commander

What is commander?

The commander npm package is a complete solution for node.js command-line interfaces. It provides a simple and flexible way to write CLI tools, allowing developers to parse command-line arguments, define commands, and automatically generate help messages.

What are commander's main functionalities?

Command parsing

This feature allows you to define options and parse command-line arguments. The code sample demonstrates how to set up a simple CLI with options for debugging, pizza size, and pizza type.

const { program } = require('commander');
program.version('0.0.1');
program
  .option('-d, --debug', 'output extra debugging')
  .option('-s, --small', 'small pizza size')
  .option('-p, --pizza-type <type>', 'flavour of pizza');
program.parse(process.argv);
if (program.debug) console.log(program.opts());

Subcommands

Commander allows you to define subcommands for your CLI application. The code sample shows how to define three subcommands: install, search, and list, with list being the default command.

const { program } = require('commander');
program
  .command('install [name]', 'install one or more packages')
  .command('search [query]', 'search with optional query')
  .command('list', 'list packages installed', { isDefault: true })
  .parse(process.argv);

Custom help

You can customize the help output of your CLI tool. The code sample demonstrates how to change the default help option and add a custom help command.

const { program } = require('commander');
program
  .helpOption('-e, --HELP', 'read more information')
  .addHelpCommand('assist', 'display help for command');
program.parse(process.argv);

Action handler

Commander allows you to attach an action handler to a command. The code sample shows how to define a command that takes a required argument and attaches an action handler to it.

const { program } = require('commander');
program
  .command('start <service>')
  .description('start the service')
  .action(function(service) {
    console.log('Starting service:', service);
  });
program.parse(process.argv);

Other packages similar to commander

yargs

Yargs is a node.js library that helps you build interactive command line tools, by parsing arguments and generating an elegant user interface. It provides a fluent API and is similar to commander but with a slightly different philosophy and syntax. Yargs offers more advanced features like command chaining and context-based help.

meow

Meow is a simpler alternative to commander, providing a minimalistic CLI helper with argument parsing. It is less feature-rich compared to commander and yargs, but it is suitable for simpler command-line applications that do not require complex command structures.

vorpal

Vorpal is a framework for building interactive CLI applications. It is inspired by commander but aims to provide an immersive command-line experience. Vorpal offers a more interactive command-line interface with features like command history and autocomplete, which are not present in commander.

caporal

Caporal is a robust framework for building command-line applications. It provides a similar feature set to commander, including argument parsing, command-specific help, and auto-completion. Caporal emphasizes validation and typed options and arguments, which can make it more suitable for applications that require strict input validation.

README

Commander.js

The complete solution for node.js command-line interfaces, inspired by Ruby's commander.
API documentation

Installation

$ npm install commander

Option parsing

Options with commander are defined with the .option() method, also serving as documentation for the options. The example below parses args and options from process.argv, leaving remaining args as the program.args array which were not consumed by options.

#!/usr/bin/env node

/**
 * Module dependencies.
 */

var program = require('commander');

program
  .version('0.1.0')
  .option('-p, --peppers', 'Add peppers')
  .option('-P, --pineapple', 'Add pineapple')
  .option('-b, --bbq-sauce', 'Add bbq sauce')
  .option('-c, --cheese [type]', 'Add the specified type of cheese [marble]', 'marble')
  .parse(process.argv);

console.log('you ordered a pizza with:');
if (program.peppers) console.log('  - peppers');
if (program.pineapple) console.log('  - pineapple');
if (program.bbqSauce) console.log('  - bbq');
console.log('  - %s cheese', program.cheese);

Short flags may be passed as a single arg, for example -abc is equivalent to -a -b -c. Multi-word options such as "--template-engine" are camel-cased, becoming program.templateEngine etc.

Note that multi-word options starting with --no prefix negate the boolean value of the following word. For example, --no-sauce sets the value of program.sauce to false.

#!/usr/bin/env node

/**
 * Module dependencies.
 */

var program = require('commander');

program
  .option('--no-sauce', 'Remove sauce')
  .parse(process.argv);

console.log('you ordered a pizza');
if (program.sauce) console.log('  with sauce');
else console.log(' without sauce');

To get string arguments from options you will need to use angle brackets <> for required inputs or square brackets [] for optional inputs.

e.g. .option('-m --myarg [myVar]', 'my super cool description')

Then to access the input if it was passed in.

e.g. var myInput = program.myarg

NOTE: If you pass a argument without using brackets the example above will return true and not the value passed in.

