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ycommands be an enhancement of yargs adding command semantics.

npm install ycommands --save

All the features of yargs are available, plus new methods define commands and execute them. The command is the first non-option argument:

./tool.js command args...

The command called may be an abbreviation of the actual command, as long as it's unambiguous.

The command list appears in the help message.

Additional methods

.command( name [, description], handler )

Define a command to be called by .execute.

.nocommand( [description ,] handler )

Define the command to be called by .execute when there is no specified command.

.execute( [args] [, callback] )

Determine and execute the proper command based on args, or by default process.argv.

callback is given to the commands, allowing them to return asynchronously. If callback is undefined, commands are still provided with a callback function which does nothing, in order to allow an asynchronous code style.

Errors happening in ycommands (no command given, unrecognized command, ambiguous command) are thrown. They are instances of ycommands.Error. callback is not called for these errors.

Command handler

The handler function has the signature

function( argv [, callback] )

argv is the usual argv object from yargs.

callback is the callback function given to .execute, allowing the function to return asynchronously.


This innovative tool may be patented in the USA. Pirates!

#!/usr/bin/env node
var fs = require('fs');
var ycommands = require('ycommands');

try {
	var config = JSON.parse(fs.readFileSync('config.json'));
} catch (err) {
	config = {};

try {
		.usage("Manage a configuration file.\nUsage: $0 command")
		.command("set key value", "Set a config key", function(argv, callback) {
			var key = argv._.shift();
			var value = argv._.shift();
			config[key] = value;
			return fs.writeFile('config.json', JSON.stringify(config), callback);
		.command("show key", "Show a config key", function(argv, callback) {
			var key = argv._.shift();
			if (!config.hasOwnProperty(key))
				return callback(new Error(key + " is not defined"));
			return callback();
		.nocommand("List all config keys", function(argv, callback) {
			Object.keys(config).sort().forEach(function(key) {
				console.log("%s = %s", key, config[key]);
			return callback();
		.execute(function(err) {
			if (err)
				throw err;
} catch (err) {

./tool.js -h
Manage a configuration file.
Usage: ./tool.js command

  -h  Show help

  set key value  Set a config key
  show key       Show a config key
no command       List all config keys

./tool.js ste foo bar
Unrecognized command: ste
Did you mean:
  set key value  Set a config key

./tool.js set foo bar

foo = bar

./tool.js s foo
Ambiguous command: s
Did you mean:
  set key value  Set a config key
  show key       Show a config key

./tool.js sh foo

./tool.js sh foot
Error: foot is not defined
	at ...

Release History


  • suggest commands when unrecognized
  • better error handling
  • command handlers are still provided with a callback when no callback is given to .execute, and are called asynchronously


  • handles commands or a default command when no command is given
  • suggest commands when ambiguous


Copyright (c) 2014 Bloutiouf aka Jonathan Giroux

MIT licence