Commander.js

The complete solution for node.js command-line interfaces, inspired by Ruby's commander. API documentation: http://tj.github.com/commander.js/

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('0.0.1')
  .option('-p, --peppers', 'Add peppers')
  .option('-P, --pineapple', 'Add pineapple')
  .option('-b, --bbq', '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.bbq) 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.

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('0.0.1')
  .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.

Git-style sub-commands

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

program
  .version('0.0.1')
  .command('install [name]', 'install one or more packages')
  .command('search [query]', 'search with optional query')
  .command('list', 'list packages installed')
  .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 find the executable script in current directory with the name scriptBasename-subcommand, like pm-install, pm-search.

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]

   Options:

     -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]
     -h, --help           output usage information

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('0.0.1')
  .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);

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 behaviours, 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('0.0.1')
  .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('  Examples:');
  console.log('');
  console.log('    $ custom-help --help');
  console.log('    $ custom-help -h');
  console.log('');
});

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()

Output help information without exiting.

.help()

Output help information and exit immediately.

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.