Version option

Calling the version implicitly adds the -V and --version options to the command. When either of these options is present, the command prints the version number and exits.

$ ./examples/pizza -V
0.0.1

If you want your program to respond to the -v option instead of the -V option, simply pass custom flags to the version method using the same syntax as the option method.

program
  .version('0.0.1', '-v, --version')

The version flags can be named anything, but the long option is required.

Command-specific options

You can attach options to a command.

#!/usr/bin/env node

var program = require('commander');

program
  .command('rm <dir>')
  .option('-r, --recursive', 'Remove recursively')
  .action(function (dir, cmd) {
    console.log('remove ' + dir + (cmd.recursive ? ' recursively' : ''))
  })

program.parse(process.argv)

A command's options are validated when the command is used. Any unknown options will be reported as an error. However, if an action-based command does not define an action, then the options are not validated.

Coercion

function range(val) {
  return val.split('..').map(Number);
}

function list(val) {
  return val.split(',');
}

function collect(val, memo) {
  memo.push(val);
  return memo;
}

function increaseVerbosity(v, total) {
  return total + 1;
}

program
  .version('0.1.0')
  .usage('[options] <file ...>')
  .option('-i, --integer <n>', 'An integer argument', parseInt)
  .option('-f, --float <n>', 'A float argument', parseFloat)
  .option('-r, --range <a>..<b>', 'A range', range)
  .option('-l, --list <items>', 'A list', list)
  .option('-o, --optional [value]', 'An optional value')
  .option('-c, --collect [value]', 'A repeatable value', collect, [])
  .option('-v, --verbose', 'A value that can be increased', increaseVerbosity, 0)
  .parse(process.argv);

console.log(' int: %j', program.integer);
console.log(' float: %j', program.float);
console.log(' optional: %j', program.optional);
program.range = program.range || [];
console.log(' range: %j..%j', program.range[0], program.range[1]);
console.log(' list: %j', program.list);
console.log(' collect: %j', program.collect);
console.log(' verbosity: %j', program.verbose);
console.log(' args: %j', program.args);

Regular Expression

program
  .version('0.1.0')
  .option('-s --size <size>', 'Pizza size', /^(large|medium|small)$/i, 'medium')
  .option('-d --drink [drink]', 'Drink', /^(coke|pepsi|izze)$/i)
  .parse(process.argv);

console.log(' size: %j', program.size);
console.log(' drink: %j', program.drink);

Variadic arguments

The last argument of a command can be variadic, and only the last argument. To make an argument variadic you have to append ... to the argument name. Here is an example:

#!/usr/bin/env node

/**
 * Module dependencies.
 */

var program = require('commander');

program
  .version('0.1.0')
  .command('rmdir <dir> [otherDirs...]')
  .action(function (dir, otherDirs) {
    console.log('rmdir %s', dir);
    if (otherDirs) {
      otherDirs.forEach(function (oDir) {
        console.log('rmdir %s', oDir);
      });
    }
  });

program.parse(process.argv);

An Array is used for the value of a variadic argument. This applies to program.args as well as the argument passed to your action as demonstrated above.

Specify the argument syntax

#!/usr/bin/env node

var program = require('commander');

program
  .version('0.1.0')
  .arguments('<cmd> [env]')
  .action(function (cmd, env) {
     cmdValue = cmd;
     envValue = env;
  });

program.parse(process.argv);

if (typeof cmdValue === 'undefined') {
   console.error('no command given!');
   process.exit(1);
}
console.log('command:', cmdValue);
console.log('environment:', envValue || "no environment given");

Angled brackets (e.g. <cmd>) indicate required input. Square brackets (e.g. [env]) indicate optional input.

Git-style sub-commands

// file: ./examples/pm
var program = require('commander');

program
  .version('0.1.0')
  .command('install [name]', 'install one or more packages')
  .command('search [query]', 'search with optional query')
  .command('list', 'list packages installed', {isDefault: true})
  .parse(process.argv);

When .command() is invoked with a description argument, no .action(callback) should be called to handle sub-commands, otherwise there will be an error. This tells commander that you're going to use separate executables for sub-commands, much like git(1) and other popular tools.
The commander will try to search the executables in the directory of the entry script (like ./examples/pm) with the name program-command, like pm-install, pm-search.

