Swift Argument Parser

Usage

Begin by declaring a type that defines the information you need to collect from the command line. Decorate each stored property with one of ArgumentParser's property wrappers, and declare conformance to ParsableCommand.

import ArgumentParser

struct Repeat: ParsableCommand {
    @Flag(help: "Include a counter with each repetition.")
    var includeCounter: Bool

    @Option(name: .shortAndLong, help: "The number of times to repeat 'phrase'.")
    var count: Int?

    @Argument(help: "The phrase to repeat.")
    var phrase: String

    // continued below…
}

Next, implement the run() method on your type, and kick off execution by calling the type's static main() method.
The ArgumentParser library parses the command-line arguments, instantiates your command type, and then either executes your custom run() method or exits with useful a message.

struct Repeat: ParsableCommand {

    // continued from above…

    func run() throws {
        let repeatCount = count ?? .max

        for i in 1...repeatCount {
            if includeCounter {
                print("\(i): \(phrase)")
            } else {
                print(phrase)
            }
        }
    }
}

Repeat.main()

ArgumentParser uses your properties' names and type information, along with the details you provide using property wrappers, to supply useful error messages and detailed help:

$ repeat hello --count 3
hello
hello
hello
$ repeat
Error: Missing required value for argument 'phrase'.
Usage: repeat [--count <count>] [--include-counter] <phrase>
$ repeat --help
USAGE: repeat [--count <count>] [--include-counter] <phrase>

ARGUMENTS:
  <phrase>                The phrase to repeat.

OPTIONS:
  --include-counter       Include a counter with each repetition.
  -c, --count <count>     The number of times to repeat 'phrase'.
  -h, --help              Show help for this command.

For more information and documentation about all supported options, see the Documentation folder at the root of the repository.

Examples

This repository includes a few examples of using the library:

• repeat is the example shown above.
• roll is a simple utility implemented as a straight-line script.
• math is an annotated example of using nested commands and subcommands.

You can also see examples of ArgumentParser adoption among Swift project tools:

• indexstore-db is a simple utility with two commands.
• swift-format uses some advanced features, like custom option values and hidden flags.

Adding ArgumentParser as a Dependency

Add the following line to the dependencies in your Package.swift file:

.package(url: "https://github.com/apple/swift-argument-parser", from: "0.0.1"),

...and then include "ArgumentParser" as a dependency for your executable target:

.product(name: "ArgumentParser", package: "swift-argument-parser"),

Note: Because ArgumentParser is under active development, source-stability is only guaranteed within minor versions (e.g. between 0.0.3 and 0.0.4). If you don't want potentially source-breaking package updates, you can specify your package dependency using .upToNextMinor(from: "0.0.1") instead.