index.js

#!/usr/bin/env node

'use strict';

var yargs = require('yargs'); // Parses arguments and displays help message
var gaze = require('gaze'); // Watches for file changes
var execshell = require('exec-sh'); // Runs commands just like npm scripts
var prettyHrtime = require('pretty-hrtime'); // Format elapsed times nicely

// Define our command line arguments and help stuff
yargs
	.usage('Usage: gaze <command> <pattern> ...\n\nIf present, the string $path in <command> will be replaced by the full path to the file that changed.')
	.example('gaze "jshint $path" "lib/**/*.js"', 'Runs jshint when a js file in the lib folder changes')
	.example('gaze "jshint $path" "**/*.js" "!node_modules/**/*"', 'Runs jshint when a js file anywhere except in node_modules changes')
	.option('version', {
		describe: 'Show version number',
		type: 'boolean'
	})
	.option('help', {
		describe: 'Print this help message',
		type: 'boolean'
	})
	.option('silent', {
		describe: 'Do not print messages',
		type: 'boolean'
	})
	.option('ignore-rename', {
		describe: 'Ignore when a file is renamed',
		type: 'boolean'
	});

var argv = yargs.argv;

// If requested, display help or version message then quit
if (argv.help) {
	console.log(yargs.help());
	return;
}
if (argv.version) {
	console.log('v' + require('./package').version);
	return;
}

// Ensure we have the proper arguments
if (argv._.length < 2) {
	console.log('You must provide a single command and at least one pattern');
	return;
}

var command = argv._[0];
var pattern = argv._.slice(1, argv._.length);

// Start the file watcher on the pattern
gaze(pattern, function(err, watcher) {
	if (err) {
		throw err;
	}
	if (!argv.silent) {
		var fileCount = 0;
		Object.keys(watcher._watched).forEach(function(watched) {
			fileCount = fileCount + watcher._watched[watched].length;
		});
		console.log('Watching ' + fileCount + ' files/directories, pattern: ', pattern);
		if (fileCount > 10000) {
			console.log('This is a lot of files, for better performance you should reduce it.');
		}
	}
	watcher.on('changed', function(filepath) {
		run(filepath);
	});
	watcher.on('added', function(filepath) {
		run(filepath);
	});
	watcher.on('renamed', function(newPath) {
		if (!argv['ignore-rename']) {
			run(newPath);
		}
	});
});

// Function to run when something changes
function run(filepath) {
	var startTime = process.hrtime();
	var uniqueCommand = command.replace('$path', filepath);
	if (!argv.silent) {
		console.log('>', uniqueCommand);
	}
	execshell(uniqueCommand);
	if (!argv.silent) {
		console.log('Finished in', prettyHrtime(process.hrtime(startTime)));
	}
}