Options can be passed with the call to .command(). Specifying true for opts.noHelp will remove the subcommand from the generated help output. Specifying true for opts.isDefault will run the subcommand if no other subcommand is specified.

If the program is designed to be installed globally, make sure the executables have proper modes, like 755.

--harmony

You can enable --harmony option in two ways:

• Use #! /usr/bin/env node --harmony in the sub-commands scripts. Note some os version don’t support this pattern.
• Use the --harmony option when call the command, like node --harmony examples/pm publish. The --harmony option will be preserved when spawning sub-command process.

Automated --help

The help information is auto-generated based on the information commander already knows about your program, so the following --help info is for free:

$ ./examples/pizza --help
Usage: pizza [options]

An application for pizzas ordering

Options:
  -h, --help           output usage information
  -V, --version        output the version number
  -p, --peppers        Add peppers
  -P, --pineapple      Add pineapple
  -b, --bbq            Add bbq sauce
  -c, --cheese <type>  Add the specified type of cheese [marble]
  -C, --no-cheese      You do not want any cheese

Custom help

You can display arbitrary -h, --help information by listening for "--help". Commander will automatically exit once you are done so that the remainder of your program does not execute causing undesired behaviors, for example in the following executable "stuff" will not output when --help is used.

#!/usr/bin/env node

/**
 * Module dependencies.
 */

var program = require('commander');

program
  .version('0.1.0')
  .option('-f, --foo', 'enable some foo')
  .option('-b, --bar', 'enable some bar')
  .option('-B, --baz', 'enable some baz');

// must be before .parse() since
// node's emit() is immediate

program.on('--help', function(){
  console.log('')
  console.log('Examples:');
  console.log('  $ custom-help --help');
  console.log('  $ custom-help -h');
});

program.parse(process.argv);

console.log('stuff');

Yields the following help output when node script-name.js -h or node script-name.js --help are run:

Usage: custom-help [options]

Options:
  -h, --help     output usage information
  -V, --version  output the version number
  -f, --foo      enable some foo
  -b, --bar      enable some bar
  -B, --baz      enable some baz

Examples:
  $ custom-help --help
  $ custom-help -h

.outputHelp(cb)

Output help information without exiting. Optional callback cb allows post-processing of help text before it is displayed.

If you want to display help by default (e.g. if no command was provided), you can use something like:

var program = require('commander');
var colors = require('colors');

program
  .version('0.1.0')
  .command('getstream [url]', 'get stream URL')
  .parse(process.argv);

if (!process.argv.slice(2).length) {
  program.outputHelp(make_red);
}

function make_red(txt) {
  return colors.red(txt); //display the help text in red on the console
}

.help(cb)

Output help information and exit immediately. Optional callback cb allows post-processing of help text before it is displayed.

Custom event listeners

You can execute custom actions by listening to command and option events.

program.on('option:verbose', function () {
  process.env.VERBOSE = this.verbose;
});

// error on unknown commands
program.on('command:*', function () {
  console.error('Invalid command: %s\nSee --help for a list of available commands.', program.args.join(' '));
  process.exit(1);
});

Examples

var program = require('commander');

program
  .version('0.1.0')
  .option('-C, --chdir <path>', 'change the working directory')
  .option('-c, --config <path>', 'set config path. defaults to ./deploy.conf')
  .option('-T, --no-tests', 'ignore test hook');

program
  .command('setup [env]')
  .description('run setup commands for all envs')
  .option("-s, --setup_mode [mode]", "Which setup mode to use")
  .action(function(env, options){
    var mode = options.setup_mode || "normal";
    env = env || 'all';
    console.log('setup for %s env(s) with %s mode', env, mode);
  });

program
  .command('exec <cmd>')
  .alias('ex')
  .description('execute the given remote cmd')
  .option("-e, --exec_mode <mode>", "Which exec mode to use")
  .action(function(cmd, options){
    console.log('exec "%s" using %s mode', cmd, options.exec_mode);
  }).on('--help', function() {
    console.log('');
    console.log('Examples:');
    console.log('');
    console.log('  $ deploy exec sequential');
    console.log('  $ deploy exec async');
  });

program
  .command('*')
  .action(function(env){
    console.log('deploying "%s"', env);
  });

program.parse(process.argv);

More Demos can be found in the examples directory.

License

MIT