command-line-args

What is command-line-args?

The command-line-args npm package is a library for parsing command-line arguments in Node.js applications. It allows developers to define options and parse them from the command line, making it easier to handle user inputs and configurations.

What are command-line-args's main functionalities?

Basic Argument Parsing

This feature allows you to define and parse basic command-line arguments. In this example, the 'file' option expects a string value, and the 'verbose' option is a boolean flag.

const commandLineArgs = require('command-line-args');

const optionDefinitions = [
  { name: 'file', type: String },
  { name: 'verbose', type: Boolean }
];

const options = commandLineArgs(optionDefinitions);
console.log(options);

Default Values

This feature allows you to set default values for options. If the user does not provide a value for 'file' or 'verbose', the defaults 'default.txt' and 'false' will be used, respectively.

const commandLineArgs = require('command-line-args');

const optionDefinitions = [
  { name: 'file', type: String, defaultValue: 'default.txt' },
  { name: 'verbose', type: Boolean, defaultValue: false }
];

const options = commandLineArgs(optionDefinitions);
console.log(options);

Multiple Values

This feature allows you to handle multiple values for a single option. In this example, the 'files' option can accept multiple string values.

const commandLineArgs = require('command-line-args');

const optionDefinitions = [
  { name: 'files', type: String, multiple: true, defaultOption: true }
];

const options = commandLineArgs(optionDefinitions);
console.log(options);

Aliases

This feature allows you to define aliases for options. In this example, 'help' can be accessed with '-h' and 'version' with '-v'.

const commandLineArgs = require('command-line-args');

const optionDefinitions = [
  { name: 'help', alias: 'h', type: Boolean },
  { name: 'version', alias: 'v', type: Boolean }
];

const options = commandLineArgs(optionDefinitions);
console.log(options);

Other packages similar to command-line-args

yargs

Yargs is a popular library for parsing command-line arguments in Node.js. It provides a rich set of features, including command handling, argument validation, and automatic help generation. Compared to command-line-args, yargs offers more advanced features and a more user-friendly API.

commander

Commander is another widely-used library for building command-line interfaces in Node.js. It supports option parsing, command definitions, and automatic help generation. Commander is known for its simplicity and ease of use, making it a good alternative to command-line-args for simpler use cases.

minimist

Minimist is a lightweight library for parsing command-line arguments. It provides basic functionality for handling options and arguments, but lacks some of the advanced features found in command-line-args, yargs, and commander. Minimist is a good choice for projects that require minimal overhead.

README

Upgraders, please read the release notes

command-line-args

A mature, feature-complete library to parse command-line options.

Synopsis

You can set options using the main notation standards (learn more). These commands are all equivalent, setting the same values:

$ example --verbose --timeout=1000 --src one.js --src two.js
$ example --verbose --timeout 1000 --src one.js two.js
$ example -vt 1000 --src one.js two.js
$ example -vt 1000 one.js two.js

To access the values, first create a list of option definitions describing the options your application accepts. The type property is a setter function (the value supplied is passed through this), giving you full control over the value received.

const optionDefinitions = [
  { name: 'verbose', alias: 'v', type: Boolean },
  { name: 'src', type: String, multiple: true, defaultOption: true },
  { name: 'timeout', alias: 't', type: Number }
]

Next, parse the options using commandLineArgs():

import commandLineArgs from 'command-line-args'
const options = commandLineArgs(optionDefinitions)

options now looks like this:

{
  src: [
    'one.js',
    'two.js'
  ],
  verbose: true,
  timeout: 1000
}

Advanced usage

Beside the above typical usage, you can configure command-line-args to accept more advanced syntax forms.

• Command-based syntax (git style) in the form:

  $ executable <command> [options]
  

  For example.

  $ git commit --squash -m "This is my commit message"
  

• Command and sub-command syntax (docker style) in the form:

  $ executable <command> [options] <sub-command> [options]
  

  For example.

  $ docker run --detached --image centos bash -c yum install -y httpd
  

Usage guide generation

A usage guide (typically printed when --help is set) can be generated using command-line-usage. See the examples below and read the documentation for instructions how to create them.

A typical usage guide example.

The polymer-cli usage guide is a good real-life example.

Further Reading

There is plenty more to learn, please see the wiki for examples and documentation.

Install

$ npm install command-line-args --save

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© 2014-24 Lloyd Brookes <[e-mail]>.

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