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# Yargs

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> Yargs be a node.js library fer hearties tryin' ter parse optstrings.

Yargs helps you build interactive command line tools, by parsing arguments and generating an elegant user interface. It gives you:

* commands and (grouped) options (`my-program.js serve --port=5000`).
* a dynamically generated help menu based on your arguments.

> <img width="400" src="/screen.png">

* bash-completion shortcuts for commands and options.
* and [tons more](/docs/api.md).

## Installation

```bash
npm i yargs --save
```

## Simple Example

````javascript
#!/opt/alt/alt-nodejs11/root/usr/bin/node
const argv = require('yargs').argv

if (argv.ships > 3 && argv.distance < 53.5) {
  console.log('Plunder more riffiwobbles!')
} else {
  console.log('Retreat from the xupptumblers!')
}
````

```bash
$ ./plunder.js --ships=4 --distance=22
Plunder more riffiwobbles!

$ ./plunder.js --ships 12 --distance 98.7
Retreat from the xupptumblers!
```

## Complex Example

```js
#!/opt/alt/alt-nodejs11/root/usr/bin/node
require('yargs') // eslint-disable-line
  .command('serve [port]', 'start the server', (yargs) => {
    yargs
      .positional('port', {
        describe: 'port to bind on',
        default: 5000
      })
  }, (argv) => {
    if (argv.verbose) console.info(`start server on :${argv.port}`)
    serve(argv.port)
  })
  .option('verbose', {
    alias: 'v',
    default: false
  })
  .argv
```

Run the example above with `--help` to see the help for the application.

## Table of Contents

* [Yargs' API](/docs/api.md)
* [Examples](/docs/examples.md)
* [Parsing Tricks](/docs/tricks.md)
  * [Stop the Parser](/docs/tricks.md#stop)
  * [Negating Boolean Arguments](/docs/tricks.md#negate)
  * [Numbers](/docs/tricks.md#numbers)
  * [Arrays](/docs/tricks.md#arrays)
  * [Objects](/docs/tricks.md#objects)
* [Advanced Topics](/docs/advanced.md)
  * [Composing Your App Using Commands](/docs/advanced.md#commands)
  * [Building Configurable CLI Apps](/docs/advanced.md#configuration)
  * [Customizing Yargs' Parser](/docs/advanced.md#customizing)
* [Contributing](/contributing.md)

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