argwerk

Define a simple command-line parser through a declarative macro.

This is not intended to be a complete command-line parser library. Instead this can be used as an alternative quick-and-dirty approach that can be cheaply incorporated into a tool.

For a more complete command-line parsing library, use clap.

We provide:

• A dependency-free command-line parsing framework using declarative macros.
• A flexible mechanism for parsing.
• Formatting of decent looking help messages.

We do not provide:

• As-close-to correct line wrapping with wide unicode characters as possible (see textwrap).
• Built-in complex command structures like subcommands (see the subcommands example for how this can be accomplished).

For how to use, see the documentation of argwerk::define and argwerk::args.

Usage

Initially when you're adding arguments to your program you can use argwerk::args. This allows for easily parsing out a handful of optional parameters.

This example is available as simple:

cargo run --example simple -- --limit 20

let args = argwerk::args! {
    /// A simple tool.
    "tool [-h]" {
        help: bool,
        limit: usize = 10,
    }
    /// The limit of the operation. (default: 10).
    ["-l" | "--limit", int] => {
        limit = str::parse(&int)?;
    }
    /// Print this help.
    ["-h" | "--help"] => {
        println!("{}", HELP);
        help = true;
    }
}?;

if args.help {
    return Ok(());
}

dbg!(args);

After a while you might want to graduate to defining a named struct containing the arguments. This can be useful if you want to pass the arguments around.

This example is available as tour:

cargo run --example tour -- --help

use std::ffi::OsString;

argwerk::define! {
    /// A command touring the capabilities of argwerk.
    #[derive(Default)]
    #[usage = "tour [-h]"]
    struct Args {
        help: bool,
        #[required = "--file must be specified"]
        file: String,
        input: Option<String>,
        limit: usize = 10,
        positional: Option<(String, Option<String>)>,
        raw: Option<OsString>,
        rest: Vec<String>,
    }
    /// Prints the help.
    ///
    /// This includes:
    ///    * All the available switches.
    ///    * All the available positional arguments.
    ///    * Whatever else the developer decided to put in here! We even support wrapping comments which are overly long.
    ["-h" | "--help"] => {
        println!("{}", Args::help());
        help = true;
    }
    /// Limit the number of things by <n> (default: 10).
    ["--limit" | "-l", n] => {
        limit = str::parse(&n)?;
    }
    /// Write to the file specified by <path>.
    ["--file", path] if !file.is_some() => {
        file = Some(path);
    }
    /// Read from the specified input.
    ["--input", #[option] path] => {
        input = path;
    }
    /// A really long argument that exceeds usage limit and forces the documentation to wrap around with newlines.
    ["--really-really-really-long-argument", thing] => {
    }
    /// A raw argument that passes whatever was passed in from the operating system.
    ["--raw", #[os] arg] => {
        raw = Some(arg);
    }
    /// Takes argument at <foo> and <bar>.
    ///
    ///    * This is an indented message. The first alphanumeric character determines the indentation to use.
    [foo, #[option] bar, #[rest] args] if positional.is_none() => {
        positional = Some((foo, bar));
        rest = args;
    }
}

// Note: we're using `parse` here instead of `args` since it works better
// with the example.
let args = Args::parse(vec!["--file", "foo.txt", "--input", "-"])?;

dbg!(args);

Time and size compared to other projects

argwerk aims to be a lightweight dependency that is fast to compile. This is how it stacks up to other projects in that regard.

The following summary was generated from the projects found here.

*: rebuild was triggered by adding a single newline to main.rs.
**: argh 0.1.4 including 11 dependencies.
***: clap 3.0.0-beta.2 including 32 dependencies.

You can try and build it yourself with:

cargo run --manifest-path tools/builder/Cargo.toml