=file").
// Below every setting supported by option arguments is discussed.
// NOTE: You DO NOT need to specify each setting, only those which apply
// to your particular case.
.arg(
Arg::new("input")
.help("the input file to use") // Displayed when showing help info
.takes_value(true) // MUST be set to true in order to be an "option" argument
.short('i') // This argument is triggered with "-i"
.long("input") // This argument is triggered with "--input"
.multiple_occurrences(true) // Set to true if you wish to allow multiple occurrences
// such as "-i file -i other_file -i third_file"
.required(true) // By default this argument MUST be present
// NOTE: mutual exclusions take precedence over
// required arguments
.requires("config") // Says, "If the user uses "input", they MUST
// also use this other 'config' arg too"
// Can also specify a list using
// 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)
)
.arg(
arg!(
-c --config <FILE> "the config file to use"
)
.required(false),
)
.arg(arg!([output] "the output file to use"))
.get_matches();
// We can find out whether or not "input" was used
if matches.is_present("input") {
println!("An input file was specified");
}
// We can also get the value for "input"
//
// NOTE: If we specified multiple_occurrences(), this will only return the _FIRST_
// occurrence
if let Some(ref in_file) = matches.value_of("input") {
println!("An input file: {}", in_file);
}
// If we specified the multiple_occurrences() setting we can get all the values
if let Some(in_v) = matches.values_of("input") {
for in_file in in_v {
println!("An input file: {}", in_file);
}
}
// We can see how many times the option was used with the occurrences_of() method
//
// NOTE: Just like with flags, if we did not specify the multiple_occurrences() setting this will only
// return 1 no matter how many times the argument was used (unless it wasn't used at all, in
// in which case 0 is returned)
println!(
"The \"input\" argument was used {} times",
matches.occurrences_of("input")
);
// Continued program logic goes here...
}