Module clap::_derive::_cookbook::escaped_positional_derive

Available on crate feature unstable-doc only.

Example (Derive API)

use clap::Parser;

#[derive(Parser)] // requires `derive` feature
#[command(version, about, long_about = None)]
struct Cli {
    #[arg(short = 'f')]
    eff: bool,

    #[arg(short = 'p', value_name = "PEAR")]
    pea: Option<String>,

    #[arg(last = true)]
    slop: Vec<String>,
}

fn main() {
    let args = Cli::parse();

    // This is what will happen with `myprog -f -p=bob -- sloppy slop slop`...
    println!("-f used: {:?}", args.eff); // -f used: true
    println!("-p's value: {:?}", args.pea); // -p's value: Some("bob")
    println!("'slops' values: {:?}", args.slop); // 'slops' values: Some(["sloppy", "slop", "slop"])

    // Continued program logic goes here...
}

This requires enabling the derive feature flag.

You can use -- to escape further arguments.

Let’s see what this looks like in the help:

$ escaped-positional-derive --help
A simple to use, efficient, and full-featured Command Line Argument Parser

Usage: escaped-positional-derive[EXE] [OPTIONS] [-- <SLOP>...]

Arguments:
  [SLOP]...  

Options:
  -f             
  -p <PEAR>      
  -h, --help     Print help
  -V, --version  Print version

Here is a baseline without any arguments:

$ escaped-positional-derive
-f used: false
-p's value: None
'slops' values: []

Notice that we can’t pass positional arguments before --:

$ escaped-positional-derive foo bar
? failed
error: unexpected argument 'foo' found

Usage: escaped-positional-derive[EXE] [OPTIONS] [-- <SLOP>...]

For more information, try '--help'.

But you can after:

$ escaped-positional-derive -f -p=bob -- sloppy slop slop
-f used: true
-p's value: Some("bob")
'slops' values: ["sloppy", "slop", "slop"]

As mentioned, the parser will directly pass everything through:

$ escaped-positional-derive -- -f -p=bob sloppy slop slop
-f used: false
-p's value: None
'slops' values: ["-f", "-p=bob", "sloppy", "slop", "slop"]