File watch and exec command cli tool

watcher

#!/usr/bin/env node

/*
 * File watch and exec command cli tool.
 *
 * Example
 *
 * $ watcher *.less -- lessc style.less style.css
 *
 */

'use strict';

var fs = require('fs');
var exec = require('child_process').exec;
var argv = process.argv.slice(2);
var separator = argv.indexOf('--');
var targets = argv.slice(0, separator);
var command = argv.slice(separator + 1).join(' ');

if (!targets.length || !command.length) {
  console.log('Usage: watcher file [file] -- command');
  console.log('');
  console.log('Example');
  console.log('$ watcher *.less -- lessc foo.less foo.css');
  process.exit();
}

targets.forEach(function(file) {
  fs.watchFile(file, function(curr, prev) {
    if (curr.mtime > prev.mtime) {
      exec(command, function(err, stdout, stderr) {
        if (err) {
          console.error(err);
        }
        if (stdout) {
          console.log(stdout);
        }
        if (stderr) {
          console.error(stderr);
        }
      });
    }
  });
});