uutils-args/docs/guide/port.md

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Porting from Clap

This chapter contains information about how common patterns in clap parsers can be ported to uutils-args.

More examples can be added here while we figure out more common patterns.

Defaults

By default, the clap command roughly equivalent to a command from uutils-args looks like this (where everything with ... is filled in automatically).

Command::new(...)
    .version(...)
    .override_usage(...)
    .about(...)
    .infer_long_args(true)
    .args_override_self(true)
    .disable_help_flag(true)
    .disable_version_flag(true)
    .arg(
        Arg::new("help")
            .long("help")
            .help("Print help information.")
            .action(ArgAction::Help),
    )
    .arg(
        Arg::new("version")
            .long("version")
            .help("Print version information.")
            .action(ArgAction::Version),
    )

Further differences are:

• Overrides are the default in uutils-args. There is no automatic conflict checking.
• Values can always start with hyphens.
• Long flags with optional arguments always require an equal sign.

ArgAction equivalents

ArgAction::SetTrue

let command = Command::new(...)
    .arg(
        Arg::new("a")
            .short('a')
            .action(ArgAction::SetTrue)
    );

let matches = command.get_matches();

let a = matches.get_flag("a");

use uutils_args::{Arguments, Options};

#[derive(Arguments)]
enum Arg {
    #[arg("-a")]
    A
}

#[derive(Default)]
struct Settings { a: bool }

impl Options<Arg> for Settings {
    fn apply(&mut self, arg: Arg) -> Result<(), uutils_args::Error> {
        match arg {
            Arg::A => self.a = true,
        }
        Ok(())
    }
}

let a = Settings::default().parse(std::env::args_os()).unwrap().0.a;

ArgAction::SetFalse

let command = Command::new(...)
    .arg(
        Arg::new("a")
            .short('a')
            .action(ArgAction::SetFalse)
    );

let matches = command.get_matches();

let a = matches.get_flag("a");

use uutils_args::{Arguments, Options};

#[derive(Arguments)]
enum Arg {
    #[arg("-a")]
    A
}

struct Settings { a: bool }

impl Default for Settings {
    fn default() -> Self {
        Self { a: false }
    }
}

impl Options<Arg> for Settings {
    fn apply(&mut self, arg: Arg) -> Result<(), uutils_args::Error> {
        match arg {
            Arg::A => self.a = false,
        }
        Ok(())
    }
}

let a = Settings::default().parse(std::env::args_os()).unwrap().0.a;

ArgAction::Count

let command = Command::new(...)
    .arg(
        Arg::new("a")
            .short('a')
            .action(ArgAction::Count)
    );

let matches = command.get_matches();

let a = matches.get_one("a").unwrap();

use uutils_args::{Arguments, Options};

#[derive(Arguments)]
enum Arg {
    #[arg("-a")]
    A
}

#[derive(Default)]
struct Settings { a: u8 }

impl Options<Arg> for Settings {
    fn apply(&mut self, arg: Arg) -> Result<(), uutils_args::Error> {
        match arg {
            Arg::A => self.a += 1,
        }
        Ok(())
    }
}

let a = Settings::default().parse(std::env::args_os()).unwrap().0.a;

ArgAction::Set

let command = Command::new(...)
    .arg(
        Arg::new("a")
            .short('a')
            .action(ArgAction::Set)
            .value_name("VAL")
    );

let matches = command.get_matches();

let a = matches.get_one("a").unwrap();

use uutils_args::{Arguments, Options};
use std::ffi::OsString;

#[derive(Arguments)]
enum Arg {
    #[arg("-a VAL")]
    A(OsString)
}

#[derive(Default)]
struct Settings { a: OsString }

impl Options<Arg> for Settings {
    fn apply(&mut self, arg: Arg) -> Result<(), uutils_args::Error> {
        match arg {
            Arg::A(s) => self.a = s,
        }
        Ok(())
    }
}

let a = Settings::default().parse(std::env::args_os()).unwrap().0.a;

ArgAction::Append

let command = Command::new(...)
    .arg(
        Arg::new("a")
            .short('a')
            .action(ArgAction::Append)
            .value_name("VAL")
    );

let matches = command.get_matches();

let a = matches.get_one("a").unwrap();

use uutils_args::{Arguments, Options};
use std::ffi::OsString;

#[derive(Arguments)]
enum Arg {
    #[arg("-a VAL")]
    A(OsString)
}

#[derive(Default)]
struct Settings { a: Vec<OsString> }

impl Options<Arg> for Settings {
    fn apply(&mut self, arg: Arg) -> Result<(), uutils_args::Error> {
        match arg {
            Arg::A(s) => self.a.push(s),
        }
        Ok(())
    }
}

let a = Settings::default().parse(std::env::args_os()).unwrap().0.a;

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